JP5339195B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system including a fuel cell.

  In recent years, a fuel cell system that uses a fuel cell that generates electric power by an electrochemical reaction of reaction gases (fuel gas and oxidizing gas) as an energy source has attracted attention. The fuel cell system supplies high-pressure fuel gas from the fuel tank to the anode of the fuel cell, and also supplies air as the oxidizing gas to the cathode, and generates an electromotive force by electrochemically reacting these fuel gas and oxidizing gas. It is what

  This type of fuel cell system has matrix data for deriving the target generated power value of the fuel cell from the remaining capacity of the secondary battery divided into a plurality of sections and the system required power divided into the plurality of sections. And the upper limit value and the lower limit value of the system required power in each section and the remaining capacity of the secondary battery are set so as to overlap each other between adjacent sections. One that includes a control unit that controls the power generation amount of the fuel cell based on the target power generation value defined for each section is known (for example, see Patent Document 1).

JP 2008-84769 A

By the way, the allowable power of the fuel cell system is obtained by adding the power consumed by the drive unit such as the drive motor, the power that can be charged to the battery, the power consumed by the high-voltage auxiliary machine, the power lost by the converter, and other losses. However, in order to prevent an excessive increase in SOC (State Of Charge), which is the remaining capacity of the battery, and to suppress deterioration of the battery, it is necessary to reduce (limit) the output in the fuel cell according to the state of the SOC. is there.
However, if the system allowable power is uniformly limited by the SOC, a malfunction may occur. For example, the power that can be charged to the battery is limited in a low-temperature environment, so even if you want to quickly warm up the fuel cell, such as when starting below freezing point, If the amount is limited, the warm-up of the fuel cell is delayed and the startability is deteriorated.

  The present invention has been made to solve the above-described problems caused by the prior art, and needs to be preferentially performed without depending on the control based on the charged state of the secondary battery and the charged state of the secondary battery. An object of the present invention is to provide a fuel cell system capable of performing control without interfering with each other.

In order to solve the above-described problems, a fuel cell system according to the present invention includes a fuel cell that receives supply of a reaction gas and generates electric power through an electrochemical reaction of the reaction gas, and charging of electric power supplied from the fuel cell. Alternatively, a fuel cell system comprising: a secondary battery that supplies power to a load; and a control unit that calculates power generation command power for the fuel cell and controls power generation of the fuel cell based on the power generation command power The control unit calculates a power generation command power within a range of system allowable power that is set depending on power that can be charged to the secondary battery at least so that the secondary battery is not overcharged , is set beyond the rechargeable power to said rechargeable battery to corresponding to the continuous and rated control, predetermined request for controlling the power generation of the fuel cell based on the power command power Calculating a power generation command power that enables previously controlled to be performed, and the short-time rating control for controlling the power generation of the fuel cell based on the power command power, in which selectively perform.

  According to the fuel cell system having such a configuration, the control based on the state of charge of the secondary battery and the control that should be preferentially performed regardless of the state of charge of the secondary battery can be performed without interfering with each other. .

  For example, during normal times, by controlling the power generation of the fuel cell with the power generation command power calculated based on the SOC state of the secondary battery, the secondary battery is prevented from being overcharged and the secondary battery is deteriorated. While it can be suppressed, for example, when measuring impedance for measuring the moisture content in a fuel cell, or when starting in a low-temperature environment (for example, below freezing) where rapid warm-up of the fuel cell is required When an irregular request occurs, the power generation command power that can meet such a request is calculated, and even if this power generation command power exceeds the system allowable power, the SOC state of the secondary battery is taken into consideration. It is possible to select the execution of the control that should be preferentially performed.

  According to the present invention, the control based on the state of the secondary battery and the control that needs to be preferentially performed without depending on the state of the secondary battery can be performed without interfering with each other.

1 is a configuration diagram schematically illustrating a fuel cell system according to an embodiment of the present invention. It is a graph which shows the correlation of SOC in the continuous rated control which adds a fixed restriction | limiting to FC power by the system permissible power based on battery SOC, a system permissible power, and the voltage of a fuel cell. It is a graph which shows the interrelationship of FC power of a fuel cell, battery power, and generated power of a fuel cell when short-time rating control is performed interruptively during continuous rating control based on battery SOC. It is a block diagram explaining the control content by a control part. It is a control block diagram explaining the modification of the control content by a control part. It is a graph which shows the correlation of SOC of a battery, system allowable power, and the presence or absence of a temporary expansion request | requirement. It is a control block diagram explaining the other modification of the control content by a control part.

  Hereinafter, an embodiment of a fuel cell system according to the present invention will be described with reference to the accompanying drawings. This embodiment demonstrates the case where the fuel cell system which concerns on this invention is used as a vehicle-mounted power generation system of a fuel cell vehicle (FCHV; Fuel Cell Hybrid Vehicle).

First, the configuration of the fuel cell system according to the present embodiment will be described with reference to FIG.
As shown in FIG. 1, the fuel cell system 1 includes a fuel cell 2 that generates electric power by an electrochemical reaction between an oxidizing gas, which is a reaction gas, and the fuel gas. The power generation state of the fuel cell 2 is controlled by a control unit 11. Controlled by.

  The fuel cell 2 is, for example, a polymer electrolyte fuel cell, and has a stack structure in which a large number of single cells are stacked. The single cell has an air electrode on one surface of an electrolyte composed of an ion exchange membrane, a fuel electrode on the other surface, and a structure having a pair of separators so as to sandwich the air electrode and the fuel electrode from both sides. It has become. In this case, hydrogen gas is supplied to the hydrogen gas flow path of one separator, and air, which is an oxidizing gas, is supplied to the oxidizing gas flow path of the other separator, and electric power is generated by the chemical reaction of these reaction gases. .

An FC boost converter 3 is connected to the fuel cell 2, and a drive motor 6 and an air compressor 7 are connected to the FC boost converter 3 via inverters 4 and 5, respectively.
The FC boost converter 3 is connected to a battery 9 as a secondary battery and various auxiliary machines 10 via a battery boost converter 8.

  The battery boost converter 8 is a DC voltage converter, and adjusts the DC voltage input from the battery 9 and outputs it to the inverters 4 and 5 side, and the DC voltage input from the fuel cell 2 or the drive motor 6. And adjusting the output to the battery 9. By such a function of the battery boost converter 8, charging / discharging of the battery 9 is realized. Further, the output voltage of the fuel cell 2 is controlled by the battery boost converter 8.

  The battery 9 refers to the power consumed by the entire load including the drive motor 6 out of the generated power of the fuel cell 2 under the control of a battery computer (not shown) with battery cells stacked and a constant high voltage as a terminal voltage. It is possible to charge the surplus power drawn or to supply power to the drive motor 6 in an auxiliary manner.

  The drive motor 6 is a three-phase AC motor, for example, and constitutes a main power source of a fuel cell vehicle on which the fuel cell system 1 is mounted. The inverter 4 to which the drive motor 6 is connected converts a direct current into a three-phase alternating current and supplies it to the drive motor 6.

  The air compressor 7 is a compressor that sends air, which is an oxidant, to the fuel cell 2. The inverter 5 to which the air compressor 7 is connected is an electric motor control unit that controls driving of the air compressor 7, converts a direct current into a three-phase alternating current, and supplies it to the motor of the air compressor 7. The inverter 5 is, for example, a pulse width modulation type PWM inverter, which converts a DC voltage output from the fuel cell 2 or the battery 9 into a three-phase AC voltage in accordance with a control command from the control unit 11, and a motor for the air compressor 7. To control the rotational torque generated at.

  The control unit 11 detects an operation amount of an acceleration operation member (accelerator or the like) provided in the fuel cell vehicle, and controls information such as an acceleration request value (for example, a required power generation amount from a power consuming device such as the drive motor 6). In response, the operation of various devices in the system is controlled. In addition to the drive motor 6, the power consuming device includes, for example, auxiliary equipment required to operate the fuel cell 2 (for example, motors of the air compressor 7 and other various auxiliary machines 10), vehicle This includes actuators used in various devices (transmissions, wheel control devices, steering devices, suspension devices, etc.) involved in traveling, air conditioning devices (air conditioners) for passenger spaces, lighting, audio, and the like.

  By the way, the FC power Pfc that is the generated power of the fuel cell 2 is composed of a system required power Pr required for operation of the fuel cell system 1 and a power P2 that can charge the battery 9 so as not to be overcharged. The system required power Pr is the motor consumption power P1 in the drive motor 6 and the air compressor 7, the high-voltage auxiliary machine consumption power P3 consumed in various auxiliary machines 10, the FC boost converter 3 and the battery boost converter 8. It consists of loss power P4.

  If the battery 9 continues to be used in a region where the SOC (State Of Charge), which is the remaining capacity of the battery 9, is extremely high or low, the battery 9 may deteriorate. For this reason, it is desirable that the battery 9 be used in an intermediate region excluding an extremely high region and an extremely low region of SOC.

  Therefore, in order to prevent an excessive increase in the SOC, which is the remaining capacity of the battery 9, it is necessary to reduce (limit) the FC power Pfc of the fuel cell 2 in accordance with the SOC state (charge state). For example, when high potential avoidance control is performed in which power generation in the fuel cell 2 is continued for a long time to avoid a high potential state, it is necessary to monitor the SOC of the battery 9 to suppress the increase in SOC.

  That is, in the fuel cell system 1 of the present embodiment, the system allowable power Ps is obtained based on the SOC of the battery 9, and the FC power Pfc is necessary as necessary so that the FC power Pfc is within the range of the system allowable power Ps. A continuous rating control for controlling the power generation of the fuel cell 2 is performed by adding a certain limitation to the above.

FIG. 2 is a graph showing a correlation between the SOC of the battery 9, the system allowable power Ps, and the voltage of the fuel cell 2 in the continuous rating control.
When the power generation state of the fuel cell 2 continues for a long time as in the high potential avoidance control shown in FIG. 2, a part of the difference between the FC power Pfc and the system allowable power Ps is charged to the battery 9. The SOC of 9 gradually increases.

  For this reason, the SOC of the battery 9 is monitored, and when the SOC reaches a predetermined value, the system allowable power Ps is decreased, and the increase in the SOC of the battery 9 is suppressed. Even after the high potential avoidance control is stopped, the system allowable power Ps is gradually decreased until the SOC of the battery 9 does not decrease until it reaches a constant value. Note that the FC voltage V that is the output voltage of the fuel cell 2 approaches the open circuit voltage OCV after the high potential avoidance control is stopped.

  In the fuel cell system 1, impedance measurement may be performed to measure the water content in the fuel cell 2. In this case, it is necessary to temporarily increase the FC power Pfc of the fuel cell 2. In the short-time rated control of the system allowable power Ps performed at the time of impedance measurement, the integrated value of the power exceeding the control start power in the charging direction with respect to the control start power of the battery 9 stored at the start of the control. This is performed until a preset power amount threshold is reached.

  On the other hand, in a low temperature environment such as below freezing point, the power P2 that can be charged by the battery 9 is also limited. In such a case, the system allowable power Ps is limited by continuous rating control based on the SOC of the battery 9. If a certain restriction is applied to the FC power Pfc, the temperature rise control of the fuel cell 2 is restricted and the fuel cell system 1 does not start for a long time, and the market adaptability deteriorates.

  Therefore, in such a case, short-time rating control is performed to temporarily increase the system allowable power Ps within a range in which the influence on the life of the battery 9 can be allowed. At this time, if necessary, the power P2 that can be charged by the battery 9 is also temporarily expanded.

  As described above, in the fuel cell system 1 of the present embodiment, for example, when there is a request that should be prioritized over the continuous rating control based on the SOC of the battery 9, such as during impedance measurement or cold start, In order to increase the FC power Pfc of the fuel cell 2, the short-time rating control is performed to increase the system allowable power Ps.

FIG. 3 shows the FC power Pfc, the battery power Pb, and the generated power of the fuel cell 2 when the short-time rated control is interrupted during the continuous rated control of the system allowable power Ps based on the SOC. It is a graph which shows a mutual relationship.
As shown in FIG. 3, when short-time rating control is performed by interruption from the state of continuous rating control (at time t1 in FIG. 3), the FC power Pfc of the fuel cell 2 increases and the battery power Pb decreases. .

  In the case of short-time rated control at the time of impedance measurement, the power excess amount integrated value that exceeds the control start power in the charge direction is the control start power of the battery 9 stored at the start of the control. When the preset electric energy threshold is reached (t2 in FIG. 3), and in the case of the short-time rated control at the time of low temperature start, the fuel cell 2 is heated to a predetermined temperature and the warm-up operation is finished. When this is done (t2 in FIG. 3), the short-time rating control ends. Then, the FC (power generation) power Pfc of the fuel cell 2 decreases to the power at the time of continuous rating control, and the battery power Pb increases to the power at the time of continuous rating control.

Next, an example of control contents by the control unit 11 in consideration of the continuous rating control and the short-time rating control will be described in detail.
FIG. 4 is a block diagram for explaining the control contents by the control unit, and FIG. 5 is a block diagram showing an embodiment of the control contents by the control unit.

The control unit 11 adds the motor consumption power P1 in the drive motor 6 and the air compressor 7, the high-voltage auxiliary machine consumption power P3 consumed in various auxiliary machines 10, and the loss power P4 in the FC boost converter 3 and the battery boost converter 8. Then, the system required power Pr is obtained (see symbol a in FIG. 4).
Then, the control unit 11 calculates a system allowable power obtained by adding the system required power Pr and the power P2 that can be charged by the battery 9, and uses the short-time rated system allowable power Ps2 used in the short-time rated control described above. To do.

  Further, the control unit 11 has a map M in which the relationship between the SOC of the battery 9 and the limiting rate is associated, obtains the limiting rate from the SOC of the battery 9 based on the map M, and obtains the limiting rate from the system. The system allowable power (see symbol b in FIG. 4) multiplied by the allowable power (added value of the system required power Pr and the power P2 that can be charged by the battery 9) is calculated, and this is continuously determined depending on the SOC of the battery 9. It is assumed that the system allowable power Ps1 at the time of continuous rating for performing rating control.

  As described above, according to the fuel cell system 1 according to the embodiment, it is possible to switch between the control based on the state of the battery 9 and the control that needs to be performed preferentially without depending on the state of the battery 9. Therefore, both controls can be performed without interfering with each other.

Thereby, deterioration of the battery 9 can be suppressed by performing the continuous rating control for controlling the fuel cell 2 with the FC command power Pfco calculated based on the SOC state of the battery 9.
In addition, when impedance measurement for moisture content measurement or warm-up operation in a low temperature environment is necessary, short-time rating control using FC command power Pfco that enables such control is performed. Can be preferentially performed.

Next, a modification of the above embodiment will be described.
The control shown in FIG. 5 switches between and selects either the continuous rated system allowable power Ps1 or the short-time rated system allowable power Ps2.

  In this control, when the SOC of the battery 9 rises and the system allowable power Ps needs to be limited, the system allowable power Ps1 at the time of continuous rating is selected (see symbol c in FIG. 5), and the FC calculated from the system required power Pr The required power Pfcr is limited by the system allowable power Ps1 (see symbol d in FIG. 5), and the limited FC required power Pfcr is compared with the system required power Pr (see symbol e in FIG. 5), whichever is greater Is the FC command power Pfco to the fuel cell 2.

  On the other hand, when a temporary enlargement request (for example, when control such as impedance measurement or operation in a low temperature environment is required) occurs, the control unit 11 calculates the short time calculated based on the system required power Pr. The system allowable power Ps2 at the time of rated control is selected (see symbol c in FIG. 5), and the FC required power Pfcr increased with the implementation of the short-time rated control is limited by the system allowable power Ps2 (see symbol d in FIG. 5). Further, the limited FC required power Pfcr and the system required power Pr are compared (see symbol e in FIG. 5), and the larger one is set as the FC command power Pfco to the fuel cell 2.

FIG. 6 is a graph showing the interrelationship between the SOC of the battery, the system allowable power, and whether or not there is a temporary expansion request, and corresponds to the control shown in FIG.
As shown in FIG. 6, when the continuous rating control is started to suppress the increase in the SOC of the battery 9, the system allowable power Ps is set to the system allowable power Ps1 at the time of continuous rating in the continuous rating control and gradually decreases ( (See the solid line of system allowable power in FIG. 6).

  Also, during this continuous rating control, a request for temporarily expanding the system allowable power Ps is generated, and when the short-time rating control is executed in an interrupted manner in response to such a request, the system allowable power Ps is set to the system allowable power at the short-time rating. Ps2 (see the broken line of the system allowable power in FIG. 6).

  That is, when a temporary enlargement request is generated and the flag is turned ON, the system allowable power Ps is changed from the continuous rated system allowable power Ps1 to the short-time rated system allowable power Ps2. When the temporary enlargement request disappears from this state and the flag is turned OFF, the system allowable power Ps is changed from the short-time rated system allowable power Ps2 to the continuous rated system allowable power Ps1 (return).

  In the embodiment described above, the map M in which the relationship between the SOC of the battery 9 and the limiting rate is associated is used for calculating the system allowable power Ps1 at the time of continuous rating, and the limiting rate is calculated from the map M and the limiting rate is calculated. Although multiplied by the system required power Pr, as shown in FIG. 7, a map M2 in which the relationship between the SOC of the battery 9 and the system allowable power is associated is held, and this map M2 may be used. .

  In this case, the control unit 11 directly calculates the system allowable power from the map M2 based on the SOC of the battery 9 at the time of continuous rating, and limits the system required power Pr by this system allowable power (see symbol f in FIG. 7). Then, the system allowable power Ps1 at the time of continuous rating is calculated.

  In the above-described embodiment, the case where the fuel cell system according to the present invention is mounted on a fuel cell vehicle is described. However, the present invention is also applied to various mobile bodies (robots, ships, aircrafts, etc.) other than the fuel cell vehicle. The fuel cell system according to the invention can be applied. Moreover, the fuel cell system according to the present invention can also be applied to a stationary power generation system used as a power generation facility for buildings (houses, buildings, etc.).

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 2 ... Fuel cell, 9 ... Battery (secondary battery), 11 ... Control part, Pfco ... FC command power (command power), Ps ... System permissible power, Ps1 ... System permissible power at continuous rating ( System allowable power), Ps2: System allowable power at short-time rating (system allowable power).

Claims (1)

A fuel cell that receives supply of a reactive gas and generates electric power by an electrochemical reaction of the reactive gas, a secondary battery that charges electric power supplied from the fuel cell or supplies electric power to a load, and the fuel cell A fuel cell system comprising: a control unit that calculates power generation command power with respect to and controls power generation of the fuel cell based on the power generation command power;
The control unit calculates a power generation command power within a system allowable power range that is set depending on power that can be charged to the secondary battery at least so that the secondary battery is not overcharged. And continuous power control for controlling the power generation of the fuel cell based on the above, and power generation that enables control to be performed preferentially set beyond the power that can be charged to the secondary battery in order to meet a predetermined requirement A fuel cell system that selectively performs short-time rating control that calculates command power and controls power generation of the fuel cell based on the power generation command power.

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