Research On Inertia And Damping Integrated Control Of DC Microgrid

DC microgrid has the ability to reliably accept clean energy,electric vehicles and DC load,and does not need to consider the problems of frequency and reactive power in AC network.It is of great significance to promote the construction of smart grid and realize the transformation of clean energy,and has become the main development trend of distributed energy generation.However,the distributed energy and constant power load(CPL)contained in the grid structure of DC microgrid will reduce the stability margin of the system,and high-power power electronic devices will isolate the inertial support of synchronous motor,which makes DC microgrid have the characteristics of weak damping and low inertia,threatening the stable operation of DC microgrid.Therefore,this paper comprehensively studies the damping and inertia of DC microgrid,and puts forward relevant optimal control.The main work is as follows:(1)The mathematical model of DC microgrid including photovoltaic,energy storage,resistive and constant power load is established,the working me chanism and control mode of each port and its converter are explored,and its state space equation and small signal model are established to lay the foundation for subsequent damping and inertia analysis.(2)According to Lyapunov stability principle,the weak damping characteristics of DC microgrid are analyzed theoretically.Based on the principle of active da mping control,a damping state feedback control strategy applied to storage load is proposed.This strategy further excavates the control potential of multiple ports of DC microgrid.Through participation factor analysis,many state variables are fed back under the condition of ensuring the accuracy of pole assignment,so as to reasonably solve the matching problem between state variables and feedback ports,so as to provide damping support for DC microgrid.(3)The proposed damping state feedback control strategy can improve the damping characteristics of the system,but it lacks inertia support ability.Therefore,based on the mathematical model of DC motor,this paper proposes an integrated inertia and damping control strategy applied to DC microgrid to provide inertia and damping support for DC microgrid.At the same time,based on the analysis results of stability and step response,the proposed control strategy is improved to provide inertial support for the system on the energy storage side and dampin g control on the load side,so as to provide sufficient dynamic support for the system bus.On this basis,the inertia sensitivity control link on the load side is designed to improve the flexible and controllable ability of inertia support,so as to compr ehensively improve the inertia and damping characteristics of the system.(4)A DC microgrid simulation platform is built in Matlab / Simulink softwa re to verify the proposed control.The simulation results show that the proposed control strategy can effectively improve the ability of DC microgrid to suppress voltage oscillation and mutation,and ensure the safe and stable operation of the system.