A Method for Suppressing Harmonic Effects of Grid-connected Inverter Grid Based on LCL Filtering

Abstract

A grid-connected inverter electric network harmonic wave effect inhibiting method based on LCL filtering belongs to a method of inhibiting voltage disturbance of an electric network by a grid-connected inverter. According to the method of the invention, outputting admittance of the grid-connected inverter is corrected. The grid-connected inverter electric network harmonic wave effect inhibiting method comprises two steps: 1. introducing an electric network voltage bandpass feedforward at a preset harmonic frequency in a grid-connected inverter current control loop, and through output admittance correction at the frequency, establishing a bandpass filter parameter design principle; 2. similarly introducing the bandpass filter into a phase-locked loop control loop, correcting an additional admittance item which is introduced by the phase-locked loop, further maximally reducing the output admittance amplitude of the grid-connected inverter at the preset frequency, thereby realizing electric network harmonic wave attenuation. The grid-connected inverter electric network harmonic wave effect inhibiting method has functions of: settling defects of compensation error in unit feedforward of electric network voltage and high difficulty in introducing a differential item into full feedback of the electric network voltage, preventing system stability reduction caused by adding the harmonic wave compensator into the current controller, and realizing relatively high electric network harmonic wave inhibiting capability and high reliability.

Description

technical field [0001] The invention relates to a method for suppressing grid voltage disturbance by a grid-connected inverter, in particular to a method for suppressing the influence of grid-connected inverter grid harmonics based on LCL filtering. Background technique [0002] In recent years, with the increasing energy demand and deteriorating environmental problems, distributed power generation systems based on renewable energy, such as wind power, solar power, and fuel cells, have attracted more and more attention. Grid-connected inverters, as the interface unit between renewable energy sources and the grid, play an important role in ensuring high-quality electrical energy is injected into the grid. [0003] The background harmonics of the power grid will introduce current harmonics of the same frequency to the output current of the grid-connected inverter, which seriously affects the output power quality of the grid-connected inverter. In practical applications, since...

AI Technical Summary

Problems solved by technology

For the L-filter grid-connected inverter, grid voltage proportional feed-forward can largely eliminate the grid voltage disturbance, but for the LCL filter, due to its high-order and strong coupling characteristics in synchronous rotating coordinates, Difficult to achieve grid decoupling

Some literatures have proposed a grid voltage full feedback strategy, which can completely eliminate grid voltage disturbances, but there are multiple differential components in the feedforward function introduced by this method, and it is too sensitive to the parameters of the filter, which is difficult to implement in practical applications. implement

Images