Disclosure of Invention
Based on this, it is necessary to provide a calibration device for a measuring switch, which aims at the problem of low accuracy and reliability of the existing calibration method for measuring switches.
The invention provides a calibrating device of a measuring switch, which comprises a standard current signal generating module, a standard voltage signal generating module and a control module, wherein the first end of the standard voltage signal generating module is connected with a power supply module, the second end of the standard voltage signal generating module and the first end of the standard current signal generating module are both connected with the first end of the control module, the second end of the standard current signal generating module and the third end of the standard voltage signal generating module are both connected with the first end of a measuring unit, and the second end of the control module is connected with the second end of the measuring unit;
The control module sends an analog voltage signal to the standard current signal generation module, and the standard current signal generation module generates a standard current signal according to the analog voltage signal and sends the standard current signal to the measurement unit;
The standard voltage signal generating module generates a standard voltage signal according to the voltage control signal and sends the standard voltage signal to the measuring unit;
the control module sends the standard measurement result to the measurement unit, and the measurement unit generates an actual measurement result according to the standard current signal and the standard voltage signal and performs calibration according to the standard measurement result and the actual measurement result.
In one embodiment, the standard current signal generating module comprises an A-phase current generating unit, a B-phase current generating unit and a C-phase current generating unit, the standard voltage signal generating module comprises an A-phase voltage generating unit, a B-phase voltage generating unit and a C-phase voltage generating unit, the first end of the A-phase current generating unit, the first end of the B-phase current generating unit and the first end of the C-phase current generating unit are all connected with the first end of the control module, the second end of the A-phase current generating unit, the second end of the B-phase current generating unit and the second end of the C-phase current generating unit are all connected with the first end of the measuring unit, the first end of the A-phase voltage generating unit, the first end of the B-phase voltage generating unit and the first end of the C-phase voltage generating unit are all connected with the first end of the control module, and the third end of the A-phase voltage generating unit, the third end of the B-phase voltage generating unit and the first end of the C-phase voltage generating unit are all connected with the first end of the measuring unit.
In one embodiment, the A-phase current generating unit, the B-phase current generating unit and the C-phase current generating unit all comprise a voltage amplifying circuit, a voltage-current converting circuit and a current converting circuit, wherein the first end of the control module is connected with the first end of the voltage amplifying circuit, the second end of the voltage amplifying circuit is connected with the first end of the voltage-current converting circuit, the second end of the voltage-current converting circuit is connected with the first end of the current converting circuit, and the second end of the current converting circuit is connected with the first end of the measuring unit;
The voltage amplifying circuit amplifies the analog voltage signal sent by the control module and sends the amplified analog voltage signal to the voltage-current conversion circuit, the voltage-current conversion circuit converts the amplified analog voltage signal into an analog current signal and sends the analog current signal to the current conversion circuit, and the current conversion circuit converts the analog current signal into a standard current signal and sends the standard current signal to the measurement unit.
In one embodiment, the voltage-current conversion circuit includes a switch tube V1 and a resistor R1, a control end of the switch tube V1 is connected to a second end of the voltage amplification circuit, a first end of the switch tube V1 is connected to a first end of the current conversion circuit, a second end of the switch tube V1 is connected to a first end of the resistor R1, and a second end of the resistor R1 is grounded.
In one embodiment, the voltage amplifying circuit includes an operational amplifier U1, a non-inverting input terminal of the operational amplifier U1 is connected to a first terminal of the control module, an output terminal of the operational amplifier U1 is connected to a control terminal of the switching tube V1, and an inverting input terminal of the operational amplifier U1 is connected to a second terminal of the switching tube V1.
In one embodiment, the current transformation circuit includes a current transformer CT1 and a bipolar TVS tube Z1, a first end of an input side of the current transformer CT1 is connected to a second end of the voltage-current transformation circuit, a second end of an input side of the current transformer CT1 is connected to a voltage source, a first end ia+ of an output side of the current transformer CT1 and a first end of the bipolar TVS tube Z1 are both connected to a positive current input end of the measurement unit, and a second end IA-of an output side of the current transformer CT1 and a second end of the bipolar TVS tube Z1 are both connected to a negative current input end of the measurement unit.
In one embodiment, the a-phase voltage generating unit, the B-phase voltage generating unit and the C-phase voltage generating unit each comprise a voltage generating circuit and an output voltage feedback circuit, wherein a first end of the voltage generating circuit is connected with the power module, a second end of the voltage generating circuit is connected with a first end of the measuring unit, a first end of the output voltage feedback circuit is connected with a second end of the voltage generating circuit, and a second end of the output voltage feedback circuit is connected with a first end of the control module;
The output voltage feedback circuit collects voltage signals output by the voltage generation circuit and sends the voltage signals to the control module, the control module generates voltage control signals according to the voltage signals and sends the voltage control signals to the voltage generation circuit, and the voltage generation circuit generates standard voltage signals according to the voltage control signals.
In one embodiment, the voltage generating circuit comprises a switching tube Z2, a switching tube Z3, a switching tube Z4, a switching tube Z5, an inductor L1, an inductor L2 and a transformer T1, wherein the control end of the switching tube Z2, the control end of the switching tube Z3, the control end of the switching tube Z4 and the control end of the switching tube Z5 are all connected with the first end of the control module, the first end of the switching tube Z2 and the first end of the switching tube Z3 are all connected with the first end of the power module, the second end of the switching tube Z2 is connected with the first end of the switching tube Z4, the second end of the switching tube Z4 and the second end of the switching tube Z5 are all connected with the second end of the power module, the second end of the switching tube Z2 and the second end of the switching tube Z3 are all connected with the first end of the inductor L1, the second end of the inductor L1 is connected with the first end of the input side of the transformer T1, the first end of the inductor L2 is connected with the second end of the inductor L2 is connected with the second end of the input side of the transformer T1, and the voltage of the input side of the transformer T1 is connected with the second end of the transformer T1.
In one embodiment, the output voltage feedback circuit comprises a resistor R6, a voltage transformer PT1, a resistor R4, a resistor R2, a resistor R5, a resistor R3 and an operational amplifier U2, wherein a first end of the resistor R6 is connected with a first output end of the voltage generating circuit, a second end of the resistor R6 is connected with a first end of an input side of the voltage transformer PT1, a second end of an input side of the PT1 is connected with a second output end of the voltage generating circuit, a first end of the resistor R2 and a first end of the resistor R4 are both connected with a first end of an output side of the PT1, a first end of the resistor R5 and a second end of the resistor R4 are both connected with a second end of the PT1, a second end of the resistor R5 and an inverting input end of the operational amplifier U2 are both connected with a reference potential point, a second end of the resistor R2 and a first end of the resistor R3 are both connected with an in-phase input end of the operational amplifier U2, and a first end of the control module is both connected with an output end of the operational amplifier U2.
In one embodiment, the control module comprises a PC upper computer, an MCU, an analog-to-digital conversion unit, a digital-to-analog conversion unit, a first RS485 communication unit and a second RS485 communication unit, wherein the first end of the PC upper computer is connected with the first end of the first RS485 communication unit, the second end of the first RS485 communication unit is connected with the second end of the measuring unit, the second end of the PC upper computer is connected with the first end of the second RS485 communication unit, the second end of the second RS485 communication unit is connected with the first end of the MCU, the second end of the MCU is connected with the first end of the digital-to-analog conversion unit, the second end of the digital-to-analog conversion unit is connected with the first end of the standard current signal generating module, the third end of the MCU is connected with the first end of the analog-to-digital conversion unit, the second end of the analog-to-digital conversion unit is connected with the second end of the standard voltage signal generating module, and the fourth end of the MCU is connected with the second end of the standard voltage signal generating module;
the PC upper computer sends a voltage output setting instruction to the MCU, the analog-to-digital conversion unit collects a voltage signal output by the standard voltage signal generation module and sends the voltage signal to the MCU, and the MCU generates a voltage control signal according to the voltage output setting instruction and the voltage signal output by the standard voltage signal generation module and sends the voltage control signal to the standard voltage signal generation module;
The PC upper computer sends a current output setting instruction to the MCU, the MCU generates a current output control signal according to the current output setting instruction, the current output control signal is sent to the digital-to-analog conversion unit, and the digital-to-analog conversion unit generates an analog voltage signal according to the current output control signal and sends the analog voltage signal to the standard current signal generation module.
The calibration device of the measuring switch comprises a standard current signal generating module, a standard voltage signal generating module and a control module, wherein the standard current signal generating module sends a standard current signal to the measuring unit, the standard voltage signal generating module sends a standard voltage signal to the measuring unit, the measuring unit generates an actual measuring result according to the standard current signal and the standard voltage signal, and calibrates according to the standard measuring result and the actual measuring result sent by the control module.
Detailed Description
The present application will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present application more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.
The structure of the measuring switch is characterized in that the measuring part is separated from the switch body, the measuring part is arranged in a pluggable measuring unit, a primary large-current signal is converted into a secondary small-current signal by a transformer in the switch body and is output to the measuring unit, the transformation ratio precision and the angle difference precision of the transformer are both fixed in a certain range, and the consistency is good, so that the large-current signal is not needed if the measuring unit is calibrated independently. The calibrating device of the measuring switch is used for calibrating the measuring unit in the measuring switch, and after the measuring unit is calibrated, the calibrated measuring unit is inserted into the switch body to complete the calibration of the measuring switch.
In one embodiment, as shown in fig. 1, a calibration device of a measurement switch is provided, which includes a standard current signal generating module 100, a standard voltage signal generating module 200 and a control module 300, wherein a first end of the standard voltage signal generating module 200 is connected to a power module, a second end of the standard voltage signal generating module 200 and a first end of the standard current signal generating module 100 are both connected to a first end of the control module 300, a second end of the standard current signal generating module 100 and a third end of the standard voltage signal generating module 200 are both connected to a first end of a measurement unit, and a second end of the control module 300 is connected to a second end of the measurement unit.
The control module 300 sends the analog voltage signal to the standard current signal generating module 100, and the standard current signal generating module 100 generates a standard current signal according to the analog voltage signal and sends the standard current signal to the measurement unit.
The standard current signal is used for simulating current conditions possibly encountered in actual operation of the measuring unit so as to calibrate the measuring unit. The analog voltage signal is a sine-wave analog voltage signal for controlling the output current of the standard current signal generating module 100. Specifically, the control module 300 may generate a corresponding analog voltage signal according to a parameter input by a user or a preset calibration algorithm of the measurement unit, and send the analog voltage signal to the standard current signal generating module 100.
The control module 300 generates a voltage control signal according to the voltage signal output by the standard voltage signal generating module 200 and transmits the voltage control signal to the standard voltage signal generating module 200, and the standard voltage signal generating module 200 generates a standard voltage signal according to the voltage control signal and transmits the standard voltage signal to the measuring unit.
The standard voltage signal is used for simulating voltage conditions possibly encountered in actual operation of the measuring unit, so that accuracy of the measuring unit in voltage measurement is ensured. Specifically, the standard voltage signal generating module 200 is powered by the power module, and the control module 300 uses the collected voltage signal output by the standard voltage signal generating module 200 as a feedback signal to regulate and control the standard voltage signal generating module 200 to output the standard voltage signal.
The control module 300 sends the standard measurement result to the measurement unit, and the measurement unit generates an actual measurement result according to the standard current signal and the standard voltage signal and performs calibration according to the standard measurement result and the actual measurement result.
The standard measurement may include, but is not limited to, voltage, current, phase angle, power value, etc. Specifically, during the calibration process, the control module 300 notifies the measurement unit of the voltage, current, phase angle, power value, etc. at this time through the communication protocol, and after the measurement unit measures the standard current signal and the standard voltage signal to obtain an actual measurement result, the measurement unit compares the actual measurement result with the standard measurement result, and if there is a difference, the measurement unit automatically adjusts the internal parameters, such as gain, offset, etc., so as to reduce the error.
Further, after the calibration is completed, the measurement unit may feed back the calibration result to the control module 300, where the calibration result may include a measurement error, a stability parameter, etc., and the control module 300 may compare the data difference before and after the calibration, evaluate whether the error is within an acceptable range, analyze the stability of the measurement unit, etc. Based on the analysis, the control module 300 then evaluates whether the calibration effect meets a predetermined requirement or criteria. If the expected requirement is not met, the control module 300 may send a verification command to the measurement unit, which again measures the same standard voltage signal and standard current signal to verify the accuracy and stability of the calibration according to the verification command.
The calibration device of the measuring switch in the embodiment comprises a standard current signal generation module 100, a standard voltage signal generation module 200 and a control module 300, wherein the standard current signal generation module 100 is used for sending a standard current signal to a measuring unit, the standard voltage signal generation module 200 is used for sending a standard voltage signal to the measuring unit, the measuring unit is used for generating an actual measuring result according to the standard current signal and the standard voltage signal and calibrating the measuring unit in the measuring switch according to the standard measuring result and the actual measuring result sent by the control module 300, and meanwhile, the calibration device does not need a large-current calibration platform body, simplifies the process, reduces the cost and improves the calibration efficiency and reliability.
In order to further improve the accuracy and flexibility of the calibration device, in one embodiment, as shown in fig. 2, the standard current signal generating module 100 includes an a-phase current generating unit 110, a B-phase current generating unit 120 and a C-phase current generating unit 130, the standard voltage signal generating module 200 includes an a-phase voltage generating unit 210, a B-phase voltage generating unit 220 and a C-phase voltage generating unit 230, the first end of the a-phase current generating unit 110, the first end of the B-phase current generating unit 120 and the first end of the C-phase current generating unit 130 are all connected to the first end of the control module 300, the second end of the a-phase current generating unit 110, the second end of the B-phase current generating unit 120 and the second end of the C-phase current generating unit 130 are all connected to the first end of the measuring unit, the first end of the a-phase voltage generating unit 210, the first end of the B-phase voltage generating unit 220 and the first end of the C-phase voltage generating unit 230 are all connected to the power supply module, and the second end of the first end of the a-phase voltage generating unit 210, and the third end of the first end of the C-phase voltage generating unit 230 are all connected to the first end of the measuring unit 230.
The standard current signal generating module 100 includes an a-phase current generating unit 110, a B-phase current generating unit 120, and a C-phase current generating unit 130, which respectively simulate each phase current in a three-phase current system. The three current generating units are connected to the control module 300 at their first ends and receive analog voltage signals from the control module 300, while their second ends are connected to the measuring unit to provide accurate standard current signals for calibration. In addition, in order to provide reliable calibration current signals to the measurement unit, the control module 300 controls the phase angles of the standard current signals output by the a-phase current generation unit 110, the B-phase current generation unit 120, and the C-phase current generation unit 130 to be the same.
Similarly, the standard voltage signal generating module 200 includes an a-phase voltage generating unit 210, a B-phase voltage generating unit 220, and a C-phase voltage generating unit 230. The first ends of the voltage generating units are connected to the power module to obtain stable power supply, the second ends are connected to the control module 300 to receive voltage control signals to adjust output voltage values, and the third ends are connected to the measuring unit to transmit standard voltage signals for calibration. Similarly, the control module 300 controls the phase angles of the standard voltage signals output by the a-phase voltage generating unit 210, the B-phase voltage generating unit 220, and the C-phase voltage generating unit 230 to be the same, and the phase angles of the standard current signals output by the a-phase current generating unit 110, the B-phase current generating unit 120, and the C-phase current generating unit 130 to be the same.
The calibration device in this embodiment generates an a-phase standard current signal through the a-phase current generating unit 110, generates a B-phase standard current signal through the B-phase current generating unit 120, generates a C-phase standard current signal through the C-phase current generating unit 130, and generates an a-phase standard voltage signal through the a-phase voltage generating unit 210, generates a B-phase standard voltage signal through the B-phase voltage generating unit 220, and generates a C-phase standard voltage signal through the C-phase voltage generating unit 230, so that the measurement accuracy of the measuring unit in a three-phase environment is comprehensively verified and calibrated. Meanwhile, the accuracy and the flexibility of calibration are further improved by independently controlling the current and the voltage of each phase.
In one embodiment, as shown in FIG. 3, each of the phase A current generating unit 110, the phase B current generating unit 120 and the phase C current generating unit 130 comprises a voltage amplifying circuit 111, a voltage-current converting circuit 112 and a current converting circuit 113, wherein a first end of the control module 300 is connected with the first end of the voltage amplifying circuit 111, a second end of the voltage amplifying circuit 111 is connected with the first end of the voltage-current converting circuit 112, a second end of the voltage-current converting circuit 112 is connected with the first end of the current converting circuit 113, and a second end of the current converting circuit 113 is connected with the first end of the measuring unit;
The voltage amplifying circuit 111 amplifies the analog voltage signal sent by the control module 300 and sends the amplified analog voltage signal to the voltage-current converting circuit 112, the voltage-current converting circuit 112 converts the amplified analog voltage signal into an analog current signal and sends the analog current signal to the current converting circuit 113, and the current converting circuit 113 converts the analog current signal into a standard current signal and sends the standard current signal to the measuring unit.
Specifically, the voltage amplifying circuit 111 is the first stage of the current generating unit, and is responsible for receiving the weak analog voltage signal from the control module 300 and amplifying it to a level suitable for the subsequent circuit processing. The amplification factor can be designed according to the system requirement so as to ensure the accuracy and stability of the signal. The amplified analog voltage signal is sent to the voltage-to-current conversion circuit 112, and the voltage-to-current conversion circuit 112 generally converts the input analog voltage signal into a corresponding analog current signal by utilizing characteristics of some elements, such as MOSFET, BJT, op-amp, resistor combination, etc., and then sends the analog current signal to the current conversion circuit 113. After receiving the analog current signal, the current conversion circuit 113 converts the analog current signal into a current signal conforming to a specific standard, such as a sinusoidal current signal of 0-75 ma standard, so as to satisfy the current range of the measurement unit.
The a-phase current generating unit 110, the B-phase current generating unit 120 and the C-phase current generating unit 130 in the present embodiment each include a voltage amplifying circuit 111, a voltage-current converting circuit 112 and a current converting circuit 113, which are operated in a multistage cooperative manner, so that high-precision control of standard current signal output is realized, and thus the reliability of the measuring switch calibration process is significantly improved. In addition, through the key parameters such as the gain of the voltage amplification circuit 111, the conversion coefficient of the voltage current conversion circuit 112, the conversion proportion of the current conversion circuit 113 and the like, the calibration device can adapt to the requirements of various different application scenes, accurately calibrate different types of measurement units, and meanwhile, the fault investigation and maintenance are more convenient and faster due to the modularized design.
In one embodiment, as shown in fig. 4, the voltage-current conversion circuit 112 includes a switch tube V1 and a resistor R1, the control end of the switch tube V1 is connected to the second end of the voltage amplifying circuit 111, the first end of the switch tube V1 is connected to the first end of the current conversion circuit 113, the second end of the switch tube V1 is connected to the first end of the resistor R1, and the second end of the resistor R1 is grounded.
The output voltage of the voltage amplifying circuit 111 can control the conduction degree of the switching tube V1, so as to change the current output by the switching tube V1. Specifically, when the output of the voltage amplifying circuit 111 changes, the on current of the switching tube V1 also changes, so that the current flowing into the current converting circuit 113 changes, and then the current converting circuit 113 converts the current into a standard current signal and sends the standard current signal to the measuring unit.
Further, as shown in fig. 4, when the switching tube is a MOSFET, a body diode may be connected between the source and the drain to prevent the MOS tube from burning out.
In this embodiment, the voltage-current conversion circuit 112 includes a switching tube V1 and a resistor R1, and the magnitude and accuracy of the output current can be flexibly controlled by adjusting the conduction degree of the switching tube V1 by the voltage output from the voltage amplification circuit 111.
In one embodiment, the voltage amplifying circuit 111 includes an operational amplifier U1, wherein a non-inverting input terminal of the operational amplifier U1 is connected to the first terminal of the control module 300, an output terminal of the operational amplifier U1 is connected to the control terminal of the switching transistor V1, and an inverting input terminal of the operational amplifier U1 is connected to the second terminal of the switching transistor V1.
Specifically, after the non-inverting input terminal of the operational amplifier U1 obtains the analog voltage signal sent by the control module 300, the output terminal thereof outputs the amplified analog voltage signal to the control terminal of the switching tube V1, and the amplitude of the voltage signal is determined by the gain of the operational amplifier U1. When the output voltage of the operational amplifier U1 changes, the on current of the switching tube V1 will also change accordingly, and when the current passes through the resistor R1, a voltage drop will be generated on R1, and this voltage drop is fed back to the inverting input terminal of the operational amplifier U1 and compared with the voltage of the non-inverting input terminal. Through a negative feedback mechanism, the operational amplifier U1 continuously adjusts its output until the circuit reaches a steady state. Furthermore, according to the actual measurement scenario, a person skilled in the art can adjust the gain of the operational amplifier U1 by designing different resistor voltage division networks of the operational amplifier U1, so as to calibrate the measurement units with different measuring ranges.
The present embodiment can effectively suppress noise and distortion by amplifying the analog voltage signal transmitted from the control module 300 using the operational amplifier, thereby improving the reliability of the standard current signal.
In one embodiment, the current transformation circuit 113 includes a current transformer CT1 and a bipolar TVS tube Z1, a first end of an input side of the current transformer CT1 is connected to a second end of the voltage-current transformation circuit 112, a second end of an input side of the current transformer CT1 is connected to a voltage source, a first end ia+ of an output side of the current transformer CT1 and a first end of the bipolar TVS tube Z1 are both connected to a positive current input end of the measurement unit, and a second end IA-of an output side of the current transformer CT1 and a second end of the bipolar TVS tube Z1 are both connected to a negative current input end of the measurement unit.
The first end of the measuring unit includes a positive current input end and a negative current input end, the first end ia+ of the output side of the current transformer CT1 and the first end of the bipolar TVS tube Z1 in the a-phase current generating unit 110, the B-phase current generating unit 120 and the C-phase current generating unit 130 are all connected to the positive current input end of the measuring unit, and the second end IA-of the output side of the current transformer CT1 and the second end of the bipolar TVS tube Z1 are all connected to the negative current input end of the measuring unit.
Specifically, the input side of the current transformer CT1 is connected to the voltage source and the second terminal of the voltage-to-current conversion circuit 112 for measuring the current flowing from the voltage-to-current conversion circuit 112. After this current has been converted by the current converter CT1, a current signal proportional to the input current is generated at the output side of the current converter CT 1. The bipolar TVS tube Z1 is connected in parallel to the output side of the current transformer CT1 for protecting the measuring unit from transient overvoltage. When overvoltage occurs in the circuit, the TVS tube is conducted rapidly to provide bi-directional overvoltage protection.
The current conversion circuit 113 in this embodiment includes the current converter CT1, and can accurately convert the current signal at the input side into the current signal which is convenient for the measurement by the measurement unit, so that the subsequent measurement unit can accurately measure.
In one embodiment, as shown in fig. 3, each of the a-phase voltage generating unit 210, the B-phase voltage generating unit 220 and the C-phase voltage generating unit 230 includes a voltage generating circuit 211 and an output voltage feedback circuit 212, wherein a first end of the voltage generating circuit 211 is connected to the power module, a second end of the voltage generating circuit 211 is connected to the first end of the measuring unit, a first end of the output voltage feedback circuit 212 is connected to the second end of the voltage generating circuit 211, and a second end of the output voltage feedback circuit 212 is connected to the first end of the control module 300.
The output voltage feedback circuit 212 collects the voltage signal output by the voltage generation circuit 211 and sends the voltage signal to the control module 300, the control module 300 generates a voltage control signal according to the voltage signal and sends the voltage control signal to the voltage generation circuit 211, and the voltage generation circuit 211 generates a standard voltage signal according to the voltage control signal.
Specifically, the voltage generating circuit 211 generates a voltage signal according to the voltage control signal of the control module 300 after receiving the power of the power module. The output voltage feedback circuit 212 monitors the voltage value output from the voltage generation circuit 211 in real time and feeds this information back to the control module 300. The control module 300 compares the fed-back voltage signal with a preset voltage target value to generate an adjusted voltage control signal. After receiving the adjusted voltage control signal, the voltage generation circuit 211 adjusts the output voltage thereof to be consistent with a preset target value or to be within a predetermined accuracy range, thereby stably generating a required standard voltage signal.
The a-phase voltage generating unit 210, the B-phase voltage generating unit 220 and the C-phase voltage generating unit 230 in the present embodiment can monitor and adjust the output of the voltage generating circuit 211 in real time by introducing a closed-loop control mechanism of the output voltage feedback circuit 212 and the control module 300, so as to ensure that the output three-phase voltage signal has high precision and stability.
In one embodiment, as shown in fig. 4, the voltage generating circuit 211 includes a switch tube Z2, a switch tube Z3, a switch tube Z4, a switch tube Z5, an inductor L1, an inductor L2, and a transformer T1, wherein the control end of the switch tube Z2, the control end of the switch tube Z3, the control end of the switch tube Z4, and the control end of the switch tube Z5 are all connected to the first end of the control module 300, the first end of the switch tube Z2 and the first end of the switch tube Z3 are all connected to the first end of the power module, the second end of the switch tube Z2 is connected to the first end of the switch tube Z4, the second end of the switch tube Z3 and the second end of the switch tube Z5 are all connected to the second end of the power module, the second end of the switch tube Z2 and the second end of the switch tube Z3 are all connected to the first end of the inductor L1, the second end of the inductor L1 is connected to the first end of the input side of the transformer T1, the first end of the inductor L2 is connected to the first end of the second end of the switch tube Z3, and the second end of the input side of the transformer T1 is connected to the input side of the transformer T1.
The first end of the measuring unit comprises a voltage input end, and the voltage input end can comprise a positive voltage input end and a negative voltage input end. The first ports of the output sides of the transformers T1 in the a-phase voltage generating unit 210, the B-phase voltage generating unit 220, and the C-phase voltage generating unit 230 may be connected to the positive voltage input terminal of the measuring unit, and the second ports of the output sides of the transformers T1 may be connected to the negative voltage input terminal of the measuring unit. The working states of the switching tube Z2, the switching tube Z3, the switching tube Z4 and the switching tube Z5 are uniformly controlled by the control module 300, and the control module 300 generates control signals of the switching tubes according to the voltage signals sent by the output voltage feedback circuit 212 and a preset target value so as to adjust the on-off state of the switching tubes and control the output of voltage. The inductors L1 and L2 are used to store and release energy to smooth the voltage waveform and assist in voltage regulation. The transformer T1 plays a role of voltage conversion to convert the input electric energy into a desired voltage level within the measuring range of the measuring unit.
Specifically, when the control module 300 sends out a control signal, the switching transistors Z2, Z3, Z4, Z5 perform switching operation according to the control signal, so as to control the flow path of the current in the circuit. By adjusting the on-off time and frequency of the switching tube, the current passing through the inductors L1 and L2 can be controlled, and the input voltage and the output voltage of the transformer T1 are further affected. The transformer T1 converts the input electric energy into a desired voltage level and outputs the voltage, the output voltage is fed back to the control module 300 in real time through the output voltage feedback circuit 212, and the control module 300 continuously adjusts the control signal by comparing the feedback voltage with a preset target value until the output voltage is stabilized at the preset value or reaches a predetermined accuracy range, thereby generating a desired standard voltage signal.
The voltage generating circuit 211 of the present embodiment realizes highly accurate and flexible adjustment of voltage output through the cooperative action of the switching tube control strategy, the inductor and the transformer. The control module 300 can respond to the voltage feedback signal in real time to quickly adjust the working state of the switching tube, thereby accurately controlling the output voltage to a preset target value and improving the response speed and the anti-interference capability of the system.
In one embodiment, as shown in fig. 4, the output voltage feedback circuit 212 includes a resistor R6, a voltage transformer PT1, a resistor R4, a resistor R2, a resistor R5, a resistor R3, and an operational amplifier U2, wherein a first end of the resistor R6 is connected to a first output end of the voltage generating circuit 211, a second end of the resistor R6 is connected to a first end of an input side of the voltage transformer PT1, a second end of the resistor PT1 is connected to a second output end of the voltage generating circuit 211, a first end of the resistor R2 and a first end of the resistor R4 are both connected to a first end of an output side of PT1, a first end of the resistor R5 and a second end of the resistor R4 are both connected to a second end of an output side of PT1, a second end of the resistor R5 and an inverting input end of the operational amplifier U2 are both connected to a reference potential point, a second end of the resistor R2 and a first end of the resistor R3 are both connected to an in-phase input end of the operational amplifier U2, and a first end of the resistor R3 and a first end of the control module 300 are both connected to an output end of the operational amplifier U2.
Wherein the second terminal of the voltage generating circuit 211 comprises a first output terminal and a second output terminal. The resistor R6 is used to sample the output voltage of the voltage generation circuit 211. The voltage transformer PT1 is used for measuring and converting a voltage difference between two output ends of the voltage generating circuit 211, so as to convert a high voltage signal into a low voltage signal, and facilitate subsequent processing. The first ends of the resistor R2 and the resistor R4 are commonly connected to the first end of the output side of the PT1 to form a voltage division network of the output voltage of the PT 1. The first terminal of the resistor R5 is connected to the second terminal of the output side of PT1, while the second terminal of the resistor R5 is connected to a reference potential point (e.g. ground), such that R5 and R4 form a further voltage divider network for generating a voltage signal related to the output voltage of PT1, which signal is used as a reference or comparison signal. The operational amplifier U2 amplifies according to the voltage difference between the inverting input terminal and the non-inverting input terminal. If the sampled value of the voltage signal output by the voltage generating circuit 211 is higher than the reference voltage, the operational amplifier will output a negative error voltage, whereas a positive error voltage is output. The magnitude of this error voltage reflects the degree of deviation of the voltage signal output from the voltage generation circuit 211 from the desired value.
The output voltage feedback circuit 212 in this embodiment improves the stability and accuracy of the output voltage and enhances the anti-interference capability and dynamic performance of the calibration device through an accurate voltage measurement and feedback mechanism.
In one embodiment, as shown in fig. 4, the control module 300 includes a PC upper computer, an MCU, an analog-to-digital conversion unit, a digital-to-analog conversion unit, a first RS485 communication unit and a second RS485 communication unit, where a first end of the PC upper computer is connected to a first end of the first RS485 communication unit, a second end of the first RS485 communication unit is connected to a second end of the measurement unit, a second end of the PC upper computer is connected to a first end of the second RS485 communication unit, a second end of the second RS485 communication unit is connected to a first end of the MCU, a second end of the MCU is connected to a first end of the digital-to-analog conversion unit, a second end of the digital-to-analog conversion unit is connected to a first end of the standard current signal generation module 100, a third end of the MCU is connected to a second end of the standard voltage signal generation module 200, and a fourth end of the MCU is connected to a second end of the standard voltage signal generation module 200.
The PC upper computer sends a voltage output setting instruction to the MCU, the analog-to-digital conversion unit collects the voltage signals output by the standard voltage signal generation module 200 and sends the voltage signals to the MCU, the MCU generates voltage control signals according to the voltage output setting instruction and the voltage signals output by the standard voltage signal generation module 200 and sends the voltage control signals to the standard voltage signal generation module 200, and the standard voltage signal generation module 200 adjusts the output voltage according to the voltage control signals.
The PC upper computer transmits a current output setting instruction to the MCU, the MCU generates a current output control signal according to the current output setting instruction, and transmits the current output control signal to the digital-to-analog conversion unit, and the digital-to-analog conversion unit generates an analog voltage signal according to the current output control signal, and transmits the analog voltage signal to the standard current signal generation module 100. The standard current signal generating module 100 adjusts its output current according to the analog voltage signal.
The control module 300 in this embodiment includes a PC host computer, an MCU, an analog-to-digital conversion unit, a digital-to-analog conversion unit, a first RS485 communication unit, and a second RS485 communication unit, and a user can conveniently adjust the calibration voltage and the calibration current of the measurement unit through remote control and real-time data feedback of the PC host computer.
In order to better understand the calibration device of the measuring unit in the above embodiment, a more detailed embodiment is provided below for explanation.
In one embodiment, as shown in fig. 4, a calibration device for a measurement unit is provided, which includes a PC host, a first RS485 communication unit, a second RS485 communication unit, an MCU (micro control unit), an ADC chip (analog to digital conversion unit), a DAC chip (digital to analog conversion unit), an a-phase current generating unit 110, a B-phase current generating unit 120, a C-phase current generating unit 130, an a-phase voltage generating unit 210, a B-phase voltage generating unit 220, a C-phase voltage generating unit 230, and a power module. The a-phase current generating unit 110, the B-phase current generating unit 120 and the C-phase current generating unit 130 have the same structure, and the a-phase current generating unit 110 includes an operational amplifier U1, a switching tube V1, a resistor R1, a current transformer CT1 and a bipolar TVS tube Z1. The a-phase voltage generating unit 210, the B-phase voltage generating unit 220 and the C-phase voltage generating unit 230 have the same structure, and the a-phase voltage generating unit 210 includes, for example, a switching tube Z2, a switching tube Z3, a switching tube Z4, a switching tube Z5, an inductor L1, an inductor L2, a transformer T1, a resistor R6, a voltage transformer PT1, a resistor R4, a resistor R2, a resistor R5, a resistor R3 and an operational amplifier U2. In this embodiment, the switching tube V1 is a MOS tube, and a body diode is connected between the source and the drain of the MOS tube, and the switching tube Z2, the switching tube Z3, the switching tube Z4, and the switching tube Z5 are all thyristors, and the filter capacitor C1 is a polar capacitor.
The first end of the PC upper computer is connected with the second end of the measuring unit through the first RS485 communication unit, and the second end of the PC upper computer is connected with the first end of the MCU through the second RS485 communication unit. The MCU is connected with the DAC chip through the SPI1 interface, the DAC_IA interface of the DAC chip is connected with the non-inverting input end of the operational amplifier U1, the DAC_IB interface of the DAC chip is connected with the non-inverting input end of the operational amplifier in the B-phase current generating unit 120, and the DAC_IC interface of the DAC chip is connected with the non-inverting input end of the operational amplifier in the C-phase current generating unit 130.
Taking the a-phase current generating unit 110 as an example, the output end of the operational amplifier U1 is connected to the gate of the MOS transistor V1, the source of the MOS transistor V1 is connected to the first end of the resistor R1, the second end of the resistor R1 is grounded, the inverting input end of the operational amplifier U1 is connected to the source of the MOS transistor V1 to form a feedback loop, the drain of the MOS transistor V1 is connected to the first end (6) of the input side of the current transformer CT1, the second end (1) of the input side of the current transformer CT1 is connected to V12P0 (voltage source), the first port (4) of the output side of the current transformer CT1 is connected to the first end of the bipolar TVS transistor, the second port (3) of the output side of the current transformer CT1 is connected to the second end of the bipolar TVS transistor, the first end of the bipolar TVS transistor is connected to the positive current input end of the measurement unit, and the second end of the bipolar TVS transistor is connected to the negative current input end of the measurement unit. The principle of the current generating unit for generating the standard current signal is that the MCU is connected with the DAC chip through the SPI, and the DAC is controlled to output an analog voltage signal with a 50Hz sine waveform, so that the current generating circuit can output an AC 0-75 mA standard sine current signal. Meanwhile, the MCUs control the phase angles of the standard current signals output from the a-phase current generating unit 110, the B-phase current generating unit 120, and the C-phase current generating unit 130 to be 120 ° through the DAC chip.
The MCU is connected with the ADC chip through an SPI2 interface, an ADC_UA interface of the ADC chip is connected with the output end of the operational amplifier U2, an ADC_UB interface is connected with the output end of the operational amplifier in the B-phase voltage generating unit 220, and an ADC_UC interface is connected with the output end of the operational amplifier in the C-phase voltage generating unit 230.
The power module comprises an alternating-current voltage source V2, a transformer T2, a rectifier bridge D1 and a filter capacitor C1. The positive pole of alternating voltage source V2 connects first end (1) of transformer T2 input side, and second end (2) of transformer T2 input side are connected to the negative pole, and rectifier bridge D1's first end (1) is connected to transformer T2 output side's first end (4), and rectifier bridge D1's second end (2) is connected to transformer T2 output side's second end (3), and capacitor C1's positive pole is connected to rectifier bridge D1's third end (3), and capacitor C1's negative pole is connected to rectifier bridge D1's fourth end (4).
Taking the a-phase voltage generating unit 210 as an example, the positive electrode of the capacitor C1 is connected to the first end of the switching tube Z2 and the first end of the switching tube Z3, the negative electrode of the capacitor C1 is connected to the second end of the switching tube Z4 and the second end of the switching tube Z5, the second end of the switching tube Z2 and the second end of the switching tube Z3 are both connected to the first end of the inductor L1, the second end of the inductor L2 is connected to the first end (1) of the input side of the transformer T1, the first end of the switching tube Z4 and the first end of the switching tube Z5 are both connected to the first end of the inductor L2, and the second end of the inductor L2 is connected to the second end (2) of the input side of the transformer T1. The control end of the switch tube Z2 is connected with the CTRL A1 interface of the MCU, the control end of the switch tube Z3 is connected with the CTRL A2 interface of the MCU, the control end of the switch tube Z4 is connected with the CTRL A3 interface of the MCU, and the control end of the switch tube Z5 is connected with the CTRL A4 interface of the MCU. The first end (4) of the output side of the transformer T1 is connected with the positive voltage input end of the measuring unit, and the second end (3) of the output side of the transformer T1 is connected with the negative voltage input end of the measuring unit. The first end of resistance R6 connects transformer T1 output side's first end (4), voltage transformer PT1 input side's first end (4) are connected to resistance R6's second end, voltage transformer PT1 input side's second end (3) are connected to transformer T1 output side's second end (3), voltage transformer PT1 output side's first end (1) are all connected to resistance R2 and resistance R4's first end, voltage transformer PT1 output side's second end (6) are all connected to resistance R4's second end and resistance R5's first end, operational amplifier U2's homophase input end is all connected to resistance R2's second end and operational amplifier U2's inverting input end, operational amplifier U2's output is all connected to resistance R3's second end.
The principle of the a-phase voltage generating unit 210 generating the standard voltage signal is that the MCU outputs control signals (CTRLA 1 to CTRLA 4) by using the IO port, and these signals precisely regulate the on-off states of the switching transistors Z2 to Z5, so as to dynamically manage the circuits in the voltage generating unit, thereby generating the required ac voltage signal. The ac voltage signal is then sampled by a sampling circuit comprising a voltage transformer PT1, a resistor R4, a resistor R2, a resistor R5, a resistor R3 and an operational amplifier U2. MCU is connected with ADC chip through SPI2 interface, realizes the digital sampling of voltage signal. The MCU takes the collected voltage signal characteristics as a feedback signal, and adjusts and controls the voltage generation unit to output a voltage signal with standard AC 0-380V according to the feedback signal. The principle of generating the standard voltage signal by the B-phase and C-phase voltage generating unit 230 is the same as that of the a-phase. Meanwhile, the MCUs control the phase angles of the standard voltage signals output from the a-phase voltage generating unit 210, the B-phase voltage generating unit 220, and the C-phase voltage generating unit 230 to be 120 ° through the ADC chips.
And the PC upper computer is communicated with the MCU through an RS485 bus. In the calibration process, a voltage output setting instruction and a current output setting instruction are sent to the MCU through a communication protocol so as to inform the MCU to output corresponding voltage and current signals.
The PC upper computer is communicated with the measuring unit through an RS485 bus. In the calibration process, the measurement unit is informed of the voltage/current/phase angle/power value of the source at the moment through a communication protocol, and the measurement unit performs calibration. After the calibration is completed, the measuring unit is put into the body of the measuring switch to verify the accuracy.
In addition, as shown in fig. 5, the present embodiment further provides a calibration system for measurement units, which includes at least one calibration device for measurement units, wherein a first end of each calibration device is connected to a PC host, and a second end of each calibration device is connected to a different measurement unit, so that calibration can be performed on one measurement unit. The calibration devices can be uniformly managed by a PC host computer, and the rest structures are the same as those of the calibration devices, and each calibration device comprises a first RS485 communication unit, a second RS485 communication unit, an MCU, an ADC chip, a DAC chip, an A-phase current generation unit 110, a B-phase current generation unit 120, a C-phase current generation unit 130, an A-phase voltage generation unit 210, a B-phase voltage generation unit 220, a C-phase voltage generation unit 230 and a power supply module. The calibration system adopts a mode that a plurality of calibration devices are connected in parallel, so that a plurality of measurement units can be calibrated simultaneously. The detailed calibration process may refer to the calibration process of the calibration device, and will not be described herein.
The calibration device of the measurement unit in the embodiment greatly improves the calibration efficiency and reliability of the measurement switch, has low cost, and can greatly reduce the economic investment of the calibration equipment; in addition, the calibration system of the measuring unit in the embodiment can calibrate a plurality of measuring units at the same time, and further improves the calibration efficiency of the measuring switch.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.