Battery charging station for electric vehicles based on bipolar dc power grid with grid-to-vehicle, vehicle-to-grid and vehicle-to-vehicle operation modes

This paper proposes an electric vehicle (EV) battery charging station (EV-BCS) based on a bipolar dc power grid with the capabilities of returning energy back to the power grid (vehicle-to-grid – V2G mode), as well as to perform power transfer between different EVs connected to the EV-BCS without drawing power from the power grid (vehicle-to-vehicle – V2V mode), besides the traditional battery charging operation (grid-to-vehicle – G2V mode). The proposed EV-BCS is modular, using three-level bidirectional dc-dc converters. In this paper, for simplicity reasons, only two converters, and hence two EVs, are considered in order to validate the previously referred operation modes. Furthermore, unbalanced operation from the EVs side is also considered for all the operation modes, aiming to consider a real scenario of operation. Simulation results verify the correct operation of the EV-BCS in all cases, with balanced and unbalanced current consumption from the EVs resulting always in balanced currents from the bipolar dc power grid side

Electric Vehicles Charging Technology Review and Optimal Size Estimation

AbstractMany different types of electric vehicle (EV) charging technologies are described in literature and implemented in practical applications. This paper presents an overview of the existing and proposed EV charging technologies in terms of converter topologies, power levels, power flow directions and charging control strategies. An overview of the main charging methods is presented as well, particularly the goal is to highlight an effective and fast charging technique for lithium ions batteries concerning prolonging cell cycle life and retaining high charging efficiency. Once presented the main important aspects of charging technologies and strategies, in the last part of this paper, through the use of genetic algorithm, the optimal size of the charging systems is estimated and, on the base of a sensitive analysis, the possible future trends in this field are finally valued

Review of Electric Vehicle Charging Technologies, Configurations, and Architectures

Electric Vehicles (EVs) are projected to be one of the major contributors to energy transition in the global transportation due to their rapid expansion. The EVs will play a vital role in achieving a sustainable transportation system by reducing fossil fuel dependency and greenhouse gas (GHG) emissions. However, high level of EVs integration into the distribution grid has introduced many challenges for the power grid operation, safety, and network planning due to the increase in load demand, power quality impacts and power losses. An increasing fleet of electric mobility requires the advanced charging systems to enhance charging efficiency and utility grid support. Innovative EV charging technologies are obtaining much attention in recent research studies aimed at strengthening EV adoption while providing ancillary services. Therefore, analysis of the status of EV charging technologies is significant to accelerate EV adoption with advanced control strategies to discover a remedial solution for negative grid impacts, enhance desired charging efficiency and grid support. This paper presents a comprehensive review of the current deployment of EV charging systems, international standards, charging configurations, EV battery technologies, architecture of EV charging stations, and emerging technical challenges. The charging systems require a dedicated converter topology, a control strategy and international standards for charging and grid interconnection to ensure optimum operation and enhance grid support. An overview of different charging systems in terms of onboard and off-board chargers, AC-DC and DC-DC converter topologies, and AC and DC-based charging station architectures are evaluated

Implementation of SiC Power Electronics for Green Energy Based Electrification of Transportation

Increase in greenhouse gas emission poses a threat to the quality of air thus threatening the future of living beings on earth. A large part of the emission is produced by transport vehicles. Electric vehicles (EVs) are a great solution to this threat. They will completely replace the high usage of hydrocarbons in the transport sector. Energy efficiency and reduced local pollution can also be expected with full implementation of electrification of transportation. However, the current grid is not prepared to take the power load of EV charging if it were to happen readily. Moreover, critics are doubtful about the long-term sustainability of EVs in terms of different supply chain issues. The first step for tackling this problem from a research perspective was to do a thorough review of the details of charging in modern day grid. The downsides and lack of futuristic vision. Findings showed that implementing end to end DC based on green energy aided by SiC power electronics. To prove the findings analysis and modelling was done for SiC based charging network. A similar approach was implemented in EV powertrain development. The implementation of SiC power electronics in charging network showed lesser losses, higher thermal conductivity, lesser charging time. The effect on long term battery health and additional circuit was also observed. The cost of production can be reduced by volume manufacturing that has been discussed. In powertrain analysis and simulation the loss and heat reduction one shown on a component-by-component basis. Therefore, this research proposes a Silicon Carbide based end to end DC infrastructure based completely on solar and wind power. The pollution will further be reduced, and energy demands will be met

Design and Advanced Model Predictive Control of Wide Bandgap Based Power Converters

The field of power electronics (PE) is experiencing a revolution by harnessing the superior technical characteristics of wide-band gap (WBG) materials, namely Silicone Carbide (SiC) and Gallium Nitride (GaN). Semiconductor devices devised using WBG materials enable high temperature operation at reduced footprint, offer higher blocking voltages, and operate at much higher switching frequencies compared to conventional Silicon (Si) based counterpart. These characteristics are highly desirable as they allow converter designs for challenging applications such as more-electric-aircraft (MEA), electric vehicle (EV) power train, and the like. This dissertation presents designs of a WBG based power converters for a 1 MW, 1 MHz ultra-fast offboard EV charger, and 250 kW integrated modular motor drive (IMMD) for a MEA application. The goal of these designs is to demonstrate the superior power density and efficiency that are achievable by leveraging the power of SiC and GaN semiconductors. Ultra-fast EV charging is expected to alleviate the challenge of range anxiety , which is currently hindering the mass adoption of EVs in automotive market. The power converter design presented in the dissertation utilizes SiC MOSFETs embedded in a topology that is a modification of the conventional three-level (3L) active neutral-point clamped (ANPC) converter. A novel phase-shifted modulation scheme presented alongside the design allows converter operation at switching frequency of 1 MHz, thereby miniaturizing the grid-side filter to enhance the power density. IMMDs combine the power electronic drive and the electric machine into a single unit, and thus is an efficient solution to realize the electrification of aircraft. The IMMD design presented in the dissertation uses GaN devices embedded in a stacked modular full-bridge converter topology to individually drive each of the motor coils. Various issues and solutions, pertaining to paralleling of GaN devices to meet the high current requirements are also addressed in the thesis. Experimental prototypes of the SiC ultra-fast EV charger and GaN IMMD were built, and the results confirm the efficacy of the proposed designs. Model predictive control (MPC) is a nonlinear control technique that has been widely investigated for various power electronic applications in the past decade. MPC exploits the discrete nature of power converters to make control decisions using a cost function. The controller offers various advantages over, e.g., linear PI controllers in terms of fast dynamic response, identical performance at a reduced switching frequency, and ease of applicability to MIMO applications. This dissertation also investigates MPC for key power electronic applications, such as, grid-tied VSC with an LCL filter and multilevel VSI with an LC filter. By implementing high performance MPC controllers on WBG based power converters, it is possible to formulate designs capable of fast dynamic tracking, high power operation at reduced THD, and increased power density

Isolated Single-stage Power Electronic Building Blocks Using Medium Voltage Series-stacked Wide-bandgap Switches

The demand for efficient power conversion systems that can process the energy at high power and voltage levels is increasing every day. These systems are to be used in microgrid applications. Wide-bandgap semiconductor devices (i.e. Silicon Carbide (SiC) and Gallium Nitride (GaN) devices) are very promising candidates due to their lower conduction and switching losses compared to the state-of-the-art Silicon (Si) devices. The main challenge for these devices is that their breakdown voltages are relatively lower compared to their Si counterpart. In addition, the high frequency operation of the wide-bandgap devices are impeded in many cases by the magnetic core losses of the magnetic coupling components (i.e. coupled inductors and/or high frequency transformers) utilized in the power converter circuit. Six new dc-dc converter topologies are propose. The converters have reduced voltage stresses on the switches. Three of them are unidirectional step-up converters with universal input voltage which make them excellent candidates for photovoltaic and fuel cell applications. The other three converters are bidirectional dc-dc converters with wide voltage conversion ratios. These converters are very good candidates for the applications that require bidirectional power flow capability. In addition, the wide voltage conversion ratios of these converters can be utilized for applications such as energy storage systems with wide voltage swings

Experimental validation of a novel architecture based on a dual-stage converter for off-board fast battery chargers of electric vehicles

The experimental validation of a novel architecture of an off-board, three-phase fast battery charger for electric vehicles (EVs) with innovative operation modes is presented in this paper. The proposed EV fast battery charger is based on a dual-stage power converter (ac-dc and dc-dc) sharing the same dc link. The ac-dc stage is used as an interface between the power grid and the dc link. It is composed of the parallel association of two full-bridge voltage-source converters, and allows control of the grid current and of the dc-link voltage. The dc-dc stage is used as an interface between the dc link and the batteries. It is constituted by a bidirectional three-level asymmetrical voltage-source converter, and controls the flux of current during the EV battery charging process. Compared with the traditional solutions used for EV fast battery chargers, the proposed architecture operates as an interleaved converter, facilitating the reduction of the passive filters size, and the grid current harmonic distortion for the same switching frequency. Throughout the paper, the ac-dc and dc-dc stages, and the digital control algorithms are described in detail. The experimental validation was performed in a laboratory using a developed EV fast battery charger prototype, operating through the grid-to-vehicle and the proposed charger-to-grid modes, exchanging active, and reactive power with the power grid.ERDF - European Regional Development Fund()info:eu-repo/semantics/publishedVersio

Multilevel Converter Topologies for Utility Scale Solar Photovoltaic Power Systems

Renewable energy technologies have been growing in their installed capacity rapidly over the past few years. This growth in solar, wind and other technologies is fueled by state incentives, renewable energy mandates, increased fossil fuel prices and environmental consciousness. Utility scale systems form a substantial portion of electricity capacity addition in modern times. This sets the stage for research activity to explore new efficient, compact and alternative power electronic topologies to integrate sources like photovoltaics (PV) to the utility grid, some of which are multilevel topologies. Multilevel topologies allow for use of lower voltage semiconductor devices than two-level converters. They also produce lower distortion output voltage waveforms. This dissertation proposes a cascaded multilevel converter with medium frequency AC link which reduces the size of DC bus capacitor and also eliminates power imbalance between the three phases. A control strategy which modulates the output voltage magnitude and phase angle of the inverter cells is proposed. This improves differential power processing amongst cells while keeping the voltage and current ratings of the devices low. A battery energy storage system for the multilevel PV converter has also been proposed. Renewable technologies such as PV and wind suffer from varying degrees of intermittency, depending on the geographical location. With increased installation of these sources, management of intermittency is critical to the stability of the grid. The proposed battery system is rated at 10% of the plant it is designed to support. Energy is stored and extracted by means of a bidirectional DC-DC converter connected to the PV DC bus. Different battery chemistries available for this application are also discussed. In this dissertation, the analyses of common mode voltages and currents in various PV topologies are detailed. The grid integration of PV power employs a combination of pulse width modulation (PWM) DC-DC converters and inverters. Due to their fast switching nature a common mode voltage is generated with respect to the ground, inducing a circulating current through the ground capacitance. Common mode voltages lead to increased voltage stress, electromagnetic interference and malfunctioning of ground fault protection systems. Common mode voltages and currents present in high and low power PV systems are analyzed and mitigation strategies such as common mode filter and transformer shielding are proposed to minimize them