Control Strategy of Modular Multilevel Converter: theoretical investigation and performance

Abstract

Modular multilevel converters (MMCs) have actually a new topology used in power applications particularly in the High DC Voltage (HVDC) transmission lines for direct current. The use of a large number of cells in the MMC converter has some advantages such as the low switching frequency of the semiconductors, which reduces the switching losses. The MMC also has drawbacks, which are reflected in the complexity of the control of the converter due to the presence of a large number of sub modules (SM). In recent years, many works have established new strategies of the MMC control. This paper presents a review of a Pulse Width Modulation (PWM) method used for the MMC control which is the Phase shifted PWM. Simulations in MATLAB-Simulink are performed to validate the control and power transfer for two different MMC. A comparative study has presented for the harmonic distortion rate of the MMC converter output voltage.