TWI754203B - Shut-down method and system of fuel cell - Google Patents

Abstract

A shut-down method and system of fuel cell is disclosed in the present invention. The method includes the following steps. Stop to provide hydrogen to the fuel cell. Then, detect the pressure and the voltage of the fuel cell during at least an adjustable load is running. Reduce the demand power of the adjustable load until the pressure of the fuel cell is not larger than a pressure threshold. Hence, the residual hydrogen inside the fuel cell can be continuously consumed. And finally, shut down the fuel cell until the voltage of the fuel cell is not larger than a final voltage threshold. Therefore, after shutting down the fuel cell, neither high voltage nor combustion reactions would be occurred due to no negative pressure.

Description

Control method and system for shutting down fuel cell

The present invention relates to a control method and system for shutting down a fuel cell, in particular to a control method for shutting down a fuel cell by detecting the gas pressure and voltage of the fuel cell to determine the timing of shutting down the fuel cell in the procedure of shutting down the fuel cell and its system.

In recent years, sustainable development has become an important issue, and the world is therefore committed to the pursuit of balanced development of energy, environmental protection and economy. In terms of means of transportation, gasoline is generally used as a power source. However, a large amount of greenhouse gases will be released in the process of converting gasoline into energy, which undoubtedly goes against the goal of pursuing environmental protection, especially after the Kyoto Protocol takes effect. Gradually release energy alternatives. Due to the recyclable characteristics of hydrogen energy, the application of fuel cell technology in transportation vehicles has become a solution that takes into account environmental protection and can also cope with the current era of high energy prices.

In the process of shutting down the fuel cell, there are still residual hydrogen and air in the fuel cell system. The residual hydrogen in the system can easily keep the fuel cell in an open circuit voltage state, and the hydrogen can easily cross over from the anode to the cathode. A combustion reaction occurs at the air side. When the fuel cell is turned on, a high voltage is easily generated when the front of the interface between hydrogen and air moves along the catalyst layer, which in turn causes the catalyst carrier to undergo an oxidation reaction, which damages the performance and life of the fuel cell. Therefore, how to control the hydrogen remaining in the system when the fuel cell is turned off is a key issue for the fuel cell. an important issue to be solved.

In the prior art, when the fuel cell is shut down, the air pressure entering the cathode and anode of the fuel cell is reduced to make the anode reach a negative pressure state, and when the negative pressure is reached, an inert gas is introduced to the anode to reduce the next The interface front problem when the fuel cell is turned on. However, the disadvantage of the prior art is that if inert gas is to be introduced, additional inert gas needs to be configured on the fuel cell, which undoubtedly causes the complexity of the system design. In addition, in actual operation, the fuel cell stack is a stack of multiple single cells When the anode reaches a negative pressure state, due to the uneven distribution of hydrogen gas, it is easy to make some parts of the battery without hydrogen gas around, causing damage to the battery. That is to say, when the negative pressure state is reached, although there is still current. However, some of the cells do not react with the appropriate hydrogen, but instead carry out the oxidation reaction of carbon, thereby causing damage to the fuel cell.

Based on the bottleneck of the above-mentioned conventional technology, the present invention provides a control method and system for shutting down a fuel cell. When the fuel cell is shut down, the hydrogen pressure and voltage of the fuel cell system are continuously detected to determine the shutdown of the fuel cell. The timing of the shutdown is to avoid the system being in a high voltage state during the shutdown process, or the catalyst carrier is damaged due to uneven distribution of hydrogen, and to avoid the problem of hydrogen passing through the electrode layer of the battery to cause a combustion reaction, thereby improving the life of the fuel cell. .

One object of the present invention is to provide a control method and system for shutting down a fuel cell. During the shutdown procedure of the fuel cell, after the supply of the fuel cell reactant is stopped, the adjustable load is used to consume the remaining fuel cell system. The reactant is detected, and the gas pressure of the hydrogen gas of the fuel cell system is detected to judge the consumption status of the reactant.

Another object of the present invention is to provide a control method for shutting down a fuel cell and a system thereof, when detecting the hydrogen pressure of a fuel cell, it also detects the voltage of the fuel cell at the same time, and uses the voltage of the fuel cell to more accurately judge the consumption status of the reactant, so as to fully consume the remaining hydrogen and avoid damage to the fuel cell , to avoid excessive residual hydrogen gas passing through the battery electrode layer, thereby causing combustion in the fuel cell system, or high voltage causing corrosion of the carbon carrier.

Another object of the present invention is to provide a control method and system for shutting down a fuel cell, which is to stop supplying air to the fuel cell system under certain circumstances, so that after the residual hydrogen reacts with the oxygen in the air, the remaining nitrogen It will be filled in the fuel cell system to avoid the formation of a hydrogen and air front when the fuel cell is turned on next time, and to avoid high voltage generation and corrosion of the carbon carrier.

In order to achieve the purpose of the above invention, the present invention proposes a control method for shutting down a fuel cell, by controlling an adjustable load coupled to the fuel cell to shut down the fuel cell system, the method includes the following steps: stopping the introduction of hydrogen gas to fuel cell; then, when the variable load is continuously operated, the remaining hydrogen in the fuel cell continues to react to rapidly consume hydrogen, and the hydrogen pressure and voltage value of the fuel cell are detected at the same time; and when the hydrogen pressure value is not greater than the gas pressure threshold , and reduce the required power of the adjustable load to continuously consume the remaining hydrogen until it is detected that the voltage value of the fuel cell is not greater than the final voltage threshold, then the fuel cell is turned off.

In the above steps, when the adjustable load includes a plurality of loads, the method for reducing the required power of the adjustable load is to turn off at least one of the adjustable loads. The manner of turning off at least one variable load is further turned off sequentially according to the demand power of the variable load from large to small.

In the above steps, the method for reducing the demand power of the adjustable load is to directly adjust the demand power of the adjustable load.

In the above steps, when the voltage value of the fuel cell is continuously detected, the voltage value of at least one single cell in the fuel cell is detected. In the above steps, the air pressure threshold is not greater than 0.5 psi.

In the above steps, the final voltage threshold is not greater than 0.1 volts.

In the above steps, when it is detected that the air pressure value of the fuel cell is not greater than the air pressure threshold value, the supply of air to the fuel cell is further stopped.

In the above steps, when it is detected that the voltage value of the fuel cell is not greater than the final voltage threshold, before closing the fuel cell, the inlet valve of the cathode of the fuel cell and the outlet valve of the fuel cell are further closed.

In order to achieve the purpose of the above invention, the present invention provides a control system for shutting down a fuel cell, which includes at least one adjustable load, a fuel cell, a voltage detector, an air pressure detector, and a control unit. The fuel cell is coupled to the adjustable load. The voltage detector is used for detecting the voltage of the fuel cell to generate the voltage value of the fuel cell. The gas pressure detector is used for detecting the gas pressure of the anode of the fuel cell to generate a gas pressure value of the anode of the fuel cell. The control unit is used for determining and judging the voltage value of the fuel cell, and according to the results of judging the gas pressure value and the voltage value, it controls to reduce the adjustable load and shut down the fuel cell.

Among them, the variable load system can be a vacuum pump, a hydrogen pump, an air pump, a circulation pump, a water pump, a radiator, a blower, a DC converter, a motor, and the like.

In summary, the present invention proposes a control method and system for shutting down a fuel cell, which utilizes the detection of the voltage and/or air pressure of the fuel cell to determine the amount of the remaining reactive gas in the fuel cell system, and matches loads with different power requirements so as not to consume the remaining reactive gas excessively, to Overcome the technical bottleneck existing in the conventional technology, so that the fuel cell will not form a front of hydrogen and air when the fuel cell is turned on next time, and after the fuel cell is turned off, there will be no hydrogen in the fuel cell system to avoid high pressure. Electricity and combustion reactions occur.

1: Fuel cell system

20: Control unit

30: Fuel Cells

41: Main load

42: Secondary load

43: Secondary battery

44: External load

50: Voltage detector

60: Air pressure detector

70: Hydrogen tank

71: Hydrogen intake valve

72: Hydrogen gas outlet valve

80: Blower

81: Air intake valve

82: Air outlet valve

90: Gas humidification unit

S01, S02, S03, S04, S05a, S05b, S06, S07a, S07b, S08: Steps

FIG. 1 is a block diagram of a control system according to an embodiment of the present invention.

FIG. 2 is a flowchart of a control method according to an embodiment of the present invention.

FIG. 3 is a block diagram of a control system according to an embodiment of the present invention.

FIG. 4 is a block diagram of a control system according to an embodiment of the present invention.

The advantages and spirit of the present invention can be further understood from the following detailed description and accompanying drawings. The construction and use of the embodiments of the present invention are described in detail as follows. It must be understood that the present invention provides many applicable innovative concepts that can be broadly implemented within a given background. This specific embodiment is merely indicative of the specific ways to make and use the invention, and not to limit the scope of the invention.

The present invention proposes a control method and a system for shutting down a fuel cell, the spirit of which is that when the fuel cell is to be shut down, first stop the introduction of hydrogen into the fuel cell, and then use a variable load coupled to the fuel cell to A faster consumption rate is used to react the hydrogen remaining in the fuel cell system until the remaining hydrogen is fully consumed, and then the fuel cell system is turned off. Further, when the hydrogen supply to the fuel cell is stopped, the reactants at the anode of the fuel cell will be gradually consumed due to the operation of the variable load, and in the process of consuming the reactants, under certain conditions Gradually reduce the required power of the adjustable load to avoid the problem of uneven distribution of reactants due to the rapid consumption rate of reactants.

The present invention proposes two ways to reduce the demand power of the variable load, one of which is when the variable load includes a plurality of loads, by turning off at least one load to change the demand power of the whole load, and all the The multiple loads described above may respectively include loads with different or same power requirements. This embodiment will take the existence of primary and secondary loads as an example to describe the process of turning off at least one adjustable load, where the primary load represents a load with a larger demand power, and the demand power of the secondary load is smaller than that of the primary load. . Please refer to FIG. 1 and FIG. 2 at the same time. FIG. 1 is a block diagram of a control system according to an embodiment of the present invention, and FIG. 2 is a flowchart of a control method according to an embodiment of the present invention. As shown in FIG. 1 , the control system 1 for shutting down the fuel cell includes a primary load 41 , a secondary load 42 , a fuel cell 30 , a voltage detector 50 , an air pressure detector 60 , and a control unit 20 .

The method implemented by using the above system includes the following steps: step S01, providing a shutdown signal to the control unit 20; step S02, then, the control unit 20 controls the hydrogen gas to stop flowing into the fuel cell 30 according to the shutdown signal. The load still maintains the original state to continue to operate. In this embodiment, the adjustable load includes the main load 41 and the secondary load 42, so that the remaining hydrogen in the fuel cell continues to react; step S03, the pressure detector 60 continues The air pressure value of the anode of the fuel cell 30 is detected, and the voltage detector 50 continuously detects the voltage value of the fuel cell 30; in step S04, the control unit 20 determines the air pressure value detected by the air pressure detector 60, and determines the air pressure value Whether it is greater than the air pressure threshold; if it is judged that it is greater than the air pressure threshold, go to step S05a, use the control unit 20 to make the fuel cell 30 continue to provide power to the main load 41 and the secondary load 42, and return to step S04a; if it is judged that it is not greater than the air pressure threshold, Proceed to step S05b, the control unit 20 controls to turn off the main load 41 and turn off the fuel cell 30 continues to provide power to the secondary load 42; step S06, the control unit 20 reads the voltage value of the fuel cell 30 detected by the voltage detector 50, and determines whether the voltage value is greater than the final voltage threshold; if it is determined to be greater than the final voltage threshold, Entering step S07a, the control unit 20 controls the fuel cell 30 to continue to provide power to the secondary load; if it is judged that the voltage is not greater than the final voltage threshold, enter step S07b, and the control unit 20 controls to turn off the secondary load; finally, in step S08, the control unit 20 controls to The fuel cell 30 is turned off.

In the above embodiment, when the control unit 20 receives the shutdown signal, it controls to stop the introduction of hydrogen into the fuel cell 30. However, even though the introduction of hydrogen has been stopped, there will still be remaining unreacted hydrogen in the fuel cell 30. That is to say, at this time, the fuel cell 30 uses the hydrogen remaining therein to react to provide power. Therefore, the amount of hydrogen remaining in the fuel cell 30 can be determined by detecting the air pressure of the fuel cell 30 at this time.

In the above embodiment, the air pressure threshold and the final voltage threshold are set so that the main load 41 and the secondary load 42 can be turned off at an appropriate time. In this embodiment, the required power of the main load 41 is greater than the required power of the secondary load 42 , in detail, the hydrogen remaining in the fuel cell 30 is gradually consumed by the reaction. As the concentration of the reactant decreases, the voltage of the fuel cell 30 also decreases. The control unit 20 reads the detected gas pressure detector 60 The gas pressure value of the fuel cell 30 and determine whether it is greater than the gas pressure threshold value. If the control unit 20 determines that it is greater than the gas pressure threshold value, it means that the hydrogen concentration is still sufficient. Since the problem of uneven distribution of hydrogen gas is less likely when the gas pressure is high, it can be used as required. The load with higher power consumes hydrogen, and the main load 41 and the secondary load 42 continue to operate to continue to rapidly consume the remaining hydrogen. If the control unit 20 determines that it is not greater than the gas pressure threshold, it means that the hydrogen concentration has been consumed to a specific concentration range, and the control The unit 20 controls the fuel cell 30 to stop supplying power to the main load 41 (turning off the main load 41 ) that requires more power, but still makes the fuel cell 30 continue to supply power to the secondary load 42 , The hydrogen remaining in the fuel cell 30 can continue to react until the control unit 20 determines that the detected voltage value of the fuel cell 30 is not greater than the final voltage threshold, the fuel cell 30 stops providing power to the secondary load 42 and shuts down the fuel cell 30 .

Further, in the above-mentioned embodiment, the load is gradually turned off according to the required power of the load. Generally speaking, after the hydrogen gas stops flowing into the fuel cell 30, there is still a relatively high content of hydrogen in the fuel cell 30, so the supply can still be The energy of the adjustable load (including the main load 41 and the secondary load 42 ) with high power can quickly consume the hydrogen gas without causing uneven distribution of the hydrogen gas, thereby impairing the life of the fuel cell. When the hydrogen pressure is not greater than the gas pressure threshold, the distribution of hydrogen in the fuel cell begins to be uneven. Usually, the main load 41 with a larger demand power is selectively turned off first, and then the secondary load 42 with a smaller demand power is turned off. , however, it is not limited to this; in addition, this embodiment does not limit the number of the main load 41 and the sub-load 42 , in other words, when there are more main loads 41 and sub-loads 42 , the number of the main loads 41 and the sub-loads 42 can be The load is turned off in sequence according to the required power.

Another method for reducing the demand power of the variable load proposed by the present invention is to directly adjust the demand power of the variable load, that is to say, when there is a variable load in the variable load, the variable load can be directly adjusted. to reduce the demand power of the overall adjustable load. Please refer to FIG. 3, which is a block diagram of a control system according to an embodiment of the present invention. As shown in FIG. 3 , the technical contents of FIG. 3 and FIG. 1 are not repeated here. The control system 1 for shutting down the fuel cell further includes a secondary battery 43 and an external load 44 .

In this embodiment, the main load 41 is a DC converter, so that the fuel cell 30 can output current to the external load 44 within a specific current range. However, when the control unit 20 receives a shutdown signal, it is necessary to reduce the fuel The DC converter can directly adjust the output power of the battery 30 Its own required power reduces the output power of the fuel cell 30. Even if the fuel cell 30 still outputs a small amount of current to the DC converter, the output current can be stored in the secondary battery through the regulation of the DC converter. 43.

In addition, when detecting the voltage value of the fuel cell, the voltage value of the single cell in the fuel cell system can be detected. When there are multiple secondary loads, when it is detected that the voltage value of the fuel cell is greater than the final voltage threshold, in addition to continuously reducing the required power of the main load, the load is also turned off at least once until the voltage value is not greater than the final voltage threshold. , and the method of shutting down the load at least once is more according to the power demand of the secondary load in descending order.

It should be noted that, if the main load 41 described in the above embodiment is a blower, and other loads use loads other than blowers, when the control unit 20 determines that the air pressure of the anode of the fuel cell 30 is not greater than the air pressure threshold, the control unit 20 is controlled so that the fuel cell 30 stops providing power to the blower, and the air stops flowing into the fuel cell 30, that is to say, the concentration of the reactants at the cathode and anode in the fuel cell 30 will gradually decrease with the progress of the reaction, so The gas pressure threshold value can be set by pre-calculating the amount of gas required for the reaction, and when the hydrogen gas of the anode of the fuel cell 30 is consumed, the oxygen in the air existing at the cathode is also consumed, so that there is still a residual gas in the fuel cell 30. The nitrogen participating in the reaction will gradually diffuse in the fuel cell 30 to fill the entire closed space, so that the cathode of the fuel cell 30 will not be in a vacuum or negative pressure state.

In the above-mentioned embodiment, the control unit 20 can stop the air from entering the fuel cell 30 by controlling the blower or closing the air inlet valve. However, the above is only for illustration, and is not intended to limit the stop of the air. means of fuel cells. In an embodiment of the present invention, the adjustable load is a load inside the fuel cell system and/or a load outside the fuel cell system load. For example, the adjustable load can be a vacuum pump, a hydrogen pump, an air pump, a circulation pump, a water pump, a radiator, a blower, a DC converter, a motor, and the like.

In an embodiment of the present invention, the gas pressure threshold is not greater than 0.5 psi, and the final voltage threshold is not greater than 0.1 volt.

In the embodiment of the present invention, before shutting down the fuel cell, all gas inlet and outlet valves of the fuel cell system are further closed, and the above gas valves can be closed at different timings according to requirements. Please refer to FIG. 4 , which is a block diagram of a control system according to an embodiment of the present invention. In this embodiment, the control system 1 for shutting down the fuel cell includes a fuel cell 30 , a main load 41 , a hydrogen tank 70 , a hydrogen inlet valve 71 , a hydrogen outlet valve 72 , a blower 80 , an air inlet valve 81 , and an air outlet valve 82 , the gas humidification unit 90 . The hydrogen inlet valve 71 is used to block the hydrogen tank 70 and the fuel cell 30, the hydrogen gas outlet valve 72 is used to block the fuel cell 30 and the external environment, the air inlet valve 81 is used to block the blower 80 and the fuel cell 30, and the air outlet valve 31 is used to block Fuel cell and external environment. It should be noted that, when the air enters the fuel cell 30 and the hydrogen and air need to be discharged to the external environment, they all need to pass through the gas humidifying unit 90 to provide gas humidification.

For example, when the fuel cell 30 continues to operate to provide power to the main load 41, the hydrogen inlet valve 71, the air inlet valve 81, and the air outlet valve 82 are continuously opened, so that the hydrogen in the hydrogen tank 70 can be supplied to the fuel The battery and the blower can supply air to the fuel cell. When the fuel cell control system 1 receives the shutdown signal, it first closes the hydrogen inlet valve 71 of the hydrogen tank 70 to stop supplying hydrogen to the fuel cell 30, and the air inlet valve Line 81 can be closed when it is detected that the air pressure value of the fuel cell 30 is not greater than the air pressure threshold value, or when the voltage value is not greater than the final voltage threshold value, the air outlet valve 82 is further closed before the fuel cell is closed. The hydrogen gas outlet valve 72 needs to be discharged Turn on when hydrogen is released.

In addition, when detecting the voltage value of the fuel cell, the voltage value of the single cell in the fuel cell system can be detected. When there are multiple secondary loads, when it is detected that the voltage value of the fuel cell is greater than the final voltage threshold, in addition to continuously turning off the main load, the load is turned off at least once until the voltage value is not greater than the final voltage threshold. The method of turning off the load at least one time is further turned off in descending order according to the power demand of the secondary load.

Therefore, the technical spirit of the present invention is to use the method of detecting voltage and air pressure to determine the timing of turning off the load and the fuel cell. When the detected air pressure is still greater than the air pressure threshold, all the adjustable loads are turned on continuously, and Continue to detect the voltage value of the fuel cell until the detected gas pressure is not greater than the gas pressure threshold, reduce the required power of the adjustable load to continue to consume the remaining gas in the fuel cell, until the detected voltage is not greater than the final voltage threshold , and then turn off the fuel cell. The present invention can include a plurality of adjustable loads, and these adjustable loads can be gradually turned off according to the energy consumption of the adjustable loads. That is, before reaching the final voltage threshold, if the detected voltage Still far greater than the final voltage threshold, each sub-load can be gradually turned off according to the required power of the sub-load, and other sub-loads that are not turned off continue to operate to consume the remaining gas in the fuel cell until the detected voltage is not greater than the final voltage. When the value of the load is reached, turn off the load with the smallest required power. In addition, you can directly adjust the required power of the load itself, that is, you do not need to turn off the load, but by reducing the required power of the load itself, to reduce the overall load. , by the above method, the hydrogen remaining in the fuel cell can be almost completely reacted.

In summary, the present invention proposes a control method and system for shutting down a fuel cell, which utilizes detection of the voltage and air pressure of the fuel cell to determine the remaining reactions in the fuel cell system The amount of gas and the load with different power requirements are used to consume the remaining reaction gas, so that when the fuel cell is turned off, only the remaining hydrogen is consumed inside the fuel cell and the original nitrogen in the air is still retained. The nitrogen will gradually fill the fuel cell, and then So that the fuel cell will not form a front of hydrogen and air when the fuel cell is turned on next time, and after the fuel cell is turned off, there will be no hydrogen in the fuel cell system, so as to avoid the occurrence of high-voltage electricity and combustion reactions.

Although the present invention is disclosed above by the aforementioned embodiments, it is not intended to limit the present invention. Anyone who is familiar with the similar arts can make some changes and modifications without departing from the spirit and scope of the present invention. The scope of patent protection shall be determined by the scope of the patent application attached to this specification.

S01, S02, S03, S04, S05a, S05b, S06, S07a, S07b, S08: Steps

Claims (8)

A control method for shutting down a fuel cell, by controlling at least one adjustable load coupled with the fuel cell to shut down the fuel cell system, the method comprises the steps of: stopping the introduction of hydrogen to the fuel cell; When the variable load is operated, the remaining hydrogen in the fuel cell is continuously reacted and a gas pressure value and a voltage value of the fuel cell are detected; and when the gas pressure value is not greater than a first gas pressure threshold, the reduction of the gas pressure The required power of the load can be adjusted until it is detected that the voltage value of the fuel cell is not greater than a final voltage threshold, then the fuel cell is turned off; wherein when the adjustable load includes a plurality of loads, when a plurality of the fuel cells are turned off When there is a load, the shutdown method is further based on the power demand of the loads, and the shutdown is performed in order from large to small. The control method for shutting down a fuel cell as claimed in claim 1, wherein the method for reducing the required power of the variable load is to shut down at least one of the loads. According to the control method for shutting down the fuel cell as described in claim 1, the method for reducing the required power of the variable load is to directly adjust the required power of the variable load. The control method for shutting down a fuel cell according to claim 1, wherein when the voltage value of the fuel cell is detected, the voltage value of at least one single cell in the fuel cell is further detected. The control method for shutting down a fuel cell as claimed in claim 1, wherein the gas pressure threshold is not greater than 0.5 psi. The control method for shutting down a fuel cell as claimed in claim 1, wherein the final voltage threshold is not greater than 0.1 volts. The control method for shutting down a fuel cell as claimed in claim 1, wherein when it is detected that the air pressure value of the fuel cell is not greater than the air pressure threshold value, the supply of air to the fuel cell is further stopped. The control method for shutting down a fuel cell as claimed in claim 1, wherein when it is detected that the voltage value of the fuel cell is not greater than the final voltage threshold, before shutting down the fuel cell, the process of the cathode of the fuel cell is further shut down. The gas valve and the gas outlet valve of the fuel cell.

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