利用虚拟同步发电机(VSG)技术，针对微电网逆变器离/并网平滑切换控制策略进行研究。首先，建立VSG数学模型，对VSG功频调节器、励磁调节器和电磁方程等控制部分进行设计，并给出相应的控制框图。其次，对传统离/并网切换原理进行分析，锁相环(PLL)的存在，导致在很大程度上影响预同步速度和精度，针对此问题提出一种改进预同步控制方法，省去PLL环节且只需要2个PI调节器，控制参数减少，切换瞬间冲击电流减小且能够抑制有功、无功功率冲击，有效实现微电网逆变器离/并网平滑切换。最后，通过基于MATLAB/Simulink的仿真结果验证了所提出控制策略的正确性和优越性。

Based on the virtual synchronous generator (VSG) technology, the off/on grid smooth switching control strategy of microgrid inverter is studied. Firstly, the mathematical model of VSG is established, and the control parts of VSG including power frequency regulator, excitation regulator and electromagnetic equation are designed. Secondly, the traditional off/on grid switching principle is analyzed. Due to the existence of phase-locked loop (PLL), the pre-synchronization speed and accuracy are greatly affected. Aiming at this problem, an improved pre-synchronization control method is proposed, which can replace the PLL section with only two PI regulators. Thus the number of control parameters is reduced, the switching instantaneous impulse current is small, and the active and reactive power impact is suppressed, resulting in the off/on grid smooth switching of microgrid inverter. Finally, the simulation results of MATLAB/Simulink verify the correctness and superiority of the proposed control strategy.