Low-frequency power transmission converter valve test system and its test method

Abstract

This application proposes a low-frequency power transmission converter valve test system and its test method. The low-frequency power transmission converter valve test system includes a frequency mixing power supply branch and a test valve tower branch. The voltage output by the frequency mixing power supply branch includes at least two or more frequencies, denoted as the first-frequency AC power supply and the second-frequency AC power supply, and the first-frequency AC power supply is not equal to the second-frequency AC power supply. The test valve tower branch includes N test valve segments, and each test valve segment includes M power sub-modules; both M and N are natural numbers greater than or equal to 1. All the test valve segments form the test valve tower branch through series or parallel connection, and this branch is connected in series with the first-frequency AC power supply, the second-frequency AC power supply, and the reactor branch to form a test circuit. By sampling the voltage and current information of the test valve tower branch and controlling the phase of the first-frequency and second-frequency voltage and current, the power operation requirements of the test valve tower branch are realized, and the live test requirements of the low-frequency power transmission converter valve during the production and manufacturing process are met.

Description

Technical Field

[0001] The present application relates to the technical field of power electronics applications. Specifically, it relates to a low-frequency power transmission converter valve test system and a test method thereof. Background Art

[0002] When the traditional power frequency power transmission system uses 50 / 60 Hz, compared with the DC power supply system, the transmission distance is limited, and the problems of system reactive power and distributed parameters also need to be considered. Although popularizing the DC power supply system has considerable advantages in the fields of new energy applications and power transmission, the costs of equipment such as DC circuit breakers and DC transformers are expensive, and most DC systems need to be newly built.

[0003] Therefore, for some cases where the transmission distance is relatively farther than that of the power frequency power transmission system but the cost requirement is limited, or some cases where equipment transformation and operation are required, a low-frequency power transmission system can be adopted.

[0004] The low-frequency power transmission system can reduce the power transmission frequency, which is beneficial to improving the problems of system reactive power and distributed parameters, so as to achieve a certain long-distance power transmission. At the same time, the power transmission line can still retain the power frequency line, so the transformation cost is also relatively lower than that of the DC power supply system.

[0005] However, the low-frequency power transmission system is inseparable from the cycloconverter for power frequency and low-frequency voltage conversion. Currently, the common and relatively mature cycloconverter is the modular multilevel matrix converter (M3C).

[0006] The modular multilevel matrix converter has a large number of bridge arms. During the production and manufacturing process, test verification is required. Generally, for large power electronic devices, module-level or valve section-level tests are mostly used. However, the bridge arm current of the M3C converter is a superimposed current of two frequencies, and the method for experimental verification is different from that of existing MMC and SVG devices.

[0007] Therefore, it is necessary to propose a low-frequency power transmission converter valve test system and a test method thereof, which can provide a superimposed current of at least two frequencies, realize the power operation requirements of the test valve tower branch, and meet the live test requirements of the low-frequency power transmission converter valve during the production and manufacturing process.

[0008] The above information disclosed in the background art section is only used to strengthen the understanding of the background of the present application. Therefore, it may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0009] The present application aims to provide a low-frequency power transmission converter valve test system and a test method thereof, which can provide superimposed currents of at least two frequencies, realize the power operation requirements of the test valve tower branch, and meet the live test requirements of the low-frequency power transmission converter valve during the production and manufacturing process.

[0010] According to one aspect of the present application, a low-frequency power transmission converter valve test system is proposed, characterized in that the low-frequency power transmission converter valve test system includes a frequency mixing power supply branch and a test valve tower branch, and the frequency mixing power supply branch and the test valve tower branch are connected in parallel, wherein:

[0011] The voltage output by the frequency mixing power supply branch includes an alternating current voltage of at least a first frequency and an alternating current voltage of a second frequency, and the first frequency is not equal to the second frequency;

[0012] The test valve tower branch includes N test valve segments, and each test valve segment includes M power sub-modules; both M and N are natural numbers greater than or equal to 1.

[0013] According to some embodiments, the test valve tower branch further includes a controller, and the controller controls the test valve segment to output an alternating current voltage that is the superposition of the alternating current voltage of the first frequency and the alternating current voltage of the second frequency.

[0014] According to some embodiments, the power sub-module is an AC-DC conversion sub-module, including an AC port and a DC port, and the AC ports of the power sub-modules are connected in series in sequence.

[0015] According to some embodiments, the power sub-module is a full-bridge module, including 4 fully controlled power devices and a capacitor:

[0016] The nodes where the fully controlled power devices connected in series in pairs are connected in parallel form the DC port of the power sub-module;

[0017] The capacitor is connected in parallel to the DC port of the power sub-module;

[0018] The midpoints of the fully controlled power devices connected in series in pairs form the AC port of the power sub-module.

[0019] According to some embodiments, the frequency mixing power supply branch includes a first AC power supply of the first frequency and a second AC power supply of the second frequency.

[0020] According to some embodiments, the frequency mixing power supply branch includes a multi-winding transformer, Q rectifier bridges and Q full-bridge modules, and a controller, where Q is a natural number greater than or equal to 1; wherein:

[0021] The primary side of the multi-winding transformer is connected to the AC power grid, and the secondary side includes Q windings;

[0022] The Q windings are respectively connected to the AC sides of the Q rectifier bridges, the DC sides of the Q rectifier bridges are connected to the DC port of the full-bridge module, and the AC ports of the Q full-bridge modules are cascaded and used as the output port of the frequency mixing power supply branch;

[0023] The controller controls the AC ports of the Q full-bridge modules to generate an AC voltage including a superposition of an AC voltage with the first frequency and an AC voltage with the second frequency.

[0024] According to some embodiments, the test system further includes P reactor branches, where P is a natural number greater than or equal to 1.

[0025] According to some embodiments, the reactor branch includes a series reactor and a starting branch;

[0026] The starting branch includes a starting resistor, a starting switch, and a bypass switch.

[0027] According to some embodiments, the low-frequency power transmission converter valve test system as described in any one of the foregoing:

[0028] The reactor branch includes a first reactor branch, a second reactor branch... a Kth reactor branch;

[0029] The X1 test valve segments of the test valve tower branch are connected in series to form a first test valve tower branch; the X2 test valve segments of the test valve tower branch are connected in series to form a second test valve tower branch... the Xk test valve segments of the test valve tower branch are connected in series to form a kth test valve tower branch, where X1 + X2... + Xk = N, k = P, N ≥ k;

[0030] The first reactor branch is connected in series with the first test valve tower branch, the second reactor branch is connected in series with the second test valve tower branch... the kth reactor branch is connected in series with the kth test valve tower branch. After these series-connected branches are connected in parallel, they are connected in parallel with the frequency mixing power supply branch.

[0031] According to one aspect of the present application, a test method for a low-frequency power transmission converter valve test system is proposed, including:

[0032] If the frequency mixing power supply branch is implemented by a power electronic circuit, start the frequency mixing power supply branch and output an AC voltage including the first frequency and the second frequency;

[0033] Close the charging switch of the starting branch to complete the charging of the test valve tower branch;

[0034] Close the bypass switch of the starting branch and unlock the test valve tower branch through the controller of the test valve tower branch;

[0035] Sample the current of the test valve tower branch circuit, and through the closed-loop control of the controller of the test valve tower branch circuit, adjust the voltage of the test valve tower branch circuit so that the series reactor of the test system and the current of the test valve tower branch circuit reach the rated state.

[0036] By sampling the voltage and current information of the test valve tower branch circuit, control the phase of the voltage and current of the first frequency and the second frequency to meet the power operation requirements of the test valve tower branch circuit and satisfy the live test requirements of the low-frequency power transmission converter valve during the manufacturing process.

[0037] It should be understood that the above general description and the following detailed description are only exemplary and do not limit the present application. Description of the Drawings

[0038] By describing its exemplary embodiments in detail with reference to the drawings, the above and other objects, features and advantages of the present application will become more obvious. The drawings described below are only some embodiments of the present application and do not limit the present application.

[0039] Figure 1 Schematic diagram of a low-frequency power transmission converter valve test system showing an exemplary embodiment;

[0040] Figure 2 Another embodiment showing a schematic diagram of a low-frequency power transmission converter valve test system;

[0041] Figure 3 Another embodiment showing a schematic diagram of a low-frequency power transmission converter valve test system;

[0042] Figure 4 Schematic circuit diagram of a full-bridge module showing an exemplary embodiment;

[0043] Figure 5 Flowchart of a test method for a low-frequency power transmission converter valve test system showing an exemplary embodiment. Detailed Description of the Embodiments

[0044] Example embodiments will now be described more fully with reference to the drawings. However, the example embodiments can be implemented in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this application will be thorough and complete and will fully convey the concept of the example embodiments to those skilled in the art. Like reference numerals in the figures denote like or similar parts, and thus their repeated description will be omitted.

[0045] The described features, structures, or characteristics can be combined in one or more embodiments in any suitable manner. In the following description, numerous specific details are provided to give a thorough understanding of the embodiments of the present disclosure. However, those skilled in the art will realize that the technical solutions of the present disclosure can be practiced without one or more of these specific details, or other methods, components, materials, devices, etc. can be adopted. In these cases, well-known structures, methods, devices, implementations, materials, or operations will not be shown or described in detail.

[0046] The flowchart shown in the drawings is only an exemplary illustration and does not necessarily include all contents and operations / steps, nor does it necessarily need to be executed in the described order. For example, some operations / steps can be decomposed, while some operations / steps can be combined or partially combined. Therefore, the actual execution order may change according to the actual situation.

[0047] The terms "first", "second", etc. in the description and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products, or devices.

[0048] Those skilled in the art can understand that the drawings are only schematic diagrams of exemplary embodiments, and the modules or processes in the drawings are not necessarily essential for implementing this application, so they cannot be used to limit the protection scope of this application.

[0049] The device embodiments of this application are described below, which can be used to execute the method embodiments of this application. For details not disclosed in the device embodiments of this application, reference can be made to the method embodiments of this application.

[0050] Figure 1 The schematic diagram of a low-frequency power transmission converter valve test system showing an exemplary embodiment is presented.

[0051] As Figure 1 shown, a low-frequency power transmission converter valve test system includes a frequency mixing power supply branch 101, reactor branches 1021 - 102P, and test valve tower branches 1031 - 103P.

[0052] According to the exemplary embodiment, the frequency mixing power supply branch 101 includes an AC power supply 101a and an AC power supply 101b connected in series. The frequency of the AC power supply 101a is the first frequency AC power supply F1, and the frequency of the AC power supply 101b is the second frequency AC power supply F2.

[0053] According to some embodiments, the voltage output by the mixing power supply branch includes at least two or more frequencies, denoted as the first frequency alternating current power supply F1 and the second frequency alternating current power supply F2, and the first frequency alternating current power supply F1 is not equal to the second frequency alternating current power supply F2.

[0054] According to an exemplary embodiment, the test valve tower branch further includes a controller 104, which can control all test valve segments to output an alternating voltage that is the superposition of the first frequency alternating current power supply F1 and the second frequency alternating current power supply F2.

[0055] According to some embodiments, the test valve tower branch includes N test valve segments, and each test valve segment includes M power sub-modules. Both M and N are natural numbers greater than or equal to 1. Refer to Figure 1 , and the power sub-modules are 10311 - 1031M, ……, 103P1 - 103PM.

[0056] According to some embodiments, the power sub-module is an AC-DC sub-module, including an AC port and a DC port. Multiple sub-modules are connected in series through the AC ports in sequence to form a test valve segment. Refer to Figure 1 , the power sub-modules 10311 - 1031M are connected in series to form the test valve tower branch 1031, the power sub-modules 10321 - 1032M are connected in series to form the test valve tower branch 1032, and the power sub-modules 103P1 - 103PM are connected in series to form the test valve tower branch 103P.

[0057] According to an exemplary embodiment, the number of test valve segments N can be greater than or equal to the number of test valve tower branches P, and the number of test valve tower branches is equal to the number of reactor branches.

[0058] According to some embodiments, when the number of test valve segments N≥k, the number of test valve tower branches P = k, and the reactor branch includes the first reactor branch, the second reactor branch … the kth reactor branch.

[0059] According to some embodiments, X1 test valve segments of the test valve tower branch are connected in series to form the first test valve tower branch; X2 test valve segments of the test valve tower branch are connected in series to form the second test valve tower branch, ……, Xk test valve segments of the test valve tower branch are connected in series to form the kth test valve tower branch; X1 + X2 …… + Xk = N.

[0060] According to some embodiments, the first reactor branch is connected in series with the first test valve tower branch, the second reactor branch is connected in series with the second test valve tower branch … the kth reactor branch is connected in series with the kth test valve tower branch; after these series-connected branches are connected in parallel, they are connected in parallel with the mixing power supply branch.

[0061] Figure 2 Another embodiment showing a schematic diagram of an exemplary low-frequency power transmission converter valve test system is presented.

[0062] As Figure 2 shown, the function of the mixing power supply branch 201 is implemented by a power electronic circuit. The power electronic circuit includes a multi-winding transformer 201c. The multi-winding transformer 201c includes a primary winding 201c0, Q secondary windings 201c1 - 201cQ, Q rectifier bridges 201a1 - 201aQ, and Q full-bridge modules 201b1 - 201bQ.

[0063] As Figure 2 shown, the low-frequency power transmission converter valve test system includes a mixing power supply branch 201, an AC power grid 202, a reactor branch 204, a test valve tower branch 205, and a controller 206.

[0064] According to the exemplary embodiment, the reactor branch 204 includes a series reactor 204a and a starting branch. The starting branch includes a bypass switch 204b, a starting switch 204c, and a starting resistor 204d. Among them, the starting switch 204c and the starting resistor 204d are connected in series and then connected in series with the bypass switch 204b.

[0065] According to the exemplary embodiment, the AC power grid 202 is connected to the primary winding 201c0. The Q secondary windings 201c1 - 201cQ are sequentially connected to the Q rectifier bridges 201a1 - 201aQ. The Q rectifier bridges 201a1 - 201aQ are sequentially connected to the Q full-bridge modules 201b1 - 201abQ. After the Q full-bridge modules 201b1 - 201bQ are sequentially connected in series, they are connected in parallel with the test valve tower branch 205.

[0066] According to the exemplary embodiment, the reactor branch 204 is connected in series to a parallel branch on one side of the full-bridge modules 201b1 - 201bQ and the test valve tower branch 205.

[0067] According to the exemplary embodiment, the controller 206 controls the mixing power supply branch 204 to output an AC voltage including an AC power supply F1 with a first frequency and an AC power supply F2 with a second frequency.

[0068] According to the exemplary embodiment, there is only one reactor branch. All the test valve segments of the test valve tower branch 205 are connected in series to form the test valve tower branch 205. The reactor branch 204, the test valve tower branch 205, and the mixing power supply branch 201 are connected in series end to end to form the test system.

[0069] Figure 3 Another embodiment showing a schematic diagram of an exemplary low-frequency power transmission converter valve test system is shown.

[0070] Figure 3 The circuit shown is basically the same as the circuit shown in Figure 2 except that: the reactor branch includes a first reactor branch and a second reactor branch. The number of test valve segments N≥2, and P = 2.

[0071] According to the exemplary embodiment, X1 test valve segments of the test valve tower branch are connected in series to form a first test valve tower branch; the remaining X2 test valve segments are connected in series to form a second test valve tower branch; X1 + X2 = N.

[0072] According to the exemplary embodiment, the first reactor branch is connected in series with the first test valve tower branch, and the second reactor branch is connected in series with the second test valve tower branch; after these series-connected branches are connected in parallel, they are connected in parallel with the mixing power supply branch.

[0073] Figure 4 The circuit schematic diagram of the full-bridge module showing an exemplary embodiment is shown.

[0074] As Figure 4 shown, the power sub-module is a full-bridge module, including 4 fully-controlled power devices connected in series in pairs and 1 capacitor; after the fully-controlled power devices connected in series in pairs are connected in parallel, the connected nodes constitute the DC port of the power sub-module. The capacitor is connected in parallel with the DC port of the power sub-module; the midpoints of the fully-controlled power devices connected in series in pairs are led out to constitute the AC port of the power sub-module.

[0075] According to some embodiments, the controller controls the test valve tower voltage by controlling the turn-on and turn-off of the power devices, indirectly controls the current of the entire loop, or directly controls the automatic adaptation of the current and voltage.

[0076] Figure 5 The flowchart of the test method of the low-frequency power transmission converter valve test system showing an exemplary embodiment is shown.

[0077] In S11, if the mixing power supply branch is implemented by a power electronic circuit, start the mixing power supply branch to output an AC voltage including an AC power supply F1 with a first frequency and an AC power supply F2 with a second frequency; otherwise, skip this step.

[0078] According to the exemplary embodiment, if the circuit structure of the low-frequency power transmission converter valve test system is as Figure 2 shown, that is, the mixing power supply branch is implemented by a power electronic circuit, then through the controller, start the mixing power supply branch to output an AC voltage including an AC power supply F1 with a first frequency and an AC power supply F2 with a second frequency.

[0079] According to the exemplary embodiment, if the circuit structure of the low-frequency power transmission converter valve test system is as Figure 1 shown, that is, the mixing power supply branch is directly implemented by series-connected AC power supplies with different frequencies, then directly skip S11 and go to S12.

[0080] In S12, close the charging switch of the starting branch to complete the charging of the test valve tower branch.

[0081] According to the exemplary embodiment, the charging switch in the closed reactor branch is closed to charge the capacitors in the power sub-modules in the test valve tower branch.

[0082] In S13, the bypass switch of the starting branch is closed, and the test valve tower branch is unlocked through the controller of the test valve tower branch.

[0083] According to the exemplary embodiment, after the charging of the capacitors in the power sub-modules in the test valve tower branch is completed, the bypass switch in the reactor branch is closed, and through the controller of the test valve tower branch, the fully-controlled power devices in the power sub-modules in the test valve tower branch are unlocked.

[0084] In S14, the current of the test valve tower branch is sampled, and through the closed-loop control of the controller of the test valve tower branch, the voltage of the test valve tower branch is adjusted so that the series reactor of the test system and the current of the test valve tower branch reach the rated state.

[0085] According to the exemplary embodiment, the current of the test valve tower branch is sampled, and through the closed-loop control of the controller of the test valve tower branch, the voltage of the test valve tower branch is adjusted so that the series reactor of the test system and the current of the test valve tower branch reach the rated state. If the current reaches the rated state, it indicates that the power sub-modules in the test valve tower branch are working properly; otherwise, it indicates that there is a fault in the power sub-modules.

[0086] It should be clearly understood that this application describes how to form and use specific examples, but this application is not limited to any details of these examples. On the contrary, based on the teachings of the content disclosed in this application, these principles can be applied to many other embodiments.

[0087] In addition, it should be noted that the above-mentioned drawings are only schematic illustrations of the processes included in the method according to the exemplary embodiments of this application, rather than for limiting purposes. It is easy to understand that the processes shown in the above-mentioned drawings do not indicate or limit the time sequence of these processes. Additionally, it is also easy to understand that these processes can be executed synchronously or asynchronously in, for example, multiple modules.

[0088] The above specifically shows and describes the exemplary embodiments of this application. It should be understood that this application is not limited to the detailed structures, setting manners or implementation methods described here; on the contrary, this application intends to cover various modifications and equivalent settings included within the spirit and scope of the appended claims.

Claims

1. A low-frequency power transmission converter valve test system, characterized in that, The low-frequency power transmission converter valve test system includes a frequency mixing power supply branch, a test valve tower branch, and P reactor branches. The frequency mixing power supply branch and the test valve tower branch are connected in parallel, where P is a natural number greater than or equal to 1. Among them: The frequency mixing power supply branch includes a first AC power supply with a first frequency and a second AC power supply with a second frequency. The voltage output by the frequency mixing power supply branch includes at least the AC voltage with the first frequency and the AC voltage with the second frequency, and the first frequency is not equal to the second frequency. The test valve tower branch includes N test valve segments and a controller. Each test valve segment includes M power sub-modules; both M and N are natural numbers greater than or equal to 1. The controller controls the test valve segment to output an AC voltage that is the superposition of the AC voltage with the first frequency and the AC voltage with the second frequency. The reactor branch includes a series reactor and a starting branch. The starting branch includes a starting resistor, a starting switch, and a bypass switch.

2. The low-frequency power transmission converter valve test system according to claim 1, characterized in that The power sub-module is an AC-DC conversion sub-module, including an AC port and a DC port, and the AC ports of the power sub-modules are connected in series in sequence.

3. The test system according to claim 2, wherein The power sub-module is a full-bridge module, including 4 fully controlled power devices and a capacitor: The nodes formed by the parallel connection of the fully controlled power devices connected in series in pairs constitute the DC port of the power sub-module. The capacitor is connected in parallel to the DC port of the power sub-module. The midpoints of the fully controlled power devices connected in series in pairs constitute the AC port of the power sub-module.

4. The test system according to claim 2, wherein The frequency mixing power supply branch includes a multi-winding transformer, Q rectifier bridges, Q full-bridge modules, and a controller, where Q is a natural number greater than or equal to 1. Among them: The primary side of the multi-winding transformer is connected to the AC power grid, and the secondary side includes Q windings. The Q windings are respectively connected to the AC sides of the Q rectifier bridges. The DC sides of the Q rectifier bridges are connected to the DC ports of the full-bridge modules, and the AC ports of the Q full-bridge modules are cascaded and used as the output port of the frequency mixing power supply branch. The controller controls the AC ports of the Q full-bridge modules to generate an AC voltage that includes the superposition of the AC voltage with the first frequency and the AC voltage with the second frequency.

5. The low-frequency power transmission converter valve test system according to claim 1, wherein: The reactor branch includes a first reactor branch, a second reactor branch... a kth reactor branch; X1 of the test valve segments of the test valve tower branch are connected in series to form a first test valve tower branch; X2 of the test valve segments of the test valve tower branch are connected in series to form a second test valve tower branch... Xk of the test valve segments of the test valve tower branch are connected in series to form a kth test valve tower branch, where X1 + X2... + Xk = N, k = P, and N ≥ k; The first reactor branch is connected in series to the first test valve tower branch, the second reactor branch is connected in series to the second test valve tower branch... the kth reactor branch is connected in series to the kth test valve tower branch. After these series-connected branches are connected in parallel, they are connected in parallel with the frequency mixing power supply branch.

6. A test method for a low-frequency power transmission converter valve test system as described in any one of claims 1-5, characterized in that, Including: If the mixing power supply branch is implemented by a power electronic circuit, start the mixing power supply branch to output an AC voltage including the first frequency and the second frequency; Close the start switch of the start branch to complete the charging of the test valve tower branch; Close the bypass switch of the start branch and unlock the test valve tower branch through the controller of the test valve tower branch; Sample the current of the test valve tower branch, and through the closed-loop control of the controller of the test valve tower branch, adjust the voltage of the test valve tower branch so that the series reactor of the test system and the current of the test valve tower branch reach the rated state.

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