A photovoltaic array cell monitoring system based on silicon carbide diodes

Abstract

The application discloses a photovoltaic array cell monitoring system based on silicon carbide diode, which comprises a photovoltaic cell array, a Buck-Boost circuit, a power control chip module, a silicon carbide APD module and a temperature sensor module. The silicon carbide APD module comprises a sliding device and a silicon carbide APD, and the silicon carbide APD is driven by the sliding device to move on the photovoltaic cell array, and is used for scanning and detecting the ultraviolet radiation intensity of the surface of each cell piece in the photovoltaic cell array. The temperature sensor module comprises a temperature sensor arranged on each cell piece and is used for detecting the real-time temperature of each cell piece. The power control chip module receives and processes the signals collected by the silicon carbide APD and the temperature sensor module, adjusts the duty cycle of the Buck-Boost circuit according to the state of each cell piece, and adjusts the output power of the photovoltaic cell array at the maximum output power point.

Description

Technical Field

[0001] This invention relates to a photovoltaic array cell monitoring system based on silicon carbide diodes, and more particularly to a system for regulating and monitoring the output of a photovoltaic cell array based on the characteristics of silicon carbide diodes, belonging to the field of power supply systems. Background Technology

[0002] Silicon carbide (SiC) avalanche photodiodes (APDs) are high-performance photodetectors that combine the avalanche multiplication mechanism with the superior properties of silicon carbide. When photons are incident on an APD, the resulting electron-hole pairs undergo avalanche multiplication under a strong electric field, thus amplifying the signal. Compared to traditional silicon-based APDs, SiC APDs have a wider bandgap and higher thermal stability, significantly improving detection sensitivity and signal-to-noise ratio, making them particularly suitable for detecting optical signals under low light intensity. SiC materials can operate stably at higher voltages and temperatures, exhibiting lower dark current and higher gain, which is especially important in aerospace, military, and industrial inspection fields. Furthermore, SiC APDs also possess fast response times and low dark current, making them widely applicable in high-speed optical communication and photon counting. Currently, SiC APDs also show broad application prospects in lidar, optical communication, space exploration, nuclear physics, and high-energy physics.

[0003] A photovoltaic (PV) power system consists of PV panels, circuit control chips, and DC-DC circuits. The PV panel is the core device for generating electricity, and its output power and efficiency determine the overall efficiency of the power system. A PV panel is an array of multiple PV cells connected in series and parallel. The output power of a PV panel is primarily determined by the surface irradiance, theoretically possessing a single maximum power point. However, in reality, different cells in a PV array may be shaded or covered by dust, leading to varying operating conditions. Shaded cells may experience a hot plate effect, reducing output power and even becoming a circuit load, affecting overall output efficiency and potentially damaging the cell. In such cases, the output curve of the entire PV array exhibits multiple peaks and multiple maximum power points. Therefore, it is necessary to detect the irradiance on the PV panel surface and calculate the power output curve of the PV array. This helps adjust the circuit voltage of the PV panel to maintain operation at the maximum power point. Simultaneously, monitoring its operating status prevents abnormal phenomena from damaging the PV panel.

[0004] Based on this, the present invention designs a system for adjusting and monitoring the output of a photovoltaic cell array based on the characteristics of silicon carbide diodes. The system utilizes silicon carbide diodes to detect the illumination received by each cell in the photovoltaic array, inputs the data into a photovoltaic panel output power model to obtain the overall power output curve under real-time operating conditions, and then adjusts the circuit voltage accordingly to improve output power and protect the circuit. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a photovoltaic array cell monitoring system based on silicon carbide diodes.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A photovoltaic array cell monitoring system based on silicon carbide diodes, comprising:

[0008] The system comprises a photovoltaic cell array, a Buck-Boost circuit, a power control chip module, a silicon carbide APD module, and a temperature sensor module. The silicon carbide APD module includes a sliding device and a silicon carbide APD, which is moved on the photovoltaic cell array by the sliding device to scan and detect the ultraviolet radiation intensity on the surface of each cell. The temperature sensor module includes a temperature sensor installed on each cell to detect the real-time temperature of each cell. The power control chip module receives and processes the signals collected by the silicon carbide APD and the temperature sensor module, and adjusts the duty cycle of the Buck-Boost circuit according to the state of each cell to regulate the output power of the photovoltaic cell array to its maximum output power point.

[0009] In the above technical solution, the sliding device further includes two sets of mutually perpendicular slide rails and a driving part, wherein the second slide rail is fixed, the first slide rail can be driven by the driving part to move along the second slide rail, the silicon carbide APD is installed on the first slide rail and can be driven by the driving part to move along the first slide rail, and the silicon carbide APD is always located above the photovoltaic cell array during the movement.

[0010] Furthermore, the photovoltaic cell array is composed of several series-connected cell arrays connected in parallel, wherein each cell has a bypass diode connected in parallel across its two ends, and an anti-backflow diode is connected in series across each series-connected cell array.

[0011] Furthermore, during each detection period, the silicon carbide APD is moved to sequentially scan each solar cell, acquiring the ultraviolet radiation intensity on the surface of each cell and transmitting it to the power chip control module. Each temperature sensor detects the temperature of each solar cell and transmits it to the power chip control module. The power chip control module converts the ultraviolet radiation intensity on the surface of each solar cell into light radiation intensity. Based on the light radiation intensity and temperature information of each solar cell, and considering the influence of bypass diodes and anti-backflow diodes, the power control chip module calculates the output power curve under the operating conditions of that detection period, adjusts the duty cycle of the Buck-Boost circuit, and makes the output voltage of the photovoltaic array located at the maximum power point.

[0012] Furthermore, the system also includes a communication module. When the power control chip module detects an abnormal temperature point on the surface of the photovoltaic cell array or a single cell being shaded, the output power of the affected cell will decrease. At this time, the bypass diode of the affected cell will be turned on, and the overall output curve will show multiple peaks. At this time, a maintenance signal is sent through the communication module.

[0013] This invention utilizes silicon carbide diodes to monitor photovoltaic array cells. Compared to existing technologies, this invention offers at least the following advantages:

[0014] 1) The Sic APD is sensitive to light intensity detection, which can more accurately calculate the radiation intensity distribution and output power curve on the surface of the photovoltaic panel, and more precisely control the output power to be at the maximum power point.

[0015] 2) The Sic APD has good environmental adaptability and can adapt to various complex environments. It can still maintain good performance in environments with high temperature and strong radiation.

[0016] 3) In cases where photovoltaic panels are obstructed or have dust on their surface, the Sic APD can calculate a multi-peak power output curve and adjust the circuit voltage to the global maximum power point to avoid getting stuck in a local maximum power point and causing energy loss.

[0017] 4) This invention takes into account the impact of bypass diodes and series diode protection circuits in the photovoltaic array on the output power under real-world conditions. It comprehensively considers these influencing factors to obtain the overall output power curve, and experiments demonstrate that the model has a high degree of fit. Compared to existing technologies, this system has better model accuracy and more precise control.

[0018] 5) The system of this invention is designed with a sliding device, which can use a single SiC APD to detect the ultraviolet intensity of each cell in a large area of ​​the photovoltaic cell array, taking into account both low cost and high efficiency. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall system architecture of the present invention.

[0020] Figure 2 This is a top view schematic diagram of the photovoltaic cell array combined with the SiC APD detector sliding rail detection device and temperature sensor.

[0021] Figure 3 This is a front view schematic diagram of the sliding rail detection device.

[0022] Figure 4 This is a schematic diagram of a photovoltaic cell array combined with bypass diodes and series diodes.

[0023] Figure 5 This is a comparison chart of the IV and PV curves of a single photovoltaic cell at different temperatures.

[0024] Figure 6 This is a comparison chart of the IV and PV curves of a single photovoltaic cell under different light intensities.

[0025] Figure 7 This is a comparison chart of the measured output voltage data of the photovoltaic cell array under different light intensities and the model data in this invention. Detailed Implementation

[0026] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation regulations.

[0027] SiC APDs are sensitive to high-energy (short-wavelength) photons, especially in the ultraviolet (UV) region (wavelengths between 100 and 400 nm). Due to their wide bandgap characteristics, SiC APDs exhibit low dark current at room temperature, reducing background noise and thus improving the signal-to-noise ratio for UV detection. Furthermore, SiC APDs can operate in high-temperature and high-radiation environments, making them suitable for UV detection applications under harsh conditions. Photovoltaic panels are often deployed in high-altitude, desert, and other areas with high solar radiation intensity and harsh natural environments. Compared to other radiation intensity detection devices, SiC APDs are better adapted to local climates and environments. In solar radiation, UV light accounts for approximately 5%–7% of the total radiation, with the UVA band (320-400 nm) accounting for about 95%. By detecting the UV radiation intensity of each cell on a photovoltaic panel, the solar radiation intensity distribution of the photovoltaic panel can be derived, which can then be used to derive the overall power output curve. In addition, SiC APDs have extremely high detection sensitivity, utilizing the avalanche multiplication effect to amplify the small number of electron-hole pairs generated by UV light, reaching 10-10. -16 The high detection sensitivity of W allows for more accurate measurement of changes in ultraviolet light. Compared to other radiation intensity detection devices, the SiC APD can more precisely calculate the power output curve of a photovoltaic panel.

[0028] According to a specific embodiment of the present invention, a photovoltaic array cell monitoring system based on silicon carbide diodes simultaneously achieves low cost and high efficiency, and can quickly adjust to complex situations. The overall system architecture is as follows: Figure 1 As shown, the system includes the following modules:

[0029] Photovoltaic cell array: A device used to convert light energy into electrical energy to generate energy.

[0030] Buck-Boost circuit: The bus connecting the photovoltaic array and the entire power system is used to control the voltage across the photovoltaic array according to the instructions of the power control chip module, and adjust the output power to its maximum output power point.

[0031] Power control chip module: Receives data from various sensors to determine the state of the photovoltaic array. It adjusts the voltage across each cell to the optimal value, regulating and protecting the circuitry. Silicon carbide APD module: Includes a sliding device for mounting the SiC APD, used to detect the light radiation intensity at various points on the photovoltaic array surface and transmit the results to the power control chip module.

[0032] Temperature sensor module: The temperature sensor should be placed on the surface of the photovoltaic cell array to measure the surface temperature of each cell and transmit the measurement data to the power control chip module.

[0033] Lithium-ion battery packs, also known as energy storage modules, are directly connected to the bus of the power system and are used to store the electrical energy generated by the photovoltaic cell array.

[0034] Communication module: When the photovoltaic array malfunctions, such as a single cell being damaged or blocked, the power control chip module will activate the communication module to transmit information to the receiver and notify maintenance personnel.

[0035] A single SiC APD can detect the ultraviolet radiation intensity of a single photovoltaic cell and infer the light intensity of that cell. However, photovoltaic arrays contain multiple sets of photovoltaic cells connected in series and parallel. Due to the high cost of SiC APDs, it is not feasible to set up a separate detection module for each photovoltaic cell for cost reasons. Therefore, the aforementioned sliding device was designed, which can use a single detector to detect the ultraviolet intensity of each photovoltaic cell. In a specific embodiment of the present invention, as shown... Figure 2 and Figure 3As shown, a photovoltaic array consisting of 16 photovoltaic cells arranged in a series and parallel configuration (4 cells in series and 4 cells in parallel) is presented. A set of Y-axis slide rails and a set of X-axis slide rails are mounted on the array, along with a drive unit. The X-axis slide rails are driven by the drive unit and can move along the Y-axis. The SiC APD is mounted on the X-axis slide rails and can be driven by the drive unit to move along the X-axis. The driving method of the drive unit is not limited and can be implemented using any existing feasible method. For example, a stepper motor and a rack and pinion combination can be used, with the stepper motor driving the gear to move on the rack and pinion slide rails. The stepper motor is connected to the power bus via a cable. When the system is powered on, the SiC APD can be adjusted to a designated position to detect ultraviolet intensity. The slide rail assembly is also equipped with a slide rail cover and a cable sheath to protect it and ensure normal operation even in harsh external environments.

[0036] At the start of a test, the temperature sensor reads the current temperature of each solar cell and transmits it to the power control chip module. Since the temperature change of the photovoltaic array is small in a short period, the temperature value of the solar cells at the start of the test is considered a constant for the entire test period. Simultaneously, the system activates a sliding rail device, which drives the SiC APD detector to detect the ultraviolet intensity of each solar cell row by row and column by column, starting from the solar cell in the upper right corner, and transmits the data to the power control chip module. When the number of solar cells in the array increases, simply increasing the length of the sliding rail is sufficient to cover the entire array without the need for additional SiC APD components. Alternatively, the entire array can be divided into regions, with one sliding rail and one SiC APD installed in each region, to detect the surface ultraviolet intensity of each solar cell during the test period and transmit the data to the power control chip module.

[0037] A photovoltaic array consists of multiple sets of photovoltaic cells connected in series and parallel. In one specific embodiment of the invention, a bypass diode is connected in parallel across both ends of each cell, and a protection diode is connected in series between every two rows of cells to prevent current backflow. A schematic diagram of a photovoltaic array is shown below. Figure 4 As shown.

[0038] The output power of a photovoltaic cell is mainly determined by light intensity and surface temperature. Higher light intensity results in a higher maximum power point voltage (MPPT) and thus a higher MPPT output power; conversely, lower surface temperature leads to a higher MPPT current and thus a higher MPPT output power. The electrical performance of a single photovoltaic cell can be determined by a single photocurrent source I. ph Parallel diode, series resistor R s and parallel resistor R sh Equivalently, the expressions for its output current and voltage are:

[0039]

[0040] Where I is the circuit current, V is the circuit voltage, q is the charge constant, k is the Boltzmann constant, and T is the temperature. ph I0 is the photocurrent, I0 is the diode reverse saturation current, n is the diode ideality factor, and R0 is the diode reverse saturation current. sh R is the equivalent parallel resistance value. s This represents the equivalent series resistance. The photocurrent of a photovoltaic cell is affected by light intensity and temperature, and is expressed as:

[0041]

[0042] Among them I ph0 S is the photocurrent under standard conditions, S0 is the standard illuminance, S is the actual illuminance, a is the temperature-current coefficient, T0 is the standard temperature, and T is the actual temperature.

[0043] The parallel resistance is inversely proportional to the light intensity:

[0044]

[0045] R sh0 This is the parallel resistance value under standard illumination;

[0046] The reverse diode current value is mainly affected by temperature:

[0047]

[0048] Eg = E g0 (1-0.0002677(T-T0))

[0049] Where Eg is the actual bandgap width, E g0 The bandgap of the material is shown at 25°C. The IV and PV curves of the solar cell for different light radiation intensities and temperatures are as follows: Figure 5 , 6 As shown. At the start of each detection segment, the temperature sensor simultaneously detects the temperature data of each solar cell and transmits it to the power chip control module. The SiC APD module detects the light intensity of each solar cell one by one via a slide rail and transmits it to the power chip control module.

[0050] In real-world photovoltaic (PV) arrays, the light intensity and temperature of each cell are not uniform, leading to different output power curves for different cells. When the circuit current exceeds the short-circuit current of the PV cell with reduced power, that cell becomes a load, consuming the energy generated by the other cells. Therefore, a bypass diode needs to be connected in parallel across each cell to allow the current from the other normally functioning cells to pass through the diode. At this point, the voltage-current relationship of this series-connected PV array is:

[0051]

[0052] Where V1 is the voltage generated by the normally operating battery cell, n d For bypass diode management, I 0d I is the reverse saturation current of the bypass diode. ph1 The photocurrent of a photovoltaic cell with reduced power output.

[0053] When several parallel-connected series photovoltaic arrays operate under inconsistent conditions, the cutoff voltages of different series arrays differ. When the circuit voltage exceeds that of the series array with the lower cutoff voltage, that series array becomes a circuit load, resulting in current backflow. To prevent this, a series diode needs to be added across the series-connected solar cells as a protection circuit to prevent current backflow. The formula after adding the series diode is as follows:

[0054]

[0055] Where V mod For the corrected voltage, V i V is the voltage of the i-th photovoltaic cell, N is the number of photovoltaic cells connected in series, and V is the voltage of the ith photovoltaic cell. ds For the voltage drop of the series diode, R loss Let I be the circuit resistance value, and I be the current of a single photovoltaic cell. When calculating the output curve of the photovoltaic array in the power control chip module, it is necessary to consider not only the effects of light intensity and surface temperature, but also the effects of the aforementioned diodes. In the photovoltaic array calculation model of the power chip control module, all of the above influencing factors must be comprehensively considered to obtain the final output curve.

[0056] like Figure 7 As shown, 1040W / m was tested respectively. 2 and 910W / m 2 The test results and model calculation data under two light intensities are compared. The curves represent the model calculation results, and the points represent the test results. The errors between the two are 2.76% and 2.94%, respectively. The power chip control module in this device can accurately simulate the output of the photovoltaic array under real-world conditions.

[0057] After the system is powered on, the bus circuit supplies power to the silicon carbide APD module, temperature sensor module, and Buck-Boost circuit module. At this time, the silicon carbide APD detection module scans the UV intensity of each cell in the photovoltaic array row by row and transmits this data to the power control chip module. The power control chip module then calculates the light intensity at that point based on the UV intensity. The temperature sensor reads the temperature value of each cell and transmits it to the power control chip module. The power control chip module contains a pre-set photovoltaic array model, whose parameters include the power output curve parameters of a single photovoltaic cell provided by the manufacturer, parameters related to light intensity and temperature effects, parameters of the array bypass diodes, parameters of the series diodes, and parameters of the protection circuit line loss. Substituting the measured values ​​into the model yields the overall output power curve of the photovoltaic array under the current conditions.

[0058] The power control chip module selects the global maximum power point (MPP) based on the overall output power curve, and obtains the voltage V at the maximum power point. mpp and its corresponding Buck-Boost circuit duty cycle D mpp D mpp The signal output to the Buck-Boost circuit makes the voltage across the photovoltaic array equal to the maximum power point voltage, which maximizes the output power of the photovoltaic array.

[0059] Because solar irradiance and ambient temperature change slowly and continuously under real-world conditions, the power output curve of the photovoltaic array continuously changes, as does the maximum power point voltage. When irradiance changes, the SiC APD transmits new measurements to the power control chip module to recalculate the maximum power point voltage and adjust the voltage value to always remain at the maximum power point. Therefore, according to a specific embodiment of the present invention, the system restarts the silicon carbide APD module and temperature sensor every 30 seconds to re-detect the irradiance and temperature of each cell in the photovoltaic array, repeating the previous calculation process to obtain a new maximum power point. This allows for timely updates to the power output curve, thereby correcting the circuit voltage and reducing energy loss.

[0060] Furthermore, photovoltaic arrays can experience sudden and significant changes in sunlight intensity for some cells due to shading from clouds, dust, or debris. This can lead to rapid changes in the power output curve within a short period, sometimes even resulting in multiple peaks. To address this, the power control system is designed with a power change threshold ΔP0. When the power change ΔP > ΔP0 within a given time period, it is considered a rapid change in the power output curve. In this case, the silicon carbide APD module and temperature sensor are immediately restarted, the previous calculation process is repeated to obtain a new maximum power point, and the voltage across the photovoltaic array is adjusted to the maximum power point voltage.

[0061] If the system detects that the surface of the photovoltaic array is blocked for a long time, or that the surface temperature of some cells is abnormal, such as when the light intensity is continuously lower than the preset light threshold for a certain period of time, or when the temperature continuously exceeds the temperature threshold for a certain period of time, the system will determine that an abnormal situation has occurred and send an early warning signal to the communication module to notify maintenance personnel to come and maintain.

[0062] This system can adjust the photovoltaic array under various complex environments to maximize cell utilization efficiency. It can sensitively detect changes in sunlight and ambient temperature, dynamically adjusting the output voltage. In special circumstances such as shading, it can avoid falling into local maximum power points. In extreme situations, it can also notify maintenance personnel, extending the lifespan of the photovoltaic cells.

[0063] The embodiments described above are merely some preferred embodiments of the present invention, and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A photovoltaic array cell monitoring system based on silicon carbide diodes, characterized in that, include: The system comprises a photovoltaic cell array, a Buck-Boost circuit, a power control chip module, a silicon carbide APD module, and a temperature sensor module. The photovoltaic cell array consists of several series-connected arrays of cells connected in parallel. Each cell has a bypass diode connected in parallel across its ends, and anti-backflow diodes are connected in series across each series-connected cell array. The silicon carbide APD module includes a sliding device and a silicon carbide APD. The silicon carbide APD is moved across the photovoltaic cell array by the sliding device to scan and detect the ultraviolet radiation intensity on the surface of each cell. The temperature sensor module includes a temperature sensor installed on each cell to detect the real-time temperature of each cell. The power control chip module receives and processes the signals collected by the silicon carbide APD and the temperature sensor module, converting the ultraviolet radiation intensity on the surface of each cell into light radiation intensity. Based on the light radiation intensity and temperature information of each cell, and considering the influence of the bypass diodes and anti-backflow diodes, the power control chip module calculates the overall output power curve under the operating conditions during the detection period. Based on this overall output power curve, the maximum output power point is determined, and the Buck-Boost circuit is adjusted according to the state of each cell. The circuit duty cycle is used to adjust the output power of the photovoltaic array at its maximum output power point.

2. The photovoltaic array cell monitoring system based on silicon carbide diodes according to claim 1, characterized in that, The sliding device includes two sets of mutually perpendicular slide rails and a driving unit. The second slide rail is fixed, and the first slide rail can be driven by the driving unit to move along the second slide rail. The silicon carbide APD is mounted on the first slide rail and can be driven by the driving unit to move along the first slide rail. During the movement, the silicon carbide APD is always located above the photovoltaic cell array.

3. The photovoltaic array cell monitoring system based on silicon carbide diodes according to claim 1, characterized in that, During each detection period, the silicon carbide APD is moved to scan each solar cell sequentially, acquiring the ultraviolet radiation intensity on the surface of each cell and transmitting it to the power chip control module. Each temperature sensor detects the temperature of each cell and transmits it to the power chip control module. The power chip control module converts the ultraviolet radiation intensity on the surface of each cell into light radiation intensity. Based on the light radiation intensity and temperature information of each cell, and considering the influence of bypass diodes and anti-backflow diodes, the power control chip module calculates the output power curve under the operating conditions of that detection period and adjusts the duty cycle of the Buck-Boost circuit so that the output voltage of the photovoltaic array is located at the maximum power point.

4. The photovoltaic array cell monitoring system based on silicon carbide diodes according to claim 1, characterized in that, The system also includes a communication module. When the power control chip module detects an abnormal temperature point on the surface of the photovoltaic cell array or a single cell is shaded, the output power of the affected cell will decrease. At this time, the bypass diode of the cell will be turned on, and the overall output curve will have multiple peaks. At this time, a maintenance signal is sent through the communication module.

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