Research On Power System Load Modeling Considering Variable Frequency Induction Motor

Power system simulation is the guarantee of power system planning and scheduling operation,and accurate component model is the basis of reliable power system simulation.With the rapid development of power electronics technology,variable frequency speed regulation technology is becoming more and more mature.Due to its high performance and high energy saving,the direct grid connection of traditional asynchronous motor is gradually replaced by variable frequency motor,which makes the load composition and characteristics of the power system quietly change.In this paper,an equivalent load model is established for the characteristics of variable frequency induction motor.Firstly,some basic research methods of load models of asynchronous motor such as statistical synthesis method,overall measurement method and fault fitting method are studied,and the commonly used load models are analyzed,which lays a theoretical foundation for the power system load modeling of variable frequency asynchronous motor.Then,based on the working principle of the variable-frequency induction motor,the load calculation model of the variable-frequency induction motor is established,and the response characteristics of the variable-frequency induction motor under different voltages and different frequency drops are compared with those of the traditional induction motor in MATLAB/Simulink platform.The results show that the active and reactive power responses of the two are different,and the load model of the traditional induction motor is no longer applicable to characterize the variable-frequency induction motor.On this basis,according to the characteristics of variable frequency induction motor,ignoring its transient dynamic process,the static equivalent model of variable frequency induction motor is constructed.The least square method is used to identify the parameters,and the final load model parameters are determined.The validity of the model is verified by comparing with the original power and reactive power response curve.Finally,the equivalent model of variable frequency induction motor is established based on PSASP user-defined modeling platform.Taking the system model established in the actual power grid as an example,the composition ratio of different load models and different fault removal time are compared with the comprehensive load model in the actual power grid.The voltage recovery characteristics of the variable frequency induction motor model are better than the comprehensive load model,but the voltage drop is more in the fault time.Therefore,in the future comprehensive statistics of different loads,the load model of variable frequency induction motor should be considered to meet the actual needs of engineering.