Design and development of a cascaded modular multi-level converter based on current-fed quadruple-active bridge converters for grid integration of photovoltaic systems

This article proposes a new topology of a cascaded modular multi-level converter (MMC) based on the current-fed quadruple active bridge (CFQAB) converters for grid integration of photovoltaic (PV) systems. The MMC topology includes multiple cascaded converter modules in each phase of a three-phase system. Each individual module is further formed by a PV-linked CFQAB dc-dc converter to integrate the PV outputs and supply it to a high-voltage dc (HVDC) bus and further to a cascaded inverter to converter to the ac voltage for the distribution grid. The proposed topology features a wide input voltage range, lower current ripple and smaller size due to the use of CFQAB converter as the building block, which makes it an ideal choice for PV applications. The operation principle of the MMC, converter modules and the control techniques have been presented in detail. A scaled-down prototype of the topology is implemented to validate the operation of the proposed topology and the control systems.