A method for weakly damped resonance suppression and fast power regulation of LCL inverters

Abstract

The invention discloses a low damping resonant suppression and rapid power adjustment method of an LCL inverter. The low damping resonant suppression and rapid power adjustment method mainly comprises robust grid-current-feedback active damping control, synchronous reference frame quasi-proportional-integral control and power feedforward control, wherein by a robust grid-current-feedback active damping controller, the low damping characteristic of the system can be overcome, the LCL resonant peak is suppressed, and the robustness of the system on impedance change of a power grid is improved; by the synchronous reference frame quasi-proportional-integral control, the reactive power can be compensated, the instant current of the power grid is adjusted to be free from the influence of frequency deflection of the power grid and is maintained with a zero-steady error all the time; and by the power feedforward control, the single-way transfer process of photovoltaic DC-side energy to power grid AC-side energy can be accelerated. By the low damping resonant suppression and rapid power adjustment method, the low damping resonant suppression of an LCL-type grid-connected distributed power generation system is achieved, the power regulation process is accelerated, and moreover, the robustness of the system on the frequency deflection of the power grid and the impedance change of the power grid is improved.

Description

technical field [0001] The invention relates to the field of new energy distributed power generation, in particular to a method for weakly damped resonance suppression and fast power adjustment of an LCL inverter. Background technique [0002] With the shortage of fossil energy and the deterioration of environmental pollution, distributed power sources such as wind energy and solar energy have attracted widespread social attention and have become a research hotspot. As a key interface between distributed generation (distributed generation, DG) and utility grid, LCL grid-connected inverter has become a widely used and cost-effective device. However, there are still some problems that need to be solved urgently: because the LCL filter is a third-order low-damping system, it is easy to generate resonance and cause system instability; It shows the characteristics of a weak grid, that is, the grid frequency and grid impedance will change with the system working status, and the g...

AI Technical Summary

Problems solved by technology

However, there are still some problems that need to be solved urgently: because the LCL filter is a third-order low-damping system, it is easy to generate resonance and cause system instability; It shows the characteristics of a weak grid, that is, the grid frequency and grid impedance will change with the system working status, and the grid voltage at the grid-connected point has serious background harmonics, which puts forward higher requirements for the grid-connected inverter

However, due to the existence of transmission lines and isolation transformers, the LCL resonant frequency always shifts with the change of grid impedance

Once the LCL resonant frequency shifts to the cutoff frequency, the potential instability of the system will be triggered

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