Lower churchill project — Multi-terminal HVdc feasibility studies

A system integration study was undertaken to evaluate the feasibility of a three-terminal HVdc system linking Labrador, Newfoundland and New Brunswick, a component of the Lower Churchill Project. The main focus was the impact of the HVdc system on the Newfoundland Island Interconnected system, a system that is currently electrically isolated from the North American grid. The 800 MW HVdc terminal on the Island system would normally serve as an infeed of power, at times supplying nearly half of the Island load. The main technical challenge was the ac system frequency decay and transient undervoltages that resulted during the temporary loss of the HVdc infeed (due to commutation failure) coupled with a disruption of generation on the Island due to an ac system fault. Mitigation measures studied included reducing the likelihood of commutation failure of the Island HVdc converter and increasing the inertia of the Island system. Preliminary investigations of the performance of a Voltage Source Converter (VSC) HVdc terminal were also undertaken.