Solar system
The solar system uses differential conductance analysis to enhance dirt detection accuracy and power management by comparing current values on an IV curve, addressing inaccuracies from external factors.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- TOYOTA JIDOSHA KK
- Filing Date
- 2024-12-05
- Publication Date
- 2026-06-17
Smart Images
Figure 2026098305000001_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to a solar system.
Background Art
[0002] Patent Document 1 discloses a solar system that determines whether a first step voltage generated during a stop and a second step voltage generated during travel match on an I-V curve showing the correlation between the current value and voltage value output from a solar panel. If the first step voltage and the second step voltage match, it is assumed that there is an object moving at the same speed as the vehicle, and thus it is assumed that dirt or the like is attached to the solar panel.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] The solar system of Patent Document 1 compares the voltage during a stop with the voltage during travel. Therefore, when external factors such as solar radiation intensity and the temperature of the solar panel change between a stop and travel, the accuracy of determining whether dirt or the like is attached to the solar panel may decrease. Therefore, a technique that can more accurately determine the state of the solar panel is desired.
Means for Solving the Problems
[0005] This disclosure can be realized in the following forms.
[0006] (1) According to one embodiment of the present disclosure, a solar system that can be mounted on a vehicle is provided. The solar system comprises a solar panel, a current sensor for measuring the current value output from the solar panel, a voltage sensor for measuring the voltage value output from the solar panel, and a control unit for determining the state of the solar panel based on the difference between a first current value and a second current value, wherein the first current value is the current value corresponding to a first voltage value which is the voltage value when the differential conductance changes from a value greater than or equal to a predetermined first threshold to a value less than the first threshold on an IV curve showing the correlation between the current value and the voltage value over a predetermined period, and the second current value is the current value corresponding to a second voltage value which is the voltage value when the differential conductance changes from a value less than the first threshold to a value greater than or equal to the first threshold on the IV curve. This type of solar system allows for a more accurate determination of the condition of the solar panels. (2) In the solar system of the above form, the control unit may determine whether or not dirt is attached to the solar panel based on the difference between the first current value and the second current value. This type of solar system allows for a more accurate determination of whether or not dirt is adhering to the solar panels. (3) In the solar system of the above form, the control unit may estimate the area of dirt attached to the solar panel based on the difference between the first current value and the second current value. This type of solar system allows for the estimation of the area of dirt adhering to the solar panels. This type of solar system allows for the precise estimation of the state of the solar panels. (4) In the solar system of the above form, the control unit may control a notification unit mounted on the vehicle to notify the occupant of the vehicle of the area of dirt adhering to the solar panel. With this type of solar system, vehicle occupants can see the area of dirt accumulated on the solar panels. (5) The control unit controls the power output from the solar panel by MPPT (Maximum Operating Point Tracking) control, and the IV curve may be obtained during the process of executing the MPPT control. This type of solar system allows for more efficient determination of the solar panel state compared to cases where the solar panel state determination and MPPT control are performed separately. [Brief explanation of the drawing]
[0007] [Figure 1] An explanatory diagram showing the configuration of a solar power system. [Figure 2] This figure shows an example of an IV curve when a solar panel is generating power normally. [Figure 3] This figure shows an example of an IV curve when the power generation of some solar cells has decreased. [Figure 4] A flowchart of the estimation process performed by the control unit. [Figure 5] This figure shows examples of IV curves and di / dv-V curves obtained during the estimation process. [Figure 6] This diagram illustrates the relationship between the difference between the first and second current values and the area of dirt adhering to the solar panel. [Modes for carrying out the invention]
[0008] A. First Embodiment: Figure 1 is an explanatory diagram showing the configuration of the solar system 100. The solar system 100 can be mounted on a vehicle 500 that can move at speed. The solar system 100 comprises a solar panel 10, a current sensor 20, a voltage sensor 30, a DC-DC converter 40, and a control unit 50.
[0009] The solar panel 10 consists of multiple clusters 11 and multiple bypass diodes 16 connected in parallel to each cluster 11. Each cluster 11 consists of multiple solar cells 12 connected in series. All solar cells 12 constituting the solar panel 10 are connected in series. In this embodiment, the solar panel 10 includes three clusters 11 and three bypass diodes 16. One cluster 11 consists of 10 solar cells 12 connected in series. Note that the number of clusters 11 and bypass diodes 16 in the solar panel 10 is not limited to three. Also, the number of solar cells 12 constituting one cluster 11 is not limited to 10.
[0010] If dirt adheres to a solar cell 12, it will be shaded, reducing the power generation of that solar cell 12. Since all solar cells 12 are connected in series, a decrease in the power generation of some solar cells 12 will reduce the power generation of the entire solar panel 10. Because the solar cell 12 with reduced power generation acts as a resistor, current flows not through the cluster 11 containing the solar cell 12 with reduced power generation, but through the bypass diode 16 connected in parallel to the cluster 11 in question. In this way, by providing the bypass diode 16, the cluster 11 containing the solar cell 12 with reduced power generation can be electrically isolated. This prevents a decrease in the overall power generation of the solar panel 10, and also prevents the dirty solar cell 12 from overheating and becoming a hot spot.
[0011] The current sensor 20 measures the current value output from the solar panel 10. The voltage sensor 30 measures the voltage value output from the solar panel 10.
[0012] The DC-DC converter 40 converts the voltage supplied from the solar panel 10 to a desired voltage and supplies it to the destination 200. The destination 200 is, for example, a battery mounted on the vehicle 500 for storing the power generated by the solar panel 10. The DC-DC converter 40 controls the output voltage of the solar panel 10 in accordance with the signal transmitted from the control unit 50.
[0013] The control unit 50 is composed of a computer equipped with a processor and memory. The control unit 50 controls the operation of the solar system 100 by having the processor execute a program pre-stored in memory. Some or all of the functions of the control unit 50 may be implemented by hardware circuits. The control unit 50 acquires the current value measured by the current sensor 20 and the voltage value measured by the voltage sensor 30, and transmits a drive command to the DC-DC converter 40. The control unit 50 controls the power output from the solar panel 10 by MPPT (Maximum Power Point Tracking) control. This makes it possible to maximize the power output from the solar panel 10.
[0014] Figure 2 shows an example of an IV curve showing the correlation between current and voltage values when the solar panel 10 is generating power normally. Figure 3 shows an example of an IV curve when the power generation of some solar cells 12 has decreased. In Figures 2 and 3, the horizontal axis shows the voltage value measured by the voltage sensor 30, and the vertical axis shows the current value measured by the current sensor 20. As shown in Figures 2 and 3, when the power generation of some solar cells 12 decreases, the current value decreases, and a step occurs in the IV curve. In this embodiment, the solar system 100 uses the step that occurs in the IV curve to estimate the area of dirt attached to the solar panel 10.
[0015] FIG. 4 is a flowchart of the estimation process executed by the control unit 50. By executing the estimation process, the control unit 50 estimates the area of the dirt adhering to the solar panel 10. In the present embodiment, the estimation process includes MPPT control. That is, in the present embodiment, the control unit 50 executes MPPT control by executing the estimation process. The time taken from the start to the completion of the execution of the estimation process is preferably within 1 second. More preferably, the time taken from the start to the completion of the execution of the estimation process is within 0.3 seconds. The estimation process is repeatedly executed at a predetermined cycle. The estimation process is preferably repeatedly executed at a cycle of once per minute. In the estimation process, the control unit 50 changes the voltage output from the solar panel 10 within a predetermined range and acquires the current value corresponding to each voltage value from the current sensor 20. FIG. 5 shows an example of an I-V curve indicating the correlation between the voltage value and the current value within a predetermined period acquired in the estimation process, and a di / dv-V curve indicating the correlation between the differential conductance and the voltage value, which will be described later. Here, the predetermined period means the period during which the estimation process is executed once. That is, the predetermined period is preferably within 1 second, and more preferably within 0.3 seconds.
[0016] In step S10, the control unit 50 acquires the voltage value and the current value output from the solar panel 10. The voltage value acquired in step S10 is the set value set by the control unit 50. The current value acquired in step S10 is the value measured by the current sensor 20 when the output voltage of the solar panel 10 is the above set value. The control unit 50 controls the voltage value output from the solar panel 10 to be the above set value by transmitting a drive command to the DC-DC converter 40. The acquired voltage value and current value are stored in the memory.
[0017] In step S20, the control unit 50 calculates the differential conductance di / dv. The differential conductance is the value obtained by differentiating the voltage value acquired in step S10 with the current value acquired in step S10. The value of the differential conductance is stored in the memory.
[0018] In step S30, the control unit 50 determines whether the differential conductance has changed from a value equal to or greater than a predetermined first threshold Th1 to a value smaller than the first threshold Th1. Specifically, the control unit 50 determines whether the differential conductance calculated in step S20 in the previous cycle is a value equal to or greater than the first threshold Th1 and whether the differential conductance calculated in step S20 in the current cycle is a value smaller than the first threshold Th1. The first threshold Th1 is stored in the memory in advance. When the differential conductance changes from a value equal to or greater than the first threshold to a value smaller than the first threshold Th1, step S40 is executed. When the differential conductance has not changed from a value equal to or greater than the predetermined first threshold to a value smaller than the first threshold Th1, step S50 is executed.
[0019] In step S40, the control unit 50 stores the current value acquired in step S10 in the memory as the first current value I1. Hereinafter, the voltage value when the differential conductance changes from a value equal to or greater than the first threshold to a value smaller than the first threshold Th1 is referred to as the first voltage value V1. That is, the first current value I1 is the current value corresponding to the first voltage value V1 on the I-V curve showing the correlation between the current value and the voltage value within a predetermined period.
[0020] In step S50, the control unit 50 determines whether the differential conductance has changed from a value smaller than the first threshold Th1 to a value equal to or greater than the first threshold. Specifically, the control unit 50 determines whether the differential conductance calculated in step S20 in the previous cycle is a value smaller than the first threshold Th1 and whether the differential conductance calculated in step S20 in the current cycle is a value equal to or greater than the first threshold. When the differential conductance changes from a value smaller than the first threshold Th1 to a value equal to or greater than the first threshold, step S60 is executed. When the differential conductance has not changed from a value smaller than the predetermined first threshold Th1 to a value equal to or greater than the first threshold, step S100 is executed.
[0021] In step S60, the control unit 50 stores the current value acquired in step S10 as the second current value I2 in memory. Hereinafter, the voltage value when the differential conductance changes from a value smaller than the first threshold Th1 to a value greater than or equal to the first threshold will be referred to as the second voltage value V2. That is, the second current value I2 is the current value corresponding to the second voltage value V2 on the IV curve which shows the correlation between current values and voltage values within a predetermined period.
[0022] In step S70, the control unit 50 determines the state of the solar panel 10 based on the difference between the first current value I1 and the second current value I2. In this embodiment, the control unit 50 determines whether or not dirt is attached to the solar panel 10 based on the difference between the first current value I1 and the second current value I2. Specifically, the control unit 50 determines whether the value obtained by dividing the difference between the first current value I1 and the second current value I2 by the first current value I1 is greater than a predetermined step reference value. The step reference value is, for example, 0.5. Hereinafter, the value obtained by dividing the difference between the first current value I1 and the second current value I2 by the first current value I1 will also be called the current difference ratio. If the current difference ratio is greater than or equal to the step reference value, the control unit 50 determines that dirt is attached to the solar panel 10. If the current difference ratio is less than the step reference value, the control unit 50 determines that there is no dirt attached to the solar panel 10. If it is determined that dirt is attached to the solar panel 10, step S80 is executed. If it is determined that no dirt is attached to the solar panel 10, step S100 is executed. If multiple first current values I1 are stored in memory, the first current value I1 stored in memory in the cycle closest to the current cycle is used to calculate the current difference ratio. The second current value I2 used to calculate the current difference ratio is the second current value I2 stored in memory in step S60 of the current cycle.
[0023] Figure 6 illustrates the relationship between the difference between the first current value I1 and the second current value I2, and the area of dirt adhering to the solar panel 10. In Figure 6, the horizontal axis represents the current difference ratio, and the vertical axis represents the ratio of the area of dirt adhering to the total area of the solar panel 10. As shown in Figure 6, the ratio of the area adhering to dirt is proportional to the current difference ratio. The correspondence between the current difference ratio and the ratio of the area adhering to dirt shown in Figure 6 is stored in memory beforehand.
[0024] In step S80, the control unit 50 estimates the area of dirt attached to the solar panel 10 based on the difference between the first current value I1 and the second current value I2. Specifically, the control unit 50 uses the current difference ratio calculated in step S70 and the correspondence shown in Figure 6 to calculate the percentage of the total area of the solar panel 10 that is covered with dirt.
[0025] In step S90, the control unit 50 controls a notification unit mounted on the vehicle 500 to notify the occupants of the vehicle 500 of the area of dirt attached to the solar panel 10. The notification unit is, for example, the instrument panel of the vehicle 500. The control unit 50 displays on the instrument panel the percentage of the total area of the solar panel 10 that is covered with dirt. Alternatively, the notification unit may be a speaker mounted on the vehicle 500. The control unit 50 may also control the speaker to output the percentage of the total area of the solar panel 10 that is covered with dirt as an audio message.
[0026] In step S100, the control unit 50 changes the voltage output from the solar panel 10 within a predetermined range from a lower limit to an upper limit, and determines whether or not it has obtained the current value corresponding to each voltage value from the current sensor 20. If the voltage has not been changed from the lower limit to the upper limit, step S110 is executed. If the voltage has been changed from the lower limit to the upper limit, step S120 is executed.
[0027] In step S110, the control unit 50 changes the voltage output from the solar panel 10. Specifically, the control unit 50 increases the set value of the voltage output from the solar panel 10 by a predetermined range. After step S110 is performed, step S10 is performed.
[0028] In step S120, the control unit 50 sets the voltage value output from the solar panel 10 so that the power output from the solar panel 10 is maximized. The control unit 50 searches for the voltage value that maximizes the power output from the solar panel 10 using the voltage and current values obtained in the repeatedly executed step S10. The control unit 50 controls the output voltage of the solar panel 10 by sending a drive command to the DC-DC converter 40 so that the voltage value output from the solar panel 10 becomes the voltage value that maximizes the power output from the solar panel 10. The estimation process is performed as described above.
[0029] As described above, the control unit 50 performs MPPT control by executing estimation processing. In this embodiment, in MPPT control, the control unit 50 changes the voltage output from the solar panel 10 from a lower limit to an upper limit to search for the voltage value that maximizes the power output from the solar panel 10. Of the estimation processing steps, steps S10, S100, S110, and S120 are processes included in MPPT control. The IV curve shown in Figure 5 shows the correlation between voltage and current values obtained by repeatedly executing step S10. That is, the IV curve shown in Figure 5 is obtained during the process of executing MPPT control.
[0030] According to the solar system 100 in the first embodiment described above, the control unit 50 determines the state of the solar panel 10 based on the difference between a first current value I1 and a second current value I2. The first current value I1 is the current value corresponding to the first voltage value V1, which is the voltage value when the differential conductance changes from a value greater than or equal to a first threshold to a value less than the first threshold Th1 on an IV curve showing the correlation between current and voltage values within a predetermined period. The second current value I2 is the current value corresponding to the second voltage value V2, which is the voltage value when the differential conductance changes from a value less than the first threshold Th1 to a value greater than or equal to the first threshold on the IV curve. As described above, the predetermined period is the period during which the estimation process is executed, and is preferably within 1 second, and more preferably within 0.3 seconds. Therefore, by determining the state of the solar panel 10 in a short period, it is possible to reduce the influence of changes in external factors such as solar radiation intensity and the temperature of the solar panel 10. Thus, the state of the solar panel 10 can be determined more accurately.
[0031] Furthermore, in this embodiment, the control unit 50 determines whether or not dirt is attached to the solar panel 10 based on the difference between the first current value I1 and the second current value I2. Therefore, it is possible to determine more accurately whether or not dirt is attached to the solar panel 10.
[0032] Furthermore, in this embodiment, the control unit 50 estimates the area of dirt adhering to the solar panel 10 based on the difference between the first current value I1 and the second current value I2. Therefore, the condition of the solar panel 10 can be specifically estimated.
[0033] Furthermore, in this embodiment, the control unit 50 controls a notification unit mounted on the vehicle 500 to notify the occupant of the vehicle 500 of the area of dirt attached to the solar panel 10. As a result, the occupant of the vehicle 500 can confirm the area of dirt attached to the solar panel 10.
[0034] Furthermore, in this embodiment, the control unit 50 controls the power output from the solar panel 10 by MPPT control. The IV curve shown in Figure 5 is obtained during the process of MPPT control being executed. Therefore, the state of the solar panel 10 can be determined more efficiently compared to the case where the state determination of the solar panel 10 and MPPT control are performed separately.
[0035] B. Other embodiments: (B-1) In the above embodiment, the control unit 50 controls a notification unit mounted on the vehicle 500 to notify the occupant of the vehicle 500 of the area of dirt attached to the solar panel 10. Alternatively, the control unit 50 does not have to control the notification unit mounted on the vehicle 500 to notify the occupant of the vehicle 500 of the area of dirt attached to the solar panel 10. In other words, step S90 of the estimation process does not have to be executed.
[0036] (B-2) In the above embodiment, the control unit 50 estimates the area of dirt attached to the solar panel 10 based on the difference between the first current value I1 and the second current value I2. However, the control unit 50 does not have to estimate the area of dirt attached to the solar panel 10. That is, step S80 of the estimation process does not have to be executed. In this form, if the control unit 50 determines in the estimation process that dirt is attached to the solar panel 10, the control unit 50 may control a notification unit mounted on the vehicle 500 to notify the occupants of the vehicle 500 that dirt is attached to the solar panel 10. Alternatively, if the control unit 50 determines in the estimation process that dirt is attached to the solar panel 10, the control unit 50 does not have to control a notification unit mounted on the vehicle 500 to notify the occupants of the vehicle 500 of the area of dirt attached to the solar panel 10.
[0037] (B-3) In the above embodiment, the control unit 50 determines whether or not dirt is attached to the solar panel 10 based on the difference between the first current value I1 and the second current value I2. Alternatively, the control unit 50 may determine whether or not the solar panel 10 is malfunctioning based on the difference between the first current value I1 and the second current value I2.
[0038] (B-4) In the above embodiment, the control unit 50 performs MPPT control by performing an estimation process. Alternatively, the control unit 50 may perform the estimation process and MPPT control independently. In this case, step S120 of the estimation process is not performed. Furthermore, in MPPT control, the control unit 50 may use the hill-climbing method to search for the voltage value that maximizes the power output from the solar panel 10.
[0039] (B-5) In the above embodiment, the solar system 100 can be mounted on a vehicle 500 that can move at speed. In contrast, the solar system 100 does not have to be mountable on a vehicle 500.
[0040] This disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features in the embodiments corresponding to the technical features in each form described in the summary of the invention can be replaced or combined as appropriate in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Explanation of symbols]
[0041] 10…Solar panel, 11…Cluster, 12…Solar cell, 16…Bypass diode, 20…Current sensor, 30…Voltage sensor, 40…DC-DC converter, 50…Control unit, 100…Solar system, 200…Supplier, 500…Vehicle, I1…First current value, I2…Second current value, Th1…First threshold, V1…First voltage value, V2…Second voltage value
Claims
1. A solar system that can be mounted on a vehicle, Solar panels and A current sensor that measures the current value output from the solar panel, A voltage sensor that measures the voltage value output from the solar panel, The system includes a control unit that determines the state of the solar panel based on the difference between a first current value and a second current value, The first current value is the current value corresponding to the first voltage value, which is the voltage value when the differential conductance changes from a value greater than or equal to a predetermined first threshold to a value less than the predetermined first threshold on the I-V curve showing the correlation between the current value and the voltage value within a predetermined period. The second current value is the current value corresponding to the second voltage value, which is the voltage value when the differential conductance changes on the I-V curve from a value smaller than the first threshold to a value greater than or equal to the first threshold. Solar system.
2. A solar system according to claim 1, The control unit determines whether or not dirt is attached to the solar panel based on the difference between the first current value and the second current value. Solar system.
3. The solar system according to claim 2, The control unit estimates the area of dirt adhering to the solar panel based on the difference between the first current value and the second current value. Solar system.
4. The solar system according to claim 3, The control unit controls a notification unit mounted on the vehicle to notify the occupant of the vehicle of the area of dirt adhering to the solar panel. Solar system.
5. A solar system according to claim 1, The control unit controls the power output from the solar panel by MPPT (Maximum Operating Point Tracking) control. The I-V curve is obtained during the process in which the MPPT control is executed. Solar system.