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A method for voltage equalization of capacitors in power modules of modular multilevel converters

A modular multi-level, power module technology, applied in the direction of converting AC power input to DC power output, output power conversion devices, electrical components, etc., can solve the problem of capacitor voltage divergence of upper and lower bridge arm power modules

Active Publication Date: 2018-01-12
INST OF ELECTRICAL ENG CHINESE ACAD OF SCI
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Problems solved by technology

[0004] The purpose of the present invention is to overcome the problem that the capacitor voltage of the upper and lower bridge arm power modules diverges when the existing AC system operates asymmetrically and the circuit parameters of the upper and lower bridge arms are different, and proposes a modular multilevel converter power Voltage equalization method of module capacitor voltage

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  • A method for voltage equalization of capacitors in power modules of modular multilevel converters
  • A method for voltage equalization of capacitors in power modules of modular multilevel converters
  • A method for voltage equalization of capacitors in power modules of modular multilevel converters

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Embodiment Construction

[0026] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0027] figure 1 It is a bridge arm reference voltage waveform diagram of the modularized multilevel converter of the present invention. figure 2 It is the waveform diagram of the total voltage and current of a certain bridge arm power module when the parameters between the bridge arms are asymmetric. The phase difference of the reference voltages of the upper and lower bridge arms is 90 degrees. There are 6 power modules in one bridge arm, where N=4,m 1 = 1; m 2 =1; M=1. The DC side voltage value is 10kV.

[0028] At t=0, sort the capacitor voltages of the six power modules of a certain bridge arm. If the current passing through the bridge arm is the charging direction at this time, the four modules with the smallest capacitor voltage among the six power modules will be ranked according to the capacitor voltage. If the current passing th...

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Abstract

A method for equalizing capacitor voltage of a modular multilevel converter power module. The method described is aimed at the case where the reference voltage waveform of the bridge arm is a trapezoidal wave. Referring to the trapezoidal wave ramp phase, pre-sorting is used to determine the order of power module input and removal, which reduces the number of sorting times in a fundamental wave cycle and reduces the difficulty of control. When the reference wave value is the DC side voltage, select a period of time to establish communication between the upper and lower bridge arms, and determine the actual number of power modules in the upper and lower bridge arms that are turned on according to the average value of the capacitor voltage of the upper and lower bridge arm power modules.

Description

technical field [0001] The invention relates to a power module capacitor voltage equalization method of a modular multilevel converter of a power system. Background technique [0002] The converter technology based on the MMC (modular multilevel converter, modular multilevel converter) technology has received extensive attention. Generally, the reference voltage of the bridge arm based on MMC technology is generally a sinusoidal waveform, and the fundamental frequency is a power frequency. When the reference voltage waveform is a trapezoidal wave, the switching frequency of the module can be reduced. From another perspective, the frequency of the AC fundamental wave can be medium to high frequency, thereby reducing the volume of the capacitive and inductive components. [0003] For modular multilevel converters, when the AC fundamental frequency is industrial frequency, the switching frequency of the power module is tens to hundreds of times of the fundamental frequency. Wh...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02M7/483
CPCH02M7/483H02M7/4835
Inventor 李耀华曲平李子欣高范强王平
Owner INST OF ELECTRICAL ENG CHINESE ACAD OF SCI
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