Frequency converter, earth short circuit detection method of IT system and storage medium

Abstract

The invention discloses a frequency converter, a ground short circuit detection method of an IT system and a storage medium. The ground short circuit detection method comprises the following steps: acquiring a bus voltage and a maximum change value of a ground voltage of a first-phase motor winding in a first time period; and determining the phase motor winding with the short circuit to ground according to the multiple relationship between the maximum change value and the bus voltage. According to the technical scheme, by introducing a low-cost signal acquisition and processing technology and combining existing acquisition signals of the frequency converter, high-precision positioning of grounding short circuit of a certain phase of the three-phase motor is achieved, strong electromagnetic interference generated by continuous operation is remarkably reduced through accurate fault positioning, the insulation pressure in the frequency converter is effectively reduced, and the service life of the frequency converter is prolonged. Therefore, the reliability and the stability of the system are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of fault detection, and in particular to a method and storage medium for detecting short circuits to ground of a frequency converter and an IT system. Background Art

[0002] At present, most frequency converters are equipped with short-circuit detection circuits. In the TT system, the frequency converter can effectively determine the short-circuit to ground at the output end by monitoring the output current change through power-on self-test. However, when the system is switched to the IT system, due to the different grounding method of the IT system, the short-circuit to ground fault cannot be identified through the same current detection method, which limits the short-circuit protection function of the frequency converter in the IT system. When the insulation failure occurs in one phase of the three-phase motor, the frequency converter still keeps running, and fails to detect and cut off the power supply in time, which not only causes the fault to continue to expand, but also may cause more serious damage to the motor equipment and peripheral equipment. After the motor winding is short-circuited, the potential between the motor housing and the ground terminal of the frequency converter changes frequently and violently, forming high-frequency electromagnetic interference, which not only interferes with other electronic equipment, but also increases the insulation pressure inside the frequency converter, affecting the long-term stability and reliability of the system. Due to environmental factors, the existing technology cannot accurately detect and locate the specific phase of the motor short-circuit to ground, which brings inconvenience to maintenance work, increases the time and cost of fault diagnosis, and delays the efficiency of system recovery. Summary of the invention

[0003] The embodiments of the present invention provide a method for detecting short circuit to ground of a frequency converter and an IT system and a storage medium to solve the above technical problems.

[0004] A first aspect of an embodiment of the present invention provides a method for detecting a short circuit to ground of an inverter IT system, comprising:

[0005] Obtaining a bus voltage and a maximum change value of a first-phase motor winding-to-ground voltage within a first time period;

[0006] The phase motor winding that is short-circuited to ground is determined based on the multiple relationship between the maximum change value and the bus voltage.

[0007] Optionally, the determining of the phase motor winding that is short-circuited to ground according to the multiple relationship between the maximum change value and the bus voltage includes:

[0008] When the multiple between the maximum change value and the bus voltage is greater than a first preset multiple, it is determined that at least one of the remaining two-phase motor windings is short-circuited to ground;

[0009] When the multiple between the maximum change value and the bus voltage is less than a second preset multiple, it is determined that the first-phase motor winding is short-circuited to ground;

[0010] Wherein, the first preset multiple is greater than the second preset multiple.

[0011] Optionally, the determining that at least one of the remaining two-phase motor windings is short-circuited to ground further includes:

[0012] Acquire the voltage of the first-phase motor winding to ground and the driving signal of each-phase motor winding within a second time period;

[0013] A time period during which the drive signal corresponding to the first phase motor winding does not change within the second time period is selected, and within the selected time period, the phase motor winding that is short-circuited to ground is obtained based on the correspondence between the first phase motor winding voltage to ground and the drive signals of the remaining phase motor windings.

[0014] Optionally, the remaining two-phase motor windings include a second-phase motor winding and a third-phase motor winding, the second-phase motor winding corresponds to a second drive signal, and the third-phase motor winding corresponds to a third drive signal;

[0015] The method of obtaining the phase motor winding that is short-circuited to the ground according to the correspondence between the voltage of the first phase motor winding to the ground and the drive signals of the remaining phase motor windings includes:

[0016] When the voltage of the first-phase motor winding to ground is consistent with the change trend of the second drive signal, it is determined that the second-phase motor winding is short-circuited to ground;

[0017] When the voltage of the first-phase motor winding to ground is consistent with the change trend of the third drive signal, it is determined that the third-phase motor winding is short-circuited to ground.

[0018] Optionally, after determining that at least one of the remaining two-phase motor windings is short-circuited to ground, the method further includes:

[0019] Acquire the voltage of the first-phase motor winding to ground and the output phase-to-phase voltage of the first-phase motor winding to the other two-phase motor windings within a third time period;

[0020] The phase motor winding that is short-circuited to the ground is obtained according to the level conversion process of the first phase motor winding to the ground voltage and the output phase-to-phase voltage of the first phase motor winding to the other two phase motor windings.

[0021] Optionally, the remaining two-phase motor windings include a second-phase motor winding and a third-phase motor winding, and the output interphase voltage includes a first interphase voltage and a second interphase voltage, the first interphase voltage is a voltage between the first-phase motor winding and the second-phase motor winding, and the second interphase voltage is a voltage between the first-phase motor winding and the third-phase motor winding;

[0022] The method of obtaining the phase motor winding that is short-circuited to ground according to the voltage of the first phase motor winding to ground and the level conversion state of the output phase-to-phase voltage comprises:

[0023] When the level conversion period of the first-phase motor winding voltage to ground is the same as the level conversion period of the first phase voltage, determining that the second-phase motor winding is short-circuited to ground;

[0024] When the level conversion period of the first-phase motor winding voltage to ground is the same as that of the second phase-to-phase voltage, it is determined that the third-phase motor winding is short-circuited to ground.

[0025] Optionally, the determining that at least one of the remaining two-phase windings is short-circuited to ground further includes:

[0026] Acquire the voltage of the first-phase motor winding to ground and the output phase-to-phase voltage of the first-phase motor winding to the other two-phase motor windings in the second time period;

[0027] The output interphase voltage includes a first interphase voltage and a second interphase voltage, the first interphase voltage is a voltage between a first-phase motor winding and a second-phase motor winding, and the second interphase voltage is a voltage between a first-phase motor winding and a third-phase motor winding;

[0028] When the level conversion period of the first-phase motor winding voltage to ground is the same as the level conversion period of the first phase voltage, determining that the second-phase motor winding is short-circuited to ground;

[0029] When the level conversion period of the first-phase motor winding voltage to ground is the same as that of the second phase voltage, it is determined that the third-phase motor winding is short-circuited to ground;

[0030] Compare and determine whether the results are consistent. If yes, output the determination result. Otherwise, re-acquire the bus voltage and the maximum change value of the voltage between the first phase motor winding and the ground within a first time period.

[0031] Optionally, obtaining a maximum change value of the voltage between the first-phase motor winding and ground within a time period includes:

[0032] The maximum and minimum values ​​of the voltage between the first-phase motor winding and the PE terminal in a first time period are obtained, and the minimum value is subtracted from the maximum value to obtain the maximum change value of the voltage between the first-phase motor winding and the ground in the time period.

[0033] A second aspect of an embodiment of the present invention provides a frequency converter, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the method described in the first aspect when executing the computer program.

[0034] A third aspect of an embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method described in the first aspect is implemented.

[0035] The technical effect of the embodiment of the present invention is as follows: the technical solution realizes high-precision positioning of a phase short circuit to ground of a three-phase motor by introducing low-cost signal acquisition and processing technology and combining the existing acquisition signals of the frequency converter. Compared with the traditional detection method that is only effective in the TT system and power-on self-test, the technical solution can also effectively detect the phase winding motor short circuit to ground during the continuous operation of the machine and in the IT system. Through accurate fault location, the technical solution significantly reduces the strong electromagnetic interference caused by continuous operation and effectively reduces the insulation pressure inside the frequency converter, thereby improving the reliability and stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0037] Figure 1 This is a flow chart of a method for detecting a short circuit to ground of an inverter IT system provided in Embodiment 1 of the present invention;

[0038] Figure 2 is a specific flow chart of step S102 in a method for detecting short circuit to ground of an inverter IT system provided in Embodiment 1 of the present invention;

[0039] Figure 3 It is a flow chart of a first implementation method after step S121 in a method for detecting a short circuit to ground of an inverter IT system provided in the first embodiment of the present invention;

[0040] Figure 4 yes Figure 3 A specific flow chart of step S202 in the first embodiment is provided;

[0041] Figure 5 It is a flow chart of a second implementation mode after step S121 in a method for detecting a short circuit to ground of an inverter IT system provided in the first embodiment of the present invention;

[0042] Figure 6 yes Figure 5 A specific flow chart of step S204 in the second embodiment is provided;

[0043] Figure 7It is a flowchart of a third implementation mode after step S121 in a method for detecting a short circuit to ground of an inverter IT system provided in the first embodiment of the present invention;

[0044] Figure 8 is a circuit diagram of a frequency converter provided by Embodiment 1 of the present invention;

[0045] Fig. 9 It is a schematic diagram of comparing the collected voltage with the bus voltage in a method for detecting a short circuit to ground of an inverter IT system provided in the first embodiment of the present invention;

[0046] Fig.10 It is a waveform diagram of comparison between a collected voltage and a drive signal in a method for detecting a short circuit to ground of an inverter IT system provided in the first embodiment of the present invention;

[0047] Fig.11 It is a waveform diagram of the comparison between the collected voltage and the U-to-V voltage in a method for detecting a short circuit to ground of an inverter IT system provided in the first embodiment of the present invention. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0050] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, wholes, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof.

[0051] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0052] As used in the specification and appended claims of this application, the term "if" can be interpreted as "when" or "uponce" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "uponce it is determined" or "in response to determining" or "uponce [described condition or event] is detected" or "in response to detecting [described condition or event]", depending on the context.

[0053] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0054] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0055] In order to fully understand the present invention, detailed structures and steps will be presented in the following description to illustrate the technical solutions proposed by the present invention. The preferred embodiments of the present invention are described in detail below, but in addition to these detailed descriptions, the present invention may also have other implementations.

[0056] Embodiment 1

[0057] This embodiment 1 provides a method for detecting a short circuit to ground of an inverter IT system. Figure 1 As shown, including:

[0058] Step S101. Obtain the bus voltage and the maximum change value of the voltage of the first-phase motor winding to ground within a first time period.

[0059] Step S102: Determine the phase motor winding that is short-circuited to ground based on the multiple relationship between the maximum change value and the bus voltage.

[0060] In step S101, the bus voltage refers to the voltage of the DC bus of the inverter, which is usually the DC voltage inside the inverter. The bus voltage is the DC voltage obtained by the inverter from the AC power supply through the rectifier bridge, and is also the main power supply for the motor drive. The first time period includes at least one working cycle, and the working cycle refers to a complete cycle of the motor drive signal. In the inverter, the working cycle usually refers to a complete sinusoidal wave change of the three-phase AC power. The cycle is related to the output frequency, for example, the cycle in the 50Hz system is 20 milliseconds. The first phase motor winding to ground voltage refers to the voltage between a certain phase of the motor (such as any one of the three-phase windings of the motor U, V, and W) and the ground terminal, and the ground terminal can be a protective ground terminal (PE terminal). When the motor is operating normally, the winding to ground voltage will have a certain fluctuation. The maximum change value refers to the maximum fluctuation range of the phase winding to ground voltage within a first time period, which is obtained by calculating the peak-to-peak value in the first time period. The maximum change value can be used to determine whether the motor winding is operating normally or in an abnormal state.

[0061] In step S102, the multiple relationship refers to the proportional relationship between the maximum change value of the motor winding voltage to the ground and the bus voltage, which is obtained through actual voltage sampling data and serves as a standard for judging whether the motor has a short circuit to the ground. By comparing the multiple relationship with the preset value, it is determined whether there is an abnormal state, thereby judging whether a short circuit to the ground is formed between the phase motor winding and the ground.

[0062] The working principle of the first embodiment is as follows:

[0063] 1. Short circuit to ground occurs in other phase windings (non-collection phase windings):

[0064] When a phase winding of a motor (such as phase V or phase W) is short-circuited to the ground, the voltage distribution is disrupted, resulting in a larger fluctuation amplitude of the voltage to the ground of the collected phase. Because the voltage of the short-circuited phase winding is pulled down to close to the ground potential, and the voltage of the remaining motor windings will be affected by the short-circuit fault, the fluctuation amplitude of the voltage to the ground is greater than normal. If a phase in the non-collected phase of the motor is short-circuited to the ground, the maximum change value of the voltage to the ground of the collected phase will increase significantly, and the multiple of the maximum change value and the bus voltage exceeds the preset threshold, it can be inferred that one of the other two phases has a short circuit. In order to further determine the faulty phase motor winding, the ground voltage of the other two phase windings can be further collected to determine the faulty phase motor winding.

[0065] 2. Short circuit to ground occurs in the acquisition phase winding:

[0066] When a collection phase winding (such as the U phase winding) is short-circuited to the ground, the collected voltage of the phase winding to the ground will be pulled to almost zero voltage. This is because the current flows directly to the ground terminal through the short-circuit path, forming a low-impedance loop, which causes the voltage fluctuation amplitude of the collection phase winding to be significantly reduced, which is manifested as a very low peak-to-peak value of the voltage to the ground. When the voltage fluctuation amplitude of the collection phase winding is very small and the multiple is lower than the preset value, the preset value is a lower value, indicating that the collection phase has a short circuit to the ground. Because when the motor is working normally, the voltage change value will not have such a low fluctuation.

[0067] The technical effect of the first embodiment is: by introducing low-cost signal acquisition and processing technology, combined with the existing acquisition signal of the frequency converter, high-precision positioning of a phase short circuit to ground of a three-phase motor is achieved. Compared with the traditional detection method that is only effective in the TT system and power-on self-test, this technical solution can also effectively detect the phase motor winding short circuit to ground during the continuous operation of the machine and in the IT system. Through accurate fault location, this technical solution significantly reduces the strong electromagnetic interference caused by continuous operation, and effectively reduces the insulation pressure inside the frequency converter, thereby improving the reliability and stability of the system.

[0068] As an implementation of step S101, obtaining a maximum change value of a first-phase motor winding-to-ground voltage within a first time period includes:

[0069] The maximum and minimum values ​​of the voltage between the first-phase motor winding and the PE terminal in a first time period are obtained, and the minimum value is subtracted from the maximum value to obtain the maximum change value of the voltage between the first-phase motor winding and the ground in the first time period.

[0070] Among them, the PE terminal (Protective Earth) is a protective grounding terminal, which connects the metal shell or conductive part of the motor to the earth to ensure that when an electrical fault occurs, the current can be directed to the earth through the PE terminal to ensure that the fault current can quickly flow to the ground to protect the safety of the equipment and operators. In this step, the PE terminal and the first phase winding of the motor form a reference point for measuring the fluctuation of the voltage between the motor winding and the ground. The function of the PE terminal is to provide a reliable potential reference for measuring the maximum change value of the voltage between the first phase winding of the motor and the ground. Through a voltage sensor or a sampling circuit, the voltage between the first phase motor winding (assuming it is the U phase) and the ground wire (PE terminal) is continuously collected within a predetermined first time period. The collection frequency is usually high enough to capture the voltage change. Within this time period, the collected voltage value is processed to extract the maximum and minimum values ​​of the voltage signal within this time period. By subtracting the minimum voltage value from the maximum voltage value collected, the maximum voltage change (ΔV) within this time period is obtained. The calculated maximum voltage change value is stored for subsequent comparison and analysis with data in other phases or other time periods.

[0071] The technical effect of this embodiment is: by monitoring the voltage changes between the first phase winding and the PE terminal, especially the maximum voltage change value, it can effectively reflect whether there is an abnormality in the phase winding, such as a ground short circuit, and can accurately detect whether the phase motor winding is short-circuited to the ground, thereby improving the safety of the system and the accuracy of fault detection.

[0072] As an implementation method, Figure 2 As shown, the phase motor winding that is short-circuited to ground is determined according to the multiple relationship between the maximum change value and the bus voltage, including:

[0073] Step S121. When the multiple between the maximum change value and the bus voltage is greater than a first preset multiple, it is determined that at least one of the remaining two-phase motor windings is short-circuited to ground.

[0074] Step S122. When the multiple between the maximum change value and the bus voltage is less than a second preset multiple, it is determined that the first-phase motor winding is short-circuited to ground; wherein the first preset multiple is greater than the second preset multiple.

[0075] Among them, the working process of this embodiment is: obtain the maximum change value of the motor winding voltage to the ground through step S101, and compare it with the bus voltage. Set the multiple threshold according to experience or historical records or experimental records. If the multiple of the maximum change value and the bus voltage is greater than the first preset multiple (for example, 1.9 times), it indicates that a serious abnormality has occurred in one phase of the motor winding, such as a short circuit to the ground. The increase in multiples is usually due to the abnormal increase in the voltage fluctuation amplitude caused by the short circuit of one phase of the other two phase motor windings. If the multiple of the maximum change value and the bus voltage is very small, less than the second preset multiple (for example, less than 0.1 times), it indicates that the acquisition phase winding has a short circuit to the ground, and at the same time indicates that the acquisition phase winding has lost its normal voltage change ability, and its voltage hardly fluctuates. Because the short circuit to the ground will cause the voltage to be forced to be pulled down to close to the ground potential, resulting in a very small fluctuation range, the short circuit to the ground will have a direct impact on the voltage fluctuation of each phase winding of the motor, causing the voltage fluctuation to exceed the normal range. The situation where the voltage changes too much or too little is related to the short circuit to the ground, while the voltage fluctuation is relatively stable during normal operation. Therefore, the winding with the short circuit to the ground can be determined by comparing the multiple with the multiple threshold.

[0076] The technical effect of this embodiment is: by comparing the maximum change value of the motor winding voltage to the ground and the multiple relationship of the bus voltage, it is possible to accurately determine whether the motor is short-circuited to the ground, and a multiple greater than or less than a preset multiple threshold means that the voltage fluctuation is abnormal, thereby effectively identifying the short-circuit fault to the ground. This method can detect the phase motor winding with a short-circuit fault to the ground without the need for large current detection based on the impact of the short circuit on the voltage fluctuation.

[0077] The above implementation can accurately detect whether the acquisition phase winding is short-circuited to the ground. When it is determined that the acquisition phase winding is not short-circuited to the ground, it will continue to determine the phase motor winding in the other two phase windings where the short-circuit fault occurs. The following judgment methods may be included: 1. Judgment of the corresponding relationship between the drive signal and the ground voltage: When the drive signal of a certain phase does not change, analyze whether the ground voltage of the phase is synchronized with the change of the drive signal of the remaining two phase motor windings. If a synchronous relationship is found, it can be preliminarily determined that the corresponding motor winding has a short circuit to the ground. 2. Judgment of the level conversion process: The level conversion process of the output phase-to-phase voltage (such as UV phase-to-phase voltage and VU phase-to-phase voltage) is collected and compared with the ground voltage of the first phase motor winding. If the level conversion is synchronized, it can be determined that a phase motor winding in the remaining two phase motor windings has a short circuit to the ground. The above two judgment methods are used at the same time to achieve accurate detection of motor short circuits to the ground at multiple levels and dimensions. Specifically include the following three implementation methods:

[0078] As a first implementation method, Figure 3As shown, it is determined that at least one of the remaining two-phase motor windings is short-circuited to ground, and then the method further includes:

[0079] Step S201: Obtain the voltage of the first-phase motor winding to ground and the drive signal of each-phase motor winding within a second time period.

[0080] Step S202. Select a time period during which the drive signal corresponding to the first phase motor winding does not change within the second time period. During the selected time period, obtain the phase motor winding that is short-circuited to ground based on the correspondence between the first phase motor winding voltage to ground and the drive signals of the remaining phase motor windings.

[0081] In step S201, the second time period refers to a fixed time window, which is usually a time period set based on the working cycle of the motor (for example, at least including a complete voltage or current cycle). During this time period, the collected data is sufficient to cover the normal operating state and voltage changes of the motor. The voltage of the first phase (for example, U phase) motor winding to the ground is collected, and the drive signals of all three-phase motor windings, including U phase, V phase and W phase, are collected at the same time. The drive signal is a control signal sent by the inverter, which is used to control the current and voltage of the motor winding.

[0082] In step S202, in the second time period, the driving signal of a certain phase is periodic, and will remain unchanged in a certain time period in the cycle, for example, when the driving signal of the U phase is stable and unchanged, the voltage of the V phase or the W phase is being adjusted), and the influence of other phase voltages on the phase voltage can be analyzed. In the second time period, the time period in which the driving signal is stable is identified, that is, the driving signal is in a constant state and is not switched or changed. The voltage fluctuation during this period of time can eliminate the interference caused by the change of the driving signal, and ensure the accuracy of the short-circuit fault judgment. The corresponding relationship refers to the mutual correlation between the voltage to ground of the first phase and the driving signals of the remaining two phases (V phase and W phase). By analyzing whether the voltage to ground of the U phase changes with the driving signal of the V phase or the W phase when the U phase driving signal is unchanged, it can be judged which phase of the V phase or the W phase has a short circuit to ground. In the time period in which the driving signal is unchanged, the voltage to ground of the first phase motor winding is compared with the driving signal of the remaining phase motor windings. If it is found that the voltage to ground of a certain phase motor winding changes significantly when the driving signal is unchanged, it is judged that the phase motor winding has a short circuit to ground fault.

[0083] The technical effect of this implementation is that by synchronously collecting the ground voltage and drive signal of each phase motor winding and analyzing the voltage change when the drive signal does not change, the phase motor winding of the other two phase motor windings that has a short circuit to the ground can be accurately located. This implementation can effectively distinguish and locate short-circuit faults, thereby improving the reliability and maintenance efficiency of the system.

[0084] As a specific determination method of the first implementation mode, Figure 4 As shown, the remaining two-phase motor windings include a second-phase motor winding and a third-phase motor winding, the second-phase motor winding corresponds to the second drive signal, and the third-phase motor winding corresponds to the third drive signal.

[0085] In step S202, the phase motor winding that is short-circuited to ground is obtained according to the corresponding relationship between the voltage of the first phase motor winding to ground and the driving signals of the remaining phase motor windings, including:

[0086] Step S221. When the voltage of the first-phase motor winding to ground is consistent with the change trend of the second drive signal, it is determined that the second-phase motor winding is short-circuited to ground.

[0087] Step S222: When the voltage of the first-phase motor winding to ground is consistent with the change trend of the third drive signal, it is determined that the third-phase motor winding is short-circuited to ground.

[0088] The change trend refers to that the change time of the first-phase motor winding voltage to ground and the driving signals of other phase motor windings in one cycle is roughly the same, that is, at the same time point, the first-phase motor winding voltage to ground and the driving signals of other phase motor windings increase, decrease or remain unchanged at about the same time. For example, if the driving signal of the second-phase motor winding increases or decreases at a certain moment, and the first-phase motor winding voltage to ground also fluctuates similarly at about the same time point, then it can be considered that their change trends are consistent.

[0089] The technical effect of this implementation is that by detecting the relationship between the driving signal and the voltage change between different phases, the specific phase where the short circuit to the ground occurs can be effectively located, avoiding the problem that the fault phase cannot be determined by simply collecting the phase voltage. The analysis is performed when the driving signal does not change, so that the change in voltage fluctuation is more easily associated with the fault phase, thereby improving the accuracy of fault judgment.

[0090] As a second implementation method, Figure 5 As shown, it is determined that at least one of the remaining two-phase motor windings is short-circuited to ground, and then the method further includes:

[0091] Step S203: Obtain the voltage between the first-phase motor winding and the ground, and the output phase-to-phase voltage between the first-phase motor winding and the other two-phase motor windings within a third time period.

[0092] Step S204: Obtain the phase motor winding that is short-circuited to ground according to the voltage of the first phase motor winding to ground and the level conversion process of the first phase motor winding outputting the phase-to-phase voltages of the other two phase motor windings.

[0093] In step S203, the third time period is a fixed time window set for collecting enough data for comparative analysis of level conversion. During this time period, the voltage of the first-phase motor winding to the ground and the output phase-to-phase voltage of the first-phase motor winding to the other two-phase motor windings are continuously collected to ensure that the collected data contains enough periodic information and can cover the complete voltage fluctuation of the motor operation. The voltage of the first-phase motor winding to the ground reflects the potential difference between the first-phase motor winding (such as the U-phase motor winding) and the ground, and is used to detect whether the first-phase motor winding is affected by other phase faults. The output phase-to-phase voltage between the first-phase motor winding and the remaining two-phase motor windings refers to the voltage difference between the first-phase motor winding and the second-phase motor winding (such as the voltage between the U-phase and the V-phase) and the voltage difference between the first-phase motor winding and the third-phase motor winding (such as the voltage between the U-phase and the W-phase), which is used to detect the working state of the two-phase motor windings and whether a short circuit to the ground occurs. By collecting the voltage of the U-phase to the V-phase and the voltage of the U-phase to the W-phase, and analyzing their level conversion, it is determined whether there is an electrical abnormality or a short circuit.

[0094] In step S204, the level conversion process refers to the change process of the voltage signal from a high level to a low level, or from a low level to a high level, which is used to determine whether the voltage fluctuation is synchronized with other phases. By analyzing the level conversion process of the first-phase motor winding to the ground voltage and the first-phase motor winding to the output phase-to-phase voltage of the remaining two-phase motor windings, it can be detected whether their voltage fluctuations are synchronized. If the level conversion of the first phase is synchronized with a certain phase-to-phase voltage, it can be determined which phase motor winding has a short circuit. When it is detected that the level conversion of the first relative voltage to the ground is synchronized with the output phase-to-phase voltage of the first-phase motor winding to the remaining two-phase motor windings, it can be inferred whether the V phase or the W phase has a short circuit. The synchronous level conversion indicates that the voltage fluctuation of the phase motor winding is abnormal, which is consistent with a short circuit.

[0095] As a specific embodiment of the second implementation, the remaining two-phase motor windings include a second-phase motor winding and a third-phase motor winding, and the output phase-to-phase voltage includes a first phase-to-phase voltage and a second phase-to-phase voltage, the first phase-to-phase voltage is the voltage between the first-phase motor winding and the second-phase motor winding, and the second phase-to-phase voltage is the voltage between the first-phase motor winding and the third-phase motor winding.

[0096] like Figure 6 As shown, the phase motor winding that is short-circuited to ground is obtained according to the level conversion process of the first phase motor winding to ground voltage and the first phase motor winding to the output phase-to-phase voltage of the other two phase motor windings, including:

[0097] Step S241: When the level conversion period of the first-phase motor winding voltage to ground is the same as the level conversion period of the first phase voltage, it is determined that the second-phase motor winding is short-circuited to ground.

[0098] Step S242: When the level conversion period of the first-phase motor winding voltage to ground is the same as the level conversion period of the second phase voltage, it is determined that the third-phase motor winding is short-circuited to ground.

[0099] Among them, the UV phase-to-phase voltage refers to the voltage difference between the first-phase motor winding (U-phase motor winding) and the second-phase motor winding (V-phase motor winding), which is used to determine the working status and voltage fluctuation of the U-phase motor winding and the V-phase motor winding. Collect the UV phase-to-phase voltage, and detect whether it is synchronized by comparing it with the level conversion cycle of the first-phase motor winding to the ground voltage. If the detection result is synchronized, it indicates that the V-phase motor winding is short-circuited. The UW phase-to-phase voltage refers to the voltage difference between the first-phase motor winding (U-phase motor winding) and the third-phase motor winding (W-phase motor winding), which complements the UV phase-to-phase voltage, which is convenient for further determination of the specific short-circuited phase. Collect the UW phase-to-phase voltage and compare it with the level conversion cycle of the first-phase motor winding to the ground voltage. If the level conversion cycles of the two are synchronized, it indicates that the W-phase motor winding is short-circuited.

[0100] The technical effect of this embodiment is that by synchronously analyzing the level conversion of the first relative ground voltage and the first phase-to-phase voltage and the second phase-to-phase voltage, the phase motor winding that is short-circuited to the ground can be quickly and accurately identified, providing a reliable short-circuit detection mechanism, which can respond quickly in the early stages of the fault, thereby reducing the risk of equipment damage and operation interruption. In a complex three-phase motor system, by collecting multiple sets of voltage data and analyzing the level conversion process, the short-circuited phase motor winding can be efficiently located, improving the efficiency and accuracy of diagnosis.

[0101] As a third implementation, based on the first implementation, the following steps are also included: Figure 7 As shown, it is determined that at least one of the remaining two-phase motor windings is short-circuited to ground, and then the method further includes:

[0102] Step S205. Obtain the voltage between the first phase motor winding and the ground in the second time period, and the output phase-to-phase voltage between the first phase motor winding and the other two phase motor windings, wherein the output phase-to-phase voltage includes a first phase-to-phase voltage and a second phase-to-phase voltage, the first phase-to-phase voltage is the voltage between the first phase motor winding and the second phase motor winding, and the second phase-to-phase voltage is the voltage between the first phase motor winding and the third phase motor winding.

[0103] Step S206: When the level conversion period of the first-phase motor winding voltage to ground is the same as the first phase-to-phase voltage, it is determined that the second-phase motor winding is short-circuited to ground.

[0104] Step S207: When the level conversion period of the first-phase motor winding voltage to ground is the same as the level conversion period of the second phase voltage, it is determined that the third-phase motor winding is short-circuited to ground.

[0105] Step S208: Compare and determine whether the results are consistent. If yes, execute step S209; if not, execute step S210.

[0106] Step S209: Output the determination result.

[0107] Step S210. Re-acquire the bus voltage and the maximum change value of the voltage between the first phase motor winding and the ground within a first time period.

[0108] Among them, in the first embodiment, the phase motor winding that is most likely to be short-circuited is determined by the correspondence between the voltage to ground of the U-phase motor winding and the drive signals of the other two-phase motor windings. When the drive signal remains unchanged, analyze whether the voltage to ground of the U-phase motor winding changes synchronously with the drive signals of the other phase motor windings. If synchronized, the first judgment result is determined. In this embodiment, the level conversion process between the voltage to ground of the first-phase motor winding and the output phase-to-phase voltage of the first-phase motor winding to the other two-phase motor windings is compared to obtain the second judgment result. When the same judgment result is obtained by two different methods, it is confirmed that the phase motor winding has a short circuit to the ground. When the results of the two judgments are inconsistent, the data is re-collected and re-analyzed to avoid misdiagnosis.

[0109] The technical effect of this implementation is that the phase motor winding that has a short circuit to ground is determined by combining comparative analysis of multiple signals, and the reliability and accuracy of the diagnosis result are ensured through a two-layer verification mechanism of the first judgment result and the second judgment result. When the two results are consistent, the fault phase is finally confirmed; if they are inconsistent, the detection and analysis will be re-performed, thereby improving the robustness and reliability of the entire fault detection system.

[0110] The third embodiment is different from the first two embodiments in that:

[0111] 1. A two-layer verification mechanism is added, namely: the first layer preliminarily determines the short-circuited phase through the corresponding relationship between the first phase voltage and the driving signals of the other two phases, and obtains a first judgment result. The second layer obtains the second judgment result through the level conversion process of the voltage to ground and the phase-to-phase voltage. Only when the phase motor windings obtained by the two layers of verification are at the same time can the phase motor winding with a short circuit be finally confirmed.

[0112] 2. The ground voltage, phase-to-phase voltage and drive signal are introduced at the same time, and multi-dimensional signal analysis is performed by comparing the level conversion synchronization and the unchanged drive signal. Combining the voltage signal and the drive signal is not just a simple voltage comparison, which increases the multi-dimensionality of the signal analysis. Through the combination of the level conversion process and the drive signal, it is easier to capture subtle electrical changes and improve the sensitivity and accuracy of detection.

[0113] 3. When confirming the result of the short-circuited phase motor winding, the phase motor winding will be determined as a short-circuited motor winding only when the first judgment result and the second judgment result are consistent. If the two results are inconsistent, it will not be confirmed immediately, but the data will be re-acquired and re-analyzed. The accuracy and robustness of the detection are guaranteed by multiple verifications and re-analysis of the results. Especially in complex motor operating environments, this double verification process can effectively reduce false positives and missed positives.

[0114] In the above embodiment, the second time period and the third time period may be the same, different, or partially the same. The first embodiment of the present invention is described below by using a specific example:

[0115] like Figure 8 The inverter includes a diode D1, a diode D2, a diode D3, a diode D4, a diode D5, a diode D6, a polar capacitor C1, a polar capacitor C2, a MOS tube Q1, a MOS tube Q2, a MOS tube Q3, a MOS tube Q4, a MOS tube Q5 and a MOS tube Q6. The cathode of the diode D1, the cathode of the diode D2, the cathode of the diode D3, the positive electrode of the polar capacitor C1, the drain of the MOS tube Q1, the drain of the MOS tube Q2 and the drain of the MOS tube Q3 are connected together. The anode of the diode D1 and the cathode of the diode D2 are connected together and then connected to the R phase power supply. The anode of the diode D3 and the cathode of the diode D4 are connected together. The MOS transistor Q1 is connected to the S-phase power supply, the anode of the diode D5 and the cathode of the diode D6 are connected to the T-phase power supply, the source of the MOS transistor Q1 and the drain of the MOS transistor Q4 are connected to the U-phase motor winding of the motor M, the source of the MOS transistor Q2 and the drain of the MOS transistor Q5 are connected to the V-phase motor winding of the motor M, the source of the MOS transistor Q3 and the drain of the MOS transistor Q6 are connected to the W-phase motor winding of the motor M, the anode of the diode D2, the anode of the diode D4, the anode of the diode D6, the negative electrode of the polarity capacitor C2, the source of the MOS transistor Q4, the source of the MOS transistor Q5, and the source of the MOS transistor Q6 are connected to each other, and the motor M is also connected to the PE line.

[0116] like Fig. 9 As shown, in the IT system, when the V-phase motor winding is short-circuited to the ground, the U-phase motor winding voltage to the ground, that is, the U-to-PE voltage, is measured and compared with the bus voltage. The bus voltage is about 540V, the maximum value of the U-to-PE voltage is greater than 540V, and the minimum value of the U-to-PE voltage is less than -540V. Therefore, when the maximum change value of the U-to-PE voltage, that is, the peak-to-peak voltage is greater than 540×1.9=1026V, it is determined that the V-phase motor winding or the W-phase motor winding is short-circuited to the ground.

[0117] like Fig.10As shown, during the time period when the U-phase drive signal (the drive signal of the U-phase motor winding) remains unchanged, the U-to-PE voltage is compared with the V-phase drive signal (the drive signal of the V-phase motor winding), and the U-to-PE voltage is compared with the W-phase drive signal (the drive signal of the W-phase motor winding). The change time of the V-phase drive signal and the U-to-PE voltage is roughly the same. Therefore, it is determined that the V-phase motor winding is short-circuited to the ground.

[0118] like Fig.11 As shown, by comparing the U-to-PE voltage with the U-to-V voltage (i.e., the phase-to-phase voltage of the U-phase motor winding to the V-phase motor winding), it can be seen that the two voltage signals are level-converted at the same time, and it is determined that the V-phase motor winding is short-circuited to the ground.

[0119] The above two methods of determining that the V-phase motor winding is short-circuited to the ground can be performed independently, that is, only one determination method is needed; or, the two determination methods can be performed simultaneously. When the conclusions of determining that the V-phase motor winding is short-circuited to the ground are the same at the same time, the determination result can be made more accurate. At this time, the inverter jumps to fault interrupt operation and displays the V-phase motor winding short-circuited to the ground on the interface.

[0120] Embodiment 2 of the present application further provides a frequency converter, which includes: at least one processor, a memory, and a computer program stored in the memory and executable on the at least one processor, wherein the processor implements the steps of any of the above-mentioned method embodiments when executing the computer program.

[0121] Embodiment 3 of the present application further provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps in the above-mentioned method embodiments can be implemented.

[0122] An embodiment of the present application provides a computer program product. When the computer program product runs on a mobile terminal, the mobile terminal can implement the steps in the above-mentioned method embodiments when executing the computer program product.

[0123] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present application implements all or part of the processes in the above-mentioned embodiment method, which can be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium can at least include: any entity or device that can carry the computer program code to the camera / terminal device, recording medium, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, RandomAccess Memory), electric carrier signal, telecommunication signal and software distribution medium. For example, a USB flash drive, a mobile hard disk, a disk or an optical disk. In some jurisdictions, according to legislation and patent practice, computer-readable media cannot be electric carrier signals and telecommunication signals.

[0124] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0125] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0126] In the embodiments provided in the present application, it should be understood that the disclosed devices / network equipment and methods can be implemented in other ways. For example, the device / network equipment embodiments described above are merely schematic. For example, the division of the modules or units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0127] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0128] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A method for detecting short circuit to ground of an inverter IT system, characterized in that: include: Obtaining a bus voltage and a maximum change value of a first-phase motor winding-to-ground voltage within a first time period; The phase motor winding that is short-circuited to ground is determined based on the multiple relationship between the maximum change value and the bus voltage.

2. The method for detecting a short circuit to ground according to claim 1, wherein: The method of determining the phase motor winding that is short-circuited to ground according to the multiple relationship between the maximum change value and the bus voltage includes: When the multiple between the maximum change value and the bus voltage is greater than a first preset multiple, it is determined that at least one of the remaining two-phase motor windings is short-circuited to ground; When the multiple between the maximum change value and the bus voltage is less than a second preset multiple, it is determined that the first-phase motor winding is short-circuited to ground; Wherein, the first preset multiple is greater than the second preset multiple.

3. The method for detecting a short circuit to ground according to claim 2, wherein: The step of determining that at least one of the remaining two-phase motor windings is short-circuited to ground further includes: Acquire the voltage of the first-phase motor winding to ground and the driving signal of each-phase motor winding within a second time period; A time period during which the drive signal corresponding to the first phase motor winding does not change within the second time period is selected, and within the selected time period, the phase motor winding that is short-circuited to ground is obtained based on the correspondence between the first phase motor winding voltage to ground and the drive signals of the remaining phase motor windings.

4. The method for detecting a short circuit to ground according to claim 3, wherein: The remaining two-phase motor windings include a second-phase motor winding and a third-phase motor winding, the second-phase motor winding corresponds to a second drive signal, and the third-phase motor winding corresponds to a third drive signal; The method of obtaining the phase motor winding that is short-circuited to the ground according to the correspondence between the voltage of the first phase motor winding to the ground and the drive signals of the remaining phase motor windings includes: When the voltage of the first-phase motor winding to ground is consistent with the change trend of the second drive signal, it is determined that the second-phase motor winding is short-circuited to ground; When the voltage of the first-phase motor winding to ground is consistent with the change trend of the third drive signal, it is determined that the third-phase motor winding is short-circuited to ground.

5. The method for detecting a short circuit to ground according to claim 2, wherein: It is determined that at least one of the remaining two-phase motor windings is short-circuited to ground, and then the method further includes: Acquire the voltage of the first-phase motor winding to ground and the output phase-to-phase voltage of the first-phase motor winding to the other two-phase motor windings within a third time period; The phase motor winding that is short-circuited to the ground is obtained according to the level conversion process of the first phase motor winding to the ground voltage and the output phase-to-phase voltage of the first phase motor winding to the other two phase motor windings.

6. The method for detecting a short circuit to ground according to claim 5, characterized in that: The remaining two-phase motor windings include a second-phase motor winding and a third-phase motor winding, and the output interphase voltage includes a first interphase voltage and a second interphase voltage, wherein the first interphase voltage is a voltage between the first-phase motor winding and the second-phase motor winding, and the second interphase voltage is a voltage between the first-phase motor winding and the third-phase motor winding; The method of obtaining the phase motor winding short-circuited to ground according to the level conversion process of the first phase motor winding to ground voltage and the output phase-to-phase voltage of the first phase motor winding to the other two phase motor windings respectively includes: When the level conversion period of the first-phase motor winding voltage to ground is the same as the level conversion period of the first phase voltage, determining that the second-phase motor winding is short-circuited to ground; When the level conversion period of the first-phase motor winding voltage to ground is the same as that of the second phase-to-phase voltage, it is determined that the third-phase motor winding is short-circuited to ground.

7. The method for detecting a short circuit to ground according to claim 4, wherein: The step of determining that at least one of the remaining two-phase windings is short-circuited to ground further includes: Acquire the voltage of the first-phase motor winding to ground and the output phase-to-phase voltage of the first-phase motor winding to the remaining two-phase motor windings in the second time period, wherein the output phase-to-phase voltage includes a first phase-to-phase voltage and a second phase-to-phase voltage, the first phase-to-phase voltage is the voltage between the first-phase motor winding and the second-phase motor winding, and the second phase-to-phase voltage is the voltage between the first-phase motor winding and the third-phase motor winding; When the level conversion period of the first-phase motor winding voltage to ground is the same as the level conversion period of the first phase voltage, determining that the second-phase motor winding is short-circuited to ground; When the level conversion period of the first-phase motor winding voltage to ground is the same as that of the second phase voltage, it is determined that the third-phase motor winding is short-circuited to ground; Compare and determine whether the results are consistent. If yes, output the determination result. Otherwise, re-acquire the bus voltage and the maximum change value of the voltage between the first phase motor winding and the ground within a first time period.

8. The method for detecting a short circuit to ground according to claim 1, wherein: Obtaining a maximum change value of the voltage of the first-phase motor winding to ground within a first time period, including: The maximum and minimum values ​​of the voltage between the first-phase motor winding and the PE terminal in a first time period are obtained, and the minimum value is subtracted from the maximum value to obtain the maximum change value of the voltage between the first-phase motor winding and the ground in the first time period.

9. A frequency converter, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 8 is implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 8 is implemented.

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