Photovoltaic array battery monitoring system based on silicon carbide diode

Abstract

The invention discloses a photovoltaic array battery monitoring system based on a silicon carbide diode. The photovoltaic array battery monitoring system comprises a photovoltaic battery array, a Buck-Boost circuit, a power supply 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, 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, and the temperature sensor module comprises a temperature sensor arranged on each cell piece. The silicon carbide APD and temperature sensor module is used for detecting the real-time temperature of each battery piece, the power supply control chip module receives and processes signals collected by the silicon carbide APD and temperature sensor module, and adjusts the duty ratio of the Buck-Boost circuit according to the state of each battery piece so as to adjust the output power of the photovoltaic battery array to be at the maximum output power point.

Description

Technical Field

[0001] The present invention relates to a photovoltaic array battery monitoring system based on silicon carbide diodes, and in particular to a system for regulating and monitoring the output of a photovoltaic battery array based on the characteristics of silicon carbide diodes, and belongs to the field of power supply systems. Background Art

[0002] Silicon carbide (SiC) avalanche photodiode (APD) is a high-performance photodetector that combines the avalanche multiplication mechanism with the excellent properties of silicon carbide materials. When photons are incident on the APD, the generated electron-hole pairs undergo avalanche multiplication under a strong electric field, thereby amplifying the signal. Compared with traditional silicon-based APDs, SiC APDs have a wider bandgap and higher thermal stability, which can significantly improve detection sensitivity and signal-to-noise ratio, and are particularly suitable for optical signal detection under low light intensity. SiC materials can work stably at higher voltages and temperatures, and have lower dark current and higher gain, which is particularly important in aerospace, military and industrial detection. In addition, SiC APDs also have fast response time and low dark current, which makes them widely used in high-speed optical communications and photon counting. At present, SiC APDs also have broad application prospects in laser radar, optical communications, space exploration, nuclear physics and high-energy physics.

[0003] The photovoltaic power supply system consists of photovoltaic panels, circuit control chips and DC-DC circuits. The photovoltaic panels are the core devices for generating electric energy. Their output power and working efficiency determine the working efficiency of the entire power supply system. Photovoltaic panels are arrays formed by multiple groups of photovoltaic cells connected in series and parallel. The output power of photovoltaic panels is mainly determined by the surface light intensity. In theory, there is a single maximum power point. However, in actual situations, different cells in the photovoltaic cell array may be blocked by shadows or dust, resulting in different operating conditions during operation. The blocked cells will have a hot plate effect, reduce output power, and even become circuit loads, affecting the overall output efficiency. In severe cases, the cells will be damaged. In this case, the output curve of the entire photovoltaic cell array presents multiple peaks and there are multiple maximum power points. Therefore, it is necessary to detect the light intensity on the surface of the photovoltaic panel and calculate the power output curve of the photovoltaic cell array, which will help adjust the circuit voltage of the photovoltaic panel so that it can maintain operation at the maximum power point. At the same time, monitor its operating status to prevent abnormal phenomena from damaging the photovoltaic panel.

[0004] Based on this, the present invention designs a system for adjusting and monitoring the output of photovoltaic cell arrays based on the characteristics of silicon carbide diodes. Silicon carbide diodes are used to detect the illumination conditions of each cell on the photovoltaic cell array, and the output power model of the photovoltaic cell panel is brought into the overall power output curve under real-time working conditions, so as to adjust the circuit voltage in a targeted manner, increase the output power, and protect the circuit. Summary of the invention

[0005] The purpose of the present invention is to provide a photovoltaic array battery monitoring system based on silicon carbide diodes in view of the deficiencies in the prior art.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

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

[0008] Photovoltaic cell array, Buck-Boost circuit, power control chip module, silicon carbide APD module, temperature sensor module; the silicon carbide APD module includes a sliding device and a silicon carbide APD, the silicon carbide APD is driven by the sliding device to move on the photovoltaic cell array, and is used to scan and detect the ultraviolet radiation intensity on the surface of each cell in the photovoltaic cell array, the temperature sensor module includes a temperature sensor set on each cell, and is used 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 Buck-Boost circuit duty cycle according to the state of each cell to adjust the output power of the photovoltaic cell array to its maximum output power point.

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

[0010] Furthermore, the photovoltaic cell array is composed of a number of series-connected cell arrays connected in parallel, wherein a bypass diode is connected in parallel at both ends of each cell, and an anti-backflow diode is connected in series at both ends of each series-connected cell array.

[0011] Furthermore, in each detection period, the silicon carbide APD is controlled to move so as to scan each cell in turn, the ultraviolet radiation intensity on the surface of each cell is obtained and transmitted to the power chip control module, and 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 the bypass diode and the anti-backflow diode, the power control chip module calculates the output power curve under the working conditions of the detection period, adjusts the duty cycle of the Buck-Boost circuit, and makes the output voltage of the photovoltaic cell array be at the voltage 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 is blocked, the output power of the affected cell will be reduced. At this time, the bypass diode of the cell will be turned on, and the overall output curve will become multi-peak. At this time, a maintenance signal is sent through the communication module.

[0013] The present invention uses silicon carbide diodes to monitor photovoltaic array cells. Compared with the prior art, the present invention has at least the following beneficial effects:

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

[0015] 2) Sic APD has good environmental adaptability and can adapt to various usage scenarios in complex environments. It can still maintain good condition in high temperature, strong radiation and other environments.

[0016] 3) In the case where the photovoltaic panel is blocked or there is dust on the 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 falling into the local maximum power point and causing energy loss.

[0017] 4) The system of the present invention takes into account the influence of the bypass diode and series diode protection circuit on the output power in the photovoltaic cell array under real conditions, and obtains the overall output power curve by combining the above-mentioned influencing factors. The model fitting degree is high through experiments. Compared with the existing technology, the model accuracy of this system is better and the regulation is more precise.

[0018] 5) A sliding device is designed in the system of the present invention, and a single SiC APD can be used 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. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0020] Figure 2 It is a top view structural schematic diagram of a photovoltaic cell array combined with a SiC APD detector slide detection device and a temperature sensor.

[0021] Figure 3 It is a front view structural schematic diagram of the slide rail detection device.

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

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

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

[0025] Figure 7 It is a comparison chart of the measured data of the output voltage of the photovoltaic cell array under different light intensities and the model data in the present invention. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation regulations.

[0027] SiC APD is sensitive to high-energy (short-wavelength) photons, especially in the ultraviolet region (wavelengths between 100 and 400 nanometers). Due to the wide bandgap characteristics, the dark current of silicon carbide APD is low at room temperature, which reduces background noise and improves the signal-to-noise ratio of ultraviolet light detection. In addition, SiC APD can operate in high-temperature and high-radiation environments, and is suitable for ultraviolet light detection applications under harsh conditions. Photovoltaic panels are mostly deployed in areas with high light radiation intensity and harsh natural environment such as plateaus and deserts. Compared with other radiation intensity detection devices, SiC APD is more adaptable to local climate and environment. In solar radiation, ultraviolet light accounts for about 5% to 7% of the total radiation, of which the UVA band (320-400nm) accounts for about 95%. By detecting the ultraviolet radiation intensity of each cell on the photovoltaic panel, the distribution of solar radiation intensity of the photovoltaic panel can be deduced, which can be used to derive the overall power output curve. In addition, SiC APD has extremely high detection sensitivity, and uses the avalanche multiplication effect to amplify the small amount of electron-hole pairs generated by ultraviolet light, which can reach 10 -16 The detection sensitivity of 100 W can more accurately measure the changes in ultraviolet light. Compared with other radiation intensity detection devices, SiC APD can more accurately calculate the power output curve of photovoltaic panels.

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

[0029] Photovoltaic cell array: A device used to generate energy by converting light energy into electricity.

[0030] Buck-Boost circuit: connects the photovoltaic cell array and the bus of the entire power system, and is used to control the voltage across the photovoltaic cell 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: used to receive the detection result data of each sensor and judge the status of the photovoltaic cell array. According to the status of each cell, it adapts the most appropriate voltage value at both ends to adjust and protect the circuit. Silicon carbide APD module: includes a sliding device for installing SiC APD, which is used to detect the light radiation intensity at various locations on the surface of the photovoltaic cell array and transmit the detection 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 battery packs are energy storage modules: they are directly connected to the busbar of the power system and are used to store the electricity generated by the photovoltaic cell array.

[0034] Communication module: When an abnormal situation occurs in the photovoltaic cell array, such as a single cell is damaged or blocked, the power control chip module will control the activation of the communication module to transmit information to the receiver and notify the maintenance personnel.

[0035] A single SiC APD can detect the ultraviolet radiation intensity of a single photovoltaic cell and infer the light intensity of the cell. However, there are multiple groups of photovoltaic cells connected in series and parallel in the photovoltaic cell array. Due to the high price of SiC APD, it is not possible to set a separate detection module for each photovoltaic cell for cost considerations. For this reason, the sliding device is designed, which can use a detector to detect the ultraviolet intensity of each photovoltaic cell. In a specific embodiment of the present invention, Figure 2 and Figure 3As shown, a photovoltaic cell array consisting of 4 series and 4 parallel connections, totaling 16 photovoltaic cells, is provided. A set of Y-axis slide rails and a set of X-axis slide rails are installed on the array, and a driving unit is provided, wherein the X-axis slide rail is driven by the driving unit and can move along the Y-axis slide rail, and the SiC APD is installed on the X-axis slide rail and can be driven by the driving unit to move along the X-axis. The driving method of the driving unit is not limited, and can be implemented by any existing feasible method, for example, a stepper motor and a gear rack combination can be used, and the stepper motor drives the gear to move on the rack-type slide rail, wherein the stepper motor is connected to the power bus through a cable, and when the system is powered on, the SiC APD can be adjusted to be located at a specified position to detect the ultraviolet intensity. A slide rail shield and a cable sheath are also provided on the outside of the slide rail device to protect it from working normally in a harsh external environment.

[0036] When a test begins, the temperature sensor reads the current temperature of each cell and transmits it to the power control chip module. Since the temperature of the photovoltaic cell array changes little in a short period of time, the temperature value of the photovoltaic cell at the beginning of the test is regarded as a fixed value during a single test. At the same time, the system will start the slide rail device, which will drive the SiC APD detector to detect the ultraviolet intensity of each cell row and column by row along the "S" shape starting from the photovoltaic cell in the upper right corner, and transmit it to the power chip control module. When the number of cells in the photovoltaic cell array increases, it is only necessary to increase the length of the slide rail to cover the entire cell array without the need for additional SiC APD components, or to divide the entire cell array into regions, and set a slide device and a SiC APD in each region, so as to detect the surface ultraviolet intensity of each cell during the detection period and transmit it to the power chip control module.

[0037] The photovoltaic cell array is composed of multiple groups of photovoltaic cells connected in series and in parallel. In a specific embodiment of the present invention, a bypass diode is connected in parallel at both ends of each cell, and a protection diode is connected in series between every two columns of cells to prevent current backflow. Figure 4 shown.

[0038] The output power of a photovoltaic cell is mainly determined by the light intensity and surface temperature. The higher the light intensity, the higher the maximum power point voltage and the higher the maximum power point output power. The lower the surface temperature of the cell, the higher the maximum power point current and the higher the maximum power point output power. The electrical performance of a single photovoltaic cell can be determined by a photocurrent source I ph , parallel diode Diode, series resistor R s And the parallel resistor R sh Equivalently, the expressions of 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, T is the temperature, and I ph is the photocurrent, I0 is the reverse saturation current of the diode, n is the diode ideal factor, R sh is the equivalent parallel resistance value, R s is the equivalent series resistance value. The photocurrent value of the photovoltaic cell is affected by the light intensity and temperature, and the expression is:

[0041]

[0042] Among them I ph0 is the photocurrent under standard conditions, S0 is the standard light intensity, S is the actual light intensity, 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 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 is the bandgap width of the material at 25°C. The IV curve and PV curve of the cell corresponding to different light radiation intensity and temperature are as follows Figure 5 , 6 At the beginning of each detection, the temperature sensor will detect the temperature data of each battery cell at the same time and transmit it to the power chip control module. The SiC APD module will detect the light intensity of each battery cell one by one through the slide rail and transmit it to the power chip control module.

[0050] The light intensity and temperature of each cell in the photovoltaic cell array under actual working conditions are not consistent, which will lead to different output power curves of different cells. When the circuit current exceeds the short-circuit current of the photovoltaic cell with reduced power, the cell becomes a load and consumes the power generated by other cells. Therefore, a bypass diode needs to be connected in parallel at both ends of each cell so that the current output by other normally working cells can pass through the diode. At this time, the relationship between the voltage and current of the series photovoltaic cell array is:

[0051]

[0052] Where V1 is the voltage generated by the normally working battery cell, n d is the ideal factor of the bypass diode, I 0d is the reverse saturation current of the bypass diode, I ph1 is the photocurrent of the photovoltaic cell with reduced power.

[0053] When the working conditions of several parallel-connected serial photovoltaic arrays are inconsistent, the cutoff voltages of different serial arrays are different. When the circuit voltage is greater than the serial array with the lower cutoff voltage, the serial array will become the circuit load, and current backflow will occur. In order to prevent such a situation from happening, it is necessary to add series diodes at both ends of 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 is the corrected voltage, V i is the voltage of the ith photovoltaic cell, N is the number of photovoltaic cells in series, V ds is the series diode voltage drop, R loss is the circuit resistance value, and I is the current of a single photovoltaic cell. When the power control chip module calculates the output curve of the photovoltaic cell array, it is necessary to consider not only the influence of light intensity and surface temperature, but also the influence of the above diodes. In the photovoltaic cell array calculation model of the power chip control module, the above factors need to be comprehensively considered to obtain the final output curve.

[0056] like Figure 7 As shown, 1040W / m 2 and 910W / m 2 The test results and model calculation data are compared under two light intensities, where the curve is the model calculation result and the point is the test result, and the errors between the two are 2.76% and 2.94% respectively. The power chip control module in this device can well simulate the output of the photovoltaic cell array under real conditions.

[0057] After the system is turned on, the bus circuit will power the silicon carbide APD module, temperature sensor module and Buck-Boost circuit module. At this time, the silicon carbide APD detection module will scan the ultraviolet intensity of each cell in the photovoltaic cell array line by line and pass it to the power control chip module. The power control chip will calculate the light intensity at that point based on the ultraviolet intensity; the temperature sensor will read the temperature value of each cell and pass it to the power control chip module. There is a pre-set photovoltaic cell array model in the power control chip module, and the parameters include the power output curve parameters of a single photovoltaic cell provided by the manufacturer, the parameters of light intensity and temperature, the bypass diode parameters of the cell array, the series diode parameters and the line loss parameters of the protection circuit. Substitute the measured value into the model to obtain the overall output power curve of the photovoltaic cell array under the current situation.

[0058] The power control chip module selects the global maximum power point (MPP) according to 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 is output to the Buck-Boost circuit to make the voltage across the photovoltaic cell array equal to the maximum power point voltage, at which time the output power of the photovoltaic cell array can be maximized.

[0059] Since the sunlight intensity and ambient temperature will continue to change slowly in real situations, the power output curve of the photovoltaic array will continue to change, and the maximum power point voltage will also continue to change. When the light intensity changes, the SiC APD transmits the new measurement value to the power control chip module, which is used to recalculate the maximum power point voltage and adjust the voltage value so that it is always at the maximum power point. To this end, according to a specific embodiment of the present invention, the system restarts the silicon carbide APD module and temperature sensor every 30 seconds, re-detects the light intensity and temperature of each cell in the photovoltaic cell array, and repeats the previous calculation process to obtain a new maximum power point. In this way, the power output curve can be updated in time, thereby adjusting the circuit voltage and reducing energy loss.

[0060] In addition, the photovoltaic cell array may also experience sudden and drastic changes in the light intensity of some cells due to obstruction by clouds, dust, debris, etc., causing the power output curve to change rapidly in a short period of time, and even multiple peaks. For this reason, the power control system is designed with a power change threshold ΔP0. When the power change ΔP>ΔP0 within a period of time, it is considered that the power output curve changes rapidly. At this time, the silicon carbide APD module and temperature sensor are immediately restarted, and the previous calculation process is repeated to obtain a new maximum power point, and the voltage across the photovoltaic cell array is adjusted to the maximum power point voltage.

[0061] If the system detects that the surface of the photovoltaic cell array is blocked for a long time, or the surface temperature of some cells is abnormal, for example, the light intensity continues to be lower than the preset light threshold for a certain period of time, or the temperature continues to exceed 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 for maintenance.

[0062] This system can adjust the photovoltaic cell array in various complex environments to maximize the utilization efficiency of the cells. It can sensitively capture changes in light and ambient temperature and dynamically adjust the output voltage. When encountering special situations such as shading, it can avoid falling into the local maximum power point. When encountering extreme special situations, it can also notify maintenance personnel to extend the life of photovoltaic cells.

[0063] The above-described embodiments are only some of the preferred solutions of the present invention, but they are not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A photovoltaic array battery monitoring system based on silicon carbide diodes, characterized in that: include: Photovoltaic cell array, Buck-Boost circuit, power control chip module, silicon carbide APD module, temperature sensor module; The silicon carbide APD module includes a sliding device and a silicon carbide APD. The silicon carbide APD is driven by the sliding device to move on the photovoltaic cell array, and is used to scan and detect the ultraviolet radiation intensity on the surface of each cell in the photovoltaic cell array. The temperature sensor module includes a temperature sensor set on each cell, which is used 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 Buck-Boost circuit duty cycle according to the state of each cell to adjust the output power of the photovoltaic cell array to its maximum output power point.

2. The photovoltaic array battery monitoring system based on silicon carbide diode according to claim 1 is characterized in that: The sliding device includes two sets of mutually perpendicular slide rails and a driving unit, wherein 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 installed 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 battery monitoring system based on silicon carbide diode according to claim 1 is characterized in that: The photovoltaic cell array is composed of a plurality of series-connected cell arrays connected in parallel, wherein a bypass diode is connected in parallel at both ends of each cell, and an anti-backflow diode is connected in series at both ends of each series-connected cell array.

4. The photovoltaic array battery monitoring system based on silicon carbide diode according to claim 3 is characterized in that: In each detection period, the silicon carbide APD is controlled to move so as to scan each cell in turn, the ultraviolet radiation intensity on the surface of each cell is obtained and transmitted to the power chip control module, and 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 the bypass diode and the anti-backflow diode, the power control chip module calculates the output power curve under the working conditions of the detection period, adjusts the duty cycle of the Buck-Boost circuit, and makes the output voltage of the photovoltaic cell array be at the voltage at the maximum power point.

5. The photovoltaic array battery monitoring system based on silicon carbide diode 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 blocked, the output power of the affected cell will be reduced. At this time, the bypass diode of the cell will be turned on, and the overall output curve will become multi-peaked. At this time, a maintenance signal is sent through the communication module.

Images