A Secondary Control Strategy for Frequency and Voltage Recovery and Power Sharing Control Method in Island Microgrid

When large capacity load switching-over takes place in the islanded microgrid, in which the traditional control strategy for virtual synchronous generator is being utilized, the voltage and frequency of the microgrid might deviate rated values, and in severe case the out-of-limit of frequency and voltage may occur, thus the secure operation of microgrid will be affected. To solve this problem, firstly, based on virtual synchronous generator control strategy a secondary self-recovery regulation and control method for voltage and frequency under the environment of islanded microgrid was proposed to implement autonomous recovery and regulation of converter’s frequency and voltage. Secondly, in allusion to the fact that the inconsistency of converter line impedance parameters led to uneven distribution of active and reactive power output from converters, the reason of this phenomenon was analyzed, and a control strategy for the uniform distribution of active and reactive power was put forward to realize the distribution control of active and reactive power. Finally, two structures, i.e., single busbar structure and meshy structure, were utilized to verify the proposed control algorithm, and both effectiveness and universality of the proposed control strategy were proved.