Modular multilevel converter using multi-state submodule

Abstract

The invention discloses a modular multilevel converter using a multi-state submodule. A basic structure of a submodule is characterized in that based on a half-bridge module topology formed by two insulated gate bipolar transistors S1 and S2 with anti-parallel diodes and a capacitor C, a parallel side positive port P3 and a parallel side negative port P4 are parallelly led out from a positive polarity end of the capacitor C; a bridge side possesses a bridge side positive port P1 and a bridge side negative port P2; two metal-oxide semiconductor field effect switch tubes S3 and S4 with the anti-paralleled diodes are reversely connected in series between the positive polarity end of the capacitor and the parallel side positive port P3 to form a bidirectional switch. The multi-state submodule topology can be operated under three kinds of modes which are investment, removing and parallel connection and real-time series-parallel switching of the adjacent modules is realized so that purposes of reaching module capacitance voltage sharing and increasing a bridge-arm equivalent capacitance are achieved. Through whole bridge arm module investment operation and series-parallel selection control, overall switch losses of the converter can be greatly reduced, and the excellent module capacitance voltage sharing and a pulsation inhibition effect are obtained.

Description

technical field [0001] The invention belongs to power electronic equipment, in particular to a modular multilevel converter using multi-state sub-modules Background technique [0002] Since the modular multilevel converter was proposed, due to its highly modular structure and easy expansion, good redundancy characteristics and flexible configuration methods, it can effectively realize power conversion at high voltage levels, and is mainly used in static Reactive power compensation, high-voltage direct current transmission and high-voltage high-power motor speed regulation fields. [0003] However, because the modules of the modular multilevel converter are independent of each other and there are differences in electrical parameters, sub-module capacitor voltage fluctuations and imbalances are prone to occur. The capacitor voltage fluctuations are proportional to the current amplitude of the AC side and are proportional to The frequency is inversely proportional to the modul...

AI Technical Summary

Problems solved by technology

Not only that, based on the carrier phase-shift PWM modulation method, each sub-module corresponds to a carrier, and its control calculation amount increases significantly with the increase of the number of levels, and the control accuracy of the phase difference will also decrease, so it is difficult to increase the output voltage

Step wave modulation has a small amount of calculation, low switching frequency, and is easy to implement, but at the same time it brings a decrease in the ability to suppress voltage fluctuations, and the module voltage equalization and sorting algorithm in the bridge arm will bring a great burden to the controller. Especially for converters with a large number of levels

[0006] The main problem of the existing technology is to increase the loss (including on-state loss and switching loss) in exchange for limited ripple suppression ability, and at the same time limit the number of levels of the multi-level converter, the controller has a large amount of calculation, which greatly limits the Application of Modular Multilevel Converter in Medium and High Voltage Field

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