THE IRRELEVANCE OF LOAD DYNAMICS FOR THE LOADING MARGIN TO VOLTAGE COLLAPSE AND ITS SENSITIVITIES

The loading margin to a saddle-node or foldbifurcation is a useful andbasic ind ex of proximity to voltage collapse. Sensitivities of the loading margin can be usedto select controls to avoidvoltage collapse. This paper justifies the use of static power models to com- pute loading margins and their sensitivities. In particular, dynamic load models may be reduced to static equations andthen simplifiedwithout affecting loading margins and their sensitivities. Alternatively, if dynamic models are not well known, the computations may be done with static models and conclusions drawn about a general and sensi- ble class of underlying dynamic models. Explicit assump- tions and mathematical underpinnings are presented.

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