This paper presents a thorough analysis of the effect of load models on frequency response, small and large disturbance stability of the power system, in order to identify the type of stability exhibiting the most sensitivity to load models, and for each type of studied stability, to pinpoint the load model that has the worst effect. The presented analysis shows clearly that transient stability is the most sensitive to load models. The number of unstable cases varies considerably with each type

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... of studied load model. The effect of the load model magnifies with the reduction in headroom of synchronous generators. The results of the frequency response of the system following an active power disturbance demonstrate that the influence of constant power loads on the frequency response of the system can be significant if the system is operating with the reduced primary frequency response at high load. High integration of RES increases the variation in the damping of electromechanical modes due to increased uncertainties, and a high proportion of induction machines can reduce the damping of inter-area modes considerably, making a well stable mode unstable for certain operating points. The influence of load models has been illustrated using 68 bus NETS-NYPS system with 30% and 52% penetration of renewable energy sources. List of Abbreviations and Symbols RES Renewable generation sources SG Synchronous generator ZL Constant impedance load PL Constant power load PfL Constant power load with frequency dependence ZIP ZIP load model Cmp Composite load model PDF Probability distribution function FRT Fault ride through fnadir Frequency nadir RoCoF Rate of change of frequency DFIG Doubly fed induction generator FCC Full converter connected