CN115327221A - Non-invasive wireless electric energy metering system and method - Google Patents
Non-invasive wireless electric energy metering system and method Download PDFInfo
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- G01R22/00—Arrangements for measuring time integral of electric power or current, e.g. electricity meters
- G01R22/06—Arrangements for measuring time integral of electric power or current, e.g. electricity meters by electronic methods
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Abstract
The invention relates to a non-invasive wireless electric energy metering system and a non-invasive wireless electric energy metering method, wherein the method comprises the following steps: 1. the voltage sampling circuit, the current sampling circuit and the temperature sampling circuit are disconnected, micro energy is collected, and the power management unit obtains electricity in an induction mode. 2. And starting the voltage sampling circuit, the current sampling circuit and the temperature sampling circuit, collecting voltage waveform, current waveform and temperature data, and when sampling is completed, closing the sampling circuit, and continuously charging the power management unit. 3. The data processing unit carries out filtering processing on direct current components and noise in the voltage waveform and the current waveform, and calculates voltage, current, power factor, power and energy. 4. And wirelessly transmitting the calculated data to a data acquisition unit for further analyzing the power utilization condition and the power grid condition. The invention can complete the measurement of parameters such as power, energy and the like of the line to be measured on the premise of non-invasion, and has the advantages of non-invasive installation, self power supply, no wiring and great implementation cost saving. And support comprehensive electrical parameter measurement.
Description
Technical Field
The invention relates to the technical field of electric energy metering, in particular to a method for calculating a power factor and metering energy in an electric power system.
Background
Energy consumption monitoring is the basis for developing energy-saving work, and the enhancement of energy consumption monitoring, particularly electric power energy consumption monitoring, has important significance for improving the energy efficiency of China, realizing the sustainable development of energy, building a conservation-oriented society, relieving the pressure of energy and the like.
The traditional energy consumption monitoring method adopts a subentry energy consumption metering method, namely, a power supply circuit is subjected to subentry metering transformation, an electric energy meter with a communication function is installed according to requirements, and data acquisition, monitoring and analysis of energy consumption (such as electric energy, current, power factor, temperature and the like) are realized. The traditional electric energy meter needs to be installed in a power failure mode, the wiring is more, and the installation and maintenance cost is high.
The wireless current temperature sensor in the market at present utilizes the electromagnetic energy of induction around the power transmission line to obtain the electric energy, and electric parameters such as the temperature of on-line monitoring cable, electric current combine radio communication to realize data wireless transmission function. Only the current, the voltage, the temperature and the like are measured, the running state of the line can be reflected to a certain degree, but the parameters of actual power, current forward and reverse, reactive four-quadrant, electric energy and the like cannot be provided, and the parameters are important for actual electricity utilization analysis.
The existing electric energy meter: can provide more comprehensive electrical parameters, but has the characteristics of large volume, intrusive installation, inconvenient installation, high cost and the like.
The existing non-invasive solutions: the device is convenient to install, self-powered, free of wiring and the like, but the device has the advantages that the electrical parameter measurement is less, only the measurement of current and temperature is supported, and the real power utilization condition cannot be represented.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a non-invasive wireless electric energy metering system and a non-invasive wireless electric energy metering method, which are used for measuring parameters such as power, energy and the like of a line to be measured on the premise of non-invasion, so that power-cut-free installation and self-power supply can be supported, and various electrical parameters can be measured.
In order to achieve the above purposes, the technical scheme adopted by the invention is as follows:
a non-intrusive wireless power metering system, comprising: the device comprises a power supply management unit, a sampling unit, a data processing unit and a wireless communication unit.
The power management unit comprises a current transformer and an energy storage device, and the energy storage device is a super capacitor or a rechargeable battery; the power management unit is responsible for micro-energy collection, and the current transformer is used for obtaining electric energy from the wire to be tested, storing and outputting the electric energy and maintaining the normal operation of the whole system.
The sampling unit comprises a voltage sampling circuit, a current sampling circuit and a temperature sampling circuit; the device is used for sampling the current waveform, the voltage waveform and the cable temperature of a wire to be tested;
the data processing unit is used for calculating voltage, current, power factor, power and energy according to the current waveform, the voltage waveform and the temperature acquired by the sampling unit;
the wireless communication unit: and the wireless transmission module is used for wirelessly transmitting the calculated voltage, current, power factor, power and energy to the data acquisition unit.
A non-invasive wireless electric energy metering method comprises the following specific steps:
step 1, disconnecting a voltage sampling circuit, a current sampling circuit and a temperature sampling circuit, collecting micro energy, and obtaining electricity by a power management unit in an induction way.
And 2, starting the voltage sampling circuit, the current sampling circuit and the temperature sampling circuit, collecting voltage waveform, current waveform and temperature data, and when sampling is completed, closing the sampling circuit and continuously charging the power management unit.
And 3, filtering the direct current components and the noise in the voltage waveform and the current waveform by the data processing unit, and calculating the voltage, the current, the power factor, the power and the energy.
And 4, wirelessly transmitting the calculated voltage, current, power factor, power and energy data to a data acquisition unit for further analyzing the power utilization condition and the power grid condition.
When the electric energy taken by the current transformer from the cable is enough to support the running and consumption of the whole system, the redundant electric energy charges the energy storage device; when the electric energy taken from the cable by the current transformer cannot meet the running consumption of the whole system, the energy storage device is switched to supply power.
The number of sampling points of the voltage and current waveforms is determined by the number of sampling cycles, the sampling frequency and the power grid frequency. The grid frequency is determined from the current zero crossing time interval.
The voltage and current are calculated according to the following formula:
wherein, the first and the second end of the pipe are connected with each other,Nnumber of sampling points, QUOTE
And QUOTE
Respectively, voltage DC bias and current DC bias, QUOTE
To the effective value of the voltage, QUOTE
Calculating coefficients for the voltages, QUOTE
Is a firstiInstantaneous value of voltage sampling waveform of point, QUOTE
Being effective values of current, QUOTE
Calculating the coefficient, QUOTE, for the current
Is a firstiThe current at the point samples the waveform instantaneous value.
Fourier transform is carried out on the voltage waveform and the current waveform to obtain the phase difference QUOTE of the voltage waveform and the current waveform
And further obtaining the power factor, wherein the formula is as follows:
wherein, QUOTE
Is the phase shift, QUOTE, of the voltage waveform of the voltage-induced primary and secondary side
Is the primary and secondary side current waveform phase shift converted by the current transformer. Phi is provided.
QUOTE 
And QUOTE
Performing phase by wireless or wired modeAnd obtaining the bit calibration.
The voltage phase calibration method comprises the following steps:
step 1: the reference device detects the voltage zero crossing and broadcasts the voltage zero crossing mark and the power grid frequency to the equipment to be calibrated in a wired or wireless mode;
and 2, step: and after the voltage zero crossing mark is received by the equipment to be calibrated, voltage induction zero crossing detection is started, phase offset is calculated by combining the power grid frequency and the wireless communication time after the voltage zero crossing is detected, and a phase offset value is stored in the equipment to be calibrated.
Power and energy are calculated according to the following formula:
wherein P is active power and time QUOTE
According to the time interval between two sampling.
The wireless transmission modes include LoRa and Ble.
The invention has the beneficial effects that: the invention can complete the measurement of parameters such as power, energy and the like of the line to be measured on the premise of non-invasion, and has the advantages of non-invasive installation, self power supply, no wiring and great implementation cost saving. In turn, support comprehensive electrical parameter measurements (voltage, current, temperature, power factor, power, energy, etc.).
Drawings
The invention has the following drawings:
FIG. 1 is a schematic diagram of a data sampling and data processing flow according to the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
A non-intrusive wireless electric energy metering system mainly comprises 4 parts: the device comprises a power management unit, a sampling unit, a data processing unit and a wireless communication unit.
A power management unit: the system at least comprises a current transformer and an energy storage device, wherein the energy storage device is a super capacitor or a rechargeable battery and is mainly responsible for micro-energy collection, and the current transformer is used for acquiring electric energy from a wire to be tested, storing and outputting the electric energy and maintaining the normal operation of the whole system.
A sampling unit: the device is mainly responsible for current waveform sampling, voltage waveform sampling and cable temperature sampling of the electric wire to be tested. The sampling unit at least comprises a voltage sampling circuit, a current sampling circuit and a temperature sampling circuit.
A data processing unit: and calculating data such as voltage, current, power factor, power, energy and the like according to the current waveform, the voltage waveform and the temperature acquired by the sampling unit.
The wireless communication unit: the calculated electrical data (voltage, current, power factor, power and energy) is wirelessly transmitted to a data collector.
A non-intrusive wireless electric energy metering method utilizes the non-intrusive wireless electric energy metering system and comprises the following specific steps:
step 1, disconnecting a voltage sampling circuit, a current sampling circuit and a temperature sampling circuit, collecting micro energy, and obtaining electricity by a power management unit in an induction way.
And 2, starting the voltage sampling circuit, the current sampling circuit and the temperature sampling circuit, collecting voltage waveform, current waveform and temperature data, and when sampling is completed, closing the sampling circuit and continuously charging the power management unit.
And 3, filtering the direct current components and the noise in the voltage waveform and the current waveform by the data processing unit, and calculating the voltage, the current, the power factor, the power and the energy.
And 4, wirelessly transmitting the calculated voltage, current, power factor, power and energy data to a data acquisition unit for further analyzing the power utilization condition and the power grid condition. The wireless transmission mode can be LoRa, ble and the like.
The above steps are specifically described below:
1. induction power taking:
according to the electromagnetic induction principle, a current transformer is utilized to directly obtain energy from an electric wire. There are two situations, more or less, of the current on the cable. When the current is large, the energy taken by the current transformer from the cable is enough to support the operation consumption of the whole system, and the redundant energy can charge the super capacitor or the rechargeable battery; when the current is small, the energy taken from the cable by the current transformer cannot meet the operation consumption of the whole system, and the super capacitor or the battery is switched to supply power.
2. Voltage, current, temperature sampling:
the number of sampling points of the voltage waveform and the current waveform is determined by the number of sampling cycles, the sampling frequency and the power grid frequency. The grid frequency is determined from the current zero crossing time interval. For example, 10 cycles, 4000Hz, 50Hz, the sampling points are 80 points per cycle and 800 points per 10 cycles.
1. Sampling of voltage waveform:
the electric field intensity radiated by the wire to be tested is inductively converted into a voltage signal which can be sampled by the ADC through the voltage sampling circuit.
2. Current waveform sampling:
and converting the current output by the secondary side of the current transformer into a voltage signal which can be sampled by the ADC through a current sampling circuit.
3. Temperature sampling:
the resistance value output by the temperature measuring chip is converted into a voltage signal which can be sampled by the ADC through the temperature sampling circuit.
3. Data processing:
1. DC component and interference filtering
The voltage signal and the current signal are both alternating current signals, and due to the characteristics of devices or interference existing in a power grid, the original waveforms of the voltage and the current can be affected, so that the direct current component and the interference in the voltage and the current need to be filtered by a software or hardware method.
2. Calculation of voltage, current, power factor, etc
The voltage and the current can be calculated according to the following formulas:
wherein the content of the first and second substances,Nfor number of samples, QUOTE
And QUOTE
Respectively, a voltage DC bias and a current DC bias, QUOTE
To an effective value of voltage, QUOTE
Calculating the coefficient, QUOTE, for the voltage
Is a firstiInstantaneous value of voltage sampling waveform of point, QUOTE
To an effective value of the current, QUOTE
Calculating coefficients for currents, QUOTE
Is a firstiThe current of the point samples the waveform instantaneous value.
Power factorpfAnd (3) calculating: the phase difference QUOTE between the voltage waveform and the current waveform can be obtained by Fourier transforming the voltage waveform and the current waveform
Phi, and then the power factor is obtained, and the formula is as follows:
QUOTE 
φ
wherein QUOTE
And QUOTE
The phase offset of the primary and secondary side waveforms is caused by hardware devices and circuits. QUOTE
Is the phase shift, QUOTE, of the voltage waveform of the voltage-induced primary and secondary side
Is the primary and secondary side current waveform phase deviation converted by the current transformer.
QUOTE 
And QUOTE
The phase calibration is obtained in a wireless or wired mode in the production stage. The wireless calibration method of the voltage phase is described below. Taking voltage phase calibration as an example, the calibration device comprises a reference device and equipment to be calibrated.
The voltage phase calibration method comprises the following steps:
step 1: the reference device detects the voltage zero crossing and broadcasts the voltage zero crossing mark and the power grid frequency to the equipment to be calibrated in a wireless or wired mode;
and 2, step: and after the voltage zero crossing mark is received by the equipment to be calibrated, voltage induction zero crossing detection is started, phase offset is calculated by combining the power grid frequency and the wireless communication time after the voltage zero crossing is detected, and a phase offset value is stored in the equipment to be calibrated.
The current phase calibration method is the same as the voltage phase calibration method.
The calibration described above may also be implemented by detecting voltage/current peaks or valleys.
The device can also realize the phase calibration of voltage and current according to the phase calibration method in a wired mode.
3. Power, energy calculation
Power and energy are calculated according to the following formulas:
wherein, P is active power.
Calculated time QUOTE
May be determined based on the time interval between two samples taken before and after the device.
4. Wireless communication:
1. data transmission:
and wirelessly transmitting the calculated electrical data (voltage, current, power factor, power and energy) to a data collector for subsequent energy consumption analysis.
The above embodiments are merely illustrative, and not restrictive, and those skilled in the relevant art can make various changes and modifications without departing from the spirit and scope of the invention, and therefore all equivalent technical solutions also belong to the scope of the invention.
Those not described in detail in this specification are well within the skill of the art.
Claims (10)
1. A non-intrusive wireless power metering system, comprising: the device comprises a power supply management unit, a sampling unit, a data processing unit and a wireless communication unit;
the power management unit comprises a current transformer and an energy storage device, and the energy storage device is a super capacitor or a rechargeable battery; the power management unit is responsible for micro-energy collection, and acquires electric energy from the wire to be tested by using the current transformer, stores and outputs the electric energy and maintains the normal operation of the whole system;
the sampling unit comprises a voltage sampling circuit, a current sampling circuit and a temperature sampling circuit; the method comprises the steps of sampling current waveforms, sampling voltage waveforms and sampling cable temperatures of wires to be tested;
the data processing unit is used for calculating voltage, current, power factor, power and energy according to the current waveform, the voltage waveform and the temperature acquired by the sampling unit;
the wireless communication unit: and the wireless transmission module is used for wirelessly transmitting the calculated voltage, current, power factor, power and energy to the data acquisition unit.
2. A non-invasive wireless power metering method using the non-invasive wireless power metering system of claim 1, comprising the steps of:
step 1, disconnecting a voltage sampling circuit, a current sampling circuit and a temperature sampling circuit, collecting micro energy, and taking electricity by a power management unit in an induction way;
step 2, starting a voltage sampling circuit, a current sampling circuit and a temperature sampling circuit, collecting voltage waveform, current waveform and temperature data, and when sampling is completed, closing the sampling circuit, and continuously charging a power supply management unit;
step 3, the data processing unit carries out filtering processing on the voltage waveform, the direct current component and the noise in the current waveform, and calculates voltage, current, power factor, power and energy;
and 4, wirelessly transmitting the calculated voltage, current, power factor, power and energy data to a data acquisition unit for further analyzing the power utilization condition and the power grid condition.
3. A non-intrusive wireless power metering method as defined in claim 2, wherein: when the electric energy taken by the current transformer from the cable is enough to support the running and consumption of the whole system, the redundant electric energy charges the energy storage device; and when the electric energy taken from the cable by the current transformer cannot meet the running consumption of the whole system, the energy storage device is switched to supply power.
4. A non-intrusive wireless power metering method as defined in claim 2, wherein: the number of sampling points of the voltage and current waveforms is determined by the number of sampling cycles, the sampling frequency and the power grid frequency; the grid frequency is determined from the current zero crossing time interval.
5. The non-invasive wireless power metering method of claim 2, wherein: the voltage and current are calculated according to the following formula:
wherein, the first and the second end of the pipe are connected with each other,Nin order to count the number of sampling points,
and
respectively a voltage dc bias and a current dc bias,
for the effective value of the voltage to be,
the coefficients are calculated for the voltage in such a way that,
is as followsiThe voltage sample waveform instantaneous value of the point,
is the effective value of the current,
a coefficient is calculated for the current flow,
is as followsiThe current of the point samples the waveform instantaneous value.
6. A non-invasive wireless power metering method according to claim 5, wherein: fourier transform is performed on the voltage waveform and the current waveform to obtain the phase difference between the voltage waveform and the current waveform
And further obtaining the power factor, wherein the formula is as follows:
wherein the content of the first and second substances,
is the phase shift of the voltage induced primary and secondary side voltage waveforms,
is the primary and secondary side current waveform phase shift converted by the current transformer.
7. The non-invasive wireless power metering method of claim 6, wherein:
and
the phase calibration is respectively carried out in a wireless or wired mode.
8. The non-invasive wireless power metering method of claim 7, wherein: the voltage phase calibration method comprises the following steps:
step 1: the reference device detects the voltage zero crossing and broadcasts the voltage zero crossing mark and the power grid frequency to the equipment to be calibrated in a wireless or wired mode;
step 2: and after the voltage zero crossing mark is received by the equipment to be calibrated, voltage induction zero crossing detection is started, phase offset is calculated by combining the power grid frequency and the wireless communication time after the voltage zero crossing is detected, and a phase offset value is stored in the equipment to be calibrated.
9. The non-invasive wireless power metering method of claim 6, wherein: power and energy are calculated according to the following formula:
wherein P is active power and time
According to the time interval between the two sampling.
10. The non-invasive wireless power metering method of claim 7, wherein: the wireless transmission method includes LoRa and Ble.
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