JP2006100152A - Fuel cell system and its inspection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the control precision of an air pressure control valve which can control the back pressure of off-gas from a fuel cell, and to effectively prevent the breakage of the fuel cell. <P>SOLUTION: A fuel sell system is provided with the back pressure control valve 28 which controls the back pressure of the air off-gas discharged from the fuel cell, and a control device 100 which controls the gas pressure of the inlet side of the fuel cell to target gas pressure corresponding to a target air flow by controlling the valve opening of the back pressure control valve 28. The valve opening of the back pressure control valve 28 is decided according to at least one of the temperature and the humidity of the air supplied to the fuel cell. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell system and a fuel cell inspection system, and more particularly to a technique effective in preventing damage to a fuel cell due to an inter-electrode differential pressure.

  A so-called solid polymer electrolyte type fuel cell has an anode (fuel electrode) and a cathode (air electrode) on both sides of an electrolyte membrane, a fuel gas typified by hydrogen gas is supplied to the anode, and a cathode is represented by air. Electricity is taken out by supplying the oxidized gas. In general, the fuel gas is stored in, for example, a high-pressure tank, adjusted to a predetermined pressure by a regulator, and supplied to the anode, and the oxidizing gas is supplied to the cathode by pressure-feeding atmospheric air by a compressor.

By the way, in such a fuel cell, there is a case where power generation is actually performed to check for defects. This inspection is performed, for example, by adjusting the supply gas to the fuel cell to an arbitrary flow rate, temperature, and humidity (see Patent Documents 1 and 2).
JP 2002-372262 A JP 2003-282115 A

  However, if the conditions such as the temperature and humidity of these supply gases are changed during inspection, the back pressure fluctuates because the temperature and humidity are factors that affect the pressure (back pressure). There is a risk of damage to the fuel cell. Further, even during operation of the fuel cell system, conditions such as the temperature and humidity of the supply gas can change with changes in the surrounding environment, so that there is a similar risk. Furthermore, when the back pressure increases, there is a problem that the power consumption of the compressor increases and the power generation efficiency of the fuel cell system decreases.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above problems by improving the control accuracy of an air pressure control valve capable of controlling the back pressure of exhaust gas from a fuel cell.

  The fuel cell system of the present invention includes an air pressure control valve capable of controlling the back pressure of gas discharged from the fuel cell, and the gas pressure on the fuel cell inlet side by controlling the valve opening degree of the air pressure control valve. In the fuel cell system comprising a gas pressure control means for controlling the target gas pressure in accordance with the target air flow rate, the valve opening degree of the air pressure control valve is at least one of gas temperature and humidity on the fuel cell inlet side It is decided according to.

  According to this configuration, even if the conditions of the gas introduced into the fuel cell change due to changes in the surrounding environment, etc., the valve opening degree of the air pressure control valve is adjusted in response to changes in the temperature and humidity of the gas. Therefore, the air pressure control valve can be controlled with high accuracy.

  The fuel cell system of the present invention includes feedforward control for setting the valve opening of the air pressure control valve using at least one of the temperature and humidity of the gas on the fuel cell inlet side, the measured value of the back pressure, and the target A configuration in which feedback control for setting the valve opening degree of the air pressure control valve according to a difference from the value can be switched under a predetermined condition.

  According to this configuration, when high responsiveness to human operation or the like is required, the former feedforward control enables the air pressure control valve to be as quickly as possible without incurring the risk of damage to the electrolyte membrane. The valve opening can be brought close to the target value. In addition, after the feedforward control is executed, the current value can be accurately matched with the target value of the back pressure by the latter feedback control.

  An inspection system for a fuel cell according to the present invention includes an air pressure control valve capable of controlling a back pressure of gas discharged from a fuel cell, and a gas on the fuel cell inlet side by controlling a valve opening degree of the air pressure control valve. Gas pressure control means for controlling the pressure to a target gas pressure corresponding to the target air flow rate, and the valve opening degree of the air pressure control valve is determined according to at least one of the temperature and humidity of the gas on the fuel cell inlet side The fuel cell is inspected by variously changing the gas conditions.

  According to this configuration, even if the conditions of the gas introduced into the fuel cell for inspection are changed, the valve opening degree of the air pressure control valve is adjusted in response to changes in the temperature and humidity of the gas. Inspection under various gas conditions is possible without causing the possibility of film breakage.

  According to the fuel cell system of the present invention, even if the condition of the gas introduced into the fuel cell changes, the valve opening degree of the air pressure control valve is adjusted in response to changes in the temperature and humidity of the gas. The control accuracy of the air pressure control valve, in other words, the control accuracy of the air pressure is improved, and the fuel cell can be effectively prevented from being damaged.

  Further, according to the fuel cell inspection system of the present invention, even if the conditions of the gas introduced into the fuel cell are changed, the valve opening degree of the air pressure control valve is adjusted in response to changes in the temperature and humidity of the gas. Therefore, it is possible to inspect under various gas conditions without incurring the risk of damage to the electrolyte membrane, and the inspection accuracy is improved.

  Hereinafter, a fuel cell system according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

  As shown in FIG. 1, the fuel cell system 1 includes a fuel cell 2 that generates power upon receiving supply of air (air) as an oxidizing gas and hydrogen gas as a fuel gas, and supplies air to the fuel cell 2. An air supply system 3, a hydrogen gas supply system 4 for supplying hydrogen gas to the fuel cell 2, a steam supply system 5 for supplying steam to the air and hydrogen gas to the fuel cell 2, and these supply systems 3 to 5 And a control device (gas pressure control means) 100 that controls the entire system such as components.

  The fuel cell 2 is configured as a stack structure in which a large number of single cells serving as basic units are stacked. The single cell is not shown in the figure, but is composed of an electrolyte membrane made of an ion exchange membrane and a pair of electrodes (anode and cathode) sandwiching the electrolyte membrane from both sides.

  The air supply system 3 includes a supply flow path 11 for supplying air to the fuel cell 2 and a discharge flow path 12 for discharging the air-off gas discharged from the fuel cell 2 to the outside. In the supply flow path 11, an air supply source 21, a flow rate sensor 22, a flow rate adjustment valve 23, a heater 24, a temperature sensor 25, and a humidity sensor 26 are arranged in this order from the upstream side. In addition, a pressure sensor 27 and a back pressure adjustment valve (air pressure control valve) 28 are disposed in the discharge flow path 12 in order from the upstream side.

  The hydrogen gas supply system 4 includes a supply flow path 15 for supplying hydrogen gas to the fuel cell 2 and a discharge flow path 16 for discharging the hydrogen off-gas discharged from the fuel cell 2 to the outside. In the supply flow path 15, a hydrogen supply source 41, a flow rate sensor 42, a flow rate adjustment valve 43, a heater 44, a temperature sensor 45, and a humidity sensor 46 are arranged in this order from the upstream side. In addition, a pressure sensor 47 and a back pressure adjustment valve 48 are disposed in the discharge flow path 16 in order from the upstream side.

  The steam supply system 5 humidifies the air and hydrogen gas supplied to the fuel cell 2 by supplying steam to the air from the air supply source 21 and the hydrogen gas from the hydrogen supply source 41. A source 51 and flow control valves 52 and 53 are provided. The flow rate adjustment valve 52 is disposed in a connection flow path from the steam supply system 5 to the air supply system 3, and the flow rate adjustment valve 53 is disposed in a connection flow path from the steam supply system 5 to the hydrogen gas supply system 4. ing.

  The air from the air supply source 21 is adjusted to a predetermined flow rate by the flow rate adjustment valve 23, is humidified by receiving the supply of steam from the steam supply source (humidifier) 51, and then heated to a predetermined temperature by the heater 24. It is supplied to the cathode side of the fuel cell 2. On the other hand, the hydrogen gas from the hydrogen supply source 41 is adjusted to a predetermined flow rate (pressure) by the flow rate adjustment valve 43, humidified by receiving the supply of steam from the steam supply source 51, and then heated to a predetermined temperature by the heater 44. And supplied to the anode side of the fuel cell 2. In the fuel cell 2, power generation is performed by an electrochemical reaction between air and hydrogen gas. The steam supply source 51 and the heaters 24 and 44 may be omitted.

  The gas pressure on the outlet side of the fuel cell 2 in the air supply system 3 is controlled to the target gas pressure corresponding to the target air flow rate by controlling the valve opening degree of the back pressure adjusting valve 28 disposed in the discharge flow path 12. Is done. On the other hand, the gas pressure on the outlet side of the fuel cell 2 in the hydrogen supply system 4 is controlled to be a constant pressure by controlling the valve opening degree of the back pressure adjusting valve 48 disposed in the discharge flow path 16. . These back pressure regulating valves 28 and 48 are controlled in valve opening by a control signal output from the control device 100.

FIG. 2 is a block diagram relating to the control system of the back pressure regulating valve 28.
The control device 100 includes a target back pressure setting unit 30, a back pressure difference detection unit 31, a back pressure feedback unit 32, a back pressure adjustment valve opening calculation unit 33, a change detection unit 34, a back pressure control switching unit 35, and a back pressure. An adjustment valve linear correction unit 38 is provided, and output signals from the pressure sensor 27, the flow sensor 22, the humidity sensor 26, and the temperature sensor 25 are input, and a control signal for the back pressure adjustment valve 28 is output.

  Next, the function of the control device 100 related to the control of the back pressure regulating valve 28 will be described according to the signal flow. First, the target value of the back pressure controlled by the back pressure adjusting valve 28 is set by the target back pressure setting unit 30 based on a human operation or a signal from another device, and the back pressure difference detecting unit 31 and the back pressure feedback unit. 32 and the change detection unit 34. On the other hand, the current value (measured value) of the back pressure is detected by the pressure sensor 27 and input to the back pressure difference detection unit 31 and the back pressure feedback unit 32.

  The back pressure difference detection unit 31 compares the current value from the pressure sensor 27 with the target value from the target back pressure setting unit 30, and uses a back pressure control as a switching signal between calculation value control (feed forward control) and feedback control. Output to the switching unit 35. The valve opening degree of the back pressure adjusting valve 28 set by feedback control is calculated by the back pressure feedback unit 32 based on the current value from the pressure sensor 27 and the target value from the target back pressure setting unit 30.

On the other hand, the valve opening of the back pressure adjusting valve 28 set by the calculation value control is determined by the back pressure adjusting valve opening calculating unit 33 based on the signals from the flow sensor 22, the humidity sensor 26, and the temperature sensor 25. Arithmetic processing is performed. The calculation in the back pressure adjusting valve opening calculation unit 33 is performed using the following formula obtained from experiments.
Y = f1 (x1) + f2 (x1, x2) + f3 (x3) + d (formula)
Here, Y: valve opening, x1: flow rate, x2: humidity, x3: temperature, d: constant, f1 (x1) is a function of setting the valve opening with x1 as a variable, f2 (x1, x2) Is a valve opening setting function with x1 and x2 as variables, and f3 (x3) is a valve opening setting function with x3 as a variable.

  Note that the back pressure adjusting valve opening calculator 33 can set the valve opening with reference to a map shown in FIG. 3, for example, instead of the numerical calculation by the above formula. In the map of FIG. 3, as the air flow rate supplied to the fuel cell 2 increases, the valve opening degree of the back pressure adjustment valve 28 also increases in a curvilinear (non-linear) manner. It is set so that the valve opening degree of the back pressure regulating valve 28 increases as the humidity increases.

  The change detection unit 34 stores the target back pressure set by the target back pressure setting unit 30, the newly set target back pressure (hereinafter, this value), and the target back pressure set before that ( Hereinafter, a difference from the previous value) or a switching signal based on the difference is output to the back pressure control switching unit 35. Switching between feedback control and calculation value control is performed by the back pressure control switching unit 35. This switching is performed according to a predetermined condition based on signals from the back pressure difference detection unit 31 and the change detection unit 34.

  For example, as shown in FIG. 4, switching from the calculation value control to the feedback control is performed when the difference between the current back pressure value and the target value (hereinafter referred to as differential back pressure) is within a preset feedback difference range. This is performed when the time until the back pressure difference converges to a predetermined range (hereinafter referred to as a stable time) has elapsed after becoming half or less. This stabilization time is preset. On the other hand, switching from feedback control to calculation value control is performed, for example, when the target back pressure change amount (difference between the previous value and the current value of the target back pressure) from the change detection unit 34 exceeds a predetermined range. .

  By the way, the feedback control and the calculation value control are optimal when the characteristics of the input and output devices are linear. In the present embodiment, the sensors 22, 25 to 27 that are input devices have linear characteristics (linear) and need not be corrected. However, the back pressure adjustment valve 28 that is an output device is almost non-linear (non-linear). Therefore, it is preferable to correct the linear characteristic. Therefore, an output signal from the control device 100 is output to the back pressure adjusting valve 28 after being corrected to a linear characteristic by the back pressure adjusting valve linear correcting unit 38.

  As described above, according to the present embodiment, when setting the valve opening degree of the back pressure regulating valve 28, not only the air flow rate supplied to the fuel cell 2 but also changes in the humidity and temperature of the air are taken into consideration. Thus, the valve opening degree of the back pressure adjusting valve 28 is controlled. For this reason, unlike the case where the valve opening degree is controlled only by the air flow rate (see FIG. 5), the air humidity does not increase and the back pressure does not increase excessively while the air flow rate is constant. .

  Therefore, the control accuracy of the valve opening, in other words, the control accuracy of the gas pressure is improved, the electrolyte membrane can be effectively prevented from being damaged, and the reliability of the fuel cell system is also improved. Further, when the air supply system 3 is provided with a compressor, it is possible to avoid an excessive increase in the back pressure, and as a result, it is possible to reduce the power consumption of the compressor and thus improve the power generation efficiency of the fuel cell system.

  Furthermore, it is possible to switch between calculation value control for setting the valve opening using the outputs from the sensors 22, 25, and 26 and feedback control for setting the valve opening based on the differential back pressure, and the change of the target back pressure When the amount is large, in other words, when high responsiveness to human operation or the like is required, the back pressure regulating valve 28 can be obtained as soon as possible by performing the former calculation value control without damaging the electrolyte membrane. The valve opening of the valve is brought close to the target value, and after the calculation value control is executed, the latter value feedback control is performed so that the current value accurately matches the back pressure target value. Compatibility improvement and response improvement can be achieved.

The above describes one embodiment of the fuel cell system according to the present invention, but the same system configuration may be applied to a fuel cell inspection system.
That is, as in the fuel cell system, the valve opening degree of the back pressure regulating valve 28 is controlled according to at least one of the temperature and humidity of the air at the fuel cell 2 inlet side, and the air condition The fuel cell 2 is inspected to determine whether or not there is a problem by changing variously.
According to the inspection system having such a configuration, the inspection can be performed under various gas conditions without damaging the electrolyte membrane, so that the inspection accuracy can be improved.

  In addition, the structure and arrangement of the air pressure control valve of the present invention are limited to the form of the back pressure adjusting valve 28 as long as the back pressure of the air off gas discharged from the fuel cell 2 can be controlled. Is not to be done.

It is a figure which shows the structure of the fuel cell system which concerns on one Embodiment of this invention. It is a control block diagram of the back pressure regulating valve according to the embodiment. It is an example of the map figure used when setting a valve opening degree. It is a figure which shows a back pressure waveform when the valve opening degree is controlled by the same embodiment. It is a figure which shows a back pressure waveform when a valve opening degree is controlled only by flow volume change.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 2 ... Fuel cell, 3 ... Air supply system, 4 ... Hydrogen gas supply system, 28 ... Back pressure adjustment valve (pressure control valve), 100 ... Control apparatus (gas pressure control means)

Claims (3)

An air pressure control valve capable of controlling the back pressure of gas discharged from the fuel cell, and a gas pressure on the fuel cell inlet side according to the target air flow rate by controlling the valve opening degree of the air pressure control valve In a fuel cell system comprising a gas pressure control means for controlling the pressure,
The valve opening degree of the air pressure control valve is determined according to at least one of gas temperature and humidity on the fuel cell inlet side.   Feedforward control that sets the valve opening of the air pressure control valve using at least one of the temperature and humidity of the gas on the fuel cell inlet side, and the difference between the measured value and the target value of the back pressure The fuel cell system according to claim 1, wherein feedback control for setting a valve opening degree of the air pressure control valve can be switched under a predetermined condition. An air pressure control valve capable of controlling the back pressure of gas discharged from the fuel cell, and a gas pressure on the fuel cell inlet side according to the target air flow rate by controlling the valve opening degree of the air pressure control valve Gas pressure control means for controlling the pressure,
The valve opening degree of the air pressure control valve is determined according to at least one of the temperature and humidity of the gas on the fuel cell inlet side, and the fuel cell is inspected by changing the gas conditions in various ways. Fuel cell inspection system.

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