Fuel cell system and its power control method
The fuel cell system optimizes power distribution by using a first converter, a second converter, and a power relay assembly to minimize converters, addressing cost and efficiency issues in hybrid energy source operation.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- HYUNDAI MOTOR CO LTD
- Filing Date
- 2022-01-19
- Publication Date
- 2026-05-11
AI Technical Summary
Fuel cell systems applied to vehicles in industrial sites require multiple converters for hybrid operation of energy sources, increasing costs due to the expense of converters.
A fuel cell system with a first converter for power output regulation, a second converter for bidirectional power flow, and a power relay assembly to control power flow between a supercapacitor, minimizing the number of converters and optimizing power distribution.
Efficient operation of multiple energy sources is achieved while reducing the number of converters, thereby lowering costs and enhancing power management.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to a fuel cell system and a method for controlling its power.
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, so continuous research and development on fuel cell systems are being carried out.
[0003] A vehicle to which a fuel cell system is applied uses a fuel cell that generates electrical energy using hydrogen fuel as the main power source, and installs a hybrid power network using a high-voltage battery as an auxiliary power source, and can switch the operation mode according to the driving situation to improve the driving efficiency.
[0004] In recent years, attempts have been made to apply fuel cell systems to vehicles used in industrial sites such as excavators.
[0005] In the case of a fuel cell system applied to a vehicle used in an industrial site, in addition to the fuel cell, a battery and a supercapacitor are applied. In this case, since the fuel cell, the battery, and the supercapacitor can be operated in a hybrid manner, the power efficiency can be increased. However, in order to operate each energy source in a hybrid manner, at least three converters must be provided in the power network, and since the converter is an expensive component, the cost will increase accordingly.
Summary of the Invention
Problems to be Solved by the Invention
[0006] The object of the present invention is to provide a fuel cell system and a power control method thereof that enables efficient operation of multiple energy sources while minimizing the number of converters and reducing costs by replacing the converters applied to the power network with power relay assemblies (PRAs).
[0007] The technical problems of the present invention are not limited to those mentioned above, and other technical problems not mentioned can be clearly understood by those skilled in the art from the following description. [Means for solving the problem]
[0008] A fuel cell system according to one embodiment of the present invention for achieving the above objectives is characterized by including a first converter that converts power output from a fuel cell stack or battery to a predetermined level of power, a second converter that converts power input to or output to the battery, a power relay assembly that controls the flow of power between a supercapacitor and the first converter, and a controller that controls the outputs of the first converter and the second converter and controls the operation of the power relay assembly according to the startup or operating state of the fuel cell system.
[0009] In one embodiment, the first converter is located at the main bus end connecting the fuel cell stack and the inverter, and the second converter is characterized in that one end is connected to the main bus end between the fuel cell stack and the first converter, and the other end is connected to the battery, thereby regulating the bidirectional flow of power.
[0010] In one embodiment, the second converter is characterized in that, when the fuel cell system is started, it uses the power discharged by the battery to supply the starting power for the fuel cell system and the charging power for the supercapacitor.
[0011] In one embodiment, the first converter is characterized in that, when the fuel cell system is started, it supplies the charging power supplied from the second converter to the supercapacitor via the power relay assembly.
[0012] In one embodiment, the power relay assembly is characterized in that, before receiving charging power through the first converter, it uses a pre-charge relay to adjust the voltage between the output terminal of the first converter and the supercapacitor, and when charging power is supplied through the first converter, it uses a main relay to provide charging power to the supercapacitor.
[0013] In one embodiment, the controller is characterized in that, when the fuel cell system is started, it drives the first converter in constant current mode and the second converter in constant voltage mode.
[0014] In one embodiment, the controller is characterized in that, when starting the fuel cell system, it sets the starting voltage of the fuel cell stack to the output voltage of the second converter, and sets the limit current of the second converter or the discharge allowable current of the battery to the limit current of the second converter.
[0015] In one embodiment, the controller sets the charging voltage of the supercapacitor to the output voltage of the first converter when the fuel cell system is started, sets the value obtained by subtracting the required current of the auxiliary equipment from the dischargeable current of the battery to the output current of the first converter, and sets the limit current of the first converter or the allowable charging current of the supercapacitor to the limit current of the first converter.
[0016] In one embodiment, the second converter adjusts and outputs the power discharged by the battery during operation of the fuel cell system, and the first converter adjusts and supplies the power output via at least one of the fuel cell stack and the second converter to the inverter during operation of the fuel cell system.
[0017] In one embodiment, the controller is characterized in that, when the fuel cell system is in operation, it drives the first converter in constant current mode and the second converter in constant voltage mode.
[0018] In one embodiment, the controller is characterized in that, during operation of the fuel cell system, it sets the output voltage of the first converter based on the measured voltage of the supercapacitor, sets the output current of the first converter based on the ratio of the combined power requirement of the fuel cell stack and the battery to the measured voltage of the supercapacitor, and sets the limiting current of the first converter based on the limiting current of the first converter.
[0019] In one embodiment, the controller is characterized in that, during operation of the fuel cell system, it sets the output voltage of the second converter based on the target voltage of the fuel cell stack, sets the output current of the second converter based on the ratio of the target power of the battery to the measured voltage, and sets the limit current of the second converter based on the discharge allowable current of the battery.
[0020] In one embodiment, the power relay assembly is characterized by supplying power discharged from the supercapacitor to the inverter during operation of the fuel cell system.
[0021] Furthermore, a power control method for a fuel cell system according to one embodiment of the present invention for achieving the above objectives is characterized by including the steps of setting the output of a first converter that adjusts the power output from a fuel cell stack or battery, and a second converter that adjusts the power input to or output to the battery, according to the starting or operating state of the fuel cell system; controlling the operation of a power relay assembly according to the starting or operating state of the fuel cell system; and controlling the power supply to the fuel cell stack, battery, and supercapacitor according to the outputs of the first converter and the second converter and the operation of the power relay assembly.
[0022] In one embodiment, the step of setting the output includes, when starting the fuel cell system, setting the starting voltage of the fuel cell stack to the output voltage of the second converter, and setting the limit current of the second converter or the discharge allowable current of the battery to the limit current of the second converter.
[0023] In one embodiment, the step of setting the output is characterized by including, when the fuel cell system is started, the step of setting the charging voltage of the supercapacitor to the output voltage of the first converter; the step of setting the value obtained by subtracting the required current of the auxiliary equipment from the dischargeable current of the battery to the output current of the first converter; and the step of setting the limit current of the first converter or the allowable charging current of the supercapacitor to the limit current of the first converter.
[0024] In one embodiment, the step of controlling the power supply is characterized in that, when the fuel cell system is started, the second converter supplies starting power to the fuel cell system using the power discharged by the battery.
[0025] In one embodiment, the steps of controlling the power supply include, at startup of the fuel cell system, the second converter supplying charging power to the supercapacitor using the power discharged by the battery, and the first converter adjusting the charging power supplied from the second converter and supplying it to the supercapacitor via the power relay assembly.
[0026] In one embodiment, the step of controlling the power supply includes: before supplying charging power to the supercapacitor, a power relay assembly connected to the supercapacitor adjusts the voltage between the output terminal of the first converter and the supercapacitor using a pre-charge relay; and when charging power is supplied through the first converter, the power relay assembly provides charging power to the supercapacitor using a main relay.
[0027] In one embodiment, the step of setting the output includes: when the fuel cell system is operating, setting the output voltage of the first converter based on the measured voltage of the supercapacitor; setting the output current of the first converter based on the ratio of the combined required power of the fuel cell stack and the battery and the measured voltage of the supercapacitor; and setting the limiting current of the first converter based on the limit current of the first converter.
[0028] In one embodiment, the step of setting the output includes: when the fuel cell system is operating, setting the output voltage of the second converter based on the target voltage of the fuel cell stack; setting the output current of the second converter based on the ratio of the target power of the battery and the measured voltage; and setting the limiting current of the second converter based on the discharge allowable current of the battery.
[0029] In one embodiment, the step of controlling the power supply includes: when the fuel cell system is operating, the second converter adjusts and outputs the power discharged by the battery; and the first converter adjusts the power output through at least one of the fuel cell stack and the second converter and supplies it to the inverter.
[0030] In one embodiment, the step of controlling the power supply is characterized in that, when the fuel cell system is in operation, the power relay assembly supplies power discharged from the supercapacitor to the inverter. [Effects of the Invention]
[0031] According to the present invention, by replacing the converters applied to the power network with power relay assemblies (PRAs), it is possible to minimize the number of converters and reduce costs while efficiently operating multiple energy sources. [Brief explanation of the drawing]
[0032] [Figure 1] This figure shows a fuel cell system according to one embodiment of the present invention. [Figure 2a] This diagram shows the energy flow during startup of a fuel cell system according to one embodiment of the present invention. [Figure 2b] This figure shows the operating state of the converter during startup of a fuel cell system according to one embodiment of the present invention. [Figure 3a] This diagram shows the energy flow during operation of a fuel cell system according to one embodiment of the present invention. [Figure 3b] This figure shows the operating state of the converter during operation of a fuel cell system according to one embodiment of the present invention. [Figure 4] This diagram shows the operation flow for a power control method of a fuel cell system according to one embodiment of the present invention. [Figure 5] This diagram shows the operation flow for a power control method of a fuel cell system according to one embodiment of the present invention. [Figure 6a] This is an illustrative diagram used to illustrate the output setting operation of a converter according to one embodiment of the present invention. [Figure 6b] This is an illustrative diagram used to illustrate the output setting operation of a converter according to one embodiment of the present invention. [Modes for carrying out the invention]
[0033] Hereinafter, some embodiments of the present invention will be described in detail with reference to illustrative drawings. It should be noted that, in assigning reference numerals to the components in each drawing, the same reference numerals will be used for the same components whenever possible when they appear in other drawings. Furthermore, in describing embodiments of the present invention, if a specific description of a related known configuration or function is deemed to hinder understanding of the embodiments of the present invention, such detailed description will be omitted.
[0034] In describing the components of embodiments of the present invention, terms such as first, second, A, B, (a), (b), etc., may be used. Such terms are merely for distinguishing a component from other components, and do not limit the nature, order, or sequence of the component. Furthermore, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as those generally understood by a person of ordinary skill in the art to which the present invention pertains. Terms as defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and not as an ideal or overly formal meaning unless explicitly defined in this application.
[0035] Figure 1 shows a fuel cell system according to one embodiment of the present invention.
[0036] Referring to Figure 1, a fuel cell system according to one embodiment of the present invention may include a fuel cell stack 110, an inverter 120, a motor 130, auxiliary equipment 140, a battery 150, a supercapacitor 160, a first converter 170, a second converter 180, and a power relay assembly (PRA) 190. The fuel cell system may further include a controller 200 that controls the flow of power in the fuel cell system.
[0037] The fuel cell stack 110 (or may be referred to as the "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 110 may include a membrane electrode assembly (MEA) in which a catalytic electrode layer where electrochemical reactions occur is attached to both sides of an electrolyte membrane on which hydrogen ions move, 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.
[0038] In the fuel cell stack 110, hydrogen, the fuel, and air (oxygen), the oxidizer, are supplied to the anode and cathode of the membrane electrode assembly via the flow path of the separator plate. Hydrogen is supplied to the anode, and air is supplied to the cathode. The hydrogen supplied to the anode is decomposed into hydrogen ions (protons) and electrons by catalysts in the electrode layers configured on both sides of the electrolyte membrane. 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 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 come into contact with oxygen in the air supplied to the cathode by the air supply device, causing a reaction that produces water. The movement of hydrogen ions that occurs at this time generates an electron flow via an external conductor, thereby generating electrical energy.
[0039] The fuel cell stack 110 is the main power source of a vehicle equipped with a fuel cell system, i.e., a fuel cell vehicle, and uses the generated electrical energy to supply the power necessary to drive the motor 130. Here, the fuel cell vehicle may include industrial vehicles used on construction sites, such as excavators.
[0040] On the other hand, the fuel cell stack 110 can also supply power to charge the battery 150 and / or the supercapacitor 160.
[0041] Here, the output of the fuel cell stack 110 can be controlled by the controller 200.
[0042] An inverter 120, a motor 130, auxiliary equipment 140, a battery 150, a supercapacitor 160, a first converter 170, a second converter 180, and a power relay assembly 190 can be connected to the main bus terminal connected to the output terminal of the fuel cell stack 110, respectively.
[0043] The inverter 120 converts the high-voltage DC power supplied from the fuel cell stack 110 via the main bus terminal into AC power for driving the motor 130 and provides it to the motor 130.
[0044] The inverter 120 can also receive a supply of high-voltage DC power from a battery 150 and / or a supercapacitor 160 connected to the main bus terminal. In this case, the inverter 120 can convert the high-voltage DC power supplied from the battery 150 or supercapacitor 160 into AC power for driving the motor 130 and provide it to the motor 130.
[0045] When the fuel cell vehicle is operating in fuel cell mode, the inverter 120 can receive power from the fuel cell stack to drive the motor 130. When the fuel cell vehicle is operating in EV mode, the inverter 120 can receive power from the battery 150 and / or the supercapacitor 160 to drive the motor 130. On the other hand, when the fuel cell vehicle is operating in hybrid mode, the inverter 120 can receive power from the fuel cell stack 110, the battery 150, and the supercapacitor 160 to drive the motor 130.
[0046] Here, the inverter 120 may include a plurality of switching elements (not shown). The plurality of switching elements can generate AC power by being controlled using pulse width modulation (PWM). Of course, the control method for the plurality of switching elements is not limited to just one, and it goes without saying that the plurality of switching elements may be controlled in other ways depending on the embodiment.
[0047] The AC power generated by the inverter 120 is supplied to the motor 130. Here, the motor 130 is driven using the AC power supplied from the inverter 120. The motor 130 generates rotational force using the AC power supplied from the inverter 120, and this rotational force can be supplied to the drive wheels of the fuel cell vehicle.
[0048] Meanwhile, the motor 130 generates electrical energy using the braking force generated during regenerative braking. In this case, the inverter 120 can convert the electrical energy generated by the motor 130 during regenerative braking and provide it as charging power for the supercapacitor 160.
[0049] The auxiliary equipment 140 may include auxiliary equipment necessary for driving the fuel cell stack 110, such as a blower, air compressor, injector, cooling water circulation pump, and various control valves.
[0050] The auxiliary equipment 140 can operate by receiving power from the fuel cell stack 110. The auxiliary equipment 140 can also operate by receiving power from the battery 150 during the initial startup of the fuel cell system.
[0051] Battery 150 is an auxiliary power source for the fuel cell vehicle and is charged using electrical energy generated by the fuel cell stack 110.
[0052] The battery 150 can discharge its stored electrical energy to supply the power necessary to drive the motor 130.
[0053] Furthermore, the battery 150 can discharge electrical energy during the initial startup of the fuel cell system to supply the power necessary to drive the auxiliary equipment 140. The battery 150 can also discharge the electrical energy it has stored during the initial startup of the fuel cell system to supply the power necessary to charge the supercapacitor 160.
[0054] Here, the discharge rate of battery 150 can be controlled by controller 200.
[0055] The supercapacitor 160, like the battery 150, is an auxiliary power source for the fuel cell vehicle and is charged using electrical energy generated by the fuel cell stack 110. The supercapacitor 160 can also be charged using power supplied from the battery 150 during the initial startup of the fuel cell system. Furthermore, the supercapacitor 160 can also be charged using power generated by the motor 130 during regenerative braking.
[0056] The supercapacitor 160 can discharge its stored electrical energy to supply the power necessary to drive the motor 130. The discharge rate of the supercapacitor 160 can be controlled by the controller 200.
[0057] The first converter 170 can be located on the main bus terminal between the fuel cell stack 110 and the inverter 120. The first converter 170 is a power converter that adjusts the power output from the fuel cell stack 110 or the battery 150 and outputs it to the main bus terminal, and can be configured as a unidirectional HDC (High voltage DC-DC converter).
[0058] For example, the first converter 170 can adjust the power output from the fuel cell stack 110 or battery 150 and provide it to the inverter 120 connected to the main bus terminal.
[0059] Furthermore, the first converter 170 can also adjust the power output from the fuel cell stack 110 or the battery 150 and provide it to the supercapacitor 160 connected to the main bus terminal so that the supercapacitor 160 is charged.
[0060] Here, the controller 200 can determine the output voltage, output current, and limiting current of the first converter 170. Therefore, the first converter 170 can adjust the power output to the main bus terminal according to the output voltage, output current, and limiting current determined by the controller 200.
[0061] The second converter 180 can be connected at one end to the main bus terminal between the fuel cell stack 110 and the first converter 170, and at the other end to the battery 150.
[0062] The second converter 180 is a power converter that adjusts the power input to or output to the battery 150, and can be configured as a BHDC (Bi-directional High Voltage DC-DC Converter) that controls the bidirectional movement of current.
[0063] For example, the second converter 180 can adjust the power supplied from the fuel cell stack 110 and supply it as charging power to the battery 150. Furthermore, during regenerative braking, the second converter 180 can adjust the power generated by the motor 130 and supply it as charging power to the battery 150.
[0064] Meanwhile, the second converter 180 adjusts the power output from the discharge of the battery 150 during the startup of the fuel cell system and outputs it to the main bus terminal. At this time, the power output to the main bus terminal may be provided as driving power for the auxiliary equipment 140, or as charging power for the supercapacitor 160.
[0065] Here, the controller 200 can determine the output voltage, output current, and limiting current of the second converter 180. Therefore, the second converter 180 can adjust the power output to the main bus terminal or battery 150 according to the output voltage, output current, and limiting current determined by the controller 200.
[0066] The power relay assembly 190 may include a main relay located on a line connecting the supercapacitor 160 to the main bus terminal, a pre-charge relay connected in parallel with the main relay, and a pre-charge resistor connected in series with one end of the pre-charge relay.
[0067] The power relay assembly 190 can apply or interrupt the power flowing between the supercapacitor 160 and the main bus terminal by switching the main relay and the precharge relay open and closed. Here, the opening and closing operation of the main relay and the precharge relay can be controlled by the controller 200.
[0068] In this case, the power relay assembly 190 can prevent the first converter 170 and inverter 120 from being damaged by the residual voltage of the supercapacitor 160 during the initial startup of the fuel cell system.
[0069] The power relay assembly 190 may further include a current sensor (not shown). The current sensor can detect the direction of the current flowing between the supercapacitor 160 and the main bus terminal.
[0070] The controller 200 can perform power control for each unit of the fuel cell system. Here, the controller 200 may also be a higher-level controller.
[0071] The controller 200 according to this embodiment may be a hardware device such as a processor or a CPU (central processing unit), or it may be a program implemented by a processor. The controller 200 is connected to each component of the fuel cell system and can perform the overall functions of the fuel cell system.
[0072] The controller 200 can control the power flow for starting the fuel cell stack 110 and charging the supercapacitor 160 when the fuel cell system is started.
[0073] In this case, the controller 200 can determine the outputs of the first converter 170 and the second converter 180 and control the operation of the power relay assembly 190.
[0074] For example, the controller 200 drives the second converter 180 in constant voltage mode to start the fuel cell stack 110. In this case, the controller 200 sets the output voltage of the second converter 180 as the starting voltage. The controller 200 also sets the limit current of the second converter 180 to the limit current of the second converter 180, which is either the limit current of the second converter 180 or the discharge allowable current of the battery 150. In this case, the controller 200 can set the limit current of the second converter 180 to be the smaller of the limit current of the second converter 180 and the discharge allowable current of the battery 150.
[0075] As a result, when the battery 150 is discharged, the second converter 180 can supply the power discharged by the battery 150 to the auxiliary equipment 140 for starting the fuel cell stack 110.
[0076] On the other hand, the supercapacitor 160 naturally loses voltage due to self-discharge when left idle, so it is necessary to charge the supercapacitor 160 during the initial startup of the fuel cell system. Therefore, when the fuel cell stack 110 is started, the controller 200 operates the power relay assembly 190 to charge the supercapacitor 160 and drives the first converter 170 in constant current mode.
[0077] In this case, the controller 200 sets the output voltage of the first converter 170 to the charging voltage of the supercapacitor 160. The controller 200 also sets the output current of the first converter 170 to the value obtained by subtracting the required current of the auxiliary equipment 140 from the dischargeable current of the battery 150. Furthermore, the controller 200 sets the limit current of the first converter 170 to the limit current of the first converter 170, which is either the limit current of the first converter 170 or the allowable charging current of the supercapacitor 160. In this case, the controller 200 can set the limit current of the first converter 170 to be the smaller of the limit current of the first converter 170 and the allowable charging current of the supercapacitor 160.
[0078] As a result, the first converter 170 and the second converter 180 can supply a portion of the power discharged by the battery 150 as power for charging the supercapacitor 160 during the initial startup of the fuel cell system. For example, the first converter 170 and the second converter 180 can supply the remaining power from the power discharged by the battery 150, after deducting the power required by the auxiliary equipment 140, to the supercapacitor 160.
[0079] Here, the power relay assembly 190 uses a precharge relay to induce the voltage of the supercapacitor 160, the output voltage of the first converter 170, and the input voltage of the inverter 120 to form the same voltage before the first converter 170 is driven. Then, when the first converter 170 is driven in constant current mode, it supplies charging power to the supercapacitor 160 via the main relay.
[0080] For a detailed explanation of the operation to control the power during startup of the fuel cell system, please refer to the embodiments shown in Figures 2a and 2b.
[0081] Figure 2a is a diagram showing the energy flow during startup of a fuel cell system according to one embodiment of the present invention, and Figure 2b is a diagram showing the operating state of the converter during startup of a fuel cell system according to one embodiment of the present invention.
[0082] Referring to Figures 2a and 2b, the controller 200 can determine the drive mode, output voltage, and limiting current of the second converter 180 in order to supply power to the auxiliary equipment 140 along the first route (R11) when the fuel cell system is started.
[0083] In this case, as shown in Figure 2b, the controller 200 can set the drive mode of the second converter 180 to constant voltage mode, set the output voltage to the starting voltage, and set the limiting current to the limiting current of the second converter 180 or the discharge allowable current of the battery 150 in order to start the fuel cell.
[0084] Furthermore, the controller 200 can set the drive mode, output voltage, output current, and limiting current of the first converter 170 in order to provide charging power to the supercapacitor 160 along the second route (R12) during the initial startup of the fuel cell system.
[0085] In this case, as shown in Figure 2b, the controller 200 can set the drive mode of the first converter 170 to constant current mode, set the output voltage to the supercapacitor 160 voltage, set the output current to the value obtained by subtracting the current required by the auxiliary equipment 140 from the dischargeable current of the battery 150, and set the limiting current to the limiting current of the first converter 170 or the allowable charging current of the supercapacitor 160.
[0086] As shown in Figure 2b, once the outputs of the first converter 170 and the second converter 180 are determined, the battery 150 discharges electrical energy, and the second converter 180 adjusts the power discharged by the battery 150 to supply starting power to the auxiliary equipment 140 along the first route (R11).
[0087] Therefore, the auxiliary equipment 140 uses the power supplied from the second converter 180 to drive the fuel cell stack 110 so that the startup is completed.
[0088] Furthermore, the second converter 180 can adjust the power discharged by the battery 150 and output power to the first converter 170 along the second route (R12). In this case, the first converter 170 adjusts the power output from the second converter 180 and supplies charging power to the supercapacitor 160 along the second route (R12).
[0089] In this case, the controller 200 can control the operation of the power relay assembly 190, which is connected to the supercapacitor 160 on the second route (R12), before the charging power is supplied from the first converter 170.
[0090] Therefore, the power relay assembly 190 transmits the charging power supplied from the first converter 170 to the supercapacitor 160, thereby enabling the supercapacitor 160 to be charged.
[0091] The controller 200 can control the operation of the power relay assembly 190 to the off state once the supercapacitor 160 has finished charging.
[0092] On the other hand, after the fuel cell stack 110 has finished starting up, the controller 200 can control the power flow to the fuel cell stack 110, the battery 150, and the supercapacitor 160 during operation.
[0093] In this case, the controller 200 can determine the outputs of the first converter 170 and the second converter 180 and control the operation of the power relay assembly 190.
[0094] For example, the controller 200 can control the output of the first converter 170 in order to supply the output power of the fuel cell stack 110 to the inverter 120 when the fuel cell system is in operation.
[0095] If the fuel cell vehicle operates in hybrid mode, the controller 200 can supply power from the battery 150 and / or supercapacitor 160 to the inverter 120 in response to load fluctuations that exceed the reference range of the fuel cell stack 110.
[0096] In this case, the controller 200 can control the output of the first converter 170 based on the sum of the combined power requirements of the fuel cell stack 110 and the battery 150. The controller 200 can also control the output of the second converter 180 based on the target power of the battery 150 for supplying power to the inverter 120 and the target voltage of the fuel cell stack 110.
[0097] Furthermore, the controller 200 can control the relay operation of the power relay assembly 190 in order to supply the power charged in the supercapacitor 160 to the inverter 120.
[0098] For a detailed explanation of the operation that controls the power during operation of the fuel cell system, please refer to the embodiments shown in Figures 3a and 3b.
[0099] Figure 3a is a diagram showing the energy flow during operation of a fuel cell system according to one embodiment of the present invention, and Figure 3b is a diagram showing the operating state of the converter during operation of a fuel cell system according to one embodiment of the present invention.
[0100] Referring to Figures 3a and 3b, during operation of the fuel cell system, the fuel cell stack 110 supplies power to the inverter 120 along the third route (R21). Here, the fuel cell stack 110 supplies power to the inverter 120 corresponding to the load fluctuation within a first range of the continuously supplied static load, which is measured when the inverter 120 and motor 130 are driven.
[0101] In this case, the first converter 170, located on the third route (R21), can adjust the power supplied from the fuel cell stack 110 and output it to the inverter 120.
[0102] The fuel cell stack 110 can also supply power to the auxiliary equipment 140 along the fourth route (R22) connected to the third route. Furthermore, the fuel cell stack 110 can supply power to the battery 150 and / or supercapacitor 160 along the fifth route (R23) and / or sixth route (R24) connected to the third route.
[0103] Battery 150 can supply power to inverter 120 along the fifth route (R23) and the third route (R21) when power supply to inverter 120 is required during operation of the fuel cell system.
[0104] Here, the battery 150 can supply power to the inverter 120 corresponding to the load fluctuations within the second range set in the Band Pass Filter (BPF) of the load of the inverter 120 measured when the inverter 120 and motor 130 are driven. The second range can correspond to the intermediate frequency range between the first range of static load supplied by the fuel cell and the third range set in the High Pass Filter (HPF), and the specific range can be modified in any way depending on the embodiment.
[0105] In this case, the second converter 180 located on the fifth route (R23) and the first converter 170 located on the third route (R21) can adjust the power supplied from the battery 150 and output it to the inverter 120.
[0106] Here, when power is supplied from the fuel cell stack 110 and the battery 150, the first converter 170 can also adjust the power based on the sum of the power from the fuel cell stack 110 and the power supplied from the battery 150 and output it to the inverter 120.
[0107] Furthermore, the supercapacitor 160 can supply power to the inverter 120 along the sixth route (R24) and the fourth route (R22) if power supply to the inverter 120 is required during the operation of the fuel cell system.
[0108] Here, the supercapacitor 160 can supply power to the inverter 120 corresponding to the load fluctuation within the third range set in the HPF (High Pass Filter) of the load of the inverter 120 measured when the inverter 120 and motor 130 are driven. Here, the third range is a rapidly fluctuating load range and can correspond to a higher frequency range than the second range, and the specific range can be changed in any way depending on the embodiment.
[0109] In this case, the power relay assembly 190 located on the sixth route (R24) can supply power from the supercapacitor 160 to the inverter 120.
[0110] Therefore, the controller 200 can control the operation of the first converter 170 and the second converter 180 and the power relay assembly 190 in order to supply power from the fuel cell stack 110, the battery 150, and the supercapacitor 160 to the inverter 120 when the fuel cell system is in operation.
[0111] In this case, the controller 200 sets the drive mode of the first converter 170 to constant current mode, as shown in Figure 3b. The controller 200 can also set the output voltage of the first converter 170 to the measured voltage of the supercapacitor 160, set the output current based on the ratio of the combined power requirements of the fuel cell stack 110 and the battery 150 to the measured voltage of the supercapacitor 160, and set the limiting current to the limiting current of the first converter 170.
[0112] Furthermore, the controller 200 sets the drive mode of the second converter 180 to constant voltage mode. The controller 200 can also set the output voltage of the second converter 180 to the target voltage of the fuel cell stack 110, set the output current based on the ratio of the target power of the battery 150 to the measured voltage of the battery 150, and set the limiting current to the discharge allowable current of the battery 150.
[0113] As shown in Figure 3b, once the outputs of the first converter 170 and the second converter 180 are determined, the fuel cell stack 110 outputs only the target power, and this output power can be supplied to the first converter 170 and the auxiliary equipment 140. The first converter 170 adjusts the power output from the fuel cell stack 110 and supplies it to the inverter 120 along the third route (R21).
[0114] Here, the target power of the fuel cell stack 110 can be obtained by adding the required power of the auxiliary equipment 140 to the required power of the fuel cell stack 110. The required power of the fuel cell stack 110 can be obtained by subtracting the target power of the battery 150 from the combined required power of the fuel cell stack 110 and the battery 150.
[0115] The combined power requirement of the fuel cell stack 110 and the battery 150 can be obtained by subtracting the target power of the supercapacitor 160 from the load measured when the inverter 120 is driven. The target power of the supercapacitor 160 can be obtained by subtracting the power calculated corresponding to the voltage obtained by subtracting the measured voltage of the supercapacitor 160 from the target voltage calculated based on the target SOC of the supercapacitor 160 from the power requirement of the supercapacitor 160 calculated by the HPF among the load of the inverter 120.
[0116] The target power of battery 150 can be obtained by subtracting the power calculated corresponding to the voltage obtained by subtracting the measured voltage of battery 150 from the target voltage calculated based on the target SOC of battery 150, from the battery 150's required power calculated by the BPF from the combined required power of the fuel cell stack 110 and battery 150.
[0117] Furthermore, the battery 150 discharges energy up to the target power, and the second converter 180 adjusts the power discharged by the battery 150 and outputs power to the first converter 170 along the fifth route (R23) and the third route (R21). At this time, the first converter 170 adjusts the power output from the second converter 180 and supplies power to the inverter 120 along the third route (R21).
[0118] Furthermore, the supercapacitor 160 discharges energy only up to the target power, and the power relay assembly 190 provides the power discharged by the supercapacitor 160 to the inverter 120.
[0119] Therefore, the inverter 120 is driven by continuously receiving power within a first range from the fuel cell stack 110, and while driving, it can efficiently receive energy by receiving power via the battery 150 for load fluctuations within a second range and via the supercapacitor 160 for rapid load fluctuations within a third range.
[0120] The operation flow of the fuel cell system according to the present invention, configured as described above, can be explained in more detail as follows.
[0121] Figure 4 is a diagram showing the operation flow of a power control method during startup of a fuel cell system according to one embodiment of the present invention.
[0122] Referring to Figure 4, the fuel cell system controls the second converter 180 to be ON (S120) and the power relay assembly (PRA) 190 to be ON (S150) when the power pack is started up (S110).
[0123] The fuel cell system starts the fuel cell stack 110 by supplying power from the battery 150 to the auxiliary equipment 140 via the second converter 180 in process "S120" (S130).
[0124] Meanwhile, the fuel cell system controls the first converter 170 to turn ON (S170) when the output voltage of the first converter 170 and the voltage of the supercapacitor 160 become equal (S160) via the precharge relay of the power relay assembly (PRA) 190 in process "S150".
[0125] Subsequently, the fuel cell system begins charging the supercapacitor 160 by supplying power from the battery 150 to the supercapacitor 160 via the second converter 180 and the first converter 170 (S180).
[0126] The fuel cell system checks whether the fuel cell stack 110 has finished starting up (S140). The fuel cell system also checks whether the supercapacitor 160 has finished charging (S190).
[0127] The fuel cell system terminates the power pack startup (S210) once it is confirmed that the fuel cell stack 110 has finished starting up and that the supercapacitor 160 has finished charging (S200).
[0128] Subsequently, the fuel cell system can begin operation.
[0129] Figure 5 is a diagram showing the operation flow of a power control method during operation of a fuel cell system according to one embodiment of the present invention.
[0130] Referring to Figure 5, the fuel cell system measures the load (S320) when the inverter 120 is in operation (S310).
[0131] The fuel cell system calculates the load fluctuations based on the HPF (High Pass Filter) among the loads measured in the "S320" process (S330), and supplies power corresponding to the load fluctuations calculated in the "S330" process from the supercapacitor 160 to the inverter 120 (S340).
[0132] Furthermore, the fuel cell system calculates the remaining power after subtracting the power supplied by the supercapacitor 160 in the "S340" process from the load measured in the "S320" process as the combined power required by the fuel cell stack 110 and the battery 150, and sets the output of the first converter 170 based on the combined power required by the fuel cell stack 110 and the battery 150 (S350).
[0133] For details on setting the output of the first converter 170 in process "S350", please refer to Figure 6a.
[0134] Referring to Figure 6a, the fuel cell system can supply the combined power requirement of the fuel cell stack 110 and the battery 150 (FC+BAT power requirement), which is obtained by subtracting the target power of the supercapacitor 160 (Scap target power) from the inverter load, via the first converter (HDC) 170.
[0135] Here, the Scap target power can be obtained by subtracting the Scap predetermined power from the Scap required power. The Scap required power can be calculated based on the HPF (High Pass Filter) among the inverter 120 loads. The Scap predetermined power can be obtained by applying the voltage value obtained by subtracting the Scap measured voltage from the Scap target voltage calculated based on the Scap target SOC to a Look Up Table (LUT).
[0136] Furthermore, the fuel cell system can set the output current of the first converter (HDC) 170 from the ratio of the FC+BAT power requirement to the measured voltage of Scap.
[0137] Furthermore, the fuel cell system can set the output voltage of the first converter (HDC) 170 based on the measured voltage of Scap.
[0138] Furthermore, the fuel cell system calculates the load fluctuation portion of the combined power demand of the fuel cell stack 110 and the battery 150 based on the Band Pass Filter (BPF) (S360). At this time, the fuel cell system can calculate the target power of the battery 150 based on the load fluctuation portion calculated in the "S360" process.
[0139] The fuel cell system sets the output of the second converter 180 based on the target power of the battery 150 and the target power of the fuel cell stack 110 (S370).
[0140] For details on the operation of setting the output of the second converter 180 in process "S370", please refer to Figure 6b.
[0141] Referring to Figure 6b, the fuel cell system can set the output current of the second converter (BHDC) 180 from the ratio of the target power of the battery 150 (BAT target power) to the measured voltage of the battery 150 (BAT measured voltage).
[0142] Here, the BAT target power can be obtained by subtracting the predetermined power of the BAT from the BAT request power. The BAT request power can be calculated based on the BPF from the combined FC + BAT request power. The predetermined power of the BAT can be obtained by applying the voltage value obtained by subtracting the BAT measurement voltage from the BAT target voltage calculated based on the BAT target SOC to a lookup table (LUT).
[0143] Furthermore, the fuel cell system can set the output voltage of the second converter (BHDC) 180 based on the target voltage of the fuel cell stack 110.
[0144] Here, the FC target voltage can be obtained by applying the FC target power to the lookup table (LUT). The FC target power can be obtained by adding the power requirements of the auxiliary equipment 140 to the FC required power. The FC required power can also be obtained by subtracting the BAT target power from the BAT + FC required power.
[0145] Once the outputs to the first converter 170 and the second converter 180 are determined through the above process, the fuel cell stack 110 and the battery 150 supply power to the inverter 120 (S380). In process S380, the fuel cell stack 110 can supply power to the inverter 120 via the first converter 170, and the battery 150 can supply power to the inverter 120 via the second converter 180 and the first converter 170.
[0146] The above description is merely illustrative of the technical concept of the present invention, and a person with ordinary skill in the art to which the present invention belongs could make various modifications and variations without departing from the essential characteristics of the present invention.
[0147] Therefore, the embodiments disclosed herein are for illustrative purposes only, not to limit the technical concept of the present invention, and the scope of the technical concept of the present invention is not limited by such embodiments. The scope of protection of the present invention must be interpreted in accordance with the claims described below, and all technical concepts within an equivalent scope should be interpreted as being included within the scope of the rights of the present invention.
Claims
1. A first converter that converts power output from a fuel cell stack or battery to a predetermined level of power, A second converter that converts the power input to or output to the aforementioned battery, A power relay assembly that controls the flow of power between a supercapacitor and the first converter, A controller that controls the output of the first converter and the second converter and controls the operation of the power relay assembly according to the starting or operating state of the fuel cell system. Includes, The first converter is A fuel cell system characterized in that, when the fuel cell system is started, the charging power supplied from the second converter is supplied to the supercapacitor via the power relay assembly.
2. The first converter is It is located at the end of the main bus connecting the fuel cell stack and the inverter, The second converter is The fuel cell system according to claim 1, characterized in that one end is connected to the main bus terminal between the fuel cell stack and the first converter, and the other end is connected to the battery, thereby regulating the bidirectional flow of power.
3. The second converter is The fuel cell system according to claim 2, characterized in that, when the fuel cell system is started, the power discharged by the battery is used to supply the starting power of the fuel cell system and the charging power of the supercapacitor.
4. The aforementioned power relay assembly is The fuel cell system according to claim 1, characterized in that, before receiving charging power via the first converter, the voltage between the output terminal of the first converter and the supercapacitor is adjusted using a precharge relay, and when charging power is supplied via the first converter, the charging power is provided to the supercapacitor using a main relay.
5. The controller is, The fuel cell system according to claim 3, characterized in that, when the fuel cell system is started, the first converter is driven in constant current mode and the second converter is driven in constant voltage mode.
6. The controller is, The fuel cell system according to claim 3, characterized in that, when starting the fuel cell system, the starting voltage of the fuel cell stack is set to the output voltage of the second converter, and the limit current of the second converter or the discharge allowable current of the battery is set to the limit current of the second converter.
7. The controller is, The fuel cell system according to claim 3, characterized in that, when the fuel cell system is started, the charging voltage of the supercapacitor is set to the output voltage of the first converter, the value obtained by subtracting the required current of the auxiliary equipment from the dischargeable current of the battery is set to the output current of the first converter, and the limit current of the first converter or the allowable charging current of the supercapacitor is set to the limit current of the first converter.
8. The second converter is During operation of the fuel cell system, the power discharged by the battery is adjusted and output. The first converter is The fuel cell system according to claim 2, characterized in that, during operation of the fuel cell system, the power output via at least one of the fuel cell stack and the second converter is adjusted and supplied to the inverter.
9. The controller is, The fuel cell system according to claim 8, characterized in that, during operation of the fuel cell system, the first converter is driven in constant current mode and the second converter is driven in constant voltage mode.
10. The controller is, The fuel cell system according to claim 8, characterized in that, during operation of the fuel cell system, the output voltage of the first converter is set based on the measured voltage of the supercapacitor, the output current of the first converter is set based on the ratio of the combined power requirements of the fuel cell stack and the battery to the measured voltage of the supercapacitor, and the limiting current of the first converter is set based on the limiting current of the first converter.
11. The controller is, The fuel cell system according to claim 8, characterized in that, during operation of the fuel cell system, the output voltage of the second converter is set based on the target voltage of the fuel cell stack, the output current of the second converter is set based on the ratio of the target power of the battery to the measured voltage, and the limiting current of the second converter is set based on the discharge allowable current of the battery.
12. The aforementioned power relay assembly is The fuel cell system according to claim 2, characterized in that, during operation of the fuel cell system, the power discharged from the supercapacitor is supplied to the inverter.
13. The steps include setting the output of a first converter that adjusts the power output from the fuel cell stack or battery according to the starting or operating state of the fuel cell system, and a second converter that adjusts the power input to or output to the battery, A step of controlling the operation of the power relay assembly according to the starting or operating state of the fuel cell system, The steps include controlling the power supply to the fuel cell stack, battery, and supercapacitor in accordance with the outputs of the first and second converters and the operation of the power relay assembly, and Includes, The step of controlling the power supply is: The first converter, A power control method for a fuel cell system, characterized by including the step of supplying the charging power supplied from the second converter to the supercapacitor via the power relay assembly when the fuel cell system is started.
14. The step of setting the output is: The steps include setting the starting voltage of the fuel cell stack to the output voltage of the second converter when starting the fuel cell system, A power control method for a fuel cell system according to claim 13, characterized by comprising the step of setting the limit current of the second converter or the discharge allowable current of the battery to the limit current of the second converter.
15. The step of setting the output is: The steps include setting the charging voltage of the supercapacitor to the output voltage of the first converter when starting the fuel cell system, The steps include setting the output current of the first converter to a value obtained by subtracting the current required by the auxiliary equipment from the dischargeable current of the battery, A power control method for a fuel cell system according to claim 13, characterized by comprising the step of setting the limit current of the first converter or the allowable charging current of the supercapacitor to the limit current of the first converter.
16. The step of controlling the power supply is: The power control method for a fuel cell system according to claim 13, characterized in that, when the fuel cell system is started, the second converter supplies starting power to the fuel cell system using the power discharged by the battery.
17. The step of controlling the power supply is: The fuel cell system starts up, and the second converter supplies power to charge the supercapacitor using the power discharged by the battery, A power control method for a fuel cell system according to claim 13, characterized in that the first converter adjusts the charging power supplied from the second converter and supplies it to the supercapacitor via the power relay assembly.
18. The step of controlling the power supply is: Before supplying charging power to the supercapacitor, the power relay assembly connected to the supercapacitor adjusts the voltage between the output terminal of the first converter and the supercapacitor using a precharge relay. A power control method for a fuel cell system according to claim 17, characterized in that when the power relay assembly is supplied with charging power via the first converter, it uses the main relay to provide charging power to the supercapacitor.
19. The step of setting the output is: During operation of the fuel cell system, the steps include setting the output voltage of the first converter based on the measured voltage of the supercapacitor, The steps include setting the output current of the first converter based on the ratio of the combined power requirements of the fuel cell stack and the battery to the measured voltage of the supercapacitor, A power control method for a fuel cell system according to claim 13, characterized by comprising the step of setting a limiting current for the first converter based on the limiting current of the first converter.
20. The step of setting the output is: During operation of the fuel cell system, the steps include setting the output voltage of the second converter based on the target voltage of the fuel cell stack, The steps include setting the output current of the second converter based on the ratio of the target power of the battery to the measured voltage, A power control method for a fuel cell system according to claim 13, characterized by comprising the step of setting a limiting current for the second converter based on the discharge allowable current of the battery.
21. The step of controlling the power supply is: During operation of the fuel cell system, the second converter adjusts and outputs the power discharged by the battery, A power control method for a fuel cell system according to claim 13, characterized in that the first converter adjusts the power output via at least one of the fuel cell stack and the second converter and supplies it to an inverter.
22. The step of controlling the power supply is: A power control method for a fuel cell system according to claim 13, characterized in that, during operation of the fuel cell system, the power relay assembly supplies power discharged from the supercapacitor to an inverter.