Method and system for controlling fuel cell electric vehicle in power saving mode

Abstract

The present disclosure provides a method and system for controlling a fuel cell electric vehicle in a power saving mode. During some operations, when the FCEV is in a parked state and power demand is low, a fuel cell system of the FCEV operates in a voltage suppression mode to reduce wear of the fuel cell system. However, in the voltage suppression mode, liquid water may accumulate in the fuel cell system due to the low flow of reaction gas that typically removes water. The water may inhibit reactant flow if the FCEV exits the park state and experiences high acceleration.

Description

[0001] Statement regarding federally sponsored research or development

[0002] This invention was completed with government support under contract number DE-EE0009858 granted by the U.S. Department of Energy. The government holds certain rights to this invention. Technical Field

[0003] This disclosure generally relates to a system or method for controlling the electricity generated by a fuel cell system in a fuel cell electric vehicle (FCEV). Background Technology

[0004] An FCEV includes one or more fuel cell stacks that provide electricity to propel the FCEV. A fuel cell stack is an electrochemical device that converts the chemical energy of hydrogen fuel and oxidant into electrical energy, with water as a byproduct. In some applications, FCEVs may also include high-voltage battery packs to provide power to propel the FCEV alone or in combination with fuel cell stacks.

[0005] When the FCEV is stopped and idling, it can operate under voltage suppression control to suppress or limit electrochemical reactions and constrain the degradation of the fuel cell stack. Summary of the Invention

[0006] In one form, this disclosure relates to a method for controlling a fuel cell electric vehicle (FCEV) having a fuel cell system. The method includes, for a power-saving mode, limiting the current draw of the fuel cell stack of the fuel cell system, and for the power-saving mode, performing at least one of the following: selectively supplying air to the fuel cell system to control the voltage of the fuel cell system, or selectively supplying air to an exhaust flow line to dilute the concentration of a fluid flowing therein.

[0007] In one form, this disclosure relates to a control system for a fuel cell electric vehicle (FCEV) having a fuel cell system. The control system includes a processor and a non-transitory computer-readable storage medium including programming instructions configured to cause the processor to implement methods for controlling the FCEV. The programming instructions include instructions for performing: limiting the current draw of the fuel cell stack of the fuel cell system for a power-saving mode of the fuel cell system; and for the power-saving mode, performing at least one of: selectively supplying air to the fuel cell system to control the voltage of the fuel cell system, or selectively supplying air to the exhaust flow line of the FCEV to dilute the concentration of fluid flowing therein. Attached Figure Description

[0008] Figure 1An exemplary fuel cell electric vehicle (FCEV) is shown;

[0009] Figure 2 This is an exemplary block diagram of a fuel cell system for FCEVs;

[0010] Figure 3 This is an exemplary block diagram of stacked battery voltage suppression control; and

[0011] Figure 4 This is a flowchart of an exemplary power-saving routine for FCEVs. Detailed Implementation

[0012] Detailed embodiments of the invention are disclosed herein as needed; however, it should be understood that the disclosed embodiments are merely examples of the invention that can be embodied in various forms and alternative forms. The drawings are not necessarily drawn to scale; some features may be enlarged or minimized to show details of specific components. Therefore, the specific structural and functional details disclosed herein are not to be construed as limiting, but only as representative bases for teaching those skilled in the art to employ the invention in various ways.

[0013] During certain operations, when the FCEV is parked and power demand is low, the FCEV's fuel cell system operates in voltage suppression mode to reduce wear on the fuel cell system. However, in voltage suppression mode, liquid water may accumulate in the fuel cell system due to the low flow rate of reactant gases, which typically remove water. If the FCEV exits the parked state and experiences high acceleration, the water can inhibit reactant flow, which can lead to poor performance or shutdown of the fuel cell system.

[0014] In one form, this disclosure relates to a method / system for controlling an FCEV in a voltage suppression mode or a power-saving mode to address not only water buildup in the fuel cell system but also other potential challenges such as, but not limited to, low pressure in the fuel cell system and exhaust H2 concentration levels. In a non-limiting example, the system of this disclosure is configured to selectively supply reactants (e.g., air) to the fuel cell system to control the voltage of the fuel cell system and / or selectively supply reactants (e.g., air) to the exhaust flow line of the FCEV to dilute the H2 concentration of the fluid flowing therein. Utilizing the additional control techniques described herein for power-saving modes, the system of this disclosure can alleviate problems associated with operating an FCEV at low power.

[0015] refer to Figure 1An exemplary fuel cell electric vehicle (FCEV) 100 includes a fuel cell system (FCS) 102 and a battery pack 104 (e.g., a traction battery) that form at least a portion of an electrical system 106 of the FCEV 100. The FCS 102 and battery pack 104 can operate independently to provide electrical power to propel the FCEV 100 via a drive system 110. Figure 1 In the diagram, dashed lines represent power lines used for high electrical power, while solid lines indicate control signals or data communication.

[0016] In one embodiment, among other components, the drive system 110 includes a powertrain 112 having one or more electric motors (EMs) 114 capable of operating as both motors and generators. As motors, the EMs 114, mechanically connected to a transmission (not shown), provide propulsion and deceleration capabilities to the FCEV 100. The EMs 114, acting as generators, can recover energy that would typically be lost as heat in a friction braking system (not shown) to recharge the battery pack 104.

[0017] FCS102 includes one or more fuel cell stacks, wherein the fuel cell stack includes multiple fuel cells electrically connected in series. See below for reference. Figure 2 Further described, FCS102 converts hydrogen fuel into electrical energy, which is used by EM 114 to propel FCEV 100 and / or to recharge battery pack 104. In one form, FCS102 includes one or more sensors 105 configured to detect various operating characteristics of FCS102, such as, but not limited to, detecting voltage, current, H2 concentration in exhaust byproducts, pressure, and / or temperature.

[0018] The FCS102 and battery pack 104 can be electrically connected to the EM 114 via a power electronic module (PEM) 116, which may include an inverter, a DC-DC converter, and other components. In one configuration, the PEM 116 is configured to transfer electrical energy from the FCS102 to the EM 114. For example, the FCS102 may provide DC power, while the EM 114 may require three-phase AC power to operate. The PEM 116 can convert the electrical energy from the FCS102 into a form compatible with operating the EM 114 or, in some applications, charging the battery pack 104. In this way, the FCEV 100 can be configured to use electrical energy from the FCS102 for propulsion.

[0019] Battery pack 104 stores electrical energy for use by EM 114 to propel FCEV 100. Battery pack 104 can also be electrically connected to EM 114 via PEM 116. PEM 116 provides the ability to transfer electrical energy bidirectionally between battery pack 104 and EM 114. In this way, FCEV 100 can also be configured to be propelled by using battery pack 104 alone or in combination with FCS 102. Furthermore, in regenerative mode, PEM 116 can convert AC electrical energy from EM 114, which acts as a generator, into DC electrical energy compatible with battery pack 104.

[0020] In one configuration, the electrical system 106 is connected to the drive system and PEM 116 via a contactor 117 to electrically connect and disconnect the electrical system 106 from other vehicle components. Although one contactor 117 is shown, one or more contactors may be used. Additionally, the contactor 117 may be positioned in other suitable locations, such as, but not limited to, integration with the PEM 116.

[0021] refer to Figure 2 An exemplary FCS 102 includes a fuel cell stack 202, a hydrogen supply-return system (hydrogen SRS) 204 for supplying hydrogen fuel to the anode side 210 of the fuel cell stack 202, and an air supply-return system (air SRS) 206 for supplying air to the cathode side 212 of the fuel cell stack 202. The fuel cell stack 202 includes a plurality of fuel cells arranged in series and having an anode member for defining the anode side 210 and a cathode member for defining the cathode side 212. Although one fuel cell stack 202 is shown, for simplicity, the FCS 102 may include more than one fuel cell stack 202.

[0022] In one form, the hydrogen SRS 204 includes a hydrogen tank 214 for storing hydrogen fuel, a fuel control valve 216 (e.g., a hydrogen pressure control valve) operable to control the fuel flow from the tank 214, and an injector valve 218 operable to supply fuel to the fuel cell stack 202. In some applications, an anode supply manifold 220 supplies fuel from the injector valve 218 to the fuel cell stack 202. It will be readily understood that the hydrogen SRS 204 may include additional components, such as, but not limited to, a sensor device as part of sensor 105, arranged at the tank 214 and along the fuel line fluidly connecting the tank 214 to the fuel cell stack 202, to measure fuel characteristics (e.g., fuel characteristics include temperature and / or pressure). In one form, the hydrogen SRS 204 may also include conduits and other components, as well as those components described herein for defining fuel flow lines at least from the tank 214 to the fuel cell stack and to the exhaust line 249.

[0023] In one embodiment, the air SRS 206 includes a compressor 222 for drawing in and supplying air to the fuel cell stack 202 via an intercooler 224 to cool the air from the compressor 222. In some aspects, a humidifier 226 is provided to regulate the air supplied to and returned from the fuel cell stack 202. A bypass valve 228 may be provided to bypass the humidifier 226, allowing air from the intercooler 224 to flow to the fuel cell stack 202. In other variations, a cathode supply manifold 230 supplies air to the cathode side 212 of the fuel cell stack 202. The air SRS 206 may include other components, such as, but not limited to, an air filter 232 upstream of the compressor 222, and one or more sensor devices as part of sensor 105, arranged between the inlet drawing air into the air SRS 206 and the cathode supply manifold 230 (e.g., temperature and / or pressure sensors). In one form, the air SRS204 may also include ducts and other components, as well as those components described herein for defining the air-cathode flow line from at least the intake air inlet to the compressor to the fuel cell stack and to the exhaust line 249.

[0024] In operation, hydrogen is injected into the anode side 210, and air is pushed towards the cathode side 212. At the anode side 210, hydrogen molecules split into electrons and protons. Protons pass through the electrolyte section, and electrons flow through the circuitry that generates current and heat. At the cathode side 212, protons, electrons, and oxygen combine to form a water byproduct. Arrow 240 provides an exemplary fuel flow along the hydrogen SRS 204 to the fuel cell stack 202, and arrow 242 provides an exemplary air flow along the air SRS 206 to the fuel cell stack 202.

[0025] Byproducts from the anode side 210 are directed from the fuel cell stack 202 to the exhaust line 249 via the return manifold 244 and the extraction valve 248. Some byproducts from the anode side 210 are directed to the anode supply manifold 220 via the recirculation line 245. Recirculation can be driven by a recirculation blower (not shown) or by an injector 219. In addition to byproducts, the return manifold 244 is also configured to remove residual gases and water supplied at the return manifold 244. The flow of byproducts / additional hydrogen along the hydrogen SRS 204 to the exhaust port is indicated by arrow 250.

[0026] Byproducts from the cathode side 212 are directed from the fuel cell stack 202 to the exhaust line 249 via the return manifold 246. In addition to the return manifold 246, the air SRS 206 may also include an electronic throttle body 234. The flow of byproducts / air in the air SRS 206 is indicated by arrow 252.

[0027] As described above, fuel cell stack 202 comprises fuel cells connected in series. The voltage of each fuel cell can depend on various factors, including but not limited to cell temperature, membrane humidity, pressure, anode hydrogen quantity, air flow rate, and / or the generated current. In a non-limiting example, the voltage of fuel cell stack 202 can be the sum of the voltages of all the fuel cells. Similarly, each fuel cell can have the same current, and the current of fuel cell stack 202 can be inferred to be the same as the current of each fuel cell. Therefore, the power provided by fuel cell stack 202 can be equal to the voltage of fuel cell stack 202 multiplied by the current of fuel cell stack 202.

[0028] Continue to refer to Figure 1 To control the temperature of FCS102, FCEV 100 also includes an FCS thermal system 119 configured to control the temperature of FCS102. In a non-limiting example, coolant may be supplied to and circulate around the fuel cell stack 202 and other components to absorb heat from the components and return it to the thermal system 119. In one form, the FCS thermal system 119 may include sensors (not shown) for measuring coolant characteristics (e.g., temperature, pressure) of the coolant entering and leaving FCS102, which may be used to control FCS102, as further described below. Figure 1 In the image, the dashed lines indicate the coolant fluid lines.

[0029] In one embodiment, the drive system 110 includes a control system 118 having one or more controllers to control and monitor the operation of the FCS 102 and the battery pack 104. In a non-limiting example, the control system 118 is configured to include a drive module 120 and a power-saving module (PCM) 122.

[0030] In one embodiment, drive module 120 determines drive demand based on, for example, the state of charge (SOC) of battery pack 104, the voltage and current of FCS 102, and the position of the brake pedal and / or accelerator pedal. Using a stored algorithm, drive module 120 determines the electrical force required to meet the drive demand (e.g., a power request) and controls FCS 102 and / or battery pack 104 to generate the required power. In a non-limiting example, control system 118 draws power from FCS 102, battery pack 104, or both FCS 102 and battery pack 104.

[0031] In one embodiment, drive module 120 is configured to detect a power-saving mode, also known as a voltage suppression mode, to cause PCM 122 to control FCS 102 to generate very little to no power. That is, sometimes FCEV 100 may not require high power, for example, to move FCEV 100, and therefore, a power-saving mode can be employed to limit wasted fuel use and / or fuel cell degradation. In a non-limiting example, drive module 120 detects a power-saving mode when FCEV 100 is parked or idling and the load demand of FCEV 100 remains low for a selected period of time (e.g., 10 seconds), which may occur when FCEV 100 is at a parking light or idling in traffic. In another example, drive module 120 detects a power-saving mode when the SOC of battery pack 104 is greater than or equal to an upper SOC threshold (e.g., 85% or 90%). In other words, the power from FCS102 can be used to charge battery pack 104, and if the SOC is high, battery pack 104 may reach or exceed manufacturing limits, potentially shortening the battery life of battery pack 104.

[0032] Once in power-saving mode, PCM 122 is configured to limit / limit the power output of fuel cell stack 202. In a non-limiting example, PCM 122 controls the flow of reactants (e.g., fuel and / or air) to fuel cell stack 202 to control the voltage of FCS 102 to a stack voltage threshold and / or limit the current drawn from fuel cell stack 202. PCM 122 is also configured to selectively supply air to the exhaust line, thereby diluting the concentration of the fluid flowing through it (e.g., diluting the H2 concentration). In one form, PCM 122 is configured to have contactor status control 130, stack voltage suppression (SCVS) control 132, exhaust H2 concentration (H2 concentration) control 134, and fuel cell refresh (FCR) control 136.

[0033] Contactor status control 130 is configured to hold contactor 117 in the closed position to electrically couple electrical system 106 to a load including drive system 110. With contactor 117 in the closed state, power can be drawn from electrical system 106 immediately upon exiting power-saving mode. In a non-limiting example, control system 118 is configured to detect when FCEV 100 is turned on or off based on an activation input (e.g., a user pressing a button associated with activating / deactivating FCEV 100). To turn FCEV 100 on, control system 118 closes contactor 117 via a power switch driver (not shown), thereby electrically coupling electrical system 106 to PEM 116. To turn FCEV 100 off, control system 118 opens contactor 117 via the power switch driver, thereby electrically decoupling electrical system 106 from PEM 116. In one form, once opened / closed, contactor 117 remains open / closed until driven again by the power switch driver. Therefore, during power-saving mode, the contactor status control 130 uses, for example, data from contactor 117 to detect the status of contactor 117, which provides data indicating the status of contactor 117. If contactor 117 is closed, the contactor status control 130 closes contactor 117 via the power switch driver.

[0034] SCVS control 132 is configured to control the voltage of fuel cell stack 202 or at least one group of cells of a plurality of cells in fuel cell stack 202, such that the voltage is provided at or between an upper and lower voltage range / threshold (e.g., FCS voltage threshold). Hereinafter, “cell voltage” (VCELL) refers to the voltage of the individual cells, and “stack voltage” (VSTACK) is the voltage of fuel cell stack 202. When the total power provided by fuel cell stack 202 is low due to, for example, a limited / no air supply, the stack voltage will be at or above the stack voltage threshold (e.g., above or at the DC-DC limit). SCVS control 132 suppresses or minimizes the maximum cell voltage by drawing a small amount of current and maintains the stack voltage by supplying air to fuel cell stack 202.

[0035] More specifically, in one form, the SCVS control 132 is configured to (1) control the current of the fuel cell stack 202 to control the maximum cell voltage to be less than or equal to a cell voltage threshold (e.g., V). maxCell,des (2) The voltage is set to, for example, 0.85V, and air is managed through the cathode side of the fuel cell stack 202 to control the stack voltage to a stack voltage threshold (e.g., V). stack,des (The compressor 222 is kept at a constant speed.) Reference Figure 3The SCVS control 132 can be visualized as two control loops including a Vcell control 302 and a Vstack control 304, which are related to control the voltage of the FCS 102, but different to provide two different control options.

[0036] Continue to refer to Figure 2 To control airflow through the fuel cell stack 202, the SCVS control 132 is configured to control the cathode throttle using at least one of the following: a cathode inlet valve (CBV inlet) (e.g., valve 260), a cathode outlet valve (CBV outlet) (e.g., valve 262), or a humidifier outlet valve (HOV) (e.g., valve 264) (collectively referred to as "cathode valves 260, 262, 264"). For example, the SCVS control 132 is configured to adjust the opening of one of the cathode valves 260, 262, 264, while the other two cathode valves remain constant at a larger opening. In one embodiment, the SCVS control 132 uses Algorithm 1 to determine the amount of current to be drawn and Algorithm 2 to determine the valve opening (θ). valve (It is a valve between 0-100%), where "I" nom " is the nominal current feedforward, which is a function of the maximum stack power (Pmax) and the stack voltage (Vstack), and "kp1" and "kp2" are positive constant gains. nom It may be small enough to keep the power low, but large enough to allow V maxCell Feedback Keep V maxCell Below V maxCell,des .

[0037] Algorithm 1: Current = I nom (Pmax, Vstack) + k p1 *(V maxCell -V maxCell,des )

[0038] Algorithm 2: θ valve =k p2 *(V stack,des -V stack )

[0039] fuel cell single cell terminal voltage (V) cellThe open-circuit voltage (OCV) is the sum of ohmic losses, activation losses, and concentration losses. These losses involve complex interactions of many variables, including but not limited to stack current, membrane humidity level, cathode pressure, O2 concentration, coolant temperature, and / or the lifetime of fuel cell stack 202. During the desired operating parameters of the energy-saving mode, where reactant is insufficient, the OCV may be sensitive to the reactant (O2) in the cathode. Losses are most sensitive and responsive to the stack current. For the desired operating parameters of the energy-saving mode, the stack voltage is suppressed to reduce the power of fuel cell stack 202, and the total stack voltage depends on how much p-value is present at the cathode of the cell. O2 .

[0040] In one configuration, the SCVS control 132 is configured to operate the compressor 222 at a constant speed setpoint, and the cathode valves 260, 262, and 264 are controlled to limit the mass air flow rate (MAF). The CBV inlet (e.g., valve 260), CBV outlet (e.g., valve 262), and HOV valve (e.g., valve 264) are arranged sequentially, with the minimum opening being the primary opening limiting the air flow rate. The SCVS control 132 is configured to control the air flow rate via p O2 The stack voltage is controlled, which has a relatively slow dynamic due to the manifold filling dynamics.

[0041] Exhaust H2 concentration control 134 is configured to monitor and control the H2 concentration level in exhaust line 249. That is, any residual hydrogen in the hydrogen SRS 204 is discharged through exhaust line 249, thereby increasing the hydrogen concentration. In a non-limiting example, the H2 concentration threshold level is selected based on standards issued by a government agency, such as, but not limited to, a hydrogen concentration of less than or equal to 4% when measured at a distance of 100 mm from the centerline of exhaust line 249 within a 3-second moving average window. Sensor 105 of FCS 102 may include means for measuring the amount of H2 supplied to exhaust line 249.

[0042] In one embodiment, to control the amount of H2 concentration, exhaust H2 concentration control 134 supplies air via a bypass flow path that bypasses pile 202 to dilute exhaust line 249. Figure 2 The H2 concentration in the fluid. For example, with bypass 268 open, air from intercooler 224 flows to exhaust line 249, thereby diluting the fluid flowing therein.

[0043] FCR control 136 is configured to periodically refresh FCS 102 by intermittently exiting power-saving mode. In one form, FCR control 136 detects that FCS 102 is in prolonged idling operation when at least one of the following is met: the duration of power suppression is greater than or equal to a prolonged power-saving threshold (e.g., 30 minutes); the temperature of the fuel stack coolant is less than or equal to a coolant operating threshold; the water level in FCS 102 is equal to or greater than a water threshold; and / or the oxygen (O2) level in the fuel cell is less than or equal to a cumulative fuel threshold. FCR control 136 may perform the refresh within a selected time period (e.g., 5 minutes) and / or if one or more thresholds are met (e.g., the temperature of the fuel stack coolant is above the coolant operating threshold, the water level is below the water threshold, and / or the oxygen level is greater than the cumulative fuel threshold).

[0044] When the FCEV 100 is in a power-saving mode (e.g., idling) for a period of time, water may accumulate in the fuel cell stack 202. Water may clog membrane pores and prevent reactants from reaching the catalyst, potentially leading to unstable operation. By exiting the power-saving mode, the FCR control 136 can draw more current to generate heat and increase the mass airflow to remove water from the fuel cell stack 202. Therefore, in one form, the FCR control 136 is configured to monitor the duration the FCEV 100 is in a power-saving mode (e.g., idling), and if it is greater than or equal to an idling time threshold (e.g., 30 minutes), the FCR control 136 operates the FCS 102 to initiate a chemical reaction in the fuel cell stack 202 to refresh the fuel cell stack.

[0045] In some variations, the FCR control 136 determines whether the temperature of the coolant returning to the thermal system 119 is less than or equal to a coolant temperature threshold. If so, the FCR control 136 refreshes the fuel cell stack 202 (e.g., supplies reactants (e.g., H2 and / or air) to the fuel cell stack 202). In another example, the FCR control determines whether the oxygen level in the fuel cell stack 202 is low by detecting when the voltage of the fuel cell stack 202 is less than or equal to a voltage threshold. If the minimum cell voltage drops too low, the FCR control 136 determines that the cell is lacking reactants (e.g., O2) and can replenish them by exiting the power-saving mode and supplying air to the fuel cell stack 202.

[0046] In some aspects, the FCR control 136 is configured to detect whether the water volume is equal to or greater than a water threshold, and if so, to reduce the amount of liquid water accumulating in the fuel cell stack 202. In a non-limiting example, water can be reduced by diverting airflow from the compressor 222 around the humidifier 226 using valve 228 and / or by reducing the coolant flow, or by increasing the coolant temperature by circulating the coolant through an electric heater provided with the thermal system 119 before supplying coolant to the fuel cell stack 202. In one form, battery flooding can be detected if the battery voltage oscillates aggressively via injector pulses.

[0047] In one configuration, PCM 122 can exit power-saving mode in various suitable ways, such as, but not limited to: pressing the accelerator pedal; requesting power equal to or greater than a selected power threshold (e.g., selected based on the nominal power required to operate EM 114); or FCEV 100 being turned off.

[0048] Although PCM 122 includes controls 130, 132, 134 and 136, PCM 122 may include one or more of the controls, and is not limited to including each of controls 130, 132, 134 and 136.

[0049] refer to Figure 4 When entering power-saving mode, the control system 118 provides and executes an exemplary power-saving routine 400. In a non-limiting example, the control system 118 controls the fuel cell system in power-saving mode in response to at least one of a power request being less than or equal to a power-saving threshold or a state of charge (SOC) of the battery pack 104 being greater than or equal to the SOC threshold.

[0050] At operation 402, system 118 determines whether contactor 117 is closed. If the contactor is not closed, then at operation 404, system 118 closes the contactor to electrically couple FCS 102 to powertrain 112 via PEM 116. In a non-limiting example, control system 118 may transmit a control signal to a power switch (not shown) associated with contactor 117 to close contactor 117.

[0051] At operation 406, system 118 determines whether the FCS voltage is within the voltage saving range, as described above in conjunction with SCVS control 132. In a non-limiting example, control system 118 determines whether the stack voltage's cell voltage is less than or equal to the corresponding FCS voltage threshold.

[0052] At operation 408, if the voltage of FCS102 is outside the saving range and specifically below the FCS voltage threshold, system 118 selectively supplies air to fuel cell stack 202 to control the voltage of FCS102. For example, system 118 provides a control signal to one or more of cathode valves 260, 262, 264 to at least partially open at least one of cathode valves 260, 262, 264.

[0053] At operation 410, system 118 determines whether the battery voltage is greater than or equal to a battery voltage threshold (e.g., a maximum battery voltage threshold). If so, system 118 draws additional current from fuel cell stack 202.

[0054] At operation 414, system 118 determines whether the exhaust gas concentration (e.g., H2 concentration) is higher than a threshold, as detailed above. If so, at operation 416, system 118 selectively supplies air to exhaust line 249 to dilute the concentration of the fluid flowing therein.

[0055] At operation 418, system 118 detects prolonged operation in power-saving mode. For example, prolonged operation in power-saving mode indicates at least one of the following: the temperature of the coolant used for FCS 102 is less than or equal to a temperature threshold, the amount of O2 in the fuel cell stack 202 is less than or equal to a reactant threshold, the amount of liquid water in the fuel cell stack 202 is greater than or equal to a water threshold, or the FCS 102 is controlled in power-saving mode for a period of time greater than or equal to a prolonged power-saving threshold.

[0056] If system 118 detects prolonged operation in power-saving mode, system 118 performs a refresh operation on fuel cell stack 202 at operation 420. In a non-limiting example, for the refresh operation, more current is drawn, the temperature of the coolant used in the thermal system may be increased to raise the temperature of fuel cell stack 202, and / or air drawn by compressor 222 bypasses humidifier 226 to limit the amount of water introduced into fuel cell stack 202.

[0057] After operation 418 or 420, system 118 repeats routine 400 until, for example, to exit power-saving mode to enter normal drive control or to shut down FCEV 100.

[0058] Routine 400 is merely one example of a power-saving mode and can be defined in various suitable ways. For example, Routine 400 may not include all the operations provided.

[0059] While exemplary embodiments have been described above, these embodiments are not intended to describe all possible forms of the invention. Rather, the terms used in this specification are descriptive rather than restrictive, and it should be understood that various changes can be made without departing from the spirit and scope of the invention. Furthermore, features of various embodiments can be combined to form other embodiments of the invention.

[0060] In this application, the term "module" may refer to, be part of, or include the following: application-specific integrated circuit (ASIC); digital, analog, or mixed analog / digital discrete circuit; digital, analog, or mixed analog / digital integrated circuit; composable logic circuit; field-programmable gate array (FPGA); processor circuitry (shared, dedicated, or grouped) that executes code (e.g., programming instructions); memory circuitry (shared, dedicated, or grouped) that stores code executed by the processor circuitry; other suitable hardware components that provide the described functionality; or combinations of some or all of the foregoing, such as in a system-on-a-chip.

[0061] The term memory is a subset of the term computer-readable medium. As used herein, the term computer-readable medium does not cover transient electrical or electromagnetic signals propagated through a medium (such as on a carrier wave); therefore, the term computer-readable medium can be considered tangible and non-transient. Non-limiting examples of non-transient tangible computer-readable media include non-volatile memory circuits (such as flash memory circuits, erasable programmable read-only memory circuits, or mask read-only circuits), volatile memory circuits (such as static random access memory circuits or dynamic random access memory circuits), magnetic storage media (such as analog magnetic tape or digital magnetic tape or hard disk drives), and optical storage media (such as USB, CD, DVD, or Blu-ray discs).

[0062] The apparatus and methods described in this application can be implemented, in part or in whole, by a dedicated computer created by configuring a general-purpose computer (e.g., a computing device) to perform one or more specific functions embodied in a computer program. Function blocks, flowchart components, and other elements described above serve as software specifications that can be translated into computer programs through the routine work of a technician or programmer.

[0063] The description in this disclosure is merely exemplary in nature, and therefore, variations without departing from the spirit and scope of this disclosure are intended to be made within its scope. Such variations should not be considered as departing from the spirit and scope of this disclosure.

[0064] According to the present invention, a method for controlling a fuel cell electric vehicle (FCEV) having a fuel cell system includes: limiting the current draw of the fuel cell stack of the fuel cell system for a power saving mode; and for the power saving mode, performing at least one of the following: selectively supplying air to the fuel cell system to control the voltage of the fuel cell system, or selectively supplying air to an exhaust flow line to dilute the concentration of a fluid flowing therein.

[0065] In one aspect of the invention, the method includes closing a contactor in response to the FCEV being turned on to electrically couple the fuel cell system to a load, wherein the fuel cell system remains electrically coupled to the fuel cell system for the energy-saving mode.

[0066] In one aspect of the invention, the method includes drawing additional current from the fuel cell system to generate electricity and exiting the power-saving mode in response to a power request equal to or greater than a selected power threshold.

[0067] In one aspect of the invention, the method includes generating power in response to detecting prolonged operation in the power-saving mode.

[0068] In one aspect of the invention, the long-term operation in the energy-saving mode is detected based on at least one of the following: the temperature of the coolant used in the fuel cell system is less than or equal to a temperature threshold, the amount of oxygen in the fuel cell stack is less than or equal to a threshold, the amount of liquid water in the fuel cell stack is greater than or equal to a water threshold, or the fuel cell system is controlled in the energy-saving mode for a period of time greater than or equal to a long-term saving threshold.

[0069] In one aspect of the invention, air is supplied to the fuel cell system in response to the fuel cell voltage being less than or equal to a fuel cell system voltage threshold to control the voltage of the fuel cell system.

[0070] In one aspect of the invention, the method includes, for the energy-saving mode, drawing current from the fuel cell stack in response to a fuel cell voltage greater than or equal to a maximum battery voltage threshold.

[0071] In one aspect of the invention, in order to selectively supply air to the fuel cell system to control the voltage of the fuel cell system, the method further includes at least partially opening at least one of a plurality of cathode valves provided along an air-cathode fluid line for supplying air to the cathode side of the fuel cell stack based on at least one of the voltage of the fuel cell stack or the voltage of one or more of the plurality of fuel cells forming the fuel cell stack.

[0072] In one aspect of the invention, the method includes controlling the fuel cell system in the energy-saving mode in response to at least one of a power request being less than or equal to a power-saving threshold or a state of charge (SOC) of the battery pack being greater than or equal to a SOC threshold.

[0073] According to the present invention, a control system for a fuel cell electric vehicle (FCEV) having a fuel cell system is provided, comprising: a processor; and a non-transitory computer-readable storage medium including programming instructions configured to cause the processor to implement a method for controlling the FCEV, wherein the programming instructions include instructions for performing: limiting current draw from the fuel cell stack of the fuel cell system for a power-saving mode of the fuel cell system; and for the power-saving mode, performing at least one of: selectively supplying air to the fuel cell system to control the voltage of the fuel cell system, or selectively supplying air to the exhaust flow line of the FCEV to dilute the concentration of fluid flowing therein.

[0074] According to an embodiment, the programming instructions further include instructions for closing a contactor to electrically couple the fuel cell system to a load in response to the FCEV being turned on, wherein the fuel cell system remains electrically coupled to the fuel cell system for the energy-saving mode.

[0075] According to an embodiment, the programming instructions also include instructions for drawing current from the fuel cell system to generate power and exiting the power-saving mode in response to a power request equal to or greater than a selected power threshold.

[0076] According to an embodiment, the programming instructions further include instructions for generating power in response to the detection of prolonged operation in the power-saving mode.

[0077] According to an embodiment, the long-term operation in the power-saving mode indicates at least one of the following: the temperature of the coolant used in the fuel cell system is less than or equal to a temperature threshold, the amount of liquid water in the fuel cell stack is greater than or equal to a threshold, the amount of oxygen in the fuel cell stack is less than or equal to a threshold, or the fuel cell system is controlled in the power-saving mode for a period of time greater than or equal to a long-term saving threshold.

[0078] According to an embodiment, air is supplied to the fuel cell system in response to the fuel cell voltage being less than or equal to a fuel cell system voltage threshold to control the voltage of the fuel cell system.

[0079] According to an embodiment, the programming instructions also include instructions for drawing current from the fuel cell stack in response to a fuel cell voltage greater than or equal to a maximum battery voltage threshold in the energy-saving mode.

[0080] According to an embodiment, in order to selectively supply air to the fuel cell system to control the voltage of the fuel cell system, the programming instructions also include instructions for at least partially opening at least one of a plurality of cathode valves provided along an air-cathode fluid line for supplying air to the cathode side of the fuel cell stack based on at least one of the voltage of the fuel cell stack or the voltage of one or more of the plurality of fuel cells forming the fuel cell stack.

[0081] According to an embodiment, the programming instructions also include instructions for performing the following operations: controlling the fuel cell system in the power-saving mode in response to at least one of a power request being less than or equal to a power-saving threshold or a state of charge (SOC) of the battery pack being greater than or equal to a SOC threshold.

[0082] According to the present invention, a fuel cell electric vehicle is provided, comprising: a fuel cell system including a fuel cell system; and one or more controllers configured to: limit the current draw of the fuel cell stack of the fuel cell system for a power saving mode of the fuel cell system, and for the power saving mode, perform at least one of the following: selectively supplying air to the fuel cell system to control the voltage of the fuel cell system, or selectively supplying air to an exhaust flow line to dilute the concentration of a fluid flowing therein.

[0083] According to an embodiment, the one or more controllers are further configured to generate electricity in response to detecting prolonged operation in a power-saving mode, wherein the prolonged operation in the power-saving mode indicates at least one of the following: the temperature of the coolant used in the fuel cell system is less than or equal to a temperature threshold, the amount of liquid water in the fuel cell stack is greater than or equal to a threshold, the amount of O2 in the fuel cell stack is less than or equal to a reactant threshold, or the fuel cell system is controlled in the power-saving mode for a period of time greater than or equal to a long-term saving threshold.

Claims

1. A method for controlling a fuel cell electric vehicle (FCEV) having a fuel cell system, comprising: defining, for a power saving mode, a current draw of a fuel cell stack of the fuel cell system; and performing, for the power saving mode, at least one of: selectively supplying air to the fuel cell system to control a voltage of the fuel cell system, or selectively supplying air to an exhaust flow line to dilute a concentration of a fluid flowing therein.

2. The method of claim 1, further comprising closing a contactor to electrically couple the fuel cell system to a load in response to the FCEV being turned on, wherein the fuel cell system remains electrically coupled to the fuel cell system for the power saving mode.

3. The method of claim 1, further comprising drawing additional current from the fuel cell system to generate power and exiting the power saving mode in response to a power request being equal to or greater than a selected power threshold.

4. The method of claim 1, further comprising generating power for the power saving mode in response to detecting a long time operation in the power saving mode.

5. The method of claim 4, wherein the long time operation in the power saving mode is detected based on at least one of: a temperature of a coolant for the fuel cell system being less than or equal to a temperature threshold, an amount of oxygen in the fuel cell stack being less than or equal to a threshold, an amount of liquid water in the fuel cell stack being greater than or equal to a water threshold, or controlling the fuel cell system in the power saving mode for a period of time greater than or equal to a long time saving threshold.

6. The method of claim 1, wherein the air is supplied to the fuel cell system to control the voltage of the fuel cell system in response to a fuel cell voltage being less than or equal to a fuel cell system voltage threshold.

7. The method of claim 1, further comprising drawing current from the fuel cell stack for the power saving mode in response to a fuel cell voltage being greater than or equal to a maximum cell voltage threshold.

8. The method of claim 1, wherein to selectively supply air to the fuel cell system to control the voltage of the fuel cell system, the method further comprises at least partially opening at least one cathode valve of a plurality of cathode valves provided along an air-cathode fluid line for supplying the air to a cathode side of the fuel cell stack based on at least one of a voltage of the fuel cell stack or a voltage of one or more fuel cells of a plurality of fuel cells forming the fuel cell stack.

9. The method of claim 1, further comprising controlling the fuel cell system in the power saving mode in response to at least one of a power request being less than or equal to a power saving threshold or a state of charge (SOC) of a battery pack being greater than or equal to an SOC threshold.

10. A control system for a fuel cell electric vehicle (FCEV) having a fuel cell system, comprising: a processor; and A non-transitory computer readable storage medium comprising programming instructions configured to cause the processor to implement a method for controlling the FCEV, wherein the programming instructions comprise instructions for: defining a current draw from a fuel cell stack of the fuel cell system for a power saving mode of the fuel cell system; and performing at least one of the following for the power saving mode: selectively supplying air to the fuel cell system to control a voltage of the fuel cell system, or selectively supplying air to an exhaust flow line of the FCEV to dilute a concentration of fluid flowing therein.

11. The control system of claim 10, wherein the programming instructions further comprise instructions for closing a contactor to electrically couple the fuel cell system to a load in response to the FCEV being turned on, wherein the fuel cell system remains electrically coupled to the fuel cell system for the power saving mode.

12. The control system of claim 10, wherein the programming instructions further comprise instructions for drawing current from the fuel cell system to generate power and exiting the power saving mode in response to a power request being equal to or greater than a selected power threshold.

13. The control system of claim 10, wherein the programming instructions further comprise instructions for generating power for the power saving mode in response to detecting a long time operation in the power saving mode.

14. The control system of claim 13, wherein the long time operation in the power saving mode indicates at least one of: a temperature of a coolant for the fuel cell system being less than or equal to a temperature threshold, an amount of liquid water in the fuel cell stack being greater than or equal to a threshold, an amount of oxygen in the fuel cell stack being less than or equal to a threshold, or controlling the fuel cell system in the power saving mode for a period of time greater than or equal to a long time saving threshold.

15. The control system of claim 10, wherein the air is supplied to the fuel cell system to control the voltage of the fuel cell system in response to a fuel cell voltage being less than or equal to a fuel cell system voltage threshold.

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