Research on parallel operation of distributed inverter based on variable droop coefficient

In the numerous strategy of distributed inverter´s parallel operation, PQ droop control is an effective method. But traditional droop control method can result in considerable output voltage frequency and amplitude deviation under the condition of high-power output. Therefore this paper proposed an improved droop control method, which using large droop coefficient when the output is small in order to ensure output power balance. When the output is large, droop coefficient becomes smaller in order to reduce output voltage frequency and amplitude deviation. In the meantime, the droop coefficient´s change has followed the principle which the inverter output power balance need to follow. This new method can improve stability and reliability of the micro-grid. Simulation results show the effectiveness of this control method.