Parallel Operation Of PV Inverter Based On Virtual Synchronous Generator Control Method

Photovoltaic power generation technology is one of the significant directions in the development of distributed energy technologies.It has several advantages such as less pollution,high reliability,and flexible installation location.This technology can effectively solve many potential problems in large-scale centralized power grids.Inverter groups are typically used to integrate photovoltaic arrays into the power grid.The use of inverter based on power electronics technology in photovoltaic grid-connected power generation systems poses a challenge in providing damping and inertial support.This challenge results in higher demands for the safe and stable operation of the power grid.Studying the coordinated control technology of distributed photovoltaic inverter group is crucial for enhancing the overall operation efficiency and reliability of photovoltaic power station.This has great theoretical and practical significance.This article focuses on studying the parallel coordinated control strategy of distributed photovoltaic parallel inverters using virtual synchronous generator control as the research basis.The objective is to ensure that the photovoltaic grid-connected systems maintain harmonics,voltage levels,and stability margin.In this study,we address the output power optimization and phase deviation issues in photovoltaic grid-connected power generation systems.To achieve this,we propose a presynchronization control strategy and a maximum power point tracking approach based on an intelligent PID control algorithm.The specific research contents include:(1)Aiming at the output power optimization control problem of photovoltaic power generation system,the nonlinear modeling of photovoltaic power generation system under shadow occlusion and solar panel aging is fully considered.Aiming at the maximum power point tracking optimization problem of photovoltaic grid-connected system,an intelligent PID control strategy is proposed.The proposed control strategy only uses the input and output data of photovoltaic grid-connected systems.Under the same simulation conditions,the tracking rate of the maximum power point tracking intelligent PID control is increased by 150%compared with P&O,and the power fluctuation range of the system is reduced from 20W to 2.5W when the output is stable.The effectiveness and superiority of the proposed control method are verified by comparative simulation experiments.(2)Based on the power decoupling algorithm and virtual impedance sagging control,the control strategy of virtual synchronous generator is improved to realize the coordinated control of photovoltaic parallel inverters.Under the same simulation conditions,compared with the sagging control,the time to reach the rated power is reduced from 0.15s to 0.09s,and the power fluctuation is reduced by 50%when the output tends to be stable.Under the proposed control strategy,the output current amplitude of the shunt inverter is about 1:1,and there is basically no circulation,which proves that the power distribution effect of the control strategy is good.(3)In order to solve the problem of phase deviation in parallel operation control of virtual synchronous generators,the problems of poor detection accuracy and loss of lock of phase-locked loop in weak grid environment are fully considered.The presynchronization control strategy of PV grid-connected virtual synchronous generator is proposed.The simulation voltage waveform of the inverter shows that after the pre-synchronization control instruction is obtained at 0.4s,it only takes 0.07s to realize the synchronization with the voltage phase of the grid,and the grid connection is successful at 0.5s,and there is basically no grid connection impact.