Multi-Stack Fuel Cell Systems and Power Distribution Method thereof

Abstract

The present invention was created to solve the various problems of the prior art described above, and aims to provide a fuel cell system applicable to residential environments by configuring a multi-stack fuel cell system based on an optimal power distribution method to reduce hydrogen consumption and increase efficiency.

Description

Technology Field

[0001] The present invention relates to a multi-stack fuel cell system and a power distribution method thereof. Background Technology

[0002] Amidst rising demand for renewable energy driven by the climate crisis and carbon neutrality issues, hydrogen is garnering attention as an energy storage source due to the intermittency of renewable energy. Consequently, interest in fuel cells, which generate energy using hydrogen, is expanding. Fuel cells are eco-friendly as they produce only electricity, water, and heat through electrochemical reactions; as carbon-free power generation devices, they can contribute to improving environmental conditions. Therefore, in preparation for a hydrogen economy, the world is continuously expanding infrastructure and developing technologies for hydrogen production, storage, transportation, and utilization, leading to a sustained increase in both the supply and demand for fuel cells. Consequently, there is a growing demand for the scale-up of fuel cells for buildings, power generation, and marine applications. Multi-stack systems are being considered as one method for achieving this scale-up. Compared to single-stack systems, multi-stack systems can improve overall system efficiency. Furthermore, they allow for continued operation even if some stacks fail, and facilitate the easy addition or removal of stacks, thereby reducing maintenance time and costs. Due to these advantages, various studies are being conducted on multi-stack systems in terms of fluid, electrical, and thermal structures, as well as power management, water, and thermal management. In particular, it is crucial for multi-stack systems to maximize efficiency by appropriately distributing power to each stack. Although there are various methods for distributing power, sufficient research has not yet been conducted on multi-stack fuel cell systems that possess the efficiency required for introduction into actual residential environments. The problem to be solved

[0003] The present invention was created to solve the various problems of the prior art described above, and aims to provide a fuel cell system applicable to residential environments by configuring a multi-stack fuel cell system based on an optimal power distribution method to reduce hydrogen consumption and increase efficiency. means of solving the problem

[0004] To achieve the above objectives, a fuel cell system according to one embodiment of the present invention comprises a fuel cell module including a plurality of fuel cell stacks and a power distribution module for distributing power to the plurality of fuel cell stacks, wherein the power distribution module can distribute power to each of the fuel cell stacks so as to maximize the overall efficiency of the fuel cell system.

[0005] A power distribution method for a fuel cell system according to one embodiment of the present invention may include a step of distributing the power of each of the fuel cell stacks to maximize the overall efficiency of the fuel cell system, in a fuel cell system comprising a fuel cell module including a plurality of fuel cell stacks and a power distribution module for distributing the power of the plurality of fuel cell stacks. Effects of the invention

[0006] According to the present invention, the operation of a fuel cell system can be optimized to increase operating efficiency.

[0007] In addition, hydrogen consumption is reduced.

[0008] In addition, by configuring a hybrid system with solar power generation, it can be applied to residential environments, reducing hydrogen consumption and improving system efficiency. Brief explanation of the drawing

[0009] Figure 1 is a configuration diagram of the fuel cell system of the present invention. Figure 2 is a configuration diagram of the fuel cell module of the present invention. FIG. 3 is a configuration diagram of a fuel cell module according to one embodiment of the present invention. Figure 4 is a configuration diagram of the power distribution module of the present invention. Figure 5 is a graph showing the experimental results and the iV curves before and after stack model parameter estimation. Figure 6 is an efficiency curve graph, where (a) is the efficiency curve of the air blower, (b) is the efficiency curve of the hydrogen recirculation blower, (c) is the efficiency curve of the water pump, (d) is the efficiency curve of the converter, (e) is the efficiency curve of the inverter, and (f) is the efficiency curve of the peripheral machinery excluding the inverter. FIG. 7 is a graph of the efficiency and output curves of an individual stack system according to one embodiment of the present invention. Figure 8 is a graph of the hourly power production of a commercial-grade solar power generation device. Figure 9 is a graph showing the power load of a solar-fuel cell hybrid system over time, where (a) shows the result of Experimental Example 1 and (b) shows the result of Experimental Example 2. Figure 10 is a graph showing the efficiency and power frequency of the experimental examples, where (a) shows the result of experimental example 1 and (b) shows the result of experimental example 2. Specific details for implementing the invention

[0010] Hereinafter, various embodiments of this document are described with reference to the accompanying drawings. The embodiments and the terms used therein are not intended to limit the technology described in this document to specific embodiments and should be understood to include various modifications, equivalents, and / or substitutions of said embodiments.

[0011] Hereinafter, preferred embodiments of a power distribution method of a fuel cell system according to the present invention will be described in detail with reference to the attached drawings.

[0013] FIG. 1 is a configuration diagram of a fuel cell system according to the present invention. Referring to FIG. 1, the fuel cell system (10) may include a fuel cell module (100) and a power distribution module (200).

[0014] Referring to FIG. 2, the fuel cell module (100) may include a plurality of fuel cell stacks (100a, 100b, 100c, 100d,...), a hydrogen supply unit (110), an air supply unit (120a, 120b, 120c, 120d,...), an inverter (130a, 130b, 130c, 130d,...) and a load (140).

[0015] Multiple fuel cell stacks (100a, 100b, 100c, 100d,...) can each be connected in parallel. That is, multiple fuel cell stacks (100a, 100b, 100c, 100d,...) can be electrically connected in parallel. (Hereafter, multiple fuel cell stacks (100a, 100b, 100c, 100d,...) will be described by substituting them for fuel cell stack (100a).) A fuel cell stack generates electricity by combining the energy of the hydrogen component in the fuel with the oxygen component in the air. A fuel cell stack can be formed in a structure capable of producing electricity through a redox reaction between a fuel (e.g., hydrogen) and an oxidant (e.g., air). For example, a fuel cell stack may include a membrane electrode assembly (MEA) in which catalytic electrode layers for electrochemical reactions are attached to both sides of an electrolyte membrane through which hydrogen ions move, a gas diffusion layer (GDL) that evenly distributes reactant gases and transmits generated electrical energy, gaskets and fastening mechanisms for maintaining airtightness and appropriate fastening pressure for the reactant gases and cooling water, and a bipolar plate for moving the reactant gases and cooling water.

[0016] In a fuel cell stack, hydrogen as fuel and air (oxygen) as an oxidant are supplied to the anode and cathode of the membrane electrode assembly, respectively, through the flow paths of the separator. Hydrogen is supplied to the anode, while air can be supplied to the cathode. The hydrogen supplied to the anode is decomposed into hydrogen ions (protons) and electrons by the catalysts in the electrode layers located on both sides of the electrolyte membrane. Of these, only hydrogen ions selectively pass through the electrolyte membrane, which acts as a cation exchange membrane, to the cathode, while electrons can simultaneously be transferred to the cathode through the conductive gas diffusion layer and the separator. At the cathode, the hydrogen ions supplied through the electrolyte membrane and the electrons transferred through the separator can react with oxygen in the air supplied to the cathode by the air supply device to produce water. The movement of hydrogen ions during this process generates a flow of electrons through the external wire, and this flow of electrons can generate an electric current.

[0017] The hydrogen supply unit (110) can supply fuel to a plurality of fuel cell stacks (100a, 100b, 100c, 100d,...). At this time, the hydrogen supply unit (110) is provided as a single configuration and can supply fuel to all of the plurality of fuel cell stacks (100a, 100b, 100c, 100d,...).

[0018] The air supply unit (120a, 120b, 120c, 120d,...) can supply air to a plurality of fuel cell stacks (100a, 100b, 100c, 100d,...) and can be provided in a number corresponding to the number of fuel cell stacks (100a, 100b, 100c, 100d,...).

[0019] The inverters (130a, 130b, 130c, 130d,...) convert power to supply AC power to the load (140), excluding the power used to drive the BOP (Balance of Plants, peripheral machinery). The BOP refers to the components or peripheral machinery other than the fuel cell stack, and performs the role of operating the fuel cell stack and the entire system. In the present invention, the inverters (130a, 130b, 130c, 130d,...) are used individually for each fuel cell stack (100a, 100b, 100c, 100d,...).

[0020] The load (140) receives electricity produced by the fuel cell from the inverter (130a, 130b, 130c, 130d,...). The load (140) can directly receive and consume the AC power converted from the inverter (130a, 130b, 130c, 130d,...).

[0021] Meanwhile, in FIG. 2, the fuel cell system (10) is shown as being composed of four fuel cell stacks (100a, 100b, 100c, 100d), but the embodiment is not limited thereto and can be composed of two or more different numbers.

[0023] Meanwhile, more specifically, with reference to FIG. 3, the fuel cell module (100) of the present invention may include, in addition to the fuel cell stack, a hydrogen supply unit, a hydrogen recirculation blower, a receiver, an air blower, a membrane humidifier, an air supply unit, a heat exchanger, a water pump 1, a water pump 2, a water tank, a DC / DC converter, a DC / AC inverter, and a load.

[0024] The above hydrogen supply unit can supply fuel (hydrogen) to the fuel cell stack.

[0025] The hydrogen recirculation blower sends unreacted hydrogen discharged from the fuel cell stack to the anode inlet side of the fuel cell stack. The moisture content of the above process can be controlled by passing through a receiver. In the present invention, the hydrogen recirculation blower and the receiver may be provided in a number corresponding to the number of fuel cell stacks.

[0026] The above air supply unit can supply a sufficient amount of air (oxygen) to the fuel cell stack through an air blower. In the present invention, the air supply unit and the air blower may be provided in a number corresponding to the number of fuel cell stacks.

[0027] The above membrane humidifier can transfer the temperature and moisture of the fuel cell stack exhaust air to the fuel cell stack intake air and control the temperature and moisture of the air supplied to the fuel cell stack. In the present invention, the membrane humidifier may be provided in a number corresponding to the number of fuel cell stacks.

[0028] The heat exchanger absorbs heat generated in the fuel cell stack to regulate the temperature. In the present invention, the heat exchanger may be provided in a number corresponding to the number of fuel cell stacks.

[0029] The above water pumps 1 and 2 can maintain the operating temperature of the fuel cell stack by discharging heat generated in the fuel cell stack. By using one water pump to transport water circulating in the fuel cell stack and one water pump to transport water circulating in the water tank, a total of two water pumps can be used for each fuel cell stack.

[0030] The above water tank can be involved in controlling the temperature and moisture of the fuel cell stack together with the above water pump and the above heat exchanger.

[0031] The above DC / DC converter converts a portion of the power output from the fuel cell stack into a voltage suitable for driving the Balance of Plants (BOP). In the present invention, the converter can be used individually for each fuel cell stack.

[0032] The above DC / AC inverter converts DC power into AC power to supply power to the above Load, excluding the power used to drive the BOP (Balance of Plants, peripheral machinery). In the present invention, an inverter can be used individually for each fuel cell stack.

[0033] The above load receives electricity produced by the fuel cell from the above DC / AC inverter. The above load can directly receive and consume the AC power converted from the above inverter.

[0034] Meanwhile, in FIG. 3, the fuel cell module (100) described above is shown as including two fuel cell stacks, but the embodiment is not limited thereto and may include three or more.

[0036] The power distribution module (200) of the present invention can distribute power from a fuel cell stack to increase the efficiency of a fuel cell system after constructing a model using the fuel cell module (100) of FIGS. 2 and 3. At this time, the modeling may be a fuel cell system efficiency modeling through fuel cell stack efficiency modeling, fuel cell BOP efficiency modeling, and fuel cell inverter efficiency modeling. The modeling method is explained in more detail in Examples 1 to 3 below.

[0038] The power distribution module (200) can designate the overall efficiency of the fuel cell system as the objective function below and designate a power allocation coefficient k corresponding to each of the fuel cell stacks as a decision variable to calculate the value of the decision variable that maximizes the objective function below.

[0039] ηsys,tot =

[0041] (η sys,tot : Overall efficiency of the fuel cell system,

[0042] η sys,i : Efficiency of each fuel cell stack (i = 1, 2, 3, 4, ..., n),

[0043] k i : Power allocation coefficients corresponding to each fuel cell stack (i = 1, 2, 3, 4, ..., n)

[0044] At this time, 'k i x η sys,i ' is added according to the number of fuel cell stacks.

[0046] The overall efficiency of the above fuel cell system can be determined from fuel cell system efficiency modeling data through fuel cell stack efficiency modeling, fuel cell BOP efficiency modeling, and fuel cell inverter efficiency modeling.

[0047] The power allocation coefficient k included in the above equation is calculated based on the GRG (Generalized Reduced Gradient) nonlinear solver algorithm, has a value between 0 and 1, and k j ≥ k j+1 (j = 1, 2, 3, 4, ..., n-1), and the sum of each power allocation coefficient can be 1. In this case, if the value of k is 0, it indicates operation stop, and if it is 1, it indicates a 100% output state.

[0049] More specifically, referring to FIG. 4, the power distribution module (200) may include, for example, a data processing unit (201) and a control unit (202).

[0050] The data processing unit (201) may include a communication unit (210), a processor (220), and a memory (230). The communication unit (210) may receive data from the fuel cell module (100). The memory (230) may store the algorithm and code for optimal power distribution described above. The processor (220) may calculate the overall efficiency of the fuel cell system (10) and determine the optimal power distribution method based on the code stored in the memory (230) and the data received by the communication unit (210). Afterward, the communication unit (210) may transmit data regarding the optimal power distribution method to the control unit (202).

[0052] The control unit (202) may include a communication unit (240) and a processor (250).

[0053] The communication unit (240) can receive data regarding the optimal power distribution method from the data processing unit (201). The processor (250) can control the output of the fuel cell module (100) based on the received data.

[0055] More specifically, the fuel cell power distribution system of the present invention is described focusing on the data processing method of the data processing unit (201).

[0056] The communication unit (210) of the data processing unit (201) can receive data from the fuel cell module (100) to obtain the overall efficiency of the fuel cell system (10). The data may include data regarding the efficiency of the fuel cell module (100). More specifically, it may receive data regarding the operating voltage of the fuel cell stack of the fuel cell module (100), air blower power consumption, hydrogen recirculation blower power consumption, pump power consumption, power generated by the stack, converter efficiency, and inverter efficiency.

[0057] A code for calculating the overall efficiency of the fuel cell system (10) may be stored in the memory (230). The code is based on the following equation (1) regarding the efficiency of the fuel cell stack, the efficiency of the BOP (wherein the following equation (1), BOP refers to a peripheral machine consisting of an air blower, a hydrogen recirculation blower, a water pump, and a converter), and the efficiency of the inverter.

[0058] Equation (1) :

[0059]

[0060] (At this time, : System efficiency, : Fuel cell stack efficiency, : Efficiency of the above BOP, : Inverter efficiency)

[0062] Additionally, a code for the overall efficiency of the fuel cell system (10) is stored in the memory (230). The code is based on the following equation (2), which sets the overall efficiency of the fuel cell system (10) as the objective function.

[0063] Equation (2) :

[0064] η sys,tot =

[0066] (η sys,tot : Overall efficiency of the fuel cell system,

[0067] η sys,i : Efficiency of each fuel cell stack (i = 1, 2, 3, 4, ..., n),

[0068] k i : Power allocation coefficients corresponding to each fuel cell stack (i = 1, 2, 3, 4, ..., n)

[0069] At this time, 'k i x η sys,i ' is added according to the number of fuel cell stacks.

[0071] The processor (220) calculates the overall efficiency of the fuel cell system (10) through Equation (1) based on the data received by the communication unit (210). Based on this, the processor (220) calculates the power allocation coefficient (k) in Equation (2) based on the GRG (Generalized Reduced Gradient) nonlinear solver algorithm.

[0072] After that, the communication unit (210) of the data processing unit (201) transmits the calculated data to the control unit (202). The communication unit (240) of the control unit (202) receives the data, and the processor (250) distributes the power output from the fuel cell module (100) based on the received data. The output power is supplied to the Load in the form of AC through an inverter.

[0074] The present invention will be described in detail below through specific embodiments.

[0075] However, the following examples are merely for illustrating the present invention and do not limit the present invention to the following examples.

[0077] Example 1

[0078] Stack Modeling

[0080] The efficiency of the stack can be calculated using the following equation (3), and to calculate this, the modeling was performed through the following steps.

[0081] Equation (3) :

[0083] First, each fuel cell stack (100a, 100b, 100c, 100d,...) included in the fuel cell module (100) has an active area of ​​350cm 2 It was modeled using 110 cells.

[0084] And we proceeded with the following assumptions.

[0085] - The fluid permeability of the membrane within the stack is constant.

[0086] - Pressure drop within the stack, cell overpotential of the anode, and concentration loss overpotential are ignored.

[0087] - There is no voltage drop in the channel and the reversible potential ( ) is assumed to be a constant.

[0089] The stack voltage was calculated by considering the theoretical potential, activation loss, and resistance loss, while neglecting concentration loss, using the equation (4) below.

[0090] Equation (4) :

[0092] Activation loss ( The Butler-Volmer equation (5) below was used. Since the hydrogen oxidation reaction is much faster than the oxygen reduction reaction, the activation loss of the anode was ignored, and only the activation loss of the cathode was considered. It can be seen that the higher the exchange current density, the smaller the activation loss.

[0093] Equation (5) :

[0095] Equation (6) :

[0097] Resistance loss ( ) considered only the resistance to ion flow in the electrolyte membrane. The water content (λ) of Nafion was simply calculated by multiplying the relative humidity RHa by the coefficient coeff(λ).

[0098] Equation (7) :

[0100] Equation (8) :

[0102] Equation (9) :

[0104] Subsequently, parameter estimation was performed to align the iV curves of the stack model with the experimental data, and the accuracy of the model was verified. Figure 5 is a graph showing the experimental results and the iV curves before and after performing stack model parameter estimation. Region of interest (0.4 A / cm² 2 After standardizing the experimental and model data (hereinafter), the Root Mean Square Error (RMSE) was calculated. The error value was 0.0608, confirming that the model predictions behaved similarly to the experimental values. Table 1 shows the reference and final values ​​of the parameters before estimation.

[0106]

[0108] Example 2

[0109] BOP modeling

[0110] The efficiency of the BOP can be calculated using the power consumed by the BOP, the power generated by the stack, and the efficiency of the converter, as shown in the equation (10) below.

[0111] Equation (10) :

[0113] To obtain this, modeling was carried out through the following steps.

[0115] First, the BOP power consumption is calculated using the following equation (11).

[0116] Equation (11): BOP Consumption Power =

[0117]

[0118] (In this context, BOP refers to peripheral machinery excluding converters and inverters.)

[0120] The power consumption of the air blower and hydrogen recirculation blower is calculated using the following equations (12) and (13).

[0121] Equation (12): P = F△h

[0122] Equation (13) :

[0123] (F: molar flow rate, η: isentropic efficiency, : enthalpy change per mole)

[0125] The power consumption of the water pump is calculated using the following equation (14).

[0126] Equation (14) :

[0127] (w: mass flow rate, g: gravitational acceleration, : the pressure difference across the pump, η= efficiency of the pump)

[0129] The power generated by the stack is calculated using the following equation (15).

[0130] Equation (15): Stack Production Power =

[0131] (i : current density ( A / cm 2 ), A : Activation area (cm²) 2 ))

[0133] The converter efficiency is calculated using the following equations (16) and (17).

[0134] Equation (16) :

[0135] Equation (17) :

[0137] (y0: 0.97, xc: 0.90873, Ag: 0.24045, tg: 0.1478)

[0139] Through the above modeling, the efficiency of the air blower, hydrogen recirculation blower, water pump, converter (301), and inverter (302) was measured and is shown in FIG. 6 (a), (b), (c), (d), and (e), respectively. FIG. 6 (f) shows the integrated efficiency curve of the BOP (peripheral machinery) excluding the inverter.

[0141] Example 3

[0142] Fuel cell system modeling

[0143] In this embodiment, following Examples 1 and 2, a final fuel cell system was constructed using four stacks.

[0144] Fuel required for stack operation was supplied through a hydrogen tank. Unreacted hydrogen and water discharged from the anode side of the stack were transferred to the anode inlet side through respective recirculation blowers. The humidification conditions of the anode were met by the water discharged from the anode. Air was supplied to the cathode through an air blower, and the humidification conditions were met by the water discharged from the cathode through a membrane humidifier. The heat generated in the fuel cell was simulated by a generator, and the heat was managed by a water pump and the transferred water. As described above, the generated power was distributed by a processor (220) based on the GRG (Generalized Reduced Gradient) nonlinear solver algorithm to calculate the power allocation coefficient (k) in Equation (2), and a processor (250) included in the control unit (202) that received the data distributed the power based on the received data. At this time, the power allocation coefficient (k) has a value between 0 and 1, where a value of k is 0 indicates operation stoppage, and a value of 1 indicates a 100% output state. Also, k j ≥ k j+1(j = 1, 2, 3), and the sum of each power allocation coefficient is 1. At this time, the control unit (202) states that each output of the stack has a current density of 0.4 A / cm² 2 The output was controlled so as not to exceed the limit.

[0145] .

[0146] The efficiency and output curves of individual stack systems were obtained by referring to Examples 1, 2, and 3 and Equation (1), and are shown in FIG. 7. (In Equation (1), the efficiency of the inverter is calculated using Equations (16) and (17) for calculating the efficiency of the converter, but for the inverter, y0: 0.93109, xc: 0.3698, Ag: 0.13637, tg: 0.05263)

[0147] Subsequently, a final fuel cell system was configured by applying the optimal power distribution method according to the present invention.

[0149] Below, a solar-fuel cell hybrid system was configured for introduction into an actual residential power consumption profile. Then, hydrogen consumption, system efficiency, and power frequency were compared by applying a total of three power distribution methods: the optimal power distribution method according to Example 3, the same power distribution method, and the Daisy-Chain power distribution method.

[0150] The above-mentioned identical power distribution method is characterized by distributing power equally to each stack and behaving similarly to a single stack or a multi-stack system electrically connected in series.

[0151] The above Daisy-Chain power distribution method distributes power sequentially to each stack. It is a method in which the (n)th stack is activated when the (n-1)th stack reaches maximum output.

[0152] The following experimental examples were conducted by setting the maximum power consumption of the house to 30kW.

[0154] Experimental Example 1

[0155] Solar-fuel cell hybrid system

[0156] The solar power generation device used in this experiment has a power production capacity that is 40 times that of the commercial-grade solar power generation device power profile shown in Fig. 8, and a maximum output of 35.52 kW. The solar power system first met the power requirements of the house, and the fuel cell system covered the shortfall. In this experiment, during daytime hours (from 7:00 to 13:00), the solar power system fully met the power consumption of the house, so the fuel cell system stopped operating. Fig. 9 (a) is a graph showing the power load of the solar-fuel cell hybrid system by time.

[0157] Afterwards, the efficiency, hydrogen consumption, and power frequency of the solar-fuel cell hybrid system according to the present experimental example, which applied the three power distribution methods described above, were compared.

[0159] Experimental Example 2

[0160] Solar-fuel cell hybrid system

[0161] The solar power generation device used in this experiment has a power production capacity that is 42 times that of the commercial-grade solar power generation device power profile shown in Fig. 8, and a maximum output of 17.76 kW. The solar power system first met the power requirements of the house, and the fuel cell system covered the shortfall. In this experiment, since the solar power system met only a portion of the house's power consumption, the fuel cell system operated 24 hours a day. Fig. 9 (b) is a graph showing the power load of the solar-fuel cell hybrid system by time.

[0162] Afterwards, the efficiency, hydrogen consumption, and power frequency of the solar-fuel cell hybrid system according to the present experimental example, which applied the three power distribution methods described above, were compared.

[0164] Figure 10 (a) is a graph showing the efficiency and power frequency of Experimental Example 1, and Figure 10 (b) is a graph showing the efficiency and power frequency of Experimental Example 2.

[0165] Experimental Example 1 has a relatively higher frequency of the high power range compared to Experimental Example 2, excluding the 7 hours when the fuel cell system is not in operation. Experimental Example 2 has a relatively higher frequency of the low power range when the fuel cell system operates for 24 hours. It can be seen that the time Experimental Example 2 operates with higher efficiency than Experimental Example 1 is 8 hours out of 24 hours.

[0166] The hydrogen consumption and average efficiency values ​​of Experimental Example 1 and Experimental Example 2 are shown in [Table 2] below.

[0168] Experimental Example 1 Experimental Example 2 Power distribution method Hydrogen consumption (kg) Average efficiency Hydrogen consumption (kg) Average efficiency Equal power distribution 552.12 54.942 % 626.28 54.815 % Daisy-Chain Power Distribution 564.12 53.756 % 636.66 53.838 % Optimal Power Distribution (Example 3) 551.43 55.012 % 621.78 55.145 %

[0169] The average efficiency was calculated using the following equation (18).

[0170] Equation (18) :

[0172] In the case of Experimental Example 1, the frequency of operation of the fuel cell system at low power is low, so the difference in hydrogen consumption and average efficiency between the identical power distribution method and the optimal power distribution method is negligible, at 0.69 kg and 0.07%p, respectively. In the case of Experimental Example 2, the frequency of operation of the fuel cell system at low power is relatively high, so the difference in hydrogen consumption and average efficiency is greater than in Experimental Example 1, at 4.5 kg and 0.33%p, respectively. It can be seen that the efficiency improvement effect of the optimal power distribution method according to the present invention increases as the frequency of operation of the fuel cell system in the low-power region, where the optimal power distribution method according to the present invention is more efficient than the identical power distribution method, increases. It is expected that if the peak point of the fuel cell system efficiency curve shifts to the high-power region, the effect of the optimal power distribution method according to the present invention can be further maximized even in the high-power operation region.

[0174] The present invention has been described above with reference to its preferred embodiments. Those skilled in the art will understand that the present invention may be embodied in modified forms without departing from the essential characteristics of the invention. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the invention is defined by the claims, not by the foregoing description, and all variations within the scope of the claims should be interpreted as being included in the invention. Explanation of the symbols

[0176] 10: Fuel cell system 100 : Fuel cell module 100a, 100b, 100c, 100d: Fuel cell stack 110: Hydrogen supply unit 120a, 120b, 120c, 120d: Air supply unit 130a, 130b, 130c, 130d: Inverter 140 : Load 200 : Power distribution module 201 : Data Processing Unit 202 : Control unit 210 : Communications Unit (Data Processing Unit) 220 : Processor (data processing unit) 230 : Memory 240 : Communication unit (control unit) 250 : Processor (Control Unit)

Claims

Claim 1 A fuel cell system comprising: a fuel cell module including a plurality of fuel cell stacks; and a power distribution module for distributing power of the plurality of fuel cell stacks, wherein the power distribution module distributes power to each of the fuel cell stacks so as to maximize the overall efficiency of the fuel cell system, and wherein the power distribution module designates the overall efficiency of the fuel cell system as the following objective function and designates a power allocation coefficient k corresponding to each of the fuel cell stacks as a decision variable, and calculates the value of the decision variable that maximizes the following objective function. sys,tot = (η sys,tot : Overall efficiency of the fuel cell system, η sys,i : Efficiency of each fuel cell stack (i = 1, 2, 3, 4, ..., n), k i : Power allocation coefficients corresponding to each fuel cell stack (i = 1, 2, 3, 4, ..., n)) Claim 2 A fuel cell system according to claim 1, characterized in that the plurality of fuel cell stacks are electrically connected in parallel. Claim 3 A fuel cell system according to claim 1, wherein the fuel cell module comprises: a hydrogen supply unit for supplying fuel to a plurality of fuel cell stacks; a plurality of air supply units for supplying air to the fuel cell stacks, provided in a number corresponding to the number of the plurality of fuel cell stacks; and a plurality of inverters for converting power output from the fuel cell stacks, provided in a number corresponding to the number of the plurality of fuel cell stacks. Claim 4 delete Claim 5 In claim 1, the power allocation coefficient k is obtained based on the GRG (Generalized Reduced Gradient) nonlinear solver algorithm and has a value between 0 and 1 (0 indicates operation stopped, 1 indicates a 100% output state), and k j ≥ k j+1 A fuel cell system characterized by (j = 1, 2, 3, 4, ..., n-1) and the sum of each power allocation coefficient being 1. Claim 6 A fuel cell system according to claim 3, characterized in that the overall efficiency of the fuel cell system is determined from fuel cell system efficiency modeling data through fuel cell stack efficiency modeling, fuel cell BOP efficiency modeling, and fuel cell inverter efficiency modeling. Claim 7 A fuel cell system comprising: a fuel cell module including a plurality of fuel cell stacks; and a power distribution module for distributing power of the plurality of fuel cell stacks, wherein the method comprises the step of distributing power to each of the fuel cell stacks such that the overall efficiency of the fuel cell system is maximized, and wherein the step of distributing power is characterized by designating the overall efficiency of the fuel cell system as the following objective function and designating a power allocation coefficient k corresponding to each of the fuel cell stacks as a decision variable, and calculating the value of the decision variable that maximizes the following objective function. sys,tot = (η sys,tot : Overall efficiency of the fuel cell system, η sys,i : Efficiency of each fuel cell stack (i = 1, 2, 3, 4, ..., n), k i : Power allocation coefficients corresponding to each fuel cell stack (i = 1, 2, 3, 4, ..., n)) Claim 8 delete Claim 9 In Clause 7, the power allocation factor k is obtained based on the GRG (Generalized Reduced Gradient) nonlinear solver algorithm and has a value between 0 and 1 (0 indicates operation stopped, 1 indicates a 100% output state), and k j ≥ k j+1 A power distribution method for a fuel cell system characterized by (j = 1, 2, 3, 4, ..., n-1) and the sum of each power allocation coefficient being 1. Claim 10 In claim 7, the overall efficiency of the fuel cell system is a power distribution method of a fuel cell system determined from fuel cell system efficiency modeling data through fuel cell stack efficiency modeling, fuel cell BOP efficiency modeling, and fuel cell inverter efficiency modeling.

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