Study On Inertial Control Of New Energy Generation Based On Virtual Synchronous Generator

With the development of human economy,the energy crisis and environmental pollution problems are increasing,in order to solve these problems,the use of renewable energy,such as wind energy and solar energy has been vigorously developed with the support of various countries.However,conventional power generation control technology usually uses the MPPT and through power electronic converter to connect to the power grid,which cannot actively respond to the frequency change and resulting in the system inertia loss.As a new control technology which can simulate the inertia of traditional synchronous generator,virtual synchronous generator has been paid more and more attention.How to apply it to new energy power generation has become a hot topic.This paper studies inertial control in wind turbine system and photovoltaic system based on virtual synchronous generator technology,the main work is as follows:Firstly,the research background and the technical background of the virtual synchronous generator are introduced as well as the research status of the inertial response of the new energy power generation.The topological structure and mathematical model of wind turbine,photovoltaic and energy storage system are studied respectively: The mathematical model and control method of wind turbine,generator and converter of PMSG are analyzed as well as photovoltaic power generation system.The battery model and bidirectional DC-DC Circuit of battery energy storage system are studied.Secondly,the theoretical model and control method of virtual synchronous generator are studied.Based on the analysis of the mathematical model of synchronous generator,this paper uses its rotor motion equation,flux equation and electromagnetic transient relation to build the virtual synchronous generator model.The power frequency control and reactive power voltage control are studied.And inertial response of the virtual synchronous generator are simulated in PSCAD.Based on the analysis of the structure and control of the wind turbine virtual synchronous generator system,a new inertial control method is proposed,which includes two parts: current-feed-forward and power-overboost.The current-feed-forward compensates the voltage of DC bus through rotational kinetic energy of the wind turbine,and the power-over-boost could improve the inertial response level of the virtual synchronous generator.A detailed model of wind power grid-connected system is built in PSCAD,and the control of virtual synchronous generator of traditional wind turbine and the inertial response effect of the proposed control strategy are compared,and the simulation results verify the effectiveness of the proposed strategy.A new variable inertial control scheme considering SOC of energy storage is proposed.This paper establishes a detailed model of PV-storage system,and introduces the SOC into the variable inertial control method.By establish a certain relation between the virtual inertia of the system and the direction of frequency change as well as the battery SOC,the new method could increase the inertial response ability of the virtual synchronous generator,which has a good practical significance for improving the stability of the system frequency.The grid-connected and off-grid system model of PV-Storage virtual synchronous generator are built in PSCAD,and the validity of the proposed strategy is verified by simulation result.