The Harmonic Stability Problem in Offshore Wind Farms and Targeted Extension of the HVDC Link Control for its Mitigation

This paper analyses the effect of the HVDC controller on the harmonic stability of the offshore wind farm. Due to the HVDC filters/ transformers and long cables wind farms have natural resonances which are normally damped by the grid itself However, improperly designed controllers could excite such resonances which may result in equipment damage. To overcome this problem, HVDC controller is extended with a resonance suppression control which is based on the main ideas of disturbance rejection technique. The effectiveness of the proposed method is analyzed for different operational conditions of the network. It is also observed that the gains of the PI voltage controller play a significant role in the harmonic stability of the offshore grid.