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Review

Research Review on Power Quality Improvement in Distribution Networks via Charging Pile Integration

by
Shasha Chen
1,
Jinghua Zhou
2,3,* and
Yifei Sun
1
1
School of Electrical and Control Engineering, North China University of Technology, Beijing 100144, China
2
School of Energy Storage Science and Engineering, North China University of Technology, Beijing 100144, China
3
Beijing Laboratory of New Energy Storage Technology, North China University of Technology, Beijing 100144, China
*
Author to whom correspondence should be addressed.
Electronics 2025, 14(7), 1284; https://doi.org/10.3390/electronics14071284
Submission received: 21 February 2025 / Revised: 17 March 2025 / Accepted: 20 March 2025 / Published: 25 March 2025
(This article belongs to the Section Power Electronics)
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Abstract

:
With the evolution of the distribution network to an active bidirectional interactive system, as an important active load interface in the distribution network, the large-scale access of charging piles not only brings challenges to the power quality of the distribution network but also provides opportunities for power quality regulation and optimization. This paper discusses the main factors affecting the power quality of the distribution network due to charging piles. The power quality problems such as voltage fluctuation and harmonics caused by charging piles are described. Then, the key technologies and potential of charging piles in power quality management are summarized, focusing on the technical progress in harmonic suppression and voltage regulation. Finally, the paper provides an outlook on the optimization directions of related technologies. This paper reveals the positive role of charging piles in power quality management of distribution networks from the perspective of devices. It provides a reference for future research on the participation of large-scale charging pile integration in power quality management.

1. Introduction

The form of distribution networks is undergoing a fundamental transformation from traditional passive, unidirectional radiative networks to active bidirectional interactive systems. The functional position is also evolving from a single power distribution service entity to an efficient platform for the source-grid-load-storage interaction mode [1]. In the context of “Double Carbon”, the distribution network illustrates the development trend in power electronics. The interaction of power electronic devices triggers power quality problems such as harmonics and voltage deviation, and the distribution of pollution is decentralized and network-wide [2,3].
The expansion of the electric vehicle market has led to the deployment of charging stations around the world. The gradual increase in the proportion of charging piles in the distribution network makes them an emerging active load interface in the distribution network [4,5]. As a typical power electronic device, large-scale access to charging piles leads to a decentralized distribution of the output and demand for electric energy, making the problem of power quality of the power grid more complicated [6,7,8]. On the one hand, the integration of charging stations into the distribution network increases harmonic distortion, exacerbating voltage fluctuations. On the other hand, the time-varying load characteristics of charging stations impose stricter requirements on the reactive power balance of the power grid [9]. In essence, charging stations are not only sources of power quality disturbances, but can also be used as distributed units that contribute to power quality management through appropriate control strategies [10].
Research on the impact of the charging infrastructure on power quality in distribution networks focuses primarily on the charger type, scale, and penetration level. Refs. [11,12,13] compare the effects of different charger types, power levels, and infrastructure integration on harmonics and voltage deviation, providing detailed quantitative analyzes. Refs. [14,15,16] investigate the impact of various charging station topologies through simulations, emphasizing harmonic characteristics and power quality assessment. Refs. [17,18,19] analyze the influence of different infrastructure scales on harmonics and voltage deviation. Refs. [15,20,21] indicate that high penetration levels and high-voltage charging exacerbate voltage deviation and imbalance. The analysis provides a foundation for research on the participation and optimization of electric vehicle charging stations in improving the power quality of distribution networks.
Currently, a research system for the participation of the charging pile in the management of the power quality of the distribution network has not yet been formed. Many scholars have explored research methodologies and system construction for improving the power quality of the distribution network under the charging pile scenario by drawing on traditional ideas for the study of the power quality of the power grid. Research on charging pile participation in distribution grid power quality management focuses mainly on harmonics, voltage regulation, and other aspects. Mainstream power quality improvement methods can be categorized into passive and active control strategies. Passive mitigation strategies employ passive filters on the AC side of charging stations or other electrical loads to attenuate high-frequency harmonics [22] or utilize switched fixed capacitors for static reactive power compensation [23]. However, as power systems with a high penetration of power electronic devices exhibit non-linear and time-varying operating characteristics, traditional passive solutions are constrained by the fixed nature of passive components, limiting their ability to provide dynamic compensation [24]. Consequently, active mitigation strategies, such as active power filters(APF) [25,26,27], static synchronous compensators (STATCOM) [28], and static var generators (SVG) [29], which enable real-time monitoring of the state of the grid and adaptive compensation, have increasingly replaced passive methods as the predominant approach to power quality management.
Notably, the front-end rectifier of the charging station’s power module shares topological consistency with active power quality mitigation devices. This hardware compatibility allows charging stations to transcend their conventional charging and discharging functions, evolving into multimodal intelligent terminals capable of harmonic suppression and reactive power support [30]. Ref. [31] proposes optimizing power module control to mitigate its impact on distribution network power quality. Studies [32,33,34] analyze the potential of Vehicle-to-Grid (V2G) technology in enhancing grid operation and improving the economic viability of electric vehicles. Ref. [35] refines power control algorithms to enable charging station power modules to provide reactive power and harmonic compensation. Additionally, studies [36,37,38,39] incorporate the inertia and droop characteristics of synchronous generators, utilizing DC-link voltage for active participation in frequency regulation and reactive power control. To enhance renewable energy utilization and reduce grid dependence, refs. [40,41,42] explore scenarios integrating renewable generation with charging stations, highlighting their roles in harmonic compensation and reactive power regulation. Furthermore, from a system-wide perspective, optimizing power quality and stability can be achieved through coordinated scheduling algorithms, considering factors such as charging station deployment [43,44], renewable energy integration [45,46], and power balancing [47,48].
Given that most existing studies focus on the adverse effects of charging station integration, such as harmonic pollution and voltage fluctuations, while overlooking their potential as distributed power electronic devices for active power quality regulation, this review systematically examines the interaction between charging stations and distribution network power quality from a bidirectional perspective. As electric vehicle penetration continues to rise, charging stations have evolved from passive electrical loads into intelligent terminals with power quality management capabilities. Recognizing the significant potential of large-scale charging stations in power quality regulation, this review analyzes their role along two key dimensions. First, from a problem-oriented perspective, it investigates typical challenges induced by large-scale integration, such as harmonic resonance and voltage deviation, along with corresponding evaluation methods. Second, from a mitigation-oriented perspective, it highlights technological advancements in active harmonic suppression and dynamic reactive power compensation. Improvements in hardware design and optimization of control strategies illustrate a paradigm shift in charging stations from passive disturbance sources to active power quality management units. By establishing an analytical framework that links problem identification with technical solutions, this review provides a theoretical foundation for the collaborative optimization of power quality in distribution networks with charging station participation.

2. Impact of Charging Piles on Distribution Systems

Due to their distribution characteristics, charging piles can flexibly provide charging services. However, issues such as voltage deviations and harmonics have become increasingly prominent. This section will discuss the main factors affecting the power quality of distribution networks, including charging pile types, topologies, scale, and electric vehicle penetration rates, as shown in Figure 1.

2.1. Types of Charging Piles

Electric vehicles typically charge through charging pile interfaces on the low-voltage side of the distribution network, thus having a broad and direct impact on the distribution network. Figure 2 shows a schematic of the connection between the charging pile and the public grid.
Charging piles are typically categorized by power level into slow charging and fast charging. According to the output voltage type, charging piles can be classified into AC and DC charging piles. Various countries have established standards for electric vehicle charging power levels, such as the the SAE J1772 standard in the U.S., IEC 61851 in Europe, CHAdeMO in Japan, and GB/T in China. Table 1 presents a simplified classification of electric vehicle charging into three categories. AC charging piles output single-phase/three-phase AC power, with lower power and slower charging speed, and are generally installed in places like residential parking lots. DC fast-charging stations, with larger capacities and faster charging speeds, typically operate as regional stations. From the perspective of the distribution network, the impact of charging piles on power quality is primarily observed on the low-voltage side, with DC charging piles being more likely to cause voltage quality issues compared to AC piles. The deployment of fast-charging stations, in particular, has a more significant impact on the power quality of the distribution network.
As a capacitive load, electric vehicles consume reactive power when charging through charging piles, leading to voltage fluctuations in the distribution network and increased harmonics [49]. Ref. [12] indicates that the primary harmonics on the AC side of the charger follow 6 k ± 1, with the 5th and 7th harmonic currents exhibiting the highest magnitudes. Ref. [11] investigates the additional impacts of electric vehicle charging on the power grid under low-temperature conditions. When the ambient temperature is close to the optimal level, the charging power remains at a high level, and the total harmonic content is low. As the temperature decreases, the charging power drops, and harmonics increase. Figure 3 shows the trend in harmonic variation with temperature. Below 5 °C, the charging power of the charging pile significantly decreases, and harmonic distortion issues become more pronounced.
Additionally, the integration of Level 1 and Level 2 single-phase charging piles into the distribution network can exacerbate the three-phase voltage imbalance, and may also impact the safe charging of electric vehicle batteries to varying degrees. Ref. [50] analyzed the random integration of single-phase charging piles in residential areas, showing that the three-phase imbalance can exceed 10% during peak periods. The data presented in [50] indicate that, at the same voltage level, switching from plug-in hybrid electric vehicles (PHEVs) to plug-in battery electric vehicles (PBEVs) can lead to an increase in voltage imbalance by up to 4%.

2.2. Power Module of Charging Pile

The power conversion module, as the core component of the charging pile, is a key factor influencing power quality. Since the harmonic source in AC charging piles originates from the onboard charger within the vehicle, this section will focus on the topology of DC charging piles.
The power conversion module in DC charging piles is generally divided into two types [14]. The first type (Figure 4a) integrates a transformer before the conversion circuit to achieve isolation from the grid [51]; the second type Figure 4b uses an isolated DC/DC converter to provide necessary isolation [52]. To meet the high-capacity charging demand, multiple modules are connected in parallel within the charging pile to increase power output, as shown in Figure 4c and Figure 4d. The topology of both solutions primarily consists of an AC/DC rectifier and a DC/DC converter circuit. Since the DC/DC converter is not directly connected to the grid, it is typically treated as a load when analyzing the impact of charging piles on the power quality of the distribution network.
Traditional AC/DC topologies include three-phase uncontrolled rectifiers and PWM rectifier systems. The three-phase uncontrolled rectifier circuit features a simple structure and low cost, but it exhibits high harmonic content, typically requiring the incorporation of active filters or power factor correction devices for power quality compensation [53]. Ref. [15] established models for three-pulse, six-pulse, and twelve-pulse uncontrolled rectifier charging stations, as well as PWM rectifier charging stations. Figure 5 illustrates the impact of various topological structures on harmonic distortion in the distribution network. As the charging power increases, the harmonics generated by the uncontrolled rectifier charging station become more significant. However, as the number of pulses in the uncontrolled rectifier increases, harmonic distortion decreases. PWM rectifier charging stations produce minimal harmonic distortion, which remains largely unaffected by the charging power.
Currently, typical PWM rectifier-based charging station topologies include NPC, T-type NPC, Vienna, Swiss Rectifier, and so on. Ref. [16] provides a comprehensive comparison of bidirectional charger topologies and concludes that the three-level T-type NPC AC/DC rectifier has lower total harmonic distortion (THD).

2.3. Scale of Charging Stations

As the number of charging piles increases, harmonic compensation or cancellation may occur due to the phase differences of the harmonic currents. The greater the number of charging piles used in a charging station, the higher the likelihood of harmonic compensation in the harmonic currents flowing through the station. Ref. [17] reported that the THD is 4.82% when a single electric vehicle is connected, whereas it increases to 19.69% when five electric vehicles are connected. Ref. [18] established a single-phase onboard charger model and analyzed the total harmonic distortion of the load current when 1, 3, and 7 charging piles were simultaneously charging, with corresponding THD values of 28.95%, 8.5%, and 3.3%, respectively. Ref. [28] equivalently modeled the high-frequency power conversion stage of a three-phase uncontrolled rectifier-based charging pile as an input resistance and investigated the impact of the number of charging piles on harmonic current distortion and the power factor. Ref. [19] analyzed the effect of the number of charging piles on the harmonic current content and power factor. Figure 6 shows that as the number of charging piles increases, the N-order harmonic content of the current will decrease. Additionally, Figure 7 shows that as the number of charging piles increases, the power factor tends to increase, with higher charging power leading to a higher system power factor.

2.4. Penetration Rate of Electric Vehicles

Due to the widespread charging demands of electric vehicles, a high penetration rate of electric vehicles significantly increases network losses in regional distribution systems and worsens the power quality of the supply system [54]. Ref. [20] discussed the impact of large-scale aggregation of electric vehicle loads on the distribution network, where the harmonics generated by electric vehicle charging stations, based on high-power electronic devices, caused an increase in distribution transformer losses by more than 6%. Ref. [21] quantitatively analyzed the effect of harmonic content on distribution network cables based on IEC 60287. At a penetration rate of 30%, charging harmonics caused a 20% increase in the temperature of distribution cables, which not only affected the cables’ thermal lifespan but also increased electricity costs for users.
At the distribution level, the power flow in the distribution network is influenced by electric vehicle charging stations, leading to node voltage deviations [55]. Ref. [15] established a distribution network model with an electric vehicle charging station, as shown in Figure 8. A 12-pulse rectifier charging station is connected to the B3 bus, and the relationship between node voltage deviations and the charging station penetration rate is presented in Figure 9. The charging station directly impacts the voltage deviation at node B3, which, in turn, affects the voltage deviation at node B1, thereby indirectly influencing nodes B4 and B5. As the charging station penetration rate increases, the node voltage drop increases, and the line shifts from light load to overload, causing a decrease in node voltage. Nodes that are not electrically connected to the charging station (B2, B6, B7) are unaffected by the charging station penetration rate. Ref. [56] investigated the impact of fast charging station integration on medium-voltage distribution networks under both normal and fault conditions. The study found that installing charging piles at downstream nodes leads to significant power losses and exacerbates voltage deviations. Under fault conditions, the fault current at nodes closer to the main substation increases significantly.
During peak charging periods, the charging behavior of electric vehicles can have a significant impact on the grid. Ref. [57] provides the maximum voltage deviation percentages corresponding to different electric vehicle penetration rates, as shown in Table 2. During peak electric vehicle charging periods, particularly at night when the penetration rate is higher, the increased demand for reactive power leads to a noticeable voltage drop issue.
The power quality issues mentioned above can be effectively addressed through various power quality management solutions, which will be discussed in detail in the next chapter.

3. Harmonic Mitigation Strategies

When designing harmonic mitigation schemes, it is essential to consider power quality standards across different countries and regions. The IEEE-519 standard in the United States and the IEC 61000 standard in Europe limit the THD of low- and medium-voltage power supplies to less than 8%, while China’s GB/T 14549 standard requires the THD of grid-connected current to be less than 5% [58]. Based on the analysis of the above power quality issues, harmonic sources can be categorized into background harmonics and distribution feeder bus harmonics (Figure 10). Background harmonics are typically caused by harmonic voltage penetration from the upstream grid and harmonic voltage effects from harmonic sources with voltage-source characteristics in the local distribution network. Therefore, they can be modeled as controlled voltage sources. Distribution feeder bus harmonics specifically refer to harmonic currents generated on a specific distribution feeder bus in the network. These harmonics are typically produced by non-linear loads with current-source characteristics within the area, such as charging piles, inverters, and so on.

3.1. Harmonic Mitigation of Distribution Feeder Bus

Conventional electric vehicle charging piles can only charge unidirectionally in a passive manner, have a low power factor, and generate significant harmonics, thereby causing harmonic pollution on the distribution feeder bus. To address harmonics generated by non-linear devices such as charging piles, harmonic factors can be considered either during the manufacturing stage or at the software control level. Typically, to eliminate higher-order harmonics introduced by power switching devices, a filtering device is added between the front-end rectifier of the charging pile and the power grid [22].
On this basis, designing harmonic suppression strategies can effectively mitigate lower-order harmonics. Ref. [59] eliminates current harmonics during the charging process through the output of an active power factor correction (PFC) control system. Ref. [60] proposes an Active Compensation-Based Harmonic Reduction (ACHR) control strategy, which employs a multi-stage filter to reduce third-order input current harmonics caused by the interaction between the voltage ripple of the output capacitor in the voltage loop and the current loop. Ref. [61] introduces a composite feedforward odd-harmonic repetitive control strategy to suppress odd harmonics in single-phase V2G inverters, enhancing dynamic response capability and harmonic suppression performance under grid frequency fluctuations. Ref. [62] addressed the harmonic issues of the distribution feeder bus by adopting an active impedance adjustment strategy to modify the output impedance of the equipment (Figure 11), optimizing the quality of the grid-side grid-connected current.
For mitigating harmonics caused by the interaction between multiple charging facilities and the power grid, point-to-point harmonic suppression can be achieved by locally installing passive or active filters. Passive filters can remove specific harmonic orders, but their compensation characteristics are easily affected by grid impedance and operating conditions, making real-time continuous adjustment difficult. Improper design can lead to reactive power injection or even cause distribution network resonance. Compared to passive filters, active filters can dynamically compensate for harmonics. By connecting active filters in parallel or series with single-phase AC charging piles or onboard chargers, they can output compensating currents to reduce harmonics and lower the THD of the grid current.
Connecting an active filter, as shown in Figure 12, at the front end of the charging facility can mitigate the harmonic impact caused by conventional charging piles. Additionally, by improving the active filter control algorithm, using resonance controllers, repetitive control, or composite controllers, the suppression effect can be further enhanced [63]. For single-phase AC charging piles, refs. [18,25] improve harmonic issues in charging stations by employing parallel active power filters (APF). Ref. [64] highlights that the performance of a shunt active power filter (SAPF) depends on the estimation of harmonic currents and the regulation of the DC bus voltage. Ref. [65] enhances the control algorithm for parallel APFs by introducing a fixed-step adaptive filter in harmonic detection and employing repetitive control to suppress harmonics in single-phase AC charging piles, effectively reducing the THD to below 5%.
Due to the randomness of electric vehicle charging, large charging stations have certain redundant capacities that can be used for power quality management. Furthermore, as shown in Figure 13, the main circuit structure of a three-phase charging pile based on a PWM rectifier circuit is consistent with the main circuit structure of a power quality management device [66]. By using advanced control algorithms, charging piles can be developed to simultaneously charge electric vehicles and provide power quality management, thus avoiding the need for additional equipment investment. As the usage cost decreases, PWM rectifier circuits are expected to become the ultimate solution for harmonic suppression in electric vehicle charging stations. Ref. [31] provided a review of AC/DC converters for improving power quality, laying the foundation for the involvement of charging piles in power quality improvement.
Ref. [67] proposes a single-phase onboard bidirectional charger for electric vehicles, incorporating a PI + PR control strategy for harmonic suppression. This charger can compensate for reactive power and harmonic currents based on the characteristics of non-linear and linear loads. Ref. [68] integrates active filtering functionality into the Conservative Power Theory (CPT) control framework and applies it to a neutral-point clamped (NPC) three-level bidirectional charger. This approach enables reverse compensation to improve power quality when reactive, non-linear, or unbalanced loads are present at the point of common coupling (PCC). Ref. [69] introduces a charger based on a T-type converter, which features APF capabilities and can switch between EV charging mode and APF mode as needed. Ref. [70] proposes an efficient control algorithm based on an adaptive notch filter (ANF) for multifunctional charging piles equipped with photovoltaic (PV) and energy storage systems. This algorithm reduces AC-side harmonics and provides ancillary services such as harmonic and reactive power compensation to the distribution network. Ref. [71] presents a control strategy based on a self-tuning filter and a sliding mode control algorithm. In grid-connected mode, the charger can perform harmonic current compensation and provide reactive power support to the power grid. Ref. [72] employed a virtual impedance control strategy with harmonic power distribution as the objective, adjusting the virtual harmonic impedance of the devices at the grid connection point based on the remaining capacity of each device. This strategy facilitates harmonic power distribution while preventing device overload and improving the power quality of the grid.

3.2. Harmonic Mitigation Strategies of the Background

To address the issue of grid interaction with background harmonic resonance suppression, the control of the converter is used to improve the impedance of multiple inverters and the cross-coupling of the grid impedance, thereby reducing resonance caused by background harmonics [73]. Ref. [74] proposed a harmonic resonance suppression strategy based on impedance matching. This strategy utilizes a harmonic voltage feedforward approach to reshape the closed-loop input harmonic impedance, bringing it closer to the characteristic impedance of the transmission cable, thereby suppressing the resonance amplification of background harmonics. This effectively improves the power quality of the rectifier’s grid-connected current and the voltage at the common coupling point, achieving resonance suppression for the terminal and cables. Ref. [75] introduced a virtual synchronous rectifier current harmonic suppression strategy suitable for distorted grids. By employing grid harmonic feedforward, the harmonic frequency impedance is increased, weakening the impact of the grid background harmonic voltage on the grid-connected current. Ref. [62] considered the suppression of the distribution feeder bus voltage and installed a passive filter between the common coupling point and the grid. This adjustment modifies the total impedance of the grid background voltage harmonic from the installation point to the grid (Figure 14), eliminating the adverse impact of grid background harmonics on grid current. This strategy implements a decoupling approach for suppressing both grid background harmonics and non-linear load harmonics. Ref. [76] explored the coupling mechanism between DC bus voltage ripple and grid harmonic current under grid voltage imbalance conditions. By optimizing controller parameters, second-order harmonics in the current were eliminated, achieving significant suppression of grid current harmonics.
The integration of renewable energy and weak grid conditions in multi-charger systems can easily lead to resonance issues. When adopting background harmonic suppression strategies, the grid voltage feedforward loop of rectifiers may introduce a positive feedback path, thereby deteriorating power quality. To address this, ref. [42] employs an adaptive comb-filter control technique, significantly reducing the THD in grid-connected mode. Ref. [56] proposes a global resonance suppression method based on virtual impedance, where an active harmonic suppression device is connected in parallel at the PCC to reshape grid impedance. This method is combined with a converter impedance reshaping strategy to suppress resonance in parallel systems. Ref. [27] employed a global resonance suppression method based on virtual impedance, where an active harmonic suppression device is connected in parallel at the common coupling point to reshape the grid impedance. This, combined with a converter impedance reshaping strategy, helps suppress resonance in parallel systems. Ref. [77] considered harmonic resonance suppression in multi-machine systems under background harmonic scenarios. By paralleling virtual admittance at the common coupling point to reshape the inverter impedance, this method effectively suppresses grid-side background harmonics in weak grids while enhancing the system’s phase margin. Refs. [78,79] focus on charging piles equipped with PV conversion systems, employing an advanced phase-locked loop (PLL) strategy to achieve accurate fundamental current tracking under a distorted grid for harmonic suppression. Additionally, in V2G mode, these charging piles provide reactive power compensation and active filtering capabilities.

4. Voltage Regulation Strategies

The classification of voltage deviation mitigation is illustrated in Figure 15. Considering voltage deviation issues in charging pile scenarios from the perspective of device control optimization, voltage fluctuation suppression can be achieved by improving the reactive power voltage loop. Ref. [80] implements voltage regulation control on both the grid side and the DC side through a front-end AC/DC converter, mitigating the negative impact of electric vehicle charging on grid voltage. Tanaka proposed a single-phase smart charger equipped with power quality compensation functionality for Japan’s single-phase three-wire distribution system. This charger employs a reactive power control algorithm to address power quality issues such as voltage deviation and imbalance [81,82,83]. Ref. [84] proposed a dual-integral sliding mode control for bidirectional charging piles, achieving voltage regulation through gain-adaptive control under non-ideal grid conditions.
From the device level perspective, the consumption of reactive power by electric vehicle charging leads to voltage deviations in the power system. By switching capacitor banks in groups, capacitive reactive power can be delivered to the system, but this approach cannot track reactive loads quickly, and improper design may result in overcompensation. SVGs can provide fast tracking of reactive loads, with simple control and low cost, making them widely used. Ref. [28] used static var generators to achieve fast compensation of system reactive current, imbalance, and zero-sequence current. Ref. [29] proposed the use of cascaded static var generators as reactive power compensation devices for charging piles, providing local or hierarchical reactive power compensation, effectively improving the power quality of the grid.
By utilizing common unidirectional AC-DC boost converter topologies available on the market, harmonic current compensation and reactive power compensation can be achieved to enhance power quality in residential applications. Ref. [85] proposed a power quality suppression scheme that utilizes existing unidirectional charging piles to achieve harmonic suppression and reactive power compensation. However, due to the distortion of the input current, the reactive power control capability is limited. Ref. [86] analyzed the reactive power support capability of uncontrolled rectifier charging pile and quantified the reactive power capacity that can be obtained from unidirectional chargers in the distribution network. The natural commutation of the diode during phase shift leads to input current distortion. The relationship between the THD of the distorted input current and the phase shift angle δ is shown in Figure 16. When the THD is below 5%, the maximum phase shift angle is 8°, and the reactive power support capability is approximately 13.9% of the total power. Therefore, unidirectional charging piles are limited by the input current and can only provide limited reactive power support. In contrast, charging piles based on PWM rectifiers have a larger phase angle, enabling higher reactive power support.
Compared to installing compensation devices to address power quality issues in distribution networks, promoting charging pile equipment based on the V2G strategy is a crucial approach to achieving effective interaction between electric vehicles and the power grid [87]. In practice, reactive power compensation does not involve active power exchange and therefore does not deplete the EV battery’s energy. With appropriately designed control strategies, the reactive power exchange process does not affect the battery’s state of charge (SoC) or battery lifespan [71]. Under the premise of meeting charging demands, the remaining capacity can be utilized to provide higher reactive power support to the grid without causing input current distortion. Additionally, charging piles can provide reverse reactive power support when not charging, absorbing or releasing reactive power as needed. Ref. [88] proposes a non-isolated single-phase bidirectional charger topology with both charging and reactive power compensation functions, suitable for Level 1 and Level 2 applications. Ref. [89] presents a control method for three-phase bidirectional chargers, enabling simultaneous battery charging and reactive power support based on grid demand. Ref. [90] introduces a direct voltage control strategy for bidirectional DC fast charging piles, extracting reactive power from the DC bus capacitor and injecting it into the distribution network to maintain voltage stability. Ref. [35] proposes a coordinated virtual impedance control strategy for three-phase four-wire inverter-based chargers, achieving harmonic suppression, power sharing, reactive power and voltage support under load variations and voltage sags, and independent regulation of DC bus voltage and neutral current. Ref. [91] presents a distributed model predictive control strategy to leverage the V2G reactive power compensation capability of EV chargers for real-time voltage regulation in distribution networks. This strategy is applicable to both balanced and unbalanced grids and enhances voltage quality without interfering with the normal charging needs of electric vehicles.
With the rise of the grid-forming concept, droop control, virtual synchronous machine (VSM) technology, and related control strategies have been applied to charging pile systems. These approaches effectively improve voltage quality in low-voltage grids and reduce voltage imbalance without relying on V2G capability or complex communication infrastructure [36]. Ref. [92] demonstrated that V2G charging piles equipped with virtual synchronous machine (VSG) technology can respond to grid demands and provide frequency regulation and reactive power support. Ref. [93] studied the active and reactive power support capabilities of a VSG-based three-phase PWM rectifier during grid voltage sag and realized a friendly interaction with the grid on the load side. Ref. [94] proposes a power decoupling method for ultra-fast bidirectional charging piles, utilizing a virtual synchronous machine (VSM) algorithm to enable grid support functions. This approach addresses the active-reactive power coupling issue that arises when ultra-fast charging piles provide grid support, enhancing grid compatibility and offering more flexible ancillary services. Ref. [95] introduces a hierarchical control strategy based on DC voltage droop, effectively coordinating electric vehicle charging and discharging behavior with the reactive power demand of the distribution network, thereby achieving a more flexible power quality management solution.
Additionally, the collaborative development of renewable energy generation and charging stations provides innovative solutions for power quality management in charging piles. In renewable energy scenarios, charging piles integrated with photovoltaic power generation, as proposed in [40], can not only achieve bidirectional active power flow but also provide reactive power compensation under grid voltage imbalance and distortion conditions, enhancing the grid’s power quality. Ref. [42] proposed an electric vehicle charging station based on distributed energy resources, using renewable energy such as solar PV and fuel cells. This infrastructure provides charging for electric vehicles through a common DC bus, maintaining stable voltage output during grid voltage instability, thereby improving voltage regulation. Ref. [96] adopts the IEEE 31-bus medium-voltage (MV) and low-voltage (LV) distribution network model, incorporating residential loads and EV integration. A hierarchical decision-making method is proposed to dynamically adjust the charging rate in real time, demonstrating that a coordinated EV charging control system can significantly reduce voltage sags and imbalance issues, particularly at load nodes in the network’s periphery.

5. Prospects of Large-Scale Charging Piles in Power Quality Management

A systematic review of the relevant research on charging stations participating in power quality management of distribution networks has been conducted based on Table 3 and Table 4. Although existing studies have explored the role of charging stations in addressing power quality issues within distribution networks, most research under high-penetration scenarios remains focused on power transmission. The investigation of charging stations actively participating in power quality management at the device level is still in its early stages. As the penetration rate of electric vehicles continues to rise, the construction and upgrading of charging infrastructure are imperative. Future charging stations will increasingly use green charging piles, and the promotion of charging piles with power quality management functions will offer multiple benefits, including cost savings, improved distribution network power quality, and higher charging pile utilization rates. With the further expansion of the charging pile scale in the future, the potential for charging piles to participate in addressing distribution network power quality issues is considerable.
  • Leveraging the inherent compatibility between the front-end circuitry of charging piles and power quality conditioning devices, optimized control strategies can be directly integrated to embed harmonic suppression and reactive power compensation functionalities, eliminating the need for additional hardware investment.
  • Utilizing the intermittent operating characteristics of charging piles, their residual capacity can be allocated during non-charging periods to implement voltage regulation, enabling a flexible resource utilization strategy that prioritizes charging during peak demand and voltage support during idle periods.
  • Charging piles are usually integrated with adjacent electrical equipment at the same PCC point, making it possible to leverage their installation location for localized management. At the same time, advanced voltage feedforward control strategies can be employed to actively suppress background harmonics originating from the upstream grid, thereby achieving broader regional power quality improvements.
  • Under grid fault conditions, large-scale charging piles can switch to an emergency control mode, injecting reactive power rapidly to prevent voltage collapse. Simultaneously, they can coordinate with higher-level power quality conditioning devices, forming a two-tier defense system comprising both local and regional mitigation strategies.
  • With the deep integration of virtual synchronous machine technology, distributed predictive control algorithms, and power IoT, charging pile clusters will surpass the regulatory limitations of individual units, playing a pivotal role in power quality management within distribution networks.

6. Conclusions

This paper systematically investigates the impact of charging piles on distribution networks, focusing on key technologies for harmonic mitigation and voltage regulation strategies, as well as future development trends of large-scale charging piles in power quality management. The study thoroughly analyzes the effects of charging pile types, topologies, scales, and penetration rates of electric vehicles on harmonics and voltage in distribution networks. Solutions for harmonic control and voltage regulation are proposed from both equipment-level and control-strategy perspectives.
  • Investigates the various scenarios in which charging stations affect the distribution network, including both steady-state and transient power quality issues;
  • Explores the current status of charging stations participating in power quality governance from a device perspective, highlighting their role in mitigating harmonics, voltage fluctuations, and other power quality disturbances.
As the scale of charging piles increases, power quality management-based charging pile systems are expected to become a critical support for the coordinated development of smart grids and electric vehicles.

Author Contributions

Conceptualization, S.C. and J.Z.; methodology, S.C.; software, S.C.; validation, S.C., J.Z. and Y.S.; formal analysis, S.C.; investigation, S.C.; resources, S.C.; data curation, S.C.; writing—original draft preparation, S.C.; writing—review and editing, S.C.; visualization, S.C.; supervision, S.C.; project administration, J.Z.; funding acquisition, J.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This paper was funded by the Beijing Municipal Natural Science Foundation (L242007).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

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Figure 1. Main factors affecting power quality with integrated charging piles.
Figure 1. Main factors affecting power quality with integrated charging piles.
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Figure 2. Schematic diagram of charging pile connection to the grid.
Figure 2. Schematic diagram of charging pile connection to the grid.
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Figure 3. Current harmonic distortion variation of DC fast charger [11].
Figure 3. Current harmonic distortion variation of DC fast charger [11].
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Figure 4. Power conversion module of DC charging pile.
Figure 4. Power conversion module of DC charging pile.
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Figure 5. Harmonic situation of distribution network caused by typical charging piles [37].
Figure 5. Harmonic situation of distribution network caused by typical charging piles [37].
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Figure 6. Change in harmonics current ratio with the number of chargers [19].
Figure 6. Change in harmonics current ratio with the number of chargers [19].
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Figure 7. Change in power factor with the number of chargers and charging power [19].
Figure 7. Change in power factor with the number of chargers and charging power [19].
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Figure 8. Distribution network topology with charging stations [15].
Figure 8. Distribution network topology with charging stations [15].
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Figure 9. Voltage deviation of distribution network caused by the twelve-pulse rectification charging station [15].
Figure 9. Voltage deviation of distribution network caused by the twelve-pulse rectification charging station [15].
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Figure 10. Harmonic source types and mitigation strategies.
Figure 10. Harmonic source types and mitigation strategies.
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Figure 11. Output harmonic impedance bode plot with non-linear load current.
Figure 11. Output harmonic impedance bode plot with non-linear load current.
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Figure 12. Active filter principle diagram.
Figure 12. Active filter principle diagram.
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Figure 13. Power quality-regulating charging piles.
Figure 13. Power quality-regulating charging piles.
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Figure 14. Total harmonic impedance bode plot with grid background voltage.
Figure 14. Total harmonic impedance bode plot with grid background voltage.
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Figure 15. Voltage regulation strategies.
Figure 15. Voltage regulation strategies.
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Figure 16. Variation of THD with input current phase shifts.
Figure 16. Variation of THD with input current phase shifts.
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Table 1. Characteristics of different electric vehicle power charging levels [11].
Table 1. Characteristics of different electric vehicle power charging levels [11].
Level 1 (Slow)Level 2 (Semi-Fast)Level 3 (Fast)
Voltage Level (V)120 (AC)208–240 (AC)50–1000 (DC)
Max Power (kW)1.44 or 1.925 or 19.280–400
Charging time (h)4–122–60.2–1.0
Phase1 phase1 or 3 phase3 phase
Charger locationOn-boardOn-boardOff-board
InstallationDomesticDomestic/CommercialCommercial
Table 2. Maximum voltage deviations percentage of uncoordinated charging [57].
Table 2. Maximum voltage deviations percentage of uncoordinated charging [57].
Charging PeriodPenetration Level0%10%20%30%
21:00–6:00Summer
Winter		3.1
4.2		3.5
4.4		4.4
4.9		5.0
5.5
18:00–21:00Summer
Winter		3.0
4.8		4.4
6.3		6.5
8.5		8.1
10.3
10:00–16:00Summer
Winter		3.0
3.7		4.1
4.9		5.6
6.4		6.9
7.7
Table 3. Summary of the literature survey related to harmonic migration strategy.
Table 3. Summary of the literature survey related to harmonic migration strategy.
ReferenceMethodTechniquesHarmonic SupressionHarmonic CompensationVoltage Compensation
[18,25,26,27,64,65]activeSAPF ✓
[22]passiveLCl/LC filter✓
[35,62,72]activeVirtual impedance✓✓✓
[40]activePower control✓✓✓
[22,41,70,71]activeAdaptive filter✓✓✓
[52,59,60,61,63,84]activeSMC/PFC/ACHR/✓
Resonant controller
[67]activeResonant controller✓✓✓
[68,69]activeServes as an APF✓
[73,74,75,76,77]activeAdmittance reshaping✓
[78,79]activeAdvanced PLL✓✓✓
The presence of a checkmark (✓) in the table denotes that the capability is included.
Table 4. Summary of the literature survey related to voltage regulation strategy.
Table 4. Summary of the literature survey related to voltage regulation strategy.
ReferenceMethodTechniquesVoltage RegulationVoltage CompensationHarmonic Supression
[23]passivefixed capacitors✓✓
[28,29]activeSVG/statcom ✓
[32,88,89,90]activepower control✓✓
[36,36]activeDRoop control✓✓
[37,38,92,93,94]activeVSG✓✓
[80,81,82,83,85]activePFC✓
The presence of a checkmark (✓) in the table denotes that the capability is included.
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Chen, S.; Zhou, J.; Sun, Y. Research Review on Power Quality Improvement in Distribution Networks via Charging Pile Integration. Electronics 2025, 14, 1284. https://doi.org/10.3390/electronics14071284

AMA Style

Chen S, Zhou J, Sun Y. Research Review on Power Quality Improvement in Distribution Networks via Charging Pile Integration. Electronics. 2025; 14(7):1284. https://doi.org/10.3390/electronics14071284

Chicago/Turabian Style

Chen, Shasha, Jinghua Zhou, and Yifei Sun. 2025. "Research Review on Power Quality Improvement in Distribution Networks via Charging Pile Integration" Electronics 14, no. 7: 1284. https://doi.org/10.3390/electronics14071284

APA Style

Chen, S., Zhou, J., & Sun, Y. (2025). Research Review on Power Quality Improvement in Distribution Networks via Charging Pile Integration. Electronics, 14(7), 1284. https://doi.org/10.3390/electronics14071284

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