Control algorithm for port power imbalance in two-stage, N-port modular multilevel cascaded photovoltaic inverters

With the increasing demand for PV technology, low cost, highly efficient, modular PV inverter system has become a pertinent issue. As a solution, modular two-stage power conversion with isolation and string-level power conversion has become an attractive choice recently. However, the complexity of the control algorithm in addressing power imbalance between modular power conversion units becomes a disadvantage to these type of configurations. This paper proposes a new control scheme for the two stage, N-port, string-connected modular multilevel cascaded inverters. Control algorithm ensures the maximum extraction of solar power along with the per port power balancing of the PV systems. Simulation of N-port multilevel dual active bridge stage along with the cascaded H-bridge stage for one phase is presented to verify the feasibility of the proposed algorithm.