Method and system for detecting and responding to single-phase ground fault on input side of high-voltage frequency converter

Abstract

The application relates to the technical field of high-voltage frequency converters, and discloses a detection and response method and system for single-phase ground fault of the input side of a high-voltage frequency converter, which comprises the following steps: S1, collecting three-phase phase voltages of the input side of the high-voltage frequency converter through a three-phase high-voltage resistance voltage division mode, and calculating the amplitudes of the three-phase phase voltages; S2, judging whether voltage abnormality and abnormal fault types occur according to the changes of the amplitudes of the three-phase phase voltages, and making corresponding response measures according to the abnormal fault types. When single-phase ground fault occurs at the high-voltage input side, the application uses the voltage detection mode of the three-phase high-voltage resistance voltage division to detect whether the fault occurs in real time, quickly judges whether single-phase ground fault occurs, and distinguishes whether the neutral point grounding mode of the single-phase ground fault power supply system is direct grounding, so that the main control system rapidly gives corresponding solutions, and the reliability and safety of the high-voltage frequency converter are improved.

Description

Technical Field

[0001] This invention relates to the field of high-voltage frequency converter technology, specifically to a method and system for detecting and responding to single-phase grounding faults on the input side of a high-voltage frequency converter. Background Technology

[0002] When a single-phase ground fault occurs on the input side of a traditional high-voltage frequency converter, failure to detect it correctly can easily lead to a major shutdown of the high-voltage frequency converter, affecting the normal operation of the entire drive system, impacting production processes, and even posing safety hazards. Therefore, it is essential to detect and resolve single-phase ground faults promptly. The impact of a single-phase ground fault on the high-voltage frequency converter differs depending on whether the power supply neutral point is directly grounded or not. Therefore, to completely resolve single-phase ground faults, it is necessary to correctly identify the type of single-phase ground fault. Specifically, when the input neutral point is not directly grounded, conventional high-voltage frequency converters use a dual-PT scheme to detect the input line voltage, making it difficult to effectively identify single-phase ground faults. Therefore, a more appropriate single-phase ground fault detection method is required. The main problems with single-phase ground faults on the input side of high-voltage frequency converters are as follows: Figure 2 As shown.

[0003] The impact of a single-phase ground fault on a high-voltage frequency converter varies depending on the grounding method. Specifically, in a power supply system where the input neutral point is not directly grounded, although one phase on the high-voltage side is grounded, causing a change in the voltage to ground, the relationship between line voltages remains unchanged. Furthermore, because the high-voltage and low-voltage sides of the phase-shifting transformer are electromagnetically coupled, the voltage applied to the primary side of the transformer remains unchanged, and consequently, the voltage on the secondary side also remains unchanged. Therefore, although a single-phase ground fault in a power supply system where the input neutral point is not directly grounded has no practical impact on the high-voltage frequency converter, it is still necessary to clearly report the fault upon detection.

[0004] In a power supply system with a directly grounded neutral point on the input side, the phase voltage of the non-faulty phase remains unchanged, while the phase voltage of the faulty phase is zero. The relationship between line voltages also changes, which causes the secondary voltage of the phase-shifting transformer to decrease, thereby causing the unit voltage to decrease. Furthermore, after the three-phase power supply is restored to normal, the current of the high-voltage frequency converter is prone to sudden changes during the restoration process, making it susceptible to overcurrent faults.

[0005] Therefore, it is essential to quickly determine whether a single-phase grounding fault has occurred and to distinguish whether the neutral point grounding method of the power system with the single-phase grounding fault is direct grounding. Summary of the Invention

[0006] This invention provides a method and system for detecting and responding to single-phase grounding faults on the input side of a high-voltage frequency converter. It utilizes a three-phase high-voltage resistor voltage divider detection method to quickly determine whether a single-phase grounding fault has occurred and to distinguish whether the neutral point grounding method of the power supply system with a single-phase grounding fault is direct grounding. Thus, the main control system can quickly provide a corresponding solution, improving the reliability and safety of the high-voltage frequency converter.

[0007] This invention is achieved through the following technical solution:

[0008] A method for detecting and handling single-phase grounding faults on the input side of a high-voltage frequency converter, including:

[0009] S1. Acquire the three-phase phase voltage on the input side of the high-voltage frequency converter by means of three-phase high-voltage resistor voltage division, and calculate the amplitude of the three-phase phase voltage;

[0010] S2. Determine whether voltage abnormality and the type of abnormal fault have occurred based on the changes in the amplitude of the three-phase phase voltage, and take corresponding countermeasures based on the type of abnormal fault.

[0011] As an optimization, the specific implementation steps of S2 are as follows:

[0012] S2.1. Determine whether a voltage anomaly has occurred based on the change in phase voltage amplitude in S1. If not, return to this step; if yes, jump to S2.2.

[0013] S2.2 Determine whether a single-phase ground fault has occurred based on the change in phase voltage amplitude. If not, proceed to S2.3; otherwise, proceed to S2.4.

[0014] S2.3 Determine that the fault is a power supply fault other than a single-phase ground fault and take appropriate measures. After the fault is cleared, proceed to S2.6.

[0015] S2.4. Determine whether the neutral point on the input side is directly grounded based on the amplitude relationship between the three-phase line voltages. If so, a single-phase grounding minor fault alarm will be triggered. After the fault is cleared, the process will jump to S2.6. Otherwise, the process will jump to S2.5.

[0016] S2.5. Handle single-phase grounding faults with direct neutral grounding, and adopt a momentary power outage and restart scheme to cross the fault area and wait for the voltage to return to normal.

[0017] S2.6, run normally and return to S2.1.

[0018] As an optimization, in S2.1, the determination of whether a voltage abnormality has occurred based on the change in phase voltage amplitude specifically involves determining whether the change in phase voltage amplitude is greater than 10% of the original phase voltage amplitude. If so, a voltage abnormality is determined to have occurred.

[0019] As an optimization, in S2.2, if the phase voltage of one of the three phase voltages is less than 5% of the rated amplitude of the phase voltage, then a single-phase ground fault is determined to have occurred.

[0020] As an optimization, in S2.4, when a single-phase ground fault with the neutral point directly grounded occurs, the phase voltage of the directly grounded fault phase is 0V, and the phase voltage of the non-faulty phase remains unchanged or changes less than the first threshold.

[0021] As an optimization, in S2.4, when a single-phase ground fault occurs where the neutral point is not directly grounded, the phase voltage of the non-directly grounded fault phase is 0V, and the phase voltage of the non-faulty phase becomes the line voltage.

[0022] As an optimization, in S2.3, other power supply faults include: symmetrical voltage drop of three-phase power grid and asymmetrical voltage drop of three-phase power grid (not single-phase grounding). The corresponding handling measures for the other power supply faults include: instantaneous power outage and restart.

[0023] As an optimization, in S2.5, the instantaneous power outage restart scheme is as follows: after the frequency converter detects the above-mentioned fault, it immediately stops transmitting waves and stops outputting. Then, after the grid voltage is detected to be restored, it detects the back EMF of the motor by outputting the PT. The main control system estimates the motor running speed, back EMF amplitude and phase angle based on the back EMF, and then retransmits the wave to output voltage based on the above information to drive the high-voltage motor again.

[0024] This invention also discloses a detection and response system for single-phase grounding faults on the input side of a high-voltage frequency converter, comprising:

[0025] The phase voltage sampling system is used to acquire the three-phase phase voltage on the input side of the high-voltage frequency converter through a three-phase high-voltage resistor voltage divider method;

[0026] The main control system, connected to the phase voltage sampling system and the high-voltage frequency converter, is used to calculate the amplitude of the three-phase phase voltage, and to determine whether voltage abnormality and abnormal fault type have occurred based on the change in the amplitude of the three-phase phase voltage, and then to take corresponding countermeasures based on the abnormal fault type.

[0027] As an optimization, the specific steps for the main control system to calculate the amplitude of the three-phase phase voltage and take corresponding countermeasures are as follows:

[0028] When the main control system detects a single-phase ground fault, it identifies whether the neutral point on the input side is directly grounded based on the changes in the amplitude of the three-phase voltage. If it is determined to be non-directly grounded, it sends fault indication code 1 to indicate a minor single-phase ground fault, and no further action is taken; the high-voltage frequency converter continues to operate normally. If it is determined to be directly grounded, it sends fault indication code 2 to indicate a single-phase ground fault, and the main control system controls the high-voltage frequency converter to adopt an instantaneous power-off and restart scheme to pass through the fault area and avoid overcurrent impact on the high-voltage frequency converter after the normal power supply is restored.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] When a single-phase ground fault occurs on the high-voltage input side, this invention utilizes a voltage detection method based on the voltage division of three-phase high-voltage resistors to detect whether the fault has occurred in real time. The main control system then determines whether the neutral point on the high-voltage side is directly grounded by observing changes in the amplitude of the three-phase line voltage and issues a corresponding fault code. If the fault code indicates that the neutral point is not directly grounded, only the fault indication (minor phase ground fault) needs to be maintained, and no further operations are required; the high-voltage frequency converter continues to operate normally. If the fault code indicates that the neutral point is directly grounded, the main control system controls the high-voltage frequency converter to use an instantaneous power-off and restart method to traverse the fault area. After detecting that the high-voltage three-phase circuit has returned to normal, power is restored to the high-voltage frequency converter. Through the above processing, both systems with directly grounded and indirectly grounded neutral points on the input side of the high-voltage frequency converter can be properly handled when a single-phase ground fault occurs. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0032] Figure 1 This is a schematic diagram of the detection and response system described in this invention;

[0033] Figure 2 A diagram illustrating the main problems associated with a single-phase ground fault on the input side of a high-voltage frequency converter;

[0034] Figure 3 The waveform diagram of the three-phase line voltage on the grid side for a single-phase direct ground fault in the power supply.

[0035] Figure 4 Waveforms of the three-phase phase voltages and their effective values ​​on the grid side during a single-phase direct ground fault in the power supply.

[0036] Figure 5The waveform diagram shows the three-phase phase voltage and RMS value of the shift transformer secondary side in the case of a single-phase direct ground fault in the power supply.

[0037] Figure 6 The waveform diagram of the unit voltage (three phases) for a single-phase direct ground fault in the power supply;

[0038] Figure 7 The waveform diagram of the three-phase output current of the frequency converter for a single-phase direct ground fault.

[0039] Figure 8 The waveform of the motor speed is shown when a single-phase direct ground fault occurs.

[0040] Figure 9 The waveform diagram of the three-phase input line voltage for a single-phase non-directly grounded fault in the power supply.

[0041] Figure 10 The input phase voltage waveform and RMS waveform diagram for a single-phase non-directly grounded fault in the power supply;

[0042] Figure 11 The waveform and RMS value of the secondary line voltage of the shifting transformer for a single-phase non-directly grounded power supply fault are shown in the figure.

[0043] Figure 12 The unit voltage waveform diagram for a single-phase non-directly grounded fault in the power supply;

[0044] Figure 13 The waveform diagram of the three-phase output current of the frequency converter under a single-phase non-directly grounded power supply fault is shown. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0046] Because conventional high-voltage frequency converters in the prior art use a dual-PT scheme to detect the input side line voltage, they cannot effectively identify the occurrence of single-phase grounding faults. Therefore, when a single-phase grounding fault occurs on the high-voltage input side, how to accurately identify the occurrence of the fault, how to accurately determine the grounding mode of the high-voltage side neutral point, and how to take corresponding solutions for different neutral point grounding modes, so as to ensure the normal operation of the high-voltage frequency converter, has become an urgent problem to be solved. Therefore, the detection and response method and system of the present invention can solve the above problems. Next, the method and system of the present invention will be specifically introduced.

[0047] Example 1 describes the detection and handling methods for single-phase grounding faults on the input side of a high-voltage frequency converter, specifically including:

[0048] S1. Acquire the three-phase phase voltages on the input side of the high-voltage frequency converter using a three-phase high-voltage resistor voltage divider method, and calculate the amplitude of the three-phase phase voltages. To detect the occurrence of a single-phase ground fault, a voltage detection scheme using a three-phase high-voltage resistor voltage divider is adopted. This scheme can quickly identify the occurrence of a fault by observing changes in phase voltage during a single-phase ground fault. The specific identification process is described in the following scheme.

[0049] like Figure 1 As shown, two resistors connected in series are connected to the three phase voltages on the input side of the high-voltage frequency converter. The other end of the three series links is grounded, and the acquisition points are set between the two resistors in the same series link.

[0050] S2. Determine whether voltage abnormality and the type of abnormal fault have occurred based on the changes in the amplitude of the three-phase phase voltage, and take corresponding countermeasures based on the type of abnormal fault.

[0051] In this embodiment, the specific implementation steps of S2 are as follows:

[0052] S2.1. Determine whether a voltage abnormality has occurred based on the change in phase voltage amplitude in S1. If not, return to this step; if yes, jump to S2.2. Specifically, determining whether a voltage abnormality has occurred based on the change in phase voltage amplitude means determining whether the change in phase voltage amplitude is greater than 10% of the original phase voltage amplitude. If yes, determine that a voltage abnormality has occurred and jump to S2.2.

[0053] S2.2 Determine whether a single-phase ground fault has occurred based on the change in phase voltage amplitude. If not, jump to S2.3; otherwise, jump to S2.4. Specifically, if the phase voltage of one of the three phase voltages is less than 5% of the rated amplitude of the phase voltage, it is determined that a single-phase ground fault has occurred, and jump to S2.4.

[0054] S2.3 Determine that the fault is a power supply fault other than a single-phase ground fault and take corresponding measures. After the fault is cleared, jump to S2.6. Specifically, other power supply faults include: symmetrical voltage drop of three-phase power grid and asymmetrical voltage drop of three-phase power grid (non-single-phase ground fault). The corresponding measures for other power supply faults include: instantaneous power outage and restart.

[0055] S2.4. Determine whether the neutral point on the input side is directly grounded based on the amplitude relationship between the three-phase line voltages. If so, trigger a single-phase ground fault alarm. After the fault is cleared, proceed to S2.6; otherwise, proceed to S2.5. Specifically, when a single-phase ground fault with a directly grounded neutral point occurs, the phase voltage of the directly grounded faulty phase is 0V, and the phase voltage of the non-faulty phase remains unchanged or changes less than a first threshold. Here, the first threshold can be the amplitude of the non-faulty phase voltage deviating from the rated amplitude by ±10%. When a single-phase ground fault with a non-directly grounded neutral point occurs, the phase voltage of the non-directly grounded faulty phase is 0V, and the phase voltage of the non-faulty phase becomes the line voltage.

[0056] S2.5. Handle single-phase grounding faults with direct neutral grounding and adopt a momentary power outage and restart scheme to cross the fault area and wait for the voltage to return to normal. The momentary power outage and restart scheme is as follows: After the frequency converter detects the above-mentioned fault, it immediately stops transmitting waves and stops outputting. Then, after the grid voltage is detected to be restored, it detects the back EMF of the motor through the output PT. The main control system estimates the motor running speed, back EMF amplitude and phase angle based on the back EMF, and then retransmits the wave output voltage based on the above information to drive the high-voltage motor again.

[0057] S2.6, run normally and return to S2.1.

[0058] like Figure 1 As shown, this invention also discloses a detection and response system for single-phase grounding faults on the input side of a high-voltage frequency converter, comprising:

[0059] The phase voltage sampling system is used to acquire the three-phase phase voltage on the input side of the high-voltage frequency converter through a three-phase high-voltage resistor voltage divider method;

[0060] The main control system, connected to the phase voltage sampling system and the high-voltage frequency converter, is used to calculate the amplitude of the three-phase phase voltage, and to determine whether voltage abnormality and abnormal fault type have occurred based on the change in the amplitude of the three-phase phase voltage, and then to take corresponding countermeasures based on the abnormal fault type.

[0061] In this embodiment, the specific steps for the main control system to calculate the amplitude of the three-phase phase voltage and take corresponding countermeasures are as follows:

[0062] The main control system calculates whether the change in the amplitude of the three-phase phase voltage is greater than 10%. If so, the "input voltage abnormality judgment flag" of the main control system is set, the main control system counts, and delays for one cycle. Since one cycle is usually tolerable for the system, delaying for one cycle can ensure the accuracy of fault judgment and avoid false alarms. When the main control system detects a single-phase ground fault, it identifies and determines whether the neutral point on the input side is directly grounded based on the change in the amplitude of the three-phase voltage. If it is determined to be non-directly grounded, fault indication code 1 is sent to indicate a minor single-phase ground fault, and no other processing is performed; the high-voltage frequency converter continues to operate normally. If it is determined to be directly grounded, fault indication code 2 is sent to indicate a single-phase ground fault, and the main control system controls the high-voltage frequency converter to adopt an instantaneous power-off and restart scheme to pass through the fault area and avoid overcurrent impact on the high-voltage frequency converter after the normal power supply is restored.

[0063] When a single-phase ground fault occurs, the main control system accurately determines the grounding mode (direct grounding or non-direct grounding) of the input side neutral point based on the changes in the three-phase line voltage amplitude, and issues a corresponding fault code. For different fault codes, if the fault code indicates a single-phase ground fault under non-direct grounding conditions, the main control system issues a fault indication (indicating a minor single-phase ground fault) and no further operations are performed; the high-voltage frequency converter continues to operate. If the fault code indicates a single-phase ground fault under direct grounding conditions, the main control system issues a fault indication (indicating a single-phase ground fault), and the high-voltage frequency converter uses an instantaneous power outage and restart method to traverse the fault area, automatically restoring power supply after power is restored.

[0064] This invention utilizes a three-phase high-voltage resistor voltage division detection method to identify whether a single-phase grounding fault has occurred in a power system where the neutral point on the input side of a high-voltage frequency converter is not directly grounded. This overcomes the limitation of dual-PT detection of input-side voltage, which cannot detect single-phase grounding faults. For different power grounding methods, it can accurately identify single-phase grounding faults under both direct and indirect grounding conditions based on the changes in the three-phase voltage amplitude, and will take corresponding fault solutions. Specifically, for single-phase grounding faults under indirect grounding conditions, it reports the fault (minor single-phase grounding fault) without further action; for single-phase grounding faults under direct grounding conditions, it reports the fault (single-phase grounding fault) and uses a momentary power outage and restart method to traverse the fault area (restoring power after restoration). This reduces the workload of testing personnel, improves the targeting and accuracy of solving single-phase grounding fault problems on the frequency converter input side, and enhances the reliability of the frequency converter.

[0065] Next, a simulation was performed for single-phase ground faults in the power grid (including ground faults with low resistance). Figure 3-8 The waveforms show the current waveforms on the input side, DC bus, and output side of the frequency converter under a single-phase direct ground fault. Figure 3-8It can be seen that in a single-phase ground fault with a directly grounded neutral point, the three-phase line voltage relationship on the grid side changes: the phase voltage of the non-faulty phase remains basically unchanged, while the phase voltage of the faulty phase is 0; simultaneously, from Figure 7 It can also be seen that if reasonable measures are not taken, the restoration of three-phase power supply will cause a relatively serious overcurrent impact on the high-voltage frequency converter.

[0066] Simulations were performed for single-phase non-direct grounding faults (including high-resistance grounding) in the power grid. Figure 9-13 The waveforms of the inverter's input side, DC bus, and output side under a single-phase non-directly grounded power supply fault are shown.

[0067] from Figure 9-13 It can be seen that in a high-voltage side neutral point non-directly grounded system, when a single phase is not directly grounded, the voltage of the grounded phase becomes zero, and the voltage of the ungrounded phase (non-fault phase voltage) becomes the line voltage. The phase voltage to ground voltage has changed, but the relationship between the line voltages remains unchanged. For the transformer, there is electromagnetic coupling between its high-voltage side and low-voltage side, so the voltage applied to the primary winding of the transformer does not change, and it will not change for the secondary side either. In a neutral point non-directly grounded system, a single-phase grounding on the input side of the high-voltage frequency converter has no effect on the high-voltage frequency converter.

[0068] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for detecting and handling single-phase grounding faults on the input side of a high-voltage frequency converter, characterized in that, include: S1. Acquire the three-phase phase voltage on the input side of the high-voltage frequency converter by means of three-phase high-voltage resistor voltage division, and calculate the amplitude of the three-phase phase voltage; S2. Determine whether voltage abnormality and the type of abnormal fault have occurred based on the changes in the amplitude of the three-phase phase voltage, and take corresponding countermeasures based on the type of abnormal fault. The specific implementation steps of S2 are as follows: S2.

1. Determine whether a voltage anomaly has occurred based on the change in phase voltage amplitude in S1. If not, return to this step; if yes, jump to S2.

2. S2.2 Determine whether a single-phase ground fault has occurred based on the change in phase voltage amplitude. If not, proceed to S2.3; otherwise, proceed to S2.

4. S2.3 Determine that the fault is a power supply fault other than a single-phase ground fault and take appropriate measures. After the fault is cleared, proceed to S2.

6. S2.

4. Determine whether the neutral point on the input side is directly grounded based on the amplitude relationship between the three-phase line voltages. If so, a single-phase grounding minor fault alarm will be triggered. After the fault is cleared, the process will jump to S2.

6. Otherwise, the process will jump to S2.

5. S2.

5. Handle single-phase grounding faults with direct neutral grounding, and adopt a momentary power outage and restart scheme to cross the fault area, and wait for the voltage to return to normal. S2.6, Run normally and return to S2.1; In S2.4, when a single-phase ground fault occurs with the neutral point directly grounded, the phase voltage of the directly grounded fault phase is 0V, and the phase voltage of the non-faulty phase remains unchanged or changes less than the first threshold; when a single-phase ground fault occurs with the neutral point not directly grounded, the phase voltage of the non-faulty phase is 0V, and the phase voltage of the non-faulty phase becomes the line voltage.

2. The method for detecting and handling single-phase grounding faults on the input side of a high-voltage frequency converter according to claim 1, characterized in that, In S2.1, determining whether a voltage anomaly has occurred based on the change in phase voltage amplitude specifically involves determining whether the change in phase voltage amplitude is greater than 10% of the original phase voltage amplitude. If so, a voltage anomaly is determined to have occurred.

3. The method for detecting and handling single-phase grounding faults on the input side of a high-voltage frequency converter according to claim 1, characterized in that, In S2.2, if the phase voltage of one of the three phase voltages is less than 5% of the rated amplitude of the phase voltage, then a single-phase ground fault is determined to have occurred.

4. The method for detecting and handling single-phase grounding faults on the input side of a high-voltage frequency converter according to claim 1, characterized in that, In S2.3, power supply faults other than single-phase grounding faults include: symmetrical voltage drop of three-phase power grid and asymmetrical voltage drop of three-phase power grid. The corresponding handling measures for power supply faults other than single-phase grounding faults include: instantaneous power outage and restart.

5. The method for detecting and handling single-phase grounding faults on the input side of a high-voltage frequency converter according to claim 1, characterized in that, In S2.5, the instantaneous power outage restart scheme is as follows: after the frequency converter detects the above-mentioned fault, it immediately stops transmitting waves and stops outputting. Then, after the grid voltage is detected to be restored, it detects the back EMF of the motor through the output PT. The main control system estimates the motor operating speed, back EMF amplitude and phase angle based on the back EMF. Then, based on the motor operating speed, back EMF amplitude and phase angle, it retransmits the output voltage to drive the high-voltage motor again.

6. A detection and response system for single-phase grounding faults on the input side of a high-voltage frequency converter, used to execute the detection and response method for single-phase grounding faults on the input side of a high-voltage frequency converter as described in any one of claims 1-5, characterized in that, include: The phase voltage sampling system is used to acquire the three-phase phase voltage on the input side of the high-voltage frequency converter through a three-phase high-voltage resistor voltage divider method; The main control system, connected to the phase voltage sampling system and the high-voltage frequency converter, is used to calculate the amplitude of the three-phase phase voltage, and to determine whether voltage abnormality and abnormal fault type have occurred based on the change in the amplitude of the three-phase phase voltage, and then to take corresponding countermeasures based on the abnormal fault type.

7. The detection and response system for single-phase grounding faults on the input side of a high-voltage frequency converter according to claim 6, characterized in that, The specific steps by which the main control system calculates the amplitude of the three-phase voltage and takes corresponding countermeasures are as follows: When the main control system detects a single-phase ground fault, it identifies whether the neutral point on the input side is directly grounded based on the changes in the amplitude of the three-phase voltage. If it is determined to be non-directly grounded, it sends fault indication code 1 to indicate a minor single-phase ground fault, and no further action is taken; the high-voltage frequency converter continues to operate normally. If it is determined to be directly grounded, it sends fault indication code 2 to indicate a single-phase ground fault, and the main control system controls the high-voltage frequency converter to adopt an instantaneous power-off and restart scheme to pass through the fault area and avoid overcurrent impact on the high-voltage frequency converter after the normal power supply is restored.

Images