Active Power Control of Hybrid-HVDC Line Connected to Offshore DFIG-based Wind Farm During Mainland Grid Voltage Fluctuations

This paper proposes a simple and effective power control technique for a Hybrid-HVDC line connected to an offshore DFIG wind farm feeding a weak onshore grid. The sending end rectifier station of the HVDC line uses a Line Commutated Converter (LCC) and a Voltage Source Inverter (VSI) at the receiving end. The generated real power by the wind farm is regulated by the LCC and transmitted to the inverter station by the HVDC line. The inverter station facilitates the generated power transfer with the mainland grid through VSI control. The wind farm consists of two 2 MW DFIGs connected to a 100 km, 100kV HVDC transmission system for simplicity. The proposed control technique effectively extracts power from DFIG. It regulates the reactive and active power over the mainland grid while minimizing the power pulsations and grid current THD owing to mainland grid voltage variations by a compensating current injection method at the inverter station. The simulated results in PSCAD/EMTDC software environment validate the performance of the onshore grid-connected Hybrid-HVDC line coupled to the wind farm in an offshore area with a proposed controller.