| Power system stability is the examination of the trajectory of the power system as it moves from an initial steady state to a new steady state (hopefully), following a disturbance. When power systems suffer a disturbance such as the loss of large generating station, the rotors of the remaining generators start to swing with respect to each other. There are various nonlinearities in the power system, included saturation, valve limits, controller ramp rates and controller limits. Power systems must stay in synchronism, otherwise islanding and potential blackout can occur. Fortunately there is an inherent synchronizing force which tends to keep ac systems in synchronism. However reach machine rotor inertia, as well as the controller parameter settings for each turbine-generator, can have an interactive effect on other parts of the power system. The various nonlinearities in the power system have an influence on the stability trajectory during the first, and subsequent, swings of the rotors of the generators. The preferred method for power system stability analysis is through time simulation. Simulation is widely used by utilities around the world. The detailed models required, the large data requirement, the geographical extent of the transmission grid, and the large number of generators involved make this a complex problem. Topics include: the elementary mathematical model relating to stability, system response to disturbances, the synchronous machine, the simulation of the synchronous machine, linear models of the synchronous machine, excitation systems, effects of excitation on stability, multimachine systems with constant impedance loads, speed governing, steam turbine prime movers, hydraulic turbine prime movers, combustion turbine and combined cycle power plants. |
