Submodule topologies and PWM techniques applied in modular multilevel converters: review and analysis

Abstract

Nowadays electrical energy presents itself as the most promising solution to satisfy the energy needs of smart cities. For electrical energy to be managed efficiently and sustainably, the use of power electronic converters is essential. The evolution of semiconductors, in terms of blocking voltages, conduted current and switching frequencies, led to the emergence of new topologies for more robust and compact power electronics converters with high-frequency galvanic isolation. However, for high and medium voltage applications, such as electric railways, wind turbines, solar photovoltaic, or energy distribution systems, the semiconductor blocking voltages are still below the values in demand. In order to solve this problem, modular multilevel converters (MMC) has been implemented, requiring more sophisticated control algorithms and complex pulse width modulation (PWM) techniques, such as space vector modulation. In this paper, different topologies to be integrated into an MMC are presented, as well as PWM techniques for MMC, making a comparative analysis based on computer simulations of different PWM techniques developed in PSIM software. An MMC consisting of 4 full-bridge DC-AC power converters connected in series was considered as the study basis for the analysis of the PWM techniques.