基于小交流信号下垂的微网二次控制方法

Small AC Signal Droop Based Secondary Control Method for Microgrid

有功功率-频率和无功功率-电压幅值的传统下垂控制方法被广泛应用于微网并联逆变器的协调控制中。然而,传统下垂控制会使变流器输出的频率和电压幅值存在偏差,进而影响微网电能供应的精确性。基于对人为注入系统的小交流信号的控制,提出了一种新型的二次控制方法,以补偿下垂控制产生的电压偏差。该方法中的小交流信号在并联逆变器中如同一种通讯信号,其频率和逆变器输出基波电压的下垂偏置呈下垂关系。通过该方法,系统频率和电压幅值可以恢复至额定值,同时,精确的功率均分可以在并联逆变器之间实现。仿真和实验结果都验证了该方法的有效性。

The traditional droop control method for active power-frequency and reactive power-voltage amplitude is widely used in the coordination control of parallel inverters in microgrids. However, this method may cause deviations of the inverter’s output frequency and voltage amplitude, which will further affect the accuracy of power supply from microgrids. Based on the control of an injected small AC voltage signal, a novel secondary control method is proposed to compensate the voltage deviation resulting from the droop control. The small AC voltage signal serves as a communication signal among the parallel inverters, and there is a droop relationship between its frequency and the droop deviation of the inverter’s output voltage. Using this method, the deviations of system frequency and voltage amplitude can be eliminated; meanwhile, an accurate power sharing can be realized among the parallel inverters. Both simulation and experimental results proved the effectiveness of the proposed method.