Search Results (274)

Microgrids (MGs) technologies, with their advanced control techniques and real-time monitoring systems, provide users with attractive benefits including enhanced power quality, stability, sustainability, and environmentally friendly energy. As a result of continuous technological development, Internet of Things (IoT) architectures and technologies are becoming more and more important to the future smart grid’s creation, control, monitoring, and protection of microgrids. Since microgrids are made up of several components that can function in network distribution mode using AC, DC, and hybrid systems, an appropriate control strategy and monitoring system is necessary to ensure that the power from microgrids is delivered to sensitive loads and the main grid effectively. As a result, this article thoroughly assesses MGs’ control systems and groups them based on their degree of protection, energy conversion, integration, advantages, and disadvantages. The functions of IoT and monitoring systems for MGs’ data analytics, energy transactions, and security threats are also demonstrated in this article. This study also identifies several factors, challenges, and concerns about the long-term advancement of MGs’ control technology. This work can serve as a guide for all upcoming energy management and microgrid monitoring systems. Full article

This article presents proposals to increase the efficiencies of energy conversion systems from renewable sources using a soft-switching technique in three-phase voltage source inverters. The first part of this article briefly presents basic systems for generating energy from renewable sources. Special attention is paid to both photovoltaic and wind power plants. The next section describes the voltage source inverter with the soft-switching system of transistors, which is resistant to disturbances in the control systems of inverters. Laboratory tests on cooperation between the voltage source inverter and the AC grid are carried out for two cases, when energy is transmitted from the DC circuit to the AC grid and vice versa. In the final part, the efficiencies of energy conversion systems operating under the voltage source inverter with the soft-switching technique are compared with those of an inverter using hard switching of transistors. A comparison is made for energy conversion systems with a rated power of 100 kW and 1 MW. Full article

This paper presents a comprehensive summary of recent advances in circuit topologies for piezoelectric energy harvesting, leading to self-powered systems (SPSs), covering the full-bridge rectifier (FBR) and half-bridge rectifier (HBR), AC-DC converters, and maximum power point tracking (MPPT) techniques. These approaches are analyzed with respect to their advantages, limitations, and overall impact on energy harvesting efficiency. Th work explores alternative methods that leverage phase shifting between voltage and current waveform components to enhance conversion performance. Additionally, it provides detailed insights into advanced design strategies, including adaptive power management algorithms, low-power control techniques, and complex impedance matching. The paper also addresses the fundamental principles and challenges of converting mechanical vibrations into electrical energy. Experimental results and performance metrics are reviewed, particularly in relation to hybrid approaches, load impedance, vibration frequency, and power conditioning requirements in energy harvesting systems. This review aims to provide researchers and engineers with a critical understanding of the current state of the art, key challenges, and emerging opportunities in piezoelectric energy harvesting. By examining recent developments, it offers valuable insights into optimizing interface circuit design for the development of efficient and self-sustaining piezoelectric energy harvesting systems. Full article

Building Integrated Photovoltaic (BIPV) systems have emerged as an option to design Net Zero Energy Buildings (NZEB), thus helping to meet sustainable development goals. Based on an exhaustive review of papers, this work identifies characteristics and solutions to address power management issues in BIPV systems through three key approaches: (1) configurations of photovoltaic arrays, (2) MPPT methods, and (3) granularity level of the MPPT action. The analysis also highlights the advantages of deploying DC buses alongside conventional AC infrastructure to reduce conversion losses. This work also provides information concerning the trends in design and performance of BIPV systems, which is useful as a background for researchers and designers. In addition, the cross-coupling phenomena occurring in distributed MPPT solutions for BIPV systems is explained and evaluated in order to propose a mitigation strategy. These findings offer practical guidelines for developing more efficient BIPV systems that effectively support the transition to sustainable buildings and cities. Full article

The technological advances in internet of things (IoT) devices have raised the demand for cost-efficient and sustainable energy sources. Piezoelectric energy harvesters (PEHs) are promising low-cost and eco-friendly energy sources but require robust power management circuits (PMCs) for voltage conversion and regulation. This work presents a complementary metal–oxide–semiconductor (CMOS)-based PMC, integrating a reconfigurable AC-DC rectifier and a low-dropout (LDO) voltage regulator designed using 0.18 µm Taiwan semiconductor manufacturing company (TSMC) CMOS technology. This design includes an intermediate coupling stage to reduce voltage drop and improve the transfer efficiency of the PMC. In addition, we develop numerical simulations of the PMC performance, achieving a voltage conversion efficiency (VCE) between 72.8% and 43.21% using input voltages from 0.7 V to 2.8 V with a 50 kΩ load resistance. Compared to previous designs, the proposed circuit demonstrates improved stability, reduced area (66.28 mm²), and extended operating voltage range, allowing its potential application for ultra-low-power IoT nodes. This PMC contributes to the development of autonomous systems with reduced battery dependency and enhanced sustainability. Full article

A grid-connected converter is the interface between renewable energy power generation systems, such as solar power generation, wind power, hydropower, etc., and the power grid, responsible for the stable and efficient transmission of electric energy generated by renewable energy power generation systems to the grid. In order to realize local access for distributed photovoltaic power generation devices and energy storage devices, a composite three-port converter has the advantages of small size, low cost and high power density compared with a combined three-port converter. In view of the current problems of the existing compound three-port (AC/DC/DC) converters, such as DC and AC circulating current in current composite three-port converters and the harmonic control problem, the proposed compound three-port topology consists of a full-bridge inverter with six switching tubes, a zigzag transformer, two sets of filter inductors and two filter capacitors. Among them, the power frequency transformer adopts the zigzag connection method, which can effectively restrain the AC circulation and eliminate the DC magnetic flux of the iron core while introducing the third port. Firstly, the principle of AC/DC and DC/DC power conversion in the composite three-port topology is analyzed, which has higher efficiency than other topologies. Secondly, the topology control strategy is analyzed, and a two-loop hybrid current control method with improved current loop is proposed. When the DC-side voltage fluctuates, the DC offset of the battery can effectively improve the stability of the network side. Through the MATLAB/Simulink simulation experiment platform, the high efficiency of energy conversion and stable grid-connected operation characteristics are verified. Finally, the experiment of integrating into the power grid was carried out. Experiments were used to verify the effectiveness and feasibility of the proposed topology and strategy. The experimental results show that Total Harmonic Distortion (THD) can be controlled below 3%. Full article

This paper presents a novel learning-based control algorithm for three-phase AC/DC converters, which are key components in DC microgrids, for reliable power conversion. In contrast with conventional model-based nonlinear controllers that rely on detailed system modeling and manual gain tuning, the proposed method is model-free and eliminates such dependencies. By integrating a recurrent equilibrium network (REN), the controller achieves an enhanced dynamic response and robust steady-state performance, while maintaining a low computational complexity. Moreover, its closed-loop stability can be rigorously verified based on contraction theory and incremental quadratic constraints. To facilitate practical implementation, a design guideline is provided. Experimental results confirm that the proposed method outperforms conventional PI and model predictive controllers in terms of response speed, harmonic suppression, and robustness under parameter variations. Additionally, the algorithm is lightweight enough for real-time execution on embedded platforms, such as a TI DSP. Full article

This paper presents a novel fully integrated radio frequency (RF) rectifier tailored for a wide power dynamic range (PDR) with multiband adaptability to efficiently convert AC RF power into DC power. The proposed rectifier utilizes the strength of interstage gate biasing to achieve high power conversion efficiency (PCE) across a broad range of input power levels. Through its reconfigurable mode, the circuit seamlessly transitions between a low-power path and high-power path to ensure optimal performance across a wide PDR. Simulated using CMOS 65 nm technology, the post-layout assessment reveals a peak PCE of 48.8% at 900 MHz and 46.4% at 1800 MHz, with an extensive PDR of 20 dB for PCE exceeding 20% at both frequencies. Full article

The AC-AC chopper converter, as a direct power conversion device without DC intermediate stages, has garnered significant attention due to its advantages of high efficiency and fast dynamic response. However, the voltage spikes induced by switching device turn-off transients (reaching 143% of the reference voltage) severely threaten system reliability, while traditional RC snubber circuit parameter design methods (e.g., empirical formula-based approaches) exhibit limited suppression effectiveness. To address this issue, this paper proposes an optimized parameter design method for RC snubber circuits in AC-AC chopper converters by establishing a turn-off transient energy transfer model to optimize snubber resistor and capacitor parameters. Experimental results from the prototype based on the TMS320F28335 digital controller demonstrate that the optimized method suppresses voltage spikes to <10% and, even under a 40% step load variation from the nominal value, maintains output voltage fluctuations stably below 5%. Full article

The deployment of photovoltaic single-phase inverters has been rapidly increasing worldwide. However, the performance of these systems is highly influenced by atmospheric conditions and load variations, necessitating the development of performance indices to enhance their efficiency and energy quality. In this study, four performance indices are proposed to evaluate the efficiency and energy quality of photovoltaic systems quantitatively. The entire process is analyzed, encompassing solar energy capture, DC-DC and DC-AC conversion, and filtering, to deliver maximum energy and quality to the load. Furthermore, eight system parameters are optimized using advanced techniques such as genetic algorithms, particle swarm optimization, and gray wolf optimization. These optimizations enhance the global performance of two critical stages: (1) the maximum power point tracking algorithm based on sliding mode control, which minimizes switching losses in the boost stage, and (2) the effective transfer of captured solar power to the load by optimizing the gains of a PI controller. The PI controller computes the switching triggers for the inverter stage, significantly improving the total harmonic distortion of voltage and current waveforms. Simulation results validate the proposed approach, demonstrating a marked improvement in overall system efficiency (95.8%) when compared to the incremental conductance method (−11.8%) and a baseline sliding mode control configuration (−1.14%). Full article

Converter stations are pivotal in high-voltage direct current (HVDC) systems, enabling power conversion between an alternating current (AC) and a direct current (DC) while ensuring efficient and stable energy transmission. Fault detection in converter stations is crucial for maintaining their reliability and operational safety. This paper focuses on image-based detection of five common faults: metal corrosion, discoloration of desiccant in breathers, insulator breakage, hanging foreign objects, and valve cooling water leakage. Despite advancements in deep learning, existing detection methods face two major challenges: limited model generalization due to diverse and complex backgrounds in converter station environments and sparse supervision signals caused by the high cost of collecting labeled images for certain faults. To overcome these issues, we propose InvMOE, a novel fault detection algorithm with two core components: (1) invariant representation learning, which captures task-relevant features and mitigates background noise interference, and (2) multi-task training using a mixture of experts (MOE) framework to adaptively optimize feature learning across tasks and address label sparsity. Experimental results on real-world datasets demonstrate that InvMOE achieves superior generalization performance and significantly improves detection accuracy for tasks with limited samples, such as valve cooling water leakage. This work provides a robust and scalable approach for enhancing fault detection in converter stations. Full article

Compared with the line-frequency transformer (LFT), the emerging power electronic transformers (PETs) have gained wide concerns due to the significant merits of higher power density, higher reliability, more flexibility, and multiple functions. However, the need for bulky energy storage elements, multi-stage power conversion and reduced conversion efficiency, and the intrinsic twice-frequency pulsating power issue are the main disadvantages of the conventional single-phase PETs. To overcome the above shortcomings of conventional single-phase PETs, this paper develops a matrix-type single-phase AC-AC PET without bulky energy storage elements. The proposed PET consists of a line-frequency commutated rectifier, a half-bridge LLC resonant converter with a fixed switching frequency, a boost converter, and a line-frequency commutated inverter. The LLC operates efficiently with unity voltage gain and acts as a high-frequency isolated DC transformer (DCX). The boost converter provides AC output voltage regulation function and the line-frequency commutated inverter unfolds the output voltage of the boost converter to generate the sinusoidal AC output voltage. As a result, high power density, reduced power conversion stages, direct AC-AC power conversion without twice-frequency pulsating power, high conversion efficiency, and high reliability are achieved. The experimental results on a 1kW PET prototype show that sinusoidal input current and output voltage, ZVS of the LLC stage, and output voltage regulation capability are realized. The experimental results verify the correctness and feasibility of the presented methods. Full article

The optimization of low-level control for DC–AC power converters is crucial for enhancing efficiency, stability, and adaptability in modern power systems. With the increasing penetration of renewable energy sources and the shift toward decentralized grid architectures, advanced control strategies are needed to address challenges such as reduced system inertia and dynamic operating conditions. This paper provides a concise review of key optimization techniques for low-level control, highlighting their advantages, limitations, and applicability. Additionally, emerging trends, such as artificial intelligence (AI)-based real-time control algorithms and hybrid optimization approaches, are explored as potential enablers for the next generation of power conversion systems. Notably, no single optimized control technique universally outperforms others, as each involves trade-offs in mathematical complexity, robustness, computational burden, and implementation feasibility. Therefore, selecting the most appropriate control strategy requires a thorough understanding of the specific application and system constraints. Full article

This paper presents a comprehensive RMS-based phasorial model of an E-STATCOM with grid-forming (GFM) control, designed to improve power system stability in isolated grids. Unlike previous approaches, this model integrates a governor with an internal power system stabilizer (PSS) and an active current limiter (ACL) to enhance frequency regulation and mitigate oscillations. Additionally, an exciter with a nonlinear modulation function is introduced to optimize voltage regulation and reactive power support. A detailed conventional supercapacitor (SC) model is also incorporated, enabling dynamic DC-voltage control based on active power variations, improving frequency stability. The proposed E-STATCOM RMS model includes algebraic equations, dynamic governor and exciter models, supercapacitor-based energy storage control, and an advanced current-limiting strategy. Simulations are conducted on the Fuerteventura–Lanzarote (Canary Islands, Spain) power system, comparing the E-STATCOM with a synchronous condenser (SynCon) in frequency response, voltage regulation, and fault performance. The results show that the E-STATCOM improves frequency stabilization and energy efficiency while complying with grid codes. This study introduces a novel RMS-based modeling approach for GFM E-STATCOMs, bridging the gap between theoretical phasorial analysis and real-world applications. The findings confirm that E-STATCOMs are a viable alternative to SynCons, enhancing grid stability in high-renewable-penetration systems. Full article

As renewable energy sources (RES) continue to expand and the use of power inverters has surged, inverters have become crucial for converting direct current (DC) from RES into alternating current (AC) for the grid, and their security is vital for maintaining stable grid operations. This paper investigates the security vulnerabilities of photovoltaic (PV) inverters, specifically focusing on their internal sensors, which are critical for reliable power conversion. It is found that both current and voltage sensors are susceptible to intentional electromagnetic interference (IEMI) at frequencies of 1 GHz or higher, even with electromagnetic compatibility (EMC) protections in place. These vulnerabilities can lead to incorrect sensor readings, disrupting control algorithms. We propose an IEMI attack that results in three potential outcomes: Denial of Service (DoS), physical damage to the inverter, and power output reduction. These effects were demonstrated on six commercial single-phase and three-phase PV inverters, as well as in a real-world microgrid, by emitting IEMI signals from 100 to 150 cm away with up to 20 W of power. This study highlights the growing security risks of power electronics in RES, which represent an emerging target for cyber-physical attacks in future RES-dominated grids. Finally, to cope with such threats, three detection methods that are adaptable to diverse threat scenarios are proposed and their advantages and disadvantages are discussed. Full article