A Medium-Voltage DC Collector Grid for PV Plants Using Multi-string MPPT Converter

Medium-voltage DC (MVDC) collector grid has been a promising solution to improve energy yield of large-scale PV farms. To enable higher energy yield, multi-string maximum power point tracking (MPPT) DC-DC converter is desirable. This paper presents an non-isolated MPPT DC-DC converter for MVDC PV collector grid. Different from traditional MPPT converters, the proposed converter can operate in both buck and boost modes, which allows strings with large voltage difference coupled to a middle DC voltage. The power processing analysis indicates that the proposed converter features partial power processing in both buck and boost operations. Simulation simulation results are presented to confirm the high efficiency of the proposed converter. Mission profile based evaluation has been conducted to demonstrate that with the proposed buck-boost converter, more energy can be captured than using the conventional boost-only converter.