A modular multilevel converter (MMC) is one of the perfect topologies for high power and medium-/high-voltage energy conversion systems. The MMC has attractive features such as modularity, voltage and current scalability, transformerless operation, fault blocking capability, reduced filter size, a reduced ripple of the output current, high efficiency, and low expense on redundancy. These features attracted industries over the past few years, notable research has been carried out on MMC topologies, their operation, and control. This study presents a review of MMC topologies and their mathematical models. Furthermore, their control schemes (classical as well as model predictive controls) and modulation techniques are discussed. Finally, MMC applications and their future challenges are highlighted.
As conventional fossil fuel reserves shrink and the danger of climate change prevailing, the need for alternative energy sources is unparalleled. A smart approach to compensate the dependence on electricity generated by burning fossil fuels is through the power generation using grid connected PV system. Partial shading on PV array affects the quantity of the output power in photovoltaic (PV) systems. To extract maximum power from PV under variable irradiance, variable temperature and partial shading condition, various MPPT algorithms are used. Incremental conductance and fuzzy based MPPT techniques are used for maximum power extraction from PV array. Basically 11 kW Solar PV system comprising of PV array coupled with an Inverter through a dc-dc converter is considered for the analysis and output of the inverter is supplied to the load through the LCL filter. An Intelligent controller for maximum power point tracking of PV power is designed. Also, a fuzzy controller for VSC is developed to improve the system performance. The above proposed design has been simulated in the MATLAB/Simulink and analyzed the system performance under various operating conditions. Finally, the performance is evaluated with IEEE 1547 standard for showing the effectiveness of the system.
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