JP6185899B2 - Control method for fuel cell system and fuel cell vehicle - Google Patents

Description

  The present invention relates to a control method for a fuel cell system that supplies power from a fuel cell and a power storage device to a load such as a drive motor, and a fuel cell vehicle in which the control method is implemented.

  Conventionally, for example, as shown in FIG. 1 of Patent Document 1, between a load including a drive motor and an inverter that drives the drive motor, and an output terminal of the fuel cell, and between the inverter and the power storage device 2. Description of the Related Art There is known a fuel cell vehicle equipped with a fuel cell system in which a boost converter is provided between each end and the load (an inverter and a motor driven by the inverter) is driven.

  In Patent Document 1, based on the correlation between the required voltage of the motor (drive required load end voltage) that is the voltage of the power applied to the load 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 drive request load terminal voltage, the fuel cell side boosting (voltage conversion) is not performed directly, and the switching loss of the fuel cell side boosting converter is suppressed. ([0011], [0012], [0068], [0069] of Patent Document 1).

  In Patent Document 1, as described above, when the fuel cell voltage is higher than the drive-requested load end voltage, the voltage is directly connected without boosting (voltage conversion) by the boost converter on the fuel cell side. Further, it is described that when the fuel cell voltage falls below the drive request load end voltage, the boost converter on the fuel cell side needs to be boosted again ([0070] of Patent Document 1).

International Publication No. 2009/084650 Pamphlet

  In Patent Document 1, the efficiency of the fuel cell system is improved by direct connection when the fuel cell voltage is higher than the drive request load end voltage.

  By the way, when the boost converter is shifted from the direct connection state to the boost state, if the boost width (the difference between the low voltage side voltage and the high voltage side voltage of the boost converter) is small, there is a problem that the controllability deteriorates. In Patent Document 1, there is no description about the solution of the above problem and there is room for improvement.

  The present invention more appropriately controls a fuel cell voltage conversion device that converts or directly connects a fuel cell voltage, and a power storage device voltage conversion device that converts or directly connects a power storage device voltage, thereby further improving system efficiency. It is a first object of the present invention to provide a fuel cell system control method and a fuel cell vehicle that can be made to operate.

  The present invention provides controllability when it is determined that the boost width (the difference between the low-voltage side voltage and the high-voltage side voltage of the boost converter) is small when the boost converter transitions from the direct connection state to the boost state. It is a second object of the present invention to provide a fuel cell system control method and a fuel cell vehicle that can prevent deterioration and suppress a decrease in system efficiency.

A control method for a fuel cell system according to the present invention includes a fuel cell that outputs a fuel cell voltage, a power storage device that outputs a power storage device voltage, a load that includes an inverter and a drive motor driven through the inverter, and the fuel A first voltage conversion device that boosts the battery voltage as a primary side voltage and applies it as a load end voltage to the DC end side of the inverter, boosts the storage device voltage as the primary side voltage, and uses the inverter voltage as the load end voltage. In a control method of a fuel cell system comprising: a second voltage converter applied to a direct current end side, a drive request load end that drives the load based on a drive request to the fuel cell system as the load end voltage voltage and the efficiency required load end voltage for driving the load efficiently, the required voltage determination step of determining, the power storage and the fuel cell voltage A comparison determination step of determining by comparing one of the voltage between the location voltage is high, the fuel when the battery voltage is determined to be high, as high as the determined fuel cell voltage, the efficiency required load end voltage When the voltage conversion operation of the first voltage converter is stopped and directly connected, or when the power storage device voltage is determined to be high, the power storage device voltage determined to be high is the efficiency required load. A voltage conversion stop step of stopping and directly connecting the voltage conversion operation of the second voltage converter when the voltage exceeds the end voltage, and one of the voltages directly connected in the first and second voltage converters Even if the primary side voltage of the converter is lower than the efficiency required load end voltage, the voltage conversion operation is stopped while the drive required load end voltage is exceeded.

  As described above, even if the primary voltage of one of the voltage conversion devices to which a high voltage is applied as the primary voltage among the fuel cell voltage and the power storage device voltage is lower than the efficiency required load end voltage, the drive request is made. While the voltage at the load end is exceeded, the voltage conversion operation is stopped, that is, the direct connection state is continued. Therefore, the duration of the direct connection state can be extended, and the system efficiency can be improved. The purpose of is achieved.

In this case, when the primary voltage of the one of the voltage converters that are directly connected falls below the drive required load terminal voltage, the efficiency required load terminal voltage and the primary side of the one voltage converter provided a differential voltage grasping step of grasping a difference voltage between the voltage, the difference voltage, when a value less than the threshold value voltage is boosted width the load end voltage becomes voltage above the efficiency required load end voltage It is preferable to further provide a step of increasing the boosting width for starting the voltage conversion operation of the one voltage converter with the set boosting width.

  As described above, when the primary side voltage of one voltage conversion device in direct connection is lower than the drive request load end voltage, the efficiency request load end voltage and the primary side voltage of the one voltage conversion device When the difference voltage is grasped and the difference voltage is less than the threshold voltage, the boost width is set such that the load end voltage exceeds the efficiency required load end voltage. Since the voltage conversion operation of one of the voltage conversion devices is started, it is possible to implement a stable voltage conversion operation with improved system efficiency while preventing the occurrence of an unstable voltage conversion operation state. The second objective can be achieved.

  The other voltage conversion device to which a low voltage is applied as the primary voltage among the fuel cell voltage and the power storage device voltage while the voltage conversion operation of the one voltage conversion device continues. Is set to a voltage difference between the primary side voltage of the other voltage converter and the load end voltage during direct connection, whereby the load end voltage is controlled by the other voltage converter. Thus, the direct connection of one of the voltage converters can be continued as much as possible, and the system efficiency is improved.

  The drive motor is for driving a vehicle, and the high voltage of the fuel cell voltage and the power storage device voltage is applied as the primary voltage of the first voltage converter and the second voltage converter. When the primary side voltage of any one of the voltage conversion devices exceeds the efficiency required load end voltage, immediately before stopping the voltage conversion operation of the voltage conversion device and directly connecting it, and stopping the voltage conversion After the step, even if the primary side voltage of the one voltage converter is lower than the efficiency required load end voltage, the voltage conversion operation is stopped while the drive required load end voltage is exceeded. Immediately before the vehicle further comprises a vehicle state grasping step for grasping a vehicle state whether or not the vehicle is in a high speed running state or an uphill state, and in the vehicle state grasping step, the vehicle is in the high speed running state. Or before If you know to be in the ascending state, the voltage conversion operation is stopped directly the voltage conversion device, when connected directly it is preferable to continue the stop state of the voltage conversion operation.

  According to the present invention, it is possible to easily determine whether or not the one of the voltage converters is in the direct connection state and to continue, and since the drive request load end voltage is secured, the merchantability is reduced. Can be prevented.

  A control method of a fuel cell system according to the present invention includes a fuel cell that outputs a fuel cell voltage, a power storage device that outputs a power storage device voltage, an inverter, and a drive motor that drives the vehicle and is driven through the inverter. A first voltage conversion device that boosts the fuel cell voltage and applies it as a load end voltage to the DC end side of the inverter, and boosts the power storage device voltage as the load end voltage to the DC end side of the inverter. In the control method of a fuel cell system having a second voltage conversion device to be applied, a drive request load end voltage for driving the load is determined as the load end voltage based on a drive request to the fuel cell system. The required voltage determination process and whether the vehicle driven by the drive motor is in an accelerated state, a high-speed traveling state, or an uphill state A vehicle state grasping step for determining; a step-by-step determining step for determining whether or not the first and second voltage converters need to be boosted based on the drive-requested load end voltage, the fuel cell voltage, and the power storage device voltage; In the boosting necessity determination step, when it is determined in the vehicle state grasping step that the vehicle is in the acceleration state, both the first and second voltage conversion devices are boosted. When the vehicle state grasping step determines that the vehicle is in the high-speed traveling state or the uphill state, the higher one of the fuel cell voltage and the power storage device voltage is applied. It is determined that one of the voltage converters of the first and second voltage converters is in a directly connected state.

  Thus, since the transition to the direct connection state of one of the first and second converters is determined based on the vehicle state, the drive request load end voltage, the fuel cell voltage, and the power storage device voltage, While improving the system efficiency, it is possible to easily determine the transition of one of the first and second converters to the directly connected state.

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

  According to this invention, even if the primary side voltage of one voltage conversion device to which a high voltage is applied as the primary side voltage among the fuel cell voltage and the power storage device voltage is lower than the efficiency required load end voltage, While the drive request load end voltage is exceeded, since the voltage conversion operation is stopped, that is, the direct connection state is continued, the duration of the direct connection state can be extended, and the voltage converter can be controlled more appropriately. The system efficiency can be further improved.

  Further, according to the present invention, when the boost converter is shifted from the direct connection state to the boost state, when it is determined that the boost width (the difference between the low voltage side voltage and the high voltage side voltage of the boost converter) is small, Since the boosting width is increased to increase the pressure, the controllability can be prevented from being deteriorated, and the decrease in system efficiency can be suppressed.

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 explanatory drawing of the power element as an example of a switching element. It is IV characteristic view of a fuel cell. It is a one part flowchart provided for operation | movement description of 1st Example-4th Example. It is a flowchart provided for operation | movement description of 1st Example. It is a flowchart with which operation | movement description of the 1st modification of 1st Example is provided. It is a flowchart provided for operation | movement description of 2nd Example. It is a flowchart provided for operation | movement description of 3rd Example. It is a flowchart with which operation | movement description of 4th Example is provided. It is a characteristic view which shows the relationship between motor request | requirement electric power and the drive request | requirement load end voltage as a load end voltage. It is a motor torque characteristic related figure. It is a timing chart used for operation | movement description of 1st Example. It is explanatory drawing of the power loss at the time of the direct connection of a converter, the time of a minute pressure | voltage rise, and the time of a bulk boost.

  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, and is a chopper type boost converter 21 (hereinafter referred to as SUC21) as a voltage converter (boost). Step Up Converter) and a step-up / down converter 22 (hereinafter referred to as SUDC 22) as a chopper-type voltage converter (buck-boost) arranged between the primary side 1sb and the secondary side 2s side. SUDC: Step Up / 1 is a schematic circuit diagram of an FC automobile 10 including a detailed configuration of an example of a 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 an inverter 16 (hereinafter referred to as a load drive circuit) that drives the drive motor 14. It is referred to as “INV16.” INV: Inverter).

  The FC system 12 includes a fuel cell 18 (hereinafter referred to as “FC18”) disposed on one primary side 1sf and a high-voltage battery 20 (hereinafter referred to as “power storage device” disposed on the other primary side 1sb). BAT20 "), the SUC21, the SUDC22, a high voltage {power storage device voltage (BAT voltage) Vbat} input fuel cell auxiliary machine (hereinafter referred to as" FC auxiliary machine ") 31, and a high voltage input. Air conditioner 32, which is a vehicle interior air conditioner, a chopper-type step-down converter 23 (hereinafter referred to as “SDC 23”; SDC: Step Down Converter) as a step-down device, and an electronic control device 24 (hereinafter referred to as a control device). And “ECU 24.” ECU: Electronic Control Unit (ECU).

  The output end of FC18 is connected to the input end (primary side 1sf) of SUC21, and the output end (secondary side 2s) of SUC21 is connected to the DC end side of INV16 and one end (boost end side) side of SUDC22.

  The input / output end of the BAT 20 is connected to the input side (primary side 1sb) of the SDC 23, the other end side (step-down end side) of the SUDC 22, and the high-pressure auxiliary machine 35 (FC auxiliary machine 31, air conditioning auxiliary machine 32).

  A low voltage battery 29 having a voltage Vbb = + 12V and a low voltage auxiliary machine 33 such as a light are connected to the output end side (secondary side) of the SDC 23. The low pressure auxiliary machine 33, the SDC 23, and the ECU 24 are collectively referred to as a low pressure auxiliary machine (low pressure load) 33 '.

  The drive motor 14 is a combined power value of 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. (Pfc + Pbatd) is supplied through the INV 16 to generate a driving force, and the wheel 28 is rotated through the transmission 26 by the driving force.

  The INV 16 has, for example, a three-phase full-bridge configuration, performs DC / AC conversion, and converts the load end voltage Vinv, which is a DC voltage obtained by boosting the FC voltage Vfc from the FC 18 via the SUC 21, into a three-phase AC voltage. Converted and supplied to the drive motor 14 (during power running).

  The INV 16 also converts the load end voltage Vinv, which is a DC voltage obtained by boosting the BAT voltage Vbat from the BAT 20 via the SUDC 22, into a three-phase AC voltage and supplies it to the drive motor 14 (during power running).

  That is, the drive motor 14 is driven by the power of the FC 18 and / or BAT 20 (during power running).

  In this embodiment, the INV 16 and the drive motor 14 are collectively referred to as a load 30. In addition to the load 30, the load includes a high-pressure auxiliary machine 35 such as an FC auxiliary machine 31 and an air conditioning auxiliary machine 32 and the low-pressure auxiliary machine 33 ′ described above.

  On the other hand, the load terminal voltage (DC terminal side voltage) Vinv generated at the input terminal (DC terminal side) of the INV 16 after AC / DC conversion accompanying the regenerative operation of the drive motor 14 is BAT voltage Vbat through the SUDC 22 operating as a step-down converter. And the SUDC 22 is directly connected (switching element 22b: off, switching element 22d: on) and supplied to the BAT 20 to charge the BAT 20.

  Further, when the power for driving the drive motor 14 by the FC 18 becomes surplus, the surplus power is supplied to the BAT 20 via the step-down SUC 21 or the direct connection SUC 21 through the step-down or direct connection SUDC 22. BAT20 is charged. The surplus power is also supplied to the high pressure auxiliary machine 35 (FC auxiliary machine 31, air conditioning auxiliary machine 32) and low pressure auxiliary machine 33 'according to the degree of surplus.

  The FC auxiliary machine 31 has an air pump (not shown) for supplying compressed air (oxidant gas) containing oxygen to a cathode channel (not shown) of the FC 18 and a cooling channel (not shown) of the FC 18. And a water pump (not shown) for supplying a cooling medium (refrigerant).

  A hydrogen tank (not shown) for supplying hydrogen (fuel gas) is connected to the anode flow path (not shown) of FC18, and 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 an oxidant gas (oxygen-containing gas) is supplied to the cathode electrode via the cathode channel, hydrogen ions, electrons, and oxygen gas react at this cathode electrode to generate water.

  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. The BAT 20 has an BAT voltage (battery voltage) Vbat, a BAT current (battery current) Ib (discharge current Ibd, a charging current Ibc), a BAT temperature (battery temperature), and an SOC (State Of Charge) that is the remaining capacity of the BAT 20 as an ECU 24. Detected or managed by

  As described above, the FC power Pfc of the FC 18 is boosted to the load end voltage Vinv via the SUC 21 and supplied to the drive motor 14 via the INV 16 (during power running), and according to the power status of the FC system 12. Then, it is distributed from the FC 18 through the SUC 21 and the SUDC 22 to each device on the primary side 1sb (the high pressure auxiliary machine 35, the low pressure auxiliary machine 33 ′, and the BAT 20).

  On the other hand, the BAT discharge power Pbatd of the BAT 20 is boosted to the load end voltage Vinv through the SUDC 22 and supplied to the drive motor 14 through the INV 16 (at the time of power running), and also in accordance with the power status of the FC system 12. It is supplied to the high-pressure auxiliary equipment 35 (FC auxiliary equipment 31, air conditioning auxiliary equipment 32) and low-pressure auxiliary equipment 33 ′ (SDC 23, ECU 24, low-pressure auxiliary equipment 33), which are the devices on the side 1sb.

  Here, SUC21, SUDC22, and SDC23 can employ various configurations, but as is well known, basically, switching elements such as MOSFETs and IGBTs, diodes, reactors, and capacitors (including smoothing capacitors). The switching element is on / off-switched (duty controlled) by the ECU 24 based on the required power of the connected load.

  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 load end voltage Vinv.

  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. Or the FC voltage Vfc is directly connected to the load end voltage Vinv (Vinv = 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.

  At the time of 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 load end voltage Vinv (during power running) ).

  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 in the off-state. The end voltage Vinv is stepped down to the BAT voltage Vbat of the BAT 20 (during 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 load end voltage Vinv (Vbat≈Vinv). Actually, the load end voltage Vinv at the time of power running by the BAT 20 in the BAT direct connection state is “Vbat−forward drop voltage of the diode 22e”, and the load end voltage Vinv at the time of charging (including during regenerative charging) is “Vbat = Vinv”. −On-voltage of the switching element 22d = Vbat (when the on-voltage of the switching element 22d is assumed to be 0 [V]) ”.

  As shown in FIG. 3, the above-described power elements such as MOSFETs or IGBTs are used for the switching elements 21b, 22b, and 22d connected between the low voltage side and the high voltage side.

  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 (Vinv / Vbat) of the SUDC 22 in the step-up state (switching state) or the step-down ratio (Vbat / Vinv) of the SUDC 22 in the step-down state (switching state) when the SUC 21 is directly connected. The determined load end voltage Vinv {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. Then, the step-up ratio (Vinv / Vfc) of the SUC 21 is determined so that the desired load end voltage Vinv 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.

  The ECU 24 is connected to the drive motor 14, INV 16, FC 18, BAT 20, SUC 21, SUDC 22, SDC 23, FC auxiliary machine 31, air conditioning auxiliary machine 32, low pressure auxiliary machine 33 ′, etc. via the communication line 68 (see FIG. 2). To control. 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.

  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 converter, etc. Input / output device, a timer as a time measuring unit, etc., and when the CPU reads and executes a program recorded in the ROM, various function realization units (function realization means), for example, a control unit, a calculation unit, It functions as a processing unit. Note that the ECU 24 can be composed of a plurality of ECUs for each of the drive motor 14, the FC 18 and the FC auxiliary machine 31, the BAT 20, the SUC 21, the SUDC 22, and the SDC 23, instead of being composed 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, FC18, BAT20, SUC21, SUDC22 and SDC23 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 high pressure auxiliary machine 35, and the low pressure auxiliary machine 33 '.

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

  Next, an example of control processing by the ECU 24 will be described with reference to the flowcharts of FIGS. Note that the execution subject of the program according to the flowchart shown below is the CPU of the ECU 24.

  In step S1, the ECU 24 inputs values from various switches and various sensors {Vfc, Ifc, Vbat, Ib, Vinv, I2 (input / output current to INV16, see FIGS. 1 and 2), Im (to the drive motor 14). The motor power required for the drive motor 14 (motor) is detected by detecting the flowing motor current, usually for two phases, see FIG. 2), Nm (rotation speed of the drive motor 14), θp (operation amount of an accelerator pedal not shown), etc. Necessary power) Pmreq [kW] is calculated.

  More specifically, the required motor power Pmreq [kW] of the drive motor 14 is calculated based on the motor rotation speed Nm [rpm] corresponding to the accelerator pedal operation amount θp and the required torque Treq [N · m]. .

  FIG. 11 shows a characteristic 72 representing the relationship between the motor required power Pmreq and the drive required load end voltage Vinvd as the load end voltage Vinv of the inverter 16 which is the lowest voltage for realizing the motor required power Pmreq. . The characteristic 72 is stored in advance in a storage device in the ECU 24.

  Therefore, in step S2, the drive request load end voltage Vinvd [V] is calculated with reference to the characteristic 72 of FIG. 11 based on the motor required power Pmreq. In step S2, the efficiency required load end voltage Vinvη [V] is calculated with reference to the characteristics shown in FIG.

  FIG. 12 illustrates motor torque characteristics 91, 92, and 93 in which the horizontal axis stored in a storage device (not shown) is the motor rotation speed Nm [rpm] and the vertical axis is the motor torque Tq [Nm], and the drive request load end voltage. The motor torque characteristic related figure which shows the relationship between Vinvd and the efficiency request | requirement load end voltage area | region 101,102,103 is shown.

  In FIG. 12, the outermost motor torque characteristic 93 viewed from the origin indicates the rated torque characteristic of the drive motor 14. Here, the drive request load end voltage Vinvd from which the rated torque characteristic (motor torque characteristic 93) is obtained is expressed as Vinvd = Vinvd3.

  At the same motor speed Nm, for example, the motor torque Tq on the motor torque characteristic 92 (drive request load end voltage Vinvd2) is compared with the motor torque Tq on the motor torque characteristic 93 (drive request load end voltage Vinvd3). The motor torque characteristic 91 is smaller than the motor torque characteristic 92 at the same motor rotational speed Nm. Note that Vinvd1 <Vinvd2 <Vinvd3.

  Here, the motor torque characteristic between the motor torque characteristic 93 (Vinvd3) and the motor torque characteristic 91 (Vinvd1) and the drive required load end voltage Vinvd can be obtained by interpolation processing or the like.

  In FIG. 12, the hatched area of the line to the left (upward to the right) indicates the area 101 of the efficiency required load end voltage Vinvη1, the halftone area indicates the area 102 of the efficiency required load end voltage Vinvη2, and the lower right ( The hatched area of the line (upward to the left) indicates the area 103 of the efficiency required load end voltage Vinvη3. In this case, the relationship is Vinvη1 <Vinvη2 <Vinvη3, and the relationship is Vinvd1 = Vinvη1, Vinvd2 = Vinvη2, and Vinvd3 = Vinvη3 with respect to the voltage value of the drive request load end voltage Vinvd.

It should be noted that the motor output, in other words, the motor required power Pmreq [kW] (Pmreq = constant × motor rotational speed Nm × motor torque Tq) is, for example, along the motor torque characteristic 91 (Vinvd1). Assuming that the efficiency required load end voltage Vinvη that secures the motor torque characteristic 91 (Vinvd1) is Vinv η 1, Vinv η 2, and Vinv η 3, all higher than the drive required load end voltage Vinvd1. It is that you are.

  An example of why the efficiency required load end voltage Vinvη is higher than the drive required load end voltage Vinvd will be described. The load end voltage Vinv is a voltage applied to the DC input end of the INV 16 (see FIG. 2). Even if the motor required power Pmreq is the same, the higher the load end voltage Vinv is, the higher the load end voltage Vinv is. Considering that the motor current Im flowing through the load 30 is reduced and the power loss (proportional to the square of the motor current Im) is reduced accordingly, the load end voltage Vinv exceeds the drive request load end voltage Vinvd. As a result, it is understood that the efficiency (system efficiency) of the vehicle system related to driving of the load 30 is improved by applying the required efficiency load end voltage Vinvη.

  The relationship between the drive required load end voltage Vinvd and the efficiency required load end voltage Vinvη shown in FIG. 12 indicates characteristics (principal characteristics) during normal travel (including constant speed travel and normal acceleration / deceleration). For example, when the accelerator pedal is so-called solid pedal {in other words, the accelerator opening is fully opened (the accelerator pedal operation amount θp is maximum)}, or when the accelerator pedal is in a state near the solid pedal, the required driving load voltage It should be noted that Vinvd rapidly increases and sticks to the vicinity of the rated motor torque characteristic 93. Therefore, at the time of the rapid acceleration or the like, the drive required load end voltage Vinvd exceeds the efficiency required load end voltage Vinvη.

  Therefore, in step S3, it is determined whether or not the efficiency required load end voltage Vinvη calculated in step S2 is higher than the drive required load end voltage Vinvd (Vinvη> Vinvd).

  As described above, during normal driving, the determination in step S3 is affirmative (step S3: YES). Next, in step S4, whether the FC voltage Vfc is higher than the BAT voltage Vbat (Vfc> Vbat) or not. Determine whether.

  If this determination is affirmative (step S4: YES, Vfc> Vbat), the program corresponding to the flowchart of FIG. 6 according to the first embodiment is executed through the connector “1”.

[First Embodiment] (Vinv η> Vinvd and Vfc> Vbat)
The first embodiment will be further described with reference to the timing chart shown in FIG.

  In the timing chart of FIG. 13, the waveform of the voltage [V] on the upper side shows an example of time change of each of the FC voltage Vfc, the efficiency required load end voltage Vinvη, and the drive required load end voltage Vinvd. For the convenience of understanding, the waveform of the voltage [V] of the upper stage is reprinted from the waveform of the voltage [V] on the upper stage side, and further, the time of the voltage of the boost target voltage Vtar, which is the secondary side voltage of the SUDC 22 on the BAT20 side. The waveform of the example of a change is added and shown.

  In step S5, it is determined whether or not the FC voltage Vfc is higher than the efficiency required load end voltage Vinvη (Vfc> Vinvη). If the FC voltage Vfc is higher (step S5: YES), the FC voltage Vfc is determined to be the drive required load end voltage Vinvd. It is determined that the voltage is sufficiently higher (Vfc >> Vinvd), and in step S6, the SUC 21 is switched to the direct connection state (switching element 21b: continuation of the OFF state), and the FC voltage Vfc of the FC 18 is changed to the load end voltage Vinv. Apply.

  In this case, in step S7, the boost target voltage Vtar of the SUDC 22 is set to the FC voltage Vfc (Vtar = Vfc), and the SUDC 22 is boosted to control the direct connection state of the SUC 21 (FC 18) and the efficiency required load end voltage Vinvη or more. Since the load 30 is driven with the voltage of V, the control of the stable load end voltage Vinv can be continued while improving the efficiency of the fuel cell system 12.

  The state in which such control is continuing (step S1 → step S2 → step S3: YES → step S4: YES → step S5: YES → step S6 → step S7) is time t0 to time t1 in the timing chart of FIG. Corresponds to the state between.

  Then, during the continuation of such control, as shown at time t1, the FC voltage Vfc drops below the efficiency required load end voltage Vinvη, and the determination in step S5 is negative (step S5: NO, Vinvη ≧ Vfc). When it becomes, in step S8, it is determined whether or not the FC voltage Vfc is lower than the drive request load end voltage Vinvd (Vfc <Vinvd).

  Even if this determination is negative (step S8: NO, Vinvη ≧ Vfc ≧ Vinvd), since the FC voltage Vfc is higher than the drive request load end voltage Vinvd, the direct connection state is maintained without increasing the SUC21. The control in step S6 and step S7 (SUC21: direct connection, boost target voltage Vtar = Vfc of SUDC22) is executed. For this reason, system efficiency improves.

  This control (step S1 → step S2 → step S3: YES → step S4: YES → step S5: NO → step S8: NO → step S6 → step S7) is continued between time t1 and time t2, and at time t2. As shown in the figure, even when the state changes to Vfc> Vinvη> Vinvd, between time t2 and time t3, the same as between time t0 and time t1, the direct connection of SUC21 and the boost target voltage Vtar of SUDC22 is the FC voltage. The state of Vfc is continued.

  As shown at time t3, when the FC voltage Vfc is lower than the drive request load end voltage Vinvd and the determination in step S8 becomes affirmative (step S8: YES, Vfc <Vinvd <Vinvη), step S9 In order to suppress a rapid decrease in efficiency, the absolute value | Vinvη−Vfc | of the difference between the efficiency required load end voltage Vinvη and the FC voltage Vfc is calculated, and the absolute value of the difference | Vinvη−Vfc | It is determined whether or not a boosting boost (described later) is necessary or not (Vinvη−Vfc | <Vth), which is a voltage that is smaller than a threshold voltage Vth of a minute voltage that may cause unstable voltage conversion operation. .

  FIG. 14 shows a correspondence relationship between the FC current Ifc, which is the passing current of the SUC 21, and the passing loss Pconvloss of the SUC 21. As shown in FIG. 14, when the SUC 21 is directly connected (Vinv = Vfc), the passing loss Pdloss of the SUC 21 is a loss (Ifc × Vd) obtained by multiplying the forward voltage (Vd) of the diode 21c by the FC current Ifc, and the reactor. The total loss of the loss (Ifc × Rr) obtained by multiplying the direct current resistance (Rr) of 21a by the FC current Ifc (referred to as direct connection loss Pdloss, Pconvloss = Pdloss) is relatively small.

  However, the difference | Vinvη−Vfc | between the load end voltage Vinv and the FC voltage Vfc is less than the threshold voltage Vth which is a minute voltage that may cause the control of about 5 [V] to 15 [V] to become unstable. When the voltage is {(Vinv−Vfc) <Vth (Vth = 5 [V] to 15 [V])}, when the SUC 21 is boosted, the switching loss of the switching element 21b is combined with the above total loss. As shown in FIG. 14, the SUC passage loss Pconvloss (referred to as a loss Pthloss during minute boosting, Pconvloss = Pthloss) suddenly becomes excessive even though the boosting width is very small (Vinv−Vfc≈Vth).

  Here, the boosting width (Vinv−Vfc) is increased to, for example, about Vup = 20 [V] to 100 [V] as the boosting voltage Vup, which is equal to the boosting voltage Vup. Vinv−Vfc = (Vup), it should be noted that the loss Pvuploss at the time of boosting does not increase so much.

  That is, at time t3, the FC voltage Vfc is lower than the drive request load end voltage Vinvd lower than the efficiency request load end voltage Vinvη, and the determination in step S9 is affirmative (step S9: YES, | Vinvη−Vfc | In the case of <Vth), in consideration of the increase voltage loss Pvuploss, in step S10, the boost width of the SUC 21 is increased to the increase voltage Vup to increase the voltage. In this case, in step S11, the boost target voltage Vtar of the SUDC 22 is determined to be Vfc + Vup and boosted. In this way, between the time points t3 and t4, by continuing the boosting (bulking voltage boosting), the system efficiency is lower than when the SUC 21 is directly connected, but the system efficiency is lower than when the SUC21 is directly connected. In addition, since the boosted voltage Vup is considerably higher than the threshold voltage Vth, it is possible to eliminate the instability of control in which the boosting width becomes a low voltage.

  Between time t3 and time t4, step S1, step S2, step S3: YES, step S4: YES, step S5: NO, step S8: YES, step S9: YES, step S10, step S11 (bulk up) The pressure increasing process) is repeated.

  When the absolute value of the difference between the FC voltage Vfc and the efficiency required load end voltage Vinvη at the time point t4 is equal to or higher than the threshold voltage Vth (| Vinvη−Vfc | ≧ Vth) (step S9: NO), As shown in the state after t4, the boosting is released, the boosting width is set so that the load end voltage Vinv becomes the efficiency required load end voltage Vinvη, the SUC 21 is boosted in step S12, and step S13 Thus, the boost target voltage Vtar of the SUDC 22 is set to the efficiency required load end voltage Vinvη, and the normal boost control is continued.

[First Modification]
Step S5: Before shifting (transitioning) from YES (Vfc> Vinvη) to the direct connection state of the SUC 21 in Step S6, or Step S8: Before continuing the direct connection state of the SUC 21 in Step S6 from NO (Vinvη ≧ Vfc ≧ Vinvd) 7, whether the vehicle 10 is in the condition J: acceleration state (high torque / medium rotational speed), condition K: non-including a high speed state or an uphill state, as shown in step S6 ′ of the flowchart of the first modification of FIG. You may make it determine whether it exists in an acceleration state (here middle torque and high rotation speed). Whether or not the vehicle is in an acceleration state can be determined from the accelerator pedal operation amount θp, the differential value of the vehicle speed Vs, the output value of an acceleration sensor (not shown), and the like. Whether or not the vehicle is in a high speed state can be determined based on whether or not the vehicle speed Vs is traveling at a substantially constant speed of about 80 [km / h] or higher. Can be determined from the vehicle speed Vs and the output of a tilt sensor (not shown) or the ratio of the rotational speed Nm [rpm] of the drive motor 14 to the rotational speed of the wheel [rpm].

  Therefore, if it is determined in step S6 ′ that the condition K is in a non-accelerated state (medium torque / high rotation speed) including a high speed state or an uphill state (step S6 ′: K), the direct connection of step S6 However, if it is determined in step S6 ′ that the condition J is in the acceleration state, the drive request load end voltage Vinvd is likely to rise, and step S9 is performed. Through the determination of whether or not the increase in pressure is required, both the SUC 21 and the SUDC 22 are shifted to the boosted state (step S10 → step S11 or step S12 → step S13) and controlled so as to meet the demand for the acceleration state. To prevent a decline in productivity (improves merchantability).

  Next, the operation of the second embodiment will be described. In addition, about the description after this 2nd Example, the process same as the process demonstrated by the 1st Example mentioned above and a 1st modification, or a process corresponding to the convenience of an understanding and avoidance of complexity. The same step number is appended with an alphabetical step number, and detailed description thereof is omitted.

[Second Embodiment] (Vinvη ≦ Vinvd and Vfc> Vbat)
The second embodiment will be described with reference to a flowchart in which the connector “2” in the flowchart in FIG. 5 is connected to the connector “2” in the flowchart in FIG.

  In step S <b> 1, the ECU 24 calculates motor required power (motor required power) Pmreq [kW] for the drive motor 14.

  In step S2, the drive request load end voltage Vinvd [V] is calculated based on the motor request power Pmreq, and the efficiency request load end voltage Vinvη [V] is calculated.

  Next, in the determination of step S3, the drive request load end voltage Vinvd and the efficiency request load end voltage Vinvη are compared, and during the rapid acceleration as described above, the drive request load end voltage Vinvd is the efficiency request load end. If it is determined that the voltage is higher than the voltage Vinvη (step S3: NO), it is determined in step S4a whether the FC voltage Vfc is higher than the BAT voltage Vbat (Vfc> Vbat). If this determination is affirmative (step S4a: YES), the program corresponding to the flowchart of FIG. 8 according to the second embodiment is executed through the connector “2”.

  Therefore, in step S9a, the drive request load end voltage Vinvd, which is higher than the efficiency request load end voltage Vinvη, is used in order to prevent a drop in merchandise that cannot be accelerated suddenly upon receiving a request for sudden acceleration. The absolute value | Vinvd−Vfc | of the difference between the FC voltage Vfc and the FC voltage Vfc is calculated, and is the absolute value of the difference | Vinvd−Vfc | smaller than the threshold voltage Vth of the minute voltage (| Vinvd−Vfc | <Vth) ) Determine whether or not.

  If the determination in step S9a is affirmative (step S9a: YES, | Vinvd−Vfc | <Vth), the boosting width of the SUC 21 is determined in step S10a in consideration of the bulk loss Pvuploss (see FIG. 14). Is increased to a voltage Vup and boosted. In this case, in step S11a, the boost target voltage Vtar of the SUDC 22 is determined to be Vtar = Vfc + Vup and boosted.

  On the other hand, if the determination in step S9a is negative (step S9a: NO, | Vinvd−Vfc | ≧ Vth), the load end voltage Vinv becomes the drive request load end voltage Vinvd without performing the boosting step-up. In step S12a, the SUC 21 is boosted, and in step S13a, the boost target voltage Vtar of the SUDC 22 is set to the drive request load end voltage Vinvd to perform boost control.

  According to the second embodiment, for example, there is a sudden acceleration request or the like (step S3: NO) during the principle control (Vinvη> Vinvd) for improving the system efficiency of the fuel cell system 12 in the first embodiment. In this case, in order to respond to the rapid acceleration request, etc., the exception control (Vinvη ≦ Vinvd) corresponding to the increase in the drive request load end voltage Vinvd can be performed, so that the rapid acceleration request can be immediately responded. It is possible to prevent deterioration of merchantability.

[Third Embodiment] (Vinvη> Vinvd and Vfc ≦ Vbat)
The third embodiment is implemented by a flowchart in which the connector “3” of the flowchart of FIG. 5 is connected to the connector “3” of the flowchart of FIG.

  Each process of the flowchart of FIG. 9 is the same process as or corresponding to each process of the flowchart of FIG. 6 described above, and is different only in that the BAT voltage Vbat, which is the premise determination in step S4, is equal to or higher than the FC voltage Vfc. ing. Therefore, an alphabet “b” will be added to the end of the same step number for a brief explanation.

  In the third embodiment, since the BAT voltage Vbat is equal to or higher than the FC voltage Vfc (Vfc ≦ Vbat), the converter to be directly connected is connected to the FC18 side where the FC voltage Vfc of the primary side 1sf is relatively low. The BAT voltage Vbat on the primary side 1sb from the SUC 21 is replaced with a BAT side SUDC 22 which is relatively high. On the other hand, the converter to be boosted constantly has a BAT 20 side SUDC 22 on which the BAT voltage Vbat on the primary side 1sb is relatively high. To the FC 18 side SUC 21 in which the FC voltage Vfc on the primary side 1sf is relatively low.

  In the third embodiment, similarly to the first embodiment, for example, when the determination in the first step S5b is affirmative {step S5b: YES, (Vbat> Vinvη)}, the SUDC 22 is set in step S6b. Directly connected, the load end voltage Vinv is set to the BAT voltage Vbat, and the step-up target voltage Vtar of the SUC 21 is set to Vtar = Vbat in step S7b to ensure improved controllability and system efficiency.

  On the other hand, even if the determination in step S5b is negative {step S5b: NO, (Vbat ≦ Vinvη)}, the determination in step S8b is negative (step S8b: NO) and the BAT voltage Vbat is greater than the drive request load end voltage Vinvd. Is high (Vbat ≧ Vinvd), the direct connection of the SUDC 22 in step S6b and the boost control in which the boost target voltage Vtar of the SUC 21 in step S7b is Vtar = Vbat are continued. And the improvement of system efficiency is ensured.

  Further, when the BAT voltage Vbat becomes lower than the drive request load end voltage Vinvd and the determination in step S8b becomes affirmative (step S8b: YES, Vbat <Vinvd <Vinvη), the efficiency is increased in step S9b. In order to suppress a rapid drop, the absolute value | Vinvη−Vbat | of the difference between the efficiency required load end voltage Vinvη and the BAT voltage Vbat is calculated, and the absolute value | Vinvη−Vbat | of the difference is a threshold voltage Vth of a minute voltage. It is determined whether or not the voltage is smaller (| Vinvη−Vbat | <Vth), that is, whether or not a boosting boost is necessary.

  When the BAT voltage Vbat is lower than the drive request load end voltage Vinvd lower than the efficiency request load end voltage Vinvη, and the determination in step S9b becomes affirmative (step S9b: YES, | Vinvη−Vbat | <Vth) The loss Pvuploss at the time of boosting (see FIG. 14, Vfc is replaced with Vbat in FIG. 14. Note that the loss Pvuploss at the time of boosting is the loss at the time of boosting of the SUDC 22 in this case. In step S10b, the SUDC 22 is increased to the voltage Vup and boosted. That is, in step S11b, the boost target voltage Vtar of the SUC 21 is determined to be Vbat + Vup and boosted. By executing this boosting boosting (bulking voltage boosting) control, the system efficiency is lower than when the SUDC 22 is directly connected, but the reduction in system efficiency can be minimized as compared with the direct connection.

  When the absolute value | Vinvη−Vbat | of the difference between the BAT voltage Vbat and the efficiency required load end voltage Vinvη is equal to or higher than the threshold voltage Vth (| Vinvη−Vbat | ≧ Vth) (step S9b: NO), the boosting boost is released, the boosting width is set so that the load end voltage Vinv becomes the efficiency required load end voltage Vinvη, the SUDC 22 is boosted in step S12b, and the boost of the SUC 21 is boosted in step S13b. The target voltage Vtar is set to the efficiency required load end voltage Vinvη, and normal boost control is performed.

  In the third embodiment, the processing of [first modification] described with reference to FIG. 7 can be executed in the same manner.

[Fourth Embodiment] (Vinvη ≦ Vinvd and Vfc ≦ Vbat)
The fourth embodiment will be described with reference to a flowchart in which the connector “4” in the flowchart in FIG. 5 is connected to the connector “4” in the flowchart in FIG.

  Since the fourth embodiment is a process in which Vfc is replaced with Vbat and the processes of the SUC 21 and SUDC 22 are replaced in the second embodiment, a brief description will be given.

  In step S <b> 1, the ECU 24 calculates motor required power (motor required power) Pmreq [kW] for the drive motor 14.

  In step S2, the drive request load end voltage Vinvd [V] is calculated based on the motor request power Pmreq, and the efficiency request load end voltage Vinvη [V] is calculated.

  Next, in the determination in step S3, the drive request load end voltage Vinvd and the efficiency request load end voltage Vinvη are compared, and it is determined that the drive request load end voltage Vinvd is higher than the efficiency request load end voltage Vinvη ( If NO in step S3, it is determined in step S4a whether the FC voltage Vfc is higher than the BAT voltage Vbat (Vfc> Vbat). If this determination is negative (step S4a: NO), the program corresponding to the flowchart of FIG. 10 according to the fourth embodiment is executed through the connector “4”.

  Therefore, in step S9c, the absolute value | Vinvd−Vbat | of the difference between the drive request load end voltage Vinvd and the BAT voltage Vbat is calculated, and the absolute value of the difference | Vinvd−Vbat | is smaller than the threshold voltage Vth of the minute voltage. It is determined whether or not the voltage is reached (| Vinvd−Vbat | <Vth).

  When the determination in step S9c is affirmative (step S9c: YES, | Vinvd−Vbat | <Vth), the loss Pvuploss during the boosting voltage boost (see FIG. 14, also in this case, Vfc is changed to Vbat in FIG. In step S10c, the SUDC 22 is increased and the voltage Vup is increased to increase the voltage. In this case, in step S11c, the boost target voltage Vtar of the SUC 21 is determined to be Vbat + Vup and boosted.

  On the other hand, when the determination in step S9c is negative (step S9c: NO, | Vinvd−Vbat | ≧ Vth), the load end voltage Vinv becomes the drive request load end voltage Vinvd without performing the boosting step-up. In step S12c, the SUDC 22 is boosted, and in step S13c, the boost target voltage Vtar of the SUC 21 is set to the drive request load end voltage Vinvd to perform boost control.

  According to the fourth embodiment, for example, when there is a sudden acceleration request or the like (step S3) during the principle control (Vinvη> Vinvd) for improving the system efficiency of the fuel cell system 12 in the third embodiment. In order to respond to the rapid acceleration request, etc., the exception control (Vinvη ≦ Vinvd) corresponding to the increase in the drive request load end voltage Vinvd can be performed, so that the rapid acceleration request can be immediately responded. It is possible to prevent the merchantability from decreasing.

[Summary of Embodiment]
As described above, the FC system 12 according to the above-described embodiment includes a load including the FC 18 that outputs the FC voltage Vfc, the BAT 20 that outputs the BAT voltage Vbat, and the drive motor 14 driven through the inverter 16 and the inverter 16. 30 and the SUC 21 as the first voltage conversion device applied as the load side voltage Vinv to the DC side of the inverter 16 and the BAT voltage Vbat as the primary side voltage. In the control method of the FC system 12 including the SUDC 22 that is applied to the DC terminal side of the inverter 16 as the load terminal voltage Vinv, the load 30 is driven as the load terminal voltage Vinv based on a drive request to the FC system 12. Drive demand load end voltage Vinvd and load 30 efficiently The required voltage determination process (step S2) for determining the efficiency required load end voltage Vinvη to be operated, and among the SUC21 and SUDC22, a high voltage of the FC voltage Vfc and the BAT voltage Vbat is applied as the primary side voltage. When the primary side voltage (in this case, the FC voltage Vfc) of any one of the voltage conversion devices (for example, SUC21) exceeds the efficiency required load end voltage Vinvη (step S5), the voltage A voltage conversion stop step (step S6) for stopping and directly coupling the voltage conversion operation of the converter (in this case, SUC21), and the primary side voltage (in this case, SUC21) of the primary side voltage (SUC21) In this case, even if the FC voltage Vfc) falls below the efficiency required load end voltage Vinvη (step S5: NO), the drive required load end voltage Vinv (Step S8: NO) (for example, between time t1 and time t2 in FIG. 13), the voltage conversion operation (in this case, SUC21) is stopped (step S6). ing.

  Thus, the primary of one of the voltage converters (the SUC21 in the first embodiment and the SUDC22 in the third embodiment) to which a high voltage is applied as the primary voltage among the FC voltage Vfc and the BAT voltage Vbat. While the side voltage (FC voltage Vfc in the first embodiment, BAT voltage Vbat in the third embodiment) is below the efficiency required load end voltage Vinvη, the voltage conversion is performed while it is above the drive required load end voltage Vinvd. Since the operation stop state, that is, the direct connection state is continued, the duration of the direct connection state can be extended and the system efficiency can be improved.

  In this case, when the voltage conversion operation is stopped (for example, when Vfc> Vbat and the SUC 21 is directly connected), step S1, step S2, step S3: YES, step S4: YES, step S5: YES → Step S6 → Step S7), the primary voltage (in this case, the FC voltage Vfc) of the one voltage converter (in this case, the SUC 21) that is directly connected is set to the drive request load end voltage Vinvd. When the voltage is lower (step S8: YES), the difference voltage (| Vinvη−Vfc |) between the efficiency required load end voltage Vinvη and the primary voltage (in this case, the FC voltage Vfc) of the one voltage converter is A difference voltage grasping step (step S9) for grasping is provided, and the difference voltage (| Vinvη−Vfc |) is converted into the one voltage converter (in this case, When the voltage conversion operation of UC21) is a value less than the threshold voltage Vth at which the voltage conversion operation becomes unstable (step S9: YES), the step-up width (bulge) that causes the load end voltage Vinv to exceed the efficiency required load end voltage Vinvη A voltage boosting step (step S11) for setting the voltage) Vup and starting the voltage conversion operation of the one of the voltage converters (in this case, SUC21) with the set boosting width Vup may be further provided.

  In this way, one of the voltage conversion operations being directly connected is in a stopped state (the process including the processes in steps S6 and S7 in FIG. 6 is being continued, or the process including the processes in steps S6b and S7b in FIG. 9). And the primary side voltage of the one directly connected voltage converter (in this case, SUC21) falls below the drive request load terminal voltage Vinvd (step S8: YES, step S8b: YES) The difference voltage (| Vinvη−Vfc |, | Vinvη−Vbat |) between the efficiency required load end voltage Vinvη and the primary side voltage of the one voltage converter is grasped (Step S9, Step S9b), and the difference The voltages (| Vinvη−Vfc |, | Vinvη−Vbat |) are values less than a threshold voltage at which the voltage conversion operation of the one voltage converter becomes unstable ((| In the case of Vinvη−Vfc | <Vth, | Vinvη−Vbat | <Vth)), the step-up width (Vfc + Vup, Vbat + Vup) is set so that the load end voltage Vinv exceeds the efficiency required load end voltage Vinvη. Since the voltage conversion operation of the one of the voltage converters (SUC21, SUDC22) is started with the boosted width, the system efficiency is improved while preventing the occurrence of an unstable voltage conversion operation state. A voltage conversion operation can be performed.

  Note that the FC voltage Vfc and the BAT voltage Vbat are used as the primary voltage while the voltage conversion operation of the one voltage converter (for example, SUC21 in the SUC21 or SUDC22) is stopped. Among the other voltage converters (in this case, SUDC22), the boost target voltage Vtar, which is a command value for the boosting width of the other voltage converter (in this case, SUDC22) to which the low voltage is applied, is used as the other voltage converter (in this case, SUDC22) Is set to a difference voltage (in this case, the difference voltage is Vinv−Vfc) between the primary side voltage and the load end voltage Vinv in direct connection (step S11, step S11b), thereby the other voltage converter. Since the load end voltage Vinv is controlled by (in this case, SUDC22), one of the voltage converters (in this case, SUC21) Can continue as much as possible formation, improves system efficiency.

  In addition, among the SUC 21 and the SUDC 22, the primary side of any one of the voltage converters (SUC 21 or SUDC 22) to which a high voltage is applied as the primary side voltage among the FC voltage Vfc and the BAT voltage Vbat. When the voltage (FC voltage Vfc or BAT voltage Vbat) exceeds the efficiency required load end voltage Vinvη, immediately before the voltage conversion operation of the voltage converter (SUC21 or SUDC22) is stopped and directly connected (step S6: SUC21). Of the one of the voltage converters (SUC21, SUDC22) immediately after the direct connection, step S6b: immediately before the direct connection of SUDC22) and after the voltage conversion stop step (step S6: direct connection of SUC, step S6b: SUDC22). Side voltage (FC voltage Vfc, BAT voltage Vbat) requires efficiency Even if the voltage is lower than the load end voltage Vinvη (step S5: NO, step S5b: NO), the voltage conversion operation is stopped while the drive required load end voltage Vinvd is higher (step S8: NO, step S8b: NO). Immediately before continuing the state (steps S6, S6b), the vehicle 10 further includes a vehicle state grasping step (step S6 ′) for grasping the vehicle state whether or not the vehicle 10 is in a high-speed running state or an uphill state. In the grasping step (step S6 ′), when it is grasped that the vehicle 10 is in the high-speed traveling state or the climbing state, the voltage conversion operation of the voltage converter (in this case, SUC21 or SUDC22) is stopped. Direct connection (steps S6 and S6b) may be performed, and in the case of direct connection, the stop state of the voltage conversion operation may be continued.

  In this way, it is possible to easily determine whether or not one of the voltage conversion devices is in the state of being directly connected and continued, and since the drive request load end voltage Vinvd is ensured, it is possible to prevent deterioration in merchantability. be able to.

  In addition, the control method of the FC system 12 according to this embodiment includes an FC 18 that outputs the FC voltage Vfc, a BAT 20 that outputs the BAT voltage Vbat, an inverter 16, and a drive motor that is driven through the inverter 16 for driving the vehicle. 14, a SUC 21 that boosts the FC voltage Vfc and applies it to the DC end side of the inverter 16 as the load end voltage Vinv, and boosts the BAT voltage Vbat and applies it to the DC end side of the inverter 16 as the load end voltage Vinv In the control method of the FC system 12 having the SUDC 22, the required voltage determination process for determining the drive request load end voltage Vinvd for driving the load 30 based on the drive request to the FC system 12 as the load end voltage Vinv. (Step S2) and a vehicle driven by the drive motor 14 A vehicle state grasping step (for example, step S6 ′) for determining whether 0 is in an acceleration state, a high-speed traveling state, or an uphill state, and the drive request load end voltage Vinvd, FC voltage Vfc, and BAT voltage Vbat. Based on a step-up necessity determination step (step S6 ′) for determining whether step-up of the SUC 21 and the SUDC 22 is necessary. In the step-up necessity determination step (step S6 ′), in the vehicle state grasping step (step S6 ′) When it is determined that the vehicle 10 is in the acceleration state, both the SUC 21 and the SUDC 22 are boosted (step S9: YES → step S10 → step S11 or step S9: NO → step S12 → step S13). In the state grasping step (step S6 ′), the vehicle 10 is in the high speed running state or the climbing state Is determined (step S6 ′: determination K), one of the voltage converters of the SUC21 and the SUDC22 to which the higher one of the FC voltage Vfc and the BAT voltage Vbat is applied (in this case) , SUC21) is determined to be in a directly connected state (step S6).

  As described above, based on the vehicle state, the drive request load end voltage Vinvd, the FC voltage Vfc, and the BAT voltage Vbat, the voltage converter of any one of the first and second converters (SUC21 and SUDC22) is brought into the direct connection state. Since the transition is determined, it is possible to easily determine the transition of one of the first and second converters (SUC21 and SUDC22) to the directly connected state while improving the system efficiency.

  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 description in this specification.

10. Fuel cell vehicle (FC vehicle)
12 ... 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)
24 ... ECU

Claims (5)

A fuel cell that outputs a fuel cell voltage;
A power storage device that outputs a power storage device voltage;
A load comprising an inverter and a drive motor driven through the inverter;
The fuel cell voltage is boosted as a primary side voltage and applied as a load end voltage to the DC end side of the inverter, and the power storage device voltage is boosted as the primary side voltage and the load end voltage is used as the load end voltage. A second voltage conversion device applied to the DC terminal side of the inverter;
In a control method of a fuel cell system comprising:
As the load end voltage, a required voltage for determining a drive required load end voltage for driving the load and an efficiency required load end voltage for efficiently driving the load based on a drive request to the fuel cell system. A decision process ;
A comparison determination step for determining which voltage of the fuel cell voltage and the power storage device voltage is higher; and
If the fuel cell voltage is determined to be high, the fuel cell voltage is determined to high, when exceeds the efficiency required load end voltage, thereby directly stops the voltage conversion operation of said first voltage conversion device If the power storage device voltage is determined to be high, the voltage conversion operation of the second voltage conversion device is stopped when the power storage device voltage determined to be high exceeds the efficiency required load terminal voltage. A voltage conversion stop process for direct connection ,
While the primary side voltage of one of the voltage converters directly connected in the first and second voltage converters is lower than the efficiency required load end voltage, while being higher than the drive required load end voltage, The control method of the fuel cell system, wherein the voltage conversion operation is stopped. In the control method of the fuel cell system according to claim 1,
When the primary side voltage of the one voltage conversion device in direct connection is lower than the drive required load end voltage, the efficiency required load end voltage and the primary side voltage of the one voltage conversion device Establish a differential voltage grasping process to grasp the difference voltage,
It said difference voltage, when a value less than the threshold value voltage is set to boost width of the load end voltage becomes the voltage in excess of the efficiency required load end voltage, the one of the voltage converted by the step-up width set A control method for a fuel cell system, further comprising: a step-up width increasing step for starting a voltage conversion operation of the device. In the control method of the fuel cell system according to claim 1,
While the stopped state of the voltage conversion operation of the one voltage converter is continuing, the boost of the other voltage converter to which a low voltage is applied as the primary voltage among the fuel cell voltage and the power storage device voltage The control value of a fuel cell system characterized by setting the command value of width to the voltage difference between the primary side voltage of the other voltage converter and the load end voltage during direct connection. In the control method of the fuel cell system according to claim 1,
The drive motor is for driving a vehicle,
Among the first voltage conversion device and the second voltage conversion device, the primary of any one of the voltage conversion devices to which a high voltage is applied as the primary side voltage among the fuel cell voltage and the power storage device voltage. When the side voltage exceeds the efficiency required load end voltage, immediately before the voltage conversion operation of the voltage conversion device is stopped and directly connected, and after the voltage conversion stop step, the primary side of the one voltage conversion device Even if the voltage is lower than the efficiency required load end voltage, while the voltage exceeds the drive required load end voltage, immediately before the voltage conversion operation is stopped, the vehicle is in a high-speed running state or an uphill state. A vehicle state grasping step for grasping the vehicle state whether or not
In the vehicle state grasping step, when it is grasped that the vehicle is in the high-speed running state or the uphill state, the voltage conversion operation of the voltage conversion device is stopped and directly connected. A control method for a fuel cell system, characterized in that the stopped state of the voltage conversion operation is continued. A fuel cell vehicle that implements the control method for a fuel cell system according to any one of claims 1 to 4 .

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