MMC sub-module voltage fluctuation suppression method for injecting common-mode voltage and circulating current

Abstract

The invention discloses an MMC sub-module voltage fluctuation suppression method for injecting common-mode voltage and circulating current, and the method comprises the steps: carrying out the information collection of an upper bridge arm and a lower bridge arm, and obtaining an upper arm current, a lower arm current, an upper arm voltage and a lower arm voltage; performing common-mode injection system control to obtain three-phase output voltage and three-phase output current; performing common-mode injection calculation to obtain a common-mode current reference value; performing circulation control according to the three-phase output current to obtain a three-phase circulation simulation reference current value; and according to the common-mode current reference value, the direct-current bus voltage feedback value and the three-phase circulating current simulated reference current value, performing current comparison calculation, obtaining a current-sharing reference value, promoting PWM to generate a trigger pulse, driving an MMC bridge arm power device, and completing voltage fluctuation suppression. According to the method, the problem of large bridge arm capacitance fluctuation is solved, the circulating current reference value is calculated by injecting the common-mode voltage and combining the typical half-bridge MMC / DC-AC topology, MMC bridge arm circulating current is effectively restrained, sub-module capacitance voltage fluctuation is reduced, and the safe and reliable operation capacity of a system is enhanced.

Description

technical field [0001] The invention relates to the technical field of voltage fluctuation suppression, in particular to a voltage fluctuation suppression method of an MMC sub-module injecting common mode voltage and circulating current. Background technique [0002] Modular multilevel converters (MMCs) have been favored by the industry due to their key features such as scalability, modularity, ease of assembly, high-quality current waveforms, less electromagnetic interference, and transformerless operation. and widespread attention from academia. [0003] However, MMC still has obvious disadvantages. Because the bridge arm current and voltage contain multiple frequency harmonics, the sub-module (SM) capacitor voltage has fundamental frequency, double, and triple frequency fluctuations, and the fluctuating SM capacitor voltage generates circulating currents that flow between phases, resulting in power loss. , The voltage ripple of the sub-module capacitor and the peak valu...

AI Technical Summary

Problems solved by technology

This method aims to solve the problem of large fluctuations in bridge arm capacitance. By injecting common-mode voltage, combined with the DC-to-AC (MMC / DC-AC) topology of a typical half-bridge modular multilevel converter, to calculate the reference value of the circulating current, Effectively suppress the circulating current of the MMC bridge arm, reduce the voltage fluctuation of the sub-module capacitor, and enhance the safe and reliable operation of the system

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