Hybrid sub-module MMC converter with direct-current fault ride-through capability

Abstract

The invention relates to a hybrid sub-module MMC (multimedia card) converter with direct-current fault ride-through capability. The hybrid sub-module MMC is similar to the half-bridge MMC in topology, namely a three-phase six-bridge structure, but the single bridge is successively cascaded by m half-bridge sub-modules (HBSM), n full-bridge sub-modules (FBSM) and one clamp dual sub-module (CDSM); the high direct-current voltage utilization rate of FBSM, the direct-current fault current self-cleaning of FBSM and CDSM and the economic advantage of HBSM are integrated to optimally select the amount of m, n and one according to the actual demand, so that the converter can be applied to a flexible direct-current transmission system, in particular, to an occasion with the higher commissioning rate, when the system has one direct-current fault, it is promoted in capacity to save the economic cost under existence of the direct-current fault ride-through capability.

Description

technical field [0001] The invention relates to the technical fields of flexible direct current transmission and distribution of power systems, power electronics and user electric power, and specifically relates to a flexible direct current transmission MMC converter valve topology with direct current fault ride-through capability. Background technique [0002] DC short-circuit fault is the most common fault in the MMC-HVDC system. Traditional MMC converters based on half-bridge sub-modules cannot cut off the feed from the AC system to the DC short-circuit point by blocking the sub-module IGBT in the event of a DC bipolar short-circuit fault. If there is a power circuit, the AC circuit breaker or DC isolating switch must be quickly tripped to clear the fault current, which not only increases the system cost, improves the technical requirements for the equipment, but also reduces the system operation rate and slows down the fault recovery speed. [0003] At present, most proj...

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Problems solved by technology

The former has a complex structure and high difficulty in control, which is not conducive to project implementation

In the latter, in addition to the DC fault ride-through capability, the full-bridge sub-module MMC can also improve the DC voltage utilization rate due to the negative voltage characteristics of the module, thereby increasing the system capacity; the clamped twin-sub-module MMC has less power than the full-bridge sub-module. The number of components is more economical, but it is still at a disadvantage compared to the half-bridge MMC

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