Study On V2G Electric Vehicle Charging Station Converter And Control Strategy

With the rapid development of electric vehicles, more and more charging stationsneed to be built, but the electric vehicle is a non-linear device, it produces a large numberof harmonics when it is charging. It is a form of pollution to grid, so it is necessary tostudy the reason of the harmonics. And the traditional charging station only confined tothe “gas station”, without considering the charging station can also serve as a bridgebetween the electric vehicles and grid, the energy can flow by it. The V2G technology isthat electric vehicles can exchange energy and information between electric vehicles andgrid under controlled condition as mobile energy storage components. When the grid isunstable, electric vehicle can provide energy to the grid through V2G charging station,making the grid more stable. In this situation, charging station becomes a part of smartgrid, so it is not just “fuel”.Firstly, this article describes V2G technology, and analyses its function in detail. Itselects V2G charging main circuit topology according to the special requirements ofelectric vehicle charging stations. Then, the mathematical model of PWM converter andhalf-bridge converter are deduced respectively. Comparing the traditional control methodsand SVPWM in simulation, the results confirms that the control performance of theSVPWM is better, because it can obtain good waveform in a lower switching frequency.Secondly, this article also establishes the V2G charging simulation model, then thecharging and discharging simulation are completed. The results can prove that the V2Gcharging station can provide energy to grid when the grid is unstable. The current injectedinto the grid is a sine wave and its phase is synchronized with the grid voltage when thecharging station is in charging mode. While the current is also a sine wave and its phasewith a difference of180°with the grid voltage when the charging station is in dischargingmode, its DC bus voltage fluctuations is small, and system dynamic performance is good,meanwhile it can achieve unity power factor correction.Finally, experiment platform is built and control system with the digital signalprocessor of TMS320F2812DSP is designed, experiment is completed with C language program, validating the control strategy. Simulation analysis and experimental resultscertify that V2G charging machine not only can own factor correction and eliminateharmonics, but also can achieve bidirectional flow of energy, it improves the stability ofgrid.