An Improved Voltage Balancing Method for Grid Connected PV System Based on MMC Under Different Irradiance Conditions

Modular Multilevel Converter (MMC) is considered as one of the most promising topologies for renewable energy application. the MMC has attractive features such as modular realization, scalability, and transformerless operation which makes it a suitable converter especially for PV system. For the satisfactory operation of MMC, it is important to maintain balanced voltage across each submodules (SMs). This paper proposes an improved balancing approach based on Space Vector Pulse Width Modulation (SVPWM) for three-phase multi-string PV system based on MMC. The proposed method along with the control strategy uses only one SVPWM, which not only reduce the calculation but also balance the SM capacitor voltage, realize the independent MPPT of each PV string and reduce the circulating current. Thereby increases the efficiency of PV system. The proposed method is varied through simulation using Matlab/Simulilnk during different operating conduction.