SOC control unit

Abstract

To provide an SOC controller capable of achieving both high fuel consumption performance and high power performance while avoiding temperature rise in a fuel cell (FC) in an FC system equipped with the FC and a secondary battery (BAT).SOLUTION: An SOC controller includes: a request power calculation device calculating request power P_req(i) with respect to an FC system at a time i; and an SOC lower limit change device changing a position and / or inclination of a forced charge line of a BAT charge / discharge control map in accordance with the P_req(i) or a physical quantity Q_req(i) capable of calculating the same. The SOC lower limit change device is provided with: a first change device which changes the position and / or inclination of the forced charge line so that the BAT can be discharged more when the P_req(i) is equal to or greater than a first threshold ε1; and a second change device which changes the position and / or inclination of the forced charge line so that the BAT can be charged more when the P_req(i) is below a second threshold ε2(≤ε1).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a SOC control device, and more particularly, to a SOC control device for controlling the state of charge (SOC) of a secondary battery in a fuel cell system including a fuel cell (FC) that generates power and a secondary battery (BAT) that stores surplus power.

Background Art

[0002] A hybrid vehicle refers to an automobile having two or more power sources (for example, a fuel cell and a secondary battery). Since a hybrid vehicle can selectively use power sources according to the situation, it has the characteristic of higher fuel efficiency than a normal vehicle having one power source. However, in a hybrid vehicle, in order to further improve the fuel efficiency, it is necessary to appropriately perform power distribution of the power sources according to the situation.

[0003] In the case of a hybrid vehicle equipped with a secondary battery as one of the power sources, usually, power distribution is performed so as to achieve the highest efficiency. However, when power distribution is performed with priority given to efficiency, the state where the state of charge (SOC) of the secondary battery is at the SOC upper limit value or the SOC lower limit value may continue. Therefore, there may be a case where the necessary power cannot be supplied when power supply from the secondary battery is required, or regenerative energy cannot be absorbed when absorption of regenerative energy is required.

[0004] Therefore, various proposals have been made conventionally to solve this problem. For example, in Patent Document 1, (a) When the SOC of the battery is lower than the lower limit value α, the SOC is increased by charging the battery while operating the engine at a power higher than the power required for running, (b) When the SOC is between the lower limit value α and the upper limit value β, the secondary battery power is utilized during light load, and the engine power is utilized for running during medium and high loads, and the SOC of the battery is allowed to change as it is, (c) If the SOC exceeds the upper limit β, the engine will be operated at a lower power than required for driving, while power will be supplied from the battery to the motor to reduce the SOC. A method for controlling the charging of hybrid vehicles has been disclosed.

[0005] The document states: (A) If the battery's SOC is higher than the target SOC, continuous discharge is performed, and if it is lower than the target SOC, continuous charging will lead to a deterioration in fuel efficiency, and (B) By introducing a dead zone (the region between α and β) in the battery's SOC correction, the deterioration of engine fuel efficiency can be suppressed. It is stated.

[0006] Patent Document 2 contains: (a) When the state of charge (SOC) of the battery is less than the threshold S1, the battery is charged in proportion to the SOC, regardless of the vehicle's speed. (b) When the SOC is greater than or equal to the threshold S1, and the vehicle is traveling at a high speed, the slope of the correction power Pchg with respect to the SOC is increased so that a larger amount of power is discharged from the battery as the SOC increases. (c) When SOC is greater than or equal to threshold S1, and the vehicle's speed is slow, the slope of Pchg with respect to SOC is reduced. A control method for hybrid vehicles has been disclosed.

[0007] The document states: (A) If the slope of Pchg with respect to SOC during discharge is kept constant, the SOC will remain high during high-speed driving due to the large regenerative power when the accelerator is released, which may lead to decreased fuel efficiency and reduced battery life, and, (B) By changing the slope of Pchg relative to SOC according to the driving speed, the battery discharges quickly during high-speed driving, which can suppress the SOC from remaining high. It is stated.

[0008] Patent documents 1 and 2 disclose a method for controlling the BAT charge / discharge power Pchg in a hybrid vehicle equipped with an engine and a secondary battery (i.e., a method of increasing or decreasing the engine power beyond the required power depending on the magnitude of the load, and absorbing excess or insufficient power by charging or discharging the secondary battery). Similar Pchg control can be applied to hybrid vehicles equipped with fuel cells and secondary batteries. However, engines are most efficient in high-load conditions, while fuel cells are most efficient in low-load conditions. Furthermore, continuous use of fuel cells at high loads can cause them to overheat, leading to fuel cell failure and / or degradation. Therefore, Pchg control applied to hybrid vehicles with engines cannot be directly applied to hybrid vehicles with fuel cells.

[0009] Furthermore, in hybrid vehicles equipped with fuel cells and secondary batteries, the output capacity of the fuel cell may be reduced in order to miniaturize and reduce the cost of the system. In this case, it may be difficult for the fuel cell alone to handle high-load driving, so it is necessary to utilize the secondary battery as well during high-load driving to ensure the required power performance. In addition, by sharing the load between the fuel cell and secondary battery during high-load driving, it is also possible to avoid overheating of the fuel cell. However, simply relying on the State of Charge (SOC) for Pchg control may result in temporary drops in the secondary battery's SOC. In such cases, when a high load is required, it becomes impossible to properly share the load between the fuel cell and the secondary battery. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 11-299004 [Patent Document 2] Japanese Patent Publication No. 2010-155512 [Overview of the project] [Problems that the invention aims to solve]

[0011] The problem that this invention aims to solve is to provide a State of Charge (SOC) control device that can achieve both high fuel efficiency and high power performance in an FC system equipped with a fuel cell (FC) and a secondary battery (BAT) while avoiding high temperatures of the FC. Another problem that the present invention aims to solve is to provide a State of Control (SOC) control device that can guarantee the maximum power performance of the FC system for a certain period of time in an FC system in which the output capacity of the FC is set lower than the maximum output of the system. [Means for solving the problem]

[0012] To solve the above problems, the SOC control device according to the present invention has the following configuration. (1) The SOC control device is used in an FC system including a fuel cell (FC) and a secondary battery (BAT) to control the state of charge (SOC) of the BAT. (2) The SOC control device is A power requirement calculation device that calculates the required power P_req(i) for the FC system at time i, or obtains a physical quantity Q_req(i) that can calculate P_req(i), A SOC lower limit changing device that changes the position and / or inclination of the forced charging line of the BAT charge / discharge control map used to control the SOC in accordance with the P_req(i) or Q_req(i) It is equipped with. (3) The FC system includes a hybrid system installed in an FC vehicle powered by the FC and the BAT, The Q_req(i) includes the accelerator opening A_req(i) at time i, and the speed v(i) of the FC vehicle at time i.

[0013] The SOC lower limit changing device is, When the P_req(i) is greater than or equal to the first threshold value ε1 (or exceeds the ε1), or in a corresponding case, a first changing device that changes the position and / or inclination of the forced charging line so that more discharging is possible from the BAT; When the P_req(i) is less than the second threshold value ε2 (≤ε1) (or is less than or equal to the ε2), or in a corresponding case, a second changing device that changes the position and / or inclination of the forced charging line so that more charging is possible for the BAT; It is preferable to be provided with.

Advantages of the Invention

[0014] When the required power P_req(i) at time i is at a high load, if the position and / or inclination of the forced charging line of the BAT charge / discharge control map (Pchg map) is changed so that more discharging is possible from the BAT, the high load can be appropriately shared between the BAT and the FC. Therefore, the frequency of operating only the FC at a high load for a long time is reduced, and the failure or deterioration of the FC can be suppressed.

[0015] On the other hand, when P_req(i) is at a low load, if the position and / or inclination of the forced charging line is changed so that more charging is possible for the BAT, the power required from the BAT when a high load is required can be supplied. Therefore, appropriate load sharing is possible, high fuel efficiency performance and high power performance can be achieved simultaneously, and the overheating of the FC can also be avoided. Also, even when the output capacity of the FC is set lower than the maximum output of the system, the maximum power performance as an FC system can be ensured for a certain period of time.

Brief Description of the Drawings

[0016] [Figure 1] It is a schematic diagram of the BAT charge / discharge control map (Pchg map). [Figure 2] It is a schematic diagram of a method for changing the position of the forced charging line. [Figure 3] It is a schematic diagram of a method for changing the inclination of the forced charging line. [Figure 4] This is a flowchart of the control method for the BAT charge / discharge control map (Pchg map) according to the first embodiment of the present invention.

[0017] [Figure 5] This is a flowchart of a control method for a BAT charge / discharge control map (Pchg map) according to a second embodiment of the present invention. [Figure 6] This is a flowchart of a control method for a BAT charge / discharge control map (Pchg map) according to a third embodiment of the present invention. [Figure 7] This is a flowchart of a control method for a BAT charge / discharge control map (Pchg map) according to a fourth embodiment of the present invention. [Modes for carrying out the invention]

[0018] One embodiment of the present invention will be described in detail below. [1. BAT Charge / Discharge Control Map (Pchg Map)] Figure 1 shows a schematic diagram of the BAT charge / discharge control map (hereinafter also referred to as the "Pchg map"). The "Pchg map" is a map used to control the charge and discharge amount of the secondary battery (BAT) according to the size of the State of Charge (SOC). In Figure 1, the horizontal axis (x-axis) represents the state of charge (SOC) of the secondary battery (BAT).

[0019] The vertical axis (y-axis) represents the correction power Pchg. The charge and discharge rates of a secondary battery are (1) From the perspective of optimizing fuel efficiency and system efficiency, (2) From the perspective of power assist utilizing secondary batteries to ensure power performance, and from the perspective of SOC control to ensure regenerative power capacity. We need to decide that first. In order to prioritize and ensure power performance over the efficiency of the fuel cell system (for example, the fuel efficiency of a hybrid vehicle), the charge and discharge amount of the BAT determined from perspective (2) must take precedence over the charge and discharge amount of the BAT determined from perspective (1). Therefore, it is preferable to select the value with the larger absolute value among the charge and discharge amounts of the BAT determined from (1) and (2). Pchg is used to determine the charge and discharge amount of the BAT from the perspective of (2). If Pchg is positive, it represents the discharge power from the BAT, and if it is negative, it represents the amount of charge to the BAT. Since the charge / discharge capacity of a battery (BAT) is finite, when the State of Charge (SOC) exceeds a certain value, Pchg becomes a positive constant value (Pmax). Similarly, when the SOC falls below a certain value, Pchg becomes a negative constant value (-Pmin).

[0020] A "forced charging line" is a line extending in the -y direction from a point on the x-axis (SOC_LB) of the Pchg map. When the SOC falls below SOC_LB, power equivalent to the Pchg on the forced charging line is charged to the BAT. Note that in Figure 1, the forced charging line is drawn as a straight line, but this is merely an example. The forced charging line may also be a curve, or a broken line with steps. The "State of Charge (SOC_LB)" refers to the intersection of the x-axis and the forced charging line. In this invention, the position of SOC_LB (i.e., the position of the forced charging line) may be variably controlled according to P_req or a physical quantity Q_req(i) from which P_req can be calculated. This point differs from the conventional invention.

[0021] The "first lower limit α1" refers to the lower limit of the operating range of SOC_LB. The value of α1 is not particularly limited. Generally, if α1 becomes too small, the battery may overcharge. On the other hand, if α1 becomes too large, the frequency of forced charging of the battery may increase, which may reduce fuel efficiency. It is preferable to select an optimal value for α1, taking these points into consideration. Although α1 depends on the type of battery, it is preferable to set it in the range of 10% to 30%.

[0022] The "second lower limit α2" refers to the upper limit of the operating range of SOC_LB. The value of α2 is not particularly limited as long as α2 > α1 is satisfied. In general, if α2 becomes too small, there may be insufficient energy for power assist during high-load driving. On the other hand, if α2 becomes too large, fuel efficiency may decrease. It is preferable to select an optimal value for α2, taking these points into consideration. Although α2 also depends on the type of BAT, it is preferable to set it in the range of 40% to 60%.

[0023] "The slope of the forced charging line" refers to, (a) When the forced charging line is a straight line, it refers to the slope of the straight line. (b) When the forced charging line is not straight, this refers to the slope of the tangent to the forced charging line at SOC_LB when the entire forced charging line is approximated by a smooth curve. In this invention, the slope of the forced charging line may be variably controlled according to P_req or a physical quantity Q_req(i) from which it can be calculated. This point differs from the conventional invention.

[0024] A "forced discharge line" is a line extending in the +y direction from a point (β) on the x-axis of the Pchg map. When the State of Charge (SOC) exceeds β, power equivalent to the Pchg on the forced discharge line is discharged from the battery (BAT). In Figure 1, the forced discharge line is depicted as a straight line, but this is merely an example. The forced discharge line may also be a curve, or a broken line with steps.

[0025] The "upper limit β" refers to the intersection point of the x-axis and the forced discharge line. In this invention, β may be fixed or variable. Furthermore, the value of β is not particularly limited. Generally, if β becomes too small, fuel efficiency may decrease. On the other hand, if β becomes too large, the battery may overcharge. It is preferable to select an optimal value for β, taking these points into consideration. β depends on the type of battery, but specifically, it is preferable to set it in the range of 60% to 90%.

[0026] The "dead zone" refers to the region between SOC_LB and β, that is, the region where Pchg remains zero even when SOC changes. In this invention, SOC_LB moves between α1 and α2. Therefore, if α2 = β, when SOC_LB reaches α2, the dead zone temporarily disappears, and fuel efficiency may decrease. For this reason, it is preferable to set α2 < β and provide a dead zone at least between α2 and β. When SOC is in the dead zone, Pchg is zero, so the charge / discharge amount of BAT becomes the value determined to maximize fuel efficiency and system efficiency (as shown in (1) above).

[0027] "The slope of the forced discharge line" refers to, (a) When the forced discharge line is a straight line, it refers to the slope of the straight line. (b) When the forced discharge line is not linear, this refers to the slope of the tangent to the forced discharge line at β when the entire forced discharge line is approximated by a smooth curve. In the present invention, the inclination of the forced discharge line may be fixed or it may be variablely controlled.

[0028] [2. SOC control device] The SOC control device according to the present invention has the following configuration. (1) The SOC control device is used in an FC system including a fuel cell (FC) and a secondary battery (BAT) to control the state of charge (SOC) of the BAT. (2) The SOC control device is A power requirement calculation device that calculates the required power P_req(i) for the FC system at time i, or obtains a physical quantity Q_req(i) that can be used to calculate P_req(i), A SOC lower limit changing device that changes the position and / or inclination of the forced charging line of the BAT charge / discharge control map used to control the SOC in accordance with the P_req(i) or Q_req(i) It is equipped with. (3) The FC system includes a hybrid system installed in an FC vehicle powered by the FC and the BAT, The Q_req(i) includes the accelerator opening A_req(i) at time i, and the speed v(i) of the FC vehicle at time i.

[0029] The SOC control device may further include an FC temperature acquisition device that acquires the temperature of the FC at time i, Temp_FC(i). In this case, the SOC lower limit changing device preferably includes a device that changes the position and / or inclination of the forced charging line in the BAT charge / discharge control map according to P_req(i) or Q_req(i) and Temp_FC(i).

[0030] [2.1. FC System] The SOC control device according to the present invention is used to control the state of charge (SOC) of a secondary battery (BAT) in an FC system comprising a fuel cell (FC) for generating electricity and a secondary battery (BAT) for storing surplus electricity. The BAT is used not only for charging and discharging but also to share a portion of P_req(i). In the present invention, the types of FC system, FC, and BAT are not particularly limited. Examples of FC systems include: (a) Hybrid systems installed in FC vehicles (e.g., passenger cars, buses, commercial vehicles, trucks, forklifts, etc.) that use FC and BAT as power sources. (b) Hybrid systems used in railways, (c) Hybrid systems used in ships, These are some examples.

[0031] The SOC control device according to the present invention is particularly preferred for controlling the SOC of an FC system in which the maximum output of the FC alone is set to be less than the maximum output required for the FC system. The SOC control device according to the present invention changes the position and / or inclination of the forced charging line according to a physical quantity Q_req(i) from which P_req(i) or Preq(i) can be calculated. Therefore, it is possible to appropriately share the load between the FC and the BAT while avoiding overheating of the FC. Furthermore, even if the output capacity of the FC is set lower than the maximum output of the system, the maximum power performance of the FC system can be guaranteed for a certain period of time.

[0032] [2.2. Required Power Calculation Device] The power requirement calculation device is a device for calculating the power requirement P_req(i) for the FC system at time i. The method for calculating P_req(i) is not particularly limited. For example, in the case of a hybrid system installed in an FC vehicle equipped with an FC and BAT, first, the accelerator opening angle operated by the driver and the speed of the FC vehicle are obtained. The method of measuring the accelerator opening angle and speed is not particularly limited. Once the accelerator opening angle and speed are known, P_req(i) can be calculated based on these values. The frequency of calculating P_req(i) is not particularly limited, and the optimal value can be selected according to the purpose.

[0033] Furthermore, the power requirement calculation device may also be a device for obtaining the physical quantity Q_req(i) from which P_req(i) can be calculated. The type of physical quantity Q_req(i) is not particularly limited, as long as it is possible to calculate P_req(i) from it (in other words, it can be considered equivalent to P_req(i)). For example, if the FC system is a hybrid system installed in an FC vehicle, the physical quantities Q_req(i) could be the accelerator opening A_req(i) at time i, the speed v(i) of the FC vehicle at time i, etc. These physical quantities Q_req(i) are positively correlated with P_req(i). Therefore, the step of calculating P_req(i) from Q_req(i) can be omitted, and the position and / or inclination of the forced charging line can be changed using the obtained Q_req(i) itself.

[0034] [2.3. FC temperature acquisition device] The FC temperature acquisition device is a device for acquiring the temperature of the FC, Temp_FC(i), at time i. The method for acquiring Temp_FC(i) is not particularly limited. "Temp_FC(i)" refers to the internal temperature of the fuel cell (FC) itself, or a temperature that can be considered equivalent to the internal temperature of the FC. Examples of temperatures that can be considered equivalent to the internal temperature of the FC include the temperature of the coolant discharged from the FC, the temperature of the coolant entering the radiator, the temperature of the coolant discharged from the radiator, and the temperature of the coolant entering the FC.

[0035] Generally, the larger P_req(i) is, the greater the load sharing of the fuel cell (FC). Also, the greater the load sharing of the FC, the higher Temp_FC(i) becomes. Therefore, when P_req(i) is large and Temp_FC(i) is high, it is preferable to control the SOC so that the load sharing of the battery (BAT) increases, thereby avoiding high temperatures for the FC. On the other hand, when Temp_FC(i) is low, there is room to increase the load sharing of the FC. Therefore, when P_req(i) is small and Temp_FC(i) is low, it is preferable to control the SOC so that the load sharing of the BAT is small and increase the SOC of the BAT.

[0036] This point is also true when using Q_req(i) for control. In other words, when the value of Q_req(i) corresponds to "P_req(i) is large", and Temp_FC(i) is high, it is preferable to control the SOC so that the load sharing of the BAT increases, thereby avoiding high temperatures of the FC. Alternatively, when the value of Q_req(i) corresponds to "P_req(i) is small", and Temp_FC(i) is low, it is preferable to control the SOC so that the load sharing of the BAT is small and increase the SOC of the BAT.

[0037] [2.4. SOC Lower Limit Adjustment Device] The SOC lower limit changing device is (a) P_req(i) or Q_req(i), or (b) P_req(i) or Q_req(i), and Temp_FC(i) Accordingly, it is a device for changing the position and / or inclination of the forced charging line in the BAT charge / discharge control map used to control the SOC. The SOC lower limit changing device may change either the position or the inclination of the forced charging line, or it may change both simultaneously.

[0038] [2.4.1. Controlling the SOC using only P_req(i) or Q_req(i)] When controlling the SOC using only P_req(i) or Q_req(i), the SOC lower limit changing device is: A first modification device that changes the position and / or inclination of the forced charging line so that more discharge from the BAT is possible when P_req(i) is equal to or greater than a first threshold ε1 (or greater than ε1) or equivalent thereto, A second modification device modifies the position and / or inclination of the forced charging line to allow more charge to the BAT when P_req(i) is less than (or less than or equal to) the second threshold ε2 (≦ε1), or equivalent thereto. It is preferable that it is equipped with [this feature].

[0039] In this invention, when we say "P_req(i) is greater than or equal to ε1 (or greater than ε1)," it means that the value on the boundary (in this case, P_req(i) = ε1) must belong to either the "true" or "false" side of the proposition. The same applies when determining the truth value of other variables. Furthermore, "the case where P_req(i) is greater than or equal to ε1" means that if P_req(i) is calculated using Q_req(i), then P_req(i) ≥ ε1 holds true. Similarly, "the case where P_req(i) is less than ε2" means that if P_req(i) is calculated using Q_req(i), then P_req(i) < ε2 holds true. In this invention, the expression "corresponding case" is used in addition to the above, but all of these mean the same as above: "when P_req(i) is calculated using Q_req(i), then a predetermined relational expression concerning P_req(i) holds true."

[0040] [A. First threshold ε1] The "first threshold ε1" refers to the threshold value of P_req(i) when changing the position and / or slope of the forced charging line to allow for more discharge from the battery. The value of ε1 is not particularly limited, and the optimal value can be selected depending on the purpose.

[0041] When P_req(i) ≥ ε1 (or P_req(i) > ε1) or equivalent, and the forced charging line is located on the high SOC side, discharge from the battery is restricted. As a result, when P_req(i) is large or equivalent, the load sharing of the fuel cell may become excessively large. Therefore, when P_req(i) is relatively large or equivalent, the forced charging line is moved to the low SOC side to encourage discharge from the battery.

[0042] Similarly, when P_req(i)≧ε1 (or P_req(i)>ε1) or equivalent, a large slope of the forced charging line makes it easier to maintain a high SOC, thus limiting discharge from the battery. Therefore, when P_req(i) is relatively large or equivalent, the slope of the forced charging line is reduced to encourage discharge from the battery.

[0043] [B. Second threshold ε2] The "second threshold ε2" refers to the threshold value of P_req(i) used when changing the position and / or slope of the forced charging line to allow more charge to be applied to the BAT. The value of ε2 is not particularly limited, and the optimal value can be selected depending on the purpose. ε2 may be the same value as ε1, or it may be a smaller value than ε1.

[0044] When P_req(i) < ε2 (or P_req(i) ≤ ε2) or equivalent, and the forced charging line is located on the low SOC side, charging to the battery is restricted. As a result, when P_req(i) increases sharply due to sudden acceleration or other reasons, the battery may not be able to supply the necessary power, and maximum output may not be achieved. Therefore, when P_req(i) is relatively small or equivalent, the forced charging line is moved to the high SOC side to encourage charging to the battery.

[0045] Similarly, when P_req(i) < ε2 (or P_req(i) ≤ ε2) or equivalent, a small slope of the forced charging line restricts charging to the battery, as this makes it easier to maintain a low SOC. Therefore, when P_req(i) is relatively small or equivalent, the slope of the forced charging line is increased to encourage charging to the battery.

[0046] [2.4.2. Controlling the SOC using P_req(i) or Q_rq(i), and Temp_FC(i)] When controlling the SOC using P_req(i) or Q_req(i) and Temp, the SOC lower limit changing device is: It is preferable to have a third modification device that changes the position and / or inclination of the forced charging line so that more discharge from the BAT is possible when P_req(i) is equal to or greater than the first threshold ε1 and Temp_FC(i) is equal to or greater than the third threshold ε3.

[0047] In addition to this, or in lieu thereof, the SOC lower limit control device is: It is preferable to have a fourth modification device that changes the position and / or inclination of the forced charging line so that more charge can be applied to the BAT when P_req(i) is less than the second threshold ε2 (≦ε1) (or ε2 or less) and Temp_FC(i) is less than the fourth threshold ε4 (≦ε3) (or ε4 or less) or equivalent.

[0048] [A. Third threshold ε3] The "third threshold ε3" refers to the threshold value of Temp_FC(i) when changing the position and / or inclination of the forced charging line to allow for more discharge from the battery. The value of ε3 is not particularly limited, and the optimal value can be selected depending on the purpose.

[0049] When P_req(i)≧ε1 (or P_req(i)>ε1) and Temp_FC(i)≧ε3 (or Temp_FC(i)>ε3), or equivalent, and the forced charging line is located on the high SOC side, discharge from the battery is restricted. As a result, when P_req(i) is large or equivalent, the load on the fuel cell may become excessively large. Furthermore, the increased load on the fuel cell may cause its temperature to rise even further. Therefore, when P_req(i) is relatively large and Temp_FC(i) is relatively high or equivalent, the forced charging line is moved to the low SOC side to encourage discharge from the battery. On the other hand, if the FC temperature is relatively low, increasing the load on the FC will not cause the FC temperature to rise excessively. In such cases, it is not necessarily required to move the forced charging line to the lower SOC side.

[0050] Similarly, when P_req(i)≧ε1 (or P_req(i)>ε1) and Temp_FC(i)≧ε3 (or Temp_FC(i)>ε3), or equivalent, and the slope of the forced charging line is large, discharge from the battery is restricted. Therefore, when P_req(i) is relatively large and Temp_FC(i) is relatively high, or equivalent, the slope of the forced charging line is reduced to encourage discharge from the battery. On the other hand, if the FC temperature is relatively low, increasing the load on the FC will not cause the FC temperature to rise excessively. In such cases, it is not necessarily required to reduce the slope of the forced charging line.

[0051] [B. Fourth threshold ε4] The "fourth threshold ε4" refers to the threshold value of Temp_FC(i) used when changing the position and / or slope of the forced charging line to allow more charge to be applied to the BAT. The value of ε4 is not particularly limited, and the optimal value can be selected depending on the purpose. ε4 may be the same value as ε3, or it may be a smaller value than ε3.

[0052] When P_req(i) < ε2 (or P_req(i) ≤ ε2) and Temp_FC(i) < ε4 (or Temp_FC(i) ≤ ε4), or when equivalent conditions are met, charging to the battery is restricted when the forced charging line is located on the low SOC side. As a result, when P_req(i) increases sharply due to sudden acceleration, etc., the battery may not be able to supply the necessary power, and maximum output may not be achieved. Therefore, when P_req(i) is relatively small and Temp_FC(i) is relatively low, or when equivalent conditions are met, the forced charging line is moved to the high SOC side to encourage charging to the battery. On the other hand, when the FC temperature is relatively high, moving the forced charging line to the higher SOC side may increase the load on the FC and further raise its temperature. In such cases, it is not always necessary to move the forced charging line to the higher SOC side.

[0053] Similarly, when P_req(i) < ε2 (or P_req(i) ≤ ε2) and Temp_FC(i) < ε4 (or Temp_FC(i) ≤ ε4), or equivalent, charging to the battery is restricted when the slope of the forced charging line is small. Therefore, when P_req(i) is relatively small and Temp_FC(i) is relatively low, or equivalent, the slope of the forced charging line is increased to encourage charging to the battery.

[0054] [2.4.3. Changing the location of the forced charging line] If the SOC lower limit changing device is a device that changes the position of the forced charging line, The first changing device preferably includes a device that moves the forced charging line toward α1 when P_req(i) is ε1 or greater (or greater than ε1) or equivalent, within a range where the lower limit of SOC (SOC_LB(i)) at time i does not fall below the first lower limit value α1. Furthermore, the second modification device preferably includes a device that moves the forced charging line toward α2 when P_req(i) is less than ε2 (≤ ε1) (or less than or equal to ε2) or equivalent, such that SOC_LB(i) does not exceed the second lower limit α2 (> α1).

[0055] When the SOC lower limit changing device is a device that changes the position of the forced charging line, and is further equipped with an FC temperature acquisition device, The third modification device preferably includes a device that moves the forced charging line toward α1 when P_req(i) is ε1 or greater (or greater than ε1) and Temp_FC(i) is ε3 or greater (or greater than ε3) or equivalent, within a range where the lower limit of SOC (SOC_LB(i)) at time i does not fall below the first lower limit value α1.

[0056] In addition to this, or in lieu thereof The fourth modification device preferably includes a device that moves the forced charging line toward α2 when P_req(i) is less than ε2 (≦ε1) (or ε2 or less) and Temp_FC(i) is less than the fourth threshold ε4 (≦ε3) (or ε4 or less), or equivalent thereto, so that SOC_LB(i) does not exceed the second lower limit α2 (>α1).

[0057] Figure 2 shows a schematic diagram of a method for changing the position of the forced charging line. In Figure 2, if light to medium load operation continues, SOC_LB is controlled to asymptotically approach the maximum value α2 (Figure 2(A)). When SOC_LB is close to α2, SOC is controlled to be greater than or equal to α2. That is, energy is stored in BAT in preparation for high load operation.

[0058] On the other hand, α1 is the minimum value of SOC_LB, and if high-load operation continues, SOC_LB asymptotically approaches α1 (Figure 2(A) → Figure 2(B) → Figure 2(C) → Figure 2(D)). When SOC_LB is close to α1, it is possible to use the battery until SOC approaches α1. In this way, by lowering SOC_LB, it becomes possible to discharge more energy from the battery. As a result, the load sharing of the fuel cell (FC) during high-load operation can be reduced, and excessive overheating of the FC can be avoided. Furthermore, even if the output capacity of the FC is set low, it becomes possible to ensure high-load operation for a certain period of time (equivalent to the energy stored in the battery).

[0059] [2.4.4. Changing the tilt of the forced charging line] If the SOC lower limit changing device is a device that changes the inclination of the forced charging line, The first modification device preferably includes a device that reduces the slope of the forced charging line in a range such that the lower limit of the SOC (SOC_LB(i)) at time i does not fall below the first lower limit value α1 when P_req(i) is ε1 or greater (or greater than ε1) or equivalent. Furthermore, the second modification device preferably includes a device that increases the slope of the forced charging line when P_req(i) is less than ε2 (≦ε1) (or ε2 or less) or equivalent, within a range where SOC_LB(i) does not exceed the second lower limit α2 (>α1).

[0060] When the SOC lower limit changing device is a device that changes the inclination of the forced charging line, and when it is further equipped with an FC temperature acquisition device, The third modification device preferably includes a device that reduces the slope of the forced charging line within a range in which the lower limit of SOC (SOC_LB(i)) at time i does not fall below the first lower limit value α1 when P_req(i) is ε1 or greater (or greater than ε1) and Temp_FC(i) is ε3 or greater (or greater than ε3) or equivalent.

[0061] In addition to this, or in lieu thereof The fourth modification device preferably includes a device that increases the slope of the forced charging line in a range in which SOC_LB(i) does not exceed the second lower limit α2 (>α1) when P_req(i) is less than ε2 (≦ε1) (or ε2 or less) and Temp_FC(i) is less than the fourth threshold ε4 (≦ε3) (or ε4 or less) or equivalent.

[0062] Figure 3 shows a schematic diagram of a method for changing the slope of the forced charging line. In Figure 3, if light to medium load operation continues, SOC_LB is fixed at α2 and the slope of the forced charging line is controlled to be at its maximum (Figure 3(A)). If SOC_LB is close to α2, SOC_LB is controlled to be greater than or equal to α2. In other words, more energy is stored in the BAT in preparation for high load operation.

[0063] On the other hand, if high-load operation continues, the slope of the forced charging line gradually decreases (Figure 3(A) → Figure 3(B) → Figure 3(C) → Figure 3(D) → Figure 3(E)). When the slope of the forced charging line is small, the SOC is less likely to exceed α2, making it possible to use the battery. Furthermore, when the slope of the forced charging line becomes zero (Figure 3(F)), SOC_LB, which was at position α2, moves to α1. In this case, it is possible to use the battery until the SOC is near α1. As a result, the load sharing of the fuel cell (FC) during high-load operation can be reduced, and excessive overheating of the FC can be avoided. Furthermore, even if the output capacity of the FC is set low, it becomes possible to ensure high-load operation for a certain period of time (equivalent to the energy stored in the battery).

[0064] [3. Flowchart] [3.1. Controlling the position of the forced charging line using P_req(i)] Figure 4 shows a flowchart of the control method for the BAT charge / discharge control map (Pchg map) according to the first embodiment of the present invention. Figure 4 is a flowchart for executing a method to control the position of the forced charging line using P_req(i).

[0065] First, in step 1 (hereinafter simply referred to as "S1"), the required power P_req(i) for the FC system at time i is calculated. For example, in the case of an FC system installed in a hybrid vehicle, as described above, the accelerator opening and the speed of the FC vehicle at time i are obtained, and P_req(i) is calculated based on these. Next, in S2, it is determined whether P_req(i) is greater than or equal to ε1. If P_req(i) is greater than or equal to ε1 (S2: YES), the process proceeds to S3.

[0066] In S3, it is determined whether SOC_LB(i) is greater than the lower limit α1. If SOC_LB(i) is not greater than α1 (S3:NO), it means that SOC_LB(i) cannot be made any smaller (Figure 2(D)). In this case, the process returns to S1 and the steps S1 to S3 described above are repeated. On the other hand, if SOC_LB(i) is greater than α1 (S3:YES), the process proceeds to S4. In S4, a predetermined difference δ1 is subtracted from SOC_LB(i), and this is taken as the charge level SOC_LB(i+1) at time (i+1), and stored in memory. Note that the magnitude of δ1 is not particularly limited, and an optimal value can be selected depending on the purpose.

[0067] Next, the process proceeds to S5. In S5, it is determined whether or not to continue control. If control is to be continued (S5: YES), the process returns to S1 and the steps S1 to S5 described above are repeated. On the other hand, if control is not to be continued (S5: NO), the control is terminated.

[0068] In S2, if P_req(i) is not greater than or equal to ε1 (S2:NO), proceed to S6. In S6, it is determined whether SOC_LB(i) is less than the upper limit α2. If SOC_LB(i) is not less than α2 (S6:NO), it means that SOC_LB(i) cannot be made any larger (Figure 2(A)). In such cases, proceed to S5 and repeat each step from S1 to S6 described above. On the other hand, if SOC_LB(i) is less than α2 (S6:YES), the process proceeds to S7. In S7, a predetermined difference δ2 is added to SOC_LB(i), and this is taken as the charge level SOC_LB(i+1) at time (i+1), and stored in memory. Note that the magnitude of δ2 is not particularly limited, and an optimal value can be selected depending on the purpose.

[0069] Next, the process proceeds to S5. In S5, it is determined whether or not to continue control. If control is to be continued (S5: YES), the process returns to S1 and the steps S1 to S7 described above are repeated. On the other hand, if control is not to be continued (S5: NO), the control is terminated.

[0070] Note that in the example shown in Figure 3, SOC_LB(i) is decreased when P_req(i) is greater than or equal to ε1, and increased when P_req(i) is less than ε1, but this is merely an example. As mentioned above, a second threshold ε2 satisfying ε2 < ε1 may also be set, and SOC_LB(i) may be increased when SOC_LB(i) < ε2 is satisfied. Furthermore, in the example shown in Figure 3, the position of SOC_LB(i) is changed according to P_req(i), but instead of P_req(i), the position of SOC_LB(i) may also be changed according to the acquired Q_req(i) value (in the above example, the accelerator opening and vehicle speed).

[0071] [3.2. Controlling the position of the forced charging line using P_req(i) and Temp_FC(i)] Figure 5 shows a flowchart of a control method for the BAT charge / discharge control map (Pchg map) according to a second embodiment of the present invention. Figure 5 is a flowchart for executing a method to control the position of the forced charging line using P_req(i) and Temp_FC(i).

[0072] First, in S11, the required power P_req(i) for the FC system at time i is calculated. Next, in S12, it is determined whether P_req(i) is greater than or equal to ε1. If P_req(i) is greater than or equal to ε1 (S12: YES), the process proceeds to S13.

[0073] In S13, it is determined whether Temp_LB(i) is greater than or equal to ε3. If Temp_LB(i) is not greater than or equal to ε3 (S13:NO), there is little risk of the FC temperature rising excessively, even if the load sharing of the FC increases. In such cases, the process returns to S11 without changing SOC_LB(i), and each step from S11 to S13 described above is repeated. On the other hand, if Temp_LB(i) is greater than or equal to ε3 (S13:YES), the process proceeds to S14.

[0074] In S14, it is determined whether SOC_LB(i) is greater than the lower limit α1. If SOC_LB(i) is not greater than α1 (S14: NO), it means that SOC_LB(i) cannot be made any smaller. In this case, the process returns to S11, and each step from S11 to S14 described above is repeated. On the other hand, if SOC_LB(i) is greater than α1 (S14: YES), the process proceeds to S15. In S15, a predetermined difference δ1 is subtracted from SOC_LB(i), and this is taken as the charge level SOC_LB(i+1) at time (i+1), and stored in memory.

[0075] Next, the process proceeds to S16. In S16, it is determined whether or not to continue control. If control is to be continued (S16: YES), the process returns to S11 and the steps S11 to S16 described above are repeated. On the other hand, if control is not to be continued (S16: NO), the control is terminated.

[0076] In S12, if P_req(i) is not greater than or equal to ε1 (S12:NO), proceed to S17. In S17, it is determined whether SOC_LB(i) is less than the upper limit α2. If SOC_LB(i) is not less than α2 (S6:NO), it means that SOC_LB(i) cannot be made any larger. In such cases, proceed to S16 and repeat each of the steps S11 to S17 described above. On the other hand, if SOC_LB(i) is less than α2 (S17:YES), proceed to S18. In S18, it is determined whether Temp_LB(i) is less than ε3. If Temp_LB(i) is not less than ε3, increasing SOC_LB(i) may cause the FC temperature to rise excessively when the load sharing of the FC increases. In such cases, proceed to S16 without changing SOC_LB(i), and repeat each step from S11 to S18 described above. On the other hand, if Temp_(i) is less than ε3, proceed to S19.

[0077] In S19, a predetermined difference δ2 is added to SOC_LB(i), and this is taken as the charge level SOC_LB(i+1) at time (i+1), and stored in memory. Next, the process proceeds to S16. In S16, it is determined whether or not to continue control. If control is to be continued (S16: YES), the process returns to S11 and the steps S11 to S19 described above are repeated. On the other hand, if control is not to be continued (S16: NO), the control is terminated.

[0078] Note that in the example shown in Figure 5, SOC_LB(i) is decreased when Temp_FC(i) is greater than or equal to ε3, and increased when Temp_FC(i) is less than ε3, but this is merely an example. As mentioned above, a fourth threshold ε4 that satisfies ε4 < ε3 may be set, and SOC_LB(i) may be increased when Temp_FC(i) < ε4 is satisfied. Furthermore, in the example shown in Figure 5, the position of SOC_LB(i) is changed according to P_req(i), but instead of P_req(i), the position of SOC_LB(i) may be changed according to the obtained value of Q_req(i).

[0079] [3.3. Controlling the slope of the forced charging line using P_req(i)] Figure 6 shows a flowchart of a control method for the BAT charge / discharge control map (Pchg map) according to a third embodiment of the present invention. Figure 6 is a flowchart for executing a method to control the slope of the forced charging line using P_req(i).

[0080] First, in S21, the required power P_req(i) for the FC system at time i is calculated. Next, in S22, it is determined whether P_req(i) is greater than or equal to ε1. If P_req(i) is greater than or equal to ε1 (S22: YES), the process proceeds to S23.

[0081] In S23, it is determined whether the slope of the forced charging line, grad_phcg(i), is greater than 0. If grad_pchg(i) is not greater than 0 (S23: NO), the forced charging line is horizontal (Figure 3(F)), meaning that grad_pchg(i) cannot be made any smaller. In this case, the process returns to S21, and each step from S21 to S23 described above is repeated. On the other hand, if grad_pchg(i) is greater than 0 (S23:YES), the process proceeds to S24. In S24, a predetermined difference δ3 is subtracted from grad_pchg(i), and this is converted to the slope grad_pchg(i+1) at time (i+1), which is then stored in memory. Note that the magnitude of δ3 is not particularly limited, and the optimal value can be selected according to the purpose.

[0082] Next, the process proceeds to S25. In S25, it is determined whether or not to continue control. If control is to be continued (S25: YES), the process returns to S21 and the steps S21 to S25 described above are repeated. On the other hand, if control is not to be continued (S25: NO), the control is terminated.

[0083] In S22, if P_req(i) is not greater than or equal to ε1 (S22:NO), proceed to S26. In S26, it is determined whether grad_pchg(i) is less than the maximum slope value grad_max. If grad_pchg(i) is not less than grad_max (S26:NO), the forced charging line is at the maximum allowable slope (Figure 3(A)), meaning that grad_pchg(i) cannot be increased any further. In such cases, proceed to S25 and repeat each step from S21 to S26 described above. On the other hand, if grad_pchg(i) is less than grad_max (S26:YES), the process proceeds to S27. In S27, a predetermined difference δ4 is added to grad_pchg(i), and this is set as the slope grad_pchg(i+1) at time (i+1), which is then stored in memory. Note that the magnitude of δ4 is not particularly limited, and an optimal value can be selected depending on the purpose.

[0084] Next, the process proceeds to S25. In S25, it is determined whether or not to continue control. If control is to be continued (S25: YES), the process returns to S21 and the steps S21 to S27 described above are repeated. On the other hand, if control is not to be continued (S25: NO), the control is terminated. In the example shown in Figure 6, the slope of the forced charge / discharge line is changed according to P_req(i), but instead of P_req(i), the slope of the forced charge / discharge line may be changed according to the acquired value of Q_req(i).

[0085] [3.4. Controlling the slope of the forced charging line using P_req(i) and Temp_FC(i)] Figure 7 shows a flowchart of a control method for the BAT charge / discharge control map (Pchg map) according to a fourth embodiment of the present invention. Figure 7 is a flowchart for executing a method to control the slope of the forced charging line using P_req(i) and Temp_FC(i).

[0086] First, in S31, the required power P_req(i) for the FC system at time i is calculated. Next, in S32, it is determined whether P_req(i) is greater than or equal to ε1. If P_req(i) is greater than or equal to ε1 (S32: YES), the process proceeds to S33.

[0087] In S33, it is determined whether Temp_LB(i) is greater than or equal to ε3. If Temp_LB(i) is not greater than or equal to ε3 (S33:NO), the process returns to S31 and repeats the steps S31 to S33 described above. On the other hand, if Temp_LB(i) is greater than or equal to ε3 (S33:YES), the process proceeds to S34.

[0088] In S34, it is determined whether grad_pchg(i) is greater than 0. If grad_pchg(i) is not greater than 0 (S34:NO), the process returns to S31, and the steps S31 to S34 described above are repeated. On the other hand, if grad_pchg(i) is greater than 0 (S34:YES), the process proceeds to S35. In S35, a predetermined difference δ3 is subtracted from grad_pchg(i), and this is taken as the slope grad_pchg(i+1) at time (i+1), and stored in memory.

[0089] Next, the process proceeds to S36. In S36, it is determined whether or not to continue control. If control is to be continued (S36: YES), the process returns to S31 and the steps S31 to S36 described above are repeated. On the other hand, if control is not to be continued (S36: NO), the control is terminated.

[0090] In S32, if P_req(i) is not greater than or equal to ε1 (S32:NO), proceed to S37. In S37, it is determined whether grad_pchg(i) is less than grad_max. If grad_pchg(i) is not less than grad_max (S37:NO), proceed to S36 and repeat the steps S31 to S37 described above. On the other hand, if grad_pchg(i) is less than grad_max (S37:YES), proceed to S38. In S38, it is determined whether Temp_LB(i) is less than ε3. If Temp_LB(i) is not less than ε3 (S38:NO), proceed to S36 and repeat the steps S31 to S38 described above. On the other hand, if Temp_(i) is less than ε3 (S38:YES), proceed to S39.

[0091] In S39, a predetermined difference δ4 is added to grad_pchg(i), and this is set as the slope grad_pchg(i+1) at time (i+1), which is then stored in memory. Next, the process proceeds to S36. In S36, it is determined whether or not to continue control. If control is to be continued (S36: YES), the process returns to S31 and the steps S31 to S39 described above are repeated. On the other hand, if control is not to be continued (S36: NO), the control is terminated. In the example shown in Figure 7, the slope of the forced charge / discharge line is changed according to P_req(i), but instead of P_req(i), the slope of the forced charge / discharge line may be changed according to the acquired value of Q_req(i).

[0092] [4. Effect] [4.1. SOC control using Pchg maps] In FC vehicles with a hybrid system consisting of an FC and a BAT, the vehicle is driven by sharing the load between the two power sources to meet the vehicle's power requirement P_req. In this case, to control the driving using both the FC and BAT, it is possible to use a BAT charge / discharge control (Pchg) map, similar to conventional hybrid systems using an engine and a BAT.

[0093] The Pchg map is used to control the load sharing of the battery (BAT) when driving with two power sources, making it dependent on the State of Charge (SOC). In hybrid vehicles using an engine, the engine's high-efficiency range lies on the higher-load side. Therefore, when the vehicle's power requirement is low, it operates in EV mode, using only the BAT. On the other hand, during high-load driving, the engine alone handles the load sharing. This type of control is implemented to improve fuel efficiency (system efficiency). Therefore, it is desirable that the battery (BAT) does not bear any load if the State of Charge (SOC) is not near its upper or lower limit during high-load driving. To achieve such characteristics, it is preferable to use a characteristic map with the widest possible dead zone in hybrid vehicles using an engine.

[0094] On the other hand, in hybrid vehicles using fuel cell (FC), unlike engines, the FC's efficiency characteristics are best suited to light loads. Therefore, it is desirable for the FC alone to handle the load during light-load driving, and for the battery (BAT) and FC to share the load during medium and high loads. However, since the available battery capacity (energy) is finite, it is impossible to continuously share the driving load during medium and high loads, where energy consumption is high, with the battery alone.

[0095] Furthermore, from a durability standpoint, the fuel cell (FC) must avoid excessively high temperatures. On the other hand, in order to miniaturize and reduce the cost of the system, the system configuration may be such that the maximum output of the FC is set lower than the maximum power required by the vehicle (system). In such cases, in addition to system efficiency, it is necessary to ensure a certain amount of BAT energy (SOC state) under light and medium load driving conditions in preparation for driving conditions that require high loads.

[0096] Therefore, in this invention, when the vehicle's power requirement is light to medium load, the State of Control (SOC) is controlled so that a certain amount of energy is secured in the Battery (BAT). Furthermore, when the vehicle's power requirement is high load, the SOC is controlled so that the load can be shared between the Fuel Cell (FC) and the Battery (BAT). Here, "high-load driving conditions" refer to conditions for high-speed driving or driving on steep inclines (uphill). It is assumed that high-load driving conditions do not continue continuously. Furthermore, it is assumed that deceleration driving and downhill driving occur after high-load driving conditions, and that even if the energy of the battery (BAT) is discharged during high-load driving, some of it is regenerated, making it possible to restore the state of charge (SOC). Furthermore, "light to medium load driving" refers to driving conditions in which the FC alone can meet the driving load, and in which the FC can generate excess power relative to the driving load. It is assumed that the surplus power generated is used to charge the BAT.

[0097] [4.2. Control of the lower limit of SOC] When controlling the state of charge (SOC) of a secondary battery (BAT) using a BAT charge / discharge control map (Pchg map), if the SOC falls below the lower limit, the output of the fuel cell (FC) is increased to greater than the required power P_req, and the surplus power generated by the FC is used to charge the BAT, thereby increasing the SOC. However, when such control is implemented, if the lower limit of the State of Charge (SOC) is fixed, the battery charge may temporarily become insufficient, and the necessary power may not be obtained from the battery. In this case, it is necessary to operate the fuel cell (FC) at a high load to obtain the necessary power, but if the FC is operated at a high load for a long period of time, there is a risk that the FC may fail or deteriorate.

[0098] In contrast, when the required power P_req(i) at time i is a high load, changing the position and / or slope of the forced charging line in the BAT charge / discharge control map (Pchg map) allows for more discharge from the BAT, thereby appropriately sharing the high load between the BAT and the fuel cell (FC). As a result, the frequency of the FC operating under high load for extended periods is reduced, suppressing FC failure or degradation.

[0099] On the other hand, if the position and / or inclination of the forced charging line is changed to allow more charge to the battery when P_req(i) is a low load, the battery can supply the necessary power when a high load is required. This enables appropriate load sharing, achieving both high fuel efficiency and high power performance, and also avoids overheating of the fuel cell (FC). Furthermore, even if the FC's output capacity is set lower than the system's maximum output, the FC system's maximum power performance can be guaranteed for a certain period of time.

[0100] Although embodiments of the present invention have been described in detail above, the present invention is not limited in any way to the above embodiments, and various modifications are possible without departing from the spirit of the present invention. [Industrial applicability]

[0101] The SOC control device according to the present invention can be used for SOC control of a hybrid vehicle equipped with a fuel cell and a secondary battery.

Claims

1. A SOC control device with the following configuration: (1) The SOC control device is used in an FC system including a fuel cell (FC) and a secondary battery (BAT) to control the state of charge (SOC) of the secondary battery (BAT). (2) The SOC control device is A device for acquiring a physical quantity Q_req(i) that can calculate the required power P_req(i) for the FC system at time i, or a device for calculating P_req(i) using the acquired Q_req(i), A lower limit SOC changing device that changes the position and / or slope of the forced charging line of the BAT charge / discharge control map used to control the state of charge (SOC) in accordance with the P_req(i) or Q_req(i) It is equipped with. (3) The FC system includes a hybrid system installed in an FC vehicle that uses the fuel cell (FC) and the secondary battery (BAT) as power sources. The Q_req(i) includes the accelerator opening A_req(i) at time i, and the speed v(i) of the FC vehicle at time i. (4) The SOC lower limit changing device is A first modification device that changes the position and / or inclination of the forced charging line so that more discharge is possible from the secondary battery (BAT) when P_req(i) is equal to or greater than a first threshold ε1 or greater than ε1, or equivalent thereto, When P_req(i) is less than or equal to the second threshold ε2 (where ε2 ≤ ε1), or equivalent thereto, a second modifying device modifies the position and / or inclination of the forced charging line to enable more charging of the secondary battery (BAT). It is equipped with.

2. The first changing device is such that the P_req(i) is the ε 1 The above or the above ε 1 If it is greater than or equivalent to this, the SOC lower limit SOC_LB(i) at time i is the first lower limit α 1 Within a range that does not fall below α, the forced charging line is set to α 1 Equipped with a device to move toward, The second changing device is such that when P_req(i) is less than ε 2 or less than or equal to ε 2 (where ε 2 ≦ ε 1 ), or in a corresponding case, the forced charging line is moved towards α 2 (where α 2 > α 1 ) within a range where the SOC_LB(i) does not exceed the second lower limit value α 2 . The device is provided with a device for moving the forced charging line towards α The SOC control device according to claim 1.

3. The first changing device is such that the P_req(i) is the ε 1 The above or the above ε 1 If it is greater than or equivalent to this, the SOC lower limit SOC_LB(i) at time i is the first lower limit α 1 The device is provided to reduce the inclination of the forced charging line within a range that does not fall below a certain value. The second changing device is such that the P_req(i) is the ε 2 Less than or the aforementioned ε 2 The following (however, ε 2 ≤ε 1 ) or equivalent thereto, if the SOC_LB(i) is the second lower limit α 2 (However, α 2 >α 1 The device includes a mechanism to increase the inclination of the forced charging line, within a range that does not exceed ) The SOC control device according to claim 1 or 2.

4. The system further includes an FC temperature acquisition device that acquires the temperature Temp_FC(i) of the fuel cell (FC) at the aforementioned time i. The SOC control device according to any one of claims 1 to 3, further comprising a device for changing the position and / or inclination of the forced charging line of the BAT charge / discharge control map in accordance with P_req(i) or Q_req(i) and Temp_FC(i).

5. The SOC lower limit changing device is such that the P_req(i) is the first threshold ε 1 The above or the above ε 1 It is greater than and the Temp_FC(i) is the third threshold ε 3 The above or the above ε 3 The SOC control device according to claim 4, further comprising a third modification device for changing the position and / or inclination of the forced charging line so that more discharge is possible from the secondary battery (BAT) when it is greater than or equivalent to this.

6. The SOC lower limit changing device is such that the P_req(i) is the second threshold ε 2 Less than or the aforementioned ε 2 The following (however, ε 2 ≤ε 1 ) and the Temp_FC(i) is the fourth threshold ε 4 Less than or the aforementioned ε 4 The following (however, ε 4 ≤ε 3 The SOC control device according to claim 4 or 5, further comprising a fourth modification device that modifies the position and / or inclination of the forced charging line so that more charge can be applied to the secondary battery (BAT) in cases where or equivalent thereto.

7. A SOC control device according to any one of claims 1 to 6, used to control the state of charge (SOC) of an FC system, wherein the maximum output of the fuel cell (FC) alone is set to be less than the maximum output required for the FC system.

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