WO2025013300A1 - Vehicle photovoltaic power generation system control method, and vehicle photovoltaic power generation system - Google Patents

Abstract

Provided is a vehicle photovoltaic power generation system control method for controlling a vehicle photovoltaic power generation system comprising: a solar cell; a vehicle drive battery; a converter that transmits power generated in the solar cell to the vehicle drive battery; a current detection unit and voltage detection unit that respectively detect the output current and output voltage of the solar cell; and a maximum power point tracking control unit that controls the step-up ratio of the converter, controls the output voltage of the solar cell, and performs a control according to a solar radiation amount. In said control method, if the output current detected by the current detection unit is at or above a preset reference value, maximum power point tracking control is performed, and if the output current detected by the current detection unit is lower than the reference value, the maximum power point tracking control is not executed, and a control to change the step-up ratio of the converter is executed such that the output voltage of the solar cell becomes a charge-ready voltage value that can charge the vehicle drive battery.

Description

Control method for vehicle solar power generation system and vehicle solar power generation system

The present invention relates to a control method for a vehicle solar power generation system and a vehicle solar power generation system, and more specifically to a control method for a vehicle solar power generation system and a vehicle solar power generation system that can generate power efficiently even if the output current of the solar cell decreases due to a decrease in the amount of solar radiation.

In a solar power generation system mounted on a vehicle, a converter connected to the solar cell is used to change the voltage or current of the solar cell, and maximum power point tracking (MPPT) control is performed to track the maximum power point (MPP) of the solar cell. When a solar cell is shaded, the solar cell itself becomes a resistor. For this reason, solar cells generally have a circuit in which the solar cell and a bypass diode are connected in parallel. As a result, when a solar cell is shaded, current flows through the bypass diode, and the output voltage of the solar cell drops. In such a case, if MPPT control is performed using the output voltage of the solar cell as the control variable, there is a possibility that the MPPT control will not be able to track the drop in the output voltage of the solar cell caused by the solar cell being shaded, and as a result, the output current of the solar cell, i.e., the power generated by the solar cell, may become zero.

To solve such problems, Patent Document 1 discloses a solar cell control device that can stabilize the output power of a solar cell mounted on a vehicle when MPPT control is performed using the power generation current of the solar cell as a control variable. This solar cell control device includes a solar cell mounted on a vehicle, a vehicle speed detection unit that detects the vehicle speed, and a control unit that is connected to the solar cell and executes MPPT control to search for the maximum power point of the solar cell while changing the input power generation current of the solar cell, and when the vehicle speed of the vehicle detected by the vehicle speed detection unit is higher than a predetermined speed, the control unit executes MPPT control while changing the power generation current within a range equal to or lower than a predetermined upper limit value. The predetermined speed is set lower than the vehicle speed at which the change in power generation current in MPPT control cannot follow the output characteristic fluctuation of the solar cell power generation current and power generation voltage that occurs in response to changes in the solar cell's power generation angle due to the behavior of the vehicle while traveling. The predetermined upper limit value is set to a value smaller than the short-circuit current of the solar cell that decreases due to the output characteristic fluctuation.

Japanese Patent No. 6131939

However, in a solar cell control device such as that disclosed in Patent Document 1, when the vehicle speed is higher than a predetermined speed, the power generation current of the solar cell is changed within a range below a predetermined upper limit value, so the solar cell cannot be operated at the maximum power point according to the amount of solar radiation, resulting in a problem of reduced power generation efficiency.

The present invention was made in consideration of the problems with the conventional technology, and aims to provide a control method for a vehicle solar power generation system and a vehicle solar power generation system that can generate power efficiently even if the output current of the solar cell decreases due to a decrease in the amount of solar radiation.

As a result of extensive research into achieving the above-mentioned objective, the inventors discovered that the above-mentioned objective could be achieved by performing maximum power point tracking control when the output current detected by the current detection unit is equal to or greater than a preset reference value, and not performing maximum power point tracking control when the output current detected by the current detection unit is less than the preset reference value, and instead performing change control of the converter's step-up ratio so that the output voltage of the solar cell becomes a chargeable voltage value that can be charged into the vehicle drive battery, thereby completing the present invention.

In other words, the control method for a vehicle solar power generation system of the present invention is a method for controlling a vehicle solar power generation system that includes a solar cell, a vehicle drive battery, a converter that transmits power generated by the solar cell to the vehicle drive battery, a current detection unit and a voltage detection unit that detect the output current and output voltage of the solar cell, respectively, and a maximum power point tracking control unit that controls the step-up ratio of the converter to control the output voltage of the solar cell and performs control according to the amount of solar radiation.
When controlling a vehicle solar power generation system, if the output current detected by the current detection unit is equal to or greater than a preset reference value, maximum power point tracking control is performed, and if the output current detected by the current detection unit is less than the preset reference value, maximum power point tracking control is not performed, and control is performed to change the step-up ratio of the converter so that the output voltage of the solar cell becomes a chargeable voltage value that can be charged into the vehicle drive battery.

Furthermore, the vehicle solar power generation system of the present invention includes a solar cell, a vehicle drive battery, a converter that transmits power generated by the solar cell to the vehicle drive battery, a current detection unit and a voltage detection unit that detect the output current and output voltage of the solar cell, respectively, and a maximum power point tracking control unit that controls the step-up ratio of the converter to control the output voltage of the solar cell and performs control according to the amount of solar radiation.
The maximum power point tracking control unit performs maximum power point tracking control when the output current detected by the current detection unit is equal to or greater than a preset reference value, and does not perform maximum power point tracking control when the output current detected by the current detection unit is less than the preset reference value, and instead performs change control of the converter's step-up ratio so that the output voltage of the solar cell becomes a chargeable voltage value that can be charged into the vehicle drive battery.

According to the present invention, when the output current detected by the current detection unit is equal to or greater than a preset reference value, maximum power point tracking control is performed, and when the output current detected by the current detection unit is less than the preset reference value, maximum power point tracking control is not performed, and instead, control for changing the converter's step-up ratio is performed so that the output voltage of the solar cell becomes a chargeable voltage value that can charge the vehicle drive battery. This makes it possible to provide a control method and a solar power generation system for vehicles that can generate power efficiently even if the output current of the solar cell decreases due to a decrease in the amount of solar radiation.

1 is a configuration diagram showing an embodiment of a vehicle solar power generation system for executing a control method for a vehicle solar power generation system of the present invention; FIG. 4 is a flow chart showing an embodiment of a control method for a vehicle solar power generation system according to the present invention. FIG. 3 is a flow diagram illustrating an example of the MPPT control shown in FIG. 2 . FIG. 3 is a flow chart showing an example of the target voltage control shown in FIG. 2 . 5 is a graph showing an example of the relationship between the vehicle speed c and the target voltage _vt shown in FIG. 4.

The vehicle solar power generation system and the control method for the vehicle solar power generation system of the present invention will be described in detail below with reference to the drawings. Note that the dimensional ratios of the drawings cited below have been exaggerated for the convenience of explanation and may differ from the actual ratios.

As shown in FIG. 1, the vehicle solar power generation system 1 of this embodiment includes a solar cell 10, a vehicle drive battery 20, a converter 30 that transmits the power generated by the solar cell 10 to the vehicle drive battery 20, a current detection unit 40 and a voltage detection unit 50 that detect the output current and output voltage of the solar cell 10, respectively, and a maximum power point tracking control unit 60 that controls the step-up ratio of the converter 30 to control the output voltage of the solar cell 10 and perform control according to the amount of solar radiation. Here, the current detection unit 40 preferably includes a conventionally known current sensor. Also, the voltage detection unit 50 preferably includes a conventionally known voltage sensor.

The maximum power point tracking control unit 60 executes maximum power point tracking control when the output current of the solar cell 10 detected by the current detection unit 40 is equal to or greater than a preset reference value. On the other hand, when the output current of the solar cell 10 detected by the current detection unit 40 is less than a preset reference value, the maximum power point tracking control unit 60 does not execute maximum power point tracking control, but executes control to change the step-up ratio of the converter so that the output voltage of the solar cell 10 becomes a chargeable voltage value capable of charging the vehicle drive battery 20. Note that when setting the reference value, it is preferable to set it so that the maximum power of the solar cell that can be realized when performing maximum power point tracking control is equal to or greater than a predetermined value of the rated power of the solar cell, for example, 20% or more.

In this invention, the converter step-up ratio means the ratio of the drive battery voltage to the solar cell output voltage detected by the voltage detection unit. The converter step-up ratio can be changed, for example, by controlling the converter to control the solar cell output voltage. Note that since the secondary side voltage of the converter is fixed by the drive battery voltage, increasing the converter step-up ratio reduces the solar cell output voltage, and decreasing the converter step-up ratio increases the solar cell output voltage.

Furthermore, the vehicle solar power generation system 1 includes a motor/inverter 80 and a vehicle speed detection unit 70 that detects the vehicle speed provided in the motor/inverter 80, and it is preferable that the chargeable voltage value is increased as the vehicle speed detected by the vehicle speed detection unit 70 increases. Here, it is preferable that the vehicle speed detection unit 70 includes a conventionally known vehicle speed sensor.

Furthermore, in the vehicle solar power generation system 1, it is preferable that the maximum power point tracking control unit 60 has an operating voltage value estimation unit 61 that estimates the operating voltage value of the maximum power point of the solar cell 10 when the amount of solar radiation is sufficient, and that the chargeable voltage value is smaller than the operating voltage value estimated by the operating voltage value estimation unit 61.

Furthermore, in the vehicle solar power generation system 1, the maximum power point tracking control unit 60 calculates the power generated by the solar cell 10 based on the output current of the solar cell 10 detected by the current detection unit 40 and the output voltage of the solar cell 10 detected by the voltage detection unit 50, and has a decline rate estimation unit 63 that estimates the decline rate of the power generated by the solar cell 10, and it is preferable that the chargeable voltage value is increased as the decline rate of the power generated by the solar cell 10 estimated by the decline rate estimation unit 63 increases.

In addition, in the vehicle solar power generation system 1 of this embodiment, the power generated by the solar cell 10 can also be supplied to the motor/inverter 80.

Next, the advantages of this embodiment will be described. When the output current detected by the current detection unit is equal to or greater than a preset reference value, the vehicle solar power generation system performs maximum power point tracking control, and when the output current detected by the current detection unit is less than the preset reference value, the vehicle solar power generation system does not perform maximum power point tracking control, and performs change control of the converter's step-up ratio so that the output voltage of the solar cell becomes a chargeable voltage value that can be charged to the vehicle drive battery. More specifically, when the output current of the solar cell is equal to or greater than a preset reference value (threshold), the vehicle solar power generation system performs maximum power point tracking control that can generate power efficiently. On the other hand, when the output current of the solar cell is less than a preset reference value (threshold), the vehicle solar power generation system does not perform maximum power point tracking control, which may cause the tracking control to fail due to the low power generation of the solar cell, and performs change control of the converter's step-up ratio so that the output voltage of the solar cell, which can continue to be controlled even if the power generation is small, becomes a chargeable voltage (target voltage). As a result, the vehicle solar power generation system can generate power efficiently even if the output current of the solar cell decreases due to a decrease in the amount of solar radiation. In addition, in vehicle solar power generation systems, it is possible to quickly recover to the operating voltage at the maximum power point when the amount of solar radiation is sufficient.

The solar power generation system for vehicles of this embodiment also includes a vehicle speed detection unit that detects the vehicle speed, and the higher the vehicle speed detected by the vehicle speed detection unit, the higher the chargeable voltage value. This makes it possible to more quickly recover to the operating voltage at the maximum power point when the amount of solar radiation is sufficient. More specifically, when the vehicle speed is fast, the value of the output current of the solar cell temporarily drops when the solar cell is partially shaded, and when the solar cell is no longer partially shaded, the amount of solar radiation becomes sufficient and the output current of the solar cell returns to its original value. Assuming such a situation, the magnitude of the chargeable voltage is set according to the vehicle speed, so that the output voltage of the solar cell is not too far from the operating voltage of the maximum power point, making it possible to more quickly recover to the operating voltage at the maximum power point when the amount of solar radiation is sufficient. Note that when the vehicle speed is slow, the step-up ratio of the converter is increased to reduce the chargeable voltage value, so control can continue.

Furthermore, the vehicle solar power generation system of this embodiment includes an operating voltage value estimation unit that estimates the operating voltage value of the maximum power point of the solar cell when the amount of solar radiation is sufficient, and the chargeable voltage value is smaller than the operating voltage value estimated by the operating voltage value estimation unit. This makes it possible to prevent the maximum power point tracking control from being unable to be executed when the amount of solar radiation is sufficient.

Furthermore, the solar power generation system for vehicles of this embodiment includes a drop rate estimation unit that calculates the power generated by the solar cell based on the output current detected by the current detection unit and the output voltage detected by the voltage detection unit, and estimates the drop rate of the power generated by the solar cell, and the chargeable voltage value is increased as the drop rate of the power generated by the solar cell estimated by the drop rate estimation unit increases. This makes it possible to recover more quickly to the operating voltage at the maximum power point when the amount of solar radiation is sufficient. More specifically, an example of a case in which the drop rate of the power generated by the solar cell is large while the vehicle is traveling is when the vehicle enters a tunnel and the entire solar cell is in shadow. In such a case, the entire solar cell is no longer in shadow and the power generated by the solar cell often returns to its original value. Assuming such a situation, the magnitude of the chargeable voltage value is set according to the vehicle speed, so that the output voltage of the solar cell is not too far from the operating voltage value of the maximum power point, making it possible to recover more quickly to the operating voltage at the maximum power point when the amount of solar radiation is sufficient.

Figures 2 to 5 are explanatory diagrams showing one embodiment of a control method for a vehicle solar power generation system.

As shown in FIG. 2, in step 1 (hereinafter referred to as "S1"), the output current i of the solar cell 10 is acquired by the current detection unit (current sensor) 40.

Next, in S2, it is determined whether the output current i of the solar cell is equal to or greater than a preset reference value (threshold value) i _th . If Yes, the process proceeds to S3, and if No, the process proceeds to S4.

Next, in S3, MPPT control is performed (see Figure 3), while in S4, target voltage (chargeable voltage) control is performed (see Figure 4).

As shown in FIG. 3, in S3-1, the voltage detection unit (voltage sensor) 50 acquires the output voltage v of the solar cell 10.

Next, in S3-2, the output current i of the solar cell 10 acquired in S1 is multiplied by the output voltage v of the solar cell 10 acquired in S3-1 to calculate the generated power _pn of the solar cell 10 (i×v=p _n ).

Next, in S3-3, it is determined whether the power generation p _n of the solar cell 10 calculated in S3-2 is equal to or greater than the power generation p _n-1 of the previous solar cell 10. If Yes, proceed to S3-4, and if No, proceed to S3-5.

Next, in S3-4, α is assigned the value 1, while in S3-5, α is assigned the value -1.

Next, in S3-6, the power generated by the solar cell 10 p _n is substituted for the previous power generated by the solar cell 10 p _n-1 .

Next, in S3-7, αΔr is added to the converter step-up ratio r to obtain the new step-up ratio r.

Also, as shown in FIG. 4, in S4-1, the vehicle speed c is acquired by the vehicle speed detection unit (vehicle speed sensor) 70.

Next, in S4-2, a target voltage (chargeable voltage) _vt is obtained from the vehicle speed c. Figure 5 shows a graph for calculating the target voltage _vt . As the vehicle speed c increases, the target voltage _vt is set to a larger value. The maximum value of the target voltage _vt is set to a value that does not exceed the operating voltage value _Vmpp of the maximum power point when the amount of solar radiation is sufficient. Note that data such as that shown in this graph may be stored in the vehicle speed detection unit or in the maximum power point tracking control unit.

Next, in S4-3, the output voltage v of the solar cell is obtained.

Next, in S4-4, it is determined whether the output voltage v of the solar cell is equal to or higher than the target voltage (chargeable voltage) _vt . If Yes, the process proceeds to S4-5, and if No, the process proceeds to S4-6.

Next, in S4-5, α is assigned the value 1, while in S4-6, α is assigned the value -1.

Next, in S4-7, αΔr is added to the converter step-up ratio r to obtain the new step-up ratio r.

The present invention has been described above using a few embodiments, but the present invention is not limited to these, and various modifications are possible within the scope of the gist of the present invention.

The present invention provides a control method and a vehicle solar power generation system that can generate power efficiently, and is based on the principle that when the output current detected by the current detection unit is equal to or greater than a preset reference value, maximum power point tracking control is performed, and when the output current detected by the current detection unit is less than the preset reference value, maximum power point tracking control is not performed, and instead, control is performed to change the step-up ratio of the converter so that the output voltage of the solar cell becomes a chargeable voltage value that can be charged into the vehicle drive battery.

Thus, in the above embodiment, a case has been described in which the maximum power point tracking control unit executes change control of the boost ratio of the above converter, but the present invention is not limited to this. In the present invention, for example, a separately provided control unit may execute change control of the above converter's boost ratio.

In addition, in the above embodiment, a case where the maximum power point tracking control unit has an operating voltage value estimator and a decline speed estimator has been described as an example, but the present invention is not limited to this. In the present invention, for example, an operating voltage value estimator and a decline speed estimator may be provided separately.

In addition, in the above embodiment, a vehicle speed detection unit, an operating voltage value estimation unit, and a decline speed estimation unit are provided, but the present invention is not limited to this. In the present invention, it is preferable to provide at least one selected from the group consisting of the vehicle speed detection unit, the operating voltage value estimation unit, and the decline speed estimation unit.

Reference Signs List 1 Vehicle solar power generation system 10 Solar cell 20 Vehicle drive battery 30 Converter 40 Current detection unit 50 Voltage generation unit 60 Maximum power point tracking control unit 61 Operating voltage value estimation unit 63 Decline speed estimation unit 70 Speed detection unit 80 Motor/inverter

Claims (5)

When controlling a vehicle solar power generation system including a solar cell, a vehicle drive battery, a converter that transmits power generated by the solar cell to the vehicle drive battery, a current detection unit and a voltage detection unit that detect an output current and an output voltage of the solar cell, respectively, and a maximum power point tracking control unit that controls a step-up ratio of the converter to control the output voltage of the solar cell according to the amount of solar radiation,
When the output current detected by the current detection unit is equal to or greater than a preset reference value, the maximum power point tracking control is performed.
a control method for a vehicle solar power generation system, characterized in that, when the output current detected by the current detection unit is less than the reference value, the maximum power point tracking control is not executed, and a change control of the step-up ratio of the converter is executed so that the output voltage of the solar cell becomes a chargeable voltage value that can charge the vehicle drive battery. The vehicle solar power generation system includes a vehicle speed detection unit that detects a vehicle speed,
The method for controlling a solar power generation system for a vehicle according to claim 1, wherein the chargeable voltage value is increased as the vehicle speed detected by the vehicle speed detection unit increases. the vehicle solar power generation system includes an operating voltage value estimation unit that estimates an operating voltage value of the solar cell at a maximum power point when an amount of solar radiation is sufficient,
3. The method for controlling a solar power generation system for a vehicle according to claim 1, wherein the chargeable voltage value is smaller than the operating voltage value estimated by the operating voltage value estimating unit. the vehicle solar power generation system includes a decrease rate estimation unit that calculates a power generated by the solar cell based on an output current detected by the current detection unit and an output voltage detected by the voltage detection unit, and estimates a decrease rate of the power generated by the solar cell;
2. The method for controlling a solar power generation system for a vehicle according to claim 1, wherein the chargeable voltage value is increased as the rate of decrease in the power generated by the solar cell estimated by the decrease rate estimation unit increases. A solar power generation system for a vehicle, comprising: a solar cell; a vehicle drive battery; a converter that transmits power generated by the solar cell to the vehicle drive battery; a current detection unit and a voltage detection unit that detect an output current and an output voltage of the solar cell, respectively; and a maximum power point tracking control unit that controls a step-up ratio of the converter to control the output voltage of the solar cell in accordance with an amount of solar radiation,
The maximum power point tracking control unit is
When the output current detected by the current detection unit is equal to or greater than a preset reference value, the maximum power point tracking control is performed.
a current detection unit that detects an output current lower than the reference value and, when the output current is lower than the reference value, the maximum power point tracking control is not executed, and instead, a change control of the step-up ratio of the converter is executed so that the output voltage of the solar cell becomes a chargeable voltage value capable of charging the vehicle drive battery.

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