JP2002216783A - Fuel cell hybrid system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell hybrid system capable of achieving a higher output and longer life of secondary batteries and restricting damages to a fuel cell. SOLUTION: The fuel cell hybrid system having a fuel cell 2 and a plurality of secondary batteries 3A-3C to be charged thereby comprises changing means 36 for connecting the plurality of secondary batteries 3A-3C in series and changing connection between the fuel cell 2 and each of the secondary batteries 3A-3C and detecting means and managing means for detecting and managing the charged conditions of the secondary batteries 3A-3C. The connection between the fuel cell 2 and each of the secondary batteries 3A-3C is changed on a time sharing basis depending on the charged conditions of the secondary batteries 3A-3C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel cell hybrid system including a fuel cell and a plurality of secondary batteries charged by the fuel cell.

[0002]

2. Description of the Related Art A fuel cell hybrid system has been proposed in which both a fuel cell and a plurality of secondary batteries charged by the fuel cell can supply power to a load such as an electric motor. Have been.

In a conventional fuel cell hybrid system, a plurality of secondary batteries are connected in series to a load so that a sufficient power can be supplied to the load, and the overall voltage is increased. ing.

However, in order to enable charging of a secondary battery connected in series, it is necessary to employ a fuel cell having an output corresponding to a high voltage. It is necessary to increase the number of stages in the stack, which causes a problem that the reliability of the fuel cell is reduced.

Therefore, the present applicant has proposed that a plurality of fuel cells be provided in a fuel cell.
A power source for connecting the secondary batteries in parallel and providing switching means for connecting and disconnecting each secondary battery and the fuel cell, and controlling the connection and disconnection of the switching means so that the secondary batteries are charged in a time-division manner; The device was proposed earlier (Japanese Patent Laid-Open No. 4-183).
No. 230).

[0006] According to the power supply device according to the above proposal, charging is performed individually for a plurality of secondary batteries, so that any fuel cell having an output voltage corresponding to the voltage of each secondary battery is used. Since the number of cell stacks of the fuel cell can be reduced, the reliability of the fuel cell can be kept high.

[0007]

However, in the above-mentioned conventional charging system, the charge management is performed only by the voltage information of the secondary battery, so that the excessive current which is particularly remarkable in the power system and the secondary battery due to the excessive current are obtained. The heat generated in the secondary battery may damage the secondary battery, which may accelerate the deterioration of the secondary battery.

Further, the output current value of the fuel cell may exceed the limit due to the large charge receiving current of the secondary battery. In such a case, there is a problem that the fuel cell is damaged.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to prevent excessive current and suppress heat generation of a fuel cell, thereby realizing high output and long life of a secondary battery. It is another object of the present invention to provide a fuel cell hybrid system capable of suppressing damage to the fuel cell.

[0010]

According to one aspect of the present invention, there is provided a fuel cell hybrid system including a fuel cell and a plurality of secondary batteries charged by the fuel cell. A battery is connected in series, switching means for switching the connection between the fuel cell and each secondary battery, detection means for detecting the state of charge of each secondary battery, and management means for managing are provided. The connection between the fuel cell and each of the secondary batteries is switched in a time-division manner according to the state of charge.

According to a second aspect of the present invention, in the first aspect of the present invention, the voltage of the fuel cell is set lower than the sum of the voltages of the secondary batteries connected in series.

According to a third aspect of the present invention, in the first aspect of the invention, a ratio of a charging time is changed according to a charged amount of each of the secondary batteries.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the charging process is skipped for the secondary battery determined to be unnecessary by the management means.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the management of the state of charge of the secondary battery by the management means is such that a controller built in each secondary battery transmits information to a main controller. It is characterized in that it is performed by doing.

According to a sixth aspect of the present invention, in the first aspect of the present invention, the detecting means comprises a sensor for detecting a current, a voltage and a temperature of the secondary battery.

Therefore, according to the present invention, it is possible to perform optimal charging according to the state of charge while detecting and managing the state of charge of each secondary battery. And a longer output and longer life of the secondary battery can be realized.

Even if the output current value of the fuel cell exceeds the limit due to the large charge receiving current of the secondary battery, the output of the fuel cell is charged by time-divisionally charging each secondary battery. Since the current value can be adjusted to be less than the limit value, the fuel cell is not damaged.

Further, since the same fuel cell can be applied to systems having different voltages, the degree of freedom in constructing a hybrid system is increased.

[0019]

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

First, the overall configuration of the fuel cell hybrid system according to the present invention will be described with reference to the block diagram shown in FIG.

In the fuel cell hybrid system according to the present invention, electric power can be supplied from both the fuel cell 2 as the power source and the battery unit 3 to the motor 1 as the load, and the plurality of motors constituting the battery unit 3 can be supplied. The secondary batteries 3A, 3B, 3C (see FIG. 3) are charged by the fuel cells.

The fuel cell 2 and the battery unit 3 are connected to the motor 1, and the fuel cell 2 and the motor 1 are connected to the motor 1.
A DC / DC converter 5, a backflow prevention diode 35, and a motor controller 13 are provided between them. A DC / DC converter 5, a backflow prevention diode 35, and a switching unit 36 are provided between the fuel cell 2 and the battery unit 3. Is provided.

The motor 1, the fuel cell 2, the battery unit 3, and the switching means 36 are connected to a main controller 4 shown by a two-dot chain line in FIG.

The DC / DC converter 5 is of a variable output type. The DC / DC converter 5 converts the voltage from the fuel cell 2 into a value required for driving the motor 1 in accordance with an output command signal, Supply. Therefore, the value of the current flowing from the fuel cell 2 to the battery unit 3 or the motor 1 is adjusted by the DC / DC converter 5 according to the operating state, the capacity of the battery unit 3 and the like.

Here, the configuration of the fuel cell 2 will be briefly described. The fuel cell 2 supplies hydrogen as a fuel to an anode, supplies air as an oxidant to a cathode, and performs an electrochemical reaction by a catalyst. The polymer ion exchange membrane is interposed between the two electrodes. Water is supplied to the ion exchange membrane in order to ensure the permeability of hydrogen ions and to make the hydrogen ions wet so as to move smoothly. A cell is formed using such an electrode pair as a unit, and a fuel cell 2 is formed by combining a plurality of cells. The fuel cell 2 outputs an electromotive force having a value obtained by adding the electromotive forces of the cells. Since each cell generates heat by an electromotive force reaction, these cells are cooled by the air or water flowing around the cell.

Hydrogen as a fuel is obtained, for example, by mixing methanol with a primary fuel such as methanol, heating and evaporating the mixture, and decomposing the mixture into hydrogen and carbon dioxide by a catalytic reaction in a reformer. After reducing the concentration of the trace amount of carbon monoxide generated in the reformer via a converter, a selective oxidation reactor, or the like, hydrogen gas is supplied to the anode of each cell of the fuel cell 2. The hydrogen gas may be directly supplied from the hydrogen cylinder to the anode of each cell of the fuel cell 2.

Air for power generation is supplied to the cathode of each cell of the fuel cell 2 by an air pump. And
The fuel cell 2 is provided with a heater 6 for preventing freezing of water in the fuel cell 2 and a cooling fan 7 for equalizing the heating temperature of the heater 6 and for cooling during power generation. .

The user switch 8 sets an operation mode such as a night charging mode. When the main switch 9 is turned on, this is detected by the main switch detection unit 10 in the main controller 4, and the controller power supply 12, the DC / DC converter 5, and the motor controller 13 are turned on via the system power supply control unit 11. Then, the power supply control of the entire system by the main controller 4 is enabled.

The timer time calculating section 14 calculates a timer time for driving the heater 6 or the fuel cell 2 itself to prevent freezing of water in the fuel cell 2 at a low temperature at night or the like, and the main switch 9 is turned off. Even in this case, the power supply is turned on via the system power supply control unit 11 to perform the warm-up operation.
This warm-up operation is determined by the warm-up operation control unit 18 based on the temperatures detected from the outside air temperature detection unit 16 and the cell temperature detection unit 17, and the heater 6 or the heater 6 is controlled via the heater control unit 19 or the FC output control unit 20. The fuel cell 2 is driven. When the heater 6 is driven, the cooling fan 7 is also driven via the cooling fan control unit 21 to make the temperature uniform. or,
When the fuel cell 2 is driven, the cooling fan 7 is driven according to the cell temperature.

The motor output calculation unit 22 includes a throttle 23
Is used to calculate the power to be supplied to the motor 1 from the throttle opening signal by the above operation. In order to protect the battery unit 3 in accordance with the remaining capacity and the temperature of the battery unit 3, 2
The secondary battery protection control unit 24 places a limit on the power sharing ratio between the fuel cell 2 and the battery unit 3, and the control signal of the motor 1
Sent to

The state-of-charge detection unit 25 determines whether the battery unit 3 is in a charged state or a discharged state, and in the case of a charged state, determines whether charging is performed by the fuel cell 2 or charging by regenerative current. That is, the current detection signal from the current sensor 26 of the battery unit 3 is used to determine whether the battery is in the charging direction or the discharging direction by the current detecting unit 27. To determine the state of charge.

The capacity calculation unit 29 calculates the capacity of the battery unit 3 based on the detection signals and the detection data from the voltage detection unit 30 and the temperature detection unit 31 of the battery unit 3 and calculates the capacity of the secondary battery protection control unit. 24, and to the FC output control unit 20 to control the power distribution of the fuel cell 2 according to the capacity of the battery unit 3.

The FC output control unit 20 includes a D / A converter 32
The electric power supplied to the motor 1 from the fuel cell 2 via the DC / DC converter 5 is controlled by the voltage instruction value. In this case, the abnormality of the fuel cell 2 (for example,
When a fuel shortage or abnormal cell temperature occurs, the detected data is sent to the abnormal data receiving unit 33. The abnormal data is sent to the FC output control unit 20 via the FC output control unit 20.
It is sent to a start / stop judging section 34, where it is judged whether or not the fuel cell 2 can be driven.
An OFF signal is sent.

As shown in FIG. 2, a switch (SW) 37 may be provided on the output side of the fuel cell 2 instead of the DC / DC converter 5 shown in FIG. In this case, DC / DC
Since a large and heavy device such as a converter can be omitted, a small and lightweight system suitable for a vehicle can be constructed.

Here, a charging system constituting the gist of the present invention will be described with reference to FIGS. 3 is a circuit diagram showing the configuration of the charging system, FIG. 4 is a circuit diagram showing the internal structure of the switching means, FIG. 5 is a timing chart showing charging timing for each secondary battery, and FIG. 6 is an output characteristic of the fuel cell. FIG. 4 is a diagram illustrating current-voltage characteristics of a secondary battery and a secondary battery.

In this embodiment, as shown in FIG. 3, the battery unit 3 includes three sets of secondary batteries 3A, 3B, 3C connected in series to each other.
The secondary batteries 3A to 3C are connected to the motor 1 in series.
The voltage of the fuel cell 2 is set lower than the sum of the voltages of the secondary batteries 3A, 3B, 3C connected in series.

As shown in FIG. 4, each of the secondary batteries 3A to 3C has a detecting means 39 for detecting the state of charge and a controller 40 as a managing means for managing the state of charge (FIG. 4 shows a secondary battery 3A). Is shown only). Here, the detecting means 39 includes a current sensor for detecting a current of each of the secondary batteries 3A to 3C, a voltage sensor for detecting a voltage, and a temperature sensor for detecting a temperature.

Further, as shown in FIG. 4, the switching means 36 includes three sets of FET switch circuits (only one set is shown in FIG. 4) 41 provided for each of the secondary batteries 3A to 3C. Each FET switch circuit 41 includes a switch 4
1a, a backflow prevention diode 41b, and a switch 41a
Circuit 41c that opens and closes the gate and an ON / OFF management unit 41d that outputs an ON / OFF signal to the gate circuit 41c
It is composed of

Thus, in the fuel cell hybrid system according to the present invention, the charging state of each of the secondary batteries 3A to 3C is detected by the built-in detecting means 39, and the charging of each of the secondary batteries 3A to 3C is performed. The state (current, voltage and temperature information) is transmitted from the built-in controller 40 to the main controller 4.

Then, the main controller 4 switches the switching means 3
6 to control the driving of each FET switch circuit 41 by transmitting a control signal to each FET switch circuit 41, so that the fuel cell 2 and each of the secondary batteries 3A to 3C are controlled according to the state of charge of each of the secondary batteries 3A to 3C. Connections are switched in a time-sharing manner.

For example, as shown in the timing chart of FIG. 5, between times t ₀ and t ₁ , the secondary battery 3A is connected to the fuel cell 2 (ON), and the secondary battery 3A is charged by the fuel cell 2 and t ₁ connected ~t ₂ in secondary batteries 3B is the fuel cell 2 (oN) has been the secondary battery 3B is charged,
And time t ₂ ~t ₃ in a secondary battery 3C is connected to the fuel cell 2 (ON) is charged the secondary battery 3C, the time t ₃ ~
In t ₄ connected to the fuel cell 2 is again 2 battery 3A (ON)
To charge the secondary battery 3A.
The secondary batteries 3A to 3C are sequentially charged in a time-division manner. In this case, the ratio of the charging time is changed according to the charged amount of each of the secondary batteries 3A to 3C. Also, the charging process is skipped for the secondary batteries (3A, 3B, 3C) for which it is determined that charging is unnecessary, and the secondary batteries (3A, 3B, 3C) are not charged.

Here, the output characteristics of the fuel cell 2 and the current-voltage characteristics of the secondary batteries 3A to 3C will be described with reference to FIG.

The output characteristic of the fuel cell 2 is shown in FIG.
The current-voltage characteristics of the secondary batteries 3A to 3C at the time of charging when the remaining charge of each of the secondary batteries 3A to 3C is large are shown by a solid curve b. The current-voltage characteristics at the time of charging the secondary batteries 3A to 3C when the remaining charge is small are indicated by a chain line curve b '. The current-voltage characteristics of the fuel cell 2 after the voltage correction are shown by a curve c, and the discharge characteristics of the secondary batteries 3A to 3C are shown by a curve d.

When the fuel cell 2 is operated in the battery charging mode without a load such as a motor, the fuel cell 2 is operated in a range between points A and B not exceeding the maximum value I _C max of the output current I _C. You.

When there is a load such as a motor, the following operation is performed.

That is, as shown in FIG. 2, when the DC / DC converter 5 shown in FIG. 1 is not provided on the output side of the fuel cell 2, the load is used when the secondary batteries 3A to 3C are discharged. Depending on the magnitude of the output of the motor 1, the maximum value I _C max
It is conceivable that a larger current flows and the fuel cell 2 is damaged. For example, when the fuel cell 2 is operated at the point G and the secondary batteries 3A to 3C are discharged at the point H, the switch (SW) 37 shown in FIG. The fuel cell 2 is protected from flowing.

When the DC / DC converter 5 is provided on the output side of the fuel cell 2 as shown in FIG.
The output voltage is reduced by the DC / DC converter 5 so that the output current I _C becomes equal to or less than the maximum value I _C max, and the fuel cell 2 is operated at, for example, a point G ′.

As described above, in the fuel cell hybrid system according to the present invention, it is possible to perform optimal charging according to the state of charge while detecting and managing the state of charge of each of the secondary batteries 3A to 3C. Excessive current can be prevented to suppress heat generation of the fuel cell 2, and high output and long life of the secondary batteries 3 </ b> A to 3 </ b> C can be realized. Since the number of stacks of the fuel cell 2 can be reduced, the number of parts and the number of assembly steps can be reduced, and the cost of the system can be reduced.

Further, even when the rated voltages of the secondary batteries 3A to 3C are higher than the output voltage of the fuel cell 2, a hybrid system can be constructed, and the degree of freedom of the system configuration is increased, so that the fuel cell 2 Is expanded.

Further, the DC / DC converter 5 shown in FIG.
By using the switch 37 shown in FIG. 2 instead of the power supply, a power device such as the DC / DC converter 5 becomes unnecessary, so that the cost of the system can be reduced.

[0051]

As is apparent from the above description, according to the present invention, in a fuel cell hybrid system including a fuel cell and a plurality of secondary batteries charged by the fuel cell,
Switching means for connecting a plurality of the secondary batteries in series and switching connection between the fuel cell and each secondary battery;
A detecting means for detecting the state of charge of each secondary battery and a managing means for managing the state of charge are provided, and the connection between the fuel cell and each secondary battery is switched in a time-sharing manner according to the state of charge of each secondary battery. It is possible to prevent excessive current, suppress heat generation of the fuel cell, achieve high output and long life of the secondary battery, suppress damage to the fuel cell, and further reduce the same fuel cell. Can be applied to systems of different voltages, so that the effect of increasing the degree of freedom when constructing a hybrid system is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the overall configuration of a fuel cell hybrid system according to the present invention.

FIG. 2 is a block diagram showing another embodiment of the fuel cell hybrid system according to the present invention.

FIG. 3 is a circuit diagram showing a configuration of a charging system in the fuel cell hybrid system according to the present invention.

FIG. 4 is a circuit diagram showing an internal structure of a switching unit of the fuel cell hybrid system according to the present invention.

FIG. 5 is a timing chart showing charging timing for a secondary battery.

FIG. 6 is a diagram showing output characteristics of a fuel cell and current-voltage characteristics of a secondary battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Motor (load) 2 Fuel cell 3 Battery unit 3A-3C Secondary battery 4 Main controller 5 DC / DC converter 36 Switching means 39 Detecting means 40 Controller (Managing means)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H02J 7/34 H02J 7/34 BF Term (Reference) 5G003 AA05 BA03 CA01 CA11 CB01 FA06 GA01 GB03 5H030 AA01 AA03 AA04 AS08 BB08 BB22 BB26 DD20 FF22 FF43 FF52

Claims (6)

[Claims] 1. A fuel cell hybrid system comprising a fuel cell and a plurality of secondary batteries charged by the fuel cell, wherein a plurality of the secondary batteries are connected in series and a connection between the fuel cell and each of the secondary batteries is provided. Switching means for switching between
Detecting means for detecting the state of charge of each secondary battery and management means for managing the state of charge are provided, and the connection between the fuel cell and each secondary battery is switched in a time-sharing manner according to the state of charge of each secondary battery. A fuel cell hybrid system comprising: 2. The fuel cell hybrid system according to claim 1, wherein a voltage of said fuel cell is set lower than a sum of respective voltages of said secondary batteries connected in series. 3. A charge time ratio according to a charge amount of each of said secondary batteries.
A fuel cell hybrid system as described. 4. The fuel cell hybrid system according to claim 1, wherein a charging process is skipped for a secondary battery determined to be unnecessary for charging by the management unit. 5. The management of the state of charge of a secondary battery by the management means is performed by a controller built in each secondary battery transmitting information to a main controller. 2. The fuel cell hybrid system according to 1. 6. The fuel cell hybrid system according to claim 1, wherein said detecting means comprises a sensor for detecting current, voltage and temperature of the secondary battery.