Control method of on-vehicle solar battery system, and on-vehicle solar battery system

Abstract

To provide a control method of an on-vehicle solar battery system, capable of suppressing or preventing deterioration of a voltage of a low-voltage battery; and provide the on-vehicle solar battery system.SOLUTION: A control method of an on-vehicle solar battery system includes: a first control step of switching a charging mode for charging a low-voltage battery by a solar battery and a discharge mode for charging a high-voltage battery by the low-voltage battery of a power conversion device in accordance with an operation state; and a second control step of controlling the power conversion device so as to keep a voltage value of the low-voltage battery within a constant range in accordance with the operation state. The first control step includes: a calculation step of calculating a switching operation voltage range target value of the low-voltage battery; and a switching step of switching the first control step to the second control step in the case where the switching operation voltage range target value is larger than a predetermined voltage range upper limit value of the low-voltage battery.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a control method for a solar cell system mounted on a vehicle and the solar cell system mounted on a vehicle, and more specifically to a control method for a solar cell system mounted on a vehicle including a solar cell, a low-voltage battery, a high-voltage battery, and a power conversion device that converts power in both directions between these batteries, and a solar cell system mounted on a vehicle that executes the control method. [Background technology]

[0002] Patent Document 1 discloses a power supply device including a solar cell, a power storage unit, a DC-DC converter, a secondary battery, a voltage detection unit, and a charge control unit. The power storage unit is charged by the electromotive force of the solar cell and stores power. The secondary battery is charged via the DC-DC converter by the power stored in the power storage unit. The voltage detection unit detects the voltage of the power storage unit, and when the voltage becomes equal to or higher than a high-level threshold voltage, holds a charge control signal for charging the secondary battery in an active mode to start charging, and thereafter, when the voltage of the power storage unit becomes a low-level threshold voltage, holds the charge control signal in a non-active mode to stop charging. The charge control unit is interposed between the DC-DC converter and the secondary battery, and when the charge control signal is in the active mode, charges the secondary battery based on the power stored in the power storage unit.

[0003] In this way, in the power supply device disclosed in Patent Document 1, the power generated by the solar cell is temporarily charged to the power storage unit, and the power charged to the power storage unit is combined via a DC-DC converter to charge the secondary battery. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4133924 Summary of the Invention [Problem to be solved by the invention]

[0005] However, a DC-DC converter such as that disclosed in Patent Document 1 does not have the function of charging the power stored in the secondary battery to a power storage unit, so when an attempt is made to apply such a DC-DC converter to a vehicle-mounted solar cell system that includes, for example, a low-voltage battery that is charged by a solar cell and supplies power to the vehicle's auxiliary systems that operate at low voltage, and a high-voltage battery that supplies power to the vehicle's drive system that operates at high voltage, a problem arises in that when the power generated by the solar cell is insufficient, the voltage of the low-voltage battery drops significantly, and the low-voltage battery cannot sufficiently supply power to the auxiliary systems.

[0006] The present invention has been made in consideration of the problems associated with the conventional technology, and aims to provide a control method for a solar cell system mounted on a vehicle, and a solar cell system mounted on a vehicle, which can suppress or prevent voltage drop in a low-voltage battery. [Means for solving the problem]

[0007] As a result of extensive research into achieving the above-mentioned objective, the inventors discovered that the above-mentioned objective can be achieved by providing a power conversion device that converts power in both directions between a low-voltage battery charged by a solar cell and a high-voltage battery, and switching the operating state of the power conversion device in accordance with a predetermined voltage value of the low-voltage battery, thereby completing the present invention.

[0008] In other words, the control method for a solar cell system mounted on a vehicle of the present invention is a control method for a solar cell system mounted on a vehicle that is equipped with a solar cell, a low-voltage battery, a high-voltage battery, and a power conversion device that converts power in both directions between these batteries. This control method includes a first control step and a second control step. The first control process includes a low-voltage battery charging mode in which the power conversion device is stopped and the low-voltage battery is charged by the solar cell, and a low-voltage battery discharging mode in which the power conversion device is operated and the high-voltage battery is charged by the low-voltage battery, and switches to the discharge mode when the voltage value of the low-voltage battery exceeds a predetermined upper limit voltage value in the charge mode, and switches to the charge mode when the voltage value of the low-voltage battery falls below a predetermined lower limit voltage value in the discharge mode. In the second control step, the power conversion device is operated to control the voltage value of the low-voltage battery so as to be kept within a certain range. The first control step includes a calculation step and a switching step. In the calculation process, a passing power target value, which is the power that needs to pass through the power conversion device, is calculated from a time ratio target value for reducing the time ratio of the discharge mode, and a switching operating voltage range target value for the low-voltage battery for reducing the switching frequency is calculated from the passing power target value and a switching frequency target value for reducing the switching frequency between the discharge mode and the charge mode. In the switching step, when the switch operating voltage range target value is greater than the upper limit value of the predetermined voltage range of the low voltage battery, the first control step is switched to the second control step.

[0009] Furthermore, the vehicle-mounted solar cell system of the present invention includes a solar cell, a low-voltage battery, a high-voltage battery, a power conversion device that converts power bidirectionally between these two batteries, and a control device. The control device includes a first control unit, a second control unit, and a third control unit. The first control unit switches to a low-voltage battery discharge mode in which the power conversion device is operated and the high-voltage battery is charged by the low-voltage battery when the voltage value of the low-voltage battery exceeds a predetermined upper limit voltage value in a low-voltage battery charging mode in which the power conversion device is stopped and the low-voltage battery is charged by the solar cell, and switches to a low-voltage battery discharge mode in which the power conversion device is operated and the high-voltage battery is charged by the low-voltage battery when the voltage value of the low-voltage battery falls below a predetermined lower limit voltage value in the discharge mode. The second control unit operates the power conversion device and controls the voltage value of the low voltage battery to be kept within a certain range. The third control unit calculates a passing power target value, which is the power that needs to pass through the power conversion device, from a time proportion target value for reducing the time proportion of the discharge mode, calculates a switchover operating voltage range target value for the low-voltage battery for reducing the switching frequency from the passing power target value and a switching frequency target value for reducing the switching frequency between the discharge mode and the charge mode, and switches the operation of the first control unit to the operation of the second control unit when the switchover operating voltage range target value is greater than a predetermined voltage range upper limit value of the low-voltage battery. Effect of the Invention

[0010] According to the present invention, a power conversion device that converts power in both directions is provided between a low-voltage battery charged by a solar cell and a high-voltage battery, and the operating state of the power conversion device is switched depending on the above-mentioned voltage value of the low-voltage battery, thereby providing a control method for a solar cell system mounted on a vehicle and a solar cell system mounted on a vehicle that can suppress or prevent voltage drop in the low-voltage battery. [Brief description of the drawings]

[0011] [Figure 1] FIG. 11 is an explanatory diagram showing the relationship between time and a low-voltage battery voltage in a first control step. [Diagram 2] FIG. 11 is an explanatory diagram showing the relationship between time and a low-voltage battery voltage in a first control step. [Diagram 3] FIG. 4 is an explanatory diagram showing the relationship between the switching operating voltage range and the switching frequency in the first control process. [Figure 4] 1 is a configuration diagram showing a schematic diagram of an embodiment of a solar cell system to be mounted on a vehicle according to the present invention; [Diagram 5] 5 is a flowchart showing the overall control of the vehicle-mounted solar cell system shown in FIG. [Figure 6] FIG. 6 is an explanatory diagram showing the ON / OFF operation states of A to D shown in FIG. 5. [Figure 7] 6 is a part of a flowchart showing control of ON / OFF operation of A shown in FIG. 5. [Figure 8] 8 is a continuation of the flowchart in FIG. 7. [Figure 9] 1 is an explanatory diagram showing the relationship between temperature, solar radiation, and optimal operating point voltage in a solar cell. [Figure 10] 6 is a part of a flowchart showing control of ON / OFF operation of B shown in FIG. 5. [Figure 11] This is a continuation of the flowchart in FIG. [Figure 12] 6 is a part of a flowchart showing control of ON / OFF operation of C shown in FIG. 5. [Figure 13] 13 is a continuation of the flowchart in FIG. 12. [Figure 14] 6 is a part of a flowchart showing control of ON / OFF operation of D shown in FIG. 5. [Figure 15] This is a continuation of the flowchart in FIG. 14. [Figure 16] 6 is a part of a flowchart showing control of continuous operation of E shown in FIG. 5. [Figure 17] This is a continuation of the flowchart in Figure 16. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The control method for a solar cell system mounted on a vehicle and the solar cell system mounted on a vehicle according to the present invention will be described in detail below with reference to the drawings. Note that the dimensional ratios of the drawings cited below are exaggerated for the convenience of explanation and may differ from the actual ratios.

[0013] The control method for a solar cell system mounted on a vehicle of the present invention is a control method for a solar cell system mounted on a vehicle that is equipped with a solar cell, a low-voltage battery, a high-voltage battery, and a power conversion device that converts power in both directions between these batteries.

[0014] This control method includes a first control step and a second control step.

[0015] The first control step includes a low-voltage battery charging mode in which the power conversion device is stopped and the low-voltage battery is charged by the solar cell, and a low-voltage battery discharging mode in which the power conversion device is operated and the high-voltage battery is charged by the low-voltage battery. In the first control step, the mode is switched to the discharge mode when the voltage value of the low-voltage battery exceeds a predetermined upper limit voltage value in the charge mode, and is switched to the charge mode when the voltage value of the low-voltage battery falls below a predetermined lower limit voltage value in the discharge mode.

[0016] In the second control step, the power conversion device is operated to control the voltage value of the low-voltage battery so as to be kept within a certain range.

[0017] Furthermore, the above-mentioned first control step includes a calculation step and a switching step.

[0018] In the calculation process, a passing power target value, which is the power that needs to pass through the power conversion device, is calculated from a time ratio target value for reducing the time ratio of the discharge mode, and a switching operating voltage range target value for the low-voltage battery for reducing the switching frequency is calculated from the passing power target value and a switching frequency target value for reducing the switching frequency between the discharge mode and the charge mode.

[0019] In the switching step, when the switch operating voltage range target value is greater than the upper limit value of the predetermined voltage range of the low voltage battery, the first control step is switched to the second control step.

[0020] In addition, in this control method, it is preferable to switch from the first control step to the second control step when the voltage value of the solar cell falls below another predetermined lower limit voltage value that is smaller than the predetermined lower limit voltage value.

[0021] Furthermore, in this control method, it is preferable to set the passing power target value to be greater than (the power value of the solar cell) / [1-(the time ratio target value)].

[0022] Furthermore, in this control method, it is preferable to set the switching operation voltage range target value greater than (solar cell power value) / [(energy value per voltage difference of low-voltage battery)×(switching frequency target value)]×[1-(solar cell power value) / (passing power target value)].

[0023] Furthermore, in this control method, it is preferable that (predetermined upper limit voltage value) - (predetermined lower limit voltage value) is greater than (passing power target value) x (internal resistance value of low-voltage battery) / (voltage value of low-voltage battery) + (switching operating voltage range target value).

[0024] Furthermore, in this control method, it is preferable that the first control step is executed only while the vehicle is stopped.

[0025] Furthermore, in this control method, when switching from the first control process to the second control process, it is preferable to make the decision using the average values ​​of the solar cell current, voltage, and power calculated by dividing a single switching control of switching between the discharge mode and the charge mode into two or more sections.

[0026] Next, the advantages of the present invention will be described. According to the present invention, by switching between the first control process of switching between the low-voltage battery charging mode and the low-voltage battery discharging mode and the second control process of operating the power conversion device in the above-mentioned predetermined case and controlling the voltage value of the low-voltage battery to be kept within a certain range, it is possible to control the power generation of the solar cell, and there is an advantage that the voltage drop of the low-voltage battery can be suppressed or prevented. In addition, there is an advantage that the time ratio of the discharge mode and the switching frequency are reduced, so that the system efficiency and the relay durability can be improved. Furthermore, there is a secondary advantage that the circuit configuration can be simplified by using a DCDC bidirectional converter.

[0027] The reasons why the above-mentioned advantages are obtained will be explained in detail. First, if the system is always in discharge mode, power consumption increases. Therefore, as shown in the upper diagram of FIG. 1, in the first control process for switching between the low-voltage battery charging mode and the low-voltage battery discharging mode, the passing power is increased as much as possible in order to reduce (shorten) the time ratio of the discharge mode (high-voltage system ON time). This reduces the ON time and increases the ratio of the OFF time, reducing power consumption and improving system efficiency. However, this also increases the switching frequency.

[0028] Therefore, as shown in the center diagram of Figure 1, the voltage range is increased to reduce the switching frequency. This reduces the switching frequency and improves the relay durability. However, the power generation efficiency decreases because the maximum power point MPP is not reached.

[0029] Therefore, as shown in the lower diagram of Fig. 1, when the target value of the switching operation voltage range becomes larger than the upper limit value of the predetermined voltage range of the low-voltage battery, the first control process is switched to the second control process (continuous operation) in which the power conversion device is operated to control the voltage value of the low-voltage battery to be kept within a certain range. This makes it possible to obtain the above-mentioned advantages.

[0030] According to a preferred embodiment of the present invention, when the voltage value of the solar cell falls below another predetermined lower limit voltage value that is smaller than the predetermined lower limit voltage value, the first control process is switched to the second control process. Therefore, the voltage conversion device that converts power in both directions as described above makes it possible to supply power from the high-voltage battery to the low-voltage battery, which has the advantage of further suppressing or preventing voltage drop in the low-voltage battery.

[0031] According to a preferred embodiment of the present invention, the passing power target value is set to be greater than (solar cell power value) / [1-(time ratio target value)], making it possible to reduce the time ratio for reducing the discharge mode according to the solar cell power, which has the advantage of suppressing or preventing a decrease in system efficiency even if the power generation state of the solar cell changes.

[0032] According to a preferred embodiment of the present invention, the target switching operation voltage range value is set to be greater than (solar cell power value) / [(energy value per voltage difference of low-voltage battery)×(target switching frequency value)]×[1-(solar cell power value) / (target passing power value)], thereby making it possible to reduce the switching frequency according to the solar cell power, and having the advantage that relay durability can be ensured even if the power generation state of the solar cell changes.

[0033] According to a preferred embodiment of the present invention, since (predetermined upper limit voltage value) - (predetermined lower limit voltage value) is greater than (passing power target value) x (internal resistance value of low-voltage battery) / (voltage value of low-voltage battery) + (switching operation voltage range target value), it is possible to reduce the switching frequency target value per unit time by taking into account voltage fluctuations caused by the internal resistance of the low-voltage battery during switching operation, which has the advantage of making it possible to ensure relay durability even if the power generation state of the solar cell changes.

[0034] The reason why the above-mentioned advantages are obtained will be explained in detail. During switching operation, voltage changes occur due to the internal resistance of the low-voltage battery. If this is not taken into consideration, the relationship between time and the low-voltage battery voltage will be as shown in the upper diagram of FIG. 2. On the other hand, if the internal resistance of the low-voltage battery is taken into consideration, the relationship between time and the low-voltage battery voltage will be as shown in the lower diagram of FIG. 2. Therefore, it is preferable to set the voltage range target value during switching operation to be larger than ΔV0+ΔV1.

[0035] ΔV0 is the voltage change width caused by the change in the direction of the current when switching ON / OFF when the internal resistance of the low-voltage battery is taken into consideration, and can be calculated as ΔV0 = (internal resistance of the low-voltage battery) x (power passing from the low-voltage battery to the DCDC converter) / (voltage of the low-voltage battery). Also, V1 is the voltage width for setting the switching frequency to a predetermined value, and can be calculated as ΔV1 = (target cycle) x (power value of the solar cell) / (energy per voltage difference of the low-voltage battery) x [1 - (power value of the solar cell) / (power passing from the low-voltage battery to the DCDC converter)].

[0036] Furthermore, since the system efficiency decreases gradually even if the switchover operating voltage range is increased beyond ΔV0+ΔV1, it is preferable to increase the switchover operating voltage range and reduce the switching frequency as shown in FIG.

[0037] According to a preferred embodiment of the present invention, the first control process is executed only when the vehicle is stopped, which has the advantage that it is possible to suppress or prevent a decrease in system efficiency and ensure relay durability when the vehicle is traveling or in other situations in which the high-voltage battery of the vehicle is automatically activated.

[0038] According to a preferred embodiment of the present invention, when switching from the first control process to the second control process, the switching control for switching between the discharge mode and the charge mode once is determined using the average values ​​of the solar cell current, voltage and power calculated by dividing the control into two or more sections. This has the advantage that even if the power of the solar cell fluctuates due to external disturbances, inappropriate repeated switching between the discharge mode and the charge mode can be prevented.

[0039] FIG. 4 is a schematic diagram showing an embodiment of a solar cell system mounted on a vehicle according to the present invention, which is capable of executing the above-mentioned method for controlling a solar cell system mounted on a vehicle according to the present invention.

[0040] As shown in FIG. 4, the solar cell system 1 mounted on a vehicle of this embodiment includes a solar cell 10, an auxiliary battery (low-voltage battery) 20, a driving battery (high-voltage battery) 30, a bidirectional converter (power conversion device that converts power in both directions) 40 provided between the two batteries 20, 30, and a controller (control device) 50. The system 1 further includes a switch 60, an electronic device 70, and a motor / inverter 80 provided between the auxiliary battery 20 and the bidirectional converter 40. When only the auxiliary battery 20 is charged by the solar cell 10 (low-voltage battery charging mode), the switch 60 is turned OFF (high-voltage battery OFF). On the other hand, when the driving battery 30 is charged by the auxiliary battery 20 (low-voltage battery discharging mode), the switch 60 is turned ON (high-voltage battery ON). Although not shown, the switch 60 may be provided between the driving battery 30 and the bidirectional converter 40.

[0041] Here, the power generated by the solar cell 10 is supplied to, for example, an auxiliary battery 20, an auxiliary system controller 50 that operates at a low voltage, an electronic device 70, etc. Also, the power charged in the auxiliary battery 20 is supplied, for example, via a bidirectional converter 40, to a drive battery 30, a drive system motor / inverter 80 that operates at a high voltage, etc.

[0042] The system 1 in the illustrated example also includes a voltage sensor 11 capable of measuring the voltage of the auxiliary battery 20 and the solar cell 10, a current sensor 12 capable of measuring the current of the solar cell 10, a temperature sensor 13 capable of measuring the temperature of the solar cell 10, a solar radiation sensor 14 capable of measuring the amount of solar radiation on the solar cell 10, and a reverse current prevention diode 15 capable of preventing current from flowing back from the auxiliary battery 20 to the solar cell 10 when the amount of solar radiation decreases, for example.

[0043] Furthermore, in the illustrated system 1, the bidirectional converter 40 has a built-in sensor (not shown) that measures the current and voltage on its low-voltage side, and the power on the low-voltage side of the bidirectional converter 40 is controlled to be a set value. Furthermore, in the illustrated system 1, the open circuit voltage of the solar cell 10 is set so as not to exceed the allowable voltage of the auxiliary battery 20.

[0044] In the illustrated system 1, the controller 50 controls the passing power of the bidirectional converter 40 based on data obtained from the voltage sensor 11, the current sensor 12, the temperature sensor 13, and the solar radiation sensor 14, thereby controlling the voltage of the auxiliary battery 20 and controlling the power generated by the solar cell 10.

[0045] More specifically, the controller 50 includes a first control unit 51, a second control unit 52, and a third control unit 53.

[0046] The first control unit 51 switches to a low-voltage battery discharge mode in which the bidirectional converter 40 is operated and the auxiliary battery 20 is charged by the solar cell 10 when the voltage value of the auxiliary battery 20 exceeds a predetermined upper limit voltage value in a low-voltage battery charging mode in which the bidirectional converter 40 is stopped and the auxiliary battery 20 is charged. When the voltage value of the auxiliary battery 20 exceeds a predetermined upper limit voltage value in the discharge mode, the first control unit 51 switches to a low-voltage battery discharge mode in which the bidirectional converter 40 is operated and the drive battery 30 is charged by the auxiliary battery 20.

[0047] The second control unit 52 operates the bidirectional converter 40 and controls it so as to keep the voltage value of the auxiliary battery 20 within a certain range.

[0048] The third control unit 53 calculates a passing power target value, which is the power that needs to pass through the bidirectional converter 40, from a time ratio target value for reducing the time ratio of the discharge mode, calculates a switchover operating voltage range target value of the auxiliary battery 20 for reducing the switching frequency from the passing power target value and a switching frequency target value for reducing the switching frequency between the discharge mode and the charge mode, and switches the operation of the first control unit 51 to the operation of the second control unit 52 when the switchover operating voltage range target value is greater than a predetermined voltage range upper limit value of the auxiliary battery 20.

[0049] Next, the advantages of this embodiment will be described. According to this embodiment, the controller 50 includes a first control unit 51 that switches between the above-mentioned low-voltage battery charging mode and low-voltage battery discharging mode, a second control unit 52 that controls the bidirectional converter 40 to keep the voltage value of the auxiliary battery 20 within a certain range, and a third control unit that switches the operation of the first control unit 51 to the operation of the second control unit 52 when the switching operation voltage range target value is greater than the upper limit value of the predetermined voltage range of the low-voltage battery 20. This makes it possible to control the power generation of the solar cell, and has the advantage of suppressing or preventing a voltage drop in the low-voltage battery. In addition, the time ratio of the discharge mode and the switching frequency are reduced, which has the advantage of improving system efficiency and relay durability. Furthermore, the use of a DCDC bidirectional converter has the secondary advantage of simplifying the circuit configuration.

[0050] Next, the operation of the solar cell system to be mounted on a vehicle according to this embodiment will be described with reference to FIGS.

[0051] As shown in Fig. 5, the solar cell system mounted on a vehicle of this embodiment switches between a first control process (A: ONOFF operation, B: ONOFF operation, C: ONOFF operation, and D: ONOFF operation) for switching between a charge mode and a discharge mode, and a second control process (E: continuous operation) for controlling the voltage value of the low-voltage battery to be kept within a certain range. In the ONOFF operations A to D shown in Fig. 5, the solar cell voltage and the solar cell current have a relationship as shown in Fig. 6, for example.

[0052] <A:ON / OFF Operation> As shown in FIGS. 7 and 8, in step 101 (hereinafter referred to as "S101"), the average value V of the photovoltaic cell voltage PV_A is obtained. In S102, the average value I of the photovoltaic cell current PV_A is obtained. In S103, the average value P of the photovoltaic cell power is calculated and obtained from the average value V of the photovoltaic cell voltage PV_A and the average value I of the photovoltaic cell current PV_A PV_A In S104, the target value T of the ratio for reducing the ratio of the discharge mode (driving battery ON) Off is obtained. Note that the target value T of the ratio Off is stored in the controller in advance. In S105, using the following formula, the target value P of the passing power, which is the power that needs to pass through the bidirectional converter to achieve the target value T of the ratio for reducing the ratio of the discharge mode (driving battery ON) Off is calculated and obtained. CT

[0053] P CT = P PV_A / (1 - T Off )

[0054] In S106, the upper limit value P of the power of the bidirectional converter CM is obtained. In S107, it is determined whether the target value P of the passing power CT is less than or equal to the upper limit value P of the power of the bidirectional converter CM . If Yes, proceed to S108; if No, proceed to S109. In S108, the target value P of the passing power of the bidirectional converter C is set to P CT . In S109, the target value P of the passing power of the bidirectional converter C is set to P CM . ​​​In S110, a switching frequency target value N for reducing the switching frequency between the discharge mode (driving battery ON) and the charge mode (driving battery OFF) is set. PV The target switching frequency N PV is stored in advance in the controller 11. In S111, the energy value E per voltage difference of the low-voltage battery ΔV The energy value per voltage difference of the low-voltage battery E ΔV is stored in advance in the controller. In S112, the target switching frequency N between the discharge mode (driving battery ON) and the charge mode (driving battery OFF) is calculated using the following formula: PV To achieve the target voltage range ΔV for low-voltage battery switching operation N1 Calculate and obtain.

[0055] ΔV N1 =P PV_A / (E ΔV ×N PV )×(1-P PV_A / P C )

[0056] In S113, the switching frequency target value N PV To achieve the upper limit of the switching voltage range for low-voltage batteries, ΔV M The upper limit of the switching voltage range ΔV M is stored in advance in the controller. In S114, the switching operation voltage range target value ΔV N1 is the upper limit of the switching voltage range ΔV M If it is Yes, proceed to S115, and if it is No, proceed to S501 (continuous operation). In S115, the internal resistance value R of the low-voltage battery is obtained. The internal resistance value R of the low-voltage battery is stored in advance in the controller. In S116, the voltage range target value ΔV is calculated using the following formula: N Calculate and obtain.

[0057] ΔV N =PC ×R / V PV_A +ΔV N1

[0058] In S117, the solar cell temperature value T S Get the. In S118, a solar radiation value I is acquired from the solar radiation sensor. In S119, the solar radiation value I and the solar cell temperature value T S From the optimum operating point voltage value V MPP Here, the relationship between the amount of solar radiation I and the optimal operating point voltage at each solar cell temperature is shown in Figure 9. This relationship is obtained in advance by a preliminary test or the like and stored in the controller in advance. In S120, the predetermined upper limit voltage value V UL Calculate and obtain.

[0059] V UL =V MPP +1 / 3×ΔV N

[0060] In addition, ΔV N The coefficient 1 / 3 multiplied by is given as an example of a coefficient for preventing the power value during switching operation from decreasing significantly from the optimal operating point power value, and other numbers may also be used.

[0061] In S121, another predetermined lower limit voltage value V LL2 In addition, other predetermined lower limit voltage values ​​V LL2 is stored in advance in the controller. In S122, the solar cell voltage value V PV Get the. In S123, the solar cell voltage value V PV is another predetermined lower limit voltage value V LL2 If the answer is Yes, the process proceeds to S124, and if the answer is No, the process proceeds to S501 (continuous operation). In S124, the solar cell voltage value V PV is the upper limit voltage V ULDetermine whether it is the above. If Yes, proceed to S125; if No, proceed to S122. In S125, update the interval average values V PV_A , I PV_A , P PV_A of the solar cell current, voltage, and power during the A interval, and proceed to S201 (B: ONOFF operation).

[0062] <B: ONOFF operation> As shown in FIGS. 10 and 11, since the content of S201 to S219 is the same as that of S101 to S119 described above, detailed description is omitted. In S220, turn on the switch. In S221, control the power value of the bidirectional converter to the power target value P C0 . In S222, obtain the solar cell voltage value V PV from the voltage sensor. In S223, determine whether the solar cell voltage value V PV is less than or equal to the optimal operating point voltage value V MMP . If Yes, proceed to S224; if No, proceed to S222. In S224, update the interval average values V PV_A , I PV_A , P PV_A of the solar cell current, voltage, and power during the B interval, and proceed to S301 (C: ONOFF operation).

[0063] <C: ONOFF operation> As shown in FIGS. 12 and 13, since the content of S301 to S319 is the same as that of S101 to S119 described above, detailed description is omitted. In S320, calculate and obtain the predetermined lower limit voltage value V LL1 using the following formula.

[0064] V LL1 = V MPP - 2 / 3 × ΔV N

[0065] Note that ΔV NThe coefficient 2 / 3 applied is an example of a coefficient for preventing the power value during the switching operation from significantly decreasing compared to the optimal operating point power value, and there is no problem even with other numbers. In S321, control the power value of the bidirectional converter to the power target value P C0 thereof. In S322, obtain the solar cell voltage value V PV from the voltage sensor. In S323, determine whether the solar cell voltage value V PV is less than or equal to a predetermined lower limit voltage value V LL1 or not. If Yes, proceed to S324; if No, proceed to S322. In S324, turn off the switch. In S325, update the interval average values V PV_A , I PV_A , P PV_A of the solar cell current, voltage, and power during the C interval, and proceed to S401 (D: ONOFF operation).

[0066] <D: ONOFF operation> As shown in FIGS. 14 and 15, since S401 to S419 have the same content as S101 to S119 described above, detailed description thereof is omitted. In S420, obtain the solar cell voltage value V PV from the voltage sensor. In S421, determine whether the solar cell voltage value V PV is greater than or equal to the optimal operating point voltage value V MPP or not. If Yes, proceed to S422; if No, proceed to S420. In S422, update the interval average values V PV_A , I PV_A , P PV_A of the solar cell current, voltage, and power during the D interval, and proceed to S101 (A: ONOFF operation).

[0067] <E: Continuous operation> As shown in FIGS. 16 and 17, in S501, turn on the switch (if it is originally in the ON state, continue as it is). In S502, the continuous time T CReset and T C Start counting. Since the contents of S503 to S506 are the same as those of S417 to S420 described above, detailed explanations will be omitted. In S507, the solar cell voltage value V PV is the optimum operating point voltage value V MPP The power value of the bidirectional converter is controlled so that In S508, the duration T C is the duration target value T C0 If it is Yes, proceed to S509, and if it is No, proceed to S502. C0 is stored in advance in the controller. In S509, the duration target value T C0 Average value of solar cell current, voltage, and power during the period V PV_A , I PV_A , P PV_A Update. Since the contents of S510 to S522 are the same as those of S101 to S113 described above, detailed explanations will be omitted. In S523, the switching operation voltage range target value ΔV N1 is the upper limit of the switching voltage range ΔV M If the answer is Yes, the process proceeds to S524, and if the answer is No, the process proceeds to S501 (continuous operation). In S524, the switch is turned OFF, and the process proceeds to S101 (A: ON / OFF operation).

[0068] Although the present invention has been described above with reference to some embodiments, the present invention is not limited to these, and various modifications are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0069] 1. Vehicle-mounted solar cell system 10. Solar Cells 11 Voltage Sensor 12 Current Sensor 13 Temperature Sensor 14 Solar radiation sensor 15 Reverse current prevention diode 20 Auxiliary battery (low voltage battery) 30 Drive battery (high voltage battery) 40 Bidirectional converter (power conversion device) 50 Controller 51 First Control Section 52 Second Control Section 53 Third Control Section 60 Switch 70 Electronic equipment 80 Motor / Inverter

Claims

1. A method for controlling a solar cell system mounted on a vehicle, the solar cell system including a solar cell, a low-voltage battery, a high-voltage battery, and a power conversion device that converts power bidirectionally between the low-voltage battery and the high-voltage battery, the method comprising the steps of: a first control process including a low-voltage battery charging mode in which the power conversion device is stopped and the low-voltage battery is charged by the solar cell, and a low-voltage battery discharging mode in which the power conversion device is operated and the high-voltage battery is charged by the low-voltage battery, the first control process switching to the discharging mode when the voltage value of the low-voltage battery exceeds a predetermined upper limit voltage value in the charging mode, and switching to the charging mode when the voltage value of the low-voltage battery falls below a predetermined lower limit voltage value in the discharging mode; a second control step of operating the power conversion device and controlling the voltage value of the low-voltage battery to be kept within a certain range; the first control step is a calculation step of calculating a passing power target value, which is power that needs to pass through the power conversion device, from a time ratio target value for reducing a time ratio of the discharging mode, and calculating a switching operating voltage range target value of the low-voltage battery for reducing a switching frequency from the passing power target value and a switching frequency target value for reducing a switching frequency between the discharging mode and the charging mode; a switching step of switching the first control step to the second control step when the switching operating voltage range target value is greater than a predetermined voltage range upper limit value of the low voltage battery.

23. A method for controlling a vehicle-mounted solar cell system comprising:

2. When the voltage value of the solar cell falls below another predetermined lower limit voltage value that is smaller than the predetermined lower limit voltage value, the first control process is switched to the second control process.

2. A method for controlling a vehicle-mounted solar cell system according to claim 1.

3. 2. The control method for a vehicle-mounted solar cell system according to claim 1, wherein the passing power target value is set to be greater than (power value of the solar cell) / [1-(the time ratio target value)].

4. The control method for a vehicle-mounted solar cell system according to claim 1, characterized in that the switching operation voltage range target value is set to be greater than (power value of the solar cell) / [(energy value per voltage difference of the low-voltage battery)×(switching frequency target value)]×[1-(power value of the solar cell) / (passing power target value)].

5. The control method for a vehicle-mounted solar cell system according to claim 1, characterized in that (the specified upper limit voltage value) - (the specified lower limit voltage value) is greater than (the passing power target value) x (the internal resistance value of the low-voltage battery) / (the voltage value of the low-voltage battery) + (the switching operation voltage range target value).

6. 2. The method for controlling a solar cell system mounted on a vehicle according to claim 1, wherein the first control step is executed only while the vehicle is stopped.

7. 2. The control method for a solar cell system mounted on a vehicle according to claim 1, characterized in that, when switching from the first control process to the second control process, a determination is made using average values ​​of the current, voltage and power of the solar cell calculated by dividing a single switching control for switching between the discharge mode and the charge mode into two or more sections.

8. A solar cell system for mounting on a vehicle, comprising a solar cell, a low-voltage battery, a high-voltage battery, a power conversion device for converting power bidirectionally between the two batteries, and a control device, a first control unit that switches the control device to a low-voltage battery discharge mode in which the control device operates the power conversion device and charges the high-voltage battery with the low-voltage battery when a voltage value of the low-voltage battery exceeds a predetermined upper voltage value in a low-voltage battery charge mode in which the control device stops operation of the power conversion device and charges the low-voltage battery with the solar cell, and switches the control device to the charge mode when a voltage value of the low-voltage battery falls below a predetermined lower voltage value in the discharge mode; A second control unit that operates the power conversion device and controls the voltage value of the low-voltage battery to be kept within a certain range; a third control unit that calculates a passing power target value, which is power that needs to be passed through the power conversion device, from a time ratio target value for reducing the time ratio of the discharging mode, calculates a switchover operating voltage range target value of the low-voltage battery for reducing the switching frequency from the passing power target value and a switching frequency target value for reducing the switching frequency between the discharging mode and the charging mode, and switches the operation of the first control unit to the operation of the second control unit when the switchover operating voltage range target value is greater than a predetermined voltage range upper limit value of the low-voltage battery.

1. A vehicle-mounted solar cell system.

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