Research On Control Strategy Of Active Participation Of Photovoltaic Generation In Power System Frequency Regulation

The development and utilization of renewable energy is a national strategy to promote the low-carbon transformation of energy and respond to environmental changes.Photovoltaic power(PV)generation network is an effective way to realize large-scale development and utilization of solar energy.PV large-scale networking degrades the power control capability of the power system.Large fluctuations of PV generation bring severe challenges to power system operation regulation.Therefore,it is urgent for PV generation to actively participate in power system frequency regulation.This paper focuses on the primary frequency regulation and secondary frequency regulation of PV generation in power system.In the research of basic operation principle of two-stage PV generation system,the matching relationship between the generation power of PV cell array and its terminal voltage under different working conditions(temperature T,illuminance S)is established.The dynamic relationship between the output power and the output voltage of photovoltaic array under variable conditions is analyzed.The topology of two-stage PV generation system and its mathematical model are established,including the topology of network-side inverter and Boost converter.The basic working principle and control strategy of two-stage PV generation are studied,including maximum power point tracking(MPPT)control strategy of PV array and operation control strategy of limited power,grid-side converter control strategy and Boost converter control strategy.The simulation model of two-stage PV generation system is established,including the switching model and equivalent model of PV inverter.The second power output performance of two-stage PV inverter is analyzed.In the research of frequency regulation of PV generation system,according to existing problems of PV generation participating in primary frequency regulation of power system,the active power-frequency droop control strategy and virtual inertia control strategy are studied.Two new frequency regulation control strategies based on p-u external characteristics are proposed,and the influence of different control strategies and control parameters on system frequency is analyzed.Considering the problems of primary frequency regulation deviation and boundary violation,a secondary frequency regulation control strategy that adapts to different grid-side AGC control modes(constant frequency control mode,constant tie line power control mode and tie line power frequency deviation control mode)is proposed,so as to realize the zero error regulation.The effectiveness and feasibility of the control strategies are verified based on the PSCAD/EMTDC simulation platform.In the research of the influence mechanism of PV frequency regulation control strategy on the system frequency characteristics,based on the dynamic frequency response model of traditional power system,a dynamic frequency response model of power system including PV generation is established.The rate of change of frequency(RoCoF),the frequency nadir fr_peak,the frequency overshoot and stability time are taken as the characteristic quantity to evaluate the dynamic process of frequency regulation.The impact and variation of novel frequency regulation control strategies and parameters on dynamic process of system frequency are qualitatively analyzed.Finally,a two-area four-machine simulation model is built in PSCAD/EMTDC simulation platform.The validity of the mechanism analysis and the feasibility of the novel frequency control strategy is verified by time-domain simulation.