Passivity-Based Control Method Of Grid-Connected Virtual Synchronous Machine

Virtual Synchronous Machine(VSM)can provide virtual inertia and damping by simulating the operation characteristics of synchronous generator,and realize frequency and voltage regulation through grid-connected inverter.So it can solve the problem of insufficient frequency support capacity of new energy power generation effectively.However,VSM has the characteristics of "negative impedance" under some operating conditions,which leads to the problems of instability.The existing control methods solve this problem by adjusting the control parameters to avoid the unstable operating domain.However,due to the real-time changes of the actual system operating parameters,this idea has limitations in application,and it cannot guarantee that the VSM can always run stably at the ideal operating point.In addition,because of the interaction between devices in the multi-VSM-connected system,it is difficult to set the control parameters.To solve this problem,a passivity-based control method for the grid-connected VSM is proposed,which ensures the essential stability of the VSM at the ideal running point,and an optimization design method is proposed to improve the dynamic performance.The main contents of this paper are as follows.(1)Taking the output current of the grid-connected VSM as the variable,the output voltage expression of the inverter circuit,the controlling equation of the active-frequency and the controlling equation of the active-voltage,the Eulerian-Lagrange mathematical model of the grid-connected VSM is established,and the running state of the VSM is described from the perspective of system energy.(2)According to the Euler-Lagrange model of the grid-connected VSM and the passive condition of the system,a passivity-based control method for the grid-connected VSM is proposed,and the grid-connected VSM is defined as a passive system.After the input of passivity-based control,the system can realize the essential stable operation at the desired operating point.Meanwhile,as a passive system,it can use its own invariance to transform the stability problem of multi-machine system into a single machine stability problem,which has more advantages in engineering practical application.(3)The influence rules of passivity-based control parameters on output performance are analyzed and summarized,and according to the influence rules,an optimization design process of passivity-based control parameters is proposed to ensure that the performance indexes in the dynamic adjustment process of the grid-connected VSM meet the constraints in the operation process after the control is put into operation.(4)PSCAD simulation software is used to build a digital simulation model of the grid-connected VSM after passivity-based control input.The stability of the grid-connected VSM under passivity-based control,the influence law of passivity-based control parameters on output performance,and the optimization design method of passivity-based control parameters are verified.The simulation results verify the feasibility of the passivity-based control method and the control parameter optimization design method proposed in this paper.