Power Quality Improvement in HVDC MMC With Modified Nearest Level Control in Real-Time HIL Based Setup

초록

The Modular Multilevel Converter (MMC) is the best topology for medium and high voltage applications. The performance of MMC and the quality of the output waveform completely depends on the control applied. Nearest Level Modulation (NLM) is the conventional method used to control MMC that produces N+1 (N is the number of submodules per arm) AC output voltages. This article proposes a modified NLM control method for the MMC, which produces 2N+1 level which is twice the number of levels produced by conventional NLM. The proposed method is easy to implement and is extended in the article to produce a 4N+1 output voltage level which is never done in the literature. The THD of the output waveform is reduced to more than one-fourth compared to conventional NLM. The cost of switching devices, capacitors and size of circuit is also reduced to one-fourth for 4N+1 output waveform compared to conventional NLM. The method is verified through LabVIEW Multisim Co-simulation and real-time simulation using Field Programmable Gate Array (FPGA) based NI PXI.

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