CN115201614A - Dry capacitor test method for flexible direct current converter valve - Google Patents
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Abstract
The invention belongs to the technical field of flexible direct current transmission, and relates to a dry capacitor test method for a flexible direct current converter valve, which comprises the following steps: aiming at the dry capacitor to be detected, carrying out an alternating current-direct current superposition endurance test to obtain an endurance test result; carrying out a terminal-to-terminal limit voltage withstand test on the dry capacitor to be detected to obtain a voltage withstand test result; aiming at the dry capacitor to be detected, performing a two-stage impulse discharge test to obtain a discharge test result; and determining the performance of the dry capacitor to be detected based on the endurance test result, the withstand voltage test result and the discharge test result to obtain a performance test result. The invention forms the test and check basis of the flexible DC converter valve capacitor corresponding to various actual operating conditions of the dry capacitor for the flexible DC converter valve, thereby ensuring that the flexible DC converter valve capacitor has enough safe operating margin.
Description
Technical Field
The invention relates to a dry capacitor test method for a flexible direct current converter valve, and belongs to the technical field of flexible direct current transmission.
Background
The flexible direct current transmission technology adopts a voltage source converter and a full-control power electronic device, can provide good dynamic reactive power support, has excellent grid-connected performance, and does not have the problem of synchronous stability. The flexible direct current transmission project has realized the task of transmitting a plurality of forms of energy such as large-scale wind power, photovoltaic, energy storage, extraction and storage, and the flexible direct current transmission is one of the best choices for realizing large-scale clean energy power generation grid connection and transmission by adopting a high-voltage direct current power grid in the future.
The converter valve is core equipment of flexible direct current transmission engineering, and the capacitor for the flexible direct current converter valve is a core group component of the converter valve and is a key hub device and an energy storage element for realizing energy interaction. The operation reliability of the converter valve is related to the operation reliability of the whole converter valve and the engineering. As a core group component in the converter valve, an international universal test method is based on a unified international standard of related power electronic capacitors, a large number of related test methods and parameter selection methods are not designed specifically for application scenes of flexible direct current transmission, steady-state and transient-state operation conditions of the flexible direct current converter valve are complicated and changeable, and the existing test method cannot check the operation state and reliability of the converter valve capacitor under the actual operation condition of the flexible direct current.
At present, the existing related national standards and IEC standards are directed at general power capacitors, but no test method and test parameter selection method are specially directed at the actual working conditions of dry capacitors for flexible direct current converter valves.
Disclosure of Invention
In view of the above problems, the present invention provides a dry capacitor testing method for a flexible dc converter valve, so as to ensure stable operation of the system and equipment safety.
In order to realize the purpose, the invention provides the following technical scheme: a dry-type capacitor test method for a flexible direct-current converter valve comprises the following steps: aiming at a dry capacitor to be detected, performing an alternating current-direct current superposition endurance test to obtain an endurance test result; carrying out a limit voltage withstand test between terminals aiming at the dry capacitor to be detected to obtain a voltage withstand test result; aiming at the dry capacitor to be detected, performing a two-stage impulse discharge test to obtain a discharge test result; and determining the performance of the dry capacitor to be detected based on the endurance test result, the withstand voltage test result and the discharge test result to obtain a performance test result, wherein the performance test result represents whether the dry capacitor to be detected meets the performance standard.
Further, the step of performing an alternating current/direct current superposition endurance test on the dry capacitor to be tested to obtain an endurance test result comprises the following steps: continuously applying voltage according to a first preset time aiming at the dry capacitor to be detected, and measuring the initial capacitance C of the dry capacitor to be detected at a target environment temperature 0 And initial loss tan delta 0 (ii) a Putting the dry capacitor to be tested into a heating box, electrifying, adjusting the cooling or heating condition of the heating box to ensure that the dry capacitor to be tested maintains the target hot spot temperature in the test process, and testing to obtain a first frequency capacitance C after reaching a second preset time 1 And a first loss tan delta 1 The voltage applied during electrifying is target running voltage of alternating current and direct current superposition during actual running of the converter valve; performing sum of preset times according to the requirements of impact discharge test at room temperatureMarking the charging and discharging current to charge and discharge, and testing to obtain a second frequency capacitance C 2 And a second loss tan delta 2 (ii) a Repeatedly carrying out pretreatment on the dry capacitor to be detected until reaching a second preset time, and then testing to obtain a first frequency capacitance C 1 And a first loss tan delta 1 Again testing to obtain a third frequency capacitance C 3 And a third loss tan delta 3 (ii) a Based on the initial capacitance C 0 And initial loss tan delta 0 First frequency capacitance C 1 And a first loss tan delta 1 A second frequency capacitance C 2 And a second loss tan delta 2 A third frequency capacitance C 3 And a third loss tan delta 3 The results of the durability test were obtained.
Further, based on the initial capacitance C 0 And initial loss tan delta 0 First frequency capacitance C 1 And a first loss tan delta 1 A second frequency capacitance C 2 And a second loss tan delta 2 Third frequency capacitance C 3 And a third loss tan delta 3 The step of obtaining the durability test result comprises: if the first frequency capacitance C 1 And a first loss tan delta 1 Initial capacitance C 0 And initial loss tan delta 0 Satisfies the following formula: i C 1 -C 0 /C 1 |≤2%，tan
1 ≤1.1tan
0 +1.0×10 -4 (ii) a And, a second frequency capacitance C 2 And a second loss tan delta 2 Initial capacitance C 0 And initial loss tan delta 0 Satisfies the following formula: i C 2 -C 0 /C 2 |≤2%，tan
2 ≤1.1tan
0 +1.0×10 -4 (ii) a And, a third frequency capacitance C 3 And a third loss tan delta 3 Initial capacitance C 0 And initial loss tan delta 0 Satisfies the following formula: i C 3 -C 0 /C 3 |≤3%，tan
3 ≤1.2tan
0 +1.0×10 -4 (ii) a Determining that the dry capacitor to be detected meets the AC/DC superposition endurance test standard; and taking the dry capacitor to be detected which meets the AC/DC superposition endurance test standard as an endurance test result.
Further, an alternating current and direct current superposition endurance test is carried out on the dry capacitor to be detected, and the dry capacitor is preprocessed before an endurance test result is obtained, wherein the preprocessing process comprises the following steps: putting the dry capacitor into static air with the temperature not lower than a fourth preset temperature, applying a voltage which is several times of the maximum value of the direct current component of the operating voltage for 16-24 hours, and putting the dry capacitor in a ventilation box with the temperature of 28-32 ℃ for not less than 12 hours in an unpowered state.
Further, the method for determining the maximum value of the direct current component of the operating voltage comprises the following steps: if the receiving end of the flexible direct current converter valve is the constant direct current voltage, the direct current voltage of the maximum port of the operation of the converter valveU dcmax The method is characterized by superposing receiving end direct current voltage, line voltage drop, control error and measurement error of the flexible direct current converter valve, wherein the line voltage drop is determined according to the maximum resistance of a line during operation, and the number of bridge arm modules is the number of modules without redundancyNFurther, the maximum value U of the DC component of the module operating voltage is calculated NDC =U dcmax /N。
Further, the method for calculating the voltage alternating current component of the dry capacitor comprises the following steps: effective value of voltage and current of dry capacitorI crms The calculation was performed as follows:
wherein, I 0 Is the maximum current on the alternating current side of the converter valve at the maximum operating point,I dc the maximum current at the direct current side of the converter valve at the maximum operating point; AC component of voltage of dry capacitorU c_ac max The calculation was performed as follows:
in the formula (I), the compound is shown in the specification,k unbalance is the coefficient of imbalance between modules, C is the capacitance of the dry capacitor,
is the fundamental frequency; the parameter of the maximum operating voltage of the AC/DC superposition isk x U NDC +U C_acmax Wherein, in the step (A),k x the endurance test voltage coefficient.
Further, the method for performing the limited withstand voltage test between the terminals on the dry capacitor to be detected to obtain the withstand voltage test result comprises the following steps: and after the dry capacitor reaches the preset temperature, applying the maximum voltage generated in the transient operation process of the converter valve to the dry capacitor, keeping the maximum endurable time in the actual working condition, and recording the capacitance and the loss tan delta variable quantity before and after the test.
Further, the method for calculating the test parameters of the maximum voltage appearing in the transient operation process of the converter valve and the maximum time endured in the actual working condition comprises the following steps: if the converter valve submodule where the dry capacitor is located is configured with the breakover thyristor, the maximum voltage is the breakdown voltage of the breakover thyristor; if the converter valve submodule where the dry capacitor is located is not provided with the turning thyristor, the maximum voltage is the breakdown voltage of an IGBT device in the converter valve submodule; maximum time tolerated in the actual operating conditionT max The calculation formula of (c) is:
wherein, the first and the second end of the pipe are connected with each other,Cis the capacitance value of the dry capacitor;R dc is the parallel resistance value in the converter valve submodule.
Further, the method for performing a two-stage impulse discharge test on the dry capacitor to be detected comprises the following steps: the impulse discharge test comprises two sections: the first stage is to design an impulse current by considering various N-1 faults occurring in a converter valve submodule; in the second stage, various N-2 faults occurring in the converter valve submodule are considered, and impulse current is designed; if the capacitor is not broken down after the preset time, performing an inter-terminal voltage test on the dry capacitor; recording the capacitance and loss tan delta variation before and after the impact discharge, wherein if the capacitance variation value delta C before and after the impact discharge, the capacitance value C and the loss tan delta after the impact discharge satisfy the following formula: determining that the dry capacitor to be detected meets the impact discharge test standard if delta C/C is less than or equal to +/-1% and tan delta is less than or equal to 1.2 tan delta 0+1 multiplied by 10 < -4 >; and taking the dry capacitor to be detected meeting the impulse discharge test standard as a discharge test result.
Further, the first stage of the loop for calculating the inrush current comprises: a capacitor, a converter valve stray inductance, an IGBT or diode device resistance with failed upper bridge arm of the module, and an inductance and a resistance of the bypass switch which are connected in series to form a loop; second section the calculation loop of the inrush current should include: the circuit comprises a capacitor, a converter valve stray inductance, an IGBT or diode device resistor with failed upper bridge arm of the module and an IGBT or diode device resistor with failed lower bridge arm of the module which are connected in series to form a loop.
Due to the adoption of the technical scheme, the invention has the following advantages: the invention forms the test and check basis of the capacitor for the flexible direct current converter valve corresponding to various actual operating conditions of the dry capacitor for the flexible direct current converter valve, thereby ensuring that the capacitor for the flexible direct current converter valve has enough safe operating margin.
Drawings
FIG. 1 is a schematic structural diagram of a dry capacitor for a flexible DC converter valve according to an embodiment of the present invention;
FIG. 2 is a flow chart of a method for testing a dry capacitor for a flexible DC converter valve in accordance with one embodiment of the present invention;
fig. 3 is a schematic structural diagram of a rush current calculation loop according to an embodiment of the present invention, and fig. 3 (a) is a schematic structural diagram of a first stage rush current calculation loop; fig. 3 (b) is a schematic structural diagram of a second stage impulse current calculation loop.
Detailed Description
The present invention is described in detail with reference to specific embodiments in order to enable those skilled in the art to better understand the technical solutions of the present invention. It should be understood, however, that the detailed description is provided for a better understanding of the invention only and that they should not be taken as limiting the invention. In describing the present invention, it is to be understood that the terminology used is for the purpose of description only and is not intended to be indicative or implied of relative importance.
As shown in fig. 1, fig. 1 is a schematic diagram of a dry capacitor structure for a flexible direct current converter valve. Since the flexible-straight support capacitor has a large capacity, the capacitor unit is generally formed by connecting cores (capacitor elements) arranged in a certain order in parallel, packaging the cores in a housing, and collectively leading out terminals from two electrodes of the capacitor elements. In order to control the current flowing through a single terminal, the number of terminals generally increases with the capacity of the capacitor. The capacitor element is formed by winding two layers of metallized film around a mandrel.
The embodiment discloses a dry capacitor test method for a flexible direct current converter valve, as shown in fig. 2, including:
s1, performing an alternating current-direct current superposition endurance test on a dry capacitor to be detected to obtain an endurance test result;
the alternating current and direct current superposition durability test aims at verifying the performance of the capacitor under the actual alternating current and direct current superposition operation condition, and the durability test is carried out on a complete unit or a model capacitor.
S1.1 before carrying out the AC/DC superposition endurance test, the dry capacitor needs to be subjected toPretreatment, wherein the pretreatment process comprises the following steps: the dry type capacitor can endure the maximum value of the direct current component of the operating voltage of 1.1U in the static air with the temperature of not less than +10 DEG C NDC The voltage of the dry capacitor is kept for 16-24 h, and the dry capacitor is placed in a ventilation box with the temperature of 28-32 ℃ for not less than 12 h under the condition of no electricity.
S1.2 after voltage is applied for 5min, measuring the initial capacitance C at the same environmental temperature 0 And tan delta 0 ；
S1.3, putting the dry capacitor to be tested into a heating box and electrifying, adjusting the cooling or heating condition of the heating box to ensure that the dry capacitor to be tested maintains the hottest point temperature of 85 ℃ in the test process, the electrified applied voltage is the maximum operating voltage of alternating current and direct current superposition when the converter valve actually operates, considering a certain safety margin, the electrified time is 250h, the electrified applied voltage is the maximum operating voltage of alternating current and direct current superposition when the converter valve actually operates, and the electrified applied voltage and time are obtained by the following parameter determination method, namelyk x U NDC +U C_acmax And/250 h. After the electrifying duration is finished, the standard test condition is recovered for 12 to 48 hours, and the corresponding frequency capacitance C is tested after the preset time is reached 1 And tan delta 1 ；
S1.4, charging and discharging for 1000 times at room temperature according to the requirements of an impact discharge test, wherein the charging and discharging current is 1.4 \206, and after the test is finished, the corresponding frequency capacitance C is tested 2 And tan delta 2 ；
S1.5 repeating the steps before the impulse discharge test, namely step S1.3, applying the AC/DC superposed maximum operating voltage when the temperature of the hottest point reaches 85 ℃,k x U NDC +U C_acmax the power-on duration is 250h, after the power-on duration is finished, the power-on duration is recovered to 12-48 h under the standard test condition, and the corresponding frequency capacitance C is tested again 3 And tan delta 3 ；
S1.6, judging whether the frequency capacitance and tan delta corresponding to each obtained test pass the standard or not.
The pass criteria were: capacitance C of the corresponding frequency obtained for the first time 1 And tan delta 1 Comparison with the initial measurements: i C 1 -C 0 /C 1 |≤2%，tan
1 ≤1.1tan
0 +1.0×10 -4 (ii) a And, a second frequency capacitance C 2 And a second loss tan delta 2 Initial capacitance C 0 And initial loss tan delta 0 Satisfies the following formula: i C 2 -C 0 /C 2 |≤2%，tan
2 ≤1.1tan
0 +1.0×10 -4 (ii) a And, a third frequency capacitance C 3 And a third loss tan delta 3 Initial capacitance C 0 And initial loss tan delta 0 Satisfies the following formula: i C 3 -C 0 /C 3 |≤3%，tan
3 ≤1.2tan
0 +1.0×10 -4 . The hottest point temperature during the experiment was recorded.
The parameter design method of the voltage applied by electrifying comprises the following steps: firstly, determining the maximum value of the direct current component, wherein the determination method comprises the following steps: according to the control strategy of the system, if the direct current voltage is fixed at the receiving end, the direct current voltage of the maximum port operated by the converter valveU dcmax The method is characterized by superposing a receiving end direct current voltage, a line voltage drop, a control error and a measurement error, wherein the line voltage drop is designed according to the maximum resistance presented when a line runs, the control error and the measurement error are respectively considered according to 1%, and all bypasses of any bridge arm redundancy module are considered at the same time, namely the number of the bridge arm modules is not redundantNumber of remaining modulesNFurther, the maximum value U of the DC component of the module operating voltage is calculated NDC =U dcmax /N。
The method for calculating the voltage alternating-current component of the dry capacitor comprises the following steps: first, the current effective value of the voltage of the dry capacitor is calculated according to the following formulaI crms ：
Wherein, I 0 Is the maximum current on the alternating side of the converter valve at the maximum operating point,I dc the maximum current of the direct current side of the converter valve at the maximum operating point is obtained;
AC component of voltage of dry capacitorU c_ac max Comprises the following steps:
in the formula (I), the compound is shown in the specification,k unbalance is the coefficient of imbalance between modules, C is the capacitance of the dry capacitor,
the fundamental frequency is generally selected to be 1 to 2%. Selecting test parameters by 2%;
the parameter of the maximum operating voltage of the AC/DC superposition isk x U NDC +U C_acmax Wherein, in the step (A),k x for the endurance test voltage coefficient, 1.3 is preferable in this embodiment.
S2, carrying out a limit voltage withstand test between terminals aiming at the dry capacitor to be detected to obtain a voltage withstand test result;
the inter-terminal polar line voltage withstand test is used for examining the voltage withstand capability of the capacitor under the actual operation limit condition of the flexible direct current converter valve.
The method for the ultimate withstand voltage test between the terminals comprises the following steps: and after the whole body of the dry capacitor reaches 70 ℃, applying the maximum voltage generated in the transient operation process of the converter valve, keeping the maximum time of the actual working condition tolerance, and recording the capacitance and the loss tan delta variable quantity before and after the test.
The pass criteria were: the capacitor should be guaranteed not to break down and not to decay in capacitance.
The design method of the test parameters of the maximum voltage and the duration which possibly appear in the transient operation process of the converter valve comprises the following steps: the converter valve submodule where the capacitors are located is provided with the breakover thyristor, and the maximum voltage is selected as the breakdown voltage of the breakover thyristor; the converter valve submodule where the plurality of capacitors are located is not provided with a turning thyristor, and the maximum voltage is selected as the breakdown voltage of the IGBT device; for a capacitor adopting a 4.5kV/3kA device and not added with a breakover thyristor, applying a direct-current voltage not lower than the rated voltage (4.5 kV) of the IGBT of the adaptor module, and keeping the time for 3R dc CIt is calculated that if C is 8mF,R dc at 50k Ω, the holding time was selected to be 20 minutes. The capacitance and loss tan delta changes before and after the test were recorded.
Duration of timeT max The calculation formula of (2) is as follows:
wherein the content of the first and second substances,Cis the capacitance value of the dry capacitor;R dc is the parallel resistance value in the converter valve submodule.
S3, performing a two-section type impact discharge test on the dry capacitor to be detected to obtain a discharge test result;
the two-stage impulse discharge test method comprises the following steps: the impulse discharge test is divided into two sections: in the first stage, various possible N-1 faults in a converter valve submodule, including working conditions such as mistakenly closing a bypass switch and the like, are considered, impact current is designed, and the times are considered according to 50 times; and in the second stage, various N-2 faults occurring in the converter valve submodule, including bridge arm direct short circuit, desaturation protection failure and the like, are considered, impact current is designed, and the times are considered according to 5 times.
The pass criteria were: and within 5min after the preset time, performing an end-to-end voltage test, measuring capacitance values, recording the capacitance and the loss tan delta variation before and after the test before and after the discharge test, wherein delta C/C is less than or equal to +/-1%, tan delta is less than or equal to 1.2 tan delta 0+1 multiplied by 10 < -4 >, delta C is the difference value of the capacitance values before and after discharge, and C is the capacitance value after discharge.
In this embodiment, the first stage of the inrush current calculation loop includes: a capacitor 1, a converter valve stray inductor 2, an IGBT or diode device resistor 3 with failed upper bridge arm of a module, an inductor 4 of a bypass switch and a resistor 5 of the bypass switch are connected in series to form a loop, and the voltage during impact is selected according to the maximum voltage of the capacitor which can be borne by the IGBT when the converter valve is unlocked and is generally 75% of the rated voltage of the IGBT; the second stage impulse current calculation loop should include: the circuit comprises a capacitor 1, a converter valve stray inductor 2, an IGBT or diode device resistor 3 with failed upper bridge arm of the module and an IGBT or diode device resistor 6 with failed lower bridge arm of the module which are connected in series to form a loop.
And S4, determining the performance of the dry capacitor to be detected based on the endurance test result, the withstand voltage test result and the discharge test result to obtain a performance test result.
Based on the same inventive concept, the embodiment of the application also provides a dry-type capacitor test method for the flexible direct-current converter valve, which comprises the following steps:
the endurance test module is used for carrying out alternating current and direct current superposition endurance test on the dry capacitor to be detected to obtain an endurance test result;
the obtained voltage withstanding test module is used for carrying out a limited voltage withstanding test between terminals aiming at the dry capacitor to be detected to obtain a voltage withstanding test result;
the discharge test module is used for carrying out a two-section type impact discharge test on the dry capacitor to be detected to obtain a discharge test result;
and the performance test module is used for determining the performance of the dry capacitor to be detected based on the endurance test result, the withstand voltage test result and the discharge test result to obtain a performance test result, wherein the performance test result represents whether the dry capacitor to be detected meets the performance standard. Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims. The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (10)
1. A dry capacitor test method for a flexible direct current converter valve is characterized by comprising the following steps:
aiming at the dry capacitor to be detected, carrying out an alternating current-direct current superposition endurance test to obtain an endurance test result;
carrying out a terminal-to-terminal limit voltage withstand test on the dry capacitor to be detected to obtain a voltage withstand test result;
aiming at the dry capacitor to be detected, performing a two-section type impact discharge test to obtain a discharge test result;
and determining the performance of the dry capacitor to be detected based on the endurance test result, the withstand voltage test result and the discharge test result to obtain a performance test result, wherein the performance test result represents whether the dry capacitor to be detected meets the performance standard.
2. The method for testing the dry capacitor for the flexible direct current converter valve according to claim 1, wherein the step of performing the alternating current/direct current superposition endurance test on the dry capacitor to be tested to obtain the endurance test result comprises the following steps:
aiming at the dry capacitor to be detected, continuously applying voltage according to a first preset time, and measuring the initial capacitance C of the dry capacitor to be detected at a target environment temperature 0 And initial loss tan delta 0 ；
Putting the dry capacitor to be detected into a heating box, electrifying, adjusting the cooling or heating condition of the heating box to ensure that the dry capacitor to be detected maintains the target hot spot temperature in the test process, and testing to obtain a first frequency capacitance C after reaching a second preset time 1 And a first loss tan delta 1 The voltage applied during electrifying is a target running voltage of alternating current and direct current superposition when the converter valve actually runs;
charging and discharging at room temperature for a preset number of times according to the requirement of an impact discharge test to obtain a second frequency capacitance C 2 And a second loss tan delta 2 ；
Repeatedly carrying out pretreatment on the dry capacitor to be detected until reaching a second preset time, and then testing to obtain a first frequency capacitance C 1 And a first loss tan delta 1 Again testing to obtain a third frequency capacitance C 3 And a third loss tan delta 3 ；
Based on the initial capacitance C 0 And initial loss tan delta 0 First frequency capacitance C 1 And a first loss tan delta 1 A second frequency capacitance C 2 And a second loss tan delta 2 A third frequency capacitance C 3 And a third loss tan delta 3 The durability test results were obtained.
3. The dry capacitor test method for flexible dc converter valves according to claim 2, wherein the initial capacitance C is based on 0 And initial loss tan delta 0 First frequency capacitance C 1 And a first loss tan delta 1 Second frequency capacitance C 2 And a second loss tan delta 2 A third frequency capacitance C 3 And a third loss tan delta 3 The step of obtaining the durability test result comprises:
if the first frequency capacitance C 1 And a first loss tan delta 1 Initial capacitance C 0 And initial loss tan delta 0 Satisfies the following formula: i C 1 -C 0 /C 1 |≤2%，tan
1 ≤1.1tan
0 +1.0×10 -4 ；
And, a second frequency capacitance C 2 And a second loss tan delta 2 Initial capacitance C 0 And initial loss tan delta 0 Satisfies the following formula:
|C 2 -C 0 /C 2 |≤2%，tan
2 ≤1.1tan
0 +1.0×10 -4 ；
and, a third frequency capacitance C 3 And a third loss tan delta 3 Initial capacitance C 0 And initial loss tan delta 0 Satisfies the following formula:
|C 3 -C 0 /C 3 |≤3%，tan
3 ≤1.2tan
0 +1.0×10 -4 determining that the dry capacitor to be detected meets the AC/DC superposition endurance test standard;
and taking the dry capacitor to be detected meeting the AC/DC superposition endurance test standard as an endurance test result.
4. The method for testing the dry capacitor for the flexible direct current converter valve according to claim 2, wherein the dry capacitor is preprocessed before an alternating current/direct current superposition endurance test is performed on the dry capacitor to be tested to obtain an endurance test result, and the preprocessing process comprises the following steps:
putting the dry capacitor into static air with the temperature not lower than a fourth preset temperature, applying a voltage which is several times of the maximum value of the direct current component of the operating voltage for 16-24 hours, and putting the dry capacitor in a ventilation box with the temperature of 28-32 ℃ for not less than 12 hours in an unpowered state.
5. The dry capacitor test method for the flexible direct current converter valve according to claim 4, wherein the method for determining the maximum value of the direct current component of the operating voltage comprises:
if the receiving end of the flexible direct current converter valve is the constant direct current voltage, the direct current voltage of the maximum port of the operation of the converter valveU dcmax The method is characterized by superposing receiving end direct current voltage, line voltage drop, control error and measurement error of the flexible direct current converter valve, wherein the line voltage drop is determined according to the maximum resistance of a line during operation, and the number of bridge arm modules is the number of modules without redundancyNFurther, the maximum value U of the DC component of the module operating voltage is calculated NDC =U dcmax /N。
6. The method for testing a dry capacitor for a flexible direct current converter valve according to claim 5, wherein the method for calculating the voltage alternating current component of the dry capacitor comprises: effective value of voltage current of dry capacitorI Crms The calculation was performed as follows:
wherein, I 0 Is the maximum current on the alternating current side of the converter valve at the maximum operating point,I dc the maximum current of the direct current side of the converter valve at the maximum operating point is obtained; voltage ac component of dry capacitorU C_ac max The calculation was performed as follows:
in the formula (I), the compound is shown in the specification,k unbalance is the coefficient of imbalance between the modules, C is the capacitance of the dry capacitor,
is the fundamental frequency; the parameter of the maximum operating voltage of the AC/DC superposition isk x U NDC +U C_acmax Wherein, in the process,k x the endurance test voltage coefficient.
7. The method for testing a dry capacitor for a flexible dc converter valve according to claim 1, wherein the method for performing an inter-terminal limit withstand voltage test on the dry capacitor to be tested to obtain a result of the withstand voltage test comprises: and after the dry capacitor reaches the preset temperature, applying the maximum voltage generated in the transient operation process of the converter valve to the dry capacitor, keeping the maximum enduring time in the actual working condition, and recording the capacitance and the loss tan delta variable quantity before and after the test.
8. The dry capacitor test method for the flexible direct current converter valve according to claim 7, wherein the test parameter calculation method for the maximum voltage appearing during the transient operation of the converter valve and the maximum time endured in the actual working condition comprises the following steps:
if the converter valve submodule where the dry type capacitor is located is configured with the breakover thyristor, the maximum voltage is the breakdown voltage of the breakover thyristor;
if the converter valve submodule where the dry capacitor is located is not provided with the turning thyristor, the maximum voltage is the breakdown voltage of an IGBT device in the converter valve submodule; maximum time tolerated in the actual operating conditionT max The calculation formula of (2) is as follows:
wherein the content of the first and second substances,Cis the capacitance value of the dry capacitor;R dc is the parallel resistance value in the converter valve submodule.
9. The method for testing the dry capacitor for the flexible direct current converter valve according to claim 1, wherein the method for performing a two-stage impulse discharge test on the dry capacitor to be tested comprises the following steps:
the impulse discharge test comprises two sections: the first stage is to design an impulse current by considering various N-1 faults occurring in a converter valve submodule; in the second stage, impact current is designed in order to consider various N-2 faults occurring in the converter valve submodule;
if the capacitor is not broken down after the preset time, performing an inter-terminal voltage test on the dry capacitor;
recording the capacitance and loss tan delta variation before and after impact discharge, wherein if the capacitance variation value delta C before and after impact discharge, the capacitance value C and the loss tan delta after impact discharge satisfy the following formula: determining that the dry capacitor to be detected meets the standard of an impact discharge test if delta C/C is less than or equal to +/-1 percent and tan delta is less than or equal to 1.2 tan delta 0+1 multiplied by 10 < -4 >;
and taking the dry capacitor to be detected meeting the impulse discharge test standard as a discharge test result.
10. A dry capacitor test method for a flexible dc converter valve according to claim 9, wherein the first stage of said inrush current calculation circuit comprises: a capacitor, a converter valve stray inductance, an IGBT or diode device resistance with failed upper bridge arm of the module, and an inductance and a resistance of the bypass switch which are connected in series to form a loop; second section the calculation loop of the inrush current should include: the circuit comprises a capacitor, a converter valve stray inductance, an IGBT or diode device resistor with failed upper bridge arm of the module and an IGBT or diode device resistor with failed lower bridge arm of the module which are connected in series to form a loop.
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