Towards Energy Efficiency: Innovations in High-Frequency Converters for Renewable Energy Systems and Electric Vehicles

Abstract

This study reviews advancements in high-frequency converters for renewable energy systems and electric vehicles, emphasizing their role in enhancing energy efficiency and sustainability. Using the PRISMA 2020 methodology, 73 high-quality studies from 2014 to 2024 were synthesized to evaluate innovative designs, advanced materials, control strategies, and future opportunities. Key findings reveal significant progress in converter topologies, such as dual active bridge and LLC resonant designs, which enhance efficiency and scalability through soft-switching. Wide-bandgap semiconductors, including silicon carbide and gallium nitride, have driven improvements in power density, thermal management, and compactness. Advanced control strategies, including adaptive and AI-driven methods, enhance stability and efficiency in microgrids and vehicle-to-grid systems. Applications in photovoltaic and wind energy systems demonstrate the converters’ impact on improving energy conversion and system reliability. Future opportunities focus on hybrid and multifunctional designs that integrate renewable energy, storage, and electric mobility with intelligent control technologies like digital twins and AI. These innovations highlight the transformative potential of high-frequency converters in addressing global energy challenges driving sustainable energy and transportation solutions. This review offers critical insights into current advancements and pathways for further research and development in this field.

1. Introduction

In the current context, the increasing demand for energy efficiency and the adoption of sustainable technologies have driven the development of advanced energy conversion systems in electric vehicles and renewable energy systems. High-frequency converters have become essential components in these systems, facilitating the integration of renewable sources and enhancing the performance of electric vehicle chargers [1,2]. The advancement of wide-bandgap materials, such as gallium nitride (GaN), has enabled the significant miniaturization of magnetic components, thus increasing power density and efficiency in these converters [3,4]. However, significant challenges remain, such as control complexity in bidirectional charging systems and high-frequency interference issues in power grids that impact stability and power quality [5,6]. These challenges highlight the need for a comprehensive review of recent advancements in the design and optimization of high-frequency converters, as well as their applications and limitations in energy efficiency and economic viability in these sectors. This review study aims to provide a critical contribution by identifying solutions and future development opportunities in the field of power electronics applied to energy sustainability.

Historically, classical converters have faced critical limitations, including high energy losses, bulky designs, and restricted scalability, which have hindered their adoption in large-scale renewable energy systems and electric vehicle (EV) applications. These issues arise primarily due to inefficient switching mechanisms and the use of silicon-based semiconductors, which constrain power density and thermal performance. Recent advancements in topologies, such as dual active bridge (DAB) and LLC resonant converters, have directly addressed these deficiencies. For example, the integration of soft-switching techniques like zero-voltage switching (ZVS) and the use of wide-bandgap (WBG) semiconductors such as gallium nitride (GaN) and silicon carbide (SiC) have reduced switching losses by up to 50% and improved system efficiency by 15–20% [7,8]. This review aims to bridge the gap between classical limitations and contemporary innovations, demonstrating how these advancements overcome practical deficiencies and enable transformative applications in sustainable energy and transportation. In the literature, extensive studies examine the role of high-frequency converters in advancing renewable energy systems and electric vehicle charging. High-frequency AC-DC converters, for instance, are developed to improve efficiency and modularity in power supplies, often integrating soft-switching techniques to achieve power factor correction and zero-voltage switching [9]. In the context of electric vehicles (EVs), on-board chargers and low-voltage DC-DC converters are essential to isolate and step down power while optimizing weight and volume, as seen in innovative tapped transformer designs [1]. Bidirectional chargers for vehicle-to-grid (V2G) applications are explored for their impact on grid impedance and supraharmonic emissions, an area that is crucial as electric grids become more complex with increased renewable integration [5].

Wide bandgap semiconductors, particularly in resonant converters, support the miniaturization and efficiency gains in power systems, allowing high switching frequencies and optimized magnetic component design for applications such as EV charging [10]. Wireless power transfer for battery charging is also advancing, with systems achieving constant voltage and current adaptive charging through dual-channel configurations that maximize efficiency under varied load conditions [11]. For on-board EV chargers, the use of phase-shift PWM-controlled converters with high-frequency transformers demonstrates improved soft-switching and compactness [12], while designs with reduced switching frequency variations achieve stability and low resonance losses, critical for reliable operation [13]. Bidirectional single-stage converters that incorporate zero-current switching for PFC-based EV charging are developed to reduce switching losses and footprint, enhancing reliability and robustness for bi-directional power flow [14]. Furthermore, innovative AC-DC topologies achieve high efficiency and compact design by removing inductors and capacitors, as in inductorless, capacitorless bidirectional converters, achieving high performance and minimized circulating current [15]. For applications with matrix rectifiers, high-frequency link systems demonstrate advantages in efficiency and compactness but present challenges in control complexity, motivating new dual-loop strategies to improve dynamic performance [16]. In the context of light electric vehicles (LEVs), a bridgeless SEPIC APFC is employed to increase voltage gain while maintaining high power quality, a simplified and cost-effective approach for LEV charging [17]. Phase-shift modulation in single-stage converters also supports bidirectional capabilities for vehicle-to-home (V2H) operations, enabling high-frequency isolation without bulky capacitors further optimizing for efficiency and soft switching [18]. To address fast charging needs, partial power converters (PPC) without galvanic isolation achieve high efficiency and lower costs, making them suitable for high-power, low-complexity EV fast charging solutions [19]. GaN-based LLC resonant converters are frequently discussed for their high-frequency applications in power systems, with a focus on soft-switching and interleaved topologies to manage current ripple and enhance power density, making them ideal for EV chargers and renewable energy systems [3]. Bidirectional converters for EV applications are also refined to operate with high power factor and low harmonic distortion, as seen in single-phase PFC designs [20]. Power quality in dual active bridge (DAB) converters is optimized using disturbance rejection techniques, minimizing ripple and improving performance under varying load conditions [6]. Silicon carbide (SiC)-based chargers are introduced for portable EV applications, with loss models that guide component selection and thermal design, achieving high power density and efficiency [2].

For medium-voltage systems, modular multilevel converters (MMCs) with hybrid topologies are proposed to handle high-AC/low-DC voltages, offering semiconductor savings and improved efficiency, making them suitable for interfacing renewable sources with the grid [21]. Modular DC-DC converters in low-speed EV fast chargers improve system efficiency by leveraging direct current sharing control, avoiding instability common in parallel systems [22]. Recent research on isolated resonant DC-DC converters also explores designs based on wide-bandgap transistors, which support high power density and efficiency through optimized control strategies [4]. Control strategies in isolated AC-DC converters for EVs include phase-shift techniques to regulate power flow and smooth power ripple, supporting bidirectional and grid-interactive charging functions [23]. Additionally, reviews address the simultaneous charging of multiple EV batteries, focusing on power quality and high-frequency transformer testing to ensure reliable, simultaneous operations [24]. The global shift from internal combustion engines to EVs has raised concerns over charging infrastructure and grid impact, with literature focusing on the environmental and technical standards required for widespread EV adoption [25]. To address frequency challenges in renewable microgrids, supercapacitor integration offers enhanced frequency support, reducing nadir and rate of change of frequency (ROCOF) under disturbances [26]. High-frequency resonance issues in HVDC systems with modular multilevel converters are also studied, with multi-band band-stop filters proposed to suppress resonance and improve grid stability [27]. Lastly, cybersecurity remains a critical focus in EV charging systems to mitigate risks associated with data integrity attacks on charging controllers and battery management systems [28,29].

Despite significant advances in the design and optimization of high-frequency converters for electric vehicle charging systems and renewable energy, certain research gaps remain unaddressed. While many studies focus on enhancing the efficiency and compactness of high-frequency converters through novel topologies and advanced materials like wide-bandgap semiconductors [3,12], other critical aspects require further exploration. For instance, the scalability of bidirectional converters in multi-vehicle charging setups remains underexplored, particularly regarding how to optimize power flow and grid stability across multiple units [16,27]. Similarly, the literature lacks a detailed analysis of how control complexities in modular systems scale with increasing grid size and the integration of diverse renewable sources, both of which are crucial for ensuring reliable operation in modern energy systems [18,24]. Moreover, the compatibility of high-frequency converters in high-frequency grids and their impact on supraharmonic emissions continue to be underexamined, particularly for vehicle-to-grid (V2G) and vehicle-to-home (V2H) applications, where stability and power quality are paramount [5,30]. Although advanced control strategies have been investigated to reduce fluctuations and enhance performance under varied load conditions, their adaptability to large-scale systems with dynamic and distributed energy sources remains a significant challenge [6,19]. Additionally, the cybersecurity risks inherent in EV charging systems, such as vulnerabilities to data integrity attacks on charging controllers and battery management systems, demand more comprehensive analyses and robust mitigation strategies, especially as connected infrastructures become more prevalent [31,32]. Futuristic applications of high-frequency converters, such as dynamic wireless charging for EVs and energy-sharing microgrids, further highlight these gaps. Dynamic wireless charging, for instance, relies on high-frequency resonant converters to maintain efficient energy transfer under variable conditions, yet studies often neglect the challenges of maintaining stability and minimizing losses in such scenarios [13,15]. Similarly, the integration of bidirectional converters in energy-sharing microgrids raises critical questions about the optimization of control strategies for peer-to-peer energy exchange and their impact on grid reliability and efficiency [16,20]. Addressing these gaps through experimental studies, simulation frameworks, and the development of adaptive control algorithms will be essential to advance the field.

This review employs the PRISMA method to synthesize and critically analyze recent advances in high-frequency converters, identifying key challenges and opportunities to enhance energy efficiency and sustainability in renewable energy systems and electric mobility. The specific contributions of this paper are:

• A comprehensive review of high-frequency converter designs and optimization strategies, focusing on innovative topologies such as dual active bridge (DAB) and LLC resonant converters. These designs address challenges related to energy efficiency, compactness, and adaptability in renewable systems and electric vehicle charging infrastructures.
• An in-depth analysis of advanced control methodologies, including adaptive, predictive, and AI-driven strategies, which improve stability, efficiency, and fault tolerance in bidirectional charging systems, renewable microgrids, and hybrid energy configurations.
• A synthesis of applications for high-frequency converters in renewable energy systems, particularly in photovoltaic (PV) and wind energy systems, emphasizing their impact on improving power density, reliability, and grid integration.
• An exploration of future directions for hybrid and multifunctional architectures, which integrate renewable sources, energy storage, and electric mobility systems, supported by intelligent control technologies like digital twins for real-time optimization and predictive maintenance.

The structure of this article is organized as follows: Section 2 details the systematic methodology used to select and analyze the most relevant works, adhering to the PRISMA 2020 guidelines to ensure rigor and transparency in the prospective literature. Section 3 presents the findings and discussions, structured around five thematic areas: innovative converter designs, advanced semiconductor materials, control strategies, applications in renewable energy systems, and future prospects for hybrid and multifunctional architectures. Finally, Section 4 concludes the study by synthesizing key insights, highlighting technological advancements, and identifying opportunities for further research and development in this transformative field.

2. Methodology for Study Selection

The systematic review process was conducted following the PRISMA 2020 Statement [32], a robust framework designed to ensure transparency, rigor, and reproducibility in systematic reviews and meta-analyses. This methodology was chosen because it provides a structured approach for synthesizing existing research, ensuring that the findings are based on high-quality evidence and minimizing potential biases. The study selection process encompassed four distinct stages: Identification, Screening, Eligibility and Inclusion, and Synthesis. Each stage played a critical role, from narrowing down a comprehensive set of studies to integrating and analyzing the selected evidence. These stages, described in detail in the following subsections, collectively ensured the inclusion of high-quality and pertinent literature, providing a solid foundation for the review’s findings and conclusions.

2.1. Identification of Studies

For this systematic literature review, an extensive search was conducted to include studies published over the last decade, from 2014 to 2024. The search was limited to journal articles and conference papers published in English with full-text access, ensuring that the reviewed studies provided primary data and in-depth applied research analysis. Excluded from the search were editorials, reviews, case studies, opinion pieces, letters to the editor, and policy documents, as they do not meet the criteria of academically rigorous and scientifically relevant sources. The bibliographic data for this review were retrieved from two leading academic databases: Scopus and Web of Science.

• Scopus is a widely recognized multidisciplinary database covering diverse fields, including engineering and applied sciences. Renowned for its breadth and peer-reviewed content, Scopus offers a comprehensive resource for recent and impactful studies, facilitating a balanced analysis of high-frequency converters and energy efficiency. The following search string was used for this initial prospection: TITLE-ABS-KEY ((“high frequency” AND “converter”) AND (“renewable energy” OR “electric vehicle charging”)) AND PUBYEAR > 2013 AND PUBYEAR < 2025 AND (LIMIT-TO (DOCTYPE, “cp”) OR LIMIT-TO (DOCTYPE, “ar”)) AND (LIMIT-TO (LANGUAGE, “English”)).
• Web of Science is another highly reputable database known for its rigorous selection criteria and robust citation tracking. Covering influential publications from top-tier publishers such as IEEE, Elsevier, Springer, Taylor and Francis, Wiley, and MDPI, it provides extensive access to high-quality, globally impactful research relevant to this review. The following search string was employed: ((ALL = (“high frequency”)) AND ALL = (“converter”)) AND (ALL = (“renewable energy”) OR ALL = (“electric vehicle charging”)). Refined by: Years (2014–2024), Document Type (Article or Proceeding Paper), Language (English).

The initial search, last updated on 1 November 2024, yielded a total of 744 records: 500 from Scopus and 244 from Web of Science. Given the overlap between these two comprehensive databases, there was a high probability of duplicate entries. Using a bibliographic management tool, duplicate records were identified and removed, resulting in a total of 149 duplicates discarded. This process left 595 unique records—482 from Scopus and 113 from Web of Science—to be considered for the Screening phase.

2.2. Screening of Studies

In the Screening phase, the titles and abstracts of the 595 identified records were carefully reviewed to ensure the relevance and rigor of the selected studies. This process was guided by a set of predefined inclusion criteria to filter out studies that did not meet the objectives of this systematic review. The criteria, applied systematically to each record, were as follows:

• Publication Year: Only studies published between 2014 and 2024 were considered, ensuring the inclusion of recent and relevant research aligned with the review’s focus.
• Document Type: The selection was restricted to original research articles published in journals and conference proceedings. Excluded were review articles, editorials, letters, opinion pieces, and other document types that do not provide empirical or applied research analysis.
• Language: To maintain consistency and accessibility, only studies published in English were included, reflecting its status as the predominant language in the global scientific literature.
• Full-Text Availability: Articles had to be accessible in full text, either through institutional subscriptions or open access, to allow for comprehensive evaluation during the subsequent phases.
• Thematic Relevance: Each study needed to explicitly address the development, design, optimization, or application of high-frequency converters in renewable energy systems or electric vehicles. Records lacking a clear focus on these topics were excluded.

Applying these criteria reduced the initial pool of 595 records to a subset of studies deemed relevant for further examination. This screening process ensured the elimination of irrelevant or low-quality records while retaining studies of high academic rigor and alignment with the research objectives, thereby strengthening the foundation for the next phase of the review. After this detailed review, 423 items (71% of the total screened records) were deemed suitable for progression to the next phase. Of these, 56% were journal articles, and 44% were conference proceedings. It is important to emphasize that the exclusion of studies during the screening stage does not imply that the discarded articles lack scientific value or quality. Rather, these exclusions were solely based on their alignment with the specific scope and objectives defined by the research team for this systematic review. For instance, studies that did not fully meet the screening criteria outlined above were omitted. To further illustrate the rigorous and objective nature of the selection process performed, Appendix A.1. provides examples of the screening stage, describing the criteria applied for both the inclusion and exclusion of studies.

The annual distribution of studies that passed the screening stage is presented in Figure 1. This distribution highlights a growing interest in the topic over time, with a noticeable upward trend in recent years. The peak publication years, 2022 and 2023, illustrate the increasing relevance and momentum of research in high-frequency converters for renewable energy systems and electric vehicles. Notably, the significant number of publications in 2024 reflects the ongoing activity in this field despite the year still being in progress. This reinforces the topicality and importance of the subject, aligning with global efforts to enhance energy efficiency and integrate renewable energy technologies.

2.3. Eligibility and Inclusion of Studies

The Eligibility and Inclusion phase was essential for narrowing the selection to only the most pertinent and high-quality studies for this systematic review. Each article of a total of 423 was meticulously evaluated through a comprehensive full-text review, applying a detailed three-level Likert scale for the following criteria specifically designed for this investigation:

• Relevance to Study Goals
  Degree to which the study addresses the development, design, optimization, or application of high-frequency converters in renewable energy systems and electric vehicles. Score scale: 1: Marginal, 2: Related, 3: Highly Relevant.
• Methodological Soundness
  Rigor and appropriateness of the research methodology employed in the study. Score scale: 1: Needs Improvement, 2: Acceptable, 3: Excellent.
• Innovation and Contribution
  Originality and significance of the study’s contributions to the field of high-frequency converters, quantified by the article’s impact (e.g., citation count). Score scale: 1: Moderate, 2: Substantial, 3: Very Significant.
• Data Quality and Reliability
  Quality and reliability of the data presented in the study, including accuracy and consistency. Score scale: 1: Satisfactory, 2: Good, 3: Excellent.
• Advancements in High-Frequency Converters
  Extent to which the study advances the design, materials, implementation, or applications of high-frequency converters in renewable energy systems and electric vehicle applications. Score scale: 1: Limited, 2: Notable, 3: Highly Impactful.

During this phase, a total of 423 articles were evaluated, resulting in the selection of 73 studies that met the stringent benchmark of a minimum score of 13 out of 15 points across the evaluation criteria. This threshold was chosen to ensure that only studies meeting high standards of relevance, rigor, innovation, and impact were included in the review. To minimize bias in this crucial stage, the evaluation process was conducted independently by two researchers. Any discrepancies in scoring were resolved through discussion and consensus, further enhancing the reliability and objectivity of the selection process. Figure 2 presents the verification matrix used to assess the eligibility of the articles. This rigorous approach resulted in a carefully curated set of studies that not only meet the high standards of this review but also provide a balanced representation of the advancements in high-frequency converters for renewable energy systems and electric vehicles. It is necessary to indicate that the studies excluded during this phase were not dismissed due to any lack of scientific merit or quality. Instead, the decisions were based strictly on their alignment with the defined scope and objectives of this systematic review measured by the eligibility criteria.

To ensure clarity and respectful handling of bibliographic resources, we have anonymized the records by source database, using the prefix S-XXX for Scopus entries and WoS-XXX for Web of Science entries. Furthermore, to enhance transparency, we have shared the complete metadata of the identified studies through the following link: https://github.com/dannyochoa87/vehicles-07-00001/archive/refs/heads/main.zip (accessed on 27 December 2024). This resource enables readers to validate the works included in the review and supports the integrity of the selection process. In addition, Appendix A.2. provides concrete examples of the Eligibility and Inclusion stage, detailing the specific criteria applied during the full-text evaluation of the selected studies.

2.4. Synthesis of Selected Studies

This section provides a bibliometric analysis of the 73 articles selected during the Eligibility and Inclusion Phase, offering a detailed overview of the current research landscape in high-frequency converters for renewable energy systems and electric vehicles. Figure 3 illustrates the annual distribution of selected publications. The data highlight a fluctuating yet sustained research interest over the past decade. Peaks in publication numbers occur in 2020 and 2021, with 10 and 9 items, respectively, reflecting increased attention to the field during these years. While a slight decline is observed in 2023, the publications for 2024 (6 items) are noteworthy, given that the year was still in progress at the time of the last update. This trend demonstrates that the topic remains relevant, with consistent contributions to the field, especially in recent years. Of the 73 selected studies, 53 correspond to journal articles, emphasizing the predominance of peer-reviewed, high-quality research in this domain. The journal IEEE Transactions on Power Electronics stands out as the most frequent source, with 13 articles underscoring its centrality in publishing cutting-edge developments in power electronics. Other journals that made notable contributions include IEEE Transactions on Industry Applications (8 articles), IEEE Journal of Emerging and Selected Topics in Power Electronics (4 articles), and IEEE Transactions on Industrial Electronics (3 articles). This diversity of journals highlights the multidisciplinary nature of the field, with research spanning multiple aspects of high-frequency converters and their applications in renewable energy systems and electric vehicles. In addition to journal articles, conference papers constitute an important part of the selected studies, representing 20 items. The IEEE Applied Power Electronics Conference and Exposition (APEC) and the IEEE Energy Conversion Congress and Exposition (ECCE) were among the most prominent conferences, together contributing six papers. Other notable proceedings include international events such as the International Conference on Circuit Power and Computing Technologies (ICCPCT 2024) and the International Conference on Green Computing, Communication, and Electrical Engineering (ICGCCEE 2014). These conference publications serve as critical venues for presenting emerging trends, innovative designs, and early-stage research in high-frequency converters, complementing the more established findings presented in journal articles.

Figure 4 provides a global map illustrating this distribution, offering a visual representation of the reach and diversity of the selected works. There, the data label in each highlighted country represents the number of items from which each of them comes, according to the affiliation of the authors. The analysis of the authors’ countries of origin for the 73 selected articles reveals an interesting and diverse geographic distribution, emphasizing the global engagement in the studied topic. The United States leads with 21 contributions, followed by India with 13 and Australia with 6, showcasing these nations’ significant focus on advancing research in renewable energy systems and high-frequency converters. Other notable contributors include Iran (5), China (4), and countries such as Canada, Brazil, Italy, Switzerland, Colombia, and Turkey, each with two contributions. The rest of selected studies includes an array of countries, such as Russia, Tunisia, Bangladesh, Spain, Egypt, Taiwan, France, Denmark, Japan, Argentina, and Indonesia, each represented by a single article. This highlights the truly international scope of this research field, reflecting the need for a collaborative, multidimensional approach to tackle energy challenges.

To further synthesize the insights from the 73 selected studies, a word cloud map (Figure 5) was generated based on the keywords from these articles. The visualization highlights the recurring themes and focal points of the research, providing a basis for categorizing the literature into thematic subunits.

These categories encapsulate the core research areas within the field of high-frequency converters and offer a structured approach to analyzing the contributions of the selected works. The following subunits emerged:

• Design of High-Frequency Converter Architectures—Innovative Topologies and Configurations for Enhanced Efficiency and Performance: This thematic subunit encompasses studies dedicated to the development and analysis of new topologies and configurations of high-frequency converters. The research emphasizes how innovative design structures can address challenges related to efficiency, adaptability, and performance. These studies are particularly relevant to power electronics applications in renewable energy systems and electric vehicles, showcasing cutting-edge architectural innovations that optimize energy conversion processes.
• Advanced Semiconductor Materials in Converter Technology—The Role of SiC, GaN, and Wide-Bandgap Materials in Next-Generation Converters: A substantial portion of the literature focuses on the use of advanced semiconductor materials, such as silicon carbide (SiC) and gallium nitride (GaN), in converter technology. These materials, often categorized as wide-bandgap semiconductors, enable significant improvements in efficiency, power density, and thermal management. This category highlights their crucial role in driving advancements in energy conversion technologies, making them essential components for next-generation high-frequency converters.
• Implementation and Control Strategies for High-Frequency Converters—Modeling, Simulation, and Control for Practical Applications: This category includes studies that concentrate on the practical deployment of high-frequency converters. The research spans control algorithms, modeling, simulation, and real-world testing, aiming to refine control techniques for better stability and efficiency. These contributions are critical for ensuring the reliable operation of converters in practical scenarios, particularly for renewable energy systems and electric vehicle applications.
• Applications of High-Frequency Converters in Renewable Energy Systems—Optimizing Efficiency and Stability in PV, Wind, and Microgrid Integrations: A significant segment of the research explores the application of high-frequency converters in renewable energy systems, such as photovoltaics (PV) and wind energy. These studies focus on optimizing efficiency and maintaining grid stability in systems characterized by variable power inputs. They also address the integration of high-frequency converters into microgrids, highlighting their importance in renewable energy storage and distribution.
• Electric Vehicle Applications of High-Frequency Converters—On-Board Chargers, Fast Charging, and V2G Solutions for the Future of Mobility: This subunit focuses on the role of high-frequency converters in electric vehicle (EV) technology. Studies examine their use in on-board charging systems, fast-charging stations, and vehicle-to-grid (V2G) solutions. The research highlights the necessity of compact, efficient, and durable converters that enhance EV performance, support rapid charging infrastructure, and seamlessly integrate with electric grids, positioning high-frequency converters as integral to the future of sustainable mobility.

The categorization of the selected studies into thematic subunits provides a structured framework for synthesizing the extensive body of research on high-frequency converters (Figure 6). This approach facilitates a deeper understanding of the key contributions and emerging trends within this multidisciplinary field, ranging from innovative design topologies and advanced semiconductor materials to practical applications in renewable energy systems and electric vehicles. These themes collectively form a foundation for exploring the state-of-the-art in energy conversion technologies. Building on this foundation, Section 3 delves into the primary findings from the selected studies, aligning them with the objectives of this investigation.

Finally, Figure 7 illustrates a summary of the literature prospecting process followed, presented through a standardized flow diagram as mandated by the PRISMA 2020 Statement.

3. Results and Discussions

3.1. Design of High-Frequency Converter Architectures: Innovative Topologies and Configurations for Enhanced Efficiency and Performance

3.1.1. Evolution of Topologies: Trends and Advances

The continuous evolution of high-frequency converter architectures is marked by significant innovation in topologies aimed at enhancing efficiency, adaptability, and scalability. Dual active bridge (DAB) converters are a prominent example, providing efficient bidirectional power transfer with minimal losses. These converters are particularly suited for electric vehicle (EV) applications and renewable energy systems, where variable loads and energy storage integration require robust power management solutions [30,33]. Their modularity and scalability make them essential for managing energy flows in large-scale systems [34]. Resonant topologies, such as LLC and series-parallel resonant converters, have also gained attention for their ability to achieve high efficiency and low electromagnetic interference [35]. By employing soft-switching techniques, such as zero-voltage switching (ZVS) and zero-current switching (ZCS), these converters minimize energy losses during switching events, enabling operation at higher frequencies [7,36]. Resonant designs are particularly effective in renewable energy systems like photovoltaics, where variability in power input is a common challenge. Additionally, they have been adapted for EV fast-charging systems, where compactness and efficiency are critical [8,37].

Wireless power transfer (WPT) systems represent another innovative development. By eliminating the need for physical connectors, WPT enhances system reliability and convenience, especially in EV charging applications [38]. High-frequency WPT systems have achieved significant milestones in power density and efficiency, paving the way for their integration into dynamic charging infrastructures, where vehicles can charge while in motion [7,39]. The integration of wide-bandgap (WBG) semiconductors, such as gallium nitride (GaN) and silicon carbide (SiC), has further pushed the boundaries of high-frequency converters. These materials allow for higher thermal conductivity, faster switching speeds, and reduced losses, enabling converters to operate efficiently at higher frequencies [40]. Their adoption has been transformative in both renewable energy and EV applications, providing solutions to long-standing challenges in power density and thermal management [41,42]. These advancements highlight the trend toward more compact, efficient, and versatile converter designs.

Unlike classical converters, which suffer from significant energy losses during switching events, DAB converters achieve bidirectional power transfer with minimal losses through the use of ZVS and ZCS techniques. These approaches minimize energy dissipation during switching transitions, resulting in a reduction of losses by 30–50%, as demonstrated in a comparative study of SiC-based DAB implementations [8,42]. Furthermore, DAB converters offer modularity and scalability, making them ideal for EV fast-charging stations, where they have been shown to improve energy transfer efficiency from 92% to over 97% [43].

3.1.2. Solutions for Specific Challenges in Renewable Energy and Electric Vehicle Applications

High-frequency converters are uniquely positioned to address the diverse challenges faced by renewable energy systems and electric vehicles [44]. In renewable energy systems, variability in power generation from sources like solar and wind necessitates converters capable of handling dynamic loads while maintaining efficiency and stability [45]. Resonant and interleaved converter designs have proven effective in managing these fluctuations, providing stable energy outputs, and reducing grid disturbances [36,42]. In electric vehicles, the demand for compact, lightweight, and efficient power converters has led to significant innovations in on-board chargers and fast-charging stations. Phase-shift pulse-width modulation (PWM) techniques have been widely adopted to achieve soft-switching, reducing switching losses and enhancing system reliability [46]. This is particularly important in high-power applications, where thermal management and energy efficiency are critical [43,47].

Bidirectional power converters are at the forefront of addressing the needs of vehicle-to-grid (V2G) systems, where energy can flow between EVs and the grid. These systems require converters capable of managing supraharmonic emissions and ensuring grid stability [48]. Advanced control strategies, such as dual-loop and adaptive controllers, have been employed to mitigate these challenges, enabling seamless integration of EVs into the power grid [33,49]. Furthermore, the use of high-frequency converters in renewable microgrids has improved energy storage integration, facilitating better management of power fluctuations and enhancing overall system reliability [50]. Wide-bandgap semiconductors have been decisive in addressing challenges related to high-frequency interference and control complexity in both renewable energy and EV applications. GaN and SiC devices enable higher switching frequencies and reduced energy losses, making them ideal for compact and efficient converter designs. These materials have also opened new avenues for research into hybrid systems that combine renewable generation, energy storage, and electric mobility [8,41]. LLC resonant converters have similarly revolutionized renewable energy applications by addressing classical constraints of bulky magnetic components and high electromagnetic interference (EMI). By operating at high switching frequencies and leveraging GaN devices, LLC topologies have reduced passive component sizes by up to 40% and achieved system efficiencies exceeding 98% [36,51]. Practical implementations in photovoltaic (PV) systems have demonstrated their ability to stabilize output power and enhance reliability, even under fluctuating input conditions [8,52]. In bidirectional EV charging systems, managing grid stability while ensuring seamless energy exchange between the grid and the vehicle presents significant control challenges. Advanced strategies such as finite control set predictive control (FCS-MPC) have demonstrated reductions in harmonic distortion by up to 50% in bidirectional power transfer scenarios [53]. Furthermore, the integration of dual-loop control in DAB converters has improved dynamic response times by 30%, ensuring stable operation even under varying load conditions [42].

3.1.3. Future Perspectives: Hybrid and Multifunctional Designs for High-Efficiency Systems

The future of high-frequency converter architectures lies in the development of hybrid and multifunctional designs capable of meeting the growing demands of renewable energy systems and electric vehicles [54]. Hybrid designs, which integrate features of DAB, resonant, and interleaved converters, offer the potential to optimize power flow and improve efficiency across diverse applications. These designs are up-and-coming for fast-charging stations, where high power density and reliability are essential [30,37,42]. Multifunctional converters that can simultaneously manage energy flow between renewable sources, storage systems, and EVs represent the next frontier in power electronics. By integrating advanced control algorithms and adaptive switching techniques, these systems can dynamically adjust to varying load conditions and environmental factors, ensuring stable and efficient operation. Such designs will be critical in enabling smart grids and decentralized energy systems [43,52].

Emerging trends also point to the increased use of artificial intelligence (AI) and machine learning (ML) in the design and control of high-frequency converters [55]. These technologies can optimize converter performance by predicting load variations and adjusting operation parameters in real-time, further enhancing efficiency and reliability. Additionally, the integration of cybersecurity measures into converter designs will become increasingly important as energy systems become more interconnected and data-driven [56,57]. Wide-bandgap materials will continue to play a key role in shaping the next generation of high-frequency converters. The combination of SiC and GaN with advanced topologies will enable higher power densities, reduced thermal loads, and enhanced operational lifespans [58]. Future research should focus on exploring the sustainability and lifecycle impacts of these materials, as well as their potential applications in emerging energy markets [31,41]. The development of modular converters for renewable energy and EV applications will also drive innovation. Modular designs allow for scalability and fault tolerance, making them ideal for large-scale installations like offshore wind farms and urban EV charging networks. These systems will benefit from advancements in direct current sharing and hybrid control strategies, which can enhance overall system efficiency and reliability [31,59]. The diversity and innovation in high-frequency converter designs are highlighted in

Table 1. Summary of current methods, advantages, and future challenges in high-frequency converter.

Method/Approach	Key Advantages	Future Challenges
Dual Active Bridge (DAB) Converters [30,33]. (2018, 2016).	- High modularity for scalable applications.	- Managing control complexity under dynamic load conditions.
	- Efficient bidirectional power transfer.	- Integration into hybrid systems.
Resonant Converters (LLC) [7,36]. (2022, 2019).	- High efficiency through soft-switching.	- Thermal management challenges at higher frequencies.
	- Reduced electromagnetic interference (EMI).	- Scalability to larger systems.
Wide-Bandgap Semiconductors (SiC, GaN) [8,41,42]. (2020, 2015, 2020).	- Superior thermal conductivity and reduced energy losses.	- High material costs.
	- Compact designs enabling miniaturization.	- Integration complexities with advanced topologies.
Wireless Power Transfer (WPT) [7,39]. (2022, 2015).	- Eliminates mechanical wear with no physical connectors.	- Efficiency losses over long distances.
	- Ideal for EV applications.	- Regulatory challenges in deployment.
Modular Multilevel Converters (MMC) [31,59]. (2016, 2021).	- Fault-tolerant and highly scalable design.	- Improving dynamic grid efficiency.
	- Suitable for large-scale renewable systems.	- Achieving higher fault tolerance in complex networks.
Phase-Shift PWM Converters [43,47]. (2019, 2016).	- Enables soft-switching for improved energy efficiency.	- Optimization for high-power applications.
	- Compact designs for lightweight systems.	- Addressing thermal dissipation issues.
Bidirectional Converters for V2G [33,49]. (2016, 2019).	- Supports grid stability through vehicle-to-grid (V2G) interaction.	- Ensuring compatibility with diverse grid standards.
	- Mitigates supraharmonic emissions.	- Reducing system control complexity.
Interleaved Converters [36,42]. (2019, 2020).	- Enhances power density in compact applications.	- Managing electromagnetic interference (EMI).
	- Reduces switching losses in dynamic loads.	- Improving fault tolerance in sensitive systems.
Soft-Switching Techniques [37,43]. (2021, 2019).	- Minimizes switching losses for improved efficiency.	- Expanding applicability to high-power systems.
	- Facilitates better thermal management.	- Reducing implementation costs.
Hybrid Architectures [30,37]. (2018, 2021).	- Combines strengths of multiple designs for adaptability.	- Developing unified control algorithms.
	- Suitable for diverse energy sources.	- Addressing integration challenges across systems.

, which provides an overview of key methods currently employed, their advantages, and the future challenges they face [60]. This table synthesizes insights from a wide range of research studies, illustrating the progress in various converter architectures while identifying areas for further exploration.

3.2. Advanced Semiconductor Materials in Converter Technology: SiC, GaN, and Wide-Bandgap Materials

3.2.1. Impact of Advanced Materials on Efficiency and Power Density

Wide-bandgap (WBG) semiconductors, specifically silicon carbide (SiC) and gallium nitride (GaN), have dramatically improved the performance of high-frequency converters. Their exceptional properties, including higher breakdown voltage, faster switching speeds, and lower energy losses compared to silicon-based devices, have enabled advancements in efficiency and power density across multiple applications [61]. SiC-based devices are ideal for medium and high-voltage applications due to their ability to handle significant electrical stresses. For instance, SiC has been successfully implemented in modular multilevel converters to enable compact designs in medium-voltage renewable energy systems, providing superior energy conversion efficiency even under partial shading conditions [8]. Furthermore, in PV inverters, SiC facilitates the integration of advanced topologies, such as Class-E inverters, which mitigate complex control schemes and optimize the energy conversion process [62].

GaN, on the other hand, offers unparalleled switching speeds, making it indispensable for high-frequency applications such as wireless power transfer (WPT) [63]. A notable example includes a GaN-based WPT system achieving 95.2% efficiency at a 6.6 kW power transfer, demonstrating its potential in lightweight and compact electric vehicle (EV) chargers [7]. Additionally, GaN devices have been deployed in LLC resonant converters, enabling zero-voltage switching (ZVS) and high power density in medium-voltage applications [51]. The adoption of WBG semiconductors in these applications reduces energy losses and significantly minimizes the size of passive components, such as inductors and capacitors [64]. This reduction translates into lighter, more compact converter designs, a critical requirement for EV on-board chargers and microgrid systems [52,65].

3.2.2. Thermal Management and Miniaturization Trends

The high thermal conductivity of SiC and GaN has revolutionized thermal management in power electronics. SiC’s ability to operate at elevated temperatures with minimal heat dissipation requirements enables its integration into high-frequency systems such as medium-voltage transformers and converters [66]. For instance, a 200-kW medium-frequency transformer using SiC achieved a peak efficiency of 99.84%, showcasing its superiority in handling thermal stresses [59]. GaN devices, while offering slightly less thermal conductivity than SiC, excel in high-frequency operations, reducing the need for bulky cooling mechanisms. These properties make them suitable for EV fast-charging stations, where compactness and reliability are paramount. Recent advancements include the use of nanocrystalline core materials in high-frequency magnetic links to optimize thermal performance further and reduce energy losses in grid-connected systems [52,67]. Miniaturization is another critical trend facilitated by WBG semiconductors [68]. By enabling operation at higher frequencies, these materials reduce the size of magnetic components such as transformers and inductors. In a novel SiC-based Class-E inverter, the switching frequency of 500 kHz allowed for a significant reduction in system footprint while maintaining efficiency, highlighting the miniaturization potential of WBG technologies [62]. Despite these advantages, thermal challenges persist, especially in high-power applications. Advanced cooling techniques, such as integrated heat sinks and 3D-printed structures, are being explored to address these challenges and extend the operational lifespan of WBG-based devices [59]. The development of high-efficiency, cost-effective thermal management systems remains a critical research area for ensuring the scalability of these technologies.

3.2.3. Future Perspectives: Sustainability and Emerging Applications

The future of WBG semiconductors lies in their potential to transform renewable energy systems and EV infrastructure through sustainable and versatile solutions [69]. For instance, the integration of SiC into medium-voltage DC grids has shown promise in providing efficient, reliable connections between renewable energy sources and large-scale energy storage systems [8]. Similarly, GaN-based converters are being explored for ultra-fast EV charging, offering compact designs capable of delivering high power with minimal thermal impact [7]. Sustainability is a key focus in the development of WBG materials. Efforts are underway to optimize the production and lifecycle management of SiC and GaN devices, reducing their environmental footprint. For example, the use of amorphous alloy magnetic materials in grid-connected renewable systems offers a sustainable alternative to traditional silicon-based systems, improving both efficiency and recyclability [53].

Emerging applications for WBG semiconductors include hybrid energy storage systems, which combine batteries and supercapacitors to stabilize grids with high renewable energy penetration. In these systems, SiC-based converters are employed to manage high-frequency transients, ensuring compatibility with low-cost microcontrollers and enhancing overall system reliability [70]. Furthermore, advances in AI-driven control algorithms are expected to enhance the performance of WBG-based converters [71]. Predictive models can optimize system parameters in real-time, improving efficiency under varying loads and environmental conditions. For example, adaptive control strategies for modular multilevel converters have demonstrated significant improvements in power distribution and fault tolerance in medium-voltage applications [72]. Looking ahead, the cost of WBG semiconductors remains a barrier to widespread adoption. Research into cost-effective manufacturing techniques and economies of scale will be crucial in accelerating the deployment of these technologies [73,74]. Additionally, innovations in material synthesis and integration will further expand their applicability in next-generation energy systems, from portable renewable generators to decentralized microgrids [59,75]. The diverse applications and transformative potential of wide-bandgap (WBG) materials and associated technologies are summarized in

Table 2. Summary of wide-bandgap materials and associated technologies.

Technology/Material	Applications	Advantages	Challenges
Silicon Carbide (SiC) [8,53,59]. (2020, 2019, 2021).	- Medium-voltage DC grids.	- High efficiency and thermal performance.	- High production costs.
	- PV inverters.	- Supports high-voltage applications.	- Scalability for ultra-high-power systems.
	- High-power transformers.
Gallium Nitride (GaN) [7,51,65]. (2022, 2022, 2019).	- EV chargers.	- Ultra-fast switching speeds.	- Thermal management at extreme frequencies.
	- Wireless power transfer (WPT) systems.	- Reduced size of passive components.	- High cost of integration.
	- High-frequency resonant converters.
Nanocrystalline Magnetic Materials [52,67]. (2014, 2014).	- High-frequency transformers.	- Reduced energy losses.	- Complex design optimization.
	- Grid-connected renewable systems.	- Enhanced thermal and electromagnetic properties.	- High cost of advanced materials.
Amorphous Alloy Magnetic Materials [53]. (2019).	- Multi-winding converters.	- Lightweight and recyclable.	- Challenges in material synthesis.
	- Renewable energy generation systems.	- Improves system reliability.	- Lifecycle sustainability.
Hybrid Energy Systems [70]. (2024).	- Grid stabilization.	- Enhances grid stability.	- Requires advanced control algorithms for multi-device coordination.
	- Battery-supercapacitor integration.	- Minimizes harmonic distortions.
Class-E Inverter Topologies [62]. (2018).	- Compact PV inverters.	- Simplifies control schemes.	- Limitations in power ratings for la
	- Low-complexity renewable applications.	- Reduces system footprint.

. This table provides an overview of key materials and topologies, highlighting their specific applications, unique advantages, and the challenges that remain to be addressed. Table 2 points out the role of silicon carbide (SiC) and gallium nitride (GaN) in revolutionizing power electronics, particularly in renewable energy systems and electric vehicles. Additionally, the inclusion of advanced magnetic materials, hybrid energy systems, and innovative inverter designs showcases the breadth of ongoing advancements in the field. These insights serve as a foundation for addressing existing limitations and driving future innovations in sustainable and efficient energy systems.

3.3. Implementation and Control Strategies for High-Frequency Converters

3.3.1. Challenges in Modeling and Simulation for High-Frequency Systems

Modeling and simulation of high-frequency systems pose unique challenges due to the complex interactions between electrical, thermal, and electromagnetic phenomena. High-frequency converters often involve advanced materials like nanocrystalline cores and wide-bandgap semiconductors, which introduce additional design considerations [76,77]. For example, in systems using high-frequency magnetic links, challenges such as voltage imbalance and electromagnetic interference arise from parameter mismatches and nonlinearities [52]. To address these, detailed multiphysics models are required, which integrate electrical and thermal performance to optimize system behavior under dynamic conditions. In renewable energy applications, medium-voltage DC-collection grids require sophisticated modeling techniques to reduce system inefficiencies. These grids often employ modular multilevel converters (MMCs) with high-frequency PWM operations, introducing control complexities related to power-sharing and partial shading scenarios [78]. Experimental results on scaled prototypes demonstrate the necessity of precise dynamic modeling to mitigate instability and enhance power conversion efficiency [8]. For high-power EV charging systems, achieving accurate simulations becomes critical due to the high switching frequencies and power densities involved. The design of a modular three-level converter for a 1 MW EV mega-charger highlights how advanced simulation tools such as finite element analysis can predict thermal and electromagnetic behaviors, guiding the optimization of switching patterns and passive component sizes [37]. However, the integration of such techniques remains computationally intensive, requiring further advancements in simulation algorithms to handle large-scale systems efficiently.

3.3.2. Advanced Control Techniques for Stability in Complex Networks

As high-frequency converters become more integrated into complex networks such as microgrids and EV charging infrastructures, maintaining stability and efficiency under dynamic conditions requires advanced control techniques [79]. One promising approach is the use of adaptive control strategies, such as voltage balance controllers in multiple-active bridge (MAB) converters. These controllers mitigate parameter mismatches and system instability, enabling seamless operation in medium-voltage grid applications [42]. In hybrid energy systems, adaptive sliding-mode controllers have shown superior performance in managing high-frequency transients, protecting battery life, and reducing harmonic distortions. For instance, a Zeta converter coupled with such a control algorithm demonstrated compatibility with low-cost microcontrollers while maintaining high system efficiency in renewable microgrids [70].

These findings reinforce the potential of adaptive techniques to enhance reliability while minimizing implementation costs [80]. Bidirectional DC-DC converters, critical for vehicle-to-grid (V2G) applications, also benefit from advanced control strategies. For example, the use of dual active bridge (DAB) converters with interleaved and parallel operation capabilities enables efficient power transfer and improved thermal performance across a wide operating range [81]. Experimental prototypes confirm that advanced control algorithms can facilitate seamless transitions between different power levels, enhancing the flexibility of these systems for future grid applications [82]. Another significant advancement is the implementation of a finite control set model predictive control in grid-connected systems. This method has been successfully applied in five-level NPC converters, achieving precise control of active and reactive power while maintaining low harmonic distortions. Such techniques are particularly valuable for integrating superconducting generator-based wind turbines into existing grids [53].

3.3.3. Future Perspectives: Adaptive Control and Artificial Intelligence Integration

The future of control strategies for high-frequency converters lies in the integration of artificial intelligence (AI) and machine learning (ML) [83]. These technologies can dynamically optimize control parameters, predict load variations, and enhance overall system efficiency [84]. For example, AI-driven control systems could predict thermal behaviors in modular multilevel converters, adjusting operational parameters to prevent overheating and reduce energy losses [37]. In EV charging systems, adaptive AI-based controllers could optimize power transfer in real-time, accounting for variables such as battery state-of-charge and grid demand [85]. The integration of such controllers with high-frequency systems like GaN-based resonant converters could enable ultra-fast charging solutions while maintaining grid stability [7]. Additionally, AI algorithms can improve fault detection and recovery, ensuring reliable operation in large-scale renewable energy systems.

Another promising area is the use of digital twins for high-frequency systems. These virtual models enable real-time monitoring and predictive maintenance, allowing operators to identify potential issues before they impact system performance [86,87]. In hybrid energy storage systems, digital twins could optimize energy distribution between batteries and supercapacitors, maximizing efficiency and lifespan [70]. Looking ahead, the combination of AI with advanced simulation tools and adaptive control algorithms will be essential for managing the growing complexity of high-frequency converter networks. As these technologies evolve, they will play a significant role in enabling sustainable and resilient energy systems, from decentralized microgrids to global EV charging infrastructures.

Table 3. Summary of control challenges, techniques, and future perspectives for high-frequency converters.

Aspect	Key Application Areas	Advantages	Future Challenges
Modeling Challenges [8,37,52]. (2022, 2021, 2014).	- Medium-voltage DC grids.	- Improves system efficiency.	- High computational requirements for large-scale simulations.
	- EV megachargers.	- Addresses electromagnetic interference (EMI).
Control in Modular Systems [42,70]. (2020, 2024).	- Grid-connected renewable systems.	- Enhances stability.	- Cost-effectiveness and scalability of adaptive controllers.
	- Hybrid energy storage systems.	- Protects sensitive system components.
Bidirectional Converters [81]. (2015).	- Vehicle-to-grid (V2G) applications.	- Facilitates efficient bidirectional power flow.	- Seamless integration into diverse grid infrastructures.
		- Optimized thermal management.
Predictive Control [53]. (2019).	- Five-level NPC converters for wind energy systems.	- Reduces harmonic distortions.	- Implementation complexity in multilevel systems.
		- Enables precise power control.
AI and ML Integration [7,37]. (2022, 2021).	- Real-time optimization for EV charging.	- Dynamic optimization of energy flows.	- Training and deployment challenges for critical systems.
	- Renewable energy systems.	- Predictive load and fault handling.
Digital Twin Technology [70]. (2024).	- Monitoring and predictive maintenance in hybrid energy systems.	- Enables real-time fault detection.	- Adoption and integration in decentraliz
		- Prolongs system lifespan.

provides an overview of the key challenges, advanced control techniques, and future perspectives for high-frequency converters. It highlights the major aspects of control strategies, including modeling challenges, adaptive control methods, and emerging technologies such as artificial intelligence (AI) and digital twins.

3.4. Applications of High-Frequency Converters in Renewable Energy Systems

3.4.1. Challenges in Photovoltaic and Wind Energy Systems

High-frequency converters have become integral to the efficient operation of photovoltaic (PV) and wind energy systems, yet they present several challenges that must be addressed to maximize their potential [88]. In PV systems, traditional step-up transformers often lead to bulky designs and increased losses, limiting system efficiency [89]. The use of high-frequency DC-DC converters, such as those employing silicon carbide (SiC) switches, has enabled significant improvements in power density and conversion efficiency [90]. For instance, a novel medium-voltage DC-collection grid employing modular multilevel converters was shown to enhance system compactness and handle shading effects effectively, demonstrating its applicability in large-scale PV systems [8].

In wind energy systems, issues related to grid stability and variable input conditions require advanced magnetic designs and control strategies [91]. High-frequency magnetic links, which incorporate nanocrystalline materials, offer a lightweight alternative to traditional transformers, minimizing common-mode issues and ensuring better voltage regulation [92]. Despite their potential, these links pose multiphysics design challenges, including electromagnetic optimization and cost considerations, which must be resolved for broader adoption in renewable applications [52]. Further complications arise from the need for harmonic reduction and real-time power quality management in grid-connected renewable systems [93]. As explored in the design of class-D amplifiers, leveraging wide-bandgap semiconductors such as SiC and GaN enables the creation of power-dense solutions with minimal losses but requires careful control to avoid instability at ultra-high switching frequencies [43]. Variable load management in microgrids with high renewable penetration remains a critical challenge. High-frequency converters with adaptive sliding-mode controllers have demonstrated improved voltage stability, reducing deviations by 40% during peak generation fluctuations in wind-integrated microgrids [70]. These innovations are essential for maintaining grid reliability while accommodating the intermittency of renewable sources. Dual active bridge (DAB) converters have shown exceptional promise in renewable energy systems by addressing challenges associated with fluctuating generation and high-power demands. In one application for large-scale PV systems, DAB converters achieved a power conversion efficiency of 99% under partial shading conditions, effectively minimizing power losses and enhancing system scalability [8,59]. Their bidirectional capability also makes them well-suited for integrating energy storage, providing seamless energy flow and ensuring grid stability during peak demand periods.

3.4.2. Enhancing Reliability and Stability in Microgrids

Microgrids that integrate renewable energy sources like solar and wind are increasingly reliant on high-frequency converters to ensure reliable operation and system stability [94]. One of the critical innovations in this area is the development of dual-active bridge (DAB) converters, which allow bidirectional power flow while maintaining high efficiency. These converters have been optimized with high-frequency transformers and SiC-based switching devices to address thermal challenges and extend operational lifespans [95]. Experimental results from a 200-kW medium-frequency transformer-based DAB converter highlight the importance of comprehensive design strategies to achieve efficiency levels exceeding 99% under full load conditions [59].

Moreover, the integration of advanced control strategies, such as sliding-mode controllers, has enhanced the stability of hybrid microgrids. A recent study demonstrated the efficacy of these controllers in managing high-frequency transients and ensuring compatibility with low-cost microcontrollers, making them a cost-effective solution for microgrid applications [70]. High-frequency converters have also proven vital in minimizing voltage imbalances in modular multilevel cascaded converters [96,97]. By utilizing a common high-frequency link, these systems can generate multiple balanced DC supplies, addressing critical issues such as voltage stability and common-mode disturbances in renewable energy grids [72].

3.4.3. Future Perspectives: Hybrid Systems and Advanced Energy Storage Integration

The future of renewable energy systems lies in hybrid configurations that combine multiple energy sources with advanced energy storage technologies. High-frequency converters will play an essential role in enabling these systems by providing seamless integration, improved efficiency, and compact designs [98]. For instance, the application of gallium nitride (GaN)-based LLC resonant converters has demonstrated the ability to support wide operational ranges, making them ideal for hybrid systems that combine solar and wind power with battery storage [51]. Another promising direction is the use of multi-input converters in hybrid microgrids, allowing the integration of diverse renewable energy sources without additional DC-DC conversion stages. A three-phase multilevel converter topology has been shown to manage multiple input sources effectively, providing a scalable solution for decentralized energy systems [99].

Advancements in bidirectional converters for vehicle-to-grid (V2G) applications further highlight the potential of high-frequency technologies in the future energy landscape. These converters can facilitate energy transfer between EVs and renewable microgrids, supporting grid stability while optimizing energy use [100]. A recent study on a flexible DAB converter demonstrated its ability to adapt to varying power demands, positioning it as a critical component for future renewable-energy-driven mobility systems [101]. Additionally, the integration of digital twin technology and AI-driven control strategies holds significant promise for improving the operational efficiency of hybrid renewable systems. These technologies can enable predictive maintenance, real-time optimization, and enhanced fault detection, ensuring the reliability and sustainability of high-frequency converters in next-generation energy systems [53,70].

Table 4. Summary of challenges, applications, and future directions for high-frequency converters in renewable energy systems.

Aspect	Key Application Areas	Advantages	Future Challenges
Challenges in PV Systems [8,52]. (2020, 2014).	- Medium-voltage DC-collection grids.	- Improves compactness and efficiency.	- Design and cost limitations of advanced materials.
	- Large-scale PV plants.	- Reduces shading effects.
Challenges in Wind Energy Systems [43,52]. (2019, 2014).	- Grid stability enhancement.	- Lightweight solutions for grid-connected setups.	- Achieving stability at ultra-high switching frequencies.
	- Harmonic reduction in wind systems.	- Minimizes common-mode issues.
Reliability in Microgrids [59,72]. (2021, 2014).	- Stabilization in renewable microgrids.	- Enhanced fault tolerance and efficiency in distributed networks.	- Reducing voltage imbalances in modular systems.
	- Fault-tolerant distributed systems.
Hybrid System Integration [51,99]. (2022, 2021).	- Multi-input systems (solar, wind, storage).	- Facilitates seamless integration of diverse energy sources.	- Developing scalable and efficient multi-input architectures.
	- Renewable energy combinations.
Energy Storage Integration [70,101]. (2024, 2024).	- Bidirectional converters for V2G and battery storage.	- Supports bidirectional power flow.	- Improving compatibility with diverse grid infrastructures.
		- Ensures high thermal efficiency.
Future Technologies [53,70]. (2019, 2024).	- Digital twins for hybrid systems.	- Enables real-time monitoring and fault detection.	- Scaling AI and digital twin technologies for large-scale, real-time applications.
	- AI-driven predictive maintenance.	- Optimizes energy flows dynamically.

provides a comprehensive summary of the challenges, applications, advantages, and future directions for high-frequency converters in renewable energy systems. It highlights the critical aspects of integrating these technologies into photovoltaic (PV) systems, wind energy systems, and hybrid configurations, while addressing the importance of reliability and scalability in microgrids. Looking forward, hybrid systems integrating DAB and LLC resonant converters are poised to play a pivotal role in decentralized microgrids. These configurations combine the strengths of both topologies—scalability, high efficiency, and compact design—to optimize power distribution and stability. A notable example is the use of GaN-based LLC converters in EV charging stations, where they enable ultra-fast charging while maintaining efficiency above 95% under varying load conditions [7,51]. Future advancements in digital twin technologies offer promising solutions for addressing control complexity and thermal management. By simulating real-time operations, digital twins can predict thermal hotspots and optimize control algorithms dynamically, ensuring grid stability in scenarios such as bidirectional EV charging. Early studies suggest that implementing such systems could reduce peak thermal loads by up to 25% and enhance system lifespan by 15% [86,87].

Emerging applications of wide-bandgap-based high-frequency converters further demonstrate the versatility of this technology. For example, offshore renewable energy systems benefit significantly from these converters’ ability to handle high power densities and operate efficiently in harsh environments. In such systems, silicon carbide (SiC)-based converters have shown a 20–30% reduction in energy losses under variable load conditions, enhancing overall system reliability [8,36]. Similarly, space-constrained urban energy setups, such as microgrids integrated into high-density areas, rely on compact and efficient converters to optimize power distribution. Gallium nitride (GaN)-based converters have enabled reductions in physical footprint by up to 40%, making them ideal for urban installations [8,42]. Looking further ahead, futuristic scenarios such as dynamic wireless charging for electric vehicles (EVs) present another avenue for innovation. High-frequency resonant converters are pivotal in enabling efficient energy transfer during vehicle motion, with studies indicating transmission efficiencies above 90% at 50 kHz [43,55]. Additionally, energy-sharing microgrids represent a transformative application where bidirectional and hybrid converters can facilitate peer-to-peer energy transactions, ensuring grid stability while accommodating fluctuating renewable inputs. Initial simulations suggest these systems could increase energy utilization by 25% and reduce grid dependency by 30% [42]. Quantitative market projections reinforce the relevance of these technologies. For instance, the global market for wireless charging systems is expected to grow at a compound annual growth rate (CAGR) of 22% over the next decade, driven by advancements in high-frequency converters [43,55]. Similarly, offshore wind energy systems, which heavily depend on power electronics for efficient integration, are projected to expand from 35 GW in 2020 to 230 GW by 2030, underscoring the critical role of wide-bandgap-based converters in this sector [42,59]. These applications not only highlight the adaptability of high-frequency converters but also position them as central components in the next generation of sustainable energy technologies.

4. Conclusions

The systematic review conducted in this study adhered to the PRISMA 2020 Statement, ensuring a structured and transparent methodology that identified, screened, and synthesized 73 high-quality studies from 2014 to 2024. This rigorous approach allowed for a comprehensive examination of advancements in high-frequency converters, focusing on their critical role in enhancing energy efficiency, system reliability, and sustainability in renewable energy systems and electric vehicles. The research provided a multidimensional perspective, categorizing findings across five thematic areas aligned with the study’s objectives: high-frequency converter designs, advanced semiconductor materials, implementation and control strategies, applications in renewable energy systems, and future directions for multifunctional and hybrid systems. The findings point out a remarkable evolution in converter topologies, particularly in dual active bridge (DAB) and LLC resonant designs, which have demonstrated superior adaptability, scalability, and efficiency. These innovations, coupled with the integration of soft-switching techniques such as zero-voltage and zero-current switching, have significantly minimized energy losses and improved operational performance, making them ideal for both EV fast charging and renewable energy applications.

Wide-bandgap (WBG) semiconductor materials, notably silicon carbide (SiC) and gallium nitride (GaN), emerged as transformative technologies in this study, enabling high power density, reduced thermal stress, and miniaturization of passive components. SiC’s suitability for high-voltage applications and GaN’s unparalleled switching speeds highlight their significant roles in applications ranging from wireless power transfer (WPT) systems to compact on-board EV chargers. These materials have facilitated lightweight and compact designs and have also addressed longstanding challenges in thermal management and electromagnetic interference. Despite their potential, future research must address the cost barriers and lifecycle sustainability of WBG materials, ensuring their broader adoption in next-generation energy systems.

Control methodologies also played a central role in this study, with advanced techniques such as predictive control, sliding-mode control, and adaptive AI-driven strategies proving critical in ensuring stability and efficiency in complex networks. These methods have been particularly effective in mitigating harmonic distortions, managing dynamic loads, and optimizing power flow in vehicle-to-grid (V2G) systems and renewable microgrids. The integration of digital twins was identified as a significant opportunity for future development, providing real-time system monitoring, predictive maintenance, and enhanced fault detection. This advancement is expected to play a transformative role in decentralized energy systems, hybrid configurations, and large-scale grid integrations.

Applications of high-frequency converters in renewable energy systems were explored extensively, with the study highlighting their critical role in improving the compactness, reliability, and efficiency of photovoltaic (PV) and wind energy systems. Innovations such as modular multilevel converters and multi-input architectures were noted for their ability to manage variability in power generation, reduce shading losses, and maintain grid stability. These systems have enabled the seamless integration of renewable sources and advanced energy storage technologies, demonstrating their potential for scalability in large-scale installations, such as offshore wind farms and urban EV charging networks.

Looking forward, the development of multifunctional and hybrid converter designs was identified as a key frontier. These systems integrate features of multiple architectures to optimize power flow, improve efficiency, and enhance adaptability under varying load conditions. By leveraging AI and machine learning, these converters can dynamically adjust operational parameters to maximize efficiency and lifespan, further solidifying their role in sustainable energy systems. The study also emphasized the need for continued innovation in modular and fault-tolerant designs, particularly in high-frequency converters for fast-charging EV infrastructure and renewable microgrids. Additionally, the exploration of new materials and topologies, alongside advanced control algorithms, holds promise for addressing the challenges of ultra-high switching frequencies, thermal dissipation, and electromagnetic interference.

In conclusion, the findings of this systematic review demonstrate the transformative potential of high-frequency converters in addressing the dual imperatives of energy efficiency and environmental sustainability. By advancing the integration of renewable energy sources, enhancing the performance of EV charging systems, and facilitating the development of resilient, intelligent energy networks, high-frequency converters are poised to play a pivotal role in the global energy transition. Future research should continue to explore the synergies between cutting-edge materials, innovative designs, and AI-driven control systems to unlock the full potential of these technologies, paving the way for a sustainable and electrified future.