A Modular Multiport Input-Independent Output-Series Photovoltaic MVDC Integration Converter

To solve the problem of unbalanced output voltage caused by photovoltaic (PV) power mismatch when PV is integration into medium voltage DC (MVDC) grid, a modular hybrid-connected three-port converters (TPCs) with output voltage balancing is proposed in this paper. The system consists of multiple modular pulse-width modulation plus phase-shift (PPS) controlled TPCs, which achieves the independent maximum power point tracking (MPPT) of all PV panels, feature low voltage stress and soft switching. The bidirectional ports of TPCs are connected in parallel to build a low-voltage DC (LVDC) bus. By adjusting the output voltage and the voltage of bidirectional ports, mismatched power of PV can be transferred between all submodules (SMs) through LVDC bus, thus achieving the output voltage balancing. The working principle of TPC is analyzed in detail, and simulation and experiment are carried out to verify the feasibility of the proposed system.