Research On Parallel Control Strategy Of Inverters In Microgrid

As a new approach of organization of distributed energy sources, Microgridhas become an important research interest for the field of distributed energysources, which can effectively integrate the advantages of distributed generationand take less impact on the utility. This paper focuses on parallel control strategy ofinverters in microgrid. The virtual synchronous generator (VSG) algorithm and thecorresponding controller have been given, then parallel inverters can effectivelysimulate the synchronous generators (SG) and conveniently extract from thevoltage and frequency control structure of the power system. The main contents ofthis article are as follow:(1) Review the concept, background, development and key technologies ofmicrogrid;(2) The common inverter control strategies are summarized. According to theanalysis and comparison of the characteristic of inverter and SG, VSG controlstrategy and its basic principle are given;(3) Describe the main circuit of VSG and its mathematical model, and take anin-depth study of VSG algorithm and its realization according to the mathematicalmodel of SG, and analyze the effect of key parameters such as the equivalent outputimpedance and inertia;(4) Refer to the basic principles of the governor and excitation controller ofSG in power system, the governor and excitation regulator of VSG are designed. Anovel excitation regulator with interface of reactive power is proposed. PQ andpre-synchronous control for VSG operating in grid-connected mode are alsodesigned;(5) Refer to the hierarchical control of power system, the hierarchical controlstructure and hierarchical frequency and voltage control strategy for microgrid inislanded operation are designed. The study focuses on the principle, process,realization and power distribution of the first frequency regulation, the secondfrequency regulation, the first voltage control and the second voltage control. Anovel method of compensating line voltage droop to achieve precise reactive power distribution is proposed;(6) Simulation for the output characteristic and the effect of importantparameters of VSG in independent operation using MATLAB/Simulink are given.Simulation of hierarchical frequency and voltage control strategy for microgrid inislanded operation is also given. The results of the simulation verify the algorithmand control strategy.