Evaluation of Fault Characteristics of Modular Multilevel Converters for High Voltage Direct Current Transmission System

The back-to-back HVDC Modular Multilevel Converter (MMC) is a power electronic system used for high voltage direct current transmission. The MMC operates by switching a series of capacitors and switching devices in a specific pattern to produce an output voltage waveform. This study focuses on modeling of a back-to-back High Voltage Direct Current (HVDC) MMC for supplying power to a passive network. The effects of DC bus pole-pole fault and DC bus pole-ground fault are also analyzed. The MMC is modeled using a simplified topology and a novel control strategy to improve its performance. The aggregated modeling strategy is employed to reduce the number of equations and improve the simulation time. The results show that the proposed strategy can improve the efficiency of the MMC while maintaining a high-power quality. This study examines into the performance of the system during a grid fault by analyzing and validating a Voltage Source Converter (VSC) based HVDC transmission system using an MMC. It is executed using a Simulink-based model of the MMC-HVDC system.