High-voltage frequency converter power unit aging system

Abstract

The utility model discloses an aging system for a power unit of a high-voltage frequency converter, which relates to the technical field of aging and is characterized in that a single-phase-to-three-phase feedback loop is formed by a first filtering module, a test module, a second filtering module and a grid-connected module and is connected to the output of a tested power unit to form a full-power cycle. Therefore, the aging test of the power unit can be completed under the real working condition, and the technical problems existing in the power unit type test or predelivery test aging of the high-voltage frequency converter can be solved.

Description

Technical Field

[0001] The utility model relates to the technical field of aging, and particularly relates to a power unit aging system for a high-voltage frequency converter. Background Art

[0002] A cascaded high-voltage frequency converter generally consists of multiple low-voltage power modules connected in series to form a three-phase high-voltage system. The input side of each power unit is connected to the secondary winding of an input phase-shifting transformer, and the output sides are connected in series. The basic structure of the power unit is as Figure 1 shown. The input of the power unit is three-phase diode full-bridge rectification. After filtering by a DC support capacitor, it becomes a stable DC voltage, and then is inverted into single-phase alternating current through four IGBT switches.

[0003] During the development and production of high-voltage frequency converters, full-capacity aging tests need to be carried out on power units. Generally, the method adopted is to connect the three-phase input side of the power unit to a power supply, and connect a resistive load or a resistive-inductive load to the AC output side, and adjust the effective value of the output voltage to make the power module reach the rated working voltage and current. This method can test small-capacity power units. When the capacity of the power unit becomes larger and larger, the requirement for the power supply capacity becomes higher and higher, and the test cost will also increase accordingly, which is not conducive to energy conservation and consumption reduction in the factory. Another method is to connect a reactor load to the AC output side of the power unit to test the characteristics and temperature rise of IGBTs under full current. Since only reactive and active power losses need to be provided for the reactor load, the aging of the inverter part of the power unit can be completed without a full-capacity power supply. However, in this method, due to the small active power loss, the current passing through the three-phase rectifier bridge is also very small, and the rectifier bridge cannot be aged tested, and the temperature rise and reliability of the power unit under real working conditions cannot be verified. Summary of the Utility Model

[0004] The purpose of the utility model is to provide a power unit aging system for a high-voltage frequency converter, which solves the technical problems existing in the prior art.

[0005] The utility model is realized by the following technical solutions:

[0006] A power unit aging system for a high-voltage frequency converter includes: a first switch module, a second switch module, a power unit to be tested, a first filtering module, a testing module, a second filtering module, and a grid connection module;

[0007] The three-phase input ends of the power unit to be tested are sequentially connected to the power grid through the second switch module and the first switch module. The single-phase output end of the power unit to be tested is filtered by the first filtering module and then connected to the single-phase input end of the testing module. The three-phase output ends of the testing module are sequentially connected to the power grid through the second filtering module and the grid connection module.

[0008] In a possible implementation manner, the first switch module includes an access switch K1. The access switch K1 includes three first switch lines. One ends of the three first switch lines are respectively connected to lines of different phases of the power grid, and the other ends of the three first switch lines are connected to the second switch module.

[0009] In a possible implementation manner, the second switch module at least includes a charging switch K2. The charging switch K2 includes three second switch lines. One ends of the three second switch lines are respectively connected to the first switch lines in one-to-one correspondence, and the other ends of the three second switch lines are respectively connected to three-phase input ends in the power unit under test.

[0010] In a possible implementation manner, the second switch module includes a resistor component R1. The resistor component R1 includes three resistors, and the three resistors are respectively connected in parallel with the three second switch lines in one-to-one correspondence.

[0011] In a possible implementation manner, the input of the power unit under test is three-phase diode full-bridge rectification. After being filtered by a DC support capacitor, it becomes a stable DC voltage, and then is inverted into single-phase alternating current through four IGBT switches.

[0012] In a possible implementation manner, the first filtering module includes a first common-mode inductor L1, a filtering capacitor C1, and a second common-mode inductor L2;

[0013] A first input end of the first common-mode inductor L1 is connected to a first single-phase output end of the power unit under test. A second input end of the first common-mode inductor L1 is connected to a second single-phase output end of the power unit under test. A first output end of the first common-mode inductor L1 is respectively connected to one end of the filtering capacitor C1 and a first input end of the second common-mode inductor L2. A second output end of the first common-mode inductor L1 is respectively connected to the other end of the filtering capacitor C1 and a second input end of the second common-mode inductor L2. A first output end and a second output end of the second common-mode inductor L2 are both connected to a single-phase input end of the test module.

[0014] In a possible implementation manner, the second input end of the first common-mode inductor L1 is connected to the second single-phase output end of the power unit under test through a single-phase switch K3.

[0015] In a possible implementation manner, the test module includes an H bridge, a charging capacitor, and a three-phase full bridge;

[0016] The two input terminals of the H-bridge are jointly used as the single-phase input terminal of the test module, and the two input terminals of the H-bridge are respectively and correspondingly connected to the first output terminal and the second output terminal of the second common-mode inductor L2. The two output terminals of the H-bridge are respectively connected to both ends of the charging capacitor, and moreover, the two output terminals of the H-bridge are respectively and correspondingly connected to the two DC terminals of the three-phase full-bridge. The three-phase terminals of the three-phase full-bridge are connected to the second filtering module.

[0017] In a possible implementation manner, the second filtering module is set as an LC filtering circuit.

[0018] In a possible implementation manner, the grid-connection module includes an isolation transformer T1 and a grid-connection switch K4;

[0019] The input terminal of the isolation transformer T1 is connected to the filtered three-phase power output by the second filtering module. The isolation transformer T1 outputs the transformed three-phase power and is connected to the power grid through the grid-connection switch K4.

[0020] A high-voltage inverter power unit aging system provided by the present utility model forms a single-phase-to-three-phase feedback loop through a first filtering module, a test module, a second filtering module, and a grid-connection module, and is connected to the output of the power unit to be tested to form a full-power cycle, enabling the power unit to work under real working conditions to complete the aging test, and solving the technical problems existing in the aging of the power unit type test or factory test of the high-voltage inverter. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present utility model, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present utility model, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can also be obtained based on these drawings without creative efforts. In the drawings:

[0022] Figure 1 is the circuit diagram of the existing power unit provided by the present utility model.

[0023] Figure 2 is the circuit diagram of a high-voltage inverter power unit aging system provided by the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] To make the objectives, technical solutions, and advantages of the present utility model more clear and understandable, the present utility model will be further described in detail below with reference to the embodiments and the drawings. The illustrative embodiments and descriptions of the present utility model are only used to explain the present utility model and are not intended to limit the present utility model.

[0025] Embodiment 1

[0026] The utility model aims to solve the problem of aging in the type test or factory test of the power unit of a high-voltage frequency converter. The general solution is to use energy consumption, but for megawatt-level power units, general factories cannot provide power sources or loads, and it is not conducive to energy conservation and consumption reduction. Another solution is to connect the output of the power unit to a single-phase reactor for full-current reactive aging. Although a full-power power source is not required, the rectifier bridge of the power unit cannot be aged simultaneously, which does not conform to the actual working conditions. The utility model designs a single-phase feedback device, which is connected to the output of the power unit to form a full-power cycle, enabling the power unit to complete the aging test under actual working conditions.

[0027] As Figure 2 shown, the utility model provides a high-voltage frequency converter power unit aging system, including: a first switch module, a second switch module, a power unit under test, a first filter module, a test module, a second filter module, and a grid connection module;

[0028] The three-phase input terminals of the power unit under test are sequentially connected to the power grid through the second switch module and the first switch module. The single-phase output terminal of the power unit under test is filtered by the first filter module and then connected to the single-phase input terminal of the test module. The three-phase output terminals of the test module are sequentially connected to the power grid through the second filter module and the grid connection module.

[0029] In a possible implementation manner, the first switch module includes an access switch K1. The access switch K1 includes three first switch lines. One ends of the three first switch lines are respectively connected to different-phase lines of the power grid, and the other ends of the three first switch lines are connected to the second switch module.

[0030] In a possible implementation manner, the second switch module at least includes a charging switch K2. The charging switch K2 includes three second switch lines. One ends of the three second switch lines are respectively connected to the first switch lines in one-to-one correspondence, and the other ends of the three second switch lines are respectively connected to the three-phase input terminals in the power unit under test.

[0031] In a possible implementation manner, the second switch module includes a resistor component R1. The resistor component R1 includes three resistors, and the three resistors are respectively connected in parallel with the three second switch lines in one-to-one correspondence.

[0032] In a possible implementation manner, the input of the power unit under test is three-phase diode full-bridge rectification. After being filtered by a DC support capacitor, it becomes a stable DC voltage, and then is inverted into single-phase alternating current through four IGBT switches.

[0033] In a possible implementation, the first filtering module includes a first common-mode inductor L1, a filtering capacitor C1, and a second common-mode inductor L2;

[0034] The first input terminal of the first common-mode inductor L1 is connected to the first single-phase output terminal of the power unit under test, the second input terminal of the first common-mode inductor L1 is connected to the second single-phase output terminal of the power unit under test, the first output terminal of the first common-mode inductor L1 is respectively connected to one end of the filtering capacitor C1 and the first input terminal of the second common-mode inductor L2, the second output terminal of the first common-mode inductor L1 is respectively connected to the other end of the filtering capacitor C1 and the second input terminal of the second common-mode inductor L2, and the first output terminal and the second output terminal of the second common-mode inductor L2 are both connected to the single-phase input terminal of the test module.

[0035] In a possible implementation, the second input terminal of the first common-mode inductor L1 is connected to the second single-phase output terminal of the power unit under test through a single-phase switch K3.

[0036] In a possible implementation, the test module includes an H bridge, a charging capacitor, and a three-phase full bridge;

[0037] The two input terminals of the H bridge together serve as the single-phase input terminal of the test module, and the two input terminals of the H bridge are respectively connected to the first output terminal and the second output terminal of the second common-mode inductor L2 in one-to-one correspondence. The two output terminals of the H bridge are respectively connected to both ends of the charging capacitor, and the two output terminals of the H bridge are respectively connected to the two DC terminals of the three-phase full bridge in one-to-one correspondence. The three-phase terminals of the three-phase full bridge are connected to the second filtering module.

[0038] In a possible implementation, the second filtering module is set as an LC filtering circuit.

[0039] In a possible implementation, the grid connection module includes an isolation transformer T1 and a grid connection switch K4;

[0040] The input terminal of the isolation transformer T1 receives the filtered three-phase power output by the second filtering module. The isolation transformer T1 outputs the transformed three-phase power and is connected to the power grid through the grid connection switch K4.

[0041] In this embodiment, the three-phase input of the power unit under test TU is connected to the power grid through a charging circuit composed of K2 and R1 and a switch K1. The single-phase output is connected to a single-phase to three-phase four-quadrant test device EU through a filtering circuit composed of a single-phase switch K3, L1, C1, and L2. The three-phase AC side of the four-quadrant test device EU is incorporated into the power grid through a filter composed of a reactor L3 and a capacitor C2, an isolation transformer T1, and a switch K4.

[0042] The working process of the entire aging system is as follows:

[0043] (1) Before startup, K1, K2, K3, and K4 are all in the off state.

[0044] (2) First, close switch K1. The power unit TU under test charges its internal capacitor through R1. After the charging is completed, close switches K2 and K3. Then, control the inverter bridge of the power unit TU under test to work in the open-loop VF mode through the controller, output the SPWM waveform. After passing through the LCL filter, the waveform becomes a sine wave, and the DC of the test device EU is charged through the H-bridge freewheeling diode of the test device EU.

[0045] (3) Close switch K4, start the three-phase full bridge of the test device EU, and work in the inverter mode with the goal of stabilizing the DC voltage.

[0046] (4) Start the H-bridge of the test device EU. Through phase-locked loop and grid connection control of the output voltage of the unit TU under test, make the H inverter bridge work in the power mode.

[0047] (5) After the system startup is completed, load the unit under test by adjusting the power of the H-bridge of the test device EU. When it is necessary to increase the power, the H-bridge of the test device EU absorbs active power from the power unit under test, causing the energy to flow into the DC bus of the test device EU and increasing the DC bus voltage. The three-phase inverter of the test device EU automatically feeds the energy into the power grid. For the unit TU under test, since its inverter part works in the VF mode, when the test device EU is loaded, the unit TU under test absorbs energy from the power grid and sends it into the test device EU through three-phase full-bridge rectification and H-bridge inversion. In this way, the unit TU under test can be loaded to full load by adjusting the power of the test device EU.

[0048] Through the above test system, as long as the capacity of the test device is sufficient, the rectification and inversion parts of the power unit under test can work in the full-load or over-load state, which is consistent with the real working state of the power unit, and can fully verify the performance and reliability of the power unit under full current.

[0049] It should be noted that based on this embodiment, changing the three-phase inverter part of the test device to one, two, or three single-phase inverters to achieve the effect of three-phase inversion, or changing the single-phase rectification circuit of the test device to an uncontrolled diode rectifier is within the protection scope of the present utility model.

[0050] Embodiment 2

[0051] This embodiment is a further example based on Embodiment 1, specifically:

[0052] The DC voltage of the test device EU is designed for a maximum of 2500V, the maximum current on the H-bridge side is 2000A, and the maximum test capacity is 3.5MW. For a 1MW high-voltage inverter power module, its three-phase AC input is 690V, the single-phase output is 660V, the rated output current is 1515A, and the overload current is 1894A. The AC power grid is supplied with 690V. Connect the power unit under test and the test device according to the main circuit diagram, and all switches are in the off state. When starting the test, first close K1, charge the DC capacitor of the unit under test through the charging resistor R1, and after the charging is completed, close K2 to short-circuit the charging resistor R1. Start the H-bridge output of the unit under test, and use the VF mode to gradually adjust the output voltage to the maximum voltage of 690V. At the same time, the DC bus voltage of the test device EU is charged to about 970V. Then close K4, start the three-phase inverter bridge of the test device, and connect to the power grid through the isolation transformer T1, with the control target being a stable DC voltage. Finally, start the single-phase H-bridge of the test device and operate in the active rectification mode to operate in parallel with the unit under test TU. When the entire system is started, adjust the rectification power of the H-bridge of the test device as needed to load the unit under test. For example, when it is necessary to increase the output power of the unit under test, the power absorbed by the rectification part of the test device increases, the DC bus of the test device is raised, and the three-phase inverter bridge of the test device, in order to maintain a stable DC voltage, will invert the absorbed energy back to the power grid and flow back from the three-phase rectification side of the unit under test, forming a power cycle. At this time, the working state of the power unit under test is consistent with the actual operating conditions, and the power unit can be aged by loading it to full power or overload state.

[0053] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A power unit aging system for a high-voltage frequency converter, characterized in that Including: A first switch module, a second switch module, a power unit under test, a first filtering module, a testing module, a second filtering module, and a grid-connection module; The three-phase input terminals of the power unit under test are connected to the power grid through the second switch module and the first switch module in sequence. After being filtered by the first filtering module, the single-phase output terminal of the power unit under test is connected to the single-phase input terminal of the testing module. The three-phase output terminals of the testing module are connected to the power grid through the second filtering module and the grid-connection module in sequence.

2. The high-voltage inverter power unit aging system according to claim 1, wherein The first switch module includes an access switch K1. The access switch K1 includes three first switch lines. One ends of the three first switch lines are respectively connected to lines of different phases of the power grid, and the other ends of the three first switch lines are connected to the second switch module.

3. The aging system of the high-voltage frequency converter power unit according to claim 2, characterized in that, The second switch module includes at least a charging switch K2. The charging switch K2 includes three second switch lines. One ends of the three second switch lines are respectively connected to the first switch lines in one-to-one correspondence, and the other ends of the three second switch lines are respectively connected to the three-phase input terminals in the power unit under test.

4. The high-voltage inverter power unit aging system according to claim 3, wherein The second switch module includes a resistor component R1. The resistor component R1 includes three resistors, and the three resistors are respectively connected in parallel with the three second switch lines in one-to-one correspondence.

5. The high-voltage inverter power unit aging system according to claim 3, characterized in that, The input of the power unit under test is three-phase diode full-bridge rectification. After being filtered by a DC support capacitor, it becomes a stable DC voltage, and then is inverted into single-phase alternating current through four IGBT switches.

6. The high-voltage inverter power unit aging system according to claim 5, characterized in that The first filtering module includes a first common-mode inductor L1, a filtering capacitor C1, and a second common-mode inductor L2; The first input terminal of the first common-mode inductor L1 is connected to the first single-phase output terminal of the power unit under test. The second input terminal of the first common-mode inductor L1 is connected to the second single-phase output terminal of the power unit under test. The first output terminal of the first common-mode inductor L1 is respectively connected to one end of the filtering capacitor C1 and the first input terminal of the second common-mode inductor L2. The second output terminal of the first common-mode inductor L1 is respectively connected to the other end of the filtering capacitor C1 and the second input terminal of the second common-mode inductor L2. The first output terminal and the second output terminal of the second common-mode inductor L2 are both connected to the single-phase input terminal of the testing module.

7. The high-voltage inverter power unit aging system according to claim 6, characterized in that The second input terminal of the first common-mode inductor L1 is connected to the second single-phase output terminal of the power unit under test through a single-phase switch K3.

8. The high-voltage inverter power unit aging system according to claim 6, characterized in that, The testing module includes an H-bridge, a charging capacitor, and a three-phase full-bridge; The two input terminals of the H-bridge are jointly used as the single-phase input terminal of the testing module, and the two input terminals of the H-bridge are respectively connected to the first output terminal and the second output terminal of the second common-mode inductor L2 in one-to-one correspondence. The two output terminals of the H-bridge are respectively connected to both ends of the charging capacitor, and the two output terminals of the H-bridge are respectively connected to the two DC terminals of the three-phase full-bridge in one-to-one correspondence. The three-phase terminals of the three-phase full-bridge are connected to the second filtering module.

9. The high-voltage inverter power unit aging system according to claim 8, characterized in that The second filtering module is set as an LC filtering circuit.

10. The high-voltage inverter power unit aging system according to claim 9, characterized in that, The grid-connection module includes an isolation transformer T1 and a grid-connection switch K4; The input end of the isolation transformer T1 is connected to the filtered three-phase power output by the second filtering module. The isolation transformer T1 outputs the transformed three-phase power and is connected to the power grid through the grid connection switch K4.

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