Improved droop control for parallel inverters in microgrids

In this paper, an improved droop control method is proposed for the parallel inverters in microgrids. The proposed strategy is based on the droop control technique, which only using the local measurable feedback information. This approach can be applied to the inverter-based microgrids where communication wires are not economic and reliable due to the distant physical locations. Unfortunately, the trade-off has to be made between the transient response and the power sharing accuracy for the conventional voltage and frequency droop control method. Moreover, the output and line impedance of the inverter presents a great impact on the power sharing accuracy. The proposed method takes into account the resistance of inverter output impedance and line impedance, and uses the active and reactive output current as the control variables, which limits the current spikes during the initial and transient states. Additionally, the derivate-integral terms are introduced to enhance the dynamic response of the inverters. Simulation results and experimental waveforms are given to validate the proposed control strategy.