Apparatus and method for simulating coexistence of direct current and harmonic electric field

Abstract

The application relates to a device and a method for simulating coexistence of direct current and harmonic electric fields, which comprises the following steps: high voltage is applied to an experimental conductor wire to generate an electric field below the conductor wire, and an electric field measuring probe is used to measure the electric field distribution characteristics below the conductor wire, so that an experimental environment for simulating coexistence of direct current and harmonic electric fields is constructed. The application can simulate the distribution characteristics and influencing factors of the electric field in a flexible direct current converter station under different working conditions, guide electromagnetic environment design of the flexible direct current converter station, reduce transient electric shock phenomenon, and ensure safety of the converter station operating personnel.

Description

Technical Field

[0001] The present invention relates to the technical field of power simulation devices, and in particular to a device and method for simulating the coexistence of direct current and harmonic electric fields. Background Art

[0002] Flexible DC transmission technology is a key enabler for large-scale renewable energy grid integration and enhancing grid flexibility. Currently, flexible DC projects are being widely adopted and implemented both domestically and internationally. Several modular multilevel converter (MMC)-based flexible DC transmission projects have been built, including the ±30kV Shanghai Nanhui Wind Farm Flexible DC Transmission Demonstration Project (commissioned in 2011), the ±200kV Zhoushan Five-Terminal Flexible DC Transmission Demonstration Project (commissioned in 2014), the ±320kV Xiamen Flexible DC Transmission Project (commissioned in 2015), the ±420kV Chongqing-Hubei DC Back-to-Back Interconnection Project (commissioned in 2019), and the ±500kV Zhangbei Flexible DC Grid Project (commissioned in 2020). With the gradual increase in voltage levels for flexible DC transmission, the electromagnetic environment within converter stations has received increasing attention. The electric field within flexible DC converter stations and the resulting transient electric shock are of particular concern to on-site operators.

[0003] Generally speaking, a Flexible DC transmission project primarily consists of a Flexible DC converter station and overhead lines / cables. Due to the unique characteristics of the Flexible DC grid, the design of a Flexible DC converter station differs from that of a conventional DC converter station. In addition to the AC and DC sections, a startup zone exists between the converter transformer and the valve hall. In this startup zone, due to the unique control strategy of the Flexible DC system, a superposition of AC and DC currents exists beneath the converter busbars, along with harmonics on the converter valve side. This results in the electric field in the startup zone containing DC, power frequency, and third and ninth harmonic components. The combined effects of these DC and multi-harmonic electric field components can result in excessive field strength, leading to frequent transient electric shocks for operators near the startup zone. These shocks are more severe and complex than those in conventional DC converter stations. Therefore, research and analysis of the complex electric field environment within the station is necessary to provide theoretical guidance for engineering practice.

[0004] At present, there is a lack of relevant research results on the electric field control values ​​and specific characteristics under DC and multi-frequency hybrid electric fields in flexible DC converter stations, and there is also a lack of relevant calculation and analysis models. Therefore, studying the basic characteristics of DC and multi-frequency hybrid fields through experimental methods is currently the most effective method to study the electric field characteristics in flexible DC converter stations.

[0005] Current research on hybrid electric fields only focuses on mixed DC and industrial frequency electric field conditions. The experimental method used is to apply pressure by connecting DC and AC power supplies in series or in parallel. This pressure application method is very inflexible and easily affects the DC and AC power supplies. This pressure application method cannot be used to simulate the conditions unique to flexible DC converter stations, where DC, industrial frequency, and third and ninth harmonic electric fields coexist and the proportions of each component are variable. Currently, there are no available experimental devices and methods. Summary of the Invention

[0006] In order to overcome the deficiencies of the prior art, an object of the present invention is to provide a device and method for simulating the coexistence of direct current and harmonic electric fields.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] A device for simulating the coexistence of DC and harmonic electric fields, comprising: an experimental wire, a first steel trough support, a second steel trough support, a grounding metal plate, a first epoxy resin cross arm, a second epoxy resin cross arm, a high voltage power supply, and a plurality of electric field measurement probes;

[0009] The first steel trough bracket and the second steel trough bracket are respectively arranged at the two ends of the grounded metal plate, and the first epoxy resin crossarm and the second epoxy resin crossarm are respectively provided on the first steel trough bracket and the second steel trough bracket; the experimental wire is erected on the first epoxy resin crossarm and the second epoxy resin crossarm; the high-voltage power supply is connected to the experimental wire, and the high-voltage power supply is used to simulate the voltage operating conditions of the flexible DC converter station to obtain the output voltage, and transmit the output voltage to the experimental wire; each of the electric field measurement probes is evenly arranged on the grounded metal plate perpendicular to the direction of the straight line where the experimental wire is located; the electric field measurement probe is used to measure the electric field distribution information released by the experimental wire.

[0010] Preferably, it also includes:

[0011] The shielding metal mesh is arranged above the experimental wire and is used for shielding the electromagnetic interference of the environment.

[0012] Preferably, the high voltage power supply comprises:

[0013] A signal generator for generating a voltage signal having a superposition of DC and harmonic components;

[0014] A voltage amplifier is connected to the experimental wire and is used to amplify the voltage signal to obtain the output voltage.

[0015] Preferably, the voltage signal is expressed as follows:

[0016]

[0017] u is the voltage signal, U DC is the voltage of the DC component contained in the voltage of the voltage signal, U m 、U 3m and U 9m are the voltage amplitudes of the power frequency, 3rd and 9th harmonic components contained in the voltage of the voltage signal respectively, and are the phases of the power frequency, third and ninth harmonic components contained in the voltage of the voltage signal respectively, and f is the frequency of the power grid.

[0018] A method for simulating the coexistence of direct current and harmonic electric fields, applied to the above-mentioned device, comprising:

[0019] Placing a test wire on the first epoxy resin crossarm and the second epoxy resin crossarm, and straightening the test wire;

[0020] Arrange the electric field measuring probe perpendicular to the wire direction on the grounded metal plate, and record the position of the electric field measuring probe;

[0021] Compiling a voltage function relationship program based on the ratio and phase of the voltage DC, power frequency, and third and ninth harmonics of the simulated flexible DC converter station, and inputting the voltage function relationship program into the high-voltage power supply;

[0022] The output voltage of the high-voltage power supply is applied to the experimental wire, and the output signal and electric field distribution characteristics of each electric field measurement probe are recorded.

[0023] Preferably, after arranging the electric field measuring probe perpendicular to the wire direction on the grounded metal plate and recording the position of the electric field measuring probe, the method further comprises:

[0024] A shielding metal mesh is placed above the experimental wire; the center line of the shielding metal mesh is parallel to the experimental wire.

[0025] Preferably, after applying the output voltage of the high-voltage power supply to the experimental wire and recording the output signal and electric field distribution characteristics of each electric field measurement probe, the method further includes:

[0026] Disconnect the high voltage power supply and discharge the experimental wire to ground.

[0027] Preferably, it also includes:

[0028] According to the preset operating conditions of the flexible DC converter station, the input voltage ratio of the high-voltage power supply is adjusted to simulate different voltage conditions.

[0029] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0030] The application provides a device and a method for simulating coexistence of direct current and harmonic electric field. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0032] Figure 1 The device overall arrangement in the embodiments provided by the present application is shown in the figure.

[0033] Figure 2 The method flow chart in the embodiments provided by the present application is shown in the figure.

[0034] Symbol explanation:

[0035] 1-first steel tank support, 2-first epoxy resin cross arm, 3-grounding metal plate, 4-electric field measurement probe, 5-shielding metal net, 6-experimental wire, 7-signal generator, 8-voltage amplifier, 9-high voltage cable, 10-second steel tank support, 11-second epoxy resin cross arm. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0037] The purpose of the present application is to provide a device and a method for simulating coexistence of direct current and harmonic electric field, which can simulate the distribution characteristics and influencing factors of electric field in the flexible direct current converter station under different working conditions, guide the electromagnetic environment design of the flexible direct current converter station, reduce the transient electric shock phenomenon, and ensure the safety of the converter station operating personnel.

[0038] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0039] Figure 1 The overall arrangement diagram of the device in the embodiment provided by the present invention is as follows: Figure 1 As shown, the present invention provides a device for simulating the coexistence of DC and harmonic electric fields, comprising: an experimental wire 6, a first steel trough support 1, a second steel trough support 10, a shielding metal mesh 5, a grounding metal plate 3, a first epoxy resin crossarm 2, a second epoxy resin crossarm 11, a high-voltage power supply, and a plurality of electric field measurement probes 4;

[0040] The first steel trough bracket 1 and the second steel trough bracket 10 are respectively arranged at the two ends of the grounded metal plate 3, and the first epoxy resin crossarm 2 and the second epoxy resin crossarm 11 are respectively provided on the first steel trough bracket 1 and the second steel trough bracket 10; the experimental wire 6 is mounted on the first epoxy resin crossarm 2 and the second epoxy resin crossarm 11; the high-voltage power supply is connected to the experimental wire 6, and the high-voltage power supply is used to simulate the voltage operating conditions of the flexible DC converter station to obtain the output voltage, and transmit the output voltage to the experimental wire 6; each of the electric field measurement probes 4 is evenly arranged on the grounded metal plate 3 perpendicular to the direction of the straight line where the experimental wire 6 is located; the electric field measurement probe 4 is used to measure the electric field distribution information released by the experimental wire 6; the shielding metal mesh 5 is covered above the experimental wire 6 to shield the electromagnetic interference of the environment.

[0041] Specifically, an electric field is generated beneath the experimental conductor 6 by applying high voltage to the conductor. The experimental conductor 6 is erected via an epoxy resin crossarm supported by a steel trough bracket, and the epoxy resin crossarm can be adjusted in height according to actual conditions. A grounded metal plate 3 is placed beneath the experimental conductor 6, and an electric field measurement probe 4 is placed on the grounded metal plate 3 to measure the electric field distribution characteristics beneath the conductor. To prevent interference with the electric field measurement from the surrounding environment, a shielded metal mesh 5 is placed above the line. In order to generate an electric field condition with superimposed DC and harmonic components beneath the conductor, the applied high-voltage power supply is composed of a signal generator 7 and a voltage amplifier 8. The output of the voltage amplifier 8 is connected to the experimental conductor 6 via a high-voltage cable 9.

[0042] In combination with the DC, power frequency, 3rd and 9th harmonic components contained in the electric field of the flexible DC converter station, the signal generator 7 in this patent can generate a voltage combination with any proportion of DC and harmonic components, which can be specifically expressed as:

[0043]

[0044] Where: u is the voltage expression applied to the wire, U DC is the voltage containing the DC component, U m 、U 3m and U 9mis the voltage amplitude of the power frequency, 3rd and 9th harmonic components contained in the voltage, and are the phases of the power frequency, 3rd and 9th harmonic components contained in the voltage respectively, and f is the frequency of the power grid, which is 50Hz.

[0045] The present invention mainly combines the different operating modes of the flexible DC converter station. The above-mentioned DC, power frequency, third and ninth harmonic components can be flexibly adjusted to facilitate the simulation of different voltage conditions. At the same time, the amplification factor of the voltage amplifier 8 is 2000 times, which can ensure that the electric field under the conductor is large enough and simulate the magnitude of the electric field under the actual converter station as much as possible.

[0046] Preferably, the high voltage power supply comprises:

[0047] A signal generator 7 is used to generate a voltage signal with a superposition of DC and harmonic components;

[0048] The voltage amplifier 8 is connected to the experimental wire 6 and is used to amplify the voltage signal to obtain the output voltage.

[0049] Preferably, the voltage signal is expressed as follows:

[0050]

[0051] u is the voltage signal, U DC is the voltage of the DC component contained in the voltage of the voltage signal, U m 、U 3m and U 9m are the voltage amplitudes of the power frequency, 3rd and 9th harmonic components contained in the voltage of the voltage signal respectively, and are the phases of the power frequency, third and ninth harmonic components contained in the voltage of the voltage signal respectively, and f is the frequency of the power grid.

[0052] Figure 2 A flow chart of the method in the embodiment provided by the present invention, such as Figure 2 As shown, this embodiment also provides a method for simulating the coexistence of DC and harmonic electric fields, which is applied to the above-mentioned device, and the method includes:

[0053] Step 100: Installing a test wire on a first epoxy resin crossarm and a second epoxy resin crossarm, and straightening the test wire;

[0054] Step 200: placing an electric field measuring probe perpendicular to the direction of the conductor on a grounded metal plate, and recording the position of the electric field measuring probe;

[0055] Step 300: compiling a voltage function relationship program based on the voltage DC, power frequency, and the proportions and phases of the third and ninth harmonics of the simulated flexible DC converter station, and inputting the voltage function relationship program into the high-voltage power supply;

[0056] Step 400: Apply the output voltage of the high-voltage power supply to the experimental wires, and record the output signals and electric field distribution characteristics of each of the electric field measurement probes.

[0057] Preferably, after step 200, the method further includes:

[0058] A shielding metal mesh is placed above the experimental wire; the center line of the shielding metal mesh is parallel to the experimental wire.

[0059] Preferably, after step 400, the method further includes:

[0060] Disconnect the high voltage power supply and discharge the experimental wire to ground.

[0061] Preferably, it also includes:

[0062] According to the preset operating conditions of the flexible DC converter station, the input voltage ratio of the high-voltage power supply is adjusted to simulate different voltage conditions.

[0063] Specifically, the experimental method of the entire device in this embodiment is described as follows:

[0064] (1) Before the experiment, the experimental wires are placed on the epoxy resin crossarms and straightened. The height can be adjusted flexibly according to the needs of the experiment.

[0065] (2) Place the electric field measurement probe perpendicular to the wire direction on the grounded metal plate and record the position of the electric field measurement probe;

[0066] (3) Place a shielding metal mesh over the wire so that the test wire is parallel to the center line of the metal mesh;

[0067] (4) Connect the signal generator to the high-voltage amplifier, and connect the output of the high-voltage amplifier to the experimental wire through a high-voltage cable;

[0068] (5) Based on the voltage DC, power frequency, 3rd and 9th harmonic ratio and phase requirements of the simulated flexible DC converter station, a voltage function relationship program is compiled using the formula and input into the signal generator;

[0069] (6) Turn on the signal generator and voltage amplifier to apply the preset voltage to the experimental wire. At this time, record the output signal and electric field distribution characteristics of each electric field measurement probe;

[0070] (7) After recording is completed, disconnect the signal generator and voltage amplifier, and discharge the wire to ground;

[0071] (8) According to the differences in the operating conditions of the flexible DC converter station, the input voltage ratio of the signal generator can be adjusted to simulate different voltage conditions.

[0072] The beneficial effects of the present invention are as follows:

[0073] The present invention can flexibly adjust the output voltage amplitude, DC and harmonic ratio, and phase according to the actual voltage operating conditions of the flexible DC converter station. It can also specifically study the distribution characteristics and influencing factors of the electric field unique to the flexible DC converter station, and ultimately guide the electromagnetic environment design of the flexible DC converter station.

[0074] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0075] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A device for simulating the coexistence of DC and harmonic electric fields, characterized in that: Includes: experimental wires, a first steel trough bracket, a second steel trough bracket, a grounding metal plate, a first epoxy resin cross arm, a second epoxy resin cross arm, a high-voltage power supply and multiple electric field measurement probes; The first steel trough bracket and the second steel trough bracket are respectively arranged at both ends of the grounded metal plate, and the first epoxy resin crossarm and the second epoxy resin crossarm are respectively provided on the first steel trough bracket and the second steel trough bracket; the experimental wires are mounted on the first epoxy resin crossarm and the second epoxy resin crossarm; the high-voltage power supply is connected to the experimental wires, and the high-voltage power supply is used to simulate the voltage operating conditions of the flexible DC converter station to obtain an output voltage, and transmit the output voltage to the experimental wires; each of the electric field measurement probes is evenly arranged on the grounded metal plate perpendicular to the direction of the straight line where the experimental wires are located; the electric field measurement probes are used to measure the electric field distribution information below the experimental wires; The high voltage power supply comprises: A signal generator for generating a voltage signal having a superposition of DC and harmonic components; a voltage amplifier connected to the experimental wire, for amplifying the voltage signal to obtain the output voltage; The formula for the voltage signal is: u is the voltage signal, U DC is the voltage of the DC component contained in the voltage of the voltage signal, U m 、U 3m and U 9m are the voltage amplitudes of the power frequency, 3rd and 9th harmonic components contained in the voltage of the voltage signal respectively, and are the phases of the power frequency, third and ninth harmonic components contained in the voltage of the voltage signal respectively, and f is the frequency of the power grid.

2. The device for simulating the coexistence of direct current and harmonic electric fields according to claim 1, characterized in that: Also includes: The shielding metal mesh is arranged above the experimental wire and is used for shielding the electromagnetic interference of the environment.

3. A method for simulating the coexistence of DC and harmonic electric fields, characterized in that: Applied to the device according to any one of claims 1 to 2, the method comprising: Placing a test wire on the first epoxy resin crossarm and the second epoxy resin crossarm, and straightening the test wire; Arrange the electric field measuring probe perpendicular to the wire direction on the grounded metal plate, and record the position of the electric field measuring probe; Compiling a voltage function relationship program based on the ratio and phase of the voltage DC, power frequency, and third and ninth harmonics of the simulated flexible DC converter station, and inputting the voltage function relationship program into the high-voltage power supply; The output voltage of the high-voltage power supply is applied to the experimental wire, and the output signal and electric field distribution characteristics of each electric field measurement probe are recorded.

4. The method for simulating the coexistence of direct current and harmonic electric fields according to claim 3, characterized in that: After arranging the electric field measuring probe perpendicular to the wire direction on the grounded metal plate and recording the position of the electric field measuring probe, the method further includes: A shielding metal mesh is placed above the experimental wire; the center line of the shielding metal mesh is parallel to the experimental wire.

5. The method for simulating the coexistence of direct current and harmonic electric fields according to claim 3, characterized in that: After applying the output voltage of the high-voltage power supply to the experimental wire and recording the output signal and electric field distribution characteristics of each electric field measurement probe, the method further includes: Disconnect the high voltage power supply and discharge the experimental wire to ground.

6. The method for simulating the coexistence of direct current and harmonic electric fields according to claim 3, characterized in that: Also includes: According to the preset operating conditions of the flexible DC converter station, the input voltage ratio of the high-voltage power supply is adjusted to simulate different voltage conditions.

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