The ConTune AC filter has electromagnetic tuning that adjusts to the inherent frequency variations and temperature variations of the filter components.
The ConTune AC filter has a high quality factor for the best filtering performance in HVDC converter stations and the lowest possible losses. The tuning frequency is automatically adjusted to provide prefect tuning irrespective of network frequency excursions and filter component variations. The ConTune filter offers:
- Maximum filter performance even at large frequency excursions
- Lower losses
- Less space
- No moving parts.
Principle of automatic tuning of the ConTune filter
The high performance of the ConTune filter is achieved by using a filter reactor with variable inductance. The variable inductance is achieved with an iron core which is placed inside the reactor. Around the iron core there is a control winding.
ConTune filter installed in the Celilo station of the Pacific Intertie HVDC transmission
By feeding a corrective direct current into the control winding, the total magnetic flux in the reactor is influenced, thereby changing the inductance, which tunes the filter to the correct frequency of the harmonic. Control of the inductance is characterised by its high linearity.