Fuel cell system

Details Fuel cell system Fuel cell system

2000-06-08

2003-12-30

Ryan, Patrick (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

With pressure equalizing means for liquid immersion operation

C429S006000, C429S006000, C323S305000

Reexamination Certificate

active

06670063

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel cell (hereinafter referred to as “FC”) system which may be provided on an electric vehicle comprising an FC and an electric energy buffer such as, for example, a rechargeable battery (hereinafter referred to as “battery”) for back up the shortage of the demand power when the transient output of the FC transient outputs and which prevents the discharge for the utilization ratio of the FC.
2. Description of Related Art
The prior art in this field is disclosed in Japanese Patent Publication No. 8-31328.
FIG. 2
is a block diagram showing the conventional FC system disclosed in the aforesaid documents.
The FC system comprises an FC
1
for generating an output current S
1
by using supplied reformed gas as a fuel corresponding to the quantity of the fuel. The FC
1
includes a fuel processor (hereinafter referred to as “FP”)
1
a
. The FP
1
a
inputs a command value S
11
a
of the mass of the reformed gas and supplies the reformed gas corresponding to the command value S
11
a
to the FC
1
and further output a limit current value S
1
a
of the FC output current S
1
. The FC output current S
1
is detected by an FC current sensor
2
. The FC current sensor
2
detects the output current S
1
and output the detected FC current value S
2
. The FC
1
is connected to an FC current controller
3
constituted with a DC/DC converter at the output thereof. The FC current controller
3
input the FC output current S
1
, control the value of the FC output current S
1
based on a given FC current control signal
31
and output an output current S
3
. The FC current controller
3
is connected to an electric energy buffer (for example, a battery)
4
for charging a part of the FC output current S
3
as a charge current S
3
a
and output a discharge current S
4
at the output thereof. The battery
4
comprises a battery temperature sensor
4
a
for detecting the temperature of the battery
4
and output a detected battery temperature S
4
a
. The charge current S
3
a
and the discharge current S
4
are detected by a battery current sensor
5
. The battery current sensor
5
detect the charge current S
3
a
or the discharge current S
4
and output a detected current value S
5
. The FC current controller
3
is connected to an output voltage sensor
6
for detecting the output voltage of the battery
4
and output a detected output voltage value S
6
.
The temperature sensor
4
a
, the battery current sensor
5
and the output voltage sensor
6
are connected to a battery controller
7
. The battery controller
7
inputs the detected battery temperature S
4
a
, the detected current value S
5
, and the detected voltage value S
6
and then calculates the state of charge (hereinafter called SOC) which shows the ratio of the remaining charge capacity to the rated capacity of the battery
4
and also calculates a battery power S
7
b
which shows the output power of the battery
4
.
The output current S
3
and the discharge current S
4
are detected by a load current sensor
8
. The load current sensor
8
detects the output current S
3
and the discharge current S
4
and outputs a detected load current S
8
. Further, the FC current controller
3
is connected to a load drive unit
9
. The load drive unit
9
inputs the output current S
3
and the discharge current S
4
and supply a load current corresponding to a given load control signal S
10
a
to a load L. The load drive unit
9
is connected to a load controller
10
. The load controller
10
input an input signal ac which show a demand value of the load current S
9
and the detected load current value S
8
and output a demand power signal S
10
b
which show the demand load current S
9
and a load control signal S
10
a.
The FP
1
a
, the FC current sensor
2
, the FC current controller
3
, the battery controller
7
and the load controller
10
are connected to a controller
11
. The controller
11
input the limit current value S
1
a
, the detected current value S
2
, the SOC S
7
a
, the battery power S
7
b
and the demand signal S
10
b
and output a command value S
11
a
and a current controlling signal S
11
b.
Next, the operation of the FC system of
FIG. 2
will be explained.
The command value S
11
a
of the mass of the reformed gas is transferred to the FP
1
a
from the controller
11
, and then the reformed gas having the mass corresponding to the command value S
11
a
is applied to the FC
1
from the FP
1
a
. The FC
1
output the FC output current S
1
corresponding to the mass of fuel. The FC output current S
1
is detected by the FC current sensor
2
and then the FC current sensor
2
output the detected FC current S
2
. Further, the FP
1
a
output the limit current value S
1
a
of the FC output current S
1
. The current controller
3
controls the value of the FC output current S
1
based on the current control signal S
11
b
and output the output FC current S
3
. The part of the output current S
3
is supplied to the battery
4
as the charge current S
3
a
and the discharge current S
4
is outputted from the battery
4
. The battery temperature sensor
4
a
detect the temperature of the battery
4
and output the detected battery temperature S
4
a
. The battery current sensor
5
detect the charge current S
3
a
and the discharge current S
4
and output the detected current value S
5
. The output voltage sensor
6
detect the voltage of the battery
4
and output the detected output voltage S
6
.
The battery controller
7
input the detected battery temperature S
4
a
, the detected current value S
5
and the detected output voltage S
6
and output the SOC S
7
a
and the power S
7
b
of the battery. Then, the load current sensor
8
detect the output current S
3
and the discharge current S
4
and output the detected load current value S
8
. The load drive unit
9
input the output current S
3
and the discharge current S
4
and supply the load current S
9
corresponding to the load control signal S
10
a
to the load L. The load controller
10
input the input signal ac which show the demand value of the load current S
9
and the detected load current S
8
and output the demand power signal S
10
b
and the load control signal S
10
a
. The controller
11
input the limit current value S
1
a
, the detected FC current S
2
, the SOC S
7
a
, the battery power S
7
b
and the demand power signal S
10
b
and output the command value S
11
a
and the current control signal S
11
b
. The controller
11
supply the stable power to the load L even if the response of the FC
1
is delayed because of the large variation of the load L. Further, the controller
11
prevents the battery
4
from over discharge and over charge by correcting the generating power of the fuel corresponding to the SOC S
7
a
of the battery.
However, the prior art battery system of
FIG. 2
has the following problems.
FIG. 3
is a graph showing the characteristics of the output current S
3
and the discharge current S
4
of FIG.
2
. The vertical axis shows the voltage and the horizontal axis shows the current.
In the FC system of
FIG. 2
, as shown in
FIG. 3
, in the region C having the output current S
3
of approximately 140 A or below, the voltage of the output current S
3
is larger than the voltage of the battery
4
at no load (approximately 325 V), which means that the battery
4
is normally charged from the FC
1
. In the region D having the output current of approximately 140 A or above, the voltage of the output current S
3
is smaller than the voltage of the battery
4
at no load, which means that the battery
4
is not charged from the FC
1
.
However, the controller
11
controls the FC
1
by correcting the generating power mass of the FC
1
corresponding to the SOC S
7
a
of the battery
4
, so that the FC output current S
1
is supplied from the FC
1
corresponding to the SOC S
7
a
and the load L. Accordingly, the output current S
1
contain the charge current for the battery
4
but the charge current is not used for the charge of the battery
4
, whi

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