Resistance-type sub-module hybrid MMC and DC fault processing strategy thereof

Abstract

The invention discloses a resistance-type sub-module hybrid MMC and a DC fault processing strategy thereof. According to the hybrid MMC, a three-phase grounding short circuit is artificially manufactured at the alternating-current side of the converter in the direct-current fault processing process, and fault current is prevented from entering a direct-current system from the alternating-current side; compared with a submodule hybrid MMC, the resistance-type sub-module hybrid MMC can reduce the number of required power electronic devices; and meanwhile, the DC fault processing speed of the hybrid MMC is high, the duration of the artificially manufactured three-phase grounding short-circuit fault in the fault processing process does not exceed 60 ms, and an AC system is not greatly influenced. The proportion of the resistance type sub-modules required by the MMC is only 30% of that of the half-bridge sub-modules, so that the cost for constructing an overhead line high-voltage flexible direct-current power transmission system is greatly reduced, and the MMC has very high reference significance and use value in engineering.

Description

technical field [0001] The invention belongs to the technical field of power electronics, and in particular relates to a resistive sub-module hybrid MMC and a DC fault processing strategy thereof. Background technique [0002] With the vigorous development of power electronics technology, high voltage direct current (HVDC) technology based on modular multilevel converter (MMC) is receiving more and more attention. MMC has the following advantages: ① Modular design, lower requirements for dynamic voltage equalization and trigger consistency of switching devices, and more convenient operation and maintenance; ② Good scalability, theoretically, the voltage can be increased by increasing the number of cascaded sub-modules ③Low loss, close to the level of traditional DC transmission (about 1%); ④The harmonic content of the output waveform is low, and no filtering device is required. At present, MMC has become the most promising converter topology for HVDC transmission applicatio...

AI Technical Summary

Problems solved by technology

Although technically feasible high-voltage DC circuit breakers have been developed, they are expensive and bulky, making it difficult to be widely used in power grids like AC circuit breakers

[0006] When using MMC with DC fault self-clearing capability to form a DC power grid, taking the full-bridge sub-module as an example, compared with the half-bridge sub-module MMC with the same capacity and voltage level, the number of power electronic devices used by the full-bridge MMC Almost twice as much, not only increases the investment cost, but also introduces more operating losses

Therefore, some literatures have proposed a sub-module hybrid MMC converter station composed of half-bridge sub-modules and full-bridge sub-modules, which not only has the ability to handle DC faults, but also reduces the number of power electronic devices to a certain extent However, in order to meet the requirements of DC fault processing speed, it is usually required that the number of full-bridge sub-modules in the sub-module hybrid type accounts for more than 50% of all sub-modules, and even reaches 75% in existing actual projects. This greatly weakens the advantages of the sub-module hybrid MMC over the full-bridge MMC, increasing construction costs and operating losses

Images