A case study on challenges for robust wide-area phasor POD
This paper illustrates the challenges towards achieving a robust phasor POD (power oscillation damping), a concept introduced and developed by ABB. A Phasor POD extracts the oscillatory part of the measured signal in the form of a phasor and applies a suitable phase shift to derive the damping control action. For a thyristor controlled series capacitor (TCSC), a phase shift of 90 degrees with respect to local power flow is recommended. However, the present case study on a simple test system with a TCSC reveals that a 90 degree phase shift on the local power does not necessarily yield the desired results. In fact, the phase shift required for satisfactory performance differs from one operating condition to another. Use of a wide-area signal (wide-area phasor POD) is shown to improve the damping functionality compared to local power flow provided an appropriate phase shift — which might not be intuitive — is given. Moreover, extraction of individual phasors out of a multi-modal signal is a challenge for practical systems exhibiting complex multi-modal behavior.