WO2023231278A1 - Vacuum on-load tap changer test system and harmonic current source - Google Patents

Abstract

The present application discloses a vacuum on-load tap changer test system. The system comprises a fundamental power supply (100) and a harmonic current source (200); the fundamental power supply (100) is used for generating a fundamental current; the harmonic current source (200) comprises a rectifier circuit (201), an inverter circuit (202), and a harmonic current control circuit (203); an input end of the rectifier circuit (201) is connected to an alternating current power supply, and an output end of the rectifier circuit (201) is connected to an input end of the inverter circuit (202); an output end of the inverter circuit (202) is connected to an input end of the harmonic current control circuit (203); an output end of the harmonic current control circuit (203) is adapted to be connected to a vacuum on-load tap changer; the fundamental power supply (100) is used for generating a fundamental current; the rectifier circuit (201) is used for converting an alternating current into a direct current; the inverter circuit (202) is used for converting the direct current into a harmonic current according to a preset harmonic current order; the harmonic current control circuit (203) is used for adjusting the amplitude and phase of the harmonic current according to target slope of a current zero-crossing point, so that the fundamental current and the harmonic current are superimposed and output to the vacuum on-load tap changer.

Description

Vacuum on-load tap changer test system and harmonic current source

Cross-references to related applications

This application requests the priority of the Chinese patent application submitted to the China Patent Office on June 2, 2022, with the application number 202210623628.1 and the invention title "A vacuum on-load tap changer test system and harmonic current source", all of which The contents are incorporated into this application by reference.

Technical field

This application relates to the technical field of power systems, and in particular to a vacuum on-load tap changer testing system and a harmonic current source.

Background technique

The on-load tap-changer is a voltage regulating device suitable for operation under transformer excitation or load, and is used to change the tap connection position of the transformer winding. The vacuum on-load tap-changer is a contact that connects and breaks the load and generates arc currents. On-load tap-changer in vacuum interrupter.

With the construction and application of DC transmission systems, the impact of harmonics generated in DC systems on power equipment such as converter transformers and flexible transformers has become increasingly obvious. The vacuum on-load tap-changer is an important component for converting voltage in converter transformers and flexible transformers. Therefore, in order to ensure that the vacuum on-load tap-changer can be used normally during system operation, the vacuum on-load tap-changer needs to be tested.

At present, during the testing process, power frequency voltage and power frequency current are mainly used to test the on-load tap changer. However, there is a working condition in which power frequency current superimposes harmonic current. The harmonic current will change the slope of the current zero-crossing point and cause the slope to increase. As a part of the vacuum on-load tap-changer, the vacuum interrupter is sensitive to the slope of the zero-crossing point of the current. When the slope of the zero-crossing point of the current increases, it will affect its ability to transfer current, cause malfunction, and cause damage to the vacuum. The test of the on-load tap-changer is inaccurate.

Therefore, how to improve the accuracy of vacuum on-load tap changer testing is an urgent technical problem that those skilled in the art need to solve.

Contents of the invention

According to various embodiments of the present application, a vacuum on-load tap changer testing system and a harmonic current source are provided.

In the first aspect, this application provides a vacuum on-load tap-changer testing system, including:

Fundamental wave power supply and harmonic current source; the harmonic current source includes: a rectifier circuit, an inverter circuit and a harmonic current control circuit; the input end of the rectifier circuit is connected to the AC power supply, and the output end of the rectifier circuit is connected to the The input end of the inverter circuit is connected, the output end of the inverter circuit is connected to the input end of the harmonic current control circuit, and the output end of the harmonic current control circuit is used to connect the vacuum on-load tap-changer;

The fundamental wave power supply is used to generate fundamental wave current;

The rectifier circuit is used to convert alternating current into direct current;

The inverter circuit is used to convert the DC current into a harmonic current according to a preset harmonic current order; the frequency of the harmonic current corresponds to the preset harmonic current order;

The harmonic current control circuit is used to adjust the amplitude and phase of the harmonic current according to the target slope of the current zero-crossing point, so that the fundamental current and the harmonic current are superimposed and output to the vacuum on-load tap changer. .

Optionally, the harmonic current control circuit is specifically configured to obtain the slope of the harmonic current zero-crossing point according to the target slope of the current zero-crossing point, and adjust the harmonic current according to the slope of the harmonic zero-crossing point. Amplitude and phase of wave current.

Optionally, the inverter circuit is specifically used for:

Sinusoidal pulse width modulation (SPWM) control is used to convert the DC current into the harmonic current.

Optionally, the harmonic current includes:

Single frequency harmonic current; or,

A multi-frequency harmonic current composed of multiple frequency harmonic currents.

Optionally, the harmonic current is a multi-frequency harmonic current, and the rectifier circuit is composed of multiple H-bridge rectifier circuits connected end to end.

Optionally, the harmonic current is a multi-frequency harmonic current, and the inverter circuit includes: multiple full-bridge inverter circuits; the input end of each full-bridge inverter circuit is connected to the corresponding H-bridge rectifier circuit. The output terminal is connected;

Each full-bridge inverter circuit is used to invert the direct current according to the preset harmonic current order to obtain single-frequency harmonic currents of different frequencies.

Optionally, the harmonic current is a multi-frequency harmonic current, and the system further includes: a multi-frequency harmonic current combination circuit;

The input end of the multi-frequency harmonic current combination circuit is connected to the output end of each full-bridge inverter circuit;

The multi-frequency harmonic current combination circuit is used to combine and superimpose single-frequency harmonic currents of different frequencies to generate multi-frequency harmonic currents.

Optionally, the switching element of the inverter circuit includes an insulated gate bipolar transistor.

Optionally, it also includes: electromagnetic interference circuit;

The electromagnetic interference circuit is connected to the output end of the fundamental wave power supply and is used to filter the fundamental wave current.

In the second aspect, a harmonic current source is provided, including a rectifier circuit, an inverter circuit and a harmonic current control circuit;

The input end of the rectifier circuit is used to connect to the AC power supply, the output end of the rectifier circuit is connected to the input end of the inverter circuit, and the output end of the inverter circuit is connected to the input end of the harmonic current control circuit. Connection; the output end of the harmonic current control circuit is used to connect with the vacuum on-load tap-changer;

The rectifier circuit is used to convert the alternating current provided by the alternating current power supply into direct current;

The inverter circuit is used to convert the DC current into a harmonic current according to a preset harmonic order; the frequency of the harmonic current corresponds to the preset harmonic order;

The harmonic current control circuit is used to adjust the amplitude and phase of the harmonic current according to the target slope of the current zero-crossing point, and output the harmonic current of the amplitude and phase.

Optionally, the harmonic current includes:

Single frequency harmonic current; or,

A multi-frequency harmonic current composed of multiple frequency harmonic currents.

Optionally, the harmonic current is a multi-frequency harmonic current, and the rectifier circuit is composed of multiple H-bridge rectifier circuits connected end to end.

Optionally, the harmonic current is a multi-frequency harmonic current, and the inverter circuit includes: multiple full-bridge inverter circuits; the input end of each full-bridge inverter circuit is connected to the corresponding H-bridge rectifier circuit. The output terminal is connected;

Each full-bridge inverter circuit is used to invert the direct current according to the preset harmonic current order to obtain single-frequency harmonic currents of different frequencies.

Optionally, the harmonic current is a multi-frequency harmonic current, and the system further includes: a multi-frequency harmonic current combination circuit;

The input end of the multi-frequency harmonic current combination circuit is connected to the output end of each full-bridge inverter circuit;

The multi-frequency harmonic current combination circuit is used to combine and superpose single-frequency harmonic currents of different frequencies to generate the multi-frequency harmonic current.

Optionally, the switching element of the inverter circuit includes an insulated gate bipolar transistor.

Optionally, it also includes: electromagnetic interference circuit;

The electromagnetic interference circuit is connected to the output end of the fundamental wave power supply and is used to filter the fundamental wave current.

The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below. Other features, objects and advantages of the application will become apparent from the description, drawings and claims.

Description of the drawings

To better describe and illustrate embodiments and/or examples of those inventions disclosed herein, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the figures should not be construed as limiting the scope of any of the disclosed inventions, the embodiments and/or examples presently described, and the best modes currently understood of these inventions.

Figure 1 is a schematic structural diagram of a vacuum on-load tap changer testing system in some embodiments;

Figure 2 is a schematic diagram of a single H-bridge rectifier circuit in some embodiments;

Figure 3 is a schematic structural diagram of a vacuum on-load tap changer testing system in other embodiments;

Figure 4 is a schematic diagram of a cascade H-bridge rectifier circuit composed of multiple H-bridge rectifier circuits connected end-to-end in some embodiments;

Figure 5 is a schematic structural diagram of a single-frequency harmonic current signal generator in some embodiments;

Figure 6 is a schematic diagram of a multi-frequency harmonic current combination circuit in some embodiments.

Detailed ways

In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are given in the accompanying drawings. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing specific embodiments only and is not intended to limit the application.

It will be understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another element.

It should be noted that when an element is said to be "connected" to another element, it can be directly connected to the other element, or connected to the other element through an intervening element. In addition, "connection" in the following embodiments should be understood as "electrical connection", "communication connection", etc. if there is transmission of electrical signals or data between the connected objects.

As used herein, the singular forms "a," "an," and "the" may include the plural forms as well, unless the context clearly dictates otherwise. It will also be understood that the terms "comprising" or "having" and the like specify the presence of stated features, integers, steps, operations, components, parts or combinations thereof, but do not exclude the presence or addition of one or more Possibility of other features, integers, steps, operations, components, parts or combinations thereof.

As described above, the on-load tap-changer is a voltage regulating device suitable for operating under transformer excitation or load and used to change the tap connection position of the transformer winding. The vacuum on-load tap-changer is a contact that connects and breaks the load. The circulating arc occurs in the vacuum interrupter of the on-load tap-changer.

Harmonic current will cause the slope of the current zero-crossing point to increase. The vacuum interrupter in the vacuum on-load tap-changer is sensitive to the slope of the current zero-crossing point. Once the slope increases, it will cause the vacuum interrupter to malfunction, thereby causing vacuum The on-load tap-changer is faulty. Therefore, the introduction of harmonic current will lead to inaccurate testing of vacuum on-load tap-changers.

After research, the inventor found that the slope of the current zero-crossing point can be solved by adjusting the amplitude and phase of the harmonic current, eliminating the impact of the introduction of high-order harmonics on the vacuum on-load tap-changer, and improving the vacuum on-load tap-changer. Switch test accuracy.

In order to enable those in the technical field to better understand the solutions of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only These are part of the embodiments of this application, but not all of them. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of this application.

In one embodiment, see Figure 1, which is a schematic structural diagram of a vacuum on-load tap changer testing system. The system includes:

fundamental wave power supply 100 and harmonic current source 200;

Among them, the fundamental wave power supply 100 is used to generate a fundamental wave current; the fundamental wave power supply 100 can be a 12kV generator set, and the fundamental wave current can be a power frequency AC current with a frequency of 50Hz;

The harmonic current source 200 may be a power supply device that provides harmonic current required for testing.

The harmonic current source 200 includes: a rectifier circuit 201, an inverter circuit 202 and a harmonic current control circuit 203; the input end of the rectifier circuit 201 is connected to the AC power supply, and the output end of the rectifier circuit 201 is connected to the inverter circuit. The input end of 202 is connected, the output end of the inverter circuit 202 is connected to the input end of the harmonic current control circuit 203, and the output end of the harmonic current control circuit 203 is connected to the vacuum on-load tap changer;

The AC power supply can be a harmonic power supply or a common mains power supply in daily life;

Among them, the rectifier circuit 201 is used to convert alternating current into direct current;

The rectifier circuit can be an H-bridge rectifier circuit;

As an example, the H-bridge rectifier circuit is shown in Figure 2.

The inverter circuit 202 is used to convert the DC current into a harmonic current according to the preset harmonic current order; the frequency of the harmonic current corresponds to the preset harmonic order;

The inverter circuit can be a full-bridge inverter circuit;

The harmonic current can be a Fourier series decomposition of the periodic alternating current to obtain a harmonic current with a frequency greater than an integer multiple of the fundamental frequency; in this embodiment, the harmonic current can be a single-frequency harmonic current;

The preset harmonic current order can be the integer ratio of the harmonic frequency to the fundamental frequency; for example, the second harmonic (100Hz/50Hz), the third harmonic (150Hz/50Hz)...nth harmonic (50nHz/50Hz) ;

When the preset harmonic current order is two, the direct current can be converted into a harmonic current with a frequency of 100Hz; when the preset harmonic current order is three, the direct current can be converted into a harmonic current with a frequency of 150Hz; By analogy, when the preset harmonic current order is n, the direct current can be converted into a harmonic current with a frequency of 50n;

The harmonic current control circuit 203 is used to adjust the amplitude and phase of the harmonic current according to the target slope of the current zero-crossing point, so that the fundamental current and the adjusted harmonic current are superimposed and output to the vacuum. load tap changer.

The target slope of the current zero-crossing point can be the target slope that needs to be achieved after the superposition of the fundamental current and the harmonic current; and the target slope can be set according to the test requirements.

As an example, the superposition process is explained as follows:

I _{fundamental wave} =sin(100πt ₁ ) (1)

Formula (1) is the expression of the fundamental current with a frequency of 50Hz, an amplitude of 1, and an initial phase angle of 0;

Formula (2) indicates that the harmonic order is n, where n≠1, the amplitude is I _B and the initial phase angle is

The expression of the nth harmonic current;

Formula (3) is the current expression after the fundamental wave current is superimposed on the harmonic current;

Assume that the target slope is di _{superposition} /dt=150π. By calculating the slope of the zero-crossing point of the fundamental current, it can be: di _{fundamental wave} /dt=100π; therefore, the amplitude and phase of the harmonic current need to be adjusted to make the slope of the harmonic current : di _harmonic /dt=50π.

The fundamental wave current is generated by the fundamental wave power supply; the alternating current is converted into direct current through the rectifier circuit, and the direct current is converted into harmonic current through the inverter circuit; the fundamental wave current and the harmonic current are superimposed to construct a fundamental wave current containing harmonics. Working conditions, and by adjusting the amplitude and phase of the harmonic current to change the slope of the current zero-crossing point, the impact of higher harmonics on the vacuum on-load tap-changer can be eliminated and the accuracy of the vacuum on-load tap-changer test can be improved.

As an example, for ease of understanding, here is a brief explanation of how to improve the accuracy of on-load tap changer testing:

The reasons for the failure of the on-load tap changer may include: (1) When the tap changer changes tap voltage and regulates voltage, continuous changes occur for more than one tap change, that is, sliding gears; (2) Tap changer insulating oil Internal seepage or lack of oil in the fuel tank; (3) Discharge failure of the tap changer. (4) The transition resistor in the auxiliary contact of the tap changer is broken down and burned during the switching process.

For example, when testing whether reason (1) causes the vacuum on-load tap-changer to malfunction, if the vacuum on-load tap-changer malfunctions at this time, it cannot be determined whether the fault is caused by reason (1) or harmonics. Caused by electric current.

Therefore, the existence of harmonic current will cause the vacuum on-load tap-changer to malfunction, which will lead to inaccurate test results. In order to complete normal testing, it is necessary to eliminate the impact of high-frequency current on the vacuum on-load tap-changer, thereby improving the accuracy of the vacuum on-load tap-changer test.

In one embodiment, see Figure 3, which is a schematic structural diagram of another vacuum on-load tap changer testing system. The system includes:

Fundamental wave power supply 300 and harmonic current source 400;

Among them, the fundamental wave power supply 300 is used to generate a fundamental wave current; the fundamental wave power supply 300 can be a 12kV generator set, and the fundamental wave current can be a power frequency AC current with a frequency of 50Hz;

The harmonic current source 400 may be a power supply device that provides the harmonic current required for testing.

The harmonic current source 400 includes: a rectifier circuit 401, an inverter circuit 402 and a harmonic current control circuit 403; the input end of the rectifier circuit 401 is connected to the AC power supply, and the output end of the rectifier circuit 401 is connected to the inverter circuit. The input end of 402 is connected, the output end of the inverter circuit 402 is connected to the input end of the harmonic current control circuit 403, and the output end of the harmonic current control circuit 403 is connected to the vacuum on-load tap changer;

Rectifier circuit 401, used to convert alternating current into direct current;

When the harmonic current is a multi-frequency harmonic current, the rectifier circuit may be composed of multiple H-bridge rectifier circuits connected end to end;

For example, it can be seen from Figure 3 that the output end of each H-bridge rectifier circuit is connected to the input end of each full-bridge inverter circuit to form a cascaded H-bridge converter directly connected to the injected harmonic current source. To increase the required test voltage of the converter, it usually requires 10 to 20 H-bridge rectifier circuits and inverter circuits to meet the withstand voltage level of the high-voltage test circuit, and then through multiple H-bridge rectifier circuits and full-bridge inverter circuits The inverter synchronously controls the high-voltage side to directly output harmonic current, realizing the direct injection of the high-voltage test circuit and the superposition of the fundamental current. Its main feature is good fault redundancy (N+1 redundancy can be achieved, that is, the system can Zhongduo adds an H-bridge rectifier circuit and a full-bridge circuit. In this way, when a fault occurs in one of the systems, it will not affect the normal operation of the system), excellent parameter control, and low loss (because the fundamental wave is implemented in this application The superposition of current and harmonic current is completed directly on the high-voltage side, so no other processing is required midway, so the waste of system power can be reduced, thereby reducing losses).

As an example, the cascaded H-bridge rectifier circuit is shown in Figure 4. It can be composed of multiple H-bridge rectifier circuits connected end to end. In addition, the cascaded multi-level structure can achieve high-frequency and high-power output by using low-voltage and low-frequency devices, and can significantly improve EMI characteristics; since the power units of each cascade have the same structure, it is easy to implement modular design. It is conducive to equipment installation and subsequent maintenance and replacement; each DC side in the structure is independent of each other, and voltage balance is easy to achieve; if the modulation is reasonable, the work of each power unit is basically symmetrical, so that the switching load is relatively balanced.

The inverter circuit 402 is used to convert the DC current into the harmonic current using sinusoidal pulse width modulation SPWM control; the switching element of the inverter circuit includes an insulated gate bipolar transistor.

As an example, the inverter circuit may be composed of three full-bridge circuits, namely full-bridge inverter circuit 1, full-bridge inverter circuit 2 and full-bridge inverter circuit 3.

When the preset harmonic current order of the full-bridge inverter circuit 1 is two, the full-bridge inverter circuit 1 can convert DC power into a harmonic current with a frequency of 100Hz; when the preset harmonic current of the full-bridge inverter circuit 2 When the order is five, the full-bridge inverter circuit 2 can convert DC power into a harmonic current with a frequency of 250Hz; when the preset harmonic current order of the full-bridge inverter circuit 3 is eight, the full-bridge inverter circuit 3 can convert the direct current into a harmonic current with a frequency of 250Hz. Direct current is converted into harmonic current with a frequency of 400Hz. The number of inverter circuits and the preset harmonic current order are not limited here. More complex harmonic currents can be constructed through multiple inverter circuits, which is closer to the actual DC transmission scenario. The performance of the vacuum on-load switch in the DC transmission scenario can be tested to make up for the current vacuum on-load tap-changer. A blank that cannot be tested in simulated DC transmission scenarios.

The sinusoidal pulse width modulation SPWM signal can be generated by a harmonic signal generator, and the SPWM signal required for a certain harmonic can be generated by collecting the phase of the fundamental current. In this embodiment, the number of harmonic signal generators and the inverter The number of circuits remains the same; as an example, the structural diagram of each inverter circuit generating single-frequency harmonics is shown in Figure 5.

When the harmonic current is a multi-frequency harmonic current, the inverter circuit includes: a plurality of full-bridge inverter circuits, and the input terminal of each full-bridge inverter circuit is connected to the input terminal of the H-bridge rectifier circuit. The output ends are connected, and each of the full-bridge inverter circuits is used to invert the direct current according to the preset harmonic current order to obtain single-frequency harmonic currents of different frequencies.

As an example, the SPWM signal that controls the full-bridge inverter circuit to convert DC power into harmonic current is generated by a single-frequency harmonic current signal generator. Each full-bridge inverter circuit is processed by the corresponding SPWM signal. Correspondingly controlled, that is to say, assuming that the system contains three full-bridge inverter circuits, then it contains three single-frequency harmonic current signal generators, and each single-frequency harmonic current signal generator is controlled according to the harmonic The frequency of the wave current generates a corresponding SPWM signal to control the inverter circuit to convert the direct current into a harmonic current of the corresponding frequency. When the harmonic is a multi-frequency harmonic current, the system further includes: a multi-frequency harmonic current combination circuit 403 as shown in Figure 6. The input end of the multi-frequency harmonic current combination circuit is connected to each of the The output ends of the full-bridge inverter circuit are connected, and the multi-frequency harmonic current combination circuit is used to combine and superimpose single-frequency harmonic currents of different frequencies to generate multi-frequency harmonic currents.

As an example, the inverter circuit can be composed of three full-bridge circuits, namely full-bridge inverter circuit 1, full-bridge inverter circuit 2 and full-bridge inverter circuit 3. The full-bridge inverter circuit 1 generates a frequency of 100Hz. Harmonic current, full-bridge inverter circuit 2 produces a harmonic current with a frequency of 250Hz, full-bridge inverter circuit 3 produces a harmonic current with a frequency of 400Hz; full-bridge inverter circuit 1, full-bridge inverter circuit 2 and full-bridge The output end of the inverter circuit 3 is connected to the input end of the multi-frequency harmonic current combination circuit. The harmonic currents of 100Hz, 250Hz and 400Hz can be superimposed to generate a harmonic current with a frequency of X. The multi-frequency in this embodiment The harmonic current combination circuit can superimpose harmonics of 12 different frequencies.

The specific method of superposition is not limited here. It is only necessary to eventually convert multiple harmonic currents of different frequencies into a single-frequency harmonic current.

By superimposing multiple harmonic currents of different frequencies, and then superimposing the superimposed multi-frequency harmonic currents with the fundamental current, the difficulty of controlling the superposition of the fundamental current and the harmonic current can be reduced. In addition, in the embodiment, the superposition of harmonic currents of different frequencies is realized by using hardware, which further reduces the control difficulty of the system and can also improve efficiency and reliability.

The harmonic current control circuit 404 is used to adjust the amplitude and phase of the harmonic current according to the target slope of the current zero-crossing point, so that the fundamental current and the adjusted harmonic current are superimposed and output to the vacuum load component. Connect the switch.

As an example, the superposition process is explained as follows:

I _{fundamental wave} =sin(100πt ₁ ) (4)

Formula (4) is the expression of the fundamental current with a frequency of 50Hz, an amplitude of 1, and an initial phase angle of 0;

Formula (5) shows that the harmonic order is n, where n≠1, the amplitude is I _B and the initial phase angle is

The expression of the nth harmonic current;

Formula (6) is the current expression after the fundamental wave current is superimposed on the harmonic current;

Assume that the target slope is di _{superposition} /dt=150π. By calculating the slope of the zero-crossing point of the fundamental current, it can be: di _{fundamental wave} /dt=100π; therefore, the amplitude and phase of the harmonic current need to be adjusted to make the slope of the harmonic current : di _harmonic /dt=50π.

Electromagnetic interference circuit; the electromagnetic interference circuit is connected to the output end of the fundamental wave power supply and is used to filter the fundamental wave current; the fundamental wave power supply can be a generator set up to 12kV. Normally, in order to prevent its output The fundamental wave current does not contain uncontrolled harmonic currents. Therefore, it is necessary to add an electromagnetic interference circuit to the output end of the fundamental wave power supply to filter out the harmonic currents that may exist in the fundamental wave current and further improve the vacuum on-load switch test. Accuracy (by avoiding uncontrolled harmonic currents in the fundamental current, which would cause an increase in the slope of the current zero-crossing point).

The fundamental wave current is generated through the fundamental wave power supply; the alternating current is converted into direct current through the cascade H-bridge rectifier circuit, and then the direct current is generated into multiple harmonic currents of different frequencies through the multi-channel inverter circuit; the multi-frequency harmonic current combination circuit is used Superimpose multiple harmonic currents of different frequencies into a single-frequency harmonic current, superimpose the fundamental current and the harmonic current to construct a working condition in which the fundamental current contains harmonics, and adjust the amplitude and sum of the harmonic currents. Phase changing the slope of the zero-crossing point of the current can eliminate the impact on the vacuum interrupter due to the introduction of higher harmonics, and improve the accuracy of the vacuum on-load tap changer test under harmonic current conditions.

In addition, the use of multiple harmonic currents of different frequencies for superposition is more in line with the actual environment of the DC transmission site. Therefore, the test system of the vacuum on-load tap changer in this embodiment can test the vacuum in the DC transmission environment. The on-load tap-changer is simulated and tested to meet the needs of testing the vacuum on-load tap-changer in multiple scenarios. This application also provides a harmonic current source. In this embodiment, the harmonic current source includes:

Rectifier circuit, inverter circuit and harmonic current control circuit;

The input end of the rectifier circuit is used to connect to the AC power supply, the output end of the rectifier circuit is connected to the input end of the inverter circuit, and the output end of the inverter circuit is connected to the input end of the harmonic current control circuit. Connection; the output end of the harmonic current control circuit is used to connect with the vacuum on-load tap-changer;

The rectifier circuit is used to convert the alternating current provided by the alternating current power supply into direct current;

The inverter circuit is used to convert the DC current into a harmonic current according to a preset harmonic current order; the frequency of the harmonic current corresponds to the preset harmonic current order;

The harmonic current control circuit is used to adjust the amplitude and phase of the harmonic current according to the target slope of the current zero-crossing point, and output the harmonic current of the amplitude and phase.

In order to simulate more test scenarios, the harmonic current output by the harmonic current source in this embodiment can be a harmonic current of only one frequency or multiple different frequencies before the harmonic current is finally output. Frequency composition of multi-frequency harmonic current.

As an example, when the test scenario only requires a single-frequency harmonic current, this embodiment may include an H-bridge rectifier circuit, a full-bridge inverter circuit, a harmonic current control circuit, and a harmonic signal generator. First, the H-bridge rectifier circuit converts alternating current into direct current. According to the test needs, the harmonic signal generator obtains the frequency of the target harmonic current to generate the SPWM signal of the corresponding frequency, which is used to control the inverter circuit to convert the direct current into the corresponding frequency through the SPWM signal. of harmonic currents.

As an example, when the test scenario has higher requirements (the test scenario can be a simulated DC transmission field environment), multi-frequency harmonic current is required. This embodiment can include a cascaded H-bridge rectifier circuit, an input terminal and a cascaded H-bridge. The inverter circuit connected to the rectifier circuit and the harmonic current signal generator that controls the corresponding inverter circuit to generate corresponding frequencies, and the multi-frequency harmonic current combination circuit that superimposes harmonic currents of different frequencies to control the harmonic current Amplitude and phase harmonic current control circuit.

The fundamental wave current is generated through the fundamental wave power supply; the alternating current is converted into direct current through the cascade H-bridge rectifier circuit, and then the direct current is generated into multiple harmonic currents of different frequencies through the multi-channel inverter circuit; the multi-frequency harmonic current combination circuit is used Superimpose multiple harmonic currents of different frequencies into a single-frequency harmonic current, superimpose the fundamental current and the harmonic current to construct a working condition in which the fundamental current contains harmonics, and adjust the amplitude and sum of the harmonic currents. The phase changes the slope of the zero-crossing point of the current, which can produce harmonic currents with controllable amplitude and phase.

In addition, the use of multiple harmonic currents of different frequencies for superposition is more in line with the actual environment of the DC transmission site. Therefore, the test system of the vacuum on-load tap changer in this embodiment can test the vacuum in the DC transmission environment. The on-load tap-changer is simulated for testing.

It should be noted that each embodiment in this specification is described in a progressive manner, and the same and similar parts between the various embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments. at. In particular, the device and system embodiments are described simply because they are basically similar to the method embodiments. For relevant details, please refer to the partial description of the method embodiments. The device and system embodiments described above are only illustrative. The units described as separate components may or may not be physically separated. The components indicated as units may or may not be physical units, that is, they may be located in One location, or it can be distributed across multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. Persons of ordinary skill in the art can understand and implement the method without any creative effort.

In the description of this specification, reference to the terms "some embodiments," "other embodiments," "ideal embodiments," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included herein. In at least one embodiment or example of the application. In this specification, schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.

The technical features of the above embodiments can be combined in any way. To simplify the description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, all possible combinations should be used. It is considered to be within the scope of this manual.

The above-described embodiments only express several implementation modes of the present application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that, for those of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all fall within the protection scope of the present application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims (10)

1. A system for testing a vacuum on-load tap changer. The system includes: a fundamental wave power supply and a harmonic current source; the harmonic current source includes: a rectifier circuit, an inverter circuit and a harmonic current control circuit; the rectifier The input end of the circuit is connected to the AC power supply, the output end of the rectifier circuit is connected to the input end of the inverter circuit, the output end of the inverter circuit is connected to the input end of the harmonic current control circuit, and the harmonic current The output end of the control circuit is used to connect the vacuum on-load tap-changer;

   The fundamental wave power supply is used to generate fundamental wave current;

   The rectifier circuit is used to convert alternating current into direct current;

   The inverter circuit is used to convert the DC current into a harmonic current according to a preset harmonic current order; the frequency of the harmonic current corresponds to the preset harmonic current order;

   The harmonic current control circuit is used to adjust the amplitude and phase of the harmonic current according to the target slope of the current zero-crossing point, so that the fundamental current and the harmonic current are superimposed and output to the vacuum on-load tap changer. .
2. The system according to claim 1, wherein the harmonic current control circuit is used to obtain the slope of the harmonic current zero-crossing point according to the target slope of the current zero-crossing point. The slope adjusts the amplitude and phase of the harmonic current.
3. The system according to claim 1, characterized in that the inverter circuit is used for:

   Sinusoidal pulse width modulation (SPWM) control is used to convert the DC current into the harmonic current.
4. The system of claim 1, wherein the harmonic current includes:

   Single frequency harmonic current; or,

   A multi-frequency harmonic current composed of multiple frequency harmonic currents.
5. The system according to claim 4, wherein the harmonic current is a multi-frequency harmonic current, and the rectifier circuit is composed of multiple H-bridge rectifier circuits connected end to end.
6. The system according to claim 5, wherein the harmonic current is a multi-frequency harmonic current, and the inverter circuit includes: a plurality of full-bridge inverter circuits; an input end of each full-bridge inverter circuit. Connected to the corresponding output end of the H-bridge rectifier circuit;

   Each full-bridge inverter circuit is used to invert the direct current according to the preset harmonic current order to obtain single-frequency harmonic currents of different frequencies.
7. The system according to claim 6, wherein the harmonic current is a multi-frequency harmonic current, and the system further includes: a multi-frequency harmonic current combination circuit;

   The input end of the multi-frequency harmonic current combination circuit is connected to the output end of each full-bridge inverter circuit;

   The multi-frequency harmonic current combination circuit is used to combine and superpose single-frequency harmonic currents of different frequencies to generate the multi-frequency harmonic current.
8. The system according to any one of claims 1 to 7, characterized in that the switching element of the inverter circuit includes an insulated gate bipolar transistor.
9. The system according to any one of claims 1-7, further comprising: an electromagnetic interference circuit;

   The electromagnetic interference circuit is connected to the output end of the fundamental wave power supply and is used to filter the fundamental wave current.
10. A harmonic current source, the harmonic current source includes: a rectifier circuit, an inverter circuit and a harmonic current control circuit;

    The input end of the rectifier circuit is used to connect to the AC power supply, the output end of the rectifier circuit is connected to the input end of the inverter circuit, and the output end of the inverter circuit is connected to the input end of the harmonic current control circuit. Connection; the output end of the harmonic current control circuit is used to connect the vacuum on-load tap-changer;

    The rectifier circuit is used to convert the alternating current provided by the alternating current power supply into direct current;

    The inverter circuit is used to convert the DC current into a harmonic current according to a preset harmonic current order; the frequency of the harmonic current corresponds to the preset harmonic current order;

    The harmonic current control circuit is used to adjust the amplitude and phase of the harmonic current according to the target slope of the current zero-crossing point, and output the harmonic current of the amplitude and phase.

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