An electric energy meter and a metering circuit thereof

Abstract

This invention belongs to the field of electricity meter metering and relates to an electricity meter and its metering circuit. In a voltage-measurement-line powered DC electricity meter, a power isolation circuit is added between the measurement line and the signal processing unit within the meter. This unit provides an additional reference ground isolated from the voltage measurement line, preventing damage to the metering chip in the processing unit from large voltages between DC+ and DC-. Simultaneously, the positive terminal of the measurement line power supply is connected to this reference ground, serving as the reference for DC signal sampling and metering of voltage and current. This ensures that the current and voltage sampling input methods of the voltage-measurement-line powered DC electricity meter are consistent with existing electricity meter calibration bench settings, and guarantees that the power input of the voltage-measurement-line powered DC electricity meter follows the conventional left-positive-right-negative input method.

Description

Technical Field

[0001] This invention belongs to the field of electricity meter measurement technology, specifically relating to an electricity meter and its metering circuit. Background Technology

[0002] With the development of DC power distribution technology, the demand for DC metering is increasing. Currently, DC energy meters are suitable for measuring the power of DC signal equipment such as DC charging piles, batteries, and photovoltaic power generation, and can also be used in modern DC power supply and distribution systems in industrial and mining enterprises, civil buildings, and building automation.

[0003] DC energy meters can be categorized into two types based on whether their power supply originates from the voltage measurement circuit: those powered by an independent power source and those powered by the voltage measurement circuit. Currently, the most commonly used energy meters in the DC metering field are those powered by an independent power source. These meters require two power inputs for normal metering: one for the measurement circuit (typically DC 700V) and the other for the meter's power supply circuit (typically DC 12V or DC 24V), with the two power sources isolated from each other. However, with the increasing demand for DC metering, in DC power supply applications such as civil buildings and building automation systems, only one measurement circuit (typically 48V) is provided on-site. Therefore, there is a need to develop DC energy meters powered by the measurement circuit.

[0004] The wiring diagram for the currently used DC energy meter powered by an independent power source, from terminal 1 to terminal 12, is as follows: Figure 1 As shown, terminal 1 is connected to the positive input of the measurement circuit, and terminal 2 is connected to the positive output of the measurement circuit. A shunt is connected in series between terminals 1 and 2 for load current signal sampling. The shunt is installed in the terminal block inside the energy meter. Terminal 3 is shorted to terminal 2 and connected to the positive terminal of the measurement circuit. Terminal 4 is connected to the negative terminal of the measurement circuit. Voltage signal sampling is performed between terminals 3 and 4 through a resistor voltage divider. The voltage and current sampling methods of the measurement circuit are as follows: Figure 2 As shown. Terminals 5 and 6 are connected to the positive and negative terminals of the independent power supply that powers the meter, respectively. The paths of the independent power supply and the measuring power supply inside the meter are as follows. Figure 2 and Figure 3 As shown. Terminals 7-12 are the functional output interfaces of the energy meter, which are not affected by the source of the power supply line.

[0005] In DC power supply applications such as civil buildings and building automation, since there is only one line to be measured (generally 48V), DC meters powered by independent power supplies cannot meet the requirements of on-site use. It is necessary to develop DC energy meters powered by the measuring line. If the power supply of the measuring line is directly connected to the power supply, the following problems will occur when using different shunt sampling methods:

[0006] When the shunt is installed at the positive terminal of the measuring power supply (DC+ / DC-), such as Figure 2 If the measuring power supply is directly connected to the power supply (terminals 5 and 6) to power the internal circuits of the energy meter, the common-mode voltage (i.e., the voltage between IIN+ and DC-, and the voltage between IIN- and DC-) introduced to the sampling pin of the sampling processing unit metering chip through the shunt (terminals 1 and 2) is equal to the voltage between DC+ and DC-, which is 48V. This is much greater than the maximum common-mode voltage that the sampling pin of the metering chip can withstand (generally 6V, and the power supply voltage of the metering chip is generally required to be DC3.3V or DC5V), which will cause damage to the metering chip.

[0007] To solve the problem of high common-mode voltage mentioned above, a shunt can be installed on the negative terminal of the measuring power supply (DC+ / DC- power supply), such as... Figure 4 As shown in the diagram, if the wiring is done as shown below, with the shunt installed between terminals 1 and 2, and a resistive voltage divider sampling between terminals 3 and 4, then the overall power supply connection method is left negative and right positive (terminals 1 / 2 / 3 connected to the negative terminal of the power supply, and terminal 4 connected to the positive terminal of the power supply). This is inconsistent with the current and voltage input lines of the existing DC energy meter testing platform (for DC energy meter testing platforms, refer to the single-phase AC energy meter testing platform, the input lines are set as follows: terminal 1 is the current sampling input line, terminal 2 is the current sampling output line, terminal 3 and terminal 2 are at the same potential, and terminal 4 is the negative terminal of the power supply). This will cause product production testing, sample delivery testing, and other processes to be unable to proceed normally. Furthermore, it is inconsistent with the conventional left positive and right negative power supply input method, making it easier to reverse the wiring on site and damage the equipment. Summary of the Invention

[0008] The purpose of this invention is to provide an energy meter and its metering circuit to solve the problem that traditional energy meters are incompatible with the DC energy metering environment of the circuit to be measured on site, resulting in the inability to perform measurements, and the problem that the improved energy meter is inconsistent with the conventional power supply left positive and right negative input method, which makes it easy to reverse the wiring on site and cause equipment damage.

[0009] To address the aforementioned technical problems, this invention provides a metering circuit for an electricity meter, comprising a sampling signal processing unit and a shunt. The shunt is connected in series on the positive terminal of the power supply. The positive and negative signal output terminals of the shunt are respectively connected to the positive and negative current input terminals of the sampling signal processing unit. The circuit also includes an isolation module and a voltage sampling module. The positive and negative input terminals of the isolation module are respectively connected to the positive and negative terminals of the power supply, and the output terminal of the isolation module is connected to the power input terminal of the sampling signal processing unit. The output terminal of the isolation module includes an output power supply terminal and a reference ground terminal, with the reference ground terminal also connected to the positive voltage input terminal of the sampling signal processing unit. The positive signal output terminal of the shunt is also connected to the reference ground terminal. The voltage sampling module includes a voltage divider branch, with both ends of the branch connected to the positive and negative terminals of the power supply, and the voltage divider point connected to the negative voltage input terminal of the sampling signal processing unit.

[0010] Its beneficial effects are as follows: In a voltage-measurement-line powered DC energy meter, this invention adds an isolation circuit between the measurement line and the signal processing unit within the meter. This provides an additional reference ground isolated from the voltage measurement line within the unit, preventing damage to the metering chip in the processing unit from large voltages between DC+ and DC-. Simultaneously, the positive terminal of the measurement line power supply is connected to this reference ground, serving as the benchmark for voltage and current sampling during DC signal sampling and measurement. This ensures that the current and voltage sampling input methods of the voltage-measurement-line powered DC energy meter are consistent with existing energy meter calibration bench settings, and guarantees that the power input of the voltage-measurement-line powered DC energy meter follows the conventional left-positive-right-negative input method.

[0011] Furthermore, the isolation module is a step-down isolation module.

[0012] Its beneficial effects are as follows: by adding a step-down isolation module between the measuring line and the signal processing unit in the meter, another reference ground isolated from the voltage measuring line is obtained in this unit, avoiding damage to the metering chip in the processing unit by the large voltage between DC+ / DC-. At the same time, the positive terminal of the power supply of the measuring line is connected to this reference ground, which serves as the reference for DC signal sampling and measurement of voltage and current.

[0013] To address the aforementioned technical problems, this invention also provides an energy meter comprising a processing module and a metering circuit. The metering circuit includes a sampling signal processing unit and a shunt. The shunt is connected in series on the positive line of the power supply. The positive and negative signal output terminals of the shunt are respectively connected to the positive and negative current input terminals of the sampling signal processing unit. The meter also includes an isolation module and a voltage sampling module. The positive and negative input terminals of the isolation module are respectively connected to the positive and negative terminals of the power supply. The output terminal of the isolation module is connected to the power input terminal of the sampling signal processing unit. The output terminal of the isolation module includes an output power supply terminal and a reference ground terminal. The reference ground terminal is also connected to the positive voltage input terminal of the sampling signal processing unit. The positive signal output terminal of the shunt is also connected to the reference ground terminal. The voltage sampling module includes a voltage divider branch. The two ends of the voltage divider branch are respectively connected to the positive and negative terminals of the power supply. The voltage divider point is connected to the negative voltage input terminal of the sampling signal processing unit.

[0014] Its beneficial effects are as follows: In a voltage-measurement-line powered DC energy meter, this invention adds an isolation circuit between the measurement line and the signal processing unit within the meter. This provides an additional reference ground isolated from the voltage measurement line within the unit, preventing damage to the metering chip in the processing unit from large voltages between DC+ and DC-. Simultaneously, the positive terminal of the measurement line power supply is connected to this reference ground, serving as the benchmark for voltage and current sampling during DC signal sampling and measurement. This ensures that the current and voltage sampling input methods of the voltage-measurement-line powered DC energy meter are consistent with existing energy meter calibration benches, and guarantees that the power input of the voltage-measurement-line powered DC energy meter follows the conventional left-positive-right-negative input method. The processing module and communication module of the invented energy meter can both utilize the scheme of the original auxiliary power-powered DC meter.

[0015] Furthermore, the processing module is a CPU module.

[0016] Its beneficial effects are: the processing module uses a CPU module to analyze and store the collected data, which improves the performance of the electricity meter.

[0017] Furthermore, it also includes a communication module, which is connected to the processing module.

[0018] Its beneficial effects are: the communication module is used to transmit data, which facilitates data analysis.

[0019] Furthermore, the communication module is an RS485 module.

[0020] Its beneficial effects are: the communication module uses an RS485 module for data transmission, which facilitates data analysis. Attached Figure Description

[0021] Figure 1This is a schematic diagram of the terminal wiring of a current DC energy meter.

[0022] Figure 2 This refers to the voltage and current sampling methods used in existing measurement circuits.

[0023] Figure 3 This is the path of the independent power supply and measuring power supply inside the meter in existing technology;

[0024] Figure 4 It is the internal path of the electricity meter after the existing technology has modified the wiring;

[0025] Figure 5 This is a diagram showing the internal path of the meter in this invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0027] Example of a metering circuit for an electricity meter:

[0028] like Figure 5 As shown, the energy meter of the present invention includes a sampling signal processing unit and a shunt. The shunt is connected in series on the positive line of the power supply. The positive signal output terminal and the negative signal output terminal of the shunt are respectively connected to the positive current input terminal and the negative current input terminal of the sampling signal processing unit. It also includes an isolation module and a voltage sampling module. The positive and negative input terminals of the isolation module are respectively used to connect to the positive and negative terminals of the power supply. The output terminal of the isolation module is connected to the power input terminal of the sampling signal processing unit. The output terminal of the isolation module includes an output power supply terminal and a reference ground terminal. The reference ground terminal is also connected to the positive voltage input terminal of the sampling signal processing unit. The positive signal output terminal of the shunt is also connected to the reference ground terminal. The voltage sampling module includes a voltage divider branch. The two ends of the voltage divider branch are respectively used to connect to the positive and negative terminals of the power supply. The voltage divider point of the voltage divider branch is connected to the negative voltage input terminal of the sampling signal processing unit.

[0029] Specifically, DC+ / DC- is the power supply provided on-site. This power supply is the power line for the electrical energy being measured and also the source of the DC meter's operating power. The current sampling shunt in the circuit is connected in series with the positive terminal of the power supply. (The shunt can be considered a high-precision, low-resistance resistor; when the load current flows through it, it generates a sampling signal proportional to the current. For ease of on-site wiring, the shunt will have four connection points, such as...) Figure 5As shown in the shunt diagram, where I+ and IIN+ are at the same potential, and I- and IIN- are at the same potential, voltage sampling is performed between the positive and negative terminals of the power supply using a resistor divider. In the sampling signal processing unit, to ensure that the common-mode voltage of the incoming sampling signal is less than 6V, an alternative reference ground (not DC-) must be found for the sampling signal in this metering system. This should not affect the shunt current sampling signal or the voltage signal sampled by the resistor divider in the DC+ / DC- lines. In this invention, by isolating the input power supply, a DVDD / GNDD power supply for the sampling processing unit is obtained, with GNDD as its reference ground. Simultaneously, the positive terminal of the input power supply (i.e., IIN+, at the same potential as I+ and DC+) is connected to the isolated reference ground GNDD (i.e., the metering sampling section uses the positive terminal of the power supply as the metering reference). After processing according to this scheme, because it is isolated from the input DC+ / DC- power supply, and the voltage between the DVDD / GNDD power supply for the sampling signal processing unit is generally DC 3.3V or DC 5V, the voltage of the current sampling input line IIN+ to its reference ground GNDD will no longer exceed 6V. Furthermore, since DC+ and GNDD are connected together, the current sampling signal is still the sampling signal generated by the load flowing through the shunt on the DC+ / DC- power supply. And because the sampling uses the positive terminal (DC+) as the reference, the current sampling obtained is a negative signal (IIN-). Voltage sampling also samples the voltage between the power supply input (DC+ / DC-), and because the sampling uses the positive terminal (DC+) as the reference, the sampled signal obtained is a negative signal (V-). When measuring electricity, both voltage and current are negative. Even if the negatives are canceled, the result is still the normal electricity.

[0030] Example of an electricity meter:

[0031] The electricity meter of the present invention includes a processing module (a CPU module in this embodiment), a communication module (a 485 module in this embodiment) and a metering circuit. The metering circuit has been described in detail in the metering circuit section of the electricity meter, and will not be repeated here.

[0032] The CPU module and 485 module in the electricity meter can be implemented using the same scheme as the original DC meter powered by the auxiliary power supply.

[0033] This invention relates to a voltage-measurement-line powered DC energy meter. By adding a power isolation circuit between the measurement line and the signal processing unit within the meter, an alternative reference ground isolated from the voltage measurement line is obtained within this unit. This prevents damage to the metering chip in the processing unit from large voltages between DC+ and DC-. Simultaneously, the positive terminal of the measurement line power supply is connected to this reference ground, serving as the benchmark for DC signal sampling and measurement of voltage and current. This ensures that the current and voltage sampling input methods of the voltage-measurement-line powered DC energy meter are consistent with existing energy meter calibration benches, and guarantees that the power input of the voltage-measurement-line powered DC energy meter follows the conventional left-positive-right-negative input method.

[0034] Specific implementation methods have been given above, but the present invention is not limited to the described implementation methods. The basic idea of ​​the present invention lies in the above basic scheme. For those skilled in the art, designing various modified models, formulas, and parameters based on the teachings of the present invention does not require creative effort. Changes, modifications, substitutions, and variations made to the implementation methods without departing from the principles and spirit of the present invention still fall within the protection scope of the present invention.

Claims

1. A metering circuit for an electricity meter, comprising a sampling signal processing unit and a shunt, wherein the shunt is connected in series on the positive terminal of the circuit under test, and the positive signal output terminal and negative signal output terminal of the shunt are respectively connected to the positive current input terminal and the negative current input terminal of the sampling signal processing unit, characterized in that, It also includes a step-down isolation module and a voltage sampling module. The positive and negative input terminals of the step-down isolation module are used to connect to the positive and negative terminals of the circuit under test, respectively. The output terminal of the step-down isolation module is connected to the power input terminal of the sampling signal processing unit to supply power to the energy meter through the circuit under test. The output terminal of the step-down isolation module includes an output power supply terminal and a reference ground terminal. The reference ground terminal is also connected to the positive voltage input terminal of the sampling signal processing unit, and the positive signal output terminal of the shunt is also connected to the reference ground terminal, so that the energy meter uses the positive terminal of the circuit under test as the measurement reference. The negative signal output terminal of the shunt outputs a negative current sampling signal to the sampling signal processing unit. The voltage sampling module includes a voltage divider branch. The two ends of the voltage divider branch are used to connect to the positive and negative terminals of the circuit under test, respectively. The voltage divider point of the voltage divider branch is connected to the negative voltage input terminal of the sampling signal processing unit, so that the voltage divider point of the voltage divider branch outputs a negative voltage sampling signal to the sampling signal processing unit.

2. The metering circuit of the energy meter according to claim 1, characterized in that, The voltage between the output power supply terminal and the reference ground terminal of the step-down isolation module is 3.3V or 5V.

3. An electricity meter, characterized in that, The system includes a processing module and a metering circuit. The metering circuit includes a sampling signal processing unit and a shunt. The shunt is connected in series with the positive terminal of the circuit under test. The positive and negative signal output terminals of the shunt are connected to the positive and negative current input terminals of the sampling signal processing unit, respectively. The system also includes a step-down isolation module and a voltage sampling module. The positive and negative input terminals of the step-down isolation module are connected to the positive and negative terminals of the circuit under test, respectively. The output terminal of the step-down isolation module is connected to the power input terminal of the sampling signal processing unit to supply power to the energy meter through the circuit under test. The output terminal of the step-down isolation module includes an output power supply terminal and a voltage sampling terminal. The reference ground terminal is also connected to the positive voltage input terminal of the sampling signal processing unit, and the positive signal output terminal of the shunt is also connected to the reference ground terminal, so that the energy meter uses the positive terminal of the circuit under test as the measurement reference, and the negative signal output terminal of the shunt outputs a negative current sampling signal to the sampling signal processing unit; the voltage sampling module includes a voltage divider branch, the two ends of which are respectively used to connect to the positive and negative terminals of the circuit under test, and the voltage dividing point of the voltage divider branch is connected to the negative voltage input terminal of the sampling signal processing unit, so that the voltage dividing point of the voltage divider branch outputs a negative voltage sampling signal to the sampling signal processing unit.

4. The electricity meter according to claim 3, characterized in that, The processing module is a CPU module.

5. The electricity meter according to claim 3, characterized in that, It also includes a communication module, which is connected to the processing module.

6. The electricity meter according to claim 5, characterized in that, The communication module is an RS485 module.

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