Method and circuit for measuring partial discharge peak value based on single-chip microcomputer

Abstract

The invention discloses a partial discharge peak value measuring method and measuring circuit based on a single-chip microcomputer, and belongs to the field of partial discharge detection and diagnosis of power equipment. According to the method, a first operational amplifier unit is adopted to collect partial discharge signals, and an inverted input end receives output signals of a second operational amplifier unit. The voltage V1 of the output signal of the first operational amplifier unit is compared with the noise voltage Vref, if V1 is larger than Vref, the first operational amplifier unit and the energy storage capacitor are conducted, V1 is further compared with the voltage V2 of the output signal of the second operational amplifier unit, if V1 is larger than V2, the energy storage capacitor is charged, and otherwise, the voltage V2 is kept by the energy storage capacitor. When V2 is larger than reference voltage VDAC, VDAC is progressively increased and stored, otherwise, the monostable multivibrator unit generates an excitation pulse, the excitation pulse controls the second analog switch to enable the energy storage capacitor to discharge, VDAC is output, and peak voltage of the partial discharge signal is calculated. Accurate peak capture of the partial discharge signal is realized through progressive comparison, and the method is applicable to monitoring of high-voltage equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of power equipment discharge detection, and particularly to a method and a circuit for measuring partial discharge peak value based on a single-chip microcomputer. Background Art

[0002] Partial discharge (PD) is the main manifestation of electrical insulation faults in power equipment. To detect and diagnose insulation defects, it is necessary to collect partial discharge signals. Signal peak detection has wide applications in the fields of wireless communication and radio frequency systems. Digital wireless communication signals have relatively stable detection envelopes, so amplitude / peak value measurement of wireless communication signals can usually be achieved using a detector. However, ultra-high frequency (UHF) partial discharge signals consist of high-speed pulse trains with a certain degree of repetition but non-fixed periods and have a low duty cycle. The bandwidth of UHF partial discharge signals can reach more than 1 GHz. Usually, after filtering and amplification, envelope detection is used to down-convert the frequency. The partial discharge signal after detection and frequency down-conversion is still a pulse signal, and its bandwidth is generally between several MHz and several tens of MHz. For example Figure 1 , the UHF partial discharge signal of the main circuit is processed by filtering, amplification and detection to obtain a detectable partial discharge signal. The partial discharge detection system of high-voltage equipment generally digitizes the detected partial discharge signal using analog-to-digital conversion (ADC), and then performs various digital signal processing according to application requirements. For applications that require peak detection, parameters such as the peak value of the partial discharge signal can be extracted by a digital processing unit. Due to the low duty cycle characteristic of the partial discharge signal, when using ADC for continuous sampling, most of the data are invalid data corresponding to 0 values or noise interference, and the valid data only exist in the short-term partial discharge pulse part. In addition, the high power consumption and high cost problems of high-speed ADCs further increase the challenges of realizing partial discharge location and classification recognition in resource-constrained power Internet of Things sensing terminals. Therefore, it is necessary to design a partial discharge signal peak detection technology with low data volume and low power consumption to be applicable to the diagnosis of insulation defects of power equipment on resource-constrained hardware platforms. Summary of the Invention

[0003] Aiming at the high-speed ultra-wideband, low duty cycle and non-stationary characteristics of UHF partial discharge signals in high-voltage equipment, the present invention provides a method and a circuit for measuring partial discharge peak value based on a single-chip microcomputer, which directly detect the discharge peak value by the single-chip microcomputer, avoiding the storage, processing and transmission of a large amount of continuously sampled partial discharge data.

[0004] The invention object of the present application can be achieved by the following technical means: A method for measuring partial discharge peak value based on a single-chip microcomputer, comprising the following steps: Step 1: The non-inverting input terminal of the first operational amplifier unit collects the partial discharge signal. The first operational amplifier unit responds to the partial discharge signal and generates an output signal, and the inverting input terminal of the first operational amplifier unit receives the output signal of the second operational amplifier unit; Step 2: Compare the voltage V1 of the output signal of the first operational amplifier unit with the noise voltage V ref , if V1 is greater than V ref , the first analog switch conducts the first operational amplifier unit and the energy storage capacitor, enter Step 3, otherwise disconnect the first operational amplifier unit and the energy storage capacitor, and return to Step 1; Step 3: Compare the voltage V1 of the output signal of the first operational amplifier unit with the voltage V2 of the output signal of the second operational amplifier unit. When V1 is greater than V2, enter Step 4. When V1 is less than V2, enter Step 7. Otherwise, the inverting input terminal of the first operational amplifier unit and the output terminal of the second operational amplifier unit are in a virtual open state, and return to Step 1; Step 4: The first diode is reverse cut-off, the second diode is forward biased, the energy storage capacitor is in a charging state, and the voltage V2 increases; Step 5: Compare V2 with the reference voltage V DAC , if V2 is greater than or equal to V DAC , V DAC increases, store the increased V DAC , and return to Step 1. Otherwise, enter Step 6; Step 6: The monostable multivibrator unit generates an excitation pulse. When the second analog switch receives the excitation pulse, it grounds both ends of the energy storage capacitor. The energy storage capacitor is in a discharging state, output V DAC and calculate the peak voltage of the partial discharge signal, and return to Step 1; Step 7: The first diode is forward conducting, the second diode is reverse biased, the voltage V2 remains unchanged, and return to Step 1.

[0005] A measurement circuit for implementing the above-mentioned method for measuring the peak value of partial discharge based on a single-chip microcomputer, comprising: A first operational amplifier unit, the non-inverting input terminal of the first operational amplifier unit is connected to the main circuit for collecting partial discharge signals; An energy storage capacitor for receiving the partial discharge signal and charging; A first diode for connecting in series the inverting input terminal and the output terminal of the first operational amplifier unit; A second diode, the second diode is located between the output terminal of the first operational amplifier unit and the energy storage capacitor; A second operational amplifier unit, the non-inverting input terminal of the second operational amplifier unit is connected to the output terminal of the first operational amplifier unit through the second diode; A single-chip microcomputer, including a noise reduction unit and a peak value measurement unit. The noise reduction unit is used to compare the voltage V1 of the output signal of the first operational amplifier unit with the noise voltage V ref, the peak measurement unit is used to compare the voltage V2 of the output signal of the second operational amplifier unit with the reference voltage V DAC ; The first analog switch is used to conduct the output terminal of the first operational amplifier unit and the energy storage capacitor when V1 is greater than V ref ; The monostable multivibrator unit is used to output an excitation pulse when V2 is less than V DAC ; The second analog switch is used to ground both ends of the energy storage capacitor when receiving the excitation pulse, where when V1 is greater than V2, the first diode is reversely cut off, the second diode is forward biased, the energy storage capacitor is in the charging state, and the voltage V2 increases, when V1 is equal to V2, the inverting input terminal of the first operational amplifier unit and the output terminal of the second operational amplifier unit are in the virtual open state, when V1 is less than V2, the first diode is forward conducting, the second diode is reversely biased, and the voltage V2 remains unchanged.

[0006] In the present invention, when V2 is greater than or equal to V DAC , the peak measurement unit increments V DAC , and stores the incremented V DAC , when V2 is less than V DAC , the peak measurement unit outputs V DAC and then resets V DAC to the initial voltage V th .

[0007] In the present invention, the inverting input terminal of the first operational amplifier unit is connected to the output terminal of the second operational amplifier unit through a current limiting resistor, and the inverting input terminal of the second operational amplifier unit is connected to the output terminal of the second operational amplifier unit.

[0008] In the present invention, the denoising unit includes a first comparator and a first converter, the first converter outputs a noise voltage to the first comparator, the peak measurement unit includes a second comparator and a second converter, the second converter outputs a reference voltage to the second comparator, and when the second comparator is at a high level, the second converter increases the reference voltage.

[0009] In the present invention, the first diode and the second diode are Schottky diodes.

[0010] In the present invention, an operation unit is further included, and the operation unit is used to calculate the peak voltage of the partial discharge signal according to V DAC .

[0011] In the present invention, the measurement circuit further includes a radio frequency band-pass filter, a low-noise amplifier, and a detector, and the radio frequency band-pass filter, the low-noise amplifier, and the detector are located between the main circuit and the non-inverting input terminal of the first operational amplifier unit.

[0012] In the present invention, the monostable multivibrator unit has an adjustable resistor and an adjustable capacitor, and controls the duration of the excitation pulse according to the adjustable resistor and the adjustable capacitor.

[0013] Implementing the method and circuit for measuring the partial discharge peak value based on a single-chip microcomputer of the present invention, the beneficial effects are as follows: 1. The present invention uses the peak value measurement unit (DAC module) in the single-chip microcomputer to hold and record the discharge peak value, simplifies the circuit structure, makes the measurement result more stable and reliable, is easy to implement, and does not affect other applications of the single-chip microcomputer function at the same time.

[0014] 2. The present invention can achieve the peak value measurement of the partial discharge signal without a high-speed ADC converter, reduces the power consumption, does not require large-capacity data storage and processing, reduces the system requirements and its cost, and is suitable for the actual on-site deployment of partial discharge sensing terminals with limited resources.

[0015] 3. The single-chip microcomputer of the present invention directly records the peak voltage, neither requires complex data processing on the ground to extract the peak voltage of the partial discharge signal, nor requires a large amount of data transmission for off-site data processing to extract the peak voltage, thereby reducing the wireless communication burden and meeting the application requirements of the power Internet of Things sensing terminal. Description of the Drawings

[0016] Figure 1 is the schematic diagram of the existing partial discharge peak measurement circuit; Figure 2 is the schematic diagram of the measurement circuit for implementing the method for measuring the partial discharge peak value based on a single-chip microcomputer of the present invention; Figure 3 is the flowchart of the method for measuring the partial discharge peak value based on a single-chip microcomputer of the present invention; Figure 4 is the discharge waveform diagram of the method for measuring the partial discharge peak value based on a single-chip microcomputer of the present invention; Figure 5 is the partial schematic diagram of the measurement circuit for implementing the method for measuring the partial discharge peak value based on a single-chip microcomputer of the present invention; Figure 6 is the schematic diagram of the partial discharge signal in the main circuit of the present invention; Figure 7 is the schematic diagram of the partial discharge signal input to the first operational amplifier unit of the present invention; Figure 8 is the schematic diagram of the output signal of the second operational amplifier unit of the present invention; Figure 9 is the schematic diagram of the radio frequency band-pass filter of the present invention; Figure 10 is the schematic diagram of the low-noise amplifier of the present invention; Figure 11 Schematic diagram of the detector of the present invention; Figure 12 Flow chart of the operation of the single-chip microcomputer of the present invention. Specific embodiments

[0017] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention.

[0018] Such as Figure 1 , the traditional partial discharge detection receiver includes front-end signal preprocessing, ADC analog-to-digital conversion, and data storage & processing units composed of filtering, amplification, and detection. The method of digitizing signals and then extracting signal features such as peaks has the disadvantages of large data volume, high power consumption, and complex data processing. To solve the above problems, the present invention adopts a partial discharge peak measurement method based on a single-chip microcomputer. Such as Figure 2 , the measurement circuit of the present invention uses a peak holding circuit, and the single-chip microcomputer realizes the peak measurement of the partial discharge signal, and finally outputs the peak voltage of the partial discharge signal through the operation unit. Further, the present invention also includes a front-end signal processing circuit composed of filtering, amplification, and detection, which receives the ultra-high frequency partial discharge signal of the main circuit, and is converted into a processable partial discharge signal output through filtering, amplification, and detection processing. Embodiment 1

[0019] Referring to Figure 3 , the partial discharge peak measurement method based on a single-chip microcomputer of the present invention described in detail in this embodiment includes the following steps.

[0020] Step 1: The in-phase input terminal of the first operational amplifier unit collects the partial discharge signal, the first operational amplifier unit responds to the partial discharge signal and generates an output signal, and the anti-phase input terminal of the first operational amplifier unit receives the output signal of the second operational amplifier unit.

[0021] Step 2: Compare the voltage V1 of the output signal of the first operational amplifier unit with the noise voltage V ref , if V1 is greater than V ref , the first analog switch conducts the first operational amplifier unit and the energy storage capacitor, and enters Step 3. Otherwise, the first operational amplifier unit and the energy storage capacitor are disconnected, and the process returns to Step 1.

[0022] Step 3: Compare the voltage V1 of the output signal of the first operational amplifier unit with the voltage V2 of the output signal of the second operational amplifier unit. When V1 is greater than V2, enter Step 4. When V1 is less than V2, enter Step 7. Otherwise, the anti-phase input terminal of the first operational amplifier unit and the output terminal of the second operational amplifier unit are in a virtual open state, and the process returns to Step 1. The voltage V2 is the voltage across the energy storage capacitor.

[0023] Step 4: The first diode is reverse-biased and cut off, the second diode is forward-biased, the energy storage capacitor is in the charging state, and the voltage V2 increases. When V1 is greater than V2, the partial discharge signal is in the rising stage. The voltage at the non-inverting input terminal of the first operational amplifier is greater than that at the inverting input terminal of the first operational amplifier. The first operational amplifier outputs the voltage V1. The first diode is reverse-biased and cut off, the second diode is forward-biased, the voltage V1 charges the energy storage capacitor through the second diode. The energy storage capacitor is connected to the non-inverting input terminal of the second operational amplifier, and the voltage V2 increases.

[0024] Step 5: Compare V2 with the reference voltage V DAC , if V2 is greater than or equal to V DAC , V DAC increases, store the increased V DAC , return to Step 1, otherwise enter Step 6. The present invention does not limit the voltage step size of the increase of V DAC . When it is necessary to quickly detect the peak voltage, a larger voltage step size is set to improve the iteration speed. When it is necessary to improve the detection accuracy, a smaller voltage step size is set.

[0025] Step 6: The monostable multivibrator unit generates an excitation pulse. When the second analog switch receives the excitation pulse, it grounds both ends of the energy storage capacitor. The energy storage capacitor is in the discharging state, output V DAC and calculate the peak voltage of the partial discharge signal, then return to Step 1. In this embodiment, the peak voltage is 1V. After outputting V DAC , reset the reference voltage.

[0026] Step 7: The first diode is forward-conducting, the second diode is reverse-biased, the voltage V2 remains unchanged, and return to Step 1. When V1 is less than V2, the partial discharge signal is in the falling stage, the voltage V1 decreases, the second diode is reverse-biased, V2 reaches the peak voltage of the partial discharge signal, and the energy storage capacitor maintains the voltage V2 unchanged. Ideally, the diode has two states: forward-conducting and reverse-biased and cut off. In a specific embodiment, forward-conducting can be understood as forward-biased or connecting the positive electrode to the P region (anode) and the negative electrode to the N region (cathode). Reverse-biased can be understood as reverse-biased and cut off or connecting the positive electrode to the N region (cathode) and the negative electrode to the P region (anode). Embodiment 2

[0027] Refer to Figures 4 to 8 , a measurement circuit for implementing the method for measuring the peak value of partial discharge based on a single-chip microcomputer, including a first operational amplifier unit, an energy storage capacitor, a first diode, a second diode, a second operational amplifier unit, a single-chip microcomputer, a first analog switch, a monostable multivibrator unit, and a second analog switch.

[0028] The non-inverting input terminal of the first operational amplifier unit is connected to the main circuit for collecting partial discharge signals. The first operational amplifier is implemented by a high-speed operational amplifier. In this embodiment, the model of the high-speed operational amplifier selected is, for example, COS8092. This high-speed operational amplifier has a 350 MHz @ -3 dB bandwidth and a quiescent operating current of 4.5 mA. The first operational amplifier unit is used to output voltage V1 and charge the energy storage capacitor.

[0029] The energy storage capacitor is used to receive partial discharge signals and charge. In this embodiment, the capacitance C1 of the energy storage capacitor is 4 nF.

[0030] The first diode is used to connect the inverting input terminal and the output terminal of the first operational amplifier unit in series. The second diode is located between the output terminal of the first operational amplifier unit and the energy storage capacitor. The first diode and the second diode are Schottky diodes. Schottky diodes have the characteristics of low forward conduction voltage drop and extremely short reverse recovery time. The model of the Schottky diode is, for example, IN5819.

[0031] The non-inverting input terminal of the second operational amplifier unit is connected to the output terminal of the first operational amplifier unit through the second diode. The inverting input terminal of the first operational amplifier unit is connected to the output terminal of the second operational amplifier unit through a current-limiting resistor. The inverting input terminal of the second operational amplifier unit is connected to the output terminal of the second operational amplifier unit. In this embodiment, the resistance value R1 of the current-limiting resistor is 1 kΩ.

[0032] The single-chip microcomputer includes a denoising unit and a peak measurement unit. The single-chip microcomputer is, for example, an STM32L476 single-chip microcomputer.

[0033] The denoising unit is used to compare the voltage V1 of the output signal of the first operational amplifier unit with the noise voltage V ref , and its physical meaning is to eliminate the interference noise of the partial discharge signal. The denoising unit includes a first comparator and a first converter. The first converter outputs the noise voltage to the first comparator. The model of the first comparator is, for example, TLV3502. The noise voltage V ref can be given by the first converter according to actual needs. When the system noise and interference in the working environment are strong, the noise voltage V ref can be appropriately increased. On the contrary, the noise voltage V ref can be appropriately decreased.

[0034] The peak measurement unit is used to compare the voltage V2 of the output signal of the second operational amplifier unit with the reference voltage V DAC . The peak measurement unit includes a second comparator and a second converter. The second converter outputs the reference voltage to the second comparator. When the second comparator is at a high level, the second converter increases the reference voltage. When V2 is greater than or equal to V DAC , the peak measurement unit increments V DAC according to the voltage step and stores the incremented V DAC, V2 is less than V DAC When, the peak measurement unit outputs V DAC After that, V DAC is reset to the initial voltage V th . The initial voltage is set to a lower value according to actual requirements. Since the peak voltages of different partial discharge signals are not stable and consistent, to ensure that the peak voltages of each partial discharge signal are monitored, the initial voltage V th should not be set too high.

[0035] Increment V DAC The voltage step can be 20 mV, and the initial voltage V th can be 0.2 V. Refer to Figure 4 , the measurement time of the peak voltage is related to the magnitude of the peak voltage and the rate of the second converter. When the rate of the second converter is fixed, the larger the peak voltage, the longer the measurement time. The accuracy of the peak voltage collected by the second converter is affected by the voltage step and the rate of the second converter. If the voltage step is large, the collected peak voltage may be much larger than the actual peak voltage, resulting in a large measurement error. If the voltage step is small, the reference voltage V DAC requires more increment times to achieve the measurement of the peak voltage, and the measurement time is longer.

[0036] In a more preferred embodiment, the initial voltage V th = max(αV min , kV ref ), the voltage step ΔV = βV0 / 2 N , where, V min is the minimum value of the recent multiple peak voltages recorded, k is the noise safety factor, k takes 1.5 - 3, α is the peak adjustment coefficient, 0.1 ≤ α ≤ 0.3, N is the resolution bits of the second converter, V0 is the reference voltage of the second converter (determined by the hardware design of the second converter), the reference voltage determines the maximum reference voltage that the second converter can output, β is the increment step, β ∈ {1, 2, 3, 4}. In this embodiment, the resolution bits of the second converter are 8, the reference voltage is 3.3 V, and β is 2, then the voltage step ΔV = 2 / 2 8 × 3.3 V = 25.78 mV. As Figure 8 , the measurement time is 75 us, and the collected peak voltage is 1 V.

[0037] The first analog switch is used to conduct the output terminal of the first operational amplifier unit and the energy storage capacitor when V1 is greater than V ref . When the first analog switch is closed, the output terminal of the first operational amplifier unit is conducted with the energy storage capacitor, and the energy storage capacitor is in a charging state. When the first analog switch is opened, the measurement circuit is in a peak hold state.

[0038] The monostable multivibrator unit is used to output an excitation pulse when V2 is less than V DAC At this time, the monostable multivibrator unit has an adjustment resistor and an adjustment capacitor, and controls the duration of the excitation pulse according to the adjustment resistor and the adjustment capacitor. In this embodiment, the model of the monostable multivibrator unit is, for example, 74LVC1G123, which is used to output an excitation pulse with a fixed duration, and the fixed duration can be set according to the adjustment resistor and the adjustment capacitor. The resistance value of the adjustment resistor is 10 kΩ, and the capacitance of the adjustment capacitor is 10 nF.

[0039] The second analog switch is used to ground both ends of the energy storage capacitor when receiving the excitation pulse. When the second analog switch is turned on, both ends of the energy storage capacitor are grounded, and the energy storage capacitor is in a discharging state. At the same time, the reference voltage V DAC of the second converter is reset to the initial voltage V th .

[0040] The working process of the measurement circuit includes: when V1 is greater than V2, the first diode is reversely cut off, the second diode is forward-biased, the energy storage capacitor is in a charging state, and the voltage V2 increases; when V1 is equal to V2, the inverting input terminal of the first operational amplifier unit and the output terminal of the second operational amplifier unit are in a virtual open state; when V1 is less than V2, the first diode is forward-conducted, the second diode is reversely biased, and the voltage V2 remains unchanged.

[0041] The measurement circuit further includes an operation unit, and the operation unit is used to calculate the peak voltage of the partial discharge signal according to the reference voltage V DAC . The operation unit, for example, according to the amplification ratio of the operational amplifier unit, converts the finally output reference voltage V DAC into the peak voltage of the ultra-high frequency partial discharge signal (UHF-PD signal). The present invention may also not include an operation unit and directly output the finally maintained reference voltage V DAC as the peak voltage.

[0042] The measurement circuit further includes a radio frequency band-pass filter, a low-noise amplifier, and a detector. The radio frequency band-pass filter, the low-noise amplifier, and the detector are located between the main circuit and the non-inverting input terminal of the first operational amplifier unit. When the ultra-high frequency partial discharge signal comes in the main circuit, the radio frequency band-pass filter filters the ultra-high frequency partial discharge signal, the low-noise amplifier low-noise amplifies the filtered signal to increase the signal amplitude, and the detector then detects the amplified signal and converts it into a processable partial discharge signal for output.

[0043] In this embodiment, as Figure 9, the radio frequency band - pass filter can retain the signals in the frequency band of 150 MHz - 530 MHz in the UHF partial discharge signals. While retaining the main partial discharge signals, it removes the electromagnetic interference generated by other electrical equipment and the clutter interference of wireless communication. The radio frequency band - pass filter includes seven capacitors and seven inductors. Among them, the capacitances of the seven capacitors are C3, C4, C5, C6, C7, C8, and C9 respectively, and the inductance values of the seven inductors are L1, L2, L3, L4, L5, L6, and L7 respectively. C3 = C9 = 2 pF, C4 = C8 = 13 pF, C5 = C6 = C7 = 9 pF, L1 = L7 = 100 nH, L2 = L6 = 15 nH, L3 = L4 = L5 = 24 nH, and both the input end and the output end of the radio frequency band - pass filter adopt a 50Ω matching design.

[0044] As Figure 10 , the low - noise amplifier adopts, for example, the AD8354 chip. The noise figure of the AD8354 chip is 4.2, the operating frequency band is 1 MHz - 2.7 GHz, and the gain is 20 dB. The AD8354 chip includes four peripheral capacitors. Among them, the capacitances of the four peripheral capacitors are C 10 , C 11 , C 12 and C 13 , C 10 = C 11 = 1 nF, C 12 = 100 pF, C 13 = 470 pF.

[0045] As Figure 11 , the detector adopts, for example, the ADL5904 chip. The ADL5904 chip has an RMS power detection function, and the operating frequency range is from DC to 6 GHz. It has the characteristics of a wide frequency range, fast response speed, and low power consumption, and can output lower - frequency and smoother partial discharge signals. The peripheral components of the ADL5904 chip include four capacitors and two resistors. Among them, the capacitances of the four capacitors are C 14 , C 15 , C 16 and C 17 , the resistance values of the two resistors are R1 and R2 respectively. C 14 = 470 nF, R1 = 82.5 Ω, C 15 = 100 nF, R2 = 4.02 Ω, C 16 = 100 nF, C 17 = 100 pF. The peak voltage of the partial discharge signal obtained after the UHF partial discharge signal passes through the filtering, amplification, and detection of the radio frequency band - pass filter, low - noise amplifier, and detector is 1 V. Embodiment Three

[0046] This embodiment further discloses the working process of the single-chip microcomputer. The embedded program process of the single-chip microcomputer is as follows Figure 12 shown, including three stages: DAC configuration and system initialization, data acquisition, and data processing and storage.

[0047] The single-chip microcomputer contains a first converter and a second converter (two-channel DAC digital-to-analog converters). In this embodiment, the single-chip microcomputer is, for example, an STM32L476 single-chip microcomputer. The STM32L476 single-chip microcomputer can be configured in 8-bit digital mode during the initialization setting stage. The DAC clock frequency is configured to 80 MHz, the reference voltage is 3.3 V, the set increment step β is 2, and the voltage step is 2 / 256 * 3.3 V = 25.78 mV. The variable d is the digital representation of the reference voltage V DAC of the second converter, and the initial voltage V th of the second converter and the noise voltage V ref of the first converter are set according to the actual situation. In this embodiment, the variable d is set to the value 0E, corresponding to a reference voltage of approximately 0.2 V.

[0048] As shown in Figure 5 , the reference voltage V DAC output by the second converter is compared with the output voltage V2 of the second operational amplifier unit. When the reference voltage V DAC is less than V2, the second comparator outputs a high level, and the variable d increases by 2 until the reference voltage V DAC output by the second converter is greater than V2. Then the second comparator outputs a low level, causing the monostable multivibrator unit to output a trigger pulse (high level) set by the adjustment capacitor and the adjustment resistor. The second analog switch closes, and the energy storage capacitor discharges. The model of the monostable multivibrator unit is, for example, 74LVC123. In this embodiment, there is no operation unit. At this time, the variable d directly output by the second converter is the peak voltage of the partial discharge signal. The variable d is stored in the array D, and the acquisition of the peak voltage is completed.

[0049] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for measuring the peak value of partial discharge based on a single-chip microcomputer, characterized in that, It includes the following steps: Step 1: The non-inverting input terminal of the first operational amplifier unit collects the partial discharge signal. The first operational amplifier unit responds to the partial discharge signal and generates an output signal. The inverting input terminal of the first operational amplifier unit receives the output signal of the second operational amplifier unit. Step 2: Compare the voltage V1 of the output signal of the first operational amplifier unit with the noise voltage V ref , if V1 is greater than V ref , turn on the first analog switch to connect the first operational amplifier unit and the energy storage capacitor, and enter Step 3; otherwise, disconnect the first operational amplifier unit and the energy storage capacitor, and return to Step 1; Step 3: Compare the voltage V1 of the output signal of the first operational amplifier unit with the voltage V2 of the output signal of the second operational amplifier unit. When V1 is greater than V2, go to Step 4; when V1 is less than V2, go to Step 7; otherwise, the inverting input terminal of the first operational amplifier unit and the output terminal of the second operational amplifier unit are in a virtual open state, and return to Step 1. Step 4: The first diode is reverse cut-off, the second diode is forward biased, the energy storage capacitor is in a charging state, and the voltage V2 increases. Step 5: Compare V2 with the reference voltage V DAC , if V2 is greater than or equal to V DAC , V DAC increases, store the increased V DAC , return to Step 1, otherwise go to Step 6; Step 6: The monostable multivibrator unit generates an excitation pulse. When the second analog switch receives the excitation pulse, both ends of the energy storage capacitor are grounded, and the energy storage capacitor is in a discharging state, and the output is V DAC and calculate the peak voltage of the partial discharge signal, and return to Step 1; Step 7: The first diode is forward conducting, the second diode is reverse biased, the voltage V2 remains unchanged, and return to Step 1.

2. A measurement circuit for implementing the method for measuring the partial discharge peak value based on a single-chip microcomputer according to claim 1, characterized in that, It includes: The first operational amplifier unit, the non-inverting input terminal of the first operational amplifier unit is connected to the main circuit for collecting the partial discharge signal; The energy storage capacitor for receiving the partial discharge signal and charging; The first diode for connecting in series the inverting input terminal and the output terminal of the first operational amplifier unit; The second diode, which is located between the output terminal of the first operational amplifier unit and the energy storage capacitor; The second operational amplifier unit, the non-inverting input terminal of the second operational amplifier unit is connected to the output terminal of the first operational amplifier unit through the second diode; The single-chip microcomputer includes a denoising unit and a peak measurement unit. The denoising unit is used to compare the voltage V1 of the output signal of the first operational amplifier unit with the noise voltage V ref , and the peak measurement unit is used to compare the voltage V2 of the output signal of the second operational amplifier unit with the reference voltage V DAC ; The first analog switch is used to conduct the output terminal of the first operational amplifier unit and the energy storage capacitor when V1 is greater than V ref ; A monostable multivibrator unit for outputting a trigger pulse when V2 is less than V DAC ; The second analog switch for grounding both ends of the energy storage capacitor when receiving the excitation pulse, where when V1 is greater than V2, the first diode is reverse cut-off, the second diode is forward biased, the energy storage capacitor is in a charging state, and the voltage V2 increases, when V1 is equal to V2, the inverting input terminal of the first operational amplifier unit and the output terminal of the second operational amplifier unit are in a virtual open state, when V1 is less than V2, the first diode is forward conducting, the second diode is reverse biased, and the voltage V2 remains unchanged.

3. The measurement circuit according to claim 2, characterized in that V2 is greater than or equal to V DAC When this occurs, the peak measurement unit increments V DAC and stores the incremented V DAC When V2 is less than V DAC the peak measurement unit outputs V DAC and then resets V DAC to the initial voltage V th .

4. The measurement circuit according to claim 2, characterized in that The inverting input terminal of the first operational amplifier unit is connected to the output terminal of the second operational amplifier unit through a current limiting resistor, and the inverting input terminal of the second operational amplifier unit is connected to the output terminal of the second operational amplifier unit.

5. The measurement circuit according to claim 2, characterized in that, The noise reduction unit includes a first comparator and a first converter. The first converter outputs a noise voltage to the first comparator. The peak measurement unit includes a second comparator and a second converter. The second converter outputs a reference voltage to the second comparator. When the second comparator is at a high level, the second converter increases the reference voltage.

6. The measuring circuit according to claim 2, wherein The first diode and the second diode are Schottky diodes.

7. The measuring circuit according to claim 2, characterized in that It further includes an arithmetic unit, which is used to calculate the peak voltage of the partial discharge signal according to V DAC ​ 8. The measuring circuit according to claim 2, characterized in that, It also includes a radio frequency band-pass filter, a low-noise amplifier, and a detector, which are located between the main circuit and the non-inverting input terminal of the first operational amplifier unit.

9. The measurement circuit according to claim 2, characterized in that, The monostable multivibrator unit has an adjustable resistor and an adjustable capacitor, and controls the duration of the excitation pulse according to the adjustable resistor and the adjustable capacitor.

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