A simplified load voltage control scheme for power conversion applications using modular multilevel converters

Modular Multilevel converters (MMCs) have gained popularity in power conversion applications such as HVDC and renewable energy systems. A major challenge in these applications is the simultaneous control of capacitor voltages, arm currents, and output voltage, since the control of one has impact on the other. This paper presents a novel control scheme to regulate the output voltage and capacitor voltages of MMC using a simplified control loop utilizing its inherent voltage balancing property. The proposed scheme reduces the number of control loops required, is easy to implement, and is scalable to higher number of sub modules. Unlike the existing control, this scheme does not use additional control loops for individual sub modules and has less computational load on the controller. The proposed method is successfully applied to control a 1.6 kVA MMC with four sub modules in the leg. Simulation and experimental results presented prove its efficacy in terms of steady state and dynamic performances.