Research On The Detection And Suppression Of Harmonics Based On Grid-connected Photovoltaic Power System

In the context of the urgent need to transform and upgrade the global energy structure,solar energy,as an eco-friendly and clean energy source,has received widespread attention due to its important role in relieving the growing load demand of the power system.In the process of grid integration,the access of power electronics and nonlinear loads will generate a large number of harmonics,which will distort the grid-connected current waveform and not only affect the stability and safety of the power system,but also interfere with the normal operation of other surrounding equipment.In this paper,based on a two-stage three-phase PV grid-connected power generation system,active power filters are added to achieve maximum power tracking control,grid-connected current harmonic detection and suppression functions.First,this paper analyzes the structure and mathematical model of the grid-connected PV system,and proposes a maximum power tracking algorithm to improve the shortcomings of the traditional algorithm.The mathematical model of DC/DC converter and three-phase inverter with L-type filter circuit is established to clarify the implementation principle of the maximum power tracking algorithm,and the perturbation observation method based on variable step size is proposed,which is simple to implement and improves the tracking effect significantly and helps to improve the power generation utilization of PV arrays significantly,and is verified by comparison in simulation experiments.Secondly,the harmonic detection method based on the three-phase instantaneous reactive power theory is studied.For the problems of system delay and response speed and limited effect of filtering accuracy when processing voltage and current signals in the ip-iq detection method with low-pass filter,the use of integral mean filter is proposed instead of the traditional Butterworth filter.Simulation verifies that the method can improve the shortcomings of the traditional low-pass filter and improve the detection accuracy of harmonics.Finally,the active filtering function is added to the grid-connected photovoltaic power generation system to monitor and analyze the harmonics in the grid in real time and realize the dynamic compensation of harmonic currents.The voltage and current double closed-loop control of the three-phase gridconnected inverter with space vector pulse-width modulation technology enables it to detect and suppress system harmonics while achieving power grid connection.The system model is built on MATLAB/Simulink simulation platform to verify the implementation of the main functions,and the total harmonic distortion(THD)of the grid-connected current is reduced from 26.25%to 1.93%,and the current waveform is significantly improved.