Tjaereborg is a demonstration project by Energinet.dk, comprising the installation and testing of an 8 MVA HVDC Light transmission system to connect a 6 MW onshore wind farm at Tjæreborg in western Denmark. The 4.3-km cable link operates at 9 kV. The project was commissioned in August 2000.
The purpose was to investigate how the controllability of HVDC Light could be used to optimally exploit wind generation by using the converter to provide a collective variable frequency to the wind turbines.
Integrating huge quantities of wind power into an electrical power system can have severe consequences for the system. Fluctuating wind power production will replace the steady power production from conventional power plants, as well as their voltage control and contribution to the reactive power balance in the grid. These problems can be overcome by using HVDC Light, which rapidly controls both active and reactive power independently of each other, to keep voltage and frequency stable.
The Tjæreborg wind farm can either be connected via the AC transmission only, or via the DC transmission only, or via the AC and the DC cables in parallel. The HVDC Light control system is designed to connect via the AC transmission automatically if wind power production is below 500 kW, and via the DC cables if the power is higher than 700 kW.
This project supports the planned installation of offshore wind farms in Denmark. Within the next 30 years, the intention is to build offshore plants totaling 4,000 MW in capacity.