A Novel Voltage Balance Topology With High Efficiency and Low Current Stress for MVdc Interface of Distributed PV

The input independent output series dc/dc converter has one stage of power conversion, which has low cost and high efficiency. However, shadow occlusion, dust coverage, and manufacturing differences will cause power mismatch of the photovoltaic panels, which in turn causes an unbalanced output voltage. To avoid device damage and power degradation caused by unbalanced voltage, a novel topology based on multiwinding transformer is proposed. By multiplexing the switches of each sub-module (SM), this topology can transmit the mismatched power among all the SMs and balance the output voltages. In the traditional method, the mismatched power can only be transferred between adjacent SMs. When the power mismatched SMs are far away, differential power will go through many SMs to reach the target one, causing unnecessary power losses. In the proposed topology, mismatched power can be directly transferred to the target SM; therefore, it has higher efficiency. Moreover, all the switches have zero voltage switching, which further improves the efficiency. One-third of the switches in the proposed topology have lower current stress than the traditional topology. The hardware cost can be reduced. Finally, the proposed topology is verified by simulation and experiment of 1 kW.