Abstract:
Aiming at the problem that the output reactive power of parallel inverters cannot be accurately divided due to the difference of line impedance, an improved adaptive droop control technology based on the virtual impedance method is proposed in this paper. A novel type of composite virtual impedance is adopted in this method, and two links, the fine tuning compensation of droop control and the adaptive droop control coefficient, are increased. By introducing this virtual impedance, not only can the influence of the resistive impedance of each branch be eliminated, but also the impedance sensitivity components of each branch can be approximately the same, thus reducing the impedance difference between parallel branches. Meanwhile, the improved droop link can further reduce the reactive power error between parallel inverters. Finally, the simulation results show that the proposed method can realize the fast and stable averaging of reactive power, reduce the circulation, improve the accuracy of averaging of reactive power, improve the dynamic response speed of the system, and make the parallel inverter operate stably.