Capacitor voltage equalizing method for power modules of modular multilevel converter
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: 2016-05-04
INST OF ELECTRICAL ENG CHINESE ACAD OF SCI
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[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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[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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The invention provides a capacitor voltage equalizing method for power modules of a modular multilevel converter. According to the method provided by the invention, aiming at the condition that reference voltage waveforms of bridge arms are trapezoidal waves, referring to a mode of pre-sorting to determine input and removal orders of the power modules at a slope stage of the trapezoidal waves, the sorting frequencies within a fundamental period are reduced and the control difficulty is lowered. When each reference wave value is equal to the magnitude of a DC side voltage, a period of time is selected, communication is built between the upper bridge arm and the lower bridge arm, and the actual conduction number of the power modules of the upper bridge arm and the lower bridge arm is determined according to the mean value of capacitor voltages of the power modules of the upper bridge arm and the lower bridge arm.
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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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