Control method for suppressing rectification start impact current of three-phase LCL type grid connection converter

Abstract

The invention discloses a control method for suppressing rectification start impact current of a three-phase LCL type grid connection converter. The control method also enables a system to have relatively good stability in the presence of a weak electric grid. The control method comprises the steps of detecting an AC side filtering capacitor voltage to serve as a synchronous voltage of a decoupled bisynchronous phase-locked loop; outputting a d-axis fundamental wave positive-sequence component of the filtering capacitor voltage by the decoupled bisynchronous phase-locked loop, and regarding the d-axis fundamental wave positive-sequence component and the filtering capacitor voltage as a feed-forward component; and adding the feed-forward component into a current loop of the grid connection converter. The start control performance f the LCL type grid connection converter is accordingly improved, and the system also can keep relatively strong robustness in the presence of the weak electric grid. On the basis of the traditional three-phase LCL type grid connection converter current control method, the control method for suppressing the rectification start impact current of the three-phase LCL type grid connection converter does not add the sampling amount, the hardware cost and the computational burden of the system.

Description

technical field [0001] The invention belongs to the technical field of new energy grid-connected power generation, and relates to a control method for suppressing the rectification start-up surge current of a three-phase LCL type grid-connected converter, and the control method can also make the system have better stability under a weak power grid. Background technique [0002] With the increase of new energy grid-connected penetration rate, countries and regions have successively formulated strict grid-connected guidelines, which put forward higher requirements for the control performance of grid-connected converters. For the LCL type grid-connected converter, a serious inrush current will be generated when the rectification starts. If there is no suitable suppression method, it will cause protection action and even damage the switching device. [0003] At present, the start-up inrush current suppression schemes of grid-connected converters are mainly divided into the follo...

AI Technical Summary

Problems solved by technology

However, under a weak grid, PCC voltage feedforward is equivalent to introducing a positive feedback about the grid impedance, which will cause a large number of harmonics in the grid current, and even lead to system instability.

[0004] In the actual megawatt-scale wind power system, the grid-connected converter is usually connected at a voltage level of 10kV or higher, and only the voltage on the low-voltage side of the transformer can be collected.

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