System and method for operating a fuel cell

Abstract

Systems and methods of operating a fuel cell. A hybrid power system includes a high voltage bus, a high voltage battery electrically connected to the high voltage bus, a fuel cell power device electrically connected to the high voltage bus, and a drive unit electrically connected to the high voltage bus. A controller is electrically connected to the drive unit, the fuel cell power device, and the high voltage battery. The controller is configured to identify an application power request for the drive unit and determine a relationship between the application power request and an optimal membrane life power for the fuel cell power plant. The controller is further configured to direct the fuel cell power device to operate between an optimal membrane life power and a second power. The application power requests a power level between the optimal membrane life power and the second power.

Description

Background Art

[0001] A fuel cell is an electrochemical device that converts the chemical energy of a fuel (e.g., hydrogen) into electricity through an electrochemical reaction. Multiple fuel cells can be combined to form a fuel cell stack to generate the desired fuel cell power output. One type of fuel cell includes a polymer electrolyte membrane fuel cell (PEMFC). The electricity generated by the fuel cell stack can be used to power an electric motor (such as an onboard traction motor or a stationary generator or a battery charger). Summary of the invention

[0002] A hybrid power system is disclosed herein. The hybrid power system includes a high-voltage bus, a high-voltage battery electrically connected to the high-voltage bus, a fuel cell power device electrically connected to the high-voltage bus, and a drive unit electrically connected to the high-voltage bus. A controller is electrically connected to the drive unit, the fuel cell power device, and the high-voltage battery. The controller is configured to identify an application power request of the drive unit and determine a relationship between the application power request and an optimal membrane life power of the fuel cell power device. The controller is also configured to direct the fuel cell power device to operate between a first power associated with the optimal membrane life power and a second power. The application power request is at a power level between the optimal membrane life power and the second power.

[0003] Another aspect of the present disclosure may be a case where the first power is within a predetermined range including an optimal membrane lifetime power, and the optimal membrane lifetime power is determined based on a function of power generated by a fuel cell power device and membrane lifetime energy of the fuel cell power device.

[0004] Another aspect of the present disclosure may be a case where the optimum membrane lifetime power corresponds to an optimum electrical power for producing optimum membrane lifetime energy.

[0005] Another aspect of the present disclosure may be a case where an optimum membrane lifetime energy is determined based on a relationship between membrane lifetime and power.

[0006] Another aspect of the present disclosure may be a case where the membrane lifetime energy is determined by multiplying the membrane lifetime of the fuel cell power device by the power generated within the membrane lifetime.

[0007] Another aspect of the present disclosure may be a situation in which the relationship between membrane life energy and power is based on a first relationship between a coolant temperature of a fuel cell power device and power generated by the fuel cell power device and a second relationship between the membrane life of the fuel cell power device and the coolant temperature of the fuel cell power device.

[0008] Another aspect of the present disclosure may be a scenario where the application power request is determined based on an average power usage of the hybrid powertrain system over a predetermined period of time.

[0009] Another aspect of the present disclosure can be a scenario wherein the controller is configured to direct the fuel cell output power to the high voltage battery when operating at an optimal membrane life power, wherein the application power request is less than the optimal membrane life power and the second power includes one of a minimum power or zero power generated by the fuel cell power device.

[0010] Another aspect of the present disclosure may be a scenario where the controller is configured to direct the fuel cell output power to the high voltage battery when operating at a second power, wherein the second power is greater than the application power request.

[0011] A method of operating a hybrid powertrain is disclosed herein. The method includes identifying an application power request for a hybrid powertrain, the hybrid powertrain including a high voltage battery, a fuel cell power device, and an electric drive unit, each of which is electrically connected to a high voltage bus. A relationship between the application power request and an optimal membrane life power for the fuel cell power device is determined. The fuel cell power device is directed to operate between a first power associated with the optimal membrane life power and a second power, wherein the application power request is at a power level between the optimal membrane life power and the second power.

[0012] Another aspect of the present disclosure may be a case where the first power is within a predetermined range including an optimal membrane lifetime power, and the optimal membrane lifetime power is determined based on a function of power generated by a fuel cell power device and membrane lifetime energy of the fuel cell power device.

[0013] Another aspect of the present disclosure may be a case where the optimum membrane lifetime power corresponds to optimum electric power that produces maximum membrane lifetime energy, and the membrane lifetime energy is determined based on a relationship between the electric power and the membrane lifetime.

[0014] Another aspect of the present disclosure may be a scenario where application power requests are analyzed over a period of time to determine when to operate between an optimal membrane lifetime power and a second power.

[0015] Another aspect of the present disclosure may include directing power generated by the fuel cell to the high voltage battery when the application power request is less than the optimal membrane life power and the second power comprises one of a minimum power or zero power generated by the fuel cell power device.

[0016] Another aspect of the present disclosure may include directing power generated by the fuel cell to the high voltage battery when the application power request is greater than the optimal membrane life power and the second power comprises one of a minimum power or zero power generated by the fuel cell power device.

[0017] Another aspect of the present disclosure may be a scenario where the time to operate between the optimum membrane lifetime power and the second power is determined based on a battery capacity associated with an application power request.

[0018] Another aspect of the present disclosure may include charging the high voltage battery with an external power source.

[0019] A method for operating a hybrid power system is disclosed herein. The method includes identifying an application power request for a hybrid power system, the hybrid power system including a high-voltage battery, a fuel cell power device, and an electric drive unit, each of which is electrically connected to a high-voltage bus. Determine a relationship between the application power request and an optimal membrane life power of the fuel cell power device. Determine the optimal membrane life power based on a function of the power generated by the fuel cell power device and the membrane life energy of the fuel cell power device. Direct the fuel cell power device to operate between the optimal membrane life power and a second power. The application power request is at a power level between a first power and a second power associated with the optimal membrane life power. Direct excess power generated by the fuel cell power device to the high-voltage battery.

[0020] Another aspect of the present disclosure may be a scenario where the time to operate between the optimum membrane lifetime power and the second power is determined based on a battery capacity associated with an application power request.

[0021] The present invention may also include the following technical solutions:

[0022] 1. A hybrid power system comprising:

[0023] High voltage bus;

[0024] a high voltage battery electrically connected to the high voltage bus;

[0025] a fuel cell power device electrically connected to the high voltage bus;

[0026] a drive unit electrically connected to the high voltage bus; and

[0027] A controller electrically connected to the drive unit, the fuel cell power device, and the high voltage battery; the controller being configured to:

[0028] identifying an application power request of a drive unit;

[0029] determining a relationship between an application power request and an optimum membrane life power for a fuel cell power device; and

[0030] The fuel cell power plant is directed to operate between a first power associated with an optimal membrane lifetime power and a second power, wherein the application power request is at a power level between the optimal membrane lifetime power and the second power.

[0031] 2. A hybrid power system according to Technical Solution 1, wherein the first power is within a predetermined range including an optimal membrane life power, and the optimal membrane life power is determined based on a function of the electric power generated by the fuel cell power device and the membrane life energy of the fuel cell power device.

[0032] 3. A hybrid power system according to Technical Solution 2, wherein the optimal membrane life power corresponds to the optimal electricity for generating optimal membrane life energy.

[0033] 4. A hybrid power system according to Technical Solution 3, wherein the optimal membrane life energy is determined based on the relationship between membrane life and electric power.

[0034] 5. A hybrid power system according to technical solution 4, wherein the membrane life energy is determined by multiplying the membrane life of the fuel cell power device by the power generated within the membrane life.

[0035] 6. A hybrid power system according to Technical Solution 4, wherein the relationship between the membrane life energy and the electric power is based on a first relationship between the coolant temperature of the fuel cell power device and the electric power generated by the fuel cell power device and a second relationship between the membrane life of the fuel cell power device and the coolant temperature of the fuel cell power device.

[0036] 7. A hybrid power system according to technical solution 1, wherein the application power request is determined based on an average power usage of the hybrid power system within a predetermined time period.

[0037] 8. A hybrid power system according to technical solution 1, wherein the controller is configured to direct the fuel cell output power to the high-voltage battery when operating at optimal membrane life power, wherein the applied power request is less than the optimal membrane life power, and the second power includes one of the minimum power or zero power generated by the fuel cell power device.

[0038] 9. A hybrid power system according to technical solution 1, wherein the controller is configured to direct the fuel cell output power to the high-voltage battery when operating at a second power, wherein the second power is greater than the application power request.

[0039] 10. A method of operating a hybrid powertrain system, the method comprising:

[0040] identifying an applied power request of a hybrid powertrain system, wherein the hybrid powertrain system includes a high voltage battery, a fuel cell power plant, and an electric drive unit, each electrically connected to a high voltage bus;

[0041] determining a relationship between an application power request and an optimum membrane life power for a fuel cell power device; and

[0042] The fuel cell power plant is directed to operate between a first power associated with an optimal membrane lifetime power and a second power, wherein the application power request is at a power level between the optimal membrane lifetime power and the second power.

[0043] 11. A method according to technical solution 10, wherein the first power is within a predetermined range including an optimal membrane life power, and the optimal membrane life power is determined based on a function of the electric power generated by the fuel cell power device and the membrane life energy of the fuel cell power device.

[0044] 12. A method according to technical solution 11, wherein the optimal membrane life power corresponds to the optimal electricity that produces the maximum membrane life energy, and the membrane life energy is determined based on the relationship between electricity and membrane life.

[0045] 13. A method according to technical solution 12, wherein application power requests are analyzed over a period of time to determine when to operate between the optimal membrane life power and the second power.

[0046] 14. The method according to technical solution 10 includes directing the power generated by the fuel cell to the high-voltage battery when the applied power request is less than the optimal membrane life power and the second power includes one of the minimum power or zero power generated by the fuel cell power device.

[0047] 15. The method according to technical solution 10 includes directing the power generated by the fuel cell to the high-voltage battery when the applied power request is greater than the optimal membrane life power and the second power includes one of the minimum power or zero power generated by the fuel cell power device.

[0048] 16. A method according to technical solution 10, wherein the time of operation between the optimal membrane life power and the second power is determined based on the battery capacity associated with the application power request.

[0049] 17. The method according to technical solution 10 includes charging the high-voltage battery with an external power source.

[0050] 18. A method of operating a hybrid powertrain system, the method comprising:

[0051] identifying an applied power request of a hybrid powertrain system, wherein the hybrid powertrain system includes a high voltage battery, a fuel cell power plant, and an electric drive unit, each electrically connected to a high voltage bus;

[0052] determining a relationship between the application power request and an optimal membrane lifetime power for the fuel cell power device, wherein the optimal membrane lifetime power is determined based on a function of the electrical power generated by the fuel cell power device and a membrane lifetime energy of the fuel cell power device; and

[0053] directing the fuel cell power device to operate between a first power associated with an optimal membrane lifetime power and a second power, wherein the application power request is at a power level between the optimal membrane lifetime power and the second power; and

[0054] Excess power generated by the fuel cell power plant is directed to the high voltage battery.

[0055] 19. A method according to technical solution 18, wherein the first power is within a predetermined range including an optimal membrane life power, and the optimal membrane life power is determined based on a function of the electric power generated by the fuel cell power device and the membrane life energy of the fuel cell power device.

[0056] 20. A method according to technical solution 18, wherein the time of operation between the optimal membrane life power and the second power is determined based on the battery capacity associated with the application power request. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] One or more embodiments will now be described, by way of example, with reference to the accompanying drawings, in which:

[0058] Figure 1 Elements of the architecture of a torque generative system according to the present disclosure are schematically illustrated, the torque generative system including a fuel cell power plant, a high voltage battery, an electric drive unit, and an associated controller.

[0059] Figure 2 An example performance characterization of a fuel cell power plant is illustrated in graphical form, showing the non-linear relationship between power and temperature.

[0060] Figure 3 Another example performance characterization of a fuel cell power device is illustrated in graphical form, showing the non-linear relationship between temperature and membrane life.

[0061] Figure 4 A method of determining a third performance characteristic and a fourth performance characteristic of a fuel cell power plant is illustrated in graphical form.

[0062] Figure 5 A third performance characterization and a fourth performance characterization of a fuel cell power plant in separate non-linear relationships are graphically illustrated.

[0063] Figure 6 A method of operating a fuel cell power plant is illustrated.

[0064] Fig. 7A The power output of the fuel cell power plant when the application power request is less than the optimum membrane life power is graphically illustrated.

[0065] Figure 7B A diagram showing the high voltage battery and Fig. 7A The power output of a fuel cell power device is related to the state of charge.

[0066] Fig. 8A The power output of the fuel cell power plant when the application power request is greater than the optimum membrane life power is graphically illustrated.

[0067] Figure 8B A diagram showing the high voltage battery and Fig. 8A The power output of a fuel cell power device is related to the state of charge. DETAILED DESCRIPTION

[0068] The components of the disclosed embodiments as described and illustrated herein may be arranged and designed in a variety of different configurations. Therefore, the following detailed description is not intended to limit the scope of the disclosure claimed for protection, but merely represents possible embodiments thereof. In addition, although many specific details are set forth in the following description in order to provide a thorough understanding of the embodiments disclosed herein, some embodiments may be practiced without some of these details. In addition, for the purpose of clarity, certain technical materials understood in the relevant art are not described in detail to avoid unnecessarily obscuring the disclosure. In addition, the disclosure as illustrated and described herein may be practiced in the absence of elements not specifically disclosed herein.

[0069] The following detailed description is exemplary in nature and is not intended to limit application and use. In addition, it is not intended to be limited by any express or implied theory presented in this article. Throughout the drawings, corresponding reference numerals indicate the same or corresponding parts and features. As used herein, the term "system" refers to a combination or collection of mechanical and electrical hardware, software, firmware, electronic control components, processing logic and / or processor devices, which include, individually or in combination, but are not limited to: application-specific integrated circuits (ASICs), electronic circuits, processors (shared, dedicated or grouped) that execute one or more software or firmware programs, memories for containing software or firmware instructions, combinational logic circuits and / or other suitable components that provide the described functions.

[0070] Figure 1Consistent with the embodiments disclosed herein, elements of the architecture of a torque generation system 100 are schematically illustrated, the torque generation system 100 including a single or array of (one or more) fuel cell power devices 20 22, a high voltage battery 10, an electric drive unit 50, an auxiliary power unit 60, and a controller 70. The torque generation system 100 is controllable to generate mechanical torque in response to a power request, where, as a non-limiting example, the power request may include an output torque request, an operator torque request, etc. The (one or more) fuel cell power devices 20 and the high voltage battery 10 are electrically connected to a high voltage power distribution system 30 via a high voltage bus 25 to supply power to the electric drive unit 50. The (one or more) fuel cell power devices 20 and the high voltage battery 10 may be employed as a DC power source for the electric drive unit 50. In one embodiment, the electric drive unit 50 may be an electric machine that may be employed on a mobile platform, i.e., a vehicle for providing traction power, and may be in the form of a commercial vehicle, an industrial vehicle, an agricultural vehicle, a passenger vehicle, an aircraft, a ship, a rail vehicle, an all-terrain vehicle, a personal mobility device, a robot, and the like, to achieve the purposes of the present disclosure. Alternatively, the electric drive unit 50 may be provided in non-vehicle applications, such as for stationary power generation, portable power generation, electronics, remote weather station operations, communication centers, etc. A single fuel cell power device 20 is indicated by a solid line, and an array 22 of fuel cell power devices 20 is indicated by a dashed line. Figure 2 Details related to the performance characterization of the fuel cell power device(s) 20 are discussed. Any number of fuel cell power devices 20 may be employed based on the specific requirements of the system, for example, including two, three, four, or more fuel cell power devices 20. As a non-limiting example, some embodiments are employing up to twenty or more fuel cell power devices 20, such as on a train locomotive.

[0071] In one embodiment, the fuel cell power device(s) 20 and the high voltage battery 10 cooperate to supply power to the electric drive unit 50, wherein the controller 70 operates the torque generating system 100 and the high voltage battery 10 in a charge depletion mode during travel, such as when the torque generating system 100 is employed on a vehicle, and a route planning and navigation routine is employed, such as user pattern learning, driver pattern input, navigation route input, etc. In one embodiment, the fuel cell power device(s) 20 and the high voltage battery 10 cooperate to supply power to the electric drive unit 50, wherein the controller 70 operates the torque generating system 100 and the high voltage battery 10 in a charge sustaining mode during travel when the torque generating system 100 is employed on a vehicle. The controller 70 may also optimize for route changes and customer inputs when operating through the charge sustaining mode and the charge depletion mode, or vice versa.

[0072] In one embodiment, the electric drive unit 50 includes a rotary motor that acts as an electric traction motor of a system having at least a partial electric transmission system and is coupled to a drive wheel via a transmission system. Non-limiting examples of rotary motors may include permanent magnet DC motors, AC motors, DC generators, AC generators, eddy current clutches, eddy current brakes, rotary converters, hysteresis dynamometers, transformers, and the like. The motor torque generated by the rotary motor may be used to propel the vehicle and / or perform other electrochemical functions. The rotary motor may also be controlled to react torque to generate electricity, such as for regenerative braking. The electric drive unit 50 may include a single motor that is connected to the wheel via a transmission system when used on the vehicle. Alternatively, the electric drive unit 50 may include multiple motors that are connected to multiple wheels via one or more transmission system devices.

[0073] In one embodiment, each fuel cell power device 20 includes a plurality of polymer electrolyte membrane fuel cells (PEMFC), and includes a cathode, an anode and an electrolyte. The anode system may include a single injector system or a multi-injector system, which is fluidically coupled to the anode and is arranged to controllably supply pressurized hydrogen from a hydrogen tank to the inlet of the anode. Each fuel cell power device 20 may also include an air supply system, which includes an air inlet and an exhaust outlet, and is arranged to supply and control the airflow to the cathode. An electrolyte (e.g., a polymer electrolyte membrane) is disposed between the cathode and the anode. Further, the fuel cell 20 may be formed by one or more membrane electrode assemblies (MEAs), which include a cathode, an anode, a plurality of flow plates, a catalyst, and a plurality of gas diffusion layers.

[0074] During operation of the fuel cell power plant 20, the hydrogen (H 2 ) and oxygen (O 2 ) can be converted into electrical energy. 2 ) can enter the anode and be catalytically split into protons (H + ) and electron (e - ). Proton (H + ) can penetrate through the electrolyte to the cathode, and the electrons (e - ) may not permeate the electrolyte, but may instead travel along an external load circuit to the cathode to produce a fuel cell power output or current. 2 ) and nitrogen (N 2 )) can enter the cathode and interact with the protons (H + ) and electrons (e -) reaction and form by-products such as water (H 2 O) and heat. The heat can be removed through the exhaust gas and / or coolant of the fuel cell. Water (H 2 O) can travel through the electrolyte to the anode and can be collected in a sump. Each (one or more) fuel cell power device 20 exhibits a reference Figure 2 The nonlinear power-temperature relationship is described.

[0075] The controller 70 includes executable control routines for operating the torque generating system 100 in the method 500 and is referred to herein as Figure 6 In one embodiment, the torque generation system 100 includes a high voltage battery 10 and a single fuel cell power device 20. Alternatively, in one embodiment, the torque generation system 100 includes a high voltage battery 10, a fuel cell power device 20, and a second one of the fuel cell power devices 20.

[0076] Figure 2 The reference is shown in a diagram Figure 1 A performance characterization 200 of an embodiment of a fuel cell power device 20 is described. The performance characterization 200 may be described with respect to power 201 on the horizontal axis and temperature of the fuel cell power device 20 on the vertical axis, wherein a non-linear power-temperature relationship 210 is illustrated. The non-linear power-temperature relationship 210 of the fuel cell power device 20 may occur as a result of system optimization, material selection, design trade-offs, etc. during product development that affect performance, durability, and robustness to achieve power goals.

[0077] Power 201 may be a quantitative measure of the net power output from the fuel cell power plant 20 and ranges between a minimum or zero power output 202 and a maximum power output 203. The maximum power output 203 indicates the maximum power output that the fuel cell power plant 20 is capable of producing.

[0078] The temperature 205 of the fuel cell power device 20 is a quantitative measure of a temperature associated with the operation of the fuel cell power device 20, such as a coolant inlet or outlet temperature or another parameter. The temperature 205 ranges between a low temperature 206 (e.g., ambient temperature) and a maximum temperature 207 (such as may occur when the fuel cell power device 20 is operating at maximum power output).

[0079] Figure 3 The reference is shown in a diagram Figure 1Another performance characterization 250 of an embodiment of a fuel cell power device 20 is described. The performance characterization 250 can be described with respect to the temperature 205 of the fuel cell power device 20 on the horizontal axis and the membrane life 254 on the left vertical axis, wherein a non-linear power-membrane life relationship 256 is illustrated. The non-linear power-membrane life relationship 256 of the fuel cell power device 20 can occur as a result of system optimization, material selection, design trade-offs, etc. during product development that affect performance, durability, and robustness to achieve power goals.

[0080] The membrane life 254 may be a measure of the operational life of a membrane in a fuel cell power device 20 based on operation at a given temperature 205 of the fuel cell power device 20. The temperature 205 of the fuel cell device ranges from a minimum 258 to a maximum 260. The membrane life 254 of the fuel cell power device 20 ranges between a maximum life 264 and a minimum membrane life 262. The maximum membrane life 254 corresponds to a lower temperature 205, and the minimum membrane life 262 corresponds to a higher temperature 205.

[0081] Figure 4 The diagram shows the Figure 1 A third performance characterization 350 of an embodiment of the fuel cell power device 20 is described. Figure 5 ) (such as power 201 to membrane life 254) and fourth performance characterization 400 ( Figure 5 ) (such as power 201 to membrane lifetime energy 404) method 300. The third performance characteristic 350 relates the first performance characteristic 200 to the second performance characteristic 250, and the fourth performance characteristic 400 is derived from the third performance characteristic 350. The third performance characteristic 350 relates the membrane lifetime 254 to the power 201 generated by the fuel cell power device 20. Figure 4 As shown in , the method 300 inputs a given power 201 into a first performance characterization 200 and outputs a corresponding temperature 205 for the given power 201 generated by the fuel cell power device 20. The corresponding temperature 205 is then input into a second performance characterization 250, which outputs a corresponding membrane life 254 for the fuel cell power device 20 at the given power 201.

[0082] Although the third and fourth performance characterizations utilize temperature as the primary independent variable in the present disclosure, the present disclosure can be extended to any membrane life model that is based on other independent operating parameters, such as humidity, pressure, or stoichiometry. In particular, the present disclosure relates the independent operating parameters to the power level in order to solve the optimal membrane life power that maximizes the life of the fuel cell power device. The optimal membrane life power associated with the maximum life can then be used as part of the hybrid control, as will be discussed in more detail below.

[0083] like Figure 5 As shown in , the third performance characterization 350 can then be expressed by a given power 201 (bottom axis in kilowatts) in terms of the membrane life 254 (left vertical axis in hours) of the fuel cell power device 20. The relationship for the third performance characterization 350 is nonlinear and is given by Figure 5 The line 358 shown in FIG.

[0084] Then, Figure 4 The method 300 multiplies the power 201 by the membrane life 254 to determine a fourth performance characterization 400 that provides a membrane life energy 404 for the fuel cell power device 20 based on the given power 201. The membrane life energy 404 defines the amount of energy that the fuel cell power device 20 can generate over its lifetime when operating at the given power 201. In the illustrated example, the membrane life energy 404 is represented in kilowatt-hours (kWh) along the right vertical axis, which is nonlinearly related to the line 402, where the given power 201 along the membrane life energy 404 is proportional to the membrane life energy 404. Figure 5 The bottom axis is expressed in kW.

[0085] In addition, if Figure 5 , the performance characterization 400 represented by line 402 illustrates the relationship between a given power 201 and a membrane life energy 404. The membrane life energy 404 includes a maximum value 406 or optimal membrane life energy, which corresponds to the optimal membrane life power of the fuel cell power device 20 over its lifetime at line 408. The maximum value 406 of the membrane life energy 404 corresponds to the optimal membrane life power (line 408) for the power 201 generated by the fuel cell power device 20, which will produce the maximum amount of lifetime energy generated by the fuel cell power device 20.

[0086] Figure 6 A method 500 of operating a fuel cell power device 20 is illustrated. In one example, the method 500 determines whether the application power requested for the fuel cell power device 20 is less than the optimal membrane life power 408 of the fuel cell power device 20 (box 502), as described above. In one example, the requested application power can be analyzed over a predetermined time period or determined based on a specific use of the fuel cell power device 20 (such as in a passenger vehicle, heavy equipment, or fixed equipment). The analysis can learn when the requested application power varies based on operation to further optimize power generation, and when to operate between the optimal membrane life power and a second power. The method 500 can also determine the requested application power by monitoring the requested application power over a predetermined length of time, creating an average application power requested by the system 100 over a predetermined time period.

[0087] When the requested application power (such as the requested average application power) is less than the optimal membrane life power 408, the fuel cell power device 20 operates between the optimal membrane life power level of the fuel cell power device 20 and the power lower limit (block 504). When operating at the optimal membrane life power level, the fuel cell power device 20 may operate at a first power within a predetermined range that includes the optimal membrane life or at a first power at the optimal membrane life. In the illustrated example, the power lower limit is lower than the requested application power and may include a minimum operating power of the fuel cell power device 20 and a zero output power of the fuel cell power device 20. In addition, the power lower limit may be selected based on thermal constraints, such as ambient temperature that may change the value of the power lower limit.

[0088] Fig. 7A is a graphical illustration 600 of the variation in power P generated by the fuel cell power plant 20 over time (t) during operation of the torque generating system 100 . Fig. 7A The diagram illustrates a use case when the requested application power is less than the optimal membrane life power of the fuel cell power device 20. In particular, line 610 illustrates the change in power output P of the fuel cell power device 20 over time (t) when operating between generating power at the optimal membrane life power 408 (at line 612) and generating power at the power lower limit (at line 614). In the illustrated example, the power lower limit is less than the requested application power. In addition, because the optimal membrane life power 408 is greater than the requested application power, the excess power generated when operating at the optimal membrane life power 408 is directed to charge the high voltage battery 10.

[0089] Figure 7B 7 is a graphical illustration 700 of the percentage of the state of charge ("SOC") of the high voltage battery 10 as a function of time (t) as indicated by line 710 during charging of the fuel cell power device 20 and depletion of the torque generating system 100. To increase the operating life of the high voltage battery 10, the high voltage battery 10 is operated between a predetermined upper SOC limit 712 and a predetermined lower SOC power limit 714. In one example, the upper SOC limit 712 corresponds to 80% SOC and the lower SOC power limit 714 corresponds to 20% SOC. The operating time of the high voltage battery 10 depends on the relative capacity of the high voltage battery 10 relative to the requested application power.

[0090] Once the SOC of the high voltage battery 10 reaches the upper limit 712 as shown by line 710, the fuel cell power device 20 reduces its power generation to the lower power limit 614 until the SOC of the high voltage battery 10 reaches the lower power limit 714. When the SOC of the high voltage battery 10 reaches the lower power limit 714, the fuel cell power device 20 is then directed to operate at the optimal membrane life power 612 until the SOC reaches the upper limit 712, or the requested application power has been reduced to zero. In addition, the fuel cell power device 20 switches between the upper power limit 612 and the lower power limit 614 when the SOC is at the upper or lower SOC limit to avoid cycling of the fuel cell power device 20.

[0091] Additionally, when the vehicle associated with the fuel cell power device 20 is not actively being used, the high voltage battery 10 can be charged by an external power source other than the fuel cell power device 20, such as a charging station. One feature of utilizing a charging source other than the fuel cell power device 20 is that the amount of power used to charge the high voltage battery 10 does not detract from the optimal membrane life energy 404 of the high voltage battery 10. Thus, the use of an external power source increases the overall life of the torque generation system 100 by sharing power generation with another source other than the fuel cell power device 20. The external power source can also charge the high voltage battery 10 at an optimal power level to reduce charging time.

[0092] Fig. 8A is a graphical illustration 800 of the variation in power P generated by the fuel cell power plant 20 over time (t) during operation of the torque generating system 100 . Fig. 8A A use case is illustrated when the requested application power is greater than the optimal membrane lifetime power (block 506). Specifically, line 810 illustrates the variation in power output P over time (t) when the fuel cell power device 20 operates between generating power at the optimal membrane lifetime power (at line 812) and generating power at a power cap (at line 814) greater than the requested application power (block 508). In the illustrated example, the power cap 814 may be selected based on thermal constraints, such as ambient temperature that may change the value of the power cap 814.

[0093] Figure 8B900 is a graphical illustration of the percentage of the state of charge (“SOC”) of the high voltage battery 10 as indicated by line 810 over time (t) during the charging of the fuel cell power device 20 and the depletion of the torque generating system 100. In order to improve the operating life of the high voltage battery 10, the high voltage battery 10 is operated between a predetermined SOC upper limit 912 and a predetermined SOC power lower limit 814. In one example, the SOC upper limit 912 corresponds to 80% SOC, and the SOC power lower limit 914 corresponds to 20% SOC. Once the SOC of the high voltage battery 10 reaches the upper limit 912 as indicated by line 910, the fuel cell power device 20 reduces its power generation to the optimal membrane life power (at line 812) until the SOC of the high voltage battery 10 reaches the SOC power lower limit 914. When the SOC of the high voltage battery 10 reaches the SOC power lower limit 914, the fuel cell power device 20 is then directed to operate at the power upper limit 814 until the SOC reaches the upper limit 912, or the requested application power is reduced to zero.

[0094] In addition, the power output change of the fuel cell power device 20 is controlled to a rate that reduces potential damage to the electrodes. In addition, the method 500 can return to box 502 to determine whether the applied power has changed to determine whether the method should continue to box 504 or 506. If the high voltage battery 10 is no longer able to provide power, the fuel cell power device 20 can change from the optimal membrane life energy.

[0095] The terms "a" and "an" do not indicate a limitation of quantity, but rather indicate the presence of at least one of the referenced items. The term "or" means "and / or" unless the context clearly indicates otherwise. References throughout the specification to "aspects" mean that a particular element (e.g., feature, structure, step, or characterization) described in conjunction with an aspect is included in at least one aspect described herein, and may or may not be present in other aspects. Furthermore, it will be understood that the described elements may be combined in any suitable manner in the various aspects.

[0096] When an element (such as a layer, film, region, or substrate) is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements present.

[0097] Unless specified to the contrary herein, the test standard is the most recent standard in effect as of the filing date of this application, or, if priority is claimed, the filing date of the earliest priority application in which the test standard appears.

[0098] Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0099] Although the above disclosure has been described with reference to exemplary embodiments, it will be appreciated by those skilled in the art that various changes may be made and elements thereof may be replaced with equivalents without departing from its scope. In addition, many modifications may be made to adapt specific situations or materials to the teachings of the present disclosure without departing from its scope. Therefore, the present disclosure is not intended to be limited to the specific embodiments disclosed, but will include embodiments falling within its scope.

Claims

1. A hybrid power system, comprising: High voltage bus; a high voltage battery electrically connected to the high voltage bus; a fuel cell power device electrically connected to the high voltage bus; a drive unit electrically connected to the high voltage bus; as well as A controller electrically connected to the drive unit, the fuel cell power device, and the high voltage battery; the controller being configured to: identifying an application power request of a drive unit; determining a relationship between an application power request and an optimum membrane life power for a fuel cell power device; and The fuel cell power plant is directed to operate between a first power associated with an optimal membrane lifetime power and a second power, wherein the application power request is at a power level between the optimal membrane lifetime power and the second power.

2. The hybrid power system according to claim 1, wherein: The first power is within a predetermined range including an optimal membrane lifetime power, and the optimal membrane lifetime power is determined based on a function of electric power generated by the fuel cell power device and a membrane lifetime energy of the fuel cell power device.

3. The hybrid power system according to claim 2, wherein: The optimum membrane lifetime power corresponds to optimum electrical power for generating optimum membrane lifetime energy.

4. The hybrid power system according to claim 3, wherein: The optimum membrane lifetime energy is determined based on the relationship between membrane lifetime and power.

5. The hybrid power system according to claim 4, wherein: The membrane lifetime energy is determined by multiplying the membrane lifetime of the fuel cell power device by the electrical power generated over the membrane lifetime.

6. The hybrid power system according to claim 4, wherein: The relationship between membrane life energy and power is based on a first relationship between a coolant temperature of a fuel cell power plant and power generated by the fuel cell power plant and a second relationship between a membrane life of the fuel cell power plant and a coolant temperature of the fuel cell power plant.

7. The hybrid power system according to claim 1, wherein: The apply power request is determined based on an average power usage of the hybrid powertrain system over a predetermined period of time.

8. The hybrid power system according to claim 1, wherein: The controller is configured to direct the fuel cell output power to the high voltage battery when operating at an optimal membrane life power, wherein the application power request is less than the optimal membrane life power and the second power comprises one of a minimum power or zero power generated by the fuel cell power device.

9. The hybrid power system according to claim 1, wherein: The controller is configured to direct the fuel cell output power to the high voltage battery when operating at a second power, wherein the second power is greater than the application power request.

10. A method of operating a hybrid powertrain system, the method comprising: identifying an applied power request of a hybrid powertrain system, wherein the hybrid powertrain system includes a high voltage battery, a fuel cell power plant, and an electric drive unit, each electrically connected to a high voltage bus; determining a relationship between an application power request and an optimum membrane life power for a fuel cell power device; and The fuel cell power plant is directed to operate between a first power associated with an optimal membrane lifetime power and a second power, wherein the application power request is at a power level between the optimal membrane lifetime power and the second power.

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