A Method of Establishing Mean Model and Small Signal Model

Abstract

The invention discloses an establishment method of a mean value model and an establishment method of a small signal model. The mean value model includes an MMC body module, a VSG control module, an alternating-current network module and a phase-locked loop module. According to the establishment method of the mean value model, the VSG control module performs calculation on the basis of received active reactive current idref and iqref so as to obtain v<dref>, v<qref>, u<ddiff, ref>, and u<qdiff, ref>; the v<dref>, v<qref>, u<ddiff, ref>, and u<qdiff, ref> obtianed by the VSG control module are sent to the MMC body module, and calculation is performed so as to obtain alternating-current side current isd and alternating-current side current isq; the alternating-current side current isd and thealternating-current side current isq are returned to the VSG control module and sent to the alternating-current network module; the alternating-current network module performs calculation on the basis of the received alternating-current side current so as to obtain PCC point voltages vsd and vsq, and then sends the PCC point voltages vsd and vsq to the phase-locked loop module; calculation is performed, a phase-locked frequency omegapll, and a phase-locked angle thetapll are obtained, and the phase-locked frequency omegapll and the phase-locked angle thetapll are returned to the VSG control module; and therefore, the problem of analysis on the stability of the access of an MMC into a (weak) grid system can be solved.

Description

technical field [0001] The patent of the present invention relates to the technical field of modular multilevel converter modeling, and more specifically, relates to a method for establishing an average value model and a small signal model. Background technique [0002] Modular multilevel converter (MMC) has excellent operating performance such as modular structure, easy expansion, and low switching loss, and has broad application prospects in the field of multi-terminal DC transmission and DC grid technology. As an interconnection device between the DC grid and the AC grid, the MMC can not only realize the independent decoupling control of active power and reactive power, but also expect it to support the AC frequency when disturbances occur on the AC side. At present, this expectation is made possible due to the emergence of VSG control technology. VSG control can realize power control, and can support the frequency of the AC side when there is a disturbance on the AC side...

AI Technical Summary

Problems solved by technology

[0003] The purpose of the embodiment of the present invention is to provide a method for establishing an average value model and a small signal model, which solves the problem of stability analysis of the MMC connected to the grid system

Images