Diode clamping hybrid MMC circuit with self-voltage-sharing capability

Abstract

The invention belongs to the power electronics technology field and especially relates to a diode clamping hybrid MMC circuit with a self-voltage-sharing capability. A bridge arm of the MMC circuit isconnected in series with a plurality of hybrid circuit sub-modules Hybrid SM. Each hybrid circuit sub-module Hybrid SM is composed of a half-bridge sub-module HBSM, a full-bridge sub-module D-FBSM and a clamping diode D1. A negative electrode of the clamping diode D1 is connected with a positive electrode of a capacitor C1 of the half-bridge sub-module HBSM, the positive electrode of the clampingdiode D1 is connected to the positive electrode of a capacitor C2 of the full-bridge sub-module D-FBSM, and the negative electrode of the half-bridge sub-module HBSM is connected with the positive electrode of the full-bridge sub-module D-FBSM. When the clamping diode D1 is conducted, automatic voltage sharing in a cascade unit is realized; and under a fault condition, a capacitor of the half-bridge sub-module is reversely connected in series into a fault loop and acts with the capacitor of the full-bridge sub-module to remove a fault current.

Description

technical field [0001] The invention belongs to the technical field of power electronics, and in particular relates to a diode-clamp hybrid MMC circuit with self-equalizing capability. Background technique [0002] Due to its modular design, the Modular Multi-level Converter (MMC) makes it easier to upgrade the system capacity and has stronger scalability. In actual operation, the MMC-HVDCs currently in operation are all back-to-back projects with no transmission distance, or use cables as their transmission lines. However, at the same voltage level and transmission power, the cost of cables is much higher than that of overhead lines. At the same time, due to the "skin effect" during the operation of the cable, the space charge problem and the insulation problem are also very serious. Therefore, in the context of the development of long-distance, high-voltage, and large-capacity DC transmission, the use of overhead line transmission with obvious economic and technological ...

AI Technical Summary

Problems solved by technology

However, the number of modules used in these two topologies is large and the cost is relatively high. Therefore, some people now propose to use a full-bridge-half-bridge hybrid topology, as shown in the attached figure 1 As shown, the number of components is reduced, but the voltage difference of the sub-module capacitors after the fault is relatively large, which is not conducive to the recovery after the fault

How to solve the problem of quickly clearing the current and voltage imbalance after the current topological fault is an urgent need to be solved

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