JP2010118252A - Control method of fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method of a fuel cell capable of smoothly extracting an output in accordance with a requirement of a load. <P>SOLUTION: The control method of a fuel cell generating power by an electrochemical reaction of an reaction gas includes a fuel cell low output determining step (Step S01) for monitoring an output state of the fuel cell and determining whether the output of the fuel cell is in a low output or not, an FC high load requirement determining step (Step S02) for determining whether an operation requirement for the fuel cell is a high load requirement or not in case the output of the fuel cell is in a low output, and a catalyst refreshing treatment step (Step S03) for refreshing activity of the catalyst of the fuel cell in case the operation requirement for the fuel cell is a high load requirement. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for controlling a fuel cell mounted on a fuel cell vehicle or the like.

In recent years, a fuel cell system that uses a fuel cell that generates electric power by an electrochemical reaction of reaction gases (fuel gas and oxidizing gas) as an energy source has attracted attention. The fuel cell system supplies high-pressure fuel gas from the fuel tank to the anode of the fuel cell, and also supplies air as the oxidizing gas to the cathode, and generates an electromotive force by electrochemically reacting these fuel gas and oxidizing gas. It is something to be made.
In such a fuel cell system, when the output performance of the fuel cell deteriorates, whether to perform the activation process of the catalyst of the fuel cell or whether to perform the refresh to recover the catalyst based on the voltage of the fuel cell. What is determined is known (see, for example, Patent Documents 1 and 2).
JP 2008-192468 A JP-A-2005-174463

  By the way, in a vehicle or the like equipped with a fuel cell system, when used at a high voltage for a long time, the catalytic activity of the fuel cell decreases, the maximum output decreases, and the power that can be supplied to the traction motor of the vehicle also decreases. In such a situation, it was difficult to obtain the acceleration performance intended by the driver corresponding to the accelerator opening.

  Accordingly, an object of the present invention is to provide a fuel cell control method capable of smoothly extracting an output according to a load request.

  The fuel cell control method of the present invention is a control method of a fuel cell that generates electricity by an electrochemical reaction of a reaction gas, and monitors the output status of the fuel cell to determine whether the output of the fuel cell is low or not. A fuel cell low output determination step for determining, a fuel cell high load request determination step for determining whether or not an operation request for the fuel cell is a high load request when the output of the fuel cell is a low output, and a fuel cell A catalyst refresh processing step of recovering the activity of the catalyst of the fuel cell when the operation request for is a high load request.

  According to such a control method, when the output of the fuel cell is low and the operation request for the fuel cell is a high load, the activity of the catalyst is recovered, so that a high output corresponding to the operation request can be obtained.

  According to the control method of the fuel cell of the present invention, it is possible to smoothly draw out the output corresponding to the load demand.

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

  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. However, not only the vehicle but also various moving bodies (for example, motorcycles 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.

FIG. 1 is a diagram showing a schematic configuration of a fuel cell system 1 according to the present embodiment.
This vehicle travels using a traction motor 14 connected to wheels 13 via a reduction gear 12 as a driving force source. The power supply of the traction motor 14 is a power supply system 21, and the power supply system 21 includes a fuel cell 23, a DC / DC converter 24, a control device 25, and the like. The direct current output from the power supply system 21 is converted into a three-phase alternating current by the inverter 22 and supplied to the traction motor 14.

  The fuel cell 23 is means for generating electric power from the supplied reaction gas (fuel gas and oxidant 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 23 includes a polymer electrolyte membrane 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 is not limited to a platinum catalyst but can be applied to a platinum cobalt catalyst (hereinafter simply referred to as a catalyst).

  The fuel electrode (anode) of the fuel cell 23 is supplied with a fuel gas such as hydrogen gas from a fuel gas supply source, while the oxygen electrode (cathode) is supplied with an oxidizing gas such as air from an oxidizing gas supply source. The

  The inverter 22 is, for example, a pulse width modulation type PWM inverter configured by a plurality of switching elements, and converts DC power output from the fuel cell 23 into three-phase AC power in response to a control command given from the control device 25. And supplied to the traction motor 14. The traction motor 14 is a motor for driving the wheels 13, and the rotation speed of the motor is controlled by an inverter 22.

  The DC / DC converter 24 is a full-bridge converter configured by, for example, four power transistors (switching elements) and a dedicated drive circuit (all not shown).

  The operation of each element described above is controlled by the control device 25. The control device 25 is configured as a microcomputer having a CPU, a ROM, and a RAM therein.

  A pedal-type accelerator sensor 31 and a brake sensor 32 are connected to the control device 25. The control device 25 adjusts the supply amounts of the fuel gas and the oxidant gas based on sensor signals that vary according to the depression amounts of the accelerator sensor 31 and the brake sensor 32, and also includes a DC / DC converter 24, an inverter 22, and the like. Control each part of the system.

Next, control of the fuel cell 23 by the control device 25 will be described.
FIG. 2 is a flowchart showing control of the fuel cell by the control device 25.
The control device 25 monitors the output status of the fuel cell 23 and determines whether or not the output of the fuel cell 23 is low (step S01: fuel cell low output determination step).

  Specifically, determination is made based on whether or not the FC current value at the lower limit voltage of the fuel cell 23 is smaller than a preset first threshold value.

  Here, the FC current value at the lower limit voltage is the maximum current value (see B in FIG. 3) when the fuel cell voltage value is the lower limit voltage (see A in FIG. 3), as shown in FIG. .

  If it is determined as a result of the above determination that the output of the fuel cell 23 is low, a fuel cell high load request determination is made as to whether or not the operation request for the fuel cell 23 is a high load request (step S02: FC high load request determination step).

  Specifically, the operation is performed when the pedal force of the brake sensor 32 is smaller than a preset second threshold value and the accelerator opening degree due to the depression of the accelerator sensor 31 is larger than a preset third threshold value. It is determined that the request is a high load request.

  As a result of the above determination, if it is determined that the operation request for the fuel cell 23 is a high load request, a catalyst refresh process is performed on the fuel cell 23 (step S03: catalyst refresh process step).

  Specifically, as shown in FIG. 4, the DC / DC converter 24 lowers the FC cell voltage to a fourth threshold set in advance as a recovery target voltage (see C in FIG. 4). Thereafter, the converter command voltage is maintained at the fourth threshold value, and the oxidizing gas is blown to make the oxygen utilization rate 100% or more (see D in FIG. 4), and the voltage drop by the converter 24 is released. In this way, the FC cell voltage is lowered to the reduction region, the oxide film on the surface of the Pt catalyst is reduced and removed, and the catalyst can be recovered.

  Thereby, the fuel cell 23 is improved in output by the catalyst refresh process, and can output in response to the operation request of the high load request.

  As described above, according to the fuel cell system according to the above embodiment, when the output of the fuel cell 23 is low and the operation request for the fuel cell 23 is a high load, the activity of the catalyst is recovered. High output according to the driving request can be obtained.

  As a result, in a vehicle equipped with the fuel cell system 1, smooth acceleration performance intended by the driver corresponding to the accelerator opening is obtained even in situations where acceleration is required, such as when starting or merging with the main line. be able to.

It is a figure showing a schematic structure of a fuel cell system concerning this embodiment. It is a flowchart which shows control of a fuel cell. It is a graph explaining fuel cell low output determination. It is a graph explaining a catalyst refresh process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 23 ... Fuel cell, 25 ... Control apparatus.

Claims (1)

A method for controlling a fuel cell that generates electricity by an electrochemical reaction of a reaction gas,
A fuel cell low output determination step of monitoring the output status of the fuel cell and determining whether the output of the fuel cell is low;
A fuel cell high load request determination step for determining whether or not the operation request for the fuel cell is a high load request when the output of the fuel cell is a low output;
A catalyst refresh processing step for recovering the activity of the fuel cell catalyst when the operation request for the fuel cell is a high load request; and
A method for controlling a fuel cell comprising:

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