JP2009076328A - Fuel cell power generation system and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell power generation system in which system reliability is improved by maintaining an appropriate fuel flow rate, and its control method. <P>SOLUTION: The fuel cell power generation system consists of a reformer 1, a fuel cell stack 2, and an electric control device 3. The electric control device 3 is to monitor temperature of the reformer 1 obtained from a reformer temperature sensor 7, cell current of the fuel cell main body 2, the number of rotations of a fuel blower 4 and a reforming water pump 5, and fuel system pressure obtained by a fuel cell system pressure sensor 8, and based on these, decides the number of rotations of the fuel blower 4 to carry out adjustment of a fuel flow rate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell power generation system and a control method thereof, and more particularly to improvement of a technique for improving the reliability of a fuel cell stack.

  Fuel cells are classified into various types depending on the difference in electrolytes, etc., but solid polymer fuel cells using a solid polymer electrolyte membrane as the electrolyte are generally used because of their low-temperature operability and high output density. This type of fuel cell is suitable for use as a power source for small-sized cogeneration systems and electric vehicles for household use, and the market scale is rapidly expanding in the future.

This solid polymer fuel cell is composed of a reformer, a fuel cell stack, an electric control device, and a heat utilization system, taking a stationary small cogeneration system for home use as an example. The reformer produces a hydrogen-containing gas from a hydrocarbon fuel represented by city gas, LPG, or the like. The fuel cell stack includes a hydrogen-rich gas containing H ₂ as a main component containing CO ₂ , CO, and N ₂ as a by-product gas produced by a CO shift converter and a CO selective oxidizer, air in the atmosphere, Are supplied to the fuel electrode and the oxidant electrode, respectively, to generate an electromotive force. The electric control device supplies electric energy generated in the fuel cell stack to an external load, and the heat utilization system recovers heat generated by power generation.

Some of such fuel cell power generation systems do not have a fuel flow meter. In this case, fuel flow control gives a reference fuel blower rotation speed from the battery current during power generation, and is corrected by the reformer temperature. (See Patent Documents 1 and 2). Further, during start-up, a reference fuel blower rotational speed is given in each state such as reformer burner ignition and temperature rise.
JP 2004-047438 A JP 2001-126748 A

  However, merely performing correction for the conventional fuel blower rotation speed as described above at the reformer temperature cannot compensate for individual differences in fuel blower capacity and individual differences in fuel system pressure loss. It was difficult to maintain properly. Even during start-up, the reformer temperature alone cannot compensate for individual differences in fuel blower capacity and individual differences in fuel system pressure loss, just as during power generation, and it is difficult to maintain an appropriate fuel flow during start-up. there were.

  If the fuel flow rate cannot be maintained properly, the amount of hydrogen supplied to the battery body will not be properly maintained, the fuel cell power generation system will not be able to continue generating electricity, and it will permanently damage the main equipment such as the battery body. There is a possibility.

  Furthermore, if the fuel flow rate cannot be maintained properly even during start-up, not only the system cannot be started due to the failure of the reformer burner, but also caused by introducing excessive fuel into the reformer burner. Incomplete combustion may occur.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a fuel cell power generation system and a control method therefor that improve the reliability of the system by keeping the fuel flow rate appropriate. .

  In order to solve the above problems, the present invention provides a reformer for generating a hydrogen-rich reformed gas from a raw fuel gas containing hydrocarbons, and the reformed gas obtained by the reformer as a fuel. A fuel cell stack that generates electric energy by an electrochemical reaction between the fuel gas and an oxidant gas, and a flow rate of the fuel gas and the oxidant gas supplied to the fuel cell stack. And a fuel cell power generation system that does not include a fuel flow sensor, and that includes a reformer temperature sensor in the reformer and supplies the fuel gas to the reformer. A fuel system pressure sensor in the system, means for calculating a reformer temperature correction coefficient from a reformer temperature obtained from the reformer temperature sensor and a preset reformer temperature setting value; and The battery current obtained from the stack is multiplied by the reformer temperature correction coefficient to calculate a fuel flow rate setting value, and the fuel flow rate obtained from the rotational speed of the fuel blower is used as a reference calculation value to this value. Means for calculating a fuel flow rate by multiplying by a fuel system pressure correction coefficient determined from a fuel system pressure obtained from a fuel system pressure sensor; and means for determining the fuel blower rotational speed from a deviation between the fuel flow rate set value and the fuel flow rate And.

  According to the present invention as described above, it is possible to accurately calculate the fuel flow rate by appropriately correcting not only the rotational speed of the fuel blower but also the reformed steam amount and the fuel system pressure in calculating the fuel flow rate. . In addition, by effectively utilizing the relationship between each state quantity during power generation and each state quantity during startup and before startup, the individual differences in the system can be grasped and responded accordingly. The fuel blower speed can be provided. Thereby, even if there is no fuel flow sensor, the fuel flow can be appropriately calculated based on the reformer temperature and the fuel system pressure, and the reliability of the system can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell power generation system which improves the reliability of a system by maintaining a fuel flow rate appropriately, and its control method can be provided.

  Hereinafter, a typical embodiment (hereinafter referred to as this embodiment) according to the present invention will be specifically described with reference to FIGS. FIG. 1 is a block diagram showing a configuration of a fuel cell power generation system in the present embodiment, and FIG. 2 is a control logic diagram of the fuel cell power generation system in the present embodiment.

[Constitution]
In FIG. 1, the fuel cell power generation system of this embodiment includes a reformer 1, a fuel cell stack 2, and an electric control device 3. The reformer 1 produces hydrogen-rich reformed gas from a hydrocarbon-based fuel typified by city gas or LPG and supplies it to the fuel cell stack 2. In order to appropriately maintain the amount of hydrogen supplied to the fuel cell stack 2, an appropriate amount of raw fuel is supplied to the system by the fuel blower 4. Further, during startup of the fuel cell power generation system, raw fuel is supplied to the burner chamber of the reformer 1 by the fuel blower 4 and air is supplied by the air blower 6 to burn at an appropriate air-fuel ratio. To do.

  The electric control device 3 includes the temperature of the reformer 1 obtained from the reformer temperature sensor 7, the cell current of the fuel cell main body 2, the rotation speed of the fuel blower 4 and the reforming water pump 5, and the fuel system pressure sensor. The fuel system pressure obtained by 8 is monitored, and based on these, the rotational speed of the fuel blower 4 is determined and the fuel flow rate is adjusted.

[Action]
FIG. 2 shows the control logic of the electric control device 3 during power generation, and is specifically as follows. First, as in the prior art, proportional integral control (hereinafter, referred to as a deviation between the reformer temperature set value determined from the battery current of the fuel cell 2 and the reformer temperature obtained from the temperature sensor 7 of the reformer 1). Reformer temperature correction coefficient is calculated using PI control). Next, the fuel flow rate set value is calculated by multiplying the fuel flow rate reference set value determined by the battery current of the fuel cell 2 by the reformer temperature correction coefficient.

  In this embodiment, the calculated value of the fuel flow rate is calculated based on the number of revolutions of the reforming water pump and the fuel system pressure in addition to the number of revolutions of the fuel blower. That is, the fuel flow rate in this embodiment is obtained by multiplying this value by the fuel system pressure correction coefficient determined from the fuel system pressure obtained from the fuel system pressure sensor 8 with the fuel flow rate obtained from the rotational speed of the fuel blower 4 as a reference calculation value. To calculate. In addition to this, it is also possible to perform further correction by multiplying the fuel flow rate reference calculated value determined by the fuel blower rotational speed by the reforming steam amount correction coefficient determined from the reforming water pump rotational speed.

  In the present embodiment, the command value for the fuel blower rotational speed is determined using PI control from the deviation between the fuel flow rate setting value calculated as described above and the fuel flow rate, and this is sent to the fuel blower 4. Based on this, the fuel blower 4 supplies the reformer 1 with an appropriate flow rate of fuel.

[effect]
According to the present embodiment as described above, by grasping the relationship between the fuel blower rotation speed and the reformer temperature or the fuel system pressure during power generation, individual differences in the fuel blower capacity and the solids of the fuel system pressure loss are obtained. The difference can be grasped. This characteristic can be used as an initial value of the rotational speed of the fuel blower during startup.

  In addition to the characteristics during power generation, the individual difference is grasped by grasping the relationship between the fuel blower rotation speed and the fuel system pressure before starting, and the initial value of the fuel blower rotating speed during startup and the fuel blower rotation A function of the number and the fuel flow reference calculation value can be given. In addition, you may comprise the said function so that it may be provided with the function automatically changed for every system with the acquired characteristic.

  As described above, the fuel flow rate can be accurately calculated by appropriately correcting not only the rotational speed of the fuel blower but also the reformed steam amount and the fuel system pressure in the calculation of the fuel flow rate. In addition, by effectively utilizing the relationship between each state quantity during power generation and each state quantity during startup and before startup, the individual differences in the system can be grasped and responded accordingly. The fuel blower speed can be provided.

  According to such a fuel cell power generation system of this embodiment, the fuel flow rate can be appropriately calculated based on the reformer temperature and the fuel system pressure without the fuel flow rate sensor, and the reliability of the system can be improved. It becomes possible.

[Other Embodiments]
The present invention is not limited to the above embodiment, and includes, for example, the following aspects. In the control logic described above, a configuration in which the reformed steam amount is calculated by a reformed steam control valve or a steam ejector instead of calculation by the reformed water pump 3 can be employed. Further, the battery current can be replaced with a state quantity representing a system load such as a power generation output, and may be a mathematical expression instead of each function. Further, the reformer temperature set value may be constant regardless of the battery current.

  Further, the order of correction may be changed when calculating the fuel flow rate. Furthermore, although the control method is generally used proportional integral control (PI control), differential control or other control methods may be used.

The block diagram which shows the structure of the fuel cell power generation system in embodiment of this invention. The control logic figure of the fuel cell power generation system in the embodiment of the present invention. The block diagram which shows the structure of the conventional fuel cell power generation system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Reformer 2 ... Fuel cell stack 3 ... Electric control device 4 ... Combustion blower 5 ... Reformed water pump, steam control valve or steam ejector 6 ... Air blower 7 ... Reformer temperature sensor 8 ... Fuel system pressure sensor

Claims (5)

A reformer for generating a hydrogen-rich reformed gas from a raw fuel gas containing hydrocarbons, and using the reformed gas obtained by the reformer as a fuel gas, the fuel gas, an oxidant gas, A fuel cell stack that generates electric energy by an electrochemical reaction of the fuel cell, and an electric control device that controls the flow rate of the fuel gas and the oxidant gas supplied to the fuel cell stack by controlling the fuel blower and the oxidant blower. In a fuel cell power generation system that does not include a fuel flow sensor,
The reformer includes a reformer temperature sensor,
A fuel system pressure sensor is provided in a system for supplying the fuel gas to the reformer,
Means for calculating a reformer temperature correction coefficient from a reformer temperature obtained from the reformer temperature sensor and a preset reformer temperature set value;
Means for multiplying the battery current obtained from the fuel cell stack by the reformer temperature correction coefficient to calculate a fuel flow rate setting value;
Means for calculating the fuel flow rate by multiplying this value by the fuel system pressure correction coefficient determined from the fuel system pressure obtained from the fuel system pressure sensor, using the fuel flow rate obtained from the rotational speed of the fuel blower as a reference calculation value;
A fuel cell power generation system comprising: means for determining the fuel blower rotational speed from a deviation between the fuel flow rate setting value and the fuel flow rate. Reformed steam amount control means for adjusting the steam amount to the fuel gas supplied to the reformer;
And a means for multiplying the reference calculation value of the fuel flow rate obtained from the rotation speed of the fuel blower by a reforming steam amount correction coefficient calculated by the reformer steam amount control means. The fuel cell power generation system according to 1.   3. The fuel according to claim 1, further comprising means for setting the fuel blower rotational speed obtained from a deviation between the fuel flow rate set value and the fuel flow rate as an initial value of the fuel blower rotational speed at the time of startup. Battery power generation system.   3. The fuel according to claim 1, further comprising means for setting the fuel blower rotational speed obtained from the deviation between the fuel flow rate set value and the fuel flow rate as a reference value for the fuel blower rotational speed during power generation. Battery power generation system. A reformer for generating a hydrogen-rich reformed gas from a raw fuel gas containing hydrocarbons, and using the reformed gas obtained by the reformer as a fuel gas, the fuel gas, an oxidant gas, A fuel cell stack that generates electrical energy by an electrochemical reaction of the fuel cell, and an electric control device that controls the flow rate of the fuel gas and the oxidant gas supplied to the fuel cell stack by controlling the fuel blower and the oxidant blower. In a control method of a fuel cell power generation system that uses a fuel flow rate sensor without using a fuel flow rate sensor,
The electrical control device
A process of calculating a reformer temperature correction coefficient from the reformer temperature obtained from the reformer temperature sensor and a preset reformer temperature set value;
A process of calculating a fuel flow rate setting value by multiplying the battery current obtained from the fuel cell stack by the reformer temperature correction coefficient;
The fuel flow rate obtained from the rotational speed of the fuel blower is used as a reference calculation value, and this value is multiplied by a fuel system pressure correction coefficient determined from the fuel system pressure obtained from the fuel system pressure sensor.
A control method for a fuel cell power generation system, comprising: performing a process of obtaining the fuel blower rotational speed from a deviation between the fuel flow rate setting value and the fuel flow rate.

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