Ripple Control Filter

Electrical utilities use distribution networks to transmit information such as tariff change and load control commands to end-users by injecting signals at low frequencies at the HV/MV substations level (ripple control system).

Independent power producers connected to the MV network change its impedance and may disturb the level of the signals. 
The FAS Active filter is designed to permit an independent power producer to connect to the MV distribution network by efficiently filtering ripple control signals. It prevents the power generators disturbing the ripple control commands sent by the utility from the HV/MV substation.  

It works by injecting in the IPP connecting feeder a signal at the ripple control frequency equal in phase and magnitude to the signal measured on the MV network.

This stops the current at the ripple control frequency going into the power generators and maintains the ripple control signals at their original values (before power generators’ connection).