High-voltage frequency converter and output-to-ground leakage detection method and circuit thereof

Abstract

The application discloses a high-voltage frequency converter and an output-to-ground leakage detection method and circuit thereof, wherein the output-to-ground leakage detection method comprises the following steps: acquiring three-phase voltages of the high-voltage frequency converter; performing instantaneous module length calculation according to the three-phase voltages to obtain a first voltage module value; performing coordinate conversion on the three-phase voltages to obtain d-axis voltages and q-axis voltages, and calculating a second voltage module value according to the d-axis voltages and the q-axis voltages; and performing output-to-ground leakage detection on the high-voltage frequency converter according to the first voltage module value and the second voltage module value, so that a third current Hall sensor does not need to be installed on a three-phase output loop of the high-voltage frequency converter, the installation space of the high-voltage frequency converter is greatly saved, the complexity and cost of a detection circuit are reduced, and the timeliness and accuracy of the output-to-ground leakage detection of the high-voltage frequency converter are improved, so that unnecessary shutdown failures caused by false alarms are prevented.

Description

Technical Field

[0001] This invention relates to the field of high-voltage frequency converter technology, and in particular to a method for detecting output-to-ground leakage current of a high-voltage frequency converter, a computer-readable storage medium, a high-voltage frequency converter, and a circuit for detecting output-to-ground leakage current of a high-voltage frequency converter. Background Technology

[0002] In related technologies, the detection of output leakage to ground of high-voltage frequency converters is generally carried out by using a current Hall transformer to detect the three-phase output current of the high-voltage frequency converter. When the sum of the three-phase output currents is zero, it is determined that the high-voltage frequency converter has no output leakage to ground; when the sum of the three-phase output currents is not zero and exceeds the set value, it is determined that the high-voltage frequency converter has output leakage to ground.

[0003] This detection method requires the installation of three current Hall sensors on the three-phase output circuit of the high-voltage frequency converter to detect the three-phase output current. It also requires a corresponding analog sampling circuit inside the high-voltage frequency converter, which not only increases the complexity of the hardware circuit but also reduces the reliability of the entire detection process.

[0004] Furthermore, since the output voltage and frequency of high-voltage frequency converters typically vary, determining whether an output-to-ground leakage fault has occurred by detecting the current requires a long filtering time, making timely and effective detection impossible. Shortening the filtering time, on the other hand, can easily lead to false alarms about output-to-ground leakage faults from the high-voltage frequency converter, causing unnecessary downtime. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, the first objective of this invention is to propose a method for detecting output-to-ground leakage current in a high-voltage frequency converter. By detecting the three-phase voltage of the high-voltage frequency converter and calculating the instantaneous modulus, output-to-ground leakage current can be detected. This eliminates the need to install three current Hall sensors on the three-phase output circuit of the high-voltage frequency converter, significantly saving installation space, reducing the complexity and cost of the detection circuit, and improving the timeliness and accuracy of output-to-ground leakage current detection, thus preventing unnecessary downtime due to false alarms.

[0006] A second objective of this invention is to provide a computer-readable storage medium.

[0007] The third objective of this invention is to provide a high-voltage frequency converter.

[0008] The fourth objective of this invention is to provide a circuit for detecting leakage current to ground at the output of a high-voltage frequency converter.

[0009] The fifth objective of this invention is to propose another type of high-voltage frequency converter.

[0010] To achieve the above objectives, a first aspect of the present invention provides a method for detecting output-to-ground leakage current of a high-voltage frequency converter. The method includes: acquiring the three-phase voltage of the high-voltage frequency converter; calculating the instantaneous magnitude based on the three-phase voltage to obtain a first voltage magnitude value; performing coordinate transformation on the three-phase voltage to obtain d-axis voltage and q-axis voltage, and calculating a second voltage magnitude value based on the d-axis voltage and q-axis voltage; and detecting output-to-ground leakage current of the high-voltage frequency converter based on the first voltage magnitude value and the second voltage magnitude value.

[0011] The high-voltage frequency converter output-to-ground leakage detection method according to an embodiment of the present invention acquires the three-phase voltage of the high-voltage frequency converter, calculates the first voltage magnitude value based on the instantaneous magnitude of the three-phase voltage, performs coordinate transformation on the three-phase voltage to obtain the d-axis voltage and q-axis voltage, calculates the second voltage magnitude value based on the d-axis voltage and q-axis voltage, and finally detects the output-to-ground leakage of the high-voltage frequency converter based on the first voltage magnitude value and the second voltage magnitude value. This eliminates the need to install three current Hall sensors on the three-phase output circuit of the high-voltage frequency converter, greatly saving installation space, reducing the complexity and cost of the detection circuit, and accurately determining whether the high-voltage frequency converter has experienced output-to-ground leakage by detecting the instantaneous magnitude of the three-phase voltage. This improves the timeliness and accuracy of output-to-ground leakage detection of the high-voltage frequency converter and prevents unnecessary downtime due to false alarms.

[0012] In addition, the high-voltage frequency converter output-to-ground leakage current detection method according to the above embodiments of the present invention may also have the following additional features:

[0013] According to one embodiment of the present invention, the first voltage magnitude is calculated according to the following formula:

[0014]

[0015] Among them, U mod1 U is the first voltage magnitude. a U b U c It is a three-phase voltage.

[0016] According to one embodiment of the present invention, the second voltage magnitude is calculated according to the following formula:

[0017]

[0018] Among them, U mod2 U is the second voltage modulus. d U is the d-axis voltage. q This is the q-axis voltage.

[0019] According to one embodiment of the present invention, coordinate transformation of three-phase voltage includes: determining U in a two-phase stationary coordinate system based on the three-phase voltage. α U β According to U in the two-phase stationary coordinate system α U β Determine the voltage phase angle; based on U in the two-phase stationary coordinate system. α U β The voltage phase angle determines the d-axis voltage and the q-axis voltage.

[0020] According to one embodiment of the present invention, the d-axis voltage and q-axis voltage are calculated according to the following formulas:

[0021]

[0022] Where θ is the voltage phase angle.

[0023] According to one embodiment of the present invention, the output-to-ground leakage current detection of a high-voltage frequency converter is performed based on a first voltage modulus value and a second voltage modulus value, including: determining the absolute value of the difference between the first voltage modulus value and the second voltage modulus value; and performing output-to-ground leakage current detection of the high-voltage frequency converter based on the relationship between the absolute value of the difference and the first voltage modulus value.

[0024] According to one embodiment of the present invention, detecting output-to-ground leakage current of a high-voltage frequency converter based on the relationship between the absolute value of the difference and the first voltage magnitude includes: ensuring that the relationship ΔU>kU is satisfied between the absolute value of the difference and the first voltage magnitude. mod1 When determining the output leakage current to ground of the high-voltage frequency converter, where ΔU is the absolute value of the difference, U mod1 Let k be the first voltage modulus, and k ranges from 0 to 1.

[0025] According to one embodiment of the present invention, obtaining the three-phase voltage of a high-voltage frequency converter includes: sampling the voltage of each phase output terminal of the three-phase output terminal of the high-voltage frequency converter separately to obtain the three-phase voltage.

[0026] According to one embodiment of the present invention, each phase arm of the high-voltage frequency converter is composed of multiple cascaded H-bridges. The method of obtaining the three-phase voltage of the high-voltage frequency converter includes: sampling the output voltage of each H-bridge and processing the output voltage of each H-bridge to obtain voltage processing data; and processing the voltage processing data to obtain the three-phase voltage of the high-voltage frequency converter.

[0027] To achieve the above objectives, a second aspect of the present invention provides a computer-readable storage medium storing a high-voltage frequency converter output-to-ground leakage detection program thereon. When the high-voltage frequency converter output-to-ground leakage detection program is executed by a processor, the high-voltage frequency converter output-to-ground leakage detection method described in the above embodiments is implemented.

[0028] According to the computer-readable storage medium of the present invention, when the stored high-voltage frequency converter output-to-ground leakage detection program is executed by the processor, the above-described high-voltage frequency converter output-to-ground leakage detection method is executed, thereby eliminating the need to install three current Hall sensors on the three-phase output circuit of the high-voltage frequency converter, greatly saving the installation space of the high-voltage frequency converter, reducing the complexity and cost of the detection circuit, and accurately determining whether the high-voltage frequency converter has experienced output-to-ground leakage by detecting the three-phase voltage and performing instantaneous modulus calculation, improving the timeliness and accuracy of the high-voltage frequency converter output-to-ground leakage detection, and preventing unnecessary downtime caused by false alarms.

[0029] To achieve the above objectives, a third aspect of the present invention provides a high-voltage frequency converter, which includes a memory, a processor, and a high-voltage frequency converter output-to-ground leakage detection program stored in the memory and executable on the processor. When the processor executes the high-voltage frequency converter output-to-ground leakage detection program, it implements the high-voltage frequency converter output-to-ground leakage detection method described in the embodiment.

[0030] According to the embodiments of the present invention, when the high-voltage frequency converter stored in the memory is executed by the processor, the output-to-ground leakage detection program of the high-voltage frequency converter is executed. By executing the above-described output-to-ground leakage detection method of the high-voltage frequency converter, it is not necessary to install three current Hall sensors on the three-phase output circuit of the high-voltage frequency converter, which greatly saves the installation space of the high-voltage frequency converter, reduces the complexity and cost of the detection circuit, and can accurately determine whether the high-voltage frequency converter has experienced output-to-ground leakage by detecting the instantaneous modulus of the three-phase voltage. This improves the timeliness and accuracy of the output-to-ground leakage detection of the high-voltage frequency converter and prevents unnecessary downtime caused by false alarms.

[0031] To achieve the above objectives, a fourth aspect of the present invention provides an output-to-ground leakage current detection circuit for a high-voltage frequency converter. The circuit includes a voltage detection module for detecting the three-phase voltage of the high-voltage frequency converter; and a controller for performing instantaneous magnitude calculation based on the three-phase voltage to obtain a first voltage magnitude value, performing coordinate transformation on the three-phase voltage to obtain d-axis voltage and q-axis voltage, calculating a second voltage magnitude value based on the d-axis voltage and q-axis voltage, and performing output-to-ground leakage current detection on the high-voltage frequency converter based on the first voltage magnitude value and the second voltage magnitude value.

[0032] According to an embodiment of the present invention, the output-to-ground leakage current detection circuit of the high-voltage frequency converter detects the three-phase voltage of the high-voltage frequency converter through a voltage detection module. The controller calculates the first voltage magnitude value by performing instantaneous magnitude calculation based on the three-phase voltage, and calculates the second voltage magnitude value based on the d-axis voltage and q-axis voltage obtained by coordinate transformation of the three-phase voltage. The controller then performs output-to-ground leakage current detection on the high-voltage frequency converter based on the first and second voltage magnitude values. This eliminates the need to install three current Hall sensors on the three-phase output circuit of the high-voltage frequency converter, greatly saving installation space and reducing the complexity and cost of the detection circuit. Furthermore, by detecting the three-phase voltage and performing instantaneous magnitude calculation, the system can accurately determine whether the high-voltage frequency converter has experienced output-to-ground leakage current detection, improving the timeliness and accuracy of output-to-ground leakage current detection and preventing unnecessary downtime caused by false alarms.

[0033] According to one embodiment of the present invention, the voltage detection module includes a first voltage divider unit, a second voltage divider unit, and a third voltage divider unit. One end of the first voltage divider unit is connected to the U-phase output terminal of the high-voltage frequency converter, one end of the second voltage divider unit is connected to the V-phase output terminal of the high-voltage frequency converter, and one end of the third voltage divider unit is connected to the W-phase output terminal of the high-voltage frequency converter. The other ends of the first voltage divider unit, the second voltage divider unit, and the third voltage divider unit are connected together and grounded. The first voltage divider unit, the second voltage divider unit, and the third voltage divider unit respectively divide the three-phase output voltage of the high-voltage frequency converter so that the controller can sample it.

[0034] According to one embodiment of the present invention, each phase arm of the high-voltage frequency converter is composed of multiple cascaded H-bridges. The voltage detection module includes: a voltage sampling and processing unit for sampling the output voltage of each H-bridge and processing the output voltage of each H-bridge to obtain voltage processing data; and a transmission unit for transmitting the voltage processing data so that the controller can process the voltage processing data to obtain the three-phase voltage of the high-voltage frequency converter.

[0035] According to one embodiment of the present invention, the controller is further configured to determine the absolute value of the difference between the first voltage magnitude and the second voltage magnitude, and to satisfy the relationship ΔU>kU between the absolute value of the difference and the first voltage magnitude. mod1 When determining the output leakage current to ground of the high-voltage frequency converter, where ΔU is the absolute value of the difference, U mod1 Let k be the first voltage modulus, and k ranges from 0 to 1.

[0036] To achieve the above objectives, a fifth aspect of the present invention provides a high-voltage frequency converter, which includes the output-to-ground leakage current detection circuit of the high-voltage frequency converter described in the above embodiments.

[0037] According to the embodiments of the present invention, the high-voltage frequency converter uses the output-to-ground leakage detection circuit described in the above embodiments to calculate the instantaneous modulus of the three-phase voltage to achieve output-to-ground leakage detection. This eliminates the need to install three current Hall sensors on the three-phase output circuit of the high-voltage frequency converter, greatly saving installation space and reducing the complexity and cost of the detection circuit. Furthermore, by detecting the three-phase voltage and calculating the instantaneous modulus, it is possible to accurately determine whether the high-voltage frequency converter has experienced output-to-ground leakage, improving the timeliness and accuracy of output-to-ground leakage detection and preventing unnecessary downtime caused by false alarms.

[0038] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0039] Figure 1 This is a flowchart of a method for detecting output-to-ground leakage current of a high-voltage frequency converter according to an embodiment of the present invention;

[0040] Figure 2 A circuit diagram for detecting output-to-ground leakage current of a high-voltage frequency converter according to an embodiment of the present invention;

[0041] Figure 3 This is a circuit diagram for detecting output-to-ground leakage current of a high-voltage frequency converter according to another embodiment of the present invention.

[0042] Figure 4 A flowchart illustrating the detection process of a high-voltage frequency converter output-to-ground leakage current detection method according to an embodiment of the present invention;

[0043] Figure 5 This is a block diagram of a high-voltage frequency converter output to ground leakage detection circuit according to an embodiment of the present invention.

[0044] Figure 6 This is a block diagram of a high-voltage frequency converter output-to-ground leakage current detection circuit according to another embodiment of the present invention.

[0045] Figure 7 This is a block diagram of a high-voltage frequency converter according to an embodiment of the present invention. Detailed Implementation

[0046] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0047] The following describes in detail, with reference to the accompanying drawings, the method for detecting output leakage current to ground of a high-voltage frequency converter, the circuit for detecting output leakage current to ground of a high-voltage frequency converter, and the high-voltage frequency converter having the circuit for detecting output leakage current to ground of the high-voltage frequency converter.

[0048] Figure 1 This is a flowchart illustrating a method for detecting output-to-ground leakage current of a high-voltage frequency converter according to an embodiment of the present invention. (Reference) Figure 1 As shown, the method for detecting leakage current to ground at the output of this high-voltage frequency converter includes the following steps:

[0049] Step S1: Obtain the three-phase voltage of the high-voltage frequency converter.

[0050] Specifically, in embodiments of the present invention, the three-phase voltage of the high-voltage frequency converter can be obtained by sampling the voltage at the three-phase output terminal of the high-voltage frequency converter, or by sampling the voltage at the three-phase input terminal of the high-voltage frequency converter.

[0051] Optionally, in one embodiment of the present invention, obtaining the three-phase voltage of the high-voltage frequency converter includes: sampling the voltage of each phase output terminal of the three-phase output terminal of the high-voltage frequency converter separately to obtain the three-phase voltage.

[0052] Specifically, refer to Figure 2 As shown, a resistor divider can be applied to the ground PE terminal at each of the three-phase output terminals of the high-voltage frequency converter, that is, x voltage divider resistors R are connected in series at the U-phase output terminal. u1 R u2 ..., R u(x-1) R ux Connect the ground PE to the V-phase output terminal, and connect x voltage divider resistors R in series. v1 R v2 ..., R v(x-1) R vx Connect the ground PE to the output terminal, and connect x voltage divider resistors R in series at the W-phase output terminal. w1 R w2 ..., R w(x-1) R wx After connecting to ground (PE), voltage sampling points a, b, and c are used as the output terminals of each voltage divider circuit. By sampling the voltage at points a, b, and c, the three-phase output sampling voltage U of the high-voltage frequency converter is obtained. α U b U c , which serves as the three-phase voltage of the high-voltage frequency converter.

[0053] Optionally, in another embodiment of the invention, each phase arm of the high-voltage frequency converter may be composed of multiple cascaded H-bridges, for example, as shown below. Figure 2As shown, each phase arm of the high-voltage frequency converter consists of five cascaded H-bridges. Thus, the input voltage of the U-phase arm of the high-voltage frequency converter is the sum of the output voltages of the five H-bridges, i.e., Ux = U1 + U2 + U3 + U4 + U5; the input voltage of the V-phase arm is the sum of the output voltages of the five H-bridges, i.e., Vx = V1 + V2 + V3 + V4 + V5; and the input voltage of the W-phase arm is the sum of the output voltages of the five H-bridges, i.e., Wx = W1 + W2 + W3 + W4 + W5. Obtaining the three-phase voltage of the high-voltage frequency converter includes: sampling the output voltage of each H-bridge in each phase arm and processing the output voltage of each H-bridge to obtain voltage processing data; transmitting the voltage processing data, for example, uploading it to the controller of the high-voltage frequency converter; and processing the voltage processing data to obtain the three-phase voltage of the high-voltage frequency converter, for example, the controller of the high-voltage frequency converter processes the voltage processing data to obtain the three-phase voltage.

[0054] Specifically, such as Figure 3 As shown, in one embodiment of the present invention, the output voltage of the H-bridge in each phase arm can be converted into a smaller voltage, such as -5V to +5V, by a differential circuit (not shown in the figure). The conditioned voltage is then converted into a digital voltage signal by an ADC chip (not shown in the figure). The digital voltage signal is then encoded to obtain voltage processing data, which is transmitted to a controller, such as an FPGA module, through each phase optical fiber (dashed line in the figure). The FPGA module processes the received voltage processing data and calculates the input voltage of each phase arm, which serves as the three-phase voltage of the high-voltage frequency converter.

[0055] Step S2: Calculate the instantaneous modulus based on the three-phase voltage of the high-voltage frequency converter to obtain the first voltage modulus value.

[0056] Optionally, in one embodiment of the present invention, the first voltage magnitude can be calculated according to the following formula:

[0057]

[0058] Among them, U mod1 U is the first voltage magnitude. a U b U c This refers to the three-phase voltage of the high-voltage frequency converter.

[0059] Step S3: Perform coordinate transformation on the three-phase voltages to obtain the d-axis voltage and q-axis voltage, and calculate the second voltage magnitude based on the d-axis voltage and q-axis voltage.

[0060] Among them, Clarke coordinate transformation and Park coordinate transformation can be used to transform the three-phase voltage U a U b U c Converted to d-axis voltage Ud and q-axis voltage U q .

[0061] Specifically, in one embodiment of the present invention, coordinate transformation of the three-phase voltage includes: determining U in a two-phase stationary coordinate system based on the three-phase voltage. α U β According to U in the two-phase stationary coordinate system α U β Determine the voltage phase angle; based on U in the two-phase stationary coordinate system. α U β The voltage phase angle determines the d-axis voltage and the q-axis voltage. It should be noted that U... α U β The stator voltage of the motor in a two-phase stationary coordinate system is U, and the d-axis voltage is U. d and q-axis voltage U q This represents the stator voltage of the motor in a two-phase synchronous rotating coordinate system.

[0062] The d-axis voltage and q-axis voltage are calculated using the following formulas:

[0063]

[0064] Where θ is the voltage phase angle, and the voltage phase angle ranges from 0 to 360°.

[0065] Optionally, in one embodiment of the present invention, the second voltage magnitude is calculated according to the following formula:

[0066]

[0067] Among them, U mod2 U is the second voltage modulus. d U is the d-axis voltage. q This is the q-axis voltage.

[0068] S4, based on the first voltage modulus and the second voltage modulus, perform output-to-ground leakage current detection on the high-voltage frequency converter.

[0069] In an embodiment of the present invention, when the high-voltage frequency converter experiences output-to-ground leakage, the three-phase voltage sampling values ​​will jump, resulting in the first voltage magnitude value and the second voltage magnitude value being unequal. Therefore, by determining the relationship between the first voltage magnitude value and the second voltage magnitude value, the output-to-ground leakage detection of the high-voltage frequency converter can be achieved.

[0070] Furthermore, in one embodiment of the present invention, as Figure 4 As shown, the output-to-ground leakage current detection of the high-voltage frequency converter is performed based on the first voltage modulus value and the second voltage modulus value, including:

[0071] S41, determine the absolute value of the difference between the first voltage magnitude and the second voltage magnitude;

[0072] S42, based on the relationship between the absolute value of the difference and the first voltage modulus, performs output-to-ground leakage current detection on the high-voltage frequency converter.

[0073] Specifically, based on the relationship between the absolute value of the voltage difference and the first voltage modulus, the output-to-ground leakage current detection of the high-voltage frequency converter is performed, including:

[0074] The absolute value of the difference and the magnitude of the first voltage satisfy the relationship ΔU>kU. mod1 When determining the output leakage current to ground of the high-voltage frequency converter, where ΔU is the absolute value of the difference, U mod1 Let k be the first voltage modulus, and k ranges from 0 to 1. When k = 0, it means that as long as there is a deviation between the first voltage modulus and the second voltage modulus, it is considered that there is leakage current to ground. Considering detection errors, k is generally greater than 0. When k = 1, the corresponding second voltage modulus is zero, so k is generally less than 1.

[0075] It should be noted that the value of k can be calibrated according to the actual situation. Generally, the smaller the value of k, the higher the detection sensitivity; conversely, the larger the value of k, the lower the detection sensitivity. For engineering reliability, in practical applications, it is preferable that the value of k ranges from 0.05 to 0.1.

[0076] In some embodiments of the present invention, when the input voltage of the high-voltage frequency converter is detected to obtain the three-phase voltage, since the input voltage frequency of the high-voltage frequency converter is around 50Hz, the corresponding k value is 0.05, which can quickly, accurately and reliably detect whether the high-voltage frequency converter has output leakage to ground.

[0077] The high-voltage frequency converter output-to-ground leakage detection method according to an embodiment of the present invention acquires the three-phase voltage of the high-voltage frequency converter, calculates the first voltage magnitude value based on the instantaneous magnitude of the three-phase voltage, performs coordinate transformation on the three-phase voltage to obtain the d-axis voltage and q-axis voltage, calculates the second voltage magnitude value based on the d-axis voltage and q-axis voltage, and finally detects the output-to-ground leakage of the high-voltage frequency converter based on the first voltage magnitude value and the second voltage magnitude value. This eliminates the need to install three current Hall sensors on the three-phase output circuit of the high-voltage frequency converter, greatly saving installation space, reducing the complexity and cost of the detection circuit, and accurately determining whether the high-voltage frequency converter has experienced output-to-ground leakage by detecting the instantaneous magnitude of the three-phase voltage. This improves the timeliness and accuracy of output-to-ground leakage detection of the high-voltage frequency converter and prevents unnecessary downtime due to false alarms.

[0078] In an embodiment of the present invention, when the high-voltage frequency converter experiences output-to-ground leakage, the three-phase voltage sampling value will jump, which will cause the first voltage magnitude calculated by the two magnitude calculation methods to be unequal to the second voltage magnitude. However, when the high-voltage frequency converter does not experience output-to-ground leakage, the first voltage magnitude calculated by the two magnitude calculation methods is equal to the second voltage magnitude. Therefore, by detecting the three-phase voltage of the high-voltage frequency converter and performing instantaneous magnitude calculation, accurate detection of output-to-ground leakage of the high-voltage frequency converter can be achieved.

[0079] Specifically, the three-phase output voltage U of the high-voltage frequency converter A U B U C It can be calculated using the following formula:

[0080]

[0081] Among them, U P U is the three-phase output terminal of the high-voltage frequency converter. A U B U C Peak value; set the voltage divider coefficient Furthermore, the three-phase sampling voltage divider resistors are symmetrical, so the voltage divider coefficients of the three phases are consistent.

[0082] Thus, when there is no output-to-ground leakage current in the high-voltage frequency converter, the three-phase voltage U of the high-voltage frequency converter... α U b U c Calculated using the following formula:

[0083]

[0084] According to formulas (1) and (5) above, the first voltage magnitude U can be calculated. mod1 :

[0085]

[0086]

[0087] Furthermore, based on the transformation relationship between the three-phase coordinate system and the α-β two-phase stationary coordinate system, the coordinate transformation is performed using the following formula to convert the three-phase voltage U of the high-voltage frequency converter. a U b U c Converted to two-phase voltage U in α-β two-phase stationary coordinate system α U β :

[0088]

[0089] In addition, the voltage phase angle is calculated using the following formula:

[0090]

[0091] Where θ is the voltage phase angle.

[0092] Therefore, the second voltage magnitude U can be calculated based on the above formulas (2), (3) and (5), (6), (7). mod2 :

[0093] It can be seen that when the high-voltage frequency converter does not experience output-to-ground leakage, the first voltage magnitude U calculated by both methods is... mod1 Second voltage magnitude U mod2 All are mU P .

[0094] When a high-voltage frequency converter experiences output-to-ground leakage, to simplify the reasoning process, let's assume, for example, that phase W of the high-voltage frequency converter experiences a short circuit to ground due to leakage. At this time, the three-phase voltage U of the high-voltage frequency converter... α U b U c Calculated using the following formula:

[0095]

[0096] The first voltage magnitude U can be calculated using formulas (1) and (8) above. mod1 :

[0097]

[0098] Furthermore, based on formulas (2), (3), (6), (7) and (8), the second voltage magnitude U can be calculated. mod2 :

[0099]

[0100]

[0101] It can be seen that when a high-voltage frequency converter experiences output-to-ground leakage, such as leakage in phase W, the first voltage modulus U in both calculation methods... mod1 for Second voltage magnitude U mod2 for The two are not equal.

[0102] Therefore, in the embodiments of the present invention, by detecting the three-phase voltage of the high-voltage frequency converter and performing instantaneous modulus calculation, the output-to-ground leakage current detection of the high-voltage frequency converter can be realized. This eliminates the need to install three current Hall sensors on the three-phase output circuit of the high-voltage frequency converter, greatly saving the installation space of the high-voltage frequency converter, reducing the complexity and cost of the detection circuit, and accurately determining whether the high-voltage frequency converter has experienced output-to-ground leakage current detection by detecting the three-phase voltage and performing instantaneous modulus calculation. This improves the timeliness and accuracy of the output-to-ground leakage current detection of the high-voltage frequency converter and prevents unnecessary downtime caused by false alarms.

[0103] It should be noted that the above embodiments provide calculation formulas for the first voltage magnitude and the second voltage magnitude when the output of the W phase of the high-voltage frequency converter leaks to ground. However, the calculation formulas for the first voltage magnitude and the second voltage magnitude when the output of other phases of the high-voltage frequency converter leaks to ground are consistent with the above derivation process and will not be repeated here.

[0104] Corresponding to the above embodiments, the present invention also proposes a computer-readable storage medium storing a high-voltage frequency converter output to ground leakage detection program thereon. When the high-voltage frequency converter output to ground leakage detection program is executed by a processor, the high-voltage frequency converter output to ground leakage detection method described in the above embodiments is implemented.

[0105] According to the computer-readable storage medium of the present invention, when the stored high-voltage frequency converter output-to-ground leakage detection program is executed by the processor, the above-described high-voltage frequency converter output-to-ground leakage detection method is executed, thereby eliminating the need to install three current Hall sensors on the three-phase output circuit of the high-voltage frequency converter, greatly saving the installation space of the high-voltage frequency converter, reducing the complexity and cost of the detection circuit, and accurately determining whether the high-voltage frequency converter has experienced output-to-ground leakage by detecting the three-phase voltage and performing instantaneous modulus calculation, improving the timeliness and accuracy of the high-voltage frequency converter output-to-ground leakage detection, and preventing unnecessary downtime caused by false alarms.

[0106] Corresponding to the above embodiments, the present invention also proposes a high-voltage frequency converter, which includes a memory, a processor, and a high-voltage frequency converter output-to-ground leakage detection program stored in the memory and executable on the processor. When the processor executes the high-voltage frequency converter output-to-ground leakage detection program, it implements the high-voltage frequency converter output-to-ground leakage detection method described in the above embodiments.

[0107] According to the embodiments of the present invention, when the high-voltage frequency converter stored in the memory is executed by the processor, the output-to-ground leakage detection program of the high-voltage frequency converter is executed. By executing the above-described output-to-ground leakage detection method of the high-voltage frequency converter, it is not necessary to install three current Hall sensors on the three-phase output circuit of the high-voltage frequency converter, which greatly saves the installation space of the high-voltage frequency converter, reduces the complexity and cost of the detection circuit, and can accurately determine whether the high-voltage frequency converter has experienced output-to-ground leakage by detecting the instantaneous modulus of the three-phase voltage. This improves the timeliness and accuracy of the output-to-ground leakage detection of the high-voltage frequency converter and prevents unnecessary downtime caused by false alarms.

[0108] Figure 5 This is a block diagram of a high-voltage frequency converter output-to-ground leakage current detection circuit according to an embodiment of the present invention. (Reference) Figure 5 As shown, the output-to-ground leakage current detection circuit 50 of the high-voltage frequency converter includes a voltage detection module 51 and a controller 52. The voltage detection module 51 detects the three-phase voltage of the high-voltage frequency converter. The controller 52 performs instantaneous magnitude calculation based on the three-phase voltage to obtain a first voltage magnitude value, performs coordinate transformation on the three-phase voltage to obtain d-axis and q-axis voltages, calculates a second voltage magnitude value based on the d-axis and q-axis voltages, and performs output-to-ground leakage current detection on the high-voltage frequency converter based on the first and second voltage magnitude values.

[0109] Optionally, in some embodiments of the present invention, reference is made to... Figure 2 As shown, the voltage detection module 51 includes a first voltage divider unit 511, a second voltage divider unit 512, and a third voltage divider unit 513. One end of the first voltage divider unit 511 is connected to the U-phase output terminal of the high-voltage frequency converter, one end of the second voltage divider unit 512 is connected to the V-phase output terminal of the high-voltage frequency converter, and one end of the third voltage divider unit 513 is connected to the W-phase output terminal of the high-voltage frequency converter. The other ends of the first voltage divider unit 511, the second voltage divider unit 512, and the third voltage divider unit 513 are connected together and then connected to ground (PE). The first voltage divider unit 511, the second voltage divider unit 512, and the third voltage divider unit 513 respectively divide the three-phase output voltage of the high-voltage frequency converter for sampling by the controller 52.

[0110] Specifically, the first voltage divider unit 511, the second voltage divider unit 512, and the third voltage divider unit 513 may each include x voltage divider resistors connected in series, with x voltage divider resistors R connected in series at the U-phase output terminal. u1 R u2 ..., R u(x-1) R ux Connect the ground PE to the V-phase output terminal, and connect x voltage divider resistors R in series. v1 R v2 ..., R v(x-1)R vx Connect the ground PE to the output terminal, and connect x voltage divider resistors R in series at the W-phase output terminal. w1 R w2 ..., R w(x-1) R wx Then connect to ground PE, and connect the voltage divider resistor R. u1 With voltage divider resistor R u2 The node between them is taken as voltage sampling point a, and the voltage divider resistor R is used as the sampling point a. v1 With voltage divider resistor R v2 The node between them is used as voltage sampling point b, and the voltage divider resistor R is used as the sampling point b. w1 With voltage divider resistor R w2 The nodes between them are used as voltage sampling points c. The controller 52 obtains the three-phase voltage of the high-voltage frequency converter by sampling the voltages at voltage sampling points a, b, and c.

[0111] Optionally, in some embodiments of the present invention, each phase arm of the high-voltage frequency converter may be composed of multiple cascaded H-bridges, for example, as shown below. Figure 2 As shown, each phase arm of the high-voltage frequency converter is composed of 5 cascaded H-bridges. Thus, the input voltage of the U-phase arm of the high-voltage frequency converter is the sum of the output voltages of the 5 H-bridges, i.e., Ux = U1 + U2 + U3 + U4 + U5. The input voltage of the V-phase arm of the high-voltage frequency converter is the sum of the output voltages of the 5 H-bridges, i.e., Vx = V1 + V2 + V3 + V4 + V5. The input voltage of the W-phase arm of the high-voltage frequency converter is the sum of the output voltages of the 5 H-bridges, i.e., Wx = W1 + W2 + W3 + W4 + W5.

[0112] And, as Figure 6 As shown, the voltage detection module 51 includes: a voltage sampling and processing unit 514, used to sample the output voltage of each H-bridge and process the output voltage of each H-bridge to obtain voltage processing data; and a transmission unit 515, used to transmit the voltage processing data so that the controller 52 can process the voltage processing data to obtain the three-phase voltage of the high-voltage frequency converter.

[0113] Specifically, such as Figure 3 As shown, in one embodiment of the present invention, the output voltage of the H-bridge in each phase arm can be converted into a smaller voltage, such as -5V to +5V, by a differential circuit (not shown in the figure). The conditioned voltage is then converted into a digital voltage signal by an ADC chip (not shown in the figure). The digital voltage signal is then encoded to obtain voltage processing data, which is transmitted to a controller, such as an FPGA module, through each phase optical fiber (dashed line in the figure). The FPGA module processes the received voltage processing data and calculates the input voltage of each phase arm, which serves as the three-phase voltage of the high-voltage frequency converter.

[0114] Optionally, in some embodiments of the present invention, the controller 52 is further configured to calculate a first voltage magnitude according to the following formula:

[0115]

[0116] Among them, U mod1 U is the first voltage magnitude. a U b U c It is a three-phase voltage.

[0117] Optionally, in some embodiments of the present invention, the controller 52 is further configured to calculate the second voltage magnitude according to the following formula:

[0118]

[0119] Among them, U mod2 U is the second voltage modulus. d U is the d-axis voltage. q This is the q-axis voltage.

[0120] Optionally, in some embodiments of the present invention, the controller 52 is further configured to determine U in a two-phase stationary coordinate system based on the three-phase voltage. α U β And based on U in the two-phase stationary coordinate system α U β Determine the voltage phase angle, and based on U in the two-phase stationary coordinate system. α U β The voltage phase angle determines the d-axis voltage and the q-axis voltage. It should be noted that U... α U β The stator voltage of the motor in a two-phase stationary coordinate system is U, and the d-axis voltage is U. d and q-axis voltage U q This represents the stator voltage of the motor in a two-phase synchronous rotating coordinate system.

[0121] Optionally, in some embodiments of the present invention, the controller 52 is further configured to calculate the d-axis voltage and the q-axis voltage according to the following formulas:

[0122]

[0123] Where θ is the voltage phase angle, and the voltage phase angle ranges from 0 to 360°.

[0124] Optionally, in some embodiments of the present invention, the controller 52 is further configured to determine the absolute value of the difference between the first voltage magnitude and the second voltage magnitude, and to satisfy the relationship ΔU>kU between the absolute value of the difference and the first voltage magnitude. mod1 When determining the output leakage current to ground of the high-voltage frequency converter, where ΔU is the absolute value of the difference, U mod1The first voltage modulus is k, which ranges from 0 to 1. When k = 0, it means that there is a deviation between the first voltage modulus and the second voltage modulus, which means that there is leakage current to ground. Considering detection errors, k is generally greater than 0. When k = 1, the second voltage modulus is zero, so k is generally less than 1.

[0125] It should be noted that the value of k can be calibrated according to the actual situation. Generally, the smaller the value of k, the higher the detection sensitivity; conversely, the larger the value of k, the lower the detection sensitivity. For engineering reliability, in practical applications, it is preferable that the value of k ranges from 0.05 to 0.1.

[0126] In some embodiments of the present invention, when the input voltage of the high-voltage frequency converter is detected to obtain the three-phase voltage, since the input voltage frequency of the high-voltage frequency converter is around 50Hz, the corresponding k value is 0.05, which can quickly, accurately and reliably detect whether the high-voltage frequency converter has output leakage to ground.

[0127] It is understood that, in the embodiments of the present invention, the detailed calculation process of the first voltage modulus and the second voltage modulus is consistent with the output-to-ground leakage current detection method of the high voltage frequency converter described in the above embodiments, and will not be repeated in detail here.

[0128] According to an embodiment of the present invention, the output-to-ground leakage current detection circuit of the high-voltage frequency converter detects the three-phase voltage of the high-voltage frequency converter through a voltage detection module. The controller calculates the first voltage magnitude value by performing instantaneous magnitude calculation based on the three-phase voltage, and calculates the second voltage magnitude value based on the d-axis voltage and q-axis voltage obtained by coordinate transformation of the three-phase voltage. The controller then performs output-to-ground leakage current detection on the high-voltage frequency converter based on the first and second voltage magnitude values. This eliminates the need to install three current Hall sensors on the three-phase output circuit of the high-voltage frequency converter, greatly saving installation space and reducing the complexity and cost of the detection circuit. Furthermore, by detecting the three-phase voltage and performing instantaneous magnitude calculation, the system can accurately determine whether the high-voltage frequency converter has experienced output-to-ground leakage current detection, improving the timeliness and accuracy of output-to-ground leakage current detection and preventing unnecessary downtime caused by false alarms.

[0129] In addition, refer to Figure 7 As shown, this embodiment of the invention also proposes a high-voltage frequency converter 60, which includes the output-to-ground leakage current detection circuit 50 of the high-voltage frequency converter described in the above embodiment.

[0130] According to the embodiments of the present invention, the high-voltage frequency converter uses the output-to-ground leakage detection circuit described in the above embodiments to calculate the instantaneous modulus of the three-phase voltage to achieve output-to-ground leakage detection. This eliminates the need to install three current Hall sensors on the three-phase output circuit of the high-voltage frequency converter, greatly saving installation space and reducing the complexity and cost of the detection circuit. Furthermore, by detecting the three-phase voltage and calculating the instantaneous modulus, it is possible to accurately determine whether the high-voltage frequency converter has experienced output-to-ground leakage, improving the timeliness and accuracy of output-to-ground leakage detection and preventing unnecessary downtime caused by false alarms.

[0131] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0132] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0133] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0134] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0135] Furthermore, the terms "first," "second," etc., used in the embodiments of this invention are for descriptive purposes only and should not be construed as indicating or implying relative importance, or implicitly specifying the number of technical features indicated in this embodiment. Therefore, features defined with terms such as "first" and "second" in the embodiments of this invention can explicitly or implicitly indicate that the embodiment includes at least one of those features. In the description of this invention, the word "multiple" means at least two or more, such as two, three, four, etc., unless otherwise explicitly specified in the embodiments.

[0136] In this invention, unless otherwise explicitly specified or limited in the embodiments, the terms "installation," "connection," "joining," and "fixing" appearing in the embodiments should be interpreted broadly. For example, a connection can be a fixed connection, a detachable connection, or an integral part; it can also be a mechanical connection, an electrical connection, etc. Of course, it can also be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components, or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific implementation.

[0137] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0138] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for detecting output-to-ground leakage current of a high-voltage frequency converter, characterized in that, include: Obtain the three-phase voltage of the high-voltage frequency converter; The instantaneous magnitude is calculated based on the three-phase voltage to obtain the first voltage magnitude value; The three-phase voltages are transformed to obtain the d-axis voltage and q-axis voltage, and the second voltage magnitude is calculated based on the d-axis voltage and q-axis voltage. The high-voltage frequency converter is subjected to output-to-ground leakage current detection based on the first voltage modulus value and the second voltage modulus value; The first voltage magnitude is calculated using the following formula: in, The first voltage modulus value, , , The three-phase voltage is referred to here.

2. The method according to claim 1, characterized in that, The second voltage magnitude is calculated using the following formula: in, The second voltage modulus, The d-axis voltage, Let be the q-axis voltage.

3. The method according to claim 2, characterized in that, The coordinate transformation of the three-phase voltage includes: Determine the two-phase stationary coordinate system based on the three-phase voltage. , ; According to the two-phase stationary coordinate system , Determine the voltage phase angle; According to the two-phase stationary coordinate system , The voltage phase angle determines the d-axis voltage and the q-axis voltage.

4. The method according to claim 3, characterized in that, The d-axis voltage and q-axis voltage are calculated using the following formulas: in, The voltage phase angle is denoted as .

5. The method according to claim 1, characterized in that, Based on the first voltage modulus and the second voltage modulus, the high-voltage frequency converter is subjected to output-to-ground leakage current detection, including: Determine the absolute value of the difference between the first voltage magnitude and the second voltage magnitude; The high-voltage frequency converter is used to detect output-to-ground leakage current based on the relationship between the absolute value of the difference and the first voltage modulus.

6. The method according to claim 5, characterized in that, Based on the relationship between the absolute value of the difference and the first voltage modulus, the high-voltage frequency converter is used to detect output-to-ground leakage current, including: The absolute value of the difference satisfies the following relationship with the first voltage magnitude. >k At that time, it was determined that the output of the high-voltage frequency converter was leaking to ground, wherein, The absolute value of the difference. Let k be the first voltage modulus, and k ranges from 0 to 1.

7. The method according to claim 1, characterized in that, Obtaining the three-phase voltage of the high-voltage frequency converter includes: The voltage of each phase output terminal of the three-phase output terminal of the high-voltage frequency converter is sampled separately to obtain the three-phase voltage.

8. The method according to claim 1, characterized in that, Each phase arm of the high-voltage frequency converter is composed of multiple cascaded H-bridges, wherein obtaining the three-phase voltage of the high-voltage frequency converter includes: The output voltage of each H-bridge is sampled and processed to obtain voltage processing data; The voltage data is processed to obtain the three-phase voltage of the high-voltage frequency converter.

9. A computer-readable storage medium, characterized in that, It stores a high-voltage frequency converter output to ground leakage detection program, which, when executed by the processor, implements the high-voltage frequency converter output to ground leakage detection method according to any one of claims 1-8.

10. A high-voltage frequency converter, characterized in that, The device includes a memory, a processor, and a high-voltage frequency converter output-to-ground leakage detection program stored in the memory and executable on the processor. When the processor executes the output-to-ground leakage detection program, it implements the high-voltage frequency converter output-to-ground leakage detection method according to any one of claims 1-8.

11. A circuit for detecting output-to-ground leakage current of a high-voltage frequency converter, characterized in that, include: The voltage detection module is used to detect the three-phase voltage of the high-voltage frequency converter; The controller is used to perform instantaneous magnitude calculation based on the three-phase voltage to obtain a first voltage magnitude value, and to perform coordinate transformation on the three-phase voltage to obtain d-axis voltage and q-axis voltage, and to calculate a second voltage magnitude value based on the d-axis voltage and q-axis voltage, and to perform output-to-ground leakage detection on the high-voltage frequency converter based on the first voltage magnitude value and the second voltage magnitude value; The first voltage magnitude is calculated using the following formula: in, The first voltage modulus value, , , The three-phase voltage is referred to here.

12. The circuit according to claim 11, characterized in that, The voltage detection module includes a first voltage divider unit, a second voltage divider unit, and a third voltage divider unit. One end of the first voltage divider unit is connected to the U-phase output terminal of the high-voltage frequency converter, one end of the second voltage divider unit is connected to the V-phase output terminal of the high-voltage frequency converter, and one end of the third voltage divider unit is connected to the W-phase output terminal of the high-voltage frequency converter. The other ends of the first, second, and third voltage divider units are connected together and grounded. The first, second, and third voltage divider units divide the three-phase output voltage of the high-voltage frequency converter respectively so that the controller can sample the voltage.

13. The circuit according to claim 11, characterized in that, Each phase arm of the high-voltage frequency converter is composed of multiple cascaded H-bridges, and the voltage detection module includes: The voltage sampling and processing unit is used to sample the output voltage of each H-bridge and process the output voltage of each H-bridge to obtain voltage processing data. The transmission unit is used to transmit the voltage processing data so that the controller can process the voltage processing data to obtain the three-phase voltage of the high-voltage frequency converter.

14. The circuit according to any one of claims 11-13, characterized in that, The controller is further configured to determine the absolute value of the difference between the first voltage magnitude and the second voltage magnitude, and to ensure that the absolute value of the difference satisfies the relationship between the first voltage magnitude and the second voltage magnitude. >k At that time, it was determined that the output of the high-voltage frequency converter was leaking to ground, wherein, The absolute value of the difference. Let k be the first voltage modulus, and k ranges from 0 to 1.

15. A high-voltage frequency converter, characterized in that, Includes an output-to-ground leakage current detection circuit according to any one of claims 11-14.

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