JP5370726B2 - 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 listed below discloses a fuel cell converter and a battery converter. In this fuel cell system, in order to stably supply electric power to the motor, the two converters are operated in cooperation.
JP 2007-209161 A

  By the way, in the battery converter provided in the fuel cell system, when the difference between the target output voltage to the motor and the output voltage of the battery is less than a predetermined voltage difference, the battery output voltage is changed to the target output voltage to the motor. Some of them have the characteristic that they cannot be boosted up to. In a fuel cell system having such a battery converter, as described above, when the battery output voltage cannot be boosted, the boost in the fuel cell converter is stopped and the output voltage to the motor is reduced. Control to reduce the output voltage of the battery is performed. However, when such control is performed, the output voltage of the fuel cell, which should originally be smaller than the output voltage to the motor, may become larger than the output voltage to the motor. In such a case, it is considered that unintended surplus power is generated in the fuel cell, the surplus power is charged in the battery, and the battery fails due to overcharge.

  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 suppressing the generation of unintended surplus power in the fuel cell. .

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. a charge reservoir portion can be charged to a power consuming device to consume power from the fuel cell and the charge reservoir portion, a first voltage conversion unit disposed between the fuel cell and the power consuming device , a second voltage converter which is disposed between the power unit and the charge reservoir unit, the output voltage to the power consuming device, the fuel cell output voltage or more and the output voltage of the charge reservoir section Control means for controlling as described above.

Thus, the output voltage of the power consuming device is a the fuel cell output voltage or more and to be controlled over the output voltage of the charge reservoir section, the following output voltage of the output voltage of the fuel cell to the power consuming device Can be maintained.

In the fuel cell system, said control means includes a demanded power generation amount from the power consuming device, by using the output voltage of the charge reservoir unit, calculates a possible output voltage to the power consuming device from the charge reservoir section When the possible output voltage is equal to or lower than the output voltage of the fuel cell, the output voltage of the fuel cell is set as the output voltage to the power consuming device, and the possible output voltage is the output voltage of the fuel cell. when more larger is to set the possible output voltage as an output voltage to the power consuming device.

In this way, the output can be output voltage to the power consuming device side from the charge reservoir unit is equal to or less than the output voltage of the fuel cell, the output voltage of the fuel cell as an output voltage to the power consuming device If the possible output voltage is set and is greater than the output voltage of the fuel cell, the output voltage to the power consuming device is set as the output voltage to the power consuming device. It can be avoided that the voltage becomes lower than the voltage.

In the fuel cell system, the control means calculates an output which is a voltage responsive output voltage to the power device corresponding to the required power generation amount from the power consuming device, from the response output voltage of the charge reservoir section subtraction value obtained by subtracting the output voltage, the second when voltage conversion unit is lower than the lower limit value of the boosted possible voltage difference, the setting responding output voltage as the possible output voltage, the subtraction value is the If it is less than the lower limit, to set the output voltage of the charge reservoir unit as the possible output voltage.

Thus, the output can be output voltage to the power consuming device side from the charge reservoir portion, it can be set according to the second step-up capability of the voltage converter.

  In the fuel cell system, the first voltage converter may be a step-up voltage converter.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that the surplus electric power which is not intended generate | occur | produces in a fuel cell.

  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).

  First, with reference to FIG. 1, the structure of the fuel cell system in embodiment is demonstrated. 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 input 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 adjusts (boosts) the DC voltage input from the battery 4 and outputs it to the traction inverter 6 on the power consuming device side, and the fuel cell 2 or the traction motor. 7 has a function of adjusting (stepping down) the DC voltage input from 7 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 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.

Control unit 8, the output voltage to the traction motor 7 that is supplied from the traction inverter 6 performs the control Gosuru load voltage control process so that the above output voltage of the fuel cell 2 and the battery 4 output voltage higher. Below, the specific processing content of the load voltage control processing performed by the control part 8 is demonstrated.

  The control unit 8 calculates a possible output voltage that is a voltage that can be output from the battery 4 to the traction motor 7 using the required power generation amount from the traction motor 7 and the output voltage of the battery 4. The control unit 8 determines whether the possible output voltage is equal to or lower than the output voltage of the fuel cell 2.

  The control unit 8 sets the output voltage of the fuel cell 2 as the output voltage to the traction motor 7 when the possible output voltage is equal to or lower than the output voltage of the fuel cell 2. When the possible output voltage is larger than the output voltage of the fuel cell 2, the control unit 8 sets the possible output voltage as the output voltage to the traction motor 7.

  Thereby, the output voltage to the traction motor 7 is maintained to be equal to or higher than the output voltage of the fuel cell 2. Further, since the output voltage to the traction motor 7 is equal to or higher than the possible output voltage, and this possible output voltage is equal to or higher than the output voltage of the battery 4, the output voltage to the traction motor 7 is maintained higher than the output voltage of the battery 4. Is done. That is, the output voltage to the traction motor 7 is maintained above the output voltage of the fuel cell 2 and above the output voltage of the battery 4.

  The possible output voltage can be calculated as follows, for example. The control unit 8 calculates a response output voltage that is a voltage output to the traction motor 7 as a response to the required power generation amount from the traction motor 7. The control unit 8 determines whether or not a subtraction value that is a value obtained by subtracting the output voltage of the battery 4 from the response output voltage is equal to or greater than a predetermined threshold value. The predetermined threshold is a value set according to the characteristics of the Bat converter 5, and for example, a lower limit value of a difference between the input voltage and the output voltage that can be boosted by the Bat converter 5 is set.

  The control unit 8 sets the response output voltage as the possible output voltage when the subtraction value is equal to or greater than a predetermined threshold value. The controller 8 sets the output voltage of the battery 4 as the possible output voltage when the subtraction value is less than the predetermined threshold value.

  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 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, the load voltage control process will be described using the flowchart shown in FIG. This load voltage control 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 response output voltage output to the traction motor 7 as a response to the required power generation amount from the traction motor 7 (step S101).

  Subsequently, the control unit 8 measures the output voltage of the battery 4 using the voltage sensor V3 (step S102).

  Subsequently, the control unit 8 determines whether or not a subtraction value obtained by subtracting the output voltage of the battery 4 measured in step S102 from the response output voltage calculated in step S101 is equal to or greater than a predetermined threshold (step S103). ). When this determination is YES (step S103; YES), the control unit 8 sets a response output voltage as a possible output voltage from the battery 4 side (step S104).

  On the other hand, when it is determined in step S103 that the subtraction value is less than the predetermined threshold (step S103; NO), the control unit 8 uses the output voltage of the battery 4 as the possible output voltage from the battery 4 side. Setting is performed (step S105).

  Subsequently, the control unit 8 measures the output voltage of the fuel cell 2 using the voltage sensor V1 (step S106).

  Subsequently, the control unit 8 determines whether or not the possible output voltage set in step S104 or S105 is equal to or lower than the output voltage of the fuel cell 2 measured in step S106 (step S107). When this determination is YES (step S107; YES), the control unit 8 sets the output voltage of the fuel cell 2 as the output voltage to the traction motor 7 (step S108).

  On the other hand, when it is determined in step S107 that the possible output voltage is larger than the output voltage of the fuel cell 2 (step S107; NO), the control unit 8 uses the possible output voltage as the output voltage to the traction motor 7. Is set (step S109).

  As described above, according to the fuel cell system 1 in the present embodiment, when the possible output voltage that can be output from the battery 4 to the traction motor 7 side is equal to or lower than the output voltage of the fuel cell 2, the traction motor 7. When the possible output voltage is larger than the output voltage of the fuel cell 2, the possible output voltage is set as the output voltage to the traction motor 7. Therefore, it is possible to avoid the output voltage to the traction motor 7 being less than the output voltage of the fuel cell 2.

  That is, according to the fuel cell system 1 in the present embodiment, the output voltage to the traction motor 7 can be controlled to be equal to or higher than the output voltage of the fuel cell 2 and higher than the output voltage of the battery 4. The output voltage of the battery 2 can be maintained below the output voltage to the traction motor 7, and unintentional surplus power can be prevented from being generated in the fuel cell.

  In the above-described embodiment, when setting the output voltage to the traction motor 7, the possible output voltage that can be output from the battery 4 to the traction motor 7 side is compared with the output voltage of the fuel cell 2. However, the comparison with the possible output voltage is not limited to the output voltage of the fuel cell 2. For example, the output voltage to the traction motor 7 may be set by comparing the possible output voltage and the open circuit voltage (OCV) of the fuel cell 2. The open circuit voltage is a voltage in a state where no current is passed through the fuel cell 2 (a state where no load is applied), and is the maximum voltage of the fuel cell 2. Therefore, by controlling the output voltage to the traction motor 7 to be equal to or higher than the open circuit voltage of the fuel cell 2, it is possible to suppress the output voltage to the traction motor 7 from being lower than the output voltage of the fuel cell 2.

  The control unit 8 in this modification determines whether or not the possible output voltage is equal to or lower than the open circuit voltage of the fuel cell 2. When the possible output voltage is equal to or lower than the open circuit voltage of the fuel cell 2, the control unit 8 sets the open circuit voltage of the fuel cell 2 as the output voltage to the traction motor 7. When the possible output voltage is larger than the open circuit voltage of the fuel cell 2, the control unit 8 sets the possible output voltage as the output voltage to the traction motor 7.

  As a result, the output voltage to the traction motor 7 is maintained at or above the open circuit voltage of the fuel cell 2. Further, since the output voltage to the traction motor 7 is equal to or higher than the possible output voltage, and this possible output voltage is equal to or higher than the output voltage of the battery 4, the output voltage to the traction motor 7 is maintained higher than the output voltage of the battery 4. Is done. That is, the output voltage to the traction motor 7 is maintained above the open circuit voltage of the fuel cell 2 and above the output voltage of the battery 4.

  In addition, since the open circuit voltage of the fuel cell 2 is a fixed value, it is possible to save time and effort for measuring the output power of the fuel cell 2 each time the output voltage to the traction motor 7 is controlled. Can be.

  Next, the load voltage control process in this modification is demonstrated using the flowchart shown in FIG. This load voltage control process is started, for example, when the ignition key is turned on, and is repeatedly executed until the operation ends. 3 are the same as the processes in steps S101 to S105 shown in FIG. 2 described in the above-described embodiment, and therefore, here, the processes shown in FIG. The processing after step S206 different from FIG.

  First, after the possible output voltage is set in step S204 or S205, the control unit 8 determines whether or not this possible output voltage is equal to or lower than the open circuit voltage of the fuel cell 2 (step S206). When this determination is YES (step S206; YES), the control unit 8 sets the open circuit voltage of the fuel cell 2 as the output voltage to the traction motor 7 (step S207).

  On the other hand, when it is determined in step S206 that the possible output voltage is larger than the open circuit voltage of the fuel cell 2 (step S206; NO), the control unit 8 can perform the possible operation as the output voltage to the traction motor 7. An output voltage is set (step S208).

  Thus, according to the fuel cell system 1 in the modified example, when the possible output voltage that can be output from the battery 4 to the traction motor 7 side is equal to or lower than the open circuit voltage of the fuel cell 2, Since the open circuit voltage of the fuel cell 2 is set as the output voltage and the possible output voltage is larger than the open circuit voltage of the fuel cell 2, the possible output voltage is set as the output voltage to the traction motor 7. It can be avoided that the output voltage to the motor 7 becomes less than the open circuit voltage of the fuel cell 2.

  That is, according to the fuel cell system 1 in this modification, the output voltage to the traction motor 7 is controlled to be equal to or higher than the open circuit voltage that is the maximum voltage of the fuel cell 2 and higher than the output voltage of the battery 4. Therefore, it is possible to maintain the output voltage of the fuel cell 2 below the output voltage to the traction motor 7, and to suppress the generation of unintended surplus power in the fuel cell.

  In the above-described embodiment, the step-up voltage converter is used as the FC converter. However, the present invention is not limited to this, and a step-up / step-down voltage converter may be used as the FC converter. In this case, the above-described possible output voltage is always set as the output voltage to the traction motor 7. When the possible output voltage is equal to or lower than the output voltage of the fuel cell, the FC converter steps down the output voltage of the fuel cell to the possible output voltage and outputs it. Thereby, when the output voltage of the fuel cell becomes larger than the output voltage to the motor, the FC converter can be used to step down the output voltage of the fuel cell below the output voltage to the motor. Even when unintended surplus power is generated in the fuel cell, it is possible to prevent the surplus power from being charged in the battery.

  In the above-described embodiment, the case where the fuel cell system according to the present invention is mounted on a fuel cell vehicle has been described. However, the present invention is also applied to various mobile bodies (robots, ships, aircrafts, etc.) other than the fuel cell vehicle. The fuel cell system according to the invention can be applied. Moreover, the fuel cell system according to the present invention can also be applied to a stationary power generation system used as a power generation facility for buildings (houses, buildings, etc.).

It is a figure which shows typically the structure of the fuel cell system in embodiment. It is a flowchart for demonstrating the flow of the load voltage control process in embodiment. It is a flowchart for demonstrating the flow of the load voltage control process in a modification.

Explanation of symbols

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

Claims (2)

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 charge reservoir section which can be charged with power generated by the said fuel cell,
A power consuming device to consume power from the fuel cell and the charge reservoir portion,
A first voltage converter disposed between the fuel cell and the power consuming device;
A second voltage converter which is disposed between the charge reservoir unit power consumption device,
Wherein the output voltage to the power consuming device, and a control means for controlling output voltage or more and the more the output voltage of the charge reservoir portion of the fuel cell,
The control means calculates a possible output voltage from the power storage unit to the power consumption device using a required power generation amount from the power consumption device and an output voltage of the power storage unit, and the possible output voltage is When the output voltage of the fuel cell is equal to or less than the output voltage of the fuel cell, the output voltage of the fuel cell is set as the output voltage to the power consuming device, and when the possible output voltage is larger than the output voltage of the fuel cell, Set the possible output voltage as the output voltage to the power consuming device,
The control means calculates a response output voltage that is an output voltage to the power consuming device corresponding to a required power generation amount from the power consuming device, and subtracts a value obtained by subtracting the output voltage of the power storage unit from the response output voltage Is greater than or equal to the lower limit value of the voltage difference that can be boosted by the second voltage converter, the response output voltage is set as the possible output voltage, and the subtracted value is less than the lower limit value. Sets the output voltage of the power storage unit as the possible output voltage,
A fuel cell system. The first voltage converter is a fuel cell system according to claim 1, characterized in that the voltage converter of the booster type.

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