Information Component Recognition in Fault Signals for Relay Protection of Electric Grids with HVDC

The faults in AC network may cause commutation failure in adjacent inverter station of HVDC, accompanied by injection of DC line discharge current into AC network. In this case a significant number of transient components arises in emergency voltages and currents, which level is comparable with level of main harmonic. Conventional protection relays may miss-operate due to error in non-adaptive orthogonal component filters during processing of such signals. The implementation of adaptive signal processing algorithms for improving relay protection stability is studied. It's shown that improving of signal recognition require proper sampling rate and adaptive signal model order. An adaptive blocking algorithm preventing protection miss-operation in poor measurement conditions is suggested.