| With the rapid development of economy,the demand for high-quality power is increasing,and the problem of voltage stability is becoming increasingly prominent.The proportion of non-linear dynamic loads such as induction motor(IM)in distribution network is increasing,and it has become an important point in the study of voltage stability.In the existing research on voltage stability of distribution network with induction motors,the interaction between loads is not considered.Especially when each induction motor is connected to different positions,the analysis results of single induction motor can not be fully applied to system with multi-induction motor loads,Therefore,it is of great theoretical and academic significance to study the voltage stability of distribution network with multi-induction motor loads.Based on the analysis of the influence of load model on voltage stability,this paper analyses the influence of multi-induction motor starting on system voltage and the voltage stability of distribution network under the condition of system fault.The main work of this paper is as follows:(1)Based on the existing load model,the influence of load characteristics on system voltage stability is analyzed.Considering the proportion of various loads in distribution network load,the influence of torque-slip characteristics and power characteristics of induction motor load on system voltage stability is emphatically analyzed,and compared with the power characteristics of static load.(2)According to the principle of power balance in power system,the dynamic coupling relationship between load slip of induction motors and system voltage in distribution network is theoretically deduced,and the effect of dynamic coupling characteristics of the two on system voltage is studied.On the basis of analyzing the starting characteristics of induction motor and defining the starting state of multi-induction motor load,the influence of motor parameters and system parameters on the system voltage during induction motor load starting is analyzed by time domain simulation.The influence of superposition starting of multi-induction motor load on the system voltage under different conditions is analyzed,and then by changing the system parameters and adopting superposition starting strategy,the serious voltage drop caused by motor starting can be avoided.(3)Based on the slip characteristics of the motor,the dynamic characteristics of the self-starting of the induction motor under the condition of system faults and the related factors affecting the self-starting of the induction motor are analyzed.The venin's equivalent method is used to solve the critical clearing time of induction motor load in distribution network with single induction motor,and the influence of motor and system parameters on the fault limit clearance time is analyzed.Because of the dynamic coupling of distribution network voltage with multiple induction motors and the slip of each motor,the calculation method of load stability of single motor is difficult to adapt to multi-machine system.Therefore,the influence of load ratio,fault location,network impedance parameters and fault duration of induction motor on voltage stability of distribution network with multiple induction motors is studied by time domain simulation.At the same time,simulation validates that fast fault load-cutting can effectively improve voltage stability. |
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