Circuit Topologies, Operation, Control Schemes and Modulation Techniques of Modular Multilevel Inverter

Abstract

The Modular Multilevel Converter (MMC) is one of the developing topology. MMC has several attractive features such as a modular structure, transformer-less operation, easily scalable in terms of voltage and current, low expense for redundancy and fault tolerant operation and excellent output waveforms quality. Due to these attractive features industry and researcher increased the interest in this converter. This interest results in the development of new power topologies, modulation strategies and control schemes. The main control objective of MMCs is to control capacitor voltages of each sub module (SM) and arm currents at its terminals. Depending on the application, it could be required to control the DC and AC voltages or currents. The MMC has no of cell in each arm, this cell has different power topologies. This paper focus on comparison of different control techniques to achieve different control objectives, like control of external voltage and current, control of average capacitor voltages, control of arm circulating current etc. Selection of the modulation techniques is also one of the research area to enhance the performance of the MMC. This paper highlights some convectional and advance pulse width modulation techniques. Various pulse width modulation (PWM) techniques based on using a single reference waveform that have been developed for MMC include: Phase Disposition(PD), Phase opposite Disposition (POD), Alternate Phase opposite Disposition (APOD), Phase Shifted carrier (PSC) and Carrier Rotation PWM scheme.

Keywords: Capacitor voltage balancing, circulating current control, modular multilevel converter, modulation techniques, switching frequency

Cite this Article

Kaumil B. Shah, Hina Chandwani. Circuit Topologies, Operation, Control Schemes and Modulation Techniques of Modular Multilevel Inverter. Journal of Power Electronics and Power Systems. 2017; 7(1): 28–40p.