An accelerated life test device and control method for converter valve damping capacitor

Abstract

The present invention relates to an accelerated life test device and control method for converter valve damping capacitors. The device comprises a charging unit, a secondary rectifier, a current-limiting resistor R1, a voltage sampling circuit, a discharge circuit, a control unit, and a temperature control box. The technical solution provided by the present invention enables accelerated life testing of converter valve damping capacitors at different acceleration factors in a relatively short period of time, saving testing time and resources. It also realistically simulates actual electrical stresses, ensuring the equivalence and consistency of accelerated life testing.

Description

Technical Field

[0001] The present invention relates to the field of power equipment testing, and in particular to an accelerated life test device and a control method for a converter valve damping capacitor. Background Art

[0002] High-voltage direct current (HVDC) transmission boasts unique advantages in long-distance, high-capacity power transmission, making it an effective means of addressing uneven energy distribution and optimizing resource allocation. Currently, HVDC transmission projects, both completed and under construction, have reached a considerable scale, with transmission capacity and voltage levels gradually increasing. Their role in the power grid is becoming increasingly important, and their safety and stability are receiving significant attention and research. Converter valves are core equipment in HVDC transmission projects. They control power by sequentially connecting three-phase AC voltage to the DC terminal to achieve the desired DC voltage. Their value accounts for approximately 22-25% of the total cost of a converter station. Converter valves consist of thyristors, damping capacitors, damping resistors, saturable reactors, and trigger plates. Damping capacitors reduce continuous voltage peaks, including commutation overshoot, and enable dynamic voltage balancing during the valve opening and closing process, minimizing damping losses and ensuring safe and stable operation.

[0003] Self-healing capacitors, with capacitance values ​​in the μF range, are widely used in converter valve damping unit designs due to their unique characteristics and advantages. As self-healing capacitors age, they lose capacitance and their damping and voltage-sharing capabilities deteriorate, adversely affecting converter valve operation and even forcing equipment shutdown. Furthermore, converter valve damping capacitors operate in specialized environments, requiring them to have high RMS and peak current carrying capacities while also handling high voltage and current change rates. Existing capacitor life testers produce inaccurate test results and take a long time to test. Therefore, there is an urgent need to improve the accuracy and speed of capacitor life testers. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention aims to provide an accelerated life test device for converter valve damping capacitors, which can accurately and quickly test the service life of capacitors.

[0005] The test device specifically includes:

[0006] Charging unit, secondary rectifier, current limiting resistor R1, voltage sampling circuit, discharge circuit, control unit and temperature control box;

[0007] The charging unit is connected to the AC input end of the secondary rectifier, the charging unit is used to output a constant resonant current, and the secondary rectifier is used to rectify the constant resonant current input by the charging unit to output a constant current;

[0008] One end of the current limiting resistor R1 is connected to the DC output end of the secondary rectifier and the other end is connected to the voltage sampling circuit;

[0009] The voltage sampling circuit and the discharge circuit are both connected in parallel at both ends of the secondary rectifier, the voltage sampling circuit is used to collect the voltage across the capacitor to be tested, and the discharge circuit is used to discharge the capacitor to be tested;

[0010] The discharge circuit is connected in parallel with the capacitor to be tested C s Both ends of

[0011] The control unit is connected to the charging unit, the voltage sampling circuit and the discharge circuit respectively, and is used to control the charging and discharging of the capacitor to be tested and output the value of the capacitor to be tested C s expected useful life;

[0012] The temperature control box is connected to the control unit and a capacitor to be tested is placed in the temperature control box for setting the capacitor to be tested C s The experimental temperature.

[0013] Preferably, the charging unit includes: a DC power supply U dc , DC bipolar contactor K1, inverter, series resonant capacitor C1, series resonant reactor L1 and transformer T;

[0014] The DC power supply U dc The positive electrode is connected to the anode common terminal of the inverter through the bipolar DC contactor K1, and the DC power supply U dc The negative pole is connected to the cathode common terminal of the inverter through the bipolar DC contactor K1;

[0015] The series resonant reactance L1 and the series resonant capacitor C1 are respectively connected in series at both ends of the primary side of the transformer T, and the other ends of the series resonant reactance L1 and the series resonant capacitor C1 are respectively connected to the inverter;

[0016] The secondary side of the transformer T is connected to the AC input terminal of the secondary rectifier.

[0017] Furthermore, the inverter is composed of a first turn-off device S1, a second turn-off device S2, a third turn-off device S3, a fourth turn-off device S4, a first freewheeling diode D1, a second freewheeling diode D2, a third freewheeling diode D3 and a fourth freewheeling diode D4;

[0018] The first turn-off device S1, the second turn-off device S2, the third turn-off device S3 and the fourth turn-off device S4 are respectively connected in anti-parallel with the first freewheeling diode D1, the second freewheeling diode D2, the third freewheeling diode D3 and the fourth freewheeling diode D4;

[0019] The first turnable device S1 and the fourth turnable device S4 are connected in series to form a first series circuit, the second turnable device S2 and the third turnable device S3 are connected in series to form a second series circuit, and the first series circuit and the second series circuit are connected in parallel;

[0020] One end of the series resonant reactor L1 is connected to the connection point between the cathode of the first turn-off device S1 and the anode of the fourth turn-off device S4;

[0021] One end of the series resonant capacitor C1 is connected to the connection point between the cathode of the second turn-off device S2 and the anode of the third turn-off device S3;

[0022] The anode common terminal of the first turn-off device S1 and the second turn-off device S2 is connected to the DC power supply U through a bipolar DC contactor K1. dc Positive connection;

[0023] The cathode common terminal of the third turn-off device S3 and the fourth turn-off device S4 is connected to the DC power supply U through a bipolar DC contactor K1. dc Negative connection.

[0024] Furthermore, the secondary rectifier is composed of a first rectifier diode d1, a second rectifier diode d2, a third rectifier diode d3 and a fourth rectifier diode d4;

[0025] The first rectifier diode d1 and the third rectifier diode d3 are connected in series to form a third series circuit, the second rectifier diode d2 and the fourth rectifier diode d4 are connected in series to form a fourth series circuit, and the third series circuit and the fourth series circuit are connected in parallel.

[0026] Furthermore, the charging unit is connected to the AC input terminal of the secondary rectifier, including:

[0027] The secondary side of the transformer T in the charging unit is respectively connected to the connection point of the first rectifier diode d1 and the third rectifier diode d3 and the connection point of the second rectifier diode d2 and the fourth rectifier diode d4 of the secondary rectifier.

[0028] Furthermore, the control unit is connected to the charging unit and includes:

[0029] The control unit outputs a PWM control pulse signal connected to the gates of the first turnable device S1, the second turnable device S2, the third turnable device S3 and the fourth turnable device S4 in the charging unit to control the on and off of the turnable devices.

[0030] Preferably, the voltage sampling circuit is composed of a resistor R2 and a resistor R3 connected in series;

[0031] One end of the resistor R2 in the voltage sampling loop is connected to the current limiting resistor R1 and the capacitor C to be measured. s The common connection point of the resistor R3 is connected to the capacitor C to be tested. s the other end;

[0032] The common connection point of the resistor R2 and the resistor R3 outputs the capacitor C to be measured s Terminal voltage division signal;

[0033] The first input interface of the control unit is connected to the common connection point of the resistor R2 and the resistor R3 for obtaining a voltage sampling signal.

[0034] Preferably, the discharge circuit is composed of a resistor R4 and a thyristor SCR connected in series;

[0035] The first output interface of the control unit is connected to the gate of the thyristor SCR, which is used to send a trigger signal to the gate of the thyristor SCR. The thyristor is turned on to turn on the capacitor C to be tested. s discharge;

[0036] The resistance of the resistor R4 is adjustable.

[0037] Based on the same inventive concept, the present invention provides a control method for an accelerated life test device for a converter valve damping capacitor, the method comprising:

[0038] Step 1: The control unit controls the temperature of the temperature control box to rise to the experimental temperature T s ;

[0039] Step 2: The control unit outputs a PWM pulse signal to control the charging unit to output a constant resonant current, and inputs the constant resonant current into the AC input terminal of the secondary rectifier, thereby causing the DC output terminal of the secondary rectifier to output a constant current I C ;

[0040] Step 3: Capacitor C to be tested s With constant current I C Charge to the capacitor C under test s The voltage rises to the target value U s When the control unit receives the voltage collected by the voltage sampling circuit and the voltage is equal to the target value signal, it stops outputting the PWM pulse signal and records the charging time as t c ;

[0041] Step 4: Place the capacitor C s The voltage is kept at the target value U s , and the holding time is t s ;

[0042] Step 5: The control unit outputs a PWM pulse signal to control the conduction of the thyristor in the discharge circuit, so that the capacitor C s Discharge until the voltage reaches zero and record the discharge time as t f ;

[0043] Step 6: Discharge the capacitor C to be tested s The voltage and charging current remain at zero for a period of time t k ;

[0044] Step 7: Get the capacitor C to be tested at the current moment s The capacitance of the capacitor to be tested is determined by the current moment C s Whether the capacitance is less than the preset capacitance value, if so, the control unit outputs the service life of the capacitor to be tested according to the duration of the entire accelerated life test, the experimental voltage target value and the experimental temperature of the capacitor to be tested, otherwise, returns to step 2.

[0045] Preferably, the control unit outputs a PWM pulse signal to control the charging unit to output a constant resonant current, including:

[0046] Step a: The control unit sets the constant current I C The difference between the corresponding current effective value and the target current value is input into the PI controller to obtain the PIout signal;

[0047] Step b: subtract the PIout signal from the triangular carrier signal zb1 and the triangular carrier signal zb2 in the PWM pulse signal output by the control unit to obtain difference signals z13 and z24;

[0048] Step c: performing a zero-crossing comparison on the difference signal z13 and the difference signal z24. When the difference signal z13 is greater than zero and the difference signal z24 is less than zero, the first turn-off device S1 and the third turn-off device S3 are controlled to be turned on, and the second turn-off device S2 and the fourth turn-off device S4 are controlled to be turned off.

[0049] When the difference signal z13 is less than zero and the difference signal z24 is greater than zero, the first turn-off device S1 and the third turn-off device S3 are controlled to be turned off, and the second turn-off device S2 and the fourth turn-off device S4 are controlled to be turned on;

[0050] Step d: Based on the first turn-off device S1 and the third turn-off device S3 in the charging unit being turned on, the second turn-off device S2 and the fourth turn-off device S4 being turned off, or the first turn-off device S1 and the third turn-off device S3 being turned off, and the second turn-off device S2 and the fourth turn-off device S4 being turned on, the current output by the DC power supply is inverted, so that the charging unit outputs a constant resonant current.

[0051] Preferably, the calculation formula for the service life τ0 of the capacitor to be tested is as follows:

[0052]

[0053] In the above formula, τ s is the duration of the entire accelerated life test, U s is the experimental voltage target value, U0 is the working voltage of the capacitor to be tested, T s is the experimental temperature of the capacitor to be tested, T0 is the operating temperature of the capacitor to be tested, and a is the voltage proportional index.

[0054] Furthermore, the phase difference between the triangular carrier signal zb1 and the triangular carrier signal zb2 is 180 degrees.

[0055] Compared with the closest prior art, the present invention has the following beneficial effects:

[0056] The present invention provides an accelerated life test device and control method for a converter valve damping capacitor, comprising: a charging unit, a secondary rectifier, a current limiting resistor R1, a voltage sampling circuit, a discharge circuit, a control unit, and a temperature control box; the charging unit is connected to the AC input end of the secondary rectifier, the charging unit is used to output a constant resonant current, and the secondary rectifier is used to rectify the constant resonant current input by the charging unit to output a constant current; one end of the current limiting resistor R1 is connected to the DC output end of the secondary rectifier and the other end is connected to the voltage sampling circuit; the voltage sampling circuit and the discharge circuit are both connected in parallel at both ends of the secondary rectifier, the voltage sampling circuit is used to collect the voltage at both ends of the capacitor to be tested, and the discharge circuit is used to discharge the capacitor to be tested; the discharge circuit is connected in parallel to the capacitor to be tested C s The control unit is respectively connected to the charging unit, the voltage sampling circuit and the discharge circuit, for controlling the charging and discharging of the capacitor to be tested and outputting the capacitor to be tested C s The expected service life of the temperature control box is connected to the control unit and the capacitor to be tested is placed in the temperature control box for setting the capacitor to be tested C s The technical solution provided by the present invention can carry out the accelerated life test of the converter valve damping capacitor in a relatively short time, saving test time and resources, and at the same time can truly simulate the experimental environment to ensure the equivalence and consistency of the accelerated life test. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 1 is a circuit diagram of an accelerated life test device for a converter valve damping capacitor provided in an embodiment of the present invention;

[0058] Figure 2This is a flow chart of a control method for an accelerated life test device for a converter valve damping capacitor provided in an embodiment of the present invention;

[0059] Figure 3 This is a schematic diagram of automatic testing of voltage, current stress and capacitance parameters of a capacitor to be tested provided in an embodiment of the present invention;

[0060] Figure 4 1 is a schematic diagram of automatic adjustment of the charging current of a capacitor to be tested provided in an embodiment of the present invention;

[0061] Figure 5 1 is a schematic diagram of automatic adjustment of the discharge current of a capacitor under test provided in an embodiment of the present invention;

[0062] Figure 6 1 is a schematic diagram of calculating the service life of a capacitor to be tested provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0063] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0064] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0065] Example 1

[0066] See also Figure 1 , Figure 1 This is a main structural block diagram of an accelerated life test device for a converter valve damping capacitor according to an embodiment of the present invention. Figure 1 As shown, the accelerated life test device for the converter valve damping capacitor in the embodiment of the present invention mainly includes: a charging unit, a secondary rectifier, a current limiting resistor R1, a voltage sampling circuit, a discharge circuit, a control unit and a temperature control box;

[0067] The charging unit is connected to the AC input end of the secondary rectifier, the charging unit is used to output a constant resonant current, and the secondary rectifier is used to rectify the constant resonant current input by the charging unit to output a constant current;

[0068] One end of the current limiting resistor R1 is connected to the DC output end of the secondary rectifier and the other end is connected to the voltage sampling circuit;

[0069] The voltage sampling circuit and the discharge circuit are both connected in parallel at both ends of the secondary rectifier, the voltage sampling circuit is used to collect the voltage across the capacitor to be tested, and the discharge circuit is used to discharge the capacitor to be tested;

[0070] The discharge circuit is connected in parallel with the capacitor to be tested C s Both ends of

[0071] The control unit is connected to the charging unit, the voltage sampling circuit and the discharge circuit respectively, and is used to control the charging and discharging of the capacitor to be tested and output the value of the capacitor to be tested C s expected useful life;

[0072] The temperature control box is connected to the control unit and a capacitor to be tested is placed in the temperature control box for setting the capacitor to be tested C s The experimental temperature.

[0073] In this embodiment, the charging unit includes: a DC power supply U dc , DC bipolar contactor K1, inverter, series resonant capacitor C1, series resonant reactor L1 and transformer T;

[0074] The DC power supply U dc The positive electrode is connected to the anode common terminal of the inverter through the bipolar DC contactor K1, and the DC power supply U dc The negative pole is connected to the cathode common terminal of the inverter through the bipolar DC contactor K1;

[0075] The series resonant reactance L1 and the series resonant capacitor C1 are respectively connected in series at both ends of the primary side of the transformer T, and the other ends of the series resonant reactance L1 and the series resonant capacitor C1 are respectively connected to the inverter;

[0076] The secondary side of the transformer T is connected to the AC input terminal of the secondary rectifier.

[0077] The inverter is composed of a first turn-off device S1, a second turn-off device S2, a third turn-off device S3, a fourth turn-off device S4, a first freewheeling diode D1, a second freewheeling diode D2, a third freewheeling diode D3 and a fourth freewheeling diode D4;

[0078] The first turn-off device S1, the second turn-off device S2, the third turn-off device S3 and the fourth turn-off device S4 are respectively connected in anti-parallel with the first freewheeling diode D1, the second freewheeling diode D2, the third freewheeling diode D3 and the fourth freewheeling diode D4;

[0079] The first turnable device S1 and the fourth turnable device S4 are connected in series to form a first series circuit, the second turnable device S2 and the third turnable device S3 are connected in series to form a second series circuit, and the first series circuit and the second series circuit are connected in parallel;

[0080] One end of the series resonant reactor L1 is connected to the connection point between the cathode of the first turn-off device S1 and the anode of the fourth turn-off device S4;

[0081] One end of the series resonant capacitor C1 is connected to the connection point between the cathode of the second turn-off device S2 and the anode of the third turn-off device S3;

[0082] The anode common terminal of the first turn-off device S1 and the second turn-off device S2 is connected to the DC power supply U through a bipolar DC contactor K1. dc Positive connection;

[0083] The cathode common terminal of the third turn-off device S3 and the fourth turn-off device S4 is connected to the DC power supply U through a bipolar DC contactor K1. dc Negative connection.

[0084] The secondary rectifier is composed of a first rectifier diode d1, a second rectifier diode d2, a third rectifier diode d3 and a fourth rectifier diode d4;

[0085] The first rectifier diode d1 and the third rectifier diode d3 are connected in series to form a third series circuit, the second rectifier diode d2 and the fourth rectifier diode d4 are connected in series to form a fourth series circuit, and the third series circuit and the fourth series circuit are connected in parallel.

[0086] Specifically, the charging unit is connected to the AC input terminal of the secondary rectifier, including:

[0087] The secondary side of the transformer T in the charging unit is respectively connected to the connection point of the first rectifier diode d1 and the third rectifier diode d3 and the connection point of the second rectifier diode d2 and the fourth rectifier diode d4 of the secondary rectifier.

[0088] Specifically, the control unit is connected to the charging unit including:

[0089] The control unit outputs a PWM control pulse signal connected to the gates of the first turnable device S1, the second turnable device S2, the third turnable device S3 and the fourth turnable device S4 in the charging unit to control the on and off of the turnable devices.

[0090] In this embodiment, the voltage sampling circuit is composed of a resistor R2 and a resistor R3 connected in series;

[0091] One end of the resistor R2 in the voltage sampling loop is connected to the current limiting resistor R1 and the capacitor C to be measured. s The common connection point of the resistor R3 is connected to the capacitor C to be tested. s the other end;

[0092] The common connection point of the resistor R2 and the resistor R3 outputs the capacitor C to be measured s Terminal voltage division signal;

[0093] The first input interface of the control unit is connected to the common connection point of the resistor R2 and the resistor R3 for obtaining a voltage sampling signal.

[0094] In this embodiment, the discharge circuit is composed of a resistor R4 and a thyristor SCR in series;

[0095] The first output interface of the control unit is connected to the gate of the thyristor SCR, which is used to send a trigger signal to the gate of the thyristor SCR. The thyristor is turned on to turn on the capacitor C to be tested. s discharge;

[0096] The resistance of the resistor R4 is adjustable.

[0097] Example 2

[0098] Based on the above experimental device, the present invention also provides a control method for an accelerated life test device for a converter valve damping capacitor, such as Figure 2 As shown, the method includes:

[0099] Step 1: The control unit controls the temperature of the temperature control box to rise to the experimental temperature T s ;

[0100] Step 2: The control unit outputs a PWM pulse signal to control the charging unit to output a constant resonant current, and inputs the constant resonant current into the AC input terminal of the secondary rectifier, thereby causing the DC output terminal of the secondary rectifier to output a constant current I C ;

[0101] Step 3: Capacitor C to be tested s With constant current I C Charge to the capacitor C under test s The voltage rises to the target value U s When the control unit receives the voltage collected by the voltage sampling circuit and the voltage is equal to the target value signal, it stops outputting the PWM pulse signal and records the charging time as t c ;

[0102] Step 4: Place the capacitor C s The voltage is kept at the target value U S , and the holding time is t s ;

[0103] Step 5: The control unit outputs a PWM pulse signal to control the conduction of the thyristor in the discharge circuit, so that the capacitor C s Discharge until the voltage reaches zero and record the discharge time as t f ;

[0104] Step 6: Discharge the capacitor C to be tested s The voltage and charging current remain at zero for a period of time t k ;

[0105] Step 7: Get the capacitor C to be tested at the current moment s The capacitance of the capacitor to be tested is determined by the current moment C s Whether the capacitance is less than the preset capacitance value, if so, the control unit outputs the service life of the capacitor to be tested according to the duration of the entire accelerated life test, the experimental voltage target value and the experimental temperature of the capacitor to be tested, otherwise, returns to step 2.

[0106] In this embodiment, if Figure 3 As shown, the capacitor to be tested is charged and discharged. The capacitor to be tested C s With constant current I C Charge to the capacitor C under test s The voltage rises to the target value U s When the control unit receives the voltage collected by the voltage sampling circuit and the voltage is equal to the target value signal, it stops outputting the PWM pulse signal and records the charging time as t c ; The capacitor C to be tested s The voltage is kept at the target value U s , and the holding time is t s The control unit outputs a PWM pulse signal to control the conduction of the thyristor in the discharge circuit, so that the capacitor C s Discharge until the voltage reaches zero and record the discharge time as t f ; After the capacitor C is discharged, s The voltage and charging current remain at zero for a period of time t k ;

[0107] Get the capacitor C to be tested at the current moment s The capacitance of the capacitor to be tested is determined by the current moment C s Whether the capacitance is less than the preset capacitance value, if so, the control unit outputs the service life of the capacitor to be tested according to the duration of the entire accelerated life test, the experimental voltage target value and the experimental temperature of the capacitor to be tested, otherwise, the above-mentioned charging and discharging behavior is continued for the experiment.

[0108] Among them, the capacitor to be tested C s The capacitance is calculated as follows:

[0109]

[0110] Where U s is the voltage target value, I C is a constant current.

[0111] In this embodiment, the control unit outputs a PWM pulse signal to control the charging unit to output a constant resonant current, such as Figure 4 Shown, including:

[0112] Step a: The control unit sets the constant current I C The difference Iout between the corresponding current effective value Ic-rms and the target current value Irms-set is input into the PI controller to obtain the PIout signal;

[0113] Step b: subtract the PIout signal from the triangular carrier signal zb1 and the triangular carrier signal zb2 in the PWM pulse signal output by the control unit to obtain difference signals z13 and z24;

[0114] Step c: performing a zero-crossing comparison on the difference signal z13 and the difference signal z24. When the difference signal z13 is greater than zero and the difference signal z24 is less than zero, the first turn-off device S1 and the third turn-off device S3 are controlled to be turned on, and the second turn-off device S2 and the fourth turn-off device S4 are controlled to be turned off.

[0115] When the difference signal z13 is less than zero and the difference signal z24 is greater than zero, the first turn-off device S1 and the third turn-off device S3 are controlled to be turned off, and the second turn-off device S2 and the fourth turn-off device S4 are controlled to be turned on;

[0116] Step d: Based on the first turn-off device S1 and the third turn-off device S3 in the charging unit being turned on, the second turn-off device S2 and the fourth turn-off device S4 being turned off, or the first turn-off device S1 and the third turn-off device S3 being turned off, and the second turn-off device S2 and the fourth turn-off device S4 being turned on, the current output by the DC power supply is inverted, so that the charging unit outputs a constant resonant current.

[0117] In this embodiment, the control unit outputs a PWM pulse signal to control the conduction of the thyristor in the discharge circuit, so that the capacitor C s During the discharge process until the voltage reaches zero, since the resistance R4 is continuously adjustable, the discharge current is continuously adjustable, such as Figure 5 As shown in the figure, when the discharge resistance of resistor R4 takes different values, the discharge current of the capacitor to be tested has different discharge current peak values ​​i peak1 and i peak1 .

[0118] In this embodiment, if Figure 6 As shown, the control unit outputs the service life of the capacitor to be tested based on the duration of the entire accelerated life test of the experimental circuit, the experimental voltage target value, and the experimental temperature of the capacitor to be tested; wherein the calculation formula of the service life τ0 of the capacitor to be tested is as follows:

[0119]

[0120] In the above formula, τ s is the duration of the entire accelerated life test, U s is the experimental voltage target value, U0 is the working voltage of the capacitor to be tested, T s is the experimental temperature of the capacitor to be tested, T0 is the operating temperature of the capacitor to be tested, and a is the voltage proportional index.

[0121] Furthermore, the phase difference between the triangular carrier signal zb1 and the triangular carrier signal zb2 is 180 degrees.

[0122] The experimental device provided by the present invention can perform accelerated life tests on converter valve damping capacitors in a relatively short period of time, saving test time and resources. The applied voltage and ambient temperature of the capacitor to be tested are adjustable, realizing accelerated life tests under different acceleration factors. At the same time, the charge and discharge currents of the capacitor to be tested are adjustable, which can truly simulate actual electrical stress and ensure the equivalence and consistency of the accelerated life tests. The experimental device can also automatically test and record the capacitance value parameters of the capacitor to be tested on a regular basis, and automatically stop the test after detecting that the sample capacitor fails, thereby reducing the workload of the test personnel and avoiding interruptions in the test process. The device has a high degree of automation and significantly shortens the test time. The device can be widely used in converter valve damping capacitor performance tests.

[0123] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0124] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0125] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0126] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A control method for an accelerated life test device for a converter valve damping capacitor, characterized in that: The method comprises: Step 1: The control unit controls the temperature of the temperature control box to rise to the experimental temperature T s ; Step 2: The control unit outputs a PWM pulse signal to control the charging unit to output a constant resonant current, and inputs the constant resonant current into the AC input terminal of the secondary rectifier, thereby causing the DC output terminal of the secondary rectifier to output a constant current I C ; Step 3: Capacitor C to be tested s With constant current I C Charge to the capacitor C under test s The voltage rises to the target value U s When the control unit receives the voltage collected by the voltage sampling circuit and the voltage is equal to the target value signal, it stops outputting the PWM pulse signal and records the charging time as t c ; Step 4: Place the capacitor C s The voltage is kept at the target value U S , and the holding time is t s ; Step 5: The control unit outputs a PWM pulse signal to control the conduction of the thyristor in the discharge circuit, so that the capacitor C s Discharge until the voltage reaches zero and record the discharge time as t f ; Step 6: Discharge the capacitor C to be tested s The voltage and charging current remain at zero for a period of time t k ; Step 7: Get the capacitor C to be tested at the current moment s The capacitance of the capacitor to be tested is determined by the current moment C s Whether the capacitance of the capacitor to be tested is less than the preset capacitance value, if so, the control unit outputs the service life of the capacitor to be tested according to the duration of the entire accelerated life test, the test voltage target value and the test temperature of the capacitor to be tested, otherwise, returns to step 2; The control unit outputs a PWM pulse signal to control the charging unit to output a constant resonant current, comprising: Step a: The control unit sets the constant current I C The difference between the corresponding current effective value and the target current value is input into the PI controller to obtain the PIout signal; Step b: subtract the PIout signal from the triangular carrier signal zb1 and the triangular carrier signal zb2 in the PWM pulse signal output by the control unit to obtain difference signals z13 and z24; Step c: performing a zero-crossing comparison on the difference signal z13 and the difference signal z24. When the difference signal z13 is greater than zero and the difference signal z24 is less than zero, the first turn-off device S1 and the third turn-off device S3 are controlled to be turned on, and the second turn-off device S2 and the fourth turn-off device S4 are controlled to be turned off. When the difference signal z13 is less than zero and the difference signal z24 is greater than zero, the first turn-off device S1 and the third turn-off device S3 are controlled to be turned off, and the second turn-off device S2 and the fourth turn-off device S4 are controlled to be turned on; Step d: Based on the first turn-off device S1 and the third turn-off device S3 in the charging unit being turned on and the second turn-off device S2 and the fourth turn-off device S4 being turned off, or the first turn-off device S1 and the third turn-off device S3 being turned off and the second turn-off device S2 and the fourth turn-off device S4 being turned on, the current output by the DC power supply is inverted, thereby causing the charging unit to output a constant resonant current; The accelerated life test device for the converter valve damping capacitor includes: a charging unit, a secondary rectifier, a current limiting resistor R1, a voltage sampling circuit, a discharge circuit, a control unit and a temperature control box; The charging unit is connected to the AC input end of the secondary rectifier, the charging unit is used to output a constant resonant current, and the secondary rectifier is used to rectify the constant resonant current input by the charging unit to output a constant current; One end of the current limiting resistor R1 is connected to the DC output end of the secondary rectifier and the other end is connected to the voltage sampling circuit; The voltage sampling circuit and the discharge circuit are both connected in parallel at both ends of the secondary rectifier, the voltage sampling circuit is used to collect the voltage across the capacitor to be tested, and the discharge circuit is used to discharge the capacitor to be tested; The discharge circuit is connected in parallel with the capacitor to be tested C s Both ends of The control unit is connected to the charging unit, the voltage sampling circuit and the discharge circuit respectively, and is used to control the charging and discharging of the capacitor to be tested and output the value of the capacitor to be tested C s expected useful life; The temperature control box is connected to the control unit and a capacitor to be tested is placed in the temperature control box for setting the capacitor to be tested C s The experimental temperature.

2. The method according to claim 1, wherein The charging unit includes: a DC power supply U dc , DC bipolar contactor K1, inverter, series resonant capacitor C1, series resonant reactor L1 and transformer T; The DC power supply U dc The positive electrode is connected to the anode common terminal of the inverter through the bipolar DC contactor K1, and the DC power supply U dc The negative pole is connected to the cathode common terminal of the inverter through the bipolar DC contactor K1; The series resonant reactance L1 and the series resonant capacitor C1 are respectively connected in series at both ends of the primary side of the transformer T, and the other ends of the series resonant reactance L1 and the series resonant capacitor C1 are respectively connected to the inverter; The secondary side of the transformer T is connected to the AC input terminal of the secondary rectifier.

3. The method according to claim 2, wherein The inverter is composed of a first turn-off device S1, a second turn-off device S2, a third turn-off device S3, a fourth turn-off device S4, a first freewheeling diode D1, a second freewheeling diode D2, a third freewheeling diode D3 and a fourth freewheeling diode D4; The first turn-off device S1, the second turn-off device S2, the third turn-off device S3 and the fourth turn-off device S4 are respectively connected in anti-parallel with the first freewheeling diode D1, the second freewheeling diode D2, the third freewheeling diode D3 and the fourth freewheeling diode D4; The first turnable device S1 and the fourth turnable device S4 are connected in series to form a first series circuit, the second turnable device S2 and the third turnable device S3 are connected in series to form a second series circuit, and the first series circuit and the second series circuit are connected in parallel; One end of the series resonant reactor L1 is connected to the connection point between the cathode of the first turn-off device S1 and the anode of the fourth turn-off device S4; One end of the series resonant capacitor C1 is connected to the connection point between the cathode of the second turn-off device S2 and the anode of the third turn-off device S3; The anode common terminal of the first turn-off device S1 and the second turn-off device S2 is connected to the DC power supply U through a bipolar DC contactor K1. dc Positive connection; The cathode common terminal of the third turn-off device S3 and the fourth turn-off device S4 is connected to the DC power supply U through a bipolar DC contactor K1. dc Negative connection.

4. The method according to claim 2, wherein The secondary rectifier is composed of a first rectifier diode d1, a second rectifier diode d2, a third rectifier diode d3 and a fourth rectifier diode d4; The first rectifier diode d1 and the third rectifier diode d3 are connected in series to form a third series circuit, the second rectifier diode d2 and the fourth rectifier diode d4 are connected in series to form a fourth series circuit, and the third series circuit and the fourth series circuit are connected in parallel.

5. The method according to claim 4, wherein The charging unit is connected to the AC input end of the secondary rectifier, and includes: The secondary side of the transformer T in the charging unit is respectively connected to the connection point of the first rectifier diode d1 and the third rectifier diode d3 and the connection point of the second rectifier diode d2 and the fourth rectifier diode d4 of the secondary rectifier.

6. The method according to claim 3, wherein The control unit is connected to the charging unit and includes: The control unit outputs a PWM control pulse signal connected to the gates of the first turnable device S1, the second turnable device S2, the third turnable device S3 and the fourth turnable device S4 in the charging unit to control the on and off of the turnable devices.

7. The method according to claim 1, wherein The voltage sampling circuit is composed of a resistor R2 and a resistor R3 in series; One end of the resistor R2 in the voltage sampling loop is connected to the current limiting resistor R1 and the capacitor C to be measured. s The common connection point of the resistor R3 is connected to the capacitor C to be tested. s the other end; The common connection point of the resistor R2 and the resistor R3 outputs the capacitor C to be measured s Terminal voltage division signal; The first input interface of the control unit is connected to the common connection point of the resistor R2 and the resistor R3 for obtaining a voltage sampling signal.

8. The method according to claim 1, wherein The discharge circuit is composed of a resistor R4 and a thyristor SCR in series; The first output interface of the control unit is connected to the gate of the thyristor SCR, which is used to send a trigger signal to the gate of the thyristor SCR. The thyristor is turned on to turn on the capacitor C to be tested. s discharge; The resistance of the resistor R4 is adjustable.

9. The method according to claim 1, wherein The calculation formula of the service life τ0 of the capacitor to be tested is as follows: In the above formula, τ s is the duration of the entire accelerated life test, U s is the experimental voltage target value, U0 is the working voltage of the capacitor to be tested, T s is the experimental temperature of the capacitor to be tested, T0 is the operating temperature of the capacitor to be tested, and a is the voltage proportional index.

10. The method according to claim 9, wherein The phase difference between the triangular carrier signal zb1 and the triangular carrier signal zb2 is 180 degrees.

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