Control strategy for wireless paralleled inverters under nonlinear load conditions

Micro grid(MG) consists of a number of parallel operating inverters. The droop control strategy is commonly used in parallel-connected inverters. The conventional PI regulator for the voltage control has little effect on restraining the voltage harmonic content under the nonlinear load conditions. So an effective and reasonable control strategy for inverters must be adopted to ensure the output power of the inverters meet the load demand and reduce the voltage harmonic. Based on this, a new droop control strategy with a capacitor voltage repetitive control loop and a capacitor current loop is presented in this paper, and the designation of the repetitive controller is given through the analysis of the mathematical model of single-phase inverter. This control strategy can effectively restrain the harmonic of the output voltage under nonlinear load conditions. The simulation and experimental results verify the validity and rationality of the droop control strategy proposed in this paper.