Stability Analysis And Control Of Power Conversion System In Charge-Discharge-Storage Power Station

To deal with energy and environmental challenges effectively and achieve the sustainability of automobile industry, the development of EV (Electric Vehicles) has become a common choice for global automotive industry in recent years. Construction of energy supply facilities is the basis of promotion of the EV, which also ushered in a period of rapid development with the industrialization of EV. Integrated EV power plant of charge, discharge and storage is a kind of multi-function smart power plants, which can complete these functions, such as battery energy injection, feedback energy to grid, accepting power dispatching from grid, economy operation. The construction and operation of integrated EV power plant can realize the integration of power station and smart grid effectively. And it will be the suitable mode of EV power plant in future. In this paper, basic theory, design methods and control technique of power conversion system in the EV power plant are studied and discussed. And some key issues are focus about charging and discharging system.Lithium-ion batteries are usually used to store energy in the EV. Operating characteristics of lithium-ion battery determine that it can not overcharge and overdischarge. Good capacity injection technology is the key to charge the battery. Considering the characteristics of lithium-ion battery, a constant current and constant voltage charging control strategy was presented in this paper A 3-kW charging device was designed and verified the proposed strategy, which adopted phase-shifted full-bridge topology.Nowadays the battery standards of EV are not uniform and the batteries of different manufacturers have different voltage or current rating. To meet the different voltage or current level of battery charging requirements, modular structure can be adopted. A hybrid combination structure of charging system was proposed in this paper. For the convenience to analyze the combination system, this paper presented a kind of modelling method based on equivalent controlled source model. And the nature of power sharing of the combination system was described. Finally, power sharing controller was designed and verified at a set of charging experiment system. Further study about stability of the voltage source in parallel and current source in series was presented.The battery packs of integrated EV power plant can be charged at off-peak hours in the evening and discharged at peak hours during the day, which improved battery life and commercial value. Grid-connected discharging devices, which used as a power control uint between storage battery and grid, can meet the need of energy feedback to the grid. This paper studied control technology of the discharge device in weak grid, and focued on its current THD (Total Harmonic Distortion). Two-stage topology of discharge device and its coordination mechanism were introduced. Then the defects of LC grid-connected mode were presented and an adaptive PIR control strategy was proposed based on grid impedance detection. Due to the resonance phenomenon of LCL filter which could affect the grid-connected current quality of electric energy, a harmonic compensation active damping method was proposed. The method introduced can reduce the number of sensor, save system cost and decrease unreliable factors caused by the excessive introduction of sensors.Among the integrated EV power plant, multiple sets of discharge devices consist of energy feedback system. The interaction of multi-inverters system poses some problems. This paper focuses on the modeling and stable operating characteristics of multi-inverter grid-connected system. Equivalent model of multi-inverter grid-connected system was deduced based on circuit network theory. And the output impedance model and its characteristics of LC and LCL grid-connected inverter were presented. A current source impedance ratio criterion was proposed, and then stability was analyzed based on the criterion.In order to improve power supply reliability and operating economics of the power plant, the utilization of renewable energy was considered by some domestic and international EV charging station. In this paper, LPSP (Loss of Power Supply Probability) and LCE (Levelied Cost of Energy) was adopted as evaluation indicator to analysis system capacity configuration. Vanadium redox flow battery and lead-acid battery were selected as energy storage unit of the EV power plant. Based on the difference of electrochemical characteristics and operating costs, the comparative analysis of these two batteries among capacity configuration was done. Because of superior characteristics, Vanadium redox flow battery could get a better economy with large-scale access.