Modular multilever converter (MMC) module topological structure applicable for flexible direct current transmission

Abstract

The invention provides a module topology which is applied to a modular multilever converter (MMC) type flexible direct current transmission system and has improved power density. The module topology comprises four insulated gate bipolar translators (IGBTs) VT1, VT2, VT3 and VT4, wherein the four IGBTs are respectively and reversely connected in parallel with diodes VD1, VD2, VD3 and VD4; a direct-current capacitor C is input or removed by controlling the switch-on or switch-off of the two IGBTs VT1 and VT2 in a first H half-bridge structure so as to generate a required alternating-current voltage; and an extra LC circuit is controlled by the two IGBTs VT3 and VT4 in a second H half-bridge structure to absorb a fundamental frequency on the direct-current capacitor and the frequency fluctuation of a second harmonic frequency, so that the frequency fluctuation is reduced, the capacitance and the volume of the direct-current capacitor are reduced. The capacitance of the direct-current capacitor can be reduced through the introduction of an auxiliary circuit, thus, the module volume is reduced, and the power density is improved.

Description

【Technical field】 [0001] The invention relates to the technical field of flexible power transmission and distribution, in particular to an MMC module topology structure applied to flexible direct current power transmission. 【Background technique】 [0002] Compared with the traditional voltage source converter, the modular multilevel converter (ModularMultileverConverter, MMC) has the advantages of good scalability, small harmonics, low switching frequency, and less requirements for consistent triggering of devices, and is especially suitable for DC transmission application occasions. [0003] For a single-phase bridge arm, the DC current, the fundamental current and the fundamental voltage produce a power fluctuation of the fundamental frequency and a double frequency. The multiplier frequency fluctuates, so when selecting a capacitor, a large capacitance is required to cope with the fluctuation of the fundamental frequency voltage, resulting in a large capacitance value, s...

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Problems solved by technology

[0003] For a single-phase bridge arm, the DC current, the fundamental current and the fundamental voltage produce a power fluctuation of the fundamental frequency and a double frequency. Frequency fluctuations, ...

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