Heavy current generating device and current transformer calibrating equipment

Abstract

The invention relates to a large current generating device and current transformer verification equipment, and relates to the field of extra-high voltage power supply equipment, and the large current generating device comprises a three-phase rectification unit, an IGBT full-bridge conversion unit, an isolation conversion transformer, a rear-end capacitance compensation unit and a control feedback unit. The three-phase rectification unit can convert three-phase alternating current into direct current, the IGBT full-bridge conversion unit is connected with the three-phase rectification unit and can convert the direct current into single-phase alternating current, and the input end of the isolation conversion transformer is connected with the IGBT full-bridge conversion unit and can increase the current of the single-phase alternating current and output large-current alternating current. The rear-end capacitance compensation unit is connected to the output end of the isolation conversion transformer to improve the power factor of the large-current alternating current, and the control feedback unit is arranged between the output end of the isolation conversion transformer and the IGBT full-bridge conversion unit, so that the output current can be improved, and the weight and the cost of the device can be reduced.

Description

Technical Field

[0001] This application relates to the field of ultra-high voltage power supply equipment, and more particularly to a high current generating device. Furthermore, this application also relates to a current transformer calibration device. Background Technology

[0002] Ultra-high voltage (UHV) refers to voltage levels of 1000kV AC and ±800kV DC and above. An UHV power grid is a power grid with UHV transmission voltage, possessing advantages such as long transmission distances, large transmission capacity, low power loss, and minimal land occupation. UHV power grids are of great significance in addressing the energy supply and demand imbalance in my country, where coal resources are concentrated in the north and northwest, hydropower resources in the southwest, and wind and solar energy resources in the northwest, while energy demand is concentrated in the east and central regions.

[0003] Substations are a crucial component of ultra-high voltage (UHV) power grids, and gas-insulated switchgear (GIS) equipment is widely used in UHV substations. During operation, it is necessary to perform on-site calibration of the UHV current transformers within the GIS equipment to measure their fundamental errors. However, UHV current transformers operate at very high currents, with rated currents ranging from 300A to 6kA. During on-site calibration, 0.1 to 1.2 times the rated current needs to be applied to the primary circuit of the current transformer. Therefore, a high-current generator is required to meet the on-site calibration requirements of the UHV current transformers.

[0004] Existing high-current generating devices mainly use voltage regulators to adjust the AC power to a suitable voltage, and then use step-up transformers to increase the output current. In order to adjust the output current to the 60V voltage and 5000A current required for the calibration of UHV current transformers, a 300kVA voltage regulator and a 300kVA step-up transformer are usually required. Due to the large insulation distance of UHV facilities, the loop length from the output of the high-current generating device to the current transformer under test and the standard current transformer is also long. Under high current conditions, a large inductive reactance will be generated, and the power factor of the step-up transformer output circuit is usually only about 0.3, which restricts the effective increase of the loop current. Summary of the Invention

[0005] In order to increase the output current of the current output device and reduce its weight and cost, this application provides a high current generating device and a current transformer calibration device.

[0006] The high-current generating device provided in this application adopts the following technical solution: A high-current generating device includes a three-phase rectifier unit, an IGBT full-bridge converter unit, an isolation transformer, a back-end capacitor compensation unit, and a control feedback unit. The three-phase rectifier unit can be connected to an external three-phase AC power supply to convert the three-phase AC power provided by the three-phase AC power supply into DC power. The IGBT full-bridge converter unit is connected to the three-phase rectifier unit to convert the DC power output by the three-phase rectifier unit into single-phase AC power. The input terminal of the isolation transformer is connected to the IGBT full-bridge converter unit to boost the single-phase AC power output by the IGBT full-bridge converter unit to output a high-current AC power. The back-end capacitor compensation unit is connected to the output terminal of the isolation transformer to improve the power factor of the high-current AC power output by the isolation transformer. The control feedback unit is located between the output terminal of the isolation transformer and the IGBT full-bridge converter unit to control the operating state of the IGBT full-bridge converter unit according to the output voltage of the isolation transformer.

[0007] By adopting the above technical solution, the three-phase rectifier unit can supply power to the high-current generator through an external three-phase AC power supply, making it easier to obtain the required power and reducing the current requirements of the power supply. The IGBT full-bridge converter unit can easily obtain single-phase AC power of different voltages, eliminating the need for a high-power voltage regulator and significantly reducing the weight and cost of the high-current generator. It can achieve an ideal output frequency f. m The operating frequency of the LcBoost topology is adjusted based on a reference frequency and controlled above the critical control frequency. This ensures that the full-bridge switches always remain above the critical switching frequency, reducing turn-off current losses and improving the power conversion efficiency of the LcBoost topology. By utilizing a rear-end capacitor compensation unit located at the output of the isolation transformer, the current phase delay caused by the output circuit inductive reactance can be counteracted, significantly improving the power factor of the isolation transformer output circuit. This allows the use of a smaller isolation transformer, further reducing the weight and cost of the high-current generating device while maintaining the required output current.

[0008] In one specific implementation, the back-end capacitor compensation unit includes multiple BC compensation capacitor modules, each of which includes a compensation switch and a compensation capacitor array. The compensation switch is connected in series with the compensation capacitor array, and the multiple BC compensation capacitor modules are connected in parallel to the output terminal of the isolation transformer.

[0009] By adopting the above technical solution, and utilizing multiple BC compensation capacitor modules connected in parallel at the output end of the isolation transformer, the number of compensation capacitor arrays connected to the output circuit of the isolation transformer can be adjusted by controlling the on / off state of the compensation switch. This allows for convenient adjustment of the size of the compensation capacitors connected to the high-current output circuit, thereby enabling the power factor of the high-current output circuit to be adjusted to a level close to 1 under different operating conditions.

[0010] In one specific implementation, the compensation capacitor array includes multiple electrolytic capacitors, the multiple electrolytic capacitors are connected in pairs with their negative terminals to form capacitor groups, and the multiple capacitor groups are connected in parallel to form the compensation capacitor array.

[0011] By adopting the above technical solution, a capacitor bank composed of electrolytic capacitors connected in pairs with negative terminals can overcome the unipolar defect of electrolytic capacitors, thus enabling the use of electrolytic capacitors in AC circuits and preventing damage to them under reverse voltage conditions. A compensation capacitor array formed by connecting multiple capacitor banks in parallel can effectively increase the capacitance of the compensation capacitor array at a lower cost, with acceptable size and weight, meeting the requirements for power factor regulation under higher current conditions.

[0012] In one specific implementation scheme, the multiple electrolytic capacitors have the same capacitance, and the capacitance of each electrolytic capacitor is determined according to the following formula: C=4I / (i×n×U) out ×ω); where i is the number of electrolytic capacitors in each compensation capacitor array, I is the output current of the isolation transformer, n is the number of BC compensation capacitor modules in the back-end capacitor compensation unit, and U out ω is the output voltage of the isolation transformer, and ω is the angular frequency of the AC output voltage of the isolation transformer.

[0013] By adopting the above technical solution and using the above calculation formula, the capacitance of each electrolytic capacitor can be easily obtained, which facilitates the selection of electrolytic capacitors and helps to comprehensively control the cost, space occupation and manufacturing workload of the compensation capacitor array.

[0014] In one specific implementation, the IGBT full-bridge converter unit includes an IGBT full-bridge circuit and an LC filter circuit. The LC filter circuit is connected to the input terminal of the isolation converter transformer, and the IGBT full-bridge circuit is connected between the three-phase rectifier unit and the LC filter circuit.

[0015] By adopting the above technical solution, the DC power output from the three-phase rectifier unit can be easily converted into AC pulses of a set frequency using the IGBT full-bridge circuit, and the frequency and amplitude of the AC pulses can be easily controlled. Using the LC filter circuit located at the output of the IGBT full-bridge circuit, the AC pulses can be converted into a sinusoidal voltage, which is then fed to the isolation transformer for current boosting and voltage transformation.

[0016] In one specific implementation, the LC filter circuit includes a capacitor C, an inductor L1, and an inductor L2. The capacitor C is connected across the two ends of the input coil of the isolation transformer, and the inductors L1 and L2 are respectively connected between one end of the input coil of the isolation transformer and the output terminal of the IGBT full-bridge circuit.

[0017] By adopting the above technical solution, using inductors L1 and L2 connected to the two ends of the input coil of the isolation transformer, and capacitor C connected between the two ends of the input coil of the isolation transformer, a symmetrical LC filter can be formed, so that the AC pulse is filtered by the LC filter to form an AC voltage that is closer to a sine wave.

[0018] In one specific implementation, the control feedback unit includes a main control circuit, a full-bridge drive circuit, and a voltage feedback circuit. The full-bridge drive circuit is connected between the main control circuit and the IGBT full-bridge converter unit, so as to control the voltage and frequency of the single-phase AC power output by the IGBT full-bridge converter unit according to the operating state controlled by the main control circuit. The voltage feedback circuit is connected between the output terminal of the isolation transformer and the main control circuit, so as to provide feedback regulation of the output voltage of the isolation transformer through the full-bridge drive circuit.

[0019] By adopting the above technical solution, the on / off state of each switch in the IGBT full-bridge converter unit can be controlled by the full-bridge drive circuit connected to the IGBT full-bridge converter unit, thereby guiding the DC power output by the three-phase rectifier unit to flow in a set direction and forming a bidirectional pulse voltage with a set frequency and a set amplitude.

[0020] In one specific implementation scheme, the control feedback unit further includes a current feedback circuit and an input protection circuit. The current feedback circuit is connected between the output terminal of the isolation transformer and the main control circuit to extract the output current signal of the isolation transformer and transmit it to the main control circuit. The input protection circuit is connected between the input terminal of the three-phase rectifier unit and the full-bridge drive circuit to control the operating state of the full-bridge drive circuit according to the input power information of the three-phase rectifier unit.

[0021] By adopting the above technical solution, and utilizing a current feedback circuit located between the output terminal of the isolation transformer and the main control circuit, the output current of the isolation transformer can be monitored. This allows the main control circuit to control the operating state of the full-bridge drive circuit and the IGBT full-bridge converter unit based on the monitored output current, ensuring the stability of the isolation transformer's output current and safety under abnormal output current conditions. Furthermore, by utilizing an input protection circuit connected between the input terminal of the three-phase rectifier unit and the full-bridge drive circuit, the operation of the IGBT full-bridge converter unit can be suspended when an abnormality occurs in the external three-phase power supply, ensuring the safety of the high-current generating device.

[0022] In one specific implementation, the high current generating device of this application further includes a display unit, which includes a power factor display module and an output voltage and current display module, which are respectively connected to the output terminal of the isolation transformer.

[0023] By adopting the above technical solution, the output voltage and current display module installed at the output end of the isolation transformer can display the output voltage and current of the isolation transformer in real time. This facilitates timely manual intervention when abnormalities occur in the output voltage and / or output current of the high-current generator, ensuring that the output voltage and current of the high-current generator remain within the set range. Furthermore, the power factor display module installed at the output end of the isolation transformer can display the real-time power factor of the high-current AC power in the output circuit of the high-current generator. This allows for timely adjustment of the capacitance of the downstream capacitor compensation unit when the power factor decreases, ensuring that the power factor of the output circuit remains close to 1 regardless of changes in the output current.

[0024] The current transformer calibration equipment provided in this application includes a current transformer calibration device and a high current generating device provided in this application. The three-phase rectifier unit is connected to an external three-phase power supply. The current transformer calibration device is connected to the output terminal of the isolation transformer. The current transformer calibration device includes an error measuring device. The current transformer under test and the standard current transformer are respectively connected to the output circuit of the isolation transformer and are respectively connected to the error measuring device.

[0025] By adopting the above technical solution and using the error measuring device connected to the current transformer under test and the standard current transformer respectively, the ratio difference and phase difference of the current transformer under test relative to the standard current transformer can be measured, thereby obtaining the basic error of the current transformer under test.

[0026] In summary, this application includes at least one of the following beneficial technical effects: By setting up a three-phase rectifier unit and an IGBT full-bridge converter unit to convert external three-phase AC power into single-phase AC power, a programmable power supply can be formed that controls the voltage and current of single-phase AC power through programming. This avoids the need to use a heavier and more expensive voltage regulating transformer to adjust the input voltage of the current booster transformer, significantly reducing the weight and cost of the high-current generating device. At the same time, the load of the three-phase power supply is more balanced, and the load requirements of the power supply are also lower.

[0027] By placing the back-end capacitor compensation unit at the output end of the isolation transformer, the power factor of the output circuit of the isolation transformer can be compensated, and the capacity of the isolation transformer and the programmable power supply can be compensated at the same time, reducing the power requirements of the isolation transformer and the programmable power supply, and further reducing the weight and cost of the high current generating device.

[0028] A capacitor bank composed of two electrolytic capacitors connected by their negative terminals can overcome the unipolarity defect of electrolytic capacitors and use electrolytic capacitors as compensation capacitors in AC circuits. It provides a compensation capacitor device with sufficient voltage resistance and large capacitance. Thus, multiple capacitor banks arranged in an array can be used to form a compensation capacitor array to meet the large capacitance requirement for capacitance compensation at the output of the isolation transformer. Attached Figure Description

[0029] Figure 1 This is a schematic block diagram of one embodiment of the high current generating device of this application.

[0030] Figure 2 This is a schematic diagram of one embodiment of the high current generating device of this application.

[0031] Figure 3 This is a schematic diagram of the back-end capacitor compensation unit in one embodiment of the high current generating device of this application.

[0032] Figure 4 This is a physical diagram of a compensation capacitor array in one embodiment of the high current generating device of this application.

[0033] Figure 5 This is a circuit diagram of an existing high-current generating device.

[0034] Figure 6 This is a circuit diagram of an existing parallel compensation high current generator at the front end of a current booster.

[0035] Figure 7 A schematic diagram showing the parallel compensation at the back end of an existing high-current generator.

[0036] Figure 8 This is an equivalent circuit diagram of the back-end capacitor compensation unit in one embodiment of the high current generating device of this application.

[0037] Figure 9 This is a schematic diagram of a current transformer calibration device in one embodiment of the current transformer calibration equipment of this application.

[0038] Explanation of reference numerals in the attached diagram: 1. Three-phase rectifier unit; 2. IGBT full-bridge converter unit; 21. IGBT full-bridge circuit; 22. LC filter circuit; 3. Isolation transformer; 4. Rear-end capacitor compensation unit; 41. Compensation switch; 42. Compensation capacitor array; 421. Electrolytic capacitor; 5. Control feedback unit; 51. Main control circuit; 52. Full-bridge drive circuit; 53. Voltage feedback circuit; 54. Current feedback circuit; 55. Input protection circuit; 6. Display unit; 61. Power factor display module; 62. Voltage and current display module; 7. Current transformer calibration device; 71. Error measurement device; 8. Three-phase AC power supply. Detailed Implementation

[0039] The specific embodiments of this application will now be described in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this application.

[0040] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "set" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0041] One embodiment of the high current generating device of this application, such as Figure 1 and Figure 2 As shown, the system includes a three-phase rectifier unit 1, an IGBT full-bridge converter unit 2, an isolation transformer 3, a back-end capacitor compensation unit 4, and a control feedback unit 5. The three-phase rectifier unit 1 can use various existing circuit units for rectifying three-phase AC power; in this embodiment, it uses the three-phase rectifier unit used in high-power three-phase input, single-phase output inverters. The input terminal of the three-phase rectifier unit 1 is connected to an external three-phase AC power supply 8, such as a field three-phase maintenance power supply, to convert the three-phase AC power supplied by the three-phase AC power supply into DC power.

[0042] An IGBT full-bridge converter refers to a full-bridge circuit composed of insulated-gate bipolar transistors (IGBTs) as switching devices. The IGBT full-bridge converter unit 2 can use various suitable IGBT full-bridge inverter / converter topologies. In this embodiment, the IGBT full-bridge converter circuit unit used in high-power inverter power supplies is used as the IGBT full-bridge converter unit 2. The IGBT full-bridge converter unit 2 is connected to the three-phase rectifier unit 1 and is used to convert the DC power output from the three-phase rectifier unit 1 into single-phase AC power at industrial frequency, and can adjust the voltage and current of the output three-phase AC power.

[0043] The isolation transformer 3 can be any suitable current-boosting transformer; in this embodiment, the IGBT isolation transformer used in high-power inverter power supplies is also used. The input terminal of the isolation transformer 3 is connected to the IGBT full-bridge converter unit 2 to boost the current of the power frequency AC output from the IGBT full-bridge converter unit 2, thereby reducing the output voltage while outputting a large current AC.

[0044] The back-end capacitor compensation unit 4 is connected to the output terminal of the isolation transformer 3. It contains a large-capacity capacitor to counteract the equivalent inductance of the current-increasing circuit when the large current AC output of the isolation transformer 3 flows in the line, thereby improving the power factor of the large current AC in the output circuit.

[0045] The control feedback unit 5 is located between the output terminal of the isolation transformer 3 and the IGBT full-bridge converter 2. It is used to obtain the voltage of the AC power output by the isolation transformer 3 and control the working state of the IGBT full-bridge converter 2 according to the magnitude of the output voltage of the isolation transformer 3, thereby adjusting the magnitude of the output voltage of the IGBT full-bridge converter 2 so that the AC power output by the isolation transformer 3 remains stable.

[0046] In some embodiments of the high current generating device of this application, such as Figure 3 As shown, the back-end capacitor compensation unit 4 consists of multiple BC compensation capacitor modules. Each BC compensation capacitor module has a certain capacity of compensation capacitor. Multiple BC compensation capacitor modules are connected in parallel to the output terminal of the isolation transformer 3.

[0047] The two ends of the output coil of the isolation transformer 3 are connected to the UHV current transformer of the GIS equipment in the UHV substation via high-current conductors. Each BC compensation capacitor module has a compensation switch 41 and a compensation capacitor array 42. One end of the compensation switch 41 is connected to a high-current conductor, and the other end is connected to the compensation capacitor array 42. The other end of the compensation capacitor array 42 is connected to another high-current conductor. The compensation capacitor array 42 contains multiple compensation capacitor cells arranged in an array, and the large capacitance of the compensation capacitor array 42 is formed by multiple compensation capacitor cells connected in parallel.

[0048] In a preferred embodiment of the high current generating device of this application, such as Figure 3 As shown, the compensation capacitor array 42 includes multiple electrolytic capacitors 421. The electrolytic capacitors 421 are selected based on their voltage rating being greater than the maximum output voltage of the isolation transformer 3 and their capacitance being relatively large. Each electrolytic capacitor 421 has the same capacitance. The capacitance of the electrolytic capacitors 421 can be determined based on the economic considerations of the total price of all electrolytic capacitors 421 required to construct a compensation capacitor array 42 with a certain capacitance.

[0049] By connecting the negative terminals of every two electrolytic capacitors 421 together to form a capacitor bank, the capacitor bank can be connected to the AC circuit, overcoming the unipolar defect of electrolytic capacitors. Multiple capacitor banks are then connected in parallel to form a compensation capacitor array 42, which significantly increases the capacitance of the compensation capacitor array 42, ensuring that the capacitance of the downstream capacitor compensation unit 4 meets the requirements for improving the power factor of high-current AC power. A physical diagram of a compensation capacitor array 42 is shown below. Figure 4 As shown.

[0050] As a specific embodiment of the high current generating device of this application, each electrolytic capacitor 421 in the compensation capacitor array 42 has the same capacitance. The capacitance value of the electrolytic capacitor used is calculated and determined according to the following formula: C=4I / (i×n×U) out ×ω); where i is the number of electrolytic capacitors in each compensation capacitor array, I is the output current of the isolation transformer, n is the number of BC compensation capacitor modules in the back-end capacitor compensation unit 4, and U out ω is the output voltage of the isolation transformer, and ω is the angular frequency of the AC output voltage of the isolation transformer.

[0051] like Figure 5As shown, traditional high-current generators typically use single-phase AC power. To regulate the voltage of the high-current AC output, a voltage regulator T1 is usually used to obtain AC voltages of different magnitudes, and a current-boosting transformer T2 is used to increase the output current to obtain a high-current AC output. To obtain the 60V voltage and 5000A current required for UHV current transformer verification, a 300kVA voltage regulator T1 and a 300kVA current-boosting transformer T2 are needed. The 300kVA voltage regulator, especially the 300kVA current-boosting transformer, is not only very heavy, but also difficult to transport and assemble, and has high production and operating costs. Because the output current is very large, a conductor with a larger cross-sectional area is required for transmission. However, conductors with a larger cross-sectional area have a larger equivalent inductance, resulting in a large inductive reactance X during high-current AC transmission. L This results in very low power factors for the AC output of the current booster transformer T2 and its upstream voltage regulator T1, typically around 0.3, which severely affects the increase in the output current of the current booster transformer.

[0052] As can be seen from the formula for calculating the capacity of a current-boosting transformer, the required capacity under high current conditions mainly depends on the inductive reactance of the output circuit. To reduce the inductive reactance of the output circuit of the current-boosting transformer T2 and increase the output AC current, common methods include reducing the cross-sectional area of ​​the space enclosed by the high-current conductors and using parallel capacitors to balance the inductive reactance with the capacitive reactance, thereby improving the power factor of the output AC current. However, the length of the conductors in the output circuit of the current-boosting transformer T2 is generally difficult to reduce, and the effect of reducing the cross-sectional area of ​​the enclosed space by changing the conductor arrangement is also limited. Therefore, improving the power factor of the output AC current is currently the most commonly used method to increase the output current.

[0053] A common method to improve the AC power factor of the output circuit is to connect a compensation capacitor in parallel with the output circuit of the transformer. The parallel capacitor compensates for the transformer's capacity, thereby reducing the capacity requirement of the transformer.

[0054] like Figure 6 As shown, the commonly used method is to connect a compensation capacitor C in parallel at the input terminal (also known as the front end) of the current-boosting transformer T2. m However, due to the compensation capacitor C m When connected in parallel in the output circuit of voltage regulator T1, it can only compensate for the capacity of voltage regulator T1 and the capacity of the power supply, but cannot compensate for the capacity of current booster transformer T2. Current booster transformer T2 still has the problems of large size and heavy weight.

[0055] The capacity of a capacitor-compensated transformer (voltage regulator) is determined by the formula Q=U. 2ωC is determined, where Q is the reactive power, U is the output voltage, ω is the angular frequency of the AC current, and C is the capacitance of the compensation capacitor. For a voltage regulator with an output voltage of 250V, a 100μF capacitor can compensate for approximately 2kvar of reactive power.

[0056] Table 1 shows the reactive power capacity that different sized compensation capacitors can compensate for at a 250V output voltage for the voltage regulator: Table 1 Comparison of current booster front compensation capacity and compensation capacity (compensation voltage 250V) If a 15mF compensation capacitor Cm is connected in parallel at the front end of the current-boosting transformer T2, the capacity of the voltage regulator T1 of about 300kvar can be compensated, so that a 100kVA voltage regulator T1 can be used to achieve an apparent power of 300kVA.

[0057] Theoretically, it is also possible to consider connecting a compensation capacitor C in parallel at the output terminal (also known as the back end) of the current-boosting transformer T2. m , forming as Figure 7 The diagram shows parallel compensation at the downstream end of the current booster transformer. If implemented, this would simultaneously compensate for the capacity of the current booster transformer T2, the voltage regulator T1, and the power supply. However, since the voltage of the current booster transformer T2 is relatively low, typically around 60V, the reactive power capacity of the voltage regulator that different sized compensation capacitors can compensate at a 60V output voltage, calculated using the aforementioned capacitor compensation capacity calculation formula, is shown in Table 2. Table 2 Comparison of Compensation Capacity and Compensation Capacity after Current Booster (Compensation Voltage 60V) As shown in Table 2, at 60V, a capacitor of 270mF (0.27F) is needed to compensate for approximately 300kvar. However, the capacitance of non-polar capacitors currently used in AC circuits is typically small, usually only reaching the microfarad level, and their price is usually high, making it difficult to build such large-capacity compensation capacitors. Although supercapacitors can achieve very large capacitances, their voltage rating is low, typically only 2.7V. Using them at 60V requires a large number of supercapacitors connected in series. Furthermore, supercapacitors have poor thermal stability, easily leading to uneven voltage distribution between individual cells. This can easily cause damage to a large number of capacitors due to overvoltage of a single cell, even posing a safety risk. Therefore, there are currently no reports of using compensation capacitors for back-end compensation applications in step-up transformers.

[0058] According to the method proposed in this application, a capacitor bank is formed by using two electrolytic capacitors 421 connected with their negative terminals, and then multiple capacitor banks are connected in parallel to construct a compensation capacitor array 42. Each compensation capacitor array 42 and a compensation switch 41 are connected in series to form a BC compensation capacitor module. A certain number of BC compensation capacitor modules are then connected in parallel to the output circuit of the isolation transformer 3 for back-end compensation. If a 1000μF / 100V electrolytic capacitor is selected as the electrolytic capacitor 421, then the capacitance of each capacitor bank is 500μF, forming a non-polarized capacitor with a withstand voltage of 100V, which fully meets the working requirements under 60V AC voltage.

[0059] To achieve a compensation capacity of 305kvar at a 60V output voltage, as shown in Table 2, a capacitance of 270mF is required. This necessitates the parallel connection of 540 500μF capacitor banks. If ten BC compensation capacitor modules are used, each compensation capacitor array 42 requires 54 capacitor banks and 108 electrolytic capacitors 421, totaling 1080 1000μF / 100V electrolytic capacitors. Currently, each 1000μF / 100V electrolytic capacitor costs approximately 1 yuan, making the cost acceptable. The weight of the back-end capacitor compensation unit 4, composed of 1080 electrolytic capacitors, along with the corresponding circuit board and compensation switch, is approximately 50Kg, which is also within an acceptable range.

[0060] The formula C=4I / (i×n×U) is used. out (×ω) can be calculated to show that the aforementioned back-end capacitor compensation unit 4 can generate 5080A of AC capacitive current, wherein each compensation capacitor array 42 can generate 508A of AC compensation current. The amount of additional compensation current provided can be controlled by controlling the number of compensation switches 41 closed. The output circuit inductive reactance that can be resisted and the magnitude of the compensation current generated when different compensation switches 41 are closed are shown in Table 3: Table 3. Comparison Table of Number of Compensating Capacitor Arrays, Matching Inductance, and Compensating Current The peak voltage of a 60V AC voltage is 60V × 1.414 = 84.84V, which is less than the rated voltage of the electrolytic capacitor (100V). Furthermore, the 50Hz power frequency does not place high demands on the charging and discharging speed of the electrolytic capacitor. Figure 8 As shown, alternating current flows through capacitor bank C. m Capacitive X C =1 / (ωc) = 6.37Ω, capacitor bank C m The generated AC compensation current I=U out / X C=9.42A. The equivalent series resistance (ESR) of the electrolytic capacitor is about 1% of the capacitive reactance, approximately 0.06Ω. The resulting voltage drop is negligible compared to the 60V operating voltage. The voltage drop caused by the capacitor's ESR accounts for less than 5% of the AC voltage.

[0061] In some embodiments of the high current generating device of this application, such as Figure 1 and Figure 2 As shown, the IGBT full-bridge converter unit 2 includes an IGBT full-bridge circuit 21 and an LC filter circuit 22. The IGBT full-bridge circuit 21 can be a high-power inverter IGBT full-bridge converter circuit used to convert the DC output of the three-phase rectifier unit 1 into a rectangular wave pulse current. The LC filter circuit 22 is connected between the input terminal of the isolation transformer 3 and the IGBT full-bridge circuit 21 to filter and shape the pulse current, converting the rectangular pulse current into a sinusoidal AC current, which is beneficial for the AC conversion of the isolation transformer 3.

[0062] In a preferred embodiment of the high current generating device of this application, such as Figure 2 As shown, the LC filter circuit 22 includes a capacitor C, an inductor L1, and an inductor L2. The capacitor C is connected across the input coil of the isolation transformer 3. One end of each of the inductors L1 and L2 is connected to one end of the input coil of the isolation transformer 3, and the other end is connected to one output line of the IGBT full-bridge circuit 21, forming a symmetrical LCL filter.

[0063] In some embodiments of the high current generating device of this application, such as Figure 1 As shown, the control feedback unit 5 includes a main control circuit 51, a full-bridge drive circuit 52, and a voltage feedback circuit 53. The full-bridge drive circuit 52 can be an IGBT full-bridge drive circuit used in high-power inverters. The full-bridge drive circuit 52 is connected between the main control circuit 51 and the IGBT full-bridge converter unit 2, and is used to control the switching timing of each insulated-gate bipolar transistor in the IGBT full-bridge converter unit 2, so that each bridge arm in the IGBT full-bridge converter unit 2 works in coordination to convert DC power into pulse wave current with a set frequency and amplitude.

[0064] The main control circuit 51 can use various suitable control modules, such as various suitable MCU chips, PLCs, etc. The main control circuit 51 is connected to the full-bridge drive circuit 52 and can send control signals to control the working state of the full-bridge drive circuit 52, thereby using the full-bridge drive circuit 52 to control the voltage and frequency of the single-phase AC power output by the IGBT full-bridge converter unit 2.

[0065] The voltage feedback circuit 53 is connected between the output terminal of the isolation transformer 3 and the main control circuit 51. It is used to extract the voltage feedback signal output by the isolation transformer 3 and send the voltage feedback signal to the main control circuit 51. The main control circuit 51 adjusts the full-bridge drive circuit 52 according to the magnitude of the voltage feedback signal, thereby adjusting the output voltage of the isolation transformer 3 so that the output voltage of the isolation transformer 3 is stably maintained at the set level.

[0066] In a preferred embodiment of the high current generating device of this application, such as Figure 1 As shown, the control feedback unit 5 also includes a current feedback circuit 54 and an input protection circuit 55. The current feedback circuit 54 is connected between the output terminal of the isolation transformer 3 and the main control circuit 51, and can extract the output current signal of the isolation transformer 3 and transmit it to the main control circuit 51. When the output current of the isolation transformer 3 exceeds the set range, the main control circuit 51 can issue a control signal to control the working state of the full-bridge drive circuit 52 and the IGBT full-bridge converter 2, ensuring the stable operation of the high-current generator and the stability of its working state.

[0067] The input protection circuit 55 is connected between the input terminal of the three-phase rectifier unit 1 and the full-bridge drive circuit 52. It is used to extract the input power information of the three-phase rectifier unit 1 and transmit it to the full-bridge drive circuit 52. It can monitor the status of the three-phase AC power supply 8 that supplies power to the three-phase rectifier unit 1. When the three-phase AC power supply 8 is abnormal, such as excessively high or low voltage, or phase loss, it controls the working state of the full-bridge drive circuit 52 and stops the operation of the IGBT full-bridge converter unit 2 to prevent the high current generating device from working under abnormal conditions, which could damage the working unit or even cause a safety accident.

[0068] In some embodiments of the high current generating device of this application, such as Figure 1 As shown, the high-current generating device of this application also includes a display unit 6. The display unit 6 includes a power factor display module 61 and a voltage and current display module 62. The power factor display module 61 is connected to the output terminal of the isolation transformer 3 and can extract the real-time voltage waveform and real-time current waveform output from the isolation transformer 3 to obtain the power factor of the high-current AC power output from the isolation transformer 3, which is then displayed through the power factor display module 61. Operators can adjust the capacitance of the downstream capacitor compensation unit 4 according to the power factor displayed by the power factor display module 61, thereby ensuring that the power factor of the high-current AC power is always kept close to 1.

[0069] The voltage and current display module 62 is connected to the output terminal of the isolation transformer 3. It can acquire and display the voltage level and current magnitude of the high-current AC output by the isolation transformer 3, thereby determining whether the high-current AC output by the high-current generating device meets the verification requirements of the UHV current transformer.

[0070] The high current generating device of this application, and as... Figure 5 The conventional high current generating device shown is, for example Figure 6 The high current generator with compensation before the current booster shown and such Figure 7 Table 4 shows a comparison of the device weights of the high current generation device after the current booster (using the back-end capacitor compensation unit 4 of this application for capacitor compensation): Table 4 Weight Comparison of Different High Current Generators As can be seen, by using the back-end capacitor compensation unit 4 of this application, the capacity of the current booster can be reduced. When outputting a 60V 5000A high-current AC power, the current booster transformer can be reduced from 300KVA to 100KVA, and its weight from 1200kg to 400kg, significantly reducing the overall weight of the equipment. Replacing the voltage regulator with a three-phase rectifier unit 1, an IGBT full-bridge converter unit 2, and a control feedback unit 5 reduces the weight of the corresponding units from at least 150kg to at most 30kg. By using the high-current generating device of this application, the total weight of the device can be significantly reduced from at least 1300kg in existing devices to approximately 480kg, greatly reducing the device's weight, improving its stability, and lowering its manufacturing and operating costs.

[0071] One embodiment of the current transformer calibration equipment of this application includes a current transformer calibration device 7 and a high-current generating device according to any embodiment of this application. The three-phase rectifier unit 1 in the high-current generating device is connected to an external three-phase AC power supply 8, and the current transformer calibration device 7 is connected to the output terminal of the isolation transformer 3 in the high-current generating device.

[0072] like Figure 9 As shown, the current transformer calibration device 7 is equipped with an error measurement device 71; the output terminal of the isolation transformer 3 is connected to multiple current transformers T under test in the GIS equipment via high-current conductors. X The primary winding of the standard current transformer T0 enables multiple tested current transformers T... X The standard current transformer T0 is connected to the output circuit of the isolation transformer 3. One current transformer T under test... X The secondary windings of the standard current transformer T0 and the standard current transformer T0 are respectively connected to the error measuring device 71, and the secondary circuits of the two form a differential current that is fed into the error measuring device 71; other current transformers under test T0...X The secondary winding terminals are short-circuited and grounded with a wire. The error measuring device 71 can be used to measure the current transformer T under test. X The ratio difference and phase difference compared to the standard current transformer T0. This allows for convenient on-site verification of the basic errors of high-voltage, high-current current transformers.

[0073] In the description of this invention, the terms "one embodiment," "specific embodiment," "preferred embodiment," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this invention, 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.

[0074] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A high-current generating device, characterized in that, The system includes a three-phase rectifier unit (1), an IGBT full-bridge converter unit (2), an isolation transformer (3), a back-end capacitor compensation unit (4), and a control feedback unit (5). The three-phase rectifier unit (1) can be connected to an external three-phase AC power supply to convert the three-phase AC power provided by the three-phase AC power supply into DC power. The IGBT full-bridge converter unit (2) is connected to the three-phase rectifier unit (1) to convert the DC power output by the three-phase rectifier unit (1) into single-phase AC power. The input terminal of the isolation transformer (3) is connected to the IGBT full-bridge converter unit (2). The IGBT full-bridge converter (2) is connected to the IGBT full-bridge converter (2) to boost the single-phase AC output and output a large current AC. The back-end capacitor compensation unit (4) is connected to the output terminal of the isolation transformer (3) to improve the power factor of the large current AC output by the isolation transformer (3). The control feedback unit (5) is located between the output terminal of the isolation transformer (3) and the IGBT full-bridge converter (2) to control the working state of the IGBT full-bridge converter (2) according to the output voltage of the isolation transformer (3).

2. The high current generating device according to claim 1, characterized in that, The back-end capacitor compensation unit (4) includes multiple BC compensation capacitor modules. Each BC compensation capacitor module includes a compensation switch (41) and a compensation capacitor array (42). The compensation switch (41) and the compensation capacitor array (42) are connected in series. Multiple BC compensation capacitor modules are connected in parallel to the output terminal of the isolation transformer (3).

3. The high current generating device according to claim 2, characterized in that, The compensation capacitor array (42) includes multiple electrolytic capacitors (421), the multiple electrolytic capacitors (421) are connected in pairs with their negative terminals to form a capacitor group, and the multiple capacitor groups are connected in parallel to form the compensation capacitor array (42).

4. The high current generating device according to claim 3, characterized in that, The multiple electrolytic capacitors (421) have the same capacitance, and the capacitance of each electrolytic capacitor is determined according to the following formula: C=4I / (i×n×U) out ×ω); In the formula, i is the number of electrolytic capacitors in each compensation capacitor array, I is the output current of the isolation transformer, n is the number of BC compensation capacitor modules in the back-end capacitor compensation unit, and U out ω is the output voltage of the isolation transformer, and ω is the angular frequency of the AC output voltage of the isolation transformer.

5. The high current generating device according to claim 1, characterized in that, The IGBT full-bridge converter unit (2) includes an IGBT full-bridge circuit (21) and an LC filter circuit (22). The LC filter circuit (22) is connected to the input terminal of the isolation transformer (3), and the IGBT full-bridge circuit (21) is connected between the three-phase rectifier unit (1) and the LC filter circuit (22).

6. The high current generating device according to claim 5, characterized in that, The LC filter circuit (22) includes a capacitor C, an inductor L1 and an inductor L2. The capacitor C is connected to both ends of the input coil of the isolation transformer (3). The inductors L1 and L2 are respectively connected between one end of the input coil of the isolation transformer (3) and the output end of the IGBT full bridge circuit (21).

7. The high current generating device according to claim 1, characterized in that, The control feedback unit (5) includes a main control circuit (51), a full-bridge drive circuit (52), and a voltage feedback circuit (53). The full-bridge drive circuit (52) is connected between the main control circuit (51) and the IGBT full-bridge converter (2) so that it can control the voltage and frequency of the single-phase AC power output by the IGBT full-bridge converter (2) according to the working state controlled by the main control circuit (51). The voltage feedback circuit (53) is connected between the output terminal of the isolation transformer (3) and the main control circuit (51) so that the output voltage of the isolation transformer (3) can be adjusted by feedback through the full-bridge drive circuit (52).

8. The high current generating device according to claim 7, characterized in that, The control feedback unit (5) further includes a current feedback circuit (54) and an input protection circuit (55). The current feedback circuit (54) is connected between the output terminal of the isolation transformer (3) and the main control circuit (51) so as to extract the output current signal of the isolation transformer (3) and transmit it to the main control circuit (51). The input protection circuit (55) is connected between the input terminal of the three-phase rectifier unit (1) and the full-bridge drive circuit (52) so as to control the working state of the full-bridge drive circuit (52) according to the input power information of the three-phase rectifier unit (1).

9. The high current generating device according to claim 1, characterized in that, It also includes a display unit (6), which includes a power factor display module (61) and a voltage and current display module (62), which are respectively connected to the output terminal of the isolation transformer (3).

10. A current transformer calibration device, characterized in that: The device includes a current transformer calibration device (7) and a high current generating device according to any one of claims 1-9. The three-phase rectifier unit (1) is connected to an external three-phase power supply. The current transformer calibration device (7) is connected to the output terminal of the isolation transformer (3). The current transformer calibration device (7) includes an error measuring device (71). The current transformer under test and the standard current transformer are respectively connected to the output circuit of the isolation transformer (3) and are respectively connected to the error measuring device (71).

Images