Device and method for measuring insulation resistance of high-voltage direct-current support capacitor

Abstract

The invention discloses a high-voltage direct-current support capacitor insulation resistance measuring device and method, and the device comprises a direct-current charging test loop, a test loop, a discharging test loop, and a control system. The direct-current charging test loop comprises a power supply, a first switch, a voltage regulator, a boosting transformer, a high-voltage silicon stack, a current-limiting resistor and a second switch, the test loop comprises a third switch, a first discharging resistor, a voltmeter and a high-voltage direct-current support capacitor to be tested, and the discharging test loop comprises a fourth switch, a second discharging resistor, a fifth switch and a voltage divider. The control system comprises a signal acquisition unit, a control output unit and a controller; the measurement method comprises the steps of capacitance measurement, voltage measurement and insulation resistance calculation. The device is simple in structure and convenient to operate, and can meet the insulation resistance measurement test requirements of the high-voltage and high-capacity direct-current support container.

Description

Technical Field

[0001] The present invention belongs to the technical field of capacitor testing, and in particular relates to a device and method for measuring the insulation resistance of a high-voltage DC support capacitor. Background Art

[0002] DC link capacitors are key components in converters, primarily serving as voltage equalizers, energy storage, and filtering. Currently, high-power converters such as high-voltage inverters (VFDs) in the tens of megawatts range, high-speed train converters, high-power STATCOMs, and DC capacitors for flexible DC transmission projects all require high-voltage, high-capacity DC link capacitors. These capacitors are characterized by high voltage and high capacity, with voltages up to 6kV DC, capacities up to 10mF, and weights up to 300kg.

[0003] This type of DC link capacitor uses metallized polypropylene film as the dielectric. Electrodes are made of a zinc-aluminum alloy vapor-deposited on the surface of the polypropylene film and lead out through a sprayed metal layer. When a weak point in the polypropylene film breaks down, the electrode evaporates and isolates the fault point, allowing the DC link capacitor to quickly recover its insulation and resume normal operation. This process is called self-healing. DC link capacitors used for voltage balancing and energy storage can withstand DC field strengths exceeding 200 V / μm. For DC link capacitors used in high-field applications, the voltage drop is measured through insulation resistance. In engineering technology, conductivity is one of the four major parameters of an insulator, and insulation resistance can also be used to reflect the performance of a dielectric.

[0004] The document "JB / T 8168-2023 Pulse Capacitors and DC Capacitors" provides insulation resistance or self-discharge time constant measurement methods, but does not provide relevant test circuits and related devices, and is mainly aimed at pulse capacitors and DC capacitors.

[0005] Document CN102435852A describes a method and device for measuring the insulation resistance of metallized film capacitors under high electric field strength. This method calculates the insulation resistance of metallized film capacitors under high electric field strength by sampling the resistor and the voltage divider ratio of the capacitor under DC voltage. This method obtains the insulation resistance by applying voltage for a long time. This method can be used for capacitors with small capacitance; however, the document does not explain whether it is applicable to high-voltage, large-capacity DC support capacitors. This method differs from the three methods provided in the document "JB / T 8168-2023 Pulse Capacitors and DC Capacitors," which is an industry standard and has a certain degree of standardization and authority.

[0006] Document CN 106655321 A describes a flexible discharge device for electrolytic capacitor leakage current / insulation resistance measurement. Because electrolytic capacitors operate at relatively low voltages, typically around 1000 VDC, while metallized film DC link capacitors have a maximum operating voltage of 6000 VDC, this flexible discharge device is not suitable for high-voltage DC link capacitors.

[0007] Currently, measuring the insulation resistance of high-voltage DC link capacitors is not a required test item for type testing. Instead, dielectric properties are primarily analyzed by measuring the insulation resistance of high-voltage DC link capacitors. Existing technologies primarily target electrolytic capacitors and metallized film capacitors operating under high field strength conditions, and are not suitable for high-voltage, high-capacity DC link capacitors. Therefore, a device and method for measuring the insulation resistance of high-voltage DC link capacitors is needed to address this issue.

[0008] In summary, this type of device and circuit has technical problems that need to be solved, and is also a key technology that needs to be solved to improve the performance indicators of high-voltage DC support capacitors. Summary of the Invention

[0009] In order to overcome the shortcomings of existing test device technology, the present invention proposes a high-voltage DC support capacitor insulation resistance measurement device and method.

[0010] The technical solutions adopted by the present invention are as follows.

[0011] The present invention provides a high-voltage DC support capacitor insulation resistance measuring device, which is mainly composed of a DC charging test circuit, a test circuit, a discharge test circuit and a control system.

[0012] The DC charging test circuit includes a power supply, a first switch, a voltage regulator, a step-up transformer, a high-voltage silicon stack, a current-limiting resistor, and a second switch.

[0013] The test circuit includes a third switch, a first discharge resistor, a voltmeter, and a high-voltage DC support capacitor to be tested.

[0014] The discharge test circuit includes a fourth switch, a second discharge resistor, a fifth switch, and a voltage divider. The voltage divider is formed by connecting a voltage divider high-voltage resistor and a voltage divider low-voltage resistor in series, with the middle connection point being the voltage output high-voltage terminal.

[0015] The control system includes signal acquisition, control output and controller. The signal acquisition of the control system comes from the test circuit and the discharge test circuit.

[0016] The output of the DC charging test circuit is connected in parallel to one end of the test circuit, and the other end of the test circuit is connected in parallel to the discharge test circuit. The control output of the control system is connected to the DC charging test circuit, the discharge test circuit, and the test circuit, respectively. The controller generates control output instructions based on signal acquisition and calculation.

[0017] One end of the power supply is connected to one end of the first switch. The other end of the first switch is connected to one end of the primary side of the voltage regulator. The other end of the power supply is connected to the other end of the primary side of the voltage regulator. The secondary side of the voltage regulator is connected in parallel with the primary side of the step-up transformer. One end of the secondary side of the step-up transformer is connected in series with a high-voltage silicon stack and a current-limiting resistor. One end of the current-limiting resistor is connected to the second switch. One end of the second switch is connected to the high-voltage side of the test circuit. The other end of the secondary side of the step-up transformer is connected in parallel with the low-voltage side of the test circuit and is grounded.

[0018] The third switch is connected in series with the first discharge resistor and then connected in parallel with the voltmeter. One end of the third switch is connected to one end of the second switch. The first discharge resistor is connected to the other end of the voltmeter and is grounded.

[0019] The high-voltage DC support capacitor to be tested is connected in parallel with the voltmeter, and one end of the DC support capacitor to be tested is connected to the connecting wire connected to the ground.

[0020] One end of the fourth switch is connected to one end of the high-voltage DC support capacitor to be tested, and the other end of the fourth switch is connected to the second discharge resistor and one end of the fifth switch, and the other end of the second discharge resistor is connected to the other end of the high-voltage DC support capacitor to be tested. The fifth switch is connected in series with a voltage divider, and the low-voltage resistor of the voltage divider is connected to the other end of the second discharge resistor and then to ground.

[0021] Signal acquisition includes voltage signals and other signals, including temperature and pressure.

[0022] The control output includes a first output, a second output, a third output, a fourth output, and a fifth output.

[0023] Specifically, the power supply is generally 220V AC.

[0024] Specifically, the capacity of the step-up transformer is 30KVA and the transformation ratio is 0.4 / 15kV.

[0025] Specifically, the voltmeter is a high-impedance digital voltmeter (input impedance 1000 MΩ).

[0026] Specifically, other signals (temperature, pressure, etc.) are detected by placing relevant sensors on the high-voltage DC support capacitor under test.

[0027] The present invention also provides a method for measuring the insulation resistance of a high-voltage DC capacitor, the method comprising the following steps: (1) Measure the actual capacitance of the DC link capacitor to be tested C , then connect the test circuit; (2) When the first and second switches are in the closed state, and the third, fourth, and fifth switches are in the open state, the DC charging test circuit charges the DC support capacitor to be tested; when the voltmeter reading reaches the test voltage value, the controller sends a relevant instruction to the control output. At this time, the first output sends an opening instruction to the second switch, and records the voltage at the beginning of self-discharge. U 0, record self-discharge time t Voltage after U t Insulation resistance R P The calculation formula is as follows R P = t / ( C *ln( U t / U 0)); (3) The controller sends a relevant instruction to the control output, the second output sends a closing instruction to the fourth switch, the second discharge resistor discharges the DC support capacitor to be tested, and the voltmeter reading is observed; 1 minute later, the controller sends a relevant instruction to the control output again, the third output sends a closing instruction to the fifth switch, and the voltage signal is connected to the acquisition signal. When the voltage signal collected is 0, the controller sends a relevant instruction to the control output, and at this time the second output sends an opening instruction to the fourth switch, and the measurement ends; (4) When the test is finished, the controller gives the fourth output instruction, and the third switch is closed to release the residual energy on the DC capacitor to be tested through the first discharge resistor. Then the controller gives the fifth output instruction, and the first switch is opened. At this time, the entire test device is in a power-off state.

[0028] (5) When the test is abnormal, other signals are abnormal, and the controller gives the fourth output instruction. After the third switch is closed, the energy on the DC support capacitor to be tested is released through the first discharge resistor. Then the controller gives the fifth output instruction and the first switch is opened. At this time, the entire test device is in a power-off state.

[0029] The beneficial effects of the present invention are: being able to realize automatic multiple repeated measurements of the insulation resistance of a high-voltage, large-capacity direct current support container; the test operation is simple, easy to maintain, highly reliable and safe.

[0030] The present invention has a simple structure and is easy to operate, and can meet the insulation resistance measurement test requirements of high-voltage and large-capacity direct current support containers. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural schematic diagram of the present invention; Figure 2 A schematic diagram of the wiring for the implementation of the present invention; In the figure, 1-DC charging test circuit; 2-test circuit; 3-discharge test circuit; 4-control system; 41-Signal acquisition; 42-Control output; 43-Controller; 411-voltage signal; 412-other signals; 421 - first output; 422 - second output; 423 - third output; 424 - fourth output; 425 - fifth output; Us - first power supply; S1 - first switch; BT - voltage regulator; T - step-up transformer; D - high-voltage silicon stack; R1 - current limiting resistor; S2 - second switch; S3 - third switch; R2 - first discharge resistor; V - voltmeter; Cx - high-voltage DC support capacitor to be tested; S4 - fourth switch; Rx - second discharge resistor; S5 - fifth switch; Vt - voltage divider; RF1 - voltage divider high-voltage resistor; RF2 - voltage divider low-voltage resistor. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0033] exist Figure 1 and Figure 2 It can be seen that the present invention: the high-voltage DC support capacitor insulation resistance measuring device is mainly composed of a DC charging test circuit (1), a test circuit (2), a discharge test circuit (3) and a control system (4); A DC charging test circuit (1) comprises a power supply (Us), a first switch (S1), a voltage regulator (BT), a step-up transformer (T), a high-voltage silicon stack (D), a current-limiting resistor (R1), and a second switch (S2); The test circuit (2) comprises a third switch (S3), a first discharge resistor (R2), a voltmeter (V), and a high-voltage DC support capacitor (Cx) to be tested; The discharge test circuit (3) includes a fourth switch (S4), a second discharge resistor (Rx), a fifth switch (S5), and a voltage divider (Vt). The voltage divider (Vt) is formed by connecting a voltage divider high-voltage resistor (RF1) and a voltage divider low-voltage resistor (RF2) in series, with the middle connection point being a voltage output high-voltage pole. The control system (4) includes a signal acquisition (41), a control output (42), and a controller (43). The signal acquisition (41) of the control system (4) comes from the test circuit (2) and the discharge test circuit (3); The output end of the DC charging test circuit (1) is connected in parallel to one end of the test circuit (2), and the other end of the test circuit (2) is connected in parallel to the discharge test circuit (3); the control output (42) of the control system (4) is connected to the DC charging test circuit (1), the discharge test circuit (2) and the test circuit (3), respectively, and the controller (43) calculates and gives an instruction for the control output (42) based on the signal acquisition (41); One end of a power supply (Us) is connected to one end of a first switch (S1), the other end of the first switch (S1) is connected to one end of a primary side of a voltage regulator (BT), the other end of the power supply (Us) is connected to the other end of the primary side of the voltage regulator (BT), the secondary side of the voltage regulator (BT) is connected in parallel to the primary side of a step-up transformer (T), one end of the secondary side of the step-up transformer (T) is sequentially connected in series with a high-voltage silicon stack (D) and a current-limiting resistor (R1), one end of the current-limiting resistor (R1) is connected to a second switch (S2), one end of the second switch (S2) is connected to a high-voltage end of a test loop (2), and the other end of the secondary side of the step-up transformer (T) is connected in parallel to a low-voltage end of the test loop (2) and is grounded; A third switch (S3) is connected in series with the first discharge resistor (R2) and then connected in parallel with the voltmeter (V), one end of the third switch (S3) is connected to one end of the second switch (S2), and the other end of the first discharge resistor (R2) is connected to the voltmeter (V) and is grounded; The high-voltage DC support capacitor (Cx) to be tested is connected in parallel with the voltmeter (V), and one end of the DC support capacitor (Cx) to be tested is connected to the connecting wire connected to the ground; One end of a fourth switch (S4) is connected to one end of a high-voltage DC support capacitor (Cx) to be tested, the other end of the fourth switch (S4) is connected to a second discharge resistor (Rx) and one end of a fifth switch (S5), the other end of the second discharge resistor (Rx) is connected to the other end of the high-voltage DC support capacitor (Cx) to be tested, the fifth switch (S5) is connected in series with a voltage divider (Vt), and a voltage divider low-voltage resistor (RF2) of the voltage divider is connected to the other end of the second discharge resistor (Rx) and then connected to ground; The signal acquisition (41) includes a voltage signal (411) and other signals (412), and the other signals (412) include temperature and pressure.

[0034] The control output (42) includes a first output (421), a second output (422), a third output (423), a fourth output (424), and a fifth output (425).

[0035] Specifically, the power supply (Us) is generally 220V AC.

[0036] Specifically, the capacity of the step-up transformer (T) is 30 kVA, and the transformation ratio is 0.4 / 15 kV.

[0037] Specifically, the voltmeter (V) is a high-impedance digital voltmeter (input impedance 1000 MΩ).

[0038] Specifically, other signals (412) (temperature, pressure) are detected by placing relevant sensors on the high-voltage DC support capacitor (Cx) to be tested.

[0039] The present invention also provides a method for measuring the insulation resistance of a high-voltage DC capacitor, the method comprising the following steps: (1) Measure the actual capacitance of the DC link capacitor (Cx) to be tested C , then connect the test circuit (2); (2) When the first switch (S1) and the second switch (S2) are both in the closed state, and the third switch (S3), the fourth switch (S4), and the fifth switch (S5) are all in the open state, the DC charging test circuit (1) charges the high-voltage DC support capacitor (Cx) to be tested; when the reading of the voltmeter (V) reaches the test voltage value, the controller (43) sends a relevant instruction to the control output (42), and at this time the first output (421) sends an opening instruction to the second switch (S2), and records the voltage at the beginning of self-discharge. U 0, record self-discharge time t Voltage after U t Insulation resistance R P The calculation formula is as follows R P = t / ( C *ln( U t / U 0)); (3) The controller (43) sends a relevant instruction to the control output (42), the second output (422) sends a closing instruction to the fourth switch (S4), the second discharge resistor (Rx) discharges the high-voltage DC support capacitor (Cx) to be tested, and the reading of the voltmeter is observed; 1 minute later, the controller (43) sends a relevant instruction to the control output (42) again, the third output (423) sends a closing instruction to the fifth switch (S5), the voltage signal (411) is connected to the signal acquisition (41), and when the voltage signal of the signal acquisition (41) is 0, the controller (43) sends a relevant instruction to the control output (42), and at this time the second output (422) sends an opening instruction to the fourth switch (S4), and the measurement ends; (4) When the test is finished, the controller (43) gives a fourth output (424) instruction, and the third switch (S3) is closed to release the residual energy on the DC capacitor (Cx) to be tested through the first discharge resistor (R2). Then the controller (43) gives a fifth output (425) instruction, and the first switch (S1) is opened. At this time, the entire test device is in a power-off state.

[0040] (5) When the test is abnormal, the other signals (412) are abnormal, the controller (43) gives the fourth output (424) instruction, the third switch (S3) is closed, and the energy on the high-voltage DC support capacitor (Cx) to be tested is released through the first discharge resistor (R2), and then the controller (43) gives the fifth output (425) instruction, the first switch (S1) is opened, and the entire test device is in a power-off state.

[0041] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A device for measuring the insulation resistance of a high-voltage DC support capacitor, characterized by: The high-voltage DC support capacitor insulation resistance measuring device includes a DC charging test circuit, a test circuit, a discharge test circuit and a control system. The DC charging test circuit includes a power supply, a first switch, a voltage regulator, a step-up transformer, a high-voltage silicon stack, a current limiting resistor and a second switch. The test circuit includes a third switch, a first discharge resistor, a voltmeter and a high-voltage DC support capacitor to be tested. The discharge test circuit includes a fourth switch, a second discharge resistor, a fifth switch and a voltage divider. The voltage divider is composed of a high-voltage resistor and a low-voltage resistor of the voltage divider connected in series. The control system includes signal acquisition, control output and a controller. The signal acquisition comes from the test circuit and the discharge test circuit. The control output of the control system is connected to the DC charging test circuit, the discharge test circuit and the test circuit respectively. The output end of the DC charging test circuit is connected in parallel to one end of the test circuit, and the other end of the test circuit is connected in parallel to the discharge test circuit; One end of the power supply is connected to one end of the first switch, the other end of the first switch is connected to one end of the primary side of the voltage regulator, the other end of the power supply is connected to the other end of the primary side of the voltage regulator, the secondary side of the voltage regulator is connected in parallel with the primary side of the step-up transformer, one end of the secondary side of the step-up transformer is connected in series with a high-voltage silicon stack and a current-limiting resistor, one end of the current-limiting resistor is connected to the second switch, one end of the second switch is connected to the high-voltage end of the test loop, the other end of the secondary side of the step-up transformer is connected in parallel with the low-voltage end of the test loop and grounded, and the third switch is connected in series with the first discharge resistor and then connected in parallel with the voltmeter. , one end of the third switch is connected to one end of the second switch, the first discharge resistor is connected to the other end of the voltmeter and grounded; the high-voltage DC support capacitor to be tested is connected in parallel with the voltmeter, one end of the fourth switch is connected to one end of the high-voltage DC support capacitor to be tested, the other end of the fourth switch is connected to the second discharge resistor and one end of the fifth switch, the other end of the second discharge resistor is connected to the other end of the high-voltage DC support capacitor to be tested, the fifth switch is connected in series with the voltage divider, and the low-voltage resistor of the voltage divider is connected to the other end of the second discharge resistor and then to ground. 2.(1) Measure the actual capacitance of the DC link capacitor to be tested C , then connect the test circuit; (2) When the first and second switches are in the closed state, and the third, fourth, and fifth switches are in the open state, the DC charging test circuit charges the DC support capacitor to be tested; when the voltmeter reading reaches the test voltage value, the controller sends a relevant instruction to the control output. At this time, the first output sends an opening instruction to the second switch, and records the voltage at the beginning of self-discharge. U 0, record self-discharge time t Voltage after U t Insulation resistance R P The calculation formula is as follows R P = t / ( C *ln( U t / U 0))； (3) The controller sends a relevant instruction to the control output, the second output sends a closing instruction to the fourth switch, the second discharge resistor discharges the DC support capacitor to be tested, and the voltmeter reading is observed; 1 minute later, the controller sends a relevant instruction to the control output again, the third output sends a closing instruction to the fifth switch, and the voltage signal is connected to the acquisition signal. When the voltage signal collected is 0, the controller sends a relevant instruction to the control output, and at this time the second output sends an opening instruction to the fourth switch, and the measurement ends; (4) When the test is finished, the controller gives a fourth output instruction, the third switch is closed, and the residual energy on the DC capacitor to be tested is released through the first discharge resistor. Then the controller gives a fifth output instruction, the first switch is opened, and the entire test device is in a power-off state; (5) When the test is abnormal, other signals are abnormal, and the controller gives the fourth output instruction. After the third switch is closed, the energy on the DC support capacitor to be tested is released through the first discharge resistor. Then the controller gives the fifth output instruction and the first switch is opened. At this time, the entire test device is in a power-off state.

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