The world's first HVDC Light® test transmission was a 3 MW ±10 kV link between Hällsjön and Grängesberg in central Sweden and represents the beginning of a completely new power transmission technology. The transmission was over a 10-km temporarily decommissioned AC line owned by VB Elnät, a subsidiary of Vattenfall AB, one of Europe's leading energy companies. A trial field operation began in March 1997.
The transmission normally served either as a feeder into the Grängesberg AC grid, or into an islanded part of that grid. In the latter case, the DC system fed into a passive load with no other source of power, with the HVDC Light® transmission alone controlling voltage level and frequency.
During the initial years a number of tests were performed to verify the HVDC Light® concept: between tests, the stations were in operation on a 24-hour schedule either in transmission mode or in SVC mode to gather experience, and Hällsjön also served as a test bench for new components and equipment.
Since the successful trial, many converter stations have been built and are operating success fully. VSC transmission can be connected to very weak networks and stabilizes voltage by injecting or absorbing reactive power as required, so power flow and voltage at the connection point can be controlled simultaneously and independently.
Through the coordinated development of converters, insulated-gate bipolar transistors (IGBTs) and HVDC Light® cable systems, VSC transmission can produce a synchronized voltage for an entire wind turbine park, and now provides an alternative to high-voltage (400 kV and 500 kV AC) power lines.
| Main data | |
|---|---|
| Commissioning year: | 1997 |
| Configuration: | Symmetrical monopole |
| Power transmitted: | 3 MW |
| Direct voltage: | ±10 kV |
| Application: | Connecting remote generation; Overhead transmission lines for HVDC |