JP2007109567A - Control device of fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of a fuel cell which eliminates shortage in supply of a transient reaction gas, at the startup of required power and achieves high response with response to the required output. <P>SOLUTION: A hydrogen supply/compressor shutdown decision section 34 makes a decision on the idle stop of a suspension of the hydrogen supply and compressor operation, based on the required power for a fuel cell system, the battery storage amounts, and status of the fuel cell system. A required power change rate deducing unit 35 deduces the change rate of the required power during the idle stop time, based on the vehicle velocity and accelerator operation variation amounts. A target determination section 38 of anode hydrogen amount/cathode oxygen amount determines target values for cathode oxygen residue and anode hydrogen residue, according to the deduced value for the required power change rate, and controls a hydrogen supply valve controller 39 and a compressor controller 40 so that actual values for the cathode oxygen residue and the anode hydrogen residue are be not less than the target values, thereby replenishing the hydrogen and air to the fuel cell which is placed into the idle stop state. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system, and more particularly to a control device for a fuel cell system with improved idle stop performance suitable for a power source of a moving body such as a fuel cell vehicle.

  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, solid polymer fuel cells using solid polymer electrolytes are attracting attention as power sources for electric vehicles because of their 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 oxygen-containing air 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 that the only exhaust material is water.

  By the way, since the fuel cell has low power generation efficiency in a region where the output is small, there is a system that is used in combination with a power storage device such as a secondary battery or a capacitor. In this system, in a region where the required load is small, by stopping the power generation of the fuel cell and performing idle stop to supply power from the power storage device, the operation with low power generation efficiency is avoided and the fuel efficiency performance of the fuel cell system is improved. be able to.

In order to ensure restartability from the idle stop state, there is an example in which the reaction gas is intermittently supplied during the idle stop. For example, in the idle stop state disclosed in Patent Document 1, every time a predetermined time elapses or when the residual gas pressure falls below a predetermined pressure, the compressor is temporarily driven or the hydrogen supply valve is opened to Air and hydrogen are supplied to the battery.
JP 2004-172028 A (page 8, FIG. 3)

  However, in the fuel cell vehicle to which the above conventional example is applied, when the accelerator is released at high speed, the required output for the fuel cell is low and the engine stops idling, but the accelerator is fully opened from that state. As a result, a rapid required output change rate occurs. At this time, there is a delay in the reaction gas supply due to the piping length and volume of the reaction gas supply system, but there is a limit to the rate of change in the air supply and the rate of change in the hydrogen supply due to the dynamic characteristics of the compressor and hydrogen supply valve. In particular, there was a problem of insufficient supply of reaction gas.

  In order to solve the above problems, the present invention provides a fuel cell in which an electrolyte membrane is sandwiched between a fuel electrode and an oxidant electrode, fuel supply means for supplying fuel gas to the fuel electrode, and the oxidation An oxidant supply unit that supplies an oxidant gas to the agent electrode, a state quantity detection unit that detects a state quantity of the fuel cell, and a power storage device that supplies power when the generated power of the fuel cell is insufficient. In the fuel cell system, an oxidant supply control unit for temporarily stopping the supply of the oxidant from the oxidant supply means to the oxidant electrode when the required power for the fuel cell becomes a predetermined value or less; And a required power change rate estimating unit that estimates a rate of change of required power for the fuel cell after the supply of the oxidant is temporarily stopped by the determination of the control unit, the oxidant supply control unit temporarily stopping the oxidant supply The remaining in the oxidizer pole after A control device for a fuel cell system, characterized in that the oxidant supply means is controlled such that an oxidant amount is equal to or greater than an amount corresponding to a change rate of required power estimated by the required power change rate estimation unit. .

  According to the present invention, it is possible to estimate the required power change rate required for the fuel cell, and to supply the oxidant to the fuel cell in which the oxidant supply is temporarily stopped based on the estimation result. There is an effect that it is possible to provide a fuel cell system that solves the transient supply shortage of reactive gas and has high responsiveness to the required output.

  Next, embodiments of the present invention will be described in detail with reference to the drawings. Although the following embodiments are not particularly limited, a fuel cell vehicle using a fuel cell as a main power source will be described.

  FIG. 1 is a system configuration diagram showing a schematic configuration of a fuel cell vehicle including a control device for a fuel cell system according to the present invention. The fuel cell system 1 includes, for example, a polymer electrolyte fuel cell 2. The fuel cell 2 has a structure in which a plurality of unit cells (cells) in which an electrolyte membrane 3 is sandwiched between an anode (fuel electrode) 4 and a cathode (oxidant electrode) 5 are stacked, but only the unit cell is illustrated. Hydrogen gas is supplied as fuel to the anode 4 and air is supplied as oxidant gas to the cathode 5, and the electrode reaction shown below proceeds to generate electric power.

Anode (fuel electrode): H ₂ → 2H ⁺ + 2e ⁻ (1)
Cathode (oxidant electrode): 2H ⁺ + 2e ⁻ + (1/2) O ₂ → H ₂ O (2)
Hydrogen as a fuel gas is supplied from the hydrogen tank 6 to the anode 4 through the hydrogen tank main valve 7, the pressure reducing valve 8, and the hydrogen supply valve 9. The high-pressure hydrogen supplied from the hydrogen tank 6 is mechanically reduced to a predetermined pressure by the pressure reducing valve 8 and further reduced by the hydrogen supply valve 9 so that the hydrogen pressure at the inlet of the anode 4 becomes a desired pressure. The hydrogen pressure at the anode inlet is detected by the anode inlet pressure sensor 10 a and input to the controller 30.

  A fuel circulation path 11 is provided for circulating the fuel gas that has not been consumed at the anode from the outlet of the anode 4 to the inlet of the anode 4. The circulation pump 12 is a circulation device that boosts and circulates the fuel gas in the fuel circulation path 11. Circulation pump 12 is driven by an electric motor (not shown), and current of this electric motor is detected by current sensor 13. Air to the cathode 5 is supplied by the compressor 14. An air pressure adjusting valve 24 is provided at the cathode outlet to control the cathode pressure.

  The power manager 15 extracts power from the fuel cell 2 and supplies power to the load device 16 or the battery 17. The battery controller 18 monitors the charge / discharge current of the battery 17 to calculate the amount of electricity stored in the battery, and transmits the amount of electricity stored to the controller 30. The voltage sensor 19 measures the voltage of each unit cell of the fuel cell 2 or each unit cell group in which a plurality of unit cells are connected in series. The controller 30 controls each actuator in the system using each sensor signal at the time of starting, stopping, and generating power of the fuel cell system.

  In order to supply air as an oxidant to the cathode 5, non-chemically reacting nitrogen permeates the electrolyte membrane 3 and accumulates in a hydrogen circulation system including the anode 4, the fuel circulation path 11 and the circulation pump 12. If the amount of nitrogen accumulated in the hydrogen circulation system increases too much, the mass density of the gas in the hydrogen circulation system increases and the gas circulation amount by the circulation pump 12 cannot be maintained, so the amount of nitrogen in the hydrogen circulation system must be managed. There is. Therefore, the gas containing nitrogen in the hydrogen circulation system is discharged to the outside by the purge valve 20 so that the circulation performance can be maintained for the amount of nitrogen present in the hydrogen circulation system. The anode outlet pressure sensor 10b is a sensor that measures the pressure at the anode outlet, the anode inlet temperature sensor 21a is a sensor that measures the temperature of the gas at the anode inlet, and the anode outlet temperature sensor 21b is a temperature sensor that measures the gas temperature at the anode outlet. The detected values are input to the controller 30.

  In this embodiment, the controller 30 is composed of a CPU, a ROM, a working RAM, and a microprocessor having an input / output interface. Then, the controller 30 executes the control program stored in the ROM to control the entire fuel cell system, as well as the oxidant supply control unit, the required power change rate estimation unit, and the fuel supply control unit in the present invention. It also serves as.

  FIG. 2 is a control block diagram for explaining the control contents of the controller 30. The required power detection unit 31 detects the required power for the fuel cell based on, for example, a vehicle speed signal detected by a vehicle speed sensor (not shown) and an accelerator operation amount signal detected by an accelerator sensor (not shown). The battery storage amount detection unit 32 reads the storage amount of the battery 17 from the battery controller 18 of FIG. The fuel cell system state quantity detection unit 33 includes a fuel electrode inlet pressure and a fuel electrode outlet pressure detected by the pressure sensors 10a and 10b in FIG. 1, a fuel electrode inlet pressure and a fuel electrode outlet pressure detected by the temperature sensors 21a and 21b. The fuel cell system state signal such as the temperature detected by the temperature sensor of the fuel cell coolant is not read, and it is determined whether or not the fuel cell 2 has been warmed up. If the fuel cell 2 is warming up, control is performed so that the warm-up is continued even if the required power is equal to or less than a predetermined value, and idling stop is not performed.

  The hydrogen supply / compressor stop determination unit 34 determines that the required power detected by the required power detection unit 31 is a predetermined value or less, the battery storage amount detected by the battery storage amount detection unit 32 is a predetermined value or more, and the fuel cell system state is warmed up. Is determined, the hydrogen supply and the idle stop which is the temporary stop of the compressor 14 are determined, and the hydrogen supply valve control unit 39 and the compressor control unit 40 are instructed to stop the supply by the idle stop. The hydrogen supply valve control unit 39 closes the hydrogen supply valve 9 and stops the supply of hydrogen to the anode 4 when receiving an instruction to temporarily stop supply by idle stop. At the same time, the circulation pump 12 that circulates fuel in the fuel circulation path 11 is stopped. When the compressor control unit 40 receives an instruction to temporarily stop supply by idle stop, the compressor control unit 40 stops driving the compressor 14 and closes the air pressure adjusting valve 24.

  As shown in FIG. 5, the required power change rate estimation unit 35 calculates a required power change rate from the vehicle speed sensor signal, the accelerator operation amount signal, and the vehicle running resistance, and obtains these maximum values to obtain the required power change. The estimated rate value is output to the target value determination unit 38 for the hydrogen amount in the anode and the oxygen amount in the cathode.

  In FIG. 5, in order to obtain the required power change rate from the vehicle speed, it is estimated with reference to a map 51 that the required power change rate increases as the vehicle speed increases. In order to obtain the required power change rate from the accelerator operation amount signal, it is estimated by referring to the map 52 that the required power change rate increases as the accelerator operation change amount increases. Further, in order to obtain the required power change rate from the running resistance, the running resistance of the vehicle is estimated from the change in the vehicle speed and the output of the vehicle drive motor as the load device 16, and the smaller the running resistance, the larger the required power change rate. It estimates with reference to the map 53 to be performed.

  After calculating the required power change rate from the vehicle speed sensor signal, the accelerator operation amount signal, and the running resistance of the vehicle, the maximum value selection unit 54 selects the maximum value of these three required power change rates and estimates the required power change rate. Value. Then, the anode hydrogen amount / cathode oxygen amount target value determination unit 38 refers to the map 55 from the estimated value of the required power change rate, and obtains the target residual hydrogen amount of the anode and the target residual oxygen amount of the cathode.

  The anode hydrogen amount detection unit 36 detects the anode hydrogen amount based on the detection value of the anode pressure sensor 10a or 10b, and outputs it to the anode hydrogen amount / cathode oxygen amount target value determination unit 38. The cathode oxygen amount detection unit 36 detects the cathode oxygen amount based on the detection value of the voltage sensor 19 and the elapsed time from the temporary stop of the compressor 14. At this time, if the anode hydrogen amount detector 36 detects a sufficient amount of hydrogen, the cathode oxygen amount is detected based on the detection value of the voltage sensor 19, and the anode hydrogen amount detector 36 detects a sufficient amount of hydrogen. If not, the cathode oxygen amount is detected based on the elapsed time from the temporary stop of the compressor 14. The detected oxygen amount is output to the anode hydrogen amount / cathode oxygen amount target value determination unit 38.

  The anode hydrogen amount / cathode oxygen amount target value determination unit 38 includes an anode hydrogen amount target value and cathode oxygen amount target corresponding to the change rate of the required power for the fuel cell system estimated by the required power change rate estimation unit 35. Determine the value. For this determination, a target value is obtained by referring to a target value map as indicated by reference numeral 55 in FIG. This map is a map in which the target value increases as the rate of change in the required power increases, and a value that satisfies the desired performance as the output rise performance of the fuel cell is obtained by experiments with a real machine or computer simulation.

  If the hydrogen amount detected by the anode hydrogen amount detection unit 36 does not reach the anode hydrogen amount target value determined by the anode hydrogen amount / cathode oxygen amount target value determination unit 38, the hydrogen supply valve control unit 39. A control signal is output to control the anode hydrogen amount to be equal to or higher than the target value. Similarly, if the oxygen amount detected by the cathode oxygen amount detection unit 37 has not reached the target oxygen amount in the cathode, a control signal is output to the compressor control unit 40 so that the cathode oxygen amount becomes equal to or greater than the target value. To control.

  Next, transfer from the normal power generation control state to the idle stop state by the controller 30 will be described with reference to the flowchart of FIG.

  First, in step (hereinafter abbreviated as S) 301, the state quantity of the fuel cell system is read from each sensor in the fuel cell system. In step S <b> 302, the storage amount of the battery 17 is read from the battery controller 18. In S303, the required power for the fuel cell system is detected based on the vehicle speed detected by the vehicle speed sensor and the accelerator operation amount detected by the accelerator sensor.

  Next, in S304, it is determined whether or not the fuel cell temperature is equal to or higher than a predetermined warm-up temperature (in the case of a polymer electrolyte fuel cell, the degree of activity of the electrode catalyst is increased to 70 ° C., for example). Determine whether the warm-up is complete. If the warm-up has not been completed, the routine proceeds to normal power generation control in S309.

  If the warm-up has been completed, it is determined in S305 whether or not the storage amount of the battery 17 is equal to or greater than a predetermined value. This predetermined value is determined in consideration of the total capacity of the battery 17, the power consumption of the load device 16, and the like. If the amount of electricity stored in the battery 17 is less than the predetermined value, the process proceeds to normal power generation control in S309. If the amount of power stored in the battery 17 is equal to or greater than a predetermined value, it is determined in S306 whether the required power for the fuel cell system is equal to or less than a predetermined value. This predetermined value is generated power at which the power generation efficiency of the fuel cell system is lower than the desired efficiency. The property of the electrolyte membrane 3 used for the fuel cell 2, the property of the electrode catalyst used for the anode 4 and the cathode 5, the cathode 5 This value is determined by the efficiency of the compressor 14 that supplies air to the air. Generally, in a polymer electrolyte fuel cell, when the power generation output is reduced, the ratio of power consumption of auxiliary equipment (compressor 14, circulation pump 12, cooling water circulation pump not shown) to the generated power increases, and the power generation efficiency decreases.

  If the required power exceeds the predetermined value in the determination in S306, the process proceeds to the normal power generation control in S309. If it is determined in S306 that the required power is equal to or less than the predetermined value, the process proceeds to S307 to perform idle stop. In S307, the hydrogen supply valve 9 is closed and the circulation pump 12 is stopped. In S308, the compressor 14 is stopped, and the air pressure adjusting valve 24 is closed to enter the idle stop state.

  FIG. 4 is a flowchart for explaining the control contents of the controller 30 in the idle stop state.

  First, in S401, it is determined whether the required power is equal to or less than a predetermined value. This predetermined value is the same value as the predetermined value used in the determination in S306. If the required power is not less than the predetermined value, the process proceeds to S414 to return from the idle stop state to the normal power generation state. In S414, the hydrogen supply valve 9 is opened and hydrogen supply is started. In S415, the operation of the compressor 14 is started, the idle stop state is terminated, and the normal power generation control is started.

  If it is determined in S401 that the required power is equal to or smaller than the predetermined value, the process proceeds to S402, and it is determined whether or not the stored amount of the battery 17 is equal to or larger than the predetermined value. This predetermined value is the same value as the predetermined value used in the determination of S305. If it is determined in S402 that the charged amount is not equal to or greater than the predetermined value, the process proceeds to S414 to return from the idle stop state to the normal power generation state.

  If it is determined in S402 that the charged amount is equal to or larger than the predetermined value, the detected value of the vehicle speed sensor is read in S403, the accelerator operation change amount is calculated in S404, and the running resistance of the vehicle is detected in S405. The running resistance of the vehicle is obtained from the output of the vehicle drive motor that is the load device 16 and the change in the vehicle speed.

  Next, the required power change rate is estimated in S405. In this estimation, as described with reference to FIG. 5, the required power change rate is obtained from the vehicle speed, the accelerator operation change amount, and the travel resistance, and the maximum of these is used as the estimated value of the required power change rate.

  Next, in S407, it is determined whether the estimated value of the required power change rate is equal to or greater than a predetermined value. If not, the process proceeds to S408. If it is equal to or greater than the predetermined value, the process proceeds to S410 and S412 that can be processed in parallel.

  In S408, it is determined whether the residual oxygen amount in the cathode is equal to or greater than a predetermined value. For this purpose, the residual oxygen amount converted from the fuel cell voltage detected by the voltage sensor 19 or the residual oxygen amount converted from the elapsed time since entering the idle stop state is compared with a predetermined value. If it is determined in S408 that the amount of oxygen remaining in the cathode is equal to or greater than the predetermined value, the process proceeds to S409, and the power manager 15 is instructed to take out current from the fuel cell 2 to reduce the amount of oxygen remaining in the cathode. The voltage of the fuel cell 2 during the idle stop is lowered to suppress the deterioration of the electrolyte membrane 3, and the electrode catalyst of the anode 4 and the cathode 5 (FIG. 8). Then, the process returns to S401.

  In S410, it is determined whether or not the amount of oxygen in the cathode is equal to or less than a predetermined value that is a lower limit oxygen amount determined according to the required power change rate. Then, air is supplied to the cathode 5 (FIG. 7), and the process returns to S401. If it is determined in S410 that the amount of oxygen in the cathode is not less than the predetermined value, the process skips S411 and returns to S401.

  In S412, it is determined whether or not the amount of hydrogen in the anode is equal to or less than a predetermined value that is a lower limit hydrogen amount determined according to the required power change rate. If it is equal to or less than the predetermined value, the process proceeds to S413 and the hydrogen supply valve 9 is temporarily set. Open, supply hydrogen to the anode 4, and return to S401. If it is determined in S412 that the amount of hydrogen in the anode is not less than the predetermined value, the process skips S413 and returns to S401.

  Next, the effect of the present invention will be described with reference to FIG. FIG. 6 shows the air required for the fuel cell when the accelerator operation amount is 0 and when the accelerator depression speed is low (indicated by a solid line) and when the accelerator depression speed is high (indicated by a broken line). The flow rate and the air flow rate that the compressor can supply are shown. In either case, the compressor supply air flow rate becomes insufficient from the start of compressor operation, that is, when current extraction is started. However, according to the present invention, the remaining fuel cell cathode remains in accordance with the estimated result of the required power change rate. Since the amount of oxygen (actually residual air) is maintained, it is possible to generate power at the start of the accelerator operation using this residual oxygen, and there is an effect that it is possible to eliminate a delay in power supply with respect to the accelerator operation. .

1 is a configuration diagram of a fuel cell system to which a control device for a fuel cell system according to the present invention is applied. FIG. It is a control block diagram of the controller which is a control apparatus of the fuel cell system of an Example. It is a flowchart explaining transfer from a normal driving | running state to an idle stop state. It is a control flowchart in an idle stop state. It is a block diagram explaining target value calculation of the amount of remaining hydrogen and the amount of remaining oxygen from estimation of a request | requirement electric power change rate. It is a time chart explaining the effect of the present invention. It is a time chart explaining control of the amount of remaining air during idle stop. It is a time chart in the case of taking out an electric current during idle stop.

Explanation of symbols

DESCRIPTION OF SYMBOLS 30 ... Controller 31 ... Required power detection part 32 ... Battery storage amount detection part 33 ... Fuel cell system state quantity detection part 34 ... Hydrogen supply / compressor stop judgment part 35 ... Required power change rate estimation part 36 ... Anode hydrogen amount detection part 37 ... cathode oxygen amount detection unit 38 ... anode hydrogen amount / cathode oxygen amount target value determination unit 39 ... hydrogen supply valve control unit 40 ... compressor control unit

Claims (7)

A fuel cell having an electrolyte membrane sandwiched between a fuel electrode and an oxidant electrode;
Fuel supply means for supplying fuel gas to the fuel electrode;
An oxidant supply means for supplying an oxidant gas to the oxidant electrode;
State quantity detection means for detecting a state quantity of the fuel cell;
A power storage device that supplies power when the power generated by the fuel cell is insufficient,
In a fuel cell system comprising:
An oxidant supply control unit for temporarily stopping the supply of the oxidant from the oxidant supply means to the oxidant electrode when the required power for the fuel cell becomes a predetermined value or less;
A required power change rate estimating unit for estimating a change rate of required power for the fuel cell after temporarily stopping the supply of the oxidant according to the determination of the oxidant supply control unit,
The oxidant supply control unit is configured so that the amount of residual oxidant in the oxidant electrode after the oxidant supply is temporarily stopped is equal to or greater than the amount according to the required power change rate estimated by the required power change rate estimation unit. The fuel cell system control apparatus further controls the oxidant supply means. A fuel supply control unit that temporarily stops the supply of fuel from the fuel supply means to the fuel electrode when the required power for the fuel cell becomes a predetermined value or less;
A required power change rate estimating unit for estimating a change rate of required power for the fuel cell after the fuel supply is temporarily stopped by the determination of the fuel supply control unit,
The fuel supply control unit is configured to supply the fuel such that the amount of remaining fuel in the anode after the fuel supply is temporarily stopped is equal to or greater than the amount corresponding to the change rate of the required power estimated by the required power change rate estimation unit. 2. The fuel cell system control device according to claim 1, wherein the control means is controlled.   The amount of residual oxidant in the oxidant electrode is estimated based on at least one of an elapsed time after the suspending of oxidant supply and a potential difference between the oxidant electrode and the fuel electrode. The control device for a fuel cell system according to claim 1 or 2.   The fuel cell system control device according to claim 2, wherein the remaining fuel amount in the fuel electrode is estimated based on a pressure of the fuel electrode.   5. The current is taken out from the fuel cell so that the fuel cell voltage becomes a predetermined voltage or less when the change rate of the required power estimated by the required power estimation unit is smaller than a predetermined value. The control apparatus for a fuel cell system according to any one of the above. The fuel cell system supplies power to a power source of a moving body,
6. The control apparatus for a fuel cell system according to claim 1, wherein the required power estimation unit estimates a change rate of the required power based on a speed of a moving body.   The fuel cell system control device according to claim 6, wherein the required power estimation unit estimates a change rate of the required power based on a change amount of the acceleration request of the moving body.

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