Fuel cell system and method of controlling a fuel cell system

Abstract

A fuel cell system and a method of controlling the fuel cell system are proposed. The fuel cell system includes a hydrogen supply unit connected to a hydrogen inlet side of a fuel cell stack, in which a supply valve and a sensor are provided, a hydrogen discharge unit connected to a hydrogen outlet side of the fuel cell stack, in which a water collector and a purge valve are provided, and a controller configured to calculate an amount of hydrogen discharged through the purge valve from an amount of hydrogen supplied to the fuel cell stack and an amount of hydrogen consumed therein, and to perform compensation control of the supply valve when the amount of hydrogen discharged is at or above a reference value.

Description

Technical Field

[0001] This disclosure relates to a fuel cell system and a method for controlling the fuel cell system. During the combined discharge of condensate from a collector and gaseous impurities from the hydrogen electrode of the fuel cell stack, while adjusting the fuel pressure on the hydrogen electrode side of the fuel cell stack, the method estimates the amount of gas discharged in the combined manner by controlling a hydrogen supply valve without using a separate sensor, and supplies additional hydrogen in a manner corresponding to the amount of gas discharged. Therefore, overshooting or undershooting of the supplied hydrogen amount can be prevented. Consequently, the power generation efficiency of the fuel cell stack can be improved, and fuel cell stack degradation can be prevented. Background Technology

[0002] Regarding the pressure control of hydrogen supply to the hydrogen electrode (anode) of the fuel cell stack, when the system starts operating, the hydrogen shut-off valve is opened, and the pressure control of the hydrogen electrode of the fuel cell stack is performed by controlling the opening degree of the hydrogen supply valve. In this case, the supply amount can be adjusted by using PWM duty cycle commands to the hydrogen supply valve.

[0003] The target pressure for supplying hydrogen to the hydrogen electrode is set according to the output required by the fuel cell stack. Specifically, as the output required by the fuel cell stack increases, the flow rate of the supplied air is increased, the pressure of the air electrode is increased, and the target pressure of the hydrogen electrode is increased.

[0004] Furthermore, PI control is designed and implemented in such a way that the actual measured hydrogen pressure at the hydrogen electrode follows the target pressure.

[0005] During operation, in order to obtain the hydrogen concentration, the purge valve is opened for a certain period of time and purge is performed. At this time, in order to pre-compensate for the pressure drop caused by hydrogen emission when the purge valve is opened, the duty cycle compensation target value for the hydrogen supply valve is set to be fed forward and adjusted according to the current in the fuel cell stack at the time when the purge valve is opened.

[0006] When the purification valve opens, the condensate in the collector is drained. After the condensate is completely drained, hydrogen purification begins naturally. Without a water level sensor to reduce system costs, it is difficult to accurately determine the timing and amount of hydrogen discharged. Furthermore, there is a risk of over- or under-pressure in the supplied hydrogen.

[0007] The foregoing is intended only to help understand the background of this disclosure and is not intended to imply that this disclosure falls within the scope of related fields known to those skilled in the art. Summary of the Invention

[0008] The purpose of this disclosure is to provide a fuel cell system and a method for controlling the fuel cell system. During the combined discharge of condensate from the collector and gaseous impurities from the hydrogen electrode of the fuel cell stack, while adjusting the fuel pressure on the hydrogen electrode side of the fuel cell stack, the method estimates the amount of gas discharged in the combined manner by controlling the hydrogen supply valve without using a separate sensor, and supplies additional hydrogen in a manner corresponding to the amount of gas discharged. Therefore, overshooting or undershooting of the supplied hydrogen amount can be prevented. Consequently, the power generation efficiency of the fuel cell stack can be improved, and fuel cell stack degradation can be prevented.

[0009] According to one aspect of this disclosure, a fuel cell system is provided, comprising: a hydrogen supply unit connected to a hydrogen inlet side of a fuel cell stack, wherein a supply valve and a sensor are provided in the hydrogen supply unit; a hydrogen emission unit connected to a hydrogen outlet side of the fuel cell stack, wherein a water collector and a purge valve are provided in the hydrogen emission unit; and a controller configured to calculate the amount of hydrogen emitted through the purge valve based on the amount of hydrogen supplied to the fuel cell stack and the amount of hydrogen consumed therein, and to perform compensation control of the supply valve when the amount of emitted hydrogen is at or above a reference value.

[0010] In a fuel cell system, the sensor can be a pressure sensor and can be positioned between the supply valve and the injector.

[0011] In a fuel cell system, a purge valve can be located below the water collector, and when the purge valve is opened, the condensate in the water collector can be discharged first, and then hydrogen can be discharged.

[0012] In a fuel cell system, the controller can calculate the amount of hydrogen supplied based on the pressure of the supplied hydrogen measured by sensors or based on the hydrogen flow rate.

[0013] In a fuel cell system, the controller can calculate the amount of hydrogen consumed based on the current output from the fuel cell stack.

[0014] In a fuel cell system, the controller can calculate the amount of hydrogen emitted by subtracting the amount of hydrogen consumed from the amount of hydrogen supplied.

[0015] In a fuel cell system, the controller can calculate the amount of hydrogen emitted based on the amount of hydrogen supplied, the amount of hydrogen consumed, and the amount of hydrogen pressurized in the fuel cell stack.

[0016] In a fuel cell system, the controller can calculate the amount of pressurized hydrogen based on the internal pressure of the hydrogen electrode in the fuel cell stack.

[0017] In a fuel cell system, the controller can calculate the amount of hydrogen emitted by subtracting the amount of hydrogen consumed and the amount of hydrogen pressurized in the fuel cell stack from the amount of hydrogen supplied.

[0018] In a fuel cell system, when the amount of hydrogen emitted is at or above a reference value, the controller can calculate a compensation value based on the amount of hydrogen emitted, and can use the value obtained by adding the compensation value to the control value used to control the supply valve to control the supply valve, thereby preventing the amount of supplied hydrogen from undershooting or overshooting.

[0019] According to another aspect of this disclosure, a method for controlling the aforementioned fuel cell system is provided, the method comprising: calculating the amount of hydrogen supplied to the fuel cell stack and the amount of hydrogen consumed therein; calculating the amount of hydrogen emitted from the amount of hydrogen supplied to the fuel cell stack and the amount of hydrogen consumed therein; determining whether the amount of emitted hydrogen is at or above a reference value; and when the amount of emitted hydrogen is at or above the reference value, performing compensatory control on the amount of hydrogen supplied through a supply valve.

[0020] In this method, the amount of hydrogen emitted can be calculated based on the amount of hydrogen supplied, the amount of hydrogen consumed, and the amount of hydrogen pressurized in the fuel cell stack.

[0021] In this method, the amount of hydrogen emitted can be calculated by subtracting the amount of hydrogen consumed and the amount of hydrogen pressurized in the fuel cell stack from the amount of hydrogen supplied.

[0022] In this method, when performing compensation control on the amount of supplied hydrogen, when the amount of emitted hydrogen is at or above a reference value, a compensation value can be calculated based on the amount of emitted hydrogen, and the supply valve can be controlled by adding the compensation value to the control value used to control the supply valve, thereby preventing the amount of supplied hydrogen from undershooting or overshooting.

[0023] By utilizing the fuel cell system and method for controlling the fuel cell system according to this disclosure, during the combined discharge of condensate from the collector and gaseous impurities from the hydrogen electrode of the fuel cell stack, while adjusting the fuel pressure on the hydrogen electrode side of the fuel cell stack, the amount of gas discharged in the combined manner is estimated by controlling the hydrogen supply valve without using a separate sensor, and additional hydrogen is supplied in a manner corresponding to the amount of gas discharged. Therefore, overshooting or undershooting of the supplied hydrogen amount can be prevented. Thus, the power generation efficiency of the fuel cell stack can be improved, and fuel cell stack degradation can be prevented. Attached Figure Description

[0024] The above and other objects, features and advantages of this disclosure will become clearer from the following detailed description, taken in conjunction with the accompanying drawings, wherein:

[0025] Figure 1 This is a view showing the configuration of a fuel cell system according to an embodiment of the present disclosure;

[0026] Figure 2 This is a block diagram illustrating the control of a fuel cell system according to an embodiment of the present disclosure;

[0027] Figure 3 It is a graph showing the control results of a fuel cell system according to an embodiment of the present disclosure; and

[0028] Figure 4 This is a flowchart illustrating a method for controlling a fuel cell system according to an embodiment of the present disclosure. Detailed Implementation

[0029] Figure 1 This is a view showing the configuration of a fuel cell system according to an embodiment of the present disclosure. Figure 2 This is a block diagram illustrating the control of a fuel cell system according to an embodiment of the present disclosure. Figure 3 This is a graph showing the control results of a fuel cell system according to an embodiment of the present disclosure. Figure 4 This is a flowchart illustrating a method for controlling a fuel cell system according to an embodiment of the present disclosure.

[0030] like Figure 1 The diagram shows a view illustrating a fuel cell system according to an embodiment of the present disclosure. The fuel cell system includes a hydrogen supply unit 100, a hydrogen emission unit 300, and a controller 700. The hydrogen supply unit 100 is connected to the hydrogen inlet side of the fuel cell stack 500. A supply valve 120 and a sensor 130 are provided in the hydrogen supply unit 100. The hydrogen emission unit 300 is connected to the hydrogen outlet side of the fuel cell stack 500. A water collector 320 and a purge valve 340 are provided in the hydrogen emission unit 300. The controller 700 calculates the amount of hydrogen emitted through the purge valve 340 based on the amount of hydrogen supplied to the fuel cell stack 500 and the amount of hydrogen consumed therein. When the amount of emitted hydrogen is at or above a reference value, the controller 700 performs compensatory control of the supply valve 120.

[0031] The fuel cell system according to this disclosure no longer includes the valve required in related technologies to be located between the water collector 320 and the hydrogen electrode outlet of the fuel cell stack 500, nor the water level sensor required in related technologies to be located within the water collector 320. The fuel cell system is based on a technology that offers significant advantages in terms of simplified configuration, thereby reducing cost and weight.

[0032] Specifically, such as Figure 1As shown, hydrogen and air are supplied to the hydrogen electrode 520 and oxygen electrode 540 of the fuel cell stack 500, respectively. This produces water and generates an electric current. Excess hydrogen is discharged through the purge valve 340 of the hydrogen emission unit 300.

[0033] Pressure adjustment is required to supply hydrogen. The shut-off valve 110 is positioned directly upstream of the supply valve 120. The shut-off valve 110 is an on / off valve. The flow rate of fluid through the supply valve 120 is controlled via PWM control.

[0034] Therefore, according to this disclosure, the hydrogen supply unit 100 is connected to the hydrogen inlet side of the fuel cell stack 500. A supply valve 120 and a sensor 130 are provided in the hydrogen supply unit 100. The sensor 130 is a pressure sensor and is disposed between the supply valve 120 and the injector 140. A sensor 150 is also provided to measure the pressure of the hydrogen electrode.

[0035] The hydrogen emission unit 300 is connected to the hydrogen outlet side of the fuel cell stack 500. A water collector 320 and a purge valve 340 are provided in the hydrogen emission unit 300. The purge valve 340 is located below the water collector 320 and has a structure such that when the purge valve 340 is opened, the condensate in the water collector 320 is first discharged due to gravity, then forms a flow path, and finally discharges the internal hydrogen. Therefore, in the absence of a water level sensor, it is crucial to accurately measure the time when all the condensate is discharged and the time when hydrogen discharge begins.

[0036] To this end, controller 700 calculates the amount of hydrogen emitted through purge valve 340 based on the amount of hydrogen supplied to fuel cell stack 500 and the amount of hydrogen consumed therein. When the amount of emitted hydrogen is at or above a reference value, controller 700 performs compensating control of supply valve 120.

[0037] For reference, the controller 700 according to an exemplary embodiment of this disclosure is implemented as a non-volatile memory (not shown) and a processor (not shown). The non-volatile memory is configured to store algorithms for controlling the operation of various components of the vehicle or data regarding software commands for executing the algorithms. The processor is configured to use the data stored in the non-volatile memory to perform the operations described below. Here, the memory and processor are implemented as separate chips. Alternatively, the memory and processor can be implemented as a single integrated chip. The processor can be a combination of two or more processors.

[0038] like Figure 2The diagram shown is a block diagram illustrating the control of a fuel cell system according to an embodiment of the present disclosure, wherein feedback control is performed by commands to the supply valve 120 in such a manner that the FP (measured hydrogen pressure) follows the FP_T (target hydrogen pressure) set according to the output level of the fuel cell stack 500.

[0039] When the flow rate of hydrogen discharged after purification valve 340 is opened to perform purification exceeds the reference value, the time point when the purification of condensate is completed can be determined as the time point for purifying hydrogen. The flow rate of discharged hydrogen is calculated using the expression "supply flow rate - discharge flow rate - pressurization flow rate".

[0040] After the purge valve 340 is opened, from the start of hydrogen purification to the end of purification, compensation control is performed by commanding the supply valve 120 to supply an additional amount of hydrogen at the same flow rate as the purified hydrogen. The reason for performing compensation control is that without this compensation, excessive pressure downsurge could occur due to hydrogen discharge.

[0041] Furthermore, if compensation control is executed too early after the purge valve 340 is opened, excessive pressure overshoot may occur due to premature compensation.

[0042] Therefore, the controller 700 calculates the amount of hydrogen discharged through the purge valve 340 based on the amount of hydrogen supplied to the fuel cell stack 500 and the amount of hydrogen consumed therein. Then, when the amount of hydrogen discharged is at or above a reference value, the controller 700 performs compensating control of the supply valve 120.

[0043] The amount of hydrogen supplied is calculated based on the pressure of the supplied hydrogen measured by sensor 130 or based on the flow rate of the hydrogen.

[0044] Then, the controller 700 calculates the amount of hydrogen consumed based on the current output from the fuel cell stack 500. Specifically, the amount of hydrogen consumed can be calculated using the following equation.

[0045] Amount consumed: (Calculation of the amount of hydrogen consumed in a fuel cell due to electric current)

[0046] Where I is the current in the fuel cell (measured value), n is the number of cells in the fuel cell stack (design value), and F is the Faraday constant.

[0047] The controller 700 calculates the amount of hydrogen emitted by subtracting the amount of hydrogen consumed from the amount of hydrogen supplied. More specifically, the controller 700 calculates the amount of hydrogen emitted based on the amount of hydrogen supplied, the amount of hydrogen consumed, and the amount of hydrogen pressurized in the fuel cell stack 500.

[0048] The amount of hydrogen consumed here is calculated based on the current output from the fuel cell stack 500. Specifically, the amount of hydrogen consumed can be calculated using the following equation.

[0049] Amount consumed: (Calculation of the amount of hydrogen consumed in a fuel cell due to electric current)

[0050] Where I is the current in the fuel cell (measured value), n is the number of cells in the fuel cell stack (design value), and F is the Faraday constant.

[0051] Then, the controller 700 calculates the amount of pressurized hydrogen based on the internal pressure of the hydrogen electrode of the fuel cell stack 500. Specifically, the amount of pressurized hydrogen can be calculated using the following equation.

[0052] The amount of pressurization: PV = nRT (Calculation of the amount of hydrogen gas used to generate anode pressure)

[0053] Where V is the volume of the anode (design value), P is the pressure of the anode (FP is the measured value, FP_T is the target value), R is the ideal gas constant, and T is the temperature of the anode (measured value) (converted to absolute temperature).

[0054] As described above, the amount of hydrogen consumed and pressurized is subtracted from the amount of hydrogen supplied to obtain the amount of hydrogen emitted. The point at which the amount of emitted hydrogen no longer becomes small but begins to increase can be considered the point at which all the condensate is discharged and hydrogen emission begins to be significant.

[0055] That is, the controller 700 calculates the amount of hydrogen emitted by subtracting the amount of hydrogen consumed and the amount of hydrogen pressurized in the fuel cell stack 500 from the amount of hydrogen supplied.

[0056] Therefore, when the amount of hydrogen emitted is at or above the reference value, the controller 700 calculates a compensation value based on the amount of hydrogen emitted, and controls the supply valve 120 with the value obtained by adding the compensation value to the control value used to control the supply valve 120, thereby preventing the amount of hydrogen supplied from undershooting or overshooting.

[0057] like Figure 3 The diagram shown is a graph illustrating the control results of a fuel cell system according to an embodiment of the present disclosure. When the purge valve 340 opens, condensate is discharged first, followed by hydrogen. Therefore, it is possible to identify point A, where the amount of hydrogen discharged increases, from the point at which the condensate discharge ends.

[0058] Therefore, when significant compensation control is performed on the hydrogen supplied after point A, the instantaneous pressure downsurge of the supplied hydrogen, as indicated by line D, can be prevented. Furthermore, overshoot, as indicated by line C, that occurs when compensation control is performed before point A can be prevented.

[0059] Therefore, the pressure of the supplied hydrogen is controlled in accordance with this disclosure to reliably follow the target pressure indicated by line B.

[0060] like Figure 4 The diagram shows a flowchart illustrating a control method for a fuel cell system according to an embodiment of the present disclosure. The control method for the fuel cell system according to the present disclosure includes: steps S100, S110, and S120, calculating the amount of hydrogen supplied to the fuel cell stack 500 and the amount of hydrogen consumed therein; step S200, calculating the amount of hydrogen emitted from the amount of hydrogen supplied to the fuel cell stack 500 and the amount of hydrogen consumed therein; step S210, determining whether the amount of emitted hydrogen is at or above a reference value; and steps S300 and S310, performing compensation control on the amount of hydrogen supplied through the supply valve 120 when the amount of emitted hydrogen is at or above the reference value.

[0061] In step S200, the amount of hydrogen emitted is calculated by subtracting the amount of hydrogen consumed and the amount of hydrogen pressurized in the fuel cell stack 500 from the amount of hydrogen supplied.

[0062] Specifically, in steps S300 and S310, when the amount of hydrogen emitted is at or above a reference value, a compensation value is calculated based on the amount of hydrogen emitted, and the supply valve 120 is ultimately controlled using the value obtained by adding the compensation value to the control value used to control the supply valve 120. Therefore, undershooting or overshooting of the supplied hydrogen amount can be prevented. When the amount of hydrogen emitted is below the reference value, the pressure of the supplied hydrogen is controlled by general feedback control in a manner that follows the target pressure (steps S400, S410, and S500).

[0063] Using the fuel cell system and method for controlling the fuel cell system according to this disclosure, during the combined discharge of condensate in the water collector 320 and gaseous impurities in the hydrogen electrode of the fuel cell stack 500, while adjusting the fuel pressure on the hydrogen electrode side of the fuel cell stack 500, the amount of gas discharged in the combined manner is estimated by controlling the hydrogen supply valve 120 without using a separate sensor, and additional hydrogen is supplied in a manner corresponding to the amount of gas discharged. Therefore, overshooting or undershooting of the supplied hydrogen amount can be prevented. Thus, the power generation efficiency of the fuel cell stack 500 can be improved, and degradation of the fuel cell stack 500 can be prevented.

[0064] Although specific embodiments of this disclosure have been described for illustrative purposes, those skilled in the art will understand that various modifications, additions, and substitutions may be made without departing from the scope and spirit of the invention as disclosed in the appended claims.

Claims

1. A fuel cell system, comprising: A hydrogen supply unit is connected to the hydrogen inlet side of the fuel cell stack, and a supply valve and a sensor are provided in the hydrogen supply unit; A hydrogen emission unit is connected to the hydrogen outlet side of the fuel cell stack, and a water collector and a purification valve are provided in the hydrogen emission unit. as well as The controller is configured to calculate the amount of hydrogen discharged through the purge valve from the amount of hydrogen supplied to the fuel cell stack and the amount of hydrogen consumed therein, and to perform compensatory control of the supply valve when the amount of hydrogen discharged is at or above a reference value. The controller calculates the amount of hydrogen emitted based on the amount of hydrogen supplied, the amount of hydrogen consumed, and the amount of hydrogen pressurized in the fuel cell stack. The controller calculates the amount of pressurized hydrogen based on the internal pressure of the hydrogen electrode in the fuel cell stack. When the amount of hydrogen emitted is at or above the reference value, the controller calculates a compensation value based on the amount of hydrogen emitted, and controls the supply valve with the value obtained by adding the compensation value to the control value used to control the supply valve, thereby preventing the amount of supplied hydrogen from undershooting or overshooting.

2. The fuel cell system according to claim 1, wherein, The sensor is a pressure sensor and is located between the supply valve and the injector.

3. The fuel cell system according to claim 1, wherein, The purification valve is located below the water collector, and when the purification valve is opened, it first discharges the condensate in the water collector, and then discharges hydrogen gas.

4. The fuel cell system according to claim 1, wherein, The controller calculates the amount of hydrogen supplied based on the pressure of the supplied hydrogen measured by the sensor or based on the flow rate of the hydrogen.

5. The fuel cell system according to claim 1, wherein, The controller calculates the amount of hydrogen consumed based on the current output from the fuel cell stack.

6. The fuel cell system according to claim 1, wherein, The controller calculates the amount of hydrogen emitted by subtracting the amount of hydrogen consumed from the amount of hydrogen supplied.

7. The fuel cell system according to claim 1, wherein, The controller calculates the amount of hydrogen emitted by subtracting the amount of hydrogen consumed and the amount of hydrogen pressurized in the fuel cell stack from the amount of hydrogen supplied.

8. A method for controlling a fuel cell system according to claim 1, the method comprising: Calculate the amount of hydrogen supplied to the fuel cell stack and the amount of hydrogen consumed therein; The amount of hydrogen emitted is calculated from the amount of hydrogen supplied to the fuel cell stack and the amount of hydrogen consumed therein; Determine whether the amount of hydrogen emitted is at or above the reference value; as well as When the amount of hydrogen emitted is at or above the reference value, compensation control is performed on the amount of hydrogen supplied through the supply valve.

9. The method according to claim 8, wherein, The amount of hydrogen emitted is calculated based on the amount of hydrogen supplied, the amount of hydrogen consumed, and the amount of hydrogen pressurized in the fuel cell stack.

10. The method according to claim 9, wherein, The amount of hydrogen emitted is calculated by subtracting the amount of hydrogen consumed and the amount of hydrogen pressurized in the fuel cell stack from the amount of hydrogen supplied.

11. The method according to claim 8, wherein, In the execution of the compensation control of the amount of supplied hydrogen, when the amount of emitted hydrogen is at or above the reference value, a compensation value is calculated based on the amount of emitted hydrogen, and the supply valve is controlled by adding the compensation value to the control value used to control the supply valve, thereby preventing the amount of supplied hydrogen from undershooting or overshooting.

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