JP5428526B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system.

  In a fuel cell system in which a fuel cell and a battery are mounted as power sources, the operation efficiency is improved by controlling the output from the fuel cell and the battery according to the operating state. Patent Document 1 below discloses a fuel cell system including a fuel cell converter and a battery converter. In this fuel cell system, two converters are operated in a coordinated manner in order to stably supply power to a motor that is a power consuming device.

JP 2007-209161 A

  By the way, in the battery converter provided in the fuel cell system, when the battery voltage is boosted, it is difficult to stably control the boosted state from the battery voltage to the predetermined voltage. Some are set as areas. In such a fuel cell system having a battery converter, when the required voltage of the motor is in a region where it cannot be boosted, the boosting operation of the fuel cell converter is stopped and the output voltage to the motor is reduced to the battery voltage. I do. If such control is performed, it becomes impossible to satisfy the required voltage of the motor, so that the power performance is lowered and the drivability deteriorates.

  The present invention has been made to solve the above-described problems caused by the prior art, and an object of the present invention is to provide a fuel cell system capable of ensuring the required voltage of the power consuming device.

  In order to solve the above-described problems, a fuel cell system according to the present invention includes a fuel cell that receives supply of a fuel gas and an oxidant gas and generates power by an electrochemical reaction between the fuel gas and the oxidant gas, and a power generated by the fuel cell. An electric power unit that can be charged, an electric power consuming device that consumes electric power from the fuel cell and the electric power unit, and an output voltage from the fuel cell disposed between the fuel cell and the electric power consuming device A first voltage conversion unit that boosts and outputs to the power consuming device, and is arranged between the livestock power unit and the power consuming device, boosts an output voltage from the livestock power unit and consumes the power When the required voltage of the second voltage conversion unit that outputs to the device and the power consuming device is higher than the output voltage of the livestock power storage unit, the lower limit value of the output voltage to the power consuming device is Boostable by the voltage converter Characterized in that it comprises a load voltage control means for setting the a minimum voltage.

  According to this invention, when the required voltage of the power consuming device is higher than the output voltage of the power storage unit, the lowest voltage that can be boosted by the second voltage converting unit is set as the lower limit value of the output voltage to the power consuming device. Can be set. As a result, even if the required voltage of the power consuming device is included in the region that cannot be boosted by the second voltage converter, the lowest voltage that can be boosted by the second voltage converter is used as the output voltage to the power consuming device. Since it can be made to output, the output voltage of an electrical storage part can be reliably raise | lifted more than the request voltage of a power consuming apparatus.

  In order to solve the above-described problems, a fuel cell system according to the present invention includes a fuel cell that receives supply of a fuel gas and an oxidant gas and generates power by an electrochemical reaction between the fuel gas and the oxidant gas, and a power generated by the fuel cell. An electric power unit that can be charged, an electric power consuming device that consumes electric power from the fuel cell and the electric power unit, and an output voltage from the fuel cell disposed between the fuel cell and the electric power consuming device A first voltage conversion unit that boosts and outputs to the power consuming device, and is arranged between the livestock power unit and the power consuming device, boosts an output voltage from the livestock power unit and consumes the power When the required voltage of the second voltage converter that outputs to the device and the power consuming device is lower than the lowest voltage that can be boosted by the second voltage converter, the output voltage to the power consuming device is Second voltage Characterized in that it and a load voltage control means for setting the boosting lowest possible voltage by section.

  According to this invention, when the required voltage of the power consuming device is lower than the lowest voltage that can be boosted by the second voltage converter, the second voltage converter can boost the output voltage to the power consuming device. A minimum voltage can be set. As a result, even if the required voltage of the power consuming device is included in the region that cannot be boosted by the second voltage converter, the lowest voltage that can be boosted by the second voltage converter is supplied to the power consuming device. Since it can be made to output as an output voltage, the output voltage of an electrical storage part can be reliably raise | lifted more than the request voltage of an electric power consumption apparatus.

  In the fuel cell system, the load voltage control means is configured such that the required voltage of the power consuming device is lower than the lowest voltage that can be boosted by the second voltage converter, and the required voltage of the power consuming device is: When the output voltage is higher than the output voltage of the livestock power storage unit, the lowest voltage that can be boosted by the second voltage conversion unit may be set as the output voltage to the power consuming device.

  In this way, when the required voltage of the power consuming device is equal to or lower than the output voltage of the livestock storage unit, that is, when boosting by the second voltage conversion unit is unnecessary, the second voltage conversion unit is driven. Therefore, unnecessary power loss can be suppressed.

  In the fuel cell system, a required power generation amount calculation unit that calculates a required power generation amount to the fuel cell according to an operation amount of an acceleration operation member, and consumption of the power consumption device corresponding to an output voltage to the power consumption device A power consumption calculating means for calculating an electric energy; and the fuel consumption when the required power generation calculated by the required power generation calculating means is greater than the power consumption calculated by the power consumption calculating means. A required power generation amount control means for setting the power consumption may be further provided as the required power generation amount for the battery.

  By doing in this way, since the electric power generation amount of a fuel cell can be restrained to the power consumption amount of a power consuming apparatus, generation | occurrence | production of the overvoltage and overcurrent resulting from the surplus electric power of a fuel cell can be suppressed.

  According to the present invention, the required voltage of the power consuming device can be secured.

It is a figure which shows typically the structure of the fuel cell system in embodiment. It is a figure for demonstrating the transition state of the output voltage to the traction motor in embodiment. It is a flowchart for demonstrating the flow of the output voltage control process to the traction motor in embodiment. It is a figure for demonstrating the transition state of the output voltage to the traction motor in a modification. It is a flowchart for demonstrating the flow of the output voltage control process to the traction motor in a modification.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a fuel cell system according to the invention will be described with reference to the accompanying drawings. In the embodiment, a case will be described in which the fuel cell system according to the present invention is used as an on-vehicle power generation system of a fuel cell vehicle (FCHV). The fuel cell system according to the present invention can also be applied to various mobile bodies (robots, ships, aircrafts, etc.) other than fuel cell vehicles, and further used as power generation equipment for buildings (housing, buildings, etc.). It can be applied to a stationary power generation system.

  First, the configuration of the fuel cell system in the present embodiment will be described with reference to FIG. FIG. 1 is a diagram schematically illustrating a fuel cell system according to an embodiment.

  As shown in the figure, a fuel cell system 1 includes a fuel cell 2 that generates electric power by an electrochemical reaction between an oxidizing gas that is a reaction gas and a fuel gas, and a DC / DC converter 3 for fuel cells (first voltage conversion). Part, hereinafter referred to as “FC converter”), battery 4 (power storage part) as a secondary battery, DC / DC converter 5 for battery (second voltage conversion part, hereinafter referred to as “Bat converter”), It has a traction inverter 6 and a traction motor 7 (power consuming device) as loads, and a control unit 8 (control means) that controls the entire system. The set of the fuel cell 2 and FC converter 3 and the set of the battery 4 and Bat converter 5 are connected in parallel to the traction inverter 6 and the traction motor 7.

  The fuel cell 2 is, for example, a polymer electrolyte fuel cell, and has a stack structure in which a large number of single cells are stacked. The single cell has an air electrode on one surface of an electrolyte composed of an ion exchange membrane, a fuel electrode on the other surface, and a structure having a pair of separators so as to sandwich the air electrode and the fuel electrode from both sides. It has become. In this case, hydrogen gas is supplied to the hydrogen gas passage of one separator, the oxidizing gas is supplied to the oxidizing gas passage of the other separator, and electric power is generated by the chemical reaction of these reaction gases.

  The FC converter 3 is a DC voltage converter, and has a function of boosting the DC voltage output from the fuel cell 2 and outputting the boosted voltage to the traction inverter 6 on the power consuming device side. The output voltage of the fuel cell 2 is controlled by the FC converter 3. A voltage sensor V1 for detecting the output voltage of the fuel cell 2 is provided on the input side of the FC converter 3, and a voltage sensor V2 for detecting the output voltage of the FC converter 3 is provided on the output side of the FC converter 3. Is provided.

  The battery 4 is configured such that battery cells are stacked and a constant high voltage is used as a terminal voltage, and the surplus power of the fuel cell 2 can be charged or supplementarily supplied by control of a battery computer (not shown). ing. Between the battery 4 and the Bat converter 5, a voltage sensor V3 for detecting the output voltage of the battery 4 is provided.

  The Bat converter 5 is a DC voltage converter, and boosts the DC voltage output from the battery 4 (hereinafter referred to as “battery voltage”) and outputs it to the traction inverter 6 on the power consuming device side. And a function of stepping down a DC voltage output from the fuel cell 2 or the traction motor 7 side and outputting it to the battery 4. The battery 4 is charged and discharged by the function of the Bat converter 5 as described above.

  The Bat converter 5 has a characteristic of stopping the boosting operation from the battery voltage to a predetermined voltage. This is because it is difficult to stably control the boosted state from the battery voltage to the predetermined voltage. In other words, when the battery converter 5 boosts the battery voltage, voltage conversion that can boost the voltage to a voltage equal to or higher than a voltage obtained by adding a predetermined voltage to the battery voltage at that time (hereinafter referred to as “the lowest voltage that can be boosted”). It is a vessel.

  The traction inverter 6 converts a direct current into a three-phase alternating current and supplies it to the traction motor 7. The traction motor 7 is, for example, a three-phase AC motor, and constitutes a main power source of a fuel cell vehicle on which the fuel cell system 1 is mounted.

  The control unit 8 detects an operation amount of an acceleration operation member (for example, an accelerator) provided in the fuel cell vehicle, and controls an acceleration request value (for example, a required power generation amount from a power consuming device such as the traction motor 7). Receives information and controls the operation of various devices in the system. In addition to the traction motor 7, the power consuming device includes, for example, auxiliary devices necessary for operating the fuel cell 2, various devices involved in traveling of the vehicle (transmission, wheel control device, steering device, Actuators used in suspension systems, etc., passenger space air conditioners (air conditioners), lighting, audio, etc.

  The control unit 8 has a function as load voltage control means for controlling an output voltage to the traction motor 7 as a load. Specifically, the control unit 8 determines whether or not the required voltage of the traction motor 7 is lower than the lowest voltage that can be boosted by the Bat converter 5. When the required voltage of the traction motor 7 is lower than the lowest voltage that can be boosted by the Bat converter 5, the control unit 8 sets the lowest voltage that can be boosted by the Bat converter 5 as the output voltage to the traction motor 7. . When the required voltage of the traction motor 7 is equal to or higher than the lowest voltage that can be boosted by the Bat converter 5, the control unit 8 sets the required voltage of the traction motor 7 as an output voltage to the traction motor 7.

  With reference to FIG. 2, the transition state of the output voltage to the traction motor 7 in the present embodiment will be described. The horizontal axis shown in FIG. 2 indicates time, and the vertical axis indicates voltage. 2 indicates an output voltage to the traction motor 7, BV indicates a battery voltage, and CV indicates a minimum voltage that can be boosted by the Bat converter 5. When the output voltage MV to the traction motor 7 is changed in accordance with the required voltage of the traction motor 7, the output voltage MV changes as shown by the dotted line from time t1 to time t2. On the other hand, according to the fuel cell system of the present embodiment, the required voltage of the traction motor 7 between time t1 and time t2 is determined to be lower than the lowest voltage CV that can be boosted by the Bat converter 5, The output voltage MV to the traction motor 7 from time t1 to time t2 is set to the lowest voltage CV that can be boosted by the Bat converter 5 as shown by the solid line. That is, during the period from the time t1 to the time t2, the transition is performed in the same state as when the lowest voltage CV that can be boosted by the Bat converter 5 is set as the lower limit value of the output voltage MV to the traction motor 7.

  The control unit 8 shown in FIG. 1 has a function as a required power generation amount calculation means for calculating a required power generation amount to the fuel cell 2 in accordance with a detection value of an accelerator sensor (not shown) that detects an accelerator operation amount. Specifically, the control unit 8 refers to a map that stores the correspondence relationship between the accelerator operation amount and the torque of the traction motor 7, calculates the torque corresponding to the detected value of the accelerator sensor, and calculates the calculated torque. The voltage required to generate is calculated. And the control part 8 calculates the power consumption of the traction motor 7 corresponding to the calculated voltage with reference to the map which memorize | stores the correspondence of the voltage provided to the traction motor 7, and the power consumption of the traction motor 7. Thus, the required power generation amount to the fuel cell 2 is calculated. Each map is stored in a memory, which will be described later, and each value stored in each map is obtained by experiments or the like.

  The control unit 8 has a function as power consumption calculation means for calculating the power consumption of the traction motor 7 corresponding to the output voltage to the traction motor 7. Specifically, the control unit 8 uses the voltage detected by the voltage sensor V2, and calculates the maximum power consumption that can be consumed by the traction motor 7 to which this voltage is input.

  When the calculated required power generation amount to the fuel cell 2 is larger than the calculated power consumption amount of the traction motor 7, the control unit 8 sets the calculated traction motor 7 to the calculated required power generation amount to the fuel cell 2. It functions as a required power generation amount control means for setting the power consumption amount. Thereby, since the power generation amount of the fuel cell 2 can be suppressed to the power consumption amount of the traction motor 7, it is possible to suppress the occurrence of overvoltage and overcurrent due to the surplus power of the fuel cell 2.

  Here, the control unit 8 physically includes, for example, a CPU, a memory, and an input / output interface. The memory includes a ROM that stores a control program and control data processed by the CPU, and a RAM that is mainly used as various work areas for control processing. These elements are connected to each other via a bus. Various sensors such as a voltage sensor and an accelerator sensor are connected to the input / output interface, and various drivers for driving the traction motor 7 and the like are connected.

  The CPU receives the detection results of the various sensors via the input / output interface according to the control program stored in the ROM, and processes them using various data in the RAM, whereby various control processes in the fuel cell system 1 are performed. Execute. Further, the CPU controls the entire fuel cell system 1 by outputting control signals to various drivers via the input / output interface.

  Next, processing for controlling the output voltage to the traction motor 7 in the present embodiment will be described using the flowchart shown in FIG. This process is started, for example, when the ignition key is turned on, and is repeatedly executed until the operation ends.

  First, the control unit 8 calculates a required voltage for the traction motor 7 (step S101). Specifically, the control unit 8 refers to a map that stores the correspondence relationship between the accelerator operation amount and the torque of the traction motor 7, calculates the torque corresponding to the detected value of the accelerator sensor, and calculates the calculated torque. The required voltage of the traction motor 7 is calculated by calculating the voltage required for generation.

  Subsequently, the control unit 8 calculates the lowest voltage that can be boosted by the Bat converter 5 (step S102). Specifically, the control unit 8 uses the voltage detected by the voltage sensor V3, adds the predetermined voltage described above to this voltage, and calculates the lowest voltage that can be boosted by the Bat converter 5.

  Subsequently, the control unit 8 determines whether or not the required voltage of the traction motor 7 calculated in step S101 is lower than the lowest voltage that can be boosted by the Bat converter 5 calculated in step S102 (step S103). ). When this determination is YES (step S103; YES), the control unit 8 sets a minimum voltage that can be boosted by the Bat converter 5 as an output voltage to the traction motor 7 (step S104).

  On the other hand, when it is determined in step S103 that the required voltage of the traction motor 7 is equal to or higher than the lowest voltage that can be boosted by the Bat converter 5 (step S103; NO), the control unit 8 moves to the traction motor 7. The required voltage of the traction motor 7 is set as the output voltage (step S105).

  As described above, according to the fuel cell system 1 in the present embodiment, when the required voltage of the traction motor 7 is lower than the lowest voltage that can be boosted by the Bat converter 5, the output voltage to the traction motor 7 is obtained. The lowest voltage that can be boosted by the Bat converter 5 can be set. As a result, even if the required voltage of the traction motor 7 is included in a region where it cannot be boosted by the Bat converter 5, the lowest voltage that can be boosted by the Bat converter 5 is output as the output voltage to the traction motor 7. Therefore, the battery voltage can be surely boosted to a voltage higher than the required voltage of the traction motor 7.

  In the above-described embodiment, the control unit 8 can boost the output voltage to the traction motor 7 with the Bat converter 5 when the required voltage of the traction motor 7 is lower than the lowest voltage that can be boosted with the Bat converter 5. However, the condition for setting the minimum voltage that can be boosted by the Bat converter 5 to the output voltage to the traction motor 7 is not limited to this. For example, when the required voltage of the traction motor 7 is lower than the lowest voltage that can be boosted by the Bat converter 5 and the required voltage of the traction motor 7 is higher than the battery voltage, the output voltage to the traction motor 7 is Bat The lowest voltage that can be boosted by the converter 5 may be set.

  With reference to FIG. 4, the transition state of the output voltage to the traction motor 7 in this modification is demonstrated. The horizontal axis shown in FIG. 4 indicates time, and the vertical axis indicates voltage. 4 indicates the output voltage to the traction motor 7, BV indicates the battery voltage, and CV indicates the lowest voltage that can be boosted by the Bat converter 5. When the output voltage MV to the traction motor 7 is changed in accordance with the required voltage of the traction motor 7, the output voltage MV changes as shown by the dotted line from the time t1 to the time t2 and from the time t3 to the time t4. . On the other hand, according to the fuel cell system of the present modification, the required voltage of the traction motor 7 between time t1 and time t2 and between time t3 and time t4 is the lowest voltage that can be boosted by the Bat converter 5. It is determined that the voltage is lower than the voltage CV and higher than the battery voltage BV, and the output voltage MV to the traction motor 7 from time t1 to time t2 and from time t3 to time t4 is shown by a solid line. The lowest voltage CV that can be boosted by the Bat converter 5 is set. That is, during the period from time t1 to time t2 and from time t3 to time t4, when the lowest voltage CV that can be boosted by the Bat converter 5 is set as the lower limit value of the output voltage MV to the traction motor 7. It will change in the same state.

  On the other hand, since the required voltage of the traction motor 7 is lower than the battery voltage BV from time t2 to time t3, the output voltage MV to the traction motor 7 changes according to the required voltage of the traction motor 7. . That is, during this time, the output of the Bat converter 5 is stopped, and the traction motor 7 is driven only by the output of the FC converter 3.

  As a result, when the required voltage of the traction motor 7 is equal to or lower than the battery voltage BV, that is, when boosting by the Bat converter 5 is not necessary, the driving of the Bat converter 5 can be stopped, so that unnecessary power is consumed. Loss can be suppressed.

  Next, processing when controlling the output voltage to the traction motor 7 in this modification will be described using the flowchart shown in FIG. This process is started, for example, when the ignition key is turned on, and is repeatedly executed until the operation ends. Note that the processes in steps S201 and S202 shown in FIG. 5 are the same as the processes in steps S101 and S102 shown in FIG. 3 described in the above-described embodiment. The processing after different step S203 will be described.

  First, in step S201, the required voltage of the traction motor 7 is calculated. In step S202, after the minimum voltage that can be boosted by the Bat converter 5 is calculated, the control unit 8 calculates the request for the traction motor 7 calculated in step S201. It is determined whether or not the voltage is lower than the lowest voltage that can be boosted by the Bat converter 5 calculated in step S202 and higher than the battery voltage detected by the voltage sensor V3 (step S203). When this determination is YES (step S203; YES), the control unit 8 sets a minimum voltage that can be boosted by the Bat converter 5 as an output voltage to the traction motor 7 (step S204).

  On the other hand, when it is determined in step S203 that the required voltage of the traction motor 7 is equal to or higher than the lowest voltage that can be boosted by the Bat converter 5 or lower than the battery voltage (step S203; NO), the control unit 8 The required voltage of the traction motor 7 is set as the output voltage to the traction motor 7 (step S205).

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 2 ... Fuel cell, 3 ... DC-DC converter for FC, 4 ... Battery, 5 ... DC-DC converter for Bat, 6 ... Traction inverter, 7 ... Traction motor, 8 ... Control part, V1, V2, V3 ... Voltage sensors.

Claims (1)

A fuel cell that receives supply of the fuel gas and the oxidizing gas and generates power by an electrochemical reaction of the fuel gas and the oxidizing gas;
A power storage unit capable of charging the power generated by the fuel cell; and
A power consuming device that consumes power from the fuel cell and the power storage unit;
A first voltage converter disposed between the fuel cell and the power consuming device, boosting an output voltage from the fuel cell and outputting the boosted voltage to the power consuming device;
A second voltage converter disposed between the power storage unit and the power consuming device, boosting an output voltage from the power storage unit and outputting the boosted voltage to the power consuming device;
When the required voltage of the power consuming device is lower than the lowest voltage that can be boosted by the second voltage converter, and the required voltage of the power consuming device is higher than the output voltage of the power storage unit, When the minimum voltage that can be boosted by the second voltage converter is set as the output voltage to the power consuming device, while the required voltage of the power consuming device is lower than the output voltage of the power storage unit, the first voltage Load voltage control means for stopping the output of the second voltage converter and driving the power consuming device only with the output of the first voltage converter ;
A fuel cell system comprising:

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