A high-precision photovoltaic meter reading collection method and device

Abstract

The application discloses a high-precision photovoltaic meter reading collection method and device, and relates to the field of photovoltaic power generation direct current side intelligent metering. The method comprises the following steps: receiving a sampling analog signal, and performing filtering and impedance matching; performing differential amplification and adjusting an amplification factor on the signal after the filtering and impedance matching; performing analog-digital conversion on the amplified signal to obtain a sampling digital signal; and performing temperature drift compensation on the sampling digital signal based on a temperature drift self-calibration algorithm to obtain corresponding physical values. The method can realize high-precision photovoltaic current collection.

Description

Technical Field

[0001] This application relates to the field of intelligent metering on the DC side of photovoltaic power generation, and in particular to a high-precision photovoltaic meter reading method and device. Background Technology

[0002] With the rapid expansion of distributed photovoltaic (PV) installations, accurate DC metering, stable data upload, and line fault self-diagnosis have become critical requirements for intelligent operation and maintenance of power plants. Traditional DC meters mostly use 12–16 bit ADCs, which have large temperature drift and a comprehensive error exceeding 0.5% across the entire range of 200 V–1500 V and 0.1 A–1000 A, failing to meet the requirements for revenue settlement and refined module-level management. PV sites commonly use single LoRa or 2G / NB-IoT modules for communication, which suffers from severe signal attenuation and packet loss rates exceeding 5% in mountainous or urban environments with shading. After a line drop, manual on-site reset is required, resulting in high maintenance costs. The large number of DC cables, aging connectors, and rodent damage can easily lead to open circuits, short circuits, or micro-arcs. Existing systems lack online detection methods, relying solely on reactive troubleshooting after abnormal power generation, posing a dual risk of fire and reduced revenue. Summary of the Invention

[0003] Therefore, it is necessary to address the problems of insufficient accuracy and lack of fault detection capability in existing photovoltaic power generation metering devices. This application proposes a high-precision photovoltaic meter reading method and device, the specific technical solution of which is as follows: Firstly, this application proposes a high-precision photovoltaic meter reading data acquisition method, comprising the following steps: Receive the sampled analog signal and perform filtering and impedance matching; Differential amplification and amplification factor adjustment are performed on the filtered and impedance-matched signal; The amplified signal is then converted from analog to digital to obtain the sampled digital signal; Temperature drift compensation is performed on the sampled digital signal based on the temperature drift self-calibration algorithm to obtain the corresponding physical quantity value.

[0004] Furthermore, the specific content of the temperature drift self-calibration algorithm is as follows: Multiple temperature points are preset, and full-range calibration is performed for preset current and preset voltage. The original analog-to-digital conversion code value and standard value of each temperature-range point are recorded, and a three-dimensional lookup table LUT(T, I, V) is established, where T represents temperature, I represents current range, and V represents voltage range. The current temperature T_now is read after a preset time interval. When the difference between T_now and the last calibration temperature T_last is greater than a preset threshold, the following calibration steps are performed: the LUT is queried at the range switching point to obtain the calibration coefficient and offset of the adjacent temperature point; the current temperature compensation coefficient is calculated by linear interpolation based on the calibration coefficient and offset; when the difference is not greater than the preset threshold, the temperature compensation coefficient obtained from the last calibration is used. The sampled digital signal is compensated based on the temperature compensation coefficient, and the corresponding physical quantity value is obtained through the mapping relationship.

[0005] Secondly, this application proposes a high-precision photovoltaic meter reading acquisition device, including a self-calibrating wide-range DC metering module, a dual-redundant wireless transmission module, and a disconnection self-diagnosis and self-recovery module. The self-calibrating wide-range DC metering module is electrically connected to the dual-redundant wireless transmission module and the disconnection self-diagnosis and self-recovery module, respectively. The dual-redundant wireless transmission module is electrically connected to the disconnection self-diagnosis and self-recovery module. The self-calibrating wide-range DC metering module is used to perform DC metering of photovoltaic power generation and transmit the metering results to the dual-redundant wireless transmission module. It is also used to receive the back-collected voltage signal output by the self-diagnosis and self-recovery module, convert it into a digital signal, and transmit it to the self-diagnosis and self-recovery module. The self-diagnosis and self-recovery module is used to determine faults and switch backup channels based on the digital signal converted from the back-collected voltage signal, and output alarm signals to the dual-redundant wireless transmission module. The dual-redundant wireless transmission module is used to receive the metering results and alarm signals and transmit them to the cloud.

[0006] Furthermore, the self-calibrating wide-range DC metering module includes an analog front-end, a differential amplifier, a programmable bias amplifier, and an analog-to-digital converter (ADC). The analog front-end selects the incoming signal through a built-in channel selector and performs filtering and impedance matching preprocessing. The preprocessed signal is differentially amplified by the differential amplifier, then the amplification factor is switched by the programmable bias amplifier, and finally converted into a digital signal by the ADC. After temperature drift compensation based on a temperature drift self-calibration algorithm, the metering result is sent to the dual-redundant wireless transmission module. The incoming signals include voltage sampling signals, current sampling signals, and temperature sampling signals. During the idle time slots of the metering chip in the ADC, the channel selector also connects the retrieval voltage signal output by the disconnection self-diagnosis and self-recovery module for fault identification. The ADC supports 24-bit analog-to-digital conversion.

[0007] Furthermore, the self-diagnostic and self-recovery module for line disconnection includes a line disconnection detection circuit, a microcontroller, and a relay switching circuit. During the idle time slot of the metering chip in the analog-to-digital converter circuit, the line disconnection detection circuit injects a pulse current into the DC bus through its terminals to obtain a sampled voltage signal. This signal is then input to the channel selector for signal processing to obtain a digital voltage signal. The microcontroller determines whether a fault exists in the sampling channel based on changes in the digital voltage signal. The relay switching circuit is used to switch to a backup channel when a fault occurs. The types of faults include open circuit, short circuit, and loose connection. When a fault exists in the line, the microcontroller sets the GPIO to drive the relay switching circuit, switching the analog front-end input to the backup sampling channel. Simultaneously, it triggers local Flash buffer continuation and reports the fault alarm signal to the dual-redundant wireless transmission module to trigger a remote alarm.

[0008] Furthermore, the fault detection method is as follows: when the voltage does not change, it is determined to be an open circuit; when the voltage drops below a preset short circuit threshold, it is determined to be a short circuit; when the number of voltage fluctuations exceeds a preset range reaches a preset number, it is determined to be a loose connection.

[0009] The faults are self-recovering. Specifically, for open-circuit faults, the sampling input is switched from the sampling channel to the backup sampling channel via a relay switching circuit, and the sampling channel is marked as open-circuit fault. For short-circuit faults, the overcurrent protection relay of the sampling channel is first disconnected, and then the sampling input is switched from the sampling channel to the backup channel via a relay switching circuit, triggering an emergency alarm. For loose connection faults, the sampling input is switched from the sampling channel to the backup channel via a relay switching circuit, and the sampling channel is marked as pending maintenance.

[0010] Furthermore, the dual-redundant wireless transmission module includes a photoelectric sampling module, an isolation interface, a communication link, and a main processor. The communication link includes a local communication link and a remote communication link. The photoelectric sampling module and the isolation interface form a meter reading channel to output the metering results to the local communication link. The main processor is used to receive the metering results and alarm signals and perform edge computing. The results of the edge computing are then reported to the cloud via the remote communication link.

[0011] Beneficial effects: This application proposes a high-precision photovoltaic meter reading acquisition method and device. By processing the sampled signal and compensating for temperature drift, it achieves high-precision acquisition of the DC side of photovoltaic power generation. At the same time, it provides fault detection and recovery methods for photovoltaic power generation lines and stable data transmission guarantee, realizing the integration of high-precision metering, stable wireless transmission, and self-testing and self-recovery after line failure. Attached Figure Description

[0012] Figure 1 This is a flowchart of a high-precision photovoltaic meter reading data acquisition method according to an embodiment of this application; Figure 2 This is a module connection diagram of a high-precision photovoltaic meter reading acquisition device according to an embodiment of this application; Figure 3 This is a circuit diagram of the channel selector in an embodiment of this application; Figure 4 This is a circuit diagram of the differential amplifier in an embodiment of this application; Figure 5 This is a circuit diagram of the programmable bias amplifier in an embodiment of this application; Figure 6 This is a schematic diagram of the disconnection detection circuit in an embodiment of this application. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0014] Example 1 This embodiment provides a high-precision photovoltaic meter reading data acquisition method, the flowchart of which is shown below. Figure 1 As shown, it includes the following steps: Receive the sampled analog signal and perform filtering and impedance matching; Differential amplification and amplification factor adjustment are performed on the filtered and impedance-matched signal; The amplified signal is then converted from analog to digital to obtain the sampled digital signal; Temperature drift compensation is performed on the sampled digital signal based on the temperature drift self-calibration algorithm to obtain the corresponding physical quantity value.

[0015] It should be noted that the analog-to-digital conversion supports 24-bit analog-to-digital conversion, and the specific content of the temperature drift self-calibration algorithm is as follows: Multiple temperature points are preset, and full-range calibration is performed for preset current and preset voltage. The original analog-to-digital converter (ADC) code value and standard value of each temperature-range point are recorded, and a three-dimensional lookup table LUT(T, I, V) is established, where T represents temperature, I represents current range, and V represents voltage range. The current temperature T_now is read after a preset time interval. When the difference between T_now and the last calibrated temperature T_last is greater than a preset threshold, the following calibration steps are performed: query the LUT at the range switching point to obtain the calibration coefficient and offset of the adjacent temperature point; calculate the current temperature compensation coefficient by linear interpolation based on the calibration coefficient and offset; when the difference is not greater than the preset threshold, use the temperature compensation coefficient of the last calibration. The sampled digital signal is compensated based on the temperature compensation coefficient, and the corresponding physical quantity value is obtained through the mapping relationship.

[0016] In one specific embodiment, three temperature points of -40℃, +25℃, and +85℃ are preset to perform full-range calibration of 0.1 A, 1 A, 10 A, 100 A, 1000 A (current) and 200 V, 500 V, 1000 V, 1500 V (voltage).

[0017] The expression for calculating the temperature compensation coefficient is as follows: k_T = k_1 + [(T_now - T_1) / (T_2 - T_1)] × (k_2 - k_1) b_T = b_1 + [(T_now - T_1) / (T_2 - T_1)] × (b_2 - b_1) Where k_1 and k_2 represent calibration coefficients, b_1 and b_2 represent offsets, T_1 represents the temperature node corresponding to k_1 and b_1, and T_2 represents the temperature node corresponding to k_2 and b_2.

[0018] The expression for compensating the sampled digital signal, i.e., the original code value of the ADC, is as follows: N_cal = k_T × N_raw + b_T N_raw represents the ADC raw code value.

[0019] This method, by supporting 24-bit analog-to-digital conversion and a temperature drift self-calibration algorithm, can achieve high-precision meter reading at the level of 0.1%.

[0020] Example 2 This embodiment provides a high-precision photovoltaic meter reading data acquisition device. The module connection diagram of the device is shown below. Figure 2 As shown, the system includes a self-calibrating wide-range DC metering module, a dual-redundant wireless transmission module, and a self-diagnostic and self-recovery module for line disconnection. The self-calibrating wide-range DC metering module is electrically connected to both the dual-redundant wireless transmission module and the self-diagnostic and self-recovery module for line disconnection. The dual-redundant wireless transmission module is also electrically connected to the self-diagnostic and self-recovery module for line disconnection. The self-calibrating wide-range DC metering module is used for DC metering of photovoltaic power generation and transmitting the metering results to the dual-redundant wireless transmission module. It is also used to receive the sampled voltage signal output by the self-diagnostic and self-recovery module, convert it into a digital signal, and transmit it to the self-diagnostic and self-recovery module. The self-diagnostic and self-recovery module is used to determine faults and switch backup channels based on the digital signal converted from the sampled voltage signal, and outputs an alarm signal to the dual-redundant wireless transmission module. The dual-redundant wireless transmission module is used to receive the metering results and alarm signals and transmit them to the cloud.

[0021] It should be noted that the self-calibrating wide-range DC metering module includes an analog front-end, a differential amplifier, a programmable bias amplifier, and an analog-to-digital converter (ADC). The analog front-end selects the incoming signal through a built-in channel selector and performs filtering and impedance matching preprocessing. The preprocessed signal is differentially amplified by the differential amplifier, then the amplification factor is switched by the programmable bias amplifier, and finally converted into a digital signal by the ADC. After temperature drift compensation based on a temperature drift self-calibration algorithm, the metering result is obtained and sent to the dual-redundant wireless transmission module via the SPI bus. The incoming signals include: voltage sampling signal, current sampling signal, and temperature sampling signal. The ADC supports 24-bit analog-to-digital conversion.

[0022] During the idle time slot of the metering chip in the analog-to-digital conversion circuit, the channel selector also connects to the sampled voltage signal output by the disconnection self-diagnosis and self-recovery module for fault identification.

[0023] In a specific embodiment, the temperature drift self-calibration algorithm is implemented as follows: (1) Factory multi-point calibration stage: In a standard constant temperature chamber, full-range calibration was performed at three temperature points: -40℃, +25℃, and +85℃ for currents of 0.1 A, 1 A, 10 A, 100 A, and 1000 A, and voltages of 200 V, 500 V, 1000 V, and 1500 V. The original ADC code values ​​and standard values ​​at each temperature-range point were recorded, and a three-dimensional lookup table LUT(T, I, V) was established.

[0024] (2) Real-time compensation during runtime: The device has a built-in digital temperature sensor (such as TMP117, with an accuracy of ±0.1℃). The MCU reads the current temperature every 10 seconds and executes the following steps: Step 1: Trigger calibration when the difference |ΔT| between T_now and the last calibration temperature T_last is greater than 5℃; Step 2: At the range switching point (the current range is automatically determined by the programmable bias amplifier), query the LUT to obtain the calibration coefficients k_1, k_2 and offset of adjacent temperature points; Step 3: Calculate the current temperature compensation coefficient using linear interpolation: k_T = k_1 + [(T_now - T_1) / (T_2 - T_1)] × (k_2 - k_1) b_T = b_1 + [(T_now - T_1) / (T_2 - T_1)] × (b_2 - b_1) Step 4: Compensate the raw ADC code values: N_cal = k_T × N_raw + b_T Step 5: Substitute N_cal into the voltage / current conversion formula to obtain the calibrated physical quantity value.

[0025] It should be noted that the self-diagnostic and self-recovery module for line disconnection includes a line disconnection detection circuit, a microcontroller (MCU), and a relay switching circuit. During the idle time slot of the metering chip in the analog-to-digital converter circuit, the line disconnection detection circuit injects pulse current into the DC bus through the terminal to obtain the sampled voltage signal. After obtaining the sampled voltage signal, it inputs it to the channel selector for signal processing to obtain a digital voltage signal. The microcontroller determines whether there is a fault in the sampling channel based on the change in the digital voltage signal. The relay switching circuit is used to switch to the backup channel when a fault occurs. The types of faults include open circuit, short circuit, and loose connection. When there is a fault in the line, the microcontroller sets the GPIO to drive the relay switching circuit, switches the analog front-end input to the sampling backup channel, and triggers the local Flash cache (dual buffer 512KB×2) to resume transmission to ensure zero data loss. The fault alarm signal is also reported to the dual redundant wireless transmission module to trigger a remote alarm.

[0026] The method for determining the type of fault is as follows: if there is no change in voltage after injecting pulse current, it is determined to be an open circuit; if the voltage drops more than a preset drop value after injecting pulse current, it is determined to be a short circuit; if the voltage fluctuation exceeds a preset range and reaches a preset number of times after continuous pulse current injection, it is determined to be a loose connection.

[0027] The faults are self-recovering. Specifically, for open-circuit faults, the sampling input is switched from the sampling channel to the sampling backup channel via a relay switching circuit, and the sampling channel is marked as open-circuit fault. For short-circuit faults, the overcurrent protection relay of the sampling channel is first disconnected, and then the sampling input is switched from the sampling channel to the sampling backup channel via a relay switching circuit, triggering an emergency alarm. For loose connection faults, the sampling input is switched from the sampling channel to the sampling backup channel via a relay switching circuit, and the sampling channel is marked as pending maintenance.

[0028] It should be noted that the dual-redundant wireless transmission module includes a photoelectric sampling module, an isolation interface, a communication link, and a main processor. The communication link includes a local communication link and a remote communication link. The photoelectric sampling module and the isolation interface form a meter reading channel, which is used to output the metering results obtained by the self-calibrated wide-range DC metering module to the local communication link. The main processor is used to receive the metering results and alarm signals and perform edge computing, and report the edge computing results to the cloud through the remote communication link.

[0029] In one specific embodiment, the local communication link uses LoRa or Wi-Fi, the remote communication link uses a 4G Cat.1 module, and the meter reading channel adopts a dual-redundancy design of "photoelectric sampling module + RS-485 isolation", compatible with DL / T 645 and Modbus protocols, to achieve electrical isolation and anti-common-mode interference, and its output is connected to the local communication link; the main processor receives 24-bit ADC output data through the SPI bus, completes edge computing, and then encrypts and sends it to the cloud data center through the 4G Cat.1 module; the dual-redundant wireless transmission module can be extended to connect to LoRa, Wi-Fi, CAN / RS-232 bus arbitrarily selected, to achieve the integration of "local high-precision acquisition - multi-protocol extension - stable wireless transmission".

[0030] Example 3 This embodiment provides a specific implementation method for a high-precision photovoltaic meter reading data acquisition device, the details of which are as follows: The channel selector of the self-calibrating wide-range DC metering module uses the CD4052BM96 chip, and the circuit diagram is shown below. Figure 3 As shown, it includes a CD4052BM96 chip, denoted as U1, terminals H1, H2, H3, H4, and four filter capacitors C1, C2, C3, and C4, where C1 and C3 are 10μF aluminum electrolytic capacitors, and C2 and C4 are 100nF ceramic capacitors. The specific connection relationships are as follows: Pin 1 of chip U1 is connected to terminal 1 of H1, pin 2 is connected to terminal 2 of H1, pin 4 is connected to terminal 1 of H2, pin 5 is connected to terminal 2 of H2, pin 15 is connected to terminal 1 of H3, pin 14 is connected to terminal 2 of H3, pin 12 is connected to terminal 1 of H4, and pin 11 is connected to terminal 2 of H4; Pin 16 (VDD) of chip U1 is connected to a +3.3V power supply, and C1 and C2 are connected in parallel to GND to form a positive power supply filter network; Pin 7 (VEE) is connected to a -3.3V power supply, and C3 and C4 are connected in parallel to GND to form a negative power supply filter network; Pin 8 (VSS) is directly grounded; Pin 9 (B) is connected to MCU pin P56, Pin 10 (A) is connected to MCU pin P57 as a channel selection control bit, Pin 6 is connected to MCU pin P11 as a channel enable pin, Pin 3 is the common output terminal of the Y channel connected to AD_Y of the subsequent amplifier circuit, and Pin 13 is the common output terminal of the X channel connected to AD_X of the subsequent amplifier circuit. During operation, the MCU controls the level combination of P56 and P57 to select one of the four inputs in each of the Y and X channel groups, and sends the external sampling signal to the AD_Y and AD_X output terminals in a time-division multiplexing manner to realize the time-division multiplexing acquisition of eight analog signals. The power supply filter capacitor is responsible for suppressing ripple and high-frequency interference to ensure the stable operation of the chip sampling.

[0031] This circuit controls the switching of the A / B pin levels of four input channels X0 to X3 via the MCU. Channel X0 is connected in series to the output of the disconnection detection circuit, while X1 to X3 are connected to voltage, current, and temperature sampling signals, respectively. This enables time-division multiplexing of multiple analog signals. This design simplifies circuit design, reduces costs, and increases the number of acquisition channels while also reducing the size of the acquisition board.

[0032] The differential amplifier of the self-calibrating wide-range DC metering module uses dual operational amplifiers LM258 for differential amplification. Its characteristics include a wide operating temperature range and strong anti-interference capability. The circuit diagram is shown below. Figure 4 As shown, Includes the dual operational amplifier U4.1 of model LM258, resistors R2, R4, R5, R6 and capacitors C5, C6, C9, C10, where R2 and R6 are 100kΩ resistors, R4 and R5 are 2kΩ resistors, C5 and C9 are 10μF aluminum electrolytic capacitors, and C6 and C10 are 100nF ceramic capacitors. The specific connection is as follows: The AD_X signal output from the pre-amplifier channel selector is connected to pin 2 of the inverting input of U4.1 via R4, and the AD_Y signal is connected to pin 3 of the non-inverting input of U4.1 via R5. The non-inverting input is also grounded via R6. Pin 1 of U4.1 is connected back to pin 2 of the inverting input via R2, forming a negative feedback amplification structure. Pin 1 is finally led out as the amplified signal AP1, which is connected to the subsequent ADC sampling circuit. Pin 8 of U4.1 is connected to a +3.3V power supply, and C5 and C6 are connected in parallel to GND to form a positive power supply filter network. Pin 4 is connected to a -3.3V power supply, and C9 and C10 are connected in parallel to GND to form a negative power supply filter network.

[0033] Based on the operational amplifier's characteristics of high gain and high input impedance, and the fact that the voltages at pins 2 and 3 are equal, we can derive the following two equations:

[0034] according to It can be concluded that In other words, the output voltage of the entire circuit is the difference between the input and output voltages multiplied by the circuit's amplification factor. This circuit is commonly used for acquiring small AC signals. It is important to note that the amplification voltage must not exceed the power supply voltage during use.

[0035] The programmable bias amplifier of the self-calibrating wide-range DC metering module is a programmable bias amplifier circuit based on the LM258 operational amplifier and CD4066BM / TR analog switch, as shown in the circuit diagram. Figure 5As shown, the components include the second channel U4.2 of the LM258 dual operational amplifier, the CD4066BM / TR four-channel analog switch chip U2, resistors R1, R3, R7, R8, R9, and R10, and capacitors C7, C8, C11, and C12. Among them, R1 and R3 are 1kΩ resistors, R7 is a 1kΩ resistor, R8 is a 10kΩ resistor, R9 is a 75kΩ resistor, R10 is a 150kΩ resistor, C7 and C11 are 10μF aluminum electrolytic capacitors, and C8 and C12 are 100nF ceramic capacitors. The specific connection is as follows: The AP1 signal output from the pre-amplifier circuit is connected to pin 5 of the non-inverting input of U4.2 via R3, and the GND signal is connected to pin 6 of the inverting input of U4.2 via R1. The inverting input is also connected to the external input signal RAIN1. Pin 7 of U4.2 is led out as RAIN2 and connected to the subsequent analog switch circuit. The Y0 and Y1 pins of analog switch U2 are connected to the RAIN2 signal, and the E0, E1, E2, and E3 pins are connected to CONR1, CONR2, CONR3, and CONR4 respectively. Four MCU control signals are used. Pins Z0, Z1, Z2, and Z3 are switch outputs. Z0 is fed back to node RAIN1 via parallel resistors R7 and R8, while Z2 and Z3 are fed back to node RAIN1 via parallel resistors R9 and R10, forming feedback loops with different amplification factors. Pin 14 (VDD) of U2 is connected to a +3.3V power supply, and C7 and C8 are connected in parallel to GND to form a positive power supply filter network. Pin 7 (VSS) of U2 is connected to a -3.3V power supply, and C11 and C12 are connected in parallel to GND to form a negative power supply filter network. This design uses an analog switching circuit CD4066BM to select the amplifier's input resistors R7, R8, R9, and R10 by controlling the high and low levels of pins E0, E1, E2, and E3, thereby controlling the circuit to operate in an appropriate amplification state. In the program, it typically scans cyclically from small to large. If the measured voltage falls within a specified range, the loop exits. In practical applications, a digital potentiometer can be used to replace this circuit.

[0036] The circuit diagram for the disconnection detection of the self-diagnostic and self-recovery module is as follows: Figure 6As shown, the system includes a gas discharge tube D3, an NPN transistor Q7, diodes D4, D5, D6, D7, D8, D9, and D11, resistors R22, R23, R24, R25, R26, and R30, and capacitors C17 and C18. Specifically, D3 is a 2RM350L-8 / B, Q7 is an S9014LT1 J6, D11 is an SOD4007-MS, D4, D5, D6, and D7 are M7, D8 is a ZMM3V3, D9 is a Zener diode, R30, R22, and R23 are 1MΩ resistors, R24 is a 10kΩ resistor, R25 is a 5.1MΩ resistor, R26 is a 10kΩ resistor, C17 and C18 are 2.2nF ceramic capacitors, and the external terminal J7 is an HX25003-2A, used to connect to the photovoltaic DC bus. The specific connection relationships are as follows: The external DC bus is connected to the circuit through terminal J7. Gas discharge tube D3 is connected in parallel across both ends of J7 to achieve surge protection. In the pulse injection branch, the MCU control pin GPIO4 is connected to the base of Q7 via R24. The emitter of Q7 is grounded, and the collector is connected to the lower terminal of J7 via R22. GPIO2 is also led out from the collector and connected in parallel with filter capacitor C17 and Zener diode D8 to GND. In the pulse recovery branch, the upper terminal of J7 is connected to GND via reverse series connections D4 and D6, and the lower terminal is connected to GND via reverse series connections D5 and D7 to form a bidirectional clamping circuit. The upper terminal of J7 is also connected to GPIO1 via R30 and D11, and the lower terminal of J7 is connected to GPIO3 via R25. The GPIO3 branch is also connected in parallel with pull-down resistor R26, filter capacitor C18, and Zener diode D9 to GND.

[0037] During the idle time slot of the metering chip, the MCU controls a constant voltage source to inject a pulse current with an amplitude of 3V and a pulse width of 100µs into the DC bus. The rising edge of the pulse triggers a high-speed sample-and-hold circuit to sample the voltage between the positive and negative terminals of the bus at 1 MHz, recording the voltage change rate dv / dt within Δt = 10µs. Open-circuit and short-circuit faults in the line are distinguished by measuring the input impedance. As shown in the figure, a 3V pulse voltage is injected through the J7 terminal, and the input impedance is calculated to distinguish between open-circuit and short-circuit faults.

[0038] Example 4 This embodiment provides the hardware circuit and action logic for self-recovery from faults, as detailed below: (1) Hardware composition The core of the self-recovery circuit is the relay switching circuit, which uses a double-pole double-throw relay (such as G5V-2-H1) and is driven by the MCU GPIO through a transistor (S8050).

[0039] The relay contact connection method is as follows: Normally closed contact: Connects to the main sampling channel (conducts during normal operation and is used for daily measurement). Normally open contact: Connects to the spare sampling channel (a redundant second set of current / voltage sampling terminals). Local Cache: The device has a built-in Flash chip (capacity ≥1 MB) and adopts a dual buffer design (Buffer A / B, 512 KB each) for temporary data storage during disconnection switching.

[0040] (2) Self-recovery action logic Based on the disconnection detection results, the MCU automatically executes a four-step self-recovery process: "detection → judgment → switching → resumption". Step 1: Testing The MCU controls the disconnection detection circuit terminals to inject a 3V / 100µs pulse current into the DC bus. The current is then sampled back through the X0 channel selector, and dv / dt is calculated to determine the line status.

[0041] Step 2: Judgment Open circuit fault: dv / dt≈0 (no voltage change after pulse injection), impedance>10 MΩ Short circuit fault: dv / dt is extremely high (voltage drop), impedance <1 Ω Loose connection fault: abnormal fluctuations in dv / dt, impedance unstable between 1 kΩ and 1 MΩ. Step 3: Switching (Core Self-Recovery Action) After a fault is identified, the MCU completes the following actions within 500ms: Setting the FAULT_RECOVER signal → GPIO outputs a high level, which drives the relay coil via the S8050 transistor. Relay energizes → Normally closed contact opens (sampling channel disconnected), normally open contact closes (standby channel connected). Analog front-end input switching → The sampling signal is automatically transferred from the sampling channel terminal to the spare channel terminal. Mark fault → Record fault channel number, fault type, and occurrence timestamp The entire process requires no manual intervention; the device automatically switches channels to ensure uninterrupted metering.

[0042] Step 4: Resume Transmission (Zero Data Loss Guarantee) During the switchover, newly acquired data is written to the currently active buffer (e.g., Buffer A) in real time: If the network is normal: Data is uploaded to the cloud in real time via the 4G module. In case of network interruption: data is temporarily stored in Flash. Once the network is restored, cached data (with timestamps) will be uploaded first, followed by real-time data.

[0043] (3) Differences in self-recovery among the three types of faults Open circuit fault self-recovery: The relay directly switches to the backup channel, and the sampling channel is marked as "open circuit fault". Cached data is stored for ≥7 days, and maintenance personnel can remotely view the location of the fault.

[0044] Short-circuit fault self-recovery: The MCU first disconnects the main relay (overcurrent protection to prevent damage to the analog front end), and then switches to the backup channel. At the same time, an emergency alarm is triggered, and the data is reported to the cloud via the 4G module within seconds. Data before and after the fault is recorded for one minute before and after the fault for post-fault analysis.

[0045] Self-recovery from loose connection faults: To avoid misjudgment, the MCU performs three consecutive checks (200 ms apart), and only performs a switchover after confirming a loose connection in all three checks. The original channel is marked "pending maintenance," and the data is taken from the backup channel. However, the reliability of the original channel data marking is reduced, reminding maintenance personnel to check the connector on-site when appropriate.

[0046] The above self-healing action logic enables online detection, isolation, and self-healing to be completed within 2 ms, achieving zero manual intervention, zero missed reports, and zero data loss.

[0047] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A high-precision photovoltaic meter reading data acquisition method, characterized in that, Includes the following steps: Receive the sampled analog signal and perform filtering and impedance matching preprocessing; Differential amplification and amplification factor adjustment are performed on the preprocessed signal; The amplified signal is then converted from analog to digital to obtain the sampled digital signal; Temperature drift compensation is performed on the sampled digital signal based on the temperature drift self-calibration algorithm to obtain the corresponding physical quantity value.

2. The high-precision photovoltaic meter reading data acquisition method according to claim 1, characterized in that, The specific content of the temperature drift self-calibration algorithm is as follows: Multiple temperature points are preset, and full-range calibration is performed for preset current and preset voltage. The original analog-to-digital conversion code value and standard value of each temperature-range point are recorded, and a three-dimensional lookup table LUT(T, I, V) is established, where T represents temperature, I represents current range, and V represents voltage range. After reading the current temperature T_now at a preset time interval, if the difference between T_now and the last calibrated temperature T_last is greater than a preset threshold, proceed to the following calibration steps: query the LUT at the range switching point to obtain the calibration coefficient and offset of the adjacent temperature point; The current temperature compensation coefficient is calculated using linear interpolation based on the calibration coefficient and offset. If the difference is not greater than the preset threshold, the temperature compensation coefficient obtained from the previous calibration is used. The sampled digital signal is compensated based on the temperature compensation coefficient, and the corresponding physical quantity value is obtained through the mapping relationship.

3. A high-precision photovoltaic meter reading acquisition device, characterized in that, The system includes a self-calibrating wide-range DC metering module, a dual-redundant wireless transmission module, and a self-diagnostic and self-recovery module for line disconnection. The self-calibrating wide-range DC metering module is electrically connected to both the dual-redundant wireless transmission module and the self-diagnostic and self-recovery module for line disconnection. The dual-redundant wireless transmission module is also electrically connected to the self-diagnostic and self-recovery module for line disconnection. The self-calibrating wide-range DC metering module is used to perform DC metering of photovoltaic power generation, obtain metering results, and transmit the metering results to the dual-redundant wireless transmission module. It is also used to receive the sampled voltage signal output by the self-diagnostic and self-recovery module, convert it into a digital signal, and transmit it to the self-diagnostic and self-recovery module. The self-diagnostic and self-recovery module is used to determine faults and switch backup channels based on the digital signal, and output alarm signals to the dual-redundant wireless transmission module. The dual-redundant wireless transmission module is used to receive the metering results and alarm signals and transmit them to the cloud.

4. The high-precision photovoltaic meter reading acquisition device according to claim 3, characterized in that, The self-calibrating wide-range DC metering module includes an analog front-end, a differential amplifier, a programmable bias amplifier, and an analog-to-digital converter. The analog front-end selects the incoming signal through a built-in channel selector and performs filtering and impedance matching preprocessing. The preprocessed signal is differentially amplified by the differential amplifier, and then the amplification factor is switched by the programmable bias amplifier. Finally, it is converted into a digital signal by the analog-to-digital converter and the metering result is obtained after temperature drift compensation based on the temperature drift self-calibration algorithm and sent to the dual-redundant wireless transmission module. The incoming signals include: voltage sampling signal, current sampling signal, and temperature sampling signal.

5. The high-precision photovoltaic meter reading acquisition device according to claim 4, characterized in that, The channel selector also receives the sampled voltage signal from the self-diagnostic and self-recovery module for fault identification.

6. The high-precision photovoltaic meter reading acquisition device according to claim 4, characterized in that, The self-diagnosis and self-recovery module for line breakage includes a line breakage detection circuit, a microcontroller, and a relay switching circuit. During the idle time slot of the metering chip in the analog-to-digital converter circuit, the line breakage detection circuit injects pulse current into the DC bus through the terminal to obtain the sampled voltage signal. After obtaining the sampled voltage signal, it is input to the channel selector for signal processing to obtain the voltage digital signal. The microcontroller determines whether there is a fault in the sampling channel based on the change of the voltage digital signal.

7. The high-precision photovoltaic meter reading acquisition device according to claim 6, characterized in that, The fault detection method is as follows: when the voltage does not change, it is determined to be an open circuit; when the voltage drops below the preset short circuit threshold, it is determined to be a short circuit; when the voltage fluctuation exceeds the preset range a preset number of times, it is determined to be a loose connection.

8. The high-precision photovoltaic meter reading acquisition device according to claim 7, characterized in that, The relay switching circuit is used to switch the sampling input from the sampling channel to the sampling backup channel when a fault occurs. The types of faults include open circuit, short circuit and loose connection. When a fault exists in the line, the microcontroller sets the GPIO to drive the relay switching circuit to switch the sampling channel, triggers the local Flash cache to resume transmission, and reports the fault alarm signal to the dual redundant wireless transmission module to trigger a remote alarm.

9. The high-precision photovoltaic meter reading acquisition device according to claim 8, characterized in that, The fault can be self-recovered. The specific method is as follows: For open circuit faults, the sampling input is switched from the sampling channel to the sampling backup channel through the relay switching circuit, and the sampling channel is marked as open circuit fault; For short circuit faults, the overcurrent protection relay of the sampling channel is first disconnected, and then the sampling input is switched from the sampling channel to the sampling backup channel through the relay switching circuit, triggering an emergency alarm. For loose connection faults, the sampling input is switched from the sampling channel to the sampling backup channel via a relay switching circuit, and the sampling channel is marked as pending maintenance.

10. The high-precision photovoltaic meter reading acquisition device according to claim 3, characterized in that, The dual-redundant wireless transmission module includes a photoelectric sampling module, an isolation interface, a communication link, and a main processor. The communication link includes a local communication link and a remote communication link. The photoelectric sampling module and the isolation interface form a meter reading channel to output the metering results to the local communication link. The main processor is used to receive the metering results and alarm signals and perform edge computing. The results of the edge computing are then reported to the cloud via the remote communication link.

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