A Versatile Reinforced Inverter Station Control Strategy for Hybrid HVDC-Based Offshore DFIG Wind Farm

A straightforward and effective power control approach for a hybrid-HVDC system linked to a DFIG-based offshore wind power farm that feeds a weak onshore grid is proposed. Real power generated from the wind farm is controlled by an LCC rectifier station at the sending end. It is efficiently transmitted to another VSC inverter station through the HVDC line under nominal onshore grid voltages. Nevertheless, the abnormalities in onshore grid voltage make the inverter station control tedious, as the power converter suffers from huge harmonic grid currents and power pulsations beyond permissible limits. To efficiently extract power from offshore DFIG and regulate active/reactive power at the onshore grid, a dynamic current control approach at the VSC inverter station via compensating current injection while minimising power oscillations, HVDC link capacitor voltage ripples and THD in the grid current instigated by voltage deviations in the onshore grid is proposed here. The performance of the hybrid HVDC system integrated offshore DFIG wind farm is validated for a 100km, 100kV HVDC link coupled to a 100MW DFIG wind farm via simulations on PSCAD/EMTDC software.