Bidirectional electric vehicle charging system based on Z-source converters and related PWM control system

Sensor network has attracted worldwide attention over two decades, particularly with the proliferation in Micro-Electro-Mechanical Systems (MEMS) technology which has facilitated the development of smart sensors. Unlike traditional networks, wireless sensor network has its own resource constraints which include a limited amount of energy, short communication range, low bandwidth, and limited processing and storage in each node. This dissertation presents the development of the cross layer optimization to solve the compensation for overload, latency or other mismatch of requirements and resources without considering the hierarchical structure of Open System Interconnection (OSI) model with strict boundaries between layers. To implement the cross layer optimization of link layer and MAC layer, in this thesis, interference mitigation without feedback channel in the wireless body area network (WBAN) and feedback overhead reduction in the smart electric vehicle charging system are investigated as applications. Firstly, the link layer optimization in the wireless body area network is presented to maximize link capacity between transmitter and receiver by considering interference mitigation. Pseudo orthogonal resource allocation patterns are proposed to mitigate the interference in the wireless body area network. To design pseudo orthogonal resource allocation patterns, it is necessary to analyze the properties of a pseudo orthogonal code (POC). By considering the properties of the distance matrix of a pseudo orthogonal code, the low bound of the length of the pseudo orthogonal code is theoretically calculated. However, to optimize data throughput of the resource allocation, the trade-off relationship between the orthogonal properties of a POC and the quantity of resource allocation of WBAN is considered. To mitigate the collisions, the two dimensional resource allocation patterns are proposed, where random assignment of codewords to time domain and that of frequency sub-channel offsets are considered. In addition, based on the properties of correlation and cyclic shift on the POC, the transmission efficiency of WBAN is calculated. Based on the low bound of a POC and the transmission efficiency, the optimal quantity of resource allocation of each WBAN is theoretically analyzed, which is exactly the ratio of the length of a POC to the number of WBANs in the system. The simulation results illuminate that the theoretical low bound of the proposed scheme is more close to the real structure of POC compared to the conventional schemes. The other application of WSN is the electric vehicle (EV) charging system in the MAC layer, which optimizes the scheduling of data transmission. The penetration of EV charging system imposes a heavy burden on the conventional power distribution system, so that the coordination of EV charging demands is required via a bi-directional real time monitoring system. However, it may cause the performance degradation in the whole EV charging system due to the significant control signal overhead. To mitigate the control signal overhead from electric vehicles to a central controller, the threshold based charging scheme in electric vehicle charging system is proposed, which only EVs with low level of battery state of charge below the predetermined charging threshold can transmit their charging request to controller. In the simulation results, the proposed threshold based charging scheme can achieve the reduction of the control signaling overhead and the satisfactory charging performance.

Misalignment between charging coils is an unavoidable problem in all electric vehicle (EV) charging systems that are based on wireless power transfer (WPT) technology. This is because variations in both self- and mutual inductances of charging coils due to coil misalignments significantly affect the charging rate and efficiency of the EV charger. As a solution, this article proposes a new control technique that maintains the rated charging power level at optimum efficiency in spite of large coil misalignments. To compensate for the variations in inductances, the technique uses the information extracted from input impedance to operate the system essentially at unique converter voltages with zero phase angle, ensuring that charging will take place at rated power with optimal efficiency despite any pad misalignments. The article presents a comprehensive mathematical model, describing the theoretical basis of the proposed control philosophy. To demonstrate the validity of the proposed control concept, a 1-kW bidirectional WPT EV charging system is built and results are presented under misaligned coil conditions. Results convincingly indicate that the proposed controller is efficient and capable of maintaining the rated charging rate despite large coil misalignments and without any dedicated wireless communication.

Today, almost the entire world is experiencing the so-called transport revolution associated with the widespread market introduction and use of both hybrid vehicles and electric vehicles, which in the European Union are collectively referred to by the abbreviation PEV – Plug-In Electric Vehicle. Each year, the number of electric vehicles continues to increase, which has already led to a situation where the issue of timely charging has become a significant challenge for users. Naturally, charging infrastructure is also developing; however, this development is accompanied by a growing level of electricity consumption, which in turn raises another important issue, namely the limitation of energy resources. In order to address these challenges, it is necessary to analyze electric vehicle charging systems, charging modes, and the capabilities of urban power systems. The problems of integrating electric vehicles into electric power systems have been considered in a significant number of scientific studies, particularly in publications indexed in the Scopus database [1–10]. The purpose of this article is to analyze technical solutions for electric vehicle charging systems from the perspective of resource conservation and electric drive operation, as well as to substantiate engineering approaches aimed at reducing energy losses in urban electric power networks. The main approaches to solving these problems can be structured as follows: Strategy of vertical integration and development of proprietary networks. Partnerships and joint ventures with vehicle manufacturers. Public–private partnerships (PPP) and financing through government programs. Integration with renewable energy sources (RES) and energy storage systems. Focus on segmented solutions and the development of charging hubs. The electric vehicle charger is an integral part of the overall electric drive system, as it directly affects the operating modes of the traction electric motor through the parameters of the battery pack. From a resource conservation perspective, reducing losses in the power elements of the electric drive, particularly in semiconductor switching devices and passive filter components, is of primary importance. Resource conservation in electric vehicle charging systems is achieved through the optimization of charging schedules, limitation of peak power demand, and improvement of the energy efficiency of power converters. An example calculation is proposed for an AC electric vehicle charging system integrated into an urban power grid, taking into account the principles of resource conservation and its impact on the electric drive. The study concludes that the most resilient solutions are hybrid strategies that combine private initiative (technology and efficiency), government support (risk mitigation), strategic partnerships (access to land and customers), and orientation toward future technologies (bidirectional charging and virtual power plants). The development of charging stations should focus on intelligent, high-speed solutions integrated with energy storage systems and unified by a single digital platform

The increasing growth of the technology and industry of electric propulsion, and consequently the growth of the industry of electric energy storage systems, including batteries, have raised challenges such as optimizing the charging process and storage of electric energy. One of the important factors in optimizing the charging process is reducing the time interval. Hence, today, topologies such as fast charging and stations equipped with this topologies are expanding. Quick charging topologies reduce the length of the charging process by optimizing the electric charge circuit and optimizing the design of switching elements and its control system. This paper first examines the electric vehicle charging system in terms of the standards that classify the input voltage level as well as the technologies that increase the flexibility and efficiency of the electric vehicle charging system. Technologies such as unidirectional and bi-directional charging system, inductive and conductive charging system, integrated and non-integrated systems are presented and discussed in this article. In the second step, these systems are transformed into switching components and features such as the possibility of development with renewable energy production systems, the possibility of injecting power from the electric vehicle energy storage system into the power grid to provide part of the power required at peak demand and also The complexity and multiplicity of key elements have been examined and compared.

The power factor of industrial facilities is typically inductive. The case study in this paper was based on a typical Malaysian 11-kV on-grid industrial system with renewable energy sources and electric vehicle charging station connected. The integration of renewable energy sources reduces energy consumption from the grid; it consecutively reduces greenhouse gas emissions. However, the integration of renewable energy sources such as solar photovoltaic operating at unity power factor results in a reduction of the industry’s power factor. According to the Malaysian Distribution Code, the power factor of a medium voltage industrial system should be more than 0.85 lagging. A long-term low power factor will reduce the related electrical equipment lifespan and increase the monthly electricity bills. A classic method to overcome this issue was by installing reactive power compensator devices, such as the synchronous condenser, static VAr compensator and static synchronous compensator. Studies had revealed that solar photovoltaic with appropriate control system design could perform short-term reactive power compensation. The control techniques used are either power factor control, active power control, reactive power control or any combination of them. However, neither the reactive power compensator devices nor the solar photovoltaic with a control system can regulate the industry’s power factor to an intended value throughout its operation. Thus, this paper presents a simple, relatively cost-effective design of a master power factor controller that is capable of regulating the industry’s power factor to an intended value throughout its operation with a single preset reference. In this research, an industry-grade system comprises an industrial load installed with a power factor-controlled capacitor bank, a power factor-controlled solar photovoltaic system, a bidirectional current-controlled electric vehicle charging system based on CHAdeMO 1.1 standard charging protocol and a master power factor controller was designed using the Matrix Laboratory/Simulink software. This paper has provided simulation results as proof that each of the designed equipment was functioning appropriately. The results also proved that the proposed master power factor controller was capable of regulating the power factor of the industrial system to above 0.85 lagging throughout its operation.

The electric vehicle (EV) charging systems employ dc-dc power converters as EV chargers. Currently, the expected high penetration of electric vehicle (EV) demands for the integration of the renewable energy sources (RES) into the electric vehicle charging system as a promising solution to cut down the load on the electrical grid. These systems interface with RES by implementing dc-dc power converters. Moreover, with the advent of high-power dc charging, the charging efficiency is largely dependent on the performance of the power converters. Hence, to improve the charging, the soft switching dc-dc converters are implemented to maintain low switching losses and to achieve high-efficiency operation. This paper reviews the non-isolated, soft switching dc-dc power converters for EV charging application. For this purpose, different types of soft switching topologies, namely the snubber, the series resonant, the shunt resonant and the pulse frequency modulated converters are investigated. The advantages and the disadvantages associated with these converters are highlighted. Furthermore, to perform a comparative evaluation, the topologies are simulated in a standard simulation platform. Consequently, the relative standing of the converters depending on several parameters, i.e. the component count, the output voltage and current ripple, the soft switching range, and the power losses are established. Finally, based on these results, the optimum applicability of the converters in the EV charging application is determined.
 GUB JOURNAL OF SCIENCE AND ENGINEERING, Vol 6(1), Dec 2019 P 60-74

This study presents the design and performance evaluation of a bidirectional electric vehicle charging system integrating solar photovoltaic energy with an Artificial Neural Network based control strategy. The proposed architecture employs a modified Single-Ended Primary Inductor Converter capable of supporting both Grid-to-Vehicle and Vehicle-to-Home operating modes while maintaining stable bidirectional power flow between the grid, photovoltaic source, and EV battery. The ANN controller dynamically regulates the duty cycle of the MOSFET switches using battery current feedback and reference current signals, enabling adaptive control under varying solar irradiance and grid conditions. Simulation results indicate that the proposed system achieves charging efficiencies above 90% while maintaining stable operation for both 72 V and 240 V EV battery configurations. Compared with conventional proportional–integral control approaches, the ANN controller demonstrates faster transient response and improved current regulation during dynamic operating conditions. The integration of solar photovoltaic energy further reduces reliance on grid power and enhances renewable energy utilization in EV charging infrastructure. These results indicate that the proposed ANN-controlled bidirectional charging system provides an efficient and flexible solution for renewable-integrated EV charging applications.

The traditional on-board charging system can only realize the one-way transmission of electric energy from the grid to the power battery. To address this issue, this paper proposes a bidirectional on-board charging system based on a three-phase wye-wye connected CLLLC resonant converter. It adopts a two-stage structure, the front-stage is a bidirectional totem pole converter and the rear-stage is a three-phase wye-wye connected CLLLC resonant converter. Based on the grid characteristics, the working principle of the front-stage converter is analyzed, the equivalent circuit model of the rear-stage converter is derived using fundamental wave analysis, and the voltage gain, impedance characteristics and zero voltage turn-on conditions are analyzed. The parameters of input inductor, DC bus capacitance and resonant network are calculated according to the design specifications of the bidirectional on-board charging system. The control strategy of bidirectional vehicle charging system is studied. The input current and input voltage are kept in the same phase by establishing the small signal circuit model of the front-stage bidirectional totem pole converter. The rear-stage three-phase wye-wye connected CLLLC resonant converter adopts pulse frequency modulation to realize constant voltage and constant current output of the charging system. Simulation software was used to simulate the bidirectional on-board charging system, and a 3.3 kW prototype was trial-produced according to the main circuit parameters. Simulation and experimental results verify the correctness of the design of the bidirectional on-board charging system.

For the bidirectional wireless electric vehicle charging system, when both the primary and secondary converters are active, the phase synchronization between the two converters are necessary to control the power flow direction. This article proposes a new phase synchronization method by tracking the maximum (or minimum, depending on the power flow direction) value of the output current, without auxiliary hardware or the real-time communication between the primary and secondary sides. First, the relationship between the output current and the phase difference of the control signals is derived. It is found that the maximum output current is determined by the relative phase-shift angle (time interval between the middle points of the primary and secondary voltages) and the internal phase-shift angles of the two converters (time interval when the output voltage equals to the dc-link voltage). Second, a new scheme for generating the control signals is proposed to ensure that the relative phase-shift angle is not influenced by the internal phase-shift angles. Third, based on the perturbation and observation method, a procedure is proposed to track the extreme value of the output current and obtain the target relative phase-shift angle for the phase synchronization state. Moreover, the relationship between the internal phase-shift angle and the transfer power is derived to regulate the magnitude of the transfer power, with the dead-time effect taken into consideration. Finally, experimental results verify the validity of the proposed method with different air gaps and power levels. The method is easy to be implemented, helpful for the optimal operation of the static and quasi-static wireless charging system and suitable for the bidirectional power flow.

<div class="section abstract"><div class="htmlview paragraph">This paper analyzes the leakage magnetic field generated by the Bi-Directional wireless charging system of Electric Vehicle(EV) and confirms the effect of the shielding coil in the Bi-Directional wireless charging system. In particular, in EV using the Inductive Power Transfer(IPT) method, the effective shielding coil position is proposed by analyzing the contribution of the leakage magnetic field of the Ground Assembly(GA) coil and the Vehicle Assembly(VA) coil according to the power transfer direction. Simulations were conducted using the WPT3/Z2 model of the standard SAE J2954, and it was confirmed that the GA coil contributed more to the leakage magnetic field due to the relatively large size compared to the VA coil regardless of power transfer direction. The same tendency was confirmed not only in alignment condition but also in misalignment condition, and it was also confirmed that the same tendency appeared in the situation where a larger current flows in the VA coil by inversely transferring power. As a result, it was concluded that the shielding coil should be located near the GA coil, which contributes greatly to the leakage magnetic field, and the simulation confirmed the effect of reducing the leakage magnetic field by about 66%.</div></div>

The large-scale integration of electric vehicle into the power grid impacts the stability of distribution grid with renewable and distributed energy sources. Therefore, there is a growing need for smart electric vehicle (EV) charging systems equipped with grid forming capability to provide ancillary services and ensure stability of distributed grid. This paper presents a grid-forming inverter (GFM) interfaced electric vehicle charging system employing droop control to enhance grid stability. The design and modeling of grid forming EV charging system is presented and implemented in Matlab/Simscape based simulation and experimentally validated using dSPACE MicroLabBox. Simulation and experimental results confirm that grid forming EV charging system has the ability to provide grid support under grid disturbances and regulate voltage and frequency under steady state and dynamic conditions. The outcomes of this research highlight the potential of GFM-enabled EV chargers as active grid participants, paving the way for resilient and flexible future distribution networks with high renewable and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$E V$</tex> penetration.

Voltage source and current source converters are used in industrial applications as either boost or buck converters for a defined power flow direction. These operational modes limit these converters to be utilized on their own in hybrid and electric vehicle (EV) applications. Z-source (impedance source) converters, on the other hand, have the capability to be operated as buck and boost converters to have a wide range of output levels. The boost ratio of the direct current link voltage of a Z-source converter is set by short-circuiting the phase legs of the converter and defining the overlap duration at each switching period. In order to have the optimum efficiency with the lowest possible total harmonic distortion, a modified space vector pulse width modulation method with an impedance network could be selected for closed-loop control of the quasi-resonant Z-source converter to drive permanent magnet synchronous motors (PMSMs). In this study, closed-loop vector-controlled drive systems built with two-level and three-level boosted voltage source converter topologies and two- and three-level quasi Z-source converters for field-oriented control of a PMSM in EV motor drive applications were compared under constant motor speed–constant load, constant speed–variable load and variable speed–constant load operating conditions.

This paper aims to investigate how an electric vehicle (EV) charger with a controller performs and affects the EV battery, integrated into the grid. A bidirectional electric vehicle charging system is designed and modeled in MATLAB/Simulink to evaluate its functionality & performance. The key questions of the study are how well the charger interacts with the grid and its effects on the battery voltage & current. The study is conducted via theoretical analysis and simulation work. The power electronics control algorithm is investigated based on total harmonic distortion (THD) analysis. Moreover, some methods for the design are presented and evaluated regarding how to improve the performance of the overall electric vehicle charger station integrated into a dynamic grid.

This paper introduces a cutting-edge solar photovoltaic (PV) tied electric vehicle (EV) charging system integrating a bilateral chopper. The system aims to optimize energy utilization and enhance grid interaction by allowing bidirectional power flow between the solar PV array, electric vehicle, and the grid. The bilateral chopper serves as a pivotal component, enabling seamless energy transfer, storage, and distribution. The proposed system incorporates advanced control algorithms to manage energy flow dynamically, considering variables such as solar irradiance, EV charging demands, and grid conditions. The bidirectional converter facilitates efficient energy exchange, allowing surplus solar energy to charge the EV and, conversely, enabling the EV to provide power back to the grid during peak demand or grid support scenarios. Key features of the system include real-time monitoring and control through a smart grid interface, enabling users to optimize charging schedules based on renewable energy convenience and grid conditions. The bilateral chopper enhances the system's flexibility, enabling it to operate in grid-tied, off-grid, or hybrid modes, contributing to increased sustainability and resilience in the overall energy ecosystem. This innovative solar PV tied electric vehicle charging system offers a compelling solution for promoting clean and sustainable transportation while effectively integrating non-conventional energy sources into the broader power grid. The research findings provide valuable insights into the feasibility, performance, and potential benefits of such integrated systems in the context of future smart and sustainable energy infrastructures.

This paper describes the design of an inductive interface for an electric vehicle (EV) charging system based on a coaxial winding power transformer. The inductive interface is a separable transformer providing a means to 'plug-in' an EV without the need for metal-to-metal contact of exposed conductors. The proposed design is 'universal' in that dimensions can be selected which will accommodate more than an order of magnitude range of power ratings without imposing significant performance degradation. Interface geometry standardization and the configuration of the core and windings are shown to have important effects on the demands on the user, the EV infrastructure, the distribution of stationary and mobile weight, and the power electronic converter requirements. Design methodology for the proposed approach is summarized and experimental results of a laboratory prototype are presented to verify the design theory.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>