A Thevenin Equivalent Global Modeling Method for Modular Multilevel Converters

Abstract

The invention relates to a theven equivalent overall modeling method of a modularized multi-level converter (MMC), belonging to the technical field of power transmission and distribution. The electromagnetic transient off-line simulation efficiency of the MMC is determined by the integral computation complexity of a converter part and a modulation voltage-sharing part of the MMC, and the two parts are respectively optimized in three levels by the overall modeling method of the MMC. The core technological scheme provided by the invention is as follows: firstly, assuming the equivalence to be an infinite resistor (ROFF= infinity) when a switch element in a theven equivalent model of the MMC; secondly, discretizing all submodule capacitors in the MMC by adopting a regressive eulerian method, so as to replace a trapezoid integral method in the known model; and finally, providing a novel sequencing and voltage-sharing algorithm by combining the infinite resistor with a turn-off characteristic and the regressive eulerian method, wherein the computation complexity of the novel sequencing and voltage-sharing algorithm is the same as the number of the bridge arm submodules of the MMC. The complexity of the electromagnetic transient simulating calculation of the MMC can be linearly changed along with the increasing of the number of the submodules under the premise of guaranteeing the simulation precision, so that the overall modeling method has important reference significance on researchers in the field of the MMC.

Description

technical field [0001] The invention belongs to the technical field of power transmission and distribution, and in particular relates to a Thevenin equivalent integral modeling method of a modular multilevel converter. Background technique [0002] In recent years, high-voltage and high-power fully-controlled power electronic devices such as IGBTs and IGCTs have been widely used in long-distance power transmission systems and low-voltage power distribution networks, especially in high-voltage direct current transmission based on voltage source converters (VSC- HVDC) technology. Compared with the traditional two-level and three-level VSC-HVDC, the topology of the modular multilevel converter (MMC) (sub-module is a half-bridge structure) proposed by Siemens has the advantages of not requiring a large number of IGBTs to be directly connected in series, and the device can withstand voltage The current change rate is low and no filter is needed. At the same time, at the same vo...

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Problems solved by technology

[0006] In view of the shortcomings mentioned in the above background technology that the simulation accuracy of the existing modular multilevel converter is poor or the calculation efficiency is low when simulating ultra-large-scale MMC, the present invention proposes a Thevenin of the modular multilevel converter Equivalent Whole Modeling Method