Realization method for residual voltage frequency measurement module of hydropower station unit

Abstract

The invention discloses a hydropower station unit residual voltage frequency measurement module implementation method, which relates to the technical field of power systems, and comprises the steps of residual voltage acquisition and preprocessing, signal filtering and amplification, signal shaping and isolation, zero-crossing capture, unit residual voltage acquisition by utilizing a PT preceding-stage loop and conversion into a low-voltage signal, signal filtering and amplification, and zero-crossing frequency measurement. Interference is removed through a secondary filtering and amplifying circuit, higher harmonics and alternating current components are filtered out, the signal amplitude and stability are improved, the amplitude, type and level of the signal are processed by means of a forward series diode and an optocoupler, and an ADC sampling signal is output for residual voltage amplitude detection. And after being amplified and filtered by an operational amplifier, the signal zero-crossing moment is detected by a voltage comparator in combination with a counter so as to calculate the frequency, so that high-precision measurement of the residual voltage amplitude and frequency of the hydropower station unit is realized, and key data support is provided for stable operation and control of the unit.

Description

Technical Field

[0001] The invention relates to the technical field of electric power systems, and in particular to a method for realizing a residual pressure frequency measurement module of a hydropower station unit. Background Art

[0002] As the global demand for clean energy grows, the development and utilization of hydropower as a renewable and pollution-free energy source has received widespread attention. Hydropower station units play an important role in energy production. In order to ensure the efficient and stable operation of hydropower stations, accurate measurement of unit operating parameters is essential, and unit residual pressure frequency measurement is one of the key measurement contents. The power grid has strict requirements on the frequency of the units connected to it. The residual pressure frequency measurement of the unit can provide accurate frequency information to ensure that the unit frequency matches the grid frequency and achieve smooth and safe grid-connected operation. If the frequency does not match, it may cause grid connection failure and even cause impact and damage to the power grid and unit equipment. Therefore, it is particularly important to invent a method for implementing a residual pressure frequency measurement module for hydropower station units.

[0003] The existing technology also has the following defects, which are specifically reflected in: 1. In the existing technology, the second-order filtering is not paid much attention to, and the high-order harmonics and low-order harmonics cannot be effectively suppressed, resulting in distortion of the signal waveform, causing signal distortion, and the AC component cannot be effectively removed, resulting in fluctuations in the signal baseline. For weak signal detection, it will cover up the truly valuable signal changes and reduce the sensitivity of signal detection.

[0004] 2. In the prior art, little attention is paid to device protection and there are no proper protective measures. When an abnormality occurs in the circuit, the current will increase sharply and may exceed the rated current of the device, increasing the probability of system failure and reducing the signal processing capability. Frequent device damage requires more maintenance and replacement work, increasing maintenance costs and increasing the time the system is shut down for maintenance.

[0005] 3. In the prior art, little attention is paid to zero-crossing capture, and the zero-crossing point of the signal cannot be accurately captured, resulting in deviations in the calculation of the signal period. For frequency measurement, since the frequency is the inverse of the period, inaccurate period measurement will directly lead to a decrease in frequency measurement accuracy, resulting in incorrect adjustment of system control parameters, causing the system to enter an unstable state. Summary of the invention

[0006] The purpose of the present invention is to provide a method for realizing a residual pressure frequency measurement module of a hydropower station unit, which solves the problems existing in the background technology.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions: The present invention provides a method for implementing a residual pressure frequency measurement module of a hydropower station unit, comprising: step one, residual pressure collection and preprocessing.

[0008] Step 2: Signal filtering and amplification.

[0009] Step 3: Signal shaping and isolation.

[0010] Step 4: Zero crossing capture.

[0011] Preferably, the residual pressure collection and preprocessing are specifically implemented by obtaining a residual pressure signal from a hydropower station unit through a PT front-stage circuit, and converting a high voltage into a low voltage signal suitable for subsequent circuit processing according to a preset ratio.

[0012] Preferably, the signal filtering and amplification are specifically implemented as follows: through a secondary filtering circuit, interference signals are filtered out, and high-order harmonics and AC components are filtered at the same time, and the signal is amplified to an amplitude suitable for subsequent circuit processing through an amplification circuit, while improving frequency response and stability.

[0013] Preferably, the signal shaping and isolation are specifically implemented as follows: in the channel isolation circuit, the sharp amplitude of the signal is limited by a forward series diode, and the unidirectional conductivity of the diode and other related circuit elements are used to shape the amplitude-limited AC signal into a DC signal, and an optocoupler is used in the post-shaped signal stage to achieve level conversion based on its internal circuit structure, converting the input signal into a signal level suitable for subsequent ADC sampling, and outputting it as an ADC sampling signal for the ADC module to perform residual voltage amplitude detection.

[0014] Preferably, the zero-crossing capture is specifically implemented as follows: the signal is amplified through a zero-crossing capture circuit, and noise and interference components in the signal are filtered out. The signal processed by the previous operational amplifier is input into a voltage comparator, and the voltage comparator compares the input signal with the zero level. When the input signal changes from a positive half-cycle to a negative half-cycle or from a negative half-cycle to a positive half-cycle, that is, at the zero-crossing moment, the output level of the comparator will jump, and the jump is detected by a counter to capture the zero-crossing moment of the input signal, thereby calculating the frequency of the signal.

[0015] The beneficial effects of the present invention are: 1. In the present invention, the attention is increased to the second-order filtering. After removing these harmonics through the second-order filtering, the signal waveform can be closer to the ideal sine wave, thereby improving the purity of the signal. After removing the AC component, the baseline of the signal is more stable, which is helpful for the subsequent analysis and processing of the signal, improves the accuracy of frequency measurement, and provides a better foundation for subsequent signal processing and function expansion.

[0016] 2. In the present invention, increased attention is paid to device protection. The bidirectional series diode and the optocoupler protection circuit can limit the voltage amplitude, so that the voltage slowly reaches the peak value, avoiding the impact of instantaneous high voltage on the subsequent devices, and reducing the risk of device damage due to overvoltage, thereby significantly extending the service life of the device, ensuring the quality of the signal received by the subsequent circuit, avoiding the current impact caused by voltage mutation, reducing the fluctuation and distortion of the signal, and ensuring the stability of the operation of the subsequent circuit.

[0017] 3. In the present invention, more attention is paid to zero-crossing capture. By quickly capturing the zero-crossing point of the signal, the signal period is accurately determined, and the interference of harmonics on frequency measurement is effectively avoided, thereby improving the accuracy of frequency measurement and the stability of the system. When a fault occurs in the power system, the zero-crossing capture circuit can detect the frequency change in time, trigger the protection device, and reduce the loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 paying creative work.

[0019] Figure 1 The present invention is a schematic flow chart of the steps for implementing the method.

[0020] Figure 2 This is a schematic diagram of the PT front-stage circuit.

[0021] Figure 3 Schematic diagram of the second-order filtering signal amplification circuit.

[0022] Figure 4 This is the simulation diagram of the secondary filtering signal amplification circuit.

[0023] Figure 5 This is a schematic diagram of the channel isolation protection circuit.

[0024] Figure 6 This is a schematic diagram of the in-phase zero-crossing capture circuit.

[0025] Figure 7 This is the simulation diagram of the in-phase zero-crossing capture circuit. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Reference Figure 1 As shown, the present invention provides a method for implementing a residual pressure frequency measurement module of a hydropower station unit, comprising:

[0028] Step 1: Residual pressure collection and preprocessing.

[0029] In a specific embodiment, the residual pressure collection and preprocessing are specifically implemented as follows: Figure 2 , obtain the residual pressure signal from the hydropower station unit through the PT front-stage circuit, and convert the high voltage into a low voltage signal suitable for subsequent circuit processing according to a preset ratio.

[0030] It should be noted that, by using the principle of electromagnetic induction, the PT realizes electrical isolation between the high voltage side and the low voltage side while collecting residual voltage, preventing high voltage from damaging the subsequent circuit, and setting corresponding circuit elements, such as resistors and capacitors, in the PT front-end circuit to limit the threshold voltage of the collected signal. When the signal voltage is higher or lower than the set threshold value, it is processed through the corresponding circuit mechanism to ensure that the signal voltage received by the subsequent circuit is within the appropriate range. Among them, the PT uses a high-precision current transformer with small size and high precision; R61 is a sampling resistor, and C50 is used to complete the pre-stage filtering of the signal; R62 and the sliding rheostat form the signal threshold voltage input setting to remove the low-level noise signal coupled into the signal when the motor is not moving.

[0031] Step 2: Signal filtering and amplification.

[0032] In a specific embodiment, the signal filtering and amplification are specifically implemented as follows: Figure 3 , through the secondary filtering circuit, the interference signal is filtered out, and the high-order harmonics and AC components are filtered at the same time. The signal is amplified to an amplitude suitable for subsequent circuit processing through the amplifier circuit, while improving the frequency response and stability.

[0033] Among them, R14 is the input signal pull-down resistor, which provides a steady-state level for the initial signal and acts as a voltage bias to adjust the input signal level; R21 is the input current limiting resistor; R143 is the matching resistor, the output impedance of the previous stage op amp is low, and the input impedance of the next stage op amp is high, to prevent signal reflection from causing signal distortion. R294 is a negative feedback resistor, used to adjust the signal gain; R142 is a balancing resistor, used to adjust the feedback voltage and reduce the zero drift phenomenon of the output point; R262 and R278 are used as matching resistors at the inverting input to solve the input offset voltage problem caused by the op amp bias current; R310 is the output matching resistor, used to solve the impedance discontinuity problem of the signal between chips; V2 two unidirectional Schottky diodes are used to clamp the voltage output.

[0034] In the present invention, more attention is paid to second-order filtering. After removing these harmonics through second-order filtering, the signal waveform can be closer to the ideal sine wave, thereby improving the purity of the signal. After removing the AC component, the baseline of the signal is more stable, which is helpful for subsequent analysis and processing of the signal, improves the accuracy of frequency measurement, and provides a better foundation for subsequent signal processing and function expansion.

[0035] Step 3: Signal shaping and isolation.

[0036] In a specific embodiment, the signal shaping and isolation are specifically implemented as follows: Figure 5 In the channel isolation circuit, the sharp amplitude of the signal is limited by a forward series diode, and the unidirectional conductivity of the diode and other related circuit elements are used to shape the AC signal with amplitude limitation into a DC signal. An optocoupler is used in the post-shaped signal stage to achieve level conversion based on its internal circuit structure, converting the input signal into a signal level suitable for subsequent ADC sampling, and outputting it as an ADC sampling signal for the ADC module to perform residual voltage amplitude detection.

[0037] It should be noted that when the signal voltage exceeds the forward conduction voltage of the diode, the diode is turned on, so that the signal voltage is clamped within a certain range to avoid excessively high spikes in the signal. The input end of the optocoupler receives the shaped signal, and the internal light-emitting diode emits light, so that the phototransistor at the output end of the optocoupler is turned on by light, thereby achieving electrical isolation between signals. Among them, DS1 and DS2 are diodes connected in series in the same direction, which rectify the negative half-cycle of the pulse signal and play a certain voltage stabilizing role when the pulse signal is converted between high and low levels; RS5 is a current limiting resistor, which is used to adjust the CTR current transfer ratio of the current, and CS1 is a filter capacitor; the optocoupler is used for isolation and level conversion.

[0038] In the present invention, more attention is paid to device protection. The bidirectional series diode and the optocoupler protection circuit can limit the voltage amplitude, so that the voltage slowly reaches the peak value, avoiding the impact of instantaneous high voltage on the subsequent devices, reducing the risk of device damage due to overvoltage, thereby significantly extending the service life of the device, ensuring the quality of the signal received by the subsequent circuit, avoiding the current impact caused by voltage mutation, reducing the fluctuation and distortion of the signal, and ensuring the stability of the operation of the subsequent circuit.

[0039] Step 4: Zero crossing capture.

[0040] In a specific embodiment, the zero-crossing capture is specifically implemented as follows: Figure 6 , the signal is amplified through the zero-crossing capture circuit, and the noise and interference components in the signal are filtered out. The signal processed by the previous operational amplifier is input to the voltage comparator, and the voltage comparator compares the input signal with the zero level. When the input signal changes from the positive half cycle to the negative half cycle or from the negative half cycle to the positive half cycle, that is, the zero-crossing moment, the output level of the comparator will jump. The jump is detected by the counter, and the zero-crossing moment of the input signal is captured, and then the frequency of the signal is calculated.

[0041] It should be noted that the front stage of the zero-crossing capture circuit uses a two-channel operational amplifier. One channel is used for signal amplification so that it can be accurately processed by the subsequent comparator; the other channel is used for signal filtering to ensure that the frequency range and amplitude of the input signal are suitable for processing by the comparator, where R1 is a current limiting resistor and R3 is a feedback resistor, which is used to control the amplification factor of the signal gain G; C1, R1, C3, R2, and C2 form a second-order bandpass filter, which is used to control the input frequency range of the signal; R4 provides a bias voltage to the comparator as the reference voltage of the comparator; R5 is a current limiting resistor to adjust the driving current of the transformer; R6 is a load or pull-up resistor, and C4 is a load capacitor. By modifying the parameter value, the overdrive voltage of the comparator can be adjusted to determine the response time of the comparator. The higher the overdrive voltage, the smaller the response time.

[0042] In the present invention, more attention is paid to zero-crossing capture. By quickly capturing the zero-crossing point of the signal and accurately determining the signal period, the interference of harmonics on frequency measurement is effectively avoided, the accuracy of frequency measurement is improved, and the stability of the system is improved. When a fault occurs in the power system, the zero-crossing capture circuit can detect the frequency change in time, trigger the protection device, and reduce the loss.

[0043] The above contents are merely examples and explanations of the concept of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the present invention, they shall all fall within the protection scope of the present invention.

Claims

1. A method for implementing a residual pressure frequency measurement module of a hydropower station unit, characterized in that: include: Step 1: Residual pressure collection and preprocessing; Step 2: Signal filtering and amplification; Step 3: Signal shaping and isolation; Step 4: Zero crossing capture.

2. A method for implementing a residual pressure frequency measurement module of a hydropower station unit according to claim 1, characterized in that: The residual pressure collection and preprocessing are specifically implemented as follows: a residual pressure signal is obtained from a hydropower station unit through a PT front-stage circuit, and a high voltage is converted into a low voltage signal suitable for subsequent circuit processing according to a preset ratio.

3. A method for implementing a residual pressure frequency measurement module of a hydropower station unit according to claim 1, characterized in that: The signal filtering and amplification is specifically implemented as follows: the interference signal is filtered out through a secondary filtering circuit, and high-order harmonics and AC components are filtered at the same time, and the signal is amplified to an amplitude suitable for subsequent circuit processing through an amplification circuit, while improving the frequency response and stability.

4. A method for implementing a residual pressure frequency measurement module of a hydropower station unit according to claim 1, characterized in that: The signal shaping and isolation is specifically implemented as follows: in a channel isolation circuit, a forward series diode is used to limit the sharp amplitude of the signal, and the unidirectional conductivity of the diode and other related circuit elements are used to shape the AC signal with amplitude limitation into a DC signal. An optical coupler is used in the post-shaped signal stage to achieve level conversion based on its internal circuit structure, and the input signal is converted into a signal level suitable for subsequent ADC sampling, and the output is an ADC sampling signal for the ADC module to perform residual voltage amplitude detection.

5. The method for implementing a residual pressure frequency measurement module of a hydropower station unit according to claim 1, characterized in that: The zero-crossing capture is specifically implemented as follows: amplifying the signal through a zero-crossing capture circuit, filtering out noise and interference components in the signal, inputting the signal processed by the front-stage operational amplifier into a voltage comparator, and the voltage comparator comparing the input signal with the zero level. When the input signal changes from a positive half cycle to a negative half cycle or from a negative half cycle to a positive half cycle, that is, at the zero-crossing moment, the output level of the comparator will jump, and the jump will be detected by a counter to capture the zero-crossing moment of the input signal, thereby calculating the frequency of the signal.

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