基于虚拟同步机的微网并离网无缝切换策略

Seamless Switching Strategy for Grid-Connection and Off-Grid Modes of Microgrid Based on Virtual Synchronous Machine

针对虚拟同步发电机在微网应用中实现并离网无缝切换的控制策略进行研究。首先阐述了微电网系统中引入VSG控制策略有利于实现微网的并离网无缝切换;其次为了消除虚拟同步发电机在并网和孤岛之间切换时的电压和电流突变,研究了电压、相位和电流跟踪策略,实现次级频率调节和电压调节,但是若相位接近于0或2π,则很小的干扰就能使锁相环输出产生较大的误差,因此在锁相环中添加了一个正弦模块。最后在MATLAB/Simulink中建立了仿真模型,验证了该控制策略可实现无缝切换。

The control strategy of virtual synchronous generator in the microgrid application to achieve seamless switching of grid-connection and off-grid modes is studied.Firstly,the introduction of the VSG control strategy in the microgrid system is beneficial to realize the seamless switching of grid-connection and off-gird modes of microgrid.Secondly,in order to eliminate the sudden changes in voltage and current of the virtual synchronous generator when switching between grid-connection and island,the voltage,phase and current tracking strategies are studied so that the inverter can achieve secondary frequency regulation and voltage regulation.However,if the phase is close to 0 or 2π,a small interference may cause a large error in the output of the phase-locked loop.Therefore,a sinusoidal module is added to the phase-locked loop to avoid this error.Finally,a simulation model is established in MATLAB/Simulink.Simulation results show that the control strategy can achieve seamless switching.