Research on Frequency Control for Microgrid in Islanded Operation

Based on electromechanical transient mathematical model of synchronous generator,a new type of inverter for microgrid,namely virtual synchronous generator(VSG),is proposed.The feasibility of leading the centralized frequency control of traditional power grid into microgrids is analyzed in detail.When microgrid is operated in islanded mode,VSGs can be divided into non-frequency regulation units and frequency regulation units,the former can generate power and participates in primary frequency control according to dispatching to mitigate system frequency deviation due to disturbances;the latter can offer referential voltage of microgrid and use secondary frequency regulation to implement no-error frequency control.The existing problems in distributed frequency control are pointed out and a basic structure of centralized frequency control is given.Simulation results by Matlab/Simulink show that the proposed control strategy is correct and feasible.