Methods, devices, systems, equipment, and storage media for diagnosing phase-to-phase short-circuit faults.

Abstract

This application relates to the field of testing and discloses a method, apparatus, system, equipment, and storage medium for diagnosing phase-to-phase short-circuit faults. In the system, a frequency converter is connected to a motor via three-phase lines, and current sensors are respectively installed on at least two phase lines. The method includes: when a fault is detected in the power device of the frequency converter or an overcurrent is detected in the frequency converter output, determining the current change rate of each phase line based on the current signals from each current sensor, and detecting whether at least two phase lines have a current change rate greater than a current change rate threshold; performing phase-to-phase short-circuit fault diagnosis based on the current change rate detection results to obtain a diagnosis result; determining the location of the phase-to-phase short-circuit fault (either the diagnosis result indicates no phase-to-phase short-circuit fault or the presence of a phase-to-phase short-circuit fault) to determine the corresponding fault protection strategy for fault protection. This solves the problem of low accuracy in phase-to-phase short-circuit fault diagnosis and improves reliability and availability by utilizing appropriate fault protection strategies.

Description

Technical Field

[0001] This application relates to the field of testing, and more particularly to a method, apparatus, system, equipment, and storage medium for diagnosing phase-to-phase short-circuit faults. Background Technology

[0002] Electric motors are crucial components in the energy conversion and power transmission systems of rail transit vehicles' traction systems and new materials industry equipment. Frequency converters convert input electrical energy into three-phase alternating current to supply the motor. A phase-to-phase short circuit fault will affect the safety of the power system containing the motor. Current methods for diagnosing phase-to-phase short circuit faults are prone to missed diagnoses and false diagnoses. Missed diagnoses result in uncontrolled short-circuit voltage and torque ripples, impacting power system safety, while false diagnoses lead to over-protection and reduced availability. Therefore, the low accuracy of phase-to-phase short circuit fault diagnosis is a critical issue that urgently needs to be addressed in the industry. Summary of the Invention

[0003] The purpose of this application is to provide at least one method, device, system, equipment, and storage medium for diagnosing phase-to-phase short-circuit faults, which can at least solve the problem of low accuracy in diagnosing phase-to-phase short-circuit faults, and at least achieve the effect of improving the accuracy of phase-to-phase short-circuit fault diagnosis and improving the reliability and availability of the power system in which the motor is located.

[0004] In a first aspect, this application provides a method for diagnosing phase-to-phase short-circuit faults, applied to a phase-to-phase short-circuit fault diagnosis system. The system includes a frequency converter and a motor, the frequency converter being connected to the motor via a three-phase line, and at least two phases of the three-phase line being respectively equipped with current sensors. The method includes:

[0005] When a fault is detected in the power device of the inverter or an overcurrent is detected in the inverter output, the current change rate of each phase of the three-phase line is determined based on the current signal of each current sensor, and it is detected whether there are at least two phases whose current change rate is greater than the current change rate threshold, so as to obtain the current change rate detection result.

[0006] Based on the current change rate detection results, phase-to-phase short-circuit fault diagnosis is performed to obtain a diagnosis result; wherein, the diagnosis result indicates the location of no phase-to-phase short-circuit fault or the location of phase-to-phase short-circuit fault, and the diagnosis result is used to determine the fault protection strategy corresponding to the diagnosis result for fault protection.

[0007] Optionally, each phase of the three-phase line has a first node, and the current sensor is disposed at the first node; the motor is a permanent magnet synchronous motor.

[0008] The phase-to-phase short-circuit fault diagnosis based on the current change rate detection result yields the following diagnostic results:

[0009] When the inverter stops working due to the blocking pulse, if the current change rate detection result shows that the current change rate of at least two phases is greater than the current change rate threshold, a phase-to-phase short circuit fault is determined to exist in the first location area. The first location area includes the motor body and the area between the motor and the first node.

[0010] If the current change rate detection result indicates that there are no two phases where the current change rate is greater than the current change rate threshold, the sum of the instantaneous current values ​​and the effective current values ​​of each phase of the three-phase circuit are obtained based on the current signals of each current sensor. Based on the output current of the inverter, the sum of the instantaneous current values ​​of each phase, and the effective current values ​​of each phase, it is determined whether the phase-to-phase short-circuit current characteristics are met, and a first determination result is obtained. The phase-to-phase short-circuit current characteristics include: the inverter is not outputting current, the sum of the instantaneous current values ​​of each phase is less than the first threshold, the maximum value of the effective current values ​​of each phase is greater than the second threshold, and the ratio of the minimum value to the maximum value of the effective current values ​​of each phase is less than the third threshold.

[0011] If the first determination result satisfies the phase-to-phase short-circuit current characteristics, it is determined that there is a phase-to-phase short-circuit fault in the second location region, and the second location region includes the region between the first node and the inverter.

[0012] If the first judgment result does not meet the phase-to-phase short-circuit current characteristics, it is determined that there is no phase-to-phase short-circuit fault.

[0013] Optionally, the phase-to-phase short-circuit fault diagnosis system further includes an isolation contactor, which is disposed between the first node and the frequency converter;

[0014] The determination that a phase-to-phase short-circuit fault exists in the second location area includes:

[0015] Disconnect the isolation contactor, and based on the output current of the inverter, the sum of the instantaneous current values ​​of each phase line, and the effective current value of each phase line, determine whether the current condition meets the phase-to-phase short-circuit current characteristics, and obtain a second judgment result.

[0016] If the second judgment result satisfies the phase-to-phase short-circuit current characteristics, it is determined that there is a phase-to-phase short-circuit fault in the third location area. The third location area includes the line between the isolation contactor and the first node and the contact of the isolation contactor near the first node.

[0017] If the second judgment result is that the phase-to-phase short-circuit current characteristics are not met, it is determined that there is a phase-to-phase short-circuit fault in the fourth location area. The fourth location area includes the line between the isolation contactor and the inverter, as well as the contact of the isolation contactor near the inverter.

[0018] The second location region includes the third location region and the fourth location region.

[0019] Optionally, the phase-to-phase short-circuit fault diagnosis system further includes an isolating contactor, which is disposed between the first node and the motor;

[0020] The determination that a phase-to-phase short-circuit fault exists in the first location area includes:

[0021] Disconnect the isolation contactor and start the frequency converter to output a test pulse;

[0022] When the inverter outputs the test pulse, it is determined whether the power device still malfunctions or the inverter outputs overcurrent, and whether the current change rate of at least two phases is greater than the current change rate threshold. If so, it is determined that there is a phase-to-phase short circuit fault in the fifth position area, which includes the line between the isolating contactor and the first node and the contact of the isolating contactor near the first node. Otherwise, it is determined that there is a phase-to-phase short circuit fault in the sixth position area, which includes the line between the isolating contactor and the motor, the contact of the isolating contactor near the motor, and the motor body.

[0023] The first location region includes the fifth location region and the sixth location region.

[0024] Optionally, the third threshold is a fixed threshold or is determined based on the current speed of the motor.

[0025] Optionally, each phase of the three-phase line has a first node, and the current sensor is disposed at the first node; two or three voltage sensors for detecting voltage signals between different phase lines are disposed on the three-phase line; each phase of the three-phase line has a second node located between the first node and the frequency converter, and the voltage sensor is disposed at the second node; the motor is a permanent magnet synchronous motor.

[0026] The phase-to-phase short-circuit fault diagnosis based on the current change rate detection result yields the following diagnostic results:

[0027] When the inverter stops working due to the blocking pulse, if the current change rate detection result shows that the current change rate of at least two phases is greater than the current change rate threshold, a phase-to-phase short circuit fault is determined to exist in the first location area. The first location area includes the motor body and the area between the motor and the first node.

[0028] If the current change rate detection result is that there are no two phases where the current change rate is greater than the current change rate threshold, the voltage value between each pair of phases of the three-phase line is obtained based on the voltage signal of each voltage sensor, and the presence of a phase-to-phase short circuit fault in the second location area is determined based on the voltage value between each pair of phases of the three-phase line. The second location area includes the area between the first node and the frequency converter.

[0029] Optionally, the phase-to-phase short-circuit fault diagnosis system further includes an isolating contactor, which is disposed between the first node and the second node;

[0030] The determination of whether a phase-to-phase short-circuit fault exists in the second location area based on the voltage value between every two phases of the three-phase line includes:

[0031] Based on the voltage values ​​between every two phases of the three-phase circuit, it is determined whether at least one phase-to-phase short-circuit voltage characteristic occurs, and a third determination result is obtained; wherein, the phase-to-phase short-circuit voltage characteristic includes: when the inverter is in operation, the voltage value drops from the normal value to below the voltage threshold; after the inverter is started from the shutdown state, the voltage value remains zero and the current sensor of the corresponding two phases experiences overcurrent.

[0032] If the third determination result is negative, it is determined that there is no phase-to-phase short-circuit fault in the second location area;

[0033] If the third judgment result is yes, disconnect the isolation contactor and start the frequency converter to output a test pulse; when the frequency converter outputs the test pulse, determine whether at least one of the phase-to-phase short-circuit voltage characteristics still occurs, and obtain the fourth judgment result;

[0034] If the fourth determination result is negative, it is determined that there is a phase-to-phase short circuit fault in the third location area. The third location area includes the line between the isolating contactor and the first node, as well as the contact of the isolating contactor near the first node.

[0035] If the fourth determination result is yes, it is determined that there is a phase-to-phase short circuit fault in the fourth location area. The fourth location area includes the line between the isolation contactor and the frequency converter, as well as the contact of the isolation contactor near the frequency converter.

[0036] The second location region includes the third location region and the fourth location region.

[0037] Optionally, the phase-to-phase short-circuit fault diagnosis system further includes an isolating contactor, which is disposed between the first node and the motor;

[0038] The determination that a phase-to-phase short-circuit fault exists in the first location area includes:

[0039] Disconnect the isolation contactor and start the frequency converter to output a test pulse;

[0040] When the inverter outputs the test pulse, it is determined whether the power device still malfunctions or the inverter outputs overcurrent, and whether the current change rate of at least two phases is greater than the current change rate threshold. If so, it is determined that there is a phase-to-phase short circuit fault in the fifth position area, which includes the line between the isolating contactor and the first node and the contact of the isolating contactor near the first node. Otherwise, it is determined that there is a phase-to-phase short circuit fault in the sixth position area, which includes the line between the isolating contactor and the motor, the contact of the isolating contactor near the motor, and the motor body.

[0041] The first location region includes the fifth location region and the sixth location region.

[0042] Optionally, the phase-to-phase short-circuit fault diagnosis system further includes an isolating contactor, which is disposed between the first node and the motor;

[0043] The determination of whether a phase-to-phase short-circuit fault exists in the second location area based on the voltage value between every two phases of the three-phase line includes:

[0044] Disconnect the isolation contactor and start the frequency converter to output a test pulse;

[0045] When the inverter outputs the test pulse, based on the voltage value between each pair of the three-phase lines, it is determined whether at least one phase-to-phase short-circuit voltage characteristic occurs; wherein, the phase-to-phase short-circuit voltage characteristic includes: the voltage value drops from the normal value to below the voltage threshold when the inverter is in operation; after the inverter is started from a shutdown state, the voltage value remains zero and the current sensor of the corresponding two phase lines experiences overcurrent;

[0046] If so, it is determined that there is a phase-to-phase short-circuit fault in the second location area;

[0047] If not, it is determined that there is no phase-to-phase short-circuit fault in the second location area.

[0048] Optionally, after obtaining the diagnosis result by performing phase-to-phase short-circuit fault diagnosis based on the current change rate detection result, the method further includes:

[0049] If the diagnostic result indicates that there is a phase-to-phase short circuit fault in the first location area, an active three-phase short circuit mode is executed for fault protection. The active three-phase short circuit mode is when all three upper bridge arms or three lower bridge arms of the frequency converter are turned on, so that the three-phase windings of the motor form a circuit through the frequency converter to achieve demagnetization and braking.

[0050] If the diagnostic result indicates that there is a phase-to-phase short-circuit fault in the third location area, the isolation contactor is closed, and the active three-phase short-circuit mode is executed for fault protection.

[0051] If the diagnostic result indicates that a phase-to-phase short-circuit fault exists in the fourth location area, the disconnected state of the isolating contactor shall be maintained for fault protection.

[0052] If the diagnostic result indicates no phase-to-phase short-circuit fault, a fault protection strategy is adopted for when the power device malfunctions or the inverter outputs an overcurrent.

[0053] Optionally, after obtaining the diagnosis result by performing phase-to-phase short-circuit fault diagnosis based on the current change rate detection result, the method further includes:

[0054] If the diagnostic result indicates that there is a phase-to-phase short circuit fault in the sixth position area, the isolation contactor is closed to execute the active three-phase short circuit mode for fault protection. The active three-phase short circuit mode is that both the three upper bridge arms and the three lower bridge arms of the frequency converter are conducting, so that the three-phase windings of the motor form a circuit through the frequency converter to achieve demagnetization and braking.

[0055] If the diagnostic result indicates that a phase-to-phase short-circuit fault exists in the fifth location area, the disconnected state of the isolating contactor shall be maintained for fault protection.

[0056] If the diagnostic result indicates that a phase-to-phase short-circuit fault exists in the second location area, the isolating contactor is disconnected for fault protection.

[0057] If the diagnostic result indicates no phase-to-phase short-circuit fault, a fault protection strategy is adopted for when the power device malfunctions or the inverter outputs an overcurrent.

[0058] Secondly, this application provides a phase-to-phase short-circuit fault diagnosis device, applied to a phase-to-phase short-circuit fault diagnosis system. The phase-to-phase short-circuit fault diagnosis system includes: a frequency converter and a motor. The frequency converter is connected to the motor via a three-phase line. At least two phases of the three-phase line are respectively equipped with current sensors. The device includes:

[0059] The rate of change detection module is used to determine the rate of change of current of each phase of the three-phase line based on the current signals of each current sensor when a fault is detected in the power device of the inverter or the inverter outputs an overcurrent, and to detect whether there are at least two phases whose rate of change of current is greater than the rate of change of current threshold, so as to obtain the rate of change of current detection result.

[0060] The short-circuit diagnosis module is used to diagnose phase-to-phase short-circuit faults based on the current change rate detection results, and obtain diagnosis results; wherein, the diagnosis results indicate the location of no phase-to-phase short-circuit fault or the location of a phase-to-phase short-circuit fault, and the diagnosis results are used to determine the fault protection strategy corresponding to the diagnosis results for fault protection.

[0061] Thirdly, this application provides a phase-to-phase short-circuit fault diagnosis system, comprising:

[0062] Electric motor;

[0063] The frequency converter is connected to the motor via a three-phase line, and a current sensor is respectively installed on at least two phases of the three-phase line.

[0064] A control device for performing the phase-to-phase short-circuit fault diagnosis method as described in any of the above.

[0065] Optionally, each phase of the three-phase line has a first node, and the current sensor is disposed at the first node;

[0066] The phase-to-phase short-circuit fault diagnosis system also includes an isolation contactor, which is disposed between the first node and the frequency converter or between the first node and the motor;

[0067] The motor is a permanent magnet synchronous motor.

[0068] Optionally, each phase of the three-phase line has a first node, and the current sensor is disposed at the first node; two or three voltage sensors for detecting voltage signals between different phase lines are disposed on the three-phase line, and each phase of the three-phase line has a second node located between the first node and the frequency converter, and the voltage sensor is disposed at the second node.

[0069] The phase-to-phase short-circuit fault diagnosis system also includes an isolating contactor, which is disposed between the first node and the second node or between the first node and the motor;

[0070] The motor is a permanent magnet synchronous motor.

[0071] Fourthly, this application provides an electronic device, comprising:

[0072] At least one processor; and,

[0073] A memory communicatively connected to the at least one processor; wherein,

[0074] The memory stores instructions that can be executed by the at least one processor to enable the at least one processor to perform any of the phase-to-phase short-circuit fault diagnosis methods described above.

[0075] Fifthly, this application provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the phase-to-phase short-circuit fault diagnosis method as described above.

[0076] The advantages of this application compared to the prior art are:

[0077] In the method of this application, when the power device of the frequency converter malfunctions or the frequency converter outputs an overcurrent, the fault may be caused by a phase-to-phase short circuit or not. To avoid missed detection or untimely detection of phase-to-phase short circuits, when the power device of the frequency converter malfunctions or the frequency converter outputs an overcurrent, the current change rate of the three-phase lines is further detected. If the short-circuit current passes through the current sensor, the current change rate of the current signal detected by the current sensor will be very large. Therefore, the current change rate can be detected by combining the current signal detected by the current sensor. Based on the current signals of each current sensor, the current change rate of each phase of the three-phase line is determined, and it is detected whether at least two phases have a large current change rate. By obtaining the current change rate detection result based on the current change rate threshold, and combining this result, phase-to-phase short circuit fault diagnosis can be accurately performed, yielding a diagnosis result indicating either no phase-to-phase short circuit fault or the location of a phase-to-phase short circuit fault. This avoids missed detections and false detections, and allows for the location of the phase-to-phase short circuit in the event of a fault, thus improving the accuracy of phase-to-phase short circuit fault diagnosis. The fault protection strategy corresponding to the diagnosis result is then used for fault protection, employing appropriate fault protection strategies for both the absence of a phase-to-phase short circuit fault and phase-to-phase short circuits at different locations. This avoids over-protection, reduces the impact of the fault, and improves the reliability and availability of the power system containing the motor.

[0078] It is understood that the beneficial effects of the second to fifth aspects mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here. Attached Figure Description

[0079] One or more embodiments are illustrated by way of example with reference to the accompanying drawings, and these illustrative descriptions do not constitute a limitation on the embodiments.

[0080] Figure 1 This is a schematic diagram of an application scenario for a phase-to-phase short-circuit fault diagnosis system provided in one embodiment of this application. Figure 1 ;

[0081] Figure 2 This is a schematic flowchart of a phase-to-phase short-circuit fault diagnosis method provided in one embodiment of this application. Figure 1 ;

[0082] Figure 3 This is a schematic diagram of an application scenario for a phase-to-phase short-circuit fault diagnosis system provided in one embodiment of this application. Figure 2 ;

[0083] Figure 4 This is a schematic diagram of the rate of change of current provided in another embodiment of this application. Figure 1 ;

[0084] Figure 5 This is a schematic diagram of the rate of change of current provided in another embodiment of this application. Figure 2 ;

[0085] Figure 6 This is a schematic diagram of an application scenario for a phase-to-phase short-circuit fault diagnosis system provided in one embodiment of this application. Figure 3 ;

[0086] Figure 7 This is a schematic diagram of the phase-to-phase short-circuit fault location provided in another embodiment of this application. Figure 1 ;

[0087] Figure 8 This is a schematic diagram of the operation of an active three-phase short-circuit mode provided in another embodiment of this application;

[0088] Figure 9 This is a schematic flowchart of a phase-to-phase short-circuit fault diagnosis method provided in one embodiment of this application. Figure 2 ;

[0089] Figure 10 This is a schematic diagram of the phase-to-phase short-circuit fault location provided in another embodiment of this application. Figure 2 ;

[0090] Figure 11 This is a schematic flowchart of a phase-to-phase short-circuit fault diagnosis method provided in one embodiment of this application. Figure 3 ;

[0091] Figure 12 This is a schematic diagram of the phase-to-phase short-circuit fault location provided in another embodiment of this application. Figure 3 ;

[0092] Figure 13 This is a schematic flowchart of a phase-to-phase short-circuit fault diagnosis method provided in one embodiment of this application. Figure 4 ;

[0093] Figure 14 This is a schematic diagram of the phase-to-phase short-circuit fault location provided in another embodiment of this application. Figure 4 ;

[0094] Figure 15 This is a schematic flowchart of a phase-to-phase short-circuit fault diagnosis method provided in one embodiment of this application. Figure 5 ;

[0095] Figure 16 This is a schematic diagram of a phase-to-phase short-circuit fault diagnosis device provided in another embodiment of this application. Figure 1 ;

[0096] Figure 17This is a schematic diagram of a phase-to-phase short-circuit fault diagnosis device provided in another embodiment of this application. Figure 2 ;

[0097] Figure 18 This is a schematic diagram of the structure of an electronic device provided in another embodiment of this application. Detailed Implementation

[0098] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the various embodiments of this application will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the various embodiments of this application to help readers better understand this application. However, the technical solutions claimed in this application can be implemented even without these technical details and various changes and modifications based on the following embodiments. The division of the various embodiments below is for the convenience of description and should not constitute any limitation on the specific implementation of this application. The various embodiments can be combined with and referenced by each other without contradiction.

[0099] See Figure 1 , Figure 2 and Figure 3 This embodiment provides a phase-to-phase short-circuit fault diagnosis method, applied to a phase-to-phase short-circuit fault diagnosis system. The phase-to-phase short-circuit fault diagnosis system includes: a frequency converter 104 and a motor M. The frequency converter 104 is connected to the motor M through a three-phase line. At least two phases of the three-phase line are respectively equipped with current sensors 108. The phase-to-phase short-circuit fault diagnosis method includes:

[0100] Step S201: When a fault is detected in the power device of the inverter or the inverter outputs an overcurrent, the current change rate of each phase of the three-phase line is determined based on the current signal of each current sensor, and it is detected whether there are at least two phases whose current change rate is greater than the current change rate threshold, so as to obtain the current change rate detection result.

[0101] For example, the motor in this embodiment can be a traction motor in the traction system of a rail transit vehicle, or it can be a motor in the power system of other equipment, such as a motor in the power system of equipment in the new materials industry.

[0102] Figure 1Taking the traction motor of the traction system as an example, the traction system may include a four-quadrant rectifier 102, a DC circuit 103, a frequency converter 104, an isolating contactor 105, and a motor M connected in sequence. The four-quadrant rectifier 102 draws power from the overhead contact line 101 through a transformer T and a pantograph. The transformer T is also grounded through a grounding device 107. The four-quadrant rectifier 102 converts the input electrical energy into DC power and supplies it to the DC circuit 103. The DC circuit 103 supplies the DC power to the frequency converter 104, which converts the input DC power into AC power and supplies it to the motor M through the isolating contactor 105.

[0103] In addition, the traction system also includes a chopper circuit 106 for maintaining the DC bus voltage.

[0104] Among them, the frequency converter 104 is an inverter that can use variable voltage variable frequency (VVVF) technology to convert the input DC power into AC power.

[0105] Here, the isolation contactor 105 is used to isolate the frequency converter 104 from the motor M in the event of a traction system malfunction.

[0106] The aforementioned current sensor 108 can be installed between the isolation contactor 105 and the frequency converter 104, or between the isolation contactor 105 and the motor M.

[0107] like Figure 3 As shown, in the traction converter of the traction system, the frequency converter 104 is connected to the three-phase U, V and W terminals of the motor M through a three-phase line. At least two phases of the three-phase line are respectively equipped with current sensors 108. That is to say, three current sensors 108 can be configured, or two current sensors 108 can be configured, and the current sensors 108 of each phase line constitute a current sensor system. Figure 3 The diagram illustrates the use of current sensors 108 in all three phases of the circuit, with the current sensors 108 positioned between the isolating contactor 105 and the motor M.

[0108] The phase-to-phase short-circuit fault diagnosis system may further include a control device 109, which can execute the phase-to-phase short-circuit fault diagnosis method of this embodiment. The control device 109 can receive current signals from the current sensors 108 on each phase line, can send DO commands (e.g., closing and opening commands) to the isolating contactor 105 to control the opening and closing of the isolating contactor 105, and can also send pulse width modulation (PWM) pulse signals to the frequency converter 104 to control the operation of the frequency converter 104, causing the frequency converter 104 to output current.

[0109] The aforementioned control device 109 can be an added control device or an existing vehicle control device, such as a transmission control device.

[0110] The frequency converter 104 has a power device fault detection function, which can detect whether a power device has malfunctioned. When a power device fault is detected, a power device fault signal is issued. The control device can determine that a power device fault has been detected in the frequency converter when a power device fault signal is detected. For example, a power device fault could be an overcurrent fault. The frequency converter's drive board has a corresponding drive stage overcurrent protection function for the power device. When an overcurrent occurs in the power device, an overcurrent fault signal (e.g., a high-level signal or a low-level signal) can be issued and overcurrent protection can be performed.

[0111] For example, inverter 104 includes three phase arms connected in parallel, each phase arm including an upper arm and a lower arm, both the upper and lower arms including a switching transistor. See also Figure 3 The frequency converter 104 includes a first switch V1, a second switch V2, a third switch V3, a fourth switch V4, a fifth switch V5, and a sixth switch V6. The first switch V1, the third switch V3, and the fifth switch V5 are located on the upper arm of each phase bridge arm, while the second switch V2, the fourth switch V4, and the sixth switch V6 are located on the lower arm of each phase bridge arm.

[0112] For example, the overcurrent detection method of inverter 104 output includes:

[0113] The instantaneous current value of each phase of the three-phase circuit is obtained based on the current signals from each current sensor 108. The instantaneous current value of each phase is compared with a fourth threshold. When the instantaneous current value of any phase is greater than the fourth threshold, it is determined that the inverter 104 outputs an overcurrent. The fourth threshold can be set according to actual needs and is not specifically limited here.

[0114] Specifically, obtaining the instantaneous current value of each phase of the three-phase line based on the current signals of each current sensor 108 can include: when current sensors 108 are installed in all three phases, obtaining the instantaneous current value of each phase line based on the current signals of the current sensors 108 in each phase line; when current sensors 108 are installed in two phases, obtaining the instantaneous current value of the two phases based on the current signals of the current sensors 108 in the two phases, and obtaining the instantaneous current value of the other phase line based on the rule that the sum of the instantaneous current values ​​of the three phases is zero.

[0115] When a fault is detected in the power device of the inverter 104 or an overcurrent is detected in the inverter 104 output, the current change rate of each phase of the three-phase line is determined based on the current signals of each current sensor 108. Specifically, the instantaneous current value of each phase line can be obtained based on the current signals of each current sensor 108. For each phase line, the current change rate di / dt is obtained based on the ratio of the difference between the current instantaneous current value and the previous instantaneous current value to the amount of time change.

[0116] When the rate of change of current di / dt exceeds the threshold value K0, it indicates that the rate of change of current is too large, potentially indicating a phase-to-phase short circuit. The specific value of K0 can be obtained through a real phase-to-phase short circuit simulation test. K0 is greater than the rate of change of current under overcurrent conditions caused by control anomalies or motor grounding, because in overcurrent caused by control anomalies or motor grounding, the current flows through the motor windings, and the current change is not very large. However, in a phase-to-phase short circuit, the current does not flow through the motor windings, resulting in a very large current change. See also... Figure 4 and Figure 5 The diagram shown is a schematic of di / dt. Figure 4 It is di / dt during phase-to-phase short circuit. Figure 5 This diagram illustrates the di / dt ratio when overcurrent occurs due to abnormal control or motor grounding. It shows that di / dt is larger during phase-to-phase short circuits.

[0117] Step S202: Perform phase-to-phase short-circuit fault diagnosis based on the current change rate detection results to obtain the diagnosis results; wherein, the diagnosis results indicate the location of no phase-to-phase short-circuit fault or the location of phase-to-phase short-circuit fault, and the diagnosis results are used to determine the fault protection strategy corresponding to the diagnosis results for fault protection.

[0118] Different diagnostic results are assigned corresponding fault protection strategies to match the diagnostic results. This avoids applying stringent fault protection strategies to all faults, thus improving the reliability and availability of the power system containing the motor.

[0119] In this embodiment, when the power devices of the frequency converter malfunction or the frequency converter outputs an overcurrent, the fault may be caused by a phase-to-phase short circuit, or it may not be caused by a phase-to-phase short circuit. To avoid missed detection of phase-to-phase short circuits or untimely detection, when the power devices of the frequency converter malfunction or the frequency converter outputs an overcurrent, the current change rate of the three-phase lines is further detected. If the short-circuit current passes through the current sensor, the current change rate of the current signal detected by the current sensor will be very large. Therefore, the current change rate can be detected by combining the current signal detected by the current sensor. Based on the current signals of each current sensor, the current change rate of each phase of the three-phase line is determined, and it is detected whether at least two phases have a large current change rate. By obtaining the current change rate detection result based on the current change rate threshold, accurate phase-to-phase short circuit fault diagnosis can be performed. The diagnosis result indicates whether there is no phase-to-phase short circuit fault or the location of the phase-to-phase short circuit fault. This avoids missed detections and false detections, and can pinpoint the location of the phase-to-phase short circuit fault, thereby improving the accuracy of phase-to-phase short circuit fault diagnosis. Fault protection strategies corresponding to the diagnosis results are then used for fault protection. Appropriate fault protection strategies are adopted for the absence of phase-to-phase short circuit faults and phase-to-phase short circuits at different locations, avoiding over-protection, reducing the impact of the fault, and improving the reliability and availability of the power system containing the motor.

[0120] For example, the motor can be a permanent magnet synchronous motor or an asynchronous motor.

[0121] In some embodiments, each phase of the three-phase line has a first node, and a current sensor is disposed at the first node; the motor is a permanent magnet synchronous motor.

[0122] Accordingly, based on the current change rate detection results, phase-to-phase short-circuit fault diagnosis is performed, and the diagnostic results are obtained, including:

[0123] If, when the inverter stops operating due to the blocking pulse, the current change rate detection result shows that the current change rate of at least two phases is greater than the current change rate threshold, a phase-to-phase short circuit fault is determined to exist in the first location area. The first location area includes the motor body and the area between the motor and the first node.

[0124] If the current change rate detection result indicates that there are no two phases where the current change rate is greater than the current change rate threshold, the sum of the instantaneous current values ​​and the effective current values ​​of each phase of the three-phase circuit are obtained based on the current signals from each current sensor. Based on the output current of the inverter, the sum of the instantaneous current values ​​of each phase, and the effective current values ​​of each phase, it is determined whether the phase-to-phase short-circuit current characteristics are met, and a first judgment result is obtained. The phase-to-phase short-circuit current characteristics include: the inverter is not outputting current, the sum of the instantaneous current values ​​of each phase is less than the first threshold, the maximum value of the effective current values ​​of each phase is greater than the second threshold, and the ratio of the minimum to the maximum value of the effective current values ​​of each phase is less than the third threshold.

[0125] If the first judgment result is that the phase-to-phase short-circuit current characteristics are met, it is determined that there is a phase-to-phase short-circuit fault in the second location area. The second location area includes the area between the first node and the frequency converter.

[0126] If the first judgment result is that the phase-to-phase short-circuit current characteristics are not met, it is determined that there is no phase-to-phase short-circuit fault.

[0127] Among them, the phase-to-phase short-circuit current characteristic is the current characteristic corresponding to the current signal of each current sensor 108 and the output current of the frequency converter 104 when a phase-to-phase short circuit exists.

[0128] The first nodes of each phase are set up side by side. In the case of two current sensors, for the phase line in the three-phase line that does not have a current sensor, the instantaneous current value of the phase line is obtained from the instantaneous current values ​​of the two phase lines with current sensors, which is the instantaneous current value of the first node. Correspondingly, the current change rate of the phase line is the current change rate of the first node.

[0129] In practical applications, when a phase-to-phase short-circuit fault occurs, if the short-circuit point (i.e., the location of the phase-to-phase short circuit) is located between the current sensor and motor M, i.e., in the first position region, it can be detected by the rate of change of current. If the short-circuit point is located between the current sensor and the inverter, the short-circuit current does not flow through the current sensor, making it impossible to accurately diagnose the characteristic of an excessively large rate of change of current. However, due to the existence of the motor's back electromotive force, there will be a characteristic that the short-circuit phase current is large, while the non-short-circuit phase current is zero or small. Therefore, extracting this characteristic can support the accurate location of phase-to-phase short-circuit faults.

[0130] When a power device in the frequency converter malfunctions or experiences an output overcurrent, a corresponding protection strategy (i.e., fault protection strategy) is triggered, causing the frequency converter to stop working by blocking the pulse; that is, the frequency converter does not start and does not output current. Therefore, the characteristic of phase-to-phase short-circuit current can include the frequency converter not outputting current.

[0131] If a ground fault occurs, there may be a situation where the rate of change of current is too large. To improve diagnostic accuracy, ground fault interference can be ruled out. The sum of the instantaneous values ​​of the three-phase currents is close to zero, indicating no ground fault characteristic. Therefore, the characteristics of the phase-to-phase short-circuit current can include the sum of the instantaneous current values ​​of each phase line being less than the first threshold K1, i.e., Ia + Ib + Ic < K1. Ia, Ib, and Ic are the instantaneous current values ​​of the three-phase lines, respectively. K1 should be a value close to zero, but sampling error needs to be considered.

[0132] The effective current value of a three-phase line is relatively large, and phase-to-phase short circuits may occur. Therefore, the phase-to-phase short circuit current characteristics can include the maximum effective current value of each phase line being greater than the second threshold K2, i.e., the maximum value Iram_Max(Ia, Ib, Ic) > K2. K2 is a relatively large current threshold, and its specific value can be obtained by combining actual short-circuit tests.

[0133] When the motor speed is low, the back electromotive force of the motor is small (the peak value is less than the DC voltage on the input side of the inverter 104), and the current of the non-short-circuit phase is close to zero. When the motor speed is high, the back electromotive force of the motor is large (the peak value is greater than the DC voltage on the input side of the inverter 104), and there is a certain current in the non-short-circuit phase, but it is less than the current in the short-circuit phase. Therefore, the characteristics of the phase-to-phase short-circuit current can include the ratio of the minimum to the maximum effective value of the current in the three-phase line being less than the third threshold K3, that is, the minimum value Iram_Min(Ia, Ib, Ic) / the maximum value Iram_Max(Ia, Ib, Ic) < K3.

[0134] The third threshold can be a fixed threshold or determined based on the motor's current speed. It can be obtained through actual phase-to-phase short-circuit tests, and can be set as a fixed threshold. Alternatively, it can be set as a variable threshold F(v) related to the motor's back electromotive force and speed characteristics. The relationship between the speed and the third threshold F(v) can be preset, and the current third threshold can be obtained by applying this relationship to the motor's current speed. In this way, by dynamically setting the third threshold, it can be matched with the influence of the back electromotive force corresponding to the current speed on the current, further improving the accuracy of phase-to-phase short-circuit fault diagnosis.

[0135] If the current phase-to-phase short-circuit current characteristics are met, it indicates that a phase-to-phase short-circuit fault exists in the second location region, which includes the area between the first node and the inverter. If the current phase-to-phase short-circuit current characteristics are not met, it indicates that there is no phase-to-phase short-circuit fault, but rather an inverter output overcurrent fault or a power device failure.

[0136] Taking the control device as an example of a transmission control device, such as Figure 6As shown, the drive control device includes a frequency converter control unit, a digital processing unit, a signal processing unit, and a logic processing unit. Each unit can be an independent board or multiple units can be integrated into one board. The overall functions of each unit are as follows:

[0137] Inverter control unit: Inverter pulse control. In normal mode, it can receive start commands for motor traction and braking control. In phase-to-phase short circuit mode, it can control the inverter to enter protection mode. It also has phase-to-phase short circuit feature extraction and overcurrent protection functions.

[0138] Digital processing unit: Controls the closing and opening of the isolating contactor and monitors its closing and opening states.

[0139] Signal processing unit: It has the signal processing functions of inverter status (whether the power device has failed) and current sensor system.

[0140] Logic processing unit: phase-to-phase short circuit fault diagnosis, timing control, and protection functions for the power system containing the motor.

[0141] Based on the above control device, a phase-to-phase short-circuit fault diagnosis method can be implemented. Specifically:

[0142] The signal processing unit receives current signals from the current sensor system and power device fault signals emitted by the inverter when power devices malfunction. Based on the current signals from each current sensor, it detects whether the inverter is outputting overcurrent, and based on the power device fault signals, it determines that a power device has malfunctioned. When a power device fault or an overcurrent is detected in the inverter, it determines the rate of change of current for each phase based on the current signals from each current sensor, and checks whether at least two phases have a rate of change of current exceeding a current rate of change threshold (i.e., the rate of change of current is too large), thus obtaining the current rate of change detection result.

[0143] The signal processing unit can obtain the motor speed by acquiring the motor speed signal and provide it to the frequency converter control unit. The frequency converter control unit can obtain the current motor speed based on this speed, and obtain the current third threshold by comparing the current motor speed with the above relationship.

[0144] The inverter control unit can determine whether the current condition meets the phase-to-phase short-circuit current characteristics to obtain the first judgment result.

[0145] The logic processing unit can integrate signals from the signal processing unit, inverter controller unit, and digital processing unit, such as power device fault signals, excessive current change rate, inverter output overcurrent fault, first judgment result of whether the phase-to-phase short circuit current characteristics are met, and the closing status of the isolation contactor, to diagnose phase-to-phase short circuit faults.

[0146] In this embodiment, with each phase of the three-phase circuit having a first node, and a current sensor installed at the first node, and the motor being a permanent magnet synchronous motor, when the power device of the inverter malfunctions or the inverter outputs an overcurrent, the overcurrent fault may be caused by a phase-to-phase short circuit, or it may not be caused by a phase-to-phase short circuit. To avoid missed detection of phase-to-phase short circuits or untimely detection, when the power device of the inverter malfunctions or the inverter outputs an overcurrent, the current change rate of the three-phase circuit is further detected. If the short-circuit current passes through the current sensor, the current change rate of the current signal detected by the current sensor will be very large. Therefore, the current change rate can be detected by combining the current signal detected by the current sensor, and the phase-to-phase short circuit fault can be diagnosed by combining this current change rate. However, if the short circuit point is located between the current sensor and the inverter, and the short circuit current does not flow through the current sensor, it cannot be accurately diagnosed by the current change rate. Therefore, when the inverter stops working due to the blocking pulse, the current signals of each current sensor, the output current of the inverter, and the preset phase-to-phase short circuit current characteristics are further combined to diagnose phase-to-phase short circuit faults. The current signals of the current sensors of each phase line and the output current of the inverter can comprehensively reflect the current situation at different locations. Combined with the phase-to-phase short circuit current characteristics, the phase-to-phase short circuit fault diagnosis can be accurately performed to obtain the diagnosis result, avoiding missed detections and false detections. Furthermore, it can further realize the accurate location of phase-to-phase short circuit faults, thereby further improving the accuracy of phase-to-phase short circuit fault diagnosis.

[0147] The applicant discovered the following main points regarding the location and cause of the phase-to-phase short circuit:

[0148] I. Stator winding phase-to-phase short circuit of the motor body: usually caused by the degradation and thinning of weak points (single point) in the inter-turn insulation layer, which leads to a gradual decrease in its equivalent resistance. Under the continuous application of the four types of failure stresses (electric, thermal, mechanical and environmental), it further expands into the failure modes of grounding, inter-turn short circuit and phase-to-phase short circuit.

[0149] 2. Short circuit between phases in the terminal block of the motor: This is usually caused by foreign objects bridging or abnormal insulation.

[0150] 3. Phase-to-phase short circuit in the output cabinet wiring terminals of the frequency converter: This is usually caused by foreign objects bridging or abnormal insulation.

[0151] IV. Short circuit between phases of the main contacts or the front and rear terminals of the main contacts of the isolating contactor: This is usually caused by foreign objects bridging or abnormal insulation.

[0152] A phase-to-phase short circuit can lead to a higher short-circuit voltage, a larger torque surge, and torque pulsation.

[0153] To further accurately diagnose the location of phase-to-phase short circuits and reduce adverse effects, the relative positions of current sensors and isolating contactors can be combined for phase-to-phase short circuit fault diagnosis, thereby covering all phase-to-phase short circuit locations as completely as possible. The following sections introduce the phase-to-phase short circuit fault diagnosis methods under two different settings.

[0154] In some embodiments, such as Figure 7 As shown, the phase-to-phase short-circuit fault diagnosis system also includes an isolating contactor 105, which is disposed between the first node and the frequency converter 104.

[0155] Accordingly, determining that a phase-to-phase short-circuit fault exists in the second location area includes:

[0156] Disconnect the isolating contactor, and based on the inverter's output current, the sum of the instantaneous current values ​​of each phase line, and the effective current value of each phase line, determine whether the current condition meets the characteristics of a phase-to-phase short-circuit current, and obtain the second judgment result.

[0157] If the second judgment result satisfies the phase-to-phase short circuit current characteristics, it is determined that there is a phase-to-phase short circuit fault in the third location area ③. The third location area ③ includes the line between the isolating contactor 105 and the first node, as well as the contacts of the isolating contactor 105 near the first node.

[0158] If the second judgment result is that the phase-to-phase short circuit current characteristics are not met, it is determined that there is a phase-to-phase short circuit fault in the fourth position area ④. The fourth position area ④ includes the line between the isolation contactor 105 and the frequency converter 104 and the contacts of the isolation contactor 105 near the frequency converter 104.

[0159] The second position region includes the third position region ③ and the fourth position region ④.

[0160] When the isolating contactor 105 is disconnected, the motor has a back electromotive force for the current sensor 108, which can act as a power source. If the phase-to-phase short-circuit current characteristics are met at this time, it indicates that there is a phase-to-phase short-circuit fault at the position from the isolating contactor 105 to the first node, i.e., the third position region ③. If the phase-to-phase short-circuit current characteristics are not met, it indicates that there is a phase-to-phase short-circuit fault at the position from the isolating contactor 105 to the inverter 104, i.e., the fourth position region ④. In this way, by controlling the disconnection of the isolating contactor 105 and combining it with the phase-to-phase short-circuit current characteristics, the location of the phase-to-phase short-circuit fault is further accurately located.

[0161] In this embodiment, for the case where the isolation contactor 105 is located between the first node and the frequency converter, by controlling the disconnection of the isolation contactor and combining the phase-to-phase short circuit current characteristics, the location of the phase-to-phase short circuit is further accurately located, thereby improving the accuracy of phase-to-phase short circuit fault diagnosis.

[0162] In some embodiments, after obtaining the diagnosis result by performing phase-to-phase short-circuit fault diagnosis based on the current change rate detection result, the method further includes:

[0163] If the diagnosis result indicates that there is a phase-to-phase short circuit fault in the first position area, the active three-phase short circuit mode is executed for fault protection. The active three-phase short circuit mode is that the three-phase upper bridge arm or the three-phase lower bridge arm of the inverter 104 is turned on, so that the three-phase windings of the motor form a circuit through the inverter 104 to achieve demagnetization and braking.

[0164] If the diagnosis indicates a phase-to-phase short-circuit fault in the third location area, close the isolating contactor 105 and execute the active three-phase short-circuit mode for fault protection.

[0165] If the diagnosis indicates a phase-to-phase short-circuit fault in the fourth position area, the isolating contactor 105 shall be kept in the open state for fault protection.

[0166] If the diagnosis result indicates no phase-to-phase short circuit fault, a fault protection strategy is adopted for power device failure or inverter 104 output overcurrent.

[0167] See Figure 8 Taking the upper bridge arm of inverter 104 as an example, in active three-phase short circuit mode, the three-phase upper bridge arm (i.e., all upper bridge arms of the three-phase bridge arm) or the three-phase lower bridge arm (i.e., all lower bridge arms of the three-phase bridge arm) of inverter 104 are turned on, so that the three-phase windings of motor M form a low-impedance circuit through inverter 104 to achieve demagnetization and braking, thereby reducing the phase-to-phase short circuit current and realizing phase-to-phase short circuit fault protection. Figure 8 In this context, Z represents the equivalent impedance of the motor. For example... Figure 6 As shown, the logic processing unit can issue an active three-phase short-circuit mode command to enable the inverter control unit to control the inverter to enter the active three-phase short-circuit mode. It can also synchronize the active three-phase short-circuit mode to other control units of the vehicle through the network control system for adaptive control.

[0168] For a vehicle, the traction system can include multiple motors. After the motor experiencing a phase-to-phase short circuit fault is isolated, the vehicle can continue to operate using other motors. Therefore, by maintaining the disconnected state of the isolating contactor 105, the vehicle can continue to travel under this protection strategy and simply return to the depot for processing.

[0169] In this embodiment, different protection measures are adopted according to the location of different phase-to-phase short-circuit faults, thereby improving system reliability and availability. For short circuits from the rear end of the isolating contactor 105 to the motor body, a novel active three-phase short-circuit mode is proposed. This mode effectively protects against phase-to-phase short-circuit faults by forming a low-impedance circuit through the inverter 104, enabling rapid demagnetization and braking, and avoiding the negative impact of phase-to-phase short circuits on the power system containing the motor. If the phase-to-phase short circuit is located between the isolating contactor 105 and the inverter 104, the short circuit can be quickly disconnected from the motor and the isolating contactor 105, thus avoiding the need to enter the active three-phase short-circuit mode. For the vehicle containing the motor, there is no need for speed reduction, reducing the impact of the fault on vehicle operation and improving vehicle safety and system availability.

[0170] The phase-to-phase short-circuit fault diagnosis method of this embodiment will be described in more detail below, taking the isolation contactor 105 set between the first node and the frequency converter 104 as an example.

[0171] In this embodiment, the motor is the traction motor of the vehicle's traction system. For example... Figure 9 As shown, after starting the operation, an initial judgment is performed. A flag indicating excessive current change rate can be pre-set to store the current change rate detection results. This flag is valid only when the current change rate of at least two phases exceeds the current change rate threshold; otherwise, it is invalid. Similarly, a flag corresponding to the phase-to-phase short-circuit current characteristics can be pre-set to store the judgment results regarding whether the phase-to-phase short-circuit current characteristics are met. This flag is valid when the phase-to-phase short-circuit current characteristics are met; otherwise, it is invalid. The specific process of the initial judgment is as follows:

[0172] When an overcurrent is detected at the inverter output or a fault in a power device, the validity of the flag indicating an excessive rate of change of current is checked. If valid, the phase-to-phase short-circuit location diagnosis indicates a phase-to-phase short-circuit fault exists in the first location region ①, and the corresponding fault protection action (i.e., the action corresponding to the fault protection strategy) is to execute the active three-phase short-circuit mode. If invalid, the validity of the flag corresponding to the phase-to-phase short-circuit current characteristic is checked again. If invalid, the phase-to-phase short-circuit location diagnosis indicates an overcurrent fault not caused by a phase-to-phase short circuit or an overcurrent fault in a power device, i.e., only an overcurrent at the inverter output or a fault in a power device, without a phase-to-phase short-circuit fault. The corresponding fault protection action is to adopt the protection strategy for when the inverter output is overcurrent or a power device is faulty (the existing protection strategy).

[0173] If the flag corresponding to the phase-to-phase short-circuit current characteristic is valid, further timing adjustments are required. Specifically, the isolating contactor 105 can be disconnected to further determine if the flag corresponding to the phase-to-phase short-circuit current characteristic is valid. If the flag corresponding to the phase-to-phase short-circuit current characteristic is valid, the phase-to-phase short-circuit position diagnosis result indicates a phase-to-phase short-circuit fault in the third position area ③. The corresponding fault protection action is to close the isolating contactor 105 and execute the active three-phase short-circuit mode. If the flag corresponding to the phase-to-phase short-circuit current characteristic is invalid, the phase-to-phase short-circuit position diagnosis result indicates a phase-to-phase short-circuit fault in the fourth position area ④. The corresponding fault protection action is to maintain the disconnected state of the isolating contactor 105; no stringent protection action is required. The vehicle can continue driving and return to the depot for processing.

[0174] The diagnosis is now complete.

[0175] In some embodiments, such as Figure 10 As shown, the phase-to-phase short circuit fault diagnosis system also includes an isolating contactor 105, which is disposed between the first node and the motor.

[0176] Accordingly, determining that a phase-to-phase short-circuit fault exists in the first location area includes:

[0177] Disconnect the isolating contactor 105 and start the frequency converter 104 to output test pulses;

[0178] When the inverter 104 outputs a test pulse, it is determined whether there is still a power device failure or an overcurrent in the inverter 104 output, and whether the current change rate of at least two phases is greater than the current change rate threshold. If so, it is determined that there is a phase-to-phase short circuit fault in the fifth position area ⑤, which includes the line between the isolating contactor 105 and the first node, as well as the contacts of the isolating contactor 105 near the first node. Otherwise, it is determined that there is a phase-to-phase short circuit fault in the sixth position area ⑥, which includes the line between the isolating contactor 105 and the motor, the contacts of the isolating contactor 105 near the motor, and the motor body.

[0179] The first position area includes the fifth position area ⑤ and the sixth position area ⑥.

[0180] When the isolating contactor 105 is disconnected, the connection between the motor and the current sensor 108 is severed. The inverter 104's pulse is blocked, and the current sensor 108 cannot detect current. At this time, the inverter 104 can be started to output a test pulse. When the inverter 104 outputs a test pulse, current flows through the current sensor 108. It is determined whether there is still a power device fault or an overcurrent in the inverter 104 output, and whether the current change rate of at least two phases is greater than the current change rate threshold. If so, it indicates a phase-to-phase short circuit fault at the position from the first node to the isolating contactor 105, i.e., the fifth position area ⑤. Otherwise, it indicates a phase-to-phase short circuit fault at the position from the isolating contactor 105 to the motor M, i.e., the sixth position area ⑥.

[0181] In this embodiment, for the case where the isolating contactor 105 is located between the first node and the motor, the inverter 104 is controlled to send test pulses, and the location of the phase-to-phase short circuit is further accurately located by combining the current change rate, thereby improving the accuracy of phase-to-phase short circuit fault diagnosis.

[0182] In some embodiments, phase-to-phase short-circuit fault diagnosis is performed based on the current change rate detection result. After obtaining the diagnosis result, the method further includes:

[0183] If the diagnosis result indicates that there is a phase-to-phase short circuit fault in the sixth position area, close the isolation contactor 105 to execute the active three-phase short circuit mode for fault protection. The active three-phase short circuit mode is that the three-phase upper bridge arm or the three-phase lower bridge arm of the inverter 104 is conducting, so that the three-phase windings of the motor form a circuit through the inverter 104 to achieve demagnetization and braking.

[0184] If the diagnosis indicates a phase-to-phase short-circuit fault in the fifth position area, the isolating contactor 105 shall be kept in the open state for fault protection.

[0185] If the diagnosis indicates a phase-to-phase short-circuit fault in the second location area, disconnect the isolating contactor 105 for fault protection.

[0186] If the diagnosis result indicates no phase-to-phase short circuit fault, a fault protection strategy is adopted for power device failure or inverter 104 output overcurrent.

[0187] For details on the active three-phase short-circuit mode, please refer to the above-mentioned relevant embodiments, which will not be repeated here.

[0188] In this embodiment, different protection measures are adopted according to different short-circuit locations, improving system reliability and availability. For short circuits from the rear end of the isolating contactor 105 to the motor body, a novel active three-phase short-circuit mode is proposed. This mode effectively protects against phase-to-phase short-circuit faults, enabling the motor's three-phase windings to form a low-impedance circuit through the frequency converter 104, achieving rapid demagnetization and braking, and avoiding the negative impact of phase-to-phase short circuits on the power system where the motor is located. If the phase-to-phase short circuit is located between the isolating contactor 105 and the frequency converter 104, the short circuit location can be separated from the motor body by quickly disconnecting the motor and the isolating contactor 105, thus avoiding the need to enter the active three-phase short-circuit mode. For the vehicle where the motor is located, the vehicle does not need to reduce speed, reducing the impact of the fault on vehicle operation and improving vehicle safety and system availability.

[0189] The phase-to-phase short-circuit fault diagnosis method of this embodiment will be described in more detail below, taking the isolation contactor 105 installed between the first node and the motor as an example.

[0190] In this embodiment, the motor is the traction motor of the vehicle's traction system. For example... Figure 11 As shown, after starting the operation, an initial judgment is performed. A flag indicating excessive current change rate can be pre-set to store the current change rate detection results. This flag is valid only when the current change rate of at least two phases exceeds the current change rate threshold; otherwise, it is invalid. Similarly, a flag corresponding to the phase-to-phase short-circuit current characteristics can be pre-set to store the judgment results regarding whether the phase-to-phase short-circuit current characteristics are met. This flag is valid when the phase-to-phase short-circuit current characteristics are met; otherwise, it is invalid. The specific process of the initial judgment is as follows:

[0191] When an overcurrent is detected at the inverter output or a power device fault is detected, the validity of the flag indicating an excessive rate of change of current is determined. If invalid, the validity of the flag corresponding to the phase-to-phase short-circuit current characteristic is further determined. If the flag corresponding to the phase-to-phase short-circuit current characteristic is valid, the phase-to-phase short-circuit location diagnosis result indicates a phase-to-phase short-circuit fault in the second location region ②, and the corresponding fault protection action is to disconnect the isolating contactor 105. If the flag corresponding to the phase-to-phase short-circuit current characteristic is invalid, the phase-to-phase short-circuit location diagnosis result indicates an overcurrent fault or power device fault not caused by a phase-to-phase short circuit, i.e., only an overcurrent at the inverter 104 output or a power device fault occurs, without a phase-to-phase short-circuit fault, and the corresponding fault protection action is to adopt the protection strategy for when the inverter 104 output is overcurrent or a power device fault occurs (the existing protection strategy).

[0192] When the excessive current change rate indicator is valid, further timing adjustments are required for further evaluation. Specifically, the isolating contactor 105 can be disconnected, and the inverter 104 can be started to output test pulses to further determine whether the excessive current change rate indicator is valid. If the excessive current change rate indicator is valid, the phase-to-phase short circuit position diagnosis result indicates a phase-to-phase short circuit fault in the fifth position area ⑤, and the corresponding fault protection action is to maintain the disconnected state of the isolating contactor 105. If the excessive current change rate indicator is invalid, the phase-to-phase short circuit position diagnosis result indicates a phase-to-phase short circuit fault in the sixth position area ⑥, and the corresponding fault protection action is to close the isolating contactor 105 and execute the active three-phase short circuit mode.

[0193] The diagnosis is now complete.

[0194] In addition to current sensors, phase-to-phase short-circuit fault diagnosis systems can also be equipped with voltage sensors. Based on this, phase-to-phase short-circuit fault diagnosis can be further combined with voltage sensors. The following is a detailed introduction through examples.

[0195] In some embodiments, such as Figure 12 and Figure 14 As shown, each phase of the three-phase line has a first node, and a current sensor 108 is installed at the first node; two or three voltage sensors 110 are installed on the three-phase line to detect the voltage signal between different phases; each phase of the three-phase line has a second node located between the first node and the frequency converter 104, and a voltage sensor 110 is installed at the second node; the motor is a permanent magnet synchronous motor. Figure 12 and Figure 14 The diagram shows three voltage sensors 110 installed in the middle.

[0196] Accordingly, based on the current change rate detection results, phase-to-phase short-circuit fault diagnosis is performed, and the diagnostic results are obtained, including:

[0197] If the inverter 104 stops working due to the blocking pulse, and the current change rate detection result shows that the current change rate of at least two phases is greater than the current change rate threshold, it is determined that there is a phase-to-phase short circuit fault in the first location area. The first location area includes the motor body and the area between the motor and the first node.

[0198] If the current change rate detection result is that there are no two phases where the current change rate is greater than the current change rate threshold, the voltage value between each pair of phases of the three-phase line is obtained based on the voltage signal of each voltage sensor 110, and the presence of a phase-to-phase short circuit fault in the second location area is determined based on the voltage value between each pair of phases of the three-phase line. The second location area includes the area between the first node and the inverter 104.

[0199] The first nodes of each phase line are set up side by side.

[0200] The second nodes between each phase line are arranged side by side. Voltage sensors 110 are connected between the second nodes of corresponding two-phase lines. The voltage value between each pair of phase lines of the three-phase line is obtained based on the voltage signals of each voltage sensor 110. Specifically, this can include: when three voltage sensors 110 are set, obtaining the voltage value between each pair of phase lines based on the voltage signals of each voltage sensor 110; when two voltage sensors 110 are set, obtaining the voltage value between two pairs of phase lines based on the voltage signals of the two voltage sensors 110, and obtaining the voltage value between the third pair of phase lines based on the obtained voltage values ​​between the two pairs of phase lines.

[0201] In practical applications, when a phase-to-phase short-circuit fault occurs, if the short-circuit point is located between the current sensor 108 and the motor M, i.e., in the first position region, it can be detected by the rate of change of current. If the short-circuit point is located between the current sensor 108 and the inverter 104, the short-circuit current does not flow through the current sensor 108, making it impossible to accurately diagnose the characteristic of excessive current change rate. Therefore, in this embodiment, voltage-assisted diagnosis is further used.

[0202] In this embodiment, with each phase of the three-phase line having a first node, and the current sensor 108 being installed at the first node, and the motor M being a permanent magnet synchronous motor, two or three voltage sensors 110 are installed on the three-phase line to detect voltage signals between different phases. Each phase of the three-phase line also has a second node located between the first node and the inverter 104, with the voltage sensor 110 installed at the second node. When a power device of the inverter 104 malfunctions or the inverter 104 outputs an overcurrent, the overcurrent fault may be caused by a phase-to-phase short circuit or not. To avoid missed detection of phase-to-phase short circuits or untimely detection, when a power device of the inverter 104 malfunctions or the inverter 104 outputs an overcurrent, the current of the three-phase line is further measured. For phase-to-phase short circuit fault diagnosis, if the short-circuit current passes through the current sensor 108, the rate of change of the current signal detected by the current sensor 108 will be very large. Therefore, the rate of change of current can be detected by combining the current signal detected by the current sensor 108 with the current change rate. However, if the short circuit point is located between the current sensor 108 and the inverter 104, and the short-circuit current does not flow through the current sensor 108, it cannot be accurately diagnosed by the rate of change of current. The voltage signals of each voltage sensor 110 can be further combined to diagnose the phase-to-phase short circuit fault. This can accurately diagnose the phase-to-phase short circuit fault and obtain the diagnostic results, avoiding missed detections and false detections. It can also further realize the accurate location of the phase-to-phase short circuit fault, thereby further improving the accuracy of phase-to-phase short circuit fault diagnosis.

[0203] To further accurately diagnose the location of phase-to-phase short circuits and reduce adverse effects, the relative positions of current sensors and isolating contactors can be combined for phase-to-phase short circuit fault diagnosis, thereby covering all phase-to-phase short circuit locations as completely as possible. The following sections introduce the phase-to-phase short circuit fault diagnosis methods under two different settings.

[0204] In some embodiments, such as Figure 12 As shown, the phase-to-phase short-circuit fault diagnosis system also includes an isolating contactor 105, which is disposed between the first node and the second node.

[0205] Accordingly, determining whether a phase-to-phase short-circuit fault exists in the second location area based on the voltage values ​​between every two phases of the three-phase line includes:

[0206] Based on the voltage values ​​between every two phases of the three-phase line, it is determined whether at least one phase-to-phase short-circuit voltage characteristic exists, and a third judgment result is obtained; wherein, the phase-to-phase short-circuit voltage characteristics include: when the inverter 104 is in operation, the voltage value drops from the normal value to below the voltage threshold; after the inverter 104 is started from the shutdown state, the voltage value remains zero and the current sensor 108 of the corresponding two phase lines experiences overcurrent;

[0207] If the third judgment result is negative, it is determined that there is no phase-to-phase short circuit fault in the second location area;

[0208] If the third judgment result is yes, disconnect the isolation contactor 105 and start the inverter 104 to output test pulses; when the inverter 104 outputs test pulses, determine whether at least one phase-to-phase short-circuit voltage characteristic still exists, and obtain the fourth judgment result;

[0209] If the fourth judgment result is negative, it is determined that there is a phase-to-phase short circuit fault in the third position area ③. The third position area ③ includes the line between the isolating contactor 105 and the first node, as well as the contacts of the isolating contactor 105 near the first node.

[0210] If the fourth judgment result is yes, it is determined that there is a phase-to-phase short circuit fault in the fourth position area ④. The fourth position area ④ includes the line between the isolation contactor 105 and the frequency converter 104, as well as the contacts of the isolation contactor 105 near the frequency converter 104.

[0211] The second position region includes the third position region ③ and the fourth position region ④.

[0212] Among the aforementioned phase-to-phase short-circuit voltage characteristics, when the inverter 104 is operating, the voltage value drops from the normal value to below the voltage threshold, indicating that the voltage value drops to zero, reflecting the voltage characteristics during a phase-to-phase short circuit. When the inverter 104 starts from a stopped state, if a phase-to-phase short circuit occurs, the voltage between two phases will be zero, and the current sensor 108 will experience overcurrent. Therefore, the phase-to-phase short-circuit voltage characteristics described above can be used for phase-to-phase short-circuit fault diagnosis.

[0213] The current sensor 108 is overcurrent when the instantaneous current value of the current sensor 108 is greater than the preset current threshold.

[0214] Specifically, it is determined whether at least one phase-to-phase short-circuit voltage characteristic occurs, that is, whether at least one of the following two phase-to-phase short-circuit voltage characteristics occurs: when the inverter 104 is in operation, the voltage value drops from the normal value to below the voltage threshold, and after the inverter 104 is started from the shutdown state, the voltage value remains zero and the current sensor 108 of the corresponding two phase lines experiences overcurrent.

[0215] In this embodiment, for the case where the isolating contactor 105 is located between the first node and the second node, by controlling the disconnection of the isolating contactor 105, the inverter 104 is started to output test pulses. Combined with the phase-to-phase short circuit voltage characteristics, the location of the phase-to-phase short circuit is further accurately located, thereby improving the accuracy of phase-to-phase short circuit fault diagnosis.

[0216] Based on this, phase-to-phase short-circuit fault diagnosis is performed based on the current change rate detection results. After obtaining the diagnosis results, the following steps are also included:

[0217] If the diagnosis result indicates that there is a phase-to-phase short circuit fault in the first position area, the active three-phase short circuit mode is executed for fault protection. The active three-phase short circuit mode is that the three-phase upper bridge arm or the three-phase lower bridge arm of the inverter 104 is turned on, so that the three-phase windings of the motor form a circuit through the inverter 104 to achieve demagnetization and braking.

[0218] If the diagnosis indicates a phase-to-phase short-circuit fault in the third location area, close the isolating contactor 105 and execute the active three-phase short-circuit mode for fault protection.

[0219] If the diagnosis indicates a phase-to-phase short-circuit fault in the fourth position area, the isolating contactor 105 shall be kept in the open state for fault protection.

[0220] If the diagnosis result indicates no phase-to-phase short circuit fault, a fault protection strategy is adopted for power device failure or inverter 104 output overcurrent.

[0221] The specific implementation of this embodiment can be found in the above related embodiments, and will not be repeated here.

[0222] The phase-to-phase short-circuit fault diagnosis method of this embodiment will be described in more detail below, taking the isolation contactor 105 disposed between the first node and the second node as an example.

[0223] In this embodiment, the motor is the traction motor of the vehicle's traction system. For example... Figure 13 As shown, after starting the operation, an initial judgment is performed. A flag indicating excessive current change rate can be pre-set to store the current change rate detection results. This flag is valid if the current change rate of at least two phases exceeds the current change rate threshold; otherwise, it is invalid. Similarly, a flag corresponding to phase-to-phase short-circuit voltage characteristics can be pre-set to store the judgment result of whether at least one phase-to-phase short-circuit voltage characteristic exists. This flag is valid if at least one phase-to-phase short-circuit voltage characteristic exists; otherwise, it is invalid. The specific process of the initial judgment is as follows:

[0224] When an overcurrent is detected at the inverter output or a fault in a power device, the validity of the flag indicating an excessive rate of change of current is determined. If valid, the phase-to-phase short circuit location diagnosis indicates a phase-to-phase short circuit fault exists in the first location region ①, and the corresponding fault protection action (i.e., the action corresponding to the fault protection strategy) is to execute the active three-phase short circuit mode. If invalid, the validity of the flag corresponding to the phase-to-phase short circuit voltage characteristic is further determined. If invalid, the phase-to-phase short circuit location diagnosis indicates an overcurrent fault not caused by a phase-to-phase short circuit or an overcurrent fault in a power device, i.e., only an overcurrent at the inverter 104 output or a fault in a power device occurs, with no phase-to-phase short circuit fault. The corresponding fault protection action is to adopt the protection strategy used when an overcurrent occurs at the inverter 104 output or a fault occurs in a power device.

[0225] If the flag corresponding to the phase-to-phase short-circuit voltage characteristic is valid, further timing adjustments are required. Specifically, the isolating contactor 105 can be disconnected, and the inverter 104 can be started to output test pulses. When the inverter 104 outputs test pulses, the validity of the flag corresponding to the phase-to-phase short-circuit voltage characteristic can be further determined. If the flag corresponding to the phase-to-phase short-circuit voltage characteristic is valid, the phase-to-phase short-circuit position diagnosis result is that a phase-to-phase short-circuit fault exists in the third position area ③. The corresponding fault protection action is to close the isolating contactor 105 and execute the active three-phase short-circuit mode. If the flag corresponding to the phase-to-phase short-circuit voltage characteristic is invalid, the phase-to-phase short-circuit position diagnosis result is that a phase-to-phase short-circuit fault exists in the fourth position area ④. The corresponding fault protection action is to maintain the disconnected state of the isolating contactor 105. No stringent protection action is required; the vehicle can continue driving and return to the depot for processing.

[0226] The diagnosis is now complete.

[0227] In some embodiments, such as Figure 14As shown, the phase-to-phase short circuit fault diagnosis system also includes an isolating contactor 105, which is disposed between the first node and the motor M.

[0228] Accordingly, determining that a phase-to-phase short-circuit fault exists in the first location area includes:

[0229] Disconnect the isolating contactor 105 and start the frequency converter 104 to output test pulses;

[0230] When the inverter 104 outputs a test pulse, it is determined whether there is still a power device failure or an overcurrent in the inverter 104 output, and whether the current change rate of at least two phases is greater than the current change rate threshold. If so, it is determined that there is a phase-to-phase short circuit fault in the fifth position area ⑤, which includes the line between the isolating contactor 105 and the first node, as well as the contacts of the isolating contactor 105 near the first node. Otherwise, it is determined that there is a phase-to-phase short circuit fault in the sixth position area ⑥, which includes the line between the isolating contactor 105 and the motor, the contacts of the isolating contactor 105 near the motor, and the motor body.

[0231] The first position area includes the fifth position area ⑤ and the sixth position area ⑥.

[0232] When the isolating contactor 105 is disconnected, the connection between the motor M and the current sensor 108 is severed. The inverter 104's pulse is blocked, and the current sensor 108 cannot detect current. At this time, the inverter 104 can be started to output a test pulse. When the inverter 104 outputs a test pulse, current flows through the current sensor 108. It is determined whether there is still a power device fault or an overcurrent in the inverter 104 output, and whether the current change rate of at least two phases is greater than the current change rate threshold. If so, it indicates a phase-to-phase short circuit fault at the location from the first node to the isolating contactor 105, i.e., the fifth position area ⑤. Otherwise, it indicates a phase-to-phase short circuit fault at the location from the isolating contactor 105 to the motor M, i.e., the sixth position area ⑥.

[0233] In this embodiment, for the case where the isolating contactor 105 is located between the first node and the motor, the inverter 104 is controlled to send test pulses, and the location of the phase-to-phase short circuit is further accurately located by combining the current change rate, thereby improving the accuracy of phase-to-phase short circuit fault diagnosis.

[0234] In some embodiments, the phase-to-phase short-circuit fault diagnosis system further includes an isolating contactor 105, which is disposed between the first node and the motor M;

[0235] Determining whether a phase-to-phase short-circuit fault exists in the second location area based on the voltage values ​​between every two phases of the three-phase line includes:

[0236] Disconnect the isolating contactor 105 and start the frequency converter 104 to output test pulses;

[0237] When the inverter 104 outputs a test pulse, it determines whether at least one phase-to-phase short-circuit voltage characteristic occurs based on the voltage value between each pair of phases of the three-phase circuit. The phase-to-phase short-circuit voltage characteristics include: when the inverter 104 is in operation, the voltage value drops from the normal value to below the voltage threshold; after the inverter 104 is started from the shutdown state, the voltage value remains zero and the current sensor 108 of the corresponding two phases experiences overcurrent.

[0238] If so, it is confirmed that there is a phase-to-phase short-circuit fault in the second location area;

[0239] If not, confirm that there is no phase-to-phase short-circuit fault in the second location area.

[0240] When the isolating contactor 105 is disconnected, the connection between the motor and the current sensor 108 is cut off. With the pulse blockade of the inverter 104, the current sensor 108 cannot detect the current. At this time, the inverter 104 can be started to output test pulses. When the inverter 104 outputs test pulses, if at least one phase-to-phase short-circuit voltage characteristic appears, it indicates that there is a phase-to-phase short-circuit fault in the second position area. Otherwise, there is no phase-to-phase short-circuit fault in the second position area.

[0241] In this embodiment, by controlling the on / off state of the isolation contactor 105, the inverter 104 is started to output test pulses. Combined with the phase-to-phase short-circuit voltage characteristics, the phase-to-phase short-circuit fault diagnosis of the second position area can be accurately performed.

[0242] Based on this, phase-to-phase short-circuit fault diagnosis is performed based on the current change rate detection results. After obtaining the diagnosis results, the following steps are also included:

[0243] If the diagnosis result indicates that there is a phase-to-phase short circuit fault in the sixth position area, close the isolation contactor 105 to execute the active three-phase short circuit mode for fault protection. The active three-phase short circuit mode is that the three-phase upper bridge arm or the three-phase lower bridge arm of the inverter 104 is conducting, so that the three-phase windings of the motor form a circuit through the inverter 104 to achieve demagnetization and braking.

[0244] If the diagnosis indicates a phase-to-phase short-circuit fault in the fifth position area, the isolating contactor 105 shall be kept in the open state for fault protection.

[0245] If the diagnosis indicates a phase-to-phase short-circuit fault in the second location area, disconnect the isolating contactor 105 for fault protection.

[0246] If the diagnosis result indicates no phase-to-phase short circuit fault, a fault protection strategy is adopted for power device failure or inverter 104 output overcurrent.

[0247] In the event that the diagnosis result indicates a phase-to-phase short circuit fault in the second location area, the isolating contactor 105 is disconnected for fault protection. Specifically, if the isolating contactor 105 is already disconnected, the disconnected state of the isolating contactor 105 is maintained for fault protection.

[0248] The specific implementation of this embodiment can be found in the above related embodiments, and will not be repeated here.

[0249] The phase-to-phase short-circuit fault diagnosis method of this embodiment will be described in more detail below, taking the isolation contactor 105 set between the first node and the motor M as an example.

[0250] In this embodiment, the motor is the traction motor of the vehicle's traction system. For example... Figure 15 As shown, after startup, an initial judgment is performed. A flag indicating excessive current change rate can be pre-set to store the current change rate detection results. This flag is valid if the current change rate of at least two phases exceeds the current change rate threshold; otherwise, it is invalid. Similarly, a flag corresponding to phase-to-phase short-circuit current characteristics can be pre-set to store the judgment results regarding whether the phase-to-phase short-circuit current characteristics are met. This flag is valid if the phase-to-phase short-circuit current characteristics are met, and invalid if they are not met. Finally, a flag corresponding to phase-to-phase short-circuit voltage characteristics can be pre-set to store the judgment results regarding the presence of at least one phase-to-phase short-circuit voltage characteristic. This flag is valid if at least one phase-to-phase short-circuit voltage characteristic exists, and invalid if no phase-to-phase short-circuit voltage characteristic exists.

[0251] The initial judgment process is as follows:

[0252] When an overcurrent is detected at the inverter output or a power device fault is detected, the validity of the flag indicating excessive current change rate is determined. If invalid, the isolating contactor 105 is disconnected, and the inverter 104 is started to output a test pulse. When the inverter 104 outputs a test pulse, the validity of the flag corresponding to the phase-to-phase short-circuit voltage characteristic is further determined. If the flag corresponding to the phase-to-phase short-circuit voltage characteristic is valid, the result of the phase-to-phase short-circuit position diagnosis is that a phase-to-phase short-circuit fault exists in the second position area ②, and the corresponding fault protection action is to disconnect the isolating contactor 105, i.e., to keep the isolating contactor 105 disconnected. If the flag corresponding to the phase-to-phase short-circuit voltage characteristic is invalid, the result of the phase-to-phase short-circuit position diagnosis is an overcurrent fault or power device fault not caused by a phase-to-phase short circuit, i.e., only the inverter 104 outputs an overcurrent or a power device fault occurs, without a phase-to-phase short-circuit fault, and the corresponding fault protection action is to adopt the protection strategy for when the inverter 104 outputs an overcurrent or a power device fault occurs.

[0253] When the excessive current change rate indicator is valid, further timing adjustments are required for further evaluation. Specifically, the isolating contactor 105 can be disconnected, and the inverter 104 can be started to output test pulses to further determine whether the excessive current change rate indicator is valid. If the excessive current change rate indicator is valid, the phase-to-phase short circuit position diagnosis result indicates a phase-to-phase short circuit fault in the fifth position area ⑤, and the corresponding fault protection action is to maintain the disconnected state of the isolating contactor 105. If the excessive current change rate indicator is invalid, the phase-to-phase short circuit position diagnosis result indicates a phase-to-phase short circuit fault in the sixth position area ⑥, and the corresponding fault protection action is to close the isolating contactor 105 and execute the active three-phase short circuit mode.

[0254] The diagnosis is now complete.

[0255] The solution proposed in this application can accurately diagnose phase-to-phase short circuits in the motor body and in the external circuits, and adopt different protection strategies to improve the availability and maintainability of the power system in which the motor is located.

[0256] The solution proposed in this application can be widely used for the precise location and protection of phase-to-phase short-circuit faults in traction systems of rail transit vehicles, locomotives, and urban rail transit. It can also be applied to other scenarios where such faults are required, such as production equipment in the new materials industry.

[0257] The above embodiments use a permanent magnet synchronous motor as an example to introduce a specific method for diagnosing phase-to-phase short-circuit faults. This method can be adjusted to also be applied to power systems equipped with asynchronous motors.

[0258] The above-mentioned embodiments can be implemented in combination according to actual needs.

[0259] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0260] Another embodiment of this application relates to a phase-to-phase short-circuit fault diagnosis device. The phase-to-phase short-circuit fault diagnosis device described below can be referred to in correspondence with the phase-to-phase short-circuit fault diagnosis method described above. The implementation details of the phase-to-phase short-circuit fault diagnosis device of this embodiment are described in detail below. The following implementation details are provided for ease of understanding and are not essential for implementing this solution. The schematic diagram of the phase-to-phase short-circuit fault diagnosis device of this embodiment can be seen as follows: Figure 16 As shown.

[0261] This embodiment relates to a phase-to-phase short-circuit fault diagnosis device, applied to a phase-to-phase short-circuit fault diagnosis system. The phase-to-phase short-circuit fault diagnosis system includes: a frequency converter and a motor. The frequency converter is connected to the motor via a three-phase line. At least two phases of the three-phase line are respectively equipped with current sensors. The device includes:

[0262] The rate of change detection module 1601 is used to determine the rate of change of current of each phase of the three-phase line based on the current signal of each current sensor when a fault is detected in the power device of the inverter or the inverter outputs an overcurrent, and to detect whether there are at least two phases whose rate of change of current is greater than the rate of change of current threshold, so as to obtain the rate of change of current detection result.

[0263] The short-circuit diagnosis module 1602 is used to perform phase-to-phase short-circuit fault diagnosis based on the current change rate detection result, and obtain a diagnosis result; wherein, the diagnosis result is the location of no phase-to-phase short-circuit fault or the location of phase-to-phase short-circuit fault, and the diagnosis result is used to determine the fault protection strategy corresponding to the diagnosis result for fault protection.

[0264] In some embodiments, each phase of the three-phase line has a first node, and the current sensor is disposed at the first node; the motor is a permanent magnet synchronous motor.

[0265] The short-circuit diagnosis module 1602 is specifically used for:

[0266] When the inverter stops working due to the blocking pulse, if the current change rate detection result shows that the current change rate of at least two phases is greater than the current change rate threshold, a phase-to-phase short circuit fault is determined to exist in the first location area. The first location area includes the motor body and the area between the motor and the first node.

[0267] If the current change rate detection result indicates that there are no two phases where the current change rate is greater than the current change rate threshold, the sum of the instantaneous current values ​​and the effective current values ​​of each phase of the three-phase circuit are obtained based on the current signals of each current sensor. Based on the output current of the inverter, the sum of the instantaneous current values ​​of each phase, and the effective current values ​​of each phase, it is determined whether the phase-to-phase short-circuit current characteristics are met, and a first determination result is obtained. The phase-to-phase short-circuit current characteristics include: the inverter is not outputting current, the sum of the instantaneous current values ​​of each phase is less than the first threshold, the maximum value of the effective current values ​​of each phase is greater than the second threshold, and the ratio of the minimum to the maximum value of the effective current values ​​of each phase is less than the third threshold.

[0268] If the first determination result satisfies the phase-to-phase short-circuit current characteristics, it is determined that there is a phase-to-phase short-circuit fault in the second location region, and the second location region includes the region between the first node and the inverter.

[0269] If the first judgment result does not meet the phase-to-phase short-circuit current characteristics, it is determined that there is no phase-to-phase short-circuit fault.

[0270] In some embodiments, the phase-to-phase short-circuit fault diagnosis system further includes an isolation contactor disposed between the first node and the frequency converter;

[0271] The short-circuit diagnosis module 1602 is specifically used for:

[0272] Disconnect the isolation contactor, and based on the output current of the inverter, the sum of the instantaneous current values ​​of each phase line, and the effective current value of each phase line, determine whether the current condition meets the phase-to-phase short-circuit current characteristics, and obtain a second judgment result.

[0273] If the second judgment result satisfies the phase-to-phase short-circuit current characteristics, it is determined that there is a phase-to-phase short-circuit fault in the third location area. The third location area includes the line between the isolation contactor and the first node and the contact of the isolation contactor near the first node.

[0274] If the second judgment result is that the phase-to-phase short-circuit current characteristics are not met, it is determined that there is a phase-to-phase short-circuit fault in the fourth location area. The fourth location area includes the line between the isolation contactor and the inverter, as well as the contact of the isolation contactor near the inverter.

[0275] The second location region includes the third location region and the fourth location region.

[0276] In some embodiments, the phase-to-phase short-circuit fault diagnosis system further includes an isolation contactor disposed between the first node and the motor;

[0277] The short-circuit diagnosis module 1602 is specifically used for:

[0278] Disconnect the isolation contactor and start the frequency converter to output a test pulse;

[0279] When the inverter outputs the test pulse, it is determined whether the power device still malfunctions or the inverter outputs overcurrent, and whether the current change rate of at least two phases is greater than the current change rate threshold. If so, it is determined that there is a phase-to-phase short circuit fault in the fifth position area, which includes the line between the isolating contactor and the first node and the contact of the isolating contactor near the first node. Otherwise, it is determined that there is a phase-to-phase short circuit fault in the sixth position area, which includes the line between the isolating contactor and the motor, the contact of the isolating contactor near the motor, and the motor body.

[0280] The first location region includes the fifth location region and the sixth location region.

[0281] In some embodiments, the third threshold is a fixed threshold or is determined based on the current speed of the motor.

[0282] In some embodiments, each phase of the three-phase line has a first node, and the current sensor is disposed at the first node; two or three voltage sensors for detecting voltage signals between different phase lines are disposed on the three-phase line, and each phase of the three-phase line has a second node located between the first node and the frequency converter, and the voltage sensor is disposed at the second node; the motor is a permanent magnet synchronous motor.

[0283] The short-circuit diagnosis module 1602 is specifically used for:

[0284] When the inverter stops working due to the blocking pulse, if the current change rate detection result shows that the current change rate of at least two phases is greater than the current change rate threshold, a phase-to-phase short circuit fault is determined to exist in the first location area. The first location area includes the motor body and the area between the motor and the first node.

[0285] If the current change rate detection result is that there are no two phases where the current change rate is greater than the current change rate threshold, the voltage value between each pair of phases of the three-phase line is obtained based on the voltage signal of each voltage sensor, and the presence of a phase-to-phase short circuit fault in the second location area is determined based on the voltage value between each pair of phases of the three-phase line. The second location area includes the area between the first node and the frequency converter.

[0286] In some embodiments, the phase-to-phase short-circuit fault diagnosis system further includes an isolation contactor disposed between the first node and the second node;

[0287] The short-circuit diagnosis module 1602 is specifically used for:

[0288] Based on the voltage values ​​between every two phases of the three-phase circuit, it is determined whether at least one phase-to-phase short-circuit voltage characteristic occurs, and a third determination result is obtained; wherein, the phase-to-phase short-circuit voltage characteristic includes: when the inverter is in operation, the voltage value drops from the normal value to below the voltage threshold; after the inverter is started from the shutdown state, the voltage value remains zero and the current sensor of the corresponding two phases experiences overcurrent.

[0289] If the third determination result is negative, it is determined that there is no phase-to-phase short-circuit fault in the second location area;

[0290] If the third judgment result is yes, disconnect the isolation contactor and start the frequency converter to output a test pulse; when the frequency converter outputs the test pulse, determine whether at least one of the phase-to-phase short-circuit voltage characteristics still occurs, and obtain the fourth judgment result;

[0291] If the fourth determination result is negative, it is determined that there is a phase-to-phase short circuit fault in the third location area. The third location area includes the line between the isolating contactor and the first node, as well as the contact of the isolating contactor near the first node.

[0292] If the fourth determination result is yes, it is determined that there is a phase-to-phase short circuit fault in the fourth location area. The fourth location area includes the line between the isolation contactor and the frequency converter, as well as the contact of the isolation contactor near the frequency converter.

[0293] The second location region includes the third location region and the fourth location region.

[0294] In some embodiments, the phase-to-phase short-circuit fault diagnosis system further includes an isolation contactor disposed between the first node and the motor;

[0295] The short-circuit diagnosis module 1602 is specifically used for:

[0296] Disconnect the isolation contactor and start the frequency converter to output a test pulse;

[0297] When the inverter outputs the test pulse, it is determined whether the power device still malfunctions or the inverter outputs overcurrent, and whether the current change rate of at least two phases is greater than the current change rate threshold. If so, it is determined that there is a phase-to-phase short circuit fault in the fifth position area, which includes the line between the isolating contactor and the first node and the contact of the isolating contactor near the first node. Otherwise, it is determined that there is a phase-to-phase short circuit fault in the sixth position area, which includes the line between the isolating contactor and the motor, the contact of the isolating contactor near the motor, and the motor body.

[0298] The first location region includes the fifth location region and the sixth location region.

[0299] In some embodiments, the phase-to-phase short-circuit fault diagnosis system further includes an isolation contactor disposed between the first node and the motor;

[0300] The short-circuit diagnosis module 1602 is specifically used for:

[0301] Disconnect the isolation contactor and start the frequency converter to output a test pulse;

[0302] When the inverter outputs the test pulse, based on the voltage value between each pair of the three-phase lines, it is determined whether at least one phase-to-phase short-circuit voltage characteristic occurs; wherein, the phase-to-phase short-circuit voltage characteristic includes: the voltage value drops from the normal value to below the voltage threshold when the inverter is in operation; after the inverter is started from a shutdown state, the voltage value remains zero and the current sensor of the corresponding two phase lines experiences overcurrent;

[0303] If so, it is determined that there is a phase-to-phase short-circuit fault in the second location area;

[0304] If not, it is determined that there is no phase-to-phase short-circuit fault in the second location area.

[0305] In some embodiments, such as Figure 17 As shown, it also includes a fault protection module 1603, which is used for:

[0306] If the diagnostic result indicates that there is a phase-to-phase short circuit fault in the first location area, an active three-phase short circuit mode is executed for fault protection. The active three-phase short circuit mode is when all three upper bridge arms or three lower bridge arms of the frequency converter are turned on, so that the three-phase windings of the motor form a circuit through the frequency converter to achieve demagnetization and braking.

[0307] If the diagnostic result indicates that there is a phase-to-phase short-circuit fault in the third location area, the isolation contactor is closed, and the active three-phase short-circuit mode is executed for fault protection.

[0308] If the diagnostic result indicates that a phase-to-phase short-circuit fault exists in the fourth location area, the disconnected state of the isolating contactor shall be maintained for fault protection.

[0309] If the diagnostic result indicates no phase-to-phase short-circuit fault, a fault protection strategy is adopted for when the power device malfunctions or the inverter outputs an overcurrent.

[0310] In some embodiments, such as Figure 17 As shown, it also includes a fault protection module 1603, which is used for:

[0311] If the diagnostic result indicates that there is a phase-to-phase short circuit fault in the sixth position area, the isolation contactor is closed to execute the active three-phase short circuit mode for fault protection. The active three-phase short circuit mode is that both the three upper bridge arms and the three lower bridge arms of the frequency converter are conducting, so that the three-phase windings of the motor form a circuit through the frequency converter to achieve demagnetization and braking.

[0312] If the diagnostic result indicates that a phase-to-phase short-circuit fault exists in the fifth location area, the disconnected state of the isolating contactor shall be maintained for fault protection.

[0313] If the diagnostic result indicates that a phase-to-phase short-circuit fault exists in the second location area, the isolating contactor is disconnected for fault protection.

[0314] If the diagnostic result indicates no phase-to-phase short-circuit fault, a fault protection strategy is adopted for when the power device malfunctions or the inverter outputs an overcurrent.

[0315] It is worth mentioning that all modules involved in this embodiment are logical modules. In practical applications, a logical unit can be a physical unit, a part of a physical unit, or a combination of multiple physical units. Furthermore, to highlight the innovative aspects of this application, this embodiment does not introduce units that are not closely related to solving the technical problems proposed in this application; however, this does not mean that other units are absent in this embodiment.

[0316] This application also relates to a phase-to-phase short-circuit fault diagnosis system, including:

[0317] Electric motor;

[0318] The frequency converter is connected to the motor via a three-phase line, and a current sensor is respectively installed on at least two phases of the three-phase line.

[0319] A control device for performing the phase-to-phase short-circuit fault diagnosis method as described in any of the above embodiments.

[0320] In some embodiments, each phase of the three-phase line has a first node, and the current sensor is disposed at the first node;

[0321] The phase-to-phase short-circuit fault diagnosis system also includes an isolation contactor, which is disposed between the first node and the frequency converter or between the first node and the motor;

[0322] The motor is a permanent magnet synchronous motor.

[0323] In some embodiments, each phase of the three-phase line has a first node, and the current sensor is disposed at the first node; two or three voltage sensors for detecting voltage signals between different phase lines are disposed on the three-phase line, and each phase of the three-phase line has a second node located between the first node and the frequency converter, and the voltage sensor is disposed at the second node;

[0324] The phase-to-phase short-circuit fault diagnosis system also includes an isolating contactor, which is disposed between the first node and the second node or between the first node and the motor;

[0325] The motor is a permanent magnet synchronous motor.

[0326] Another embodiment of this application relates to an electronic device, such as... Figure 18 As shown, it includes: at least one processor 1801; and a memory 1802 communicatively connected to the at least one processor 1801; wherein the memory 1802 stores instructions executable by the at least one processor 1801, the instructions being executed by the at least one processor 1801 to enable the at least one processor 1801 to perform the phase-to-phase short-circuit fault diagnosis method in the above embodiments.

[0327] The memory and processor are connected via a bus, which can include any number of interconnecting buses and bridges, connecting various circuits of one or more processors and memories. The bus can also connect various other circuits, such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art and will not be described further herein. The bus interface provides an interface between the bus and the transceiver. The transceiver can be a single element or multiple elements, such as multiple receivers and transmitters, providing a unit for communicating with various other devices over a transmission medium. Data processed by the processor is transmitted over the wireless medium via an antenna, which further receives data and transmits it to the processor.

[0328] The processor manages the bus and general processing, and also provides various functions, including timing, peripheral interfaces, voltage regulation, power management, and other control functions. Memory is used to store data used by the processor during operation.

[0329] Another embodiment of this application relates to a computer-readable storage medium storing a computer program. When executed by a processor, the computer program implements the method embodiments described above.

[0330] That is, those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. This program is stored in a storage medium and includes several instructions to cause a device (which may be a microcontroller, chip, etc.) or processor to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0331] Those skilled in the art will understand that the above embodiments are specific embodiments for implementing this application, and in practical applications, various changes can be made to them in form and detail without departing from the spirit and scope of this application.

Claims

1. A method for diagnosing phase-to-phase short-circuit faults, characterized in that, An application is made in a phase-to-phase short-circuit fault diagnosis system, the system comprising: a frequency converter and a motor, the frequency converter being connected to the motor via a three-phase line, wherein at least two phases of the three-phase line are respectively equipped with current sensors, the method comprising: When a fault is detected in the power device of the inverter or an overcurrent is detected in the inverter output, the current change rate of each phase of the three-phase line is determined based on the current signal of each current sensor, and it is detected whether there are at least two phases whose current change rate is greater than the current change rate threshold, so as to obtain the current change rate detection result. Based on the current change rate detection results, phase-to-phase short-circuit fault diagnosis is performed to obtain a diagnosis result; wherein, the diagnosis result indicates the location of no phase-to-phase short-circuit fault or the location of phase-to-phase short-circuit fault, and the diagnosis result is used to determine the fault protection strategy corresponding to the diagnosis result for fault protection. Each phase of the three-phase circuit has a first node, and the current sensor is disposed at the first node; the motor is a permanent magnet synchronous motor. The phase-to-phase short-circuit fault diagnosis based on the current change rate detection result yields the following diagnostic results: When the inverter stops working due to the blocking pulse, if the current change rate detection result shows that the current change rate of at least two phases is greater than the current change rate threshold, a phase-to-phase short circuit fault is determined to exist in the first location area. The first location area includes the motor body and the area between the motor and the first node. If the current change rate detection result indicates that there are no two phases where the current change rate is greater than the current change rate threshold, the sum of the instantaneous current values ​​and the effective current values ​​of each phase of the three-phase circuit are obtained based on the current signals of each current sensor. Based on the output current of the inverter, the sum of the instantaneous current values ​​of each phase, and the effective current values ​​of each phase, it is determined whether the phase-to-phase short-circuit current characteristics are met, and a first determination result is obtained. The phase-to-phase short-circuit current characteristics include: the inverter is not outputting current, the sum of the instantaneous current values ​​of each phase is less than the first threshold, the maximum value of the effective current values ​​of each phase is greater than the second threshold, and the ratio of the minimum value to the maximum value of the effective current values ​​of each phase is less than the third threshold. If the first determination result satisfies the phase-to-phase short-circuit current characteristics, it is determined that there is a phase-to-phase short-circuit fault in the second location region, and the second location region includes the region between the first node and the inverter. If the first judgment result does not meet the phase-to-phase short-circuit current characteristics, it is determined that there is no phase-to-phase short-circuit fault.

2. The phase-to-phase short-circuit fault diagnosis method according to claim 1, characterized in that, The phase-to-phase short-circuit fault diagnosis system also includes an isolation contactor, which is disposed between the first node and the frequency converter; The determination that a phase-to-phase short-circuit fault exists in the second location area includes: Disconnect the isolation contactor, and based on the output current of the inverter, the sum of the instantaneous current values ​​of each phase line, and the effective current value of each phase line, determine whether the current condition meets the phase-to-phase short-circuit current characteristics, and obtain a second judgment result. If the second judgment result satisfies the phase-to-phase short-circuit current characteristics, it is determined that there is a phase-to-phase short-circuit fault in the third location area. The third location area includes the line between the isolation contactor and the first node and the contact of the isolation contactor near the first node. If the second judgment result is that the phase-to-phase short-circuit current characteristics are not met, it is determined that there is a phase-to-phase short-circuit fault in the fourth location area. The fourth location area includes the line between the isolation contactor and the inverter, as well as the contact of the isolation contactor near the inverter. The second location region includes the third location region and the fourth location region.

3. The phase-to-phase short-circuit fault diagnosis method according to claim 2, characterized in that, After obtaining the diagnosis result by performing phase-to-phase short-circuit fault diagnosis based on the current change rate detection result, the method further includes: If the diagnostic result indicates that there is a phase-to-phase short circuit fault in the first location area, an active three-phase short circuit mode is executed for fault protection. The active three-phase short circuit mode is when all three upper bridge arms or three lower bridge arms of the frequency converter are turned on, so that the three-phase windings of the motor form a circuit through the frequency converter to achieve demagnetization and braking. If the diagnostic result indicates that there is a phase-to-phase short-circuit fault in the third location area, the isolation contactor is closed, and the active three-phase short-circuit mode is executed for fault protection. If the diagnostic result indicates that a phase-to-phase short-circuit fault exists in the fourth location area, the disconnected state of the isolating contactor shall be maintained for fault protection. If the diagnostic result indicates no phase-to-phase short-circuit fault, a fault protection strategy is adopted for when the power device malfunctions or the inverter outputs an overcurrent.

4. The phase-to-phase short-circuit fault diagnosis method according to claim 1, characterized in that, The phase-to-phase short-circuit fault diagnosis system also includes an isolating contactor, which is disposed between the first node and the motor; The determination that a phase-to-phase short-circuit fault exists in the first location area includes: Disconnect the isolation contactor and start the frequency converter to output a test pulse; When the inverter outputs the test pulse, it is determined whether the power device still malfunctions or the inverter outputs overcurrent, and whether the current change rate of at least two phases is greater than the current change rate threshold. If so, it is determined that there is a phase-to-phase short circuit fault in the fifth position area, which includes the line between the isolating contactor and the first node and the contact of the isolating contactor near the first node. Otherwise, it is determined that there is a phase-to-phase short circuit fault in the sixth position area, which includes the line between the isolating contactor and the motor, the contact of the isolating contactor near the motor, and the motor body. The first location region includes the fifth location region and the sixth location region.

5. The phase-to-phase short-circuit fault diagnosis method according to claim 4, characterized in that, After obtaining the diagnosis result by performing phase-to-phase short-circuit fault diagnosis based on the current change rate detection result, the method further includes: If the diagnostic result indicates that there is a phase-to-phase short circuit fault in the sixth position area, the isolation contactor is closed to execute the active three-phase short circuit mode for fault protection. The active three-phase short circuit mode is that both the three upper bridge arms and the three lower bridge arms of the frequency converter are conducting, so that the three-phase windings of the motor form a circuit through the frequency converter to achieve demagnetization and braking. If the diagnostic result indicates that a phase-to-phase short-circuit fault exists in the fifth location area, the disconnecting contactor shall be maintained in the open state for fault protection. If the diagnostic result indicates that a phase-to-phase short-circuit fault exists in the second location area, the isolating contactor is disconnected for fault protection. If the diagnostic result indicates no phase-to-phase short-circuit fault, a fault protection strategy is adopted for when the power device malfunctions or the inverter outputs an overcurrent.

6. The phase-to-phase short-circuit fault diagnosis method according to claim 1, characterized in that, The third threshold is either a fixed threshold or determined based on the current speed of the motor.

7. A method for diagnosing phase-to-phase short-circuit faults, characterized in that, An application is made in a phase-to-phase short-circuit fault diagnosis system, the system comprising: a frequency converter and a motor, the frequency converter being connected to the motor via a three-phase line, wherein at least two phases of the three-phase line are respectively equipped with current sensors, the method comprising: When a fault is detected in the power device of the inverter or an overcurrent is detected in the inverter output, the current change rate of each phase of the three-phase line is determined based on the current signal of each current sensor, and it is detected whether there are at least two phases whose current change rate is greater than the current change rate threshold, so as to obtain the current change rate detection result. Based on the current change rate detection results, phase-to-phase short-circuit fault diagnosis is performed to obtain a diagnosis result; wherein, the diagnosis result indicates the location of no phase-to-phase short-circuit fault or the location of phase-to-phase short-circuit fault, and the diagnosis result is used to determine the fault protection strategy corresponding to the diagnosis result for fault protection. Each phase of the three-phase line has a first node, and the current sensor is disposed at the first node; two or three voltage sensors for detecting voltage signals between different phases are disposed on the three-phase line; each phase of the three-phase line has a second node located between the first node and the frequency converter, and the voltage sensor is disposed at the second node; the motor is a permanent magnet synchronous motor. The phase-to-phase short-circuit fault diagnosis based on the current change rate detection result yields the following diagnostic results: When the inverter stops working due to the blocking pulse, if the current change rate detection result shows that the current change rate of at least two phases is greater than the current change rate threshold, a phase-to-phase short circuit fault is determined to exist in the first location area. The first location area includes the motor body and the area between the motor and the first node. If the current change rate detection result is that there are no two phases where the current change rate is greater than the current change rate threshold, the voltage value between each pair of phases of the three-phase line is obtained based on the voltage signal of each voltage sensor, and the presence of a phase-to-phase short circuit fault in the second location area is determined based on the voltage value between each pair of phases of the three-phase line. The second location area includes the area between the first node and the frequency converter.

8. The phase-to-phase short-circuit fault diagnosis method according to claim 7, characterized in that, The phase-to-phase short-circuit fault diagnosis system also includes an isolating contactor, which is disposed between the first node and the second node; The determination of whether a phase-to-phase short-circuit fault exists in the second location area based on the voltage value between every two phases of the three-phase line includes: Based on the voltage values ​​between every two phases of the three-phase circuit, it is determined whether at least one phase-to-phase short-circuit voltage characteristic occurs, and a third determination result is obtained; wherein, the phase-to-phase short-circuit voltage characteristic includes: when the inverter is in operation, the voltage value drops from the normal value to below the voltage threshold; after the inverter is started from the shutdown state, the voltage value remains zero and the current sensor of the corresponding two phases experiences overcurrent. If the third determination result is negative, it is determined that there is no phase-to-phase short-circuit fault in the second location area; If the third judgment result is yes, disconnect the isolation contactor and start the frequency converter to output a test pulse; when the frequency converter outputs the test pulse, determine whether at least one of the phase-to-phase short-circuit voltage characteristics still occurs, and obtain the fourth judgment result; If the fourth determination result is negative, it is determined that there is a phase-to-phase short circuit fault in the third location area. The third location area includes the line between the isolating contactor and the first node, as well as the contact of the isolating contactor near the first node. If the fourth determination result is yes, it is determined that there is a phase-to-phase short circuit fault in the fourth location area. The fourth location area includes the line between the isolation contactor and the frequency converter, as well as the contact of the isolation contactor near the frequency converter. The second location region includes the third location region and the fourth location region.

9. The phase-to-phase short-circuit fault diagnosis method according to claim 8, characterized in that, After obtaining the diagnosis result by performing phase-to-phase short-circuit fault diagnosis based on the current change rate detection result, the method further includes: If the diagnostic result indicates that there is a phase-to-phase short circuit fault in the first location area, an active three-phase short circuit mode is executed for fault protection. The active three-phase short circuit mode is when all three upper bridge arms or three lower bridge arms of the frequency converter are turned on, so that the three-phase windings of the motor form a circuit through the frequency converter to achieve demagnetization and braking. If the diagnostic result indicates that there is a phase-to-phase short-circuit fault in the third location area, the isolation contactor is closed, and the active three-phase short-circuit mode is executed for fault protection. If the diagnostic result indicates that a phase-to-phase short-circuit fault exists in the fourth location area, the disconnected state of the isolating contactor shall be maintained for fault protection. If the diagnostic result indicates no phase-to-phase short-circuit fault, a fault protection strategy is adopted for when the power device malfunctions or the inverter outputs an overcurrent.

10. The phase-to-phase short-circuit fault diagnosis method according to claim 7, characterized in that, The phase-to-phase short-circuit fault diagnosis system also includes an isolating contactor, which is disposed between the first node and the motor; The determination that a phase-to-phase short-circuit fault exists in the first location area includes: Disconnect the isolation contactor and start the frequency converter to output a test pulse; When the inverter outputs the test pulse, it is determined whether the power device still malfunctions or the inverter outputs overcurrent, and whether the current change rate of at least two phases is greater than the current change rate threshold. If so, it is determined that there is a phase-to-phase short circuit fault in the fifth position area, which includes the line between the isolating contactor and the first node and the contact of the isolating contactor near the first node. Otherwise, it is determined that there is a phase-to-phase short circuit fault in the sixth position area, which includes the line between the isolating contactor and the motor, the contact of the isolating contactor near the motor, and the motor body. The first location region includes the fifth location region and the sixth location region.

11. The phase-to-phase short-circuit fault diagnosis method according to claim 10, characterized in that, After obtaining the diagnosis result by performing phase-to-phase short-circuit fault diagnosis based on the current change rate detection result, the method further includes: If the diagnostic result indicates that there is a phase-to-phase short circuit fault in the sixth position area, the isolation contactor is closed to execute the active three-phase short circuit mode for fault protection. The active three-phase short circuit mode is that both the three upper bridge arms and the three lower bridge arms of the frequency converter are conducting, so that the three-phase windings of the motor form a circuit through the frequency converter to achieve demagnetization and braking. If the diagnostic result indicates that a phase-to-phase short-circuit fault exists in the fifth location area, the disconnected state of the isolating contactor shall be maintained for fault protection. If the diagnostic result indicates that a phase-to-phase short-circuit fault exists in the second location area, the isolating contactor is disconnected for fault protection. If the diagnostic result indicates no phase-to-phase short-circuit fault, a fault protection strategy is adopted for when the power device malfunctions or the inverter outputs an overcurrent.

12. The phase-to-phase short-circuit fault diagnosis method according to claim 7, characterized in that, The phase-to-phase short-circuit fault diagnosis system also includes an isolating contactor, which is disposed between the first node and the motor; The determination of whether a phase-to-phase short-circuit fault exists in the second location area based on the voltage value between every two phases of the three-phase line includes: Disconnect the isolation contactor and start the frequency converter to output a test pulse; When the inverter outputs the test pulse, based on the voltage value between each pair of the three-phase lines, it is determined whether at least one phase-to-phase short-circuit voltage characteristic occurs; wherein, the phase-to-phase short-circuit voltage characteristic includes: the voltage value drops from the normal value to below the voltage threshold when the inverter is in operation; after the inverter is started from a shutdown state, the voltage value remains zero and the current sensor of the corresponding two phase lines experiences overcurrent; If so, it is determined that there is a phase-to-phase short-circuit fault in the second location area; If not, it is determined that there is no phase-to-phase short-circuit fault in the second location area.

13. A phase-to-phase short-circuit fault diagnosis device, characterized in that, An application is provided in a phase-to-phase short-circuit fault diagnosis system, the system comprising: a frequency converter and a motor, the frequency converter being connected to the motor via a three-phase line, and at least two phases of the three-phase line being respectively equipped with current sensors; the device includes: The rate of change detection module is used to determine the rate of change of current of each phase of the three-phase line based on the current signals of each current sensor when a fault is detected in the power device of the inverter or the inverter outputs an overcurrent, and to detect whether there are at least two phases whose rate of change of current is greater than the rate of change of current threshold, so as to obtain the rate of change of current detection result. The short-circuit diagnosis module is used to diagnose phase-to-phase short-circuit faults based on the current change rate detection results and obtain a diagnosis result; wherein, the diagnosis result indicates the location of no phase-to-phase short-circuit fault or the location of a phase-to-phase short-circuit fault, and the diagnosis result is used to determine the fault protection strategy corresponding to the diagnosis result for fault protection. Each phase of the three-phase circuit has a first node, and the current sensor is located at the first node; the motor is a permanent magnet synchronous motor; the short-circuit diagnosis module is specifically used for: When the inverter stops working due to the blocking pulse, if the current change rate detection result shows that the current change rate of at least two phases is greater than the current change rate threshold, a phase-to-phase short circuit fault is determined to exist in the first location area. The first location area includes the motor body and the area between the motor and the first node. If the current change rate detection result indicates that there are no two phases where the current change rate is greater than the current change rate threshold, the sum of the instantaneous current values ​​and the effective current values ​​of each phase of the three-phase circuit are obtained based on the current signals of each current sensor. Based on the output current of the inverter, the sum of the instantaneous current values ​​of each phase, and the effective current values ​​of each phase, it is determined whether the phase-to-phase short-circuit current characteristics are met, and a first determination result is obtained. The phase-to-phase short-circuit current characteristics include: the inverter is not outputting current, the sum of the instantaneous current values ​​of each phase is less than the first threshold, the maximum value of the effective current values ​​of each phase is greater than the second threshold, and the ratio of the minimum value to the maximum value of the effective current values ​​of each phase is less than the third threshold. If the first determination result satisfies the phase-to-phase short-circuit current characteristics, it is determined that there is a phase-to-phase short-circuit fault in the second location region, and the second location region includes the region between the first node and the inverter. If the first judgment result does not meet the phase-to-phase short-circuit current characteristics, it is determined that there is no phase-to-phase short-circuit fault.

14. A phase-to-phase short-circuit fault diagnosis device, characterized in that, An application is provided in a phase-to-phase short-circuit fault diagnosis system, the system comprising: a frequency converter and a motor, the frequency converter being connected to the motor via a three-phase line, and at least two phases of the three-phase line being respectively equipped with current sensors; the device includes: The rate of change detection module is used to determine the rate of change of current of each phase of the three-phase line based on the current signals of each current sensor when a fault is detected in the power device of the inverter or the inverter outputs an overcurrent, and to detect whether there are at least two phases whose rate of change of current is greater than the rate of change of current threshold, so as to obtain the rate of change of current detection result. The short-circuit diagnosis module is used to diagnose phase-to-phase short-circuit faults based on the current change rate detection results and obtain a diagnosis result; wherein, the diagnosis result indicates the location of no phase-to-phase short-circuit fault or the location of a phase-to-phase short-circuit fault, and the diagnosis result is used to determine the fault protection strategy corresponding to the diagnosis result for fault protection. Each phase of the three-phase line has a first node, and the current sensor is disposed at the first node; two or three voltage sensors for detecting voltage signals between different phases are disposed on the three-phase line; each phase of the three-phase line has a second node located between the first node and the frequency converter, and the voltage sensor is disposed at the second node; the motor is a permanent magnet synchronous motor. The short-circuit diagnostic module is specifically used for: When the inverter stops working due to the blocking pulse, if the current change rate detection result shows that the current change rate of at least two phases is greater than the current change rate threshold, a phase-to-phase short circuit fault is determined to exist in the first location area. The first location area includes the motor body and the area between the motor and the first node. If the current change rate detection result is that there are no two phases where the current change rate is greater than the current change rate threshold, the voltage value between each pair of phases of the three-phase line is obtained based on the voltage signal of each voltage sensor, and the presence of a phase-to-phase short circuit fault in the second location area is determined based on the voltage value between each pair of phases of the three-phase line. The second location area includes the area between the first node and the frequency converter.

15. A phase-to-phase short-circuit fault diagnosis system, characterized in that, include: Electric motor; The frequency converter is connected to the motor via a three-phase line, and a current sensor is respectively installed on at least two phases of the three-phase line. A control device for performing the phase-to-phase short-circuit fault diagnosis method as described in any one of claims 1 to 6.

16. The phase-to-phase short-circuit fault diagnosis system according to claim 15, characterized in that, Each phase of the three-phase line has a first node, and the current sensor is disposed at the first node; The phase-to-phase short-circuit fault diagnosis system also includes an isolation contactor, which is disposed between the first node and the frequency converter or between the first node and the motor; The motor is a permanent magnet synchronous motor.

17. A phase-to-phase short-circuit fault diagnosis system, characterized in that, include: Electric motor; The frequency converter is connected to the motor via a three-phase line, and a current sensor is respectively installed on at least two phases of the three-phase line. A control device for performing the phase-to-phase short-circuit fault diagnosis method as described in any one of claims 7 to 12.

18. The phase-to-phase short-circuit fault diagnosis system according to claim 17, characterized in that, Each phase of the three-phase line has a first node, and the current sensor is disposed at the first node; two or three voltage sensors for detecting voltage signals between different phase lines are disposed on the three-phase line; each phase of the three-phase line has a second node located between the first node and the frequency converter, and the voltage sensor is disposed at the second node. The phase-to-phase short-circuit fault diagnosis system also includes an isolating contactor, which is disposed between the first node and the second node or between the first node and the motor; The motor is a permanent magnet synchronous motor.

19. An electronic device, characterized in that, include: At least one processor; as well as, A memory communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor to enable the at least one processor to perform the phase-to-phase short-circuit fault diagnosis method as described in any one of claims 1 to 12.

20. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the phase-to-phase short-circuit fault diagnosis method as described in any one of claims 1 to 12.

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