JP2003221205A - Temperature control for fuel reforming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique capable of attaining good reformed gas quality even if a load fluctuation happens to occur. <P>SOLUTION: Each objective temperature tri in a plurality of parts in a fuel reforming device is set, corresponding to a requested load to a fuel reforming device, and each present temperature twi is obtained by measuring or estimation, for the deviation Δtwi of present temperature from the objective temperature at the part nonuniform weights fi is applied for sum of product operation, thereby amount of air flow ua necessary for partial oxidation is determined. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel reformer control technique for producing a hydrogen-rich fuel gas from a raw fuel containing a hydrocarbon compound.

[0002]

2. Description of the Related Art A fuel reformer produces hydrogen-rich fuel gas (also called "reformed gas") from a reforming raw material containing a hydrocarbon compound by a reforming reaction using a reforming catalyst. The fuel gas generated by the fuel reformer is generally used in a fuel cell. In recent years, a vehicle equipped with a fuel cell system including a fuel reformer has been under development.

In a vehicle equipped with a fuel cell system, the load request (output request) to the fuel cell greatly changes according to the operating state of the vehicle, and as a result, the load request to the fuel reformer (output of fuel gas). Demand) will also change significantly. 2. Description of the Related Art Conventionally, various measures have been made to control the reforming reaction in the reforming section and maintain the quality of the reformed gas when the load demand on the fuel reformer changes.

For example, in the technique disclosed in Japanese Patent Laid-Open No. 8-273685, the average temperature of the temperatures detected at a plurality of points of the reforming catalyst is obtained, and the temperature of the reforming catalyst is controlled according to this average temperature. There is.

[0005]

When the load demand on the fuel reformer changes, the temperature distribution in the reformer also changes accordingly. However, it has been found that the quality of the reformed gas is considerably affected by the temperature distribution in the reforming section. Therefore, even if the control is performed using the average temperature of the reforming catalyst as in the conventional case, the desired reformed gas quality may not always be obtained. Such a problem is not limited to a fuel reformer mounted on a vehicle, but is generally a problem common to fuel reformers in which load demand fluctuations are expected.

The present invention has been made in order to solve the above-mentioned conventional problems, and an object thereof is to provide a technique capable of achieving a good reformed gas quality even when there is a load change. And

[0007]

In order to achieve at least a part of the above objects, a fuel reformer according to the present invention is provided with a hydrogen-rich fuel gas from a reforming raw material containing a hydrocarbon compound. A reforming unit for accommodating a reforming catalyst for promoting a reforming reaction of the reforming raw material, and a reforming unit for supplying the reforming raw material supplied to the reforming unit. A flow rate adjusting unit for adjusting the flow rate of a specific raw material forming at least a part, and a control unit for controlling the flow rate adjusting unit are provided. In addition, the control unit, in accordance with the required load to the fuel reformer, a target temperature setting unit that sets target temperatures at a plurality of parts in the reformer, and measures the current temperature at the plurality of parts or Based on the calculated value obtained by applying a non-uniform weight to the deviation between the target temperature and the current temperature in the plurality of parts, the temperature acquisition unit obtained by estimation,
A feedback control unit that generates a control signal to be supplied to the flow rate adjustment unit.

In this fuel reforming apparatus, uneven weights are applied to the deviations between the target temperature and the current temperature at a plurality of parts in the reforming section, so that the current temperatures at a plurality of parts approach the target temperature. Control can be performed. Further, the distribution of the target temperature in the plurality of parts is changed according to the load change. As a result, it is possible to achieve good reformed gas quality even when there is a load change.

The weight for the plurality of parts is
It is preferable that the weight of a specific portion, which is the portion closest to the outlet of the reforming unit, of the plurality of portions has a larger value than the weight of other portions.

With this configuration, when the temperature at the specific portion closest to the outlet has the greatest effect on the reformed gas quality,
It is effective in obtaining good reformed gas quality.

The feedback control unit may generate the control signal by using a temporal integrated value of a deviation between the target temperature and the current temperature at the specific portion and the calculated value. .

According to this structure, it is possible to eliminate the temperature offset in the specific portion closest to the outlet, so that it is possible to obtain a better reformed gas quality.

It is preferable that the target temperature setting unit sets the target value of the temperature at the specific portion so that it falls within a predetermined temperature range smaller than the entire temperature range of the target temperature distribution. Particularly, it is preferable to set the target value of the temperature at the specific portion to a constant temperature that does not depend on the load demand.

With such a structure, it is possible to obtain a better reformed gas quality.

The present invention can be implemented in various modes, for example, a fuel reformer and a control method thereof, a fuel cell system including a fuel reformer and a fuel cell, and a control method thereof. A mobile body including those devices or systems and a control method thereof, a computer program for realizing the functions of those methods or devices,
It can be realized in the form of a recording medium recording the computer program, a data signal containing the computer program and embodied in a carrier wave, or the like.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described in the following order based on examples. A. Device Configuration: B. First Example: C.I. Second embodiment: D. Modification:

A. Device Configuration: FIG. 1 is a schematic configuration diagram of an electric vehicle as an embodiment of the present invention. The wheel drive mechanism of this electric vehicle (hereinafter simply referred to as “vehicle”) is
It has a motor 20, a torque converter 30, and a transmission 40. The rotating shaft 13 of the motor 20 is coupled to the torque converter 30. The output shaft 14 of the torque converter is coupled to the transmission 40. The output shaft 15 of the transmission 40 is connected to an axle 17 of a wheel 18 via a differential gear 16.

The motor 20 includes a rotor 22 and a stator 2
4 is a three-phase synchronous motor. A plurality of permanent magnets are provided on the outer peripheral surface of the rotor 22. Also,
A three-phase coil for forming a rotating magnetic field is wound around the stator 24. The motor 20 is rotationally driven by the interaction between the magnetic field generated by the permanent magnet provided in the rotor 22 and the magnetic field generated by the three-phase coil of the stator 24. Further, when the rotor 22 is rotated by an external force, an electromotive force is generated at both ends of the three-phase coil due to the interaction of these magnetic fields. In this case, the motor 20
Acts as a generator.

The motor 20 is equipped with two power sources, a fuel cell system 60 as a main power source and a battery (secondary battery) 50 as an auxiliary power source. The battery 50 supplies insufficient power to the motor 20 when the fuel cell system 60 fails, or when the fuel cell system 60 cannot output sufficient power such as when the vehicle is started. The power of the battery 50 is further supplied to a control unit 70 that controls the vehicle and power equipment (not shown) such as a lighting device.

Electric power from the two power sources 50 and 60 is supplied to the motor 20 through the drive circuits 51 and 52 and the changeover switch 80, respectively. The changeover switch 80 can arbitrarily switch the connection state among the battery 50, the fuel cell system 60, and the motor 20. The stator 24 is electrically connected to the battery 50 via the changeover switch 80 and the first drive circuit 51, and
It is connected to the fuel cell system 60 via the changeover switch 80 and the second drive circuit 52. Two drive circuits 5
Reference numerals 1 and 52 are each composed of a transistor inverter, and each of the three phases of the motor 20 is provided with a plurality of transistors with two sets on the source side and the sink side as one set. These drive circuits 51 and 52 are electrically connected to the control unit 70.

The control unit 70 includes a shift lever 72.
Then, various controls for the vehicle are executed based on the driver's commands given from the accelerator pedal 74 and the brake pedal 76. The control unit 70 has a drive circuit 51,
When the on / off time of each transistor of 52 is PWM-controlled, a pseudo three-phase alternating current using the battery 50 and the fuel cell system 60 as a power source flows in the three-phase coil of the stator 24 to form a rotating magnetic field. The motor 20 functions as an electric motor or a generator as described above by the action of the rotating magnetic field.

Various control operations of the control unit 70 are realized by the control unit 70 executing a computer program stored in a memory (not shown) built in the control unit 70. As this memory, various recording media such as a ROM and a hard disk can be used.

FIG. 2 is an explanatory view showing the structure of the fuel cell system 60. The fuel cell system 60 includes an FC controller 100, a fuel reformer 200, and a fuel cell 300.
It has and. The fuel reformer 200 includes an evaporator 210.
And a reforming section 220 and a CO purifying section 230.

The evaporation section 210 includes a combustion gas flow path 212,
And a reforming raw material flow path 214. Combustion gas flow path 21
2 has a shape in which a plurality of horizontal flow channels 212a are sequentially connected by a substantially U-shaped folded portion 212b. In the example of FIG. 2, the combustion gas passage 212 has two folded portions 21.
It has three horizontal flow paths 212a connected by 2b. The reforming material flow path 214 is divided into a large number of vertical direct current paths 214a extending vertically from the lower part of the evaporation part 210 to the upper part. The horizontal flow path 212a of the fuel gas and the vertical flow path 214a of the reforming raw material constitute a so-called orthogonal heat exchanger.

Combustion air, combustion raw materials (for example, methanol or natural gas), and anode exhaust gas of the fuel cell 300 are supplied to the uppermost inlet portion of the combustion gas passage 212. The flow rates of the combustion air and the combustion raw material are adjusted by the respective actuators 242 and 244. The flow rate of the anode exhaust gas is the anode exhaust gas flow path 26.
It is adjusted by the flow rate adjusting valve 262 provided at zero.

An electrically heated combustion catalyst section 216 (referred to as "EHC") is provided near the inlet of the combustion gas flow passage 211. The EHC 216 has a combustion catalyst for promoting the oxidation reaction of the hydrogen gas in the combustion raw material and the anode exhaust gas, and an electrically heated heater. Evaporator 210
At the time of startup, it is possible to start the combustion reaction of the combustion raw material and the anode exhaust gas early by raising the temperature of the EHC 216 by electric heating. The evaporation unit 2
The EHC 216 in 10 is referred to as "combustion EHC".

The combustion gas containing the combustion raw material and the anode exhaust gas flows from the uppermost stage to the lowermost stage of the combustion gas passage 212 while burning, and the exhaust gas is discharged from the outlet of the lowermost stage. On the other hand, the liquid reforming raw material is the reforming raw material flow path 214.
It is supplied from the lower inlet of the fuel cell and flows upward in the vertical flow path 214a while being heated by the combustion gas and evaporated.
As the liquid reforming raw material, a mixture of methanol and water, a mixture of gasoline and water, or the like can be used.
Below, the case where a mixture of methanol and water is used as the reforming raw material will be mainly described.

The gaseous reforming raw material (referred to as "reforming raw material gas") vaporized in the evaporation section 210 is introduced into the reforming section 220 together with the partial oxidizing air. The reforming section 220 accommodates the reforming catalyst 222. The reforming catalyst 222 is supported on, for example, a honeycomb carrier. The electrically heated reforming catalyst unit (E
HC) 224, respectively. These EH
C224 has a reforming catalyst for promoting the reforming reaction of the reforming raw material gas, and an electric heating type heater. At the time of starting the fuel reforming apparatus 200, it is possible to start the reforming reaction early by raising the temperature of these EHC 224 by electric heating. In addition, EHC2 of the central part
24 may be omitted. In the following, E in the reforming section 220
HC224 is called "reforming EHC."

In the reforming section 220, a partial oxidation reaction represented by the following equation (1) and a steam reforming reaction represented by the equation (2) mainly occur.

[0030]

[Equation 1]

[Equation 2]

The partial oxidation reaction of the formula (1) is an exothermic reaction, and the steam reforming reaction of the formula (2) is an endothermic reaction. Therefore, during steady operation of the fuel reforming apparatus 200, it is possible to maintain the reforming section 220 at an appropriate operating temperature by performing both at an appropriate ratio. The reformer 2
The air supplied to 20 is used for the above partial oxidation reaction, and is therefore referred to as "air for partial oxidation".

The flow rate of the partial oxidation air has various effects on the state of the reforming section 220 as follows. When the flow rate of the partial oxidation air is low, the amount of heat generated by the partial oxidation reaction decreases, and the temperature inside the reforming section 220 decreases. As a result,
The reaction rate of the steam reforming reaction decreases, and the unreformed gas component (for example, methanol) contained in the gas discharged from the reforming section 220 (hereinafter, simply referred to as “reformed gas”) increases. On the other hand, when the flow rate of the partial oxidation air is large, the amount of heat generated by the partial oxidation reaction increases and the temperature inside the reforming section 220 also rises. As a result, carbon monoxide contained in the reformed gas increases, and the possibility that the reforming catalyst deteriorates increases. As described above, the flow rate of the partial oxidation air is set to the reforming section 22.
Since there is a close relationship with the reaction within 0, it is preferable to introduce an appropriate flow rate of air into the reforming section 220.

The reformed gas produced in the reforming section 220 usually contains carbon monoxide. The CO purification unit 230 has a function of reducing carbon monoxide in the reformed gas. C
As a reaction in the O purification unit 230, a shift reaction or a selective oxidation reaction is used. For example, when a reforming raw material containing methanol and water is used, only the selective oxidation reaction is used in the CO purification unit 230. On the other hand, when the reforming raw material containing gasoline and water is used, both the shift reaction and the selective oxidation reaction are used in the CO purification unit 230. In the latter case, the CO purification section 230 is divided into a shift reaction section and a selective oxidation section.

From the CO purification unit 230, hydrogen-rich fuel gas containing less carbon monoxide is discharged. This fuel gas is supplied to the anode side of the fuel cell 300, and air is supplied to the cathode side. The flow rate of the fuel gas supplied to the fuel cell 300 is controlled by the flow rate adjusting valve 254. In addition to the pressure sensor 252, a temperature sensor, a flow rate sensor, and the like (not shown) are provided on the fuel gas flow path from the fuel reformer 200 to the fuel cell 300. F
The C control unit 100 controls the operating states of the fuel reformer 200 and the fuel cell 300 in response to signals from these various sensors and commands from the control unit 70 (FIG. 1) of the vehicle body.

B. First Embodiment: FIG. 3 is an explanatory diagram showing elements related to control of the reforming section 220 in the first embodiment. The reforming catalyst 222 is, for example, a honeycomb-shaped carrier on which the reforming catalyst is carried. In the example of FIG. 3, the reforming catalyst 222 is virtually divided into six sections (referred to as “cells”) 222a to 222f by a dashed-dotted section line. Temperature sensors 226a to 226f for measuring the catalyst temperature are installed in the cells 222a to 222f, respectively. In the example of FIG. 3, temperature sensors 226a to 226 are used.
f is installed in the substantially central part of the cross section of the reformed gas. The reason is that the temperature of the central portion of the cross section of the reformed gas is higher than that of the peripheral portion, and the temperature control of this portion is important for the quality of the reformed gas. However, the temperature sensor does not have to be provided at the central portion of the flow path cross section, and may be arranged at a place other than the central portion.

The FC controller 100 includes a temperature sensor 226a.
The temperatures tw1 to tw6 of the cells 222a to 222f measured at ˜226f are used to generate the control signal ua to be applied to the actuator 244. This actuator 244 is
This is for adjusting the flow rate of the partial oxidation air supplied to the reforming section 220. As the actuator 244, an air pump, a flow rate adjusting valve, or the like can be used. As will be described later, the FC control unit 100 adjusts the flow rate of the partial oxidation air to change the reforming unit 220.
It has the function of controlling the temperature distribution along the flow direction of the gas inside.

FIG. 4 is a modification section 220 in the first embodiment.
2 is a block diagram showing the configuration of the control system of FIG. The FC control unit 100 includes a target value setting unit 110 and a subtractor 112.
And a sum-of-products calculator 114.

The target value setting section 110 is used for the fuel reformer 20.
The target value xr is set according to the load request (or load condition) for 0. Here, the “load request to the fuel reformer 200” means, for example, the flow rate (required hydrogen amount) of the reformed gas that the fuel reformer 200 should generate. The flow rate of the reformed gas depends on the amount of the reforming raw material (reforming fuel and water) input to the evaporation unit 210, the flow rate of the reforming raw material vapor, the pressure in the reforming unit 220, and the like. One of
The target value xr may be set according to one or more parameters. Alternatively, the amount of electric power required for the fuel cell system 60 can be used as the required load for the fuel reformer 200.

The target value xr is a target value for the state variable x representing a plurality of internal states of the reforming section 220. The state variable x includes temperature distributions tw1 to tw6 (hereinafter, referred to as “current temperature distribution”) measured at a plurality of sites in the reforming section 220. The state variable x and its target value xr are both represented as a vector containing a plurality of components.

FIG. 5 shows the target temperature distribution t in the reforming section 220.
6 is a graph showing an example of r. Here, 6 shown in FIG.
The distributions of the target values tr of the temperatures tw1 to tw6 at the two sites are shown. The target temperature tr of each part tends to increase as the load increases, for example. The target temperature distribution according to the specific required load amount on the fuel reformer 200 is
It is determined from the actual temperature distribution when the fuel reformer 200 is steadily operated with the required load amount. In the example of FIG. 5, the target value of the temperature tw6 (hereinafter, simply referred to as “outlet temperature”) at the portion closest to the outlet of the reforming section 220 is kept constant for the following reasons. .

FIG. 6 shows the outlet temperature tw6 of the reforming section 220,
6 is a graph showing the relationship with the quality of reformed gas discharged from the reforming section 220 (methanol concentration and carbon monoxide concentration). It is desirable that the methanol concentration and carbon monoxide concentration in the reformed gas be as low as possible. In FIG. 6, the levels of the target values Cmt and Cco of the methanol concentration and the carbon monoxide concentration are indicated by broken lines. When the outlet temperature tw6 rises, the methanol concentration decreases, and conversely, the carbon monoxide concentration tends to increase. Therefore, in order to generate a high-quality reformed gas that satisfies both target values Cmt and Cco, it is preferable to keep the outlet temperature tw6 within a predetermined range Rt regardless of the required amount of reformed gas. In the example of FIG. 6, particularly, the reforming unit 22
The outlet temperature tw6 of 0 is preferably within the range of 250 ± 5 ° C. However, the appropriate target temperature is appropriately determined according to the type of the reforming raw material.

The target temperature distribution shown in FIG. 5 has the target value of the outlet temperature tw6 of the reformer 220 regardless of the load demand on the fuel reformer 200, in consideration of such reformed gas quality. This is an example of a case where a constant value (for example, 250 ° C.) is set. However, the target value of the outlet temperature tw6 may not always be set to a constant value, but may be set to any temperature within the predetermined range Rt (FIG. 6) according to the load request. Also in this case, the range Rt that the target value of the outlet temperature tw6 can take is limited to a range that is sufficiently smaller than the total temperature range that the entire target temperature distribution takes.

The target value xr output from the target value setting unit 110 (FIG. 4) is at least the target temperature distribution t
Contains r. The subtracter 112 obtains a deviation e (= xr −x) between the target value xr and the current state variable x, and inputs the deviation e to the product-sum calculator 114. Multiply-accumulator 114
Is the control signal u by the product-sum operation shown in the following equation (3).
To generate.

[0044]

[Equation 3]

Here, the coefficient fi is the i-th deviation component e
It is a weight for i. When the control signal ua is generated by using the target temperatures tr1 to tr6 for the temperatures tw1 to tw6 of the six parts as the target value xr, the formula (3) can be rewritten as the following formula (4).

[0046]

[Equation 4]

FIG. 7 is a graph showing an example of the target temperature distribution tri and the current temperature distribution twi. The deviation Δtwi (= tri between the target temperature tri and the current temperature twi in the six parts
-Twi) is present. In the product-sum calculation of the equation (4), the weight fi to each deviation Δtwi is the temperature deviation Δ at the reforming section outlet.
The weight f6 for tw6 is equal to the temperature deviation Δtw1 of other parts.
It is set to take a value larger than the weights f1 to f5 for Δtw5. The reason is that the temperature in the vicinity of the outlet of the reforming section 220 has a greater influence on the quality of the reformed gas than the temperature in other portions in the reforming section 220. If the weight f6 for the temperature deviation Δtw6 at the outlet is maximized, the reaction in the reforming section 220 is controlled so that the reforming section outlet temperature tw6 falls within the constant range Rt shown in FIG. 6 as soon as possible. It is possible to However, since the quality of the reformed gas is affected not only by the outlet temperature but also by the temperature of other parts, the control signal of the actuator 244 is also taken into consideration in consideration of the temperature of the parts other than the outlet as in the above formula (4). is generating ua. By such weighting, it is possible to realize the control for achieving the target temperature distribution tri while making the outlet temperature tW6 reach the target value tr6 as soon as possible.

The value of the weight fi may be set empirically, but it can be obtained through the following optimization design. Here, the state in the reforming section 220 is as follows (5
It can be modeled by the system equation represented by the equations a) and (5b).

[0049]

[Equation 5]

Here, x is a state variable vector representing the state inside the reforming section 220, x dot (the dot above x) is its time differential value, and u is the reforming section 220 and the actuator 244. An input vector representing an input to the controlled object 200 (FIG. 4) including and, y is an output vector representing an output of the controlled object 200, and A, B, and C are matrices. The block G drawn in the reforming section 220 of FIG.
Means the transfer function represented by the state equation of the equation (5a).

As an example, for simplification, the reforming section 22
It is assumed that the reforming catalyst inside 0 is divided into two cells. At this time, the state variable vector x and the input vector u
And the output vector y can be expressed as in the following equations (6a) to (6c).

[0052]

[Equation 6]

The superscript T means that it is a transposed matrix. The meaning of each variable is as follows. -Tw1, tw2: core temperatures in the cells 1 and 2. -Tg1, tg2: Gas temperatures in the cells 1 and 2. -Nm1, nm2: the amount of methanol existing in the cells 1 and 2. Um: Methanol vapor flow rate. Ua: Air flow rate for partial oxidation. * Tm: methanol vapor temperature. -Ta: Air temperature for partial oxidation.

The term "core" means a catalyst and its carrier. Four input variables um, ua, tm, ta
Are values relating to methanol or air introduced into the reforming section 220.

At this time, the matrices A, B, and C of the equations (5a) and (5b) are derived using the core heat balance equation, the gas heat balance equation, and the mass balance equation shown below. .

Heat balance equation of core:

[Equation 7]

Here, the subscript # of each symbol indicates the cell number, and each parameter has the following meaning. Cw #: heat capacity of the core of each cell. Rpo #: Coefficient relating to reaction rate of partial oxidation reaction in each cell. -ΔHpo: Reaction enthalpy of partial oxidation reaction. -ΔHsr: Reaction enthalpy of steam reforming reaction. Kwg: Coefficient relating to heat transfer between the core and gas in the cell. -Kwa: A coefficient related to heat radiation from the cell core to the outside. -Kww: A coefficient related to heat transfer between cells.

That is, the first term on the right side of the equation (7) represents the amount of heat generated by the partial oxidation reaction, the second term on the right side is the amount of heat generated by the steam reforming reaction, and the third term on the right side is the core in the cell. -The amount of heat transfer between gases, the fourth term on the right side shows the amount of heat released from the core in the cell to the outside, and the fifth term on the right side shows the amount of heat transfer between cells.

Gas heat balance equation:

[Equation 8]

The meaning of each parameter is as follows. Cg #: heat capacity of gas in each cell. -Kgg: A coefficient related to the heat transfer amount of gas. Kwg: Coefficient relating to heat transfer between the core and gas in the cell. -Kga: A coefficient related to heat radiation from the cell gas to the outside.

That is, the first term on the right side of the equation (8) indicates the heat transfer amount due to the movement of gas between cells, and the second term on the right side indicates the heat transfer amount between the core and gas in the cell, and the third side on the right side. The terms indicate the amount of heat released from the gas in the cell to the outside.

Mass balance equation:

[Equation 9]

Here, each parameter has the following meanings. Kmf: Coefficient relating to the transfer rate of methanol from cell 1 to cell 2.・ Qst1, Qst2: Consumption ratio of methanol in cells 1 and 2.

That is, the first term on the right side of the equation (9a) shows the amount of methanol introduced into the cell 1, and the second term on the right side shows the amount of methanol consumed by the reforming reaction in the cell 1. Similarly, the first term on the right side of the equation (9b) represents the amount of methanol introduced into the cell 2, and the second term on the right side represents the amount of methanol consumed by the reforming reaction in the cell 2.

These (7), (8), (9a), (9
By rearranging the equation b) and applying concrete values, for example, matrices A, B, and C as the following equation (10) are obtained.

[0066]

[Equation 10]

In the equations (6) to (10), the number of cells in the reforming section 220 is set to 2 for the sake of simplicity. However, these equations generally indicate that the reforming section 220 has N cells. It can be easily expanded even when it is divided into (N is an integer of 2 or more).

From FIG. 4, the target value setting unit 110 and the subtractor 11
By omitting 2 and 2, the control system shown in FIG. 8 is obtained. In the system of FIG. 8, the problem of obtaining the feedback coefficient F1 of the state variable x is a well-known optimal regulator problem. At this time, the feedback coefficient F1
Is a quadratic form evaluation function J given by the following expression (11a).
It can be obtained as a definition of the optimum control input u in the equation (11b) that minimizes the value of.

[0069]

[Equation 11]

The matrices Q and R in the equation (11a) are weighting matrices representing weighting factors for each variable, and are set when the control system is designed. The matrix P included in (11c) is given as satisfying the Riccati equation of the following expression (12).

[0071]

[Equation 12]

In the equation (12), the matrices A and B are known from the state equation of the equation (5a). Further, the matrices Q and R are weighting matrices set in the equation (11a), which are also known. Therefore, the matrix P can be obtained by solving this Riccati equation, and further,
The feedback coefficient F1 can be obtained from (11c).

The weighting matrices Q and R in the equation (11a) are represented as diagonal matrices. For example, assuming that the state variable x includes n components and the input u includes only one component (air amount ua), the matrices Q and R have the following (13a), (13).
It looks like b).

[0074]

[Equation 13]

Here, q1 to qn, r are weighting factors.

The weighting factors q1 to qn of the weighting matrix Q include the weighting factors q1 to qj with respect to the catalyst temperature at j sites (j is an integer of 2 or more) in the reforming section 220. At this time, among the weighting factors q1 to qj relating to the catalyst temperature, the value of the weighting factor qj relating to the temperature at the portion closest to the outlet of the reforming section 220 is set to a value sufficiently larger than the values of the other weighting factors. . By doing so, it is possible to set the value of the feedback coefficient F1 (that is, the value of the weighting coefficient fi in the equation (4)) so that the value related to the outlet temperature is larger than the value related to the temperature of other parts. .

The feedback coefficient F1 obtained from the equations (11a) to (11c) relates to the control system shown in FIG. On the other hand, the control system of FIG.
In the control system shown in FIG. 8, it can be considered that the zero point of each component of the state variable x is shifted. Therefore, the feedback coefficient F1 obtained with respect to FIG.
The control system of FIG. 4 can be similarly applied.

FIG. 9 is a modification section 220 in the first embodiment.
3 is a flowchart showing the control procedure of FIG. Step S1
Then, the target value setting unit 110 sets the target temperature distribution in accordance with the load condition (request load) of the fuel reformer 200.
In step S2, the temperature sensor 226a of the reforming unit 220 is used.
˜226f (FIG. 3) measures the catalyst temperatures tw1 to tw6 (that is, the current temperature distribution) of the cells 222a to 222f. In step S3, according to the deviation between the target temperature distribution and the current temperature distribution, the control signal u
Calculate a. Then, in step S4, the flow rate of the partial oxidation air is adjusted by instructing the actuator 244 (FIG. 3) with this control signal ua. Then, if the load condition is changed, the process returns from step S5 to step S1, and if not changed, steps S2 to S2.
S4 is repeatedly executed.

As described above, in the first embodiment, the reforming section 2
When controlling the amount of air supplied to the air conditioner 20, the deviation between the target temperature distribution and the current temperature distribution at a plurality of locations in the reforming section 220 is obtained, and the temperature deviation closest to the outlet is multiplied by the largest weight to sum the products. The air amount ua is determined by calculation. As a result, using this one control input ua,
It is possible to achieve a favorable temperature distribution that produces a high quality reformed gas. Further, in particular, since the target temperature distribution is changed according to the required load of the fuel reforming apparatus 200, even when the required load fluctuates significantly, the required temperature can be maintained while maintaining good quality of the reformed gas. It is possible to follow quickly.

C. Second Embodiment: FIG. 10 is a block diagram showing the configuration of the control system of the reforming section 220 in the second embodiment. This control system includes the adder 116, the integrator 118, and the multiplier 120 in addition to the system shown in FIG.
Is added, and the other configuration is the same as that of FIG.

The deviation e obtained by the subtractor 112 is temporally integrated by the integrator 118. As described in the first embodiment, the most important deviation e is the deviation Δtw6 (FIG. 7) of the outlet temperature of the reforming section 220. Therefore, in the second embodiment, the integrator 118 executes the time integration of the deviation Δtw6 of the outlet temperature as given by the following equation (14).

[0082]

[Equation 14]

The multiplier 120 multiplies the integral value v by the feedback coefficient F2 and supplies the result to the adder 116. The feedback coefficient F2 is generally a vector containing a plurality of components, but in the second embodiment, the integrator 1
Since 18 outputs are 1, the feedback coefficient F2 is also 1.
It is a component (that is, a scalar).

The adder 116 takes the sum of the output of the product-sum calculator 114 and the output of the multiplier 120 and generates the control signal ua of the actuator 244 according to the following equation (15).

[0085]

[Equation 15]

As described above, if the control signal ua of the actuator 244 includes the time integral v of the outlet temperature deviation, the offset relating to the outlet temperature can be eliminated. Therefore, it is possible to achieve a more preferable temperature distribution than that of the first embodiment.

D. Third Embodiment: FIG. 11 is an explanatory diagram showing the sections of the reforming section 220 in the third embodiment. In the third embodiment, the reforming catalyst 222 is virtually divided into ten cells 222a to 222j by the one-dotted chain line, and some of the cells 222a, 222c, 222 are divided.
e, 222f, 222h, 222j only temperature sensor 2
26a, 226c, 226e, 226f, 226h, 2
26j is installed.

FIG. 12 is a modification section 22 in the third embodiment.
It is a block diagram which shows the structure of the control system of No. 0. This control system is obtained by adding a state estimator (observer) 130 to the system shown in FIG. 10, and other configurations are the same as those in FIG.

As is well known, the state estimator 130 calculates the estimated value x hat of the state variable x from the input u and the output y. In addition, in this hot summer,
The "x hat" is a mountain-shaped code "hat" on the letter x.
Means the ones with. The state estimator 130 of the third embodiment includes a cell 222 in which a temperature sensor is not provided.
It has a function of estimating the catalyst temperatures of b, 222d, 222g, 222j (FIG. 11). Such a state estimator 130 can be configured by, for example, a Kalman filter that minimizes the least square error between the temperature measurement values tw1 to tw6 at the temperature measurable locations and the estimated values thereof.
The estimated temperature value x hat obtained by the state estimator 130 is given to the subtractor 112, and the above-mentioned feedback control is performed according to the difference between the estimated temperature value x hat and the target temperature xr.

When the state estimator 130 is used, the above equations (5a) and (5b) are expressed by the following (16a) and (16).
It can be rewritten as in equation (b).

[0091]

[Equation 16]

Here, L is the gain (Kalman gain) of the state estimator 130. When the state estimator 130 is composed of a discrete-time Kalman filter, the state equation of the equation (16a) can be rewritten as the following equations (17a) and (17b).

[0093]

[Equation 17]

Here, “x hat (k)” means the estimated value of the state variable x at time k, and “x bar (k)” is the expected value of the state variable x at time k. y
(K) "is the measured value of the output at time k," y bar (k) "is the expected value of the output y at time k," x hat (k-1) "is the state variable x at time (k-1). The estimated value of “u (k−1)” is the value of the input u at time (k−1). It should be noted that the "x bar" means the character x with a bar attached. The matrices G and H are (1
The matrices A and B in the equation 6a) are rewritten for the discrete time system, and the following (18a) and (18b)
Given by the formula.

[0095]

[Equation 18]

Where I is the identity matrix and T is the time interval of the discrete time system.

As shown in the equation (17b), the expected value x bar (k) of the state variable x at the time k is the estimated value x hat (k-1) at the time (k-1) and the input u. It is obtained from (k-1). Further, as shown in the equation (17a), the estimated value x hat (k) at the time k is calculated from the expected value x bar (k) and the measured value y (k) of the output y at the time k. To be done.

When such a state estimator 130 is used, a part of the temperature distribution of the reforming section 220 is estimated by the state estimator 130 in step S2 of FIG.
FIG. 13 is a flowchart showing a detailed procedure of step S3 when estimating a part of the temperature distribution of the reforming section 220. In step S11, the input u (k) at the current time k is acquired. Specifically, the input u (k) is the above (6
As shown in the equation (b), the flow rate um and the temperature tm of the reformed gas introduced into the reforming section 220, and the flow rates ua and the temperature ta of the partial oxidizing air. In step S2, the output y (k) is measured. Specifically, the output y (k) is the catalyst temperature tw1 to tw6 at the six parts shown in FIG.

In step S13, the above-mentioned (17
The estimated value x hat (k) of the temperature distribution in the reforming section 220 is calculated according to the equations (a) and (17b). That is, the estimated temperature value x hat (k) is calculated from the expected temperature value x bar (k) and the measured output value y (k).

In step S14, the model of the reforming section 220 is updated. Here, “model updating” means updating the matrices G and H in accordance with the current state of each unit in the reforming unit 220. Note that the updating of the matrices G and H is realized by changing the matrices A and B of the equation (5a) based on the temperature and gas concentration of each part in the reforming unit 220 at the current time. The reason for updating such a model is that the equation (5a) is obtained by approximating the non-linear behavior related to the heat balance and the mass balance in the reforming section 220 by a linear equation. This is because more accurate control can be performed by changing according to the state of the current time. When updating the model, the FC control unit 100 first calculates the heat balance and the mass balance in the reforming unit 220 using a non-linear model, and then, according to the calculation result, the matrix A,
Change B. For example, the reaction rate coefficient Rpo # of the partial oxidation reaction in each cell shown in the above equation (7) is
It is determined by calculating the amount of oxygen consumed by the partial oxidation reaction in each cell using a nonlinear model, and then calculating the ratio of the amount of oxygen consumed in each cell to the total amount of oxygen supplied to the reforming section 220. It

At step S15, the next time (k + 1)
The expected temperature value x bar (k + 1) and the Kalman gain L used in the above are calculated. As is well known, the Kalman gain L is updated at each time according to the covariance matrix regarding the state variable x and the output y from time 0 to k.

As described above, in the third embodiment, the reforming section 2
The temperature is measured only in a part of the plurality of 20 parts, the temperature in the other parts is estimated using the state estimator 130, and the current temperature distribution is acquired using these measured values and estimated values. is doing. By doing so, a finer current temperature distribution can be obtained as compared with the case where only the measured values are used. Further, since the flow rate of the partial oxidation air is controlled according to the deviation between the current temperature distribution and the target temperature distribution, it is possible to more appropriately control the transient change in the temperature distribution. Further, the state estimator 130 includes the reformer 22.
Since the temperature distribution is estimated based on the model of 0, it is possible to configure a control system that is robust against errors in the mounting position of the temperature sensor, variations in sensor characteristics, and the like. Further, there is an advantage that the influence of the number of sensors on the control performance can be suppressed to be small.

E. Modifications: The present invention is not limited to the above-described embodiments and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are also possible. is there.

E1. Modification 1: In each of the embodiments described above,
Although the control is executed according to the temperature distribution of the catalyst in the reforming section 220, instead of this, the control may be executed according to the temperature distribution of the reformed gas flowing in the reforming section 220. .

Further, in each of the above-mentioned embodiments, the temperature deviation in the portion closest to the outlet in the reforming section 220 is given the largest weight, but the temperature deviation in the portion other than the outlet is given the largest weight. You may However, as described in the first embodiment, since the outlet temperature usually has the largest influence on the quality of the reformed gas, it is preferable to give the greatest weight to the deviation of the outlet temperature.

E2. Modified Example 2: In each of the above-described embodiments, the product-sum operation shown in the equation (4) is used as the operation for obtaining the control signal ua to the actuator 244. However, a control signal using an arithmetic expression different from this product-sum operation You may ask for ua.
That is, generally, the control signal ua may be obtained based on the calculated value calculated by applying the uneven weight to the deviation between the target temperature distribution and the current temperature distribution.

E3. Modification 3: In each of the above-described embodiments, the flow rate of the partial oxidation air is adjusted mainly according to the temperature distribution in the reforming section 220. However, in addition to or instead of this, another reforming is performed. The flow rates of the raw material components may be adjusted. That is, in general, the reforming unit 220 may be controlled by adjusting the flow rate of a specific raw material forming at least a part of the reforming raw material supplied to the reforming unit 220. However, as described in the first embodiment, the flow rate of the partial oxidation air has a great influence on the reaction in the reforming section 220, and the response to the request for a change in the flow rate is quicker than that of methanol vapor. Therefore, if the flow rate of the partial oxidation air is adjusted, there is an advantage that control with good responsiveness can be performed.

E4. Modification 4: In each of the above embodiments, only feedback control is used, but feedforward control may also be used in combination. For example, adder 1 of FIG.
The feedforward amount according to the load request to the fuel reformer 200 may be further added to 16.

E5. Modification 5: As the reforming fuel, various hydrocarbon fuels other than methanol and gasoline can be used. For example, alcohols other than methanol, and various hydrocarbon compounds such as aldehydes, ethers and natural gas can be used.

E6. Modification 6: In each of the above embodiments, an example of an electric vehicle using the fuel cell system 60 has been described, but the present invention is a hybrid using two prime movers, a motor and an internal combustion engine, as a prime mover for driving wheels. It can also be applied to automobiles (hybrid vehicles).
The present invention is also applicable to moving bodies other than automobiles, such as ships and trains. That is, the present invention can be applied to a moving body including a fuel cell, a fuel reformer, and a prime mover driven by electric power supplied from a power source including the fuel cell. The present invention is also applicable to a stationary fuel reformer.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an electric vehicle as an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an internal configuration of a fuel cell system 60.

FIG. 3 is an explanatory diagram showing elements related to control of a reforming section 220.

FIG. 4 is a block diagram showing a configuration of a control system of a reforming section 220 in the first embodiment.

FIG. 5 is a graph showing an example of a target temperature distribution in the reforming section 220.

FIG. 6 is an outlet temperature T6 of the reforming section 220 and the reforming section 220.
The graph which shows the relationship with the quality (methanol concentration and carbon monoxide concentration) of the reformed gas discharged | emitted from.

FIG. 7 is a graph showing an example of a target temperature distribution tri and a current temperature distribution twi.

FIG. 8 is a block diagram showing a control system in which a target value setting unit 110 and a subtractor 112 are omitted.

FIG. 9 is a flowchart showing a control procedure of the reforming section 220 in the first embodiment.

FIG. 10 is a block diagram showing the configuration of a control system of a reforming section 220 in the second embodiment.

FIG. 11 is an explanatory view showing sections of a reforming section 220 in the third embodiment.

FIG. 12 is a block diagram showing the configuration of a control system of a reforming section 220 in the third embodiment.

FIG. 13 is a flowchart showing a temperature distribution estimation procedure.

[Explanation of symbols]

13 ... Rotation axis 14 ... Output shaft 15 ... Output shaft 16 ... Differential gear 17 ... Axle 18 ... Wheels 20 ... Motor 22 ... rotor 24 ... Stator 30 ... Torque converter 40 ... Transmission 50 ... Battery 51, 52 ... Driving circuit 60 ... Fuel cell system 70 ... Control unit 72 ... Shift lever 74 ... accelerator pedal 76 ... Brake pedal 80 ... Changeover switch 100 ... FC control unit 110 ... Target value setting section 112 ... Subtractor 114 ... Product-sum calculator 116 ... Adder 118 ... integrator 120 ... Multiplier 130 ... State estimator 200 ... Fuel reformer (control target) 210 ... Evaporator 211, 212 ... Combustion gas flow path 212a ... Horizontal flow path 212b ... Folding part 214 ... Reforming material flow path 214a ... Vertical DC path 216 ... Electrically heated combustion catalyst section (combustion EHC) 220 ... reforming section 222 ... Reforming catalyst 222a to 222j ... cells 224 ... Electric heating type reforming catalyst section (reforming EHC) 226a to 226f ... Temperature sensor 230 ... CO purification unit 242, 244 ... Actuator 252 ... Pressure sensor 254 ... Flow rate adjusting valve 260 ... Anode exhaust gas flow path 262 ... Flow rate adjusting valve 300 ... Fuel cell

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01M 8/06 H01M 8/06 GF term (reference) 4G040 EA02 EA03 EA06 EA07 EB41 EB43 5H004 GA17 GB12 HA01 HB01 JA30 JB08 JB20 JB23 JB30 KB05 KC17 KC28 LA12 5H027 AA02 BA01 DD03 KK42 MM00 MM12

Claims (7)

[Claims] 1. A fuel reforming apparatus for producing a hydrogen-rich fuel gas from a reforming raw material containing a hydrocarbon compound, the reforming catalyst for promoting a reforming reaction of the reforming raw material. A reforming unit to be stored, a flow rate adjusting unit for adjusting the flow rate of a specific raw material forming at least a part of the reforming raw material supplied to the reforming unit, and a flow rate adjusting unit for controlling the flow rate adjusting unit. A control unit, wherein the control unit sets a target temperature in a plurality of parts in the reforming unit according to a required load to the fuel reformer, and a target temperature setting unit in the plurality of parts. A temperature acquisition unit that acquires the current temperature by measurement or estimation; and based on a calculated value that is calculated by applying unequal weights to the deviation between the target temperature and the current temperature in the plurality of parts, the flow rate adjustment System to supply to department The fuel reforming apparatus, characterized in that it comprises a feedback controller for generating a signal. 2. The fuel reformer according to claim 1, wherein the weight for the plurality of parts is a weight for a specific part that is a part of the plurality of parts that is closest to an outlet of the reforming section. A fuel reformer set to have a value greater than the weights at other locations. 3. The fuel reformer according to claim 2, wherein the feedback control unit calculates a temporal integrated value of a deviation between the target temperature and the current temperature at the specific portion and the calculated value. A fuel reformer for generating the control signal using the fuel reformer. 4. The fuel reformer according to claim 3, wherein the target temperature setting unit sets the target value of the temperature at the specific portion to a predetermined temperature smaller than the entire temperature range of the target temperature distribution. Fuel reformer set to fit within the range. 5. The fuel reformer according to claim 4, wherein the target temperature setting unit sets a target value of the temperature at the specific portion to a constant temperature that does not depend on the load request. Quality equipment. 6. The fuel reformer according to claim 1, wherein the specific raw material is air. 7. A method for controlling a fuel reforming apparatus, comprising a reforming section containing a reforming catalyst for producing a hydrogen-rich fuel gas from a reforming raw material containing a hydrocarbon-based compound,
(A) a step of setting target temperatures at a plurality of parts in the reforming section according to a required load to the fuel reformer; and (b) acquisition of current temperatures at the plurality of parts by measurement or estimation. And (c) based on a calculation value calculated by applying a non-uniform weight to the deviation between the target temperature and the current temperature in the plurality of parts,
Adjusting the flow rate of a specific raw material that constitutes at least a part of the reforming raw material supplied to the reforming section.