We suggest a new mechanism for interarea electric power system oscillations in which two oscillatory modes interact near a strong resonance to cause one of the modes to subsequently become unstable. The possibility of this mechanism for oscillations is shown by theory and computational examples. Theory suggests that passing near strong resonance can be expected in general power system models. The mechanism for oscillations is illustrated in 3-and 9-bus examples with detailed generator models.
This paper discusses the relationships between types of bifurcations in power systems and their expected occurrence for voltage regulated and unregulated synchronous machines. A time-scale decomposition is performed to identify critical dynamics in the slow and fast subsystems. For singlemachine systems, the existence of an unstable limit cycle prior to Hopf bifurcation is analysed in the context of the region of attraction.
Spinning contingency reserve is idle capacity connected to the system to ensure reliable operations in the case of equipment outages. The reserve has an economic value since it reduces the outage costs. In several electricity markets, reserve demand functions have been implemented to take into account the value of reserve in the market clearing process. These often take the form of a step-down function at the reserve requirement level, and as such they may not appropriately represent the reserve value. The value of spinning contingency reserve is impacted by the reliability and dynamic characteristics of system components, the system operation policies, and the economic aspects such as the risk preferences of the demand. In this paper, we take into account these aspects to approximate the reserve value and construct reserve demand functions. The results are obtained in closed form. Illustrative examples show that the demand functions constructed have similarities with those implemented in some markets.
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