LCL grid-connected inverter impedance remodeling method for restraining influence of power grid background harmonic waves

Abstract

The invention relates to an LCL grid-connected inverter impedance remodeling method for restraining the influence of power grid background harmonic waves. The method comprises the following steps of:establishing a frequency domain model of an inverter grid-connected system, under the condition of considering a power grid operation mode, determining the value range of the system cutoff frequency,and introducing common point voltage feedforward compensation to perform advanced compensation on the phase of a frequency band near the cutoff frequency of the output impedance of the inverter; and increasing the phase angle stability margin of the system; and performing optimizing according to the target of the suppression effect of the background harmonic of the power grid and by taking the factors that the increasing of the fundamental frequency impedance of the inverter does not influence the output efficiency of the inverter and the phase stability margin of the medium-low frequency bandafter correction is larger than 30 degrees as constraint conditions, and determining the maximum value of the gain compensation coefficient of the compensation link within a limit value. The LCL grid-connected inverter impedance remodeling method for restraining the influence of power grid background harmonic waves has the advantages that the suppression effect on the background harmonic waves ofthe power grid is optimal while the stability of the grid-connected system is considered.

Description

technical field [0001] The invention relates to a method for reshaping the impedance of an LCL grid-connected inverter for suppressing the influence of background harmonics of a grid. Background technique [0002] The current distortion problem of the inverter grid-connected system has always been a research hotspot in new energy power generation. The grid-connected current harmonic component comes from two parts, one part is the inverter output voltage distortion caused by power electronic devices such as IGBT, and the other part is from the grid background harmonics. LCL filters are widely used in inverter grid-connected systems because of their advantages such as good high-frequency attenuation capability and low cost. However, LCL only has a good suppression effect on the harmonics from the inverter side, and cannot effectively suppress the influence of the grid background harmonic voltage on the grid-connected current. Moreover, the inherent resonance point of LCL wil...

AI Technical Summary

Problems solved by technology

The feedback quantity of GCF control is the grid-side current, which includes the background harmonic information of the grid, so to a certain extent, it can suppress the influence of the background harmonics of the grid on the grid-connected current. However, because there are multiple resonance points in the GCF control system, it is difficult to ensure the Network System Stability

Another type of method is that the voltage feedforward compensation control increases the output impedance of the inverter, which also reduces the stability of the current control loop.

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