Method for controlling the operation of a fuel cell system (FCS) and an electrical energy storage system (EES) - Patents.com
Patent Information
- Application Number
- JP2024556791
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-03-28
- Filing Date
- 2023-03-23
- Publication Date
- 2026-03-02
AI Technical Summary
Fuel cell systems (FCS) and electrical energy storage systems (EES) used in vehicles are prone to deterioration during use, leading to a reduction in their useful life.
A method for controlling the operation of FCS and EES by adjusting operating constraints between soft and hard constraints, based on the deviation between actual and predicted health states, to extend the useful life of the systems.
Operating FCS with soft constraints reduces unexpected degradation and extends the useful life of the coupled system by allowing more EES usage compared to operating with hard constraints.
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Abstract
Description
[Technical field]
[0001] The present invention relates to a method for controlling the operation of a fuel cell system (FCS) and an electric energy storage system (EES), and also to a control unit, a propulsion system, a vehicle, a computer program, and a computer readable medium.
[0002] The present invention is applicable to large vehicles such as trucks, buses, and construction equipment, etc. Although the present invention is described with respect to trucks, the invention is not limited to this particular vehicle and may also be used with other vehicles such as wheel loaders, excavators, dump trucks, passenger cars, etc. [Background technology]
[0003] There are many different technologies for generating propulsion for a vehicle. One such technology is to use electrical power to drive one or more electric machines in the vehicle. The electric machines can be powered by using an electrical energy storage system, e.g., a battery comprising multiple battery cells, such as lithium-ion cells. Additionally, the electric machines can also be powered using a fuel cell system.
[0004] A fuel cell is an electrochemical cell that converts chemical energy into electricity. Fuel cells convert the chemical energy of a fuel, usually hydrogen, and an oxidant, usually oxygen, into electricity. Thus, fuel cells can be used as an alternative to or a complement to batteries. Recently, fuel cells have been considered for powering electric vehicles, such as pure electric vehicles and hybrid electric vehicles.
[0005] For example, fuel cell systems and electrical energy storage systems used in combination to power vehicles are subject to degradation during use, which has a detrimental effect on the useful life of the system, and therefore it is very important to try to reduce the amount of degradation in the system, thereby extending its useful life.
[0006] In view of the above, efforts are being made to extend the useful life of such systems, and the present invention is directed to situations when fuel cell systems and electrical energy storage systems are used to provide power. Summary of the Invention
[0007] It is therefore an object of the present invention to provide an improved method for controlling the operation of a fuel cell system (FCS) and an electric energy storage system (EES). In particular, it is an object of the present invention to provide a method in which the useful life of at least the FCS is extended. Additionally or alternatively, it is an object of the present invention to provide a method in which the useful life of the combined system is extended. Other objects of the present invention are to provide improvements in the control unit, the propulsion system, the vehicle, the computer program, and the computer readable medium.
[0008] According to a first aspect of the present invention, at least one of the objects is at least partially achieved by a method as claimed in claim 1.
[0009] Thus, a method is provided for controlling operation of a fuel cell system (FCS) and an electric energy storage system (EES), where the FCS is adapted to operate with an adjustable set of operating constraints adjustable between soft and hard constraints, and where operating the FCS with the hard constraints is associated with a higher expected degradation of the FCS than the expected degradation when operating the FCS with the soft constraints.
[0010] The method comprises: - estimating the actual health state of the FCS and the actual health state of the EES associated with a common point in time; determining a forecast of a health state of the FCS and a forecast of a health state of the EES associated with a common point in time, the forecast of the health state being based on a history of usage of the FCS and the EES, respectively; controlling operation of the FCS and the EES based on deviations between actual health states of the FCS and the EES and predicted health states, respectively; When the actual health state of the FCS is worse than its predicted health state and the actual health state of the EES is better than its predicted health state, the FCS operates at a soft constraint.
[0011] By providing the method disclosed herein, at least the useful life of the FCS may be extended. This is achieved by operating the FCS with soft constraints as described above, which allows the EES to be used compared to when the FCS was operated with hard constraints instead. For example, the present invention is based on the recognition that the prediction of the health state based on the usage history of each system is not necessarily the same as the actual health state. The reason for this is that it may be difficult to evaluate the actual operating state of the system. Thus, depending on the actual operating state during use, i.e. during operation, the systems may deteriorate to more or less the same extent than expected. Thus, by controlling the operation based on the deviations described above, unexpected deterioration of the FCS, which is higher than the prediction of deterioration based on the usage history, can be managed by allowing the EES to be used more compared to when the FCS was operated with hard constraints. As a result, the useful life of the combined system may be extended since it is based on the useful life of the weakest system.
[0012] Associated with a common point in time means herein with respect to a common point in time during operation for the actual health state and the forecast of the health state of the system. Associated with a common point in time may not necessarily mean that the health states are estimated / determined at the same point in time, but may additionally or alternatively mean that the health states are estimated / determined at different points in time that are less than a maximum time period from each other. For example, the maximum time period may be 5 hours (h), such as 4 hours, 3 hours, 2 hours, 1 hour, 0.5 hours, or less, etc. In view of the above, by way of example, the estimated actual health state of the FCS and the estimated actual health state of the EES may relate to the same or similar point in time(s). As another example, the estimated actual health state of the FCS and the forecast of the determined health state of the FCS may relate to the same or similar point in time(s). As yet another example, the estimated actual health state of the EES and the forecast of the determined health state of the EES may relate to the same or similar point in time(s). Thus, similar time points can mean that the time points are less than a maximum period from each other.
[0013] Operating an FCS with soft constraints typically means that the FCS operates with lower operating dynamics and / or in a narrower operating window compared to when the FCS operates with hard constraints. As used herein, the operating dynamics of a system refers to how the system's operation changes over time. For example, a large and / or fast fluctuation of an operating parameter during use represents a high operating dynamics of the system compared to a situation in which the operating parameter fluctuates less and / or slower. As used herein, the operating window refers to a window or range within which an operating parameter falls during use. As an example, the operating parameter may refer to the power output from the system. Thus, the operating dynamics may be defined as the power dynamics of the FCS, such as how quickly the FCS can go from low power to high power or full power. Other non-limiting examples of operating parameters are voltage levels, ampere levels, and power throughput. As yet another non-limiting example, the operating parameter may relate to whether or not a system shutdown is permitted. For example, too many FCS shutdowns may lead to degradation.
[0014] Optionally, operating the FCS with soft constraints includes operating the FCS with low operating dynamics and / or a narrow operating window such that use of the EES is increased.
[0015] Optionally, the method further includes controlling operation of the FCS and the EES based on a deviation between an actual health state and a predicted health state of the FCS and the EES, respectively; When the actual health state of the FCS is better than its predicted health state and the actual health state of the EES is worse than its predicted health state, the FCS operates at a hard constraint.
[0016] This can extend the service life of the EES, which in turn can extend the service life of the combined system.
[0017] Optionally, operating the FCS with hard constraints includes operating the FCS with high operating dynamics and / or a wide operating window such that use of the EES is reduced.
[0018] Optionally, one of the FCS and the EES is a predetermined preferred system relative to the other system, the method further comprising controlling operation of the FCS and the EES based on a deviation between an actual health state and a predicted health state of the FCS and the EES, respectively; When the actual health state of the FCS is worse than its predicted health state and the actual health state of the EES is worse than its predicted health state, the FCS operates with a set of operating constraints such that degradation of a predetermined preferred system is reduced.
[0019] Thus, if the actual health state of the FCS and EES is each worse than expected, degradation of the more desirable system may be reduced. For example, one of the systems, such as the FCS, may be more expensive than the other system. Thus, operating the FCS in a way that reduces degradation of the more expensive system represents cost efficiency.
[0020] Optionally, the FCS usage history indicates at least one of the following: -Power output of the FCS in operation, - the power cycle frequency of the operating FCS, - ambient temperature conditions during operation, Ambient air conditions during operation, such as the level of contamination, - ambient weather conditions during operation, - Start / Stop History, -FCS coolant temperature history, -Operation time, for example.
[0021] Optionally, the EES usage history indicates at least one of the following: - power output of the EES during operation, - Ambient temperature conditions, - ambient weather conditions during operation, - The power cycle and energy throughput of the EES during operation.
[0022] Optionally, the method is updated at a predetermined update frequency, for example, the update frequency corresponds to a predetermined number of operation hours of the FCS and / or EES. Updating at a predetermined update frequency means a more reliable method. For example, the predetermined update frequency can be set so that the deviation of the actual and predicted degree of health status does not deviate too much. In other words, the predetermined update frequency can be set so that it is not too low.
[0023] Optionally, the predetermined update frequency is variable, for example variable with respect to at least one of the ambient temperature conditions and the ambient weather conditions. A variable update frequency means a more flexible method, for example allowing the update frequency to vary depending on the ambient conditions. For example, more difficult ambient conditions may suggest a need for a higher update frequency and vice versa.
[0024] Optionally, the predetermined update frequency is modified during operation based on the magnitude of deviation between the actual health state of the FCS and / or EES and the predicted health state, e.g., a larger deviation implies a higher update frequency and vice versa. Thereby, for example, if it is determined that the deviation between the actual health state and the predicted health state is relatively large, the update frequency may be increased. Similarly, for example, if it is determined that the deviation between the actual health state and the predicted health state is relatively small, the update frequency may be decreased. This represents a more flexible method.
[0025] According to a second aspect of the invention, at least one of the objects is at least partly achieved by a control unit as claimed in claim 11.
[0026] Thus, there is provided a control unit for controlling the operation of a fuel cell system (FCS) and an electric energy storage system (EES), the control unit being configured to perform the steps of the method according to any one of the embodiments of the first aspect of the present invention.
[0027] The advantages and benefits of the second aspect of the invention are similar to those of the first aspect of the invention, and vice versa.
[0028] According to a third aspect of the invention, at least one of the objects is at least partly achieved by a propulsion system for a vehicle as claimed in claim 12.
[0029] There is therefore provided a propulsion system for a vehicle comprising a fuel cell system (FCS) and an electric energy storage system (EES), and further comprising a control unit according to any one of the embodiments of the second aspect of the invention.
[0030] The advantages and effects of the third aspect of the invention are similar to those of the first and second aspects of the invention, and vice versa.
[0031] According to a fourth aspect of the invention, at least one of the objects is at least partly achieved by a vehicle as claimed in claim 13.
[0032] There is therefore provided a vehicle comprising a propulsion system according to any one of the embodiments of the third aspect of the present invention.
[0033] The advantages and effects of the fourth aspect of the invention are similar to those of the first, second and third aspects of the invention, and vice versa.
[0034] According to a fifth aspect of the present invention, at least one of the objects is at least partly achieved by a computer program as claimed in claim 14.
[0035] There is therefore provided a computer program comprising program code means for performing any of the steps of the embodiments of the first aspect of the invention when said program is run on a computer such as a control unit according to the second aspect of the invention.
[0036] According to a fifth aspect of the present invention, at least one of the objects is at least partly achieved by a computer readable medium as claimed in claim 15.
[0037] There is therefore provided a computer readable medium carrying a computer program comprising program code means for performing any of the steps of the embodiments of the first aspect of the invention, when said program product is executed on a computer such as a control unit according to the second aspect of the invention.
[0038] Further advantages and advantageous features of the present invention are disclosed in the following description and in the dependent claims.
[0039] A more detailed description of embodiments of the invention follows below, given as examples, with reference to the accompanying drawings. [Brief description of the drawings]
[0040] [Figure 1] 1 shows a side view of a vehicle according to an embodiment of the present invention. [Diagram 2] 1 is a flowchart of a method according to an embodiment of the present invention. [Diagram 3] 4 is another flowchart of a method according to an embodiment of the present invention. [Figure 4] 1 is a graph showing predicted and actual health status over time. [Diagram 5] 1 is a schematic diagram of a propulsion system in accordance with an exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0041] 1 shows a vehicle 100 in the form of a large truck. In this example, the large truck 100 is a so-called towing vehicle, configured to tow one or more trailers (not shown). However, the invention is not only applicable to this type of vehicle, but can also be used with many other types of vehicles and watercraft, such as construction machines, including but not limited to wheel loaders, dump trucks, excavators, etc., other trucks, buses, passenger cars, etc.
[0042] In the embodiment shown, the vehicle 100 comprises a propulsion system 1. The propulsion system 1 may for example be the propulsion system shown in Fig. 5, which is further described below. The vehicle 100 further comprises a control unit 110 according to an exemplary embodiment of the second aspect of the invention.
[0043] Specifically, the propulsion system 1 includes a fuel cell system (FCS) and an electric energy storage system (EES). The electric energy storage system (EES) may be, for example, a battery including a plurality of battery cells, such as lithium-ion cells.
[0044] Typically, such a propulsion system 1 of a vehicle 1 is adapted such that during operation, the FCS contributes most to the propulsion of the vehicle 1, while the EES is used to compensate for situations when the FCS cannot provide or is not adequate to provide all of the required propulsion.
[0045] 2 illustrates a flow chart of a method according to an exemplary embodiment of the present invention for controlling the operation of a fuel cell system (FCS) and an electrical energy storage system (EES), where the FCS is adapted to operate with an adjustable set of operating constraints that are adjustable between soft and hard constraints, and where operating the FCS with the hard constraints is associated with a higher expected degradation of the FCS than the expected degradation when operating the FCS with the soft constraints.
[0046] Thus, operating the FCS with hard constraints means that the EES usage is reduced during operation, and operating the FCS with soft constraints means that the EES usage is increased during operation.
[0047] The method comprises: S1: Includes estimating the actual health state of the FCS and the actual health state of the EES associated with a common point in time.
[0048] For example, the actual state of health of the FCS and / or EES can be estimated by the well-known so-called electrochemical impedance spectroscopy method, and there are also other methods to estimate the actual state of health, such as ESS coulomb counting to estimate degradation, comparison of polarization curves between used and new or fresh FCS, etc.
[0049] The method further comprises: S2: determining a forecast of a health state of the FCS and a forecast of a health state of the EES associated with a common point in time, the forecast of the health state being based on a history of usage of the FCS and the EES, respectively; S3: The deviation (Δ) between the actual and predicted health states of the FCS and EES, respectively. FCS and controlling operation of the FCS and the EES based on the When the actual health state of the FCS is worse than its predicted health state and the actual health state of the EES is better than its predicted health state, the FCS operates at a soft constraint.
[0050] For example, a predicted health state based on a usage history may be determined by comparing the current usage to the maximum usage. For example, the FCS may be assumed to last for a certain operating time, such as 1000 hours, in a particular application. During this time, the degradation characteristics may be assumed to be known, such as linear. Thus, for example, if the FCS has been operating for 500 hours, then by linear logic, the predicted health state should be 50%. This is a fairly simple and therefore efficient approach to estimating the predicted health state. However, more advanced approaches are also feasible. For example, by considering at least one of the other below-mentioned usage histories, any events related to the degradation of the FCS, such as ambient temperature, start / stop history, etc., can be taken into account to obtain a value of the predicted health state at a common point in time that is closer to the actual health state at the common point in time. As a result, the update frequency of the method may be reduced accordingly.
[0051] An example of the actual and predicted health state over time of one of the systems (in this case the FCS) is shown in Figure 4. Figure 4 shows a graph in which the health state is represented on the y-axis and time or years on the x-axis. The dotted curve represents the health SoH A The solid line represents the actual state of health SoH E In the example shown, the expected SoH E forms approximately a straight line based on the system's usage history. A straight line may mean, for example, that the usage is substantially static during operation. For example, the power cycle frequency, the ambient temperature conditions during operation, etc. may not change substantially over time. Of course, the usage history may additionally or alternatively change over time, resulting in a change in the degradation rate over time. Thereby, the health state prediction may not be simply represented by an apparent straight line. Usage history as used herein may refer to any previous usage of the respective system.
[0052] As mentioned above, step S3 is to check the actual state of health SoH of the FCS and EES. A and the expected state of health SoH EThe deviation Δ between FCS In FIG. 4, the FCS includes two deviations Δ FCS Each of the illustrated deviations is relative to a common instant in time. However, as noted herein, there may be a period between each actual health state and the predicted health state. The second deviation on the right side of the figure is the actual health state SoH of the FCS. A But the expected health state SoH E represents the situation when the actual health state of the EES is worse than its predicted health state. Thus, by using the method, from this point on, and when the actual health state of the EES is better than its predicted health state, the FCS will operate with soft constraints. For example, this could mean that the operation of the FCS is changed from operating with hard constraints to instead operating with soft constraints, or if the FCS is already operating with soft constraints, the FCS will continue to operate with soft constraints. The deviation Δ FCS After the method is performed when occurs, the degradation rate of the FCS may be reduced, i.e., by changing from operating the FCS with soft constraints instead of hard constraints.
[0053] Operating the FCS with soft constraints typically involves operating the FCS with low operating dynamics and / or a narrow operating window such that use of the EES is increased.
[0054] In addition, the method further comprises determining a deviation Δ between the actual and predicted health states of the FCS and EES, respectively. FCS and controlling operation of the FCS and the EES based on the When the actual health state of the FCS is better than its predicted health state and the actual health state of the EES is worse than its predicted health state, the FCS operates at a hard constraint.
[0055] The deviation Δ, which is first shown in Fig. 4 FCSi.e., the left side of the diagram may represent such a situation when the actual health state of the FCS is better than the prediction of its health state and the actual health state of the EES (not shown) is worse than the prediction of its health state. Thus, by using the present method, from this point on, the FCS operates with hard constraints. For example, this may mean that the operation of the FCS is changed from operating with soft constraints to operating with hard constraints instead, or, if the FCS is already operating with hard constraints, the FCS continues to operate with hard constraints. In the example shown, the degradation rate of the FCS increases with a first deviation Δ FCS It can be seen that the increase occurs after
[0056] Operating an FCS with hard constraints typically involves operating the FCS with high operating dynamics and / or a wide operating window such that the use of the EES is reduced.
[0057] One of the FCS and the EES may be a predetermined preferred system relative to the other system. Thus, the method further comprises determining a deviation Δ FCS and controlling operation of the FCS and the EES based on the When the actual health state of the FCS is worse than its predicted health state and the actual health state of the EES is worse than its predicted health state, the FCS operates with a set of operating constraints such that degradation of a predetermined preferred system is reduced.
[0058] The history of FCS usage may indicate at least one of the following: -Power output of the FCS in operation, - the power cycle frequency of the operating FCS, - ambient temperature conditions during operation, Ambient air conditions during operation, such as the level of contamination, - ambient weather conditions during operation, - Start / Stop History, -FCS coolant temperature history, - Operating time, such as the number of operating hours.
[0059] The EES usage history may indicate at least one of the following: - power output of the EES during operation, - Ambient temperature conditions, - ambient weather conditions during operation, - The power cycle and energy throughput of the EES during operation.
[0060] Furthermore, the method may be updated at a predefined update frequency, e.g., the update frequency corresponds to a predefined number of operation hours of the FCS and / or EES. Furthermore, the predefined update frequency may be variable, e.g., variable with respect to at least one of ambient temperature conditions and ambient weather conditions. For example, the predefined update frequency may be modified during operation based on the magnitude of deviation between the actual health state of the FCS and / or EES and a forecast of the health state, e.g., a larger deviation implies a higher update frequency and vice versa.
[0061] FIG. 3 shows a flow chart of an exemplary embodiment of the method disclosed herein.
[0062] The method begins at box 200 where an update is requested. At box 210, an actual health state of the FCS and an actual health state of the EES are estimated. At box 220, a predicted health state of the FCS and a predicted health state of the EES are determined based on historical usage of the FCS and the EES. The method then continues to box 230 where a determination is made as to whether the actual health state of the FCS is worse than its predicted health state. If yes, the method continues to box 240. If no, the method instead continues to box 250.
[0063] In box 240, a determination is made as to whether the actual health state of the EES is better than its predicted health state. If yes, the method continues to box 241. If no, the method instead continues to box 242.
[0064] In box 241 it is determined whether the current operating constraints are operating with soft constraints. If they are not, the operation of the FCS is changed to make the FCS operate with soft constraints, as represented by box 243. However, if the FCS is already operating with soft constraints, the soft constraints are maintained, as represented by box 244.
[0065] In box 242, a determination is made as to whether the current operating constraints of the FCS are lower than the hard constraints. If yes, the method continues to box 245, where the constraints are modified, if necessary, to reduce degradation of the given preferred system.
[0066] If in box 230 it is determined that the actual health state of the FCS is not worse than its predicted health state, the method instead continues to box 250, as described above. In box 250, similar to box 240, it is determined whether the actual health state of the EES is better than its predicted health state. If yes, the method continues to box 251. If no, the method instead continues to box 252.
[0067] In box 251, the current motion constraints are maintained. However, in box 252, it is determined whether the current motion constraints of the FCS are lower than the hard constraints. If yes, the method continues to box 253, where the motion constraints are changed to the hard constraints. However, if the motion constraints are not lower than the hard constraints, the motion constraints of the FCS are maintained, which is represented by box 254.
[0068] FIG. 5 shows a schematic diagram of a propulsion system 1 for a vehicle according to an exemplary embodiment of the invention. The propulsion system 1 comprises a fuel cell system (FCS) and an electric energy storage system (EES). The propulsion system 1 may be part of a vehicle 100, for example, as shown in FIG. 1. In the embodiment shown, the propulsion system 1 further comprises a DC / DC converter 20, a junction box 30, and an electric machine 40 drivingly connected to at least one traction wheel 50 of the vehicle 100. Thus, the lines between the parts of the diagram represent electrical connections, with the exception of the lines between the electric machine 40 and at least the traction wheel 50, which represent instead mechanical drive connections. The operation of the FCS and the EES is controlled by a control unit 110. The control unit 110 may also be used to control the operation of the propulsion system 1, i.e., for example, to control the electric machine. The FCS is preferably adapted to be the main contributor for providing propulsive power to the at least one traction wheel 50. Thus, the EES preferably adapts to provide additional propulsion in situations when the full required power cannot be provided by the FCS, or when it is not appropriate to provide the full required power by the FCS.
[0069] Herein, the control unit 110 may be an electronic control unit. The electronic control unit may comprise a processing circuit adapted to execute the computer program disclosed herein. The control unit 110 may comprise hardware and / or software for performing the method according to the present invention. In an embodiment, the control unit 110 may be represented by a computer. The control unit 110 may be composed of one or more separate sub-control units. Furthermore, the control unit 110 may communicate with the propulsion system 1 using wired and / or wireless communication means. The control unit 110 may be part of the vehicle 100 as shown in FIG. 1. It is further noted that, although the control unit 110 is preferably a vehicle on-board control unit, the control unit may additionally or alternatively be a vehicle off-board control unit, such as a control unit that is part of a computer cloud system.
[0070] It should be understood that the present invention is not limited to the embodiments described above and shown in the drawings, but rather, those skilled in the art will recognize that many variations and modifications may be made within the scope of the appended claims.
Claims
1. 1. A method for controlling the operation of a fuel cell system (FCS) and an electric energy storage system (EES), wherein the FCS is adapted to operate with an adjustable set of operating constraints that are adjustable between soft constraints and hard constraints, and wherein operating the FCS with the hard constraints is associated with an expected degradation of the FCS that is higher than an expected degradation when operating the FCS with the soft constraints, the method comprising: - estimating (S1) an actual health state of the FCS and an actual health state of the EES associated with a common point in time, said method further comprising: - determining (S2) a predicted health state of the FCS and a predicted health state of the EES associated with the common point in time, the predicted health state being based on historical usage of the FCS and the EES, respectively; - controlling (S3) the operation of the FCS and the EES based on the deviation (ΔFCS) between the actual and predicted health states of the FCS and the EES, respectively; The method, wherein the FCS operates with soft constraints when the actual health state of the FCS is worse than the predicted health state of the FCS and the actual health state of the EES is better than the predicted health state of the EES.
2. The method of claim 1 , wherein operating the FCS with soft constraints includes operating the FCS with low operating dynamics and / or a narrow operating window such that use of the EES is increased.
3. controlling operation of the FCS and the EES based on the deviation between the actual health state and the predicted health state of the FCS and the EES, respectively; 2. The method of claim 1, wherein the FCS operates at a hard constraint when the actual health state of the FCS is better than the predicted health state of the FCS and the actual health state of the EES is worse than the predicted health state of the EES.
4. The method of claim 3 , wherein operating the FCS with hard constraints includes operating the FCS with high operating dynamics and / or a wide operating window such that use of the EES is reduced.
5. one of the FCS and the EES is a predetermined preferred system relative to the other system, the method further including controlling operation of the FCS and the EES, respectively, based on the deviation between the actual health state and the predicted health state of the FCS and the EES; 2. The method of claim 1, wherein when the actual health state of the FCS is worse than the predicted health state of the FCS and the actual health state of the EES is worse than the predicted health state of the EES, the FCS operates with a set of operational constraints such that degradation of the predetermined preferred system is reduced.
6. The usage history of the FCS indicates at least one of the following: - the power output of said FCS during operation; - the power cycle frequency of said FCS during operation, - ambient temperature conditions during operation, ambient air conditions during operation, such as the level of contamination, - ambient weather conditions during operation, - Start / Stop history, - the coolant temperature history of the FCS, - operating time, The method of claim 1.
7. The usage history of the EES indicates at least one of the following: - power output of said EES during operation; - ambient temperature conditions, - ambient weather conditions during operation, - the power cycle and energy throughput of the EES during operation; The method of claim 1.
8. The method of claim 1 , wherein the method is updated at a predetermined update frequency, for example, the update frequency corresponds to a predetermined number of operating hours of the FCS and / or the EES.
9. The method of claim 8 , wherein the predetermined update frequency is variable, for example variable with respect to at least one of ambient temperature conditions and ambient weather conditions.
10. 9. The method of claim 8, wherein the predetermined update frequency is modified during operation based on the magnitude of the deviation between the actual health state of the FCS and / or the EES and the predicted health state, e.g., a larger deviation means a higher update frequency and vice versa.
11. A control unit (110) for controlling the operation of a fuel cell system (FCS) and an electric energy storage system (EES), said control unit (110) being configured to perform the steps of the method according to any one of claims 1 to 10.
12. A propulsion system (1) for a vehicle comprising a fuel cell system (FCS) and an electric energy storage system (EES), and further comprising a control unit according to claim 11.
13. A vehicle (100) comprising a propulsion system according to claim 12.
14. A computer program comprising program code means for performing the steps of any of claims 1 to 10 when the computer program is run on a computer such as a control unit as claimed in claim 11.
15. 12. A computer readable medium carrying a computer program, said computer program comprising program code means for performing the steps of any of claims 1 to 10 when said computer program is run on a computer such as a control unit according to claim 11.