Sub-module topology with direct-current fault clearing capability

Abstract

The invention relates to a sub-module topology with a direct-current fault clearing capability, and belongs to the technical field of high-voltage flexible direct-current power transmission. The sub-module topology comprises a half-bridge sub-module SM1, an improved full-bridge sub-module SM2, a bidirectional switch S1 and a diode D7. The half-bridge sub-module SM1 and the improved full-bridge sub-module SM2 are connected in a cascading mode, the diode D7 is arranged between the positive electrode of the capacitor C1 in the half-bridge sub-module SM1 and the positive electrode input port of the improved full-bridge sub-module SM2 in a series connection mode, and the bidirectional switch S1 is arranged between the negative electrode output port of the half-bridge sub-module SM1 and the positive electrode input port of the improved full-bridge sub-module SM2 in a series connection mode. The method can realize rapid self-cleaning of fault current, has a direct current side fault self-cleaning capability, and is suitable for an offshore wind power flexible direct current power transmission system. Compared with a half-bridge MMC topology, the MMC topology has the direct current side fault clearing capability, and compared with a full-bridge MMC topology, the MMC topology has the advantages that the number of insulated gate bipolar transistors is reduced, and the cost is reduced.

Description

technical field [0001] The invention relates to a sub-module topology capable of clearing DC faults, and belongs to the technical field of high-voltage flexible DC transmission. Background technique [0002] With the continuous development of high-voltage direct current transmission technology, modular multilevel converter (MMC) is the most widely used and most common converter in the field of flexible direct current transmission. Compared with other converters, MMC has The manufacturing difficulty is reduced, the loss is doubled, the step voltage is reduced, the waveform quality is high, and the fault handling ability is strong. The probability of faults in the flexible DC transmission system is extremely high, and the flexible DC transmission system based on MMC must have fault ride-through capability. [0003] In recent years, my country has launched a number of offshore wind power flexible DC transmission projects, including Jiangsu Rudong Offshore Wind Power Flexible D...

AI Technical Summary

Problems solved by technology

When the MMC DC side fails and the sub-modules are locked, the fault current can form a loop through the anti-parallel diodes of the sub-modules. The fault current is large and does not have the ability to self-block the fault current. In severe cases, it may cause damage to the device and the converter station. shut down

[0004] At present, when the MMC DC fault occurs, the fault current is often cleared by inputting a negative level. Therefore, it is hoped that there will be a sub-module topology that can realize the self-clearing of the fault DC, and solve the problem that the current is too large to be cut off by the circuit breaker in the flexible DC transmission of offshore wind power. circuit problem

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