Temperature rise test circuit and method for flexible direct current capacitor

Abstract

The invention discloses a temperature rise test circuit and method for a flexible DC capacitor, and the method comprises the steps: adjusting a basic voltage provided by a basic voltage source to a to-be-boosted voltage through a voltage regulator, boosting the to-be-boosted voltage to a first target voltage through a boosting transformer, rectifying the first target voltage through a high-voltage diode, and obtaining a high-voltage DC voltage; and the step-down transformer reduces the basic voltage to a second target voltage, and the frequency converter increases the frequency of the second target voltage to obtain a high-frequency current, so that the high-voltage DC voltage and the high-frequency current are applied to the tested flexible DC capacitor. Therefore, the ripple frequency is improved to the target frequency value by adopting a direct current superposition alternating current mode, which can be equivalent to the same current test on three capacitors by adopting a direct current superposition processing frequency ripple power supply, so that the tested flexible direct current capacitor achieves the same temperature rise effect; therefore, the capacitor cost of the temperature rise test can be saved by adopting a single capacitor to complete the temperature rise test.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and more specifically, to a temperature rise test circuit and method for a flexible capacitor. Background Art

[0002] In the field of power electronics technology, the DC support capacitor for flexible DC transmission converter valve is a key component in the flexible DC transmission converter valve, and its performance plays a vital role in the performance of the converter valve. Among them, thermal stability is an extremely important performance indicator, and the core purpose of the thermal stability test is to measure the temperature rise of the capacitor.

[0003] At present, the power supply for thermal stability test is not specified in detail in the power electronic capacitor standard. In order to make the test closer to the actual use environment of flexible DC capacitors, the power grid company has formulated a special industry standard for this type of capacitor, stipulating that three capacitor units are used for testing at the same time, and the capacitor test pieces are placed according to the actual installation method of the converter valve. Therefore, the middle capacitor is currently used as the tested capacitor, and its temperature rise data is used as the test data. The two adjacent capacitors are used as accompanying test capacitors, and the temperature rise test is carried out by using a DC superimposed power frequency ripple power supply.

[0004] However, there must be three test pieces, and the DC support capacitors used in the flexible DC transmission converter valves have the characteristics of high voltage, large capacity and large current. The capacitance of a single unit reaches several mF level, and the material cost of a single unit is as high as more than 10,000 yuan, so the cost of testing is relatively high.

[0005] How to design a capacitor temperature rise test to reduce the cost of the temperature rise test is a problem that needs to be solved. Summary of the invention

[0006] In view of the above problems, the present application provides a temperature rise test circuit and method for a flexible capacitor, so as to use fewer capacitor devices to complete the temperature rise test, reduce the cost of the temperature rise test and thus improve the efficiency of the temperature rise test.

[0007] In order to achieve the above objectives, the specific plan is proposed as follows:

[0008] A temperature rise test circuit for a flexible DC capacitor comprises a basic voltage source, a voltage regulator, a step-up transformer, a high-voltage diode, a step-down transformer and a frequency converter;

[0009] The voltage regulator is used to adjust the basic voltage provided by the basic voltage source to the voltage to be boosted;

[0010] The step-up transformer is used to increase the voltage to be stepped up to a first target voltage;

[0011] The high-voltage diode is used to rectify the first target voltage to obtain a high-voltage DC voltage to be applied to the flexible DC capacitor under test;

[0012] The step-down transformer is used to reduce the basic voltage to a second target voltage;

[0013] The frequency converter is used to increase the frequency of the second target voltage to obtain a high-frequency current to be applied to the tested flexible DC capacitor.

[0014] Optionally, the temperature rise test circuit further includes a main power air switch, a main power electromagnetic relay, a DC circuit air switch, a DC circuit current limiting resistor and a DC circuit electromagnetic relay;

[0015] The basic voltage source is connected to the voltage regulator in sequence through the main power air switch, the main power electromagnetic relay, the DC circuit air switch and the DC circuit current limiting resistor;

[0016] The DC circuit electromagnetic relay is connected to both ends of the DC circuit current limiting resistor.

[0017] Optionally, the temperature rise test circuit further includes an AC circuit air switch, an AC circuit current limiting resistor and an AC circuit electromagnetic relay;

[0018] The basic voltage source is connected to the step-down transformer in sequence through the main power air switch, the main power electromagnetic relay, the AC circuit air switch and the AC circuit current limiting resistor;

[0019] The AC circuit electromagnetic relay is connected to both ends of the AC circuit current limiting resistor.

[0020] Optionally, the temperature rise test circuit further includes an isolation transformer;

[0021] The frequency converter is connected to the tested flexible DC capacitor through the isolation transformer.

[0022] Optionally, the temperature rise test circuit further includes a reactance, and the output end of the isolation transformer is connected to the tested flexible DC capacitor through the reactance.

[0023] Optionally, the temperature rise test circuit further includes a supporting capacitor, a voltage dividing resistor, a discharge resistor group and a discharge resistor switch;

[0024] The support capacitor, the voltage-dividing resistor group and the discharge resistor are connected in parallel between the high-voltage diode and the tested flexible DC capacitor;

[0025] The discharge resistance switch is connected in series with the discharge resistor.

[0026] Optionally, the temperature rise test circuit further includes a voltage monitor, the voltage divider resistor group includes two voltage divider resistors, and the voltage monitor is connected to both ends of one of the voltage divider resistors in the voltage divider resistor group to detect the output voltage.

[0027] A temperature rise test method for a flexible capacitor, characterized in that it is applied to the operation or running of the temperature rise test circuit as described above, and the temperature rise test method includes:

[0028] When the temperature rise test circuit is turned on so that a high-voltage DC voltage and a high-frequency current are applied to the flexible DC capacitor under test, the temperature rise data of the flexible DC capacitor under test is tested.

[0029] Optionally, when the temperature rise test circuit is turned on so that a high-voltage DC voltage and a high-frequency current are applied to the flexible DC capacitor under test, the temperature rise data of the flexible DC capacitor under test is tested, including:

[0030] When the discharge resistance switch in the temperature rise test circuit is disconnected, and the remaining switches except the discharge resistance switch are closed, so that the high-voltage DC voltage and the high-frequency current are applied to the tested flexible DC capacitor, the temperature rise data of the tested flexible DC capacitor is tested.

[0031] Optionally, when the temperature rise test circuit is turned on so that a high-voltage DC voltage and a high-frequency current are applied to the flexible DC capacitor under test, after testing the temperature rise data of the flexible DC capacitor under test, the method further includes:

[0032] After the temperature rise data test of the tested flexible DC capacitor is completed, the AC circuit electromagnetic relay and the DC circuit electromagnetic relay of the temperature rise test circuit are disconnected, and the discharge resistance switch of the temperature rise test circuit is closed to form a discharge loop.

[0033] By means of the above technical scheme, the present application adjusts the basic voltage provided by the basic voltage source to the voltage to be boosted through the voltage regulator, and then the boost transformer increases the voltage to be boosted to the first target voltage, and then the high-voltage diode rectifies the first target voltage to obtain a high-voltage DC voltage, and the step-down transformer reduces the basic voltage to the second target voltage, and then the frequency converter increases the frequency of the second target voltage to obtain a high-frequency current, thereby applying the high-voltage DC voltage and the high-frequency current to the tested flexible DC capacitor. It can be seen that by adopting the DC superimposed AC mode to increase the ripple frequency to the target frequency value, it can be equivalent to using a DC superimposed industrial frequency ripple power supply to perform the same current test on three capacitors, so that the tested flexible DC capacitor achieves the same temperature rise effect, so using a single capacitor to complete the temperature rise test can save the capacitor cost of the temperature rise test. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Also, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0035] Figure 1 A schematic diagram of a circuit structure for implementing a temperature rise test of a flexible capacitor provided in an embodiment of the present application;

[0036] Figure 2 A detailed structural diagram of a circuit for implementing a temperature rise test of a flexible capacitor provided in an embodiment of the present application. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0038] Figure 1 A schematic diagram of a circuit structure for implementing a temperature rise test provided in an embodiment of the present application, such as Figure 1 As shown, the circuit structure may include:

[0039] Basic voltage source, voltage regulator, step-up transformer, high-voltage diode, step-down transformer, frequency converter and tested flexible DC capacitor. The basic voltage source is connected to the first end of the tested flexible DC capacitor through the voltage regulator, step-up transformer and high-voltage diode in sequence, and the basic voltage source is connected to the second end of the tested flexible DC capacitor through the step-down transformer and frequency converter in sequence.

[0040] The voltage regulator can adjust the basic voltage provided by the basic voltage source to the voltage to be boosted.

[0041] Specifically, Figure 1 As shown, the basic voltage provided by the basic voltage source may be 380 V. The voltage to be boosted represents a voltage value that can be boosted by the boost transformer.

[0042] The boost transformer can boost the voltage to be boosted to a first target voltage.

[0043] Specifically, the first target voltage may represent a voltage value higher than 380V.

[0044] The high voltage diode can rectify the first target voltage to obtain a high voltage DC voltage to be applied to the tested flexible DC capacitor.

[0045] The step-down transformer may step down the base voltage to a second target voltage.

[0046] Specifically, the second target voltage may represent a voltage value lower than 380V.

[0047] The frequency converter can increase the frequency of the second target voltage to obtain a high-frequency current to be applied to the tested flexible DC capacitor.

[0048] Specifically, the frequency converter can also be used as a step-down transformer at the same time, first reducing the voltage and then increasing the frequency.

[0049] It is understandable that, since the temperature rise test of a single flexible capacitor adopts the method of DC superimposed on AC, the ripple frequency can be increased to 400Hz-600Hz, so the frequency of the high-frequency current can be between 400Hz-600Hz.

[0050] The temperature rise test circuit of the flexible DC capacitor provided in this embodiment adjusts the basic voltage provided by the basic voltage source to the voltage to be boosted by the voltage regulator, and then the voltage to be boosted is increased to the first target voltage by the boost transformer, and then the first target voltage is rectified by the high-voltage diode to obtain a high-voltage DC voltage, and the step-down transformer reduces the basic voltage to the second target voltage, and then the frequency converter increases the frequency of the second target voltage to obtain a high-frequency current, thereby applying the high-voltage DC voltage and high-frequency current to the flexible DC capacitor under test. It can be seen that the use of the DC superimposed AC mode to increase the ripple frequency to the target frequency value can be equivalent to using a DC superimposed industrial frequency ripple power supply to perform the same current test on three capacitors, so that the tested flexible DC capacitor achieves the same temperature rise effect, so using a single capacitor to complete the temperature rise test can save the capacitor cost of the temperature rise test.

[0051] In some embodiments of the present application, based on Figure 1 The structure of the temperature rise test circuit shown provides a temperature rise test method for a flexible capacitor. The method can be applied to the operation or running of the temperature rise test circuit of the above-mentioned embodiment. The method may specifically include:

[0052] The voltage regulator adjusts the basic voltage provided by the basic voltage source to the voltage to be boosted;

[0053] The step-up transformer increases the voltage to be stepped up to a first target voltage;

[0054] The high voltage diode rectifies the first target voltage to obtain a high voltage DC voltage to be applied to the tested flexible DC capacitor;

[0055] The step-down transformer reduces the base voltage to a second target voltage;

[0056] The frequency converter increases the frequency of the second target voltage to obtain a high-frequency current to be applied to the tested flexible DC capacitor.

[0057] When the temperature rise test circuit is turned on, so that high voltage DC voltage and high frequency current are applied to the flexible DC capacitor under test, the temperature rise data of the flexible DC capacitor under test is tested.

[0058] It can be understood that by adopting the DC superimposed AC mode and increasing the ripple frequency to 400Hz-600Hz, when the temperature rise test circuit is connected, the high-voltage DC voltage and high-frequency current are applied to the flexible DC capacitor under test, which is equivalent to the temperature rise effect achieved by using a DC superimposed industrial frequency ripple power supply to perform the same current test on three capacitors, thereby measuring the equivalent temperature rise data of the flexible DC capacitor under test.

[0059] In some embodiments of the present application, the temperature rise test circuit mentioned in the above embodiments is further introduced. In addition to the basic voltage source, voltage regulator, step-up transformer, high-voltage diode, step-down transformer, frequency converter and tested flexible DC capacitor, the temperature rise test circuit may also include a main power air switch, a main power electromagnetic relay, a DC circuit air switch, a DC circuit current limiting resistor, a DC circuit electromagnetic relay, an AC circuit air switch, an AC circuit current limiting resistor, an AC circuit electromagnetic relay, an isolation transformer, a reactance, a supporting capacitor, a voltage divider resistor, a discharge resistor group, a discharge resistor switch and a voltage monitor.

[0060] like Figure 2 As shown, the basic voltage source is connected to the step-down transformer U1 through the main power air switch K0, the main power electromagnetic relay J0, the AC circuit air switch K1 and the AC circuit current limiting resistors R1~R3 ​​in sequence.

[0061] Among them, the step-down transformer U1 is also a frequency converter and can be used for frequency conversion.

[0062] The AC circuit electromagnetic relay J1 is connected to both ends of the AC circuit current limiting resistors R1~R3.

[0063] The inverter U1 is connected to the second end of the tested flexible DC capacitor through the isolation transformer BG.

[0064] Furthermore, the output end of the isolation transformer BG is connected to the second end of the tested flexible DC capacitor through the reactance L.

[0065] It can be understood that the 380V AC voltage A2 B2 C2 N1 is taken from the voltage source, enters the inverter U1 through the AC circuit air switch K1 and the AC circuit electromagnetic relay J1, and outputs low voltage, high frequency, and high current; and then outputs to the LC resonant circuit through the output end of the isolation transformer BG, forming a high-frequency and high-current on L and the flexible DC capacitor, which is applied to the flexible DC capacitor under test for testing.

[0066] Furthermore, the basic voltage source is connected to the voltage regulator ty through the main power air switch K0, the main power electromagnetic relay J0, the DC circuit air switch K2 and the DC circuit current limiting resistors R4~R5 in sequence.

[0067] The DC circuit electromagnetic relay J2 is connected to both ends of the DC circuit current limiting resistors R4~R5.

[0068] Between the high-voltage diode ZQ and the first end of the tested flexible DC capacitor, a support capacitor C0, a voltage-dividing resistor group r1~r2 and a discharge resistor r3~r4 are connected in parallel.

[0069] The discharge resistor switches J3-J4 are connected in series with the discharge resistors r3-r4, wherein the discharge resistor r3 is connected in series with the discharge resistor switch J3, and the discharge resistor r4 is connected in series with the discharge resistor switch J4.

[0070] It can be understood that the A2 N1 380V voltage is taken from the voltage source, enters the voltage regulator Ty through the DC circuit air switch K2 and the DC circuit electromagnetic relay J2, is adjusted to the required voltage, and then enters the step-up transformer Bz to increase to high voltage, and then rectified by the high-voltage diode ZQ to output DC high voltage and added to the tested flexible DC capacitor.

[0071] Furthermore, the voltage divider resistor group r1~r2 may include two voltage divider resistors r1 and r2, and the voltage monitor may be connected to both ends of one of the voltage divider resistors r2 in the voltage divider resistor group to detect the output voltage of r2, thereby monitoring the output voltage in real time to ensure that the temperature rise test proceeds normally.

[0072] Based on this, the process of testing the temperature rise data of the tested flexible DC capacitor when the temperature rise test circuit is turned on so that the high voltage DC voltage and the high frequency current are applied to the tested flexible DC capacitor mentioned in the above embodiment may specifically include:

[0073] When the discharge resistance switch in the temperature rise test circuit is disconnected and the other switches except the discharge resistance switch are closed so that high voltage DC voltage and high frequency current are applied to the tested flexible DC capacitor, the temperature rise data of the tested flexible DC capacitor is tested.

[0074] Specifically, when K0, J0, K1, K2, J1 and J2 are all closed and J3 and J4 are disconnected, high-voltage DC voltage and high-frequency current will be applied to the flexible DC capacitor under test. At this time, the flexible DC capacitor under test achieves a temperature rise effect, so that the temperature rise data of the flexible DC capacitor under test can be tested.

[0075] Furthermore, after the temperature rise data test of the flexible DC capacitor under test is completed, the AC circuit electromagnetic relay J1 and the DC circuit electromagnetic relay J2 can be disconnected, and the discharge resistor switches J3 and J4 can be closed to form a discharge circuit to discharge the DC voltage of the flexible DC capacitor under test to 0 potential.

[0076] Next, the temperature rise test of three capacitors was conducted by combining DC superimposed power frequency ripple power supply, and compared with the mode of DC superimposed AC (ripple frequency is 500Hz) for a single capacitor. Taking the test data of 2.8kV-7.5mF capacitor as an example, the following comparative data can be obtained:

[0077]

[0078] It can be seen that the temperature rise test of a single flexible DC capacitor using the DC superimposed AC (ripple frequency is 500Hz) mode can be equivalent to the temperature rise effect achieved by using a DC superimposed industrial frequency ripple power supply to test three capacitors with the same current, so that only one flexible DC capacitor is needed for each temperature rise test, reducing the investment cost of the capacitor. Moreover, with the same investment, three schemes can be tested. For capacitor research and development, more schemes can be tested and more data can be obtained.

[0079] Furthermore, the power of the experimental power supply can be reduced by using a single flexible DC capacitor in a DC superimposed AC (ripple frequency of 500Hz). Taking the above 7.5mF capacitor data as an example, the actual test current reached 2475A when three capacitors were used together; while the actual test current was only 825A when a single flexible DC capacitor was used.

[0080] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0081] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can refer to each other.

[0082] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A temperature rise test circuit for a flexible capacitor, characterized in that: Includes basic voltage sources, voltage regulators, step-up transformers, high voltage diodes, step-down transformers and frequency converters; The voltage regulator is used to adjust the basic voltage provided by the basic voltage source to the voltage to be boosted; The step-up transformer is used to increase the voltage to be stepped up to a first target voltage; The high-voltage diode is used to rectify the first target voltage to obtain a high-voltage DC voltage to be applied to the flexible DC capacitor under test; The step-down transformer is used to reduce the basic voltage to a second target voltage; The frequency converter is used to increase the frequency of the second target voltage to obtain a high-frequency current to be applied to the tested flexible DC capacitor.

2. The temperature rise test circuit according to claim 1, characterized in that: It also includes a main power air switch, a main power electromagnetic relay, a DC circuit air switch, a DC circuit current limiting resistor and a DC circuit electromagnetic relay; The basic voltage source is connected to the voltage regulator in sequence through the main power air switch, the main power electromagnetic relay, the DC circuit air switch and the DC circuit current limiting resistor; The DC circuit electromagnetic relay is connected to both ends of the DC circuit current limiting resistor.

3. The temperature rise test circuit according to claim 2, characterized in that: It also includes an AC circuit air switch, an AC circuit current limiting resistor and an AC circuit electromagnetic relay; The basic voltage source is connected to the step-down transformer in sequence through the main power air switch, the main power electromagnetic relay, the AC circuit air switch and the AC circuit current limiting resistor; The AC circuit electromagnetic relay is connected to both ends of the AC circuit current limiting resistor.

4. The temperature rise test circuit according to claim 3, characterized in that: Also included is an isolation transformer; The frequency converter is connected to the tested flexible DC capacitor through the isolation transformer.

5. The temperature rise test circuit according to claim 4, characterized in that: It also includes a reactance, and the output end of the isolation transformer is connected to the tested flexible DC capacitor through the reactance.

6. The temperature rise test circuit according to any one of claims 3 to 5, characterized in that: It also includes a supporting capacitor, a voltage dividing resistor, a discharge resistor group and a discharge resistor switch; The support capacitor, the voltage-dividing resistor group and the discharge resistor are connected in parallel between the high-voltage diode and the tested flexible DC capacitor; The discharge resistance switch is connected in series with the discharge resistor.

7. The temperature rise test circuit according to claim 6, characterized in that: It also includes a voltage monitor. The voltage-dividing resistor group includes two voltage-dividing resistors. The voltage monitor is connected to both ends of one of the voltage-dividing resistors in the voltage-dividing resistor group to detect the output voltage.

8. A temperature rise test method for a flexible capacitor, characterized in that: Applied to the operation or running of the temperature rise test circuit according to any one of claims 1 to 8, the temperature rise test method comprises: When the temperature rise test circuit is turned on so that a high-voltage DC voltage and a high-frequency current are applied to the flexible DC capacitor under test, the temperature rise data of the flexible DC capacitor under test is tested.

9. The temperature rise test method according to claim 8, characterized in that: When the temperature rise test circuit is turned on so that a high-voltage DC voltage and a high-frequency current are applied to the flexible DC capacitor under test, the temperature rise data of the flexible DC capacitor under test is tested, including: When the discharge resistance switch in the temperature rise test circuit is disconnected, and the remaining switches except the discharge resistance switch are closed, so that the high-voltage DC voltage and the high-frequency current are applied to the tested flexible DC capacitor, the temperature rise data of the tested flexible DC capacitor is tested.

10. The temperature rise test method according to claim 8, characterized in that: When the temperature rise test circuit is turned on so that a high-voltage DC voltage and a high-frequency current are applied to the flexible DC capacitor under test, after testing the temperature rise data of the flexible DC capacitor under test, the method further includes: After the temperature rise data test of the tested flexible DC capacitor is completed, the AC circuit electromagnetic relay and the DC circuit electromagnetic relay of the temperature rise test circuit are disconnected, and the discharge resistance switch of the temperature rise test circuit is closed to form a discharge loop.

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