A Fast Method To Compute The Transient Response Of Induction Motor Loads Considering The Influence Of The Negative Sequence Components

Digital simulation is an important way to control the operation characteristics of large power grid.Because of the load characteristics,there is a terrible influence on power system stability.The proportion of the induction motor in the power load is as high as 60%～70%.Whether the digital simulation can accurately simulate the transient response of the induction motor directly affects the reliability of the stability analysis result of the power system and the correctness of the control strategy formulated accordingly.At present,the third order model of induction motor is widely used in the stability analysis of large power grid.The model is based on the condition that the bus voltage of the motor is positive fundamental sequence.The paper evaluates the calculation accuracy of the third-order model under symmetric and asymmetric fault and put forward a rapid algorithm to compute the dynamic response of IM loads considering the negative-sequence components in dynamic characteristic study.The following briefly describes the content of this paper.Firstly,numerical integration algorithm is used to solve the third-order model of induction motor in the single-machine-load system.The difference between the traditional transient simulation and electromagnetic transient simulation results under symmetric and asymmetric voltage sags is compared to evaluate the performance and accuracy of the third-order model of induction motor.Secondly,the voltage equation and flux linkage equation of stator and rotor windings of induction motor under the influence of negative sequence voltage in the d-q reference system are derived,and the equation is transformed into a convenient form in order to analyze and calculate.The influence of negative sequence components on the electromagnetic torque,active power consumption and reactive power consumption of induction motor is taken into account.Finally,the characteristics of negative sequence current,negative sequence transient potential,negative sequence torque,negative sequence active power consumption andnegative sequence reactive power consumption in magnitude are analyzed,and a fast and simplified calculation method of negative sequence component is put forward to compute the dynamic response of induction motor loads.Several induction motors recommended by IEEE are taken as examples to verify the effectiveness of the model and algorithm.The method which is put forward in the paper can greatly improve the simulation accuracy of induction motor under asymmetric fault without increasing computational cost highly.If the algorithm is integrated into the transient simulation program of the power system,the accuracy of stability analysis and calculation of the large power grid under asymmetric fault can be improved.It has some reference value for the development of modeling and simulation technology of large power grid.