High-Frequency Isolated Medium-Voltage AC Grid-connected PV Power Generation System Structure based on DC Bus Collection

This paper proposes an isolated medium-voltage AC grid-connected PV power generation system structure based on DC bus collection with high-frequency link concept. The proposed system structure consists of centralized photovoltaic power plant, inverter unit based on isolated bridge converter (I-BC), and capacitor at the junction of dc bus. PV plant is divided into many arrays, each PV array is connected in parallel with each phase inverter unit. Inverter unit is composed of two I-BC. Compare with conventional two-stage PV inverter, I-BC can totally eliminate the individual DC-link capacitors at the high-voltage side, which leads to extremely reduced system volume and voltage-balancing control between individual capacitors. Second harmonic power oscillations seen in typical system structure can also be eliminated or reduced through use of the proposed system. This paper presents the analysis and operation of the proposed PV system structure with experimental results on a scaled-down laboratory.