JP5446025B2 - FUEL CELL SYSTEM AND FUEL CELL OUTPUT CONTROL METHOD - Google Patents

Description

  The present invention relates to a fuel cell system and a fuel cell output control method.

The fuel cell system uses, as an energy source, a fuel cell that generates electricity by an electrochemical reaction between a fuel gas that is a reaction gas and an oxidizing gas. When such a fuel cell system is mounted on a vehicle, it is required to extend the travel distance as much as possible by efficiently consuming the fuel gas. Patent Document 1 below discloses a fuel cell system that limits a power generation region of a fuel cell to a high efficiency region when the remaining amount of fuel gas becomes a predetermined amount or less in order to extend the travel distance. In this fuel cell system, after the power generation area is limited to the high efficiency area, if the internal pressure (medium pressure) of the fuel supply flow path falls below a predetermined pressure, the output of the fuel cell is limited based on the internal pressure of the flow path. Determine the value to limit the output of the fuel cell. Thereafter, when the pressure in the flow path reaches a predetermined supply limit, a gas shortage display is made, the output of the fuel cell stops, and the vehicle stops.
JP 2006-296106 A

  By the way, the pressure in the flow path is affected by the pressure loss in the piping, and is therefore lower than the supply pressure in the fuel supply source. Such a decreasing tendency of the pressure in the flow path becomes more prominent as the supply pressure in the fuel supply source decreases. On the other hand, if the pressure in the flow path becomes too low, the fuel supply capability is reduced, and fuel corresponding to the amount of fuel consumed cannot be supplied sufficiently. Therefore, conventionally, the supply limit is set slightly higher with reference to the pressure in the flow path so that the fuel supply capacity does not decrease. However, if the supply limit is set based on the pressure in the flow path, the point in time when the pressure in the flow path reaches the supply limit even though there is still room for fuel stored in the fuel supply source. As a result, the output of the fuel cell is stopped. That is, although the fuel stored in the fuel supply source still has room, the vehicle cannot continue running.

  The present invention has been made to solve the above-described problems caused by the prior art, and a fuel cell system capable of operating for a longer time while effectively consuming fuel with a small remaining amount, and output control of the fuel cell. It aims to provide a method.

  In order to solve the above-described problems, a fuel cell system according to the present invention receives a supply of a reaction gas and generates power by an electrochemical reaction of the reaction gas, and supplies a fuel gas of the reaction gas. A pressure sensor for detecting the supply pressure of the fuel gas in the fuel supply source; and an output limiting means for limiting the output of the fuel cell when the supply pressure detected by the pressure sensor is equal to or lower than a predetermined lower limit value. It is characterized by that.

  The output control method for a fuel cell according to the present invention is a method for controlling the output of a fuel cell that receives supply of a reaction gas and generates electric power by an electrochemical reaction of the reaction gas. A pressure detection step for detecting the supply pressure of the fuel gas in the fuel supply source for supplying the fuel gas, and the output of the fuel cell is limited when the supply pressure detected in the pressure detection step is below a predetermined lower limit value. And an output limiting step.

  According to these inventions, the output of the fuel cell can be limited when the remaining amount of the fuel gas decreases and the supply pressure of the fuel gas in the fuel supply source becomes a predetermined lower limit or less. Therefore, the fuel gas consumption can be reduced. Therefore, it is possible to operate for a longer time while effectively consuming fuel with a small remaining amount.

  In the fuel cell system, the output limiting means can limit the output of the fuel cell by reducing the upper limit value of the output current of the fuel cell according to the supply pressure.

  By doing so, when the remaining amount of the fuel gas is reduced and the supply pressure of the fuel gas in the fuel supply source becomes a predetermined lower limit value or less, the output current of the fuel cell according to the supply pressure Since the upper limit value of the fuel gas can be reduced, the consumption amount of the fuel gas can be limited in accordance with the decreasing supply pressure.

  In the fuel cell system, the output limiting means can calculate the upper limit value of the output current of the fuel cell using an output permission rate that decreases in accordance with a preset upper air supply pressure.

  By doing so, when the remaining amount of the fuel gas is reduced and the fuel gas supply pressure in the fuel supply source becomes equal to or lower than a predetermined lower limit value, the output permission rate decreases according to the supply pressure. Can be used to lower the upper limit value of the output current of the fuel cell, so that the consumption of fuel gas can be limited according to the decreasing supply pressure.

  In the fuel cell system, the pressure sensor is provided in a fuel supply passage for supplying fuel gas to the fuel cell, and the sensor value when the output of the fuel cell is stopped is set to the supply pressure. Can be output as By doing in this way, the structure of a fuel cell system can be simplified.

  In the fuel cell system, the pressure sensor can be provided in a fuel supply source. By doing in this way, the supply pressure of the fuel gas in a fuel supply source can be detected easily.

  According to the present invention, it is possible to operate for a longer time while effectively consuming fuel with a small remaining amount.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a fuel cell system and a fuel cell output control method according to the present invention will be described with reference to the accompanying drawings. This embodiment demonstrates the case where the fuel cell system which concerns on this invention is used as a vehicle-mounted power generation system of a fuel cell vehicle (FCHV; Fuel Cell Hybrid Vehicle).

  The fuel cell system according to the present embodiment reduces the upper limit value of the output current of the fuel cell according to the supply pressure of the fuel gas when the supply pressure of the fuel gas in the fuel supply source becomes a predetermined lower limit value or less. Thus, the output of the fuel cell is limited.

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

  As shown in FIG. 1, 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 reactive gas and the fuel gas, and an oxidizing gas that supplies air as the oxidizing gas to the fuel cell 2. It has a piping system 3, a hydrogen gas piping system 4 that supplies hydrogen as fuel gas to the fuel cell 2, and a control unit 5 that performs overall control of the entire system.

  The fuel cell 2 has a stack structure in which a plurality of single cells that generate power upon receiving a reaction gas are stacked. A part of the DC power generated by the fuel cell 2 is stepped down by a DC / DC converter (not shown) and charged to a secondary battery (not shown) which is a battery. The fuel cell 2 is provided with a current sensor A that detects a current during power generation.

  The oxidizing gas piping system 3 compresses air taken in through the filter 30 and sends out compressed air as oxidizing gas, and an air supply flow path 32 for supplying the oxidizing gas to the fuel cell 2. And an air discharge passage 33 for discharging the oxidizing off-gas discharged from the fuel cell 2. The air supply flow path 32 and the air discharge flow path 33 are provided with a humidifier 34 that humidifies the oxidizing gas pumped from the compressor 31 using the oxidizing off gas discharged from the fuel cell 2. The oxidizing off gas that has undergone moisture exchange or the like in the humidifier 34 is finally exhausted into the atmosphere outside the system as exhaust gas.

  The hydrogen gas piping system 4 includes a hydrogen tank 40 as a fuel supply source storing high-pressure hydrogen gas, and a hydrogen supply channel 41 as a fuel supply channel for supplying the hydrogen gas in the hydrogen tank 40 to the fuel cell 2. And a circulation flow path 42 for returning the hydrogen off-gas discharged from the fuel cell 2 to the hydrogen supply flow path 41. The hydrogen gas piping system 4 is an embodiment of the fuel supply system in the present invention. Instead of the hydrogen tank 40 in the present embodiment, for example, a reformer that reforms a hydrocarbon-based fuel into a hydrogen-rich fuel gas using water vapor, and a fuel gas reformed in the reformer with a high pressure A high-pressure gas tank that accumulates pressure in a state can be employed as a fuel supply source. A tank having a hydrogen storage alloy can also be employed as a fuel supply source.

  The hydrogen supply channel 41 includes a main stop valve 43 that shuts off or allows the supply of hydrogen gas from the hydrogen tank 40, regulators 44 and 45 that adjust the hydrogen gas pressure to a preset secondary pressure, and hydrogen gas And an injector 46 for adjusting the flow rate and pressure. Further, on the downstream side of the regulator 45 and the downstream side of the regulator 44, a pressure sensor P1 and a pressure sensor P2 for detecting the pressure of the hydrogen gas in the hydrogen supply channel 41 are provided.

  The circulation channel 42 is provided with a hydrogen pump 47 that pressurizes the hydrogen off-gas in the circulation channel 42 and sends it to the hydrogen supply channel 41 side. Further, a discharge flow path 50 is connected to the circulation flow path 42 via a gas-liquid separator 48 and an exhaust drain valve 49. The gas-liquid separator 48 recovers moisture from the hydrogen off gas. The exhaust / drain valve 49 discharges (purges) the water collected by the gas-liquid separator 48 and the hydrogen off-gas containing impurities in the circulation flow path 42 in accordance with a command from the control unit 5. The hydrogen off-gas discharged from the exhaust / drain valve 49 is diluted by the diluter 51 and merges with the oxidizing off-gas in the air discharge passage 33.

  The control unit 5 detects an operation amount of an acceleration operation member (accelerator or the like) provided in the fuel cell vehicle, and provides control information such as an acceleration request value (for example, a required power generation amount from a power consumption device such as a traction motor). In response, the operation of various devices in the system is controlled. In addition to the traction motor, the power consuming device includes, for example, auxiliary equipment necessary for operating the fuel cell 2 (for example, the motor of the compressor 31 and the hydrogen pump 47), and various devices involved in traveling of the vehicle. These include actuators used in (transmissions, wheel control devices, steering devices, suspension devices, etc.), air conditioning devices (air conditioners) for passenger spaces, lighting, audio, and the like.

  The control unit 5 detects the supply pressure of the fuel gas in the hydrogen tank 40 (hereinafter referred to as “tank original pressure”) using the pressure sensor P1. Specifically, the control unit 5 detects the sensor value of the pressure sensor P1 when the output of the fuel cell 2 is stopped as the tank original pressure. Here, when the output of the fuel cell 2 is stopped, the hydrogen gas is not supplied to the fuel cell 2 and the flow of the hydrogen gas in the hydrogen supply channel 41 is stopped. Does not occur. That is, the sensor value of the pressure sensor P1 detected when the output of the fuel cell 2 is stopped is equivalent to the tank original pressure. Examples of when the output of the fuel cell 2 stops include when the vehicle is stopped, when driving at a low load, and during regenerative braking.

  The control unit 5 limits the output of the fuel cell by lowering the upper limit value of the output current of the fuel cell according to the supply pressure when the tank original pressure becomes a predetermined lower limit value or less. For example, the lower limit value can be set to a value that can be determined that the remaining amount of hydrogen gas is small, and that is larger than the supply limit value. The supply limit value is a residual pressure value used when determining that there is a gas shortage.

  As a method of reducing the upper limit value of the output current according to the supply pressure, for example, there is a method of using an output restriction map shown in FIG. FIG. 2 is a diagram illustrating an output restriction map, in which the horizontal axis indicates the tank original pressure [kPa], and the vertical axis indicates the output permission rate [%]. In the output restriction map shown in FIG. 2, when the lower limit value of the tank original pressure is set to the first pressure PA and the tank original pressure exceeds the lower limit value, the output permission rate is 100%. When the tank original pressure is equal to or lower than the lower limit value, it is indicated that the output permission rate decreases according to the tank original pressure. Specifically, for example, when the tank base pressure is the second pressure PB, the output permission rate is 80%, and when the tank base pressure is the third pressure PC, the output permission rate is 68%. When the pressure is the fourth pressure PD, the output permission rate is 46%, and when the tank base pressure is equal to or lower than the fifth pressure PE, the output permission rate is 28%.

  The control unit 5 refers to the output restriction map, derives the output permission rate corresponding to the tank original pressure, and calculates the output permission rate for the rated value of the output current as the upper limit value of the output current. Therefore, for example, when the tank original pressure is the second pressure PB, 80% is derived as the output permission rate, and a value corresponding to 80% of the rated value is calculated as the upper limit value of the output current. In this case, for example, when the required output value corresponding to the accelerator opening is equal to or greater than the value corresponding to 80% of the rated value, the current corresponding to 80% of the rated value set as the upper limit value of the output current is the fuel cell 2. Will be output. On the other hand, when the required output value corresponding to the accelerator opening is less than 80% of the rated value, the current of the required output value is output from the fuel cell 2.

  Here, the control unit 5 physically includes, for example, a CPU, a ROM and an HDD that store control programs and control data processed by the CPU, and a RAM that is mainly used as various work areas for control processing. And an input / output interface. These elements are connected to each other via a bus. Various sensors such as pressure sensors P1, P2 and current sensor A are connected to the input / output interface, and various drivers for driving the compressor 31, the main stop valve 43, the hydrogen pump 47, the exhaust drain valve 49, and the like. Is connected.

  The CPU controls the output of the fuel cell 2 by receiving the detection result of the pressure sensor P1 through the input / output interface according to the control program stored in the ROM and processing it using various data in the RAM. To do. Further, the CPU controls the entire fuel cell system 1 by outputting control signals to various drivers via the input / output interface.

  Next, the output limiting process of the fuel cell in this embodiment will be described using the flowchart shown in FIG. This output restriction process is repeatedly performed while an output request output according to the accelerator opening is received by the control unit 5.

  First, when the control unit 5 receives the output request, the control unit 5 acquires the latest tank pressure detected (step S1). The tank original pressure is detected using the pressure sensor P1 when the output of the fuel cell 2 is stopped, and is stored in the RAM.

  Subsequently, the control unit 5 determines whether or not the tank original pressure acquired in Step S1 is equal to or lower than a predetermined lower limit value (Step S2). When this determination is YES (step S2; YES), the control unit 5 refers to the output restriction map and derives an output permission rate corresponding to the tank original pressure (step S3).

  Subsequently, the control unit 5 calculates the upper limit value of the output current of the fuel cell using the rated value of the output current and the output permission rate derived in step S3 (step S4).

  Subsequently, the control unit 5 determines whether or not the output request value corresponding to the output request is greater than or equal to the upper limit value calculated in Step S4 (Step S5). When this determination is YES (step S5; YES), the control unit 5 instructs to output the output current of the fuel cell 2 at the upper limit value (step S6).

  On the other hand, when it is determined in step S5 described above that the output request value is less than the upper limit value (step S5; NO), the control unit 5 outputs the output current of the fuel cell 2 as the output request value. (Step S8).

  On the other hand, when it is determined in step S2 described above that the tank original pressure is not less than or equal to the predetermined lower limit value (step S2; NO), the control unit 5 determines that the required output value is greater than or equal to the rated value of the output current. It is determined whether or not there is (step S7). When this determination is NO (step S7; NO), the control unit 5 instructs the output current of the fuel cell 2 to be output with the output request value (step S8). On the other hand, when the determination in step S7 is YES (step S7; YES), the control unit 5 instructs the output current of the fuel cell 2 to be output at the rated value (step S9).

  As described above, according to the fuel cell system 1 in the present embodiment, when the remaining amount of hydrogen gas is reduced and the tank base pressure becomes equal to or lower than the predetermined lower limit value, the fuel cell system 1 depends on the tank base pressure. As a result, the output permission rate is reduced and the output of the fuel cell is limited, so that the consumption of hydrogen gas can be reduced according to the decreasing tank base pressure. As a result, it is possible to extend the travel distance while effectively consuming hydrogen gas with a small remaining amount. In addition, the remaining amount of hydrogen gas that cannot be used up can be further reduced.

  In the above-described embodiment, the value of the pressure sensor P1 when the output of the fuel cell 2 is stopped is detected as the tank original pressure, but the sensor used for detection is not limited to the pressure sensor P1. For example, the value of the pressure sensor P2 when the output of the fuel cell 2 is stopped may be detected as the tank original pressure. Further, a pressure sensor may be further provided in the hydrogen tank 40, and the value of the tank pressure sensor may be detected as the tank original pressure. When the tank pressure sensor is used, it is not necessary to consider the pressure loss. Therefore, the sensor value at that time can be adopted as the tank original pressure regardless of the output of the fuel cell 2.

  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 lineblock diagram showing typically the fuel cell system in an embodiment. It is a figure which shows an output restriction map. 3 is a flowchart for explaining output limiting processing of a fuel cell in the fuel cell system shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 2 ... Fuel cell, 3 ... Oxidation gas piping system, 4 ... Hydrogen gas piping system, 5 ... Control part, 30 ... Filter, 31 ... Compressor, 32 ... Air supply flow path, 33 ... Air exhaust flow 34, humidifier, 40 ... hydrogen tank, 41 ... hydrogen supply channel, 42 ... circulation channel, 43 ... main stop valve, 44, 45 ... regulator, 46 ... injector, 47 ... hydrogen pump, 48 ... gas-liquid Separator 49 ... exhaust drain valve, 50 ... discharge flow path, 51 ... diluent, P1, P2 ... pressure sensor, A ... current sensor.

Claims (4)

A fuel cell that receives supply of a reactive gas and generates electric power by an electrochemical reaction of the reactive gas;
A pressure sensor for detecting a supply pressure of the fuel gas in a fuel supply source for supplying a fuel gas of the reaction gas;
Output limiting means for limiting the output of the fuel cell when the supply pressure detected by the pressure sensor is equal to or lower than a predetermined lower limit value at which it can be determined that the remaining amount of the fuel gas is low. ,
The output limiting means has a preset output permission rate that is a ratio that permits output with respect to a rated value defined as a use limit of the output current of the fuel cell as the supply pressure decreases. using the relationship, the deriving the output permission rate corresponding to the supply pressure detected by the pressure sensor, the output permission index component in the rated value of the output current of the fuel cell, the output of the fuel cell Calculate as the upper limit value of the current, and limit the output of the fuel cell using the upper limit value,
A fuel cell system.   The pressure sensor is provided in a fuel supply flow path for supplying the fuel gas to the fuel cell, and outputs a sensor value when the output of the fuel cell is stopped as the supply pressure. The fuel cell system according to claim 1, wherein:   The fuel cell system according to claim 1, wherein the pressure sensor is provided in the fuel supply source. A method of controlling the output of a fuel cell that receives a supply of a reaction gas and generates electric power by an electrochemical reaction of the reaction gas,
A pressure detection step of detecting a supply pressure of the fuel gas in a fuel supply source for supplying a fuel gas of the reaction gas;
An output limiting step of limiting the output of the fuel cell when the supply pressure detected in the pressure detection step is equal to or lower than a predetermined lower limit value that can be determined that the remaining amount of the fuel gas is low. Including
In the output limiting step, as the supply pressure decreases, an output permission rate that is a ratio of permitting output with respect to a rated value defined as a use limit of the output current of the fuel cell decreases as the supply pressure decreases. using the relationship, the deriving the output permission rate corresponding to said detected supply pressure in the pressure detecting step, the output permission index component in the rated value of the output current of the fuel cell, the fuel cell Calculate as the upper limit value of the output current, and limit the output of the fuel cell using the upper limit value,
An output control method for a fuel cell.

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