Research And Implementation Of Three-phase Photovoltaic Inverter Control Technology

At present,the problems of environmental pollution and energy crisis need to be solved urgently.Renewable energy has received extensive attention,and the world is strengthening the use of renewable energy.Photovoltaic power generation is a relatively important component and a rapidly growing new energy generation technology.However,with the largescale integration of photovoltaic power generation systems based on power electronics technology,it will have a significant negative impact on the stable operation of the power system.The fundamental reason is that traditional power electronics devices do not possess the inertia and damping of traditional synchronous generators,thereby reducing the inertia and damping of the entire power system.Therefore,this article focuses on the virtual synchronous generator technology of three-phase photovoltaic inverters.This article introduces the architecture of a three-phase photovoltaic energy storage power generation system and the functions of its components,and determines the grid side three-phase inverter as the research object.A mathematical model of the grid side inverter constructed for a three-phase two-level PWM converter was established in the abc coordinate system.After undergoing Clark and Park transformations,the mathematical model in the d-q coordinate system was obtained.The traditional voltage and current double closed-loop decoupling control strategy was analyzed,and on this basis,the virtual synchronous generator control strategy was studied in the paper,and the operating mechanism of the synchronous generator in the power grid was analyzed,The mathematical model of virtual synchronous generator control in grid side inverters was derived based on its physical significance;The parameter design methods for the active frequency control loop and reactive voltage control loop of VSG were provided,and the traditional active loop and improved active loop were compared and analyzed,and the main control parameters were set.The paper studied the grid connection pre synchronization control strategy of virtual synchronous generators,and provided a grid connection pre synchronization control method based on phase-locked loop and a grid connection pre synchronization control method without phase-locked loop.After comparing and analyzing these two grid connection pre synchronization methods,it was found that the effect of the grid connection pre synchronization control strategy without phase-locked loop is more superior.The paper proposes a bridge isolation type three-phase AC overvoltage fault detection and protection circuit,which uses resistance voltage sharing and current limiting on the basis of uncontrolled rectification,and combines optocoupler isolation technology to construct a cost-effective grid side AC overvoltage detection circuit.The overvoltage detection signal is sent to the general IO port of the main control chip,and the CPU implements fault decision-making and protection.In order to scientifically design the parameters of the protection circuit,A mathematical model for overvoltage fault detection and protection circuit has been established.The paper establishes a simulation model and experimental prototype of a 12kW threephase photovoltaic inverter based on virtual synchronous generator control.On the basis of theoretical analysis,the inverter in the photovoltaic energy storage grid connected system was designed,and the design methods for the main parameters such as power switch tubes,LCL filters,and DC side bus capacitors were provided;A simulation model of a three-phase inverter based on virtual synchronous generator control was built using Matlab/Simulink and PSIM simulation softw are,and a physical prototype was implemented.The correctness of the voltage and current dual closed-loop decoupling control,active and reactive power scheduling,primary frequency regulation and voltage regulation,and pre synchronization control strategies of the three-phase inverter virtual synchronous generator were verified through simulation and experiments.