Topology, Operation and Control of Modular Multilevel Converter for Grid Application: A Review

Abstract

Modular multilevel converter (MMC) is a widely accepted technology for high voltage direct-current (HVDC) application. Due to its modularity, scalability, power quality, and no need of bulky filter on ac side, they are widely used as voltage source converters in HVDC applications. This paper presents a comprehensive study on MMC technology for grid applications along with different modulation techniques and voltage balancing strategies which are essential for the converter to work as a rectifier or an inverter. The paper provides a general overview of the topology along with the operation of MMC. The main focus of the paper is on the control strategy of the MMC. Out of all the available topologies, the most suitable strategy is discussed and highlighted.
Keywords: Modular multilevel converter (MMC) modulation techniques, circulating current control, high-voltage direct-current transmission, capacitor voltage balancing