A Voltage-Balancer-Based Cascaded DC-DC Converter with a Novel Power Feedforward Control for the Medium-Voltage DC Grid Interface of Photovoltaic Systems

Abstract

DC-DC converters with output-series cascaded submodules (SMs) are required for the medium-voltage direct current (MVDC) grid interface of photovoltaic (PV) systems. However, the mismatched power of PV arrays can cause an imbalance among the output voltages of SMs. In order to address this problem, in this paper, a multi-port cascaded DC-DC converter is established on the basis of a voltage balancer (VB) with a novel power feedforward voltage-balancing control strategy. The converter has multiple input terminals for the PV arrays and an output terminal connected to the MVDC grid. The differential power is regulated from one SM to another through the VB, ensuring that the SM output voltages are equalized. Simulation and experimental results suggest that the proposed converter has an excellent voltage-balancing capacity and dynamic performance.