Modular multilevel converter capable of cutting off direct current short-circuit fault current

Abstract

The invention relates to a modular multilevel converter capable of cutting off a direct current short-circuit fault current, and belongs to the technical field of power electronic power conversion. The positive electrode ends of three upper current conversion bridge arms are connected together to be connected with the positive electrode of an energy absorption branch thyristor and one end of a quick mechanical switch; the other end of the quick mechanical switch is connected with one end of an auxiliary electronic switch; the other end of the auxiliary electronic switch is used as the direct current positive electrode end of the converter; the negative electrode ends of three lower current conversion bridge arms are connected together to be connected with the negative electrode of an energy absorption capacitor and the negative electrode of a fly-wheel diode to be used as the direct current negative electrode end of the converter; each bridge arm is formed by multiple same power modules in a serial connection way; and the alternating current port of each power unit is connected with a group of bidirectional bypass thyristors in parallel separately. According to the modular multilevel converter capable of cutting off the direct current short-circuit fault current, the modular multilevel converter can have the capability of cutting off the direct current fault current through the simple quick mechanical switch and the energy absorption circuit.

Description

technical field [0001] The invention relates to a modular multilevel converter capable of cutting off a DC short-circuit fault current, belonging to the technical field of power electronic power conversion. Background technique [0002] Flexible DC transmission has become the most potential new power transmission method at present. Because the modular multilevel converter has a common DC terminal, and has the characteristics of easy expansion, decoupling control of active and reactive power, excellent harmonic characteristics, and low loss of switching devices, it is very suitable for flexible DC transmission systems. However, in the event of a short-circuit fault on the DC line, the modular multilevel converter will produce an uncontrolled rectifier effect, and the modular multilevel converter using conventional half-bridge power modules cannot clear the DC short-circuit fault current by itself , which limits the use of DC overhead lines in engineering. [0003] One type ...

AI Technical Summary

Problems solved by technology

[0005] The purpose of the present invention is to solve the problem that the current half-bridge modular multilevel converter does not have the ability to clear the DC short-circuit fault current, and the power module improved modular multilevel converter has a relatively large increase in cost and loss, while High-voltage DC circuit breakers still have disadvantages such as low technical maturity, large cost, and large size. A modular multilevel converter that can cut off the DC short-circuit fault current is proposed. When a DC short-circuit fault occurs, the power module is bypassed The thyristor is turned on to limit the DC voltage, and the thyristor of the energy absorbing branch is triggered to turn on the energy absorbing capacitor branch, and the DC short-circuit fault current is forced to be transferred to the energy absorbing capacitor and the freewheeling diode by turning off the auxiliary electronic switch, and quickly decays to Zero, making the fast mechanical switch break at zero current and zero voltage, realizing the cutting off of DC fault current

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