Research On Photovoltaic Energy Storage Grid-connected Control Strategy Based On VS

Solar energy is a low-carbon and environmentally friendly renewable and clean energy,with strong development potential,but with a large number of photovoltaic power generation through the power electronic equipment into the power grid,it will lead to the inertia and damping of the power grid,and it is difficult to maintain the stable operation of the power system using traditional control schemes.In order to solve this problem,the virtual synchronous generator(VSG)control technology of the grid-connected system of photovoltaic power generation and hybrid energy storage module is designed.This thesis does the following work on this content.1)The model is built according to the mathematical formula of photovoltaic cells on MATLAB/Simulink,and the maximum power tracking of photovoltaic cells is realized and simulated by using the disturbance observation method.Then,the combination of supercapacitor and battery is used to complement each other,and the functional characteristics of the two energy storage devices are modeled and analyzed separately.2)Two bidirectional DC/DC converters are used to control the energy interaction between the energy storage module and the photovoltaic power generation module for the connection structure of hybrid energy storage.For the control method of the two energy storage devices,the power distribution of the two energy storage is improved on the basis of the two-stage lowpass filtering method,and the adaptive fuzzy PI control is used to maintain the stability of the DC link voltage,so that the hybrid energy storage module and photovoltaic power generation can better interact with the power.3)By using the operating characteristics of the synchronous generator to establish the active-frequency controller and reactive-voltage controller of VSG,the output of the gridconnected inverter is controlled so that it has the same active-frequency and reactive-voltage regulation characteristics as the synchronous generator.At the same time,for the control of voltage and current double closed loop,the voltage loop uses proportional resonance(PR)control to quickly track system changes,and the current loop uses proportional(P)control to improve dynamic performance.Then,the root trajectory is used to analyze the transient process of VSG control strategy grid-connected,and it is found that a single change in the magnitude of moment of inertia(J)and damping coefficient(D)cannot take into account the stability and dynamic response of the system at the same time.Based on this,an improved transient VSG control method is adopted,and a new closed-loop transfer function is constructed by adding a lead compensation function in the transient damping link,and then the size of the lead compensation coefficient is adjusted to improve the transient response of the system.4)Combine photovoltaic power generation modules,hybrid energy storage modules,and improved transient VSG grid-connected control into a system for simulation,setting three different scenarios based on load changes and different VSG command values.The simulation results show that the improved transient VSG control strategy can spontaneously adjust the frequency of the system and reduce the oscillation of the system when the active power of the system changes,and the hybrid energy storage module can maintain the dynamic balance of system power by charging and discharging on the DC side.