Operation and control of a novel multi-input PV grid-connected system

This paper proposes a three-phase grid- connected PV system based on dual-active-bridge (DAB) converters and cascaded multi-level DC/AC converters (CMCs). PV array strings will be connected to DAB converters which will be collected in series by the CMC. In this system, the output power of the PV arrays will be unbalanced once the operating states of the PV arrays are not identical. The unbalanced output power will lead to the asymmetric of the grid-side currents of the CMC. In order to achieve the symmetric of grid-side currents of the CMC, a control strategy of grid-side currents balancing is proposed. A 10kV/4.5MW PV system with the proposed control strategy is built in PSCAD/EMTDC. The simulation results verify the effectiveness of the proposed system topology and control strategies.