Transient Stability Enhancement Brought by Rotor Angle Droop Control When Tie-line Faults Happen

In order to use remote wind power/solar energy, the scale of power grid interconnection grow rapidly. If transient stability can be increased when faults happen on tie lines, the transmission capacity can be increased too. Dynamic braking can increase transient stability by increasing deceleration area, but it's difficult to coordinate several braking devices and calculate braking amount in real time. Things are no longer so after rotor angle droop (RAD) controllers are deployed across the power system. Since all rotor angles of generators will be fixed in rotating coordination system determined by global position system (GPS) pulse per second (PPS) signal, dynamic braking amount can be calculated by RAD controller by using local speed and rotor measurement. This paper shows the revised equal area criteria (EAC) when this kind of dynamic braking is used. The relationships between RAD controller parameter (saturation threshold) and the braking effect are also investigated. Simulation results in IEEE 68 nodes system show that, by applying dynamic braking on several generators simultaneously, critical clearing time can be increased dramatically when faults happen on tie lines.