Study Of Charging-Discharging Control System For Electric Vehicle Chraging Pile With Storage

With the increasingly serious issues on environment and energy, electric vehicles (EVs) and new energy power generation (NEPG) emerge. The EVs with the advantages of energy conservation, environmental protection and high efficiency have become a main direction of modern automobile industry’s development, but EVs’ random charging behavior will influence the power grid. NEPG has gradually been an efficient way to reduce environmental pollution, meet load increasement, improve energy utilization efficiently and power supply reliability, but it has strong intermittence. However, energy storage technology can be used to make up for the deficiency of EVs charging and NEPG, with the functions of reducing peak and filling valley, smoothing load and improving power grid characteristics. Therefore, through combining energy storage technology and the charging devices, building the energy-storing EVs charging pile has important significance on the application of EVs.In this paper, energy-storing charging pile is studied and a simulation experiment system is designed on the basis of the research on battery charge-discharge efficiency test system. The experiment system can realize condition monitoring and power conversion among AC power grid, energy storage battery and EV’s battery. The main work can be summarized as follows:(1) The feasibility of energy-storing charging pile is analyzed. The main problems of traditional charging pile are summarized after studying on its working principle, charge-discharge characteristics of battery and capacity detection. The advantages and disadvantages of energy-storing charging pile are concluded after analyzing the configuration of energy-storing capacity and operation modes. On this basis, combined with the technology of the traditional charging pile, the design indexs and the overall design scheme of the simulation experiment system are given.(2) The analysis of power conversion system. According to the advantages and disadvantages of the topologies of power supply and DC/DC converter, DC bus supply mode, single-phase uncontrolled rectifier, Buck and bidirectional half bridge DC/DC converter are chosen. Then using state-space average method, the dynamic models of Buck and Boost converter are established. Finally, the closed-loop operation principle of Buck and Boost is verified by Matlab simulation, which provides a theoretical basis for the system debugging.(3) The hardware design. The hardware circuits of power conversion system and control system are designed according to the design indexs and the overall design scheme. The DSP TMS320F28335 microcontroller is set as the main control unit.And DSP minimal system, power conversion system, isolated driving circuit, sampling circuit, communication circuit, internal resistance detection circuit, and auxiliary power circuit are designed.(4) The software design and experiment test. Under CCS5.2 software development environment, the software of system is completed by C language, including the main program, interrupt service, charge-discharge, communication and PI controller subroutines. On the basis of the system software and hardware design and implementation, the accuracy of internal resistance module and key waveforms of the simulation experiment system are tested and analyzed. Based on the data, the charge-discharge characteristics and efficiency of battery are analyzed. The experimental results show that the system can meet the require-ments of the original design, and achieves the functions of charge-discharge and the condition monitoring to battery.