Transient stability enhancement in multimachine power systems using braking resistors

In certain situations, it is necessary to consider the use of an alternate control means to enhance and insure power system stability such as an emergency state control. A class of switchable supplementary controls, such as dynamic brakes, shunt reactor or series capacitors could be utilized. The effectiveness of network switching on a one machine system has been well established. However the interaction between closely coupled machines and groups of machines as a result of a control action has not been fully considered. The contribution of the paper is in the area of multimachine control, and, in particular, a power system emergency state control. Topics concerning control models, optimization criteria and characteristics of supplementary controls have been addressed. Dynamic programming is used to derive a switching strategy which takes the form of a closed-loop control. The control strategy is evaluated through the digital simulation of a two machine test system.