Research On Control Strategies For Virtual Synchronous Generators In The Low-voltage Microgrid

Microgrid is a small power generation and distribution system that integrates distributed power supplies,loads,energy storage devices and power electronics devices together.It has become a research hotspot at home and abroad,because it is beneficial to the utilization of local renewable energy and it can improve the reliability of the power supply for the key load.The conventional inverter can't provide inertia for the microgrid,while the virtual synchronous generator adds inertia to the control algorithm,so that the inverter has similar external characteristics with the synchronous generator,which can improve the stability of the microgrid.When the virtual synchronous generators with different capacity run in parallel in a microgrid,how to realize the proportional distribution of power is an urgent problem that needs to be solved.Firstly,the virtual synchronous generator control strategy is studied and the electrical model of the virtual synchronous generator is analyzed in the paper in order to solve the power distribution problem of parallel virtual synchronous generators.The simulation model of virtual synchronous generator is built in MATLAB/Simulink,and the control effect of the virtual synchronous generator control strategy is simulated and verified.Secondly,the problem of power coupling caused by resistive circuits is discussed,and power decoupling algorithm is applied to virtual synchronous generator control strategy in order to modify the conventional control strategy.The comparison simulation of the two control strategies proves that the improved control strategy can improve the power distribution effect of parallel virtual synchronous generators.Then,an improved control strategy is proposed in order to solve control problem of parallel virtual synchronous generators with unbalanced load.The simulation shows that the proposed control strategy can reduce the voltage unbalance of the AC bus and make the inverters work normally.Finally,an experimental system of virtual synchronous generators is built by using dSPACE real-time simulation system.A single virtual synchronous generator operation experiment,parallel virtual synchronous generators power distribution experiment and parallel virtual synchronous generators with unbalanced load experiment are carried out,so the effectiveness of the proposed control strategy is proved by the experiment.