Multi-phase permanent magnet motor turn-to-turn short circuit fault degree identification method based on virtual short circuit coil model

Abstract

The invention discloses a multi-phase permanent magnet motor turn-to-turn short circuit fault degree identification method based on a virtual short circuit coil model, belongs to the field of motor fault diagnosis, and aims to solve the problem that the multi-phase permanent magnet motor turn-to-turn short circuit fault degree is difficult to identify due to complex and diversified turn-to-turn short circuit fault states. The method comprises the following steps: S1, constructing a virtual short-circuit coil model; s2, calculating an additional voltage component of each phase of the motor based on the virtual short-circuit coil model; s3, according to the additional voltage component, calculating the amplitude of an additional flux linkage component introduced into each phase flux linkage by the virtual short-circuit coil; and S4, identifying whether a turn-to-turn short circuit fault occurs in the motor and the severity according to the amplitude of the additional flux linkage component introduced into each phase of flux linkage. The method is used for identifying the turn-to-turn short circuit fault of any phase in the multi-phase permanent magnet motor.

Description

Technical Field

[0001] The present invention relates to a method for identifying the degree of inter-turn short-circuit fault of a multi-phase permanent magnet motor based on a virtual short-circuit coil model, belonging to the field of motor fault diagnosis. Background Technique

[0002] Permanent magnet motors have been widely used in fields such as electric vehicles, aerospace, and industrial servo due to their advantages in power density and efficiency. Due to the redundancy of the number of phases of multi-phase permanent magnet motors, they have the ability to continue fault-tolerant operation in the case of a fault in a certain phase winding. Therefore, multi-phase permanent magnet motors have good application prospects in application scenarios with high requirements for reliability.

[0003] Inter-turn short circuit is one of the typical fault types of permanent magnet motor windings, and the inter-turn short circuit fault usually causes local abnormal heating of the motor winding and obvious torque fluctuations, which seriously affects the safe operation of the motor. To achieve the fault-tolerant operation of multi-phase permanent magnet motors, it is necessary to first effectively diagnose the motor faults. However, due to the parallel winding structure of the motor winding, the short-circuit form and the number of short-circuit turns of the inter-turn short circuit fault are both uncertain, and the fault characteristics such as voltage and current of the motor under the inter-turn short circuit fault state show complex changes, making it difficult to quantitatively evaluate the severity of the inter-turn short circuit fault of multi-phase permanent magnet motors. Therefore, establishing a method for identifying the degree of inter-turn short circuit fault that can comprehensively consider the complex state of the inter-turn short circuit fault of multi-phase permanent magnet motors can provide guidance for the selection and design of fault-tolerant control strategies for multi-phase permanent magnet motors, and play an important role in ensuring the safe and stable operation of multi-phase permanent magnet motors. Summary of the Invention

[0004] In order to solve the problem that it is difficult to identify the degree of inter-turn short circuit fault of multi-phase permanent magnet motors due to the complex and diverse states of inter-turn short circuit faults, the present invention provides a method for identifying the degree of inter-turn short circuit fault of multi-phase permanent magnet motors based on a virtual short-circuit coil model.

[0005] The method for identifying the degree of inter-turn short circuit fault of a multi-phase permanent magnet motor based on a virtual short-circuit coil model according to the present invention includes the following steps: S1. Construct a virtual short-circuit coil model; S2. Calculate the additional voltage components of each phase of the motor based on the virtual short-circuit coil model; S3. Calculate the amplitude of the additional magnetic flux linkage component introduced by the virtual short-circuit coil in the magnetic flux linkage of each phase according to the additional voltage component; S4. Identify whether the motor has an inter-turn short circuit fault and its severity according to the amplitude of the additional magnetic flux linkage component introduced in the magnetic flux linkage of each phase.

[0006] Preferably, the process of constructing the virtual short - circuit coil model in step S1 is as follows: The short - circuited turns are separately extracted from the multi - phase permanent - magnet motor winding to form an independent virtual short - circuit coil. The multi - phase permanent - magnet motor under the single - strand wire turn - to - turn short - circuit form and the turn - to - turn short - circuit form between different parallel - wound wires is equivalent, and the virtual short - circuit coil model is constructed. The model is expressed by the voltage equation of any one phase as: In the formula, \(Y\) is any one phase, \(Y = A,B,C,\cdots\); \(X\) is the sequence number of other phases except phase \(Y\). is the magnetic flux of phase \(Y\). is the permanent - magnet magnetic flux of phase \(Y\). is the current of phase \(Y\). is the current of other phases except phase \(Y\). is the current of the virtual short - circuit coil. is the self - inductance of phase \(Y\). is the mutual inductance between the virtual short - circuit coil and phase \(Y\). is the mutual inductance between phase \(Y\) and other phases. is the voltage of phase \(Y\). is the back - EMF of phase \(Y\) under no - load. is the resistance of phase \(Y\), \(t\) is time. is the additional voltage component introduced by the virtual short - circuit coil in phase \(Y\).

[0007] Preferably, the process of calculating the additional voltage components of each phase of the motor based on the virtual short - circuit coil model in step S2 is as follows: The voltage of phase \(Y\) , the current of phase \(Y\) and the current of other phases except phase \(Y\) are collected in real - time, and the additional voltage components of each phase of the motor are calculated based on the virtual short - circuit coil model: (1) In the formula, the back - EMF of phase \(Y\) (2) Substitute formula (2) into formula (1) to obtain: (3) In the formula, , are the voltage and current of phase \(Y\) under the normal state of the motor; is the current of other phases except phase \(Y\) under the normal state of the motor; Substitute the voltage of phase \(Y\) , the current of phase \(Y\) , the current of other phases except phase \(Y\) collected in real - time and , , Substitute into formula (3) to obtain the additional voltage components of each phase of the motor.

[0008] Preferably, the amplitude of the additional magnetic flux linkage component introduced by the virtual short - circuit coil in each phase magnetic flux linkage in step S3 is calculated according to the following formula: In the formula, is the amplitude of the additional voltage component , is the electrical frequency of the motor.

[0009] Preferably, the identification process of step S4 is as follows: Under the normal state of the motor, the amplitude of the additional magnetic flux linkage component introduced by the virtual short - circuit coil in each phase magnetic flux linkage , is a minimum value less than or equal to 1 mWb; if the of a certain phase, phase Y, is greater than , it is considered that there is a turn - to - turn short - circuit fault in this phase; The larger the

[0010] , the more serious the fault is characterized.

[0011] Preferably, the method is only applicable to the case of a short - circuit in one phase.

[0012] Preferably, the method is suitable for motors with three or more phases.

[0012] Advantages of the present invention: The present invention discloses a method for identifying the degree of turn - to - turn short - circuit fault of a multi - phase permanent - magnet motor based on a virtual short - circuit coil model. By using the virtual short - circuit coil model to equivalently simulate the turn - to - turn short - circuit fault of a single - strand wire and the turn - to - turn short - circuit fault between different parallel - wound wires in a multi - phase permanent - magnet motor simultaneously, the analysis process of the turn - to - turn short - circuit fault of a multi - phase permanent - magnet motor can be simplified. By calculating the additional magnetic flux linkage components introduced by the virtual short - circuit coil in each phase of the multi - phase permanent - magnet motor in this model, the identification of the severity of the turn - to - turn short - circuit fault of the multi - phase permanent - magnet motor is realized, and the identification accuracy is high. Description of the Drawings

[0013] Figure 1 is a schematic diagram of the virtual short - circuit coil model for a six - phase turn - to - turn short - circuit fault; Figure 2 is an equivalent circuit diagram of the turn - to - turn short - circuit of a single - strand wire in the fault phase; Figure 3 is an equivalent circuit diagram of the turn - to - turn short - circuit between different parallel - wound wires in the fault phase. Detailed Embodiments

[0014] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0015] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0016] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but it is not limited to the present invention.

[0017] Specific Embodiment 1: The following will be described in conjunction with Figures 1 to 3 to illustrate this embodiment. The method for identifying the degree of inter-turn short-circuit fault of a multi-phase permanent magnet motor based on a virtual short-circuit coil model includes the following steps: S1. Construct a virtual short-circuit coil model; S2. Calculate the additional voltage components of each phase of the motor based on the virtual short-circuit coil model; S3. Calculate the amplitude of the additional magnetic flux component introduced by the virtual short-circuit coil in the magnetic flux of each phase according to the additional voltage component; S4. Identify whether the motor has an inter-turn short-circuit fault and its severity according to the amplitude of the additional magnetic flux component introduced in the magnetic flux of each phase.

[0018] The method is only applicable to the case where a short circuit occurs in one phase.

[0019] The method is suitable for motors with three or more phases.

[0020] In step S1, when constructing the virtual short-circuit coil model, the multi-phase permanent magnet motor with inter-turn short-circuit fault is equivalent to the multi-phase permanent magnet motor under the form of single-strand wire inter-turn short-circuit and the form of inter-turn short-circuit between different parallel-wound wires by establishing the virtual short-circuit coil model of the multi-phase permanent magnet motor. For single-strand wire inter-turn short-circuit and inter-turn short-circuit between different parallel-wound wires, see Figure 2 and Figure 3 ; In the virtual short-circuit coil model of the multi-phase permanent magnet motor with inter-turn short-circuit fault, the shorted turns are separately extracted from the multi-phase permanent magnet motor winding to form an independent virtual short-circuit coil 1, and each phase winding 2 is a multi-phase winding with all parameters the same as those of the multi-phase permanent magnet motor winding in the normal state. See Figure 1 for illustration with a six-phase motor as an example.

[0021] Other conditions for constructing the model: The number of turns of the virtual short - circuited coil is equal to the number of short - circuited turns, and the current of the virtual short - circuited coil is equal to the current flowing through the short - circuit contact position; Determination of the number of turns of the virtual short - circuited coil: When a single - strand wire turn - to - turn short - circuit occurs, the number of turns of the virtual short - circuited coil is equal to the number of turns of the short - circuited part of the wire; when a turn - to - turn short - circuit occurs between different parallel - wound wires, the number of turns of the virtual short - circuited coil is equal to the difference in the number of turns from one end of the winding to the short - circuit position of the two wires; There is mutual inductance between the virtual short - circuited coil and each phase winding. By considering the virtual short - circuited coil as a virtual coil located at the position of the slot where the short - circuit fault occurs and not occupying the physical space of the faulty phase, the mutual inductance between the virtual short - circuited coil and each phase is calculated; Thus, the mathematical expression form of the virtual short - circuited coil model for the turn - to - turn short - circuit fault of the multi - phase permanent - magnet motor established is as follows: In the formula, Y is any one of the phases, Y = any one of A, B, C...; X is the sequence number of the other phases except phase Y, is the magnetic flux of phase Y, is the permanent - magnet magnetic flux of phase Y, is the current of phase Y, is the current of the other phases except phase Y, is the current of the virtual short - circuited coil, is the self - inductance of phase Y, is the mutual inductance between the virtual short - circuited coil and phase Y, is the mutual inductance between phase Y and the other phases, is the voltage of phase Y, is the no - load back - electromotive force of phase Y, is the resistance of phase Y, t is time, is the additional voltage component introduced by the virtual short - circuited coil in phase Y.

[0022] Derivation process of the model: According to Figure 2 the fault form of the single - strand wire turn - to - turn short - circuit shown, the magnetic flux of the faulty phase Y is: In the formula, is the magnetic flux of the faulty phase, is the permanent - magnet magnetic flux of is the permanent - magnet magnetic flux of is the current of the faulty phase, 、 、 is Figure 2 the current at each position shown, is the self - inductance of the faulty phase, 、 、 , , , , are Figure 2 the self-inductance and mutual inductance of each part of the winding shown, such as is and the mutual inductance between, are the currents of other phases, is the mutual inductance between the faulty phase and other phases.

[0023] In the formula, the magnetic flux, current and inductance have the following relationship: In the formula, is the permanent magnet magnetic flux of the faulty phase, is Figure 2 the current at the short-circuit contact position shown.

[0024] When a single-turn short circuit occurs between turns of a wire, since the number of turns of the virtual short-circuit coil is defined to be equal to the number of turns of the short-circuited part of the wire, then it can be defined that:

[0025] Furthermore, according to the relationship between the above magnetic flux, current and inductance, the simplified magnetic flux equation of the faulty phase is obtained as:

[0026] Differentiating the magnetic flux equation of the faulty phase and considering the resistance voltage drop at the same time, the voltage equation of the faulty phase is obtained as: In the formula, is the no-load back electromotive force of the faulty phase, is the resistance of the faulty phase, and t is the time.

[0027] According to Figure 3 the fault form of short circuit between turns of different parallel wires shown, the magnetic flux of phase Y of the faulty phase is: In the formula, is the magnetic flux of the faulty phase, is the permanent magnet magnetic flux of, is the permanent magnet magnetic flux of, is the current of the faulty phase, to is Figure 3 the currents at each place shown, is the self-inductance of the faulty phase, , , to , to are Figure 3 the self - inductance and mutual - inductance of each part of the winding shown, such as is and the mutual - inductance between them, are the currents of other phases, is the mutual - inductance between the faulty phase and other phases.

[0028] In the formula, the magnetic flux, current and inductance have the following relationship: In the formula, is the permanent - magnet magnetic flux of the faulty phase, is Figure 3 the current at the short - circuit contact position shown.

[0029] When inter - turn short - circuit occurs between different parallel - wound wires, since the number of turns of the virtual short - circuit coil is defined as the difference between the number of turns from one end of the winding to the short - circuit position of the two wires, then it can be defined that: Furthermore, according to the above relationship between magnetic flux, current and inductance, the simplified magnetic - flux equation of the faulty phase is obtained as: Differentiating the magnetic - flux equation of the faulty phase and considering the resistance voltage drop, the voltage equation of the faulty phase is obtained as: In the formula, is the no - load back - electromotive force of the faulty phase, is the resistance of the faulty phase, and t is time; Its result is the same as the magnetic - flux equation and voltage equation of the faulty phase in the case of single - wire inter - turn short - circuit fault form.

[0030] By the same method, the magnetic - flux and voltage equations of the non - faulty phases are derived, and their expression forms are the same as those of the faulty phase.

[0031] The process of calculating the additional voltage components of each phase of the motor based on the virtual short - circuit coil model in step S2 is as follows: Real - time collect the Y - phase voltage , the Y - phase current and the currents of other phases except the Y - phase , and calculate the additional voltage components of each phase of the motor based on the virtual short - circuit coil model: (1) In the formula, the no - load back - electromotive force of the Y - phase (2) Substitute formula (2) into formula (1) to obtain: (3) In the formula, , are the phase Y voltage and current under normal motor conditions; the current of each phase other than phase Y under normal motor conditions; The phase Y voltage is collected in real time , the phase Y current , the current of each phase other than phase Y and the , , under normal motor conditions are substituted into formula (3) to obtain the additional voltage component of each phase of the motor .

[0032] The amplitude of the additional flux linkage component introduced by the virtual short - circuit coil in each phase flux linkage in step S3 is calculated according to the following formula: In the formula, is the amplitude of the additional voltage component , is the electrical frequency of the motor.

[0033] The amplitude of the additional flux linkage component introduced into each phase flux linkage is obtained .

[0034] The identification process of step S4 is as follows: Under normal motor conditions, the amplitude of the additional flux linkage component introduced into each phase flux linkage , is a minimum value less than or equal to 1 mWb; if the of a certain phase (phase Y) is greater than , it is considered that a turn - to - turn short - circuit fault has occurred in this phase; for example = 0, 0.01, 0.02, 0, 0.03, 0.02, = 1.4, then it can be determined that a turn - to - turn short - circuit fault has occurred in phase A.

[0035] The larger the , the more serious the fault; The larger the

[0036] , the higher the degree of the fault; Af1 and Ψ Af1 amplitudes obtained by the method of the present invention for a six - phase permanent - magnet motor with 24 slots and 14 poles under different degrees of turn - to - turn short - circuit faults, and U Af1 and ΨAf1 The actual amplitude values, as shown in Table 1 and Table 2, are further used to illustrate the effectiveness of the method described in the present invention for identifying the degree of inter-turn short-circuit faults in multi-phase permanent magnet motors. Among them, in this embodiment, each phase winding of the motor is distributed in 8 slots, each phase winding includes 4 groups of coils, the number of turns of each group of coils is 35, the number of parallel conductors of the winding is 16, the motor speed in this embodiment is 600 rpm, and the load current is 20 A.

[0037] Table 1 Additional voltage components obtained by the method described in the present invention under single-strand wire inter-turn short circuit Amplitude And the amplitude of the additional magnetic flux component Compared with the actual value Table 2 Additional voltage components obtained by the method described in the present invention under inter-turn short circuit between different parallel conductors Amplitude And the amplitude of the additional magnetic flux component Compared with the actual value It can be seen that the amplitudes of U Af1 and Ψ Af1 obtained by the method described in the present invention accurately reflect the additional voltage component and additional magnetic flux component introduced by the virtual short-circuit coil in the faulty phase under both single-strand wire inter-turn short circuit and inter-turn short circuit between different parallel conductors, reflecting the influence degree of the inter-turn short-circuit fault on the faulty phase, and realizing the identification of the severity of the inter-turn short-circuit fault of the motor.

[0038] Although the present invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed, as long as they do not deviate from the spirit and scope of the present invention defined by the appended claims. It should be understood that different dependent claims and the features described herein can be combined in a manner different from that described in the original claims. It should also be understood that the features described in connection with a single embodiment can be used in other described embodiments.

Claims

1. A method for identifying the degree of inter-turn short-circuit fault of a multi-phase permanent magnet motor based on a virtual short-circuit coil model, characterized in that, The method includes the following steps: S1. Construct a virtual short-circuit coil model; S2. Calculate the additional voltage components of each phase of the motor based on the virtual short-circuit coil model; S3. Calculate the amplitudes of the additional flux linkages introduced by the virtual short-circuit coil in the flux linkages of each phase according to the additional voltage components; S4. Identify whether the motor has a turn-to-turn short-circuit fault and its severity according to the amplitudes of the additional flux linkages introduced in the flux linkages of each phase.

2. The method for identifying the degree of inter-turn short-circuit fault of a multiphase permanent magnet motor based on a virtual short-circuit coil model according to claim 1, wherein, The process of constructing the virtual short-circuit coil model in step S1 is as follows: The shorted turns are separately extracted from the multi-phase permanent magnet motor winding to form an independent virtual short-circuit coil. The multi-phase permanent magnet motor under the form of turn-to-turn short-circuit of a single-strand wire and the form of turn-to-turn short-circuit between different parallel-wound wires is equivalent, and a virtual short-circuit coil model is constructed. The model is expressed by the voltage equation of any one phase as: In the formula, Y represents any one phase, where Y can be any one of A, B, C...; X represents the sequence numbers of the other phases except phase Y. is the flux linkage of phase Y. is the permanent magnet flux linkage of phase Y. is the current of phase Y. is the currents of the other phases except phase Y. is the current of the virtual short - circuit coil. is the self - inductance of phase Y. is the mutual inductance between the virtual short - circuit coil and phase Y. is the mutual inductance between phase Y and the other phases. is the voltage of phase Y. is the no - load back electromotive force of phase Y. is the resistance of phase Y, and t is time. is the additional voltage component introduced by the virtual short - circuit coil in phase Y.

3. The method for identifying the degree of inter-turn short circuit fault of a multiphase permanent magnet motor based on a virtual short-circuit coil model according to claim 2, wherein The process of calculating the additional voltage components of each phase of the motor based on the virtual short-circuit coil model in step S2 is as follows: The Y-phase voltage is collected in real time , the Y-phase current , and the currents of each phase other than the Y-phase , and the additional voltage components of each phase of the motor are calculated based on the virtual short-circuit coil model : （1） In the formula, the no-load back electromotive force of phase Y (2) Substituting formula (2) into formula (1) gives: （3） Wherein, , are the Y-phase voltage and current under the normal state of the motor; the currents of other phases except the Y-phase under the normal state of the motor; Collect the Y-phase voltage in real time , the Y-phase current , the currents of each phase other than the Y-phase and under the normal state of the motor , , Substitute them into formula (3) to obtain the additional voltage components of each phase of the motor.

4. The method for identifying the degree of inter-turn short circuit fault of a multi-phase permanent magnet motor based on a virtual short-circuit coil model according to claim 3, wherein, The amplitude of the additional magnetic flux linkage component introduced by the virtual short-circuit coil in each phase magnetic flux linkage in step S3 is calculated according to the following formula: In the formula, is the amplitude of the additional voltage component , is the electrical frequency of the motor.

5. The method for identifying the degree of inter-turn short circuit fault of a multiphase permanent magnet motor based on a virtual short-circuit coil model according to claim 4, wherein The identification process of step S4 is as follows: Under normal conditions of the motor, the amplitude of the additional magnetic flux component introduced into each phase of the magnetic flux , is a minimum value less than or equal to 1 mWb; if the of a certain phase, phase Y, is greater than , it is considered that an inter-turn short circuit fault has occurred in this phase; The larger it is, the more serious the fault is characterized.

6. The method for identifying the degree of inter-turn short circuit fault of a multi-phase permanent magnet motor based on a virtual short circuit coil model according to claim 1, characterized in that, The method is only applicable to the case where one phase has a short circuit.

7. The method for identifying the degree of inter-turn short circuit fault of a multi-phase permanent magnet motor based on a virtual short-circuit coil model according to claim 1, characterized in that The method is suitable for motors with three or more phases.

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