Note: Descriptions are shown in the official language in which they were submitted.
CA 02616758 2008-01-31
FUEL CELL POWER SYSTEMS AND METHODS OF CONTROLLING A FUEL
CELL POWER SYSTEM
Technical Field
The present invention relates to fuel cell power systems and methods of
controlling a fuel cell power system.
Background Art
Fuel cells are known in the art. The fuel cell is an electrochemical device
which
reacts hydrogen, and oxygen, which is usually supplied from the ambient air,
to
produce electricity and water. The basic process is highly efficient and fuel
cells fueled
directly by hydrogen are substantially pollution free. Further, since fuel
cells can be
assembled into stacks of various sizes, power systems have been developed to
produce a wide range of electrical power output levels and thus can be
employed in
numerous industrial applications.
Although the fundamental electrochemical processes involved in all fuel cells
are well understood, engineering solutions have proved elusive for making
certain fuel
cell types reliable, and for others economical. In the case of polymer
electrolyte
membrane (PEM) fuel cell power systems reliability has not been the driving
concern
to date, but rather the installed cost per watt of generation capacity has. In
order to
further lower the PEM fuel cell cost per watt, much attention has been
directed to
increasing the power output of same. Historically, this has resulted in
additional
sophisticated balance-of-plant systems which are necessary to optimize and
maintain
high PEM fuel cell power output. A consequence of highly complex balance-of-
plant
systems is that they do not readily scale down to low capacity applications.
Consequently, cost, efficiency, reliability and maintenance expenses are all
adversely
effected in low generation applications.
It is well known that single PEM fuel cells produce a useful voltage of only
about 0.45 to about 0.7 volts D.C. per cell under a load.Practical PEM fuel
cell plants
have been built from multiple cells stacked together such that they are
electrically
connected in series. It is further well known that PEM fuel cells can operate
at higher
power output levels when supplemental humidification is made available to the
proton
exchange membrane (electrolyte). In this regard, humidification lowers the
resistance
of proton exchange membranes to proton flow. To achieve this increased
humidification, supplemental water can be introduced into the hydrogen or
oxygen
streams by various methods, or more directly to the proton exchange membrane
by
means of the physical phenomenon known as of wicking, for example. The focus
of
1
CA 02616758 2008-01-31
investigations, however, in recent years has been to develop membrane
electrode
assemblies (MEA) with increasingly improved power output when running without
supplemental humidification. Being able to run an MEA when it is self-
humidified is
advantageous because it decreases the complexity of the balance-of-plant with
its
associated costs. However, self-humidification heretofore has resulted in fuel
cells
running at lower current densities and thus, in turn, has resulted in more of
these
assemblies being required in order to generate a given amount of power.
While PEM fuel cells of various designs have operated with varying degrees of
success, they have also had shortcomings which have detracted from their
usefulness. For example, PEM fuel cell power systems typically have a number
of
individual fuel cells which are serially electrically connected (stacked)
together so that
the power system can have a increased output voltage. In this arrangement, if
one of
the fuel cells in the stack fails, it no longer contributes voltage and power.
One of the
more common failures of such PEM fuel cell power systems is where a membrane
electrode assembly (MEA) becomes less hydrated than other MEAs in the same
fuel
cell stack. This loss of membrane hydration increases the electrical
resistance of the
effected fuel cell, and thus results in more waste heat being generated. In
turn, this
additional heat dries out the membrane electrode assembly. This situation
creates a
negative hydration spiral. The continual overheating of the fuel cell can
eventually
cause the polarity of the effected fuel cell to reverse such that it now
begins to
dissipate electrical power from the rest of the fuel cells in the stack. If
this
condition is not rectified, excessive heat generated by the failing fuel cell
may
cause the membrane electrode assembly to perforate and thereby leak
hydrogen. When this perforation occurs the fuel cell stack must be completely
disassembled and repaired. Depending upon the design of fuel cell stack being
employed, this repair or replacement may be a costly, and time consuming
endeavor.
Further, designers have long sought after a means by which current
densities in self-humidified PEM fuel cells can be enhanced while
simultaneously not increasing the balance-of-plant requirements for these same
devices.
Summary of the invention
According to the present invention there is provided a method of controlling a
fuel cell power system comprising:
providing a plurality of fuel cells configured to convert chemical energy into
2
CA 02616758 2008-01-31
electricity;
providing a first terminal coupled with the fuel cells;
providing a second terminal coupled with the fuel cells;
shunting the fuel cells according to a specified order; and
controlling the shunting using a control system.
Brief Description of the Drawings
Preferred embodiments of the invention are described below with reference to
the following accompanying drawings.
Fig. 1 is a prospective view of one embodiment of a fuel cell power
system according to the present invention.
Fig. 2 is an illustrative representation of a control system coupled with
components of the fuel cell power system.
Fig. 3 is an exploded perspective view of one configuration of a fuel cell
cartridge of the fuel cell power system.
Fig. 4 is a schematic representation of one embodiment of circuitry
coupled with plural fuel cells of the fuel cell cartridge.
Fig. 5 is a functional block diagram of one configuration of the control
system for the fuel cell power system.
Fig. 6 is a functional block diagram of a cartridge analysis slave
controller of the control system coupled with associated circuitry and
components.
Fig. 7 is a functional block diagram of an auxiliary valve slave controller
of the control system coupled with associated circuitry and components.
Fig. 8 is a functional block diagram of a fan slave controller of the control
system coupled with associated circuitry and components.
Fig. 9 is a functional block diagram of an interface slave controller of the
control system coupled with associated circuitry and components.
Fig. 10 is a functional block diagram of an external port slave controller of
the
control system coupled with associated circuitry and components.
Fig. 11 is a functional block diagram of a system analysis slave controller of
the control system coupled with associated circuitry and components.
Fig. 12 is a functional block diagram of a sensor slave controller of the
control
system coupled with associated circuitry and components.
Fig. 13 is a functional block diagram of an air temperature slave controller
of
the control system coupled with associated circuitry and components.
3
CA 02616758 2008-01-31
Fig. 14 is a functional block diagram of a shunt slave controller of the
control
system coupled with associated circuitry and components.
Fig. 15 is a functional block diagram of a switch slave controller of the
control
system coupled with associated circuitry and components.
Figs. 16-16A are a flow chart illustrating exemplary operations of a master
controller of the control system.
Fig. 17 is a flow chart illustrating an exemplary start-up operation of the
master
controller.
Figs. 18-18A are a flow chart illustrating exemplary error operations of the
master controller.
Figs. 19-19B are a flow chart of exemplary operations of the cartridge
analysis slave controller.
Figs. 20-20A are a flow chart illustrating exemplary operations of the
auxiliary
valve slave controller of the control system.
Figs. 21-21A are a flow chart illustrating exemplary operations of the fan
slave
controller of the control system.
Fig. 22 is a flow chart illustrating exemplary operations of the interface
slave
controller of the control system.
Fig. 23 is a flow chart illustrating exemplary operations of the external port
slave controller of the control system.
Figs. 24-24A are a flow chart illustrating exemplary operations of the system
analysis slave controller of the control system.
Fig. 25 is a flow chart illustrating exemplary operations of the sensor slave
controller of the control system.
Fig. 26 is a flow chart illustrating exemplary operations of the air
temperature slave controller of the control system.
Fig. 27 is a flow chart illustrating exemplary operations of the shunt slave
controller of the control system.
Fig. 28 is a flow chart illustrating exemplary operations of the switch slave
controller of the control system.
Best Modes for Carrying Out the Invention and Disclosure of Invention
Referring to Fig. 1, one configuration of a fuel cell power system 10 is
illustrated. The depicted configuration of fuel cell power system 10 is
exemplary and
other configurations are possible. As shown, fuel cell power system 10
includes a
4
CA 02616758 2008-01-31
housing 12 provided about a plurality of fuel cell cartridges 14. Housing 12
defines a
subrack assembly in the described embodiment.
Fuel cell power system 10 is configured to utilize one or more of fuel cell
cartridges 14. Twelve such fuel cell cartridges 14 are utilized in the
embodiment of
fuel cell power 10 described herein. As described below, individual fuel cell
cartridges 14 include a plurality of fuel cells. In the described
configuration,
individual fuel cell cartridges 14 include four fuel cells.
Such fuel cells can comprise polymer electrolyte membrane (PEM) fuel cells.
In the described embodiment, the fuel cells can comprise membrane electrode
assembly (MEA) fuel cells or membrane electrode diffusion assembly (MEDA) fuel
cells. Further details of one configuration of fuel cells and fuel cell
cartridges 14 are
described in U.S. Patent No. 6,030,178, entitled "A Proton Exchange Membrane
Fuel Cell Power System", issued on February 29, 2000, and naming William A.
Fuglevand, Dr. Shiblihannal Bayyuk, Greg A. Lloyd, Peter D. De Vries, David R.
Lott, John P. Scartozzi, Gregory M. Somers and Ronald G. Stokes as inventors.
Housing 12 additionally includes an operator interface 16. In the present
embodiment, operator interface 16 includes a display 18 and interface switches
20.
Operator interface 16 is configured to indicate operation of fuel cell power
system 10
and also enable an operator to control various functions of fuel cell power
system
10.
Display 18 of operator interface 16 is configured to emit a human perceptible
signal, such as visible signals, to indicate operation of fuel cell power
system 10. In
the depicted embodiment, display 18 comprises a plurality of light emitting
diode
(LED) bar graph arrays to indicate operational conditions of respective fuel
cell
cartridges 14. In one configuration, individual bar graph arrays of display 18
indicate
high and low voltages of fuel cells within the corresponding fuel cell
cartridge 14.
Interface switches 20 permit a user to control operations of fuel cell power
system 10. For example, one interface switch 20 can be provided to enable a
user to
turn on fuel cell power system 10. In addition, another interface switch 20
can include
a load enable switch which permits a user to selectively apply power from fuel
cell
power system 10 to a load 22 coupled with the fuel cell power system 10.
Another
interface switch 20 can control a cartridge reset function described below.
Referring to Fig. 2, some components of fuel cell power system 10 are shown.
The components are internal and external of housing 12 of fuel cell power
system 10.
Internally, only three fuel cell cartridges 14 are shown for purposes of
discussion
herein. More fuel cell cartridges 14 are provided in typical configurations.
5
CA 02616758 2008-01-31
Fuel cell power system 10 is shown c o u p l e d with a remote device 24. Fuel
cell power system 10 is p refe ra b I y configured to communicate with remote
device
24. An exemplary remote device 24 comprises an off-site control and monitoring
station. Fuel cell power system 10 receives communications from remote device
24
which may comprise data and commands. Fuel cell power system 10 is also
configured to output data, requests, etc. to remote device 24.
The depicted components include the plural fuel cell cartridges 14 and
operator
interface 16 discussed above. In addition, fuel cell power system 10 includes
a control
system 30. One configuration of control system 30 is described below in
detail. The
illustrated control system 30 is coupled with a power supply sensor 31
associated with
a power supply 32, and charge circuitry 34. Control system 30 is additionally
coupled
with fuel cell cartridges 14 and operator interface 16. Further, control
system 30 is
coupled with a communication port 36, switching device 38 and current sensor
40.
Control system 30 is additionally coupled with a bleed solenoid 42 associated
with a
bleed valve 43.
The depicted fuel cell power system 10 includes a fuel delivery system 28.
Fuel
delivery system 28 couples with a fuel supply 23 to supply fuel to fuel cell
cartridges
14. Exemplary fuel comprises hydrogen gas in the described embodiment. Other
fuels
may be possible.
The depicted fuel delivery system 28 includes a main valve 47 and plural
auxiliary valves 45 associated with respective fuel cell cartridges 14. Main
valve 47
controls the flow of fuel from fuel supply 23 into fuel cell power system 10.
Auxiliary
valves 45 control the flow of fuel to respective fuel cell cartridges 14.
Control system 30
is coupled with plural auxiliary solenoids 44 of associated auxiliary valves
45. Control
system 30 is further coupled with a main solenoid 46 of associated main valve
47.
The depicted fuel cell power system 10 includes an air temperature control
assembly 50. The illustrated air temperature control assembly 50 includes a
plenum
51 having associated ports 52 corresponding to fuel cell cartridges 14. Within
plenum 51 of air temperature control assembly 50, a temperature modifying
element 53, fan 54, te m p e ra t u re sensor 55 and fuel sensor 61 are
provided.
A controllable air flow device or air passage 56 couples plenum 51 to exterior
ambient air outside of housing 12. Air passage 56 can permit the intake of air
into
plenum 51 as well as the exhaustion of air from plenum 51. Control system 30
is
coupled with control circuitry 51 of modifying element 53, control circuitry
48 and
monitoring circuitry 49 of fan 54, temperature circuitry 68 associated with
temperature
sensor 55, control circuitry 57 of air passage 56, and heater 75 of fuel
sensor 61.
6
CA 02616758 2008-01-31
A first fuel sensor 58 is provided within housing 12 and outside of plenum 51
as
shown. First fuel sensor 58 is operable to monitor for the presence of fuel
within
housing 12. A second fuel sensor 61 is provided within plenum 51 to monitor
for the
presence of fuel within plenum 51. Control system 30 is configured to couple
with fuel
detection circuitry 64 associated with fuel sensors 58, 61. Fuel detection
circuitry 64
can condition measurements obtained from sensors 58, 61.
Heaters 74, 75 are coupled with respective fuel sensors 58, 61 to provide
selective heating of fuel sensors 58, 61 responsive to control from control
system 30.
Heaters 74, 75 are integral of fuel sensors 58, 61 in some configurations. An
exemplary fuel sensor configuration with an integral heater has designation
TGS 813
available from Figaro Engineering, Inc. Such heaters are preferably provided
in a
predefined temperature range to assure proper operation. Other configurations
of
sensors 58, 61 are possible.
An external temperature sensor 59 is provided outside of housing 12 in one
embodiment. Control system 30 is also coupled with temperature circuitry 67
associated with temperature sensor 59 to monitor the exterior temperature.
Temperature circuitry 67 conditions signals received from temperature sensor
59.
Control system 30 is configured to at least one of control and monitor at
least
one operation of fuel cell power system 10. During operation, fuel from fuel
supply 23
is applied to main valve 47. Main valve 47 is coupled with auxiliary valves 45
as
shown. Responsive to control from control system 30, main valve 47 and
auxiliary
valves 45 apply fuel to respective fuel cell cartridges 14. Responsive to the
supply of
fuel, and in the presence of oxygen, fuel cell cartridges 14 produce
electrical power.
A power bus 60 couples the fuel cell cartridges 14 in series. Power bus 60 is
coupled with external terminals 62, 63 which may be connected with an external
load
22 (shown in Fig. 1). Terminal 62 provides a positive terminal and terminal 63
provides
a negative terminal of fuel cell power system 10.
Air temperature control assembly 50 applies oxygen to the respective fuel cell
cartridges 14 via ports 52. Fuel cell cartridges 14 are individually operable
to convert
chemical energy into electricity. As described below, fuel cartridges 14
individually
contain plural fuel cells individually having an anode side and a cathode
side. Auxiliary
valves 45 apply fuel to the anode sides of the fuel cells. Plenum 51 directs
air within
the cathode sides of the fuel cells.
Air temperature control assembly 50 preferably provides circulated air within
a
predetermined temperature range. Such circulated air can be exterior air
and/or
recirculated air. In the preferred embodiment, air temperature control
assembly 50
7
CA 02616758 2008-01-31
provides air within plenum 51 within an approximate temperature range of 25
Celsius
to 80 Celsius.
Upon start-up conditions of fuel cell power system 10, modifying element 53
may be controlled via control system 30 using element control circuitry 41 to
either
increase or decrease the temperature of air present within plenum 51. Fan 54
operates
to circulate the air within plenum 51 to respective fuel cell cartridges 14.
Fan control
circuitry 48 and fan monitor circuitry 49 are shown coupled with fan 54.
Responsive to
control from control system 30, fan control circuitry 48 operates to control
air flow rates
(e.g., speed of rotation) of fan 54. Fan monitor circuitry 49 operates to
monitor the
actual air flow rates induced by fan 54 (e.g., circuitry 49 can comprise a
tachometer for
rotational fan configurations).
Control system 30 monitors the temperature of the air within plenum 51 using
temperature sensor 55. During operation, heat is generated and emitted from
fuel cell
cartridges 14. Thus, it may be necessary to decrease the temperature of air
within
plenum 51 to provide efficient operation of fuel cell power system 10.
Responsive to
control from control system 30, air passage 56 can be utilized to introduce
exterior air
into plenum 51 and exhaust air from plenum 51 to ambient.
Control system 30 communicates with control circuitry 57 to control air
passage
56. In one embodiment, air passage 56 includes a plurality of vanes and
control
circuitry 57 operates to control the position of the vanes of air passage 56
to selectively
introduce exterior air into plenum 51. The vanes of air passage 56 can
preferably be
provided in a plurality of orientations between an open position and a closed
position to
vary the amount of exterior fresh air introduced into plenum 51 or the amount
of air
exhausted from plenum 51 responsive to control from control system 30. Air
circulated
within plenum 51 can comprise recirculated and/or fresh ambient air.
Utilizing temperature sensor 59, control system 30 can also monitor the
temperature of ambient air about housing 12. Control system 30 can utilize
such
exterior temperature information from temperature sensor 59 to control the
operation of
air passage 56. Temperature sensor 59 is located adjacent air passage 56 in a
preferred embodiment.
As described in further detail below, control system 30 controls air flow
rates of
fan 54 using fan control circuitry 48. Fan monitor circuitry 49 provides air
flow rate
information to control system 30. Control system 30 can monitor the total
system
voltage being delivered via power bus 60 by summing the individual cell
voltages.
Control system 30 can also monitor the electrical load being delivered via
power bus
60 using current sensor 40. With knowledge of the system bus voltage and load,
8
CA 02616758 2008-01-31
control system 30 can calculate waste thermal power and provide a desired
cooling air
flow.
More specifically, the efficiency of one or more fuel cells may be determined
by dividing the respective fuel cell voltage by 1.23 (a theoretical maximum
voltage of a
single fuel cell). An average efficiency can be determined for all fuel cells
90 of fuel
cell power system 10. The remaining energy (energy not associated to
electricity) as
determined from the efficiency calculation is waste thermal power. The
determined
waste thermal power may be utilized to provide a desired cooling air flow.
Control
system 30 controls the air flow rates of fan 54 depending upon the waste
thermal
power in accordance with one aspect of the described fuel cell power system
10.
During operation of fuel cell cartridges 14, non-fuel diluents such as cathode-
side water and atmospheric constituents can diffuse from the cathode side of
the fuel
cell through a membrane electrode assembly of the fuel cell and accumulate in
the
anode side of the fuel cell. In addition, impurities in the fuel supply
delivered directly
to the anode side of the fuel cell also accumulate. Without intervention,
these diluents
can dilute the fuel sufficiently enough to degrade performance. Accordingly,
the
anode side of the individual fuel cells is connected to a bleed manifold 65.
Bleed
manifold 65 is additionally coupled with bleed valve 43.
Control system 30 selectively o p e r a t e s bleed solenoid 42 to selectively
open
and close bleed valve 43 permitting exhaustion of matter such as entrained
diluents
and p e r h a p s some fuel via a bleed exhaust 66 within housing 12. Control
system 30
can operate to open and close bleed valve 43 on a periodic basis. The
frequency of
openings and closings of bleed valve 43 can be determined by a number of
factors,
such as electrical load co u p l e d with terminals 62, 63, etc. Although not
shown, a fuel
recovery system may be coupled with bleed exhaust 66 to retrieve unused fuel
for
recirculation or other uses.
Following a start-up condition either inputted via interface or from remote
device
24, control system 30 selectively controls switching device 38 to couple power
bus 60
with positive terminal 62. Switching device 38 can comprise parallel MOSFET
switches
to selectively couple power bus 60 with an external load 22.
For example, control system 30 may verify when an appropriate operational
temperature within plenum 51 has been reached utilizing temperature sensor 55.
In
addition, control system 30 can verify that at least one electrical
characteristic, such as
voltage and/or current, of respective fuel cell cartridges 14 has been reached
before
closing switching device 38 to couple power bus 60 with an associated load 22.
Such
9
CA 02616758 2008-01-31
provides proper operation of fuel cell power system 10 before coupling bus 60
with an
external load 22.
Power supply 32 includes power supplies having different voltage potentials in
the described embodiment. For example, power supply 32 can provide a 5-volt
supply
voltage for operating the digital circuitry of fuel cell power system 10, such
as control
system 30. Power supply 32 can also provide higher voltage potentials, such as
+/- 12
volts for operation of components such as fan 54 within fuel cell power system
10.
Further, power supply 32 can include a battery powering components during
start-up procedures. Following start-up procedures, power supply 32 can be
coupled
with power bus 60 and internal power utilized by fuel cell power system 10 can
be
derived from electrical power generated from fuel cell cartridges 14. Charge
circuitry
34 is provided to selectively charge batteries of power supply 32 utilizing
power from
power bus 60. Control system 30 is configured to monitor electrical conditions
of the
batteries and the supplied voltages of power supply 32 using power supply
sensors
31. Control system 30 can operate charge circuitry 34 to charge batteries of
power
supply 32 depending upon such monitoring operations.
Control system 30 is also coupled with communication port 36 providing
communications to an external device such as a remote device 24. An exemplary
remote device 24 comprises an external control system or monitoring system off-
site
from fuel cell power system 10. Control system 30 can output data including
requests,
commands, operational conditions, etc., of fuel cell power system 10 using
communication port 36. In addition, control system 30 can receive data
including
commands, requests, etc., from remote device 24 using communication port 36.
Referring to Fig. 3, an exemplary fuel cell cartridge 14 is shown. Further
details of fuel cell cartridge 14 are disclosed in detail in U. S. Patent No.
6,030,718.
The depicted fuel cell cartridge 14 includes a fuel distribution frame 70 and
a force
application assembly which includes plural cathode covers 71 which partially
occlude respective cavities housing membrane electrode assemblies (MEA) or
membrane electrode diffusion assemblies (MEDA) within fuel distribution frame
70.
The depicted fuel cell cartridge 14 includes four fuel cells (individually
shown as
reference numeral 90 in Fig. 4). Other configurations are possible.
The respective cathode covers 71 individually cooperate or otherwise mate
with each other, and with the fuel distribution frame 70. Individual apertures
72
which are defined by the cathode cover, define passageways 73 which permit air
from plenum 51 to circulate to the cathode side of the membrane electrode
diffusion
assembly contained within fuel distribution frame 70. The circulation of air
through
CA 02616758 2008-01-31
the fuel cell cartridge 14 is discussed in significant detail in U. S. patent
No.
6,030,178.
Conductive members 63 extend outwardly from a main body of individual fuel
cells within fuel cell cartridge 14. Conductive members 63 are designed to
extend
through respective gaps or openings which are provided in fuel distribution
frame 70.
Each conductive member 63 is received between and thereafter electrically
coupled
with pairs of conductive contacts which are mounted on a rear wall of a
subrack
described in greater detail below.
Fuel cell cartridge 14 is operable to be serially electrically coupled with a
plurality of other fuel cell cartridges 14 by way of a subrack which is
generally
indicated by the numeral 76. Subrack 76 has a main body 77 having top and
bottom
portions 78, 79, respectively. The top and bottom portions are joined together
by a
rear wall 80. Elongated channels 81 are individually formed in top and bottom
portions
78, 79 and are operable to slidably receive individual spines 74 which are
formed on
fuel distribution frame 70.
Subrack 76 is made of a number of mirror image portions 85, which when
joined together, form the main body 77 of subrack 76. These mirror image
portions 85
are fabricated from a moldable dielectric substrate. Power bus 60 is affixed
on rear
wall 80 of the subrack 90. A repeating pattern of eight pairs of conductive
contacts 84
are attached on rear wall 80 and are coupled with power bus 60. Electrical
coupling of
fuel cells within fuel cell cartridge 14 with power bus 60 is implemented
using contacts
84 in the described embodiment.
First and second conduits 86, 87 are also attached to rear wall 80 and are
operable to matingly couple in fluid flowing relation to the fuel distribution
frame 70.
The respective first and second conduits 86, 87 extend through rear wall 80
and
connect with suitable external conduits (not shown). First conduit 86 is
coupled in fluid
flowing relation with fuel supply 23 (Fig. 1) and with anode sides of internal
fuel cells.
Further, second conduit 87 exhausts from the anode sides of the fuel cells to
bleed
manifold 65 (Fig. 2).
Individual fuel cell cartridges 14 may be selectively deactivated. For
example,
fuel cell cartridges 14 are individually physically removable from fuel cell
power system
10. Removal of one or more fuel cell cartridges 14 may be desired for
maintenance,
replacement, etc. of the fuel cell cartridges 14. The remaining fuel cell
cartridges 14
and internal fuel cells thereof may continue to supply power to an associated
load 22
with one or more of the fuel cell cartridges 14 deactivated.
11
CA 02616758 2008-01-31
Individual contacts 84 may be configured to maintain electrical continuity of
bus 60 upon physical removal of a fuel cell cartridge 14 from an associated
subrack
76. As shown, individual contacts 84 comprise make before break contacts which
individually include plural conductive members configured to receive an
associated
contact 69 of a fuel cell cartridge 14. Individual contacts 69 can comprise a
tang or
knife. Upon physical removal of fuel cell cartridge 14 and the corresponding
terminals
69, conductive members of contacts 84 are mechanically coupled together to
maintain
a closed circuit within bus 60 intermediate terminals 62, 63. Such maintains a
supply
of electrical power to load 22 coupled with terminals 62, 63 during removal of
one or
more fuel cell cartridges 14 from fuel cell power system 10.
Referring to Fig. 4, a schematic representation of four fuel cells 90 of a
fuel cell
cartridge 14 is shown. Individual fuel cells 90 have plural contacts 84 as
described
above. Fuel cells 90 are typically coupled in series using power bus 60.
Control
system 30 is configured to monitor at least one electrical characteristic of
individual
fuel cells 90 using analysis circuitry 91 in the described embodiment.
More specifically, analysis circuitry 91 includes a voltage sensor 92 which
may
be provided electrically coupled with contacts 84 as shown. Such coupling
enables
voltage sensor 92 to monitor the voltages of the individual respective fuel
cells 90.
Fuel cells 90 have been observed to typically produce a useful voltage of
about 0.45 to
about 0.7 volts DC under a typical load.
An exemplary configuration of voltage sensor 92 is implemented as a
differential amplifier for monitoring voltages. Voltage sensor 92 is
preferably
configured to monitor voltage magnitude across individual fuel cells 90 as
well as
polarity of individual fuel cells 90.
Analysis circuitry 91 can additionally include plural current sensors 94, 97.
Individual current sensors may be coupled with contacts 84 of individual fuel
cells 90
to monitor current flowing through respective individual fuel cells 90 in an
alternative
arrangement (not shown). Control system 30 is coupled with current sensors 94,
97
and is configured to monitor corresponding respective currents through fuel
cells 90
and outputted to load 22 via bus 60.
Current sensor 94 is coupled intermediate one of fuel cells 90 and a coupling
with internal power supply 93. Current sensor 94 is coupled intermediate the
coupling
with internal power supply 93 and external terminal 62 coupled with an
associated
load.
Following start-up operations, power for internal use within fuel cell power
system 10 (e.g., power provided to the circuitry of control system 30) is
provided from
12
CA 02616758 2008-01-31
:
fuel cell cartridges 14. Internal power supply 93 extracts current from bus 60
as shown
to provide internal power to fuel cell power system 10.
Accordingly, current sensor 94 provides information regarding current flow
through serially coupled fuel cell cartridges 14. Current sensor 97 provides
information
regarding current flow to a load coupled with terminal 62 (i.e., load 22 shown
in Fig. 1).
Plural switching devices 96 are also provided which correspond to respective
fuel cells 90. Switching devices 96 can be individually provided intermediate
contacts
84 of respective fuel cells 90 as illustrated. In the depicted configuration,
switching
devices 96 can comprise MOSFET devices. Gate electrodes of switching devices
96
are coupled with control system 30.
Control system 30 is operable to selectively shunt electrodes 84 using
switching
devices 96 corresponding to a desired one or more of fuel cells 90 to
electrically
bypass or deactivate such fuel cells 90. For example, if control system 30
observes that
an electrical characteristic (e.g., voltage) of a fuel cell 90 as sensed via
sensors 92, 94
is below a desired range, control system 30 can instruct a respective
switching device
96 to turn on and shunt the respective fuel cell 90. In addition, individual
fuel cells 90
can be selectively shunted using respective switching devices 96 to enhance
the
performance of fuel cells 90.
In one configuration, fuel cells 90 can be shunted according to a duty cycle.
The duty cycle may be adjusted by control system 30 depending upon operation
of fuel
cell cartridges 14 and fuel cell power system 10. Fuel cells 90 can be shunted
by
sequential order as determined by control system 30. Shunting is also helpful
during
startup operations to generate heat within housing 12 to bring fuel power
system 10 up
to operating temperature in an expedient manner.
Alternatively, individual fuel cells 90 may be shunted for extended periods of
time if control system 30 observes such fuel cells are operating below desired
ranges
(e. g., low voltage conditions, reverse polarity conditions).
Referring to Fig. 5, one configuration of control system 30 is illustrated. In
the
depicted arrangement, control system 30 includes a distributed control system
including a plurality of controllers 100-120. Individual controllers 100-120
comprise
programmable microcontrollers in the described embodiment. Exemplary
microcontrollers have trade designation MC68HC705P6A available from Motorola,
Inc.
In the described embodiment, controllers 100-120 individually comprise a
controller
configured to execute instructions provided within executable code. In an
alternative
configuration, the steps described with reference to Figs. 16-28 below are
implemented
within hardware.
13
CA 02616758 2008-01-31
Individual controllers can include random access memory (RAM), read only
memory (ROM), analog-to-digital (AID) converters, serial input/output port
(SIOP)
communications, timers, digital input/output (I/O), timer interrupts and
external
interrupts. Individual controllers 102-120 have internal digital processing
circuitry
configured to execute a set of software or firmware instructions. Such
Instructions can
be stored within the internal read only memory of the respective controllers
100-120.
Other configurations of control system 30 are possible.
Among other functions, master controller 100 functions as a communication
router to implement communications intermediate master controller 100 and
individual
slave controllers 102-120. In the described embodiment, communications are
implemented in a limited full-duplex mode. Other communication protocols may
be
utilized.
Master controller 100 outputs messages to slave controllers 102-120.
Outputted messages are seen by all slave controllers 102-120. Individual
slaves 102-
120 identified by the outgoing message process the corresponding message.
Thereafter, receiving slave controllers 102-120 can output a message to master
controller 100. In addition, master controller 100 can sequentially poll slave
controllers
102-120 to determine whether such slave controllers 102-120 have
communications
for master controller 100. Master controller 100 can also supply clock
information to
slave controllers 102-120 to establish a common timing reference within
control
system 30.
Individual slave controllers 102-120 perform specific tasks in control system
30
including a plurality of distributed controllers. Individual slave controllers
102-120 can
monitor specified functions of fuel cell power system 10 and report to master
controller
100. Further, master controller 100 can direct operations of individual slave
controllers
102-120
Referring to Fig. 6, cartridge analysis slave controller 102 is coupled with
master controller 100 and associated circuitry. In particular, cartridge
analysis slave
controller 102 is coupled with analysis circuitry 91 which is in turn coupled
with fuel
cells 90 and power bus 60 as previously described. Utilizing voltage sensor 92
and
current sensor 94 of analysis circuitry 91, cartridge analysis slave
controller 102 can
monitor electrical characteristics such as the voltage of individual fuel
cells 90 as well
as the current through fuel cells 90. Further, cartridge analysis slave
controller 102 can
monitor current flowing through power bus 60 to load 22 using current sensor
97 of
analysis circuitry 91. As described below, cartridge analysis slave controller
102 can
communicate such electrical characteristics to master controller 100.
14
CA 02616758 2008-01-31
Referring to Fig. 7, auxiliary valve slave controller 104 is shown coupled
with
master controller 100 and auxiliary solenoids 44 and bleed solenoid 42. In
turn,
auxiliary solenoids 44 are coupled with auxiliary valves 45 and bleed solenoid
42 is
coupled with bleed valve 43 as discussed above. Responsive to control
communications from master controller 100, auxiliary valve slave controller
104 is
configured to operate auxiliary solenoids 44 and bleed solenoid 42 to control
auxiliary
valves 45 and bleed valve 43, respectively.
Referring to Fig. 8, fan slave controller 106 is coupled with fan control
circuitry
48 and fan monitor circuitry 49. As described above, fan control circuitry 48
and fan
monitor circuitry 49 are individually coupled with fan 54. Upon receiving
instruction from
master controller 100, fan slave controller 106 is operable to control
operation of fan 54
using fan control circuitry 48. For example, fan slave controller 106 controls
on/off
operational modes of fan 54 and the air flow rate of fan 54. Using fan monitor
circuitry
49, fan slave controller 106 can monitor operation of fan 54. Fan slave
controller 106
can output fan status information (e.g., RPM for a rotational fan) to master
controller
100.
Referring to Fig. 9, interface slave controller 108 is coupled with master
controller 100 and operator interface 16. Master controller 100 supplies
operational
status information from other slave controllers to interface slave controller
108.
Thereafter, interface slave controller 108 can control operator interface 16
to convey
such status information to an operator. Exemplary indications can include a
light
emitting diode (LED) array, bar graph display, audio warning buzzer, etc.
Referring to Fig. 10, external port slave controller 110 is coupled with
communication port 36 and memory 37 as well as master controller 100. As
described
previously, communication port 36 is additionally coupled with a remote device
24.
Communication port 36 and memory 37 operate to provide bi-directional
communications intermediate external port slave controller 110 and remote
device 24.
Although memory 37 is shown external of external port slave controller 110, in
some
configurations such memory 37 can be implemented as internal circuitry of
external
port slave controller 110.
Memory 37 operates to buffer data passing to remote device 24 or data received
from remote device 24 within external port slave controller 110. External port
slave
controller 110 operates to forward received communications to master
controller 100
according to timing of master controller 100. External port slave controller
110 operates
to output messages from master controller 100 to remote device 24 using
CA 02616758 2008-01-31
communication port 36 according to an agreed-upon communication protocol
intermediate external port slave controller 110 and remote device 24.
Referring to Fig. 11, system slave controller 112 is coupled with master
controller 100 as well as main solenoid 46, charge circuitry 34, power supply
sensors
31, current sensor 40 and element control circuitry 41. Responsive to control
from
master controller 100, system slave controller 112 is configured to control
the operation
of main valve 47 using main solenoid 46. Further, responsive to control from
master
controller 100, system slave controller 112 can selectively charge a battery
35 of power
supply 30 using charge circuitry 34.
Slave controller 112 can implement the charging of battery 35 responsive to
information from power supply sensors 31. Power supply sensors 31 provide
electrical
characteristic information of battery 35 and internal power sources 39 to
system slave
controller 112. Internal power sources 39 of power supply 32 include the 5
Volt DC
source and +/- 12 Volt DC source previously described.
Using current sensor 40, system slave controller 112 can monitor current
flowing
through power bus 60. Such provides load information and output power of fuel
cell
power system 10 to system slave controller 112. Thereafter, system slave
controller
112 can provide such current and load information to master controller 100.
System slave controller 112 is also coupled with element control circuitry 41
utilized to control modifying element 53. Such is utilized to control the
temperature
within plenum 51. Modifying element 53 can be controlled to provide circulated
air
within plenum 51 within a desired operational temperature range. Modifying
element 53
is advantageously utilized in some start-up situations to bring the
temperature within
plenum 51 within the operational range in an expedient manner.
Referring to Fig. 12, sensor slave controller 114 is coupled with master
controller 100, heaters 74, 75, fuel detection circuitry 64 and temperature
circuitry 67.
Fuel detection circuitry 64 is associated with plural fuel sensors 58, 61
provided within
housing 12 and plenum 51, respectively. Temperature circuitry 67 is coupled
with
temperature sensor 59 located outside of housing 12. Sensor slave 114 can
control
heaters 74, 75 to selectively bring fuel sensors 58, 61 within an appropriate
temperature range for operation.
Fuel detection circuitry 64 receives data from fuel sensors 58, 61 and can
condition such information for application to sensor slave controller 114. If
fuel is
detected using fuel sensors 58, 61, fuel detection circuitry 64 can process
such
information and provide such data to sensor slave controller 114. Such
information can
indicate the concentration of fuel detected within housing 12 or plenum 51
using fuel
16
CA 02616758 2008-01-31
sensors 58, 61, respectively. Sensor slave controller 114 can in turn provide
such
information to master controller 100.
Temperature sensor 59 provides information regarding the temperature of the
surroundings of fuel cell power system 10. Temperature circuitry 67 receives
outputted
signals from temperature sensor 59 and can condition such signals for
application to
sensor slave controller 114 monitoring the external temperature. Sensor slave
controller 114 can provide external temperature information to master
controller 100.
Referring to Fig. 13, air temperature slave controller 116 is coupled with
master
controller 100 and temperature circuitry 68 and passage control circuitry 57.
Temperature circuitry 68 is associated with temperature sensor 55 provided
within
plenum 51. Passage control circuitry 57 operates to control air passage 56.
For
example, passage control circuitry 57 can control the position of vanes of air
passage
56 in an exemplary embodiment.
Temperature sensor 55 is positioned within plenum 51 to monitor the
temperature of circulated air within plenum 51. Temperature circuitry 68
receives the
sensor information from temperature sensor 55 and conditions the information
for
application to air temperature slave controller 116. Thereafter, air
temperature slave
controller 116 may operate to output the temperature information to master
controller
100.
During operation of fuel cell power system 10, air temperature slave
controller
116 operates to control the flow of air into housing 12 using air passage 56
as well as
the exhaustion of air within plenum 51 to the exterior of housing 12. Air
temperature
slave controller 116 controls air passage 56 using passage control circuitry
57 to
maintain the temperature of circulated air within plenum 51 within the desired
operational temperature range. Further, modifying element 63 of Fig. 11 can be
controlled as previously discussed to raise or lower the temperature of the
circulated
air. Such control of air passage 56 by air temperature slave controller 116
can be
responsive to information from temperature sensor 55 and external temperature
sensor
59. Further, efficiency information regarding fuel cells 90 can be calculated
by air
temperature slave controller 116 to determine waste thermal power. Air passage
56
may be controlled responsive to the calculated waste thermal power.
Referring to Fig. 14, shunt slave controller 118 is coupled with master
controller
100 and switch control circuitry 95. Plural switching devices 96 are coupled
with switch
control circuitry 95. As described above, switching devices 96 are provided to
implement selective shunting of respective fuel cells 90 of fuel cell
cartridges 14.
Master controller 100 can be configured to output shunt information to shunt
slave
17
CA 02616758 2008-01-31
controller 118 for selectively shunting using switching devices 96.
Alternatively, shunt
slave controller 118 can execute internally stored code to provide controlled
selective
shunting of switching devices 96.
Such shunting operations of fuel cells 90 can be utilized to provide increased
power, to expedite start-up procedures, to shunt a faulty fuel cell cartridge
14, and to
monitor for fuel leaks in exemplary embodiments. Switch control circuitry 95
is provided
to provide conditioning of control signals intermediate shunt slave controller
118 and
switching devices 96.
Referring to Fig. 15, switch slave controller 120 is coupled with master
controller
100 and switch control circuitry 33 and switch conditioning circuitry 19.
Switch control
circuitry 33 is coupled with switching device 38 provided in series with power
bus 60.
Responsive to master controller 100, switch slave controller 120 can instruct
switch
controller circuitry 33 to control switching device 38. Switching device 38
provides
selective coupling of power bus 60 to an external load 22. Such can be
utilized to
assure proper operation of fuel cell power system 10 prior to coupling power
bus 60
with load 22.
Switch slave controller 120 can also monitor the status of operator interface
switches 20 which may be set by an operator of fuel cell power system 10.
Exemplary
switches include power on/off of fuel cell power system 10, enable load,
cartridge reset,
etc. Switch conditioning circuitry 19 can filter signals provided from
switches 20 and
provide corresponding information regarding switch position to switch slave
controller
120. Thereafter, switch siave controller 120 can output the switch status
information to
master controller 100.
Referring to Figs. 16-16A, a flow chart illustrating exemplary operations of
master controller 100 of control system 30 is shown. Initially, master
controller 100
performs a communications check at step S10. Communication checks may be
implemented on a periodic interrupt basis to verify communications of master
controller
100 and slave controllers 102-120.
At step S12, master controller 100 determines whether a communication error
was discovered. If such an error is present, master controller 100 issues a
shut down
command to slave controllers 102-120 at step S14. Respective slave controllers
102-
120 implement shut down operations to bring fuel cell power system 10 into a
shut
down condition. Interface slave controller 108 can indicate the shut down
status using
operator interface 16. Further, master controller 100 can instruct external
port slave
controller 110 to notify remote device 24 of the shut down condition.
18
CA 02616758 2008-01-31
Alternatively, if no communication error is present in step S12, master
controller
100 instructs system slave controller 112 to open main valve 47 at step S16.
In
addition, master controller 100 instructs fan slave controller 106 to start
fan 54 at step
S16. At step S18, master controller 100 instructs auxiliary valve slave
controller 104 to
open auxiliary valves 45 using auxiliary solenoids 44. Next, master controller
100
issues a command to auxiliary valve slave controller 104 to open bleed valve
43 using
bleed solenoid 42 at step S20. Thereafter, master controller 100 may execute a
start-
up subroutine as set forth in Fig. 17 at step S22. Following successful
execution of the
start-up subroutine, master controller 100 outputs a load enable "ready"
signal to switch
slave controller 120 at step S24. Switch slave controller 120 controls, using
switch
control circuitry 33, switching device 38 to couple power bus 60 with an
external load.
At step S26 of Fig. 16A, master controller 100 extracts data from slave
controllers 102-120. More specifically, master controller 100 can receive
information
from cartridge analysis slave controller 102, auxiliary valve slave controller
104, fan
slave controller 106, external port slave controller 110, system slave
controller 112,
sensor slave controller 114, air temperature slave controller 116 and switch
slave
controller 120.
Next, master controller 100 proceeds to step S28 where it is determined if a
cartridge reset request has been issued. An operator can implement a cartridge
reset
condition using switches 20. If a cartridge reset is indicated, master
controller 100
proceeds to step S30 and issues an on-line command to change the status of all
off-
line fuel cell cartridges 14 to being on-line. Thereafter, master controller
100 initiates a
bleed cycle utilizing auxiliary valve slave controller 104 at step S32. During
the bleed
cycle, fuel may be applied to individual fuel cell cartridges 14 and the bleed
valve 43
can be opened to allow exhaust operations using bleed manifold 65 and bleed
exhaust
66.
If no cartridge reset request is indicated at step S28, or after the bleed
cycle is
initiated at step S32, master controller 100 proceeds to step S34 to determine
whether
a communication error is present. If a communication error is present, master
controller
100 issues a shut down command at step S36.
If no communication error is present at step S34, master controller 100
proceeds to step S38 to execute an error subroutine as described in Figs. 18-
18A
below. At step S40, master controller 100 calculates operating parameters
utilizing the
data obtained at step S26. Based upon the calculated operating parameters
(e.g.,
setting of fan 54, modifying element 53, etc.), master controller 100 sends
the system
settings at step S42 to the appropriate slave controllers 102-120.
19
CA 02616758 2008-01-31
Referring to Fig. 17, a start-up subroutine executable by master controller
100
is described. Initially, data from sensor slave controller 114 is analyzed to
determine
whether the temperature within plenum 51 is less than 15 Celsius. If yes,
master
controller 100 turns on modifying element 53 utilizing system slave controller
112 at
step S52. Alternatively, master controller 100 instructs systems slave
controller 112 to
turn off modifying element 53 if appropriate at step S54.
Thereafter, master controller 100 proceeds to step S56 and instructs shunt
slave controller 118 to set a shunting duty cycle to maximum. At step S58,
master
controller 100 again retrieves the temperature within plenum 51 from air
temperature
slave controller 116. At step S58, master controller 100 determines whether
the
temperature within plenum 51 is less than 30 Celsius. If so, master
controller loops at
step S58 until the temperature within plenum 51 is equal to or greater 30
Celsius.
Next, at step S60, master controller 100 can calculate a new duty cycle for
application
to shunt slave controllers 118. Thereafter, master controller 100 returns to
the main set
of instructions described in Figs. 16-16A.
Referring to Figs. 18-18A, a flow chart illustrating exemplary error
operations of
master controller 100 is illustrated. Initially, at step S62, master
controller 100
determines whether fan operation is proper. Master controller 100 observes
data from
fan slave controller 106 and outputs a fan error message to interface slave
controller
108 at step S64 if fan operation is not proper. Thereafter, a shut down
command is
issued at step S66 to initiate a shut down procedure of fuel cell power system
10.
At step S68, it is determined whether internal power supplies are operating
properly. More specifically, master controller 100 interfaces with system
slave controller
112 to determine whether values monitored by power supply sensors 31 are
within
range. If not, master controller 100 sends a power supply error message to
interface
slave controller 108 at step S70. Thereafter, master controller 100 issues a
shut down
command at step S72.
At step S74, master controller 100 determines whether auxiliary valve
operation
is proper. Such is determined by data received from auxiliary valve slave
controller 104
regarding the status of auxiliary valves 45. This can be additionally
performed by
monitoring the voltage of a deactivated fuel cell 90. A zero voltage should
result if
auxiliary valve operation is proper. Master controller 100 outputs an
auxiliary valve
error message at step S76 to interface slave controller 108 if operation is
not proper.
Such error message can thereafter be displayed using operator interface 16. At
step
S78, master controller 100 issues a shut down command.
CA 02616758 2008-01-31
Alternatively, master controller 100 proceeds to step S80 and determines
whether a major fuel leak is present. Such is determined by monitoring data
received
from sensor slave controller 114 responsive to the monitoring of fuel sensors
58, 61. If
a major fuel leak is detected, master controller 100 sends a major fuel leak
error
message to interface slave controller 108 at step S82. Thereafter, a shut down
command is issued at step S84.
If no major fuel leak is determined, master controller 100 proceeds to step
S86
to determine whether a minor fuel leak is present. In one configuration, a
major fuel
leak may be defined as >_5000 ppm and a minor fuel leak may be defined as 1000-
4999
ppm. In some applications, the ranges may be varied for increased or decreased
sensitivity to fuel.
If a minor fuel leak is determined at step S86, master controller 100 proceeds
to
step S88 to try to determine if one of fuel cell cartridges 14 is faulty and
the source of
the fuel leak. Accordingly, a first fuel cell cartridge 14 is deactivated at
step S88. Next,
master controller 100 attempts to determine whether the fuel leak is gone.
Deactivation
of the fuel cell cartridge 14 ceases the supply of fuel to the fuel cell
cartridge 14 using
the appropriate auxiliary valve 45. If it is determined that the fuel leak is
gone, an error
message is sent at step S92 to interface slave controller 108 for conveyance
to
operator interface 16.
If the fuel leak remains as determined at step S90, master controller 100
proceeds to step S94 to reactivate the previously deactivated fuel cell
cartridge 14 and
deactivate a subsequent fuel cell cartridge 14. At step S96, master controller
100
determines whether an index has led past the last fuel cell cartridge 14. If
not, master
controller 100 returns to steps S90-S94 to continue with the minor leak
analysis.
Alternatively, master controller 100 proceeds to step S98 and ignores the
minor leak for
a specified period of time. Once the specified period of time has elapsed, and
the fuel
leak is still present, master controller 100 can issue a shut down command
which will
cease the supply of fuel from fuel supply 23 into housing 12 using main valve
47.
At step S100, master controller 100 determines whether there is a failed fuel
cell cartridge 14. If so, master controller 100 shuts off the supply fuel to
the failed fuel
cell cartridge 14 using the appropriate auxiliary valve 45 at step S102. In
addition, a
full-time shunt command for the failed fuel cell cartridge 14 is applied to
shunt slave
controller 118 at step S104. At step S106, master controller 100 sends an
error
message to interface slave controller 108 for conveyance using operator
interface 16.
At step S108, master controller 100 determines whether enough fuel cell
cartridges 14 are currently on-line. In one exemplary arrangement, master
controller
21
CA 02616758 2008-01-31
100 determines whether less than eight fuel cell cartridges 14 are on-line. If
not enough
cartridges are on-line, master controller 100 sends an error command at step
S110 to
interface slave controller 108. Such error message can be conveyed to an
operator
using operator interface 16. Next, at step S112, master controller 100 issues
a shut
down command for fuel cell power system 10. If enough fuel cell cartridges 14
are on-
line at step S108, master controller 100 proceeds to the main set of
instructions defined
in the flow chart of Figs. 16-16A.
Referring to Figs. 19-19B, a flow chart illustrating exemplary operations of
cartridge analysis slave controller 102 is shown. Initially, at step S120,
slave controller
102 indexes to a first fuel cell 90 within fuel cell power system 10. A
transient counter
described below is cleared at step S121. Slave controller 102 obtains a
voltage reading
of the indexed fuel cell 90 at step S122. At step S124, slave controller 102
determines
whether the polarity of the indexed fuel cell 90 is proper. If not, slave
controller 102
proceeds to step S126 and sets the indicated fuel cell voltage to zero.
Thereafter, the
voltage for the currently indexed fuel cell 90 is posted to a fuel cell array
at step S134.
Alternatively, if the polarity of the indexed fuel cell 90 is proper at step
S124,
slave controller 102 determines whether the voltage is proper at step S128. If
not, slave
controller 102 increments a ride-through transient counter at step S130.
Thereafter,
slave controller 102 determines whether the transient counter is at a maximum
value at
step S132. If not, slave controller 102 returns to step S122. If the transient
counter has
reached a maximum value, slave controller 102 proceeds to step S134 to post
the
voltage to the fuel cell array.
At step S136, slave controller 102 determines whether all of the fuel cells 90
have been indexed. If not, slave controller 102 indexes to a next fuel cell 90
at step
S138 and thereafter returns to step S122. If all fuel cells 90 have been
analyzed using
analysis circuitry 91, slave controller 102 proceeds to step S140 to arrange
the fuel cell
readings into readings for respective fuel cell cartridges 14.
Next, slave controller 102 proceeds to step S141 to index to a first of fuel
cell
cartridges 14. Slave controller 102 then proceeds to step S142 to determine
whether
any of the fuel cell cartridges 14 were previously provided in a down or off-
line
condition. If so, slave controller 102 proceeds to step S160 to determine
whether the
last fuel cell cartridge 14 has been indexed. Otherwise, slave controller 102
proceeds
to step S144 to determine whether a voltage of any of the fuel cells of a
currently
indexed fuel cell cartridge 14 have an unacceptable voltage condition (e.g.,
low
voltage). If so, slave controller 102 increments a low voltage counter at step
S146.
Next, slave controller 102 proceeds to step S148 to determine whether the low
voltage
22
CA 02616758 2008-01-31
counter is at a maximum value. The maximum value is selected to provide the
unacceptable fuel cell with a chance to recover and provide an acceptable
voltage
during a subsequent pass through the flow chart. If the low voltage counter is
at
maximum, slave controller 102 proceeds to step S150 to set the currently
indexed fuel
cell cartridge 14 status as deactivated (e.g., down or off-line). Slave
controller 102
instructs master controller 100 to shut off fuel to the currently indexed fuel
cell cartridge
14 at step S152. Master controller 100 thereafter instructs auxiliary valve
slave
controller 104 to shut off fuel to the respective fuel cell cartridge 14. At
step S154,
master controller 100 additionally outputs a command to shunt slave controller
118 to
shunt the appropriate fuel cell cartridge 14. Also, master controller 100 can
output the
message to interface slave controller 108 to convey the status of the
currently indexed
fuel cell cartridge 14 using operator interface 16.
If the currently indexed fuel cell cartridge 14 has a proper voltage as
determined
at step S144, slave controller 102 proceeds to step S145 to clear the low
voltage
counter. Slave controller 102 associates the fuel cells with respective low
voltage
counter values. The low voltage counter for a given fuel cell previously
determined to
be unacceptable during the current pass through the flow chart is cleared at
step S145
if the voltage is deemed acceptable at step S144.
Slave controller 102 proceeds to step S156 to post high and low voltages of
the
fuel cells of the currently indexed fuel cell cartridge 14 to memory. At step
S158, slave
controller 102 outputs the high and low voltage information of the fuel cells
of the fuel
cell cartridge 14 to master controller 100. Master controller 100 processes
the high and
low voltages for the fuel cell cartridge 14 and can instruct interface slave
controller 108
to display or otherwise convey the voltages to an operator using operator
interface 16.
At step S160, slave controller 102 determines whether the last fuel cell
cartridge
14 has been indexed If not, slave controller 102 indexes to a next fuel cell
cartridge 14
at step S162 and thereafter returns to step S142. If the last fuel cell
cartridge 14 has
been indexed at step S160, slave controller 102 proceeds to step S164 to
determine
whether too many fuel cell cartridges 14 are down (e.g., less than seven fuel
cell
cartridges 14 are down or off-line). If so, slave controller 102 sends an
appropriate
message to master controller 100 at step S166.
At step S168, slave controller 102 monitors for the reception of messages from
master controller 100. If a message is received, slave controller 102
processes the
incoming message at step S170. At step S172, slave controller 102 can transmit
fuel
cell data and any messages. Thereafter, slave controller 102 returns to step
S120 to
index the first fuel cell 90 to repeat the analysis.
23
CA 02616758 2008-01-31
Referring to Figs. 20-20A, a flow chart illustrating exemplary operations of
auxiliary valve slave controller 104 is shown. Initially, slave controller 104
performs a
communication check at step S180 to assure proper communications with master
controller 100. At step S182, slave controller 104 listens for a start-up
signal from
master controller 100. At step S184, it is determined whether the appropriate
start-up
signal has been received. Once the start-up signal is received, slave
controller 104
instructs auxiliary solenoids 44 to open respective auxiliary valves 45 at
step S186. At
step S188, slave controller 104 commences to perform a bleed procedure wherein
slave controller 104 instructs bleed solenoid 42 to open bleed valve 43 for a
defined
length of time.
At step S190, slave controller 104 reads data and messages from master
controller 100. Slave controller 104 determines whether the master is off-line
at step
S192. If so, slave controller 104 closes auxiliary valves 45 at step S194.
Otherwise,
slave controller 104 proceeds to step S196 to determine whether a shut down
request
has been issued by master controller 100. If so, slave controller 104 proceeds
to step
S194. Otherwise, slave controller 104 proceeds to step S198 to determine
whether a
change in status of any fuel cell cartridges 14 has been made. If so, slave
controller
104 controls respective auxiliary valves 45 at step S200 to either supply fuel
if the
corresponding fuel cell cartridge 14 is on-line, or cease supply of fuel if
the fuel cell
cartridge 14 has been taken off-line.
At step S202, slave controller 104 monitors to determine whether it is time
for a
bleed cycle. Slave controller 104 can be configured to periodically implement
a bleed
cycle using bleed solenoid 42 and bleed valve 43 according to a bleed timer.
If it is time
for a bleed cycle, slave controller 104 proceeds to step S204 to reset the
bleed timer
and thereafter commence a bleed procedure at step S206. As shown, slave
controller
104 cycles back to step S190 to read any new data from master controller 100.
Referring to Figs. 21-21A, a flow chart illustrating exemplary operations of
fan
slave controller 106 is illustrated. Slave controller 106 initially proceeds
to step S210
and performs a communications check to verify proper communications with
master
controller 100. At step S212, slave controller 106 listens for an appropriate
fan start-up
signal from master controller 100.
Once the appropriate start-up signal is received as determined at step S214,
slave controller 106 proceeds to step S216 to start operation of fan 54 at a
maximum
air flow setting. Thereafter, slave controller 106 reads fan status
information from fan
monitoring circuitry 49 at step S218. At step S220, slave controller 106
determines
24
CA 02616758 2008-01-31
whether fan 54 is operating properly. If not, slave controller 106 issues a
shut down
request to master controller 100 at step S222.
Otherwise, slave controller 106 receives any updated fan setting from master
controller 100 at step S224. At step S226, slave controller 106 can output
appropriate
signals to fan control circuitry 48 to adjust the operation of fan 54. At step
S228, slave
controller 106 determines whether a shut down command has been issued by
master
controller 100. If not, slave controller 106 returns to step S218 to read the
status of fan
54. Otherwise, slave controller 106 proceeds to step S230 to shut off fan 54.
Referring to Fig. 22, a flow chart illustrating exemplary operations of
interface
slave controller 108 is shown. Initially, slave controller 108 proceeds to
step S240 to
perform a communications check with master controller 100. Thereafter, slave
controlier 108 outputs appropriate message information to operator interface
16 for
conveyance to an operator. In the described embodiment, operator interface 16
displays the message information received from master controller 100.
Slave controller 108 listens for updates to operator interface 16 at step
S244. At
step S246, it is determined whether master ontroller 100 is off-line. If so,
slave
controller 108 sends an error message to operator interface 16 to indicate
master
controller 100 is off-line. Otherwise, slave controller 108 proceeds to step
S250 to
determine whether there was a change in the status of operator interface 16.
If not,
slave controller 108 proceeds to step S244 and listens for updates for
operator
interface 16. If a change in interface status is indicated at step S250, slave
controller
108 proceeds to step S252 to update operator interface 16.
Referring to Fig. 23, a flow chart illustrating exemplary operations of
external
port slave controller 110 is illustrated. Initially, slave controller 110
performs a
communications check with master controller 100 at step S260. Thereafter,
slave
controller 100 reads any input communication from remote device 24 and
communication port 36. At step S264, slave controller 110 sends any received
communications to master controller 100. At step S266, slave controller 110
receives
any communications from master controller 100. Slave controller 110 proceeds
to
forward any communications to communication port 36 and remote device 24 at
step
S268.
Referring to Figs. 24-24A, a flow chart illustrating exemplary operations of
system slave controller 112 is shown. Initially, at step S270, slave
controller 112
performs a communications check with master controller 100. Next, slave
controller 112
can read status information from power supply sensors 31 and current sensor 40
at
step S272. At step S274, it is determined by slave controller 112 whether the
inputted
CA 02616758 2008-01-31
status values are within appropriate ranges. If not, slave controller 112 can
generate an
error message at step S276 for application to master controller 100.
Otherwise, slave controller 112 proceeds to step S278 and listens for a main
valve open command from master controller 100. At step S280, it is determined
whether the open valve command was received. Once the open valve command is
received, slave controller 112 proceeds to step S282 to activate main valve 47
using
main solenoid 46. At step S284, slave controller 112 listens for a shut down
command
from master controller 100.
Proceeding to step S286, slave controller 112 determines whether the master
controller 100 is off-line. If so, slave controller 112 proceeds to step S296
to shut off
power supply 32 and main valve 47 using main solenoid 46. If master controller
100 is
on-line, slave controller 112 proceeds to step S288 to again read status
values from
power supply sensors 31 and current sensor 40. Slave controller 112 can
control
charge circuitry 34 to charge battery 35, if necessary, at step S290
responsive to the
values read at step S288.
At step S292, slave controller 112 determines whether the values are within
the
appropriate ranges. If not, slave controller 112 proceeds to step S294 to
generate an
error message for application to master controller 100. Otherwise, at step
S296, slave
controller 112 monitors for the presence of a shut down command or request
from
master controller 100. If no shut down command is issued, slave controller 112
returns
to step S284. If a shut down request or command is received at step S296,
slave
controller 112 proceeds to step S296 to shut off main valve 47 using main
solenoid 46
as well as turn off power supply 32.
Referring to Fig. 25, a flow chart illustrating exemplary operations of sensor
slave controller 114 is shown. Initially, at step S300, slave controller 114
performs a
communication check with master controller 100. At step S302, slave controller
114
controls heaters 74, 75, if necessary, to bring associated fuel sensors 58, 61
within
proper operating temperature ranges. Thereafter, slave controller 114 is
configured to
read information from fuel detection circuitry 64 and corresponding fuel
sensors 58, 61.
Responsive to reading the fuel sensor values, slave controller 114 determines
at
step S306 whether a major leak was detected. If so, slave controller 114
forwards an
appropriate major leak message to master controller 100 at step S308. At step
S310,
the fuel sensor values are analyzed to determine whether a minor leak was
detected. If
so, slave controller 114 sends an appropriate minor leak message to master
controller
100 at step S312.
26
CA 02616758 2008-01-31
At step S314, slave controller 114 reads external temperature information from
temperature circuitry 67 and associated temperature sensor 59. At step S316,
slave
controller 114 sends external temperature values to master controller 100.
Referring to Fig. 26, a flow chart illustrating exemplary operations of air
temperature slave controller 116 is shown. Initially, slave controller 116
performs a
communication check with master controller 100 at step S320. Thereafter, slave
controller 116 reads temperature values from temperature circuitry 68 and
associated
temperature sensor 55 located within air plenum 51. At step S324, slave
controller 116
reads a temperature set point as calculated from master controller 100.
At step S326, slave controller 116 sets recirculation using air passage 56 and
fan 54 to maintain a set point temperature. Slave controller 116 outputs the
air
temperature of plenum 51 as determined by temperature sensor 55 to master
controller
100 at step S328.
Referring to Fig. 27, a flow chart illustrating exemplary operations of shunt
slave
controller 118 is shown. Initially, at step S330, slave controller 118
performs a
communication check with master controller 100. At step S332, slave controller
118
reads data from master controller 100.
At step S334, it is determined whether there was a change in status of the
fuel
cell cartridges 14. If so, slave controller 118 proceeds to step S336 to
determine
whether there is a change of any of the fuel cell cartridges 14 to an off-line
condition. If
not, the appropriate switching device 96 for the respective fuel cell
cartridge 14 is
latched to an off position at step S338. Alternatively, slave controller 118
proceeds to
step S340 to latch the appropriate switching device 96 for the respective fuel
cell
cartridge 14 in an on position.
Following processing of steps S338 or S340, or alternatively if there is no
change in status of fuel cell cartridges 14 as determined at step S334, slave
controller
118 proceeds to step S342 to cyclically shunt fuel cells 90 within fuel cell
cartridges 14.
Referring to Fig. 28, a flow chart illustrating exemplary operations of switch
slave controller 120 is shown. Slave controller 120 performs a communication
check
with master controller 100 at step S350. Thereafter, slave controller 120
reads switch
status information from switches 20 and switch conditioning circuitry 19 at
step S352.
At step S354, slave controller 120 reads load enable status information from
master
controller 100.
Slave controller 120 determines whether a power off request was received from
master controller 100 at step S356. If yes, slave controller 120 proceeds to
step S358
to send a shut down message to master controller 100. Otherwise, slave
controller 120
27
CA 02616758 2008-01-31
proceeds to step 5360. Slave controller 120 determines whether a load enable
request
was provided from switches 20. If so, slave controller 120 proceeds to step
S362 to
determine whether master controller 100 has indicated fuel cell power system
10 is
ready to provide power as determined in step S354. If so, slave controller 120
proceeds
to step S364 to enable switching device 38.
At step S366, siave controller 120 determines whether the master controller
100
is in an off-line condition. If so, slave controller 120 disables switching
device 38 at step
S368. Otherwise, slave controller 120 proceeds to step S370 to determine
whether a
cartridge reset has been indicated from switches 20. If so, slave controller
120
proceeds to send a cartridge reset message to master controller 100 at step
S372.
Slave controller 120 then returns to step S352 to read switch status from
switch
conditioning circuitry 19 and associated switches 20 at step S352.
In compliance with the statute, the invention has been described in language
more or less specific as to structural and methodical features. It is to be
understood,
however, that the invention is not limited to the specific features shown and
described,
since the means herein disclosed comprise preferred forms of putting the
invention into
effect. The invention is, therefore, claimed in any of its forms or
modifications within the
proper scope of the appended claims.
28
