Multi-channel electronic collection unit connected to wideband voltage transformer

Abstract

The present invention belongs to the technical field of voltage transformer measurement, and in particular to a multi-channel electronic collection unit connected to a wideband voltage transformer. In order to solve the problem in the prior art of an electronic collection unit not being applicable to wideband voltage measurement due to the fact that signals output by the electronic collection unit are in a single mode and the output signals are only in communication with a combining unit, in the present invention, a conditioning circuit in an electronic collection unit is improved, such that at least two analog quantity signals are output after data collected by a voltage transformer is conditioned by means of the conditioning circuit, wherein at least one analog quantity signal is converted into a digital quantity signal and is output by the electronic collection unit, and the remaining at least one analog quantity signal is directly output by the electronic collection unit, and thus a high-order voltage harmonic is collected, and an analog quantity signal and a digital quantity signal are output to the outside, thereby ensuring the safe and stable operation of a power grid; in addition, a power frequency signal, a harmonic and a transient signal are accurately measured, thereby facilitating the upgrade and update of the voltage transformer.

Description

A multi-channel electronic acquisition unit connected to a wide-band voltage transformer Technical Field

[0001] The invention belongs to the technical field of voltage transformer measurement, and in particular relates to a multi-channel electronic acquisition unit connected to a broadband voltage transformer. Background Art

[0002] In smart substations, there are two application scenarios for the acquisition electronic circuit used to access voltage transformer signals:

[0003] Scenario 1: The electronic acquisition unit is connected to a traditional ferromagnetic voltage transformer. The output signal of the traditional ferromagnetic voltage transformer is a standard 100V analog signal. The electronic acquisition unit is integrated into the merging unit chassis in the form of a plug-in card. The electronic acquisition unit conditions the voltage signal transmitted by the ferromagnetic voltage transformer and then transmits it to the merging unit AD sampling circuit through the chassis backplane for digital conversion. The application schematic is shown in Figure 1.

[0004] Scenario 2: The electronic acquisition unit is connected to an electronic voltage transformer with a resistor, capacitor, or resistor-capacitor voltage divider. The input signal is an analog voltage. The electronic acquisition unit is an independently packaged unit module. It converts the analog voltage signal output by the electronic voltage transformer into a digital FT3 signal and then sends the collected digital voltage to the merging unit. The application schematic is shown in Figure 2.

[0005] The above-mentioned principle description of the voltage transformer electronic acquisition unit covers the basic technical principles in the current industry. This mode is mostly used for measuring power frequency signals, and the output voltage acquisition FT3 signal mode is single, which is not suitable for the field of broadband voltage measurement.

[0006] Summary of the Invention

[0007] The object of the present invention is to provide a multi-channel electronic acquisition unit connected to a wide-band voltage transformer, so as to solve the problem in the prior art that the signal mode of the single output of the electronic acquisition is single and thus unsuitable for wide-band voltage measurement.

[0008] In order to solve the above technical problems, the present invention provides a multi-channel electronic acquisition unit connected to a wide-band voltage transformer, including a conditioning loop module and an analog-to-digital conversion module. The conditioning loop module includes at least two conditioning branches, and the input end of each conditioning branch is connected and connected to the input end of the conditioning loop module through a preliminary conditioning circuit. The preliminary conditioning circuit is used to perform common-mode suppression and signal amplification on the analog signal input by the electronic acquisition unit. The output end of each conditioning branch is respectively connected to the different output ends corresponding to the conditioning loop module, and an amplitude conditioning circuit and a filter conditioning circuit are serially arranged on each conditioning branch, wherein at least one output end of the conditioning loop module is connected to the input end of the analog-to-digital conversion module for converting the conditioned analog signal into a digital signal, and at least one of the remaining output ends of the conditioning loop module is directly connected to the analog output port on the electronic acquisition unit.

[0009] Its beneficial effects are: in order to solve the problem in the prior art that the signal mode output by the electronic acquisition unit is single and the output signal only communicates with the merging unit, resulting in unsuitability for wide-band voltage measurement, the present invention improves the conditioning circuit in the electronic acquisition unit so that the data collected by the voltage transformer is conditioned by the conditioning circuit and outputs at least two analog signals, at least one of which is converted into a digital signal and output to the electronic acquisition unit, and the remaining at least one analog signal is directly output from the electronic acquisition unit, thereby realizing the collection of high-order voltage harmonics and the external transmission of analog and digital signals to ensure the safe and stable operation of the power grid, and can simultaneously achieve accurate measurement of power frequency signals and accurate measurement of harmonics and transient signals, promote the upgrading of voltage transformers, build a new generation of digital full-frequency domain perception and application system, and improve the overall perception and application level of new power systems.

[0010] Furthermore, the amplitude conditioning circuit is in a scale-down mode.

[0011] Its beneficial effects are: the analog signal output by the wide-band voltage transformer is amplified by adjusting the primary voltage divider ratio of the wide-band voltage transformer, or amplified by differential conditioning. Here, the analog amplitude is reduced in a proportional reduction mode to increase or decrease the amplitude according to demand to obtain an analog quantity of the required amplitude.

[0012] Furthermore, the scaling-down mode adopts a resistance amplitude modulation mode.

[0013] The beneficial effect is that: considering the fast transient transmission characteristics, the resistance amplitude modulation mode is used for amplitude modulation, which makes the amplitude modulation speed faster.

[0014] Furthermore, the preliminary conditioning circuit is a differential amplifier circuit.

[0015] Furthermore, the differential amplifier circuit and the filter conditioning circuit are both implemented based on operational amplifiers.

[0016] The beneficial effect is that the differential amplifier circuit and the filter conditioning circuit are conditioned by an operational amplifier, making the conditioning loop simple and stable.

[0017] Furthermore, the amplitude range of the analog signal output by the analog output port is expressed as follows:

[0018] |x·K1·K2|<|ax|<|Y1|

[0019] |ax|=|y1|

[0020] Wherein, x is the analog voltage signal output by the wide-band voltage transformer; a is the maximum amplification factor of the primary voltage amplitude range under lightning voltage; K1 is the amplification factor of the differential amplifier circuit; K2 is the amplification factor of the amplitude conditioning circuit on the corresponding conditioning branch; Y1 is the range of amplitudes allowed for external access devices at the analog output port; and y1 is the amplitude of the analog signal output from the analog output port.

[0021] Its beneficial effect is that the electronic acquisition unit can limit the amplification circuit in the conditioning branch of the output analog signal while meeting the technical index requirements, so that the analog signal output by the final analog output port meets the requirements.

[0022] Furthermore, the amplitude range of the digital signal output by the electronic acquisition unit is expressed as follows:

[0023] |x·K1·K3|<|ax|<|Y2|

[0024] |ax|=|y2|

[0025] Among them, x is the analog voltage signal output by the wide-band voltage transformer; a is the maximum amplification factor of the primary voltage amplitude range under lightning voltage; K1 is the amplification factor of the differential amplifier circuit; K3 corresponds to the amplification factor of the amplitude conditioning circuit on the conditioning branch; Y2 is the range of amplitudes allowed for external access devices of the digital signal output by the electronic acquisition unit; y2 is the amplitude of the analog signal output by the electronic acquisition unit.

[0026] The beneficial effect is that the electronic acquisition unit can limit the amplification circuit in the conditioning branch of the output digital signal while meeting the technical index requirements, so that the analog signal output by the electronic acquisition unit can finally meet the requirements.

[0027] Furthermore, the formula for determining the sampling rate of the analog-to-digital conversion module is as follows:

[0028] N s =bf max

[0029] Among them, Ns is the sampling rate; f max is the maximum frequency measured; b is the frequency coefficient.

[0030] Furthermore, the operational amplifier obtains a gain bandwidth BGP>70M and a slew rate SR>2000V / μs according to the technical specifications met by the electronic acquisition unit.

[0031] Furthermore, the electronic acquisition unit further includes a metal shielding cap for accommodating the analog output port to protect the analog output port and shield the electromagnetic field.

[0032] The beneficial effect is that when the analog output port is not in use, the metal shielding cap can shield the influence of the electromagnetic field on the analog output port and play a role in mechanical protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG1 is a schematic diagram of an electronic acquisition unit connected to a traditional ferromagnetic voltage transformer in the prior art;

[0034] FIG2 is a schematic diagram of an electronic acquisition unit connected to an electronic voltage transformer in the prior art;

[0035] FIG3 is a schematic diagram of the electronic acquisition unit of the present invention;

[0036] FIG4 is a schematic diagram of a conditioning circuit in an electronic acquisition unit of the present invention;

[0037] FIG5 is a schematic diagram of the amplitude conditioning in the conditioning circuit of the electronic acquisition unit of the present invention;

[0038] FIG6 is a schematic diagram of the terminal structure of the analog voltage signal output of the electronic acquisition unit of the present invention;

[0039] FIG7 is a circuit diagram of a differential conditioning circuit of the present invention;

[0040] FIG8 is a circuit diagram of the filter conditioning circuit of the present invention.

[0041] Among them: 1-power module; 2-conditioning circuit module; 3-high-speed AD module; 4-FPGA module; 5-optical port driver module; 6-wideband VT; 7-serial port debugging; 8-electronic acquisition unit housing; 9-output port; 10-second amplitude conditioning circuit; 11-first filter conditioning circuit; 12-second filter conditioning circuit; 13-differential conditioning circuit; 14-first amplitude conditioning circuit; 15-shielded aviation terminal; 16-metal shielding cap. DETAILED DESCRIPTION

[0042] The basic concept of the present invention is to improve the conditioning circuit in the electronic acquisition unit so that the data collected by the voltage transformer is conditioned by the conditioning circuit and output as at least two analog voltage signals. At least one of these analog voltage signals is directly output through an analog output terminal provided by the electronic acquisition unit, while at least one of the remaining analog voltage signals is converted and output as a voltage acquisition FT3 signal. This allows the electronic acquisition unit to output both analog and digital signals. Based on this concept, the present invention can realize a multi-channel electronic acquisition unit connected to a wideband voltage transformer.

[0043] The present invention will be described in detail below with reference to the accompanying drawings and method embodiments.

[0044] Example of a multi-channel electronic acquisition unit connected to a wide-band voltage transformer:

[0045] A multi-channel electronic acquisition unit connected to a broadband voltage transformer of the present invention has a schematic diagram as shown in Figure 3, which includes a power module 1, a conditioning circuit module 2, a high-speed AD module 3, an FPGA module 4, an optical port driver module 5, an electronic acquisition unit housing 8 and an output port 9 (analog voltage signal output terminal). The power module is used to convert externally supplied AC or DC power to power the electronic acquisition unit; the conditioning circuit module is used to condition the analog voltage signal output by the broadband TV6 (broadband voltage transformer) to obtain two conditioned analog voltage signals; the high-speed AD module is used to convert one of the analog voltage signals output by the conditioning circuit module into a digital voltage signal; the FPGA module is used to control the electronic acquisition unit and convert the digital voltage signal output by the high-speed AD module into an FT3 level protocol signal; the optical port driver module is used to convert the FT3 level protocol signal output by the FPGA module into an FT3 optical pulse signal; the electronic acquisition unit housing is made of metal and adopts single-point grounding during use to achieve electromagnetic field shielding and mechanical protection; the analog voltage signal output terminal is used to output another analog voltage signal output by the conditioning circuit module.

[0046] Among them, the electronic acquisition unit must meet the following technical indicators: at an amplitude of 0.5 to 5 times the rated primary voltage, the measurement amplitude deviation of 1.2 / 50μs lightning impulse voltage shall not exceed 10%, and the wavefront response time error shall not exceed 10%; the voltage measurement bandwidth of 50Hz to 1MHz shall not be less than -3dB; the measurement amplitude deviation of harmonic voltage of 20kHz and below shall not exceed 5%.

[0047] The specific working steps of the electronic collection unit include:

[0048] 1) The conditioning circuit module conditions the analog voltage signal output by the wideband voltage transformer. As shown in Figure 4, the conditioning circuit module includes differential conditioning (i.e., suppression and amplification module), amplitude conditioning, and filtering conditioning. The specific working method is as follows:

[0049] The conditioning loop module first performs differential conditioning on the analog voltage signal (x) output by the wide-band voltage transformer, i.e., performs common-mode suppression and preliminary signal conditioning amplification (with an amplification factor of K1). After differential conditioning, the signal is divided into two signals for transmission, namely, the first conditioning branch output conditioning quantity 1 (y1) and the second conditioning branch output conditioning quantity 2 (y2). Each conditioning branch is provided with amplitude conditioning and filtering conditioning. The first conditioning branch is provided with a first amplitude conditioning circuit 14 and a first filtering conditioning circuit 11 in series, and the second conditioning branch is provided with a second amplitude conditioning circuit 10 and a second filtering conditioning circuit 12 in series. Among them, filtering conditioning is reflected in: the field fast transient voltage (VFFO) is superimposed on the operating voltage of the equipment, with a wider spectrum and possibly a faster rise time; when determining the amplitude of the fast transient voltage, the system operating voltage is used as a reference. This fastest transient often has a high-frequency component of up to 100MHz. According to the design goal of this technical solution, "a voltage measurement bandwidth of not less than -3dB from 50Hz to 1MHz," the filter conditioning circuit primarily filters out transient voltage signals with a fast transient voltage (VFFO) of 1MHz or above. Since the analog voltage signal output by the wideband voltage transformer can be amplified by adjusting the primary voltage divider ratio of the wideband voltage transformer or by differential conditioning, the amplitude conditioning on the two conditioning branches is designed to reduce the amplitude ratio. Taking into account the fast transient transmission characteristics, a resistor amplitude modulation mode is adopted. Specifically, as shown in Figure 5, the amplitude conditioning formula on the two conditioning branches is as follows:

[0050] In the above formula, K2 is the amplification factor of the first amplitude conditioning circuit; R1 and R2 are the amplitude modulation resistance values ​​of the resistors in the first amplitude conditioning circuit; K3 is the amplification factor of the second amplitude conditioning circuit; R3 and R4 are the amplitude modulation resistance values ​​of the resistors in the second amplitude conditioning circuit.

[0051] According to the applicable technical indicators of the electronic acquisition unit, the maximum amplitude range of the primary voltage under the lightning voltage is 5 times, and the amplitude adjustment range formula of the adjustment value 1 is as follows:

[0052] |x·K1·K2|<|5x|<|Y1|

[0053] |5x|=|y1|

[0054] In the above formula, x is the analog voltage signal output by the wide-band voltage transformer; K1 is the amplification factor of the differential conditioning circuit; y1 is the amplitude of the conditioned variable 1 output by the first conditioning branch; ±Y1 is the amplitude range allowed by the external access device of conditioned variable 1;

[0055] The formula for the amplitude adjustment range of adjustment quantity 1 is as follows:

[0056] |x·K1·K3|<|5x|<|Y2|

[0057] |5x|=|y2|

[0058] In the above formula, y2 is the amplitude of the conditioned variable 2 output by the second conditioning branch; Y2 is the range of the amplitude allowed for the high-speed AD externally connected to the conditioned variable 2;

[0059] The first filter conditioning circuit, the second filter conditioning circuit, and the differential conditioning circuit are all implemented using operational amplifiers. Key technical specifications met by the operational amplifiers include gain bandwidth (BGP) > 5 MHz and slew rate (SR) > 60 V / μs. The bandwidths of both the first and second filter conditioning circuits are above 1 MHz. Considering a 5x overload, BGP > 1 MHz × 5 = 5 MHz, and SR > 60 V / μs / 1000 = 0.06 V / ns. For example, under rated conditions, if the analog output of a wide-band voltage transformer is 4 V, then the analog input rises to 20 V at 5x, requiring 333 ns. The goal is to ensure bandwidth with a fast rise time, namely, bandwidth (fup) = 0.35 / 333 ns = 1.05 MHz, which puts the bandwidth within the design range of approximately 1 MHz.

[0060] Among them, the circuit schematic diagram of the differential conditioning circuit is shown in Figure 7, and The first filtering and conditioning circuit and the second filtering and conditioning circuit are shown in FIG8 .

[0061] 2) The conditioned quantity 1 output by the first conditioning branch is output from the shielded aviation terminal 15 through the output port to a high-speed oscilloscope or a high-speed sampling electronic circuit outside the electronic acquisition unit. A metal shielding cap 16 is also installed outside the analog voltage signal output terminal. The metal shielding cap 16 and the shielded aviation terminal 15 are separate structures. The metal shielding cap 16 is a threaded rotary packaging method for achieving electromagnetic field shielding and mechanical protection, as shown in Figure 6.

[0062] The second conditioning branch outputs conditioning quantity 2 and inputs it into the high-speed AD module. The high-speed AD module performs high-speed voltage acquisition on conditioning quantity 2 to convert the analog conditioning quantity 2 into a digital quantity. The sampling rate formula is as follows:

[0063] N s =4·f max

[0064] In the above formula, Ns is the sampling rate; f max is the maximum frequency measured.

[0065] According to the applicable technical indicators of the electronic acquisition unit, the voltage measurement bandwidth is 50Hz to 1MHz, so the high-speed AD sampling rate is not less than 4MHz.

[0066] 3) The FPGA module receives the digital signal output by the high-speed AD module and controls the electronic acquisition unit to convert the digital signal into an FT3 level protocol signal. The FPGA module is debugged via the serial port 7 to configure its own program to implement the host computer control function.

[0067] 4) The optical port driver module receives the FT3 level protocol signal output by the FPGA module and converts the FT3 level protocol signal into an FT3 optical pulse signal.

[0068] The present invention can realize the collection of high-order voltage harmonics and the external transmission of analog and digital signals, which is a key measure to ensure the safe and stable operation of the power grid. It can also accurately measure the power frequency signals and harmonics and transient signals at the same time, which can promote the upgrading of voltage transformers. It is a key step in building a new generation of digital full-frequency domain perception and application system and improving the overall perception and application level of new power systems. This technology can be widely used in AC substations with new energy access, and has broad market prospects.

Claims

1. A multi-channel electronic acquisition unit connected to a wide-band voltage transformer, comprising a conditioning circuit module and an analog-to-digital conversion module, characterized in that: The conditioning loop module includes at least two conditioning branches, the input end of each conditioning branch is connected to the input end of the conditioning loop module through a preliminary conditioning circuit, the preliminary conditioning circuit is used to perform common-mode suppression and signal amplification on the analog signal input by the electronic acquisition unit, the output end of each conditioning branch is respectively connected to different output ends corresponding to the conditioning loop module, and an amplitude conditioning circuit and a filter conditioning circuit are serially arranged on each conditioning branch, wherein at least one output end of the conditioning loop module is connected to the input end of the analog-to-digital conversion module for converting the conditioned analog signal into a digital signal, and at least one of the remaining output ends of the conditioning loop module is directly connected to the analog output port on the electronic acquisition unit.

2. The multi-channel electronic acquisition unit connected to the wide-band voltage transformer according to claim 1, characterized in that: The amplitude conditioning circuit is in a scale-down mode.

3. The multi-channel electronic acquisition unit connected to the wide-band voltage transformer according to claim 2, characterized in that: The scaling down mode adopts a resistance amplitude modulation mode.

4. The multi-channel electronic acquisition unit connected to a wide-band voltage transformer according to claim 1, characterized in that: The initial conditioning circuit is a differential amplifier circuit.

5. The multi-channel electronic acquisition unit connected to the wide-band voltage transformer according to claim 1, characterized in that: The differential amplifier circuit and the filter conditioning circuit are both implemented based on operational amplifiers.

6. The multi-channel electronic acquisition unit connected to a wide-band voltage transformer according to claim 1, characterized in that: The amplitude range of the analog signal output by the analog output port is expressed as follows: |x·K1·K2|<|ax|<|Y1| |ax|=|y1| Among them, x is the analog voltage signal output by the wide-band voltage transformer; a is the maximum amplification factor of the primary voltage amplitude range under lightning voltage; K1 is the amplification factor of the differential amplifier circuit; K2 is the amplification factor of the amplitude conditioning circuit on the corresponding conditioning branch; Y1 is the range of amplitudes allowed for external access devices at the analog output port; y1 is the amplitude of the analog signal output from the analog output port.

7. The multi-channel electronic acquisition unit connected to a wide-band voltage transformer according to claim 1, characterized in that: The amplitude range of the digital signal output by the electronic acquisition unit is expressed as follows: |x·K1·K3|<|ax|<|Y2| |ax|=|y2| Among them, x is the analog voltage signal output by the wide-band voltage transformer; a is the maximum amplification factor of the primary voltage amplitude range under lightning voltage; K1 is the amplification factor of the differential amplifier circuit; K3 is the amplification factor of the amplitude conditioning circuit on the conditioning branch corresponding to K3; Y2 is the range of amplitudes allowed for external access devices of the digital signal output by the electronic acquisition unit; y2 is the amplitude of the analog signal output by the electronic acquisition unit.

8. The multi-channel electronic acquisition unit connected to a wide-band voltage transformer according to claim 1, characterized in that: The formula for the sampling rate of the analog-to-digital conversion module is as follows: s =bf max Among them, N s is the sampling rate; f max is the maximum frequency measured; b is the frequency coefficient.

9. The multi-channel electronic acquisition unit connected to a wide-band voltage transformer according to claim 5, characterized in that: The operational amplifier obtains a gain bandwidth BGP>70M and a slew rate SR>2000V / μs according to the technical specifications met by the electronic acquisition unit.

10. The multi-channel electronic acquisition unit connected to a wide-band voltage transformer according to claim 1, characterized in that: The electronic acquisition unit also includes a metal shielding cap for accommodating the analog output port to protect the analog output port and shield the electromagnetic field.

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