Modelling and investigating the impact of asynchronous inertia of induction motor on power system frequency response

摘要

Besides synchronous inertia, asynchronous inertia of induction motor also widely exists in power systems, but its effect on system frequency response has not been well studied. A simplified transfer function model of induction motor is derived based on the detailed model. The model is regarded as a decaying proportion of the consumed power to the frequency deviation. Three key features of the model are the immediate proportion, the steady-state proportion and the decaying time constant. Their affecting factors are also studied. Then the model is added to the system frequency response model to study the effect of induction motor. There are three key factors of induction motor affecting frequency response, the sensitivity of electromagnetic torque to slip, the sensitivity of mechanical load torque to rotor speed, and the inertia. Their effects are analytically analyzed. The asynchronous inertia only affects the maximum frequency deviation, and a large inertia reduces the maximum frequency deviation. However, it is acceptable to neglect the asynchronous inertia and represent the induction motor with static model considering steady-state frequency sensitivity. The derived conclusions are validated with simulation results.