Active and Reactive Power Control Strategy of the Modular Multilevel Converter for Grid-Connected Large Scale Photovoltaic Conversion Plants

Abstract

Power converter design play an essential role in harvesting cheap and reliable electrical energy from solar energy. In the design of the converters, an appropriate trade-off between power converter output power quality and complexity should be made. Meanwhile, modular multilevel converters (MMC) are such a popular choice due to significant advantages like modularity, switching redundancy, the high number of voltage levels, lower output harmonics, elimination of expensive and huge output filters, etc. In this paper, a modified control strategy considering photovoltaic array structure for a high power MMC is presented. The proposed approach results in enormous faster dynamic and decoupled injected active and reactive power control. Also, using a single carrier modulation technique, and applying it to the capacitor voltage balancing algorithm, the capacitor voltage ripple is constrained to the allowed limits, which significantly decreases the circulation current. A 3MW 9-level MMC has been evaluated by MATLAB/Simulink to approve the operation of suggested modified current loop MMC controller.