Single-Stage IIOS Converter With Auto-Voltage-Sharing for Distributed Photovoltaic MVDC Collection System

A single-stage input-independent output series converter is proposed for the distributed photovoltaic (PV) medium voltage dc (MVDC) collection system, which can realize autovoltage-sharing without other auxiliary circuit. The submodule (SM) is a three-port converter (TPC), which is integrated by an interleaved parallel boost unit and a full-bridge LC series resonant unit. Every TPC's input port is connected to an independent PV array and the simple pulse width modulation is adopted to realize the maximum power point tracking (MPPT). The output port of every TPC is in series connection to accommodate MVDC bus voltage. Moreover, all the intermediate ports are paralleled as the shared dc bus. Since the full-bridge LC series resonant unit operates as a DC transformer and the intermediate ports are paralleled, the output voltage of every TPC is shared without extra control. Hence, the proposed converter can realize autovoltage-sharing and only the PV voltage and current need sampling to realize MPPT. Moreover, the zero-voltage-switching can be realized for switches and zero-current-switching realized for all rectifier diodes. A 1.5 kW prototype with three SMs is built to verify the characteristics and effectiveness of the proposed converter.