Impedance-based analysis of harmonic instabilities in HVDC-connected Offshore Wind Power Plants

摘要

HVDC-connected Offshore Wind Power Plants (OWPPs) with a large number of power converters are prone to instabilities due to interactions with converter controllers. This paper analyzes harmonic instabilities in OWPPs connected through HVDC due to interactions with the offshore HVDC converter and the wind turbine converters. An impedance-based model is used to represent a detailed OWPP with fully-rated converter based wind turbines, including the offshore HVDC converter, wind turbine converters, submarine cables and transformers of the offshore AC grid. Harmonic stability is evaluated both from the grid connection point of the offshore HVDC converter and the WT grid side converters. As a result, the influence that parameters of converter control systems and the offshore grid configuration have on harmonic resonant frequencies and stability conditions is analyzed in depth through a sensitivity analysis. Active damping implemented as a feed-forward control is coordinated in all converters to mitigate the harmonic instabilities. Examples of harmonic instabilities and active damping application are validated with time domain simulations in PSCAD/EMTDC.