Method for controlling the cooling water temperature in a fuel cell system

Abstract

To more finely control the temperature of a coolant by adjusting an opening degree of a valve.SOLUTION: A controller may be configured to: set a target temperature at an inlet of the fuel cell stack (10) and a correction coefficient for controlling an opening degree of valves (20, 40); measure a first coolant temperature at an outlet of the fuel cell stack (10) and a second coolant temperature at an outlet of a first radiator (60); calculate the opening degree of the valves (20, 40) based on the first coolant temperature, the second coolant temperature, the target temperature, and the correction coefficient; and correct the correction coefficient based on comparison of a third coolant temperature at the inlet of the fuel cell stack (10) and the target temperature, in response to the opening degree being within a first range.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The embodiments disclosed in this document relate to a technique for controlling the cooling water temperature in a fuel cell system.

Background Art

[0002] A fuel cell system can generate electrical energy using a fuel cell stack. For example, when hydrogen is used as the fuel of the fuel cell stack, it can be an alternative to solve global environmental problems, and thus continuous research and development on fuel cell systems are being carried out. A fuel cell system includes a fuel cell stack that generates electrical energy, a fuel supply device that supplies fuel (hydrogen) to the fuel cell stack, an air supply device that supplies oxygen in the air, which is an oxidant required for the electrochemical reaction, to the fuel cell stack, and a thermal management system (TMS) that removes the reaction heat of the fuel cell stack to the outside of the system, controls the operating temperature of the fuel cell stack, and performs a water management function.

[0003] The thermal management system is a type of cooling device that circulates an antifreeze liquid that serves as cooling water through the fuel cell stack to maintain an appropriate temperature (for example, 60 to 70°C). It can include a TMS line through which the cooling water circulates, a reservoir in which the cooling water is stored, a pump that circulates the cooling water, an ion filter that removes ions contained in the cooling water, and a radiator that releases the heat of the cooling water to the outside. In addition, the thermal management system can include a heater that heats the cooling water, and an air conditioning unit (for example, a heater for heating) that cools and heats the interior of a device (e.g., a vehicle) in which the fuel cell system is included using the cooling water. The thermal management system can maintain the appropriate temperature not only of the fuel cell stack but also of the electrical components of the vehicle.

Summary of the Invention

Problems to be Solved by the Invention

[0004] One function of the thermal management system is to release the heat generated in the fuel cell stack into the atmosphere via the radiator, thereby adjusting the temperature of the cooling water flowing into the fuel cell stack inlet to a target temperature. Controlling the rotation speed of the pump and cooling fan is a crucial task in adjusting the cooling water temperature to the target temperature. However, since the rotation speed of the pump and cooling fan fluctuates considerably, more precise control is required to reduce the difference between the cooling water temperature and the target temperature. [Means for solving the problem]

[0005] A fuel cell system according to one embodiment disclosed herein includes a fuel cell stack, a first cooling line through which first cooling water circulates via the fuel cell stack, a first radiator positioned on the first cooling line and configured to cool the first cooling water, a valve configured to switch the flow path of the first cooling water to the fuel cell stack or the first radiator, and a control unit connected to the valve, wherein the control unit may be configured to set a target temperature at the inlet of the fuel cell stack and a correction coefficient for controlling the opening amount of the valve, measure the first cooling water temperature at the outlet of the fuel cell stack and the second cooling water temperature at the outlet of the first radiator, calculate the opening amount of the valve based on the first cooling water temperature, the second cooling water temperature, the target temperature, and the correction coefficient, and correct the correction coefficient based on a comparison between the third cooling water temperature at the inlet of the fuel cell stack and the target temperature if the opening amount is within a specified first range.

[0006] A method for operating a fuel cell system including a fuel cell stack according to one embodiment disclosed herein may include: setting a target temperature at the fuel cell stack inlet and a correction coefficient for controlling the valve opening; measuring a first coolant temperature at the fuel cell stack outlet and a second coolant temperature at the first radiator outlet; calculating the valve opening based on the first coolant temperature, the second coolant temperature, the target temperature, and the correction coefficient; and correcting the correction coefficient based on a comparison between the third coolant temperature at the fuel cell stack inlet and the target temperature, provided that the opening is within a specified first range. [Effects of the Invention]

[0007] According to the embodiments disclosed herein, the fuel cell system can more precisely control the cooling water temperature by adjusting the valve opening.

[0008] According to the embodiments disclosed herein, the fuel cell system can more quickly adjust the cooling water temperature at the fuel cell stack inlet to a target temperature.

[0009] According to embodiments disclosed herein, a fuel cell system can control the cooling water temperature while rapidly responding to load fluctuations through the combined control of a pump, a cooling fan, and a valve.

[0010] In addition, a variety of other effects may be conveyed, either directly or indirectly, through this document. [Brief explanation of the drawing]

[0011] [Figure 1] This document illustrates fuel cell systems in various embodiments. [Figure 2] This document illustrates fuel cell systems in various embodiments. [Figure 3] A block diagram of a fuel cell system through which the first cooling water flows is shown in various embodiments. [Figure 4a] This shows the flow of cooling water at different valve openings in various embodiments. [Figure 4b] This shows the flow of cooling water at different valve openings in various embodiments. [Figure 4c] This shows the flow of cooling water at different valve openings in various embodiments. [Figure 5] Block diagrams of fuel cell systems in various embodiments are shown. [Figure 6] The following are operational flowcharts for controlling the valve opening and correction coefficient using various embodiments. [Figure 7] A more detailed operational flowchart for controlling the valve opening and correction coefficient through various embodiments is shown.

[0012] In relation to the description of the drawings, the same or similar reference numerals may be used for the same or similar components. [Modes for carrying out the invention]

[0013] Various embodiments of the present invention are described below with reference to the drawings. However, this should not be understood as limiting the present invention to any particular embodiment, but rather as including various modifications, equivalents, and / or alternatives to the embodiments of the present invention.

[0014] The various embodiments and terminology used herein are not intended to limit the technical features described herein to any particular embodiment, but should be understood to include various modifications, equivalents, or substitutes of such embodiments. In relation to the description of the drawings, similar or related reference numerals may be used for similar or related components. The singular form of a noun corresponding to an item may include one or more of such items unless otherwise indicated to be clearly different in the context. In this document, each phrase such as “A or B,” “at least one of A and B,” “at least one of A or B,” “A, B or C,” “at least one of A, B and C,” and “at least one of A, B or C” may include any one of the items listed together in the phrase, or any possible combination thereof. Terms such as “first,” “second,” or “first,” or “second” may be used merely to distinguish one component from other such components, and do not limit the component in any other respect (e.g., importance or order). When a component (e.g., the first) is referred to as "coupled" or "connected" with or without such terms, it means that the first component can be connected to the other component directly (e.g., by wire), wirelessly, or via the third component.

[0015] The term "module," as used in various embodiments of this document, may include units embodied in hardware, software, or firmware, and may be used interchangeably with terms such as logic, logic block, component, or circuit. A module can be a single component, or the smallest unit or part thereof of such component that performs one or more functions. For example, according to one embodiment, a module may be embodied in the form of an ASIC (application-specific integrated circuit).

[0016] Various embodiments of this document may be embodied in software (e.g., a program) containing one or more instruction words stored in a machine-readable storage medium (e.g., internal memory or external memory). For example, a machine may invoke and perform at least one instruction from the one or more instruction words stored in the storage medium. This enables the machine to be operated to perform at least one function by the invoked at least one instruction word. The one or more instruction words may include code generated by a compiler or code that can be performed by an interpreter. The machine-readable storage medium may be provided in the form of a non-transitory storage medium. Here, "non-transitory" simply means that the storage medium is a tangible device and does not contain signals (e.g., electromagnetic waves), and this term does not distinguish between cases where data is stored semi-permanently and cases where it is stored temporarily on the storage medium.

[0017] According to one embodiment, the methods according to the various embodiments disclosed herein may be provided as part of a computer program product. The computer program product may be traded as a commodity between a seller and a buyer. The computer program product may be distributed in the form of a device-readable storage medium (e.g., compact disc read-only memory (CD-ROM)) or online (e.g., download or upload) via an application store or directly between two user devices. In the case of online distribution, at least a portion of the computer program product may be temporarily stored or temporarily generated in a device-readable storage medium such as the memory of a manufacturer's server, an application store server, or an intermediary server.

[0018] According to various embodiments, each of the components (e.g., modules or programs) described above may include one or more individuals, and some of the multiple individuals may be separately arranged from other components. According to various embodiments, one or more of the above-described components or operations may be omitted, or one or more other components or operations may be added. Alternatively or additionally, multiple components (e.g., modules or programs) may be integrated into one component. In such a case, the integrated component can perform one or more functions of each of the multiple components in the same or similar manner as performed by the component among the multiple components before the integration. According to various embodiments, the operations performed by a module, program, or other component may be executed sequentially, in parallel, iteratively, or heuristically, or one or more of the operations may be executed in a different order, omitted, or one or more other operations may be added.

[0019] FIGS. 1 to 2 show a fuel cell system according to various embodiments.

[0020] Referring to FIG. 1, a vehicle fuel cell system may include a first cooling line 110 through which a first cooling water circulates via a fuel cell stack 10 of the vehicle, and a second cooling line 120 through which a second cooling water circulates via power electronic parts 200 of the vehicle. In an embodiment, the fuel cell system may further include a heat exchanger 300 that mutually exchanges heat between the first cooling water and the second cooling water, but it can be omitted.

[0021] The fuel cell system may form a heating loop (heating circulation path, or heating loop) with the first cooling line 110, or may include a first connecting line 130, a second connecting line 150, and a third connecting line 140 to form a cooling line with the first cooling line 110. The first coolant may be cooled or heated while circulating through the first connecting line 130, the second connecting line 150, or the third connecting line 140. For example, the first cooling line 110 may form a heating loop with the first connecting line 130 and the third connecting line 140 to ensure cold-start capability in the initial starting state of the vehicle, and during driving, it may form a cooling loop through which the first coolant passes the first radiator 60 so that the heat generated in the fuel cell stack 10 can be released to the outside. In another embodiment, if the outside air is as high as a specified temperature, the first cooling line 110 may not form a heating loop, and the fuel cell system may be able to ensure starting capability by the heat of the fuel cell stack 10. A fuel cell stack 10, a first valve 20, a first pump 30, a second valve 40, and a first radiator 60 may be arranged on the first cooling line 110 through which the first cooling water circulates.

[0022] A fuel cell stack 10 (or may be referred to as a "fuel cell") can be formed into a structure capable of producing electricity through a redox reaction between a fuel (e.g., hydrogen) and an oxidizer (e.g., air). As an example, the fuel cell stack 10 may include a membrane electrode assembly (MEA) with a central electrolyte membrane on which hydrogen ions move, and catalytic electrode layers attached to both sides of the membrane where electrochemical reactions occur; a gas diffusion layer (GDL) that uniformly distributes the reaction gas and transmits the generated electrical energy; gaskets and fasteners for maintaining airtightness and proper fastening pressure of the reaction gas and first coolant; and a bipolar plate for moving the reaction gas and first coolant.

[0023] In the fuel cell stack 10, hydrogen, which is the fuel, and air (oxygen), which is the oxidizer, are supplied to the anode and cathode of the membrane electrode assembly via the flow path of the separator plate. Hydrogen can be supplied to the anode, and air to the cathode. The hydrogen supplied to the anode is decomposed into hydrogen ions (protons) and electrons by the catalyst of the electrode layer configured on both sides of the electrolyte membrane. Of these, only the hydrogen ions are selectively transferred to the cathode through the electrolyte membrane, which is a cation exchange membrane, while electrons can be transferred to the cathode simultaneously via the gas diffusion layer, which is a conductor, and the separator plate. At the cathode, the hydrogen ions supplied via the electrolyte membrane and the electrons transferred via the separator plate can react with oxygen in the air supplied to the cathode by the air supply device to produce water. During this process, the movement of hydrogen ions generates a flow of electrons through an external conductor, and this flow of electrons can generate an electric current.

[0024] The first valve 20 can switch the flow path of the first cooling water on the first cooling line 110 to either the first connecting line 130 where the heater 50 is located or the fuel cell stack 10. For example, the first valve 20 may be connected to one end of the first pump 30, one end of the first connecting line 130, and one end of the fuel cell stack 10 on the first cooling line 110. The first valve 20 may include a variety of valve means that can selectively switch the flow path of the first cooling water. As an example, the first valve 20 may be a three-way valve. In this case, the first valve 20 may include a first port 21 connected to the first cooling line 110 so that the first cooling water pumped by the first pump 30 flows into it, a second port 22 connected to the first cooling line 110 so that the first cooling water passing through the first valve 20 flows into the fuel cell stack 10, and a third port 23 connected to one end of the first connecting line 130. By opening and closing the second port 22 and third port 23 of the first valve 20, the flow path of the first cooling water may be switched to either the heater 50 of the first connecting line 130 or the fuel cell stack 10. That is, if the second port 22 is opened and the third port 23 is closed, the first cooling water flows into the fuel cell stack 10, and conversely, if the third port 23 is opened and the second port 22 is closed, the first cooling water may flow into the heater 50 via the first connecting line 130.

[0025] The first connecting line 130 can form a heating loop (heating circulation path) with the first cooling line 110 to heat the first cooling water. For example, the first cooling water flowing along the first connecting line 130 may be heated as it passes through a heater 50 provided in the first connecting line 130. One end of the first connecting line 130 may be connected to the first cooling line 110 at a first point located between the outlet of the first pump 30 and the fuel cell stack 10, and the other end of the first connecting line 130 may be connected to the first cooling line 110 at a second point located between the inlet of the first pump 30 and the fuel cell stack 10. Here, the inlet of the first pump 30 may be defined as the inlet through which the first cooling water flows into the first pump 30. The outlet of the first pump 30 may be defined as the outlet through which the first cooling water that has passed through the first pump 30 is discharged. Furthermore, the section between the outlet of the first pump 30 and the fuel cell stack 10 can be defined as the section through which the first cooling water discharged from the first pump 30 flows to the first cooling water inlet (not shown) of the fuel cell stack 10. Also, the section between the inlet of the first pump 30 and the fuel cell stack 10 can be defined as the section through which the first cooling water discharged from the cooling water outlet (not shown) of the fuel cell stack 10 flows to the inlet of the first pump 30.

[0026] The first pump 30 may be configured to force the flow of the first cooling water. The first pump 30 may include a variety of means for pumping the first cooling water, and the type and number of the first pump 30 are not limited in this document.

[0027] The second valve 40 can switch the flow path of the first coolant on the first cooling line 110 to either the first radiator 60 or the fuel cell stack 10. For example, the second valve 40 may be provided on the first cooling line 110 so as to be located between the first pump 30 and the first radiator 60, and may be connected to one end of the third connecting line 140 and to the outlet of the first radiator 60. The second valve 40 may include a variety of valve means that can selectively switch the flow path of the first coolant to either the first radiator 60 or the fuel cell stack 10. As an example, the second valve 40 may be a four-way valve or a three-way valve. In the case of a three-way valve, the second valve 40 includes a first port 41 connected to a third connecting line 140, a second port 42 connected to a first cooling line 110 so that the first coolant passing through the first radiator 60 flows in, and a third port 44 connected to the first cooling line 110 so that the first coolant flows into the first pump 30. A four-way valve of the second valve 40 may further include a third port 43 connected to one end of the second connecting line 150. The flow path of the first coolant may be switched to the first radiator 60 or the fuel cell stack 10 by opening or closing the first port 41 or the second port 42 of the second valve 40. In other words, if the first port 41 is opened and the second port 42 is closed, the first coolant flows into the fuel cell stack 10 without passing through the first radiator 60. Conversely, if the second port 42 is opened and the first port 41 is closed, the first coolant may flow into the fuel cell stack 10 after passing through the first radiator 60.

[0028] The second connection line 150 can form a heating loop with the first cooling line 110 to heat the HVAC unit 90. For example, the second connection line 150 can form a loop to heat a heating heater (not shown) of the HVAC unit 90. One end of the second connection line 150 is connected to the first cooling line 110 between a first point (where one end of the first connection line 130 is connected to the first cooling line 110) and the inlet of the fuel cell stack 10, so that a portion of the first cooling water can circulate through the second connection line 150. The other end of the second connection line 150 may be connected to the first cooling line 110 between the first pump 30 and a second point (where the other end of the first connection line 130 is connected to the first cooling line 110).

[0029] The second connection line 150 may be equipped with an ion filter 95 for filtering ions from the first cooling water that has passed through the air conditioning unit 90. If the electrical conductivity of the first cooling water increases due to system corrosion or exudation, electricity will flow through the first cooling water, causing problems such as a short circuit in the fuel cell stack 10 or current flowing to the first cooling water side. Therefore, the first cooling water must maintain a low electrical conductivity. The ion filter 95 may be set to remove ions contained in the first cooling water so that the electrical conductivity of the first cooling water can be maintained below a certain level. In this way, during a cold start when the supply of first cooling water flowing to the fuel cell stack 10 is cut off (the second port 22 of the first valve 20 is cut off), the first cooling water circulates via the heater 50 of the first connection line 130 (heating loop) and at the same time circulates along the second connection line 150, so that filtering (removal of ions contained in the first cooling water) by the ion filter 95 provided in the second connection line 150 is possible even during a cold start. Therefore, it is possible to obtain the advantageous effect of maintaining the electrical conductivity of the first cooling water flowing into the fuel cell stack 10 immediately after cold start below a certain level.

[0030] The third connecting line 140 can form a cooling loop with the first cooling line 110 to cool the first cooling water. For example, one end of the third connecting line 140 may be connected to the first cooling line 110 between the first pump 30 and the first radiator 60, and the other end of the third connecting line 140 may be connected to the first cooling line 110 between the cooling water outlet of the fuel cell stack 10 and the first radiator 60.

[0031] The first radiator 60 may be configured to cool the first coolant. The first radiator 60 may be formed in a variety of structures capable of cooling the first coolant, and the present invention is not limited or restricted by the type and structure of the first radiator 60. The first radiator 60 may be connected to a first reservoir 62 in which the first coolant is stored.

[0032] The fuel cell system may include a first temperature sensor 112 that measures the temperature of the first coolant between the fuel cell stack 10 and a first point (first valve 20), a second temperature sensor 114 that measures the temperature of the first coolant between the other end of the first connecting line 130 and the first pump 30, and a third temperature sensor 116 that measures the temperature of the first coolant at the heater 50. The fuel cell system may also include a fourth temperature sensor 118 that measures the temperature of the first coolant at the outlet of the first radiator 60. Based on the temperatures measured by the first temperature sensor 112, the second temperature sensor 114, the third temperature sensor 116, and the fourth temperature sensor 118, the fuel cell system can control the inflow rate of the first coolant flowing into the fuel cell stack 10. For example, if the measured temperature of the first coolant circulating along the first cooling line 110 is lower than a preset target temperature, the inflow rate of the first coolant can be controlled to be lower than a preset set flow rate. Thus, when the measured temperature of the first cooling water is low, by controlling the inflow rate of the first cooling water flowing into the fuel cell stack 10 to a low level, it is possible to obtain the advantageous effect of minimizing thermal shock and performance degradation caused by the difference between the temperature of the first cooling water stagnating inside the fuel cell stack 10 and the temperature of the first cooling water flowing into the fuel cell stack 10.

[0033] The second cooling line 120 is configured to pass through the vehicle's electrical components 200, and the second coolant can circulate along the second cooling line 120. Here, the vehicle's electrical components 200 may be understood as components that use the vehicle's power supply as an energy source, and the present invention is not limited or restricted by the type and number of electrical components 200. As an example, the electrical components 200 may include at least one of the following: a BHDC (bi-directional high voltage DC-DC converter) 210 provided between the fuel cell stack 10 and the vehicle's high-voltage battery (not shown); a BPCU (blower pump control unit) 220 that controls a blower (not shown) that supplies outside air for driving the fuel cell stack 10; an LDC (low-voltage DC-DC converter) 230 that converts the DC high voltage supplied by the high-voltage battery to DC low voltage; an air compressor (ACP) 240 that compresses the air supplied to the fuel cell stack 10; and an air cooler 250. Although not shown in Figures 1 or 2, the electrical component 200 may further include a DC-DC buck / boost converter.

[0034] A second pump 205 may be provided on the second cooling line 120 for forcibly circulating the second cooling water. The second pump 205 may include pumping means capable of pumping the second cooling water, and the type and characteristics of the second pump 205 are not limited or restrictive.

[0035] A second radiator 70 for cooling the second coolant may be located on the second cooling line 120. The second radiator 70 may be formed in a variety of structures capable of cooling the second coolant, and the type and structure of the second radiator 70 are not limited or restricted. The second radiator 70 may be connected to a second reservoir 72 in which the second coolant is stored.

[0036] In one embodiment, the first radiator 60 and the second radiator 70 may be configured to be cooled simultaneously by a single cooling fan 80, as shown in Figure 1. For example, the first radiator 60 and the second radiator 70 may be arranged side by side, and the cooling fan 80 may be configured to blow outside air onto the first radiator 60 and the second radiator 70. By having the first radiator 60 and the second radiator 70 cooled simultaneously by a single cooling fan 80, the structure of the fuel cell system can be simplified, design flexibility and space utilization can be improved, and the power consumption for cooling the first radiator 60 and the second radiator 70 can be minimized.

[0037] In other embodiments, as shown in Figure 2, a first cooling fan 80 for cooling the first radiator 60 and a second cooling fan 85 for cooling the second radiator 70 may be separately provided. In this case, the fuel cell system can eliminate parameters related to the thermal load of the electrical components 200 when controlling the rotational speed of the first cooling fan 80. The embodiments described below are based on the fuel cell system structure of Figure 1, but the same principles may be applied to the fuel cell system structure of Figure 2.

[0038] The heat exchanger 300 may be configured to allow the first coolant and the second coolant to exchange heat with each other. When the heat exchanger 300 is included, the first cooling line 110 and the second cooling line 120 can constitute a thermal management system (TMS) line in which the first and second coolants can flow while exchanging heat. In this case, the first or second coolant may be used as a cooling medium or heat medium on the TMS line. For example, since the temperature of the second coolant that cools the electrical components is set to be relatively lower than the temperature of the first coolant that cools the fuel cell stack 10, the fuel cell system can lower the temperature of the first coolant without increasing the capacity of the first radiator 60 and the cooling fan 80 by allowing the first and second coolants to exchange heat with each other, thereby improving the cooling efficiency of the fuel cell stack 10 and obtaining advantageous effects that improve safety and reliability. Furthermore, since the fuel cell system can lower the temperature of the first cooling water while the vehicle is stopped and airflow cannot be used (for example, construction machinery), it can ensure high-power operation of the fuel cell stack 10, thereby providing advantageous effects that improve safety and durability.

[0039] In one embodiment, the heat exchanger 300 is connected to a first cooling line 110 between the outlet of the first radiator 60 and the fuel cell stack 10, and a second cooling line 120 can connect the outlet of the second radiator 70 to electrical components via the heat exchanger 300. For example, the first coolant may flow along the heat exchanger 300 connected to the first cooling line 110, and the second cooling line 120 can pass through the inside of the heat exchanger 300 so as to be exposed to the first coolant (for example, the first coolant flows along the second cooling line 120). In this way, the fuel cell system can lower the temperature of the first coolant flowing into the fuel cell stack 10 through mutual heat exchange between the first and second coolants. The first temperature of the first coolant after passing through the first radiator 60 may be higher than the second temperature of the second coolant after passing through the second radiator 70, and the third temperature of the first coolant after passing through the heat exchanger 300 may be lower than the first temperature. For example, the first temperature of the first coolant may be approximately 10°C higher than the second temperature of the second coolant, and the third temperature of the first coolant after passing through the heat exchanger 300 (exchanging heat with the second coolant) may be 1°C lower than the first temperature.

[0040] The heat exchanger 300 shown in Figures 1 and 2 is positioned separately from the first radiator 60, but in other embodiments, the heat exchanger 300 may be directly connected to the first radiator 60. For example, the heat exchanger 300 may be connected to a designated position (upper left end) of the first radiator 60, but is not limited thereto.

[0041] In the case of the first cooling line 11 through which the first cooling water flows, the fuel cell system can measure the first cooling water temperature at the inlet of the fuel cell stack 10 via the first temperature sensor 112 and control the rotation speed of at least one of the first pump 30 or cooling fan 80 so that the measured first cooling water temperature reaches the target temperature. However, since the rotation speeds of the first pump 30 and cooling fan 80 fluctuate greatly, it may be difficult to narrow the difference between the temperature measured via the first temperature sensor 112 and the target temperature. In the embodiment, the fuel cell system can finely control the first cooling water temperature to the target temperature by adjusting the opening of the second valve 40. Furthermore, in the embodiment, the fuel cell system can control the first cooling water temperature more accurately by adjusting the opening of the second valve 40 using the first cooling water temperature at the outlet of the fuel cell stack 10 measured via the second temperature sensor 114 and the first cooling water temperature at the outlet of the first radiator 60 measured via the fourth temperature sensor 118.

[0042] Figure 3 shows a block diagram of a fuel cell system through which the first cooling water flows in various embodiments, and Figures 4a to 4c show the flow of the cooling water depending on the valve opening. Among the configurations shown in Figure 3, configurations with the same reference number perform the same function as the configurations shown in Figure 1 or Figure 2, and redundant explanations will be omitted below.

[0043] Referring to Figure 3, m represents the flow rate of the first coolant. For example, m1 could represent the flow rate of the first coolant leaving the fuel cell stack 10 and entering the second valve 40 without passing through the first radiator 60, m2 could represent the flow rate of the first coolant leaving the fuel cell stack 10 and entering the second valve 40 via the first radiator 60, m3 could represent the flow rate of the first coolant entering the fuel cell stack 10 and leaving the second valve 40, m4 could represent the flow rate of the first coolant leaving the first valve 20 and entering the first pump 30 via the ion filter 95, and m5 could represent the flow rate of the first coolant leaving the first pump 30 and passing through the first valve 20. Also, T represents the temperature of the first coolant. For example, T1 could represent the temperature of the first coolant at the outlet of the fuel cell stack 10, T2 could represent the temperature of the first coolant at the outlet of the first radiator 60, T3 could represent the temperature of the coolant at the inlet of the fuel cell stack 10, and T4 could represent the temperature of the first coolant passing through the heater 50. The flow rate and temperature of the first cooling water may be expressed as shown in [Equation 1] below.

[0044]

number

[0045] The fuel cell system can adjust the mixing ratio of the first coolant and the temperature of the first coolant by adjusting the opening of the second valve 40. For example, Figure 4a shows the second valve 40 in a closed state (opening amount = 0), in which case the second port 42 of the second valve 40 is closed, so the first coolant coming out of the fuel cell stack 10 can flow onto the third connecting line 140 without passing through the first radiator 60. Figure 4b shows the second valve 40 in an open state (0 < opening amount < 1), in which case the first port 41 and the second port 42 of the second valve 40 are partially opened, so a portion of the first coolant can flow onto the third connecting line 140, and the remaining portion can pass through the first radiator 60. Figure 4c shows the second valve 40 in a fully open state (open state) (opening amount = 1). In this case, the first port 41 of the second valve 40 is shut off, so all of the first cooling water coming out of the fuel cell stack 10 can pass through the first radiator 60.

[0046] The first cooling water temperature T1 at the inlet of the fuel cell stack 10 may be expressed as shown in [Equation 2] below.

[0047]

number

[0048] In equation 2, OR (open ratio) indicates the opening degree of the second valve 40. K This can mean a correction factor used to determine the opening amount of the second valve 40. The fuel cell system can determine the opening amount of the second valve 40 so that the first cooling water temperature T3 at the inlet of the fuel cell stack 10 reaches the target temperature more precisely by setting the correction factor.

[0049] The fuel cell system has a target temperature of T3. 3c The opening angle (OR) of the second valve 40 can be calculated using the following [Equation 3] to satisfy the condition.

[0050]

number

[0051] Figure 5 shows block diagrams of fuel cell systems according to various embodiments. The configurations shown in Figure 5 may be hardware devices or programs (or applications) containing instruction words.

[0052] Referring to Figure 5, the first temperature sensor 512, the second temperature sensor 514, and the third temperature sensor 516 each have the same or similar structure as the first temperature sensor 112, the second temperature sensor 114, and the fourth temperature sensor 118 in Figure 1, and can perform the same or similar functions. The valve 532, the pump 534, and the cooling fan 536 each have the same or similar structure as the second valve 40, the first pump 30, and the cooling fan 80 in Figure 1, and can perform the same or similar functions.

[0053] The control unit 520 may be a hardware device such as a processor or CPU (central processing unit), or a program implemented by a processor. The control unit 520 is connected to a plurality of temperature sensors 512, 514, 516, a valve 532, a pump 534, and a cooling fan 536, and can perform the overall functions of the fuel cell system for controlling the cooling water temperature. For this purpose, the control unit 520 may include a correction coefficient setting unit 522, an opening amount calculation unit 524, a valve control unit 526, a pump control unit 528, and a cooling fan control unit 530. Each of the components included in the control unit 520 may exist separately or be implemented in a single integrated module.

[0054] The correction coefficient setting unit 522 can set a correction coefficient for controlling the opening amount of the valve 532. For example, the correction coefficient setting unit 522 can set the initial value of the correction coefficient to 1 and adjust the correction coefficient based on the difference between the cooling water temperature at the inlet of the fuel cell stack 10, measured via the first temperature sensor 512, and the target temperature.

[0055] The valve opening amount calculation unit 524 can calculate the valve opening amount of valve 532 based on the coolant temperature at the outlet of the fuel cell stack 10 measured via the second temperature sensor 514, the coolant temperature at the outlet of the first radiator 60 measured via the third temperature sensor 516, a previously set target temperature, and a correction coefficient. For example, the valve opening amount calculation unit 524 can calculate the valve opening amount of valve 532 using the formula 3 described above.

[0056] The valve control unit 526 adjusts the opening degree of the valve 532 according to the opening degree calculation unit 524, and the pump control unit 528 and the cooling fan control unit 530 can control the rotation speed of the pump 534 and the cooling fan 536, respectively.

[0057] Figure 6 shows an operational flowchart for controlling the valve opening and correction coefficient in various embodiments. The operations described below can be implemented by a fuel cell system or by a component included in the fuel cell system (e.g., control unit 520).

[0058] Referring to Figure 6, in operation 610, the control unit 520 can set a target temperature for the fuel cell stack 10 inlet and a correction coefficient for controlling the opening amount of the valve 532.

[0059] In operation 620, the control unit 520 can measure the coolant temperature at the outlet of the fuel cell stack 10 (hereinafter referred to as the "first coolant temperature") and the coolant temperature at the outlet of the first radiator 60 (hereinafter referred to as the "second coolant temperature").

[0060] In operation 630, the control unit 520 can calculate the valve opening amount based on the first coolant temperature, the second coolant temperature, the target temperature, and the correction coefficient.

[0061] In operation 640, the control unit 520 can correct the correction coefficient based on a comparison between the cooling water temperature at the fuel cell stack inlet (hereinafter referred to as "third cooling water temperature") and the target temperature, provided that the calculated opening amount is within a specified range (e.g., greater than 0 and less than or equal to 1).

[0062] Figure 7 shows a more detailed operational flowchart for controlling the valve opening and correction coefficient in various embodiments.

[0063] Referring to Figure 7, in operation 705, the control unit 520 can set the correction coefficient. For example, the control unit 520 can set the initial value of the correction coefficient to 1.

[0064] In operation 710, the control unit 520 can set a target temperature and measure the first and second cooling water temperatures.

[0065] In operation 715, the control unit 520 can calculate the opening amount of the valve 532 based on the first and second cooling water temperatures, the target temperature, and the correction coefficient.

[0066] In operation 720, the control unit 520 can check whether the calculated opening amount exceeds 1.

[0067] If the opening amount exceeds 1, the control unit 520 can no longer control the third cooling water temperature to the target temperature via the opening of the valve 532, and therefore, in operation 725, the rotation speed of the pump 534 and the cooling fan 536 can be controlled.

[0068] If the opening amount does not exceed 1, the control unit 520 can check whether the opening amount is 0 during operation 730. If the opening amount is 0, the control unit 520 can repeat operations 705 to 720 without opening the valve 532 (keeping it closed). For example, when the fuel cell system is in the initial heating phase, the third cooling water temperature is lower than the target temperature, so the control unit 520 may not need to open the valve 532.

[0069] If the opening amount is not greater than 1 and is not 0, in operation 735, the control unit 520 can check whether the third coolant temperature is the same as the target temperature. As another example, even if the third coolant temperature is not the same as the target temperature, the control unit 520 can check whether the difference is within a specified range (e.g., 1%). If the third coolant temperature is the same as the target temperature or the difference is within the specified range, the control unit 520 can repeat operations 705 to 720 without correcting the correction coefficient.

[0070] If the difference between the third cooling water temperature and the target temperature exceeds a specified range, in operation 740, the control unit 520 can check whether the target temperature is greater than or equal to the third cooling water temperature. If the target temperature is greater, the control unit 520 can decrease the correction coefficient (operation 745), and conversely, if the target temperature is less than or equal to the target temperature, the control unit 520 can increase the correction coefficient (operation 750).

Claims

1. A fuel cell system, Fuel cell stack and A first cooling line through which the first cooling water passing through the fuel cell stack is circulated, A first radiator is positioned on the first cooling line and configured to cool the first coolant, A valve configured to switch the flow path of the first cooling water to the fuel cell stack or the first radiator, The control unit includes a control unit connected to the valve, and the control unit is The target temperature of the fuel cell stack inlet and a correction coefficient for controlling the opening amount of the valve are set. The first coolant temperature at the outlet of the fuel cell stack and the second coolant temperature at the outlet of the first radiator are measured. A relational expression for the opening amount determined by the first cooling water temperature, the second cooling water temperature, the target temperature, and the correction coefficient is set in advance. Substitute the correction coefficient into the above relational expression to calculate the opening amount. A fuel cell system configured to correct the correction coefficient based on a comparison between the third cooling water temperature at the fuel cell stack inlet and the target temperature, provided that the opening amount is within a specified first range.

2. The control unit, If the difference between the third cooling water temperature and the target temperature is within the specified second range, the correction coefficient is set to the same value as before. If the difference between the third cooling water temperature and the target temperature exceeds the second range and the target temperature is greater than the third cooling water temperature, the correction coefficient is reduced, and The fuel cell system according to claim 1, wherein the correction coefficient is set to increase when the difference between the third cooling water temperature and the target temperature exceeds the second range and the target temperature is smaller than the third cooling water temperature.

3. A first temperature sensor is positioned at the inlet of the fuel cell stack, A second temperature sensor is positioned at the outlet of the fuel cell stack, The fuel cell system according to claim 1, further comprising a third temperature sensor disposed at the outlet of the first radiator.

4. A cooling fan is positioned on the first cooling line and configured to blow outside air onto the first radiator, The present invention further includes a pump positioned on the first cooling line and configured to pump the first cooling water, The control unit, The fuel cell system according to claim 1, wherein the rotational speed of at least one of the cooling fan and the pump is controlled when the opening amount exceeds the first range.

5. The control unit, The fuel cell system according to claim 4, wherein the rotation speed of the cooling fan and the rotation speed of the pump are controlled to minimize the total power consumption while the third cooling water temperature reaches the target temperature, by decreasing the rotation speed of the cooling fan and increasing the rotation speed of the pump, and the total power consumption is the sum of the power consumption corresponding to the rotation speed of the cooling fan and the power consumption corresponding to the rotation speed of the pump.

6. The control unit, A valve control unit that controls the opening amount of the valve, A cooling fan control unit that controls the rotation speed of the cooling fan, The fuel cell system according to claim 4, further comprising a pump control unit for controlling the rotational speed of the pump.

7. The fuel cell system according to claim 6, wherein the valve control unit, the cooling fan control unit, and the pump control unit are integrated into a single module.

8. The second cooling line through which the second coolant, passing through electrical components, A second radiator is positioned on the second cooling line and configured to cool the second cooling water, The present invention further includes a heat exchanger configured to exchange heat between the first cooling water and the second cooling water, The fuel cell system according to claim 4, wherein the cooling fan is configured to cool at least one of the first radiator or the second radiator.

9. Fuel cell stack and A first cooling line through which the first cooling water passing through the fuel cell stack is circulated, A first radiator is positioned on the first cooling line and configured to cool the first coolant, A method for operating a fuel cell system, comprising a valve configured to switch the flow path of the first cooling water to the fuel cell stack or the first radiator, The operation of setting the target temperature of the fuel cell stack inlet and a correction coefficient for controlling the opening amount of the valve, The operation involves measuring the first coolant temperature at the fuel cell stack outlet and the second coolant temperature at the first radiator outlet, A relational expression for the opening amount determined by the first cooling water temperature, the second cooling water temperature, the target temperature, and the correction coefficient is set in advance. The operation of substituting the correction coefficient into the above relational expression to calculate the opening amount, A method comprising: correcting the correction coefficient based on a comparison between the third cooling water temperature at the fuel cell stack inlet and the target temperature, provided that the opening amount is within a specified first range.

10. The operation to correct the aforementioned correction coefficient is: If the difference between the third cooling water temperature and the target temperature is within the specified second range, the correction coefficient is set to the same value as before. If the difference between the third cooling water temperature and the target temperature exceeds the second range and the target temperature is greater than the third cooling water temperature, the correction coefficient is reduced. The method according to claim 9, further comprising: an action to increase the correction coefficient when the difference between the third cooling water temperature and the target temperature exceeds the second range and the target temperature is smaller than the third cooling water temperature.

11. The method according to claim 9, further comprising the operation of controlling the rotational speed of at least one of the following when the opening amount exceeds the first range: a cooling fan located on the first cooling line and configured to blow outside air to the first radiator, and a pump located on the first cooling line and configured to pump the first coolant.

12. The operation of controlling the rotational speed of at least one of the cooling fan and the pump is as follows: The method according to claim 11, comprising: an operation to control the rotation speed of the cooling fan and the rotation speed of the pump such that the total power consumption is minimized while the third cooling water temperature reaches the target temperature, wherein the total power consumption is the sum of the power consumption corresponding to the rotation speed of the cooling fan and the power consumption corresponding to the rotation speed of the pump.

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