JP6186344B2 - Control method for fuel cell system and fuel cell vehicle - Google Patents

Description

  The present invention relates to a fuel cell, a power storage device, a voltage conversion device that performs voltage conversion between a power storage device voltage as a primary side voltage and a motor drive voltage as a secondary side voltage, and the power storage device voltage is applied The present invention relates to a control method of a fuel cell system having an air pump that is driven through an air pump drive unit that supplies an oxidant gas to the fuel cell, and a fuel cell vehicle that implements the control method.

  Conventionally, as shown in FIG. 1 of Patent Document 1, for example, a boost converter is provided between an inverter that drives a drive motor and an output terminal of a fuel cell, and between the inverter and an input / output terminal of a power storage device. There is known a fuel cell vehicle equipped with a fuel cell system in which a load (the inverter and the drive motor) is driven.

  In Patent Document 1, based on the correlation between the required motor drive voltage supplied to the load from the two power sources (the fuel cell and the power storage device) and the fuel cell voltage in order to cause the load to exert a predetermined driving force. When the fuel cell voltage is higher than the motor drive required voltage, the fuel cell side is directly connected without boosting by the boost converter on the fuel cell side so as to reduce the switching loss of the boost converter on the fuel cell side. Have been disclosed (Patent Document 1, [0011], [0012]).

International Publication No. 2009/084650 Pamphlet

  Incidentally, in the fuel cell system, it is always desired to improve the efficiency of the fuel cell system.

  However, since Patent Document 1 does not disclose a technique for reducing the switching loss of the converter on the power storage device side, there is room for improvement.

  The present invention has been made in consideration of such problems, and an object of the present invention is to provide a control method for a fuel cell system and a fuel cell vehicle that can further improve the efficiency of the fuel cell system. And

  A fuel cell system according to the present invention includes a fuel cell that generates power by reacting an oxidant gas and a fuel gas to output a fuel cell voltage, a power storage device that outputs a power storage device voltage, and a motor that is driven through a motor drive unit. A voltage converter that performs voltage conversion between the power storage device voltage as a primary side voltage and a motor required voltage as a secondary side voltage that needs to be applied to the motor drive unit, and the power storage device voltage An air pump that is driven through an applied air pump drive unit and supplies the oxidant gas to the fuel cell, and a monitoring method for monitoring the SOC of the power storage device or the voltage of the power storage device. In the monitoring step, when the SOC of the power storage device is equal to or higher than a predetermined value or the power storage device voltage is higher than a predetermined voltage at which the air pump can be driven, The power consumption of the pump is substantially covered by the power storage power of the power storage device, and the power consumption of the motor is substantially covered by the power generated by the fuel cell, so that the conduction current between the power storage device and the voltage conversion device is increased. And an independent power supply step for making the value substantially zero.

  According to this invention, when the SOC of the power storage device is equal to or higher than the predetermined value or the power storage device voltage is equal to or higher than the predetermined voltage, the motor is driven by the fuel cell, and the air pump is driven independently by the power storage device. The current flowing through the voltage converter arranged between the input terminal of the motor drive unit and the power storage device can be made substantially zero (including the zero value), resulting in zero power loss in the voltage converter. As a result, the system efficiency of the entire fuel cell system can be further improved.

  In this case, an air pump required voltage calculating step for calculating an air pump required voltage that needs to be applied to the air pump drive unit according to a target generated power of the fuel cell and a required air pump required voltage are satisfied before the monitoring step. A power storage device voltage setting step for setting the power storage device voltage as described above, and charging the power storage device through the voltage conversion device with a part of the target generated power, and the power storage device voltage exceeds the air pump required voltage. When the predetermined voltage is reached, the independent power supply process can be performed more reliably by performing the independent power supply process.

  In the power storage device voltage setting step, if the required air pump voltage is less than the air pump threshold voltage that can ensure the maximum rotation speed of the air pump, the voltage is equal to or higher than the air pump threshold voltage. It is preferable to set the power storage device voltage as described above.

  According to the present invention, since the air pump threshold voltage that can cover the maximum number of revolutions of the air pump is set, drivability is not impaired even when the FC target power generation amount increases or decreases.

  The fuel cell system further includes another voltage converter that uses the fuel cell voltage as a primary side voltage and the motor required voltage as a secondary side voltage. In the independent power supply step, the motor required voltage And a voltage comparison step for comparing the fuel cell voltage, and when the voltage comparison step determines that the fuel cell voltage is higher than the motor required voltage, the other voltage conversion device To the motor through the other voltage converter in the directly connected state and the motor drive unit, and the fuel cell voltage is lower than the required voltage of the motor. If it is determined that the fuel cell voltage is present, the fuel cell voltage is boosted to the required motor voltage by the other voltage conversion device, and the generated power of the fuel cell is increased to the other voltage conversion device and the previous voltage conversion device. With the configuration as to supply to the motor through the motor drive unit, can properly control the operation of the other voltage conversion device, it is possible to improve the efficiency of the entire fuel cell system.

  Each of the above inventions is suitable for implementation in a fuel cell vehicle.

  According to this invention, when the SOC of the power storage device is equal to or higher than the predetermined value or the power storage device voltage is equal to or higher than the predetermined voltage, the motor is driven by the fuel cell, and the air pump is driven independently by the power storage device. The conduction current of the voltage converter arranged between the input terminal of the motor drive unit and the power storage device can be made substantially zero (including zero value), resulting in zero power loss in the voltage converter. Since the value becomes substantially zero, the effect that the system efficiency of the entire fuel cell system can be further improved is achieved.

1 is a schematic overall configuration diagram of a fuel cell vehicle to which a fuel cell system according to an embodiment of the present invention is applied. FIG. 2 is a schematic circuit diagram including a detailed configuration of an example of a boost converter and a step-up / down converter in the fuel cell automobile of FIG. 1. It is IV characteristic view of a fuel cell. It is a characteristic view which shows the relationship between an air pump request | requirement rotation speed and an air pump required voltage. It is a characteristic view which shows the relationship between motor request | requirement electric power and a motor required voltage. It is a timing chart used for operation | movement description of embodiment. It is a flowchart provided for operation | movement description of embodiment. It is a flowchart provided for control description of the boost converter in an independent power supply process. It is a conceptual diagram provided for operation | movement description of the comparative example of a fuel cell vehicle. FIG. 10A, FIG. 10B, and FIG. 10C are conceptual diagrams each briefly explaining the operation of the embodiment. FIG. 11A, FIG. 11B, and FIG. 11C are conceptual diagrams used for explaining the operation of the modification.

  Hereinafter, a control method for a fuel cell system according to the present invention will be described with reference to the accompanying drawings by citing preferred embodiments in relation to a fuel cell vehicle that implements the control method.

  FIG. 1 schematically shows a fuel cell vehicle 10 (hereinafter referred to as “FC vehicle 10” or “vehicle 10”) to which a fuel cell system 12 (hereinafter referred to as “FC system 12”) according to this embodiment is applied. FIG.

  FIG. 2 is a fuel cell side converter disposed between the primary side 1sf and the secondary side 2s side and is a chopper type boost converter 21 (hereinafter referred to as SUC21) as a first voltage converter (booster). SUC: Step Up Converter) and a chopper-type bidirectional buck-boost as a second voltage converter (buck-boost) that is a power storage device side converter disposed between the primary side 1sb and the secondary side 2s side 1 is a schematic circuit diagram of an FC automobile 10 including a detailed configuration of an example of a converter 22 (hereinafter referred to as SUDC 22; SUDC: Step Up / Down Converter).

  As shown in FIGS. 1 and 2, the FC automobile 10 includes an FC system 12, a drive motor 14 that is a motor / generator for running a vehicle, and a load drive circuit (motor drive unit) that drives the drive motor 14. And an inverter 16 (hereinafter referred to as “INV16”; INV: Inverter).

  The FC system 12 is basically a high voltage that is a fuel cell 18 (hereinafter referred to as “FC18”) disposed on one primary side 1sf and a power storage device disposed on the other primary side 1sb. The battery 20 (hereinafter referred to as “BAT 20”), the SUC 21, the SUDC 22, the air pump unit 40 with the primary voltage V1 input, and the electronic control device 24 (hereinafter referred to as “ECU 24” as a control device; ECU: Electronic Control Unit).

  The air pump unit 40 includes an air pump (A / P) 31 that pumps air to the FC 18, an air pump motor 29 that rotates a fan of the air pump 31, and an air pump inverter 23 that serves as an air pump driving unit that drives the air pump 31 through the air pump motor 29. It consists of.

  The output end of the FC 18 is connected to the input end (primary side 1sf) of the SUC 21, and the output end (secondary side 2 s) of the SUC 21 is connected to one end (boost end side) side of the INV 16 and SUDC 22.

  The DC end side of the air pump inverter 23 and the input / output end of the BAT 20 are connected to the other end side (step-down end side) of the SUDC 22 via a contactor 33 that is switched on and off (closed and open) by the ECU 24. Is done. The primary side voltage V1, that is, the power storage device voltage (BAT voltage) Vbat is applied to the air pump inverter 23 as the air pump drive voltage Vap.

  The input / output terminal of the BAT 20 is connected to a low voltage battery such as + 12V, a low voltage auxiliary machine such as the ECU 24 and a light through a step-down converter (not shown).

  The drive motor 14 generally includes FC generated power (FC power) Pfc (Pfc = Vfc × Ifc) supplied from the FC 18 and BAT discharge power Pbatd (Pbatd = Vbat × Ibd) which is stored power supplied from the BAT 20. ) Is supplied through the INV 16 to generate a driving force, and the wheels 28 are rotated through the transmission 26 by the driving force.

  As will be described in detail later, in this embodiment, an independent power supply process is provided for controlling the fuel cell system 12 so that the BAT discharge power Pbatd supplied from the BAT 20 to the INV 16 through the SUDC 22 becomes Pbatd = 0 [kW]. ing.

  The INV 16 has, for example, a three-phase full-bridge configuration, performs DC / AC conversion, and converts the secondary voltage V2 that is the DC voltage obtained by boosting the FC voltage Vfc from the FC 18 via the SUC 21 to the three-phase AC voltage. And converted to (i) and supplied to the drive motor 14 (during power running).

  In this embodiment, the INV 16 and the drive motor 14 are collectively referred to as a load 30. In practice, in addition to the load 30, the load includes the air pump unit 40, an air conditioner (not shown), and the low-pressure auxiliary device described above.

  On the other hand, the secondary side voltage (DC side voltage) V2 generated on the secondary side 2s of the input end (DC side) of the INV 16 after AC / DC conversion accompanying the regeneration operation of the drive motor 14 operates as a step-down converter. The BAT voltage Vbat is stepped down through the SUDC 22 and supplied to the BAT 20, or the SUDC 22 is directly connected (switching element 22b: off, switching element 22d: on) and supplied to the BAT 20, and charges the BAT 20.

  In addition, when the SOC (State Of Charge) that is the remaining capacity of the BAT 20 falls below the lower remaining capacity threshold value SOCth1 of SOC = about 40 [%] (or about 50 [%]), the BAT 20 The surplus power of the power for driving the drive motor 14 by the FC 18 is supplied through the SUC 21 and the SUDC 22 until the upper remaining capacity threshold value SOCth2 of SOC = 50 [%] (or 60 [%]) is reached, and the BAT 20 is charged. Is done.

  The air pump inverter 23 as an air pump drive unit converts the air pump drive voltage Vap into a three-phase AC voltage and drives the air pump motor 29. The air pump 31 driven by the output of the air pump motor 29 supplies compressed air (oxidant gas) containing oxygen from the channel inlet to the cathode channel (not shown) of the FC 18 by rotating the fan. To do.

  Furthermore, a hydrogen tank 37 for supplying hydrogen (fuel gas) to the anode flow path (not shown) of the FC 18 is provided outside the FC 18. Hydrogen and oxidant gas are referred to as reaction gases, respectively.

  The FC 18 has, for example, a stack structure in which fuel cell cells (hereinafter referred to as “FC cells”) formed by sandwiching an electrolyte membrane between an anode electrode and a cathode electrode from both sides, and through the anode flow path. The hydrogen-containing gas supplied to the anode electrode is hydrogen ionized on the electrode catalyst, moves to the cathode electrode through the electrolyte membrane, and electrons generated during the movement are taken out to an external circuit, It is used as electrical energy for generating a DC voltage (FC voltage Vfc). Since the oxidant gas (oxygen-containing gas) is supplied to the cathode electrode via the cathode channel, hydrogen ions, electrons, and oxygen gas react to generate water at the cathode electrode. .

  By generating water, the electrolyte membrane can be kept in a wet state, that is, a membrane moisture content (membrane humidity) can be kept high, and the reaction can be performed smoothly.

  The BAT 20 is a power storage device (energy storage) including a plurality of battery cells, and for example, a lithium ion secondary battery, a nickel hydrogen secondary battery, or the like can be used. A capacitor can also be used as the power storage device. In this embodiment, a lithium ion secondary battery is used. In the BAT 20, the BAT voltage (battery voltage) Vbat, the BAT current (battery current) Ib (discharge current Ibd, charging current Ibc), the BAT temperature (battery temperature), and the SOC that is the remaining capacity of the BAT 20 are detected or managed by the ECU 24. The

  The SUC 21 and the SUDC 22 can adopt various configurations, but as is well known, they are basically composed of switching elements such as MOSFETs and IGBTs, diodes, reactors, and capacitors (including smoothing capacitors). Based on the required power of the connected load, the ECU 24 performs on / off switching control (duty control) by the ECU 24.

  Specifically, as shown in FIG. 2, the SUC 21 is disposed between a reactor (inductor) 21a, a switching element 21b, a diode 21c (unidirectional current passing element, reverse current blocking element), and a primary side 1sf. The switching element 21b is switched to the switching state (duty control) through the ECU 24 that functions as a converter controller, and is configured to include the FC voltage. Vfc is boosted to a predetermined secondary voltage V2.

  When the duty (drive duty) is set to 0 [%] and the switching element 21b is maintained in the off state (open state), the FC 18 and the load 30 are directly connected (FC directly connected state) through the reactor 21a and the diode 21c. The FC voltage Vfc is directly connected to the secondary side voltage V2 (V2 = Vfc−Vd≈Vfc, Vd << Vfc, Vd: forward drop voltage of the diode 21c). The diode 21c operates for boosting or direct coupling and for preventing backflow. Accordingly, the SUC 21 performs a backflow prevention operation and a direct connection operation (such as during power running) in addition to the boost operation (such as during power running).

  On the other hand, as shown in FIG. 2, the SUDC 22 is disposed between the reactor 22a, the switching elements 22b and 22d, the diodes 22c and 22e connected in parallel to the switching elements 22b and 22d, respectively, and the primary side 1sb. And a smoothing capacitor C2b disposed between the secondary sides 2s.

  During boosting, the ECU 24 turns off the switching element 22d and switches (duty control) the switching element 22b, thereby boosting the BAT voltage Vbat (power storage device voltage) to a predetermined secondary voltage V2 (powering). Time).

  At the time of step-down, the ECU 24 turns off the switching element 22b and switches (duty control) the switching element 22d, so that the diode 22c functions as a flywheel diode when the switching element 22d is off. The secondary voltage V2 is stepped down to the BAT voltage Vbat of the BAT 20 (at the time of regenerative charging and / or charging by the FC 18).

  Further, the BAT 20 and the load 30 are directly connected (the BAT directly connected state or the BATVCU) by setting the switching element 22b to an off state with a duty of 0 [%] and the switching element 22d to an on state with a duty of 100 [%]. It is referred to as a directly connected state (powering, charging, or driving an auxiliary load).

  In the BAT direct connection state, the BAT voltage Vbat of the BAT 20 becomes the secondary side voltage V2 (Vbat≈V2). Actually, the secondary side voltage V2 during power running by the BAT 20 in the BAT direct connection state becomes “Vbat−forward drop voltage of the diode 22e”, and the secondary side voltage V2 during charging (including during regenerative charging) is “Vbat”. = V2-ON voltage of the switching element 22d = Vbat (assuming that the ON voltage of the switching element 22d is 0 [V]).

  For the switching elements 21b, 22b, and 22d, a power element such as an IGBT is used in addition to the illustrated MOSFET.

  In the FC system 12, although not shown, the DC voltage of the SUC 21 or SUDC 22 when the SUC 21 is directly connected (consent with the direct connection of the FC 18) or when the SUDC 22 is directly connected (during powering) (with the direct connection of the BAT 20). In order to reduce the descent, a diode having an anode terminal connected to the primary side 1sf of the SUC 21 and a cathode terminal connected to the secondary side 2s and / or an anode terminal connected to the primary side 1sb of the SUDC 22 and the secondary side 2s A diode having a cathode terminal connected thereto may be provided.

  The FC 18 has a known current-voltage (IV) characteristic 70 in which the FC current Ifc increases as the FC voltage Vfc decreases from the FC open circuit voltage Vfcocv, as indicated by an IV (current-voltage) characteristic 70 in FIG. That is, the FC current Ifch when the FC voltage Vfc is a relatively low FC voltage Vfcl is larger than the FC current Ifcl when the FC voltage Vfc is a relatively high FC voltage Vfch. The FC power Pfc increases as the FC current Ifc increases (the FC voltage Vfc decreases).

  The FC voltage Vfc of the FC 18 is the step-up ratio (V2 / Vbat) of the SUDC 22 in the step-up state (switching state) or the step-down ratio (Vbat / V2) of the SUDC 22 in the step-down state (switching state) when the SUC 21 is directly connected. The determined secondary side voltage V2 {the command voltage (target voltage) of SUDC22. } And the FC voltage Vfc is determined, the FC current Ifc is controlled (determined) along the IV characteristic 70.

  Further, when the SUC 21 is boosted and when the SUDC 22 is directly connected, the voltage on the primary side 1 sf of the SUC 21, that is, the FC voltage Vfc is set as the command voltage (target voltage) of the SUC 21, and the FC current Ifc is determined along the IV characteristic 70. The step-up ratio (V2 / Vfc) of the SUC 21 is determined so that the desired secondary side voltage V2 is obtained.

  In this embodiment, when the SUC 21 is boosted, feedback (F / B) in which the duty of the switching element 21b is adjusted by the ECU 24 as a converter controller so that the FC voltage Vfc becomes a command value (set value, target value). However, since there is a unique relationship based on the IV characteristic 70 between the FC voltage Vfc and the FC current Ifc, the ECU 24 controls the FC current Ifc to be a command value (set value, target value). It is also possible to perform feedback (F / B) control for adjusting the duty of the switching element 21b.

  ECU24 controls each part, such as drive motor 14, INV16, FC18, BAT20, SUC21, SUDC22, air pump unit 40, via communication line 68 (refer to Drawing 2). In the control, a program stored in a memory (ROM) of the ECU 24 is executed, and various sensors (not shown voltage sensor, current sensor, temperature sensor, pressure sensor, hydrogen concentration sensor, various rotation speed sensors, accelerator) The detected value of the pedal opening sensor, etc., and on / off information of various switches (air conditioning switch, ignition switch, etc.) are used.

  Here, the ECU 24 is a computer including a microcomputer, a CPU (Central Processing Unit), a ROM (including EEPROM) as a memory, a RAM (Random Access Memory), an A / D converter, a D / A It has an input / output device such as a converter, a timer as a timer, and the like, and the CPU reads and executes the program recorded in the ROM so that various function realization units (function realization means), for example, a control unit , Functions as a calculation unit, a processing unit, and the like. Note that the ECU 24 can be composed of a plurality of ECUs instead of only one ECU.

  The ECU 24 determines the load (load power) required for the FC system 12 as a whole of the FC vehicle 10 determined based on the input values from various switches and various sensors in addition to the state of the FC 18, the state of the BAT 20, and the state of the drive motor 14. , While arbitrating the load (load power) that the FC 18 should bear, the load (load power) that the BAT 20 should bear, and the load (load power) that the regenerative power source (drive motor 14) should bear The drive motor 14, INV16, air pump unit 40, FC18, BAT20, SUC21, and SUDC22 are controlled. That is, the ECU 24 performs energy management control of the entire fuel cell vehicle 10 including the FC 18, the BAT 20, the load 30, the air pump unit 40, and the low-pressure auxiliary machine.

  Here, the characteristics of the air pump unit 40 (air pump 31) will be described. FIG. 4 shows a characteristic 74 that represents the relationship between the required air pump speed Napreq [rpm] and the required air pump voltage Vapd [V]. The characteristic 74 is obtained in advance through experiments or simulations and stored in a storage device in the ECU 24.

  When the required air pump voltage Vapd is set to a voltage range (Vapth ≦ Vapd ≦ Vapmax) from the air pump threshold voltage Vapth to the air pump upper limit voltage Vapmax, the performance guarantee range of the air pump unit 40 is set, and the rated range (minimum rotation speed Napmin to The air pump 31 can be used up at a maximum speed Napmax). When the required air pump voltage Vapd is set to a voltage range from the air pump threshold voltage Vapth to the air pump lower limit voltage Vapmin (Vapmin ≦ Vapd ≦ Vapth), the operation guaranteed range of the air pump unit 40 is set, and the rated range (minimum) The rotational speed of the air pump 31 (air pump rotational speed Nap) is limited (the performance is restricted) to a predetermined rotational speed between the rotational speed Napmin and the maximum rotational speed Napmax).

  That is, if the required air pump voltage Vapd is a voltage from the voltage equal to or lower than the air pump threshold voltage Vapth to the air pump lower limit voltage Vapmin corresponding to the operation guaranteed minimum rotation speed Napmin, the operation guarantee range is set and the performance of the air pump 31 is restricted.

  The air pump unit 40 (air pump 31) is damaged when a voltage exceeding the air pump upper limit voltage Vapmax is applied, and becomes uncontrollable when a voltage lower than the air pump lower limit voltage Vapmin is applied.

  The FC automobile 10 to which the fuel cell system 12 according to this embodiment is applied is basically configured as described above.

  Here, basic control of energy management of the FC automobile 10 to which the fuel cell system 12 is applied will be described.

[Basic control of energy management]
The ECU 24 satisfies the required motor voltage Vmd, the required air pump voltage Vapd, and the required air pump voltage Vapd required for traveling every several milliseconds to several tens of milliseconds when an ignition switch (not shown) is on. The BAT voltage Vbat is calculated. These calculation processes are a motor required voltage calculation process, an air pump required voltage calculation process, and a BAT voltage setting process (power storage device voltage setting process), respectively, and these calculation processes are collectively referred to as a travel basic control process.

  When calculating the required motor voltage Vmd in the required motor voltage calculation step, the ECU 24 first determines the motor rotation speed Nm [rpm] according to the accelerator pedal operation amount θp of the accelerator pedal (not shown) and the vehicle speed Vs [km / h]. ], The required motor power Pmreq [kW] is calculated with reference to a characteristic map (not shown) of the necessary torque Treq [N · m].

  Next, a required motor voltage Vmd [V] proportional to the motor required power Pmreq is calculated with reference to the characteristic 72 shown in FIG. The required motor voltage Vmd is the minimum required voltage of the secondary side voltage V2 of the SUC 21 or SUDC 22 applied to the DC terminal of the inverter 16 for realizing the required motor power Pmreq.

  Next, when calculating the air pump required voltage Vapd in the air pump required voltage calculating step, the ECU 24 first requires the required power of the air pump unit 40 and auxiliary equipment such as an air conditioner (not shown) in addition to the motor required power Pmreq. The target generated power (target FC power) Pfctar for FC18 that covers the FC is calculated, and the shortage of FC18 target FC power Pfctar (discharge power of BAT20) or surplus (charge power of BAT20) is calculated as BAT power Pbat. To do.

  Next, an air pump required rotational speed Napreq capable of generating a target air flow rate supplied to the FC 18 necessary for generating the target FC power Pfctar is calculated.

  In this case, the hydrogen flow rate is basically set corresponding to the target FC power Pfctar. For example, when the hydrogen flow rate increases, the supply amount of hydrogen supplied from the hydrogen tank 37 through a regulator (not shown) increases. It is configured as follows.

  Next, with reference to the characteristic 74 shown in FIG. 4, the required air pump voltage Vapd that can satisfy the required air pump speed Napreq [rpm] is calculated.

  The air pump required voltage Vapd may be calculated (determined) based on the air pump target power consumption and the air pump torque, in addition to being calculated (determined) based on the air pump required rotation speed Napreq.

  Finally, in the BAT voltage setting step, the BAT voltage Vbat is set so as to satisfy the required air pump voltage Vapd. In this embodiment, the BAT voltage Vbat is the driving voltage of the air pump unit 40 (air pump 31). Since the BAT 20 and the air pump unit 40 (air pump 31) are electrically connected to the same potential so as to be equal to the voltage Vap, the BAT voltage Vbat always exceeds the required air pump voltage Vapd set as the air pump drive voltage Vap. It is preset so as to be a voltage, and is further preset so that the minimum voltage of the air pump required voltage Vapd is higher than the air pump threshold voltage Vapth of the air pump 31.

  In this embodiment, when the required motor voltage Vmd is set to the secondary voltage V2, the primary voltage V1 (V1 = Vbat) of the BAT voltage Vbat that satisfies the required air pump voltage Vapd or the SOC of the BAT20 is set. In this case, direct connection or step-up control of the SUC 21, direct connection control of the SUDC 22 (power flow from the primary side 1 sb to the secondary side 2 s or power flow from the secondary side 2 s to the primary side 1 s) or step-up / down control {Power step-up control of BAT voltage Vbat to required motor voltage Vmd or step-down control of secondary side voltage V2 (voltage by FC power Pfc or voltage by regenerative power of drive motor 14) to BAT voltage Vbat} It is carried out while controlling (system efficiency) as much as possible, that is, controlling so as to reduce power loss.

  Based on such [basic control of energy management], referring to the timing chart of FIG. 6 and the flowchart of FIG. 7, details of [travel control] aiming at improving the system efficiency according to this embodiment Will be described. Note that the execution subject of the program according to the flowchart shown in FIG. 7 is the CPU of the ECU 24.

[Running control]
In FIG. 6, the vertical axis indicates the following items in order from the top.

  Change in SOC [%] of BAT 20 with time (upper remaining capacity threshold SOCth2 and lower remaining capacity threshold SOCth1 are also displayed).

  Time change of the contactor 33 in the on / off state (closed in the on state and opened in the off state).

  Change over time in target FC power Pfctar and motor required power Pmreq (0 [kW] line is also displayed).

  As the voltage change, the time change of the BAT voltage Vbat (the upper BAT threshold voltage Vbatth2 and the lower BAT threshold voltage Vbatth1 are also displayed) and the time change of the air pump required voltage Vapd (the air pump threshold voltage Vapth is also displayed).

  Time change of BAT power Pbat (BAT discharge power Pbatd and BAT charge power Pbatc) (0 [kW] line is also displayed).

  In FIG. 6, the motor required power Pmreq having a constant value in the period from time t0 to time t6 means that the FC automobile 10 is in cruise driving such as a high speed with a constant vehicle speed Vs. ing. In FIG. 6, it is assumed that the actual FC power Pfc follows the target FC power Pfctar.

  Simultaneously with the travel control in the flowchart of FIG. 7, the above-described travel basic control process is executed in parallel by the ECU 24.

  Accordingly, in step S1 of the flowchart of FIG. 7, the ECU 24 determines whether or not the SOC of the BAT 20 is equal to the upper remaining capacity threshold value SOCth2.

  During the period from time t0 to time t1, the BAT 20 is charged and the SOC of the BAT 20 gradually increases. When SOC = SOCth2 (step S1: YES) at time t1, the condition for starting independent power supply is satisfied. At this time, in step S2, the contactor 33 is turned off (time point t1). Thereby, in the period from the time point t1 to the time point t2, in step S3, the drive motor 14 is driven through the load 30, that is, the inverter 16, only by the FC power Pfc of the FC 18 (Pfc = Pfctar≈Pmreq). On the other hand, in step S4, the air pump unit 40 (air pump 31) is driven only by the BAT power Pbat of the BAT 20 (BAT discharge power Pbatd becomes equal to the air pump power consumption Pap. Pbatd≈Pap).

  As described above, in steps S3 and S4, the drive motor 14 is driven only by the FC power Pfc, and the air pump unit 40 (air pump 31) is driven only by the BAT power Pbat, and is driven by being supplied with power independently. This is called an independent power supply process.) In this case, since the conduction current Isudc of the SUDC 22 becomes a zero value (0 [A]), the power loss (power consumption) of the SUDC 22 becomes a substantially zero value and the system efficiency is improved.

  In other words, the power consumption (total power consumption) of the air pump unit 40 (typically the air pump 31) is covered by the BAT discharge power Pbatd (power storage power) of the BAT 20, and the load 30 (typically the drive motor 14). By controlling the power consumption (total power consumption) to be covered by the FC power Pfc of the FC 18, the conduction current Isudc between the BAT 20 and the SUDC 22 can be set to a substantially zero value (including a zero value).

  Therefore, the process of switching the contactor 33 to the OFF state in step S2 can be changed to a process subsequent to the processes of steps S3 and S4.

  After the process of step S4, the determination of step S1 becomes negative (step S1: NO), and until the time t2, the determination of step S5, that is, whether or not the SOC of the BAT 20 is greater than the lower remaining capacity threshold SOCth1 The determination becomes affirmative (step S5: YES).

  As a result, in the period from time t1 to time t2, the process of the independent power supply process of step S1: NO → step S5: YES → step S2 to step S4 → step S1: NO.

  In this independent power supply process, as shown in FIG. 8, after the contactor 33 is turned off in step S2, whether or not the FC voltage Vfc is higher than the required motor voltage Vmd is compared in step S2a. If it is determined that the voltage is higher than the required motor voltage Vmd (Vfc> Vmd, step S2a: YES), the switching element 21b is held in the OFF state and the SUC 21 is controlled to be in the direct connection state in step S2b. By controlling the SUC 21 to be in a directly connected state, the switching loss of the switching element 21b is reduced and a voltage higher than the motor required voltage Vmd is applied to the input terminal of the inverter 16, so that the current flowing through the inverter 16 is As a result of being reduced and the passage loss being reduced, the system efficiency is further improved. If the determination in step S2a is negative (Vfc ≦ Vmd), in step S2c, the FC voltage Vfc is increased to the required motor voltage Vmd by the SUC 21 to drive the inverter 16.

  Next, when the discharge of the BAT 20 progresses during the period from the time point t1 to the time point t2, the SOC decreases, and the determination in step S5 becomes negative (step S5: NO), the contactor 33 is turned on from the off state in step S6. State (time t2).

  Then, in step S7, that is, in the period from time t2 to time t5, as shown in the waveform of the target FC power Pfctar, the target FC power Pfctar is added to the power generation amount (generated power) for the motor required power Pmreq. Thus, the power generation amount (power generation power) is increased by adding the power generation amount (power generation power) corresponding to the air pump required power Papd and the BAT charging power Pbatc (Pfctar = Pmreq + Papd + Pbatc).

  Since the power generation amount (generated power) of FC18 has a characteristic of gradually increasing without rapidly increasing, a part of the air pump necessary power Papd is covered by the BAT discharge power Pbatd from time t2 to time t3. Therefore, after the delay time Td from the time point t2 to the time point t3, the BAT 20 starts charging with the BAT charging power Pbatc. When the SOC of the BAT 20 recovers to the lower remaining capacity threshold SOCth1 at time t4, thereafter, the target FC power Pfctar is gradually decreased toward time t5.

  Note that when the SOC of the BAT 20 recovers to the lower remaining capacity threshold SOCth1 at time t4, the target FC power Pfctar may be held constant instead of gradually decreasing toward time t5. When the target FC power Pfctar is kept constant, the SOC of the BAT 20 reaches the upper remaining capacity threshold SOCth2 earlier by that amount.

  After the process of step S7, it is determined in step S8 whether or not the SOC of the BAT 20 has become equal to the upper remaining capacity threshold value SOCth2.

  While the determination in step S8 is negative (step S8: NO), the processes of step S6, step S7, and step S8: NO are repeated.

  If the determination in step S8 becomes affirmative at step t5 (step S8: YES), the determination in step S1 naturally becomes affirmative and the process proceeds to step S2. That is, the process after time t1 is repeated.

[Summary of Embodiment and Modifications]
Here, description will be made with reference to the conceptual diagram of the comparative example of FIG. 9, the conceptual diagram of the embodiment of FIGS. 10A to 10C, and the conceptual diagram of the modified example of FIGS. 11A to 11C. In these drawings of FIGS. 9, 10A to 10C, and 11A to 11C, arrows indicate the flow of electric power.

  In the FC automobile 10R to which the FC system 12R of the comparative example of FIG. 9 is applied, power is supplied from the FC 18 to the drive motor 14 via the SUC 21, and the air pump constituting the air pump unit 40 from the FC 18 via the SUC 21 and SUDC 22 31. Further, the electric power charged in the BAT 20 is supplied to the drive motor 14 via the SUDC 22 as necessary. In this case, the conduction current Isudc (see FIG. 1) always flows through the SUDC 22, and the power loss is accumulated. Thereby, the system efficiency deteriorates.

  Therefore, in this embodiment, the SOC of the BAT 20 or the BAT voltage Vbat is monitored (step S1), and in the monitoring process, the SOC of the BAT 20 is equal to or higher than SOC = SOCth2 (upper remaining capacity threshold value which is a predetermined value) or When the BAT voltage Vbat becomes equal to or higher than a predetermined voltage (the upper BAT threshold voltage Vbatth2 that is a predetermined voltage equal to or higher than the air pump required voltage Vapd) capable of driving the air pump 31, as shown in FIG. 10A, the air pump unit 40 (typically Substantially covers the power of the air pump 31) with the BAT discharge power Pbatd of the BAT 20 (power storage power of the power storage device), and the power of the load 30 (typically the drive motor 14) (referred to as motor power Pm). It is possible to communicate between BAT20 and SUDC22 by using Pfc (generated power). Independent power supply step of the current Isudc substantially zero value (step S2, S3, S4), and a.

  As described above, when the SOC of the BAT 20 is equal to or higher than the upper remaining capacity threshold SOCth2 or the BAT voltage Vbat is equal to or higher than the upper BAT threshold voltage Vbatth2, the drive motor 14 is driven by the FC 18 and the air pump 31 is driven independently by the BAT 20. As a result, the conduction current Isudc of the SUDC 22 arranged between the secondary side 2s, which is the input end of the INV 16 serving as the motor drive unit, and the BAT 20 can be set to a substantially zero value (including a zero value) as a result. Since the power loss in the SUDC 22 becomes a zero value or a substantially zero value, the system efficiency of the entire FC system 12 can be further improved.

  Further, in this embodiment, an air pump required voltage calculating step for calculating an air pump required voltage Vapd that needs to be applied to the air pump inverter 23 and the air pump motor 29 as an air pump drive unit according to the target FC power Pfctar of the FC 18, and an air pump required voltage The BAT voltage setting step for setting the BAT voltage Vbat so as to satisfy Vapd, and the upper BAT threshold value at which the BAT voltage Vbat is a predetermined voltage equal to or higher than the air pump required voltage Vapd while charging the BAT20 through the SUDC 22 with a part of the FC power Pfc. When the voltage Vbatth2 is reached, the conduction current Isudc between the BAT20 and the SUDC22 is set to a zero value (the contactor 33 is in the open state in the OFF state), and the BAT discharge power Pbatd, which is the power of the BAT20, is used as the air pump drive unit. And an independent power supply step of supplying the target FC power Pfctar of the FC 18 to the drive motor 14 through the INV 16 as a motor drive unit, while supplying the air pump 31 through the up-pump inverter 23 and the air pump motor 29. .

  That is, when the BAT voltage Vbat reaches the upper BAT threshold voltage Vbatth2 (the upper remaining capacity threshold SOCth2 where the SOC of the BAT20 is, for example, 50 [%]) which is a predetermined voltage equal to or higher than the air pump required voltage Vapd, FIG. As shown, since an independent power supply process for supplying power from the FC 18 to the drive motor 14 via the SUC 21 and supplying the air pump 31 from the BAT 20 is provided, the conduction current Isudc of the SUDC 22 has a zero value. The power loss due to the passage of the passing current Isudc through the SUDC 22 can be made zero, and the system efficiency of the entire FC system 12 can be improved.

  In the BAT voltage setting step described above, when the required air pump voltage Vapd is a voltage lower than the air pump threshold voltage Vapth that can ensure the maximum rotation speed Napmax of the air pump 31, a voltage equal to or higher than the air pump threshold voltage Vapth. The BAT voltage Vbat is set so that (see FIG. 6). Thus, since the air pump threshold voltage Vapth that can cover the maximum rotation speed Napmax of the air pump 31 is set, drivability is not impaired even when the target FC power Pfctar increases or decreases.

  The independent power supply step may further include a voltage comparison step (step S2a) for comparing the motor required voltage Vmd and the FC voltage Vfc as shown in the flowchart of FIG. 8 under the power supply shown in FIG. 10A. preferable. If it is determined in this voltage comparison step that the FC voltage Vfc is higher than the motor required voltage Vmd (step S2a: YES), the SUC 21 is controlled to the direct connection state, and the FC power Pfc of the FC 18 is set to the direct connection state. By supplying the drive motor 14 through the SUC 21 and the inverter 16, the SUC 21 can be appropriately controlled, and the efficiency of the entire fuel cell system 12 can be further improved.

  When the SOC of the BAT 20 becomes lower than the lower remaining capacity threshold SOCth1 (time point t2), the contactor 33 is turned on (closed), and the power from the FC 18 is supplied to the SUC 21 and the INV 16 as shown in FIG. 10B. And the charging is started so that the SOC of the BAT 20 again becomes the upper remaining capacity threshold value SOCth2. Since FC power Pfc of FC18 (= target FC power Pfctar) does not rise suddenly, during the period from time t2 to time t3, the increase in FC power Pfc and the decrease in BAT discharge power Pbatd from BAT20 are the air pump drive power. It is controlled so as to be equal to Papd.

  From time t3, as shown in FIG. 10C, power from the FC 18 is supplied to the drive motor 14 via the SUC 21 and INV 16, and is supplied to the air pump 31 via the SUDC 22, and the BAT 20 is charged. In the state of FIG. 10C, when the SOC of the BAT 20 becomes the upper remaining capacity threshold SOCth2 again (time point t5), the independent power supply process shown in FIG. 10A is started again.

[Modification 1]
The present invention is applied to a fuel cell vehicle 10A including a fuel cell system 12A in which the SUC 21 is omitted, as shown in FIGS. 11A to 11C, when an FC 18 that can output an FC voltage Vfc that is always higher than the required motor voltage Vmd can be adopted. be able to.

  Each operation in FIG. 11A, FIG. 11B, and FIG. 11C is the same as each operation in FIG. 10A, FIG. 10B, and FIG.

[Modification 2]
In the above-described embodiment (including [Modification 1]), in the independent power supply process, the contactor 33 is turned off (opened) so that the conduction current Isudc does not flow through the SUDC 22. Even when the SUDC 22 is directly and physically connected to the BAT 20 and the air pump unit 40 of the primary side 1sb without using the contactor 33, the period from the time point t1 to the time point t2 and the period after the time point t5 The switching elements 22b and 22d constituting the SUDC 22 may be controlled to be in an off state so that the primary side 1sb and the SUDC 22 are disconnected.

[Modification 3]
Even if the SUDC 22 is directly and physically connected to the BAT 20 and the air pump unit 40 on the primary side 1sb without using the contactor 33, the motor power Pm, which is the actual power of the load 30, is described above. The FC power Pfc may be feedback-controlled so that the FC power Pfc having the same value as the motor power Pm is supplied from the FC 18 to the secondary side 2s. If controlled in this way, there is a case where a small amount of the flowing current Isudc flows (the flowing current Isudc is substantially zero) due to a feedback delay, but in terms of circuit theory, the flowing current Isudc is It will not pass.

  Note that the present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be adopted based on the contents described in this specification.

10, 10A ... Fuel cell vehicle (FC vehicle)
12, 12A ... Fuel cell system (FC system)
14 ... Drive motor 16 ... Inverter (INV)
18 ... Fuel cell (FC) 20 ... Power storage device, High voltage battery (BAT)
21 ... Boost converter (booster, voltage converter, SUC)
22 ... Buck-boost converter (buck-boost, voltage converter, SUDC)
23 ... Air pump inverter 24 ... ECU
29 ... Air pump motor 31 ... Air pump 40 ... Air pump unit

Claims (6)

A fuel cell that generates power by reacting an oxidant gas and a fuel gas and outputs a fuel cell voltage;
A power storage device that outputs a power storage device voltage;
A motor driven through a motor drive,
A voltage converter that performs voltage conversion between the power storage device voltage as a primary side voltage and a motor required voltage as a secondary side voltage that needs to be applied to the motor drive unit;
An air pump that is driven through an air pump driving unit to which the power storage device voltage is applied and supplies the oxidant gas to a fuel cell;
A control method for a fuel cell system comprising:
A monitoring step of monitoring the SOC of the power storage device or the voltage of the power storage device;
In the monitoring step, if the SOC of the power storage device is equal to or higher than a predetermined value or the power storage device voltage is equal to or higher than a predetermined voltage at which the air pump can be driven during travel control, the power consumption of the air pump is Independent power supply step of making the current flowing between the power storage device and the voltage conversion device substantially zero by substantially covering the stored power with the power consumption of the motor and the power generated by the fuel cell. When,
A control method for a fuel cell system, comprising: In the control method of the fuel cell system according to claim 1,
In the previous process of the monitoring process,
An air pump required voltage calculating step for calculating an air pump required voltage that needs to be applied to the air pump drive unit according to a target generated power of the fuel cell;
A power storage device voltage setting step for setting the power storage device voltage so as to satisfy the required air pump voltage,
When the power storage device voltage becomes the predetermined voltage equal to or higher than the air pump required voltage while charging the power storage device through the voltage conversion device with a part of the target generated power, the independent power supply step is performed. A control method for a fuel cell system. In the control method of the fuel cell system according to claim 2,
In the power storage device voltage setting step,
When the voltage required for the air pump is less than an air pump threshold voltage capable of ensuring the maximum rotation speed of the air pump, the power storage device voltage is set to be a voltage equal to or higher than the air pump threshold voltage. A control method for a fuel cell system. In the control method of the fuel cell system according to any one of claims 1 to 3,
The fuel cell system further includes another voltage conversion device that uses the fuel cell voltage as a primary voltage and the required motor voltage as a secondary voltage,
In the independent power supply step,
A voltage comparison step of comparing the required motor voltage and the fuel cell voltage;
When it is determined in the voltage comparison step that the fuel cell voltage is higher than the motor required voltage, the other voltage conversion device is controlled to be in a directly connected state, and the generated power of the fuel cell is changed to the directly connected state. When the fuel cell voltage is supplied to the motor through the other voltage conversion device and the motor driving unit, and the fuel cell voltage is determined to be lower than the motor required voltage, the fuel cell voltage is changed to the other voltage. A control method for a fuel cell system, wherein the converter boosts the voltage required for the motor to supply the generated power of the fuel cell to the motor through the other voltage converter and the motor drive unit. In the control method of the fuel cell system according to any one of claims 1 to 4,
A DC terminal side of the air pump drive unit and an input / output terminal of the power storage device are connected to the step-down terminal side of the voltage converter.
A control method for a fuel cell system. A fuel cell vehicle that implements the control method for a fuel cell system according to any one of claims 1 to 5 .

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