Research On The Control Method Of VSM Coordinating The Constraints Of AC-side And DC-side

Renewable energy is connected to the power grid through grid-connected converters that can respond quickly,which leads to the decrease of inertia of the power grid and the increase of sensitivity to frequency fluctuations.By simulating the rotor motion equation and the stator electrical equation of synchronous generator,virtual synchronous generator controls grid-connected inverters to have the output characteristics of synchronous generator.The virtual snychronous generators can provide virtual inertia,participate in power grid regulation independently,and solve problems such as insufficient support capacity of new energy generation.In this paper,a virtual synchronous generator system model based battery energy storage system is established,and the physical constraints of the virtual synchronous generator are studied.Besides,a method of inertia measurement for the virtual synchronous generator is proposed,and a method of ac-dc side coordination control for the virtual synchronous generator is proposed on the basis of triple physical constraints and real-time measurement of inertia.The main research contents include:1)In this paper,the mathematical models and simulation models of virtual synchronous generator in the micro-grid are established,including the virtual synchronous generator DC-side battery energy storage system equivalent circuit model,which consists of controlled voltage source in series of a fixed resistors,mathematical model of the battery voltage-SOC characteristics,bidirection buck-boost circuit model with double closed loop control,and small signal model of virtual synchronous generator.2)Considering that the energy storage capacity,DC/DC converter capacity and inverter capacity of virtual synchronous generator are fixed in engineering applications,the physical constraints of virtual synchronous generator are analysed in this paper,and the AC-side power constraint of virtual synchronizer is proposed.The virtual synchronous generator breaks through the DC-side energy constraint,the DC-side power constraint or the AC-side power constraint are qualitatively analyzed.3)On the basis of studying the existing method of inertia measurement for synchronous machine,this paper proposes a method of inertia measurement for virtual synchronous generator.4)Based on the study of AC and DC side physical constraints of the virtual synchronous generator and the method of inertia measurement,an AC and DC side coordination control method for the virtual synchronous generator is proposed.A virtual synchronous machine digital simulation model is build in the PSCAD/EMTDC(?)simulation software,and the related theory analysis are discussed and verified.Simulation results demonstrate the effectiveness of the proposed method.