A temperature rise test circuit and method for a flexible direct capacitor

Abstract

The application discloses a temperature rise test circuit and method of a flexible direct capacitor. The method adjusts a basic voltage provided by a basic voltage source to a voltage to be boosted by a voltage regulator, then raises the voltage to be boosted to a first target voltage by a step-up transformer, rectifies the first target voltage by a high-voltage diode to obtain a high-voltage direct current, lowers the basic voltage to a second target voltage by a step-down transformer, and then raises the frequency of the second target voltage by a frequency converter to obtain a high-frequency current, so as to apply the high-voltage direct current and the high-frequency current to the tested flexible direct capacitor. As can be seen, the mode of superimposing alternating current on direct current can raise the ripple frequency to a target frequency value, which is equivalent to using a direct current superimposed alternating current ripple power supply to conduct the same current test on three capacitors, so that the tested flexible direct capacitor can achieve the same temperature rise effect, and therefore, the temperature rise test can save the capacitor cost.

Description

Technical Field

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

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

[0003] Currently, power electronic capacitor standards do not specify the power supply for thermal stability tests in detail. To make the test more closely resemble the actual operating environment of flexible DC capacitors, power grid companies have drafted industry standards specifically for this type of capacitor, stipulating that three capacitor units be tested simultaneously, and the capacitor test samples be arranged according to the actual installation method of the converter valve. Therefore, currently, the intermediate capacitor is used as the tested capacitor, and its temperature rise data is used as the test data. The two adjacent capacitors are auxiliary test capacitors, and the temperature rise test is conducted using a DC superimposed power frequency ripple power supply.

[0004] However, three units must be tested, and the DC support capacitors for flexible DC transmission converter valves are characterized by high voltage, large capacity, and large current. The capacitance of a single unit reaches several mF, and the material cost of a single unit is as high as tens of thousands of yuan, making the test cost quite high.

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

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

[0007] To achieve the above objectives, the following specific solutions are proposed:

[0008] A temperature rise test circuit for a flexible DC capacitor includes a base 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 base voltage provided by the base voltage source to the voltage to be boosted;

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

[0011] The high-voltage diode is used to rectify the first target voltage to obtain a high-voltage DC voltage, which is then applied to the tested flexible DC capacitor.

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

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

[0014] Optionally, the temperature rise test circuit may also include a main power circuit breaker, a main power electromagnetic relay, a DC circuit circuit breaker, a DC circuit current-limiting resistor, and a DC circuit electromagnetic relay.

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

[0016] The electromagnetic relay of the DC circuit is connected across the current-limiting resistor of the DC circuit.

[0017] Optionally, the temperature rise test circuit may also include an AC circuit air switch, an AC circuit current-limiting resistor, and an AC circuit electromagnetic relay.

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

[0019] The electromagnetic relay of the AC circuit is connected across the current-limiting resistor of the AC circuit.

[0020] Optionally, the temperature rise test circuit may also include 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 also includes a reactance, and the output terminal of the isolation transformer is connected to the tested flexible DC capacitor through the reactance.

[0023] Optionally, the temperature rise test circuit may also include a support capacitor, a voltage divider resistor, a discharge resistor group, and a discharge resistor switch;

[0024] The supporting capacitor, the voltage divider resistor group, and the discharge resistor are connected in parallel between the high-voltage diode and the tested flexible DC capacitor.

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

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

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

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

[0029] Optionally, when the temperature rise test circuit is turned on, causing a high-voltage DC voltage and a high-frequency current to be applied to the tested flexible DC capacitor, testing the temperature rise data of the tested flexible DC capacitor includes:

[0030] When the discharge resistor switch in the temperature rise test circuit is turned off, all other switches except the discharge resistor switch are turned on, so that when the high voltage DC voltage and the high frequency current are applied to the test flexible DC capacitor, the temperature rise data of the test flexible DC capacitor is tested.

[0031] Optionally, after measuring the temperature rise data of the tested flexible DC capacitor when the temperature rise test circuit is turned on, causing a high-voltage DC voltage and a high-frequency current to be applied to the tested flexible DC capacitor, 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 resistor switch of the temperature rise test circuit is closed to form a discharge circuit.

[0033] Using the above technical solution, this application adjusts the base voltage provided by the base voltage source to the voltage to be boosted using a voltage regulator, then the voltage to be boosted is increased to the first target voltage by a step-up transformer, and then the first target voltage is rectified by a high-voltage diode to obtain a high-voltage DC voltage. A step-down transformer reduces the base voltage to the second target voltage, and then a frequency converter increases the frequency of the second target voltage to obtain a high-frequency current. Thus, the high-voltage DC voltage and high-frequency current are applied to the tested flexible DC capacitor. Therefore, by using a DC-AC superimposed mode to increase the ripple frequency to the target frequency value, it is equivalent to using a DC-AC superimposed power frequency ripple power supply to perform the same current test on three capacitors, thereby achieving the same temperature rise effect for the tested flexible DC capacitor. Therefore, using a single capacitor to complete the temperature rise test can save on the capacitor cost for the temperature rise test. Attached Figure Description

[0034] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

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

[0036] Figure 2 This is a detailed circuit diagram for implementing a temperature rise test of a flexible DC capacitor, as provided in an embodiment of this application. Detailed Implementation

[0037] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort 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 this application is shown below. Figure 1 As shown, the circuit structure may include:

[0039] The system consists of a base voltage source, a voltage regulator, a step-up transformer, a high-voltage diode, a step-down transformer, a frequency converter, and a flexible DC capacitor under test. The base voltage source is connected to the first terminal of the flexible DC capacitor under test in sequence through the voltage regulator, the step-up transformer, and the high-voltage diode. The base voltage source is connected to the second terminal of the flexible DC capacitor under test in sequence through the step-down transformer and the frequency converter.

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

[0041] Specifically, such as Figure 1 As shown, the base voltage provided by the base voltage source can be 380V. The voltage to be boosted represents the voltage value that can be boosted by the step-up transformer.

[0042] A step-up transformer can increase the voltage to be stepped up to the first target voltage.

[0043] Specifically, the first target voltage can 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, which can be applied to the tested flexible DC capacitor.

[0045] A step-down transformer can reduce the base voltage to a second target voltage.

[0046] Specifically, the second target voltage can represent a voltage value below 380V.

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

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

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

[0050] The temperature rise test circuit for the flexible DC capacitor provided in this embodiment adjusts the base voltage provided by the base voltage source to the voltage to be boosted using a voltage regulator. Then, a step-up transformer increases the voltage to be boosted to a first target voltage. A high-voltage diode rectifies the first target voltage to obtain a high-voltage DC voltage. A step-down transformer reduces the base voltage to a second target voltage. Finally, a frequency converter increases the frequency of the second target voltage to obtain a high-frequency current. Thus, the high-voltage DC voltage and high-frequency current are applied to the flexible DC capacitor under test. Therefore, by using a DC-AC superimposed mode to increase the ripple frequency to the target frequency value, it is equivalent to using a DC-AC superimposed power frequency ripple power supply to perform the same current test on three capacitors, thereby achieving the same temperature rise effect for the tested flexible DC capacitors. Therefore, using a single capacitor to complete the temperature rise test can save on the capacitor cost for the temperature rise test.

[0051] In some embodiments of this application, based on Figure 1 The structure of the temperature rise test circuit shown provides a method for testing the temperature rise of a flexible DC capacitor. This method can be applied to the operation or running of the temperature rise test circuit of the aforementioned embodiment. Specifically, the method may include:

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

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

[0054] The high-voltage diode rectifies the first target voltage to obtain a high-voltage DC voltage, which is then applied to the tested flexible DC capacitor.

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

[0056] The inverter increases the frequency of the second target voltage to obtain a high-frequency current, which is then applied to the tested flexible DC capacitor.

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

[0058] It is understandable that by using a DC-AC superposition mode to increase the ripple frequency to 400Hz-600Hz, when the temperature rise test circuit is turned on, the high voltage DC voltage and high frequency current applied to the tested flexible DC capacitor can achieve the same temperature rise effect as when using a DC-AC superposition power frequency ripple power supply to perform the same current test on three capacitors, thereby obtaining the equivalent temperature rise data of the tested flexible DC capacitor.

[0059] In some embodiments of this application, the temperature rise test circuit mentioned in the above embodiments is further described. In addition to including a base 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 circuit breaker, a main power electromagnetic relay, a DC circuit circuit breaker, a DC circuit current-limiting resistor, a DC circuit electromagnetic relay, an AC circuit circuit breaker, an AC circuit current-limiting resistor, an AC circuit electromagnetic relay, an isolation transformer, a reactor, 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 in sequence through the main power circuit breaker K0, the main power electromagnetic relay J0, the AC circuit circuit breaker K1, and the AC circuit current limiting resistors R1~R3.

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

[0062] The electromagnetic relay J1 in the AC circuit is connected across the current-limiting resistors R1 to R3 in the AC circuit.

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

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

[0065] Understandably, a 380V AC voltage is taken from the voltage source A2 B2 C2 N1, and enters the frequency converter U1 through the AC circuit air switch K1 and the AC circuit electromagnetic relay J1, outputting low voltage, high frequency, and high current; then it is output to the LC resonant circuit through the output terminal of the isolation transformer BG, forming a high frequency and high current on L and the flexible DC capacitor, which is applied to the tested flexible DC capacitor for testing.

[0066] Furthermore, the base voltage source is connected to the voltage regulator ty in sequence 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.

[0067] The electromagnetic relay J2 in the DC circuit is connected across the current-limiting resistors R4~R5 in the DC circuit.

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

[0069] Discharge resistor switches J3~J4 are connected in series with discharge resistors r3~r4. Specifically, discharge resistor r3 is connected in series with discharge resistor switch J3, and discharge resistor r4 is connected in series with discharge resistor switch J4.

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

[0071] Furthermore, the voltage divider resistor group r1~r2 may include two voltage divider resistors r1 and r2. A voltage monitor can 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 is carried out normally.

[0072] Based on this, the process mentioned in the foregoing embodiments, which involves testing the temperature rise data of the tested flexible DC capacitor when the temperature rise test circuit is turned on, thereby applying a high-voltage DC voltage and a high-frequency current to the tested flexible DC capacitor, may specifically include:

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

[0074] Specifically, when K0, J0, K1, K2, J1 and J2 are all closed, and J3 and J4 are open, the high voltage DC voltage and high frequency current applied will be applied to the tested flexible DC capacitor. At this time, the tested flexible DC capacitor will achieve a temperature rise effect, thereby allowing the temperature rise data of the tested flexible DC capacitor to be measured.

[0075] Furthermore, after the temperature rise data test of the tested flexible DC capacitor 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 and discharge the DC voltage of the tested flexible DC capacitor to 0 potential.

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

[0077]

[0078] Therefore, it can be seen that using a single flexible DC capacitor to conduct a temperature rise test in the mode of DC superimposed AC (ripple frequency of 500Hz) can achieve the same temperature rise effect as using a DC superimposed power frequency ripple power supply to conduct the same current test on three capacitors. This means that only one flexible DC capacitor needs to be used for each temperature rise test, reducing the cost of capacitor investment. Moreover, with the same investment, three schemes can be tested, allowing for more scheme testing and obtaining more data for capacitor research and development.

[0079] Furthermore, using a single flexible DC capacitor with DC superimposed AC (ripple frequency of 500Hz) can reduce the power consumption of the experimental power supply. Taking the aforementioned 7.5mF capacitor data as an example, using three capacitors together resulted in an actual test current of 2475A; while using a single flexible DC capacitor, the actual test current was only 825A.

[0080] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

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

[0082] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily 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 this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A temperature rise test circuit for a flexible DC capacitor, characterized in that, This includes a basic voltage source, voltage regulator, step-up transformer, high-voltage diode, step-down transformer, and frequency converter; The voltage regulator is used to adjust the base voltage provided by the base voltage source to the voltage to be boosted; The step-up transformer is used to increase the voltage to be stepped up to the first target voltage; The high-voltage diode is used to rectify the first target voltage to obtain a high-voltage DC voltage, which is applied to the tested flexible DC capacitor, wherein the tested flexible DC capacitor is a single capacitor. The step-down transformer is used to reduce the base voltage to the second target voltage; The frequency converter is used to increase the frequency of the second target voltage to obtain a high-frequency current, which is then 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 circuit breaker, a main power electromagnetic relay, a DC circuit circuit breaker, a DC circuit current-limiting resistor, and a DC circuit electromagnetic relay; The base voltage source is connected to the voltage regulator in sequence through the main power circuit breaker, the main power electromagnetic relay, the DC circuit circuit breaker, and the DC circuit current-limiting resistor; The electromagnetic relay of the DC circuit is connected across the current-limiting resistor of the DC circuit.

3. The temperature rise test circuit according to claim 2, characterized in that, It also includes AC circuit air switches, AC circuit current-limiting resistors, and AC circuit electromagnetic relays; The base voltage source is connected to the step-down transformer in sequence through the main power circuit breaker, the main power electromagnetic relay, the AC circuit circuit breaker, and the AC circuit current-limiting resistor; The electromagnetic relay of the AC circuit is connected across the current-limiting resistor of the AC circuit.

4. The temperature rise test circuit according to claim 3, characterized in that, It also includes isolation transformers; 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, the output of which is connected to the tested flexible DC capacitor via the reactance.

6. The temperature rise test circuit according to any one of claims 3-5, characterized in that, It also includes a support capacitor, a voltage divider resistor, a discharge resistor group, and a discharge resistor switch; Between the high-voltage diode and the tested flexible DC capacitor, the supporting capacitor, the voltage divider resistor group and the discharge resistor are connected in parallel, and the voltage divider resistor group includes two voltage divider resistors; The discharge resistor 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, which is connected across one of the voltage divider resistors in the voltage divider resistor group to detect the output voltage.

8. A method for testing the temperature rise of a flexible DC capacitor, characterized in that, The temperature rise test method is applied to the operation or function of the temperature rise test circuit as described in any one of claims 1-7, and includes: When the temperature rise test circuit is turned on, so that high voltage DC voltage and high frequency current are applied to the test flexible DC capacitor, the temperature rise data of the test flexible DC capacitor is measured.

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 tested flexible DC capacitor, the temperature rise data of the tested flexible DC capacitor is measured, including: When the discharge resistor switch in the temperature rise test circuit is turned off, all other switches except the discharge resistor switch are turned on, so that when the high voltage DC voltage and the high frequency current are applied to the test flexible DC capacitor, the temperature rise data of the test flexible DC capacitor is tested.

10. The temperature rise test method according to claim 8, characterized in that, After measuring the temperature rise data of the tested flexible DC capacitor when the temperature rise test circuit is turned on, causing a high-voltage DC voltage and a high-frequency current to be applied to the tested flexible DC capacitor, 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 resistor switch of the temperature rise test circuit is closed to form a discharge circuit.

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