No-load pressurization test method and system for CLCC converter

Abstract

The invention discloses a no-load pressurization test method and system for a CLCC converter, and the method comprises the steps: selecting a positive electrode / negative electrode in a bipolar system as a test electrode, carrying out the independent control of the test electrode, putting a preset protection device into operation, starting a no-load pressurization test device, and adjusting the DC voltage according to a trigger angle. When a first test mode starting condition is met, the converter valve enters a first mode, the trigger angle is kept unchanged in a set first time period, and after the trigger angle is kept unchanged in a set time period, the trigger angle is continuously adjusted to enable the direct-current voltage value of the test electrode to change according to a set change rate, and when a second test mode starting condition is met, the direct-current voltage value of the test electrode is changed according to a set change rate; the converter valve enters a second mode, the trigger angle is kept unchanged in a set time period, and a no-load pressurization test is completed; and after the test is finished, the output voltage of the no-load pressurization test device is reduced until the voltage is reduced to zero, and the test pole is automatically locked. The method has the outstanding advantages of low cost, high reliability and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronic commutation, and in particular to a no-load pressurization test method and system for a CLCC converter. Background Art

[0002] The high-voltage DC open line test (OLT) is referred to as the open line test, also known as the no-load pressure test. This experiment is a basic test that must be carried out before the UHV DC transmission system or the HVDC transmission system is put into operation. The main functions of this experiment include testing the insulation performance and voltage resistance performance of the high-voltage DC equipment and lines after a long period of shutdown or maintenance, testing the opening and closing capabilities of the converter valve, checking whether the functions of the DC control system hardware and software are normal, such as whether the trigger optical fiber is normal and whether the sequence of the trigger timing is correct, etc., and checking whether the protection system is operating normally, that is, whether it can correctly respond to the DC control system under the set conditions, and whether the DC transmission circuit is normal. The OLT test avoids the DC pole from being started when there is a ground fault in the line, thereby improving the reliability and stability of the system.

[0003] See attached Figure 1 , is a schematic diagram of the current conduction path in the CLCC operation mode, where the light-colored path is the current conduction path in the CLCC operation mode. Under the rated operating condition CLCC operation mode, the IGBT unit and the main branch thyristor valve are triggered to conduct at the same time, and the flow path of the low-voltage IGBT valve in the conduction state; see the attached Figure 2 , is a schematic diagram of the current conduction path in the LCC operation mode, where the light-colored path is the current conduction path in the LCC operation mode. When the low-voltage IGBT valve does not meet the CLCC operation mode requirements, such as when the number of IGBT redundancy is reduced to the engineering specified value, or when power reverse is required, the IGBT series unit can be locked and the bypass thyristor series unit can be triggered to make the converter operate in the LCC mode. In addition, when the DC system needs to reverse power, the converter will change from the inverter operation condition to the rectifier operation condition. At this time, the system short-circuit current will be much greater than the inverter condition, and the converter operation condition also needs to be changed to the LCC state. The bypass thyristor series unit is composed of a number of high-voltage and high-power thyristors directly connected in series.

[0004] Therefore, when performing OLT tests on CLCC converters, each pole OLT test needs to be performed twice. One test is performed in LCC mode to complete no-load pressurization of the thyristor; and one test is performed in CLCC mode to complete no-load pressurization of the IGBT. Testing each pole twice takes a long time and may cause insulation aging, equipment damage and other hazards.

[0005] CN114460397A discloses a no-load pressure test system and method for voltage source converters. The system includes a test control device and a DC control protection device connected to each other. The test control device is used to perform a no-load pressure test. The no-load pressure test includes an uncontrolled charging stage, a controllable charging stage, a DC voltage raising stage and a steady-state stage. The DC control protection device is optimized for the DC voltage raising stage, and the number of upper and lower bridge arm input submodules of the voltage source converter is adjusted dynamically in real time. The invention is aimed at the voltage source, which is actually different from the present invention, and requires multiple upper and lower bridge arm submodules, which is more expensive. Summary of the invention

[0006] In order to solve the shortcomings of the prior art such as high cost and long time consumption, the present invention provides a no-load pressurization test method and system for a CLCC converter.

[0007] The present invention adopts the following technical solution.

[0008] The present invention discloses a no-load pressure test method for a CLCC converter, comprising: In the bipolar system, the positive or negative electrode is selected as the test electrode, and the test electrode is independently controlled; Put the preset protection device into operation, then start the no-load pressure test device and load the output DC voltage to the corresponding test pole of the CLCC converter; The trigger angle of each thyristor of the CLCC converter is adjusted according to the set first trigger angle command value, thereby adjusting the DC voltage. When the first test mode start condition is met, the converter valve enters the first mode of the CLCC converter and keeps the trigger angle command value unchanged within the set first time period; After keeping the trigger angle command value unchanged within the set first period, continue to adjust the trigger angle so that the DC voltage value of the test pole changes according to the set change rate. When the start condition of the second test mode is met, the converter valve enters the second mode of the CLCC converter and keeps the trigger angle command value unchanged within the set second period, thereby completing the no-load pressurization test; After the test is completed, the output voltage of the no-load pressure test device is reduced at a set rate until the voltage drops to zero, and the test pole is automatically locked.

[0009] More preferably, The preset protection devices include an overcurrent protection device, an overvoltage protection device, a differential protection device and a grounding protection device.

[0010] More preferably, The first trigger angle command value is set according to the following formula: ; Where k represents the kth sampling point; is the trigger angle command value at the kth sampling point; is the initial test value of the trigger angle; is the DC voltage change correlation coefficient.

[0011] More preferably, The DC voltage change correlation coefficient is shown in the following formula: ; in, is the voltage regulation factor, is the rated DC voltage of the test pole.

[0012] More preferably, The voltage adjustment factor is shown below: ; in, is the trigger angle command value at the kth sampling point, is the trigger angle measurement value at the kth sampling point.

[0013] More preferably, The first test mode start condition is: ; in, is the trigger angle command value at the kth sampling point, is the test mode start coefficient, is the trigger angle measurement value at the kth sampling point.

[0014] More preferably, The first mode of the CLCC converter is the CLCC mode. After the converter valve enters the CLCC mode, a no-load pressure test is performed on the IGBT.

[0015] More preferably, The start condition of the second test mode is as follows: ; in, is the DC voltage at the kth sampling point, is the test mode start coefficient, is the rated DC voltage of the test pole.

[0016] More preferably, The second mode of the CLCC converter is the LCC mode. After the converter valve enters the LCC mode, a no-load pressure test is performed on the thyristor.

[0017] On the other hand, the present invention discloses a no-load pressurization test system based on a no-load pressurization test method, including a test pole control module, a test start module, a first trigger angle adjustment module, a second trigger angle adjustment module and a test termination module: The test pole control module selects the positive pole / negative pole as the test pole in the bipolar system and independently controls the test pole; The test start module puts the preset protection device into operation, then starts the no-load pressure test device to load the output DC voltage to the test pole corresponding to the CLCC converter; The first trigger angle adjustment module adjusts the trigger angle of each thyristor of the CLCC converter according to the set first trigger angle command value, thereby adjusting the DC voltage. When the first test mode start condition is met, the converter valve enters the first mode of the CLCC converter and keeps the trigger angle command value unchanged within the set first time period; The second trigger angle adjustment module, after the operation of the first trigger angle adjustment module is completed, continues to adjust the trigger angle so that the DC voltage value of the test pole changes according to the set change rate. When the start condition of the second test mode is met, the converter valve enters the second mode of the CLCC converter and keeps the trigger angle command value unchanged within the set second time period, thereby completing the no-load pressurization test; The test termination module reduces the output voltage of the no-load pressurization test device at a set rate after the test is completed until the voltage drops to zero, and automatically locks the test pole.

[0018] The beneficial effects of the present invention are as follows: When the present invention performs an OLT test on the CLCC converter, each pole OLT test only needs to be performed once, which greatly shortens the time required for the OLT test and reduces the risk of hazards such as insulation aging and equipment damage. Since the IGBT and thyristor are subjected to no-load voltage tests in the CLCC mode and the LCC mode respectively during the OLT test process of the present invention, it is necessary to perform two voltage increases. In order to avoid the problem that the first voltage increase process is too fast, that is, the trigger angle changes too much, resulting in inaccurate OLT test results, and the voltage increase process is too slow, resulting in unnecessary time consumption, the present invention proposes a calculation formula for the first trigger angle command value, which not only avoids inaccurate OLT test results, but also avoids unnecessary time consumption; Since the present invention needs to switch between the CLCC mode and the LCC mode when the voltage is constantly changing, the present invention specifically proposes a first test mode start-up condition and a second test mode start-up condition, thereby ensuring the reliability of the present invention and the accuracy of the test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1It is a schematic diagram of the current conduction path of the CLCC converter in the CLCC operation mode; Figure 2 It is a schematic diagram of the current conduction path of the CLCC converter in the LCC operation mode; Figure 3 It is a schematic flow chart of a no-load pressurization test method for a CLCC converter according to the present invention. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, other embodiments obtained by ordinary technicians in this field without creative work are all within the scope of protection of the present invention.

[0021] This application discloses a no-load pressure test method for CLCC converters. Figure 3 ,include: In the bipolar system, the positive or negative electrode is selected as the test electrode, and the test electrode is independently controlled; Put the preset protection device into operation, then start the no-load pressure test device and load the output DC voltage to the corresponding test pole of the CLCC converter; The preset protection devices include an overcurrent protection device, an overvoltage protection device, a differential protection device and a grounding protection device.

[0022] Adjusting the trigger angle of each thyristor of the CLCC converter according to the set first trigger angle command value, thereby adjusting the conduction time of each thyristor, and further adjusting the DC voltage; Those skilled in the art should know that the DC voltage of the test pole can be changed by adjusting the trigger angle, whether the DC voltage of the test pole is continuously increased, or the DC voltage of the test pole is continuously decreased, or the DC voltage of the test pole is increased or decreased according to a set rule. As long as the set conditions are met, the trigger angle remains unchanged within a set time period, and the OLT test can be completed; those skilled in the art can adjust the first trigger angle command value according to actual conditions; in order to improve calculation accuracy, the calculation of the first trigger angle command value proposed in the embodiment of the present invention is only a preferred embodiment, and is not an inevitable limitation for implementing the no-load pressurization test method for CLCC converters of the present invention.

[0023] Those skilled in the art should know that the initial test value of the trigger angle is generally 150°~170°. Therefore, in the preferred embodiment of the present invention, the OLT test is performed by gradually lowering the trigger angle and continuously increasing the voltage, thereby further shortening the test time of the OLT test.

[0024] The first trigger angle command value is set according to the following formula: ; Wherein, k represents the kth sampling point, that is, the kth first trigger angle command value calculation point; is the trigger angle command value at the kth sampling point; is the initial test value of the trigger angle; is the DC voltage variation correlation coefficient. Preferably, the sampling interval is set to 1 second; the sampling interval is the calculation interval.

[0025] The DC voltage change correlation coefficient is shown in the following formula: ; in, is the voltage regulation factor, It is the rated DC voltage of the test pole, and its unit is kV.

[0026] The voltage adjustment factor is shown below: ; in, is the trigger angle command value at the kth sampling point, is the trigger angle measurement value at the kth sampling point.

[0027] When the start-up conditions of the first test mode are met, the converter valve enters the first mode of the CLCC converter, and maintains the trigger angle and the trigger angle command value unchanged within the set first time period by pausing the reference value through pole control; the preferred value range of the set first time period is 2.5~3.5 minutes.

[0028] The first test mode start condition is: ; in, is the trigger angle command value at the kth sampling point, is the test mode start coefficient, is the trigger angle measurement value at the kth sampling point.

[0029] The first mode of the CLCC converter is the CLCC mode. After the converter valve enters the CLCC mode, a no-load pressure test is performed on the IGBT.

[0030] After keeping the trigger angle command value unchanged in the set first period, continue to adjust the trigger angle so that the DC voltage value of the test pole changes according to the set change rate; Those skilled in the art should know how to adjust the trigger angle so that the DC voltage value of the test pole increases or decreases at a set frequency; preferably, the DC voltage change rate is set to 1 kV / s.

[0031] When the start-up conditions of the second test mode are met, the converter valve enters the second mode of the CLCC converter and keeps the trigger angle command value unchanged within the set second time period, thereby completing the no-load pressurization test; the preferred value range of the set second time period is 2.5~3.5 minutes.

[0032] The start condition of the second test mode is as follows: ; in, is the DC voltage at the kth sampling point, is the test mode start coefficient, is the rated DC voltage of the test pole.

[0033] The second mode of the CLCC converter is the LCC mode. After the converter valve enters the LCC mode, a no-load pressure test is performed on the thyristor.

[0034] After the test is completed, the output voltage of the no-load pressure test device is reduced at a set rate until the voltage drops to zero, and the test pole is automatically locked.

[0035] Example 1 A no-load pressurization test method for CLCC converters.

[0036] Check whether the test equipment is intact, including OLT test device, IGBT, thyristor, DC power supply, oscilloscope, preset protection device, etc.

[0037] In the bipolar system, the positive or negative electrode is selected as the test electrode, and the test electrode is independently controlled; Independent control of the test pole in the bipolar system means that the test pole is controlled and adjusted separately, so that the test pole is not affected by other factors (such as the overall state of the system). This control method has the characteristics of strong pertinence, simple operation and high flexibility.

[0038] Those skilled in the art should know how to independently control the test pole in a bipolar system. Those skilled in the art can independently control the test pole according to actual conditions.

[0039] The application of independent control in bipolar system not only improves the flexibility and reliability of the system, but also enables more precise control under different working conditions to meet specific needs and goals.

[0040] The no-load pressurization test device is connected to the CLCC converter and its control system.

[0041] The no-load pressure test device and the preset protection device are connected to the CLCC converter and its control system through electrical connections. The connection may include signal lines, power lines, etc., and the connection is used to transmit monitoring data, control instructions, etc. Through the connection, the no-load pressure test device and the preset protection device can realize the voltage application and monitoring functions of the converter.

[0042] The preset protection device is put into operation. In a preferred embodiment of the present invention, the preset protection device includes an overcurrent protection device, an overvoltage protection device, a differential protection device and a grounding protection device.

[0043] Then the no-load pressure test device is started, and during the test, the output DC voltage is applied to the corresponding test pole of the CLCC converter; Those skilled in the art should know that during the no-load pressure test, the preset protection device protects the CLCC converter and its control system to ensure the safe operation of the CLCC converter and its control system during the no-load pressure test. The preset protection device monitors the operating status and voltage parameters of the converter, and when an abnormality is found, it immediately takes measures such as cutting off the power supply or sounding an alarm to prevent equipment damage or accidents.

[0044] Those skilled in the art should know that the no-load voltage test operation includes an uncontrolled charging stage, a controlled charging stage, a DC voltage raising stage, and a steady-state stage, etc. In these stages, the no-load voltage test device will send corresponding control instructions to the converter to adjust its output voltage.

[0045] The present invention adjusts the trigger angle of each thyristor of the CLCC converter according to the set first trigger angle command value in the controllable charging stage, thereby adjusting the conduction time of each thyristor, and then adjusting the DC voltage to ensure that the voltage rise process is smooth without abnormal fluctuations. In a preferred embodiment of the present invention, the first trigger angle command value is set based on the initial test value of the trigger angle, the rated DC voltage of the test pole, etc.

[0046] The first trigger angle command value is set according to the following formula: ; Wherein, k represents the kth sampling point, that is, the kth first trigger angle command value calculation point; is the trigger angle command value at the kth sampling point; is the initial test value of the trigger angle; is the DC voltage variation correlation coefficient. Preferably, the sampling interval is set to 1 second; the sampling interval is the calculation interval.

[0047] The DC voltage change correlation coefficient is shown in the following formula: ; in, is the voltage regulation factor, is the rated DC voltage of the test pole.

[0048] The voltage adjustment factor is shown below: ; in, is the trigger angle command value at the kth sampling point, is the trigger angle measurement value at the kth sampling point.

[0049] When the start-up conditions of the first test mode are met, the converter valve enters the first mode of the CLCC converter, and keeps the trigger angle and the trigger angle command value unchanged within the set first time period by means of suspending the reference value through pole control; The first test mode start condition is: ; in, is the trigger angle command value at the kth sampling point, is the test mode start coefficient, is the trigger angle measurement value at the kth sampling point.

[0050] The first mode of the CLCC converter is the CLCC mode. After the converter valve enters the CLCC mode, a no-load pressure test is performed on the IGBT.

[0051] Preferably, after keeping the trigger angle command value unchanged during the set first period, the trigger angle can be continuously adjusted to make the DC voltage value of the test pole change according to the set change rate. When the start condition of the second test mode is met, the converter valve enters the second mode of the CLCC converter, and keeps the trigger angle command value unchanged during the set second period, then enters the DC voltage raising stage, and finally enters the steady state stage, thereby completing the no-load pressurization test. The set change rate is 1 kV / s.

[0052] The start condition of the second test mode is as follows: ; in, is the DC voltage at the kth sampling point, is the test mode start coefficient, is the rated DC voltage of the test pole.

[0053] The second mode of the CLCC converter is the LCC mode. After the converter valve enters the LCC mode, a no-load pressure test is performed on the thyristor.

[0054] Preferably, after keeping the trigger angle command value unchanged within the set first time period, the DC voltage rise stage is entered, the DC voltage is automatically increased to the rated voltage, and the DC voltage value of the test pole is changed according to the set change rate. When the start condition of the second test mode is met, the converter valve enters the second mode of the CLCC converter, and then enters the steady state stage, thereby completing the no-load pressurization test; After the test is completed, the output voltage of the no-load pressure test device is reduced at a set rate until the voltage drops to zero, and the test pole is automatically locked. The set rate is 1 kV / s.

[0055] Check whether the IGBT module, thyristor module and other test equipment have any abnormal phenomena, such as overheating, damage, etc. If any abnormality is found, it should be handled in time.

[0056] The present application also discloses a no-load pressurization test system for a CLCC converter based on a no-load pressurization test method, comprising a test pole control module, a test start module, a first trigger angle adjustment module, a second trigger angle adjustment module and a test termination module: The test pole control module selects the positive pole / negative pole as the test pole in the bipolar system and independently controls the test pole; The test start module puts the preset protection device into operation, then starts the no-load pressure test device to load the output DC voltage to the test pole corresponding to the CLCC converter; The first trigger angle adjustment module adjusts the trigger angle of each thyristor of the CLCC converter according to the set first trigger angle command value, thereby adjusting the DC voltage. When the first test mode start condition is met, the converter valve enters the first mode of the CLCC converter and keeps the trigger angle command value unchanged within the set first time period; The second trigger angle adjustment module, after the operation of the first trigger angle adjustment module is completed, continues to adjust the trigger angle so that the DC voltage value of the test pole changes according to the set change rate. When the start condition of the second test mode is met, the converter valve enters the second mode of the CLCC converter and keeps the trigger angle command value unchanged within the set second time period, thereby completing the no-load pressurization test; The test termination module reduces the output voltage of the no-load pressurization test device at a set rate after the test is completed until the voltage drops to zero, and automatically locks the test pole.

[0057] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0058] A computer-readable storage medium may be a tangible device that can hold and store instructions used by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the above. More specific examples (a non-exhaustive list) of computer-readable storage media include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination of the above. The computer-readable storage medium used herein is not to be interpreted as a transient signal itself, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted through a wire.

[0059] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, optical fiber transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in the computer-readable storage medium in each computing / processing device.

[0060] The computer program instructions for performing the operations of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages, such as C++, etc., and conventional procedural programming languages, such as "C" language or similar programming languages. The computer-readable program instructions may be executed entirely on the user's computer, partially on the user's computer, as a separate software package, partially on the user's computer, partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., using an Internet service provider to connect through the Internet). In some embodiments, by using the state information of the computer-readable program instructions to personalize an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), the electronic circuit may execute the computer-readable program instructions, thereby implementing various aspects of the present disclosure.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A no-load pressure test method for a CLCC converter, characterized in that: include: In the bipolar system, the positive or negative electrode is selected as the test electrode, and the test electrode is independently controlled; Put the preset protection device into operation, then start the no-load pressure test device and load the output DC voltage to the corresponding test pole of the CLCC converter; The trigger angle of each thyristor of the CLCC converter is adjusted according to the set first trigger angle command value, thereby adjusting the DC voltage. When the first test mode start condition is met, the converter valve enters the first mode of the CLCC converter and keeps the trigger angle command value unchanged within the set first time period; After keeping the trigger angle command value unchanged within the set first period, continue to adjust the trigger angle so that the DC voltage value of the test pole changes according to the set change rate. When the start condition of the second test mode is met, the converter valve enters the second mode of the CLCC converter and keeps the trigger angle command value unchanged within the set second period, thereby completing the no-load pressurization test; After the test is completed, the output voltage of the no-load pressure test device is reduced at a set rate until the voltage drops to zero, and the test pole is automatically locked.

2. The no-load pressurization test method according to claim 1, characterized in that: The preset protection devices include an overcurrent protection device, an overvoltage protection device, a differential protection device and a grounding protection device.

3. The no-load pressurization test method according to claim 1, characterized in that: The first trigger angle command value is set according to the following formula: ； Where, k represents the kth sampling point; is the trigger angle command value at the kth sampling point; is the initial test value of the trigger angle; is the DC voltage change correlation coefficient.

4. The no-load pressurization test method according to claim 3, characterized in that: The DC voltage change correlation coefficient is shown in the following formula: ； in, is the voltage regulation factor, is the rated DC voltage of the test pole.

5. The no-load pressurization test method according to claim 4, characterized in that: The voltage adjustment factor is shown below: ； in, is the trigger angle command value at the kth sampling point, is the trigger angle measurement value at the kth sampling point.

6. The no-load pressurization test method according to claim 1, characterized in that: The first test mode start condition is: ； in, is the trigger angle command value at the kth sampling point, is the test mode start coefficient, is the trigger angle measurement value at the kth sampling point.

7. The no-load pressurization test method according to claim 1, characterized in that: The first mode of the CLCC converter is the CLCC mode. After the converter valve enters the CLCC mode, a no-load pressure test is performed on the IGBT.

8. The no-load pressurization test method according to claim 1, characterized in that: The start condition of the second test mode is as follows: ； in, is the DC voltage at the kth sampling point, is the test mode start coefficient, is the rated DC voltage of the test pole.

9. The no-load pressurization test method according to claim 1, characterized in that: The second mode of the CLCC converter is the LCC mode. After the converter valve enters the LCC mode, a no-load pressure test is performed on the thyristor.

10. A no-load pressure test system for a CLCC converter using the no-load pressure test method according to any one of claims 1 to 9, characterized in that: It includes a test pole control module, a test start module, a first trigger angle adjustment module, a second trigger angle adjustment module and a test termination module: The test pole control module selects the positive pole / negative pole as the test pole in the bipolar system and independently controls the test pole; The test start module puts the preset protection device into operation, then starts the no-load pressure test device to load the output DC voltage to the test pole corresponding to the CLCC converter; The first trigger angle adjustment module adjusts the trigger angle of each thyristor of the CLCC converter according to the set first trigger angle command value, thereby adjusting the DC voltage. When the first test mode start condition is met, the converter valve enters the first mode of the CLCC converter and keeps the trigger angle command value unchanged within the set first time period; The second trigger angle adjustment module, after the operation of the first trigger angle adjustment module is completed, continues to adjust the trigger angle so that the DC voltage value of the test pole changes according to the set change rate. When the start condition of the second test mode is met, the converter valve enters the second mode of the CLCC converter and keeps the trigger angle command value unchanged within the set second time period, thereby completing the no-load pressurization test; The test termination module reduces the output voltage of the no-load pressurization test device at a set rate after the test is completed until the voltage drops to zero, and automatically locks the test pole.

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