JP5060527B2 - Fuel cell power generation control method - Google Patents

Description

  The present invention relates to a fuel cell power generation control method, and more particularly, to a fuel cell power generation control method in a so-called hybrid fuel cell power supply system including a fuel cell and a transient response-compliant electric energy buffer.

  In recent years, so-called fuel cell electric vehicles equipped with fuel cells have been actively developed. As one of the fuel cell electric vehicles, a so-called hybrid type fuel cell electric vehicle is known which has a transient response-compatible electric energy buffer such as a fuel cell and a battery as a power source. In this hybrid type fuel cell electric vehicle, current is supplied by the fuel cell when it is within the fuel cell response speed range. In addition, if the fuel cell alone cannot supply a sufficient current or cannot follow the required speed due to a delay in the fuel supply system, the current is supplied from the transient response-compatible electrical energy buffer during a transition such as acceleration. The supplied output current is controlled.

  However, in this output current control, since a constant current is supplied from the fuel cell, when the external load is small, surplus power is consumed by a resistance load provided separately, which is wasted. An electric current was generated.

  In order to prevent such waste, Patent Document 1 discloses a fuel cell power supply system that controls the output current of a fuel cell. As shown in FIG. 5, the fuel cell power supply system M ′ includes a fuel cell 51, a DC / DC converter 52, and a battery 53 that is a transient response-compliant electric energy buffer. Further, a control device 55 is provided for controlling the current supply amount of the fuel cell 51 and the output limit value of the DC / DC converter 52 in accordance with the required external load (required load) 54. Further, an ammeter 56 for measuring the output current of the fuel cell 51 and an ammeter 57 for measuring the output current of the battery 53 are provided. Furthermore, the output circuit of the DC / DC converter 52 is provided with a voltmeter 58 for measuring the output voltage.

  In this fuel cell power supply system M ′, an output current to the fuel cell 51 is measured by an ammeter 56 and an output current of the battery 53 is measured by an ammeter 57. Further, the output voltage of the DC / DC converter 52 is controlled based on the measured value of the voltmeter 58 and the measured value of a thermometer (not shown) provided in the battery 53.

  When the external load 54 increases rapidly, the DC / DC converter 52 limits the output of current based on the measured values of these ammeters 56 and 57, and the fuel cell 51 limits the output current of the fuel cell 51. It is changed at a speed that can be followed. On the other hand, a shortage of current with respect to the external load 54 is supplied from the battery 53. In this way, control is performed so that current can be stably supplied even when the external load 54 rapidly increases. These controls are all performed by the control device 55.

JP-A-5-151983

  However, the conventional technology does not deal with cases where the external load suddenly decreases, such as when the hybrid fuel cell electric vehicle suddenly decelerates or stops, or when power is regenerated from there. Absent. In this way, when the external load is suddenly reduced, if the current generated in the fuel cell is reduced corresponding to the reduction in the external load, the amount of hydrogen supplied from the hydrogen storage alloy (not shown) to the fuel cell is also reduced. Of course, it must be reduced.

  However, a certain delay is inevitable when reducing the hydrogen supply. As a result, excess hydrogen is supplied to the fuel cell, and hydrogen under pressure remains inside the fuel cell. As a result, the pressure balance with the oxygen system may be lost, pressure balance may not be achieved, and the fuel cell may be brought to an emergency stop. Furthermore, the reaction membrane of the fuel cell may be damaged.

  Therefore, the problem of the present invention is that when the external load is suddenly reduced or regenerated, the residual hydrogen in the fuel cell is safely consumed and always supplies stable power to the external load without emergency stop. It is to perform power generation control of the fuel cell so that it can be performed.

The present invention that has solved the above problems includes a fuel cell that generates power using hydrogen supplied from a hydrogen supply source and oxygen in the air supplied from an air pump, and an electric energy buffer capable of storing the power generated by the fuel cell. And a control device, and is configured to be able to supply electric power to the external load from the fuel cell and the electric energy buffer , and the control device has a fuel cell output current target value according to a required load of the fuel cell power supply system. And a fuel cell output current command value is determined according to the fuel cell output current target value, and a current corresponding to the fuel cell output current command value is output from the fuel cell. In the power generation control method, the control device: (1) When the fuel cell output current target value decreases, the control device decreases the fuel cell output current target value according to the decrease in the fuel cell output current target value. The reduction rate of the fuel cell output current command value lack is, to process the surplus hydrogen often to power generation to the fuel cell by said fuel cell output current target value reduction ratio smaller rather gradual reduction rate than the performs a surplus hydrogen treatment, (2) the excess by hydrogen treatment was performed, the reduction rate of the fuel cell output current before the target value that more is greater Symbol fuel cell output current command value, the fuel cell output current Even when the target value is increased, regardless of the value of the fuel cell output current target value, the surplus hydrogen treatment is continued with the moderate decrease rate being reduced , and (3) when the surplus hydrogen is treated. The fuel cell power generation control method is characterized in that the generated power is stored in the electric energy buffer .

In the present invention, when the fuel cell output current target value decreases, the rate of decrease in the fuel cell output current command value that is decreased in accordance with the decrease in the fuel cell output current target value is reduced. most is power generation in the fuel cell performs a surplus hydrogen treatment for treating the excess hydrogen by a small gradual reduction rate than the rate, greater than Ri燃 charge the battery output current target value by the fact of performing the surplus hydrogen treatment is in the reduction rate of the fuel cell output current command value that have, even if the fuel cell output current target value is increased, regardless of the value of the fuel cell output current target value, to reduce as remains moderate reduction rate By continuing the surplus hydrogen treatment, it is possible to suppress the residual hydrogen under pressure in the fuel cell. Moreover, it can prepare for acceleration.

  According to the present invention, when the external load is suddenly reduced or regenerated, the residual hydrogen inside the fuel cell is safely consumed and stable power is always supplied to the external load without emergency stop. In addition, it is possible to perform power generation control of the fuel cell.

1 is a block diagram of an electric system of a fuel cell power supply system in which power generation control according to the present invention is performed. It is a block diagram of a fuel system of a fuel cell power supply system in which power generation control according to the present invention is performed. It is a graph which shows the example of the change of the electric current value at the time of performing the electric power generation control in this invention. It is a flowchart which shows the procedure which performs the electric power generation control which concerns on this invention. It is a block diagram of the conventional hybrid type fuel cell power supply system.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. FIG. 1 is a block diagram of an electric system in a fuel cell power supply system in which power generation control according to the present invention is performed, and FIG. 2 is a block diagram of the fuel supply system. Since the fuel cell power supply system M is used mounted on, for example, a fuel cell electric vehicle, an example in which the fuel cell power supply system M is mounted on a fuel cell electric vehicle (not shown) will be described here.

  As shown in FIG. 1, the electric system M <b> 1 in the fuel cell power supply system M includes a fuel cell 1. The fuel cell 1 is connected via a DC / DC converter 2 to a battery 3 that is an electrical energy buffer for transient response. Further, a current required according to an external load 4 including a required load of a main motor and auxiliary devices not shown is supplied from the fuel cell 1 and the battery 3 to the main motor and auxiliary devices not shown. The external load 4 is calculated based on the current value detected by the ammeter 8.

  Further, a control device 5 is provided for controlling the current supply amount of the fuel cell 1 and controlling the output limit value of the DC / DC converter 2. Further, ammeters 6 and 7 that measure output currents from the fuel cell 1 and the battery 3 and an ammeter 8 that measures an external load current are provided. A voltmeter 9 for measuring the output voltage from the DC / DC converter 2 is also provided. The current values and voltage values measured by these ammeters 6, 7, 8 and voltmeter 9 are sent to the control device 5. In the control device 5, the output current value of the fuel cell 1, the output limit value of the DC / DC converter 2, and the output voltage value of the DC / DC converter 2 are controlled based on these current values and voltage values. .

  As shown in FIG. 2, in the fuel supply system M2, hydrogen is supplied to the fuel cell 1 from a hydrogen supply source 11 made of, for example, an occluded hydrogen alloy via a regulator 12 and an ejector 13. In the regulator 12, the supply amount of supplied hydrogen is controlled, and hydrogen is directly ejected to the fuel cell 1 by the ejector 13.

  Furthermore, oxygen-rich air is supplied to the fuel cell 1. Air is supplied to the fuel cell 1 by the action of the air pump 14, but before the air is sucked by the air pump 14, dust is captured by the air filter 15, and after being discharged from the air pump 14, the heat exchanger Air is cooled by 16. The subsequent air is supplied to the fuel cell 1 via the filter 17.

  Hydrogen and air (oxygen) are supplied to the fuel cell 1 to the hydrogen electrode and the oxygen electrode, respectively, and the inside of the fuel cell 1 is humidified by the humidifier 18 to promote the electrochemical reaction between hydrogen and oxygen in the air. To do. In the fuel cell 1, hydrogen and oxygen in the air react electrochemically to generate an electric current. Although an electric current is generated by the electrochemical reaction and surplus water is generated, the surplus water generated here is removed through the demister 19. The surplus water contains hydrogen mixed with impurities, and this hydrogen is released into the atmosphere via the demister 19 and the purge valve 20.

  Further, in the fuel cell 1, the pressure balance is properly maintained by the air pressure regulating valve 21 so that the pressure balance of the differential pressure between the hydrogen electrode and the oxygen electrode does not collapse. When the pressure balance in the fuel cell 1 is likely to collapse, the pressure is adjusted by appropriately opening the air pressure regulating valve 21 with air.

Next, a power generation control method for a fuel cell according to the present invention will be described. FIG. 3 is a graph showing an example of a change in current value when power generation control in the present invention is performed. Here, as shown by a solid line in FIG. 3, control when the fuel cell output current target value (hereinafter referred to as “target value”) I _CMD according to the external load 4 varies will be described. The target value I _CMD is calculated in the control device 5 based on the current value of the ammeter 8 that detects the external load 4.

The target value _ICMD is 0 in the idling state (region A) before the start of running of the fuel cell electric vehicle. Next, when the accelerator is depressed and the fuel cell electric vehicle starts running, the external load 4 increases rapidly and the target value _ICMD increases instantaneously, then stabilizes at a constant value I1 (area B), and the required load is stabilized. It becomes a state.

Subsequently, for example, when the fuel cell electric vehicle suddenly decelerates and the external load 4 rapidly decreases, the target value _ICMD rapidly decreases at a reduction rate exceeding a predetermined reduction rate (region C) and eventually enters a negative region. In a regenerative state (area D). After that, when the accelerator is stepped on again and the external load 4 increases again, the target value _ICMD increases to escape from the regenerative state (region E), and when the traveling speed becomes constant, the external load 4 becomes stable and the target value _ICMD also increases. Stable at a constant value I2. Then, the target value _ICMD is in a state of maintaining a constant value I2 (region F).

Thus, when the external load 4 fluctuates, control of the fuel cell output current limit value (hereinafter referred to as “limit value”) _ILMT will be described first. The limit value I _LMT calculated here is transmitted to the DC / DC converter 2, and this limit value I _LMT is used as the current limit value of the DC / DC converter 2.

In the region A where the target value I _CMD is 0, the limit value I _LMT is set to a value I3 that is slightly higher than the target value I _CMD so as to have a slight margin. Next, when the accelerator is stepped on and the target value _ICMD increases instantaneously, in the subsequent region B, the limit value _ILMT is increased in consideration of the delay in the current generated from the fuel cell 1. At this time, the limit value I _LMT may be increased instantaneously as with the target value I _CMD , but the increase rate of the limit value I _LMT is limited by the performance of the hydrogen supply source 11 and the like. Therefore, the limit value I _LMT cannot be increased instantaneously, and the limit value I _LMT is increased with the maximum size in the performance of the hydrogen supply source 11. This and maximum with the size increase of increasing the limit value I _LMT to a value slightly higher than the target value I _CMD maintained at that value I4.

Thereafter, in the region C in which the external load 4 rapidly decreases, the limit value I _LMT is also decreased in accordance with the decrease in the target value I _CMD . Here, the magnitude of the reduction rate when the target value I _CMD is reduced is not particularly affected by the performance of the hydrogen supply source 11. Furthermore, in the region D the external load 4 is regenerated, with reduced also limits _{I LMT} in response to a decrease of the target value _{I CMD,} the limit value _{I LMT} according to an increase in the target value _{I CMD} also increases. Then, in the region E from be out regenerative state until the external load 4 also becomes a constant value I2 stable target value I _CMD, a limit value I _LMT according to an increase in the target value I _CMD increases, the target in the region value _{I CMD} is stabilized at a constant value I2 F, the limit value _{I LMT} stabilizes slightly larger value I5 than a predetermined value I2 of the target value _{I CMD.}

Control of the fuel cell output current command value (hereinafter referred to as “command value”) I _REF in a situation where the target value I _CMD and the limit value I _LMT are set in this way will be described. The command value I _REF is transmitted to the fuel cell 1, and the fuel cell 1 outputs a current having a value given by the command value I _REF .

In the region A where the target value I _CMD is zero, the command value I _REF is also set to zero. Next, in the region B after the target value I _CMD has increased instantaneously, it is desirable to raise the command value I _REF as much as possible, but when the command value I _REF exceeds the limit value I _LMT , excess hydrogen is generated, etc. The harmful effects of On the other hand, when the command value _{I REF} is increased while matching the limit value _{I LMT,} the command value _{I REF} is a concern that exceed the limit value _{I LMT.} Therefore, when the command value I _REF matches the value obtained by subtracting the specified value α from the limit value I _LMT , the command value I _REF is increased while being matched with the value obtained by subtracting the specified value α from the limit value I _LMT . The specified value α is a margin given so that the command value I _REF does not exceed the fuel cell output current value. Specifically, the specified value α can be set to about 1A, for example, 1A. . In this region B, and it increases the command value I _REF until it reaches the value I1 is eventually target value I _CMD continues to increase while matches the value obtained by subtracting the prescribed value α from the limit value I _LMT (area B1 ). In this region B1, since the command value I _REF is smaller than the target value I _LMT , the fuel cell 1 alone cannot supply the current required by the external load 4. The current shortage at this time can be covered by taking out from the battery 3.

Then, the command value _{I REF} is since after reaching a value I1 which is a target value _{I CMD,} to remain command value _{I REF} matches the value I1 which is a target value _{I CMD} (area B2). In a state where the command value I _REF coincides with the value I 1 that is the target value I _CMD , the current required by the external load 4 can be supplied only from the fuel cell 1.

Thereafter, in the region C the external load 4 rapidly decreases, with the decrease of the target value _{I CMD,} the command value _{I REF} also reduces. At this time, if the command value I _REF is decreased at the same rate as the target value I _CMD , surplus hydrogen in the fuel cell 1 due to a control delay of the hydrogen gas supplied from the hydrogen supply means 11 to the fuel cell 1 or the like. Will remain. This in order to prevent residual excess hydrogen, smaller than the decrease rate of the target value I _CMD, decreases the command value I _REF at a reduced rate determined in accordance with the target value I _CMD (region C1). Thus, by reducing the decrease rate of the command value I _REF , it is possible to significantly reduce or eliminate the surplus hydrogen remaining due to the control delay.

When the command value I _REF is decreased at this decrease rate, the limit value I _LMT has a larger decrease rate, so the command value I _REF and the limit value I _LMT eventually meet. Reducing the command value I _REF a decrease in this state, the command value I _REF may exceed the limit value I _LMT, also cause the excess hydrogen remaining in the fuel cell 1. Therefore, it is conceivable to make the command value I _REF coincide with the limit value I _LMT when the command value I _REF becomes the limit value I _LMT . However, the command value _{I REF} exceeds the command value _{I REF} and limits _{I LMT} and match the command value _{I REF} the limit value _{I LMT} when it becomes the limit value _{I LMT} is concerned. Therefore, when the command value I _REF becomes a value obtained by subtracting the specified value α from the limit value I _LMT , the command value I _REF is decreased while being matched with the value obtained by subtracting the specified value from the limit value I _LMT (region C2). . In this way, surplus hydrogen can be prevented from remaining.

Thereafter, in the region D where the external load 4 is regenerated, the limit value I _LMT is also decreased in the region D1 where the target value I _CMD is decreasing. Here, the command value _{I REF} is therefore consistent with the limit value _{I LMT,} to subsequently decrease the command value _{I REF} while being consistent with the limit value _{I LMT.} Subsequently, in the regenerative state, when the target value I _CMD increases due to acceleration or the like, the limit value I _LMT also increases accordingly (region D2). At this time, the command value I _REF is decreased again at the same decrease rate as the decrease rate of the command value I _REF in the region C1.

Then, the vehicle becomes a required load stable state again (region E), the command value I _REF even in the required load stable state does not coincide with the target value I _CMD, it is still toward the command value I _REF It is larger than the target value _ICMD . Here, the command value I _REF is decreased at the same reduction rate as the command value I _REF in the region C1 until the command value I _REF reaches the target value I _CMD . Then, when the command value I _REF meets the target value I _CMD , the command value I _REF is matched with the target value I _CMD (region F).

Note that, in the region C to the region E, the command value I _REF exceeds the target value I _CMD . Therefore, an extra current is generated with respect to the current required for the external load 4, and the battery 3 can be charged with this extra current.

Next, the power generation control procedure so far will be described based on the flowchart shown in FIG. This power generation control is performed in the control device 5. First, when power generation control is started (S1), the difference between the current target value _ICMD and the previous target value _ICMDOLD is determined according to a predetermined rule in order to determine whether or not the target value _ICMD is rapidly decreasing. It is determined whether it is smaller than the value β (S2). The specified value β at this time can be set, for example, in a range of approximately −700 A / sec to −1300 A / sec. Here, if the absolute value of the specified value β is too large, the pressure cannot be compensated and the ion exchange membrane of the fuel cell may be damaged. On the other hand, if the absolute value of the specified value β is too small, the efficiency of the entire system is lowered. Here, when it is determined that the difference between the current target value I _CMD and the previous target value I _CMD OLD is smaller than the predetermined regulation value β, the target value I _CMD is in a state of rapidly decreasing. Therefore, it progresses to step S6 mentioned later. On the other hand, when it is determined that the difference between the current target value I _CMD and the previous target value I _CMD OLD is not smaller than the predetermined regulation value β, the target value I _CMD is rapidly decreasing. Absent. In this case, it is determined whether or not the target value I _CMD is less than 0 in order to determine whether or not the engine is in a regenerative charging state such as applying a so-called engine brake or going down a steep hill. (S3).

Here, when it is determined that the target value I _CMD is less than 0, since the regenerative charging state is set, the process proceeds to step S6 described later. On the other hand, when it is determined that the target value _ICMD is not less than 0, the regenerative charge state is not established. In this case, in order to determine whether or not surplus hydrogen treatment is being performed, it is determined whether or not the command value I _REF is larger than the target value I _CMD (S4). If it is determined that the command value I _REF is larger than the target value I _CMD , the surplus hydrogen process is being performed, and the process proceeds to step S6 described later. On the other hand, when it is determined that the command value I _REF is not larger than the target value I _CMD , the demanded load is stable or is in a rising transient state, not in a decreasing transient state.

Here, it is determined whether or not the limit value I _LMT is larger than the target value I _{CMD in} order to determine which state is the required load stable state or the rising transient state (S5). When the limit value _{I LMT} is larger than the target value _{I CMD} is because the required load steady state, the target value _{I CMD} as a command value _{I REF} (S5-1). On the other hand, if it is determined that the limit value I _LMT is not larger than the target value I _CMD , it is in an up-transition state such as at the time of acceleration, so the value obtained by subtracting the specified value α from the limit value I _LMT is the command value. Set to I _REF (S5-2).

In step S2, the difference between the current target value I _CMD and the previous target value I _CMD OLD is smaller than a predetermined regulation value β. In step S3, the target value I _CMD is less than 0. In step S4, In step S6, which is proceeded when it is determined that the command value I _REF is larger than the target value I _CMD , the state is in a decreasing transition state. If the command value I _REF is sharply reduced in this decreasing transition state, surplus hydrogen remains in the fuel cell 1. Therefore, the command value I _REF must be decreased at a predetermined decrease rate. On the other hand, as the target value _ICMD decreases rapidly, the limit value _ILMT also decreases rapidly. In this case, lowering the rate of decrease of the command value _{I CMD,} Tomosureba command value _{I CMD} is that exceeds the limit value _{I LMT.} When the command value I _CMD exceeds the limit value I _LMT , excessive hydrogen is _fed into the fuel cell 1 and causes excess hydrogen. Therefore, it is determined whether or not the limit value I _LMT is equal to or less than the command value I _CMD (S6).

Then, in step S6, since the value obtained by subtracting the prescribed value α from the limit value _{I LMT} is when: the command value _{I CMD} is to make the command value _{I CMD} does not exceed the limit value _{I LMT,} the limit value I setting a value obtained by subtracting the prescribed value α from _LMT as a command value _{I CMD} (S6-1). On the other hand, the limit value _{I LMT} is when not less than the command value _{I CMD} sets the value obtained by subtracting the predetermined specified value γ from the previous command value _{I CMD} OLD as a command value _{I CMD} (S6-2). Here, the specified value γ can be set within a range of −300 A / sec to −100 A / sec, for example, −200 A / sec. If the absolute value of the specified value γ is too large, the pressure cannot be compensated and the ion exchange membrane of the fuel cell 1 may be damaged. On the other hand, if the absolute value of the specified value γ is too small, there is a problem that the efficiency of the entire system is lowered.

In this way, the steps S5-1, S5-2, S6-1, in S6-2, after the command value _{I CMD} is set, it is determined whether the operation is continued (S7). And when driving | running is continued, it returns to step S2 and the same control is repeated. On the other hand, control is complete | finished when driving | operation is not continued and it stops (S8).

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and can be applied, for example, when the fuel cell electric vehicle stops and does not regenerate.

1 Fuel cell 2 DC / DC converter 3 Battery (electric energy buffer for transient response)
4 External load (required load)
5 Control devices 6, 7, 8 Ammeter 9 Voltmeter M Fuel cell power supply system

Claims (1)

A fuel cell that generates power using hydrogen supplied from a hydrogen supply source and oxygen in the air supplied from an air pump; an electric energy buffer capable of storing the generated power of the fuel cell; and a control device, It is configured to be able to supply power from a fuel cell and the electric energy buffer to an external load ,
The control device determines a fuel cell output current target value according to a required load of the fuel cell power supply system, and determines a fuel cell output current command value according to the fuel cell output current target value;
In the fuel cell power generation control method in the fuel cell system in which a current corresponding to the fuel cell output current command value is output from the fuel cell,
The controller is
When the fuel cell output current target value decreases, a decrease rate of the fuel cell output current command value that is decreased in accordance with a decrease in the fuel cell output current target value is expressed as a decrease rate of the fuel cell output current target value. performs a surplus hydroprocessing the fuel most by power generation in the cell to handle the excess hydrogen by a small rather gradual reduction rate than,
Wherein Ri by the fact of performing the surplus hydrogen treatment, the reduction rate of the pre-Symbol fuel cell output current before is larger than the target value Symbol fuel cell output current command value, even if the fuel cell output current target value is increased the regardless of the value of the fuel cell output current target value, to reduce continuously the excess hydrogen treatment step, while the gradual reduction rate,
A power generation control method for a fuel cell , wherein power generated when the surplus hydrogen is processed is stored in the electric energy buffer .

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