SUPPLEMENTARY CONTROL STRATEGIES FOR THE TRANSIENT STABILITY ENHANCEMENT OF MULTIMACHINE POWER SYSTEMS
Abstract
In order to maintain a high degree of reliability, power system design has been traditionally determined by abnormal or transient conditions rather than steady state operation. Power system designers have concentrated on minimizing the effect of major disturbances by using circuit breakers to isolate and clear disturbances as quickly as possible and by improving system interconnections so that no one machine or set of machines could be easily isolated from the rest of the grid. In certain situations, it might be necessary to consider the use of an alternate control means, such as an emergency state control. This control would be used in place of expensive transmission and provide an effective means of damping electromechanical oscillations. A class of switchable supplementary controls, such as dynamic braking, shunt reactor or series capacitors could be utilized to enhance power system stability. 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. It would seem more reasonable to consider the use of a centrally placed switchable control to accomplish the following: the prevention of instability between closely coupled machines making up a subsystem, and instability between groups of machines. The machine models to be used are nonlinear. The contribution of this research 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 feedback control. Since an optimal switching strategy is difficult to implement, suboptimal switching strategies are also considered. Control strategies are evaluated through digital and analog simulation of one and two machine test systems as well as a full-scale ten machine test system. Methods for obtaining dynamic equivalents of groups of generators are used to reduce the number of variables necessary for calculating a control.
Degree
Ph.D.
Subject Area
Electrical engineering
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