HiDC-PV-Kraftwerke (HiDC PV Power Stations) – Development and Construction of a PV Power Station Technology with a Voltage Level of +/- 1.500 V

Duration:  August 2013 - July 2016
Contracting Authority/ Sponsors: German Federal Ministry for Economic Affairs and Energy (BMWi)
Project Partners: Bonfiglioli Vectron GmbH
Multi-megawatt PV power station.
© Fraunhofer ISE
Multi-megawatt PV power station.
Prototype of the DC/DC converter for use in large PV power stations.
© Fraunhofer ISE
Prototype of the DC/DC converter for use in large PV power stations.
Overview of the investigated power station concepts with a DC voltage level of 1000 V to +/- 1500 V. With the new concepts, the potential for a maximum AC voltage of 1000 V allowed by the Low Voltage Directive can be fully exploited.
© Fraunhofer ISE
Overview of the investigated power station concepts with a DC voltage level of 1000 V to +/- 1500 V. With the new concepts, the potential for a maximum AC voltage of 1000 V allowed by the Low Voltage Directive can be fully exploited.

The maximum system voltage in PV power stations today is usually 1000 V. In the ”HiDC-PV-Kraftwerke“ project, power station technology is being developed which operates with the maximum possible voltages corresponding to the Low Voltage Directive. Appreciable savings in costs and resources can be achieved due to the correspondingly reduced currents. Different power electronics concepts with DC voltages of 1000 V to +/- 1500 V were compared to each other. Not only were the costs for the balance-of-system components (BOS) determined but also the efficiency of the power electronics systems was investigated.

A power station concept corresponding to the state of the art was defined as a starting point (Fig. 3, Case A). In order to investigate the effect of the power on the costs, this concept was scaled up to 3 MW. This results in savings in the BOS costs of 16 %. The influence of the voltage level was demonstrated by analysis of three further concepts with raised voltage levels (Fig. 3, Cases B to D). Each of these three concepts leads to a further reduction in the BOS costs of 15 % compared to the 3 MW reference concept.

Simulation calculations were made to determine the losses and efficiency values of the concepts. A conventional 2-stage topology was simulated for reference case A, whereas a 3-stage topology was chosen for cases B to D due to the elevated voltage. In case C, the same power converter can be used as in case B, but featuring a rated power which is 50 % higher due to the fixed voltage operation. For case D, the power converter must be equipped with semiconductor components which can tolerate higher voltages. Efficiency values exceeding 98 % are possible with all topologies. Only case D showed weaknesses at high voltages.

For the DC/DC converter needed in case C, we have used an innovative topology which has great advantages compared to a conventional DC/DC converter. A prototype with a power rating of 250 kW and an efficiency value exceeding 99 % has already been constructed. In cooperation with the project partners, implementation of a 3-level power converter is planned.