Analysis on the effect of rotor angle control for transient stability enhancement

For the time being, the absolute rotor angle of every generator is changing from time to time, so it's less likely to improve transient stability by use of rotor angle measurement. Things are no longer so after absolute rotor angle controllers are deployed across the power system. The frequency of the power system will remain constant, and the absolute rotor angle of every generator will be kept at the aim value given by dispatching center most of the time. After fault happens, every generator can know its position in entire system through local PMU (phasor measurement unit) measurement. The angle controller can then give order to turbine valve or power electronic braking devices to accelerate or decelerate the generator rotor so that it comes back to its original position. Consequently, stability and order will be restored. The changing magnitude of turbine valve is restricted in the angle controller, so there is no damage to thermal system. Besides, valve operation and dynamic braking can be integrated seamlessly to get better results. Simulations results show that this principle can increase critical fault-clearing time and transient stability in both SMIB and multi machine system.