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2023 Электротехника, информационные технологии, системы управления № 46 Научная статья
DOI: 10.15593/2224-9397/2023.2.01 УДК: 621.314.58
Х.М. Джассим, А.М. Зюзев, А.В. Костылев, М.В. Мудров, А.И. Хабаров
Уральский федеральный университет, Уральский энергетический институт, Екатеринбург, Российская Федерация
ТОПОЛОГИИ И ТЕХНОЛОГИИ СТАНЦИЙ БЫСТРОЙ ЗАРЯДКИ ЭЛЕКТРОМОБИЛЕЙ: ОБЗОР И СРАВНЕНИЕ
Электромобили все чаще используются в транспортном секторе развитых стран. Это связано с экологическими и экономическими преимуществами, которые они предлагают по сравнению с автомобилями с двигателями внутреннего сгорания. Понимание архитектуры их зарядных устройств, характеристик и различий между ними чрезвычайно важно для исследователей и инженеров, занимающихся разработками в этой области. Цель: всесторонний обзор зарядных станций и применяемых в них технологий, широко востребованных специалистами. Тем не менее текущие обзорные статьи в основном ориентированы на конкретный аспект темы, не предоставляя целостного обзора аргументов, проблем и технологий, связанных с проектированием зарядных станций для электромобилей. Кроме того, в некоторых исследовательских статьях представлено лишь ограниченное сравнение между специальными типами этих зарядных устройств, что исключает общее понимание свойств и связанных с ними рабочих характеристик базовых схем преобразователей. Методы: в статье представлен обширный обзор станций и технологий быстрой зарядки электромобилей. Обзор расширен, чтобы объединить топологии зарядных устройств, а также общие проблемы проектирования и технологии зарядки, представленные в литературе. Кроме того, включены актуальные темы, чтобы пролить свет на предстоящее направление исследований в этой области и возможные достижения. Что еще более важно, в статье проведено всестороннее сравнение между некоторыми из наиболее распространенных зарядных устройств для электромобилей на основе рабочих характеристик встроенных в них преобразователей энергии. Результаты: проведено сравнение зарядных устройств электромобилей на основе компьютерных моделей, построенных в среде MatLab/SIMULINK, результаты проанализированы и оценены. На основании оценки основных характеристик даны рекомендации по использованию конкретной архитектуры при разработке зарядной станции для электромобилей, соответствующей российским и мировым стандартам.
Ключевые слова: зарядное устройство для электромобилей, топологии преобразователей, выпрямители, зарядная станция.
Haider M. Jassim, Anatolii Ziuzev, Aleksey Kostylev, Mikhail Mudrov, Andrey Khabarov
Ural Federal University, Ural Power Institute, Yekaterinburg, Russian Federation
TOPOLOGIES AND TECHNOLOGIES OF ELECTRIC VEHICLE FAST CHARGING STATION: REVIEW AND COMPARISON
Electric vehicles are increasingly adopted in the transportation sector of developed countries. This is due to the environmental and economic advantages they offer as compared to internal combustion engine vehicles. Understanding the architecture of their battery chargers, their characteristics, and the differences between them are essentially important for researchers and engineers pursuing future development in the field. Purpose: a comprehensive review of the charging station facility and related technologies is widely demanded to facilitate the acquisition of this knowledge. Nevertheless, the current review articles are mostly oriented toward a specific aspect of the topic without providing a holistic overview of the arguments, issues, and technologies involved in the electric vehicle charging station design. Furthermore, some research articles provided only a limited simulation-based comparison between special types of these chargers which undermines the general understanding of the properties of basic converters and associated operational behaviors. Methods: in this article, an extensive review of electric vehicle's fast charging stations and their related technologies is presented. The review is inclusively extended to combine the topologies of these chargers along with the common design issues and charging technologies utilized in the literature. Additionally, future trending topics are also included to shed light on the forthcoming direction of research in this field and possible opportunities. More crucially, this article provided a comprehensive comparison between some of the most common electric vehicle chargers based on the operational properties of their integrated power converters. Results: the comparison between the constructed models of electric vehicle chargers is conducted in MatLab / Sim-ulink environment. Battery voltage, battery current, battery state-of-charge, and switching losses of the DC/DC converter were analyzed for the tested chargers, and results were evaluated. Based on the evaluation, a recommendation has been made for the utilization of specific architecture in developing an electric vehicle charging station that adheres to Russian and global standers.
Keywords: Electric Vehicle Charger, Converter Topologies, Rectifiers, Charging Station.
Introduction
The exhaustion of fossil fuels, price fluctuations, and the damage they inflict on the environment have created a growing interest in the development of battery-powered electric vehicles (BEVs). The electrification of the transportation sector assisted in the alleviation of global warming problems as this sector is responsible for 28 % of the total greenhouse gas emissions worldwide [1-3]. Furthermore, this process of modernization and decarbonization of the transportation sector has been adopted by most governments around the world, which tend to reflect on the stage of development, and has paved the way for researchers to work on different aspects of electric vehicle technology [4, 5]. In 2020, the total number of deployed EVs exceeded 3.1 million vehicles, despite the pandemic, and it is projected
to double to reach 14 million in 2025 [6]. This is due to the competitiveness offered by these vehicles as compared to the internal combustion engine vehicles in terms of vehicular performance, reduced environmental fingerprint, and the plummeting cost of operation caused by the exponential decrease in lithium-ion battery prices [7].
The main factor that contributed to the current wide adoption of EVs is the rapid enhancement of their charging facility. The chargers are classified into on-board and off-board chargers where the off-board charging devices are being used for high-power charging [2]. Both types of chargers are further categorized into three sub-categories [8]:
1) Level 1: these chargers have the lowest charging time and take the longest time to fully charge the vehicle's battery. They are usually singlephase chargers with a maximum charging capacity of (3,7 kW).
2) Level 2: this type of charger is gaining tremendous commercial popularity due to its cost and suitability for most current EV battery technology. The maximum peak power produced by this charger is around (22 kW) which means it can charge the vehicle overnight to full capacity.
3) Level 3: these chargers may refer to also as fast-dc chargers and can charge the battery with a charging power of (50-300 kW) which means that the vehicle can reach full charge within (30 minutes). These chargers are more specialized and require non-residential charging infrastructure usually like petrol stations.
Nevertheless, the properties and specific standers of EV chargers significantly depend on the manufacturing company and the county it is being utilized. For instance, the new Tesla Model X which has a battery capacity of (100 kWh) can charge with the advanced fast-dc charger with a charging power between (100-200 kW) using a supercharger-type connector, while Porsche Taycan uses CCS type2 connector to charge its (79,2 kWh) battery with a charging capacity of (225 kW) [2]. Fast chargers are structured as two stages: AC/DC rectification stage and DC/DC conversion stage. The AC/DC stage is responsible for rectifying the waveform and stabilizing the DC voltage and current to desired values. While the DC/DC stage controls the injected power into the battery system depending on the battery management system BMS dynamic requirements. There are numerous standards that govern the construction and configuration [9]. These standers set the minimum achievable specifications like power factor, efficiency, total harmonic distortion THD, maximum leakage current, electromagnetic interfer-
ence, and DC power level. For example, the international standers of IEC 62955:2018, and IEC 61851-1:2017 require the constructed charger to have a leakage current of less than (30 mA) to prevent electric shocks which indicate that isolation using high or low-frequency transformers must be employed to achieve such protection.
The utilized converter topology in each stage and the implemented control algorithm are essential for achieving reliable and low-cost operation while providing high charging power to the vehicle's battery. High penetration of EV chargers can cause critical degradation in the efficiency and quality of the delivered power by the distribution network. Therefore, the selection of the proper topology that adheres to the current standers and optimizing the management system are essential factors for the operation of charging stations [10]. The grid operator also may be referred to as an aggregator in the case of EV charging facilitator, may be enforced to alter the infrastructure or employ scheduling algorithms to mitigate the impact of increased load [11]. Harmonic distortion is another issue that must be addressed by the synthesized converters and implemented control algorithms. Power factor compensation PFC techniques are used at the rectifier stage to minimize the THD to less than (5 %) which is the obligatory limit set by the distribution network operator [1, 2]. This indicates that uncontrolled rectification is out of the picture for such applications. However, there are a significant number of research articles for hybrid three-phase rectifies which use passive and active rectification in parallel to achieve high power and the required compensation and control [12]. As illustrated previously, for the DC/DC conversion stage, it is recommended to utilize a high-frequency transformer as isolation to prevent electric shocks [2]. Another solution is to use a low-frequency transformer in the AC/DC stage. Though, this solution causes a significant increase in the cost and bulkiness of the designed power system [13]. Moreover, the DC/DC converter is developed to control both the delivered voltage and current to the battery system since they may be dynamically changing. The converter bridge needs to be well maintained by the control system to achieve a wide range of output voltage, high efficiency, soft switching properties, low voltage and current output ripples, and stable overall operation [2]. Another aspect to consider when selecting converter topology is the bidirectional operation capabilities of the charger. This functionality enables the battery of the electric vehicle to discharge the stored energy back into the AC side of the converter when required. During
the discharge phase, the EV can be viewed as a source of energy that can be utilized to perform critical services on the demand side of the grid [14, 15]. These services include voltage and frequency regulation, load curve leveling and shaving, reactive power compensation, harmonics filtering, and enhancing the penetration of renewable energy sources [16]. However, this technology is still under development and not fully embraced by all grid operators around the world due to the high level of sophistication involved in the bidirectional exchange of power. Some of the limitations of this technology are the increased number of active power electronic elements which is associated with higher cost, impact on the reliability of the charger, slight decrease in power density, and amplification of problems related to injected harmonics when the technology is deployed [1, 2, 9].
In this article, technologies and trends that are associated with EV charging facilities are reviewed. The goal is to provide a comprehensive piece of research that composes fundamental details about this field and the technologies that are involved to allow researchers and technicians to make an informed selection when dealing with EV chargers. A comparison between different charger configurations based on their performance and properties is essential for technical and commercial purposes. An evaluation and recommendation are provided to establish a ground truth for designers to enable them to decide on configuration and control algorithms. The contributions of this research are as follows:
• This review is different from other research in the field by the technical and simulation-based comparison between the most common converters employed in EV chargers. The Power factor, THD, switching losses of the DC/DC converter, and the battery charging time response are to be evaluated for each configuration. In sense of fairness, the comparison is conducted between the basic converters with the basic control system. To our knowledge, no review paper has provided simulation-based results which is essential for selecting the proper converter topology.
• This review combines the power electronic converters and the trends and technologies of EV chargers which provides a sufficient scope of topics to cover most aspects of the field.
• Unlike other reviews, this research addresses the obligatory conditions and requirements set by the Russian government to manufacture and produce an electric vehicle charger. These requirements include high output DC voltage and low associated THD, to name a few.
Fig. 1. General architecture of EV charging system
The rest of this paper is organized as follows: section (2) reviews the topologies of AC/DC rectifiers, while DC/DC converter topologies are reviewed in section (3). Charging methods are briefly discussed and introduced in section (4), and the battery model which can be used in experimentation and simulation is described in section (5). Section (6) explores the concepts of hard and soft switching. Section (7) is dedicated for the simulation-based comparison between different chargers, where analysis and evaluation of the charger performance were conducted based on obtained results from MatLab models. Future trends in the field of electric vehicle charging stations are provided in section (8), while section (9) is the conclusion and final recommendation.
1. AC/DC Rectifier Topology
This converter is responsible for transferring the three-phase AC power to DC power. Although most of these rectifiers are single-stage configurations, there are hybrid-type rectifiers that employ two converter circuits in parallel to achieve better performance and higher power [12]. This research confined the discussion to the single-stage structure since they are the most popular architecture to be utilized in practice. It is of the utmost importance to use a rectifier with power factor compensation PFC capabilities due to the previously mentioned requirements and standers set by the grid operators and the scientific communities. Therefore, active power electronic elements are essential in their architecture. The main objectives of the control system are to stabilize the output DC bus voltage and the internal currents of the converter by producing proper switching patterns for the power transistors. This indicates that digital computers and different sensors are intuitively integrated into the design of this rectifier.
2.1. Active Front End AFE
It is distinguished by its simplicity, high power density, controllability, and high efficiency. Due to these properties, it is considered a benchmark rectifier for commercial purposes especially since the modulation signals are designed to maintain the voltage and current on each leg (phase). This reduces the synchronization and harmonic distortion issues because they are implicitly addressed in the control algorithm [17-20]. It is, however, limited due to its two-level switching operation which increases the switching stress and reduces its output power capability. For this reason, commercial rectifiers are designed to be multi-level or use redundant switches [1]. AFE can be designed to act as a buck or boost converter depending on the pre- and post-filtering circuits and it can provide a wide range of output voltage and current. The generalized architecture of the AFE rectifier is demonstrated in figure (2), where leg shoot-through protection is provided inherently in the control system by supplying the upper transistor with the inverse signal of the lower transistor. The switching stress issue was reduced by employing an eight-transistors design instead of the classical six-transistors configuration [21].
Fig. 2. Active front end rectifier AFE
However, due to the high switching losses in EV applications, a study in [22] has suggested a new design by splitting the freewheeling diodes into two diodes serially connected to the neutral point which reduced the losses significantly. The THD problem was compensated using a transfer matrix-based digital controller which reduced both input current harmonics and output voltage ripple [23]. A novel structure was introduced to suppress the harmonics caused by parasitic capacitance during low load conditions without sophisticated phase-locked loop PLL calculations [24].
Other research studies addressed the unbalanced AC input of boost type AFE which reduces its efficiency and introduces harmonics in the DC bus [25]. A simple controllable active filter was suggested to mitigate this problem [26]. Finally, to address the problem of hard switching, An AFE was utilized followed by a DC/DC buck converter [27]. This configuration helped to achieve a near-zero voltage switching but restricted the range of the output duty ratio which created another problem to be addressed by the control system.
2.2. Vienna Rectifier
The configuration of the three-phase Vienna rectifier is shown in figure (3) where the rectifier is implemented using six diodes and only three bipolar switches. These switches are more compatible with high-efficiency power flow applications [28].
Fig. 3. Vienna rectifier
Unity power factor, reduced number of switches, high efficiency compared to other rectifiers, very low THD, and simplicity of the control system are some of the properties of this rectifier that qualified it to be the most adopted solution for EV charger design by many manufacturers [2, 29]. Moreover, it requires half of the volume of other converters and experiences half of the dc voltage stress on the switches on the dc side which makes it a compact and efficient choice for on-board and off-board charging applications [30]. In [1, 31], different variations of the Vienna rectifier design have been reviewed and compared. The six switches Vienna rectifiers are an adaptation of the neutral point clamped rectifier which has the advantages of very high efficiency, more than (98 %) and facilitating the pre-charging process of the output capacitors [31, 32]. On the other hand, the
three-switches configuration has the advantage of less active element at the expense of increasing the power diodes to (18) which is very expensive as compared to the basic configuration of the converter [1, 2]. The T-type Vienna rectifier is combined with interleaved techniques to achieve an efficiency of (99,24 %). However, it required some thermal management for the devices due to cell fast commutation and carried currents during both cycles of operation [1, 31]. Other adaptations of the Vienna rectifiers are not suitable for EV applications since they sacrifice the three-level functionality like in Y-type and Д-type Vienna rectifiers. The biggest drawback of this converter is the unidirectional operation which limits its future adaptation for V2X applications. This has been addressed by [33], who presented a new concept for a bidirectional Vienna rectifier by replacing the input diode bridge with power MOSFETs. Although the configuration does not sacrifice the efficiency of the converter, it is significantly harder to control.
2.3. Swiss Rectifier
A three-phase rectifier that has an architecture comparable to the Vienna rectifier except for the pre- and post-power circuits. The input filter is executed as a complicated damping circuit for each phase while the output circuit consists of additional transistors and power diodes to ensure the balance of the two capacitor voltages and reduce the voltage and current ripples significantly [34]. This converter has higher efficiency, lower switching losses, and lower common-mode noise and conduction than the AFE rectifier. This converter is usually integrated with interleaved type DC/DC converter to boost the efficiency, increase the bandwidth, and notably minimize the voltage and current ripples [35, 36]. A high-power Swiss rectifier has been developed by [37] for high-power battery chargers but the circuit control system became very complicated. Furthermore, adding extra power components enables the Swiss rectifier to be operated bidirectionally, though the control system also increased in complexity [38].
2.4. Multilevel Rectifiers
These rectifiers utilize lower voltage power components to synthesize higher-power devices [39]. They are generally categorized into neutral point clamped, flying capacitor, and cascade H-bridge topologies [2]. They are characterized by their staircase output waveform which reduces the switching losses on the power devices significantly. They also are implemented
with fewer magnetic components which means lower THD and electromagnetic interference EMI which made them a favorable choice for high-power ultra-fast charging stations. Despite their numerous merits, each configuration of these rectifiers has its own limitation. Although the cascade H-bridge converter is simple, robust, and easily implemented, critical issues like restricted modulation signal and capacitors voltage balancing downgrade its performance [40]. Flying capacitor rectifier can solve the problem of voltage ripple at the fundamental frequency which requires large capacitors on the AC side for compensation [41]. Flying capacitor structure can help to scale down the input active filter significantly [42]. However, this requires a special feedforward controller that alleviates the problems caused by smaller-sized inductors which causes a leading phase current [43]. The main problem of flying capacitors is the voltage balancing and capacitance shift which may require a sophisticated control loop for regulation.
3. DC/DC Converter Topology
These converters link the AC/DC output to the battery pack. They are required to be operated by high-precision controllers since they control the charging current and voltage of the battery that are dynamically requested by the battery management system BMS. This stage encounters significant switching losses and operates with a relatively higher switching frequency than the previous stage. Thus, special care must be taken concerning their design and heat dissipation. Furthermore, as illustrated before, it is necessary to use some sort of isolation either in this stage in the form of a high-frequency transformer or prior to the AC/DC stage in form of low bulky magnetic components [2].
3.1. LLC Resonant Converter
Due to their numerous advantages, they are wildly used in practice to implement the DC/DC converter of the EV charger. These advantages may include a wide range of output voltage regulation even with light loads, zero voltage switching ZVS and ZCS capabilities, and architecture-based controllable efficiency [44-46]. The general structure of LLC converters is demonstrated in figure (4). The voltage is regulated by manipulating the converter switching frequency while the gain of the converter is set by the resonant tank and the transformer ratio [45]. The resonant frequency fr is decided by the capacitor and the inductor of the resonant tank and the magnetization
inductor .
Fig. 4. Resonant LLC Converter
The converter operates in the optimized mode, soft switching of the input bridge, and soft commutation of the output diodes when the switching frequency is equal to the resonant frequency. However, due to the nature of the control mechanism of this converter, the switching frequency is the control variable and changes in accordance with the error signal. Thus, the switching frequency can deviate from the resonant one and cause growth in the losses of the converter. The design procedure of the LLC converter becomes significantly complicated when operating with active loads like the battery system due to the induced back electromotive force and different modes of operation [45]. During the constant voltage mode, the light load conditions can cause serious issues leading to nonlinear characteristics and undermining the benefits of such structure. Nevertheless, the authors in [47] highlighted the operation of LLC converter in three modes. The research proved that ZVS and high efficiency can be obtained in all modes when a restriction is imposed on the fluctuation of the switching frequency to prevent a large deviation from the resonant frequency.
3.2. Phase-Shifted Converter
This converter has many features that made it very attractive for EV charging applications. These features may include soft-switching capabilities, simple design and control, constant frequency, low EMI, and reduced current stress on the input bridge. The control mechanism is based on the phase difference between the input switches which is translated to a PWM signal that dives the gates of the transistors. However, this topology encounters several challenges like the non-ZVS during the turn-on periods, reverse recovery of the diodes, and large output inductor which reduces the power density of the converter. Many modifications have been introduced in the
literature to overcome these limitations including the transformer leakage inductor and snubber circuit to minimize the circulating currents and improve the ZVS characteristics [48, 49]. Moreover, The authors in [50] have proposed an auxiliary passive circuit to reduce the voltage spikes on the diodes of the secondary bridge. This improved the ZVS and the transient voltage response, though it increases the overall losses of the converter. other modifications may include fusing the converter with other types of DC/DC converters in the parallel form are reviewed in [9, 12]. The original configuration of the phase-shifted converter is shown in figure (5).
Fig. 5. Phase-shifted Converter
3.3. Dual Active Bridge DAB Converter
High efficiency, inherent soft switching, high power density, and bidirectional power flow are some of the features that established the DAB as a suitable candidate for EV charging applications. The DAB, which is illustrated in figure (6), is usually controlled by a phase shift algorithm that determines the direction of power by adjusting the phase of the modulation signals [51, 52].
Fig. 6. Dual Active Bridge Converter
When the phase shift is positive the power is flowing from the grid to the vehicle's side and, hence, charging the battery. While a negative phase shift flips the direction of power flow and discharges the battery to the grid. This is a very important propriety when dealing with V2G and Microgrid applications. Single, dual, and three-phased DAB modulation techniques are compared in [51] to evaluate their ZVS capabilities. The research concluded that the three-phase DAB can fully secure this feature even in no-load conditions. The three modes are incorporated into one design to achieve low losses over a wide range of loads, though this will significantly increase the complexity of the design and control system [53]. The DAB transformer can reach saturation when the magnetic flux density is offset to a certain point in the B-H curve that produces a current spike. The authors in [54], proposed a new algorithm based on the current measurement and providing certain margins to ensure that the switching frequency is high enough to avoid transformer saturation. While a transformer current optimization procedure was introduced to enhance the efficiency of the converter and attain a wide range of operations in [55].
3.4. DAB Resonant Converter
This is an adaptation of the DAB circuit in an attempt to optimize its operation and reduce switching losses. The resonant tank can be designed in different configurations depending on the preferred feature to achieve [56-59]. Although the LC configuration is considered the easiest tunable and controllable tank configuration, it suffers from hard switching which negates its design purposes. Thus, a more advanced tank configuration is required and preferably with a higher level of operation. According to the reviewed literature, CLLC tank resonant configuration can achieve ZVS properties with high operating frequency and over a wide range of loads [56, 57]. Additional active devices and power elements were utilized to implement a novel reconfigurable converter that operates in both full and halfbridge modes [59]. Despite the gained soft switching and low-loss capabilities, the additional component increased the volume and cost of the overall system. A major limitation to the extensive adoption of DAB resonant converters in applications is the synchronization and paralleling problems between the two bridges due to asymmetricity and sophisticated mathematical models [2].
3.5. Partial DC/DC Converter
These converters provide a path for the power flow to bypass directly to the load. Thus, only a fraction of the power is regulated using the converter configuration. These converters have been found to have 3 % higher efficiency than their counterparts which made them attractive for EV fast charging applications [60]. Since only partial power is allowed through the converter, loess and magnetic components are minimized. The research in [61] analyzed the functionality of these converters using and concluded that, due to their nature, they can be operated without galvanic isolation. However, the major drawback lies in the fact that only part of the power can be controlled while the other part relies on the stability of the previous stage and is directly injected into the battery pack. From a practical point of view, this is a hazardous operation, especially with active and fire susceptible loads like lithium-ion batteries.
3.6. Quadratic Double Boost Converter
Implemented by the superposition of two boost converters while overlapping the supply with the power capacitor to achieve more efficient charging [62]. It is a suitable choice when the input/rectified voltage is low, and a sufficiently large boosting characteristic is required. It is found, however, that double boost converter is a lot more complicated to control than regular converters due to the voltage superimposing diodes [63].
4. Charging Methods
Several advantages made Li-ion batteries a preferable choice for electric vehicle applications. These may include high power density, high energy, and low memory effect [64]. However, the charging must be carefully conducted since it affect the internal electrochemical reactions of the battery cells and, hence, significantly affects the battery life cycle [65]. For this reason, it is required to find an optimal charging method that can quickly and safely charge the battery pack without damaging the internal cells or reducing their life cycle. Many charging methods, not limited to EV applications, have been reviewed and discussed in [66, 67]. The first and most common approach is the constant current-constant voltage (CC-CV) changing method. This method, which is demonstrated in figure 7, a, is based on dividing the charging profile into two regions. In the first region, the charging controller operates as a constant current controller and monitors the voltage of
each cell until it reaches a certain level. This level is usually set to 4.2 V/cell with a tolerance of ±50 mv. When the cut-off voltage is reached the management system changes the charging objective to constant voltage while the full charge is reached only when the current is decreased to between 3-5 % of the rated current. The second charging technique is called time pulsed charging, and it is mainly utilized for the fast charging of electronic devices. Figure 7, b shows the principle of this approach where the charging current is supplied in form of time pulses such that there is a rest period. This period will ensure that the ions can diffuse and neutralize which can slow down the polarization process and improve the overall life cycle of the battery [64].
Fig. 7. Charging modes: a - CC-CV, b - time pulsed charging
The charging rate can be changed by manipulating the width of the pulses. Because of the promised advantages, this method is actively being studied for EV charging applications. Another charging method uses a five-stage charging pattern with five levels of constant current. The charging time is divided into five regions with a slowly increasing voltage target and constant current that corresponds to the reach voltage in each stage. This method is argued to be safer and faster than the CC-CV method [64]. However, the arrangement of time divisions and the corresponding constant current for each stage is quite complicated and has proven to be inefficient [67]. Almost all these algorithms depend only on the voltage and current of the battery to produce the charging pattern without considering other battery parameters like the internal electrochemical processes, thermal response, and the aging factor. Alternatively, a new state-of-art charging algorithm has
been proposed to develop a charging profile that is induced by the electrochemical dynamical model of the battery [68, 69]. This involves estimating the parameters of the electrochemical dynamics of the battery using partial differential equations which can be time-consuming for real-time applications of EV BMS and require high computational power. A nonlinear model productive controller NMPC was proposed to control the charging pattern depending on the single particle model which is considered a simplified model for the battery with fewer interacting variables and fewer parameters to be estimated [70]. Another approach is to utilize modern artificial intelligence techniques like reinforced learning to estimate the internal parameters of the battery in a real-time fashion based on a pre-trained model [71]. These algorithms can achieve a better battery state of health than any other charging method.
5. Battery Model
As mentioned before, developing a mathematical representation of the battery system is vitally important. Such a model can be used to estimate the battery run-time parameters and, hence, predict the charging status and the internal dynamics of the battery which will help the EV BMS to produce informed decisions. Although in this research we are more concerned with the general dynamic behavior of the battery while charging which requires a simplified electrical representation of the battery circuit, the literature is rich with research articles that address the full electrochemical representation of the battery cell [65,68]. A simplified battery model can assist the charging station designer to test and verify his designs in real-time without endangering or damaging EV batteries. Several representations of battery systems are introduced over the years that can capture certain aspects of battery behavior. Thevenin representation can predict the battery state of charge SOC in the transient mode of load event. This representation, however, assumes a constant open circuit voltage which greatly limits its applications. Another model utilizes the electrochemical impedance spectroscope to approximate the chemical impedance of the battery to an AC equivalent. Nevertheless, this method is very difficult and non-intuitive. The authors in [72] suggested a hybrid model that combines different representations and is capable of operating in real-time based on the I-V performance of the battery to estimate the battery parameters. This model employed controlled-current and con-trolled-voltage sources along with an electrical equivalent circuit to approx-
imate the battery dynamics. A high-fidelity model was developed to represent the transient, steady state, and thermal characteristics of the battery system [73]. The model was developed in a MatLab environment and specialized real-time software tools were used to compare the experimental and simulated data. A generic simplified model was introduced by [74] to estimate the charging characteristics of the battery system. The developed model has the following dynamics:
E= E0-K(^)+Ae^ -\ (1)
Vb a t = E — R in t ■ lb a ^ (2)
5 0 C = 1 0 1—j), (3)
where is the open circuit voltage, is the battery capacity (Ah), i is the battery current, K is the coefficient of the polarization resistor, Rint is the battery internal resistor, A is the amplitude of the exponential region, B is the inverse time constant of the exponential area. This model has been extensively used in the literature, and later adopted by software packages to represent the battery behavior with certain modifications.
6. Hard and Soft Switching
One of the most important issues to consider while designing an EV charger is the hard switching of the converter transistors. The issue is generated by the fact that power MOSFETs are not ideal devices and when we turn them on and off the voltage and current change linearly instead of instantaneously. For example, when we turn off the transistor the output current will respectively fall to zero and the voltage will gradually grow to VDS. This transition does not happen immediately and the intersection between voltage and current will generate what is called hard switching losses that are demonstrated in figure (8).
These losses are common in all converters, but more specifically discussed for the second stage of EV chargers due to their high switching operation and intensive voltages and currents passing through them. The switching losses equations can be formulated as [75]:
Plos s = 2 ■ VDS■ h ■ ToN^fswi (4)
where is the transistor on period and is the switching frequency.
VDS
IL
—>
time
Fig. 8. Principle of Hard Switching
Methods for tackling the hard switching problem are topology or control-inspired that focus on manipulating the voltage and current of the transistor to reduce or eliminate the intersection region. Topology-inspired solutions suggest an auxiliary circuit that is integrated into the input or output bridge to a cause current or voltage shift and, thus, reduce the associated losses [75-77]. Resonant converters can inherently provide ZVS and ZCS by proper design of their parameters. Many resonant DC/DC converters have been reviewed in [76] like quasi-resonant converters, multi-resonant converters, and resonant transition converters. These converters can reduce losses and noise due to voltage and current stress reduction. However, they also encounter circulating current and conduction losses due to their special design requirements. Another way is to modify the configuration of each device to achieve zero switching conditions. This can be realized by using a snubber circuit which is a diode and capacitor connected in parallel with the transistor [48, 76, 78]. The general concept of such configuration is shown in figure (9). When the transistor is turned off the capacitor will be discharged due to the input current flow. This will result in tuning on the diodes which makes them a voltage source with a significantly lower voltage than the output voltage. This automatically reduces the value in equation (4) and inductively reduces the switching losses. Though, a small deadtime period that corresponds to the values of the capacitors must be included in the PWM controller such that all transistors are switched off before turning on certain pair of them. The research in [78] utilized this concept and employed the center-clamped circuit of the output diode bridge of the converter to guarantee a momentous reduc-
tion in losses for both input and output circuits. In addition to the increased efficiency and reduced circulating currents, the design minimized the volume of the output inductor which reduced EMI and noise.
Fig. 9. Snubber Configuration for Soft Switching
7. Simulation-Based Comparison Between Common Chargers
In this section, combinations of the most utilized converters in the two-stage of EV charger are tested and compared. This comparison adds value to the review since it can confirm the previously established knowledge. It is critical to compare the designs when being operated by the most common and most basic controllers that can guarantee efficient operation to ensure fairness. For this reason, this section provided a quick description of such controllers. Then, converters reviewed in previous sections and controllers described in this section are modelled in MatLab/Simulink to test the performance of the associated charger. Results were obtained from the constructed models and evaluated to understand the specific features of each charger.
7.1. AC/DC controllers
The objective of these controllers is to synchronize the charging station with the power site and stabilize the rectified DC voltage. Figure (10) exhibits the utilized control algorithm in regulating the Vienna rectifier. As shown in the figure, phase locked loop PLL algorithm is employed to achieve synchronization between the three phases of the converter. A PID controller is used to regulate the DC voltage and compare it with the output of the PLL and the phase current. The output capacitors balancing controller is vitally needed in this case to attain the required voltage. The result is applied to the hysteresis loop which represents the current controller.
Fig. 10. The Control Algorithm of Vienna Rectifier
Fig. 11. The Control Algorithm of AFE
The active front-end rectifier employs a different strategy to generate the switching patterns of the converter transistors. This includes converting the voltage and currents to the dq-frame as seen in figure (11). Although this conversion is computationally expensive, it can significantly simplify the problem to two-channel controllers. Consequently, an inverse Clark transformation is necessary to convert the signals from dq-frame to regular abcframe before being translated to PWM signals by the PWM generator.
7.2. DC/DC controllers
These controllers are operated with a much higher frequency than the previous ones to catch up with the switching frequency of the DC/DC converter. They are mainly tasked with regulating the battery voltage and current based on the required charging profile previously discussed. Thus, the voltage and current reference signals are obtained from the EV BMS. The first algorithm demonstrated in figure (12) utilizes two PI controllers for voltage and current regulation. Then a phase shift algorithm is employed to generate the switching pattern and ensure forward biasing of the input bridge of the phase-shifted converter. This controller is characterized by its intuitive design and high modularity. The battery voltage is set to (1000 V) to meet the manufacturing requirement set by Russian standers, while the voltage and current can be simultaneously controlled using the reference signals.
time Frequency Fig. 12. The Control Algorithm of Phase-shifted Converter
On the other hand, the operation of a resonant converter needs a special type of controller that manipulate the switching frequency of the transistors instead of the duty cycle of the PWM signal. The controller consists of one PID algorithm that produces the switching frequency reference signal and then, passes it to the pulse generator. The algorithm is more complicated than the previous one and if the reference frequency is diverted from the resonant frequency the switching losses dramatically increase.
Fig. 13. The Control Algorithm of Resonant LLC Converter
7.3. Simulation Results
The simulation was conducted based on the different combinations between AC/DC and DC/DC converters. The rectifiers that have been selected for testing are the diode bridge, the Vienna type, and the active front end, while the tested converter in the DC/DC stage is the resonant LLC and the phase-shifter converters. The models for the converters and battery system were developed in MatLab environment and the design procedure for each converter and the related controller was formulated according to the reviewed literature. In this simulation, the battery capacity is assumed to be (200 Ah) and the nominal full charge voltage is (407 V) which corresponds to the majority of currently utilized EV batteries. Figure (14) demonstrates the battery current, voltage, and state of charge SOC responses corresponding to the EV charger designed by combining a diode bridge rectifier and a phase-shifted converter. As seen in the figure, the battery voltage and current are maintained between certain margins while the SOC linearly increases.
Fig. 14. Battery Response to (Diode bridge + Phase-shifted Converter) Charger
The significant impulse in the current response can be ignored since no restriction was imposed on the current in the simulation which is non-realistic for a practical system that cannot produce such a signal. Figure (15)
illustrates the average transistor losses of the DC/DC converter and the rectified DC voltage. Although switching losses are relatively small, the inability to compensate the DC voltage and the significant THD which was found to be (206 %) made the diode bridge an unapplicable solution as an EV charger.
600
400
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IZ
200 0
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Fig. 15. Average Switching Losses and Rectified DC Voltage for (Diode bridge + Phase-shifted Converter) case
Figure (16) shows the battery states response to the combination of the Vienna rectifier and resonant LLC converter. Significant fluctuations in the current were observed that are related to the nature of the selected DC/DC converter. The nominal level of the drown current, however, does not reflect the reference set level which may be due to the employed frequency-based control method and not having enough controllability over the transistor setting of the converter. On the other hand, this current tremendously accelerated the charging process and the battery charged faster than in the previous case. The average switching losses exhibited in figure (17) are relatively large which opposes the whole concept of utilizing a resonant-based converter. Again, this might be related to the selected basic control method and the way it is regulating the converter. DC rectifier voltage is larger than in the previous case, though a certain dip in the response was recorded which
corresponded to the increased switching losses. For this combination, the THD simulation was found to be (5.7 %) which violates the (5 %) limit set by the standers.
20000
<
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CD 400
% 200
I 0
0.76 0.78 Of
0.1 0.2 0.3 0.4 0.5 0.6 0.7 время (сек.)
0.8 0.9
0.1 0.2 0.3 0.4 0.5 0.6 0.7 время (сек.)
Fig. 16. Battery Response to (Vienna rectifier + Resonant LLC Converter) Charger
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0,9 1 время (сек.)
380.5
380 0.592 0.596
50.01
0.8 0.9 1
Fig. 17. Average Switching Losses and Rectified DC Voltage for (Vienna rectifier + Resonant LLC Converter) case
When the Vienna rectifier is replaced with an active front end, there were no noteworthy changes observed in the battery response results demonstrated in figure (18). On the other hand, figure (19) shows a smother DV voltage response but with relatively slower transient characteristics. Moreover, the average switching losses still experience a high peak with relatively high steady-state losses.
Fig. 18. Battery Response to (AFE + Resonant LLC Converter) Charger
Fig. 19. Average Switching Losses and Rectified DC Voltage or (AFE + Resonant LLC Converter) case
Hence, it is evident that these losses are the product of the basic nature of the resonant LLC circuit and the employed control system. However, the THD was found to be (2.7 %) which is well below the required limit.
Figure (20) demonstrates the battery response when a phase-shifter converter is incorporated with Vienna rectifier. Since the used control method is well-defined and fully modifiable, the level of the battery current can be changed according to the required reference current with an instantaneous effect on the results. However, a nominal (39 A) reference has been used corresponding to some practical examples reviewed in the literature. The battery voltage is fairly stable at the selected time scale. However, is slowly and gradually increasing toward the full charge voltage.
Fig. 20. Battery Response to (Vienna rectifier + Phase-shifted Converter) Charger
In figure (21), the voltage response is quite nicely shaped with a fast transient response. Although the DC/DC converter part has no control over the input rectified DC voltage, by substituting the resonant converter with a phase-shifted converter the DC bus quality significantly improved. Furthermore, a tremendous decrease in the average switching losses was recorded as compared to the LLC converter case while the THD was found to be (2.76 %).
Fig. 21. Average Switching Losses and Rectified DC Voltage for (Vienna rectifier + Phase-shifted Converter) case
When the Vienna-type rectifier in the previous simulation is replaced by AFE, the voltage and current of the battery experienced higher chattering as can be seen in figure (22).
Fig. 22. Battery Response to (AFE + Phase-shifted Converter) Charger
The performance, however, is maintained and the efficiency of the compacted charger did not vary. Figure (21) shows the DC response of the tested charger. The response is found to be slower but without overshoot which has been experienced in the (Vienna + Phase-shifted converter) case. The average switching losses is quite acceptable while this combination recorded the lowest THD response with (2.03 %).
X
750 -1-1-1-1-1-1-1-1-1-
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
время (сек.)
Fig. 21. Average Switching Losses and Rectified DC Voltage for (AFE + Phase-shifted Converter) case
Finally, to make a comprehensive comparison between EV chargers, the bidirectional charger capabilities had to be tested and verified. The only suitable combination to enable such functionality is to use the AFE as a rectifying circuit and dual active bridge DAB as DC/DC converter. The DAB is controlled by a phase shift algorithm with a small modification in expanding the range of the phase control to (180°) Figure (22) demonstrates the battery response to the bidirectional charger where the battery charged for 0.2 seconds and then started to discharge to the grid. This can be observed from the sign of the battery current which flipped from negative in the case of charging to positive when discharging. Meanwhile, the battery voltage slightly changed which indicates that the controller maintained perfect operation. The THD was found to be (2.07 %) while the average losses were similar to the previous case.
О 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
время (сек.)
500
450
о-400
со
50.0005
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485 - 484.5 V : 0.160.19 0.2 0.220.24 |
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
время (сек.)
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
время (сек.)
Fig. 22. Battery Response of Bidirectional Charger
8. Future Trends
In this section, trending research topics on EV charging facilities are provided. This small collection of topics provides futuristic opportunities for researchers aiming to participate in developing the field. It is, however, worth mentioning that these topics are generally focused on the application level of the EV charger instead of its internal design.
8.1. Renewable Energy based and Multi-port Charging
This concept means that the EV charger is operated in a smart Microgrid situation where different resources like energy storage devices, local generators including renewable energy, and smart power management technologies are utilized in one coherent structure to provide stable, and probably even sustainable, operation [79]. It is referred to as multi-port charging because the charger incorporates different DC and AC sources integrated directly into the proper stage. Photovoltaic-based charging has been one of the most developed forms of multi-port charging due to the convenience of simply integrating the output DC voltage of the solar panel converter to the DC bus of the charger's DC/DC stage [15, 80, 81]. The additional integrated resources can increase the overall charger efficiency and improve power quality by preventing load shading during peak hours. Addi-
tionally, the extra power can be used to inject active and reactive power back into the Microgrid to perform certain services. The theoretical setup for such an operation has been well-developed in the literature by utilizing concepts like droop grid-forming controllers to sustain the operation of domestic loads while charging the EV [82]. The main difference between multiport chargers is the configuration of the DC/DC stage which enables the integration of N number of resources. In [15, 81], a solar panel has been incorporated into the design using a two-port structure. The PV solar system employed a unidirectional converter while the rectifier and the DC/DC converter were bidirectionally operated. A charger that embodies a triple active bridge, AC/DC active rectifier, and PV solar panel was developed to integrate N number of DC generators using the multi-winding transformer [83]. This design offered higher power density, higher efficiency, and galvanic isolation for multiple connected resources. However, it suffered from hard switching at high power delivery due to the configuration of the triple converter. Finally, this multi-port configuration resembles the actual structure of a non-residential EV charging station because it can service many connected EVs at the same time due to its multiple output transformers capabilities. The research in [84] addressed such an application by proposing an optimized charging technique that reduced the cost of operation. The design included a PV solar system which has been utilized to boost efficiency.
8.2. Wireless Charging
Wireless charging had tremendous success with small electronic devices which offered a promising future for the technology in the field of EV charging. Wireless power transfer WPT has the advantage of being flexible, convenient, safe, and compatible with automated applications [85]. Near-field wireless charging is mainly classified into capacitive, inductive, and resonance charging. However, according to [1], inductive charging occupied the vast majority of the research in this field due to the associated high efficiency and simple maintenance. In these methods, the power transmitter and the receiver are placed within close range while the charging process is performed. On the other hand, optic and microwave charging methods have been developed for far-field charging which does not require close approximation between power-exchanging devices. Nevertheless, they are still underdeveloped with currently achieved efficiency of less than 20 % which made them cost-ineffective. On the contrary, near-filed methods are well-
established both in the literature and in practice and have relatively high efficiency with inherent galvanic isolation. Many practical considerations of wireless inductive chargers have been provided in [86] with a special focus on the recent on-road technologies. The road, in this case, is embedded with small transmitting coils while the vehicle is equipped with a pickup coil. Although this allows the vehicle to be charged continuously while deriving on the track, many problems related to the cost of the infrastructure, mutual negative inductance between the transmitters, and the synchronization between transmitting and pickup coils are also discussed in the research. Another research pushed technological concepts further by proposing a dynamic wireless charging system that enables the exchange of power between two moving vehicles [87]. Although the premise of the technology is remarkable, application with human drivers can create hazardous situations.
8.3. Autonomy
This indicates that the vehicle is navigated using specialized computers and navigation sensors. This technology has been realized recently previous years to increase road safety, reduce congestion and environmental footprint, and boost personal productivity. This can be ensured by a high computational device that operates to calculate the best route and optimize the car driving style to match the internal battery state of charge. However, greater computational power requires larger power demand [9]. Therefore, an auxiliary battery is needed to supply the extra functionality which opens the question of redesigning the entire energy supply system of the vehicle to be more viably operated. This leads us again to the wireless charging principles discussed previously which can provide such efficiency and autonomy. Moreover, this functionality generates more questions related to the previously reviewed classical EV chargers and their applicability in such scenarios.
8.4. Vehicle to Grid V2G Technology
This is the most popular futuristic technology addressed in the literature. This is since EVs can be used to alleviate the grid-related issues that they cause by offering their stored energy during times of need. These issues are generated by the unplanned fast charging of a group of electric vehicles which may result in power quality degradation, reduced grid stability, voltage and frequency deviation, increased peak loading, downgraded system
reliability, and overloading [88]. The research [89] analyzed the impact of fast charging of multiple EVs simultaneously and found a significant change in the power demand profile during the charging period. The research concluded that advanced technologies like the integration of renewable energy sources and utilization of V2G technologies can assist in minimizing the implications. Enabling this technology requires the power electronic converters of the EV charger to be naturally bidirectional such that the energy can be exchanged between the battery and the grid at any instant [14]. The extracted power can be employed to perform grid services including peak shaving, voltage and frequency regulation, injecting reactive power to enhance the power quality near industrial sites, and harmonic filtering. The adoption of this technology becomes more valuable when a fleet of electric vehicles is connected to a multi-port charging station which offers more energy for flexible manipulation [90]. However, this adds more complexity to the distribution network since specialized intelligent devices are needed to perform the management and scheduling of the charging and discharging maneuvers of EVs. Extensive research studies have been conducted on the V2G technology that explored topics like the practical implementation of this technology, incentives and pricing schemes that encourage participants, the effect of the technology on the health of the battery system, and the advanced management and control system developed to perform the power exchange. However, we will not dive into these topics due to their vastness and direction which is out of the topic of this paper.
9. Conclusion
The main contributor to the extensive adoption of EVs is the increased capability of the charging facility that they can be considered a viable and reliable transportation. In this article, technologies related to EV charging systems are reviewed and evaluated. The research focused on the power electronic components of the EV charger and different variations and combinations that have been used both in the literature and practice. Furthermore, the article addressed a few related design topics like charging strategies and soft/hard switching. A simulation-based comparison between different chargers was conducted in MatLab environment with the focus on battery response characteristics, switching losses, and THD on the input side of the charger. In light of the provided comparison, this research recommends further development of a charging station that composes a Vienna
rectifier and phase-shifted DC/DC converter since it yielded the best performance among the tested combinations. Despite this recommendation, it is worth noting that this research tested the basic circuit configuration of each converter which was controlled with a primary-type controllers. Other research in this field may claim the superiority of different charger configurations based on, structurally, more advanced converters or more sophisticated control systems.
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About the authors
Haider M. Jassim (Yekaterinburg, Russian Federation) - Graduate Student of the Department "Electric Drive and Automation of Industrial Installations" of the Ural Energy Institute Ural Federal University named after
the first President of Russia B.N. Yeltsin (620002, Yekaterinburg, 19, Mira str., e-mail: khdzhassim@urfu.ru).
Anatoly M. Zyuzev (Yekaterinburg, Russian Federation) - Doctor of Technical Sciences, Associate Professor of the Department of "Electric Drive and Automation of Industrial Installations" Ural Energy Institute Ural Federal University named after the first President of Russia B.N. Yeltsin (620002, Yekaterinburg, 19, Mira str., e-mail: a.m.zyuzev@urfu.ru).
Aleksey V. Kostylev (Yekaterinburg, Russian Federation) - Ph. D. in Technical Sciences, Associate Professor, Head of the Department "Electric Drive and Automation of Industrial installations" of the Ural Energy Institute of the Ural Federal University named after the first President of Russia B.N. Yeltsin (620002, Yekaterinburg, 19, Mira str., e-mail: a.v.kostylev@urfu.ru).
Mikhail V. Mudrov (Yekaterinburg, Russian Federation) - Ph. D. in Technical Sciences of the Department "Electric Drive and Automation of Industrial Installations" of the Ural Energy Institute of the Ural Federal University named after the first President of Russia B.N. Yeltsin (620002, Yekaterinburg, 19, Mira str., e-mail: m.v.mudrov@urfu.ru).
Andrey I. Khabarov (Yekaterinburg, Russian Federation) - Ph. D. in Technical Sciences of the Department "Electric Drive and Automation of Industrial Installations" of the Ural Energy Institute of the Ural Federal University named after the First President of Russia B.N. Yeltsin (620002, Yekaterinburg, 19, Mira str., e-mail: tempaih@yandex.ru).
Сведения об авторах
Джассим Хайдер Майтам (Екатеринбург, Российская Федерация) - аспирант кафедры «Электропривод и автоматизация промышленных установок» Уральского энергетического института Уральского федерального университета им. первого Президента России Б.Н. Ельцина (620002, Екатеринбург, ул. Мира, 19, e-mail: khdzhassim@urfu.ru).
Зюзев Анатолий Михайлович (Екатеринбург, Российская Федерация) - доктор технических наук, доцент кафедры «Электропривод и автоматизация промышленных установок» Уральского энергетического института Уральского федерального университета им. первого Президента России Б.Н. Ельцина (620002, Екатеринбург, ул. Мира, 19, e-mail: a.m.zyuzev@urfu.ru).
Костылев Алексей Васильевич (Екатеринбург, Российская Федерация) - кандидат технических наук, доцент, заведующий кафедрой
«Электропривод и автоматизация промышленных установок» Уральского энергетического института Уральского федерального университета им. первого Президента России Б.Н. Ельцина (620002, Екатеринбург, ул. Мира, 19, e-mail: a.v.kostylev@urfu.ru).
Мудров Михаил Валентинович (Екатеринбург, Российская Федерация) - кандидат технических наук кафедры «Электропривод и автоматизация промышленных установок» Уральского энергетического института Уральского федерального университета им. первого Президента России Б.Н. Ельцина (620002, Екатеринбург, ул. Мира, 19, e-mail: m.v.mudrov@urfu.ru).
Хабаров Андрей Игоревич (Екатеринбург, Российская Федерация) - кандидат технических наук кафедры «Электропривод и автоматизация промышленных установок» Уральского энергетического института Уральского федерального университета им. первого Президента России Б.Н. Ельцина (620002, Екатеринбург, ул. Мира, 19, e-mail: tempaih@yandex.ru).
Поступила: 21.04.2023. Одобрена: 30.05.2023. Принята к публикации: 01.09.2023.
Финансирование. Исследование не имело спонсорской поддержки.
Конфликт интересов. Авторы заявляют об отсутствии конфликта интересов по отношению к статье.
Вклад авторов. Все авторы сделали эквивалентный вклад в подготовку статьи.
Просьба ссылаться на эту статью в русскоязычных источниках следующим образом:
Топологии и технологии станций быстрой зарядки электромобилей: обзор и сравнение / Х.М. Джассим, А.М. Зюзев, А.В. Костылев, М.В. Мудров, А.И. Хабаров // Вестник Пермского национального исследовательского политехнического университета. Электротехника, информационные технологии, системы управления. -2023. - № 46. - С. 5-46. DOI: 10.15593/2224-9397/2023.2.01
Please cite this article in English as:
Jassim Haider M., Ziuzev A., Kostylev A., Mudrov M., Khabarov A. Topologies and Technologies of Electric Vehicle Fast Charging Station: Review and Comparison.
Perm National Research Polytechnic University Bulletin. Electrotechnics, information technologies, control systems, 2023, no. 46, pp. 5-46. DOI: 10.15593/22249397/2023.2.01
