Dynamic performance of the upgraded 1400 MW New Zealand HVDC project

The existing HVDC scheme connecting the North Island and the South Island of New Zealand is currently being upgraded. During this upgrade also known as the New Zealand Inter Island HVDC Pole 3 Project, the existing HVDC Pole 1 based on mercury arc valves is replaced by a new HVDC Pole 3 based on light triggered thyristor vales. Both poles, the existing Pole 2 and the new Pole 3 are then operated as a non balanced bipolar HVDC scheme. In this study, a power system stability analysis of the HVDC Pole 2 and Pole 3 connecting the North Island and the South Island is performed. Focus is hereby on the stable operation of both power systems, especially during faults and severe contingencies. Using the fast controllability of the HVDC, it is possible to enhance both power systems using special modulation functions.