DESC:FIELD OF THE INVENTION

The present invention relates to fuel composition for gas-based power generating devices like fuel cells etc. and more particularly relates to a system and a method for operating a fuel cell for a variable fuel composition.

BACKGROUND

A solid oxide fuel cell (SOFC) is capable of using multiple fuels as input fuels that includes wide variety of gaseous fuels (Natural gas, Biomethane, LPG, Biogas etc). However, the fuels are reformed into hydrogen rich reformate externally in the partial oxidation reformer (POX), or auto thermal reformer (ATR), or steam methane reformer (SMR), before being supplied to core SOFC stack. Further, the composition of gaseous fuels supplied to an SOFC system varies depending upon various factors involved in upstream processes. The change in fuel composition and inclusion of higher hydrocarbons (>C1) changes the oxygen demand inside the reformer.

Conventionally the air/steam flow rates are adjusted based on reading from gas analyzer for a fuel inlet composition. In certain methods the inlet fuel composition has higher hydrocarbons in the fuel, such air/steam dosing may not be enough and lead to carbon formation in the reformer and the SOFC stack. Adequate amount of oxygen to the reformer can have significant effect on the SOFC stack and reformer performance. The deposition of carbon in reformer degrades the reformer catalyst thereby increasing the incidence of hydrocarbon slippage directly to the SOFC stack, which affects the life and performance of the SOFC stack. The deposition of carbon in the reformer and the SOFC stack over an extended period significantly affects the performance of the reformer and SOFC stack. The stack performance degradation becomes prominent causing significant drop in the power generation and reducing overall life of the system.

Therefore, there is a need for an improved solution for operating the fuel cell system for a variable fuel composition.

SUMMARY

In an embodiment of the present disclosure, a system for operating a fuel cell system for a variable fuel composition is disclosed. The system includes a controlling module in communication with the fuel cell system. The controlling module includes a first controlling unit in communication with a fuel cell module of the fuel cell system and an after-burner unit of the fuel cell system. The first controlling unit is configured to control a flow rate of fuel supplied to a reformer unit of the fuel cell system based on a value of temperature associated with the after-burner unit. Further, the controlling module includes a second controlling unit in communication with the fuel cell module. The second controlling unit is configured to control a flow of preheated air from a heat exchanger of the fuel cell system to the fuel cell module based on a value of temperature associated with the fuel cell module. The controlling module includes a third controlling unit in communication with the reformer unit. The third controlling unit is configured to control a value of oxygen-carbon ratio supplied to the reformer unit.

In an embodiment of the present disclosure, a fuel cell system is disclosed. The fuel cell system includes a reformer unit adapted to receive a flow of air, a flow of oxygen, a flow of steam, and a flow of fuel. The fuel cell system is adapted to generate a flow of reformate based on the flow of air, the flow of oxygen, the flow of steam, and the flow of fuel. Further, the fuel cell system includes a fuel cell module in communication with the reformer unit and having a plurality of fuel cells. The fuel cell module is adapted to receive the flow of reformate from the reformer unit at an anode inlet of the fuel cell module to generate a power output. The fuel cell module is in communication with an after-burner unit and a heat exchanger. Further, the fuel cell system includes a controlling module in communication with the fuel cell module, the reformer unit, and the after-burner unit. The controlling module includes a first controlling unit in communication with the fuel cell module and the after-burner unit of the fuel cell system. The first controlling unit is configured to control a flow rate of fuel supplied to the reformer unit based on a value of temperature associated with the after-burner unit. Further, the controlling module includes a second controlling unit in communication with the fuel cell module. The second controlling unit is configured to control a flow of preheated air from the heat exchanger to the fuel cell module based on a value of temperature associated with the fuel cell module. The controlling module includes a third controlling unit in communication with the reformer unit. The third controlling unit is configured to control a value of oxygen-carbon ratio supplied to the reformer unit. The first controlling unit, the second controlling unit, and the third controlling unit in combination control generation of the power at the fuel cell module.

In an embodiment of the present disclosure, a method for operating a fuel cell system for a variable fuel composition is disclosed. The method includes determining a value of power generated by a fuel cell module of the fuel cell system. Further, the method includes comparing the value of power with a predefined value of power to be generated by the fuel cell module. The method includes comparing a value of temperature associated with an after-burner of the fuel cell system with a predefined value of temperature if the value of power is less than the predefined value of power. Further, the method includes controlling a value of oxygen-carbon ratio supplied to a reformer unit of the fuel cell system based on the comparison of the value of temperature with the predefined value of temperature.

To further clarify advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

Figure 1a illustrates a block diagram of a fuel cell system having a system for operating the fuel cell system, according to an embodiment of the present disclosure;

Figure 1b a schematic view of the fuel cell system, according to an embodiment of the present disclosure;
Figure 2a and 2b illustrates block diagrams depicting the system for operating the fuel cell system, according to an embodiment of the present disclosure; and

Figure 3 illustrates a flowchart depicting a method for operating the fuel cell system 100, according to an embodiment of the present disclosure.

Further, skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and may not have been necessarily been drawn to scale. For example, the flow charts illustrate the method in terms of the most prominent steps involved to help to improve understanding of aspects of the present invention. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.

DETAILED DESCRIPTION OF FIGURES

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

Figure 1a illustrates a block diagram of a fuel cell system 100 having a system 101 for operating the fuel cell system 100, according to an embodiment of the present disclosure. Figure 1b a schematic view of the fuel cell system 100, according to an embodiment of the present disclosure. In an embodiment, the fuel cell system 100 may be embodied as an electric generator that uses fuels, such as Hydrogen and Hydrocarbons, to generate electricity. For instance, the fuel cell system 100 may be adapted to covert chemical energy associates with the fuels into electrical energy which is further used as electricity. Referring to Figure 1b, in an embodiment, the fuel cell system 100 may include, but is not limited to, a fuel cell module 102, a reformer unit 104, an after-burner unit 106, and a heat exchanger 108.

The fuel cell module 102 may include a plurality of fuel cells arranged within the fuel cell module 102. Each of the plurality of fuel cells may be connected with each other in a series configuration. In an embodiment, the plurality of fuel cells may interchangeably be referred to as the fuel cells, without departing from the scope of the present disclosure. Each of the fuel cells may include a cathode end and an anode end distal to the cathode end. In an embodiment, each of the fuel cells may be embodied as a Solid Oxide Fuel Cell (SOFC), without departing from the scope of the present disclosure. Therefore, the fuel cell module 102 may interchangeably be referred to as the SOFC stack 102.

The SOFC stack 102 may be adapted to operate within a high temperature range. For instance, in the illustrated embodiment, the SOFC stack 102 may operate within a temperature range of approximately 750°C to 850°C. The SOFC stack 102 may be adapted to receive a flow of hydrogen (H2)/hydrogen fuel and a flow of oxygen (O2). Upon receiving the flow of H2 and the flow of O2, the SOFC stack 102 may perform an electrochemical reaction of the hydrogen fuel with the flow of O2 or any other oxidizing agent.

As shown in Figure 1, in the illustrated embodiment, the SOFC stack 102 may be adapted to receive hydrocarbons to perform the electrochemical reaction in order to generate electrical energy/power. In the present disclosure, operation of the fuel cell system 100 is explained with respect to the hydrocarbons, such as Methane (CH4). However, it should be appreciated by a person skilled in the art that it should not be construed as limiting, and the fuel cell system 100 may be employed for different hydrocarbons with variable compositions, without departing from the scope of the present disclosure.

Further, the SOFC stack 102 may be in communication with the reformer unit 104. In an embodiment, the reformer unit 104 may be embodied as one of a partial oxidation reformer (POX), or an auto thermal reformer (ATR), or a steam methane reformer (SMR). A type of the reformer unit 104, such as POX, ATR, and SMR, may be selected based on a type of fuel to be used. In an embodiment, the reformer unit 104 may be connected to the SOFC stack 102 through an anode inlet provided at the anode side of the SOFC stack 102. The reformer unit 104 may be adapted to receive a flow of air, a flow of oxygen, a flow of steam, and a flow of fuel.

In the illustrated embodiment, the reformer unit 104 may be in communication with a steam generator 110 to receive the flow of steam. The steam generator 110 may be in communication with a water pump 112 to receive a flow of water which is used for generating the flow of steam. The steam generator 124 may use excess of SOFC generate steam for feeding to the reformer unit 104. Further, the reformer unit 104 may be in communication with an oxidant pump 114-1 to receive the flow of oxygen. The reformer unit 104 may be in communication with an air pump 114-2 to receive the flow of air.

Furthermore, the reformer unit 104 may be in communication with a fuel pump 116 to receive the flow of fuel. In one embodiment, if the reformer unit 104 is embodied as the POX reformer, then the reformer unit 104 may receive the flow of oxygen from the oxidant pump 114-1. In another embodiment, if the reformer unit 104 is embodied as the ATR reformer, then the reformer unit 104 may receive the flow of steam and the flow of oxygen from the steam generator 110 and the oxidant pump 114-1, respectively. In yet another embodiment, if the reformer unit 104 is embodied as the SMR reformer, then the reformer unit 104 may receive the flow of steam from the steam generator 110.

In an embodiment, the reformer unit 104 may be operated within a temperature range of approximately 660°C to 800°C. The reformer unit 104 may be adapted to generate a flow of reformate based on the flow of air, the flow of oxygen, the flow of steam, and the flow of fuel. The reformer unit 104 may perform a reforming process in order to break hydrocarbons associated with the flow of fuel. In the illustrated embodiment, the reformer unit 104 may perform the reforming process on the flow of fuel, such as CH4, as given in reaction (1):

CH4 + ½ O2 CO + 2 H2 (1)

Upon completion of the reforming process, the reformer unit 104 may generate the flow of reformate which includes Hydrogen (H2) and Carbon Monoxide (CO). Subsequently, the reformer unit 104 may supply the flow of reformate to the SOFC stack 102 for generation of electricity. The flow of reformate may be supplied to the anode side of the SOFC stack 102.

Referring to Figure 1, the SOFC stack 102 may be adapted to perform the electrochemical reaction to generate the electrical energy. In order to perform the electrochemical reaction, the SOFC stack 102 may receive the flow of reformate from the reformer unit 104 and a flow of preheated air. In the illustrated embodiment, the SOFC stack 102 may be in communication with an air blower 118, interchangeably referred to as the cathode air blower 118. The cathode air blower 118 may be connected to the SOFC stack 102 and the heat exchanger 108 via a three-way proportional valve 120. The cathode air blower 118 may be connected to a cathode inlet provided at the cathode side of the SOFC stack 102. The cathode air blower 118 may be adapted to supply ambient air to the cathode side of the SOFC stack 102 through a mixer 122. The mixer 122 may be provided upstream to the three-way proportional valve 120 and downstream to the SOFC stack 102.

Further, the mixer 122 may be in communication with the heat exchanger 108. The mixer 122 may be adapted to receive a flow of preheated air from the heat exchanger. Operational details of the heat exchanger 108 are explained in subsequent sections of the present disclosure. Subsequently, the mixer 122 may be adapted to use the flow of preheated air from the heat exchanger to increase a temperature of ambient air received from the cathode air blower. The mixer 122 may mix the ambient air received from the cathode air blower with the flow of preheated air received from the heat exchanger to generate another flow of preheated air. Such flow of preheated air may be supplied to the cathode side of the SOFC stack 102. The flow of preheated air received at the cathode side of the SOFC stack 102 may act as a reactant for the electrochemical reaction and a carrier for heat to the SOFC stack 102.

Upon receiving the flow of preheated air at the cathode side and the flow of reformate at the anode side, the SOFC stack 102 may perform the electrochemical reaction at each of the fuel cells, as given by reactions (2)-(4), to generate the electrical energy.

(2)
(3)

(4)

Upon completion of the electrochemical reaction within the SOFC stack 102, a flow of anode off-gas and a flow of cathode off-gas may egress from an anode exhaust provided at the anode side and an cathode exhaust provided at the cathode side, respectively. The flow of anode off-gas may be fed to the reformer through a recycling unit. In an embodiment, the reformer 104 may be adapted to receive the flow of anode off-gas from the anode exhaust of the SOFC stack 102. The flow of anode-off gas may include, but is not limited to, unconverted fuel and water. The flow of anode-off gas may be utilized to increase overall efficiency of the reformer 104, which is explained later in the present disclosure.

Further, referring to Figure 1, the SOFC stack 102 may be in communication with the after-burner unit 106. The after-burner unit 106 may be adapted to receive a flow of cathode off-gas from the SOFC stack 102. In an embodiment, the after-burner unit 106 may receive the flow of cathode off-gas from a cathode exhaust provided at the cathode side of the SOFC stack 102. The cathode off-gas may be associated with the fuel which remains unreacted during the electrochemical reaction within the SOFC stack 102. The after-burner unit 106 may be adapted to oxidize the flow of cathode off-gas received from the SOFC stack 102. During oxidation of the flow of cathode off-gas within the after-burner unit 106, heat may be generated which is supplied from the after-burner unit 106 to the heat exchanger 108. In an embodiment, the after-burner 106 may be operated within a temperature range of approximately 760°C to 950°C.

In an embodiment, the heat exchanger 108 may interchangeably be referred to as the air preheater 108, without departing from the scope of the present disclosure. As explained earlier, the air preheater 108 may be in communication with the after-burner unit 106. The air preheater 108 may be adapted to receive a flow of air from the cathode air blower through the three-way proportional valve 120. Further, the air preheater 108 may be adapted to receive the oxidized cathode off-gas from the after-burner unit 106. Further, the air preheater 108 may be adapted to use heat from the oxidized cathode off-gas to increase temperature of the flow of air received from the cathode air blower 118, and thereby generating the flow of preheated air. As explained earlier, the air preheater 108 may be adapted to supply the flow of preheated air to the mixer 122 which is in communication with the SOFC stack 102.

Referring to Figure 1a and 1b, the fuel cell system 100 may be provided with the system 101 for operating the fuel cell system 100. The system 101 may include a controlling module which is configured to control various operating characteristics associated with different components, such as the SOFC stack, the reformer, the fuel pump, the air/oxidant pump, the water pump, of the fuel cell system 100. The system 101 may operate the fuel cell system 100 by controlling various operating characteristics based on chemical composition of the fuel to be used for generating electrical power in the SOFC stack. Construction and operational details of the system 101 are explained in detail with respect to Figure 2a, Figure 2b, and Figure 2c of the present disclosure.

Figure 2a and 2b illustrates block diagrams depicting the system 101 for operating the fuel cell system 100, according to an embodiment of the present disclosure. For the sake of brevity, features of the fuel cell system 100 that are already explained in detail in the description of Figure 1 are not explained in detail in the description of Figures 2a and 2b.

Referring to Figure 1a and 2a, the system 101 may include a controlling module in communication with the fuel cell system 100. The system 101 may include a first controlling unit 212 in communication with the SOFC stack 102 and the after-burner unit 106. The first controlling unit 212 may be configured to control a flow rate of fuel supplied to the reformer unit 104 based on a value of temperature associated with the after-burner unit 106. In an embodiment, the flow rate of fuel may interchangeably be referred to as the chemical power input, without departing from the scope of the present disclosure. The first controlling unit 212 may include a first feedback controller 214 and a second feedback controller 216 in communication with the first feedback controller 214.

The first feedback controller 214 may be configured to determine a maximum value of flow rate of the fuel corresponding to a maximum value of power based on the value of temperature associated with the after-burner unit 106. The maximum value of flow rate of fuel is associated with a maximum power output generated by the SOFC stack 102. The second feedback controller 216 may be configured to determine a minimum value of flow rate of fuel based on the value of temperature associated with the after-burner unit 106. The minimum value of flow rate of fuel is associated with a minimum power output generated by the SOFC stack 102.

Further, the first controlling unit 212 includes a controller 218 in communication with the first feedback controller 214 and the second feedback controller 216. In an embodiment, the controller 218 may interchangeably be referred to as the third feedback controller 218, without departing from the scope of the present disclosure. Further, the first feedback controller 214, the second feedback controller 216, and the third feedback controller 218 may collectively be referred to as the power controllers. The third feedback controller 218 may be configured to receive the maximum value of flow rate of fuel and the minimum value of flow rate of fuel from the first feedback controller 214 and the second feedback controller 216, respectively.

Further, the third feedback controller 218 may be configured to determine the flow rate of fuel supplied to be supplied to the SOFC stack 102 based on the maximum value of flow rate of fuel and the minimum value of the flow rate of fuel. In real-time, the third feedback controller 218 may be configured to receive a value of power output associated with the SOFC stack 102. Thereafter, based on the maximum value of the flow rate of fuel, the minimum value of the flow rate of fuel and the value of power output, the third feedback controller 218 may determine the flow rate of the fuel to be supplied to the SOFC stack 102. The third feedback controller 218 may be in communication with the fuel pump 116 which is adapted to supply fuel to the reformer unit 104. Further, the third feedback controller may be configured to operate the fuel pump 116 to control the flow rate of fuel supplied to the reformer unit 104.

Referring to Figure 2a, the system 101 may include a second controlling unit 220 in communication with the SOFC stack 102. The second controlling unit 220 may be configured to control the flow of preheated air from the heat exchanger 108 to the SOFC stack 102 based on a value of temperature associated with the SOFC stack 102. The second controlling unit 220 may include a first controller 222 and a second controller 224 in communication with the first controller 222. The first controller 222 may be configured to determine a value of temperature at an outlet of the SOFC stack 102. The second controller 224 may be configured to determine a value of temperature at an inlet of the SOFC stack 102. In an embodiment, the first controller 222 and the second controller 224 may collectively be referred to as the stack temperature controllers, without departing from the scope of the present disclosure.

The first controller 222 may be configured to compare the value of temperature at the inlet of the SOFC stack 102 with a predefined value of temperature associated with the inlet of the SOFC stack 102. Further, the second controller 224 may be configured to control the three-way proportional valve 120 based on the comparison. As explained earlier, the three-way proportional valve 120 may be disposed between the cathode air blower 118 and the heat exchanger 108 which is adapted to supply the flow of preheated air to the SOFC stack 102 through the inlet of the SOFC stack 102.

Further, the system 101 may include a third controlling unit 226 in communication with the reformer unit 108. The third controlling unit 226 may be configured to control a value of oxygen-carbon ratio supplied to the reformer unit 108. The third controlling unit 226 may include a controller configured to determine a value of temperature associated with an outlet of the reformer unit 108. Further, the third controlling unit 226 may control the value of oxygen-carbon ratio supplied to the reformer unit 108 based on the determined value of temperature. The controller may be in communication with at least one of the fuel pump 104, the oxidant pump 106, and the water pump 120. The controller may be configured to operate the at least one of the fuel pump 104, the oxidant pump 106, and the water pump 120 to control the value of oxygen-carbon ratio supplied to the reformer unit 108. Accordingly, the first controlling unit 212, the second controlling unit 220, and the third controlling unit 226 in combination control generation of the power at the SOFC stack 102 of the fuel cell system 100.

Figure 2c illustrates an exemplary implementation of the system 101 for operating the fuel cell system 100, according to an embodiment of the present disclosure. Referring to Figure 1b, 2a, 2b, and 2c, the system 101 may be implemented for controlling oxygen to carbon ration i.e. optimizing stochiometric ratio of air/steam and fuel for improved performance, avoid coking and prevent reformer & stack damage in SOFC system. The system 101 may enable optimizing the air/steam to fuel ratio for any inlet fuel composition, without the use of gas composition analyzer. The fluctuations in gas compositions could be moderate to severe. In many cases gas composition are not actively controlled and monitored at the source. The online measurement of gas composition at the point of consumption is costly, tedious and time consuming. For fuel cells it is desirable to have a fixed gas composition and most of the control strategies do not work well for variable gas compositions. The change in composition alters energy content of the fuel which in turn changes performance of the reformer unit 104 and the SOFC stack 102, and further disturbs thermal equilibrium of the fuel cell system 100.

The system 101 may comprise a boost controller 228. The boost controller 228 may be configured to provide boost in a form of cell voltage to the SOFC stack 102 to achieve the defined or required power. The system 101 may further comprise a reformer controller, such as the third controlling unit 226. The reformer controller 226 may be configured to verify the cell voltage of the stack and after compare verified with the required cell voltage. Further based on the comparison the reformer controller 226, may be configured to increases or decreases input to the system. The increase or the decrease of the input may be controlled by a minimum controller, such as the second feedback controller 216 and a maximum controller, such as the first feedback controller 214. The minimum controller 216 may define the temperature, after comparing with set-point minimum temperature for the after-burner unit 106. Further based on the defined temperature it may, decide the minimum limit of fuel (in terms of chemical power) that should go in the system.

Further the maximum controller 214 check the after-burner temperature and after comparing with set maximum temperature for the after-burner unit 106. Further checking the temperature, it may decide the maximum limit of fuel that should go in the system. The limit of fuel going to into system can be controlled through the fuel pump 116 and further the oxygen carbon ratio may be adjusted based on the fuel limit by controlling oxygen supply via the oxidant pump 114-2, thus enabling control over the oxygen carbon ratio.

Figure 3 illustrates a flowchart depicting a method 300 for operating the fuel cell system 100, according to an embodiment of the present disclosure. This loop will be activated in steady operation. For the sake of brevity, features of the fuel cell system 100 that are already explained in detail in the description of Figure 1 and Figures 2a-2c are not explained in detail in the description of Figure 3.

Referring to Figure 3, the method 300 includes determining a value of power generated by the SOFC stack of the fuel cell unit. At step 302, the method 300 includes comparing the value of power with a predefined value of power to be generated by the SOFC stack 102. Subsequently, if the value of power is more than the predefined value of power, then the method 300 branches to step 308. Further, if the value of power is less than the predefined value of power, then the method 300 branches to the step 304. At step 304, the method 300 includes comparing a value of temperature associated with the after-burner unit 106 of the fuel cell system 100 with a predefined value of temperature, if the value of power is less than the predefined value of power.

At step 304, if the value of temperature associated with the after-burner unit 106 is higher than the predefined value of temperature, then the method 300 branches to the step 306. At step 306, the method 300 includes controlling the value of oxygen-carbon ratio supplied to the reformer unit 104 based on the comparison of the value of temperature with the predefined value of temperature. At the step 306, the value of oxygen-carbon ratio supplied to the reformer unit 104 is increased. Further, at step 304, if the value of temperature associated with the after-burner unit 106 is less than the predefined value of temperature, then the method 300 branches to step 310. At step 310, the method 300 includes comparing a value of partial oxidizer temperature (PoX or SMR) with a predefined value of temperature. Further, if the value of partial oxidizer temperature is higher than the predefined value of temperature, then the method 300 branches to step 312. At step 312, the value of oxygen-carbon ration supplied to the reformed unit 103 is decreased.

While specific language has been used to describe the present subject matter, any limitations arising on account thereto, are not intended. As would be apparent to a person in the art, various working modifications may be made to the method in order to implement the inventive concept as taught herein. The drawings and the foregoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment.
,CLAIMS:1. A system for operating a fuel cell system for a variable fuel composition, the system comprising:
a controlling module in communication with the fuel cell system, the controlling module comprising:
a first controlling unit in communication with a fuel cell module of the fuel cell system and an after-burner unit of the fuel cell system, wherein the first controlling unit is configured to control a flow rate of fuel supplied to a reformer unit of the fuel cell system based on a value of temperature associated with the after-burner unit;
a second controlling unit in communication with the fuel cell module, wherein the second controlling unit is configured to control a flow of preheated air from a heat exchanger of the fuel cell system to the fuel cell module based on a value of temperature associated with the fuel cell module; and
a third controlling unit in communication with the reformer unit, wherein the third controlling unit is configured to control a value of oxygen-carbon ratio supplied to the reformer unit;

2. The system as claimed in claim 1, wherein the first controlling unit includes a first feedback controller and a second feedback controller in communication with the first feedback controller, the first feedback controller and the second feedback are configured to determine a maximum value of flow rate of fuel corresponding to a maximum value of power and a minimum value of flow rate of fuel, respectively, based on the value of temperature associated with the after-burner unit.

3. The system as claimed in claim 2, wherein the maximum value of flow rate of fuel is associated with a maximum power output generated by the fuel cell module and the minimum value of flow rate of fuel is associated with a minimum power output generated by the fuel cell module.

4. The system as claimed in claim 3, wherein the first controlling unit includes a controller in communication with the first feedback controller and the second feedback controller, the controller is configured to determine the flow rate of fuel supplied to be supplied to the fuel cell module based on the maximum value of flow rate of fuel and the minimum value of the flow rate of fuel.

5. The system as claimed in claim 4, wherein the controller is in communication with a fuel pump adapted to supply fuel to the reformer unit, the controller is configured to operate the fuel pump to control the flow rate of fuel supplied to the reformer unit.

6. The system as claimed in claim 1, wherein the second controlling unit includes a first controller and a second controller in communication with the first controller, the first controller is configured to determine a value of temperature at an outlet of the fuel cell module and a second controller is configured to determine a value of temperature at an inlet of the fuel cell module.

7. The system as claimed in claim 6, wherein:
the first controller is configured to compare the value of temperature at the inlet of the fuel cell module with a predefined value of temperature associated with the inlet of the fuel cell module; and
the second controller is configured to control a three-way proportional valve based on the comparison, wherein the three-way proportional valve is disposed between an air blower and an heat exchanger adapted to supply a flow of preheated air to the fuel cell module through the inlet of the fuel cell module.

8. The system as claimed in claim 1, wherein the third controlling unit includes a controller configured to:
determine a value of temperature associated with an outlet of the reformer unit; and
control the value of oxygen-carbon ratio supplied to the reformer unit based on the determined value of temperature.

9. The system as claimed in claim 8, wherein the controller is in communication with at least one of a fuel pump, an oxidant pump, and a water pump, the controller is configured to operate the at least one of the fuel pump, the oxidant pump, and the water pump to control the value of oxygen-carbon ratio supplied to the reformer unit.

10. A fuel cell system comprising:
a reformer unit adapted to receive a flow of air, a flow of oxygen, a flow of steam, and a flow of fuel, and adapted to generate a flow of reformate based on the flow of air, the flow of oxygen, the flow of steam, and the flow of fuel;
a fuel cell module in communication with the reformer unit and having a plurality of fuel cells, the fuel cell module is adapted to receive the flow of reformate from the reformer unit at an anode inlet of the fuel cell module to generate a power output, wherein the fuel cell module is in communication with an after-burner unit and a heat exchanger; and
a controlling module in communication with the fuel cell module, the reformer unit, and the after-burner unit, the controlling module comprising:
a first controlling unit in communication with the fuel cell module and the after-burner unit of the fuel cell system, wherein the first controlling unit is configured to control a flow rate of fuel supplied to the reformer unit based on a value of temperature associated with the after-burner unit;
a second controlling unit in communication with the fuel cell module, wherein the second controlling unit is configured to control a flow of preheated air from the heat exchanger to the fuel cell module based on a value of temperature associated with the fuel cell module; and
a third controlling unit in communication with the reformer unit, wherein the third controlling unit is configured to control a value of oxygen-carbon ratio supplied to the reformer unit,
wherein the first controlling unit, the second controlling unit, and the third controlling unit in combination control generation of the power at the fuel cell module.

11. The fuel cell system as claimed in claim 10, wherein the reformer unit is in communication with a steam generator, an oxidant pump, and a fuel pump to receive the flow of air, the flow of oxygen, the flow of steam, and the flow of fuel, respectively.

12. The fuel cell system as claimed in claim 10, wherein the reformer is adapted to receive a flow of anode off-gas from an anode exhaust of the fuel cell module.

13. The fuel cell system as claimed in claim 12, wherein the controlling module is configured to;
determine a set of characteristics associated with the flow of anode off-gas received by the reformer from the anode exhaust of the fuel cell module, wherein the set of characteristics includes at least one of an amount of air, an amount of oxygen, and an amount of fuel present in the anode off-gas; and
control at least one of the flow of air, the flow of oxygen, the flow of steam, and the flow of fuel to the reformer based on the determined set of characteristics.

14. The fuel cell system as claimed in claim 10, wherein the after-burner unit is adapted to receive a flow of cathode off-gas from a cathode exhaust of the fuel cell module and adapted to oxidize the flow of cathode off-gas.

15. The fuel cell system as claimed in claim 14, wherein the heat exchanger is in communication with the after-burner unit, the heat exchanger is adapted to receive the oxidized cathode off-gas from the after-burner unit and supply a flow of preheated air to the fuel cell module.

16. The fuel cell system as claimed in claim 10, wherein the first controlling unit includes a first feedback controller and a second feedback controller in communication with the first feedback controller, the first feedback controller and the second feedback are configured to determine a maximum value of flow rate of fuel corresponding to a maximum value of power and a minimum value of flow rate of fuel, respectively, based on the value of temperature associated with the after-burner unit.

17. The fuel cell system as claimed in claim 16, wherein the maximum value of flow rate of fuel is associated with a maximum power output generated by the fuel cell module and the minimum value of flow rate of fuel is associated with a minimum power output generated by the fuel cell module.

18. The fuel cell system as claimed in claim 17, wherein the first controlling unit includes a controller in communication with the first feedback controller and the second feedback controller, the controller is configured to determine the flow rate of fuel supplied to be supplied to the fuel cell module based on the maximum value of flow rate of fuel and the minimum value of the flow rate of fuel.

19. The fuel cell system as claimed in claim 18, wherein the controller is in communication with a fuel pump adapted to supply fuel to the fuel cell module, the controller is configured to operate the fuel pump to control the flow rate of fuel supplied to the reformer unit.

20. The fuel cell system as claimed in claim 10, wherein the second controlling unit includes a first controller and a second controller in communication with the first controller, the first controller is configured to determine a value of temperature at an outlet of the fuel cell module and a second controller is configured to determine a value of temperature at an inlet of the fuel cell module.

21. The system as claimed in claim 20, wherein the first controller is configured to:
the first controller is configured to compare the value of temperature at the inlet of the fuel cell module with a predefined value of temperature associated with the inlet of the fuel cell module; and
the second controller is configured to control a three-way proportional valve based on the comparison, wherein the three-way proportional valve is disposed between an air blower and an heat exchanger adapted to supply a flow of pre-heated air to the fuel cell module through the inlet of the fuel cell module.

22. The system as claimed in claim 10, wherein the third controlling unit includes a controller configured to:
determine a value of temperature associated with an outlet of the reformer unit; and
control the value of oxygen-carbon ratio supplied to the reformer unit based on the determined value of temperature.

23. A method for operating a fuel cell system for a variable fuel composition, the system comprising:
determining a value of power generated by a fuel cell module of the fuel cell system;
comparing the value of power with a predefined value of power to be generated by the fuel cell module;
comparing a value of temperature associated with an after-burner unit of the fuel cell system with a predefined value of temperature if the value of power is less than the predefined value of power; and
controlling a value of oxygen-carbon ratio supplied to a reformer unit of the fuel cell system based on the comparison of the value of temperature with the predefined value of temperature.