Droop Control of Three-phase Microgrid Inverter Under Unbalanced Load with Particle Swarm Optimization Algorithm

When connected to the unbalanced load, a three-phase microgrid inverter (MGI) based on traditional droop control would produce an unbalanced output voltage, which will lower the system's power quality. This paper proposes a voltage balance control strategy based on positive-negative sequence separation to solve those problems. It achieves this by introducing a positive-negative sequence voltage-current control loop on the foundation of traditional droop control to generate the reference output voltage of the Bridge arm side, thereby improving the THD of current and reducing the voltage unbalance factor (VUF) of voltage. Considering that the introduction of positive-negative sequence separation makes controller parameters more numerous and difficult to be tuned, a particle swarm optimization (PSO) algorithm for tuning the parameters of the voltage loop controller is designed. Finally, the experimental results are included to confirm the feasibility of the proposed method.