Precision measurement device for primary frequency modulation electrical parameters

Abstract

The present invention discloses a frequency modulation electrical parameter precision measuring device, comprising an AC plug-in, a power measurement waveform conditioning circuit, a frequency measurement waveform conditioning circuit, a three-phase isolation sampling circuit, an A / D converter, an embedded system, a D / A converter and a special thick film integrated V / I converter. The power and frequency are respectively processed before calculation by the power measurement waveform conditioning circuit and the frequency measurement waveform conditioning circuit. The signal is implemented by a hardware circuit in the conditioning process, and the time is short. The frequency waveform conditioning circuit conditions the sine wave signal into a half-cycle square wave signal, and the voltage signal is converted into a 4-20ma current signal by a D / A converter with a conversion time of microseconds, in cooperation with a V / I conversion circuit. The active power, reactive power, power factor, frequency and other electrical quantities of the generator can be measured quickly and accurately, and the generator power automatic regulation system and the DCS system can be used, which can provide a guarantee for the safe and stable operation of the unit.

Description

Technical Field

[0001] The present invention relates to the technical field of power system frequency regulation, and in particular to a device for accurately measuring electrical parameters of primary frequency regulation. Background Art

[0002] In the control system of the generator set, electrical quantities such as voltage, current, power, and frequency are collected by transmitters through PT and CT signals, converted into 4-20mA current signals, and then transmitted to the DCS system. Most of the transmitters currently used are conventional transmitters, which are manufactured based on analog components and integrated circuit components. They have poor anti-interference ability, long response time, poor transient characteristics, no record of abnormal conditions, low measurement accuracy, and are affected by harmonics. Since electrical quantities such as active power are controlled by the DCS system of the unit, there have been many cases of abnormal operation and even tripping of the unit due to these problems of conventional transmitters for a long time. In recent years, Huaneng Group alone has experienced unit tripping accidents caused by intercom interference, unit load drop events caused by high-frequency harmonics, and load fluctuation events caused by excitation inrush current. With the large-scale and mature application of microcomputer technology in the field of relay protection, electrical quantity transmitters based on microcomputer technology have gradually begun to be used in power systems in the past two years. Since microcomputer technology has the advantages of strong anti-interference ability, high precision, and short response time, digital electrical quantity transmitters implemented using microcomputer technology have obvious advantages over conventional transmitters, and can greatly improve the control performance of the unit and improve the safety of unit operation, and the market demand is strong. However, at present, there are only one or two small companies producing digital electrical quantity transmitters on the market, and the existing digital electrical quantity transmitters have the following defects and deficiencies: (1) The transmitter time constant is too large to meet the requirements of rapid response to system faults; (2) The problem of transient saturation of the measurement-level current transformer caused by the non-periodic component in the response inrush current cannot be solved. Summary of the invention

[0003] In view of the problems existing in the prior art, the present invention provides a frequency modulation electrical parameter precise measurement device, which can quickly and accurately measure the active power, reactive power, power factor, frequency and other electrical quantities of the generator, for use in the generator power automatic regulation system and DCS system, and can provide guarantee for the safe and stable operation of the unit.

[0004] The present invention is achieved through the following technical solutions:

[0005] A precise measurement device for primary frequency modulation electrical parameters, including an AC plug-in, a power measurement waveform conditioning circuit, a frequency measurement waveform conditioning circuit, a three-phase isolation sampling circuit, an A / D converter, an embedded system, a D / A converter, and a dedicated thick film integrated V / I converter;

[0006] The input end of the AC plug-in is provided with an input interface for accessing two groups of measurement voltages, one group of measurement currents and one group of protection currents, and the output end is respectively connected to a power measurement waveform conditioning circuit and a frequency measurement waveform conditioning circuit;

[0007] The power measurement waveform conditioning circuit is connected to the input end of the embedded system via the three-phase isolation sampling circuit and the A / D converter in sequence; the power measurement waveform conditioning circuit is used to filter the four groups of input signals of the AC plug-in and condition them into high-quality sine wave signals, the three-phase isolation sampling circuit is used to sample the conditioned sine wave signals, and the A / D converter is used to convert the sampled signals into digital signals;

[0008] The frequency measurement waveform conditioning circuit is used to condition one set of measurement voltages into two square wave pulse signals with a phase difference of 180 degrees, and connect them to the input end of the embedded system;

[0009] The output end of the embedded system outputs a digital signal of power and frequency, and sequentially connects to a D / A converter and a special thick film integrated V / I converter to output a 4-20mA analog output, which is connected to the input end of the unit DCS system.

[0010] Preferably, the input interface of the AC plug-in is connected to two sets of measurement voltages U a1 , U b1 , U c1 , U n1 and U a2 , U b2 , U c2 , U n2 , a set of measurement current I a ,I b ,I c And a set of protection current mI a 、mI b 、mI c 14 analog inputs.

[0011] Preferably, the frequency measurement waveform conditioning circuit comprises a second-order low-pass filter, a voltage limiting circuit, a zero-crossing hysteresis comparator and an optocoupler isolation circuit connected in sequence;

[0012] The second-order low-pass filter is used to filter the conditioned measurement voltage;

[0013] The voltage limiting circuit is used to limit the sine wave signal output by the second-order low-pass filter;

[0014] The zero-crossing hysteresis comparator comprises a comparator unit, and a voltage follower and a voltage inverter arranged in parallel; the output ends of the voltage follower and the voltage inverter are respectively connected to the two input ends of the comparator unit, and the two output ends of the comparator unit respectively output two square wave signals to a first in-phase amplifier and a second in-phase amplifier;

[0015] The optical coupling isolation circuit is used for isolating the square wave signals output by the first in-phase amplifier and the second in-phase amplifier and outputting them to the embedded system.

[0016] Preferably, the three-phase isolation sampling circuit includes a double PT three-phase isolation circuit consisting of 6 levels of voltage transformer units and a double CT three-phase isolation circuit consisting of 6 levels of current transformer units;

[0017] The voltage transformer unit or the current transformer unit correspondingly includes a voltage transformer or a current transformer whose primary end is connected to the input voltage signal, and whose secondary end is connected in parallel to a Zener diode; one end of the Zener diode is connected to one end of a capacitor via a first inductor and a resistor, and the other end of the Zener diode is connected to the other end of the capacitor via a second inductor, and both ends of the capacitor are connected in parallel to an A / D converter.

[0018] Preferably, the three voltage transformers in the dual PT three-phase isolation circuit constitute a first group of measurement-level three-phase voltage transformer circuits, the remaining three voltage transformers constitute a second group of measurement-level three-phase voltage measurement circuits, the three current transformers in the dual CT three-phase isolation circuit constitute a measurement-level three-phase current transformer circuit, and the remaining three current transformers constitute a protection-level three-phase current transformer circuit.

[0019] Preferably, the embedded system adopts a controller with dual ARM chips.

[0020] Preferably, the dedicated thick film integrated V / I converter comprises a first V / I conversion circuit and a second V / I conversion circuit for converting analog signals of power and frequency respectively.

[0021] Preferably, the A / D converter adopts a 16-bit A / D conversion circuit, including two AD7606 sampling chips.

[0022] Preferably, the D / A converter adopts a digital-to-analog converter provided in the embedded system.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects:

[0024] The present invention processes the power and frequency signals before calculation respectively through a power measurement waveform conditioning circuit and a frequency measurement waveform conditioning circuit. The signal is realized by hardware circuit in the conditioning process, and the time is short. The frequency waveform conditioning circuit conditions the sine wave signal into a square wave signal of half a cycle, and then transmits the voltage signal into a 4-20ma current signal through a D / A converter with a conversion time of microsecond level and a V / I conversion circuit. Therefore, it can ensure that the power transmission response time is not more than 40ms, and the frequency transmission response time is not more than 50ms, so as to solve the problem that the current transmitter has a too large time constant and is difficult to meet the demand for rapid response to system failures. Data acquisition, processing, communication, recording and intelligent identification and transmission of measurement signals and protection signals are realized, and lossless and effective transmission of various signals is realized. It meets the technical specifications of frequency modulation operation of power system, has a simple system structure, a wide range of applications, strong practicality and low maintenance cost.

[0025] Furthermore, the present invention filters and limits the AC measurement voltage signal input by the AC plug-in using a second-order low-pass filter and a voltage limiting circuit, and then uses a zero-crossing hysteresis comparator to condition the AC measurement voltage signal into two square wave signals, and outputs them to the embedded system after isolation by an optocoupler isolation circuit. The embedded system captures a half-cycle count value and compares it with a reference value of 50HZ to obtain a frequency signal with a measurement accuracy of no more than 0.1%. The embedded system transmits the measured frequency signal to the DCS system through a D / A converter and a dedicated thick-film integrated V / I converter.

[0026] Furthermore, the present invention processes the AC measurement voltage, measurement current and protection current signals inputted into the AC plug-in in sequence through a power measurement waveform conditioning circuit, a three-phase isolation sampling circuit and an A / D converter, and then inputs them into an embedded system. The embedded system uses a full-wave Fourier algorithm to obtain a measurement power signal with an accuracy of no more than 0.2% and a protection power signal with an accuracy of no more than 0.5%. When the measured system is in a steady state, the embedded system transmits the measurement power signal to a DCS system through a D / A converter and a V / I conversion circuit; when the measured system is in a fault state, the embedded system transmits the protection power signal to the DCS system through a D / A converter and a V / I conversion circuit. This solves the problem that the non-periodic component during a fault causes a transient saturation of a measurement-level current transformer, resulting in a large power measurement error. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a block diagram of the device principle of the present invention.

[0028] Figure 2a This is a first V / I conversion circuit diagram of the dedicated thick-film integrated V / I converter described in an example of the present invention.

[0029] Figure 2bThis is a second V / I conversion circuit diagram of the dedicated thick-film integrated V / I converter described in an example of the present invention.

[0030] Figure 3 This is a three-phase isolated sampling circuit diagram of dual CT and dual PT described in an example of the present invention.

[0031] Figure 4 This is a frequency measurement waveform conditioning circuit diagram described in an example of the present invention.

[0032] Figure 5a Schematic diagram of chip U1 used in the 16-bit A / D conversion circuit described in an example of the present invention.

[0033] Figure 5b Schematic diagram of chip U2 used in the 16-bit A / D conversion circuit described in an example of the present invention.

[0034] Figure 6 It is a square wave signal obtained by conditioning a sine wave in the frequency measurement described in the example of the present invention.

[0035] In the figure: 1-AC plug-in; 2-power measurement waveform conditioning circuit; 3-frequency measurement waveform conditioning circuit; 4-three-phase isolation sampling circuit; 5-A / D converter; 6-embedded system; 7-D / A converter; 8-special thick film integrated V / I converter. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0037] The present invention can solve the problem of transient saturation of the measurement-level current transformer caused by the non-periodic component in the response inrush current, ensure the stability of the power feedback signal, thereby ensuring the stability of the system power regulation, and effectively alleviate the problem of PLU malfunction due to disturbance in the system.

[0038] The present invention provides a device for accurately measuring primary frequency modulation electrical parameters, such as Figure 1 As shown, it includes an AC plug-in 1, a power measurement waveform conditioning circuit 2, a frequency measurement waveform conditioning circuit 3, a three-phase isolation sampling circuit 4, an A / D converter 5, an embedded system 6, a D / A converter 7 and a dedicated thick film integrated V / I converter 8; wherein the AC plug-in 1 includes two groups of measurement voltage U a1 , U b1 , U c1 , U n1 and U a2 , U b2 , U c2 , U n2 , measure the current I a ,I b ,Ic , and protection current mI a 、mI b 、mI c ; Through the 14 analog inputs in the AC plug-in 1, the measured voltage, measured current, and protection current are sent to the power measurement waveform conditioning circuit 2 and the frequency measurement waveform conditioning circuit 3, and the waveform conditioned by the power measurement waveform conditioning circuit 2 is sent to the three-phase isolation sampling circuit 4 using double CT and double PT, and the output of the three-phase isolation sampling circuit 4 is sent to the embedded system 6 at the same time as the output of the frequency measurement waveform conditioning circuit 3 after passing through the A / D converter 5 for data collection, processing, wave recording, switch output control, and data exchange with the host. Finally, the stable power and frequency electrical quantities are converted into 4-20mA analog outputs through the D / A converter 7 and the dedicated thick film integrated V / I converter 8 for use by the unit DCS system.

[0039] like Figure 4 As shown, the frequency measurement waveform conditioning circuit 3 is composed of a second-order low-pass filter, a voltage limiting circuit, a zero-crossing hysteresis comparator and an optocoupler isolation circuit connected in sequence; wherein,

[0040] The second-order low-pass filter is composed of a resistor R10, a resistor R11, a capacitor C12, and a capacitor C13, and is used to filter the sinusoidal wave signal output by the voltage transformer; capacitor C12 and capacitor C13 are connected in parallel at both ends of the input voltage, resistor R10 is connected between capacitor C12 and the live wire end, and resistor R11 is connected between the live wire ends of capacitor C12 and capacitor C13.

[0041] The voltage limiting circuit is composed of a diode D1 and a diode D2, and the voltage limiting circuit limits the sine wave signal output by the second-order low-pass filter; the diode D1 and the diode D2 are connected in reverse parallel and then in series after the capacitor C13.

[0042] The zero-crossing hysteresis comparator is composed of an operational amplifier U1A, a resistor R12, an operational amplifier U1B, a resistor R13, an operational amplifier U7, a resistor R14, a resistor R15, a resistor R16, a resistor R17, a resistor R18, a resistor R19, an operational amplifier U1C, a resistor R20, a resistor R21 and an operational amplifier U1D. The operational amplifier U1A and the resistor R12 constitute a voltage follower, and the operational amplifier U1B and the resistor R13 constitute a voltage inverter. The zero-crossing hysteresis comparator outputs the waveform after limiting to a comparator unit composed of an operational amplifier U7, a resistor R14, a resistor R15, a resistor R16 and a resistor R17 after passing through the voltage follower and the voltage inverter respectively. The comparator unit further outputs two square wave signals to a first in-phase amplifier composed of a resistor R18, a resistor R19 and an operational amplifier U1C and a second in-phase amplifier composed of a resistor R20, a resistor R21 and an operational amplifier U1D respectively.

[0043] The optocoupler isolation circuit is composed of an optocoupler U6 , a resistor R22 , a resistor R23 and a resistor R24 ​​, and is used to isolate the square wave signals output by the first common-phase amplifier and the second common-phase amplifier and output them to the embedded system 6 .

[0044] like Figure 3As shown, the three-phase isolated sampling circuit 4 of double CT and double PT includes a voltage transformer T1, a voltage transformer T2, a voltage transformer T3, a voltage transformer T4, a voltage transformer T5, a voltage transformer T6, a current transformer T7, a current transformer T8, a current transformer T9, a current transformer T10, a current transformer T11, a current transformer T12, a voltage regulator tube Z1 to Z6, a resistor R1 to R12, a capacitor C1 to C12, and an inductor CR1 to CR24, wherein the voltage transformer T1, the voltage transformer T2, the voltage transformer T3, the voltage transformer T4, the voltage transformer T5, the voltage transformer The current transformer T6 constitutes a double PT three-phase isolation circuit; the current transformer T7, the current transformer T8, the current transformer T9, the current transformer T10, the current transformer T11, and the current transformer T12 constitute a double CT three-phase isolation circuit; the primary end of the voltage transformer T1 is connected to the input voltage signal, the secondary end of the voltage transformer T1 is connected in parallel to the voltage regulator Z1, one end of the voltage regulator Z1 is connected to one end of the capacitor C1 via the inductor CR1 and the resistor R1, the other end of the voltage regulator Z1 is connected to the other end of the capacitor C1 via the inductor CR2, and the two ends of the capacitor C1 are connected in parallel to the A / D converter 5; The circuit connection relationship of the voltage transformer T2, voltage transformer T3, voltage transformer T4, voltage transformer T5, voltage transformer T6, current transformer T7, current transformer T8, current transformer T9, current transformer T10, current transformer T11, and current transformer T12 is the same as that of the voltage transformer T1; the voltage transformer T1, voltage transformer T2, and voltage transformer T3 form a first group of measurement-level three-phase voltage transformer circuits, the voltage transformer T4, voltage transformer T5, and voltage transformer T6 form a second group of measurement-level three-phase voltage measurement circuits, and the current transformer T7, current transformer T8 and current transformer T9 constitute a measurement-level three-phase current transformer circuit, and the current transformer T10, current transformer T11, and current transformer T12 constitute a protection-level three-phase current transformer circuit; the three-phase isolation sampling circuit 3 adopts a dual-CT, dual-PT channel intelligent power transmission solution, which uses measurement-level voltage and current transformer data during normal operation, and uses protection-level current transformer data during system disturbances. The dual-CT, dual-PT measurement method solves the problem of transient saturation of the measurement-level current transformer and voltage transformer disconnection caused by the non-periodic component in the response inrush current, thereby ensuring the stability of the power feedback signal and system power regulation.

[0045] The embedded system 6 uses a dual ARM controller. The main ARM chip mainly completes data acquisition, processing, wave recording, switch output control and data exchange with the host. The slave ARM chip mainly completes human-machine interaction such as real-time data display, historical data query, fault alarm, etc.

[0046] The generator frequency signal is homologous to the power intelligent transmission system, and the output current has a high load capacity, and the load impedance limit is not greater than 600 ohms. The present invention uses a V / I conversion circuit to output a 4-20mA DC signal. Figure 2a As shown, the circuit of the dedicated thick film integrated V / I converter includes a first V / I conversion circuit and a second V / I conversion circuit, wherein the first V / I conversion circuit includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, an operational amplifier U1A, an operational amplifier U1B, a transistor Q1, an input port P1, an output port P2, and a voltage sampling port P3; the resistor R4, the resistor R1, the resistor R2, the resistor R3, the operational amplifier U1A, and the transistor Q1 form a proportional amplifier circuit, the operational amplifier U1B forms a voltage follower circuit, one end of the voltage sampling port P3 is connected to the output end of the operational amplifier U1B, and the other end of the voltage sampling port P3 is connected to the emitter of the transistor Q1, and the voltage sampling port P3 is used to feed back the current signal output by the first V / I conversion circuit to the embedded system 6 via the A / D converter 5, so as to accurately adjust the magnitude of the output current signal of the first V / I conversion circuit. One input end of the operational amplifier U1A is grounded via resistor R2, and is connected to one end of the voltage sampling port P3 via resistor R1. The other input end of the operational amplifier U1A is connected to one end of the input port P1 via resistor R4, and is connected to the other end of the voltage sampling port P3 via resistor R6. The output end of the operational amplifier U1A is connected to the base of the transistor Q1 via resistor R3, the collector of the transistor Q1 is connected to 12VCCA, the emitter is connected to the other end of the voltage sampling port P3, the emitter is connected to one end of the output port P2 via resistor R5, and the other end of the output port P2 is grounded. The input end of the operational amplifier U1B is connected to an output end and to one end of the voltage sampling port P3, and the other output end is connected to one end of the output port P2.

[0047] like Figure 2bAs shown, the second V / I conversion circuit includes a resistor R8, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, an operational amplifier U1C, an operational amplifier U1D, a transistor Q2, an input port P4, an output port P5, and a voltage sampling port P6. The resistor R8, the resistor R9, the resistor R11, the resistor R10, the operational amplifier U1C, and the transistor Q2 form a proportional amplifier circuit, the operational amplifier U1D forms a voltage follower circuit, one end of the voltage sampling port P6 is connected to the output end of the operational amplifier U1D, and the other end of the voltage sampling port P3 is connected to the emitter of the transistor Q2. The voltage sampling port P3 is used to feed back the current signal output by the second V / I conversion circuit to the embedded system 6 via the A / D converter 5, so as to accurately adjust the magnitude of the current signal output by the second V / I conversion circuit. The connection is the same as the first V / I conversion circuit.

[0048] like Figure 5a and Figure 5b As shown, the 16-bit A / D conversion circuit of the present invention includes an AD7606 sampling chip U1 and an AD7606 sampling chip U2. The 49th pin, the 51st pin, the 53rd pin and the 55th pin of the AD7606 sampling chip U1 are respectively connected to the VAout1 port, the Vaout2 port, the VBout1 port and the Vbout2 port of the dedicated thick film integrated V / I converter; the 57th pin, the 59th pin, the 61st pin and the 63rd pin of the AD7606 sampling chip U1 are respectively connected to the The three-phase isolated sampling circuit AI0 port, AI1 port, AI2 port, and AI3 port of the dual CT and dual PT are connected; the 49th pin, the 51st pin, the 53rd pin, the 55th pin, the 57th pin, the 59th pin, the 61st pin, and the 63rd pin of the AD7606 sampling chip U2 are respectively connected to the three-phase isolated sampling circuit AI4 port, AI5 port, AI6 port, AI7 port, AI8 port, AI9 port, AI10 port, and AI11 port of the dual CT and dual PT.

[0049] In this embodiment, the D / A converter 7 adopts the digital-to-analog converter of the embedded system 6. The use of the built-in D / A converter can further reduce the complexity of the hardware circuit and reduce the hardware investment cost. At the same time, it has good compatibility with the embedded system 6 and maximizes the conversion performance of the D / A converter.

[0050] In this embodiment, the power measurement waveform conditioning circuit adopts an existing mature waveform conditioning module to filter the input AC signal, provide a high-quality signal for the subsequent three-phase isolation sampling circuit, and further enhance the anti-interference capability of the entire system.

[0051] In this embodiment, the full-cycle Fourier algorithm is used to calculate the active power and reactive power. When the current of the protection-level CT is greater than 1.1 times the rated current, the protection-level CT current is used for power calculation, otherwise the measurement-level CT current is used.

[0052] In this embodiment, Figure 6 As shown, for frequency measurement, a second-order low-pass filter, a voltage limiting circuit, a phase-locked loop circuit and a zero-crossing hysteresis comparison circuit are used to condition the sine wave into two square wave signals with a phase difference of 180 degrees. The signal frequency is collected by capturing the rising and falling edges of the square wave signals.

[0053] Capture the half-cycle count value and compare it with the reference value T=50HZ, and calculate the frequency as follows:

[0054]

[0055]

[0056] In this embodiment, the three-phase isolation sampling circuit 3 adopts an intelligent power transmission solution with dual CT and dual PT channels. During normal operation, the measurement CT data is used, that is, the first group of measurement-level three-phase voltage transformer circuits composed of the voltage transformer T1, the voltage transformer T2, and the voltage transformer T3 are used, the second group of measurement-level three-phase voltage measurement circuits composed of the voltage transformer T4, the voltage transformer T5, and the voltage transformer T6 are used, and the current transformer T7, the current transformer T8, and the current transformer T9 are used to form a measurement-level three-phase current transformer circuit. When the system is disturbed, the protection CT data is used, that is, the first group of measurement-level three-phase voltage transformer circuits composed of the voltage transformer T1, the voltage transformer T2, and the voltage transformer T3 are used, the second group of measurement-level three-phase voltage measurement circuits composed of the voltage transformer T4, the voltage transformer T5, and the voltage transformer T6 are used, and the current transformer T10, the current transformer T11, and the current transformer T12 are used to form a protection-level three-phase current transformer circuit. In this embodiment, the hardware platform ARM, STM32F1 series, main frequency 72MHz, counter 16 bits, minimum frequency division counting step length are selected, so the minimum time division frequency is met. Since 0.138 and 0.16 are in the same order of magnitude, in order to leave enough margin, it can be changed to STM32F7 series, main frequency 216MHz, minimum frequency division counting step length.

[0057] In this embodiment, the embedded system 6 adopts a dual ARM control mode. The main ARM chip mainly completes data acquisition, processing, wave recording, switch output control and data exchange with the host. The slave ARM chip mainly completes human-machine interaction such as real-time data display, historical data query, fault alarm, etc.

[0058] In this embodiment, the generator frequency signal is homologous to the power intelligent transmission system and requires the output current to have a higher load capacity and a load impedance limit of no more than 600 ohms. Therefore, the dedicated thick-film integrated V / I converter 7 is a V / I conversion circuit constructed using 4 LM324s.

[0059] The primary frequency modulation electrical parameter precision measurement device of the present invention is a high-performance 32-bit device. According to the "General Technical Regulation of Power Transmitter Devices for Generator Set Control", the device was subjected to a formal evaluation experiment, and good results were achieved through on-site testing. The present invention not only realizes the precise measurement of power and frequency, that is, the power measurement accuracy is not greater than 0.2%, and the frequency measurement accuracy is not greater than 0.001Hz; but also ensures the rapidity of power and frequency transmission, the power transmission response time is not greater than 100ms, and the frequency transmission response time is not greater than 50ms; at the same time, it solves the shortcomings of traditional generator transmitters, such as poor anti-interference ability, poor transient characteristics, and no wave recording and communication functions.

[0060] The above is only a preferred embodiment of the patent of the present invention, and does not impose any limitation on the patent of the present invention. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A precise measurement device for primary frequency modulation electrical parameters, characterized in that: It includes an AC plug-in (1), a power measurement waveform conditioning circuit (2), a frequency measurement waveform conditioning circuit (3), a three-phase isolation sampling circuit (4), an A / D converter (5), an embedded system (6), a D / A converter (7) and a dedicated thick film integrated V / I converter (8); The input end of the AC plug-in (1) is provided with an input interface for receiving two groups of measurement voltages, one group of measurement currents and one group of protection currents, and the output end is respectively connected to a power measurement waveform conditioning circuit (2) and a frequency measurement waveform conditioning circuit (3); The power measurement waveform conditioning circuit (2) is connected to the input end of the embedded system (6) via the three-phase isolation sampling circuit (4) and the A / D converter (5) in sequence; the power measurement waveform conditioning circuit (2) is used to filter the four groups of input signals of the AC plug-in (1) and condition them into high-quality sine wave signals, the three-phase isolation sampling circuit (4) is used to sample the conditioned sine wave signals, and the A / D converter (5) is used to convert the sampled signals into digital signals; The frequency measurement waveform conditioning circuit (3) is used to condition one set of measurement voltages into two square wave pulse signals with a phase difference of 180 degrees, and connect them to the input end of the embedded system (6); The output end of the embedded system (6) outputs a digital signal of power and frequency, and is connected in sequence to a D / A converter (7) and a dedicated thick film integrated V / I converter (8) to output a 4-20mA analog output, which is connected to the input end of the unit DCS system.

2. The device for accurately measuring primary frequency modulation electrical parameters according to claim 1, characterized in that: The input interface of the AC plug-in (1) is respectively connected to two groups of measuring voltages U a1 , U b1 , U c1 , U n1 and U a2 , U b2 , U c2 , U n2 , a set of measurement current I a ,I b ,I c And a set of protection current mI a 、mI b 、mI c 14 analog inputs.

3. The device for accurately measuring primary frequency modulation electrical parameters according to claim 1, characterized in that: The frequency measurement waveform conditioning circuit (3) comprises a second-order low-pass filter, a voltage limiting circuit, a zero-crossing hysteresis comparator and an optical coupling isolation circuit which are connected in sequence; The second-order low-pass filter is used to filter the conditioned measurement voltage; The voltage limiting circuit is used to limit the sine wave signal output by the second-order low-pass filter; The zero-crossing hysteresis comparator comprises a comparator unit, and a voltage follower and a voltage inverter arranged in parallel; the output ends of the voltage follower and the voltage inverter are respectively connected to the two input ends of the comparator unit, and the two output ends of the comparator unit respectively output two square wave signals to a first in-phase amplifier and a second in-phase amplifier; The optical coupling isolation circuit is used to isolate the square wave signals output by the first in-phase amplifier and the second in-phase amplifier and then output them to the embedded system (6).

4. The device for accurately measuring primary frequency modulation electrical parameters according to claim 1, characterized in that: The three-phase isolation sampling circuit (4) comprises a double PT three-phase isolation circuit consisting of 6 levels of voltage transformer units and a double CT three-phase isolation circuit consisting of 6 levels of current transformer units; The voltage transformer unit or the current transformer unit correspondingly comprises a voltage transformer or a current transformer whose primary end is connected to an input voltage signal, and whose secondary end is connected in parallel to a voltage regulator tube; one end of the voltage regulator tube is connected to one end of a capacitor via a first inductor and a resistor, and the other end of the voltage regulator tube is connected to the other end of the capacitor via a second inductor, and both ends of the capacitor are connected in parallel to an A / D converter (5).

5. The device for accurately measuring primary frequency modulation electrical parameters according to claim 4, characterized in that: The three voltage transformers in the double PT three-phase isolation circuit form a first group of measurement-level three-phase voltage transformer circuits, and the remaining three voltage transformers form a second group of measurement-level three-phase voltage measurement circuits. The three current transformers in the dual-CT three-phase isolation circuit form a measurement-level three-phase current transformer circuit, and the remaining three current transformers form a protection-level three-phase current transformer circuit.

6. The device for accurately measuring primary frequency modulation electrical parameters according to claim 1, characterized in that: The embedded system (6) adopts a controller with dual ARM chips.

7. The device for accurately measuring primary frequency modulation electrical parameters according to claim 1, characterized in that: The dedicated thick film integrated V / I converter (8) comprises a first V / I conversion circuit and a second V / I conversion circuit for converting analog signals of power and frequency respectively.

8. The device for accurately measuring primary frequency modulation electrical parameters according to claim 1, characterized in that: The A / D converter (5) adopts a 16-bit A / D conversion circuit, including two AD7606 sampling chips.

9. The device for accurately measuring primary frequency modulation electrical parameters according to claim 1, characterized in that: The D / A converter (7) uses a digital-to-analog converter provided in the embedded system (6).

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