Virtual impedance optimization method for microgrid reactive power sharing control

Due to mismatched feeder impedances and other factors, the conventional droop control method always has reactive power sharing issues. The application of virtual impedance method can reduce reactive power sharing errors. However, conventional virtual impedance methods have not fully considered the mismatch factors in microgrid network. To improve the reactive power sharing accuracy, a virtual impedance optimization method based on the minimization of system global reactive power sharing error was proposed. Through the modeling of microgrid network, an estimation method for network reactive power sharing error was derived. Then, the transmission characteristic of reactive power was analyzed, with an adaptive controller for virtual impedance designed. Based on this, a calculation function for the global reactive power sharing error was established and optimized in order to obtain the best parameters for adaptive controller. The proposed method didn't require communication, and it could be applied to complex structure microgrids. Compared with existing methods, the virtual impedance control after optimization had network self-adaption capability and also better reactive power sharing performance. The effectiveness of the proposed method is proved through both simulation and experimental results. © 2016 Chin. Soc. for Elec. Eng.