基于虚拟阻抗的储能微网VSG控制策略研究

Research on VSG Control Strategy for Energy Storage Microgrid Based on Virtual Impedance

[目的]为了使储能微网并网变流器(Power Conversion System,PCS)具备同步发电机一样的旋转、励磁特性,提出一种在储能微网并网PCS控制系统中采用虚拟同步机(Virtual Synchronous Generation,VSG)控制策略。[方法]针对传统VSG不具备低电压穿越(Low Voltage Ride Through,LVRT)能力,文章构建VSG虚拟阻抗无功控制环节,实时修正电压控制输入信号,提高系统暂态压降支撑能力;为了得到虚拟阻抗的幅值及阻感比,将LVRT工况分为线路对称和不对称短路障,研究正、负序电压、电流,得出虚拟阻抗参数。[结果]为了验证所提控制策略的性能,通过Matlab/Simulink进行仿真,设置仿真工况为:储能微网外接输电线路分别发生三相接地和单相接地故障。[结论]仿真结果表明:将虚拟阻抗引入VSG控制系统中,可以提高短路情况下储能微网并网PCS输出电压,起到LVRT期间电压暂态支撑作用,使储能微网具备LVRT能力,可为实际应用提供指导。

[Introduction]In order to make the grid-connected power conversion system(PCS)for the energy storage microgrid has the same rotation and excitation characteristics as the synchronous generator,the virtual synchronous generation(VSG)control strategy is proposed in the grid-connected PCS control system for the energy storage microgrid.[Method]In this paper,in view of the fact that the traditional VSG did not have the low voltage ride through(LVRT)capability,the virtual impedance reactive power control link of VSG was constructed to modify the voltage control input signal in real time and improve the support ability of system transient voltage drop.In order to obtain the amplitude and resistance inductance ratio of virtual impedance,LVRT operating conditions were divided into symmetrical and asymmetrical short-circuit failures of the line,and the positive and negative sequence voltage and current were studied to obtain the virtual impedance parameters.[Result]In order to verify the performance of the proposed control strategy,simulation is performed using Matlab/Simulink,and the simulation conditions are set as follows:three-phase grounding and single-phase grounding faults occur in the external transmission line of the energy storage microgrid respectively.[Conclusion]The simulation results show that the introduction of virtual impedance into VSG control system can improve the output voltage of the grid-connected PCS for the energy storage microgrid in case of short circuit,play the role of voltage transient support during LVRT,make the energy storage microgrid has LVRT capability,and provide guidance for practical application.