VSG Energy Storage Unit Configuration And Cost Analysis Taking Into Account Primary Frequency And Inertia Support

Due to the increasing global energy shortage problem,more and more distributed power sources are connected to the grid through inverters,and the power system is developing in the direction of low inertia and low damping.In order to improve the stability of system operation,domestic and foreign scholars have proposed the concept of virtual synchronous generators,that is,by designing a specific control strategy,the distributed power inverter can have similar external characteristics as a synchronous machine,thereby providing inertia and damping for the system.The energy storage unit is the physical basis and energy source of the virtual inertia,and its configuration directly affects the performance and cost of the virtual synchronous generator.In this paper,mathematical modeling is performed based on the two basic functions of inertia support and primary frequency regulation of a virtual synchronous generator,and the configuration and cost of the energy storage unit are studied.Firstly,the topology and control strategy of the virtual synchronous generator are introduced,and its small-signal model is established based on the typical control strategy.Then,a time-domain model of the energy storage unit’s output during inertia support and one-time frequency modulation is established.The lower power constraint and the lower capacity constraint of the energy storage unit configuration are given.Based on the established mathematical model,this paper analyzes the influence of the control parameters on the energy storage output curve and the energy storage configuration constraints,and performs simulation verification on the MATLAB/Simulink platform.Secondly,the established mathematical model is extended,a hybrid energy storage system is applied to a virtual synchronous generator,and a first-order low-pass filtering link is constructed for output distribution.The energy storage medium assumes different frequency modulation tasks according to the difference in performance.The constraint conditions for the configuration of different energy storage media and the law that the energy storage configuration is affected by control parameters are obtained.Simulation results verify the correctness of the theoretical analysis.Finally,the full life cycle cost model of the virtual synchronous generator energy storage unit is constructed,and the cost analysis of three energy storage configuration schemes is performed based on the measured data of the grid frequency.The economic advantages and disadvantages of different energy storage methods are compared,which provides a theoretical basis for the selection of energy storage methods.