Fault Ride-Through Capability Enhancement of VSC HVDC connected Offshore Wind Power Plants

This paper presents a feed forward direct current (DC) voltage control based fault ride-through (FRT) scheme for voltage source converter (VSC) high voltage DC (HVDC) connected offshore wind power plants (WPPs) in order to achieve active control of the WPP collector network AC voltage magnitude, and to improve the FRT capability. During steady state operation, an open loop AC voltage control is implemented at the WPP side VSC of the HVDC system such that any possible control interactions between the WPP side VSC and the wind turbine VSC are minimized. Whereas during any grid faults, a dynamic AC voltage reference is applied based on both the DC voltage error and the AC active-current from the WPP collector system which ensures fast and robust FRT of the VSC HVDC connected offshore WPPs. Under unbalanced fault conditions in the host power system, the resulting oscillatory DC voltage is directly used into the WPP side VSC AC voltage controller such that the unbalance in the main grid is also reflected at the WPP collector system voltage. Time domain simulations have been carried out to verify the efficacy of the proposed feed forward DC voltage control based FRT scheme. The time domain simulation results have shown satisfactory FRT responses of the VSC HVDC connected offshore WPP under balanced and unbalanced faults in the host power system, and under a severe fault at the WPP collector network.