Adaptive Control Strategy for Frequency Support From MTDC Connected Offshore Wind Power Plants

Grid integration of large-scale power electronic interfaced renewable energy sources leads to a low inertia system, thus resulting in a high rate of change of frequency (RoCoF) and frequency deviations in the power system following a credible contingency. In this article, a realistic adaptive communication-independent control strategy for effective inertial and primary frequency support from multiterminal HVDC (MTDC) connected offshore wind farms (OWFs) has been proposed. The proposed strategy can identify and distinguish the grid under disturbance among the other healthy grids in the MTDC system by an adaptive droop frequency support (ADFS) scheme at each receiving end converter (REC). On the OWF side, the control system of wind turbine generators has been designed to coordinate with the ADFS scheme to comply with the grid code regulations (GCRs) for inertial and primary frequency support. The proposed ADFS control scheme ensures that while providing frequency support to the grid under disturbance, frequency deviation limits of the healthy neighboring grids are not breached. Moreover, the proposed strategy complies adequately with the maximum permissible limits of HVDC voltage deviation. Furthermore, the proposed strategy is dependent on only local measurements and can be easily customized to comply with any applicable GCR. The reliability and effectiveness of the proposed robust control strategy have been demonstrated on three power systems interconnected through the MTDC system to two OWFs.