A Nonlinear Characteristic Testing System and Method for an Overvoltage Protection Device of a Generator

Abstract

The present invention provides a test system and method for the non-linear characteristics of an over-voltage protection device for a generator. The signal conversion and latching unit is used to output the test current input to the protection device under test to the main control unit; the voltage feedback unit is used to output the test voltage input to the over-voltage protection device of the generator under test to the PWM control unit and the main control unit; the main control unit adjusts the reference voltage value according to the voltage signal output by the signal conversion and latching unit and the voltage feedback signal output by the voltage feedback unit, and outputs the adjusted reference voltage value to the PWM control unit; the PWM control unit judges the magnitude relationship between the voltage value fed back by the voltage feedback unit and the reference voltage value received, and outputs a pulse width modulation signal to adjust the test voltage input to the over-voltage protection device of the generator under test. High-voltage and low-voltage tests of the over-voltage protection device can be realized without additional high-voltage boosting equipment.

Description

Technical Field

[0001] The invention belongs to the field related to the performance test of power systems, and particularly relates to a test system and method for the nonlinear characteristics of a generator overvoltage protection device. Background Technique

[0002] The statements in this part only provide background technical information related to the present invention and do not necessarily constitute prior art.

[0003] The generator field suppression overvoltage protection device is an important protection technical means to prevent the overvoltage generated during the operation of the generator excitation system from endangering the rotor winding and related circuits. Field suppression is the process of quickly weakening the magnetic field generated by the excitation current in the generator rotor winding to as small as possible when a fault occurs inside the generator set under the condition that the rotor insulation permits. Due to its fast field suppression speed and good voltage limiting effect, zinc oxide nonlinear resistors have been widely used in domestic large and medium-sized generator sets. Therefore, the test of the nonlinear characteristics of zinc oxide resistors is particularly important. As the last barrier for the safety of the generator set, the reliability and safety of the operation of the field suppression device are also emphasized by major power plants.

[0004] The current traditional test method for the nonlinear characteristics of the generator field suppression overvoltage protection device needs to use special high-voltage equipment such as a step-up transformer, and slowly increase the output voltage of the step-up transformer. When the instantaneous value of the applied sine wave voltage reaches the action value of the rotor overvoltage protection device, the trigger TR acts to trigger the thyristor V. At this time, the voltage waveform change at both ends of the overvoltage protection device can be observed by using an oscilloscope. When it is found that the peak of the sine wave voltage is flattened and the positive or negative flat-top peak voltage no longer changes significantly with the increase of the power supply voltage, it indicates that the positive or negative overvoltage protection has acted to limit the voltage. After quickly recording the overvoltage action UOP value shown in the oscilloscope at this time, then reduce the output voltage to complete a test work. This test method through the waveform change and recording the action amplitude can accurately and intuitively test whether the overvoltage action value of the rotor overvoltage protection device is qualified.

[0005] In the on-site test during the unit overhaul, on the one hand, there is a lack of special high-voltage equipment such as step-up transformers. On the other hand, due to the unfamiliarity of some power plant maintenance personnel with the operating performance of the rotor overvoltage protection device, or the concern that directly applying high voltage to the thyristor trigger element and non-linear energy-absorbing resistor during the test may affect or damage the element characteristics, the overvoltage protection performance detection is not carried out in the conventional overhaul. However, we know that in the operation, maintenance and test regulations such as DL / T419-2008 and DL / T489-2006, there are regulatory requirements for the detection of the rotor overvoltage protection device. For the important protection function configuration that can effectively suppress the overvoltage generated during the operation of the generator excitation system and endanger the rotor winding and rectifier elements, it is necessary to seek and optimize and summarize a simple, safe and effective detection method for the generator excitation rotor overvoltage protection function to confirm the correct operation of this protection function, which has practical application significance for on-site maintenance tests and ensuring the reliable operation of generator sets. Summary of the Invention

[0006] To overcome the deficiencies of the above-mentioned prior art, the present invention provides a non-linear characteristic test system and method for a generator overvoltage protection device, which can realize high-voltage testing and low-voltage testing of the excitation overvoltage protection device, verify the function of the excitation overvoltage protection device, and do not require additional high-voltage boosting equipment.

[0007] To achieve the above object, one or more embodiments of the present invention provide the following technical solutions: A non-linear characteristic test system for a generator overvoltage protection device, including a PWM control unit, a main control unit, a signal conversion and latching unit, and a voltage feedback unit;

[0008] The signal conversion and latching unit is used to output the test current input to the protection device under test to the main control unit;

[0009] The voltage feedback unit is used to output the test voltage input to the generator overvoltage protection device under test to the PWM control unit and the main control unit;

[0010] The main control unit adjusts the reference voltage value according to the voltage signal output by the signal conversion and latching unit and the voltage feedback signal output by the voltage feedback unit received, and outputs the adjusted reference voltage value to the PWM control unit;

[0011] The PWM control unit judges the magnitude relationship between the voltage value fed back by the voltage feedback unit received and the reference voltage value, and outputs a pulse width modulation signal to adjust the test voltage input to the generator overvoltage protection device under test.

[0012] The second aspect of the present invention provides a non-linear characteristic test method for a generator overvoltage protection device, including:

[0013] Receive the issued control instruction and provide a test voltage to the overvoltage protection device of the generator under test according to the control instruction;

[0014] The test voltage starts from the initial voltage and changes step by step with the stepping motor and the stepping time as the amplitude to the final test voltage of the overvoltage protection device of the generator under test;

[0015] Collect the output data of the overvoltage protection device of the generator under test, perform conversion processing and analysis.

[0016] The above one or more technical solutions have the following beneficial effects:

[0017] In the present invention, the reference signal of the PWM control unit is controlled by the main control unit. The main control unit can change the duty cycle of the PWM signal by changing the reference signal, thereby adjusting and stabilizing the test voltage of the protection device under test with high adjustment accuracy.

[0018] The test system provided by the present invention has multiple test modes, can realize the high-voltage test and low-voltage test of the excitation overvoltage protection device, verify the function of the excitation overvoltage protection device, and does not require additional high-voltage boosting equipment.

[0019] The present invention can realize the self-protection function after a sudden short circuit in a high-voltage output environment and the automatic recovery function after the short circuit is eliminated, and the above steps can be repeated multiple times.

[0020] The present invention can realize the automatic storage of test data and curves without manual intervention, ensuring the real-time and accuracy of the data.

[0021] The advantages of the additional aspects of the present invention will be partly given in the following description, partly will become obvious from the following description, or will be understood through the practice of the present invention. Brief Description of the Drawings

[0022] The specification drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0023] Figure 1 It is a schematic diagram of the hardware architecture of the test system according to Embodiment 1 of the present invention;

[0024] Figure 2 It is a schematic diagram of the software architecture of the test method according to Embodiment 2 of the present invention;

[0025] Figure 3 It is a circuit diagram of the PWM main control unit and the voltage output unit according to Embodiment 1 of the present invention;

[0026] Figure 4 It is a circuit diagram of the protection unit according to Embodiment 1 of the present invention;

[0027] Figure 5 Circuit diagram of the current sampling circuit of the signal conversion and latching unit according to the first embodiment of the present invention;

[0028] Figure 6 It is a schematic diagram of the software control flow according to the second embodiment of the present invention. Specific embodiments

[0029] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0030] Embodiment 1

[0031] As Figure 1 shown, this embodiment discloses a non-linear characteristic test system for a generator overvoltage protection device, including a PWM control unit, a main control unit, a signal conversion and latching unit, and a voltage feedback unit;

[0032] The signal conversion and latching unit is used to output the test current input to the protection device under test to the main control unit;

[0033] The voltage feedback unit is used to output the test voltage input to the generator overvoltage protection device under test to the PWM control unit and the main control unit;

[0034] The main control unit adjusts the reference voltage value according to the voltage signal output by the signal conversion and latching unit and the voltage feedback signal output by the voltage feedback unit, and outputs the adjusted reference voltage value to the PWM control unit;

[0035] The PWM control unit judges the magnitude relationship between the voltage value fed back by the voltage feedback unit and the reference voltage value, and outputs a pulse width modulation signal to adjust the test voltage input to the generator overvoltage protection device under test.

[0036] In this embodiment, when overcurrent occurs, the signal conversion and latching unit converts the signal into a digital quantity and sends it to the main control unit, and the original overcurrent analog signal is sent to the PWM control unit after being processed, and the PWM control unit adjusts the output according to the overcurrent signal.

[0037] In this embodiment, a voltage output unit is further included, and the voltage output unit specifically includes a rectification circuit, an inversion circuit, a boost rectification circuit, and a commutation and interlock circuit connected in sequence;

[0038] After the 220V AC power supply is converted into an adjustable AC voltage through a rectification circuit and an inversion circuit, it is then rectified and boosted to output a DC voltage, which is switched in direction through a commutation and interlock circuit and output to the input end of the overvoltage protection device of the generator under test; the PWM control unit is connected to the inversion circuit to adjust the AC voltage output by the inversion circuit.

[0039] As Figure 3 shown, the boost rectification circuit includes a boost transformer and a rectification circuit. The output of the inversion circuit is connected to the input of the boost transformer, and the output of the boost transformer is connected to the input of the rectification circuit. The boost transformer electrically isolates the adjustable AC voltage output by the inversion circuit and outputs two sets of AC voltages. The two sets of AC voltages are respectively converted into DC voltages through the rectification circuit, and then the direction is switched through the commutation and interlock circuit, and finally the test voltage of the overvoltage protection device of the generator under test is output.

[0040] The main control unit also outputs a high-voltage DC output state control signal to the commutation and interlock circuit. According to the commutation and interlock circuit, the main control unit can change the high-voltage DC output state to forward output, reverse output, and lock the high-voltage output respectively.

[0041] In this embodiment, the PWM control unit includes a PWM transformer.

[0042] In this embodiment, the test voltage of the overvoltage protection device of the generator under test is output to the PWM control unit and the main control unit through the voltage feedback unit. The PWM control unit judges the magnitude relationship between the high-voltage feedback signal (BF) and the reference voltage (DA) to provide a pulse width modulation signal with a settable frequency. The pulse width modulation signal is amplified by the PWM transformer and then triggers the IGBT in the inversion circuit. The output of the inversion circuit passes through the boost transformer in the boost rectification module and then outputs a high-voltage pulse. After continuing to be rectified in the boost rectification module, it becomes high-voltage DC and is output after passing through the current-limiting protection circuit. Among them, the main control unit adjusts the value of the reference voltage (DA) according to the real-time output needs and logical judgment and operation with each feedback signal to control the pulse width modulation signal output by the PWM control module, and finally changes the high-voltage DC output value, that is, the high-voltage DC output to the protection device under test through the commutation and interlock circuit.

[0043] In this embodiment, the current-limiting protection circuit is actually a resistor connected in series to the high-voltage output circuit and the high-voltage sampling circuit at both ends. When the main control reads that the voltage difference across the above resistor is too large, it is equivalent to that the current of the high-voltage output is too large, and a protection action dominated by the main control and coordinated by other modules can be performed. The protection action has nothing to do with the current-limiting protection circuit. The naming of the current-limiting protection circuit is to distinguish it from ordinary current sampling and the overcurrent protection circuit via the signal latching unit. The overcurrent signal of the overcurrent protection circuit is converted into a digital quantity by the signal latching unit and sent to the main control, and the original overcurrent analog signal is sent to the PWM control unit after being processed. The signal of the current-limiting protection circuit is only sent to the main control unit. Among them, the overcurrent protection circuit is Figure 4 the overcurrent protection 1 in Figure 4 ; the current-limiting protection circuit is

[0044] such as Figure 3 shown, in this embodiment, the PWM control unit uses the PWM controller KA3525A. The PWM controller KA3525A is connected to the PWM isolation transformer, and the PWM isolation transformer is connected to the IGBT switching tubes (Q1, Q2). The PWM controller (IC1) judges the magnitude relationship between the high-voltage feedback (BF) and the reference voltage (DA), and provides a pulse-width modulation signal with a settable frequency to the IGBT switching tubes (Q1, Q2) through the PWM isolation transformer (T1). The IGBT switching tubes (Q1, Q2) drive the PWM transformer, boost the input PWM transformer, invert it through the inverter circuit to output a high-voltage pulse, and then double-voltage rectify it into a DC high voltage through the boost rectifier circuit and output it through the current-limiting protection circuit.

[0045] Among them, the left circuit of the current sampling transformer (T2) is the current feedback protection circuit, and the series-connected R5 to R11 are the current sampling protection.

[0046] such as Figure 5 described, it is the current sampling circuit applied to the signal conversion and latching unit, Figure 5 in which "E" is the negative terminal connecting to the high-voltage DC output. All the current of the high-voltage DC passes through the load, goes through the current sampling circuit from the E terminal and then grounds.

[0047] In this embodiment, the detection system only detects the current value output from the inside of the system to the outside. The sampling of the current refers to the current value of the high-voltage DC output from the inside of the detection system to the protected device under test through the commutation and interlock circuit.

[0048] For the sampling of small currents, when the current I is low, the voltage at the upper end of R90 is lower than the voltage at pin 2 of U14 (OP07). U14 outputs a low level, and Q12 (TIP41C) is cut off. The only path for the current is through R90, L5, then through R97, and input to pin 10 of the output of U16 (ICL7650), generating a negative voltage U1 linearly related to the current at pin 10 of U16. This negative voltage U1 passes through an inverting proportional amplifier composed of U17 (ICL7650) and its configuration circuit to generate a positive voltage IN1 linearly related to the current I.

[0049] Among them, the small current sampling circuit includes: Point E is connected to one end of capacitor C97 after being connected in series with R90 and L5. U16 and U17 are connected in series. A parallel combination of capacitor C79 and resistor R97 is connected between pin 4 and pin 10 of U16. Pin 10 of U16 is connected to pin 4 of U17 after being connected in series with resistor R101. A resistor R96 and a potentiometer RP3 are connected in series between pin 4 and pin 10 of U17. Pin 10 of U17 outputs IN1 after being connected in series with resistor R103. A parallel combination of D34 and capacitor C85 is connected between resistor R103 and the output IN1. D34 is a protection circuit for the AD signal. A protection circuit for the small current sampling part, which is a parallel combination of D33, R102, D36, R98, and D35, is connected to U16.

[0050] The main control unit receives the positive voltage IN1, performs AD conversion, program filtering, and proportional conversion to obtain the current I of the high-voltage output. This sampling method has high sampling accuracy and a low lower limit. However, when the current I of the high-voltage output is greater than or equal to the current upper limit I1 input to U16, the relationship between the finally obtained voltage IN1 and the actual current is distorted. Therefore, a large current sampling is designed and added.

[0051] For the sampling of large currents, when the current I is greater than or equal to the low-gear current sampling limit I1, the voltage at the upper end of R90 is approximately equal to the voltage at pin 2 of U14. U14 outputs a high level, and Q12 conducts, causing the current I2 exceeding the low-gear current sampling limit I1 to flow to ground through R83, Q12, and R93. At this time, a positive voltage U2 linearly related to the current I2 is generated at the upper end of R93. The positive voltage U2 passes through a proportional amplifier composed of U13 and its configuration circuit to generate a positive voltage IN2 linearly related to the current I2. When U14 outputs a high level to enable high-gear current sampling, Q13 also conducts, and a signal H_I is sent to the main control unit through an optocoupler to set the position, enabling the main control unit to determine the current sampling gear. After that, the main control unit performs AD conversion, program filtering, and proportional conversion on this voltage IN2 and adds the low-gear current sampling I1 to obtain the high-voltage output current I.

[0052] For the circuit of high - current sampling: Point E is connected to one end of resistor R87. The other end of resistor R87 is connected to pin 3 of operational amplifier U14. A resistor R86 is connected in series to pin 6 of operational amplifier U14. The other end of resistor R86 is connected to the base of transistor Q12 and one end of resistor R95 respectively. The collector of transistor Q12 is connected to point E after series - connecting circuit R83. One end of the emitter of transistor Q12 is connected to resistor R93 and resistor R84 respectively. The other end of resistor R93 is grounded, and the other end of resistor R84 is connected to operational amplifier U13 (OP07). A resistor R80 is connected in series between pin 2 and pin 6 of operational amplifier U13. After connecting resistor R79 to one end of R80, IN2 is output. A parallel - connected D31 and C71 are connected between R79 and output IN2. The other end of R80 is also connected to resistor R78 and then grounded. D31 is the protection circuit for AD signals. A voltage zero - adjustment circuit composed of R91, RP2, and R92 in series is connected to U14.

[0053] The other end of resistor R95 is connected to the base of transistor Q13 (9013). The collector of transistor Q13 is connected to optocoupler IC4, and the emitter of transistor Q13 is grounded.

[0054] As Figure 4 shown, it also includes a protection unit, and the functions of the protection unit are as follows:

[0055] High - voltage emergency stop 1: The 25V generated by LM317 (U1) is the power supply for the PWM control module. When the main control unit determines that it is necessary to emergently stop the PWM control unit from the power supply, the main control unit controls LM317 (U1) to cut off the 25V power supply through the Hv - shut signal, thus achieving the effect of emergency stop.

[0056] High - voltage emergency stop 2: The main control unit controls the SD signal through S +, S - signals. The SD signal is connected to the SD emergency stop pin of the PWM controller KA3525A of the PWM control unit. The PWM controller KA3525A adjusts or shuts off the output pulse - width modulation signal according to the SD signal, changing the final high - voltage DC output to achieve the protection effect.

[0057] Current protection 1: The current - sampling transformer generates a sub - current linearly related to the main current by inducing the main current at the primary end of the step - up transformer leading to the step - up rectification module. A voltage is generated by grounding through R7 and R8, and after being adjusted by the potentiometer POT1, the final signal is the voltage OII linearly related to the main current. Then it is connected to the SD emergency stop pin of the PWM controller KA3525A. When the current is too large, the PWM controller KA3525A can adjust the output pulse - width modulation signal according to the SD signal, finally changing the high - voltage DC output to achieve the protection effect.

[0058] Current protection 2: The current-limiting sampling resistors R13 to R19 are connected in series to the output of the high-voltage DC. The main control unit has high-voltage sampling circuits at both the HDC and L ends of the current-limiting sampling resistors R13 to R19. The difference between the two sampling circuits is taken to obtain the pressure difference ΔU of the current-limiting sampling resistor group R13 to R19. When the current of the high-voltage DC output increases, since the resistance remains unchanged (ignoring temperature drift), ΔU will also increase. After debugging, the main control unit can take corresponding actions based on the value of ΔU to achieve the second-stage current protection function.

[0059] Overcurrent protection latching: When the current is too large, the voltage OII that is linearly related to the main current also increases. When OII is greater than or equal to the reference voltage POT, a rising edge will be generated at pin 7 of the comparator LM311 (U2), triggering the latch CD4013 (U3) to output a latching signal OI to the main control unit. This latching signal will continue until the main control unit controls the RSOI signal to reset the latch CD4013 (U3) after making a judgment and taking action.

[0060] Temperature protection: A temperature switch is installed on the heat sink of the IGBT in the internal boost module of the detection system. When the temperature is too high, the temperature switch acts, and the over-temperature signal is transmitted to the main control unit through the isolation circuit, and the main control unit realizes the over-temperature protection action.

[0061] Embodiment 2

[0062] As Figure 2 shown, this embodiment provides a method for testing the non-linear characteristics of a generator over-voltage protection device. The testing process is controlled by software. The software architecture of this embodiment is based on the hardware architecture of Embodiment 1. The software as a whole includes a centralized control layer, a communication module, and a device layer. The centralized control layer includes a self-check module, a parameter management module, a data analysis module, a display module, and a storage module; the communication module includes a communication interface unit and a data conversion and processing unit; the device layer includes a self-protection module, an output control module, a data acquisition module, and a debugging module.

[0063] The software architecture can implement functions such as instrument self-check, test mode selection, test voltage control, device communication, data analysis, test result display, and storage.

[0064] Using RS232 communication, the tester conducts human-computer interaction with the device through the touch screen, controlling the device to convert the power supply into a test voltage to test the generator over-voltage protection device under test.

[0065] The software control flow is as Figure 6 shown, and the specific process is as follows:

[0066] 1) First, perform instrument self-check. If there is no abnormality in the self-check, proceed to the next step. If an abnormality is found in the self-check, block the voltage output and repair the instrument.

[0067] 2) Test parameter setting. After the self-check is completed, the tester needs to select the test mode and preset the change parameters of the output voltage.

[0068] 3) After the parameters are set, the main control unit issues a control command to control the test voltage output to the overvoltage protection device of the generator under test.

[0069] In the automatic mode, the output voltage starts from the initial voltage and changes step by step automatically to the final voltage in steps with the step voltage and step time as the amplitude; in the manual mode, the output voltage is adjusted by the tester's rotation of the encoder.

[0070] 4) The collected test data is uploaded to the main control unit for data conversion, processing, and analysis and calculation of various test indicators.

[0071] 5) The test results are transmitted to the display screen for display and stored in the memory.

[0072] The control commands sent by the centralized control layer are processed by the communication module and then sent down to the device layer; the data collected by the device layer is format-converted through the communication module and then sent up to the centralized control layer to complete all index calculations. The specific functions of the software are as follows:

[0073] 1. Adaptive upper and lower limits: The voltage change rate of the high-voltage mode setting item of the device is in the form of V / S as an integer, and the initial, turning, and final voltages are all adjusted in a gradient of 5V. This results in a non-divisible problem that is likely to occur when the user sets the corresponding parameters. To solve this problem, the software automatically calculates the divisor and remainder and automatically modifies the corresponding setting item to the nearest turning and final voltage values that are divisible and greater than the original setting value to facilitate the test.

[0074] 2. Self-filling form and automatic scaling curve function: To more clearly display the curve on the screen of the existing device, the device will calculate the expected maximum voltage and test time after the setting items are set and before the test starts. Before the test starts, the scale lines of voltage, current, and time are automatically filled with parameters. And the sampled value curve is automatically scaled according to this coordinate system.

[0075] 3. Automatic judgment of critical points: The device uses the median value averaging filtering method for each sampled value, which can effectively prevent accidentally occurring pulse-type interference and eliminate the sampling deviation caused by pulse interference. Calculate the change rates of the real-time output current and output voltage of the overvoltage protection device of the generator under test. When the growth rate of the output current is continuously greater than the growth rate of the output voltage and keeps increasing after the output voltage rises, it is judged that the leakage current of the overvoltage protection device of the generator under test increases, and the current critical point output current value and output voltage value are recorded.

[0076] Those skilled in the art should understand that the various modules or steps of the present invention described above can be implemented by a general-purpose computer device. Optionally, they can be implemented by program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, or they can be separately fabricated into individual integrated circuit modules, or multiple modules or steps among them can be fabricated into a single integrated circuit module for implementation. The present invention is not limited to any specific combination of hardware and software.

[0077] Although the specific implementation manners of the present invention have been described above in conjunction with the accompanying drawings, it is not a limitation on the protection scope of the present invention. Those skilled in the art should understand that various modifications or deformations that can be made without creative efforts by those skilled in the art on the basis of the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A non-linear characteristic test system for an overvoltage protection device of a generator, characterized in that, it includes a PWM control unit, a main control unit, a signal conversion and latching unit, and a voltage feedback unit; The signal conversion and latching unit is used to output the test current input to the protection device under test to the main control unit; The voltage feedback unit is used to output the test voltage input to the overvoltage protection device of the generator under test to the PWM control unit and the main control unit; The main control unit adjusts the reference voltage value according to the voltage signal output by the signal conversion and latching unit and the voltage feedback signal output by the voltage feedback unit, and outputs the adjusted reference voltage value to the PWM control unit; The PWM control unit judges the magnitude relationship between the voltage value fed back by the voltage feedback unit and the reference voltage value, and outputs a pulse width modulation signal to adjust the test voltage input to the overvoltage protection device of the generator under test; The signal conversion and latching unit includes a current sampling circuit; Current sampling refers to the current value of the high-voltage direct current output to the protection device under test through the commutation and interlocking circuit inside the detection system; When the current signal input to the overvoltage protection device of the generator under test is too large, the signal conversion and latching unit performs large-current sampling on the current signal, and the main control unit executes overcurrent protection latching after judging according to the output voltage of the conversion and latching unit.

2. A non-linear characteristic test system for an overvoltage protection device of a generator according to claim 1, characterized in that, it further includes a voltage output unit, and the voltage output unit specifically includes a rectification circuit, an inversion circuit, a boost rectification circuit, and a commutation and interlocking circuit connected in sequence; After the AC power supply is converted into an AC voltage with adjustable amplitude through the rectification circuit and the inversion circuit, it outputs a DC voltage through the boost rectification circuit, and switches the direction through the commutation and interlocking circuit and outputs it to the input end of the overvoltage protection device of the generator under test; The PWM control unit is connected to the inversion circuit to adjust the AC voltage output by the inversion circuit.

3. A non-linear characteristic test system for an overvoltage protection device of a generator according to claim 1, characterized in that, The main control unit controls the power on and off of the PWM control unit to execute high-voltage emergency stop protection; Or, the PWM control unit adjusts or turns off the output pulse width modulation signal according to the SD signal sent by the main control unit, and changes the high-voltage direct current input to the overvoltage protection device of the generator under test to execute protection.

4. A non-linear characteristic test system for an overvoltage protection device of a generator according to claim 1, characterized in that, The conversion and latching unit processes the received overcurrent analog signal and sends it to the PWM control unit, and the PWM control unit adjusts the output pulse width modulation signal according to the output of the conversion and latching unit, and changes the test voltage input to the overvoltage protection device of the generator under test.

5. A non-linear characteristic test system for an overvoltage protection device of a generator according to claim 1, characterized in that, The main control unit makes a difference between the test voltage input to the overvoltage protection device of the generator under test and the voltage value after the high-voltage direct current output input to the overvoltage protection device of the generator under test passes through a series-connected sampling resistor, and performs corresponding actions to execute current protection.

6. A nonlinear characteristic test system for a generator overvoltage protection device as claimed in claim 2, It is characterized in that A temperature switch is installed on the switch tube in the boost rectifier circuit, and the main control unit judges the temperature signal to perform over-temperature protection action.

7. A method for testing the nonlinear characteristics of a generator overvoltage protection device, using a nonlinear characteristics testing system for a generator overvoltage protection device as claimed in claim 1, It is characterized in that include: Receive the issued control instructions, and provide the test voltage to the overvoltage protection device of the generator under test according to the control instructions; The test voltage starts from the initial voltage, with the stepper motor and step time as the amplitude, and changes step by step to the final test voltage of the generator overvoltage protection device under test; The output data of the overvoltage protection device of the generator under test is collected and converted for analysis.

8. A method for testing the nonlinear characteristics of a generator overvoltage protection device as claimed in claim 7, It is characterized in that The final test voltage of the generator overvoltage protection device under test can be manually adjusted by the tester.

9. A method for testing the nonlinear characteristics of a generator overvoltage protection device as claimed in claim 7, It is characterized in that Calculate the real-time output current and output voltage change rates of the overvoltage protection device of the generator under test. When the calculated output current growth rate is continuously greater than the output voltage growth rate and continues to increase after the output voltage increases, it is determined that the leakage current of the overvoltage protection device of the generator under test increases and record the current critical point output current value and output voltage value.

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