JP2009043645A - Degradation judgment system for fuel cells - Google Patents

Abstract

A fuel cell deterioration determination system capable of accurately determining deterioration of a fuel cell while suppressing manufacturing cost.
A control device obtains an activation overvoltage based on the amount of generated electricity (step S120 → step S130) when reducing the catalyst of each cell constituting the fuel cell (for example, during refresh control), and obtains the obtained activity. The FC voltage is estimated from the conversion overvoltage (step S140). Then, the estimated FC voltage is compared with the actual FC voltage detected by the voltage sensor, and deterioration of the fuel cell is determined based on the comparison result (step S150).
[Selection] Figure 5

Description

  The present invention relates to a technique for determining deterioration of a fuel cell.

  In the fuel cell system, when the fuel cell deteriorates, there arises a problem that the output power corresponding to the required power cannot be obtained. Therefore, various methods for determining the deterioration of the fuel cell have been conventionally proposed. For example, Patent Document 1 below discloses a technique for detecting the exhaust gas flow rate of a fuel cell, estimating the time for the exhaust gas flow rate to reach a reference value, and calculating the remaining life.

JP-A-11-283653

  However, as described above, the method of measuring the flow rate of the fuel gas has a problem that the flow meter is large, so that it is not suitable for an in-vehicle fuel cell system and the manufacturing cost increases. Furthermore, there is a problem that it is impossible to accurately determine the deterioration of the fuel cell only by estimating the time for the gas flow rate to reach the reference value.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a fuel cell deterioration determination system capable of accurately determining deterioration of a fuel cell while suppressing manufacturing cost.

  In order to solve the above-described problems, a fuel cell deterioration determination system according to the present invention includes a fuel cell including an electrode catalyst, a derivation unit that derives an activation overvoltage of the fuel cell during the reduction process of the electrode catalyst, and a derivation The estimation means for estimating the output voltage of the fuel cell based on the activated overvoltage, the voltage detection means for detecting the output voltage of the fuel cell, and the comparison result between the estimated output voltage and the detected output voltage. And determining means for determining deterioration of the fuel cell.

  According to such a configuration, when the electrode catalyst of the fuel cell is reduced, the activation overvoltage of the fuel cell is derived from the generated amount of electricity, and the output voltage of the fuel cell is estimated from the derived activation overvoltage. Then, the estimated output voltage is compared with the actual output voltage of the fuel cell detected by a voltage sensor or the like, and the deterioration of the fuel cell is determined based on the comparison result. For this reason, it becomes possible to hold down manufacturing cost compared with the past which judged the deterioration of a fuel cell using a flow meter. Furthermore, since the estimated output voltage and the actual output voltage detected by a voltage sensor or the like are compared to determine the deterioration of the fuel cell, it is possible to improve the accuracy of the determination of the deterioration of the fuel cell compared to the conventional case. It becomes.

  Here, in the above configuration, the apparatus further includes current detection means for detecting the output current of the fuel cell, and the estimation means outputs the output of the fuel cell from the derived activation current and the detected output current. A mode in which the voltage is estimated is preferable.

  In the above configuration, it is more preferable that the determination unit determines that the fuel cell has deteriorated when the detected output voltage falls below the estimated output voltage.

  Furthermore, in the above configuration, it is preferable that the information processing apparatus further includes a notification unit that notifies that the fuel cell has deteriorated when it is determined that the fuel cell has deteriorated.

  As described above, according to the present invention, it is possible to accurately detect the deterioration of the fuel cell while suppressing the manufacturing cost.

  Embodiments according to the present invention will be described below with reference to the drawings.

A. 1. Embodiment FIG. 1 is a diagram showing a main configuration of a fuel cell system 100 according to this embodiment. In the present embodiment, a fuel cell system mounted on a vehicle such as a fuel cell vehicle (FCHV), an electric vehicle, or a hybrid vehicle is assumed, but not only the vehicle but also various moving bodies (for example, two-wheeled vehicles and ships). , Airplanes, robots, etc.). Furthermore, the present invention is not limited to a fuel cell system mounted on a moving body, but can be applied to a stationary fuel cell system and a portable fuel cell system.

  This vehicle travels using the synchronous motor 61 connected to the wheels 63L and 63R via the reduction gear 12 as a driving force source. The power source of the synchronous motor 61 is the power supply system 1. The direct current output from the power supply system 1 is converted into a three-phase alternating current by the inverter 60 and supplied to the synchronous motor 61. The synchronous motor 61 can also function as a generator during braking. The power supply system 1 includes a fuel cell 40, a battery 20, a DC / DC converter 30, and the like.

  The fuel cell 40 is means for generating electric power from supplied reaction gas (fuel gas and oxidizing gas), and various types of fuel cells such as a solid polymer type, a phosphoric acid type, and a molten carbonate type can be used. it can. The fuel cell 40 includes a polymer electrolyte membrane 41 made of a proton conductive ion exchange membrane formed of a fluorine-based resin or the like, and a Pt catalyst (electrode catalyst) is applied to the surface of the polymer electrolyte membrane. . The catalyst applied to the polymer electrolyte membrane 41 is not limited to a platinum catalyst, but can be applied to a platinum cobalt catalyst (hereinafter simply referred to as a catalyst). Each cell constituting the fuel cell 40 includes a membrane / electrode assembly 44 in which an anode electrode 42 and a cathode electrode 43 are formed on both surfaces of a polymer electrolyte membrane 41 by screen printing or the like. The fuel cell 40 has a stack structure in which a plurality of single cells are stacked in series.

  The output voltage (hereinafter referred to as FC voltage) and output current (hereinafter referred to as FC current) of the fuel cell 40 are detected by a voltage sensor 140 and a current sensor 150, respectively. A fuel gas such as hydrogen gas is supplied from the fuel gas supply source 10 to the fuel electrode (anode) of the fuel cell 40, while an oxidizing gas such as air is supplied from the oxidizing gas supply source 70 to the oxygen electrode (cathode). Supplied.

The fuel gas supply source 10 includes, for example, a hydrogen tank, various valves, and the like, and controls the amount of fuel gas supplied to the fuel cell 40 by adjusting the valve opening, the ON / OFF time, and the like.
The oxidizing gas supply source 70 includes, for example, an air compressor, a motor that drives the air compressor, an inverter, and the like, and adjusts the amount of oxidizing gas supplied to the fuel cell 40 by adjusting the rotational speed of the motor.

  The battery 20 is a chargeable / dischargeable secondary battery, and is composed of, for example, a nickel metal hydride battery. Of course, instead of the battery 20, a chargeable / dischargeable capacitor (for example, a capacitor) other than the secondary battery may be provided. The battery 20 and the fuel cell 40 are connected in parallel to an inverter 60 for a traction motor, and a DC / DC converter 30 is provided between the battery 20 and the inverter 6.

  The inverter 60 is, for example, a pulse width modulation type PWM inverter, and converts DC power output from the fuel cell 40 or the battery 20 into three-phase AC power in accordance with a control command given from the control device 10. To supply. The traction motor 61 is a motor for driving the wheels 63 </ b> L and 63 </ b> R, and the rotation speed of the motor is controlled by the inverter 60.

  The DC / DC converter (voltage conversion device) 30 is a full-bridge converter configured by, for example, four power transistors and a dedicated drive circuit (all not shown). The DC / DC converter 30 functions to step up or step down the DC voltage input from the battery 20 and output it to the fuel cell 40 side, and step up or step down the DC voltage input from the fuel cell 40 or the like to the battery 20 side. It has a function to output. In addition, charging / discharging of the battery 20 is realized by the function of the DC / DC converter 30.

  An auxiliary machine 50 such as a vehicle auxiliary machine or an FC auxiliary machine is connected between the battery 20 and the DC / DC converter 30. The battery 20 is a power source for these auxiliary machines 50. The vehicle auxiliary equipment refers to various electric power devices (lighting equipment, air conditioning equipment, hydraulic pump, etc.) used during vehicle operation, and the FC auxiliary equipment is used to operate the fuel cell 40. It refers to various power devices (pumps for supplying fuel gas and oxidizing gas, etc.).

The operation of each element described above is controlled by the control device 10. The control device 10 is configured as a microcomputer having a CPU, ROM, and RAM therein.
The control device 10 includes a pressure regulating valve 71 provided in the fuel gas passage, a pressure regulating valve 81 provided in the oxidizing gas passage, a fuel gas supply reduction 70, an oxidizing gas supply source 80, and a battery 20 based on the input sensor signals. , DC / DC converter 30, inverter 60 and other parts of the system are controlled. The control device 10 includes, for example, the supply pressure of the fuel gas detected by the pressure sensor 91, the FC voltage of the fuel cell 40 detected by the voltage sensor 92, the FC current of the fuel cell 40 detected by the current sensor 93, and the SOC. Various sensor signals such as an SOC value representing a state of charge (SOC) of the battery 20 detected by the sensor 21 are input.

  In this embodiment, when the catalyst of each cell constituting the fuel cell 40 is reduced, the FC voltage is estimated from the amount of electricity generated, and the estimated FC voltage is compared with the actual FC voltage detected by the voltage sensor 92. However, it is characterized in that the deterioration of the fuel cell 40 is determined based on the comparison result. Hereinafter, features of the present embodiment will be described in detail.

<Oxidation / reduction process of catalyst>
In the fuel cell system, power generation on the low potential side and power generation on the high potential side are repeatedly performed according to fluctuations in the system power requirement. Along with this power generation operation, an oxidation reaction shown in the following formula (1) and a reduction reaction shown in the following formula (2) are performed on the surface of the catalyst of the fuel cell 40. FIG. 2 shows a CV curve of the catalyst, and the change during the oxidation reaction is indicated by a solid line, and the change during the reduction reaction is indicated by a dotted line. Pt + 2H ₂ O → Pt (OH) ₂ + 2H ⁺ + 2e ⁻ (1)
Pt (OH) ₂ + 2H ⁺ + 2e ⁻ → Pt + 2H ₂ O (2)

  FIG. 3 is a diagram showing temporal changes in the FC voltage and FC current when the catalyst is subjected to the reduction treatment. The change in FC voltage is indicated by a solid line, and the change in FC current is indicated by a dotted line. In the present embodiment, it is assumed that the reduction process of the catalyst is performed during the intermittent operation of the fuel cell 40 (see α portion shown in FIG. 3), but a high load state or the like (for example, the cell voltage is 0.8 V). It can be applied to any case where the reduction reaction is performed on the surface of the catalyst. Here, the intermittent operation of the fuel cell 40 is to temporarily stop the power supply from the fuel cell 40 to the load (such as the auxiliary machinery 50) and supply the power from the battery 20 to the load. During the intermittent operation, the catalyst is reduced by generating power of the fuel cell 40 using the residual gas (by performing so-called refresh control).

When the reduction treatment of the catalyst is performed, the FC voltage decreases as shown by β in FIG. 3, while the FC current once increases and then decreases again (upward convex change). First, the control device 10 uses the following equation (3) to obtain the amount of electricity Q associated with the catalytic reduction process from the change in the FC current I (see β shown by the hatched lines in FIG. 3).
Q = ∫Idt (3)
I: FC current

  Then, the control device (derivation means) 10 derives the activation overvoltage ηa from the obtained electric quantity Q. More specifically, the control device 10 stores a map (activation overvoltage derivation map) indicating the relationship between the quantity of electricity Q obtained in advance through experiments or the like and the activation overvoltage ηa. When the amount of electricity Q is obtained using Equation (3), the control device 10 derives the activation overvoltage ηa corresponding to the amount of electricity Q with reference to the activation overvoltage derivation map.

The control device (estimating means) 10 substitutes the obtained activation overvoltage ηa and the FC current I0 detected by the current sensor (current detection means) 93 into the following equation (4), so that the output voltage V0 of the fuel cell 40 is obtained. Is estimated. In the following description, the estimated output voltage V0 is referred to as an estimated FC voltage V0.
V0 = ηa * I0 (4)

  The control device (determination means) 10 uses the estimated FC voltage V0 obtained in this way, and the actual FC voltage V1 of the fuel cell 40 detected by the voltage sensor (voltage detection means) 92 (hereinafter, detected FC voltage V1). And compare. FIG. 4 is a diagram showing the IV characteristics of the fuel cell 40. The actual IV characteristics detected by each sensor or the like are indicated by solid lines, and the IV characteristics estimated using the equation (4) are indicated by dotted lines. When the control device (determination means) 10 compares the estimated FC voltage V0 with the detected FC voltage V1 and detects that the detected FC voltage V1 is lower than the estimated FC voltage V0, the fuel cell 40 has deteriorated. Judgment is made and a warning lamp (notification means) is turned on or a voice message is output from a speaker (notification means) or the like to notify the driver or the like that the fuel cell 40 has deteriorated.

  When the catalyst of each cell constituting the fuel cell 40 is reduced, the FC voltage is estimated from the amount of electricity generated, the estimated FC voltage is compared with the actual FC voltage detected by the voltage sensor 92, and the comparison result is obtained. Based on this, the deterioration of the fuel cell 40 is determined. For this reason, it becomes possible to hold down manufacturing cost compared with the past which judged the deterioration of a fuel cell using a flow meter. Further, since the deterioration of the fuel cell 40 is determined by comparing the estimated FC voltage with the actual FC voltage detected by the voltage sensor 92, the accuracy of the determination of the deterioration of the fuel cell 40 is improved as compared with the conventional case. Is possible. Hereinafter, the deterioration determination process of the fuel cell according to the present embodiment will be described.

FIG. 5 is a flowchart showing a fuel cell deterioration determination process executed by the control device 10.
When the control device 10 starts the reduction process of the catalyst by performing the refresh control during the intermittent operation (step S110; see FIG. 2), the controller 10 calculates the electric quantity Q accompanying the catalyst reduction process using the above equation (3). (Step S120; see β shown in FIG. 3).

  And the control apparatus 10 calculates | requires activation overvoltage (eta) a from the electric quantity Q calculated | required using the activation overvoltage derivation map (step S130). Further, the control device 10 estimates the output voltage V0 of the fuel cell 40 by substituting the obtained activation overvoltage ηa and the FC current I0 detected by the current sensor 93 into the above equation (4) (step S140). .

  The control device 10 compares the estimated FC voltage V0 obtained in this way with the detected FC voltage V1 detected by the voltage sensor 92 (step S150; see FIG. 4). When the control device 10 compares the estimated FC voltage V0 with the detected FC voltage V1 and detects that the detected FC voltage V1 is equal to or higher than the estimated FC voltage V0, the fuel cell 40 is not deteriorated (normally (Step S150; NO), and the process is terminated. On the other hand, when it is detected that the detected FC voltage V1 is lower than the estimated FC voltage V0 (step S150; YES), it is determined that the fuel cell 40 has deteriorated, and a warning lamp (not shown) is turned on or a voice message is displayed. After notifying the driver or the like that the fuel cell 40 has deteriorated by output or the like (step S160), the process is terminated.

  As described above, according to the present embodiment, when the catalyst of each cell constituting the fuel cell 40 is reduced, the FC voltage is estimated from the generated electricity, and the estimated FC voltage and the voltage sensor 92 detect the FC voltage. The actual FC voltage is compared, and the deterioration of the fuel cell 40 is determined based on the comparison result. For this reason, it becomes possible to hold down manufacturing cost compared with the past which judged the deterioration of a fuel cell using a flow meter. Further, since the deterioration of the fuel cell 40 is determined by comparing the estimated FC voltage with the actual FC voltage detected by the voltage sensor 92, the accuracy of the determination of the deterioration of the fuel cell 40 is improved as compared with the conventional case. Is possible.

B. Modification (1) In the above-described embodiment, it is determined that the fuel cell 40 has deteriorated when the detected FC voltage V1 is lower than the estimated FC voltage V0. For example, the detected FC voltage V1 and the estimated FC voltage V0 When the difference d1 (= V0−V1; see FIG. 4) is equal to or larger than the set difference threshold value ds, it may be determined that the fuel cell 40 has deteriorated. Whether it is judged to be deteriorated can be appropriately changed according to the system design or the like.

(2) In the above-described embodiment, the case where the catalyst is reduced in the normal operation mode has been described. However, the present invention is also applicable to the case where the catalyst is reduced in the low efficiency operation mode. Here, the low-efficiency operation mode refers to an operation mode in which the reaction gas is insufficient and the power loss is increased compared to the normal operation mode. In other words, the normal operation mode is a comparison. The low-efficiency operation mode is an operation mode with relatively low power generation efficiency. Thus, the present invention is applicable to any case where the catalyst is reduced.

It is a figure which shows the principal part structure of the fuel cell system which concerns on this embodiment. It is a figure which shows the CV curve of a catalyst. It is a figure which shows the time-dependent change of FC voltage and FC electric current in case the reduction process of a catalyst is performed. It is a figure which shows the IV characteristic of a fuel cell. It is a flowchart which shows the deterioration determination process of a fuel cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Power supply system, 10 ... Control apparatus, 20 ... Battery, 30 ... DC-DC converter, 40 ... Fuel cell, 41 ... Polymer electrolyte membrane, 42 ... Anode Electrode, 43 ... Cathode electrode, 44 ... Membrane / electrode assembly, 50 ... Auxiliary machinery, 60 ... Inverter, 70 ... Fuel gas supply source, 80 ... Oxidation gas supply source , 92 ... voltage sensor, 93 ... current sensor, 100 ... fuel cell system.

Claims (4)

A fuel cell with an electrode catalyst;
Deriving means for deriving an activation overvoltage of the fuel cell during the reduction treatment of the electrode catalyst;
Estimating means for estimating the output voltage of the fuel cell based on the derived activation overvoltage;
Voltage detecting means for detecting the output voltage of the fuel cell;
A fuel cell deterioration determination system comprising: determination means for determining deterioration of the fuel cell based on a comparison result between the estimated output voltage and the detected output voltage. A current detecting means for detecting an output current of the fuel cell;
2. The fuel cell deterioration determination system according to claim 1, wherein the estimating means estimates the output voltage of the fuel cell from the derived activation overvoltage and the detected output current.   3. The fuel cell deterioration determination according to claim 1, wherein the determination unit determines that the fuel cell has deteriorated when a detected output voltage falls below an estimated output voltage. 4. system. The fuel cell according to any one of claims 1 to 3, further comprising notification means for notifying that the fuel cell is deteriorated when it is determined that the fuel cell is deteriorated. Degradation judgment system of

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