Ultra-high voltage converter station AC / DC filter capacitance detection device and method based on low voltage frequency conversion

Abstract

The invention discloses an extra-high voltage converter station AC / DC filter capacitance detection device and method based on low-voltage frequency conversion, and the device comprises a main control unit which is disposed in the device and is composed of a high-frequency voltage signal collection unit, a high-frequency current collection unit and a test control unit, and the test control unit is in communication connection with a high-frequency voltage generation unit. The main control unit is in communication connection with the wiring unit, and the wiring unit is electrically connected with a plurality of parallel capacitor banks outside the device; the high-frequency current acquisition unit acquires a plurality of input currents of a plurality of external parallel capacitor banks through the wiring unit, and the high-frequency voltage signal acquisition unit acquires input voltages of the plurality of external parallel capacitor banks through the wiring unit; high-frequency and low-voltage voltage signals can be generated and applied to the capacitors of the extra-high-voltage converter station, each capacitor of a plurality of parallel capacitor banks can be measured in sequence, line disconnection is not needed, the measurement is automatically completed, test data of the capacitors each time can be automatically recorded, and a capacitance value change curve graph is generated.

Description

Technical Field

[0001] The present invention relates to the field of devices of ultra-high voltage direct current (UHV) converter stations, and in particular to an AC / DC filter capacitance detection device and method for ultra-high voltage converter stations based on low voltage frequency conversion. Background Art

[0002] With the rapid development of 800 kV and 1100 kV UHV DC projects, the AC and DC filter capacitors in converter stations are showing the characteristics of higher and higher voltage levels, larger single-phase capacity, more and more capacitor banks, and more and more heavy maintenance workload. Large AC filter capacitor banks have a large number of capacitor units, and the probability of failure in symmetrical positions cannot be ignored. The initial unbalanced value is mainly related to the manufacturing deviation of the capacitor and the temperature characteristics of the capacitor. Although the manufacturing deviation of the capacitor can be improved by balancing inside the capacitor bank, it will eventually be limited by the measurement accuracy. According to the view of IEEE C37.99-2000 "IEEE Parallel Capacitor Bank Protection Guidelines", the requirement of two-stage protection is to add a first-level alarm before tripping, and once it is determined that the internal fuse has operated, it will operate on the alarm to arrange planned maintenance. During the maintenance process, the capacitance value of each capacitor unit is measured. Due to the large number of capacitor units, the workload is large; At present, the relevant domestic UHV DC converter station AC and DC filter capacitor detection mainly has the following shortcomings: 1. The capacitance detection method uses the bridge method, which has low accuracy. 2. The AC / DC filter capacitors of UHV DC converter stations are often composed of multiple capacitors connected in parallel and then in series. The parallel capacitors need to be uncoupled and measured before being restored, which increases the intensity and difficulty of the work. The capacitor tester can only test a single capacitor, and the value needs to be manually tested and recorded. Therefore, it is necessary to design a UHV converter station AC / DC filter capacitance detection device based on low-voltage frequency conversion to solve the above problems. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a UHV converter station AC / DC filter capacitor detection device and method based on low-voltage frequency conversion, which can generate a high-frequency low-voltage voltage signal applied to the UHV converter station capacitor and can measure each capacitor under multiple parallel capacitor groups in turn, without the need to untie the wires, and can be completed automatically. It can automatically record each test data of the capacitor and generate a capacitance change curve chart. According to the change trend of the capacitance change curve chart, the number of internal fuses of the UHV converter station AC / DC filter capacitor that have been blown can be judged, the capacitor failure can be predicted early, and the maintenance items and periodic maintenance methods can be reasonably arranged according to the predicted fault information, so as to ensure the safety of the operation process of the UHV converter station AC / DC filter.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a capacitor detection device for AC / DC filters of ultra-high voltage converter stations based on low-voltage frequency conversion, comprising a main control unit composed of a high-frequency voltage signal acquisition unit, a high-frequency current acquisition unit and a test control unit arranged inside the device, the test control unit is communicatively connected to a high-frequency voltage generating unit; the main control unit is communicatively connected to a wiring unit, and the wiring unit is electrically connected to a plurality of parallel capacitor groups outside the device; the high-frequency current acquisition unit acquires a plurality of input currents of the external plurality of parallel capacitor groups through the wiring unit, and the high-frequency voltage signal acquisition unit acquires the input voltages of the external plurality of parallel capacitor groups through the wiring unit; the test control unit is connected to the wiring unit, and the high-frequency voltage generating unit outputs voltages for the external plurality of parallel capacitor groups through the wiring unit; the parallel capacitor groups are electrically connected to the wiring unit through a measuring voltage loop, an output voltage loop and a plurality of current clamps; the wiring unit acquires a plurality of input currents, a measuring voltage and an output voltage of the parallel capacitor groups.

[0005] Preferably, the high-frequency voltage generating unit is provided with a short-circuit protection interface and an overload protection interface.

[0006] Preferably, the test control unit is connected to the high-frequency voltage generating unit via Ethernet.

[0007] Preferably, the test control unit is connected to the wiring unit via a parallel bus.

[0008] Preferably, the test control unit and the high-frequency voltage signal acquisition unit are connected via an SPI bus.

[0009] Preferably, the test control unit is connected to the high-frequency current acquisition unit via an SPI bus.

[0010] Furthermore, the test control unit drives the high-frequency voltage generating unit to generate a variable-frequency low-voltage AC source to be loaded onto the parallel capacitor group, the test control unit controls the external multiple parallel capacitor group wiring units to select the current parallel capacitor group, the high-frequency voltage signal acquisition unit samples the voltage of the parallel capacitor group applied to the current test, the high-frequency current acquisition unit samples the current of each capacitor applied to the external parallel capacitor group, and the test control unit calculates the capacitive reactance by collecting the voltage and current, thereby calculating the capacitance of each capacitor under the parallel capacitor group.

[0011] Furthermore, the test control unit includes ADSP-21992, which controls the test process and calculates the capacitance value based on the collected signal.

[0012] Furthermore, the high-frequency voltage signal acquisition unit includes AD4080, which acquires the high-frequency voltage applied to the capacitor group.

[0013] Furthermore, the high-frequency current acquisition unit includes LTC2385-16, which acquires the current flowing through each capacitor on the capacitor group.

[0014] Furthermore, the high-frequency voltage generating unit includes AD5781, which outputs a 0-20V 1000HZ adjustable frequency and voltage voltage.

[0015] Furthermore, the external multiple parallel capacitor group wiring unit includes MK60DN512, which controls the input of the external 8 parallel capacitor groups.

[0016] Preferably, the above-mentioned method for detecting capacitance of AC / DC filter in ultra-high voltage converter station based on low voltage frequency conversion comprises: S1, the test control unit drives the high-frequency voltage generating unit to generate a variable-frequency low-voltage AC source; S2, the low voltage AC source loads the output voltage to the parallel capacitor group through the wiring unit; S3, numbering multiple parallel capacitor groups connected to the outside of the device through the wiring unit, controlling the connection and disconnection of the wiring unit through the test control unit, and connecting the parallel capacitor group with the currently selected number; S4, the high-frequency voltage signal acquisition unit acquires the voltage of the parallel capacitor group applied to the current test, and the high-frequency current acquisition unit samples the current of each capacitor applied to the external parallel capacitor group; S5, based on the capacitive reactance calculation formula and the capacitance calculation formula, the test control unit calculates the capacitive reactance through the collected voltage and current, and thus calculates the capacitance value of each capacitor in the parallel capacitor group: ; ; ; ; In the formula, Xc represents the capacitive reactance, π is the circumference of the circle, f is the frequency of the output voltage, C is the capacitance of the AC / DC capacitor filter; U represents the collected voltage value, and I represents the collected current value; S6, generating a capacitance change curve diagram according to the input capacitance factory value and the actual values ​​of the capacitance detected in the past.

[0017] The beneficial effects of the ultra-high voltage converter station AC / DC filter capacitance detection device based on low voltage frequency conversion provided by the present invention are: The present invention applies low-frequency high voltage to the parallel capacitor group of the AC / DC filter of the converter station. During the test, the current of each capacitor on the parallel capacitor group can reach more than 1A, so an open current clamp can be clamped on the output line of each capacitor of the parallel capacitor group to achieve measurement without disconnecting the line; the present invention can simultaneously connect and automatically measure multiple parallel capacitor groups on the platform of the AC / DC filter of the converter station, and does not need to measure each capacitor manually; the present invention establishes a model for the AC / DC filter, records the factory value and previous measurement values ​​of each capacitor unit, produces a capacitance change curve, judges the number of internal fuses of the capacitors of the AC / DC filter of the ultra-high voltage converter station that have been blown, predicts the failure of the capacitor early, and reasonably arranges maintenance items and periodic maintenance methods according to the predicted fault information, so as to ensure the safety of the operation process of the AC / DC filter of the ultra-high voltage converter station; the device calculates the unbalanced current of the AC / DC filter according to the measurement value of each capacitor of the AC / DC filter; the present invention realizes automatic balancing according to the measurement value of each capacitor of the AC / DC filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 It is a schematic diagram of a connection block diagram of the present invention; Figure 2 A schematic diagram of the connection relationship of the main control unit of the present invention; Figure 3 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0019] Embodiment 1: like Figure 1-2 As shown, a capacitor detection device for AC / DC filters of ultra-high voltage converter stations based on low-voltage frequency conversion includes a main control unit composed of a high-frequency voltage signal acquisition unit, a high-frequency current acquisition unit and a test control unit arranged inside the device, the test control unit is communicatively connected to a high-frequency voltage generating unit; the main control unit is communicatively connected to a wiring unit, and the wiring unit is electrically connected to a plurality of parallel capacitor groups outside the device; the high-frequency current acquisition unit acquires a plurality of input currents of the plurality of external parallel capacitor groups through the wiring unit, and the high-frequency voltage signal acquisition unit acquires input voltages of the plurality of external parallel capacitor groups through the wiring unit; the test control unit is connected to the wiring unit, and the high-frequency voltage generating unit outputs voltages for the plurality of external parallel capacitor groups through the wiring unit; the parallel capacitor groups are electrically connected to the wiring unit through a measuring voltage loop, an output voltage loop and a plurality of current clamps; the wiring unit acquires a plurality of input currents, a measuring voltage and an output voltage of the parallel capacitor groups.

[0020] Preferably, the high-frequency voltage generating unit is provided with a short-circuit protection interface and an overload protection interface.

[0021] Preferably, the test control unit is connected to the high-frequency voltage generating unit via Ethernet.

[0022] Preferably, the test control unit is connected to the wiring unit via a parallel bus.

[0023] Preferably, the test control unit and the high-frequency voltage signal acquisition unit are connected via an SPI bus.

[0024] Preferably, the test control unit is connected to the high-frequency current acquisition unit via an SPI bus.

[0025] Furthermore, the test control unit includes ADSP-21992, which controls the test process and calculates the capacitance value based on the collected signal.

[0026] Furthermore, the high-frequency voltage signal acquisition unit includes AD4080, which acquires the high-frequency voltage applied to the capacitor group.

[0027] Furthermore, the high-frequency current acquisition unit includes LTC2385-16, which acquires the current flowing through each capacitor on the capacitor group.

[0028] Furthermore, the high-frequency voltage generating unit includes AD5781, which outputs a 0-20V 1000HZ adjustable frequency and voltage voltage.

[0029] Furthermore, the external multiple parallel capacitor group wiring unit includes MK60DN512, which controls the input of the external 8 parallel capacitor groups.

[0030] Embodiment 2: like Figure 3 As shown, a method for detecting capacitance of an AC / DC filter in a UHV converter station based on low voltage frequency conversion includes: S1, the test control unit drives the high-frequency voltage generating unit to generate a variable-frequency low-voltage AC source; S2, the low voltage AC source loads the output voltage to the parallel capacitor group through the wiring unit; S3, numbering multiple parallel capacitor groups connected to the outside of the device through the wiring unit, controlling the connection and disconnection of the wiring unit through the test control unit, and connecting the parallel capacitor group with the currently selected number; S4, the high-frequency voltage signal acquisition unit acquires the voltage of the parallel capacitor group applied to the current test, and the high-frequency current acquisition unit samples the current of each capacitor applied to the external parallel capacitor group; S5, based on the capacitive reactance calculation formula and the capacitance calculation formula, the test control unit calculates the capacitive reactance through the collected voltage and current, and thus calculates the capacitance value of each capacitor in the parallel capacitor group: ; ; ; ; In the formula, Xc represents the capacitive reactance, π is the circumference of the circle, f is the frequency of the output voltage, C is the capacitance of the AC / DC capacitor filter; U represents the collected voltage value, and I represents the collected current value; S6, generating a capacitance change curve diagram according to the input capacitance factory value and the actual values ​​of the capacitance detected in the past.

[0031] The above embodiments are only preferred technical solutions of the present invention and should not be regarded as limiting the present invention. The protection scope of the present invention shall be the technical solutions recorded in the claims, including equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A capacitance detection device for AC / DC filter of ultra-high voltage converter station based on low voltage frequency conversion, characterized in that: The invention comprises a main control unit composed of a high-frequency voltage signal acquisition unit, a high-frequency current acquisition unit and a test control unit which are arranged inside the device, wherein the test control unit is communicatively connected with the high-frequency voltage generating unit; the main control unit is communicatively connected with the wiring unit, and the wiring unit is electrically connected with multiple parallel capacitor groups outside the device; the high-frequency current acquisition unit acquires multiple input currents of multiple external parallel capacitor groups through the wiring unit, and the high-frequency voltage signal acquisition unit acquires input voltages of multiple external parallel capacitor groups through the wiring unit; the test control unit is connected with the wiring unit, and the high-frequency voltage generating unit outputs voltages for multiple external parallel capacitor groups through the wiring unit; the parallel capacitor groups are electrically connected with the wiring unit through a measuring voltage loop, an output voltage loop and multiple current clamps; the wiring unit acquires multiple input currents, measuring voltages and output voltages of the parallel capacitor groups.

2. The ultra-high voltage converter station AC / DC filter capacitance detection device based on low voltage frequency conversion according to claim 1 is characterized in that: The high-frequency voltage generating unit is provided with a short-circuit protection interface and an overload protection interface.

3. The ultra-high voltage converter station AC / DC filter capacitance detection device based on low voltage frequency conversion according to claim 1 is characterized in that: The test control unit is connected to the high-frequency voltage generating unit via Ethernet.

4. The ultra-high voltage converter station AC / DC filter capacitance detection device based on low voltage frequency conversion according to claim 1 is characterized in that: The test control unit is connected with the wiring unit via a parallel bus.

5. The ultra-high voltage converter station AC / DC filter capacitance detection device based on low voltage frequency conversion according to claim 1 is characterized in that: The test control unit is connected to the high-frequency voltage signal acquisition unit via an SPI bus.

6. The ultra-high voltage converter station AC / DC filter capacitance detection device based on low voltage frequency conversion according to claim 1 is characterized in that: The test control unit is connected to the high-frequency current acquisition unit via an SPI bus.

7. A method for detecting capacitance of an AC / DC filter in a UHV converter station based on low voltage frequency conversion according to any one of claims 1 to 6, characterized in that: include: S1, the test control unit drives the high-frequency voltage generating unit to generate a variable-frequency low-voltage AC source; S2, the low voltage AC source loads the output voltage to the parallel capacitor group through the wiring unit; S3, numbering multiple parallel capacitor groups connected to the outside of the device through the wiring unit, controlling the connection and disconnection of the wiring unit through the test control unit, and connecting the parallel capacitor group with the currently selected number; S4, the high-frequency voltage signal acquisition unit acquires the voltage of the parallel capacitor group applied to the current test, and the high-frequency current acquisition unit samples the current of each capacitor applied to the external parallel capacitor group; S5, based on the capacitive reactance calculation formula and the capacitance calculation formula, the test control unit calculates the capacitive reactance through the collected voltage and current, and thus calculates the capacitance value of each capacitor in the parallel capacitor group: ； ； ； ； In the formula, Xc represents the capacitive reactance, π is the circumference of the circle, f is the frequency of the voltage, C is the capacitance of the AC / DC capacitor filter; U represents the collected voltage value, and I represents the collected current value; S6, generating a capacitance change curve diagram according to the input capacitance factory value and the actual values ​​of the capacitance detected in the past.

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