A high-frequency impedance-based inter-turn fault diagnosis method for permanent magnet synchronous motor

Abstract

The application discloses a high-frequency impedance-based inter-turn fault diagnosis method for a permanent magnet synchronous motor and belongs to the technical field of motor control. The high-frequency impedance-based inter-turn fault diagnosis method for the permanent magnet synchronous motor comprises the following steps: injecting a three-phase symmetrical high-frequency voltage into a control system; collecting three-phase currents and extracting high-frequency component amplitudes in the three-phase currents; calculating three-phase voltages through drive signals of an inverter and extracting high-frequency component amplitudes in the three-phase voltages; calculating three-phase high-frequency impedances by using the high-frequency component amplitudes in the three-phase currents and the high-frequency component amplitudes in the three-phase voltages; comparing the three-phase high-frequency impedances to determine whether an inter-turn fault occurs in the motor; and the inter-turn fault of the motor can be diagnosed without using hardware structures and detection equipment, so that the hardware cost is saved.

Description

Technical Field

[0001] This invention belongs to the field of motor control technology, specifically relating to a method for diagnosing inter-turn faults in a permanent magnet synchronous motor based on high-frequency impedance. Background Technology

[0002] The high efficiency and high power density of permanent magnet synchronous motors (PMSMs) have led to their increasingly widespread application. However, due to the uncontrollable flux linkage of permanent magnets, large fault currents can be generated when inter-turn short circuits occur in the windings of PMSMs, severely affecting the safe and reliable operation of the motor and its drive system. To improve the application of PMSMs in high-reliability systems such as aerospace and electric vehicles, it is necessary to perform rapid and reliable detection of inter-turn short circuit faults to prevent further deterioration and to provide a foundation for subsequent fault-tolerant operation of the motor. Currently, many scholars have conducted research on inter-turn short circuit fault diagnosis methods.

[0003] Existing inter-turn short-circuit fault diagnosis technologies for permanent magnet synchronous motors (PMSMs) mostly rely on detection equipment or added hardware structures. Detection equipment methods often require the motor to be stopped for testing, while adding hardware structures increases the cost of the motor drive system. To save on hardware costs and achieve real-time protection of the stator windings of PMSMs, online diagnosis of inter-turn faults in PMSMs is necessary. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a method for diagnosing inter-turn faults in permanent magnet synchronous motors based on high-frequency impedance, thereby solving the technical problems in the prior art.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A method for diagnosing inter-turn faults in a permanent magnet synchronous motor based on high-frequency impedance includes the following steps:

[0007] Inject a three-phase symmetrical high-frequency voltage into the control system;

[0008] Collect three-phase current and extract the high-frequency components from the three-phase current;

[0009] The three-phase voltage is calculated using the inverter's drive signal, and the high-frequency components in the three-phase voltage are extracted.

[0010] The high-frequency components of the three-phase current and the three-phase voltage are used to calculate the three-phase high-frequency impedance.

[0011] By comparing the three-phase high-frequency impedances, it can be determined whether the motor has experienced an inter-turn fault.

[0012] Furthermore, the formula for calculating the high-frequency voltage is as follows:

[0013]

[0014] Among them, u ah u bh u ch These are the injected three-phase high-frequency voltages, u h θ represents the amplitude of the injected high-frequency voltage. h The phase angle for injecting high-frequency voltage.

[0015] Furthermore, the steps for extracting the high-frequency components from the three-phase current are as follows:

[0016] S21, assuming the injected high-frequency voltage frequency is kHz, i p Multiplying (p = a, b, c) by sinkθ and coskθ respectively yields the high-frequency component and DC component at 2kHz:

[0017]

[0018] Among them, i p For p-phase current, I ph Let θ be the amplitude of the p-phase high-frequency current, and θ be the rotor angle. pi The initial phase angle of the phase current;

[0019] S22 filters out high-frequency components using a low-pass filter, thus allowing the DC component to be obtained. and

[0020] S23. Calculate the root mean square (RMS) of the DC component obtained in S22, sum the results, and multiply by 2 to obtain the amplitude of the high-frequency component of phase p; the calculation formula is:

[0021]

[0022] Further, the steps for calculating the three-phase voltages include:

[0023] S31 calculates the voltage to ground at the midpoint of the three-phase bridge arm of the inverter using the drive signal of the power transistor;

[0024] S32 obtains the three-phase voltage of the motor through the ground voltage at the midpoint of the three-phase bridge arm of the inverter.

[0025] Furthermore, in S31, the formula for calculating the voltage to ground at the midpoint of the three-phase bridge arm of the inverter is:

[0026]

[0027] Among them, u ag u bg u cgS1 and S3 are the voltages to ground at the midpoints of the three-phase bridge arms of the inverter, respectively, and S1-S3 are the drive signals for the three upper transistors of the inverter. These are the inverses of the drive signals for the three lower transistors of the inverter, u. dc This is the DC bus voltage.

[0028] Furthermore, when the motor is in a healthy state, the formula for calculating the three-phase voltage is:

[0029]

[0030] Among them, u an u bn u cn These are the three-phase voltages.

[0031] Furthermore, when an inter-turn fault occurs in the motor, the formula for calculating the three-phase voltage is:

[0032]

[0033] Among them, u an_f u bn_f u cn_f These are the three-phase voltages after the fault, R is the phase resistance, μ is the short-circuit turns ratio, and i f For short-circuit current, L σ For motor leakage inductance;

[0034] It is evident that an additional identical bias component appears in the three-phase voltage after the fault. Therefore, the three-phase voltage can still be calculated and the high-frequency component extracted using the voltage formula under healthy conditions. The steps for extracting the high-frequency component from the three-phase voltage are as follows:

[0035] Further, the steps for calculating the three-phase voltages include:

[0036] The calculated three-phase voltage u pn Multiplying (p = a, b, c) by sinkθ and coskθ respectively yields the high-frequency component and DC component at 2 kHz.

[0037]

[0038] Among them, u pn For the p-phase voltage, U pnh Let θ be the amplitude of the p-phase high-frequency current, and θ be the rotor angle. pu The initial phase angle of the phase voltage;

[0039] By filtering out high-frequency components with a low-pass filter, the DC component can be obtained. and

[0040] The root mean square (RMS) of the DC component obtained after low-pass filtering is calculated, and the sum of the RMS results is multiplied by 2 to obtain the amplitude of the high-frequency voltage of phase p; the calculation formula is:

[0041]

[0042] Furthermore, the formula for calculating the three-phase high-frequency impedance is:

[0043]

[0044] Among them, Z ah Z bh Z ch These are the three-phase high-frequency impedances.

[0045] Furthermore, the steps for determining inter-turn faults include:

[0046] The maximum and minimum values ​​of the three-phase high-frequency impedance are defined as Z. max =max{Z ah Z bh Z ch}、Z min =min{Z ah Z bh Z ch};

[0047] If Z max -Z min If Z < ε, the system determines that the permanent magnet synchronous motor is operating normally; if Z max -Z min If ≥ε, the system determines that an inter-turn fault has occurred in the permanent magnet synchronous motor.

[0048] A fault diagnosis system for inter-turn permanent magnet synchronous motors based on high-frequency impedance, comprising:

[0049] Voltage input module: Injects a three-phase symmetrical high-frequency voltage into the control system;

[0050] Current component extraction module: Collects three-phase current and extracts the high-frequency components from the three-phase current;

[0051] Voltage component extraction module: Calculates the three-phase voltage using the inverter's drive signal and extracts the high-frequency components from the three-phase voltage;

[0052] Impedance calculation module; calculates three-phase high-frequency impedance using the high-frequency components of the three-phase current and the three-phase voltage;

[0053] Fault diagnosis module: By comparing the three-phase high-frequency impedance, determine whether the motor has experienced an inter-turn fault.

[0054] The beneficial effects of this invention are:

[0055] 1. Reliability detection of inter-turn faults was achieved without adding hardware or testing equipment.

[0056] 2. Compared with existing detection methods, the fault characteristics of high-frequency impedance are more obvious. Attached Figure Description

[0057] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0058] Figure 1 This is a flowchart of the fault diagnosis method of the present invention;

[0059] Figure 2 This is a cross-sectional view of the permanent magnet synchronous motor that this invention addresses;

[0060] Figure 3 This is a schematic diagram of the three-phase inverter circuit of the present invention;

[0061] Figure 4 This is a high-frequency injection strategy diagram of the present invention. Detailed Implementation

[0062] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0063] Figure 2 This is a cross-sectional view of the permanent magnet synchronous motor to which the diagnostic method of this invention is applied. Figure 3 It is a three-phase inverter circuit;

[0064] like Figure 1 As shown, a method for diagnosing inter-turn faults in a permanent magnet synchronous motor based on high-frequency impedance includes the following steps:

[0065] S1. Modern motor drive systems generally employ a dual closed-loop control strategy based on speed and current. However, it is difficult to detect inter-turn faults directly based on existing measurement data. To highlight the fault characteristics of inter-turn faults and facilitate their detection, a three-phase symmetrical high-frequency voltage is injected into the motor control system, as shown in the following equation:

[0066]

[0067] Among them, uah u bh u ch These are the injected three-phase high-frequency voltages, u h θ represents the amplitude of the injected high-frequency voltage. h The phase angle for injecting high-frequency voltage.

[0068] S2, collect the three-phase current i from the motor stator winding. a i b i c And extract the high-frequency component I from the three-phase current. ah I bh I ch ;

[0069] The steps for extracting high-frequency components include:

[0070] S21, assuming the injected high-frequency voltage frequency is kHz, i p Multiplying (p = a, b, c) by sinkθ and coskθ respectively yields the high-frequency component and DC component at 2 kHz.

[0071]

[0072] Among them, i p For p-phase current, I ph Let θ be the amplitude of the p-phase high-frequency current, and θ be the rotor angle. pi The initial phase angle of the phase current;

[0073] S22 filters out high-frequency components using a low-pass filter, thus allowing the DC component to be obtained. and

[0074] S23. Calculate the root mean square (RMS) of the DC component obtained in S22, sum the results, and multiply by 2 to obtain the amplitude of the high-frequency component of phase p; the calculation formula is:

[0075]

[0076] S3 calculates the three-phase voltage u using the inverter's drive signal. an u bn u cn And extract the amplitude U of the high-frequency component in the three-phase voltage. anh U bnh U cnh To avoid adding an additional voltage sensor to the motor drive system;

[0077] Among them, the calculation of three-phase voltage u an u bn u cn The specific steps are as follows:

[0078] S31, in such Figure 3 In the three-phase inverter circuit shown, the voltage u at the midpoint of the three-phase bridge arm of the inverter is calculated using the drive signal of the power transistor. ag u bg u cg ;

[0079]

[0080] Where s1-s3 are the drive signals for the three upper transistors of the inverter, respectively. These are the inverses of the drive signals for the three lower transistors of the inverter, u. dc This is the DC bus voltage;

[0081] S32 obtains the three-phase voltage u of the motor through the ground voltage at the midpoint of the three-phase bridge arm of the inverter. an u bn u cn The inverter circuit has the following relationship:

[0082]

[0083] Among them, u ng Common-mode voltage;

[0084] Adding the three equations above together, we get:

[0085] u an +u bn +u cn +3u ng =u ag +u bg +u ag

[0086] When the motor is in a healthy state, the following exists:

[0087] u an +u bn +u cn =0

[0088] Therefore, we can conclude that:

[0089]

[0090] When an inter-turn fault occurs in the motor, the three-phase voltage equations become:

[0091]

[0092] Where R is the phase resistance, L a L b L c These are three-phase self-inductance, Mab M ac M bc The AB phase, AC phase, and BC phase are mutually inductive, respectively. a e b e c These are the three back potentials, μ is the short-circuit turns ratio, and i f This is the short-circuit current;

[0093] At this time, the following exists:

[0094]

[0095] We can obtain:

[0096]

[0097] Therefore, the three-phase voltage equations after an inter-turn fault can be obtained as follows:

[0098]

[0099] Among them, u an_f u bn_f u cn_f These are the three-phase voltages after the fault, L σ For motor leakage inductance;

[0100] It is evident that after the fault, the three-phase voltage has an additional identical bias component, therefore the three-phase voltage can still be calculated using the voltage formula under healthy conditions.

[0101] In addition, from the three-phase voltage u an u bn u cn In the process, the amplitude U of the high-frequency component in the three-phase voltage is extracted. anh U bnh U cnh The steps are as follows:

[0102] S33, will u pn Multiplying (p = a, b, c) by sinkθ and coskθ respectively yields the high-frequency component and DC component at 2 kHz.

[0103]

[0104] Among them, u pn For the p-phase voltage, U pnh Let θ be the amplitude of the p-phase high-frequency current, and θ be the rotor angle. pu The initial phase angle of the phase voltage;

[0105] S34 filters out high-frequency components using a low-pass filter, thus allowing the DC component to be obtained. and

[0106] S35, calculate the root mean square (RMS) of the DC component obtained in S322, sum the results, and multiply by 2 to obtain the amplitude of the high-frequency voltage of phase p; the calculation formula is:

[0107]

[0108] The three-phase voltage u is calculated using the inverter's drive signal. an u bn u cn And extract the amplitude U of the high-frequency component in the three-phase voltage. anh U bnh U cnh This is to avoid adding an additional voltage sensor to the motor drive system.

[0109] S4. Calculate the three-phase high-frequency impedance Z using the high-frequency voltage component amplitude obtained in S3 and the high-frequency current component amplitude obtained in S2. ah Z bh Z ch As shown in the following formula:

[0110]

[0111] S5, compare the three-phase high-frequency impedance to determine whether the motor has an inter-turn fault;

[0112] The maximum and minimum values ​​of the three-phase high-frequency impedance are defined as Z. max =max{Z ah Z bh Z ch}、Z min =min{Z ah Z bh Z ch}; If Z max -Z min If Z < ε, the system determines that the permanent magnet synchronous motor is operating normally; if Z max -Z min If the threshold value is ≥ε, the system determines that an inter-turn fault has occurred in the permanent magnet synchronous motor; where ε is the threshold value.

[0113] By following the steps above, the inter-turn faults in the windings of a permanent magnet synchronous motor can be diagnosed without adding any testing equipment.

[0114] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0115] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for diagnosing inter-turn faults in a permanent magnet synchronous motor based on high-frequency impedance, characterized in that, Includes the following steps: Inject a three-phase symmetrical high-frequency voltage into the control system; Collect three-phase current and extract the amplitude of the high-frequency component from the three-phase current; The three-phase voltage is calculated using the inverter's drive signal, and the amplitude of the high-frequency component in the three-phase voltage is extracted. The three-phase high-frequency impedance is calculated using the amplitudes of the high-frequency components in the three-phase current and the three-phase voltage. By comparing the three-phase high-frequency impedances, it can be determined whether the motor has experienced an inter-turn fault; The steps for extracting the amplitude of the high-frequency component in a three-phase current are as follows: S21, let the frequency of the injected high-frequency voltage be... Hz, will ( Multiply by ) and It can be obtained High-frequency components and DC components at a given frequency: in, for Phase current, for Phase high frequency current amplitude, For rotor angle, The initial phase angle of the phase current; S22 filters out high-frequency components using a low-pass filter, thus allowing the DC component to be obtained. and ; S23, calculate the root mean square (RMS) of the DC component obtained in S22, sum the results of the RMS results, and multiply by 2 to obtain the final result. The amplitude of the high-frequency component of the phase; the calculation formula is: ； The formula for calculating the three-phase high-frequency impedance is: in, , , Three-phase high-frequency impedance , , These are the amplitudes of the high-frequency components in the three-phase voltage; The steps for diagnosing inter-turn faults include: The maximum and minimum values ​​of the three-phase high-frequency impedance are defined as follows: ; like The system determines that the permanent magnet synchronous motor is operating normally; if The system determined that an inter-turn fault had occurred in the permanent magnet synchronous motor.

2. The method for diagnosing inter-turn faults in a permanent magnet synchronous motor based on high-frequency impedance according to claim 1, characterized in that, The formula for calculating the high-frequency voltage is: in , , These are the injected three-phase high-frequency voltages, The amplitude of the injected high-frequency voltage, The phase angle for injecting high-frequency voltage.

3. The method for diagnosing inter-turn faults in a permanent magnet synchronous motor based on high-frequency impedance according to claim 1, characterized in that, The steps for calculating the three-phase voltages include: S31 calculates the voltage to ground at the midpoint of the three-phase bridge arm of the inverter using the drive signal of the power transistor; S32 obtains the three-phase voltage of the motor through the ground voltage at the midpoint of the three-phase bridge arm of the inverter.

4. In the method for diagnosing inter-turn faults in a permanent magnet synchronous motor based on high-frequency impedance according to claim 3, in S31, the formula for calculating the voltage to ground at the midpoint of the three-phase bridge arm of the inverter is: in, , , These are the voltages to ground at the midpoints of the three-phase bridge arms of the inverter, respectively. - These are the drive signals for the three upper transistors of the inverter. - These are the inverses of the drive signals for the three lower transistors of the inverter. This is the DC bus voltage.

5. According to claim 3, in the method for diagnosing inter-turn faults in a permanent magnet synchronous motor based on high-frequency impedance, when the motor is in a healthy state, the formula for calculating the three-phase voltage is: in, , , These are the three-phase voltages.

6. According to claim 3, in a method for diagnosing inter-turn faults in a permanent magnet synchronous motor based on high-frequency impedance, the formula for calculating the three-phase voltage when an inter-turn fault occurs in the motor is: in, , , These are the three-phase voltages after the fault. For phase resistance, The short-circuit turns ratio, This is the short-circuit current. This refers to the leakage inductance of the motor.

7. A fault diagnosis system for inter-turn permanent magnet synchronous motors based on high-frequency impedance, comprising the method described in any one of claims 1-6, characterized in that, include: Voltage input module: Injects a three-phase symmetrical high-frequency voltage into the control system; Current component extraction module: Collects three-phase current and extracts the amplitude of high-frequency components from the three-phase current; Voltage component extraction module: Calculates the three-phase voltage using the inverter's drive signal and extracts the amplitude of the high-frequency components in the three-phase voltage; Impedance calculation module; calculates the three-phase high-frequency impedance using the amplitude of the high-frequency component in the three-phase current and the amplitude of the high-frequency component in the three-phase voltage; Fault diagnosis module: By comparing the three-phase high-frequency impedance, determine whether the motor has experienced an inter-turn fault.

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