微网逆变器无缝切换控制策略研究

Research on Seamless Switching Control Strategy without PLL for Microgrid Inverter

为了保证良好的并网电能质量,目前并网逆变器大多采用锁相环(PLL)与大电网保持同步,而弱电网下PLL会使并网逆变器的稳定性下降。因此本文通过研究PLL的等效阻抗影响稳定性的机理,选择可以实现并网自同步运行的直流母线电压控制逆变器,实现并网逆变器的离/并网无缝切换。并将其应用于弱电网的情形下,实现了弱电网下的虚拟功率预同步无缝切换控制。最后将所提控制策略在Plecs仿真平台验证了其有效性。

In order to ensure good grid connected power quality,at present,most grid connected inverters use phase-locked loop(PLL)to keep synchronization with large power grid.However,PLL will degrade the stability of grid connected inverter in weak grid.Therefore,by studying the mechanism of PLL equivalent impedance affecting stability,the DC bus voltage control inverter which can realize grid connected self-synchronous operation is selected to realize seamless switching between grid connected inverter and grid connected inverter.And it is applied to the case of weak power grid to realize the virtual power pre synchronization seamless switching control.Finally,the effectiveness of the proposed control strategy is verified on the PLECS simulation platform.