微网逆变器低电压穿越控制策略

微网逆变器一般采用下垂控制或虚拟同步机控制,其低电压穿越方式及特性与基于PQ控制的逆变器不同。下垂控制或虚拟同步机控制的逆变器低电压穿越的主要问题是在故障期间逆变器电压与电网电压之间不断产生相位的偏移,该相位偏移会严重影响并网电流恢复的速度。针对上述问题,提出一种在故障期间对功角等变量进行记忆保持的策略,使变量在故障前后基本保持一致,以实现故障后系统的快速恢复。针对故障期间产生的负序分量,采用在双同步旋转坐标系下对正、负序电流进行独立控制并引入电网电压前馈的方法。仿真和实验均验证了控制策略的正确性和有效性。

Low Voltage Ride-through Control Strategy of Microgrid Inverter

The microgrid inverter is generally controlled by droop controller or virtual synchronous generator, and the methods and characteristics of low voltage ride-through(LVRT)are different from inverters with PQ controller. The main problem of the LVRT strategy of the microgrid inverter is phase shift between the inverter voltage and the grid voltage during the fault, which would greatly affect the recovery speed of the grid-connected current. To solve the problems above, a strategy for memory retention of variables such as power angle during faults is proposed so that the variables before and after the fault are basically consistent to achieve rapid recovery of the system after the fault. The positive and negative sequence currents are separately controlled in the double synchronous rotating coordinate system and the forward feeding of the grid voltage is introduced to eliminate the negative sequence component during faults. Both the simulation and the experiment verify the correctness and effectiveness of the control strategy.