A hybrid mmc start-up charging method

Abstract

The invention discloses a hybrid MMC starting charging method, which solves the technical problem of overmodulation of a converter. The method comprises the following steps of: 1, pre-charging all half-bridge sub-modules and all full-bridge sub-modules; step 2, when the pre-charging voltage is reached, entering a step 3; step 3, entering a controlled charging stage 1: calculating a reference number nrefu of an upper bridge arm input sub-module; if the nrefu is greater than or equal to 0 and less than or equal to N1, entering a step 4; if <->N1<nrefu<=N1+N2, entering the step 5; if cN2<=nrefu<0, entering a step 6; step 4, inputting nrefu half-bridge sub-modules into the upper bridge arm, and inputting nrefl half-bridge sub-modules into the lower bridge arm; step 5; putting N1 half-bridge sub-modules into the upper bridge arm, and putting <->nrefl full-bridge sub-modules to output a positive level, and inputting <->nrefl full-bridge sub-modules into a lower bridge arm to output a negative level; step 6, inputting N1 half-bridge sub-modules into the lower bridge arm, and inputting <->nrefl full-bridge sub-modules output a positive level; and putting <->nrefl full-bridge sub-modules into the upper bridge arm to output a negative level; 7, judging whether the voltage is increased to the rated voltage UC, m or not; if yes, entering a step 7; if not, returning to the step 3; and 8, entering a controlled charging stage 2.

Description

technical field [0001] The invention belongs to the technical field of electric power transmission and distribution, and in particular relates to a hybrid MMC start-up charging method. Background technique [0002] With the rapid development of modern power electronics technology, new turn-off power electronic devices represented by insulated gate bipolar transistors (Insulated Gate Bipolar Transistor, IGBT) and pulse width modulation (Pulse Width Modulation, PWM) as the theoretical basis of the voltage source Converters began to be used in direct current transmission, which is usually called flexible direct current transmission in our country. Compared with conventional high-voltage direct current transmission technology, flexible direct current transmission has the advantages of independent control of active power and reactive power, no risk of commutation failure, voltage polarity unchanged when power flow reverses, and power supply to passive loads. , Distributed new en...

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Problems solved by technology

However, in terms of hybrid MMC start-up charging, a suitable charging strategy has not yet been obtained, especially due to the complexity of the hybrid MMC topology, the hybrid MMC startup has the problems of controlled charging current impact and bridge arm over-modulation, thus Cause hybrid MMC failure or damage

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