A three-phase coupled carrier communication phase switching system and method

Abstract

This invention proposes a three-phase coupled carrier communication phase switching system and method, comprising a three-phase coupling circuit, a three-phase signal switching module, a carrier power amplifier, and a carrier MCU connected in sequence. The control signal output terminal of the carrier MCU is connected to the corresponding control signal input terminal of the three-phase signal switching module. The carrier MCU is used to parse the received carrier data frames, extract the signal strength and signal-to-noise ratio, select the optimal phase, and generate a control signal to drive the transistors in the three-phase signal switching module, dynamically adjusting the coupling phase of the three-phase carrier communication. This invention can achieve communication coupling phase switching based on ambient noise and power line conditions without affecting carrier communication performance, thereby achieving higher meter reading communication efficiency.

Description

Technical Field

[0001] This invention belongs to the field of energy meter carrier communication modules, specifically involving a low-cost solution for providing phase switching function for three-phase coupled carrier communication circuits. Background Technology

[0002] In the field of power line carrier communication technology, there is a clear market demand for carrier coupling of all three phases of power lines to adapt to complex field environments and improve communication reliability. An ideal solution needs to maintain the performance of single-phase coupling communication while possessing the ability to dynamically switch coupling phases based on channel conditions to cope with different line conditions.

[0003] Currently, common carrier coupling schemes have obvious limitations: although single-phase coupling is simple in structure, communication will be interrupted when the noise of the phase line is too high or an open circuit occurs; while the design of simply connecting three-phase coupling circuits in parallel can achieve three-phase coupling function, the carrier signal will be greatly attenuated during transmission due to impedance mismatch and other reasons, which will affect the communication quality and transmission distance.

[0004] To achieve phase switching while avoiding signal loss, theoretically, three independent carrier MCUs, three carrier transmission circuits, and three coupling circuits are required, along with an additional main control MCU responsible for switching logic control. While this architecture can achieve the desired function, it significantly increases system complexity and the number of components, leading to a substantial increase in production costs and making it uncompetitive in the market.

[0005] Therefore, there is an urgent need to develop a new carrier coupling circuit structure that can achieve three-phase adaptive switching coupling, maintain signal integrity, and has cost advantages, in order to meet the market's urgent demand for high-performance, low-cost three-phase carrier communication solutions. Summary of the Invention

[0006] The purpose of this invention is to address the market demand for single-phase coupling performance, and to propose a three-phase coupled carrier communication phase switching system and method that allows for phase switching based on environmental conditions. This system enables phase switching of communication coupling based on environmental noise and power line conditions without affecting carrier communication performance, thereby achieving higher meter reading communication efficiency.

[0007] The technical solution of this invention is: This invention provides a low-cost three-phase coupled carrier communication phase switching system. The system includes a three-phase coupling circuit, a three-phase signal switching module, a carrier power amplifier, and a carrier MCU connected in sequence. The control signal output terminal of the carrier MCU is connected to the corresponding control signal input terminal of the three-phase signal switching module. The three-phase coupling circuit, corresponding to phases A, B, and C respectively, is used to couple the carrier signal to the power grid; The three-phase signal switching module corresponds to phase A, phase B and phase C respectively, and each includes a carrier transmission signal switching circuit and a carrier reception signal switching circuit. The carrier MCU is used to parse the received carrier data frames, extract the signal strength and signal-to-noise ratio, select the optimal phase and generate control signals to drive the transistors in the three-phase signal switching module, and dynamically adjust the coupling phase of the three-phase carrier communication.

[0008] Furthermore, the carrier transmission signal switching circuit includes transistors Q1, Q3, Q5, and Q7, and resistors R1, R3, R5, R7, R9, and R11; The control signal of the carrier MCU is connected to one end of resistor R9. The other end of resistor R9 is connected to the base of transistor Q5. The emitter of transistor Q5 is grounded, and the collector is connected to one end of resistor R5. The other end of resistor R5 is connected to one end of resistor R3 and the base of transistor Q1. The other end of resistor R3 is connected to the emitter of transistor Q1 and connected to the drive power supply VPLC of the carrier power amplifier. The collector of transistor Q1 is connected to one end of resistors R1, R7, and R11. The other end of resistor R11 is grounded. The other end of resistor R1 is connected to the base of transistor Q3. The other end of resistor R7 is connected to the base of transistor Q7. The collectors of transistors Q3 and Q7 are connected to the positive and negative output terminals of the corresponding phase-coupled transformers, respectively. The emitters of transistors Q3 and Q7 are connected to the positive input terminal OUT_P and the negative input terminal OUT_N of the carrier power amplifier, respectively.

[0009] Furthermore, the carrier receiving signal switching circuit includes transistors Q2, Q4, Q6, Q8 and resistors R2, R4, R6, R8, R10, R12; The control signal of the carrier MCU is connected to one end of resistor R10. The other end of resistor R10 is connected to the base of transistor Q6. The emitter of transistor Q6 is grounded, and the collector is connected to one end of resistor R6. The other end of resistor R6 is connected to one end of resistor R4 and the base of transistor Q2. The other end of resistor R4 is connected to the emitter of transistor Q2 and connected to the VPLC drive power supply of the carrier power amplifier. The collector of transistor Q2 is connected to one end of resistors R2, R8, and R12. The other end of resistor R12 is grounded. The other end of resistor R2 is connected to the base of transistor Q4. The other end of resistor R8 is connected to the base of transistor Q8. The collectors of transistors Q4 and Q8 are connected to the positive input terminal RX_+ and the negative input terminal RX_- of the input filter circuit of the carrier MCU. The emitters of transistors Q4 and Q8 are connected to the positive and negative output terminals of the corresponding phase-coupled transformers.

[0010] Furthermore, the carrier MCU performs the following carrier data frame parsing steps; During carrier MCU initialization, the three-phase carrier transmit control signal A / B / C_TX_CTL and the three-phase carrier receive control signal A / B / C_RX_CTL are pulled low to disable three-phase carrier communication. The carrier MCU sequentially pulls up the A / B / C_RX_CTL control signals to enable the A, B, and C phases to receive and acquire the data frame signals sent by the concentrator. Extract the signal strength and signal-to-noise ratio of each phase received data frame, and select the optimal coupling phase based on the maximum value of the signal strength and signal-to-noise ratio.

[0011] Furthermore, the optimal coupling phase is selected based on the signal strength and the maximum signal-to-noise ratio as follows: If the maximum signal strength and the maximum signal-to-noise ratio correspond to the same phase, then that phase is selected as the communication phase. If the maximum signal strength and the maximum signal-to-noise ratio correspond to different phases, then the signal strength difference and signal-to-noise ratio difference between the two phases are further compared. When the signal strength difference is less than the first threshold and the signal-to-noise ratio difference is less than the second threshold, the phase with the higher signal-to-noise ratio is selected; when the signal strength difference is greater than the first threshold and the signal-to-noise ratio difference is less than the second threshold, the phase with the higher signal strength is selected; when the signal-to-noise ratio difference is greater than the second threshold, the phase with both higher signal strength and higher signal-to-noise ratio is selected.

[0012] Furthermore, the first threshold is 4-6 dBuV, and the second threshold is 4-6.

[0013] A low-cost phase switching method for three-phase coupled carrier communication, based on the aforementioned system, includes the following steps: Step 1: After the power meter supplies power, the carrier MCU pulls the three-phase carrier transmit control signal A / B / C_TX_CTL and the three-phase carrier receive control signal A / B / C_RX_CTL low to close the three-phase carrier communication channel; Step 2: Sequentially enable the carrier reception control signals A_RX_CTL, B_RX_CTL, and C_RX_CTL for phases A, B, and C, respectively, so that each phase can receive the data frame signal sent by the concentrator. Step 3: The carrier MCU parses the data frame signals received by each phase, extracts and saves the signal strength and signal-to-noise ratio information; Step 4: Based on the signal strength and signal-to-noise ratio information, select the optimal communication phase and enable the corresponding carrier transmission and reception channels.

[0014] Furthermore, in the carrier transmission signal switching circuit, when the control signal is high, transistor Q5 is turned on, its collector is pulled low, driving transistor Q1 to turn on, which in turn turns on transistors Q3 and Q7, completing the path switching of the corresponding phase carrier transmission signal.

[0015] Furthermore, in the carrier receiving signal switching circuit, when the control signal is high, transistor Q6 is turned on, its collector is pulled low, driving transistor Q2 to turn on, which in turn turns on transistors Q4 and Q8, completing the path switching of the corresponding phase carrier receiving signal.

[0016] Furthermore, when communication between the concentrator and the energy meter fails, the carrier MCU re-executes steps two through four to reselect the optimal communication phase based on the updated information.

[0017] The beneficial effects of this invention are: This invention, through optimized circuit design and integrated control architecture, can achieve precise switching of three-phase coupled channels using only three general-purpose I / O lines of the carrier MCU. While significantly simplifying the system circuit structure and reducing manufacturing costs, it effectively ensures the timeliness and accuracy of the phase switching process, providing a feasible technical implementation path for the high reliability and low cost application of power line carrier communication equipment.

[0018] This invention provides a three-phase coupled carrier communication system and method. The system includes a carrier transmission and reception signal switching circuit and a carrier MCU. The carrier MCU dynamically adjusts the three-phase coupling phase through control lines, evaluating and selecting the optimal phase in real time based on the received signal strength and signal-to-noise ratio (SNR). In case of communication anomalies, the evaluation and switching are repeated to ensure communication stability. When selecting the optimal phase, both signal strength and SNR difference are considered, prioritizing phases with higher SNR and signal strength, thus balancing communication efficiency and anti-interference capability. This invention significantly improves the reliability and adaptability of power line carrier communication, reduces the impact of signal attenuation, and ensures stable communication in complex power grid environments.

[0019] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0020] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the invention.

[0021] Figure 1 A block diagram illustrating the principle of the three-phase coupled carrier communication phase switching system of the present invention is shown.

[0022] Figure 2 A circuit diagram of a carrier transmission signal switching according to an embodiment of the present invention is shown.

[0023] Figure 3 A circuit diagram for switching carrier reception signals according to an embodiment of the present invention is shown.

[0024] Figure 4 A flowchart of the three-phase coupled carrier communication phase switching method of the present invention is shown. Detailed Implementation

[0025] Preferred embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0026] Example 1

[0027] Figure 1 A block diagram illustrating the principle of the three-phase coupled carrier communication phase switching system of the present invention is shown.

[0028] like Figure 1 As shown, the present invention provides a low-cost three-phase coupled carrier communication phase switching system, comprising a three-phase coupling circuit, a three-phase signal switching module, a carrier power amplifier, and a carrier MCU connected in sequence. The control signal output terminal of the carrier MCU is connected to the corresponding control signal input terminal of the three-phase signal switching module. The three-phase coupling circuit, corresponding to phases A, B, and C respectively, is used to couple the carrier signal to the power grid; The three-phase signal switching module corresponds to phase A, phase B and phase C respectively, and each includes a carrier transmission signal switching circuit and a carrier reception signal switching circuit. The carrier MCU is used to parse the received carrier data frames, extract the signal strength and signal-to-noise ratio, select the optimal phase and generate control signals to drive the transistors in the three-phase signal switching module, and dynamically adjust the coupling phase of the three-phase carrier communication.

[0029] Figure 2 A carrier transmission signal switching circuit diagram according to an embodiment of the present invention is shown. Figure 2As shown, the carrier transmission signal switching circuit includes transistors Q1, Q3, Q5, and Q7, and resistors R1, R3, R5, R7, R9, and R11. The carrier MCU's control signal A_TX_CTL is connected to one end of resistor R9, and the other end of resistor R9 is connected to the base of transistor Q5. The emitter of transistor Q5 is grounded, and its collector is connected to one end of resistor R5. The other end of resistor R5 is connected to one end of resistor R3 and the base of transistor Q1, and the other end of resistor R3 is connected to the emitter of transistor Q1 and connected to the carrier signal. The power amplifier's drive power supply is VPLC; the collector of transistor Q1 is connected to one end of resistors R1, R7, and R11, the other end of resistor R11 is grounded, the other end of resistor R1 is connected to the base of transistor Q3, and the other end of resistor R7 is connected to the base of transistor Q7; the collectors of transistors Q3 and Q7 are connected to the positive output terminal OUTA_+ and the negative output terminal OUTA_- of the A-phase coupling transformer, respectively, and the emitters of transistors Q3 and Q7 are connected to the positive input terminal OUT_P and the negative input terminal OUT_N of the carrier power amplifier, respectively.

[0030] Figure 3 A carrier reception signal switching circuit diagram according to an embodiment of the present invention is shown. Figure 3 As shown, the carrier receiving signal switching circuit includes transistors Q2, Q4, Q6, Q8 and resistors R2, R4, R6, R8, R10, R12; The carrier MCU's control signal A_RX_CTL is connected to one end of resistor R10. The other end of resistor R10 is connected to the base of transistor Q6. The emitter of transistor Q6 is grounded, and its collector is connected to one end of resistor R6. The other end of resistor R6 is connected to one end of resistor R4 and the base of transistor Q2. The other end of resistor R4 is connected to the emitter of transistor Q2 and connected to the carrier power amplifier's drive power supply VPLC. The collector of transistor Q2 is connected to one end of resistors R2, R8, and R12. The other end of resistor R12 is grounded. The other end of resistor R2 is connected to the base of transistor Q4. The other end of resistor R8 is connected to the base of transistor Q8. The collectors of transistors Q4 and Q8 are connected to the positive input terminal RX_+ and the negative input terminal RX_- of the carrier MCU's input filter circuit. The emitters of transistors Q4 and Q8 are connected to the positive output terminal RXA_P and the negative output terminal RXA_N of the A-phase coupling transformer.

[0031] The carrier MCU performs the following carrier data frame parsing steps: During carrier MCU initialization, it pulls the A / B / C_TX_CTL and A / B / C_RX_CTL control signals low to disable three-phase carrier communication; The carrier MCU sequentially pulls the A / B / C_RX_CTL control signals high to enable the A, B, and C phases to receive and acquire the data frame signals sent by the concentrator; The signal strength and signal-to-noise ratio of the received data frames for each phase are extracted, and the optimal coupling phase is selected based on the maximum value of the signal strength and signal-to-noise ratio. Specifically, if the maximum signal strength and the maximum signal-to-noise ratio (SNR) correspond to the same phase, then that phase is selected as the communication phase; if the maximum signal strength and the maximum SNR correspond to different phases, then the difference in signal strength and the difference in SNR between the two phases are further compared; when the difference in signal strength is less than 5 dBuV and the difference in SNR is less than 5, the phase with the higher SNR is selected; when the difference in signal strength is greater than 5 dBuV and the difference in SNR is less than 5, the phase with the higher signal strength is selected; when the difference in SNR is greater than 5, the phase with both higher signal strength and higher SNR is selected.

[0032] Example 2

[0033] This invention provides a low-cost phase switching method for three-phase coupled carrier communication. Based on the system described above, the method includes the following steps: Step 1: After the power meter supplies power, the carrier MCU pulls the three-phase carrier transmit control signal A / B / C_TX_CTL and the three-phase carrier receive control signal A / B / C_RX_CTL low to close the three-phase carrier communication channel; Step 2: Sequentially enable the carrier reception control signals A_RX_CTL, B_RX_CTL, and C_RX_CTL for phases A, B, and C, respectively, so that each phase can receive the data frame signal sent by the concentrator. Step 3: The carrier MCU parses the data frame signals received by each phase, extracts and saves the signal strength and signal-to-noise ratio information; Step 4: Based on the signal strength and signal-to-noise ratio information, select the optimal communication phase and enable the corresponding carrier transmission and reception channels.

[0034] In the carrier transmission signal switching circuit, when the control signal A_TX_CTL is high, transistor Q5 is turned on, its collector is pulled low, driving transistor Q1 to turn on, which in turn turns on transistors Q3 and Q7, completing the path switching of the A-phase carrier transmission signal. In the carrier reception signal switching circuit, when the control signal A_RX_CTL is high, transistor Q6 is turned on, its collector is pulled low, driving transistor Q2 to turn on, which in turn turns on transistors Q4 and Q8, completing the path switching of the A-phase carrier reception signal. When communication between the concentrator and the energy meter fails, the carrier MCU re-executes steps two through four to reselect the optimal communication phase based on the updated information.

[0035] In one example, after the electricity meter and carrier module are powered on, the carrier MCU enables the three-phase carrier coupling channels A, B, and C in turn.

[0036] like Figure 2 The control signal shown in the carrier transmission signal switching circuit is controlled by the carrier MCU. At this time, the carrier MCU controls A_TX_CTL to switch from low level 0V to high level 3.3V, and the voltage drop between the base and emitter of transistor Q5;

[0037] V Q5be >0.7V, the collector and emitter of transistor Q5 are connected. Because the emitter of transistor Q5 is grounded, its collector is pulled low. At this time, VPLC is divided to ground through resistors R3 and R5, and VPLC supplies 15V, which is the base voltage of transistor Q1.

[0038] At this time, the voltage drop between the base and emitter of transistor Q1;

[0039] V Q1be >0.7V, the collector and emitter of transistor Q1 are conducting, then the base voltage of transistor Q3 is VPLC. The emitter of the transistor is connected to the carrier power amplifier. This signal is a differential signal. The maximum amplitude of the single-ended signal is about 7V, which is the minimum voltage drop between the base and emitter of transistor Q3.

[0040] V Q3be When the voltage is greater than 0.7V, the collector and emitter of transistor Q3 are turned on, meaning that the A-phase carrier coupled phase carrier transmission circuit is successfully enabled.

[0041] like Figure 3 In the carrier receiving signal switching circuit, the carrier MCU controls A_RX_CTL to switch from low level 0V to high level 3.3V, and the voltage drop between the base and emitter of transistor Q6;

[0042] V Q6be >0.7V, the collector and emitter of transistor Q6 are conducting. Because the emitter of transistor Q6 is grounded, its collector is pulled low. At this time, VPLC is divided to ground through resistors R4 and R6, and VPLC supplies 15V, which is the base voltage of transistor Q2.

[0043] At this time, the voltage drop across the base and emitter of transistor Q2;

[0044] V Q2be If the voltage is greater than 0.7V, the collector and emitter of transistor Q2 are conducting, then the base voltage of transistor Q4 is VPLC. The emitter of the transistor is connected to the carrier power amplifier. This signal is a differential signal, and the maximum amplitude of the single-ended signal is about 0.2V, which is the minimum voltage drop between the base and emitter of transistor Q4.

[0045] V Q4be When the voltage is greater than 0.7V, the collector and emitter of transistor Q4 are turned on, meaning that the phase carrier coupling phase carrier receiving circuit of phase A is successfully enabled.

[0046] Table 1 Truth Table for Communication Coupling Phase Logic Control

[0047] Furthermore, if the carrier MCU can receive the data frame signal sent by the connected concentrator, it will parse out and save the received signal strength and signal-to-noise ratio in the received data frame; if it still does not receive the data frame signal sent by the connected concentrator after waiting for 2 minutes, it will switch the coupling phase of the carrier transmission and reception loop to phase B according to the above process. After the coupling phase of the carrier transmission and reception circuit is switched to phase B, if the carrier MCU can receive the data frame signal sent by the connected concentrator, it will parse out the received signal strength and the signal-to-noise ratio of the received data frame and save it; if it still does not receive the data frame signal sent by the connected concentrator after waiting for 2 minutes, it will switch the coupling phase of the carrier transmission and reception circuit to phase C according to the above procedure. After the coupling phase of the carrier transmission and reception loop is switched to phase C, if the carrier MCU can receive the data frame signal sent by the connected concentrator, it can parse out and save the received signal strength and signal-to-noise ratio in the received data frame. If no data frame signal is received from the connected concentrator after waiting for 2 minutes, check if phases A and B have received the data frame signal from the concentrator. If phases A, B, and C have not received the data frame signal from the concentrator, repeat the above steps. As long as one phase receives the data frame signal from the concentrator, proceed to the next step.

[0048] Compare the stored received signal strengths of phases A, B, and C, and sort them from largest to smallest; compare the stored signal-to-noise ratio values ​​of phases A, B, and C, and sort them from largest to smallest. If the maximum value of the received signal strength and the maximum value of the received signal-to-noise ratio are in the same phase, then that phase is selected as the carrier communication coupling phase; if the maximum value of the received signal strength and the maximum value of the received signal-to-noise ratio are not in the same phase, then the difference between the received signal strength and the received signal-to-noise ratio of the two phases is further compared.

[0049] If the difference in received signal strength is less than 5 dBuV and the difference in received signal-to-noise ratio is less than 5, then the phase with the stronger received signal-to-noise ratio is selected as the carrier communication coupling phase. If the difference in received signal strength is greater than 5 dBuV and the difference in received signal-to-noise ratio is less than 5, then the phase with the stronger received signal strength is selected as the carrier communication coupling phase. If the difference in the received signal-to-noise ratio is greater than 5, then the phase with the stronger received signal-to-noise ratio and the stronger received signal strength is selected as the carrier communication coupling phase.

[0050] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A low-cost three-phase coupled carrier communication phase switching system, characterized in that, The system includes a three-phase coupling circuit, a three-phase signal switching module, a carrier power amplifier, and a carrier MCU connected in sequence. The control signal output terminal of the carrier MCU is connected to the corresponding control signal input terminal of the three-phase signal switching module. The three-phase coupling circuit, corresponding to phases A, B, and C respectively, is used to couple the carrier signal to the power grid; The three-phase signal switching module corresponds to phase A, phase B and phase C respectively, and each includes a carrier transmission signal switching circuit and a carrier reception signal switching circuit. The carrier MCU is used to parse the received carrier data frames, extract the signal strength and signal-to-noise ratio, select the optimal phase and generate control signals to drive the transistors in the three-phase signal switching module, and dynamically adjust the coupling phase of the three-phase carrier communication. The carrier MCU performs the following carrier data frame parsing steps; During carrier MCU initialization, the three-phase carrier transmit control signal A / B / C_TX_CTL and the three-phase carrier receive control signal A / B / C_RX_CTL are pulled low to disable three-phase carrier communication. The carrier MCU sequentially pulls up the A / B / C_RX_CTL control signals to enable the A, B, and C phases to receive and acquire the data frame signals sent by the concentrator. Extract the signal strength and signal-to-noise ratio of each phase received data frame, and select the optimal coupling phase based on the maximum value of the signal strength and signal-to-noise ratio.

2. The three-phase coupled carrier communication phase switching system according to claim 1, characterized in that, The carrier transmission signal switching circuit includes transistors Q1, Q3, Q5, Q7 and resistors R1, R3, R5, R7, R9, R11; The control signal of the carrier MCU is connected to one end of resistor R9. The other end of resistor R9 is connected to the base of transistor Q5. The emitter of transistor Q5 is grounded, and the collector is connected to one end of resistor R5. The other end of resistor R5 is connected to one end of resistor R3 and the base of transistor Q1. The other end of resistor R3 is connected to the emitter of transistor Q1 and connected to the drive power supply VPLC of the carrier power amplifier. The collector of transistor Q1 is connected to one end of resistors R1, R7, and R11. The other end of resistor R11 is grounded. The other end of resistor R1 is connected to the base of transistor Q3. The other end of resistor R7 is connected to the base of transistor Q7. The collectors of transistors Q3 and Q7 are connected to the positive and negative output terminals of the corresponding phase-coupled transformers, respectively. The emitters of transistors Q3 and Q7 are connected to the positive input terminal OUT_P and the negative input terminal OUT_N of the carrier power amplifier, respectively.

3. The three-phase coupled carrier communication phase switching system according to claim 1, characterized in that, The carrier receiving signal switching circuit includes transistors Q2, Q4, Q6, Q8 and resistors R2, R4, R6, R8, R10, R12; The control signal of the carrier MCU is connected to one end of resistor R10. The other end of resistor R10 is connected to the base of transistor Q6. The emitter of transistor Q6 is grounded, and the collector is connected to one end of resistor R6. The other end of resistor R6 is connected to one end of resistor R4 and the base of transistor Q2. The other end of resistor R4 is connected to the emitter of transistor Q2 and connected to the VPLC drive power supply of the carrier power amplifier. The collector of transistor Q2 is connected to one end of resistors R2, R8, and R12. The other end of resistor R12 is grounded. The other end of resistor R2 is connected to the base of transistor Q4. The other end of resistor R8 is connected to the base of transistor Q8. The collectors of transistors Q4 and Q8 are connected to the positive input terminal RX_+ and the negative input terminal RX_- of the input filter circuit of the carrier MCU. The emitters of transistors Q4 and Q8 are connected to the positive and negative output terminals of the corresponding phase-coupled transformers.

4. A low-cost three-phase coupled carrier communication phase switching method, based on the system described in any one of claims 1 to 3, characterized in that, The method includes the following steps: Step 1: After the power meter supplies power, the carrier MCU pulls the three-phase carrier transmit control signal A / B / C_TX_CTL and the three-phase carrier receive control signal A / B / C_RX_CTL low to close the three-phase carrier communication channel; Step 2: Sequentially enable the carrier reception control signals A_RX_CTL, B_RX_CTL, and C_RX_CTL for phases A, B, and C, respectively, so that each phase can receive the data frame signal sent by the concentrator. Step 3: The carrier MCU parses the data frame signals received by each phase, extracts and saves the signal strength and signal-to-noise ratio information; Step 4: Based on the signal strength and signal-to-noise ratio information, select the optimal communication phase and enable the corresponding carrier transmission and reception channels.

5. The three-phase coupled carrier communication phase switching method according to claim 4, characterized in that, In the carrier transmission signal switching circuit, when the control signal is high, transistor Q5 is turned on, its collector is pulled low, driving transistor Q1 to turn on, which in turn turns on transistors Q3 and Q7, completing the path switching of the corresponding phase carrier transmission signal.

6. The three-phase coupled carrier communication phase switching method according to claim 4, characterized in that, In the carrier receiving signal switching circuit, when the control signal is high, transistor Q6 is turned on, its collector is pulled low, driving transistor Q2 to turn on, which in turn turns on transistors Q4 and Q8, completing the path switching of the corresponding phase carrier receiving signal.

7. The three-phase coupled carrier communication phase switching method according to claim 4, characterized in that, When communication between the concentrator and the energy meter fails, the carrier MCU re-executes steps two through four to reselect the optimal communication phase based on the updated information.

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