低压微网逆变器孤岛运行控制策略研究

Study on islanding control strategy of inverter in low voltage microgrid

低压微网系统中的逆变器孤岛运行时,由于失去电网电压和频率的支撑,逆变器的控制变得困难。在负载突变情况下,容易引起微网交流母线电压和频率幅值的波动,导致微网系统无法提供可靠的电能;当逆变器并联处于孤岛运行时,微网系统要求各台逆变器能够按各自容量实现功率精确分配,同时还应具有较快的动态响应能力。针对以上问题,文章逆变器的外环控制采用改进功率下垂系数调节的电压PI控制、内环采用瞬时电流PR双闭环控制,保证负载突变时具有较快的动态响应速度和无稳态误差控制。仿真结果验证了文章控制策略的可靠性。

Without support of grid voltage and frequency, it becomes more difficult for inverter to control in low voltage system when the inverter is operating in islanding mode. A drastic change of load will lead to fluctuation of system bus voltage and frequency, even to cause micro-grid fault. When islanding inverters are operation in parallel, the inverters output should be accurately distributed according to their capacity, and the inverters should have a fast dynamic response. To solve the problems above,in this paper an inverter, which has an outer loop controller of improved adjustable power droop voltage PI control,and an inner PR instantaneous current control, is proposed to rapidly response to drastic change of load without steady-state error. The simulation results verify reliability of the effective control strategy.