Switching value acquisition system for relay protection based on voltage frequency conversion

Abstract

The invention discloses a switching value acquisition system for relay protection based on voltage frequency conversion, which relates to the technical field of power system protection, and is characterized in that the input end of a switching value voltage division loop is connected with an external switching value input voltage, and the output end of the switching value voltage division loop is connected with an amplification loop and a voltage-controlled frequency conversion oscillation loop respectively; the output end of the voltage-controlled frequency conversion oscillation loop is connected with the feedback loop and the band-pass filtering and waveform shaping loop, the output end of the feedback loop is connected to the input end of the amplification loop, and the output end of the band-pass filtering and waveform shaping loop is connected with the signal isolation loop. And the output end of the signal isolation loop is connected with the frequency measurement loop and the switching value judgment processor loop. The switching value acquisition circuit can adapt to switching value acquisition of different voltage levels, reduces the hardware types of a switching value acquisition loop, and can meet the requirement that multiple switching value acquisition channels are isolated from one another in the same module.

Description

Technical Field

[0001] The present invention relates to the technical field of power system protection, and in particular to a switch quantity acquisition system for relay protection based on voltage-frequency conversion. Background Art

[0002] The relay protection device of the power system collects external switch quantity information through the collection device. This type of switch quantity mainly includes various pressure plates, connecting pieces, switching switch contacts, knife switch positions, tap positions, various protection safety device action alarm signals, operating relay contacts and other public signals on the panel cabinet. This switch quantity information is an important basis for judging the correct and reliable operation of power protection.

[0003] Considering the isolation requirements of the power system for the switch quantity acquisition circuit, most of the existing switch quantity acquisition circuits adopt the design scheme with optocouplers as the main components. The switch quantity acquisition system determines the state of the switch quantity through the high or low level signal output by the optocoupler. This method realizes the acquisition and signal isolation of the external switch quantity signal. In practical applications, the rated voltage values ​​of the switch quantity include various voltage levels such as DC 220V, DC 110V and DC 48V. In order to meet the requirements of the power system that the starting voltage value of the switch quantity circuit should not be greater than 0.7 times the rated switch quantity input voltage value, and not less than 0.55 times the rated switch quantity input voltage value, the switch quantity acquisition system needs to be configured with a variety of boards with different hardware parameters, which leads to a large variety of switch quantity acquisition boards, which brings many inconveniences to management and maintenance.

[0004] In order to solve the problem of too many types of switch quantity acquisition boards, the switch quantity acquisition system in the power system also uses ADC chips to perform analog sampling of the input voltage, and sends the digital value of the sampled value to the main controller through a digital isolation device, and judges the state of the switch quantity by the size of the sampled value. This solution only requires one switch quantity acquisition board in hardware to meet the switch quantity input acquisition of different rated voltage levels, reducing the hardware version. However, this solution requires ADC chips, isolated power supplies, digital quantity isolation and other devices, making this solution relatively expensive. At the same time, it cannot meet the requirements for applications that require isolation between multiple switch quantity acquisition channels in the same board. Summary of the invention

[0005] When dealing with switch quantities of different voltage levels, the switch quantity acquisition system in the existing relay protection device often designs a variety of boards with different hardware parameters, which leads to a large variety of switch quantity acquisition boards, causing many inconveniences in management and maintenance; the switch quantity input voltage is converted into a digital quantity through ADC and sent to the main controller for voltage identification, but there is an application limitation that multiple switch quantity acquisition channels on the same board cannot be isolated from each other.

[0006] The purpose of the present invention is to provide a switch quantity acquisition system for relay protection based on voltage-frequency conversion in order to solve at least one of the above technical problems.

[0007] In the first aspect, an embodiment of the present invention provides a switch quantity acquisition system for relay protection based on voltage-frequency conversion, comprising: a switch quantity voltage dividing circuit, an amplifying circuit, a voltage-controlled frequency conversion oscillation circuit, a feedback circuit, a band-pass filtering and waveform shaping circuit, a signal isolation circuit, a frequency measuring circuit and a switch quantity judgment processor circuit; wherein, the input end of the switch quantity voltage dividing circuit is connected to the external switch quantity input voltage, the output end of the switch quantity voltage dividing circuit is respectively connected to the amplifying circuit and the voltage-controlled frequency conversion oscillation circuit, the output end of the voltage-controlled frequency conversion oscillation circuit is respectively connected to the feedback circuit and the band-pass filtering and waveform shaping circuit, the output end of the feedback circuit is connected to the input end of the amplifying circuit, and the output end of the band-pass filtering and waveform shaping circuit is connected to the signal isolation circuit. The output end of the signal isolation circuit is connected to the frequency measurement circuit and the switch quantity judgment processor circuit; the voltage-controlled frequency conversion oscillation circuit is used to convert the output signal of the amplification circuit and the switch quantity voltage division signal output by the switch quantity voltage division circuit into a sinusoidal oscillation signal; the bandpass filtering and waveform shaping circuit is used to filter and waveform shape the sinusoidal oscillation signal output by the voltage-controlled frequency conversion oscillation circuit to obtain the oscillation signal after filtering and shaping; the signal isolation circuit is used to convert the oscillation signal after filtering and shaping into an isolated periodic pulse signal, and input the isolated periodic pulse signal into the frequency measurement circuit and the switch quantity judgment processor circuit; the frequency measurement circuit and the switch quantity judgment processor circuit are used to judge the switch quantity state based on the isolated periodic pulse signal.

[0008] Furthermore, it also includes a power supply circuit, which is connected to the amplification circuit and the signal isolation circuit respectively, and is used to supply power to the amplification circuit and the signal isolation circuit.

[0009] Furthermore, the input signal of the amplification circuit is a superposition signal of the switch voltage division signal and the sinusoidal oscillation signal output by the voltage-controlled variable frequency oscillation circuit.

[0010] Furthermore, the frequency of the sinusoidal oscillation signal output by the voltage-controlled variable frequency oscillation circuit corresponds one-to-one to the voltage value of the external switch input voltage.

[0011] Furthermore, the frequency measurement circuit and the switch quantity judgment processor circuit are also used to: measure the signal frequency value of the isolated periodic pulse signal; determine the voltage value of the external switch quantity input voltage based on the signal frequency value; and determine the switch quantity state based on the voltage value of the external switch quantity input voltage.

[0012] Furthermore, the voltage-controlled variable frequency oscillation circuit is composed of a capacitor, an inductor and a varactor diode.

[0013] Furthermore, the isolation device in the signal isolation loop includes but is not limited to a photoelectric coupler.

[0014] Furthermore, the frequency measurement circuit and the switch quantity determination processor circuit include an MCU or an FPGA.

[0015] The present invention provides a switch quantity acquisition system for relay protection based on voltage-frequency conversion, which converts the switch quantity input voltage signal into an oscillation signal of corresponding frequency, and the frequency of the oscillation signal corresponds to the switch quantity input voltage. By measuring the frequency of the oscillation signal, the voltage value of the switch quantity is calculated and the state of the switch quantity is judged. The present invention can adapt to the acquisition of switch quantities of different voltage levels, reduce the types of hardware of the switch quantity acquisition circuit, and also meet the requirements of isolating multiple switch quantity acquisition channels in the same module. The above characteristics also make the present invention highly versatile and meet the needs of wide-range promotion and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 A schematic diagram of the architecture of a switch quantity acquisition system for relay protection based on voltage-frequency conversion provided by an embodiment of the present invention;

[0018] Figure 2 A circuit diagram of a switch quantity acquisition system for relay protection based on voltage-frequency conversion provided by an embodiment of the present invention.

[0019] In the figure: 1. Switching quantity voltage dividing circuit, 2. Amplification circuit, 3. Voltage-controlled frequency conversion oscillation circuit, 4. Feedback circuit, 5. Bandpass filtering and waveform shaping circuit, 6. Signal isolation circuit, 7. Frequency measurement circuit and switching quantity judgment processor circuit, 8. Power supply circuit. DETAILED DESCRIPTION

[0020] 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.

[0021] Embodiment 1

[0022] Figure 1 FIG. 1 is a schematic diagram of the architecture of a switch quantity acquisition system for relay protection based on voltage-frequency conversion according to an embodiment of the present invention. Figure 1 As shown, the system includes: a switching quantity voltage dividing circuit 1, an amplifying circuit 2, a voltage-controlled frequency conversion oscillation circuit 3, a feedback circuit 4 of the amplifying circuit 2, a bandpass filtering and waveform shaping circuit 5, a signal isolation circuit 6, a frequency measuring circuit and a switching quantity judgment processor circuit 7.

[0023] Specifically, Figure 1 As shown, the input end of the switching voltage divider circuit 1 is connected to the external switching input voltage, the output end of the switching voltage divider circuit 1 is respectively connected to the amplifier circuit 2 and the voltage-controlled frequency conversion oscillation circuit 3, the output end of the voltage-controlled frequency conversion oscillation circuit 3 is respectively connected to the feedback circuit 4 and the band-pass filter and waveform shaping circuit 5, the output end of the feedback circuit 4 is connected to the input end of the amplifier circuit 2, the output end of the band-pass filter and waveform shaping circuit 5 is connected to the signal isolation circuit 6, and the output end of the signal isolation circuit 6 is connected to the frequency measurement circuit and the switching judgment processor circuit 7.

[0024] Specifically, the switch voltage dividing circuit 1 is used to divide the external switch input voltage to obtain a switch voltage dividing signal;

[0025] The voltage-controlled variable frequency oscillation circuit 3 is used to convert the output signal of the amplification circuit 2 and the switching voltage-dividing signal output by the switching voltage-dividing circuit 1 into a sinusoidal oscillation signal;

[0026] The bandpass filtering and waveform shaping circuit 5 is used to filter and waveform shape the sinusoidal oscillation signal output by the voltage-controlled variable frequency oscillation circuit 3 to obtain an oscillation signal after filtering and shaping;

[0027] The signal isolation circuit 6 is used to convert the oscillation signal after filtering and shaping into an isolated periodic pulse signal, and input the isolated periodic pulse signal into the frequency measurement circuit and the switch value judgment processor circuit 7;

[0028] The frequency measurement circuit and the switch quantity judgment processor circuit 7 are used to judge the switch quantity state based on the isolated periodic pulse signal.

[0029] Specifically, Figure 1 The system further comprises a power supply circuit 8 , which is respectively connected to the amplifying circuit 2 and the signal isolating circuit 6 , and is used to supply power to the amplifying circuit 2 and the signal isolating circuit 6 .

[0030] In the embodiment of the present invention, the input signal of the amplifier circuit 2 is a superposition signal of the switch voltage-divided signal and the sinusoidal oscillation signal output by the voltage-controlled variable frequency oscillation circuit 3. After the input signal passes through the amplifier circuit 2, the amplitude of the oscillation signal output gradually increases, and when the output amplitude voltage limit of the amplifier circuit 2 is reached, the oscillation signal becomes a constant amplitude oscillation.

[0031] Specifically, the frequency of the output signal of the voltage-controlled variable frequency oscillation circuit 3 is controlled by the magnitude of the switch input voltage. The input voltage value can change the oscillation circuit parameters, and the frequency of its sinusoidal oscillation signal corresponds one-to-one to the voltage value of the external switch input voltage.

[0032] Specifically, the bandpass filtering and waveform shaping circuit 5 filters out the DC bias and high-frequency signal in the sinusoidal oscillation signal and shapes the oscillation signal, and the shaped signal is input into the signal isolation circuit 6 .

[0033] Specifically, the frequency measurement circuit and the switch value judgment processor circuit 7 are also used for:

[0034] Measure the signal frequency value of the isolated periodic pulse signal;

[0035] Based on the signal frequency value, determine the voltage value of the external switch input voltage;

[0036] The switch quantity state is determined based on the voltage value of the external switch quantity input voltage.

[0037] In an optional implementation provided by an embodiment of the present invention, the frequency measurement circuit and the switch value judgment processor circuit 7 calculate the voltage value of the corresponding switch value input by measuring the signal frequency value. When the calculated input voltage value is greater than or equal to 0.625 times the rated voltage value, the switch value judgment processor determines that the switch value is in operation; when the calculated input voltage value is less than 0.625 times the rated voltage value, the switch value judgment processor determines that the switch value is not in operation.

[0038] The embodiment of the present invention provides a switch quantity acquisition system for relay protection based on voltage-frequency conversion, which realizes isolation of multiple switch quantity acquisition channels from each other in the same module, and the same hardware parameters can adapt to switch quantity acquisition of different switch quantity voltage levels.

[0039] Embodiment 2

[0040] Figure 2 1 is a circuit diagram of a switch quantity acquisition system for relay protection based on voltage-frequency conversion according to an embodiment of the present invention. Figure 2As shown in the figure, R1~R4 form a switch voltage divider circuit 1, which divides the high voltage of the switch input to meet the voltage input range requirements of the subsequent circuit. V10 is a bidirectional TVS tube used to clamp the voltage to prevent the subsequent circuit from being damaged by the transient high voltage input. The diode D10 and safety capacitor CY1 in Figure 2 are used to resist power frequency, prevent the switch input from being reversed, and resist external electromagnetic interference.

[0041] In the embodiment of the present invention, the voltage-controlled variable frequency oscillation circuit 3 is composed of a capacitor, an inductor and a variable capacitance diode.

[0042] Specifically, Figure 2 As shown, Q1 is an NPN transistor, and Q1, resistors R6-R7, capacitors C1-C4, inductor L1 and varactor diode form a common emitter capacitor feedback type LC oscillation circuit. The transistor Q1 and resistors R6-R7 form an amplification circuit 2, and capacitors C1-C4, inductor L1, resistors R8-R9 and varactor diode D1 form a voltage-controlled variable frequency oscillation circuit 3 and a feedback circuit 4.

[0043] After the amplifier loop 2 amplifies the input signal to a sufficient amplitude, a part of the signal is fed back to the input end through the feedback loop 4, and the feedback signal is amplified again through the amplifier loop 2, forming a positive feedback loop. Due to the existence of the feedback signal, the amplifier loop 2 will continuously amplify the input signal and continuously replenish energy through the feedback signal, so that the system will produce a self-excited oscillation state.

[0044] In order to achieve the above state, the initial parameters of the loop should make the product of the amplification factor A and the feedback factor F greater than 1. Due to the nonlinearity of the transistor and the limitation of the power supply voltage, when the amplitude of the oscillation reaches a certain value, the product of the amplification factor A and the feedback factor F is equal to 1, and the equilibrium state oscillation is equal amplitude oscillation. The feedback factor can be approximated by the formula Calculation, generally 0.1 ~ 0.5; the amplification factor A is related to the DC operating point and load of the transistor, and its value where g m is the transistor transconductance, g' L is the output equivalent conductance, g i is the input equivalent conductance.

[0045] Capacitance range of varactor diode C D1 should be much smaller than the capacitance of C3 and C4, so the LC oscillation frequency can be simplified to Where C D1 is the capacitance of the varactor diode. In the embodiment of the present invention, the capacitance value of the varactor diode is different under different reverse voltages, and the capacitance value is inversely proportional to the voltage within a certain voltage range. The larger the reverse voltage, the smaller the capacitance value, and the larger the oscillation frequency, thereby achieving the purpose of controlling the oscillation frequency by the voltage input of the switching quantity.

[0046] For transistor Q1, select its maximum transmission frequency f T It should be at least 3 times greater than the LC oscillation frequency, and the amplification factor β should be selected from 50 to 120. The resistance values ​​of resistors R6 to R7 should make the transistor static operating Ic current between 1mA and 4mA.

[0047] Specifically, Figure 2 As shown, capacitors C5, C6 and diode D11 form a bandpass filter and waveform shaping circuit 5. C5 and C6 are used to filter out the DC bias and high-frequency signal in the oscillation signal, and diode D11 performs half-wave rectification on the oscillation signal. The above measures ensure that only the oscillation signal can meet the requirements of the subsequent isolation device for the input signal.

[0048] In an optional implementation provided by the embodiment of the present invention, the signal isolation circuit 6 includes a photoelectric coupler.

[0049] Specifically, Figure 2 As shown, the U11 optocoupler in the figure constitutes a signal isolation circuit 6, which is used to convert the oscillation signal level and isolate the signal. In order to meet the isolation requirements of the power system for the switch quantity acquisition system, the primary and secondary isolation withstand voltage of the optocoupler is required to be greater than 3kV. At the same time, for the embodiment of the present invention, since the frequency of the oscillation signal to be transmitted is relatively high, the maximum transmission rate of the optocoupler needs to be considered, and the maximum transmission rate of the optocoupler should be greater than 3 times the oscillation frequency.

[0050] Preferably, the frequency measurement circuit and the switch quantity determination processor circuit 7 include a processor unit such as an MCU or an FPGA.

[0051] Specifically, Figure 2 As shown in the figure, U2 is a frequency measurement and switch quantity judgment processor, and the processor can be an MCU or FPGA. The pulse signal output from the optocoupler is connected to the GPIO pin of the processor. The processor measures and calculates the frequency of the pulse signal based on the curve of the reverse voltage and capacitance value of the varactor diode and the oscillation frequency. The reverse voltage of the varactor diode is calculated, and then the voltage value of the input switch quantity is inferred through the resistance values ​​of R1, R2, R3, and R4 in the voltage divider circuit, thereby judging the state of the switch quantity. It should be noted that since the devices used in the voltage divider, amplification, LC oscillation and other circuits in the implementation of the present invention are all discrete devices, their parameter errors may make the output frequency more discrete, thereby affecting the processor's calculation value of the input voltage, causing the processor to misjudge the state of the switch quantity. Therefore, the embodiment of the present invention needs to calibrate each circuit before leaving the factory, and the processor stores the calibration value in a local storage unit so that it can be directly used on site.

[0052] Specifically, the embodiment of the present invention provides a switch quantity acquisition system for relay protection based on voltage-frequency conversion, and the specific working principle is as follows: Figure 2 As shown, when there is external switch input, the switch input voltage is processed by resistor voltage division, TVS tube limiting, etc., and the signal is input into the oscillation circuit composed of a triode amplifier and an LC resonant circuit, wherein the capacitance value in the LC resonant circuit can be controlled by the switch voltage, so that when the switch input voltage changes, the capacitance value in the LC oscillation circuit changes, causing the frequency of the oscillation waveform output by the LC oscillation circuit to change. The output oscillation waveform is isolated and high-frequency interference waves are filtered out by a bandpass filter, and then after signal isolation and voltage conversion, the signal is input into the frequency measurement and switch judgment processor. The frequency measurement and switch judgment processor measures the frequency of the input signal to calculate the size of the switch input voltage, and then judges whether the switch is in action based on the voltage value of the switch, and sends the switch state to the main controller module or the background through communication. In this way, the judgment of the switch state by voltage-frequency conversion is realized.

[0053] From the above description, it can be seen that the embodiment of the present invention provides a switch quantity acquisition system for relay protection based on voltage-frequency conversion, which realizes the acquisition of switch quantities of different voltage levels by using only one switch quantity acquisition board configured with hardware parameters, and meets the requirement of isolating the switch quantity channels from each other. The present invention has the characteristics of simple structure, easy implementation, and low overall system price. The above characteristics make the present invention highly versatile and meet the requirements of wide-range promotion and use.

[0054] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0055] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A switch quantity acquisition system for relay protection based on voltage-frequency conversion, characterized in that: include: Switching quantity voltage dividing circuit, amplification circuit, voltage-controlled variable frequency oscillation circuit, feedback circuit, bandpass filtering and waveform shaping circuit, signal isolation circuit, frequency measurement circuit and switching quantity judgment processor circuit; among them, The input end of the switch quantity voltage divider circuit is connected to the external switch quantity input voltage, the output end of the switch quantity voltage divider circuit is respectively connected to the amplification circuit and the voltage-controlled variable frequency oscillation circuit, the output end of the voltage-controlled variable frequency oscillation circuit is respectively connected to the feedback circuit and the band-pass filter and waveform shaping circuit, the output end of the feedback circuit is connected to the input end of the amplification circuit, the output end of the band-pass filter and waveform shaping circuit is connected to the signal isolation circuit, and the output end of the signal isolation circuit is connected to the frequency measurement circuit and the switch quantity judgment processor circuit; The voltage-controlled variable frequency oscillation circuit is used to convert the output signal of the amplification circuit and the switching voltage-dividing signal output by the switching voltage-dividing circuit into a sinusoidal oscillation signal; The bandpass filtering and waveform shaping circuit is used to filter and waveform shape the sinusoidal oscillation signal output by the voltage-controlled variable frequency oscillation circuit to obtain an oscillation signal after filtering and shaping; The signal isolation circuit is used to convert the oscillation signal after filtering and shaping into an isolated periodic pulse signal, and input the isolated periodic pulse signal into the frequency measurement circuit and the switch value judgment processor circuit; The frequency measurement circuit and the switch quantity judgment processor circuit are used to judge the switch quantity state based on the isolated periodic pulse signal.

2. The switch quantity acquisition system for relay protection based on voltage-frequency conversion according to claim 1 is characterized in that: It also includes a power supply circuit, which is connected to the amplifying circuit and the signal isolation circuit respectively, and is used to supply power to the amplifying circuit and the signal isolation circuit.

3. The switch quantity acquisition system for relay protection based on voltage-frequency conversion according to claim 1 is characterized in that: The input signal of the amplification circuit is a superposition signal of the switch voltage division signal and the sinusoidal oscillation signal output by the voltage-controlled variable frequency oscillation circuit.

4. The switch quantity acquisition system for relay protection based on voltage-frequency conversion according to claim 1 is characterized in that: The frequency of the sinusoidal oscillation signal output by the voltage-controlled variable frequency oscillation circuit corresponds one-to-one to the voltage value of the external switch input voltage.

5. The switch quantity acquisition system for relay protection based on voltage-frequency conversion according to claim 1 is characterized in that: The frequency measurement circuit and the switch value judgment processor circuit are also used for: Measuring the signal frequency value of the isolated periodic pulse signal; Determining a voltage value of the external switch input voltage based on the signal frequency value; The switch value state is determined based on the voltage value of the external switch value input voltage.

6. The switch quantity acquisition system for relay protection based on voltage-frequency conversion according to claim 1 is characterized in that: The voltage-controlled variable frequency oscillation circuit is composed of a capacitor, an inductor and a variable capacitance diode.

7. The switch quantity acquisition system for relay protection based on voltage-frequency conversion according to claim 1 is characterized in that: The isolation device in the signal isolation loop includes but is not limited to a photoelectric coupler.

8. The switch quantity acquisition system for relay protection based on voltage-frequency conversion according to claim 1 is characterized in that: The frequency measurement circuit and the switch quantity judgment processor circuit include an MCU or an FPGA.

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