Influence of induction motor modelling for undervoltage load shedding studies

This paper explores the influence of modelling induction motor loads for undervoltage load shedding studies. A first order and a third order dynamic load model in terms of real power, reactive power and voltage are defined using the ´slip´ and ´slip flux´ induction motor models, respectively. In a voltage unstable situation it is shown that the real power and reactive power responses of the load models differ, owing to the dynamic characteristics of the respective load model. Consequently, the amount of load to shed at a given voltage is significantly influenced by the dynamic load model. The objective is to reveal how different load models influence the analysis and the calculation, for undervoltage load shedding to be successful. It is also shown that the use of generic dynamic load models (GDLMs) to capture induction motor loads lead to over shedding.