An electric energy meter calibrating device and a method of using the same

Abstract

This invention relates to the field of electricity meter calibration devices, specifically disclosing an electricity meter calibration device comprising: a power supply system and a voltage and current power source; the power supply system receives mains power input and outputs voltage to the voltage and current power source; the power supply system monitors the frequency of the output of the voltage and current power source and adjusts the output frequency of the power source according to the frequency; wherein, the power supply system includes an IGBT module, a low-pass filter, a voltage transformer, a main control MCU module, and a main amplifier circuit-comparator module; the main control module generates a 30kHz triangular wave waveform and an AC signal, and measures the output voltage and current frequency of the power source; the main amplifier circuit-comparator module receives the 30kHz triangular wave waveform, the AC signal, and the electrical signal output by the voltage transformer, and compares the amplified output signal with the triangular wave signal to generate a PWM waveform. This invention reduces beat frequency interference in the entire calibration device system, and for high-precision test benches, greatly improves the stability and anti-interference capability of the device.

Description

Technical Field

[0001] This invention relates to the field of electricity meter calibration devices, specifically to an electricity meter calibration device and its usage method. Background Technology

[0002] Currently, the internal components of the calibration device include various types of wires such as high voltage lines, high current lines, power lines, control lines, and signal lines. During operation, various interferences will be generated, affecting the accuracy of the device's measurement. Especially for high-precision platforms with a precision of 0.01 level, even slight interferences can affect the stability of voltage and current output, thus having various impacts on metrological calibration.

[0003] Most existing high-level verification devices have implemented wiring modifications, such as using shielded signal lines; separate voltage and high-current lines, preventing them from sharing with other types of lines; separate power lines; reliable grounding of the device; and the use of isolated transformers for power supply. These methods can shield most interference, and devices of level 0.02 and above can generally meet the requirements for metering performance. However, power frequency interference cannot be completely avoided. The entire device is filled with a 50Hz power frequency magnetic field, and the operating verification frequency of the electricity meter is also 50Hz. This can easily cause the current signal to be interfered with by the power frequency magnetic field. For 0.01 level verification devices, especially those with small currents in the milliampere range, the verification error may exhibit beat frequency phenomena, affecting the metering performance of the electricity meter verification device. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes an electricity meter calibration device that solves the defects of existing 0.01-level calibration devices, especially those with small currents in the milliampere range, where the calibration error exhibits beat frequency phenomenon, affecting the metering performance of the electricity meter calibration device.

[0005] The technical solution adopted in this invention is as follows:

[0006] An energy meter calibration device includes: a power supply system and a voltage and current power source; the power supply system receives mains power input and outputs voltage to the voltage and current power source; the power supply system monitors the frequency of the output of the voltage and current power source and adjusts the output frequency of the power source according to the frequency; wherein, the power supply system includes an IGBT module, a low-pass filter, a voltage transformer, a main control MCU module, and a main amplifier circuit-comparator module; the main control module generates a 30kHz triangular wave waveform and an AC signal, and measures the output voltage and current frequency of the power source; the main amplifier circuit-comparator module receives the triangular wave waveform, the AC signal, and the electrical signal output by the voltage transformer, and compares the amplified output signal with the triangular wave signal to generate a PWM waveform; the IGBT module receives DC power from a three-phase rectifier module, converts it into AC power, and receives the PWM waveform; the low-pass filter receives the electrical signal from the IGBT module and performs feedback sampling; the voltage transformer receives the signal output by the low-pass filter.

[0007] Optionally, the low-pass filter outputs the voltage (power frequency voltage) after interference elimination to the platform, and simultaneously outputs an electrical signal to the voltage transformer, with feedback sampling performed during the process.

[0008] Optionally, the power system further includes a frequency capture module, which is used to acquire the current and voltage signals of the power source and transmit them to the main control MCU module.

[0009] Optionally, the power system includes a three-phase rectifier module for rectifying three-phase AC power into DC power.

[0010] Optionally, the main amplifier circuit-comparator module includes a main amplifier circuit and a comparator module. The main amplifier circuit is used to receive AC signals generated by the voltage transformer and the main control MCU module, and transmit electrical signals to the comparator.

[0011] Optionally, the main amplifier circuit-comparator module includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a first amplifier, a second amplifier, a third amplifier, a first capacitor, a second capacitor, a third capacitor, and a fourth capacitor.

[0012] Optionally, the input terminal of the first resistor is used to receive an AC signal, and the output terminal of the first resistor is electrically connected to a first sub-circuit formed by the third resistor, the first capacitor, and the first amplifier in parallel. The output terminal of the first sub-circuit is electrically connected to a fifth resistor.

[0013] Optionally, the input terminal of the second resistor is used to receive feedback signals from the voltage and current power source, and the output terminal of the second resistor is electrically connected to a second sub-circuit formed by the fourth resistor, the second capacitor, and the second amplifier in parallel. The output terminal of the second sub-circuit is electrically connected to a sixth resistor. The seventh resistor, the third amplifier, and the third capacitor in parallel form a third sub-circuit. The output terminals of the fifth and sixth resistors are electrically connected to the third sub-circuit, and the output terminal of the third sub-circuit is electrically connected to the fourth capacitor. The output terminal of the fourth capacitor outputs a signal.

[0014] Optionally, the IGBT module includes an IGBT and an IGBT driver, wherein the IGBT is used to receive DC power from the three-phase rectifier module and convert it into AC power.

[0015] Optionally, the IGBT driver is used to receive signals from the main amplifier circuit-comparator module and output signals to the IGBT.

[0016] The present invention also discloses a method for using an electricity meter calibration device, comprising the following steps:

[0017] 1) After the mains power is input, a triangular wave signal and an AC signal are generated, and the mains power is rectified into DC power to supply the IGBT;

[0018] 2) Amplify the difference between the AC signal and the feedback signal from the low-pass filter;

[0019] 3) The amplified output signal is compared with the triangular wave signal to generate a PWM waveform;

[0020] 4) Amplify the PWM waveform and output it, then restore it to the power frequency voltage through a low-pass filter.

[0021] Beneficial effects

[0022] 1. This invention provides power to the calibration device by adding a new power supply system. By measuring the output voltage, current and frequency of the power source, the power supply frequency is adjusted in real time, reducing the beat frequency interference of the entire calibration device system. For high-precision test benches, this greatly improves the stability and anti-interference of the device.

[0023] 2. By employing the above method, most interference can be shielded, but power frequency interference cannot be completely avoided. The entire device is filled with a 50Hz power frequency magnetic field, and the working verification frequency of the electricity meter is also 50Hz. This can easily cause the current signal to be interfered with by the power frequency magnetic field. For 0.01-level verification devices, especially for small currents in the milliampere level, the verification error will exhibit a beat frequency phenomenon, affecting the metering performance of the electricity meter verification device. Attached Figure Description

[0024] Figure 1This is a flowchart of the electricity meter calibration device according to Embodiment 1 of the present invention;

[0025] Figure 2 This is a logic flowchart of the energy meter calibration device according to Embodiment 1 of the present invention;

[0026] Figure 3 This is a circuit diagram of the main amplifier circuit-comparator module of Embodiment 2 of the present invention. Detailed Implementation

[0027] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the invention.

[0028] In the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" or "linked" should be interpreted broadly, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0029] In this invention, IGBT refers to Insulated Gate Bipolar Transistor, which is a composite fully controllable voltage-driven power semiconductor device composed of BJT (Bipolar Junction Transistor) and MOS (Insulated Gate Field Effect Transistor), combining the advantages of high input impedance of MOSFET and low on-state voltage drop of GTR.

[0030] In this invention, MCU refers to Microcontroller Unit.

[0031] In this invention, PID (proportional-integral-derivative) control is a widely used engineering control technique that adjusts system error through three control methods: proportional, integral, and derivative.

[0032] In this invention, a low-pass filter (LPF) is an electronic or digital signal processing device that selectively attenuates high-frequency signals while retaining low-frequency signals. Its core function can be summarized as frequency-selective filtering, that is, allowing signals to pass below a specified cutoff frequency while suppressing or attenuating components above that frequency.

[0033] In this invention, PWM stands for Pulse Width Modulation, which is a pulse waveform with a variable duty cycle. Pulse Width Modulation is a method for digitally encoding analog signal levels. Using a high-resolution counter, the duty cycle of a square wave is modulated to encode the level of a specific analog signal. The PWM signal remains digital because at any given moment, the full-amplitude DC power supply is either fully on or fully off. The voltage or current source is applied to the analog load as a repeating pulse sequence of on / off states. On means the DC power supply is applied to the load, and off means the power supply is disconnected. Any analog value can be encoded using PWM, provided the bandwidth is sufficient.

[0034] Example 1

[0035] The technical solution adopted in this invention is as follows:

[0036] like Figure 1 and Figure 2 As shown, this invention discloses an electricity meter calibration device, comprising: a power supply system and a voltage and current power source; the power supply system receives mains power input and outputs voltage to the voltage and current power source; the power supply system monitors the frequency of the voltage and current power source output and adjusts the power supply output frequency according to the frequency. The voltage and current power source outputs a signal to the meter holder.

[0037] In this embodiment, a three-phase four-wire mains power supply powers the power system, which outputs single-phase voltages L0 and N0 to power the device. When calibrating the energy meter, the voltage and current power source outputs voltage U, current I, and frequency F as analog signals for the energy meter's calibration. The power system monitors the frequency F output by the voltage and current power source and adjusts the frequencies of L0 and N0 based on F, ensuring that their frequencies differ by approximately ±5% to eliminate beat frequency interference.

[0038] The power supply system includes an IGBT module, a low-pass filter, a voltage transformer, a main control MCU module, and a main amplifier circuit-comparator module. The main control module generates a 30kHz triangular wave waveform and an AC signal, and measures the output voltage and current frequency of the power source. The main amplifier circuit-comparator module receives the 30kHz triangular wave waveform, the AC signal, and the electrical signal output from the voltage transformer, and compares the amplified output signal with the triangular wave signal to generate a PWM waveform. The IGBT module receives DC power from the three-phase rectifier module, converts it into AC power, and receives the PWM waveform. In this embodiment, the IGBT receives the PWM waveform, and by adjusting the frequency and amplitude of the triangular wave, the duty cycle of the PWM signal can be changed, thereby adjusting the effective value of the output voltage or the current waveform, achieving efficient energy conversion.

[0039] It is particularly important to note that in this embodiment, the low-pass filter receives the electrical signal from the IGBT module and suppresses DC power supply ripple, filters out power supply noise, and suppresses high-frequency noise. In electromagnetic interference suppression, it protects the circuit from high-frequency interference and ultimately restores the voltage to the power frequency. The low-pass filter outputs the interference-free voltage (power frequency voltage) to the platform on one hand; on the other hand, it outputs an electrical signal to the voltage transformer, during which feedback sampling is performed.

[0040] The functions of feedback sampling are as follows: 1) By sampling the output voltage of the low-pass filter through a voltage transformer, the actual value of the current output voltage is obtained, providing a real-time feedback signal to the system for real-time monitoring of the output status. 2) The voltage signal sampled by feedback is transmitted to the main control MCU via the main amplification circuit and compared with the preset target value. If there is a deviation, the main control MCU dynamically adjusts the system output by adjusting the PWM output (driving ICBTs, etc.), forming a closed-loop control logic of "monitoring - comparison - adjustment" to achieve closed-loop control. 3) When factors such as load changes and input fluctuations affect the output voltage, feedback sampling can capture the changes in a timely manner, assisting the system to respond quickly and correct deviations, ensuring the stability and accuracy of the final output voltage, improving the system's anti-interference capability, and ultimately achieving stable output accuracy.

[0041] The voltage transformer is used to receive the signal output from the low-pass filter. In this embodiment, the voltage transformer performs the core functions of signal conversion, safety isolation, real-time monitoring, and protection control in the power supply system.

[0042] The power system also includes a frequency acquisition module, which collects the current and voltage signals of the power source and transmits them to the main control MCU module. The main control MCU module outputs a triangular wave electrical signal to the comparator and an AC signal to the main amplifier circuit. Here, the AC signal and the feedback signal are conditioned by amplifiers A1 and A2, then amplified by amplifier A3 before being output to the comparator, where they are modulated with the triangular wave to generate a PWM waveform.

[0043] The power supply system includes a three-phase rectifier module, which rectifies three-phase AC power into DC power. The main amplifier circuit-comparator module includes a main amplifier circuit and a comparator module. The main amplifier circuit receives AC signals generated by the voltage transformer and the main control MCU module, and transmits electrical signals to the comparator.

[0044] The IGBT module includes an IGBT and an IGBT driver. The IGBT receives DC power from the three-phase rectifier module and converts it into AC power. The IGBT driver receives signals from the main amplifier circuit-comparator module and outputs signals to the IGBT.

[0045] In this embodiment, after the mains power supply is input, the main control MCU starts working, generating a 30kHz triangular wave and a 45-55Hz variable frequency AC signal. Then, a PWM waveform is generated to drive the IGBT module. After low-pass filtering, a 220V voltage with a frequency of 45-55Hz is output to power the device. This achieves the conversion of 50Hz three-phase power into a power supply with an adjustable frequency of 45Hz-55Hz.

[0046] After power input, the main control MCU in the power system starts working, generating a triangular wave and an AC signal. The three-phase rectifier module rectifies the mains power into DC power to supply the IGBTs. The IGBT output signal is sent to the amplifier circuit after interference elimination by a low-pass filter and voltage transformer. During this process, the output signal of the low-pass filter is sampled for feedback. The amplifier circuit amplifies the signal by the difference between the AC signal and the feedback signal. The output signal is compared with the triangular wave signal to generate a PWM waveform. The IGBT driver drives the IGBT module to work. The output signal is then filtered by the low-pass filter to output a 220V AC voltage to power the device. The main control MCU monitors the frequency of the power source voltage and current signals in real time and adjusts the frequency of the AC signal accordingly, making the two frequencies differ by about 5%, thereby changing the frequency of the output 220V AC voltage to eliminate beat frequency interference. Ultimately, the added power system mainly eliminates beat frequency interference between the mains power frequency and the voltage and current source output frequency in the device by ensuring that they are not on the same frequency.

[0047] Example 2

[0048] like Figure 3As shown, the difference between Embodiment 2 and Embodiment 1 is that the main amplifier circuit-comparator module includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, a first amplifier A1, a second amplifier A2, a third amplifier A3, a first capacitor C1, a second capacitor C2, a third capacitor C3, and a fourth capacitor C4. The input terminal of the first resistor R1 is used to receive AC signals, and the output terminal of the first resistor R1 is electrically connected to a first sub-circuit formed by the third resistor R3, the first capacitor C1, and the first amplifier A1 in parallel. The output terminal of the first sub-circuit is electrically connected to the fifth resistor R5. The input terminal of the second resistor R2 is used to receive the feedback signal from the voltage and current power source. The output terminal of the second resistor R2 is electrically connected to the second sub-circuit formed by the fourth resistor R4, the second capacitor C2, and the second amplifier A2 in parallel. The output terminal of the second sub-circuit is electrically connected to the sixth resistor R6. The seventh resistor R7, the third amplifier A3, and the third capacitor C3 in parallel form the third sub-circuit. The output terminals of the fifth resistor R5 and the sixth resistor R6 are electrically connected to the third sub-circuit. The output terminal of the third sub-circuit is electrically connected to the fourth capacitor C4. The output terminal of the fourth capacitor C4 outputs a signal.

[0049] In this embodiment, the AC signal and the feedback signal are conditioned by amplifiers A1 and A2, and then amplified by amplifier A3 before being output to the comparator, where they are modulated with a triangular wave to generate a PWM waveform. Example

[0050] The present invention also discloses a method for using an electricity meter calibration device, comprising the following steps:

[0051] 1) After the mains power is input, a triangular wave signal and an AC signal are generated, and the mains power is rectified into DC power to supply the IGBT;

[0052] 2) Amplify the difference between the AC signal and the feedback signal from the low-pass filter;

[0053] 3) The amplified output signal is compared with the triangular wave signal to generate a PWM waveform;

[0054] 4) Amplify the PWM waveform and output it, then restore it to the power frequency voltage through a low-pass filter.

[0055] The above description is merely a preferred embodiment of the present invention and does not limit the scope of patent protection of the present invention. Any equivalent structural transformations made based on the description and drawings of the present invention, whether directly or indirectly applied to other related technical fields, are similarly included within the scope of protection of the present invention.

Claims

1. A device for calibrating an electricity meter, characterized in that, include: The system includes a power supply system and a voltage and current power source. The power supply system receives AC power input and outputs voltage to the voltage and current power source. The power supply system monitors the frequency of the voltage and current power source output and adjusts the frequency of the AC signal output by the power supply according to the frequency. The power supply system includes an IGBT module, a low-pass filter, a voltage transformer, a main control MCU module, and a main amplifier circuit-comparator module. The power supply system also includes a three-phase rectifier module for rectifying three-phase AC power into DC power. The main control MCU module is used to generate a 30kHz triangular wave waveform and an AC signal, and to measure the voltage and current output frequency of the voltage and current power source. The main amplifier circuit-comparator module is used to receive the triangular wave waveform, the AC signal, and the electrical signal output by the voltage transformer, and compares the amplified output signal with the triangular wave signal to generate a PWM waveform. The IGBT module is used to receive the DC power sent by the three-phase rectifier module, convert it into AC power, and receive the PWM waveform. The low-pass filter is used to receive the electrical signal from the IGBT module, perform feedback sampling, and restore it to the power frequency voltage. The voltage transformer is used to receive the signal output by the low-pass filter.

2. The electricity meter calibration device as described in claim 1, characterized in that, The power system also includes a frequency capture module, which is used to collect the current and voltage signals of the power source and transmit them to the main control MCU module.

3. The electricity meter calibration device as described in claim 1, characterized in that, The main amplifier circuit-comparator module includes a main amplifier circuit and a comparator module. The main amplifier circuit is used to receive AC signals generated by the voltage transformer and the main control MCU module, and transmit electrical signals to the comparator.

4. A power meter calibration device as described in claim 1, 2, or 3, characterized in that, The main amplifier circuit-comparator module includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a first amplifier, a second amplifier, a third amplifier, a first capacitor, a second capacitor, a third capacitor, and a fourth capacitor. The input terminal of the first resistor is used to receive an AC signal, and the output terminal of the first resistor is electrically connected to a first sub-circuit formed by the third resistor, the first capacitor, and the first amplifier in parallel. The output terminal of the first sub-circuit is electrically connected to the fifth resistor. The input terminal of the second resistor is used to receive a feedback signal from a voltage transformer, and the output terminal of the second resistor is electrically connected to a second sub-circuit formed by the fourth resistor, the second capacitor, and the second amplifier in parallel. The output terminal of the second sub-circuit is electrically connected to the sixth resistor. The seventh resistor, the third amplifier, and the third capacitor in parallel form a third sub-circuit. The output terminals of the fifth and sixth resistors are electrically connected to the third sub-circuit, and the output terminal of the third sub-circuit is electrically connected to the fourth capacitor. The output terminal of the fourth capacitor outputs a signal.

5. An energy meter calibration device as described in claim 1, 2, or 3, characterized in that, The IGBT module includes an IGBT and an IGBT driver. The IGBT is used to receive DC power from the three-phase rectifier module and convert it into AC power.

6. The electricity meter calibration device as described in claim 5, characterized in that, The IGBT driver is used to receive signals from the main amplifier circuit-comparator module and output signals to the IGBT.

7. A method of using an electricity meter calibration device, characterized in that, The energy meter testing device is the energy meter testing device according to any one of claims 1 to 6, and includes the following steps: 1) After the mains power is input, a triangular wave signal and an AC signal are generated, and the mains power is rectified into DC power to supply the IGBT; 2) Amplify the difference between the AC signal and the feedback signal from the low-pass filter; 3) The amplified output signal is compared with the triangular wave signal to generate a PWM waveform; 4) Amplify the PWM waveform and output it, then restore it to the power frequency voltage through a low-pass filter.

Images