US 12,381,241 B1 · Methods and systems for optimizing lifetime of fuel cell system based on adjustment and constraint of thermoelectric ratio

Abstract

A method and a system for optimizing a lifetime of a fuel cell system based on adjustment and constraint of a thermoelectric ratio are provided. The method includes obtaining initial reference voltages of a plurality of single-machine fuel cell systems, and performing a durability test under a normal operating condition to obtain variation relationships of reference voltage over time; monitoring an operating voltage of each of the single-machine fuel cell systems in real-time under the normal operating condition to obtain a real-time monitored voltage and a real-time voltage deviation; calculating a performance expected attenuation profile of each of the single-machine fuel cell systems under the normal operating condition; obtaining current density distribution and actual available heat of each of the single-machine fuel cell systems, and calculating a health state boundary of each of the single-machine fuel cell systems in stable operation, so as to optimize operating modes of the systems.

A method for optimizing a lifetime of a fuel cell system based on adjustment and constraint of a thermoelectric ratio, applied to a multi-machine fuel cell system including a plurality of single-machine fuel cell systems, the method comprising:

obtaining an initial reference voltage of each of the plurality of single-machine fuel cell systems in the multi-machine fuel cell system under a normal operating condition, and performing a durability test on the plurality of single-machine fuel cell systems to obtain a variation relationship of a reference voltage over time of each of the plurality of single-machine fuel cell systems;
monitoring an operating voltage of each of the plurality of single-machine fuel cell systems during a real operation in real-time under the normal operating condition to obtain a real-time monitored voltage and a real-time voltage deviation of each of the plurality of single-machine fuel cell systems;
calculating, according to the variation relationship of the reference voltage over time and the real-time monitored voltage of each of the plurality of single-machine fuel cell systems, a performance expected attenuation profile of each of the plurality of single-machine fuel cell systems under the normal operating condition;
obtaining a performance expected attenuation profile and an available heat profile of each of the plurality of single-machine fuel cell systems when operating at each of one or more current density points, and calculating a health state boundary of each of the plurality of single-machine fuel cell systems in stable operation;
optimizing an operating mode of each of the plurality of single-machine fuel cell systems by using the available heat profile, the performance expected attenuation profile, and the health state boundary of each of the plurality of single-machine fuel cell systems;
wherein
the obtaining the initial reference voltage of each of the plurality of single-machine fuel cell systems in the multi-machine fuel cell system under the normal operating condition further includes that:
an initial voltage matrix of the plurality of single-machine fuel cell systems is expressed as:
Vinitial=[V1,V2,V3,V4 . . . ] (2)
wherein, Vinitial is an initial reference voltage of a fuel cell subsystem, V1, V2, V3, and V4 are the initial reference voltages of the plurality of single-machine fuel cell systems No. 1, No. 2, No. 3, No. 4 in a specified state;
if the initial reference voltage of each of the plurality of single-machine fuel cell systems is deviated from each other by a preset deviation value, the plurality of single-machine fuel cell systems need to be replaced at an initial stage;
the performing the durability test on the plurality of single-machine fuel cell systems to obtain the variation relationship of the reference voltage over time of each of the plurality of single-machine fuel cell systems further includes:
obtaining a corresponding fitting formula according to performance differences of different single-machine fuel cell systems;
using a fitting manner of subtracting a reference voltage at a start of the durability test from a reference voltage at an end of the durability test or a linear fitting manner in a fitting process, and a prediction voltage matrix Vpc of the variation relationship of the reference voltage over time of the multi-machine fuel cell systems being expressed as:
Vpc=[M1,M2,M3,M4 . . . ] (3)
wherein, 1, 2, 3, and 4 are numbers of the plurality of single-machine fuel cell systems, and M1, M2, M3, and M4 are forms of the prediction voltage of the plurality of single-machine fuel cell systems No. 1, No. 2, No. 3, and No. 4—variation relationship of the reference voltage over time;
the monitoring the operating voltage of each of the plurality of single-machine fuel cell systems during the real operation in real-time under the normal operating condition to obtain the real-time monitored voltage and the real-time voltage deviation of each of the plurality of single-machine fuel cell systems further includes that:
a real-time monitored voltage matrix Vrt of the variation relationship of each of the plurality of single-machine fuel cell systems over operating time is:
Vrt=[Vrt1,Vrt2,Vrt3,Vrt4 . . . ] (4)
wherein, 1, 2, 3, and 4 are numbers of the plurality of single-machine fuel cell systems;
correcting a prediction voltage matrix Vpcn in a control policy in real-time according to a real-time voltage monitoring situation;
Vpcn=[M1+ε1M1,M2+ε2M2,M3+ε3M3,M4+ε4M4 . . . ] (5)
ε
1
=
V
rt
⁢
1
-
M
1
M
1
,
ε
2
=
V
rt
⁢
2
-
M
2
M
2
,
…
(
6
)
wherein, ε is a correction coefficient;
obtaining a real-time voltage deviation matrix ηrt between each of the plurality of single-machine fuel cell systems;
η
rt
=
[
η
1
,
η
2
,
η
3
,
η
4
⁢
…
]
(
7
)
η
1
=
Max
[
V
rt
⁢
1
,
V
rt
⁢
2
,
V
rt
⁢
3
,
V
rt
⁢
4
⁢
…
]
-
V
rt
⁢
1
Max
[
V
rt
⁢
1
,
V
rt
⁢
2
,
V
rt
⁢
3
,
V
rt
⁢
4
⁢
…
]
×
100
⁢
%
η
2
=
Max
[
V
rt
⁢
1
,
V
rt
⁢
2
,
V
rt
⁢
3
,
V
rt
⁢
4
⁢
…
]
-
V
rt
⁢
2
Max
[
V
rt
⁢
1
,
V
rt
⁢
2
,
V
rt
⁢
3
,
V
rt
⁢
4
⁢
…
]
×
100
⁢
%
wherein, η is a deviation percentage;
the calculating, according to the variation relationship of the reference voltage over time and the real-time monitored voltage of each of the plurality of single-machine fuel cell systems, the performance expected attenuation profile of each of the plurality of single-machine fuel cell systems under the normal operating condition further includes:
obtaining a prediction voltage deviation matrix ηprt between each of the plurality of single-machine fuel cell systems according to a prediction voltage matrix Vpc of the variation relationship of the reference voltage over time of each of the plurality of single-machine fuel cell systems and a real-time corrected prediction voltage matrix Vpcn as the performance expected attenuation profile of each of the plurality of single-machine fuel cell systems under the normal operating condition;
η
prt
=
[
η
p
⁢
1
,
η
p
⁢
2
,
η
p
⁢
3
,
η
p
⁢
4
⁢
…
]
(
8
)
η
p
⁢
1
=
Max
[
M
1
+
η
1
⁢
M
1
,
M
2
+
η
2
⁢
M
2
,
M
3
+
η
3
⁢
M
3
,
M
4
+
η
4
⁢
M
4
⁢
…
]
-
(
M
1
+
η
1
⁢
M
1
)
Max
[
M
1
+
η
1
⁢
M
1
,
M
2
+
η
2
⁢
M
2
,
M
3
+
η
3
⁢
M
3
,
M
4
+
η
4
⁢
M
4
⁢
…
]
×
100
⁢
%
η
p
⁢
2
=
Max
[
M
1
+
η
1
⁢
M
1
,
M
2
+
η
2
⁢
M
2
,
M
3
+
η
3
⁢
M
3
,
M
4
+
η
4
⁢
M
4
⁢
…
]
-
(
M
2
+
η
2
⁢
M
2
)
Max
[
M
1
+
η
1
⁢
M
1
,
M
2
+
η
2
⁢
M
2
,
M
3
+
η
3
⁢
M
3
,
M
4
+
η
4
⁢
M
4
⁢
…
]
×
100
⁢
%
…
calculating an expected performance attenuation rate matrix φprt of each of the plurality of single-machine fuel cell systems:
φ
prt
=
[
φ
p
⁢
1
,
φ
p
⁢
2
,
φ
3
,
φ
4
⁢
…
]
(
9
)
φ
p
⁢
1
=
V
1
-
M
1
V
1
φ
p
⁢
2
=
V
2
-
M
2
V
2
…
wherein an expected performance attenuation rate deviation matrix δprt of each of the plurality of single-machine fuel cell systems is calculated:
δ
prt
=
[
δ
p
⁢
1
,
δ
p2
,
δ
p
⁢
3
,
δ
p
⁢
4
⁢
…
]
(
10
)
δ
p
⁢
1
=
Max
[
φ
p
⁢
1
,
φ
p
⁢
2
,
φ
p
⁢
3
,
φ
p
⁢
4
⁢
…
]
-
φ
p
⁢
1
Max
[
φ
p
⁢
1
,
φ
p
⁢
2
,
φ
p
⁢
3
,
φ
p
⁢
4
⁢
…
]
×
100
⁢
%
δ
p
⁢
2
=
Max
[
φ
p
⁢
1
,
φ
p
⁢
2
,
φ
p
⁢
3
,
φ
p
⁢
4
⁢
…
]
-
φ
p
⁢
2
Max
[
φ
p
⁢
1
,
φ
p
⁢
2
,
φ
p
⁢
3
,
φ
p
⁢
4
⁢
…
]
×
100
⁢
%
…
wherein formula (8) represents performance deviation between each of the plurality of single-machine fuel cell systems;
formula (10) represents expected performance attenuation rate deviation between each of the plurality of single-machine fuel cell systems;
the obtaining the performance expected attenuation profile and the available heat profile of each of the plurality of single-machine fuel cell systems when operating at each of the one or more current density points, and calculating the health state boundary of each of the plurality of single-machine fuel cell systems in stable operation further includes that:
heat generation Q is shown in formula (11) and output power P is shown in formula (12):
Q=Qr+Qc (11)
wherein Qr represents reaction heat generation, Qc represents ohmic heat, and both are related to a current density during operation;
P=VrtI (12)
wherein I represents the current during the operation, which is equal to a current density multiplied by an active area, and the active area is a known design parameter;
obtaining a prediction voltage matrix Vpci of the variation relationship of the reference voltage over time under different current densities at an interval of every 0.2 A/cm2 when each of the plurality of single-machine fuel cell systems operates at a preset current density range:
V
pci
-
0.8
=
[
N
1
,
N
2
,
N
3
,
N
4
⁢
…
]
(
13
)
V
pci
-
1.
=
[
S
1
,
S
2
,
S
3
,
S
4
⁢
…
]
V
pci
-
1.2
=
[
G
1
,
G
2
,
G
3
,
G
4
⁢
…
]
…
wherein N, S, and G have the same meaning as M in formula (3), and if the prediction voltage matrix M of a single-machine fuel cell system of the plurality of single-machine fuel cell systems with a certain number is adjusted to a form in N, S, and G, corresponding calculation is replaced in formula (9);
0.8, 1.0, and 1.2 are current density values, in units of A/cm2;
a relationship matrix Qp between actual available heat and the current density is obtained by using formula (14):
Q
p
=
[
Q
p
0.8
,
Q
p
1.
,
Q
p
1.2
,
Q
p
1.4
,
Q
p
1.6
,
Q
p
1.8
⁢
…
]
(
14
)
Q
p
0.8
=
cm
0.8
⁢
Δ
⁢
T
0.8
Q
p
1.
=
cm
1.
⁢
Δ
⁢
T
1.
…
wherein c represents a heat capacity of a coolant, which is a known amount determined according to a type of the coolant, m represents a coolant flow rate, which is a known amount read by a flow meter, ΔT is a temperature difference of the coolant at inlet and outlet of the plurality of single-machine fuel cell systems, which is a known amount read by temperature sensors at the inlet and the outlet, 0.8, 1.0, and 1.2 are the current density values, in units of A/cm2;
by using formula (15), an available heat Qu in the normal operating condition is obtained:
Qu=cmuΔTu (15)
formula (15) is applicable to all the plurality of single-machine fuel cell systems before adjustment, mu represents a coolant flow rate under the normal operating condition, and ΔTu represents a temperature difference of the coolant at the inlet and outlet of the system under the normal operating condition;
after operating conditions of a portion of the plurality of single-machine fuel cell systems are adjusted by using formula (13) and formula (14), a total heat output obtained by summing each of the plurality of single-machine fuel cell systems is consistent with the total available heat Qu during normal operation before the adjustment;
the optimizing the operating mode of each of the plurality of single-machine fuel cell systems by using the available heat profile, the performance expected attenuation profile, and the health state boundary of each of the plurality of single-machine fuel cell systems further includes:
adjusting the operating mode of each of the plurality of single-machine fuel cell systems by using the prediction voltage deviation matrix between each of the plurality of single-machine fuel cell systems and the expected performance attenuation rate deviation matrix of each of the plurality of single-machine fuel cell systems, wherein a relationship matrix between the actual available heat and the current density is used as a constraint condition to obtain a heat output;
if the voltage deviation in the real-time voltage deviation matrix between each of the plurality of single-machine fuel cell systems is not less than a first preset value when each of the plurality of single-machine fuel cell systems is in stable operation, performing an adjustment;
the optimizing the operating mode of each of the plurality of single-machine fuel cell systems by using the performance expected attenuation profile and the health state boundary of each of the plurality of single-machine fuel cell systems further includes:
if the performance of a portion of the plurality of single-machine fuel cell systems is degraded, using a hybrid operating mode including that:
the portion of the plurality of single-machine fuel cell systems whose performance is degraded operates in an operating condition with a low attenuation rate calculated by the formula (13), if total output power or heat is insufficient, one or more single-machine fuel cell systems with a minimum attenuation calculated by the formula (8) operate in an operating condition with a high current density in formula (13);
combined total power and heat output values of the operating current and output voltage required by all the single-machine fuel cell systems are calculated by using the formulas (12), (14), and (15).

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Methods and systems for optimizing lifetime of fuel cell system based on adjustment and constraint of thermoelectric ratio

Life of this patent

Methods and systems for optimizing lifetime of fuel cell system based on adjustment and constraint of thermoelectric ratio

Life of this patent

Abstract

Claims3