Asynchronous motor driver power tube open-circuit fault diagnosis method based on current coding

Abstract

The invention relates to the technical field of intelligent operation and maintenance, and provides an asynchronous motor driver power tube open-circuit fault diagnosis method based on current coding, and the method comprises the following steps: S1, sequentially carrying out the normalization and current coding of a three-phase current obtained through sampling; s2, determining whether an open-circuit fault occurs or not according to the current coding jump value of each phase at adjacent moments, and determining the position of a fault phase; and S3, according to a fault phase positioning result, positioning a fault tube in combination with the current coding jump values of the other two phases. The open-circuit fault phase and the specific fault tube position can be accurately positioned in real time by performing operation processing on the three-phase current, sampled in real time, of the asynchronous motor, the method is particularly suitable for open-circuit fault diagnosis of the asynchronous motor driver power tube under the variable speed condition, and the method has the advantages of being high in diagnosis speed, high in diagnosis precision and suitable for variable speed and variable load.

Description

Technical Field

[0001] The present invention relates to the technical field of intelligent operation and maintenance, and more specifically, to a method for diagnosing open - circuit faults of power tubes in an asynchronous motor driver based on current coding. Background Art

[0002] Asynchronous motors have simple structures, are easy to maintain, and have good starting performance, a wide speed regulation range, and low costs. They are widely used in many scenarios such as household appliances and industrial equipment. The control of asynchronous motors usually uses a two - level driver for driving. This driver contains power devices such as power tubes, and an inverter circuit composed of multiple power devices is used to invert the two - level power supply into a three - phase power supply suitable for the operation of the asynchronous motor. This inverter circuit is the core of its function realization. However, affected by factors such as high temperature, high voltage, internal and external stresses, power tubes are prone to failures, and open - circuit failure is one of its failure modes. It is necessary to design a fault diagnosis method to accurately determine the faulty tube to ensure the reliable operation of the asynchronous motor. Summary of the Invention

[0003] In view of the technical problems existing in the prior art, the present invention provides a method for diagnosing open - circuit faults of power tubes in an asynchronous motor driver based on current coding. The purpose is to timely diagnose the faulty tube when an open - circuit fault occurs in the power tube of the driver for an asynchronous motor in its application scenarios, so as to timely eliminate the fault and ensure the reliable operation of the asynchronous motor.

[0004] According to the first aspect of the present invention, there is provided a method for diagnosing open - circuit faults of power tubes in an asynchronous motor driver based on current coding, including:

[0005] S1, performing normalization and current coding processing on the sampled three - phase currents in sequence;

[0006] S2, determining whether an open - circuit fault occurs according to the current coding jump value of each phase at adjacent moments, and determining the position of the faulty phase;

[0007] S3, locating the faulty tube based on the faulty phase positioning result and combining the current coding jump values of the other two phases.

[0008] On the basis of the above - mentioned technical solution, the present invention can also be improved as follows.

[0009] Optionally, step S1 includes:

[0010] S101, calculating the normalized three - phase currents i a 、i b and i c corresponding to the sampled three - phase sinusoidal currents i am 、i bm and i cm ;

[0011] S102. Encode the calculation points of the normalized three-phase currents \(i\) am 、\(i\) bm and \(i\) cm to obtain the three-phase current encoded values \(i\) aL 、\(i\) bL and \(i\) cL .

[0012] Optionally, step S101 includes:

[0013] Let \(i\) d 、\(i\) q and \(i\) m be the calculation intermediate values, and calculate the corresponding normalized three-phase current values \(i\) a 、\(i\) b and \(i\) c of the sampled three-phase sinusoidal currents \(i\) am 、\(i\) bm and \(i\) cm in real time:

[0014]

[0015] Optionally, step S102 includes:

[0016] Let the intersection amplitude of the normalized three-phase currents be \(k\), and encode the calculation points of the normalized three-phase currents \(i\) am 、\(i\) bm and \(i\) cm to obtain the three-phase current encoded values \(i\) aL 、\(i\) bL and \(i\) cL :

[0017]

[0018]

[0019] Optionally, step S2 includes:

[0020] S201. Subtract the current encoded values of each phase at adjacent moments respectively to obtain the corresponding current encoded jump values \(i\) ad 、\(i\) bd and \(i\) cd ;

[0021] S202. When the current encoded jump value of any phase is greater than the preset value, it is determined that a power transistor open circuit fault has occurred; otherwise, it is determined that no power transistor open circuit fault has occurred;

[0022] S203. If a fault is determined to exist, determine the position of the fault phase according to the magnitudes of the current encoded jump values of each phase.

[0023] Optionally, in step S201, the jump values i ad 、i bd and i cd of the three-phase current coding are calculated respectively according to the following formula:

[0024] i adt =|i aLt -i aL(t-1) |

[0025] i bdt =|i bLt -i bL(t-1) |

[0026] i cdt =|i cLt -i cL(t-1) |

[0027] Wherein, i adt 、i bdt and i cdt are the jump values of the three-phase current coding at time t respectively, i aLt 、i bLt and i cLt are the three-phase current coding values at time t respectively, and i aL(t-1) 、i bL(t-1) and i cL(t-1) are the three-phase current coding values at the previous moment of time t respectively.

[0028] Optionally, in step S202, the judgment formula for whether there is an open-circuit fault of the power tube is:

[0029]

[0030] Optionally, in step S203, the judgment formula for determining the position of the faulty phase according to the magnitude of the current coding jump value of each phase is:

[0031]

[0032] Optionally, in step S3, the positioning of the faulty tube by combining the current coding jump values of the other two phases according to the faulty phase positioning result includes:

[0033] Determine the current coding value of the leading phase of the faulty phase according to the faulty phase positioning result, and determine the position of the faulty tube in the faulty phase according to the jump mode of the current coding value of the leading phase of the faulty phase.

[0034] Optionally, determining the position of the faulty tube in the faulty phase according to the jump mode of the current coding value of the leading phase of the faulty phase includes:

[0035] When the current coding value of the leading phase of the faulty phase jumps from -1 to 1, it is determined that the lower tube of the faulty phase has an open-circuit fault;

[0036] When the current coding value of the leading phase of the faulty phase jumps from 1 to -1, it is determined that an open - circuit fault occurs in the upper switch of the faulty phase.

[0037] According to the second aspect of the present invention, there is provided a power transistor open - circuit fault diagnosis system for an asynchronous motor drive based on current coding, including:

[0038] A pre - processing module for successively performing normalization and current coding processing on the sampled three - phase currents;

[0039] A faulty - phase positioning module for determining whether an open - circuit fault occurs according to the current coding jump value of each phase at adjacent moments and determining the position of the faulty phase;

[0040] A faulty - transistor positioning module for positioning the faulty transistor according to the faulty - phase positioning result and combining the current coding jump values of the other two phases.

[0041] According to the third aspect of the present invention, there is provided an electronic device including a memory and a processor. When the processor executes a computer management program stored in the memory, the steps of the above - mentioned power transistor open - circuit fault diagnosis method for an asynchronous motor drive based on current coding are implemented.

[0042] According to the fourth aspect of the present invention, there is provided a computer - readable storage medium on which a computer management program is stored. When the computer management program is executed by a processor, the steps of the above - mentioned power transistor open - circuit fault diagnosis method for an asynchronous motor drive based on current coding are implemented.

[0043] A power transistor open - circuit fault diagnosis method, system, electronic device and storage medium for an asynchronous motor drive based on current coding provided by the present invention can accurately and real - time locate the open - circuit fault phase and the specific position of the faulty transistor by performing arithmetic processing on the real - time sampled three - phase currents, and is especially suitable for on - line monitoring. Compared with other monitoring methods, the present invention has the following advantages:

[0044] (1) Without a diagnosis threshold, the method provided by the present invention can diagnose without any diagnosis threshold designed by artificial experience, and the diagnosis result is more objective and accurate.

[0045] (2) Strong adaptability to working conditions, the method provided by the present invention does not need to collect diagnosis signals other than current, and has a wide range of applicable scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a flowchart of a power transistor open - circuit fault diagnosis method for an asynchronous motor drive based on current coding provided by the present invention;

[0047] Figure 2 It is the verification result of using the method of the present invention under the fault of the upper switch of phase a in a certain embodiment;

[0048] Figure 3 Verification results of the method of the present invention under the a-phase lower transistor failure provided for a certain embodiment;

[0049] Figure 4 Block diagram of a power transistor open-circuit fault diagnosis system for an asynchronous motor drive based on current coding provided by the present invention;

[0050] Figure 5 Schematic diagram of the hardware structure of a possible electronic device provided by the present invention;

[0051] Figure 6 Schematic diagram of the hardware structure of a possible computer-readable storage medium provided by the present invention. Detailed implementation manners

[0052] The following combines the accompanying drawings and embodiments to further describe in detail the specific implementation manners of the present invention. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0053] Figure 1 Flowchart of a power transistor open-circuit fault diagnosis method for an asynchronous motor drive based on current coding provided by an embodiment of the present invention. At the same time, it shows the circuit topology structure composed of power transistors in the asynchronous motor drive. Figure 1 In which, T a1 and T a2 are respectively the upper transistor and the lower transistor of the a-phase power transistor; T b1 and T b2 are respectively the upper transistor and the lower transistor of the b-phase power transistor; T c1 and T c2 are respectively the upper transistor and the lower transistor of the c-phase power transistor; i a , i b , i c are the three-phase currents output by the drive to the motor, C is the DC-side capacitor, E is the DC source, and the load is the asynchronous motor M.

[0054] As Figure 1 shown, an embodiment of the present invention provides a power transistor open-circuit fault diagnosis method for an asynchronous motor drive based on current coding, including the following steps S1 to S3:

[0055] S1, perform normalization and current coding processing on the sampled three-phase currents in sequence;

[0056] S2, determine whether an open-circuit fault occurs according to the current coding jump value of each phase at adjacent moments, and determine the position of the fault phase;

[0057] S3, according to the fault phase positioning result, combine the current coding jump values of the other two phases to perform the positioning of the fault transistor.

[0058] It is understandable that, based on the deficiencies in the background art, an open-circuit fault diagnosis method for power transistors of an asynchronous motor drive based on current coding is proposed in an embodiment of the present invention. This method calculates by collecting three-phase current signals to obtain an accurate open-circuit fault diagnosis result and accurately locate the faulty transistor. It is especially applicable to the open-circuit fault diagnosis of power transistors of an asynchronous motor drive under variable-speed conditions, and has the advantages of fast diagnosis speed and applicability to variable-speed and variable-load conditions.

[0059] In a possible embodiment, step S1 includes sub-steps S101 to S102.

[0060] S101, sample three-phase sinusoidal currents i a 、i b and i c , let i d 、i q and i m be intermediate calculation values, and calculate the normalized three-phase currents i a 、i b and i c corresponding to the sampled three-phase sinusoidal currents i am 、i bm and i cm according to the following formula:

[0061]

[0062] S102, encode the calculation points of the normalized three-phase currents i am 、i bm and i cm according to the intersection amplitude of the normalized three-phase currents to obtain the three-phase current coding values i aL 、i bL and i cL .

[0063] Specifically, let the intersection amplitude of the normalized three-phase currents be k, and encode the calculation points of the normalized three-phase currents i am 、i bm and i cm according to the following formula to obtain the three-phase current coding values i aL 、i bL and i cL :

[0064]

[0065] Taking the intersection amplitude k = 0.5 of the normalized three-phase currents as an example, there is:

[0066]

[0067]

[0068] In a possible embodiment, step S2 includes sub-steps S201 to S203.

[0069] S201, take the difference between the current coding values of each phase current at adjacent moments to obtain the corresponding current coding jump values i ad , i bd and i cd . Among them, the jump values i ad , i bd and i cd of the three-phase current coding are calculated respectively according to the following formula:

[0070] i adt = |i aLt - i aL(t-1) |

[0071] i bdt = |i bLt - i bL(t-1) |

[0072] i cdt = |i cLt - i cL(t-1) |

[0073] Among them, i adt , i bdt and i cdt are the three-phase current coding jump values at time t respectively, i aLt , i bLt and i cLt are the three-phase current coding values at time t respectively, i aL(t-1) , i bL(t-1) and i cL(t-1) are the three-phase current coding values at the previous moment of time t respectively. The moment here can be considered as the sampling moment.

[0074] S202, when the current coding jump value of any one phase is greater than the preset value, it is determined that a power transistor open circuit fault occurs, otherwise it is determined that no power transistor open circuit fault occurs.

[0075] It can be understood that when an open circuit fault occurs in a power transistor of a certain phase, the current of that phase becomes distorted to 0 in a half cycle, resulting in the equal amplitude and opposite direction of the currents of the other two phases. The current normalization operation will cause the normalization values of the amplitudes of the currents of the other two phases to suddenly change from 1 to -1 and from -1 to 1 at the zero crossing point. Therefore, fault detection can be performed according to the magnitude of the current coding jump value. When the current coding jump value of any one phase is 2 (that is, from -1 to 1, or from 1 to -1), a power transistor open circuit fault occurs, otherwise no fault occurs.

[0076] Specifically, in sub-step S202, the judgment formula for whether there is an open-circuit fault in the power tube is:

[0077]

[0078] S203. If it is determined that there is a fault, determine the position of the faulty phase according to the magnitude of the current coding jump value of each phase.

[0079] It can be understood that the position of the faulty phase can be located simultaneously at the moment when the fault is detected. Since the phase current of the faulty phase is always 0 during the faulty half cycle, the coding value of the normalized current does not jump during this half cycle. Therefore, the phase with the non-jumping coding value of the normalized current is the faulty phase.

[0080] Therefore, in step S203, determine the position of the faulty phase according to the magnitude of the current coding jump value of each phase, and the judgment formula is:

[0081]

[0082] In a possible implementation manner, in step S3, the positioning of the faulty tube by combining the current coding jump values of the other two phases according to the faulty phase positioning result includes:

[0083] Determine the current coding value of the leading phase of the faulty phase according to the faulty phase positioning result, and determine the position of the faulty tube in the faulty phase according to the jump mode of the current coding value of the leading phase of the faulty phase.

[0084] It can be understood that the leading phase of each phase during motor operation can be obtained according to the output phase sequence of the motor driver. For example, in this embodiment, let the leading phase of phase a be phase c, the leading phase of phase b be phase a, and the leading phase of phase c be phase b.

[0085] As shown in the following judgment formula, when the current coding value of the leading phase of the faulty phase jumps from -1 to 1, it is determined that the lower tube of the faulty phase has an open-circuit fault; when the current coding value of the leading phase of the faulty phase jumps from 1 to -1, it is determined that the upper tube of the faulty phase has an open-circuit fault:

[0086]

[0087] As Figure 2 shown is the verification result of a certain embodiment using the method of the present invention under the fault of the upper tube T of phase a; as a1 shown is the verification result of a certain embodiment using the method of the present invention under the fault of the lower tube T of phase a. Figure 3 shown is the verification result of a certain embodiment using the method of the present invention under the fault of the lower tube T of phase a; as a2 shown is the verification result of a certain embodiment using the method of the present invention under the fault of the lower tube T of phase a.

[0088] Taking Figure 2 as an example, a fault is set at 0.35 s, and at about 0.37 s, i bd = 2 and icd = 2, according to the judgment rule in step S2, it can be determined that an open - circuit fault has occurred. Since at about 0.37 s, i ad = 0, according to the positioning rule in step S2, it can be determined that a fault has occurred in phase a. Then in step S3, according to i cL jumps from 1 to - 1, then it can be judged that the upper switch tube T a1 in phase a has failed.

[0089] Take Figure 3 as an example. A fault is set at 0.35 s. At about 0.37 s, i bd = 2 and i cd = 2. According to the judgment rule in step S2, it can be determined that an open - circuit fault has occurred. Since at about 0.37 s, i ad = 0; according to the positioning rule in step S2, it can be determined that a fault has occurred in phase a. Then in step S3, according to i cL jumps from - 1 to 1, then it can be judged that the lower switch tube T a2 in phase a has failed.

[0090] It is verified that the method provided by the present invention is applicable to the open - circuit fault diagnosis of the power tubes of an asynchronous motor drive under variable - speed conditions, and has the advantages of fast diagnosis speed, applicability to variable - speed and variable - load conditions, and accurate diagnosis.

[0091] Figure 4 The following is the structural diagram of an open - circuit fault diagnosis system for the power tubes of an asynchronous motor drive based on current coding provided by an embodiment of the present invention. As Figure 4 shown, an open - circuit fault diagnosis system for the power tubes of an asynchronous motor drive based on current coding includes a pre - processing module, a fault - phase positioning module, and a fault - tube positioning module, where:

[0092] The pre - processing module is used to perform normalization and current coding processing on the sampled three - phase currents in sequence;

[0093] The fault - phase positioning module is used to determine whether an open - circuit fault occurs according to the current coding jump value of each phase at adjacent times, and determine the position of the fault phase;

[0094] The fault - tube positioning module is used to perform the positioning of the fault tube according to the fault - phase positioning result and in combination with the current coding jump values of the other two phases.

[0095] It can be understood that a power transistor open - circuit fault diagnosis system for an asynchronous motor drive based on current encoding provided by the present invention corresponds to the power transistor open - circuit fault diagnosis method for an asynchronous motor drive based on current encoding provided in the foregoing embodiments. The relevant technical features of the power transistor open - circuit fault diagnosis system for an asynchronous motor drive based on current encoding can refer to the relevant technical features of the power transistor open - circuit fault diagnosis method for an asynchronous motor drive based on current encoding, and will not be elaborated here.

[0096] Please refer to Figure 5 , Figure 5 which is a schematic diagram of an embodiment of an electronic device provided by an embodiment of the present invention. As Figure 5 shown, an embodiment of the present invention provides an electronic device 500, including a memory 510, a processor 520, and a computer program 511 stored in the memory 510 and executable on the processor 520. When the processor 520 executes the computer program 511, the following steps are implemented:

[0097] S1, successively perform normalization and current encoding processing on the sampled three - phase currents;

[0098] S2, determine whether an open - circuit fault occurs according to the current encoding jump value of each phase at adjacent moments, and determine the position of the faulty phase;

[0099] S3, according to the faulty - phase positioning result, combine the current encoding jump values of the other two phases to perform the positioning of the faulty transistor.

[0100] Please refer to Figure 6 , Figure 6 which is a schematic diagram of an embodiment of a computer - readable storage medium provided by the present invention. As Figure 6 shown, this embodiment provides a computer - readable storage medium 600, on which a computer program 611 is stored. When the computer program 611 is executed by a processor, the following steps are implemented:

[0101] S1, successively perform normalization and current encoding processing on the sampled three - phase currents;

[0102] S2, determine whether an open - circuit fault occurs according to the current encoding jump value of each phase at adjacent moments, and determine the position of the faulty phase;

[0103] S3, according to the faulty - phase positioning result, combine the current encoding jump values of the other two phases to perform the positioning of the faulty transistor.

[0104] A method, system, electronic device, and storage medium for diagnosing open-circuit faults of power tubes in an asynchronous motor driver based on current encoding provided by an embodiment of the present invention can accurately locate the open-circuit fault phase and the specific fault tube position in real time by performing arithmetic processing on the three-phase currents sampled in real time, and is particularly suitable for online monitoring. Compared with other monitoring methods, the present invention has the following advantages:

[0105] (1) Without a diagnostic threshold, the method proposed by the present invention can diagnose without any diagnostic threshold designed by artificial experience, and the diagnostic result is more objective and accurate.

[0106] (2) Strong adaptability to working conditions, the method proposed by the present invention does not need to collect diagnostic signals other than current, and has a wide range of applicable scenarios.

[0107] It should be noted that in the above embodiments, the descriptions of the respective embodiments have their own emphases. For the parts not detailedly described in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0108] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can 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.

[0109] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (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, and the combination of processes and / or blocks in the flowcharts and / or block diagrams, can be realized by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded computer, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate means for realizing the functions specified in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0110] These computer program instructions can 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 generate a manufactured product including an instruction device, and the instruction device realizes the functions specified in Figure 1 one process or multiple processes and / or blocks Figure 1 [[ID=

[0111] These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus, causing a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, so that the instructions executed on the computer or other programmable apparatus provide steps for implementing the functions specified in one process or a plurality of processes and / or blocks Figure 1 one process or a plurality of processes and / or blocks Figure 1 or steps for implementing the functions specified in a plurality of blocks.

[0112] Although the preferred embodiments of the present invention have been described, additional changes and modifications can be made by those skilled in the art once they learn of the basic inventive concept. Therefore, the appended claims are intended to be construed to cover the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0113] It is obvious that those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A method for diagnosing open - circuit faults of power transistors in an asynchronous motor drive based on current coding, characterized in that, It includes the following steps: S1. Normalize and process the current encoding for the three-phase current obtained by sampling in sequence; S2. Determine whether an open-circuit fault occurs according to the current encoding jump value of each phase at adjacent moments, and determine the position of the faulty phase; S3. Locate the faulty transistor in combination with the current encoding jump values of the other two phases according to the faulty phase positioning result.

2. The method for diagnosing the open - circuit fault of the power tube of an asynchronous motor driver based on current coding according to claim 1, wherein, Step S1 includes: S101, calculate the normalized three-phase currents i a , i b and i c corresponding to the sampled three-phase sinusoidal currents i am , i bm and i cm ; S102, encode the calculation points according to the intersection amplitude of the normalized three-phase currents for the normalized three-phase currents i am 、i bm and i cm to obtain the three-phase current encoded values i aL 、i bL and i cL .

3. A method for diagnosing an open-circuit fault of a power transistor of an asynchronous motor driver based on current coding according to claim 2, characterized in that Step S101 includes: Let i d , i q and i m be intermediate calculation values, and calculate in real time the normalized three-phase current values i a , i b and i c corresponding to the sampled three-phase sinusoidal currents i am , i bm and i cm :

4. A method for diagnosing the open - circuit fault of power tubes in an asynchronous motor driver based on current coding according to claim 3, characterized in that, Step S102 includes: Let the intersection amplitude of the normalized three-phase current be k, and encode the calculation points of the normalized three-phase currents i am 、i bm and i cm to obtain the three-phase current encoded values i aL 、i bL and i cL :

5. A method for diagnosing an open - circuit fault of a power transistor in an asynchronous motor driver based on current coding according to claim 4, characterized in that, Step S2 includes: S201, subtract the current coding values of each phase current at adjacent moments respectively to obtain the corresponding current coding jump values i ad , i bd and i cd ; S202. When the current encoding jump value of any phase is greater than the preset value, it is determined that a power transistor open-circuit fault occurs; otherwise, it is determined that no power transistor open-circuit fault occurs; S203. If it is determined that there is a fault, determine the position of the faulty phase according to the magnitude of the current encoding jump values of each phase.

6. A method for diagnosing the open - circuit fault of the power transistor of an asynchronous motor driver based on current coding according to claim 5, characterized in that, In step S201, the jump values i ad 、i bd and i cd of the three-phase current coding are calculated respectively according to the following formula: i adt = |i aLt - i aL(t-1) | i bft = |i bLt - i bL(t-1) | i cdt = |i cLt - i cL(t-1) | Among them, i adt , i bdt and i cdt are the three-phase current coding jump values at time t, respectively. i aLt , i bLt and i cLt are the three-phase current coding values at time t, respectively. i aL(t-1) , i bL(t-1) and i cL(t-1) are the three-phase current coding values at the previous moment of time t, respectively.

7. A method for diagnosing an open - circuit fault of a power transistor in an asynchronous motor driver based on current coding according to claim 5, characterized in that, In step S202, the judgment formula for whether there is a power transistor open-circuit fault is:

8. A method for diagnosing an open - circuit fault of a power transistor in an asynchronous motor driver based on current coding according to any one of claims 5 to 7, characterized in that In step S203, the judgment formula for determining the position of the faulty phase according to the magnitude of the current encoding jump values of each phase is:

9. A method for diagnosing an open - circuit fault of a power transistor in an asynchronous motor driver based on current coding according to any one of claims 5 to 7, characterized in that Step S3, locating the faulty transistor in combination with the current encoding jump values of the other two phases according to the faulty phase positioning result, includes: Determine the current encoding value of the leading phase of the faulty phase according to the faulty phase positioning result, and determine the position of the faulty transistor in the faulty phase according to the jump mode of the current encoding value of the leading phase of the faulty phase.

10. A method for diagnosing an open - circuit fault of a power transistor in an asynchronous motor driver based on current coding according to claim 9, characterized in that, The determining the position of the faulty transistor in the faulty phase according to the jump mode of the current encoding value of the leading phase of the faulty phase includes: When the current encoding value of the leading phase of the faulty phase jumps from -1 to 1, it is determined that the lower transistor of the faulty phase has an open-circuit fault; When the current encoding value of the leading phase of the faulty phase jumps from 1 to -1, it is determined that the upper transistor of the faulty phase has an open-circuit fault.

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