A wind farm with series de collection can potentially eliminate the costly offshore platform and its step-up components. Multiple series strings can be connected in parallel to extend the power capacity for a given voltage. In such arrangement, the DC/DC converters for individual generators are rated at only a fraction of the transmission voltage. The maturity of superconducting cable technology will eliminate the difficulty of transmission losses with high current low voltage systems. This paper presents a feasibility study on the DC/DC converter design for a parallel-series-connected wind farm. The isolated front-to-front (F2F) mixed voltage source converter (VSC) and current source converter (CSC) is examined with power back-feeding capability during wind calm periods for a 15 MW generator. A novel configuration using 3-level (3L) VSC and thyristor-based CSC with combinational control of AC voltage magnitude, frequency, and thyristor delay angle is proposed and evaluated for a 1 GW/100 kV parallel/series wind farm based on the superconducting cable. Detailed converter model including power loss estimation in PSCAD is presented to support the converter design recommendations.
The authors are thankful to SuperNode Ltd. for the financial support of this study.
- Offshore wind farm
- Series DC collection
- High-voltage DC (HVDC) transmission
- Superconducting cable
- Medium frequency high power DC/DC converter
- Voltage source converter (VSC)
- Current source converter (CSC)
- Bidirectional power flow