Design and experience of a back-to-back HVDC link in western Canada

The 150 MW back-to-back HVDC convertor station at McNeill is the first interconnection between the western and central electrical networks of Canada and allows Alberta Power and SaskPower to trade energy and share the standby capacity of the two networks. At the heart of the convertor station is a new generation of liquid cooled thyristor valves and electronic controls. In addition to the latest convertor technology McNeill also has many design features which represent advances to DC power transmission. These include: thyristors cooled directly by an ethylene/glycol solution which provides frost protection down to -50°C; no DC reactor between the two HVDC valve groups; and stable steady state operation and good post-fault recovery when operating under very weak AC system conditions. The McNeill convertor station has now been in service for 18 months and, of some 60 stations so far commissioned around the world, is the first to demonstrate a capacity for truly unmanned operation