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Configuration and Control of a MVDC Hybrid Charging Station of Electric Vehicles with PV/Battery/Hydrogen System
This paper presents a new supervisory control system (SCS) designed to maintain the power balance and obtain economic benefit by selling energy to the grid in a microgrid based on Z-source converters (ZSCs) with renewable energy, energy storage systems (ESSs), and charging station for electric vehicles (EV) connected to a medium voltage direct current (MVDC) link. The main components of the microgrid are a photovoltaic (PV) system, battery (BAT) and green hydrogen system with a fuel cell (FC), electrolyzer (LZ) and hydrogen tank as ESSs, a local grid connection and two units of fast chargers for EVs. Owing to the proposed configuration, the output voltages of the components can be adapted to the MVDC to control their output power and reduce the number of power converters compared to the common configuration without ZSCs. Thus, the configuration by itself and the SCS can be considered the main novelties of this paper. The simulation results and the hardware-in-the-loop tests show that the proposed system (ZSC-based configuration and SCS) is perfectly valid for the microgrid, and confirm the proper operation of the SCS to achieve an economic benefit from the use of the grid.
This paper presents a new Energy Management System (EMS) designed for the optimized operation of power sources of a hybrid charging station for electric vehicles (EV) and fuel cell vehicles (FCV). It is composed of a photovoltaic (PV) system, a battery and a hydrogen system as energy storage systems (ESS), a connection to the local grid, six fast charging units (rated power, 300kW) and a hydrogen supplier. The objective of the proposed EMS is to reduce the utilization costs of the ESS and make them work, as much as possible, around their maximum efficiency points. The optimization function depends on a cost prediction system that calculates the net present cost of the components from their previous performance and a fuzzy logic system designed for improving their efficiency. Finally, a Particle Swarm Optimization (PSO) algorithm is used to solve the optimization function and obtain the required power for each ESS. The behaviour of the proposed EMS is checked under MATLAB-Simulink environment for long term simulations (25 years, expected lifespan of the hybrid charging station). By comparing the EMS with a simpler one that also optimizes the costs but without considering the efficiencies, it is proved that the proposed EMS achieves better efficiency of the charging station (+7.35%) and a notably reduction in the loss of power supply probability (-57.32%) without compromising excessively its average utilization cost (+1.81%).
This paper presents a new bidirectional DC-DC converter with high gains, based on impedance source. The
design of the impedance network has been studied in step-up and step-down modes. The most significant innovations of
the proposed converter are the linearity of the high gains in step-up and step-down modes with respect to the cycle
variations and a full use of the duty cycle, very few passive and semiconductor elements are needed to implement the
converter. The switching techniques are very simple, since only the switching of a single transistor in each mode is required.
To improve efficiency, the cores of the inductors have been constructed with nanocrystalline material and the resistance
of Z-red has been reduced as much as possible. Finally, a laboratory prototype has been implemented.
A hybrid microgrid-powered charging station reduces transmission losses with better power flow control in the modern power system. However, the uncoordinated charging of battery electric vehicles (BEVs) with the hybrid microgrid results in ineffective utilization of the renewable energy sources connected to the charging station. Furthermore, planned development of upcoming charging stations includes a multiport charging facility, which will cause overloading of the utility grid. The paper analyzes the following technical issues: (1) the energy management strategy and converter control of multiport BEV charging from a photovoltaic (PV) source and its effective utilization; (2) maintenance of the DC bus voltage irrespective of the utility grid overloading, which is caused by either local load or the meagerness of PV power through its energy storage unit (ESU). In addition, the charge controller provides closed loop charging through constant current and voltage, and this reduces the charging time. The aim of an energy management strategy is to minimize the usage of utility grid power and store PV power when the vehicle is not connected for charging. The proposed energy management strategy (EMS) was modeled and simulated using MATLAB/Simulink, and its different modes of operation were verified. A laboratory-scale experimental prototype was also developed, and the performance of the proposed charging station was investigated.
For micro-grid systems dominated by new energy generation, DC micro-grid has become a micro-grid technology research with its advantages. In this paper, the DC micro-grid system of photovoltaic (PV) power generation electric vehicle (EV) charging station is taken as the research object, proposes the hybrid energy storage technology, which includes flywheel energy storage and battery energy storage. Flywheel energy storage is used to stabilize high frequency power fluctuations and some low frequency power. Lithium iron phosphate (LiFePO4) battery is used for balancing the reference power to maintain the DC bus voltage balance. Composition of the DC micro-grid and various operating modes are analyzed, a hierarchical coordinated control based on the power monitoring steps of the 5-layer DC bus voltage is proposed. Finally, simulation analysis is carried out on the MATLAB/Simulink software platform. Under different working states such as PV input power change, AC and DC loads change, EV charging condition change, and battery over-discharge, the proposed control strategy can make the DC bus voltage at different voltage layers effectively switch, and keep the DC bus voltage balance, thus to achieve flexible and reliable operation of the DC micro-grid system.
Although electric vehicles (EVs) are experiencing a considerable upsurge, the technology associated with them is still under development. This study focused on the control and operation of a medium-voltage direct-current (MVDC) microgrid with an innovative decentralized control system, which was used as a fast charging station (FCS) for EVs. The FCS was composed of a photovoltaic (PV) system, a Li-ion battery energy storage system (BESS), two 48 kW fast charging units for EVs, and a connection to the local grid. With this configuration and thanks to its decentralized control, the FCS was able to work as a stand-alone system most of the time though with occasional grid support. This paper presents a new decentralized energy management system (EMS) with two options to control the power sources of the FCS. The choice of the power source depends on the MVDC bus voltage, the state-of-charge (SOC) of the BESS, and the control option of the EMS. This control was tested by simulating the FCS, when connected to several EVs and under different sun irradiance conditions. Simulation results showed that the FCS operated smoothly and effectively, which confirms the feasibility of using this technology in EVs.
The use of distributed charging stations based on renewable energy sources for electric vehicles has increased in recent years. Combining photovoltaic solar energy and batteries as energy storage system, directly tied into a medium voltage direct current bus, and with the grid support, results to be an interesting option for improving the operation and efficiency of electric vehicle charging stations. In this paper, an electric vehicle charging station supplied by photovoltaic solar panels, batteries and with grid connection is analysed and evaluated. A decentralized energy management system is developed for regulating the energy flow among the photovoltaic system, the battery and the grid in order to achieve the efficient charging of electric vehicles. The medium voltage direct current bus voltage is the key parameter for controlling the system. The battery is controlled by a model predictive controller in order to keep the bus voltage at its reference value. Depending on the state-of-charge of the battery and the bus voltage, the photovoltaic system can work at maximum power point tracking mode or at bus voltage sustaining mode, or even the grid support can be needed. The results demonstrate the proper operation and energy management of the electric vehicle charging station under study.
Impedance Source Power Electronic Converters brings together state of the art knowledge and cutting edge techniques in various stages of research related to the ever more popular impedance source converters/inverters.
Significant research efforts are underway to develop commercially viable and technically feasible, efficient and reliable power converters for renewable energy, electric transportation and for various industrial applications. This book provides a detailed understanding of the concepts, designs, controls, and application demonstrations of the impedance source converters/inverters.
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