Hybrid fuel cell system and method of operating same

Abstract

The invention relates to a hybrid fuel cell system and a method of operating the same. A hybrid fuel cell system is disclosed. The hybrid fuel cell includes a fuel cell adapted to supply power to a load. The hybrid fuel cell also includes an electric air compressor (EAC) unit operatively coupled with the fuel cell. Further, the hybrid fuel cell includes an auxiliary power source connected to the EAC unit via a direct current to alternating current (DC-AC) converter. Further, the hybrid fuel cell includes a converter circuit configured to perform at least one of: during an initialization phase of the fuel cell, enable the auxiliary power source to replenish the fuel cell to provide a collective power supply to the load; during an operating phase of the fuel cell, enabling the fuel cell to provide an input power supply or a supplemental power supply to the EAC unit; or enabling the fuel cell to charge the auxiliary power source.

Description

Cross Reference to Related Applications

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 573233, filed April 2, 2024, which is incorporated by reference herein in its entirety. TECHNICAL FIELD

[0002] The present disclosure relates to proton exchange membrane fuel cells (PEMFCs), and more particularly, to a hybrid fuel cell system and method of operating the same. BACKGROUND

[0003] Proton exchange membrane fuel cells (PEMFCs) are the most commonly used energy devices for various applications including transportation and stationary power generation. However, cold start of PEMFCs presents a significant challenge and is one of the continuing areas of industrial research and development. This difficulty is due to the dependence of PEMFC power output on operating factors such as stack humidity and operating temperature. During cold start, the PEMFC stack tends to be dry and has a low operating temperature, limiting the capacity of the PEMFC to effectively meet initial load demands.

[0004] Further, in conventional PEMFC systems, an electrically driven air compressor (EAC) is powered solely via the PEMFC, which is used to supply the required amount of oxygen from air to the PEMFC stack for the required electrochemical reactions to occur. However, as discussed above, during cold start, the PEMFC takes some time to reach operating conditions, which extends the EAC start-up time and thus further delays the start-up of the PEMFC.

[0005] Accordingly, it is desirable to provide systems and methods that improve the cold start of a PEMFC or fuel cell. SUMMARY

[0006] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the DETAILED DESCRIPTION. This Summary is neither intended to identify key or essential inventive concepts nor to determine the scope of the disclosure.

[0007] In one or more embodiments of the present disclosure, a hybrid fuel cell system is disclosed. The hybrid fuel cell system includes a fuel cell adapted to supply power to a load. Further, the hybrid fuel cell system includes an electrically driven air compressor (EAC) unit operatively coupled with the fuel cell. The hybrid fuel cell system includes an auxiliary power source connected to the EAC unit via a direct current to alternating current (DC-AC) converter. The auxiliary power source is configured to provide an input power supply to the EAC unit at least during an initialization phase of the fuel cell. Further, the hybrid fuel cell system includes a converter circuit configured to at least one of: enable the auxiliary power source to supplement the fuel cell to provide a collective power supply to the load during the initialization phase of the fuel cell; enable the fuel cell to provide an input power supply or a supplemental power supply to the EAC unit during an operational phase of the fuel cell; or enable the fuel cell to charge the auxiliary power source.

[0008] In one or more embodiments, the hybrid fuel cell system further includes a downstream power electronics (DPE) circuit connected to the fuel cell, the auxiliary power source, and the load. The DPE circuit is configured to generate a collective power supply for the load based on power supplies received from the fuel cell and the auxiliary power source.

[0009] In one or more embodiments, the DPE circuit includes at least one of a DC-DC boost converter, an inverter, and a single-stage boost inverter.

[0010] In one or more embodiments, the auxiliary power source includes at least one of a supercapacitor, an ionic battery, a low temperature metal battery, and a low temperature gel battery.

[0011] In one or more embodiments, the hybrid fuel cell system further includes a controller configured to control the DC-AC converter to regulate the input power supply from the auxiliary power source to the EAC unit during the initialization phase of the fuel cell.

[0012] In one or more embodiments, the hybrid fuel cell system further includes an air flow controller connected to the EAC, wherein the air flow controller is configured to maintain an air flow rate within the fuel cell during at least one of the initialization phase and the operational phase of the fuel cell.

[0013] In one or more embodiments of the present disclosure, a method of operating a hybrid fuel cell system including at least one fuel cell and an auxiliary power source is disclosed. The method includes providing, via the auxiliary power source, an initial input power to a load for a first timer interval during an initialization phase of the fuel cell. The method further includes determining whether a temperature of the fuel cell reaches an operating temperature of the fuel cell. In addition, the method includes operating the fuel cell in an operating phase if the temperature of the fuel cell reaches the operating temperature.

[0014] In one or more embodiments, the initialization phase corresponds to a time period required by the fuel cell to reach an operating condition associated with the operating temperature from a low temperature condition.

[0015] In one or more embodiments, the method further includes selectively controlling the power supply from the auxiliary power source and the fuel cell to supply a collective power supply to the load for a second time interval during the initialization phase of the fuel cell based at least on a state of charge (SOC) of at least one of the auxiliary power source or the fuel cell.

[0016] In one or more embodiments, the method further includes selectively controlling the power supply from the auxiliary power source and the fuel cell to power an electric air compressor (EAC) unit during the initialization phase of the fuel cell based at least on an SOC of at least one of the auxiliary power source or the fuel cell.

[0017] To further clarify the advantages and features of the methods, systems and apparatuses / devices, a more particular description will be rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the present disclosure and are therefore not to be considered limiting of its scope. The present disclosure will be described and explained with additional specificity and detail through the use of the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0018] These and other features, aspects, and advantages of the present application will become better understood with reference to the following detailed description when considered in connection with the accompanying drawings, in which like reference numerals represent like parts throughout. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the present application.

[0019] Figure 1 a block diagram illustrating a hybrid fuel cell system, in accordance with one or more embodiments of the present disclosure;

[0020] Figure 2 an exemplary graph depicting a timing diagram of different types of current flow across a hybrid fuel cell system, in accordance with one or more embodiments of the present disclosure;

[0021] Figure 3FIGURE illustrates an exemplary graph depicting timing diagrams illustrating different operating characteristics of a hybrid fuel cell system in accordance with one or more embodiments of the present disclosure; and

[0022] Figure 4 FIGURE illustrates a flowchart depicting a method for operating a hybrid fuel cell system in accordance with one or more embodiments of the present disclosure.

[0023] Further, those of ordinary skill in the art will appreciate that the elements in the figures are illustrated for simplicity and that not necessarily all of the elements are necessarily present in any particular set of embodiments. For example, flowcharts are illustrative of the methods to be implemented in accordance with the teachings herein and that steps illustrated in the flowcharts are not necessarily to be performed in the order shown. Further, one or more of the steps can be performed in parallel. Additionally, some of the steps can be performed by different entities. Additionally, the individuals performing the steps can be different, and the functionality of two or more of the individuals can be performed by the same individual or entity. Additionally, in some embodiments, one or more of the steps can be performed by a different entity or individual than the entity or individual that performs one or more of the other steps. Additionally, one or more of the steps can be omitted in some embodiments. Further, to the extent that they can be described, not all of the aforementioned changes, modifications, substitutions, permutations, and further applications of the principles of the present disclosure will depart from the spirit and scope of the present disclosure. DETAILED DESCRIPTION

[0024] For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to various embodiments and specific language will be used to describe the same. It will, nevertheless, be understood that no limitation of the scope of the disclosure is thereby intended, such alterations and further modifications in the illustrated system and device, and such further applications of the principles of the present disclosure as described herein being contemplated as would normally occur to one skilled in the art to which the present disclosure relates.

[0025] Those skilled in the art will appreciate that the foregoing general description and the following detailed description are explanatory only and are not intended to be limiting.

[0026] Reference throughout this specification to "an aspect", "another aspect" or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Accordingly, appearances of the phrases "in one embodiment", "in another embodiment", "in some embodiments", "in one or more embodiments", or similar language in various places throughout this specification are not necessarily referring to the same embodiment.

[0027] The term "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not necessarily include only those steps but can include other not expressly listed steps or steps inherent to such process or method. Similarly, one or more devices or subsystems or elements or structures or components or additional devices or additional subsystems or additional elements or additional structures or additional components that were not expressly listed in the 'comprising' clause are also expressly included in the present disclosure.

[0028] The term "unit" used herein can imply a unit including one of, for example, hardware, software, and firmware, or a combination of two or more of them. The "unit" can be used interchangeably with terms such as logic, a logic block, a component, a circuit, etc. The "unit" can be the smallest system component for performing one or more functions, or can be a part thereof.

[0029] Embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0030] The terms proton exchange membrane fuel cell, PEMFC, fuel cell stack, and PEMFC stack have been used interchangeably throughout the description.

[0031] The term "AC" can correspond to "alternating current", and the term "DC" can correspond to "direct current".

[0032] Generally, the output power of a proton exchange membrane fuel cell (PEMFC) is affected by operating characteristics such as stack humidity and operating temperature. During cold start conditions, the fuel cell stack is dry and the operating temperature is low, which limits the capacity of the fuel cell to meet the initial power demand from the load device. Further, an electrically driven air compressor (EAC) configured to supply the required amount of oxygen to the fuel cell stack from air is also powered via the fuel cell, causing further lag in reaching the operating temperature of the fuel cell.

[0033] The present disclosure provides a hybrid fuel cell system comprising an auxiliary power source for providing an input power supply to an EAC unit during an initialization phase of the fuel cell. This prevents the lag associated with the EAC by allowing the EAC to operate at full capacity from zero time interval (i.e., from the start of the PEMFC start event), even during cold start conditions. The present disclosure also provides different power strategies to efficiently maintain the power requirements of different components of the hybrid fuel cell system, including the load, the EAC, and / or the auxiliary power source. Thus, the present disclosure improves the cold start performance of the fuel cell.

[0034] Figure 1A block diagram of a hybrid fuel cell system 100 (hereinafter “system 100”) is illustrated in accordance with one or more embodiments of the present disclosure. In the illustrated embodiment, the system 100 can include, but is not limited to, a fuel cell 102, a downstream power electronics (DPE) circuit 104, a bidirectional DC-DC converter 110 (interchangeably referred to as “BDDC 110”), an auxiliary energy storage device (AESD) 112 (interchangeably referred to as “auxiliary power source 112”), a DC-AC converter 108, and an electric air compressor (EAC) unit 114 (interchangeably referred to as “EAC 114”). The fuel cell 102, the DPE circuit 104, the bidirectional DC-DC converter 110, the AESD 112, the DC-AC converter 108, and the EAC 114 can be in communication with each other and with a load 106. The system 100 can be configured to supply power to the load 106. In one or more embodiments, the fuel cell 102 and the AESD 112 can be configured to selectively supply power to the load 106.

[0035] In an exemplary embodiment, as discussed above, the fuel cell 102 can correspond to a PEMFC. In one non-limiting embodiment, the system 100 can include a fuel cell stack composed of a plurality of individual fuel cells 102 that can be electrically connected in series or in parallel to supply the required power to the load 106. Generally, the fuel cell 102 can include components such as, but not limited to, an anode, a cathode, a PEM, an electrolyte, and bipolar plates. At the anode, hydrogen molecules split into protons (H+) and electrons (e-). At the cathode, oxygen (O2) is introduced, and oxygen molecules combine with electrons (from the external circuit) and protons (transported through the electrolyte) to form water (H2O). The PEM is positioned between the anode and the cathode and allows only protons to pass while blocking electrons. The PEM acts as an electrolyte in the PEMFC. Bipolar plates are placed on either side of the PEM to distribute the reactants (hydrogen and oxygen) and collect the generated electric current. The fuel cell 102 can also include one or more additional components, however, detailed descriptions and corresponding descriptions of such components have been omitted for the sake of brevity. Primarily, the fuel cell 102 can be configured to supply the required power supply to the load 106 via the DPE circuit 104 during an operational phase. The operational phase can correspond to a time interval in which the fuel cell 102 is sufficiently humidified and has reached an operational temperature and is configured to supply power at full capacity. Further, the fuel cell 102 can also be configured to selectively supply power to the EAC 114 during the operational phase and / or to supply power to the AESD 112 for charging the AESD 112. In an exemplary embodiment, during the operational phase, the DPE circuit 104 can extract a fuel cell current (i FC ) from the fuel cell 102.

[0036] In the illustrated embodiment, the AESD 112 can correspond to, but is not limited to, one of an ultracapacitor, an ionic battery, a cryogenic metal battery, and a cryogenic gel battery. The AESD 112 can be connected to the EAC 114 via the DC-AC converter 108. In one non-limiting embodiment, the AESD 112 can be configured to provide an input power supply to the EAC 114 during an initialization phase of the fuel cell 102. The input power supply can correspond to an amount of power required for operation of the EAC 114 such that the EAC 114 is able to operate from a zero time instance. The initialization phase of the fuel cell 102 can correspond to a time interval required for the fuel cell 102 to reach an operating temperature and / or to generate power at its full capacity. In particular, the AESD 112 can act as a DC power source configured to supply power for operation of the EAC 114 at least during the initialization phase of the fuel cell 102. The AESD 112 can also be electrically connected with the load 106 and the fuel cell 102. In one embodiment, the AESD 112 can selectively supply power to the load 106 during the initialization phase of the fuel cell 102. Thus, the AESD 112 can act as a primary power source for the EAC 114 during start-up of the fuel cell 102. In the illustrated embodiment, the AESD 112 can supply the required power / input power supply to the EAC 114 via the DC-AC converter 108. Further, an AESD current (i AESD ) can flow across the AESD 112.

[0037] The DC-AC converter 108 can be configured to facilitate conversion of a voltage level associated with the AESD 112 to an operating voltage of the EAC 114. In particular, the DC-AC converter 108 can be configured to convert a DC power supply from the AESD 112 to an AC power supply as required by the EAC 114. In an exemplary embodiment, the DC-AC converter 108 can employ one or more switching circuits to modulate a received DC power supply from the AESD 112 to an AC power output at a desired voltage and frequency as required for operation of the EAC 114. In one or more embodiments, the DC-AC converter 118 can include, but is not limited to, a voltage control function, a current control function, and a frequency converter.

[0038] The EAC 114 is operatively coupled with the fuel cell 102 and can be deployed in the air flow path of the fuel cell 102 to maintain the required air flow in the fuel cell 102. In a conventional approach / solution, the EAC 114 is powered via the fuel cell. However, as mentioned above, during cold start, the fuel cell stack is dry and the fuel cell also has a low operating temperature. Therefore, the fuel cell is unable to meet the power requirement of the EAC 114, which limits the capacity of the EAC 114 to maintain the required air flow. Therefore, in the example embodiment, the EAC 114 is powered via the AESD 112, which prevents this limitation and enables the EAC 114 to operate at full capacity from zero time interval (i.e., from the start of the fuel cell 102). In particular, the EAC 114 powered using the AESD 112 is able to supply the required oxygen to the fuel cell 102 from zero time instance. In one non-limiting embodiment, an energy management scheme (EMS) can be used to control the EAC 114 to effectively maintain the air flow rate at the fuel cell 102. The EMS can control the EAC current (i EAC ) flowing across the EAC 114. In one non-limiting embodiment, the EMS can be implemented by an air flow controller 116. The air flow controller 116 can regulate the amount of air supplied to the fuel cell stack 102 via the EAC 114 based on various factors such as, but not limited to, power requirement, temperature, and system efficiency. In a fuel cell system, maintaining the correct air to fuel ratio is critical for optimal performance and efficiency. The air flow controller 116 ensures that the right amount of air is supplied to the fuel cell stack 102 under any given operating condition. Therefore, the air flow controller 116 can monitor various operating conditions of the fuel cell 102 to regulate the operation of the EAC 114.

[0039] In an example embodiment, the BDDC 110 (may also be referred to as a converter circuit 110) can be configured to electrically connect the AESD 112 to the load 106. Further, the BDDC 110 can be configured to electrically connect the fuel cell 102 to the EAC 114 and / or the AESD 112. In the illustrated embodiment, the BDDC 110 can connect the AESD 112 and the fuel cell 102 in parallel and to the DPE circuit 104. The BDDC 110 can be configured to maintain a desired voltage level at each of the fuel cell 102 and the AESD 112. For example, during an initialization phase of the fuel cell 102, the BDDC 110 can enable the AESD 112 to supplement the fuel cell 102 to provide a collective power supply to the load 106. This ensures that the fuel cell 102 gets sufficient time for power-up and meets the power demand of the load 106 without significant delay. In one embodiment, the BDDC 110 can also be configured to enable the fuel cell 102 to provide an input power supply or a supplemental power supply to the EAC 114 during an operational phase of the fuel cell 102. Thus, the BDDC 110 can prevent the voltage level of the AESD 112 from exceeding a predetermined threshold. One non-limiting example of such a predetermined threshold can be 50% of a state of charge (SOC) of the AESD 112. Further, the BDDC 110 can be configured to enable the fuel cell 102 to charge the AESD 112 during the operational phase when the SOC of the AESD 112 is below the predetermined threshold. Thus, the BDDC 110 effectively maintains a desired voltage level at each of the fuel cell 102 and the AESD 112. The current flowing across the BDDC 110 can be referred to as a BDDC current (i BDDC ) In one or more embodiments, the BDDC 110 can include, but is not limited to, a voltage control function, a current control function, and a frequency converter.

[0040] In the illustrated embodiment, the DPE circuit 104 can be connected to the fuel cell 102, the AESD 112, and the load 106. The DPE circuit 104 can be configured to generate a collective power supply for the load 106 based on the power supplies received from the fuel cell and the AESD 112. Specifically, during an initialization phase of the fuel cell 102, the DPE circuit 104 can effectively utilize the fuel cell 102 and the AESD 112 to meet the power demands of the load 106. The DPE circuit 104 can include components such as, but not limited to, DC-DC boost converters, inverters, and single-stage boost inverters. The components of the DPE circuit 104 can enable efficient conversion of the received power supplies to a desired power supply as required by the load 106. The DPE circuit 104 can be configured to amplify or scale down the received power supplies to meet the power demands of the load 106. In one or more embodiments, the DPE circuit 104 can include, but is not limited to, voltage control functions, current control functions, and frequency converters.

[0041] In an exemplary embodiment, the load 106 can correspond to a transport refrigeration unit (TRU). The TRU can be adapted to provide desired environmental parameters, such as, but not limited to, temperature, pressure, humidity, carbon dioxide, ethylene, ozone, light exposure, vibration exposure, and other conditions, to a cargo compartment of a container and / or a vehicle. In one or more embodiments, the vehicle can be used to transport and distribute goods, such as perishable and environmentally sensitive goods, referred to herein as perishable goods. The perishable goods can include, but are not limited to, fruits, vegetables, grains, legumes, nuts, eggs, dairy products, seeds, flowers, meats, poultry, fish, ice, blood, pharmaceuticals, and any other suitable goods requiring cold chain transportation. In one or more embodiments, the TRU and / or the load 106 can include, but is not limited to, a compressor, an electric compressor motor, a condenser that can be air-cooled, a condenser fan assembly, a receiver, a filter-dryer, a heat exchanger, an expansion valve, an evaporator, an evaporator fan assembly, a suction modulation valve, and a controller that can include a computer-based processor (e.g., a microprocessor).

[0042] The system 100 may also include an EMS controller 118 configured to control the BDDC 110, the EAC 114, and / or the DC-AC converter 108 to achieve the desired EMS. In one embodiment, the EMS controller 118, in conjunction with the air flow controller 116, may maintain an air flow rate to ensure sufficient oxygen in the fuel cell stack. In one or more embodiments, the EMS controller 118 may be a standalone unit or integrated with the system 100. The EMS controller 118 may be configured to determine various operating parameters associated with the fuel cell 102 and the AESD 112. In an embodiment, the EMS controller 118 may be configured to monitor and maintain the SoC of the fuel cell 102 and / or the AESD 112.

[0043] In an exemplary embodiment, the EMS controller 118 may be configured to determine at least one operating characteristic associated with the fuel cell 102. The at least one operating characteristic may indicate at least an air flow rate in the fuel cell, a stack consumption rate, a stack temperature, and a stack humidity. In one or more embodiments, the system 100 may include one or more sensing mechanisms connected to the EMS controller 118 and the fuel cell 102 to enable effective detection of the operating characteristics of the fuel cell 102. As previously mentioned, based on the monitored SoC and the determined operating characteristics, the EMS controller 118 may be configured to maintain a desired power level at each of the fuel cell 102 and the AESD 112. In one or more embodiments, the EMS controller 118 may implement different power strategies during the initialization phase and / or the operation phase of the fuel cell 102 based on the monitored SoC and the determined operating characteristics. For example, during a startup command at time instance zero, the EMS controller 118 may initialize the fuel cell 102 and the EAC 114. However, the EMS controller 118 may limit the DPE circuit 114 from operating during the first time interval (i.e., [0, t1]( Figure 2 )) draws a fuel cell current (I) from the fuel cell 102 FC ). In addition, the EMS controller 118 may allow the EAC 114 to operate at full capacity by providing power supply to the EAC 114 via the AESD 112. During the second time interval (ie, [t1, t2]( Figure 2During the second time interval [t1, t2], the EMS controller 118 can control the BDDC 110 and the DPE circuit 104 to allow the AESD 112 to supplement the fuel cell 102 to supply power to the load 106. Further, after the second time interval [t1, t2], the fuel cell 102 can be in an operational phase, and the EMS controller 118 can control the DPE circuit 104 such that the load 106 is powered entirely via the fuel cell 102.

[0044] Further, during the operational phase, the EMS controller 118 can control the BDDC 110 such that the fuel cell 102 can be capable of powering up the EAC 114 and / or the AESD 112 based at least on the SOC of the AESD 112.

[0045] In one or more embodiments, each of the air flow controller 116 and the EMS controller 118 can include a processor, a memory, modules, and data. The modules and the memory are coupled to the processor. The processor can be a single processing unit or multiple units, all of which can include multiple computing units. The processor can be implemented as one or more microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, state machines, logic circuitries, and / or any devices that manipulate signals based on operational instructions. Among other capabilities, the processor is configured to fetch and execute computer-readable instructions and data stored in the memory.

[0046] The memory can include any non-transitory computer-readable medium known in the art including, for example, volatile memory (such as static random access memory (SRAM) and dynamic random access memory (DRAM)), and / or non-volatile memory (such as read-only memory (ROM), erasable programmable ROM, flash memory, hard disks, optical disks, and magnetic tapes).

[0047] The modules include, among other capabilities, routines, programs, objects, components, data structures, etc., that perform particular tasks or implement data types. The modules can also be implemented as signal processing circuitries, state machines, logic circuitries, and / or any other devices or components that manipulate signals based on operational instructions.

[0048] Furthermore, the modules can be implemented in hardware, by instructions executed by a processing unit, or by a combination thereof. The processing unit can include a computer, a processor such as a processor, a state machine, a logic array, or any other suitable device that is capable of processing instructions. The processing unit can be a general purpose processor that executes instructions to cause the general purpose processor to perform the required tasks, or the processing unit can be dedicated to performing the required functions. In another aspect of the disclosure, the modules can be machine-readable instructions (software) that, when executed by a processor / processing unit, perform any of the functionality described.

[0049] Figure 1 The embodiments illustrated in the figures are exemplary in nature and the system 100 can include any additional components that can be required to support the desired functionality of the system 100, i.e., to improve the cold start of the fuel cell 102.

[0050] Figure 2 An exemplary graph 200 depicting a timing diagram of different types of current flowing across the hybrid fuel cell system 100, in accordance with one or more embodiments of the present disclosure is illustrated. The graph 200 corresponds to a time interval t0-t2, which is further divided into two time intervals, i.e., a first time interval [0-t1] and a second time interval [t1-t2]. The time interval [0-t2] can correspond to an initialization period of the fuel cell 102 from a cold start condition. At the zero time interval, the system 100 and / or the EMS controller 118 can receive a fuel cell initialization command (e.g., FC_start_signal) to supply power to the load 106. The two time intervals, i.e., the first time interval [0-t1] and the second time interval [t1-t2] can enable a soft cold start of the fuel cell 102. In particular, during the first interval, i.e., the time interval [0, t1], the fuel cell 102 starts from a low temperature condition after a long-haul period, which means that the fuel cell stack is dry and the operating temperature is low. Therefore, during the first time interval, the fuel cell 102 can not be able to supply the start-up load / transient power demand to the load 106. Therefore, during the first time interval, the system 100 and / or the EMS controller 118 can maintain (i FC) is 0 to accelerate the heating process of the fuel cell 102. Further, during the first time interval [0, ti], the system 100 and / or the EMS controller 118 can power up the EAC 114 via the AESD 112. This can prevent hysteresis associated with the EAC 114, and the EAC 114 can initiate supplying an air flow to the fuel cell 102 from time instance 0. Thus, the EAC 114 can have sufficient time to maintain and / or reach the required air flow rate in the fuel cell stack. In an exemplary embodiment, during the first time interval [0, ti], the current flowing across the system 100 can be defined by Equation 1 below: a) i EAC = i AESD , and i FC = i BDDC = 0 (1)

[0051] In particular, during the first time interval [0, ti], the system 100 can wait and pause supplying power to the load 106.

[0052] During the second time interval [ti, t2], the EAC 114 can have pumped enough air to the fuel cell 102, and the fuel cell 102 can also start ramping up power generation. In particular, at time instance ti, the fuel cell 102 can be ready to supply power to the load. However, to ensure that the fuel cell stack reaches its operating temperature (e.g., 65 °C) and is able to supply power at full capacity, during the second time interval [ti, t2], the AESD 112 can supplement the fuel cell 102 to supply the collective power supply to the load 106. In particular, for the interval [ti, t2], the system 100 and / or the EMS controller 118 can consider all the operational constraints to slowly ramp up the fuel cell power. Further, the heat generated due to the current drawn from the fuel cell 102 helps to reach the operating temperature faster. In some embodiments, during the second time interval [ti, t2], the EAC 114 can be partially powered via the AESD 112, and partially powered by the bidirectional DC-DC converter 110 via the fuel cell 102. Thus, during the second time interval [ti, t2], i EAC may be given by Equation 2 below: | i_EAC | = k * | i_BDDC | + (1 - k) * | i_AESD |, and i_FC = - i_BDDC (2)

[0053] Here, k can correspond to a portion of the EAC current supplied by the fuel cell through the bidirectional DC-DC converter 110, and (1 - k) can correspond to a portion of the current supplied by the AESD 112. The value of k can depend on a ramp-up rate set by the controller.

[0054] Figure 3 An exemplary graph 300 illustrating a timing diagram depicting different operating characteristics of the hybrid fuel cell system, in accordance with one or more embodiments of the present disclosure, is shown. During the interval [0, ti], the controller can maintain a required / set air flow rate (referred to as ), for ensuring sufficient oxygen in the fuel cell 102, thereby allowing the fuel cell 102 to be ramped up controllably during the second time interval [ti, t2]. Further, during the first time interval [0, ti], the air stack consumption of the fuel cell 102 can be zero, thereby resulting in an extremely high Oxygen Access Ratio (OER) defined as The OER can be defined by Equation 3 mentioned below:

[0055] Figure 4 A flowchart illustrating a method 400 for operating a hybrid fuel cell system, in accordance with one or more embodiments of the present disclosure, is shown. The method 400 can be implemented by the system 100.

[0056] At step 402, the method 400 can include providing an initial input power to the load 106 via the auxiliary power source 112 for a first timer interval [0, ti] during an initialization phase of the fuel cell 102.

[0057] At step 404, the method 400 can include determining whether a temperature of the fuel cell 102 reaches an operating temperature of the fuel cell 102.

[0058] At step 406, the method 400 can include operating the fuel cell 102 in an operating phase if the temperature of the fuel cell 102 reaches the operating temperature.

[0059] In one embodiment, the initialization phase corresponds to a time period required by the fuel cell to reach an operating condition associated with the operating temperature from a low temperature condition.

[0060] The method 400 can further include selectively controlling the power supply from the auxiliary power source 112 and the fuel cell 102 to supply a collective power supply to the load 106 for the second time interval [ti, t2] based at least on a state of charge (SOC) of at least one of the auxiliary power source 112 or the fuel cell 102.​

[0061] The method 400 can also include selectively controlling the supply of power from the auxiliary power source 112 and the fuel cell 102 to power the EAC 114 based at least on the SOC of at least one of the auxiliary power source 112 or the fuel cell 102.

[0062] Although the above steps of the method 400 are shown and described in a particular order, according to various embodiments of the present disclosure, the steps can be performed in variations of that order. Moreover, details relating to individual steps of the method 400 have not been discussed in detail herein for the sake of brevity in the description relating to the Figure 4 Figures 1-3 Figure 4

[0063] Accordingly, the present disclosure improves the cold start performance of a fuel cell. Moreover, the present disclosure releases the hysteresis associated with the EAC during the cold start of the fuel cell. Furthermore, the present disclosure enables an effective and efficient power strategy to adequately supply power to a load and maintain the SOC at the fuel cell and / or auxiliary power source.

[0064] Although the subject matter has been described in language specific to structural features, it is to be understood that the subject matter defined in the broadest possible terms is the invention, and thus the specific language is to not be construed as limiting. It is contemplated that the various embodiments presented herein will not be limited to the above-described embodiments but can be carried out in various ways utilizing the essential features of the application. The figures and the preceding description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements can well be combined into a single functional element. Alternatively, certain elements can be split into multiple functional elements. Elements from one embodiment can be added to another embodiment.​​​

Claims

1. A hybrid fuel cell system comprising: a fuel cell adapted to supply power to a load; an electric air compressor (EAC) unit operatively coupled to the fuel cell; an auxiliary power source connected to the EAC unit via a direct current to alternating current (DC-AC) converter, wherein the auxiliary power source is configured to provide an input power supply to the EAC unit at least during an initialization phase of the fuel cell; as well as A converter circuit configured to perform at least one of the following: enabling the auxiliary power source to supplement the fuel cell during the initialization phase of the fuel cell to provide an aggregate power supply to a load; enabling the fuel cell to provide the input power supply or supplemental power supply to the EAC unit during an operating phase of the fuel cell; as well as The fuel cell is enabled to charge the auxiliary power source.

2. The hybrid fuel cell system according to claim 1, further comprising: Downstream power electronics (DPE) circuitry is connected to the fuel cell, the auxiliary power source, and the load, wherein the DPE circuitry is configured to generate the aggregate power supply for the load based on power supplies received from the fuel cell and the auxiliary power source.

3. The hybrid fuel cell system according to claim 2, wherein: The DPE circuit includes at least one of a DC-DC boost converter, an inverter, and a single-stage boost inverter.

4. The hybrid fuel cell system according to claim 1, wherein: The auxiliary power source includes at least one of a supercapacitor, an ion battery, a low-temperature metal battery, and a low-temperature gel battery.

5. The hybrid fuel cell system of claim 1 , comprising a controller configured to control the DC-AC converter to regulate the input power supply from the auxiliary power source to the EAC unit during the initialization phase of the fuel cell.

6. The hybrid fuel cell system of claim 1 , further comprising an air flow controller connected to the EAC, wherein the air flow controller is configured to maintain an air flow rate within the fuel cell during at least one of the initialization phase and the operation phase of the fuel cell.

7. A method of operating a hybrid fuel cell system comprising at least a fuel cell and an auxiliary power source, the method comprising: providing initial input power to a load via the auxiliary power source within a first timer interval during an initialization phase of the fuel cell; determining whether the temperature of the fuel cell reaches an operating temperature of the fuel cell; as well as If the temperature of the fuel cell reaches the operating temperature, the fuel cell is operated in an operating phase.

8. The method according to claim 7, wherein: The initialization phase corresponds to the time period required by the fuel cell to reach operating conditions associated with the operating temperature from low temperature conditions.

9. The method according to claim 7, further comprising: During the initialization phase of the fuel cell: Power supply from the auxiliary power source and the fuel cell is selectively controlled to supply an aggregate power supply to the load during a second time interval based at least on a state of charge (SOC) of at least one of the auxiliary power source or the fuel cell.

10. The method according to claim 7, further comprising: During the operating phase of the fuel cell: Based at least on the SOC of at least one of the auxiliary power source or the fuel cell, power supply from the auxiliary power source and the fuel cell is selectively controlled to power an electric air compressor (EAC) unit.

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