An improved droop control strategy for the DVR parallel system

This paper shows the application of the improved droop control strategy in Dynamic Voltage Restorer (DVR) parallel system. Firstly, the traditional droop control strategy for DVR parallel system is shown. And then analyze the different impact on the parallel system by introducing the virtual impedance control, which could reduce the influence of the line impedance. However, the virtual impedance could not completely eliminate the differences of the equivalent output impedance between the parallel inverter units. So, this paper proposes an improved droop control strategy to eliminate the coupling of the active power and reactive power. Based on this control strategy, the circulating current between the parallel units is also suppressed. Simulation and experimental results are presented to verify the validity of this approach.