New application of voltage source converter ( VSC ) HVDC to be installed on the gas platform

Voltage source converter (VSC) HVDC and cable wound high voltage motor (High Voltage Motor) are novel technologies that enable powering of offshore installations with electrical power from shore. On the gas platform Troll A in the North Sea 65 km west of Bergen, Norway, the world’s first HVDC transmission system, which will be designed to operate as an electric drive system based on these technologies, will be installed. Gas production capacity will thereby be maintained and expanded on Troll A – economically and environmentally friendly as more gas turbines can be avoided.. The system in Troll A includes a voltage source converter (VSC) on shore and dc cables for transmission of power to the platform. On the Troll A platform, another VSC is directly connected, i.e. in a unit connection, to a cable wound high voltage motor acting as a variable-speed synchronous machine. The motor drives a gas compressor. As the compressor speed is variable, the machine is supplied with variable frequency and variable voltage, from zero to max speed, including smooth starting and acceleration. By means of modest filters on the output of the converter, the motor winding stress is kept at a safe level. This paper describes design aspects of the electrical drive system for Troll A.