A two-way smart meter circuit

Abstract

The application discloses a bidirectional intelligent electric meter circuit, which comprises a live wire L1, a live wire L2, a zero wire N, a switch unit, a current sensor, an auxiliary power supply unit, a collection unit, a processor unit, a communication and display unit, the L1 and the N constitute a wiring port 1, the L2 and the N constitute a wiring port 2, the auxiliary power supply unit is connected with the wiring port 1 and the wiring port 2 through V AC and V BC respectively, the auxiliary power supply unit sequentially supplies power for the collection unit, the processor unit, the communication and display unit, the current sensor unit and the switch unit, the current sensor outputs a voltage V DE， , the collection unit collects V AC , V BC and V DE , transmits the signals to the processor unit after signal processing, the processor unit judges the state of the input voltage and current by analyzing the incoming signals, and finally sends a control instruction to control the switch unit to be disconnected or turned on.

Description

Technical Field

[0001] This invention relates to the field of electricity meter technology, and in particular to a bidirectional smart meter circuit. Background Technology

[0002] With the gradual promotion of smart photovoltaic grid systems and smart charging stations for electric vehicles, smart meters with functions such as detection and recording, communication, and load switching control are gradually emerging in the industry. However, most smart meters on the market have the following shortcomings:

[0003] 1. Most smart meters on the market do not capture the phase (zero crossing point) of the sinusoidal AC current when controlling the internal switching relay to close or open the load. If the relay closes at the peak of the sinusoidal AC current, due to the large voltage difference across the relay contacts and the large current drawn by the load at the moment of closure, the internal contacts of the relay are prone to arcing before full contact, causing the metal of the relay contacts to melt and stick together, resulting in relay failure and inability to perform the switching function.

[0004] 2. Most smart meters on the market are only capable of one-way flow, meaning they can only switch on and measure power supply from the grid to the device when the grid is energized. They cannot switch on and measure power supply from the inverter to the grid when only the device (such as a photovoltaic inverter) is energized. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a bidirectional smart meter circuit with high reliability. It avoids erroneous actions caused by power grid interference, ensuring that the processor unit correctly captures the zero-crossing point of the AC voltage, thus effectively improving reliability and accuracy.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a bidirectional smart meter circuit, including a live wire L1, L2, a neutral wire N, a switching unit, a current sensor, an auxiliary power supply unit, a data acquisition unit, a processor unit, and a communication and display unit. L1 and N form connection port 1, and L2 and N form connection port 2. The auxiliary power supply unit connects to V... AC and wiring port 1, via V BC Connected to terminal 2, the auxiliary power supply unit sequentially powers the acquisition unit, processor unit, communication and display unit, current sensor unit, and switch unit. The current sensor outputs a voltage V. DE， The acquisition unit acquires V AC V BC V DEAfter signal processing, the signal is transmitted to the processor unit. The processor unit analyzes the incoming signal to determine the current state of the input voltage and current, and finally issues a control command to control the switching unit to open or close.

[0007] As a preferred embodiment of the present invention, the communication and display unit is the external interaction channel of the smart meter, used to display the voltage, current and power of the L and N lines passing through the meter, and to interact with the terminal user or the main control unit through wired, wireless WIFI, Bluetooth and other means.

[0008] As a preferred embodiment of the present invention, the auxiliary power supply unit includes diode D1, diode D2, filter capacitor E1, an AC-DC isolated power supply module, and a DC-DC power supply module. Diode D1 and filter capacitor E1, and diode D2 and filter capacitor E1, each form a half-wave rectifier filter unit. The two half-wave rectifier filter units are sequentially connected to port 1 and port 2 to convert the AC input voltage V... AC or V BC Rectification and filtering to DC voltage V FC The V FC The auxiliary unit outputs two DC voltages, +12V and +5V, through an AC-DC isolated power transformer. The +5V voltage is then transformed by a DC-DC power circuit to output two DC voltages, +3.3V and +1.625V. The DC voltages output by the auxiliary unit are used by the switching unit, current sensor, acquisition unit, processor unit, communication and display unit.

[0009] As a preferred embodiment of the present invention, the acquisition unit includes a voltage sampling processing module and a current sampling processing module connected to the processor unit. The voltage sampling processing module includes resistors R1, R2, R3, R4, R5, R6, R7, and R8, filter capacitors C1 and C2, operational amplifier 1A, and comparator 1B. Taking port 1 as the input, R1, R2, R3, R4 and operational amplifier 1A are combined to form a differential proportional amplifier circuit. The comparator 1B and resistors R6, R7, and R8 form a hysteresis comparator circuit. The processor unit includes a DSP module and a Tri module. The DSP module is connected to the output terminal of the differential proportional amplifier circuit, and the Tri module is connected to the output terminal of the hysteresis comparator circuit.

[0010] In a preferred embodiment of the present invention, the input terminals of the differential proportional amplifier circuit are connected to port 1 and +1.625V respectively. The differential proportional amplifier circuit outputs a voltage in the range of 0V to 3.3V. The differential proportional amplifier circuit transmits the signal to the DSP module of the processor unit for conversion into a digital signal through resistor R5 and filter capacitor C1. The output terminal of the differential proportional amplifier circuit is connected to the "-" terminal of the hysteresis comparator circuit. The "+" terminal of the hysteresis comparator circuit is connected to +1.625V. When the voltage at the "-" terminal is greater than +1.624V, the output of the hysteresis comparator circuit flips from high level to low level. When the voltage at the "-" terminal is less than +1.621V, the hysteresis comparator circuit flips from low level to high level. The hysteresis comparator circuit is filtered by resistor R9 and capacitor C2 and then transmitted to the Tri module of the processor unit. The DSP module of the processor unit makes a dual determination by judging the trigger signal of the Tri module and combining it with the waveform envelope of the voltage sampled at port 1 to determine whether to trigger the control signal of the closed or open switch unit.

[0011] As a preferred embodiment of the present invention, the current sampling and processing module includes resistors R10, R11, R12, R13, and R14, a filter capacitor C3, and an operational amplifier 2A. R11, R12, R13, R14, and operational amplifier 2A are combined to form another differential proportional amplifier circuit. The "-" terminal of this differential proportional amplifier circuit is connected to the current sensor, and the "+" terminal is connected to +1.625V. The voltage converted by the current sensor is proportionally amplified. The differential proportional amplifier circuit transmits the current to the processor unit for sampling via resistor R10 and capacitor C3. After digital-to-analog conversion processing by the DSP module, the processor unit determines the magnitude and phase of the processed voltage signal. Combined with the magnitude and phase of the voltage sampled at port 1, it calculates the instantaneous power of the circuit meter, which terminal is the input, and the accumulated power consumption.

[0012] As a preferred embodiment of the present invention, the switching unit includes an SCR driving circuit 1, an SCR driving circuit 2, SCR transistors Q1 and Q2, an electromagnetic relay RL1, a diode D3, a transistor Q3, and resistors R15 and R16. The SCR driving circuit 1 and SCR driving circuit 2 are connected to port 1 and port 2 in sequence. The auxiliary power supply unit is connected to the switching unit through transistor Q3. The electromagnetic relay RL1 is located at the connection of L1 and L2. Taking port 1 as the input terminal, when the processor unit analyzes and needs to close the switching unit, it sends DR_Q2 and RL_ON high levels. DR_Q2 passes through the SCR driving circuit... 2. After the isolation transformer is activated, Q2 is turned on. After it is turned on, the L-line current flows through Q2, and the voltage between points A and B of the relay drops to about 0V. The RL_ON signal drives the transistor Q3 to turn on after being divided and current-limited by R16 and R15. The coil of relay RL1 stores energy and closes contacts 4 and 3. The relay is closed and points A and B are fully connected. After it is turned on, the L-line current basically flows through the RL1 relay. When the processor unit analyzes and needs to disconnect the switching unit, it sends DR_Q2 and RL_ON to a low level. Q1 and relay RL1 are simultaneously disconnected at the zero-crossing point of the AC voltage. At the moment of disconnection, the freewheeling diode D3 consumes the current in the relay coil, protecting the switching transistor Q3.

[0013] As a preferred technical solution of the present invention, taking the SCR driving circuit 2 as an example, the SCR driving circuit 2 includes resistors R17, R18, and R19, diodes D4, D5, and D6, switching transistor Q4, isolation transformer T1, and filter capacitor C4. The DR_Q1 signal drives the transistor Q4 to turn on after being divided and current-limited by resistors R17 and R18. The +12V is transformed by transformer T1 and then current-limited by diodes D5 and R19, driving the GK terminals of Q1 to turn on Q1. The filter capacitor C4 filters the current to prevent interference and mis-driving. Diodes D4 and D6 are both freewheeling clamping diodes to prevent Q4 from being damaged by excessive voltage due to the freewheeling and coupling effect of the transformer coil after Q4 is turned off.

[0014] Compared with the prior art, the beneficial effects that this invention can achieve are:

[0015] 1. This patented circuit proposes a bidirectional smart meter with a switching function. The auxiliary power supply unit adopts a dual-port AC half-wave rectification method to obtain power. As long as there is AC voltage at one end, the smart meter can work normally. It also has multiple functions such as switching, voltage and current acquisition and data analysis, display, and communication.

[0016] 2. The AC voltage zero-crossing capture process of this patented circuit adopts a dual excitation of differential proportional amplifier circuit envelope detection and hysteresis comparator circuit zero-crossing trigger. The hysteresis comparator circuit can prevent the back-end circuit from malfunctioning due to repeated reverse output caused by voltage fluctuations near the AC voltage zero-crossing point. It has high reliability and avoids the processor unit from misjudging and issuing malfunctions due to power grid interference, etc., ensuring that the processor unit correctly captures the AC voltage zero-crossing point, effectively improving reliability and accuracy.

[0017] 3. The switching unit of this patented circuit uses a parallel connection of a silicon controlled rectifier (SCR) and a relay. This can effectively protect the relay from arcing, melting, and sticking of the contact points, overcome the problem of the relay's slow response speed causing it to be unable to close accurately near the zero crossing point, and reduce the reactive power loss caused by the presence of the SCR.

[0018] 4. The auxiliary power supply unit and SCR drive circuit module both adopt transformer isolation, which isolates the high-voltage AC mains power and the low-voltage side control circuit, improving the safety of users.

[0019] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a block diagram illustrating the circuit structure of the meter of the present invention.

[0022] Figure 2 This is a schematic diagram of the auxiliary power supply unit circuit in this invention;

[0023] Figure 3 This is a schematic diagram of the acquisition unit circuit in this invention;

[0024] Figure 4 This is a schematic diagram of the switching unit circuit in this invention;

[0025] Figure 5 This is a schematic diagram of the SCR driving circuit in this invention. Detailed Implementation

[0026] To make the technical means, creative features, and achieved objectives and effects of this invention easier to understand, the invention is further described below with reference to specific embodiments. However, the following embodiments are merely preferred embodiments of this invention and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments described herein without creative effort are all within the protection scope of this invention. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods, and the materials and reagents used in the following embodiments are commercially available unless otherwise specified.

[0027] See Figures 1-5 As shown, this invention provides a bidirectional smart meter circuit, including live wires L1 and L2, neutral wire N, a switching unit, a current sensor, an auxiliary power supply unit, a data acquisition unit, a processor unit, and a communication and display unit. L1 and N form connection port 1, and L2 and N form connection port 2. The auxiliary power supply unit connects to V... AC and wiring port 1, via V BC Connecting to port 2, the auxiliary power supply can be used by the user as an AC voltage input and port 2 as an AC voltage output, or port 1 as an output and port 2 as an input. Regardless of which port is used as the input, the auxiliary power supply can normally output the DC voltage required by the circuit. The auxiliary power supply unit sequentially powers the acquisition unit, processor unit, communication and display unit, current sensor unit, and switch unit. The current sensor outputs a voltage V. DE， The acquisition unit acquires V AC V BC V DE After signal processing, the signal is transmitted to the processor unit. The processor unit analyzes the incoming signal to determine the current state of the input voltage and current, and finally issues a control command to control the switching unit to open or close.

[0028] The communication and display unit is the external interaction channel of the smart meter, used to display the voltage, current and power of the L and N lines passing through the meter, and to interact with end users or the main control unit through wired (such as RS485 communication protocol), wireless WIFI, Bluetooth and other means.

[0029] Preferably, the auxiliary power supply unit includes diode D1, diode D2, filter capacitor E1, an AC-DC isolated power supply module, and a DC-DC power supply module. Diode D1 and filter capacitor E1, and diode D2 and filter capacitor E1, each form a half-wave rectifier filter unit. Two of these half-wave rectifier filter units are connected sequentially to port 1 and port 2 to convert the AC input voltage V... AC or V BC Rectification and filtering to DC voltage V FCThis ensures that regardless of which port is used as the input port, the auxiliary power supply can normally output the DC voltage required by this circuit, V. FC The AC-DC isolated power supply outputs two DC voltages, +12V and +5V. The +5V voltage is then transformed by the DC-DC power supply circuit to output two DC voltages, +3.3V and +1.625V. The DC voltages output by the auxiliary unit are used by the switching unit, current sensor, acquisition unit, processor unit, communication and display unit. It should be noted that the AC-DC isolated power supply and DC-DC power supply are industry-standard circuits and are not innovative aspects of this patented circuit. Therefore, detailed circuit and component information is not presented here.

[0030] Preferably, the acquisition unit includes a voltage sampling processing module and a current sampling processing module connected to the processor unit. The voltage sampling processing module includes resistors R1, R2, R3, R4, R5, R6, R7, and R8, filter capacitors C1 and C2, operational amplifier 1A (such as an ANX7002 chip), and comparator 1B (such as an LM293 chip). Taking port 1 as the input, R1, R2, R3, R4 and operational amplifier 1A combine to form a differential proportional amplifier circuit, and comparator 1B and resistors R6, R7, and R8 form a hysteresis comparator circuit. The processor unit includes a DSP module (such as an STM32F103) and a Tri module. The DSP module is connected to the output of the differential proportional amplifier circuit, and the Tri module is connected to the output of the hysteresis comparator circuit.

[0031] The input terminals of the differential proportional amplifier circuit are connected to port 1 and +1.625V respectively, and the V of port 1 is converted to V. ACThe AC sinusoidal voltage is proportionally reduced and superimposed on +1.625V. The differential proportional amplifier circuit outputs a voltage in the range of 0V to 3.3V. The differential proportional amplifier circuit transmits the signal to the DSP module of the processing unit for conversion into a digital signal through resistor R5 and filter capacitor C1. Simultaneously, the output terminal of the differential proportional amplifier circuit is connected to the "-" terminal of the hysteresis comparator circuit, and the "+" terminal of the hysteresis comparator circuit is connected to +1.625V. (Using a hysteresis comparator circuit prevents repeated reverse output due to voltage fluctuations near the zero-crossing point of the AC voltage, thus preventing malfunctions in the downstream circuitry and ensuring high reliability.) When the voltage at the "-" terminal is greater than +1.624V, the hysteresis... The comparator circuit output flips from high to low. When the voltage at the "-" terminal is less than +1.621V, the hysteresis comparator circuit flips from low to high. The hysteresis comparator circuit is filtered by resistor R9 and capacitor C2 and then sent to the Tri module of the processor unit. The level flip is triggered instantaneously, and the processor unit responds. The DSP module of the processor unit makes a double judgment by judging the trigger signal of the Tri module and combining it with the waveform envelope of the voltage sampled at port 1 (to avoid erroneous actions caused by power grid interference, etc.) to determine whether to trigger the control signal of the closed or open switch unit. Similarly, the same applies when port 2 is used as input, which will not be elaborated here.

[0032] The current sampling and processing module includes resistors R10, R11, R12, R13, and R14, a filter capacitor C3, and an operational amplifier 2A (such as an ANX7002 chip). Figure 3 As shown, R11, R12, R13, R14 and operational amplifier 2A are combined to form another differential proportional amplifier circuit. The "-" terminal of the differential proportional amplifier circuit is connected to the current sensor, and the "+" terminal is connected to +1.625V. The voltage converted by the current sensor is proportionally amplified. The differential proportional amplifier circuit sends the current to the processor unit for current sampling through resistor R10 and capacitor C3. After digital-to-analog conversion processing by the DSP module, the magnitude and phase of the processed voltage signal are determined, and combined with the magnitude and phase of the voltage sample at port 1 (e.g., if the phase difference between the two is 180°, then port 1 is the input; otherwise, port 2 is the input), the instantaneous power of the circuit meter, which terminal is the input terminal, and the cumulative power consumption information are calculated.

[0033] Preferably, the switching unit includes an SCR drive circuit 1, an SCR drive circuit 2, SCR transistors Q1 and Q2, an electromagnetic relay RL1, a diode D3, a transistor Q3, and resistors R15 and R16. The SCR drive circuit 1 and SCR drive circuit 2 are connected to port 1 and port 2 in sequence. The auxiliary power supply unit is connected to the switching unit through transistor Q3. The electromagnetic relay RL1 is located at the connection of L1 and L2. Taking port 1 as the input terminal as an example (the principle is the same for port 2 as the input terminal), when the processor unit analyzes and needs to close the switching unit, it sends DR_Q2 and RL_ON high levels. DR_Q2 drives Q2 to conduct after being isolated and transformed by the SCR drive circuit 2. Q2 is a semiconductor device with extremely fast response speed and can achieve the closing effect instantly. After conduction, the L line current flows through Q2, and the voltage between points A and B of the relay drops to about 0V. The RL_ON signal is divided and limited by R16 and R15. After the current flows, transistor Q3 is turned on, and the coil of relay RL1 stores energy and closes contacts 4 and 3. The relay closes, achieving a state where points A and B are fully connected. After conduction, the L-line current basically flows through relay RL1. The entire response process takes about 4ms (energy storage time of the relay coil). Because Q1 is fully turned on first, the voltage difference at the contact points before the relay closes is extremely small, preventing arcing. After the relay closes, the L-line current basically does not flow through Q1. This reduces reactive power loss on Q1, effectively protects the relay from contact damage due to sticking, and also achieves the goal of quickly closing the switching unit near the AC voltage zero crossing. When the processor unit analyzes and needs to disconnect the switching unit, it sends DR_Q2 and RL_ON to low levels. Q1 and relay RL1 simultaneously disconnect at the AC voltage zero crossing. At the moment of disconnection, freewheeling diode D3 consumes the current in the relay coil, protecting switching transistor Q3.

[0034] Preferably, the SCR drive circuit 2 includes resistors R17, R18, and R19, diodes D4, D5, and D6, a switching transistor Q4, an isolation transformer T1, and a filter capacitor C4. Taking the SCR drive circuit 2 in this patent circuit as an example (the SCR drive circuit 1 operates on the same principle), the DR_Q1 signal drives the transistor Q4 to turn on after being divided and current-limited by resistors R17 and R18. The +12V voltage is transformed by transformer T1 and then current-limited by diodes D5 and R19 before driving the GK terminals of Q1 to turn on. The filter capacitor C4 filters the current to prevent interference and mis-driving. Diodes D4 and D6 are both freewheeling clamping diodes to prevent Q4 from being damaged by excessive voltage due to the freewheeling and coupling effect of the transformer coil after Q4 is turned off.

[0035] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0036] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A bidirectional smart meter circuit, characterized in that: Includes live wires L1 and L2, neutral wire N, a switching unit, a current sensor, an auxiliary power supply unit, a data acquisition unit, a processor unit, and a communication and display unit. L1 and N form connection port 1, and L2 and N form connection port 2. The auxiliary power supply unit connects to V... AC and wiring port 1, via V BC Connected to terminal 2, the auxiliary power supply unit sequentially powers the acquisition unit, processor unit, communication and display unit, current sensor unit, and switch unit. The current sensor outputs a voltage V. DE， The acquisition unit acquires V AC V BC V DE After signal processing, the signal is transmitted to the processor unit. The processor unit analyzes the incoming signal to determine the current state of the input voltage and current, and finally issues a control command to control the switching unit to open or close. The sampling unit includes five terminals: A, B, C, D, and E. The communication and display unit is the external interaction channel of the smart meter, used to display the voltage, current and power of the L and N lines through the meter, and to interact with the end user or the main control unit through wired, wireless WIFI, Bluetooth and other means. The auxiliary power supply unit includes diode D1, diode D2, filter capacitor E1, an AC-DC isolated power supply module, and a DC-DC power supply module. Diode D1 and filter capacitor E1, and diode D2 and filter capacitor E1, each form a half-wave rectifier filter unit. Two of these half-wave rectifier filter units are connected sequentially to port 1 and port 2 to convert the AC input voltage V... AC or V BC Rectification and filtering to DC voltage V FC The V FC The auxiliary unit outputs two DC voltages, +12V and +5V, through an AC-DC isolated power supply transformer. The +5V voltage is then transformed by a DC-DC power supply circuit to output two DC voltages, +3.3V and +1.625V. The DC voltages output by the auxiliary unit are used by the switching unit, current sensor, acquisition unit, processor unit, communication and display unit. The acquisition unit includes a voltage sampling processing module and a current sampling processing module connected to the processor unit. The voltage sampling processing module includes resistors R1, R2, R3, R4, R5, R6, R7, and R8, filter capacitors C1 and C2, operational amplifier 1A, and comparator 1B. R1, R2, R3, R4 and operational amplifier 1A are combined to form a first differential proportional amplifier circuit. The comparator 1B and resistors R6, R7, and R8 form a hysteresis comparator circuit. The processor unit includes a DSP module and a Tri module. The DSP module is connected to the output terminal of the differential proportional amplifier circuit, and the Tri module is connected to the output terminal of the hysteresis comparator circuit. The negative input terminal of the first differential amplifier circuit is connected to terminal A of the sampling unit, and the positive input terminal is connected to terminal C of the sampling unit and +1.625V. The first differential amplifier circuit outputs a voltage in the range of 0V to 3.3V. The first differential amplifier circuit transmits the signal to the DSP module of the processor unit for conversion into a digital signal through resistor R5 and filter capacitor C1. The output terminal of the first differential amplifier circuit is connected to the "-" terminal of the hysteresis comparator circuit, and the "+" terminal of the hysteresis comparator circuit is connected to +1.625V. When the voltage at the "-" terminal is greater than +1.624V, The output of the hysteresis comparator circuit flips from high to low. When the voltage at the "-" terminal is less than +1.621V, the hysteresis of the comparison level of the hysteresis comparator can be adjusted by adjusting the resistance value of resistor R7, thereby improving the accuracy of the comparator circuit operation. The output of the hysteresis comparator circuit flips from low to high. After being filtered by resistor R9 and capacitor C2, the hysteresis comparator circuit is sent to the Tri module of the processor unit. The DSP module of the processor unit makes a dual determination by judging the trigger signal of the Tri module and combining it with the waveform envelope of the voltage sampled at port 1 to determine whether to trigger the control signal of the closed or open switch unit.

2. The bidirectional smart meter circuit according to claim 1, characterized in that: The current sampling and processing module includes resistors R10, R11, R12, R13, and R14, a filter capacitor C3, and an operational amplifier 2A. R11, R12, R13, R14, and operational amplifier 2A are combined to form a second differential proportional amplifier circuit. The negative input terminal of the second differential proportional amplifier circuit is connected to the sampling unit D terminal, and the positive input terminal of the second differential proportional amplifier circuit is connected to the sampling unit E terminal and +1.625V. This circuit amplifies the voltage converted from the current sensor proportionally. The current is then fed to the processor unit for sampling via resistor R10 and capacitor C3. After digital-to-analog conversion by the DSP module, the processor unit determines the magnitude and phase of the processed voltage signal. Combined with the magnitude and phase of the voltage sampled at port 1, it calculates the instantaneous power of the circuit meter, the input terminal, and the accumulated power consumption.

3. The bidirectional smart meter circuit according to claim 1, characterized in that: The switching unit includes an SCR drive circuit 1, an SCR drive circuit 2, SCR transistors Q1 and Q2, an electromagnetic relay RL1, a diode D3, a transistor Q3, and resistors R15 and R16. The SCR drive circuits 1 and 2 are connected sequentially to port 1 and port 2. The auxiliary power supply unit is connected to the switching unit via transistor Q3. The electromagnetic relay RL1 is located at the connection point of L1 and L2. When the processor unit analyzes the data and needs to close the switching unit, it sends a high-level signal DR_Q2 and RL_ON. After DR_Q2 is isolated and transformed by SCR drive circuit 2, it drives Q2 to conduct. After conduction, the L1 line current flows through Q2, and the voltage between points A and B of the relay drops to about 0V. The RL_ON signal drives the transistor Q3 to turn on after being divided and current limited by R16 and R15. The coil of relay RL1 stores energy and closes contacts 4 and 3. The relay closes and reaches the state where points A and B are fully connected. After conduction, the L1 line current basically flows through the RL1 relay. When the processor unit analyzes and needs to disconnect the switching unit, it sends DR_Q2 and RL_ON to low level. Q2 and relay RL1 are disconnected at the AC voltage zero crossing point. At the moment of disconnection, the freewheeling diode D3 consumes the current in the relay coil, protecting the switching transistor Q3.

4. The bidirectional smart meter circuit according to claim 3, characterized in that: The SCR drive circuit 1 includes resistors R17, R18, and R19, diodes D4, D5, and D6, a switching transistor Q4, an isolation transformer T1, and a filter capacitor C4. The DR_Q1 signal drives the transistor Q4 to turn on after being divided and current-limited by resistors R17 and R18. The +12V voltage is transformed by transformer T1 and then current-limited by diodes D5 and R19 before driving the GK terminals of Q1 to turn on Q1. The filter capacitor C4 filters the current to prevent interference and mis-driving. Diodes D4 and D6 are both freewheeling clamping diodes to prevent Q4 from being damaged by excessive voltage due to the freewheeling and coupling effect of the transformer coil after Q4 is turned off.

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