A constant current source device for DC circuit breaker characteristic testing

Abstract

The present invention discloses a constant current source device for testing the characteristics of a DC circuit breaker, comprising: a DC generator main circuit, comprising a slow-start unit connected to an AC power supply, an isolation transformer connected to the output end of the slow-start unit, a rectifier connected to the output end of the isolation transformer, a converter connected to the output end of the rectifier, and a filter unit connected to the output end of the converter; an output voltage control unit, the output end of which is connected to the DC circuit breaker, comprising an output voltage transformer, an RC absorption unit, and a voltage control module, wherein the output voltage transformer is connected to the output end of the DC generator main circuit, the RC absorption unit absorbs the remaining energy in the circuit, and the voltage control module limits the contact voltage of the DC circuit breaker under test. The present invention does not require the provision of a guide wave and impedance estimation, and can not only achieve high-precision DC constant current output over a wide range, reaching a steady-state constant current set value within milliseconds, but also has a good protective effect on the DC circuit breaker under test.

Description

Technical Field

[0001] The present invention relates to the field of constant current sources, and in particular to a constant current source device for testing characteristics of a DC circuit breaker. Background Art

[0002] DC circuit breakers are widely used in power systems, rail transit and electric locomotives, new energy, and marine power. They are important electrical products in these applications. During the R&D and production inspection of DC circuit breakers, their temperature rise, nominal delay, and instantaneous tripping characteristics must be tested to ensure product quality and reliability. Therefore, a high-current DC constant current source device with a wide output range, fast dynamic response, and excellent protection for DC circuit breakers in test environments is needed.

[0003] Currently, existing high-current, wide-range DC constant current source devices generally utilize a voltage stabilizer plus rectifier filtering. This approach applies a small current pilot wave, samples the voltage and current amplitude at the output, and estimates the impedance of the output circuit. After calculating the estimated impedance, a closed-loop control system adjusts the output DC voltage to control the test current. The need to pre-set the pilot wave and calculate and calibrate the output impedance takes a long time, resulting in low detection efficiency. Furthermore, the impedance of different circuit breaker products varies, and the output voltage is low, resulting in limited sampling accuracy. Therefore, achieving high-precision output is impossible.

[0004] Therefore, a DC high current constant current device is needed to solve the existing guide wave and impedance estimation requirements, quickly output a wide range and high-precision test current, and have a DC circuit breaker test protection function. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a constant current source device for DC circuit breaker characteristic testing, particularly a high-precision DC constant current source device that meets a wide range of requirements and satisfies multiple characteristic test items, and a high-current DC constant current device that has a protective function for the DC circuit breaker under test, without the need for guided waves and impedance estimation methods. The technical solution is as follows:

[0006] The present invention provides a constant current source device for DC circuit breaker characteristic testing, which can achieve a steady-state constant current setting value within milliseconds, including:

[0007] The DC generator main circuit includes a slow-start unit connected to an external AC power supply (such as a 220V / 380V AC mains power supply), an isolation transformer connected to the output end of the slow-start unit, a rectifier connected to the output end of the isolation transformer, a converter connected to the output end of the rectifier, and a filter unit connected to the output end of the converter;

[0008] An output voltage control unit, whose output end is connected to the DC circuit breaker to be tested, includes an output voltage transformer, an RC absorption unit, and a voltage control module. One end of the output voltage transformer is connected to the output end of the DC generator main circuit. The RC absorption unit is used to absorb residual energy in the circuit. The voltage control module is used to limit the contact voltage of the DC circuit breaker under characteristic test.

[0009] Furthermore, the constant current source device provided by the present invention also includes a control unit, the main control unit of the control unit is connected to the other end of the output voltage transformer of the output voltage control unit, and the main control unit is also connected to the converter of the main circuit of the DC generator through a power conversion control interface unit, and the power conversion control interface unit is used to adjust the output current of the converter.

[0010] Furthermore, the DC generator main circuit includes a plurality of group modules, each group module includes a one-to-one corresponding converter and filter unit, and the plurality of group modules are arranged in parallel.

[0011] Furthermore, the converter is a DC-DC converter circuit, and the filtering unit is an LC filtering circuit.

[0012] Furthermore, the control unit also includes a measuring unit and a human-machine interface, the measuring unit is used to sample data from the output of the DC generator main circuit and / or the output voltage control unit, and the human-machine interface is connected to the main control unit via a communication unit.

[0013] Specifically, the main control unit includes a DSP and an FPGA, and the main control unit is also connected to a slow-start unit of a main circuit of a DC generator.

[0014] Preferably, the converter is a DC-DC full-bridge converter based on IGBT or MOSFET.

[0015] The present invention has the following technical effects:

[0016] a. The constant current source device uses direct closed-loop control of the output current, without the need to set a guide wave and complex impedance calculation. The test current rises quickly and has successfully met the requirements of second-level test volume in practice.

[0017] b. On the basis of achieving the test performance of the DC circuit breaker, ensure the safety of the DC circuit breaker in the test environment and ensure that it does not affect the working performance of the DC circuit breaker. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 1 is a schematic structural diagram of a constant current source device for DC circuit breaker characteristic testing provided by an embodiment of the present invention;

[0020] Figure 2 1 is a schematic structural diagram of an output voltage control unit of a constant current source device provided by an embodiment of the present invention;

[0021] Figure 3 This is a test waveform interface diagram of a DC circuit breaker using the constant current source device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0022] To help those skilled in the art better understand the present invention and more clearly grasp its objectives, technical solutions, and advantages, the following describes the technical solutions in the embodiments of the present invention in a clear and complete manner, in conjunction with specific embodiments and with reference to the accompanying drawings. It should be noted that implementations not depicted or described in the accompanying drawings are known to those skilled in the art. Furthermore, while examples of parameters with specific values may be provided herein, it should be understood that the parameters do not need to be exactly equal to the corresponding values, but rather may be approximated to the corresponding values within acceptable error tolerances or design constraints. Clearly, the described embodiments are merely a portion of the embodiments of the present invention, not all of them. All other embodiments derived by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention. Furthermore, the terms "comprising" and "having," and any variations thereof, in the specification and claims of the present invention, are intended to cover non-exclusive inclusions. For example, a process, method, apparatus, product, or device comprising a series of steps or units need not be limited to the steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to the process, method, product, or device.

[0023] In one embodiment of the present invention, a constant current source device for DC circuit breaker characteristic testing is provided, which can achieve a steady-state constant current setting value within milliseconds, such as Figure 1 As shown, the constant current source device includes a DC generator main circuit, an output voltage control unit and a control unit, which are specifically as follows:

[0024] like Figure 1As shown, the DC generator main circuit includes a slow-start unit, an isolation transformer, a rectifier, a converter, and a filter unit connected in sequence, that is, the slow-start unit is connected to an external AC power source, the output end of the slow-start unit is connected to the isolation transformer, the output end of the isolation transformer is connected to the rectifier, the output end of the rectifier is connected to the converter, and the output end of the converter is connected to the filter unit; specifically, the converter is a DC-DC conversion circuit, preferably a DC-DC full-bridge converter based on IGBT, and the filter unit is an LC filter circuit. It should be noted that the IGBT in the converter can also be partially or completely replaced by other controllable switching devices, such as MOSFETs, transistors, etc.

[0025] like Figure 2 As shown, an output voltage control unit has its output end connected to the DC circuit breaker to be tested. The output voltage control unit includes an output voltage transformer, an RC absorption unit, and a voltage control module. One end of the output voltage transformer is connected to the output end of the DC generator main circuit. The RC absorption unit is used to absorb residual energy in the circuit. The voltage control module is used to limit the contact voltage of the DC circuit breaker during the characteristic test.

[0026] like Figure 1 As shown, the main control unit of the control unit is connected to the other end of the output voltage transformer of the output voltage control unit. The main control unit is also connected to the converter of the DC generator main circuit via a power conversion control interface unit. Specifically, the main control unit includes a DSP and an FPGA and is also connected to the slow-start unit of the DC generator main circuit. The power conversion control interface unit is used to adjust the output current of the converter. In one embodiment of the present invention, the control unit also includes a measurement unit and a human-machine interface. The measurement unit is used to sample data from the output of the DC generator main circuit and / or the output voltage control unit. The human-machine interface is connected to the main control unit via a communication unit.

[0027] like Figure 1As shown, in a specific embodiment of the present invention, the DC generator main circuit includes a plurality of group modules, each group module includes a one-to-one corresponding converter and filter unit, and the plurality of group modules are arranged in parallel. In this embodiment, the main control unit performs PI adjustment according to the preset current value, calculates the output PWM wave to control the converter units in parallel in the plurality of group modules, and adjusts the output current of the multi-module parallel converter units. For the wide range of output current setting, this embodiment adopts a multi-speed filtering and sampling method to enhance the current output capacity of the multi-module parallel converter unit and improve the accuracy of the output current. Since the direct current output control method is adopted, there is no need to set the guide wave and complex impedance calculation, so the dynamic response of the output current is fast, and the set value current can be achieved in milliseconds within the entire output current range. The constant current source device of this embodiment is applied to the characteristic test of the DC circuit breaker, and the corresponding test waveform is as follows Figure 3 As shown, line ① is the current flowing through the DC circuit breaker, and line ② is the terminal voltage at both ends of the DC circuit breaker. Figure 3 It can be seen that the rising speed of the DC test current is very fast, and it can reach the set value of 2000A (and below) within 4ms (each unit of the horizontal axis is 1ms), and the highest accuracy of the output current is within 0.5%, without setting a guide wave and complex impedance calculation. In addition, it can be seen from the test that the present embodiment is used to output a steady-state constant current of 300A (and below) in a time of about 1ms (within 2ms); for outputting a steady-state constant current in the range of 2000A to 4000A, the time required is 6 to 7ms. Therefore, the constant current source device of the present invention can achieve a steady-state constant current set value in milliseconds within a wide output current range, that is, an output of a steady-state constant current of 4000A and below is achieved within 10ms.

[0028] The output voltage control unit is as follows: Figure 2 As shown, one end is connected in parallel with the output terminal and the other end is connected to the main control unit. When the output current reaches the measured instantaneous tripping current of the DC circuit breaker, the circuit breaker contact impedance gradually increases during the tripping process, and then the voltage across the contacts increases. Therefore, during the process of the tripping current decreasing, the energy accumulated in the circuit breaker will cause significant damage to the contact surface, especially for small circuit breakers. The constant current source device of this embodiment is used for DC circuit breaker characteristic testing. The voltage across the contacts of the circuit breaker during the characteristic test is detected. When the voltage reaches the set value, the output voltage control unit is immediately triggered to limit the contact voltage to a lower value. At the same time, the current flowing through the circuit breaker is reduced, and the RC absorption circuit is used to consume the remaining energy, effectively protecting the contacts during the instantaneous tripping characteristic test, ensuring that the working characteristics of the circuit breaker after the test are not affected.

[0029] The present invention also advocates the application of the above-mentioned constant current source device in the DC circuit breaker characteristic test, that is, using the above-mentioned constant current source device as the power supply for the DC circuit breaker characteristic test, that is, advocating the protection of a DC circuit breaker characteristic test system, which uses the above-mentioned constant current source device as the power supply for the test system to provide a constant current that reaches a steady state within seconds.

[0030] In summary, through the above settings, the constant current source device for DC circuit breaker characteristic testing in this embodiment adopts direct closed-loop control of the output current, which does not require setting of guide waves and impedance estimation, thereby improving the test accuracy and test efficiency. It can not only achieve high-precision DC constant current output over a wide range, but also meet the goal of reaching the steady-state constant current set value in less than 4ms, and also has a good protective effect on the DC circuit breaker in the test environment.

[0031] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A constant current source device for DC circuit breaker characteristic testing, characterized in that: Without the use of guided waves and impedance estimation methods, the steady-state constant current setting value can be achieved within milliseconds, including: A DC generator main circuit includes a slow-start unit connected to an external AC power source, an isolation transformer connected to the output end of the slow-start unit, a rectifier connected to the output end of the isolation transformer, a converter connected to the output end of the rectifier, and a filter unit connected to the output end of the converter, wherein the converter is a DC-DC conversion circuit; an output voltage control unit, whose output end is connected to the DC circuit breaker to be tested, and comprises an output voltage transformer, an RC absorption unit, and a voltage control module, wherein one end of the output voltage transformer is connected to the output end of the DC generator main circuit, the RC absorption unit is used to absorb residual energy in the circuit, and the voltage control module is used to limit the contact voltage of the DC circuit breaker under characteristic test; and A control unit, wherein the main control unit is connected to the other end of the output voltage transformer of the output voltage control unit, and the main control unit is also connected to the converter of the main circuit of the DC generator through a power conversion control interface unit, and the power conversion control interface unit is used to adjust the output current of the converter; The DC generator main circuit includes a plurality of group modules, each group module includes a one-to-one corresponding converter and filter unit, the plurality of group modules are arranged in parallel, and the main control unit performs PI regulation according to a preset current value, including: calculating and outputting PWM waves to control the output current of the converters in parallel in the plurality of group modules; The output voltage control unit is connected to the main control unit. When the output current reaches the measured instantaneous tripping current of the DC circuit breaker and the voltage across the circuit breaker contacts reaches a set value, the output voltage control unit is triggered to limit the contact voltage within a preset range and reduce the current flowing through the circuit breaker.

2. The constant current source device according to claim 1, wherein: The control unit further includes a measuring unit and a human-machine interface. The measuring unit is used to sample data from the output of the DC generator main circuit and / or the output voltage control unit. The human-machine interface is connected to the main control unit via a communication unit.

3. The constant current source device according to claim 1, wherein: The main control unit includes a DSP and an FPGA, and is also connected to a slow-start unit of a main circuit of a DC generator.

4. The constant current source device according to claim 1, wherein: The filtering unit is an LC filtering circuit.

5. The constant current source device according to claim 1, wherein: The converter is a DC-DC full-bridge converter based on IGBT or MOSFET.

6. Application of the constant current source device according to any one of claims 1 to 5 in a DC circuit breaker characteristic test.

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