A method and system for analyzing dynamic characteristics of an induction motor

Abstract

The present invention discloses a method and system for analyzing the dynamic characteristics of an induction motor. The method comprises: obtaining the change in the angular velocity of the induction motor after a disturbance based on the first-order mechanical transient equation of the induction motor; obtaining the slip of the induction motor based on the change in the angular velocity; obtaining the change in the transient electromotive force based on the slip and the transient electromotive force differential equation; and obtaining the current and power response of the induction motor after the disturbance based on the change in the transient electromotive force. The fast analytical algorithm for the dynamic characteristics of an induction motor under asymmetric fault voltage drop proposed in the present invention can quickly evaluate the dynamic response characteristics of an induction motor after an asymmetric fault, avoid tedious time-domain simulation calculations, and improve the accuracy of the obtained dynamic response characteristics.

Description

Technical Field

[0001] The present invention relates to the technical field of solving the dynamic response characteristics of an induction motor load, and more particularly, to a method and system for analyzing the dynamic characteristics of an induction motor. Background Art

[0002] With the rapid development of power grids, the diversification of power sources, the complexity of grid structures, and the diversification of load components are increasing. This is increasing the pressure on the safe and stable operation of power grids, and the requirements for the accuracy of simulation models are becoming increasingly stringent. The selection of load models, especially dynamic load models, has a significant impact on the credibility of system stability calculation results. Receiving systems are heavily loaded, and the proportion of induction motor loads is high. During grid faults and recovery, induction motors often absorb large amounts of dynamic power due to the decrease in electromagnetic torque and the increase in slip, making it difficult to recover transient voltages in the system.

[0003] Scholars at home and abroad have recognized the importance of studying the interaction between the dynamic characteristics of induction motors and voltage drops, and have proposed three research methods: experimental, time-domain simulation, and analytical. The experimental method uses a voltage drop generator to produce various types of voltage drop waveforms and record the motor's output response. The time-domain simulation method utilizes power system electromagnetic transient or electromechanical transient simulation programs, considers a more accurate motor dynamic model, and explores the problem through numerical calculations. The advantage of both methods is that the results are reliable, but to reveal the influence of a specific factor, multiple experiments or simulations are often required. In addition to being tedious and time-consuming, both methods are inadequate for analyzing and interpreting experimental and simulation phenomena. The analytical method, which draws on circuit and motor analysis theory to explicitly solve the interaction between the induction motor's dynamic response and system voltage, is the most fundamental and thorough research method, but it is relatively difficult.

[0004] Existing technologies still use a third-order transient model of induction motors, derived from three-phase symmetrical positive-sequence voltage, as their simulation model. This third-order electromechanical transient model cannot accurately simulate the dynamic characteristics of induction motor loads or accurately determine the conditions under which induction motor load instability may occur. In actual simulations, positive-sequence voltage or rotor slip calculated using the third-order electromechanical transient equation is used as the criterion based on engineering experience. Consequently, the calculation accuracy is low when asymmetric faults occur.

[0005] Therefore, a technology is needed to quickly analyze the dynamic characteristics of an induction motor under an asymmetric fault voltage drop and improve the analysis accuracy. Summary of the Invention

[0006] The technical solution of the present invention provides a method and system for analyzing the dynamic characteristics of an induction motor, so as to solve the problem of how to quickly analyze the dynamic characteristics of an induction motor under an asymmetric fault voltage drop.

[0007] In order to solve the above problems, the present invention provides a method for analyzing the dynamic characteristics of an induction motor, the method comprising:

[0008] Obtaining a change in the angular velocity of the induction motor after the disturbance based on a first-order mechanical transient equation of the induction motor, and obtaining a slip rate of the induction motor based on the change in the angular velocity;

[0009] Obtaining a change in transient electromotive force based on the slip rate and the transient electromotive force differential equation;

[0010] Based on the change of the transient electromotive force, the current and power response of the induction motor after the disturbance is obtained.

[0011] Preferably, the obtaining of the change in the angular velocity of the induction motor after the disturbance based on the first-order mechanical transient equation of the induction motor, and obtaining the slip rate of the induction motor based on the change in the angular velocity include:

[0012] Build a third-order mechanical transient model of an induction motor:

[0013]

[0014]

[0015]

[0016] Among them, T j is the inertia time constant of the motor; ω m is the motor speed; s is the rotor slip rate, s=(ω s -ω m ) / ω s ;T e and T m are electromagnetic torque and mechanical load torque, T m is a constant; E′ d and E′ q are the d-axis and q-axis components of the rotor transient electromotive force E′ respectively; V ds and V qs The external stator voltage is The d-axis and q-axis components of I ds and I qs The stator currents are The d-axis and q-axis components of the stator are T′0, the stator open circuit and the rotor circuit transient time constant, X is the rotor open circuit reactance, X′ is the rotor short circuit reactance, ω s is the synchronous speed of the induction motor, ω m is the motor speed;

[0017]

[0018] Among them, R s is the stator resistance, V ds is the external stator voltage The d-axis component, V qs is the external stator voltage The q-axis component of

[0019] Based on the third-order mechanical transient model, ignoring the electromagnetic transient characteristics of the rotor winding, obtaining the first-order mechanical transient equation of the induction motor;

[0020] Power P of the sending end induction motor eq +jQ eq and the power P of the receiving induction motor d +jQ d satisfy:

[0021]

[0022] Among them, P eq is the active power of the sending-end induction motor, Q eq is the reactive power of the sending-end induction motor, P d is the active power of the receiving induction motor, Q d is the reactive power of the receiving induction motor, V s is the external applied voltage, R eq is the line resistance, X eq is the line reactance;

[0023] Among them, the positive and negative sequence voltages at the motor terminals are calculated as:

[0024]

[0025]

[0026] in, is the positive sequence voltage at the motor end, is the negative sequence voltage at the motor terminal, is the power supply positive sequence voltage, is the power supply negative sequence voltage, P eq1 is the active power of the sending-end induction motor, P eq2 is the active power of the sending-end induction motor, Q eq1 is the reactive power of the sending-end induction motor, Q eq2 is the reactive power of the sending-end induction motor;

[0027] Ignore the excitation reactance X m The impact of

[0028] (R s +R r s)2 +(X s +X r ) 2 ≈(R r / s) 2 , 2-s≈2,

[0029] Formula 5

[0030] Among them, R r is the rotor resistance, X s is the stator reactance, X r is the rotor reactance;

[0031] Positive and negative sequence voltages of induction motors have:

[0032]

[0033]

[0034]

[0035]

[0036] in, is the stator positive sequence current phasor, is the rotor positive sequence current phasor, is the stator negative sequence current phasor, is the rotor negative sequence current phasor, T e1 is the negative sequence electromagnetic torque, T e2 is the negative sequence electromagnetic torque; K1 and K2 are constants,

[0037] K1=3 / (R r ω s )

[0038]

[0039] During an asymmetric fault voltage sag, the rotor motion equation of the induction motor is:

[0040]

[0041] After the voltage drop is cleared, the stator voltage does not contain the negative sequence voltage component, and the rotor motion equation no longer contains the negative sequence electromagnetic torque T e2 ,have:

[0042]

[0043] Assume the initial angular velocity of the induction motor is ω n , the voltage drops continuously from the moment t0 when the voltage drops to the moment t1 when the fault is cleared, and the angular velocity of the induction motor drops to ω'm , by solving the rotor motion equation of the induction motor, the angular velocity ω of the induction motor during the fault period is obtained m-dur The approximate analytical expression of is:

[0044]

[0045] Get the angular velocity ω of the induction motor after the fault is cleared m-after The approximate analytical expression of is:

[0046]

[0047] Based on the angular velocity ω of the induction motor during the fault m-dur and the angular velocity ω of the induction motor after the fault is cleared m-after , obtain the slip rate s of the induction motor.

[0048] Preferably, the obtaining of the change of transient electromotive force based on the slip rate and the transient electromotive force differential equation includes:

[0049] When positive sequence voltage is applied to the stator terminal of the induction motor When , Equation 1 and Equation 2 are written in phasor form:

[0050]

[0051]

[0052] in, and are the rotor positive sequence transient electromotive force and stator positive sequence current phasor respectively;

[0053] The phasor form of the rotor positive sequence transient electromotive force differential equation is obtained from Equation 10:

[0054]

[0055] When negative sequence voltage is applied to the stator terminal of the induction motor When negative sequence current flows A negative rotating magnetic field is established, and the negative sequence slip is 2-s; where s is the slip;

[0056] The phasor form of the rotor negative sequence transient electromotive force differential equation is:

[0057]

[0058] in, is the rotor negative sequence transient electromotive force;

[0059] Based on Equation 11 and Equation 12, we establish:

[0060]

[0061] At the same time

[0062] Among them, K E1 , K E2 , B E As a known quantity, substitute into formula 15;

[0063] Simplify Equation 14 to:

[0064]

[0065] Based on Equation 15, the expression of the transient electromotive force differential equation of the induction motor during an asymmetric fault is obtained:

[0066]

[0067]

[0068] in, and are the initial values ​​of the positive and negative sequence transient electromotive force of the induction motor, is the positive sequence voltage at the stator terminal of the induction motor, is the negative sequence voltage at the stator terminal of the induction motor, E′ d1-dur is the positive sequence transient electromotive force of the induction motor during an asymmetric fault, E′ d2-dur is the negative sequence transient electromotive force of the induction motor during an asymmetric fault, t is the time after the voltage sag, and t0 is the time when the voltage sag occurs;

[0069]

[0070] During the recovery process after the voltage drop is cleared, the stator voltage does not contain negative sequence voltage components, and the transient electromotive force of the induction motor contains only positive sequence components:

[0071]

[0072] in, It is the positive sequence transient electromotive force of the induction motor at the moment of voltage sag clearing.

[0073] Preferably, the obtaining of the current and power response of the induction motor after the disturbance based on the change of the transient electromotive force comprises:

[0074] The transient electromotive force of the motor rotor during the fault period obtained by calculating Equation 16 is and The d-axis component E′ ql-dur , E′ q2-dur and the q-axis component E′ ql-dur , E′q2-dur Substitute into Equation 2 to obtain the positive sequence stator current I of the motor d and q axes during the voltage drop period ds1 , I qsl and negative sequence stator current I ds2 , I qs2 During the voltage drop, the active power consumed by the induction motor is P d and reactive power Q d They are:

[0075]

[0076] Among them, P d1 、P d2 are positive and negative sequence active power respectively; Q d1 , Q d2 are positive and negative sequence reactive power, V ds1 is the positive sequence stator voltage of the motor d axis during voltage sag, I ds1 is the positive sequence stator current of the motor d axis during voltage sag, V qs1 is the positive sequence stator voltage of the motor q axis during voltage sag, I qs1 is the positive sequence stator current of the motor q axis during voltage sag, V ds2 is the negative sequence stator voltage of the motor d axis during voltage sag, I ds2 is the negative sequence stator current of the motor d axis during voltage sag, V qs2 is the negative sequence stator current of the motor q axis during voltage sag, I qs2 is the negative sequence stator current of the motor q axis during voltage sag;

[0077] After the voltage drop is cleared, the stator voltage no longer contains negative sequence voltage components, and the transient electromotive force calculated by formula 18 is The d-axis component E′ d1-after and the q-axis component E′ q1-after Substitute into Equation 2 to obtain the positive sequence stator current I of the d and q axes of the induction motor during the voltage sag. ds1 , I qs1 , the active power P consumed by the induction motor d and reactive power Q d They are:

[0078]

[0079] Calculate the power consumption P of the induction motor d +jQ d After that, the stator current positive sequence component Negative sequence component They are:

[0080]

[0081] The current value of each phase is obtained based on the symmetrical component method.

[0082] According to another aspect of the present invention, the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and the computer program is used to execute any one of the methods described above.

[0083] According to another aspect of the present invention, the present invention provides an electronic device, comprising: a processor and a memory; wherein,

[0084] The memory is a memory for storing instructions executable by the processor;

[0085] The processor is configured to read the executable instructions from the memory and execute the instructions to implement any one of the above methods.

[0086] According to another aspect of the present invention, the present invention provides a system for analyzing dynamic characteristics of an induction motor, the system comprising:

[0087] a first acquiring unit, configured to acquire a change in the angular velocity of the induction motor after the disturbance based on a first-order mechanical transient equation of the induction motor, and acquire a slip rate of the induction motor based on the change in the angular velocity;

[0088] a second acquiring unit, configured to acquire a change in transient electromotive force based on the slip rate and a transient electromotive force differential equation;

[0089] The third acquisition unit is configured to acquire the current and power response of the induction motor after the disturbance based on the change of the transient electromotive force.

[0090] Preferably, the first acquisition unit is configured to acquire a change in the angular velocity of the induction motor after the disturbance based on a first-order mechanical transient equation of the induction motor, and to acquire a slip rate of the induction motor based on the change in the angular velocity, specifically for:

[0091] Build a third-order mechanical transient model of an induction motor:

[0092]

[0093]

[0094]

[0095] Among them, T j is the inertia time constant of the motor; ω m is the motor speed; s is the rotor slip rate, s=(ω s -ω m) / ω s ;T e and T m are electromagnetic torque and mechanical load torque, T m is a constant; E′ d and E′ q are the d-axis and q-axis components of the rotor transient electromotive force E′ respectively; V ds and V qs The external stator voltage is The d-axis and q-axis components of I ds and I qs The stator currents are The d-axis and q-axis components of the stator are T′0, the stator open circuit and the rotor circuit transient time constant, X is the rotor open circuit reactance, X′ is the rotor short circuit reactance, ω s is the synchronous speed of the induction motor, ω m is the motor speed;

[0096]

[0097] Among them, R s is the stator resistance, V ds is the external stator voltage The d-axis component, V qs is the external stator voltage The q-axis component of

[0098] Based on the third-order mechanical transient model, ignoring the electromagnetic transient characteristics of the rotor winding, obtaining the first-order mechanical transient equation of the induction motor;

[0099] Power P of the sending end induction motor eq +jQ eq and the power P of the receiving induction motor d +jQ d satisfy:

[0100]

[0101] Among them, P eq is the active power of the sending-end induction motor, Q eq is the reactive power of the sending-end induction motor, P d is the active power of the receiving induction motor, Q d is the reactive power of the receiving induction motor, V s is the external applied voltage, R eq is the line resistance, X eq is the line reactance;

[0102] Among them, the positive and negative sequence voltages at the motor terminals are calculated as:

[0103]

[0104]

[0105] in, is the positive sequence voltage at the motor end, is the negative sequence voltage at the motor terminal, is the power supply positive sequence voltage, is the power supply negative sequence voltage, P eq1 is the active power of the sending-end induction motor, P eq2 is the active power of the sending-end induction motor, Q eq1 is the reactive power of the sending-end induction motor, Q eq2 is the reactive power of the sending-end induction motor;

[0106] Ignore the excitation reactance X m The impact of

[0107] (R s +R r s) 2 +(X s +X r ) 2 ≈(R r / s) 2 , 2-s≈2,

[0108] Formula 5

[0109] Among them, R r is the rotor resistance, X s is the stator reactance, X r is the rotor reactance;

[0110] Positive and negative sequence voltages of induction motors have:

[0111]

[0112]

[0113]

[0114]

[0115] in, is the stator positive sequence current phasor, is the rotor positive sequence current phasor, is the stator negative sequence current phasor, is the rotor negative sequence current phasor, T e1 is the negative sequence electromagnetic torque, T e2 is the negative sequence electromagnetic torque; K1 and K2 are constants,

[0116] K1=3 / (R r ω s )

[0117]

[0118] During an asymmetric fault voltage sag, the rotor motion equation of the induction motor is:

[0119]

[0120] After the voltage drop is cleared, the stator voltage does not contain the negative sequence voltage component, and the rotor motion equation no longer contains the negative sequence electromagnetic torque T e2 ,have:

[0121]

[0122] Assume the initial angular velocity of the induction motor is ω n , the voltage drops continuously from the moment t0 when the voltage drops to the moment t1 when the fault is cleared, and the angular velocity of the induction motor drops to ω′ m , by solving the rotor motion equation of the induction motor, the angular velocity ω of the induction motor during the fault period is obtained m-dur The approximate analytical expression of is:

[0123]

[0124] Get the angular velocity ω of the induction motor after the fault is cleared m-after The approximate analytical expression of is:

[0125]

[0126] Based on the angular velocity ω of the induction motor during the fault m-dur and the angular velocity ω of the induction motor after the fault is cleared m-after , obtain the slip rate s of the induction motor.

[0127] Preferably, the second acquisition unit is used to acquire the change of transient electromotive force based on the slip rate and the transient electromotive force differential equation, specifically for:

[0128] When positive sequence voltage is applied to the stator terminal of the induction motor When , Equation 1 and Equation 2 are written in phasor form:

[0129]

[0130]

[0131] in, and are the rotor positive sequence transient electromotive force and stator positive sequence current phasor respectively;

[0132] The phasor form of the rotor positive sequence transient electromotive force differential equation is obtained from Equation 10:

[0133]

[0134] When negative sequence voltage is applied to the stator terminal of the induction motor When negative sequence current flows A negative rotating magnetic field is established, and the negative sequence slip is 2-s; where s is the slip;

[0135] The phasor form of the rotor negative sequence transient electromotive force differential equation is:

[0136]

[0137] in, is the rotor negative sequence transient electromotive force;

[0138] Based on Equation 11 and Equation 12, we establish:

[0139]

[0140] At the same time

[0141] Among them, K E1 , K E2 , B E As a known quantity, substitute into formula 15;

[0142] Simplify Equation 14 to:

[0143]

[0144] Based on Equation 15, the expression of the transient electromotive force differential equation of the induction motor during an asymmetric fault is obtained:

[0145]

[0146]

[0147] in, and are the initial values ​​of the positive and negative sequence transient electromotive force of the induction motor, is the positive sequence voltage at the stator terminal of the induction motor, is the negative sequence voltage at the stator terminal of the induction motor, E′ d1-dur is the positive sequence transient electromotive force of the induction motor during an asymmetric fault, E′ d2-dur is the negative sequence transient electromotive force of the induction motor during an asymmetric fault, t is the time after the voltage sag, and t0 is the time when the voltage sag occurs;

[0148]

[0149] During the recovery process after the voltage drop is cleared, the stator voltage does not contain negative sequence voltage components, and the transient electromotive force of the induction motor contains only positive sequence components:

[0150]

[0151] in, It is the positive sequence transient electromotive force of the induction motor at the moment of voltage sag clearing.

[0152] Preferably, the third acquisition unit is used to acquire the current and power response of the induction motor after the disturbance based on the change of the transient electromotive force, specifically for:

[0153] The transient electromotive force of the motor rotor during the fault period obtained by calculating Equation 16 is and The d-axis component E′ d1-dur , E′ d2-dur and the q-axis component E′ ql-dur , E′ q2-dur Substitute into Equation 2 to obtain the positive sequence stator current I of the motor d and q axes during the voltage drop period ds1 , I qs1 and negative sequence stator current I ds2 , I qs2 During the voltage drop, the active power consumed by the induction motor is P d and reactive power Q d They are:

[0154]

[0155] Among them, P d1 、P d2 are positive and negative sequence active power respectively; Q d1 , Q d2 are positive and negative sequence reactive power, V ds1 is the positive sequence stator voltage of the motor d axis during voltage sag, I ds1 is the positive sequence stator current of the motor d axis during voltage sag, V qs1 is the positive sequence stator voltage of the motor q axis during voltage sag, I qs1 is the positive sequence stator current of the motor q axis during voltage sag, V qs2 is the negative sequence stator voltage of the motor d axis during voltage sag, I ds2 is the negative sequence stator current of the motor d axis during voltage sag, V qs2 is the negative sequence stator current of the motor q axis during voltage sag, I qs2is the negative sequence stator current of the motor q axis during voltage sag;

[0156] After the voltage drop is cleared, the stator voltage no longer contains negative sequence voltage components, and the transient electromotive force calculated by formula 18 is The d-axis component E′ d1-after and the q-axis component E′ q1-after Substitute into Equation 2 to obtain the positive sequence stator current I of the d and q axes of the induction motor during the voltage sag. ds1 , I qs1 , the active power P consumed by the induction motor d and reactive power Q d They are:

[0157]

[0158] Calculate the power consumption P of the induction motor d +jQ d After that, the stator current positive sequence component Negative sequence component They are:

[0159]

[0160] The current value of each phase is obtained based on the symmetrical component method.

[0161] The technical solution of the present invention provides a method and system for analyzing the dynamic characteristics of an induction motor. The method includes: obtaining the change in the angular velocity of the induction motor after a disturbance based on the first-order mechanical transient equation of the induction motor, and obtaining the slip of the induction motor based on the change in angular velocity; obtaining the change in transient electromotive force based on the slip and transient electromotive force differential equation; and obtaining the current and power response of the induction motor after a disturbance based on the change in transient electromotive force. The fast analytical algorithm for the dynamic characteristics of an induction motor under asymmetric fault voltage drop proposed in the present invention can quickly evaluate the dynamic response characteristics of an induction motor after an asymmetric fault. BRIEF DESCRIPTION OF THE DRAWINGS

[0162] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings:

[0163] Figure 1 A flow chart of a method for analyzing dynamic characteristics of an induction motor according to a preferred embodiment of the present invention;

[0164] Figure 2 A schematic diagram of a transient equivalent circuit of an induction motor according to a preferred embodiment of the present invention;

[0165] Figure 3 Schematic diagram of a power supply system for a single-unit induction motor according to a preferred embodiment of the present invention;

[0166] Figure 4 Schematic diagram of the dynamic response of a motor during an asymmetric voltage drop according to a preferred embodiment of the present invention;

[0167] Figure 5 Schematic diagram of the dynamic response of a motor during a symmetrical voltage drop according to a preferred embodiment of the present invention;

[0168] Figure 6 A parameter table of an induction motor load model according to a preferred embodiment of the present invention; and

[0169] Figure 7 4 is a structural diagram of a system for analyzing the dynamic characteristics of an induction motor according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0170] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to provide a thorough and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments shown in the accompanying drawings is not intended to limit the present invention. In the accompanying drawings, identical elements are denoted by the same reference numerals.

[0171] Unless otherwise specified, the terms used herein (including technical terms) have the meanings commonly understood by those skilled in the art. In addition, it is understood that terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0172] Figure 1 This figure is a flow chart of a method for analyzing the dynamic characteristics of an induction motor according to a preferred embodiment of the present invention. The fast analytical algorithm for analyzing the dynamic characteristics of an induction motor under asymmetric fault voltage drop proposed in this invention can quickly evaluate the dynamic response characteristics of an induction motor after an asymmetric fault and avoid tedious time-domain simulation calculations. The method proposed in this invention first solves the rotor's first-order mechanical transient equations and then expands them to perform various calculations, greatly simplifying the computational process and difficulty compared to traditional analytical methods.

[0173] The invention relates to an algorithm for dynamic response characteristics of an induction motor, in particular to a fast analytical algorithm for calculating the dynamic characteristics of an induction motor under an asymmetric fault voltage drop in a power system.

[0174] like Figure 1 As shown, the present invention provides a method for analyzing the dynamic characteristics of an induction motor, the method comprising:

[0175] Step 101: obtaining a change in the angular velocity of the induction motor after the disturbance based on a first-order mechanical transient equation of the induction motor, and obtaining a slip rate of the induction motor based on the change in the angular velocity;

[0176] The analytical algorithm proposed in the present invention first solves the first-order mechanical transient equation of the rotor to obtain the speed and slip changes of the rotor after the disturbance.

[0177] Step 102: Obtaining a change in transient electromotive force based on the slip rate and the transient electromotive force differential equation;

[0178] The present invention solves the transient electromotive force differential equation in rotor phasor form to obtain the change of transient electromotive force.

[0179] Step 103: Based on the change of the transient electromotive force, obtain the current and power response of the induction motor after the disturbance.

[0180] The present invention accurately obtains the current and power response of the induction motor after the disturbance.

[0181] The present invention ignores the electromagnetic transient characteristics of the stator winding and lists the third-order electromechanical transient model of the induction motor as follows. The corresponding motor transient equivalent circuit is as follows: Figure 2 .

[0182] Preferably, obtaining a change in the angular velocity of the induction motor after the disturbance based on a first-order mechanical transient equation of the induction motor, and obtaining the slip rate of the induction motor based on the change in the angular velocity includes:

[0183] Build a third-order mechanical transient model of an induction motor:

[0184]

[0185]

[0186]

[0187] Among them, T j is the inertia time constant of the motor; ω m is the motor speed; s is the rotor slip rate, s=(ω s -ω m ) / ω s ;T e and T m are electromagnetic torque and mechanical load torque, T m is a constant; E′ d and E′ q are the d-axis and q-axis components of the rotor transient electromotive force E′ respectively; V ds and V qs The external stator voltage is The d-axis and q-axis components of I ds and I qs The stator currents are The d-axis and q-axis components of the stator are T′0, the stator open circuit and the rotor circuit transient time constant, X is the rotor open circuit reactance, X′ is the rotor short circuit reactance, ω s is the synchronous speed of the induction motor, ω m is the motor speed;

[0188]

[0189] Among them, R s is the stator resistance, V ds is the external stator voltage The d-axis component, V qs is the external stator voltage The q-axis component of

[0190] The present invention further ignores the electromagnetic transient characteristics of the rotor winding and only retains the third formula in Formula 1 to obtain the first-order mechanical transient model of the induction motor;

[0191] The present invention builds Figure 3 The single-unit induction motor power supply system shown in the figure has a power supply through an impedance of Z eq =R eq +jX eq The power supply network supplies power to the induction motor IM; because the induction motor is generally not connected to the neutral line, there is no zero-sequence current, so it is only necessary to analyze the impact of the positive-sequence and negative-sequence voltage components on the induction motor.

[0192] Based on the third-order mechanical transient model, the electromagnetic transient characteristics of the rotor winding are ignored to obtain the first-order mechanical transient equation of the induction motor;

[0193] Power P of the sending end induction motor eq +jQ eq and the power P of the receiving induction motor d +jQ d satisfy:

[0194]

[0195] Among them, P eq is the active power of the sending-end induction motor, Q eq is the reactive power of the sending-end induction motor, P d is the active power of the receiving induction motor, Q d is the reactive power of the receiving induction motor, V s is the external applied voltage, R eq is the line resistance, X eq is the line reactance;

[0196] Among them, the positive and negative sequence voltages at the motor terminals are calculated as:

[0197]

[0198]

[0199] in, is the positive sequence voltage at the motor end, is the negative sequence voltage at the motor terminal, is the power supply positive sequence voltage, is the power supply negative sequence voltage, P eq1 is the active power of the sending-end induction motor, P eq2 is the active power of the sending-end induction motor, Q eq1 is the reactive power of the sending-end induction motor, P eq2 is the reactive power of the sending-end induction motor; the superscript * indicates the conjugate value.

[0200] Ignore the excitation reactance X m The impact of

[0201] (R s +R r s) 2 +(X s +X r ) 2 ≈(R r / s) 2 , 2-s≈2,

[0202] Formula 5

[0203] Among them, R r is the rotor resistance, X s is the stator reactance, X r is the rotor reactance;

[0204] Positive and negative sequence voltages of induction motors have:

[0205]

[0206]

[0207]

[0208]

[0209] in, is the stator positive sequence current phasor, is the rotor positive sequence current phasor, is the stator negative sequence current phasor, is the rotor negative sequence current phasor, Te1 is the negative sequence electromagnetic torque, T e2 is the negative sequence electromagnetic torque; K1 and K2 are constants,

[0210] K1=3 / (R r ω s )

[0211]

[0212] During an asymmetric fault voltage sag, the rotor motion equation of the induction motor is:

[0213]

[0214] After the voltage drop is cleared, the stator voltage does not contain the negative sequence voltage component, and the rotor motion equation no longer contains the negative sequence electromagnetic torque T e2 ,have:

[0215]

[0216] Assume the initial angular velocity of the induction motor is ω n , the voltage drops continuously from the moment t0 when the voltage drops to the moment t1 when the fault is cleared, and the angular velocity of the induction motor drops to ω' m , by solving the rotor motion equation of the induction motor, the angular velocity ω of the induction motor during the fault period is obtained m-dur The approximate analytical expression of is:

[0217]

[0218] In the present invention, after the voltage drop is cleared, the rotor angular velocity of the induction motor is restored after a period of time.

[0219] Get the angular velocity ω of the induction motor after the fault is cleared m-after The approximate analytical expression of is:

[0220]

[0221] Based on the angular velocity ω of the induction motor during the fault m-dur and the angular velocity ω of the induction motor after the fault is cleared m-after , obtain the slip rate s of the induction motor.

[0222] Preferably, obtaining the change of transient electromotive force based on the slip rate and the transient electromotive force differential equation includes:

[0223] When positive sequence voltage is applied to the stator terminal of the induction motor When , Equation 1 and Equation 2 are written in phasor form:

[0224]

[0225]

[0226] in, and are the rotor positive sequence transient electromotive force and stator positive sequence current phasor respectively;

[0227] The phasor form of the rotor positive sequence transient electromotive force differential equation is obtained from Equation 10:

[0228]

[0229] When negative sequence voltage is applied to the stator terminal of the induction motor When negative sequence current flows A negative rotating magnetic field is established, and the negative sequence slip is 2-s; where s is the slip;

[0230] The phasor form of the rotor negative sequence transient electromotive force differential equation is:

[0231]

[0232] in, is the rotor negative sequence transient electromotive force;

[0233] Based on Equation 11 and Equation 12, we establish:

[0234]

[0235] At the same time

[0236] Among them, K E1 , K E2 , B E As a known quantity, substitute into formula 15.

[0237] Simplify Equation 14 to:

[0238]

[0239] Based on Equation 15, the expression of the transient electromotive force differential equation of the induction motor during an asymmetric fault is obtained:

[0240]

[0241]

[0242] in, and are the initial values ​​of the positive and negative sequence transient electromotive force of the induction motor, is the positive sequence voltage at the stator terminal of the induction motor, is the negative sequence voltage at the stator terminal of the induction motor, E′d1-dur is the positive sequence transient electromotive force of the induction motor during an asymmetric fault, E′ d2-dur is the negative sequence transient electromotive force of the induction motor during an asymmetric fault, t is the time after the voltage sag, and t0 is the time when the voltage sag occurs;

[0243]

[0244] During the recovery process after the voltage drop is cleared, the stator voltage does not contain negative sequence voltage components, and the transient electromotive force of the induction motor contains only positive sequence components:

[0245]

[0246] in, It is the positive sequence transient electromotive force of the induction motor at the moment of voltage sag clearing.

[0247] Preferably, obtaining the current and power response of the induction motor after the disturbance based on the change of the transient electromotive force includes:

[0248] The transient electromotive force of the motor rotor during the fault period obtained by calculating Equation 16 is and The d-axis component E′ d1-dur , E′ d2-dur and the q-axis component E′ q1-dur , E′ q2-dur Substitute into Equation 2 to obtain the positive sequence stator current I of the motor d and q axes during the voltage drop period ds1 , I qsl and negative sequence stator current I ds2 , I qs2 During the voltage drop, the active power consumed by the induction motor is P d and reactive power Q d They are:

[0249]

[0250] Among them, P d1 、P d2 are positive and negative sequence active power respectively; Q d1 , Q d2 are positive and negative sequence reactive power, V ds1 is the positive sequence stator voltage of the motor d axis during voltage sag, I ds1 is the positive sequence stator current of the motor d axis during voltage sag, V qs1 is the positive sequence stator voltage of the motor q axis during voltage sag, I qs1 is the positive sequence stator current of the motor q axis during voltage sag, V ds2 is the negative sequence stator voltage of the motor d axis during voltage sag, Ids2 is the negative sequence stator current of the motor d axis during voltage sag, V qs2 is the negative sequence stator current of the motor q axis during voltage sag, I qs2 is the negative sequence stator current of the motor q axis during voltage sag;

[0251] After the voltage drop is cleared, the stator voltage no longer contains negative sequence voltage components, and the transient electromotive force calculated by formula 18 is The d-axis component E′ d1-after and the q-axis component E′ q1-after Substitute into Equation 2 to obtain the positive sequence stator current I of the d and q axes of the induction motor during the voltage sag. ds1 , I qs1 , the active power P consumed by the induction motor d and reactive power Q d They are:

[0252]

[0253] Calculate the power consumption P of the induction motor d +jQ d After that, the stator current positive sequence component Negative sequence component They are:

[0254]

[0255] The current value of each phase is obtained based on the symmetrical component method. The current of each phase can be easily obtained by the symmetrical component method, and the above algorithm can be programmed and implemented in the Matlab environment.

[0256] Preferably, the computer-readable storage medium stores a computer program for executing a method for analyzing dynamic characteristics of an induction motor.

[0257] Preferably, the electronic device comprises: a processor and a memory; wherein,

[0258] Memory for storing processor-executable instructions;

[0259] The processor is configured to read executable instructions from the memory and execute the instructions to implement a method for analyzing dynamic characteristics of an induction motor.

[0260] The present invention utilizes the phasor form of the rotor transient electromotive force differential equation to achieve simultaneous analytical solution of the third-order electromechanical transient model of the induction motor, and can relatively accurately obtain the transient slip, electromotive force, power and current of the induction motor under symmetrical and asymmetrical fault voltage drops.

[0261] The calculation models of the present invention are all algebraic expressions, which have obvious advantages in calculation speed compared with the simultaneous solution of differential-algebraic equations for electromechanical and electromagnetic transient simulation of power systems;

[0262] The present invention takes into account the influence of negative sequence components on the dynamic response of the motor during asymmetric faults, and the calculation accuracy is higher than that of electromechanical transient simulation that only considers positive sequence fundamental components.

[0263] The present invention explicitly calculates the mechanical and electrical parameters of the motor, making it easy to analyze and explain the results and phenomena.

[0264] Experimental test results show that the analytical algorithm for analyzing the dynamic characteristics of induction motor loads overcomes the time-consuming nature of solving high-order differential equations in time-domain simulations, effectively improving the computational speed of power system electromagnetic transient simulations. Furthermore, the algorithm considers the impact of negative-sequence voltage components generated by asymmetric fault voltage sags on the dynamic characteristics of induction motor loads, improving the computational accuracy of the induction motor's third-order electromechanical transient simulation model and demonstrating the superior computational accuracy of the analytical algorithm under asymmetric fault voltage sags.

[0265] The present invention conducts the following simulation experiments based on steps 101 , 102 , and 103 of the above method for analyzing the dynamic characteristics of an induction motor.

[0266] The present invention adopts Figure 6 The motor parameters in the table are built in the electromagnetic transient simulation program PSCAD / EMTDC Figure 3 The simulation model of the 10kV power supply system shown in the figure compares the following two situations: ① Set the power supply to have an asymmetric fault voltage drop of 0.2s at 0.2s. Before voltage drop: E eqa，pre =1.0∠0°(pu),E eqb，pre =1.0∠-120°(pu), E eqc，pre =1.0∠120°(pu); voltage drop period: E eqa，dur =0.0∠10°(pu),E eqb，dur =1.0∠-130°(pu),E eqc，dur =1.0∠130°(pu). Figure 6 The capacity of the motor in the table is 1.4MW. (2) Set the power supply to have a symmetrical fault voltage drop of 0.2s duration at 0.2s. Before voltage drop: E eqa，pre =1.0∠0°(pu),E eqb，pre =1.0∠-120°(pu), E eqc，pre =1.0∠120°(pu); voltage drop period: E eqa，dur =0.6∠0°(pu),E eqb，dur=0.6∠-120°(pu), E eqc，dur =0.6∠120°(pu). Figure 6 The capacity of the induction motor in the table is 1MW. In the calculation example, the induction motor is operated with rated load, the load torque Tm is 1.0 (pu), and the system equivalent impedance Z eq =(1.3+j3.8)Ω, the PSCAD / EMTDC simulation step is 100μs, the analytical algorithm calculation step is 0.01s, and the calculation results are as follows Figure 4 and Figure 5 As shown in the figure, the solid line, dashed line and dotted line are the calculation results of the method of the present invention, the analytical method of the literature and PSCAD / EMTDC, respectively, which are marked as "method of this paper", "analytic method 2" and "PSCAD" in the figure.

[0267] This paper compares the proposed analytical algorithm with simulation results, demonstrating its effectiveness in overcoming the time-consuming nature of solving high-order differential equations in time-domain simulations, effectively improving the computational speed of power system electromagnetic transient simulations. The analytical algorithm explicitly provides calculation expressions for the mechanical and electrical parameters of the induction motor's dynamic load after a power system fault. This algorithm can be used to quickly assess the interaction between induction motor load and voltage sag and has the potential to be applied to power system stability analysis.

[0268] Figure 7 FIG. 1 is a structural diagram of a system for analyzing the dynamic characteristics of an induction motor according to a preferred embodiment of the present invention. Figure 7 As shown, the present invention provides a system for analyzing the dynamic characteristics of an induction motor, the system comprising:

[0269] A first acquiring unit 701 is configured to acquire a change in the angular velocity of the induction motor after the disturbance based on a first-order mechanical transient equation of the induction motor, and acquire a slip rate of the induction motor based on the change in the angular velocity;

[0270] A second acquiring unit 702 is configured to acquire a change in transient electromotive force based on the slip rate and the transient electromotive force differential equation;

[0271] The third acquisition unit 703 is configured to acquire the current and power response of the induction motor after the disturbance based on the change of the transient electromotive force.

[0272] Preferably, the first acquiring unit 701 is configured to acquire a change in the angular velocity of the induction motor after the disturbance based on the first-order mechanical transient equation of the induction motor, and to acquire the slip rate of the induction motor based on the change in the angular velocity, specifically for:

[0273] Build a third-order mechanical transient model of an induction motor:

[0274]

[0275]

[0276]

[0277] Among them, T j is the inertia time constant of the motor; ω m is the motor speed; s is the rotor slip rate, s=(ω s -ω m ) / ω s ;T e and T m are electromagnetic torque and mechanical load torque, T m is a constant; E′ d and E′ q are the d-axis and q-axis components of the rotor transient electromotive force E′ respectively; V ds and V qs The external stator voltage is The d-axis and q-axis components of I ds and I qs The stator currents are The d-axis and q-axis components of the stator are T′0, the stator open circuit and the rotor circuit transient time constant, X is the rotor open circuit reactance, X′ is the rotor short circuit reactance, ω s is the synchronous speed of the induction motor, ω m is the motor speed;

[0278]

[0279] Among them, R s is the stator resistance, V ds is the external stator voltage The d-axis component, V qs is the external stator voltage The q-axis component of

[0280] Based on the third-order mechanical transient model, the electromagnetic transient characteristics of the rotor winding are ignored to obtain the first-order mechanical transient equation of the induction motor;

[0281] Power P of the sending end induction motor eq +jQ eq and the power P of the receiving induction motor d +jQ d satisfy:

[0282]

[0283] Among them, P eq is the active power of the sending-end induction motor, Q eqis the reactive power of the sending-end induction motor, P d is the active power of the receiving induction motor, Q d is the reactive power of the receiving induction motor, V s is the external applied voltage, R eq is the line resistance, X eq is the line reactance;

[0284] Among them, the positive and negative sequence voltages at the motor terminals are calculated as:

[0285]

[0286]

[0287] in, is the positive sequence voltage at the motor end, is the negative sequence voltage at the motor terminal, is the power supply positive sequence voltage, is the power supply negative sequence voltage, P eq1 is the active power of the sending-end induction motor, P eq2 is the active power of the sending-end induction motor, Q eq1 is the reactive power of the sending-end induction motor, Q eq2 is the reactive power of the sending-end induction motor;

[0288] Ignore the excitation reactance X m The impact of

[0289] (R s +R r s) 2 +(X s +X r ) 2 ≈(R r / s) 2 , 2-s≈2,

[0290] Formula 5

[0291] Among them, R r is the rotor resistance, X s is the stator reactance, X r is the rotor reactance;

[0292] Positive and negative sequence voltages of induction motors have:

[0293]

[0294]

[0295]

[0296]

[0297] in, is the stator positive sequence current phasor, is the rotor positive sequence current phasor, is the stator negative sequence current phasor, is the rotor negative sequence current phasor, T e1 is the negative sequence electromagnetic torque, T e2 is the negative sequence electromagnetic torque; K1 and K2 are constants,

[0298] K1=3 / (R r ω s )

[0299]

[0300] During an asymmetric fault voltage sag, the rotor motion equation of the induction motor is:

[0301]

[0302] After the voltage drop is cleared, the stator voltage does not contain the negative sequence voltage component, and the rotor motion equation no longer contains the negative sequence electromagnetic torque T e2 ,have:

[0303]

[0304] Assume the initial angular velocity of the induction motor is ω n , the voltage drops continuously from the moment t0 when the voltage drops to the moment t1 when the fault is cleared, and the angular velocity of the induction motor drops to ω' m , by solving the rotor motion equation of the induction motor, the angular velocity ω of the induction motor during the fault period is obtained m-dur The approximate analytical expression of is:

[0305]

[0306] Get the angular velocity ω of the induction motor after the fault is cleared m-after The approximate analytical expression of is:

[0307]

[0308] Based on the angular velocity ω of the induction motor during the fault m-dur and the angular velocity ω of the induction motor after the fault is cleared m-after , obtain the slip rate s of the induction motor.

[0309] Preferably, the second acquisition unit 702 is configured to acquire a change in transient electromotive force based on the slip rate and the transient electromotive force differential equation, specifically for:

[0310] When positive sequence voltage is applied to the stator terminal of the induction motor When , Equation 1 and Equation 2 are written in phasor form:

[0311]

[0312]

[0313] in, and are the rotor positive sequence transient electromotive force and stator positive sequence current phasor respectively;

[0314] The phasor form of the rotor positive sequence transient electromotive force differential equation is obtained from Equation 10:

[0315]

[0316] When negative sequence voltage is applied to the stator terminal of the induction motor When negative sequence current flows A negative rotating magnetic field is established, and the negative sequence slip is 2-s; where s is the slip;

[0317] The phasor form of the rotor negative sequence transient electromotive force differential equation is:

[0318]

[0319] in, is the rotor negative sequence transient electromotive force;

[0320] Based on Equation 11 and Equation 12, we establish:

[0321]

[0322] At the same time

[0323] Among them, K E1 , K E2 , B E As a known quantity, substitute into formula 15;

[0324] Simplify Equation 14 to:

[0325]

[0326] Based on Equation 15, the expression of the transient electromotive force differential equation of the induction motor during an asymmetric fault is obtained:

[0327]

[0328]

[0329] in, and are the initial values ​​of the positive and negative sequence transient electromotive force of the induction motor, is the positive sequence voltage at the stator terminal of the induction motor, is the negative sequence voltage at the stator terminal of the induction motor, E′ d1-dur is the positive sequence transient electromotive force of the induction motor during an asymmetric fault, E′ d2-dur is the negative sequence transient electromotive force of the induction motor during an asymmetric fault, t is the time after the voltage sag, and t0 is the time when the voltage sag occurs;

[0330]

[0331] During the recovery process after the voltage drop is cleared, the stator voltage does not contain negative sequence voltage components, and the transient electromotive force of the induction motor contains only positive sequence components:

[0332]

[0333] in, It is the positive sequence transient electromotive force of the induction motor at the moment of voltage sag clearing.

[0334] Preferably, the third acquisition unit 703 is configured to acquire the current and power response of the induction motor after the disturbance based on the change of the transient electromotive force, specifically for:

[0335] The transient electromotive force of the motor rotor during the fault period obtained by calculating Equation 16 is and The d-axis component E′ d1-dur , E′ d2-dur and the q-axis component E′ q1-dur , E′ q2-dur Substitute into Equation 2 to obtain the positive sequence stator current I of the motor d and q axes during the voltage drop period ds1 , I qsl and negative sequence stator current I ds2 , I qs2 During the voltage drop, the active power consumed by the induction motor is P d and reactive power Q d They are:

[0336]

[0337] Among them, P d1 、P d2 are positive and negative sequence active power respectively; Q d1 , Q d2 are positive and negative sequence reactive power, V ds1 is the positive sequence stator voltage of the motor d axis during voltage sag, I ds1 is the positive sequence stator current of the motor d axis during voltage sag, Vqs1 is the positive sequence stator voltage of the motor q axis during voltage sag, I qs1 is the positive sequence stator current of the motor q axis during voltage sag, V ds2 is the negative sequence stator voltage of the motor d axis during voltage sag, I ds2 is the negative sequence stator current of the motor d axis during voltage sag, V qs2 is the negative sequence stator current of the motor q axis during voltage sag, I qs2 is the negative sequence stator current of the motor q axis during voltage sag;

[0338] After the voltage drop is cleared, the stator voltage no longer contains negative sequence voltage components, and the transient electromotive force calculated by formula 18 is The d-axis component E′ d1-after and the q-axis component E′ q1-after Substitute into Equation 2 to obtain the positive sequence stator current I of the d and q axes of the induction motor during the voltage sag. ds1 , I qs1 , the active power P consumed by the induction motor d and reactive power Q d They are:

[0339]

[0340] Calculate the power consumption P of the induction motor d +jQ d After that, the stator current positive sequence component Negative sequence component They are:

[0341]

[0342] The current value of each phase is obtained based on the symmetrical component method.

[0343] A system 700 for analyzing dynamic characteristics of an induction motor according to a preferred embodiment of the present invention corresponds to a method 100 for analyzing dynamic characteristics of an induction motor according to a preferred embodiment of the present invention, and will not be described in detail herein.

[0344] It will be understood by those skilled in the art that the embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention may be implemented in various computer languages, for example, the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0345] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0346] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0347] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 The steps for the function specified in one or more boxes.

[0348] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0349] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

[0350] The invention has been described above with reference to a few embodiments. However, it is readily apparent to a person skilled in the art that other embodiments than the ones disclosed above are equally within the scope of the invention, as defined by the appended patent claims.

[0351] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / / the [means, component, etc.]" are to be interpreted openly as referring to at least one instance of a means, component, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not necessarily need to be performed in the exact order disclosed, unless explicitly stated otherwise.

Claims

1. A method for analyzing dynamic characteristics of an induction motor, the method comprising: The method includes obtaining a change in the angular velocity of the induction motor after a disturbance based on a first-order mechanical transient equation of the induction motor, and obtaining a slip rate of the induction motor based on the change in the angular velocity. Build a third-order mechanical transient model of an induction motor: Among them, T j is the inertia time constant of the motor; ω m is the motor speed; s is the rotor slip rate, s=(ω s -ω m ) / ω s ;T e and T m are electromagnetic torque and mechanical load torque, T m is a constant; E′ d and E′ q are the d-axis and q-axis components of the rotor transient electromotive force E′ respectively; V ds and V qs The external stator voltage is The d-axis and q-axis components of I ds and I qs The stator currents are The d-axis and q-axis components of the stator are T′0, the stator open circuit and the rotor circuit transient time constant, X is the rotor open circuit reactance, X′ is the rotor short circuit reactance, ω s is the synchronous speed of the induction motor, ω m is the motor speed; Among them, R s is the stator resistance, V ds is the external stator voltage The d-axis component, V qs is the external stator voltage The q-axis component of Based on the third-order mechanical transient model, ignoring the electromagnetic transient characteristics of the rotor winding, obtaining the first-order mechanical transient equation of the induction motor; Power P of the sending end induction motor eq +jQ eq and the power P of the receiving induction motor d +jQ d satisfy: Among them, P eq is the active power of the sending-end induction motor, Q eq is the reactive power of the sending-end induction motor, P d is the active power of the receiving induction motor, Q d is the reactive power of the receiving induction motor, V s is the external applied voltage, R eq is the line resistance, X eq is the line reactance; Among them, the positive and negative sequence voltages at the motor terminals are calculated as: in, is the positive sequence voltage at the motor end, is the negative sequence voltage at the motor terminal, is the power supply positive sequence voltage, is the power supply negative sequence voltage, P eq1 is the active power of the sending-end induction motor, P eq2 is the active power of the sending-end induction motor, Q eq1 is the reactive power of the sending-end induction motor, Q eq2 is the reactive power of the sending-end induction motor; Ignore the excitation reactance X m The impact of (R s +R r s) 2 +(X s +X r ) 2 ≈(R r / s) 2 ,2-s≈2, Formula 5 Among them, R r is the rotor resistance, X s is the stator reactance, X r is the rotor reactance; Positive and negative sequence voltages of induction motors have: in, is the stator positive sequence current phasor, is the rotor positive sequence current phasor, is the stator negative sequence current phasor, is the rotor negative sequence current phasor, T e1 is the negative sequence electromagnetic torque, T e2 is the negative sequence electromagnetic torque; K1 and K2 are constants, K1=3 / (R r oh s ) During an asymmetric fault voltage sag, the rotor motion equation of the induction motor is: After the voltage drop is cleared, the stator voltage does not contain the negative sequence voltage component, and the rotor motion equation no longer contains the negative sequence electromagnetic torque T e2 ,have: Assume the initial angular velocity of the induction motor is ω n , the voltage drops continuously from the moment t0 when the voltage drops to the moment t1 when the fault is cleared, and the angular velocity of the induction motor drops to ω m , by solving the rotor motion equation of the induction motor, the angular velocity ω of the induction motor during the fault period is obtained m-dur The approximate analytical expression of is: Get the angular velocity ω of the induction motor after the fault is cleared m-after The approximate analytical expression of is: Based on the angular velocity ω of the induction motor during the fault m-dur and the angular velocity ω of the induction motor after the fault is cleared m-after , obtain the slip rate s of the induction motor; Obtaining a change in transient electromotive force based on the slip rate and the transient electromotive force differential equation; Based on the change of the transient electromotive force, the current and power response of the induction motor after the disturbance is obtained.

2. The method according to claim 1, wherein obtaining the change of transient electromotive force based on the slip rate and the transient electromotive force differential equation comprises: When positive sequence voltage is applied to the stator terminal of the induction motor When , Equation 1 and Equation 2 are written in phasor form: in, and are the rotor positive sequence transient electromotive force and stator positive sequence current phasor respectively; The phasor form of the rotor positive sequence transient electromotive force differential equation is obtained from Equation 10: When negative sequence voltage is applied to the stator terminal of the induction motor When negative sequence current flows A negative rotating magnetic field is established, and the negative sequence slip is 2-s; where s is the slip; The phasor form of the rotor negative sequence transient electromotive force differential equation is: in, is the rotor negative sequence transient electromotive force; Based on Equation 11 and Equation 12, we establish: At the same time Among them, K E1 , K E2 , B E As a known quantity, substitute into formula 15; Simplify Equation 14 to: Based on Equation 15, the expression of the transient electromotive force differential equation of the induction motor during an asymmetric fault is obtained: in, and are the initial values ​​of the positive and negative sequence transient electromotive force of the induction motor, is the positive sequence voltage at the stator terminal of the induction motor, is the negative sequence voltage at the stator terminal of the induction motor, E′ d1-dur is the positive sequence transient electromotive force of the induction motor during an asymmetric fault, E′ d2-dur is the negative sequence transient electromotive force of the induction motor during an asymmetric fault, t is the time after the voltage sag, and t0 is the time when the voltage sag occurs; During the recovery process after the voltage drop is cleared, the stator voltage does not contain negative sequence voltage components, and the transient electromotive force of the induction motor contains only positive sequence components: in, It is the positive sequence transient electromotive force of the induction motor at the moment of voltage sag clearing.

3. The method according to claim 2, wherein obtaining the current and power response of the induction motor after the disturbance based on the change of the transient electromotive force comprises: The transient electromotive force of the motor rotor during the fault period obtained by calculating Equation 16 is and The d-axis component E′ d1-dur , E′ d2-dur and the q-axis component E′ q1-dur , E′ q2-dur Substitute into Equation 2 to obtain the positive sequence stator current I of the motor d and q axes during the voltage drop period da1 , I qs1 and negative sequence stator current I ds2 , I qs2 During the voltage drop, the active power consumed by the induction motor is P d and reactive power Q d They are: Among them, P d1 、P d2 are positive and negative sequence active power respectively; Q d1 , Q d2 are positive and negative sequence reactive power, V ds1 is the positive sequence stator voltage of the motor d axis during voltage sag, I ds1 is the positive sequence stator current of the motor d axis during voltage sag, V qs1 is the positive sequence stator voltage of the motor q axis during voltage sag, I qs1 is the positive sequence stator current of the motor q axis during voltage sag, V ds2 is the negative sequence stator voltage of the motor d axis during voltage sag, I ds2 is the negative sequence stator current of the motor d axis during voltage sag, V qs2 is the negative sequence stator current of the motor q axis during voltage sag, I qs2 is the negative sequence stator current of the motor q axis during voltage sag; After the voltage drop is cleared, the stator voltage no longer contains negative sequence voltage components, and the transient electromotive force calculated by formula 18 is The d-axis component E′ d1-after and the q-axis component E′ q1-after Substitute into Equation 2 to obtain the positive sequence stator current I of the d and q axes of the induction motor during the voltage sag. ds1 , I qs1 , the active power P consumed by the induction motor d and reactive power Q d They are: Calculate the power consumption P of the induction motor d +jQ d After that, the stator current positive sequence component Negative sequence component They are: The current value of each phase is obtained based on the symmetrical component method. 4 . A computer-readable storage medium storing a computer program, wherein the computer program is configured to execute the method according to claim 1 .

5. An electronic device, comprising: processor and memory; wherein, The memory is a memory for storing instructions executable by the processor; The processor is configured to read the executable instructions from the memory and execute the instructions to implement the method according to any one of claims 1 to 3.

6. A system for analyzing dynamic characteristics of an induction motor, the system comprising: The first acquisition unit is configured to acquire a change in the angular velocity of the induction motor after the disturbance based on a first-order mechanical transient equation of the induction motor, and to acquire a slip rate of the induction motor based on the change in the angular velocity, specifically for: Build a third-order mechanical transient model of an induction motor: Among them, T j is the inertia time constant of the motor; ω m is the motor speed; s is the rotor slip rate, s=(ω s -ω m ) / ω s ;T e and T m are electromagnetic torque and mechanical load torque, T m is a constant; E′ d and E′ q are the d-axis and q-axis components of the rotor transient electromotive force E′ respectively; V ds and V qs The external stator voltage is The d-axis and q-axis components of I ds and I qs The stator currents are The d-axis and q-axis components of the stator are T′0, the stator open circuit and the rotor circuit transient time constant, X is the rotor open circuit reactance, X′ is the rotor short circuit reactance, ω s is the synchronous speed of the induction motor, ω m is the motor speed; Among them, R s is the stator resistance, V ds is the external stator voltage The d-axis component, V qs is the external stator voltage The q-axis component of Based on the third-order mechanical transient model, ignoring the electromagnetic transient characteristics of the rotor winding, obtaining the first-order mechanical transient equation of the induction motor; Power P of the sending end induction motor eq +jQ eq and the power P of the receiving induction motor d +jQ d satisfy: Among them, P eq is the active power of the sending-end induction motor, Q eq is the reactive power of the sending-end induction motor, P d is the active power of the receiving induction motor, Q d is the reactive power of the receiving induction motor, V s is the external applied voltage, R eq is the line resistance, X eq is the line reactance; Among them, the positive and negative sequence voltages at the motor terminals are calculated as: in, is the positive sequence voltage at the motor end, is the negative sequence voltage at the motor terminal, is the power supply positive sequence voltage, is the power supply negative sequence voltage, P eq1 is the active power of the sending-end induction motor, P eq2 is the active power of the sending-end induction motor, Q eq1 is the reactive power of the sending-end induction motor, Q eq2 is the reactive power of the sending-end induction motor; Ignore the excitation reactance X m The impact of (R s +R r s) 2 +(X s +X r ) 2 ≈(R r / s) 2 , 2-s≈2, Equation 5 Among them, R r is the rotor resistance, X s is the stator reactance, X r is the rotor reactance; Positive and negative sequence voltages of induction motors have: in, is the stator positive sequence current phasor, is the rotor positive sequence current phasor, is the stator negative sequence current phasor, is the rotor negative sequence current phasor, T e1 is the negative sequence electromagnetic torque, T e2 is the negative sequence electromagnetic torque; K1 and K2 are constants, K1=3 / (R r oh s ) During an asymmetric fault voltage sag, the rotor motion equation of the induction motor is: After the voltage drop is cleared, the stator voltage does not contain the negative sequence voltage component, and the rotor motion equation no longer contains the negative sequence electromagnetic torque T e2 ,have: Assume the initial angular velocity of the induction motor is ω n , the voltage drops continuously from the moment t0 when the voltage drops to the moment t1 when the fault is cleared, and the angular velocity of the induction motor drops to ω' m , by solving the rotor motion equation of the induction motor, the angular velocity ω of the induction motor during the fault period is obtained m-dur The approximate analytical expression of is: Get the angular velocity ω of the induction motor after the fault is cleared m-after The approximate analytical expression of is: Based on the angular velocity ω of the induction motor during the fault m-dur and the angular velocity ω of the induction motor after the fault is cleared m-after , obtain the slip rate s of the induction motor; a second acquiring unit, configured to acquire a change in transient electromotive force based on the slip rate and a transient electromotive force differential equation; The third acquisition unit is configured to acquire the current and power response of the induction motor after the disturbance based on the change of the transient electromotive force.

7. The system according to claim 6, wherein the second acquisition unit is configured to acquire a change in transient electromotive force based on the slip rate and the transient electromotive force differential equation, specifically configured to: When positive sequence voltage is applied to the stator terminal of the induction motor When , Equation 1 and Equation 2 are written in phasor form: in, and are the rotor positive sequence transient electromotive force and stator positive sequence current phasor respectively; The phasor form of the rotor positive sequence transient electromotive force differential equation is obtained from Equation 10: When negative sequence voltage is applied to the stator terminal of the induction motor When negative sequence current flows A negative rotating magnetic field is established, and the negative sequence slip is 2-s; where s is the slip; The phasor form of the rotor negative sequence transient electromotive force differential equation is: in, is the rotor negative sequence transient electromotive force; Based on Equation 11 and Equation 12, we establish: At the same time Among them, K E1 , K E2 , B E As a known quantity, substitute into formula 15; Simplify Equation 14 to: Based on Equation 15, the expression of the transient electromotive force differential equation of the induction motor during an asymmetric fault is obtained: in, and are the initial values ​​of the positive and negative sequence transient electromotive force of the induction motor, is the positive sequence voltage at the stator terminal of the induction motor, is the negative sequence voltage at the stator terminal of the induction motor, E′ d1-dur is the positive sequence transient electromotive force of the induction motor during an asymmetric fault, E′ d2-dur is the negative sequence transient electromotive force of the induction motor during an asymmetric fault, t is the time after the voltage sag, and t0 is the time when the voltage sag occurs; During the recovery process after the voltage drop is cleared, the stator voltage does not contain negative sequence voltage components, and the transient electromotive force of the induction motor contains only positive sequence components: in, It is the positive sequence transient electromotive force of the induction motor at the moment of voltage sag clearing.

8. The system according to claim 7, wherein the third acquisition unit is configured to acquire the current and power response of the induction motor after the disturbance based on the change of the transient electromotive force, specifically configured to: The transient electromotive force of the motor rotor during the fault period obtained by calculating Equation 16 is and The d-axis component E′ d1-dur , E′ d2-dur and the q-axis component E′ q1-dur , E′ q2-dur Substitute into Equation 2 to obtain the positive sequence stator current I of the motor d and q axes during the voltage drop period ds1 , I qs1 and negative sequence stator current I ds2 , I qs1 During the voltage drop, the active power consumed by the induction motor is P d and reactive power Q d They are: in, P d1 、P d2 are positive and negative sequence active power respectively; Q d1 , Q d2 are positive and negative sequence reactive power, V ds1 is the positive sequence stator voltage of the motor d axis during voltage sag, I ds1 is the positive sequence stator current of the motor d axis during voltage sag, V qs1 is the positive sequence stator voltage of the motor q axis during voltage sag, I qs1 is the positive sequence stator current of the motor q axis during voltage sag, V ds2 is the negative sequence stator voltage of the motor d axis during voltage sag, I ds2 is the negative sequence stator current of the motor d axis during voltage sag, V qs2 is the negative sequence stator current of the motor q axis during voltage sag, I qs2 is the negative sequence stator current of the motor q axis during voltage sag; After the voltage drop is cleared, the stator voltage no longer contains negative sequence voltage components, and the transient electromotive force calculated by formula 18 is The d-axis component E′ d1-after and the q-axis component E′ q1-after Substitute into Equation 2 to obtain the positive sequence stator current I of the d and q axes of the induction motor during the voltage sag. ds1 , I qs1 , the active power P consumed by the induction motor d and reactive power Q d They are: Calculate the power consumption P of the induction motor d +jQ d After that, the stator current positive sequence component Negative sequence component They are: The current value of each phase is obtained based on the symmetrical component method.

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