The strategy of virtual synchronous generator ( VSG ) control for grid connected inverters in microgrid is studied. Firstly,the power frequency regulation section and the excitation regulation section of VSG control have been built. VSG simulates the inertia and damping characteristics of synchronous generator,which can realize the independent operation of grid connected and grid disconnected. But,during switching process of grid connected and disconnected,voltage and current shocks may occur. In order to realize smooth switching,a control strategy of constant voltage and constant frequency control in the off-network mode and VSG control in grid connected mode is proposed. In grid disconnected operation, constant frequency and constant voltage control provides the voltage and frequency support for the load. In grid connected operation,these are supplied by the VSG control mode. Then,the influences of the adjustment coefficient,the damping coefficient and the moment of inertia on the power frequency characteristics are analyzed. Finally,the effectiveness of the proposed control strategy is verified by a simulation model based on Matlab/Simulink. The simulation results show that the control strategy solves the seamless switching between different operation modes of microgrid;compared with the traditional switching process, the voltage and current shocks in switching process are reduced and the stability of the micro grid in the operation process is improved; it can be used in micro grid which consists of multiple micro sources in parallel.%对微电网中并网逆变器的虚拟同步发电机(VSG)控制策略进行了研究.首先,搭建了VSG控制的功频调节部分和励磁调节部分.VSG通过模拟同步发电机的惯性和阻尼特性,实现了并网和离网的独立运行,但是在并离网切换时容易出现电流和电压冲击.为实现并离网的平滑切换,提出了一种离网模式下恒压/恒频控制、并网模式下VSG控制的控制策略.在离网运行时,恒压/恒频控制模式为负载提供电压和频率的支撑;在并网运行时,由VSG控制模式提供.同时,详细地分析了调差系数、阻尼系数和转动惯量对功频特性的影响.最后,利用Matlab/Simulink搭建仿真模型,验证该控制策略的有效性.仿真结果表明:该控制策略解决了微电网在不同模式之间的无缝切换问题;与传统的切换过程相比,减小了切换过程中的电压和电流冲击,提高了微电网在运行过程中的稳定性,可以应用于多微源并联的微电网.
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