A Control Method for Suppressing Small-Signal Disturbance of Phase-locked Loop of Three-phase lcl Type Grid-connected Converter in Weak Power Grid

Abstract

The invention discloses a control method for suppressing small signal disturbance of a three-phase LCL-type grid-connected converter phase-locked loop under a weak power grid. Phase-locked loop small signal disturbance suppressing signals with phase-locked loop synchronous voltage as input are added in grid-connected converter current control, that is, q-axis capacitance voltage Ucq and a current disturbance suppressor GPLLi are multiplied to acquire current disturbance suppressing signals IPLLs, and the current disturbance suppressing signals IPLLs are added to q-axis grid-connected current feedback; and q-axis capacitance voltage Ucq and a voltage disturbance suppressor GPLLu are multiplied to acquire voltage disturbance suppressing signals UPLLs, and the voltage disturbance suppressing signals UPLLs are added to q-axis control voltage. Thus, the performance of suppressing the phase-locked loop small signal disturbance by the LCL-type grid-connected converter under the weak power grid is thus improved, and the system can keep strong robustness under the weak power grid.

Description

technical field [0001] The invention belongs to the technical field of new energy grid-connected power generation, and in particular relates to a three-phase LCL grid-connected converter system and a control method for suppressing small-signal disturbance of a phase-locked loop of the three-phase LCL grid-connected converter under a weak 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. Since new energy sources are usually far away from the load center, the power grid presents the characteristics of a weak power grid, and the grid impedance cannot be ignored. Usually, the short-circuit ratio (the ratio of the short-circuit capacity of the grid to the rated capacity of the grid-connected converter) is used to indicate the strength of the grid. When...

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Problems solved by technology

A high PLL bandwidth can speed up the dynamic response of the grid-connected converter, but it will cause resonance between the grid-connected converter and the grid under a weak grid, making the system unstable

Reduce the bandwidth of the phase-locked loop, and the influence of the small-signal disturbance of the phase-locked loop on the grid-connected current in a weak grid can be suppressed, but it will slow down the dynamic response of the grid-connected current, which is not conducive to the fault ride-through of the system

Therefore, it is impractical to suppress the small-signal disturbance effect of the phase-locked loop on the grid-connected current control in a weak grid by adjusting the bandwidth of the phase-locked loop

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