JP4882216B2 - Control device for fuel cell system - Google Patents

Description

  The present invention relates to a control device for a fuel cell system.

  In a fuel cell, a fuel gas such as hydrogen gas and an oxidizing gas containing oxygen are electrochemically reacted through an electrolyte, and electric energy is directly taken out between electrodes provided on both surfaces of the electrolyte. In particular, a polymer electrolyte fuel cell using a polymer electrolyte has attracted attention as a power source for electric vehicles because of its low operating temperature and easy handling. That is, a fuel cell vehicle is equipped with a hydrogen storage device such as a high-pressure hydrogen tank, a liquid hydrogen tank, or a hydrogen storage alloy tank in the vehicle, and reacts by supplying hydrogen supplied therefrom and air containing oxygen to the fuel cell. This is the ultimate clean vehicle that drives the motor connected to the drive wheels with the electric energy extracted from the fuel cell, and the only exhaust material is water.

  In applications with large load fluctuations such as fuel cell vehicles, if the amount of reaction gas corresponding to the output of the fuel cell is not supplied, the fuel cell voltage drops or, in extreme cases, abnormal reactions such as inversion in some cells. May occur.

For this reason, a technique is known in which a load amount of an auxiliary machine necessary for power generation of a fuel cell such as an air compressor is detected, and a gas supply amount is determined based on the detected load amount (for example, Patent Document 1).
Japanese Patent Laid-Open No. 10-040962 (page 9, FIG. 6)

  However, the above-described conventional technique has a problem that in a transient operation state in which the load of the fuel cell fluctuates, the gas supply amount may be insufficient with respect to the required power generation amount due to a delay in gas supply. It was.

  FIG. 11 is a diagram showing power that can be generated by the fuel cell, power consumption of auxiliary equipment, and gas supply amount when the load of the fuel cell fluctuates in the prior art.

  If the net power required for the fuel cell system (net generated power excluding fuel cell auxiliary machine power consumption) changes as indicated by C, the response of the gas corresponds to the change in the required net power. When the target gas supply amount is changed as G in consideration of the delay, the change in the auxiliary machine power consumption changes as indicated by E. However, in order to realize the required net power shown in C, it is necessary to add the increment of the auxiliary machine power consumption to the generated power. Therefore, the actual auxiliary machine power consumption shown in D is detected and the auxiliary machine power consumption is detected. When the target supply gas amount is increased based on the electric power, the target supply gas amount changes as indicated by F.

  As a result, the actual gas supply amount changes as indicated by H, and the gross power that can be generated by the fuel cell (generated power including auxiliary machine power consumption) changes as indicated by B. On the other hand, in this case, the sum of the required net power and the auxiliary machine power consumption changes as shown in A, so that the gross power that can be generated is insufficient and the gas supply amount is insufficient with respect to the required net power. I understand that.

  As described above, the conventional technique has a problem that the performance deterioration of the fuel cell may be caused if the power generation is performed in a state where the gas supply amount is insufficient.

In order to solve the above problems, the present invention provides a fuel cell system including a fuel cell that generates electric power by an electrochemical reaction between a fuel gas and an oxidant gas, and an auxiliary device for generating the fuel cell. Auxiliary power consumption detecting means for detecting the power consumption of an auxiliary machine for generating the fuel cell, a required output power calculating means for calculating required output power that is output power required by the fuel cell system, Based on the sum of the power consumption of the auxiliary machine detected by the auxiliary machine power consumption detection means and the required output power, the generated power control means for controlling the generated power of the fuel cell , and the fuel cell system outputs the required output power. Steady-state auxiliary machine power consumption calculating means for calculating a stationary auxiliary machine power consumption that is the power consumption required by the auxiliary machine, and the stationary auxiliary machine power consumption and the required output power Based on the sum, which is the control device of a fuel cell system according to subject matter that and a gas supply control means for controlling the supply of the oxidizing agent gas and the fuel gas to the fuel cell.

  According to the present invention, since the gas supplied to the fuel cell is controlled prior to the change in the auxiliary power consumption of the fuel cell, the gas supply can be accelerated and the auxiliary power consumption of the fuel cell system varies. In the transient operation state, the response of the output power of the fuel cell system can be accelerated and the shortage of gas supply can be prevented.

  In addition, since there is no shortage of gas supply to the fuel cell, there is an effect that deterioration of the fuel cell can be prevented.

Next, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing a basic configuration of an embodiment of a control apparatus for a fuel cell system according to the present invention. In FIG. 1, the control device of the fuel cell system includes a required output power calculation unit 101 that calculates output power required by the fuel cell system, and a value whose change temporally precedes auxiliary power consumption. Based on the required output power, the steady-state auxiliary machine power consumption calculation means 103 for calculating the auxiliary machine power consumption required for the fuel cell system to output the required output power regularly, and the required output power calculation means 101 have calculated. Adding means 102 for calculating the sum of the required output power and the power calculated by the stationary auxiliary machine power consumption calculating means 103, the auxiliary power consumption detecting means 106 for detecting the power consumption of the auxiliary equipment, and the required output power calculating means An adding means 107 for calculating the sum of the required output power calculated by 101 and the auxiliary machine power consumption detected by the auxiliary machine power consumption detecting means 106, and the requested output calculated by the adding means 107 Based on the sum of electric power and auxiliary machine power consumption, generated power control means 109 for controlling the generated power of the fuel cell, and on the basis of a value whose change temporally precedes the auxiliary machine power consumption, And a gas supply control means 105 for controlling the supply of the fuel gas and the oxidant gas.

  In FIG. 1, the first target generated current calculation means 104 is a means for calculating the target generated current from the addition value of the addition means 102. The second target generated current calculating means 108 is means for calculating the target generated current from the added value of the adding means 107.

  FIG. 2 is a schematic configuration diagram illustrating a configuration example of a fuel cell system to which the present invention is applied. The fuel cell system includes an ejector 1, a hydrogen circulation channel 2, a fuel cell stack 3, a hydrogen purge valve 4, a compressor 6, an air supply channel 7, a hydrogen inlet temperature sensor 8, a hydrogen inlet pressure sensor 9, and an exhaust air channel 11. , Air pressure control valve 12, controller 13, hydrogen pressure control valve 14, air inlet pressure sensor 15, air flow sensor 16, current sensor 17, voltage sensor 18, tank temperature sensor 21, tank pressure sensor 22, hydrogen tank 23, power A control device 24 is provided.

  Hydrogen supplied from the hydrogen tank 23 is supplied to the ejector 1 via the hydrogen pressure control valve 14. The ejector 1 is mixed with hydrogen that has passed through the hydrogen circulation channel 2 and supplied to the fuel cell stack 3. The hydrogen temperature and pressure at the inlet of the fuel cell stack 3 are measured by a hydrogen inlet temperature sensor 8 and a hydrogen inlet pressure sensor 9, respectively.

  The control of the hydrogen pressure control valve 14 is performed by the controller 13 based on the pressure measured by the hydrogen inlet pressure sensor 9. During normal operation, the hydrogen purge valve 4 is closed so that the hydrogen discharged from the fuel cell stack 3 flows into the hydrogen circulation passage 2. The temperature and pressure in the hydrogen tank 23 are measured by a tank pressure sensor 21 and a tank temperature sensor 22, respectively.

  Air serving as an oxidant is supplied by the compressor 6. The air supplied by the compressor 6 is measured by the air flow rate sensor 16 and then supplied to the fuel cell stack 3. The air pressure at the inlet of the fuel cell stack 3 is measured by the air inlet pressure sensor 15 and controlled by the air pressure control valve 12.

  The output current of the fuel cell stack 3 is measured by the current sensor 17, and the output voltage is measured by the voltage sensor 18. Further, the electric power taken out from the fuel cell stack 3 is controlled by the electric power control device 24.

  The power control device 24 is a step-up / step-down DC / DC converter, which is disposed between the fuel cell stack 3 and the load device 25 and controls the generated power of the fuel cell stack 3. In the DC / DC converter, the switching elements to be operated are different in step-up conversion and step-down conversion, and a desired voltage can be output according to the duty ratio of a control signal applied to the switching elements. At the time of step-up, the switching element is controlled so as to output a voltage equal to or higher than the input voltage, and at the time of step-down, the switching element is controlled so as to output a voltage lower than the input voltage.

  In this embodiment, the operating pressure of the fuel cell stack 3 is a variable pressure. That is, the operating pressure is increased when the output power extracted from the fuel cell stack 3 is high, and the operating pressure is decreased when the output power is low.

  When water overflow (hereinafter referred to as flooding) or the like occurs in the fuel cell stack 3, when nitrogen gas accumulates in the anode and the hydrogen circulation passage 2 of the fuel cell, or when the operating pressure of the fuel cell stack 3 is reduced. Opens the hydrogen purge valve 4 to discharge the hydrogen existing in the hydrogen circulation passage 2 and the fuel cell stack 3 out of the system.

  Outputs of all these sensors 8, 9, 15, 16, 17, 18 and actuator drive signals such as the air pressure control valve 12, the hydrogen pressure control valve 14, and the hydrogen purge valve 4 are connected to the controller 13.

  The controller 13 controls these actuators based on signals detected by these sensors. The controller 13 is not particularly limited. In this embodiment, the controller 13 is composed of a CPU, a program ROM, a working RAM, and a microprocessor having an input / output interface. The controller for the fuel cell system shown in FIG. Is realized by program control.

  FIG. 3 is a flowchart showing details of power generation control and gas supply control by the controller 13, and is executed at a predetermined time period (for example, 10 [msec] period).

  First, in step 301 (hereinafter, step is abbreviated as S), a required output power of the fuel cell system (a net generated output power excluding auxiliary machine power consumption, also referred to as target net generated power) is calculated.

  Next, in S302, compressor power consumption (steady-time compressor power consumption) is calculated as auxiliary machine power consumption necessary for steady output of the required output power. In S303, the target value for gas supply control is calculated. A target power generation current (first target power generation current) to be used is calculated, and gas supply control of the fuel cell is performed in S304.

  Next, in S305, power consumption of the compressor (actual compressor power consumption) is detected, and in S306, a target generated current (second target generated current) used as a target value for the generated power control of the fuel cell is calculated, and S307. Then, the generated power of the fuel cell is controlled.

Next, details of processing in each step of S301 to S307 will be described.
First, the process in S301 will be described. Here, the required output power is calculated based on the operating state of the load device 25 connected to the fuel cell system. For example, FIG. 4 shows an example of processing when the fuel cell system is mounted on a hybrid electric vehicle. This will be described with reference to the flowchart shown in FIG.

  In S401, the accelerator operation amount of the driver is detected based on the output of the accelerator sensor provided in the vehicle. In S402, the vehicle speed is detected based on the output of the vehicle speed sensor provided in the vehicle.

  Next, in S403, a basic value of the required output power is calculated. This is calculated, for example, using the map data shown in FIG. 5 based on the accelerator operation amount and the vehicle speed. In this way, the required output power is calculated based on the operating state of the vehicle that is the load device of the fuel cell system, and the sum of the required output power and the value whose change temporally precedes the auxiliary machine power consumption. Therefore, the supply of fuel gas and oxidant gas to the fuel cell is controlled, so that the gas supply control can be performed in advance of the change in the generated power required for the fuel cell. There is an effect that the supply of gas can be accelerated with respect to the extraction of electric power.

  Next, in S404, a change rate restriction process is performed on the basic value of the required output power to calculate the required output power. The change rate is limited by, for example, a method of setting the upper and lower limit values of the change rate per unit time to limit the change rate, a method of performing filter processing such as first order lag, etc. The upper and lower limit values of the change rate and the filter characteristics are set so as not to exceed the upper limit of the change speed at which the output power can be changed.

  As a result, the required output power can be changed within a range in which the gas supply is in time, and this is required without causing a shortage of gas supply in a transient operation state in which the output power required for the fuel cell system fluctuates. There is an effect that it is possible to output power.

  Next, the process in S302 will be described. Here, based on the required output power, the power consumption of the compressor (steady-time compressor power consumption) necessary for constantly outputting the required output power is calculated. This is calculated using the map data shown in FIG. 6 based on the required output power and the atmospheric pressure, for example. The atmospheric pressure is detected based on the output of the atmospheric pressure sensor provided in the vehicle. Further, the map data can be set by performing a steady operation test by a bench test of the fuel cell system and confirming the relationship between the required output power and the power consumption of the compressor.

  In this embodiment, the auxiliary machine power consumption of the fuel cell system is only the compressor power consumption, but it may be calculated including the power consumption of the pump and cooling fan for circulating the coolant of the fuel cell.

  Next, the process in S303 will be described. Here, a target generated current (first target generated current) used as a target value for gas supply control is calculated based on the required output power and the steady-state compressor power consumption.

  First, the first target generated power (first target gross generated power) is calculated from the sum of the required output power and the steady-state compressor power consumption. Next, based on the first target generated power, a first target generated current is calculated using the map data shown in FIG. In this map data, the characteristics of the voltage with respect to the current of the fuel cell are set in the map data, and this characteristic can be confirmed by a bench test of the fuel cell system. The temperature of the fuel cell can be detected by a coolant temperature sensor provided in the fuel cell system.

  This makes it possible to perform gas supply control using the current value, which is a parameter for determining gas consumption in power generation of the fuel cell, as a control amount, and to provide the gas supply amount required for the output power required for the fuel cell system. There is an effect that control can be performed.

  Next, the process in S304 will be described. Here, gas supply control of the fuel cell system is performed based on the first target generated current.

  First, based on the first target generated current, the target gas pressure is calculated using the table data shown in FIG. This table data is set in consideration of the power generation efficiency of the fuel cell.

  Next, based on the first target generated current, the target air flow rate is calculated using the table data shown in FIG. This table data is set so that the air utilization rate is such that local shortage of air supply does not occur inside the fuel cell.

  Next, based on the target gas pressure and the target air flow rate, the compressor command rotational speed is calculated using the map data shown in FIG. This map data is set based on the characteristics of the air flow rate with respect to the rotation speed of the compressor 6 and the pressure ratio. Further, the compressor command rotational speed calculated here is instructed from the controller 13 to the compressor drive circuit, and the compressor 6 is driven according to the command rotational speed.

  Next, the air pressure is controlled by operating the air pressure control valve 12 based on the target gas pressure. The operation of the air pressure control valve 12 determines the command opening of the air pressure control valve 12 by F / B control based on the deviation between the air pressure of the fuel cell detected by the air inlet pressure sensor 15 and the target gas pressure. Is executed. The F / B control can be configured by a generally well-known method such as PI control or model reference control. Further, the command opening degree of the air pressure control valve 12 calculated here is instructed from the controller 13 to the drive circuit of the air pressure control valve 12, and the air pressure control valve 12 is driven according to the command opening degree.

  Next, the hydrogen pressure is controlled by operating the hydrogen pressure control valve 14 based on the target gas pressure. The operation of the hydrogen pressure control valve 14 determines the command opening of the hydrogen pressure control valve 14 by F / B control based on the deviation between the hydrogen pressure of the fuel cell detected by the hydrogen inlet pressure sensor 9 and the target gas pressure. Is executed. The F / B control can be configured by a generally well-known method such as PI control or model reference control. The command opening degree of the hydrogen pressure control valve 14 calculated here is instructed from the controller 13 to the drive circuit of the hydrogen pressure control valve 14, and the hydrogen pressure control valve 14 is driven according to the command opening degree.

  Next, the process in S305 will be described. Here, the power actually consumed by the compressor 6 (actual compressor power consumption) is detected. The compressor power consumption can be detected by detecting the rotation speed and torque of the compressor motor in the compressor drive circuit and calculating the product of the rotation speed and torque. Note that power loss in the compressor motor may be taken into account. In that case, power loss characteristics with respect to the rotation speed and torque may be set in map data and calculated. Further, similarly to the processing in S302, the power consumption of a pump or a cooling fan for circulating the coolant of the fuel cell may be detected.

  Next, the process in S306 will be described. Here, a target generated current (second target generated current) used as a target value for the generated power control of the fuel cell is calculated based on the required output power and the actual compressor power consumption.

  First, the second target generated power (second target gross generated power) is calculated from the sum of the required output power and the actual compressor power consumption. Next, based on the second target gross generated power, a second target generated current is calculated using the map data shown in FIG. This map data is the same map data used in the processing in S303.

  Next, the process in S307 will be described. Here, the generated power of the fuel cell is controlled based on the second target generated current.

First, the voltage of the fuel cell is detected based on the output of the voltage sensor 18 provided in the fuel cell. Next, the power generation command power of the fuel cell is calculated from the product of the detected fuel cell voltage and the second target generated current. This power generation command power is instructed from the controller 13 to the power control device 24, and the power generation power of the fuel cell is controlled according to the power generation command power.

  Thus, by controlling the power generated by the fuel cell and controlling the gas supply, when the load on the fuel cell fluctuates, the power that can be generated by the fuel cell, the auxiliary power consumption, and the gas supply amount are: It changes as shown in FIG.

  When the required output power required for the fuel cell system changes as indicated by C, the auxiliary machine power consumption (steady-time auxiliary machine power consumption) required to output the required output power constantly is D. It changes as shown. On the other hand, when the target gas supply amount corresponding to the required net power is changed as indicated by G, the target gas supply amount including the gas supply amount corresponding to the stationary auxiliary machine power consumption changes as indicated by F. As a result, since the actual gas supply amount changes as indicated by H, the gross power that can be generated by the fuel cell changes as indicated by B. Further, since the sum of the required net power and the actual auxiliary power consumption shown in E changes as shown in A, it can be seen that the required net power can be output including the auxiliary power consumption.

It is a control block diagram explaining the principal part structure of the control apparatus of the fuel cell system which concerns on this invention. 1 is a system configuration diagram illustrating a configuration of a fuel cell system to which a control device for a fuel cell system according to the present invention is applied. It is a flowchart explaining the method of the electric power generation control and gas supply control of a fuel cell system in the Example of this invention. It is a flowchart which shows the detail of the request | requirement output power calculation process of S301. It is an example of the map data referred in the required output power basic value calculation process of S403. It is an example of the map data for calculating the power consumption (compressor power consumption at the time of compressor) required for steadily outputting the required output power in S302. It is an example of the map data for calculating a target generated current from the target gross generated power in S303 and S306. It is an example of the table data for calculating a target gas pressure in S304. It is an example of the table data for calculating a target air flow rate in S304. It is an example of the map data for calculating a compressor command rotation speed in S304. In a prior art, it is a figure which shows the change of the electric power of a fuel cell, auxiliary machine power consumption, and gas supply amount when the load of a fuel cell fluctuates. In this invention, when the load of a fuel cell fluctuates, it is a figure which shows the change of the electric power of a fuel cell, auxiliary machine power consumption, and gas supply amount.

Explanation of symbols

101 ... Required output power calculation means 102 ... Addition means 103 ... Steady state auxiliary machine power consumption calculation means 104 ... First target generated current calculation means 105 ... Gas supply control means 106 ... Auxiliary machine power consumption detection means 107 ... Addition means 108 ... Second target generated current calculation means 109 ... generated power control means

Claims (4)

In a fuel cell system including a fuel cell that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas, and an auxiliary device for generating the fuel cell,
Auxiliary machine power consumption detecting means for detecting the power consumption of an auxiliary machine for generating the fuel cell ;
Requested output power calculating means for calculating required output power that is output power required by the fuel cell system;
On the basis of the sum of the power consumption of the auxiliary power detector accessory which detects and said required output power, the generated power control means for controlling the generated power of the fuel cell,
Steady-time auxiliary machine power consumption calculating means for calculating steady-time auxiliary machine power consumption that is the power consumption required by the auxiliary machine for the fuel cell system to constantly output the required output power;
Gas supply control means for controlling the supply of the fuel gas and the oxidant gas to the fuel cell based on the sum of the auxiliary power consumption during normal operation and the required output power ;
A control apparatus for a fuel cell system, comprising: On the basis of the sum of the power consumption of the auxiliary power detector accessory which detects and said required output power includes a target generated current calculating means for calculating a target generated current of the fuel cell,
2. The fuel cell system according to claim 1, wherein the gas supply control means is means for controlling supply of the fuel gas and the oxidant gas to the fuel cell based on the target generated current. Control device. The required output power calculation means includes
3. The fuel according to claim 1, wherein a change speed of the required output power is limited so as not to exceed an upper limit of a change speed at which the output power of the fuel cell system can be changed. Battery system control device. The auxiliary machine power consumption detecting means is
The fuel cell system according to any one of claims 1 to 3, characterized in that it comprises a compressor power consumption detecting means for detecting the power consumption of the compressor for supplying the oxidant gas to the fuel cell Control device.

Images