MMC frequency coupling impedance modeling method under model prediction AC voltage control

Abstract

The invention discloses an MMC frequency coupling impedance modeling method under model prediction AC voltage control. An MMC under AC voltage control is predicted by using a model to serve as a modeling object; through circuit equation frequency domain small signal modeling and model prediction AC voltage control loop frequency domain small signal modeling, an MMC small signal impedance model isobtained through derivation, and the model is composed of MMC positive sequence impedance, MMC negative sequence impedance and positive sequence impedance and negative sequence impedance frequency coupling terms caused by MMC internal complex harmonic dynamic characteristics. The accuracy of the small signal impedance model established by the method is verified by simulation, and the method and the basis can be provided for MMC small signal impedance modeling and stability analysis based on an MMC system.

Description

technical field [0001] The invention belongs to the technical field of power electronic equipment modeling, in particular to a method for modeling frequency coupling impedance of an MMC (modular multilevel converter) under the control of a model pre-determined alternating voltage. Background technique [0002] High-voltage flexible direct current transmission (HVDC) based on MMC has a series of advantages such as low output harmonic content, low switching loss, no need for reactive power compensation, black start capability, and high modularity. It is the preferred solution for large-scale and long-distance power transmission. ; Typical projects that have been put into operation include the Borwin3 flexible DC transmission project in Germany and the four-terminal flexible DC transmission project in Zhangbei, China, which have produced huge economic and environmental benefits. [0003] The basic structure of MMC is as follows figure 1 As shown, it mainly includes 3-phase 6 b...

AI Technical Summary

Problems solved by technology

Existing studies on the establishment of the impedance model of the MMC converter station are not yet complete. The current mainstream modeling ideas only establish the MMC positive sequence impedance and negative sequence impedance models under the traditional constant AC voltage control, and consider the positive sequence impedance, negative sequence impedance The sequence impedances are decoupled from each other; in fact, due to the internal harmonic dynamic process of MMC, there is a frequency coupling effect between positive and negative sequence impedances, so the established MMC impedance model is not accurate

In addition, the current mainstream modeling ideas do not carry out impedance modeling for the MMC under the control of the model-based predetermined AC voltage, and cannot analyze the instability and resonance problems faced by the MMC system under the control of the model-based predetermined AC voltage.

Images