Power Electronics for Utility Scale PV Power Plants with Voltages Up to +/- 1500 VDC

Large grid-connected PV systems has shown a strong growth in their market share in the recent past. To build and monitor these power plants, cost efficient new inverter stations with a higher power and voltage levels are in demand. In this work four power plant models were compared. A state of the art model with 1000 VDC and a near future model with 1500 VDC unipolar and floating PV generators were investigated. Furthermore a two stage concept with a fixed voltage inverter and additional active string combiner is discussed. The string combiners have two inputs with a maximum input voltage of 1500 VDC each. The outputs are connected to a fixed-voltage DC-bus. The last model has a bipolar PV generator with a maximum voltage of +/- 1500 VDC. With the last two models an output voltage of 1000 VAC can be realized. This leads to the maximum utilization of the voltage levels according to the European Low Voltage Directive [1]. As the simulation shows that for all models, the power electronic concepts with efficiencies of more than 98% are possible. An active string combiner required for the third concept has been developed. The device shows very high power density and an efficiency of more than 99 %. Measurement results are also analyzed in this paper