Research On The Operation Characteristics Of Multi-Virtual Synchronous Machine System Based On Hybrid Simulation Of Hardware-in-the-Loop

With the large-scale access of new energy to the power system,the "dual high"characteristics of high proportion of renewable energy access and high proportion of power electronic equipment applications,as well as the "dual random" characteristics of supply side randomness and demand side randomness,are profoundly affecting the morphology and operational characteristics of power grids.The dominant position of synchronous generators is gradually being shaken,and the traditional power grid built by synchronous institutions will be transformed into a new power grid with a large amount of new energy access.The significant reduction in inertia and damping in the system leads to a lack of dynamic regulation capability in the power system.Therefore,new power system dynamic response and control technologies for new energy access have received widespread attention and research.Virtual synchronous machines have the external characteristics of traditional synchronous generators,which can provide inertia and damping for the power grid,thereby improving the dynamic stability of new energy power systems.They have important theoretical value and significance for building new energy connected power systems.This paper focuses on the operation characteristics and control strategies of virtual synchronous machines in large power grids.By constructing state space equations and Lyapunov functions,it analyzes the dynamic interaction between virtual synchronous machines and power grids as well as their operation characteristics,aiming to reveal the factors that affect the operation characteristics of virtual synchronous machine access systems,and theoretically guide the design and improvement of virtual synchronous machine systems,To further improve the dynamic response and stable operation characteristics of virtual synchronous machines in new energy power systems,the main tasks are as follows:(1)According to the different operating scenarios,analytical models suitable for multi virtual synchronous machine systems in small and large disturbance scenarios are derived.In the case of small disturbances,the method of small signal analysis is used,focusing on power angle characteristics and simplifying voltage characteristics.On this basis,the rotor motion equation is linearized to obtain a state space equation.In the case of large disturbances,especially for short circuit faults,linearization methods have failed.Therefore,by considering the changes in operating state variables such as power angle and corresponding voltage and current,a state equation is constructed,and a Lyapunov energy function is constructed as the basis for analyzing transient operating characteristics.(2)The dynamic characteristics of multi virtual synchronous machine systems transitioning from different initial operating points to steady-state operating points are analyzed,and a sliding mode variable structure control strategy is proposed.Using the method of phase diagram,the influence of different virtual inertia values on the operational characteristics of multi virtual synchronous machine systems is discussed,and the transfer function of multi virtual synchronous machine systems containing virtual inertia can be obtained.Based on this result,the configuration constraints of virtual inertia that can make the multi virtual synchronous machine system run stably are analyzed and obtained.Finally,based on virtual inertia constraints,a sliding mode variable structure control strategy is proposed to ensure the stable operation of multi virtual synchronous machine systems under small disturbances.(3)This paper analyzes the power angle characteristics of the output of the virtual synchronous unit when a short circuit fault occurs and presents an optimal control strategy to prevent instability.Through the analysis of transient operation characteristics,it is known that virtual inertia affects the transient stability of multi virtual synchronous machine systems.Therefore,the Lyapunov energy function is used to analyze the impact of virtual inertia configuration on the transient operation characteristics of multi virtual synchronous machine systems,and an optimization method for transient operation characteristics is derived,so that the multi virtual synchronous machine systems do not lose stability and can smoothly transition to stable operation state in the event of short circuit faults.(4)Build a RT Box digital physical hybrid simulation to verify the operating characteristics of the multi virtual synchronous machine system during stable operation.The power angle characteristics and voltage characteristics of the virtual synchronous machine are verified when the load fluctuates.It is verified whether the virtual synchronous machine can smoothly transition from one steady state to another when a short circuit fault occurs in the system.The effectiveness of the proposed sliding mode variable structure control and transient optimization control methods is verified.