JP4852481B2 - Fuel cell system and generator system - Google Patents

Description

  The present invention relates to a fuel cell system.

  In a fuel cell hybrid vehicle, supply of FC power by power generation of a fuel cell (FC) is assisted by supply of battery power by discharge of a power storage device (battery) to drive a vehicle drive motor.

The distribution of FC power and battery power is determined so that energy efficiency is maximized (see, for example, Patent Document 1).
FIG. 2 is an explanatory diagram of various losses associated with the supply of FC power and battery power. As shown in FIG. 2A, FC loss occurs when the fuel cell generates power, and as shown in FIG. 2B, discharge loss occurs when the battery discharges. When FC loss is smaller than discharge loss, only FC power is supplied (fuel cell follow-up mode). When discharge loss is smaller than FC loss, FC power is assisted by battery power supply. Yes (assist mode).
JP 2005-94917 A

When battery power is supplied, it is necessary to charge the battery in the future, but charging loss occurs when the battery is charged. Further, when the power for charging the battery is supplied by the power generation of the fuel cell, FC loss occurs during the power generation. Therefore, when battery power is supplied, future loss may increase.
On the other hand, if the power for charging the battery can be covered by regenerative power generation of the motor, the above-described new charge loss and FC loss do not occur. As a result, future losses may not increase. Thus, the conventional technique has a problem that energy efficiency is not always maximized.

  Therefore, an object of the present invention is to provide a fuel cell system capable of improving energy efficiency.

In order to solve the above-mentioned problem, the invention according to claim 1 is directed to a fuel cell (for example, the fuel cell 10 in the embodiment) that generates power by supplying a reaction gas by an air pump, and the fuel cell or the power storage device (for example, A motor (for example, the motor 30 in the embodiment) that is driven by power supply from the battery 20 in the embodiment, and the power storage device is a fuel that is charged by the power of the fuel cell and the regenerative power from the motor A battery system (for example, the fuel cell system 101 in the embodiment), which is a fuel cell system required power calculation unit (for example, a motor required power calculation unit 44 in the embodiment) that calculates the required power for operating the fuel cell system. ) And how much charging can be expected with regenerative power when charging the power storage device The expected regeneration value calculation means for calculating the expected regeneration value (for example, the expected regeneration value calculation unit 50 in the embodiment), and the fuel cell system required power is less than a predetermined power value (for example, the upper limit limit FU in the embodiment). when, select the fuel cell tracking mode to follow the power supply from the fuel cell to the fuel cell system required output, when the fuel cell system power requirements of the above predetermined power value, said fuel from said fuel cell An operation mode switching unit (for example, the operation mode switching unit 40 in the embodiment) that selects an assist mode that assists power supply to the battery system with the discharge power of the power storage device, and calculates an integrated value of the fuel cell system required power Fuel cell system required power integration means (for example, motor required power integration unit 54 in the embodiment) The regenerative power integration means for calculating an integrated value of regenerative power (e.g., the regenerative power integration section 52 in the embodiment) equipped with a, the regenerative expectation value calculation unit, the regeneration of the fuel cell system required power integration value A ratio occupied by the integrated power value is set as the expected regeneration value, and the operation mode switching unit sets the predetermined power value lower as the expected regeneration value increases.

The invention according to claim 2 includes fuel cell power generation efficiency calculation means for calculating the power generation efficiency of the fuel cell, and the operation mode switching unit increases the predetermined power value as the power generation efficiency of the fuel cell increases. It is characterized by setting.

The invention according to claim 3 is characterized in that the regenerative expected value calculation means suppresses a rapid change in the ratio of the fuel cell system required power integrated value and the regenerative power integrated value by a smoothing filter.

The invention according to claim 4 is characterized in that the fuel cell power generation efficiency calculating means suppresses a rapid change in the fuel cell power generation efficiency by a smoothing filter.

The invention according to claim 5, wherein the fuel cell system required power power distribution means for distributing to the assistance request power to the required power and the power storage device to the fuel cell (e.g., power distribution in the embodiment in the assist mode 15), and the power distribution means subtracts a difference between the assist request power and the assist power upper limit from the assist request power when the assist request power is greater than an assist power upper limit. It adds to electric power, It is characterized by the above-mentioned.

The invention according to claim 6 is characterized in that the power distribution means increases the required fuel cell power as the required assist power approaches the upper assist power limit.

The invention according to claim 7 is a converter that boosts the assist power supplied from the power storage device to the motor (for example, the DC / DC converter 62 in the embodiment), and stops the operation of the converter in a mode other than the assist mode. Then, converter stop means (for example, DC / DC converter stop means 60 in the embodiment) for stopping the supply of the assist power to the motor is provided.

The invention according to claim 8 includes a converter that boosts the assist power from the power storage device to the motor, and assist power detection means that detects the assist power (for example, the current voltmeter 64 in the embodiment), Converter stopping means for stopping operation of the converter and stopping supply of the assist power to the motor when the assist power is equal to or less than a predetermined value.
The invention according to claim 9 includes a generator and a motor driven by power supply from the generator or the power storage device, and the power storage device is charged by the power of the generator and the regenerative power from the motor. A generator system required power calculation means for calculating required power for operating the generator system, and how much charging is expected by regenerative power when charging the power storage device An expected regeneration value calculating means for calculating an expected regeneration value indicating whether or not the generator system required power is less than a predetermined power value, and the power supply from the generator follows the generator system required output When the generator follow-up mode is selected and the generator system required power is equal to or greater than the predetermined power value, the power supply from the generator to the generator system is transmitted to the power storage device. An operation mode switching unit that selects an assist mode that assists with the discharge power of the generator, a generator system required power integration unit that calculates an integrated value of the generator system required power, and a regenerative power integration that calculates an integrated value of the regenerative power And the regenerative expected value calculation means uses the regenerative power integrated value as a proportion of the generator system required power integrated value as the regenerative expected value, and the operation mode switching unit includes the regenerative expected value. The predetermined power value is set to be lower as the value increases.

According to the first aspect of the invention, by changing the mode switching threshold according to the expected regeneration value, it is possible to take into account the loss that will occur when charging the battery in the future, and to switch the operation mode at an efficient timing. be able to. In particular, when the regenerative expected value is large, the loss that occurs when the battery is charged in the future becomes small. Therefore, the system can be efficiently operated by setting the predetermined power value low to widen the assist mode range.
In addition, since the ratio of the regenerative power integrated value to the fuel cell system required power integrated value indicates the actual regeneration value up to the present, it is possible to determine the expected future regeneration value with extremely high accuracy. As a result, the operation mode can be accurately switched at an efficient timing.

According to the second aspect of the present invention, when the fuel cell power generation efficiency is high, the system can be operated efficiently by setting the predetermined power value high to widen the range of the fuel cell follow-up mode.

According to the invention which concerns on Claim 3 , it becomes possible to suppress the rapid change of a predetermined electric power value, and to suppress the rapid change of an air pump rotation speed. Thereby, it becomes possible to suppress generation | occurrence | production of the sound accompanying the increase in rotation speed, and can improve merchantability.

According to the invention which concerns on Claim 4 , it becomes possible to suppress the rapid change of the predetermined electric power value, and to suppress the rapid change of the air pump rotation speed. Thereby, it becomes possible to suppress generation | occurrence | production of the sound accompanying the increase in rotation speed, and can improve merchantability.

According to the invention which concerns on Claim 5 , the upper limit of assist electric power can be observed. In addition, by covering the portion exceeding the upper limit with the electric power from the fuel cell, it is possible to prevent the drivability from being lowered.

According to the invention which concerns on Claim 6 , it becomes possible to change the operating sound of the air pump at the time of assist mode according to a fuel cell system, and can reduce a driver | operator's discomfort and can improve merchantability.

According to the invention which concerns on Claim 7 , it becomes possible to prevent the loss in a converter and can improve the energy efficiency at times other than assist mode.

According to the eighth aspect of the present invention, it is possible to prevent the loss in the converter by stopping the converter when the assist power is small, and the power efficiency can be improved.

Hereinafter, embodiments and reference embodiments of the present invention will be described with reference to the drawings.
(First reference form)
FIG. 1 is a block diagram of a fuel cell system according to the first reference embodiment. The fuel cell system 101 according to the first reference embodiment distributes FC power generated by the power generation of the fuel cell 10 and battery power generated by discharge of the battery 20 by the power distributor 15 and supplies it to the motor 30.

  A fuel cell (FC stack) 10 has a membrane electrode structure formed by sandwiching a solid polymer electrolyte membrane from both sides with an anode electrode and a cathode electrode, and a pair of separators are arranged on both sides of the membrane electrode structure to form a flat plate shape. The unit fuel cell (hereinafter referred to as “unit cell”) is constructed, and a plurality of the unit cells are stacked. In this fuel cell, hydrogen gas is supplied as a fuel gas between the anode electrode and the separator, and air is supplied as an oxidant gas between the cathode electrode and the separator. As a result, the hydrogen ions generated by the catalytic reaction at the anode electrode pass through the solid polymer electrolyte membrane and move to the cathode electrode, causing an electrochemical reaction with oxygen in the air at the cathode electrode to generate power. It has become.

A hydrogen tank 12 for supplying hydrogen gas is connected to the fuel cell 10. In addition, an air pump (A / P) 14 for supplying air is connected. In addition to the air pump, various auxiliary machines for driving the fuel cell 10 are connected.
The motor 30 rotates the wheels of a vehicle equipped with a fuel cell system. A motor PDU (Power Drive Unit) 32 that controls the motor 30 is provided.

The fuel cell 10 and the battery 20 are connected to the motor 30 via the power distributor 15. The power distributor 15 supplies FC power generated by the fuel cell 10 and battery power generated by the discharge of the battery 20 to the motor 30 at a predetermined distribution ratio.
The battery (power storage device) 20 is charged with FC power generated by the fuel cell 10 and regenerative power generated by the motor 30. The battery 20 is provided with an SOC sensor (storage amount detection means) 22 that detects the storage amount.

  On the other hand, a motor required power calculation unit 44 that calculates the amount of power required by the motor 30 from the operation of the motor PDU 32 and the opening of the accelerator pedal 42 is provided. The motor required power calculation unit 44 outputs the calculated motor request output to the operation mode switching unit 40.

  The operation mode switching unit 40 switches between a fuel cell follow-up mode in which the power supply from the fuel cell follows the required motor output and an assist mode in which the power supply from the fuel cell to the motor is assisted by the battery discharge power. It is. Further, the operation mode switching unit 40 includes a regenerative expectation value calculating unit that calculates a regenerative expectation value that represents how much rechargeable power can be expected when the battery 20 is charged. The expected regeneration value calculation means sets the expected regeneration value larger as the battery SOC increases.

(FC efficiency, battery efficiency)
Next, FC efficiency and battery efficiency in the case where electric power P is extracted from the fuel cell 10 or the battery 20 and supplied to the motor 30 will be described.
FIG. 2A is an explanatory diagram of FC efficiency. When the electric power P indicated by a1 is generated by the fuel cell, an FC loss indicated by a2 occurs. FC loss includes purge loss of fuel gas discharged without being consumed for power generation in the fuel cell, FC loss that is generated by the fuel cell but not taken out, and power consumption of auxiliary equipment such as air pumps AP loss etc. which are are included.
As described above, the FC efficiency (the amount of power generated by the fuel cell that can be extracted from unit energy) is represented by a1 / a2.

FIG. 2B is an explanatory diagram of battery efficiency. When the electric power P shown in b1 is discharged from the battery, a discharge loss shown in b2 occurs. The discharge loss is a power loss generated in a battery, a converter (Voltage Control Unit; VCU), or the like during discharge.
The electric power discharged from the battery needs to be charged in the future. What is necessary to charge the battery at b3 is the same amount of power as that of b2, and is the amount of power obtained by adding a discharge loss to the power P discharged from the battery.

  As shown in b <b> 3, for charging the battery 20, in addition to the FC power C <b> 1 generated by the fuel cell 10, regenerative power C <b> 2 generated by regenerative power generation of the motor 30 can be used. Of these, the regenerative power C2 is for recovering the kinetic energy of the vehicle, so that no power loss is conceived. On the other hand, when charging with the FC power C1, a charging loss shown in b4 occurs. This charging loss is a power loss generated in a battery, a converter, or the like during discharging.

Furthermore, in order to obtain FC power C1, it is necessary to generate power with a fuel cell. What needs to be generated by the fuel cell in b5 is the same amount of power as in b4, which is the amount of power obtained by adding a charging loss to FC power C1. The power generation of the fuel cell is accompanied by the purge loss, FC loss, and AP loss described above.
As described above, the battery efficiency (the amount of discharge of the battery that can be extracted from the unit energy) is represented by b1 / b5.

(Operation mode)
Then, the FC efficiency and the battery efficiency are compared, and in principle, the electric power P is taken out from the higher efficiency. However, the magnitude relationship between the FC efficiency and the battery efficiency varies depending on various factors.
FIG. 3A is a graph showing the relationship between motor required power and FC power generation amount, and FIG. 3B is a graph showing the relationship between motor required power and battery discharge amount.

As shown in FIG. 3A, a lower limit FL and an upper limit FU are provided for the FC power generation amount. In general, the FC efficiency increases as the output of the fuel cell decreases. However, when the output of the fuel cell becomes extremely small, the loss (AP loss) due to the power consumption of an auxiliary device such as an air pump becomes relatively large, and the FC efficiency is lowered. Therefore, a lower limit FL of the FC power generation amount is set near the peak of the FC efficiency. Even when the motor required power is extremely small, the FC power generation amount is held at the lower limit FL. The FC power generated exceeding the motor required power is used for charging the battery.
On the contrary, when the output of the fuel cell increases, the FC efficiency decreases and becomes lower than the battery efficiency. Therefore, the place where the FC efficiency is lower than the battery efficiency is set as the upper limit FU of the FC power generation amount.

When the motor required power is equal to or higher than the lower limit FL of the FC power generation amount and less than the upper limit FU, the FC efficiency exceeds the battery efficiency, so that the FC power is made to follow the motor required power. That is, between AB in FIG. 3A, the power supply from the fuel cell is made to follow the motor required output (fuel cell follow-up mode). On the other hand, the battery discharge amount is set to 0 below B in FIG. In the fuel cell follow-up mode, it is not limited to the case in which the FC power generation amount is completely followed by the motor required power M in FIG. 3A. Assist by a battery discharge (two-point difference line G for correction of error, SOC, etc.) ) Or charging the battery (two-point difference line H).
When the motor required power is equal to or greater than the upper limit FU of the FC power generation amount, the battery efficiency exceeds the FC efficiency, and thus assist power is taken out from the battery. That is, between the BCs in FIG. 3B, the power supply from the fuel cell to the motor is assisted by the discharge power of the battery (assist mode).

  When the motor required power is less than the upper limit FU, the operation mode switching unit 40 shown in FIG. 1 selects the fuel cell follow mode that causes the power supply from the fuel cell 10 to follow the motor required output, and the motor required power is When the upper limit FU is exceeded, an assist mode is selected in which power supply from the fuel cell 10 to the motor 30 is assisted by the discharge power of the battery 20. The selected mode is output to the power distributor 15 as a power distribution command.

  By the way, as shown in FIG. 3B, an upper limit BU is also provided for the battery discharge amount. This is because if the battery discharge amount becomes extremely large, there is a risk of deviating from an appropriate range of the remaining battery capacity (State Of Charge; SOC). At C or higher in FIG. 3B when the battery discharge amount has reached the upper limit limit BU, the battery discharge amount is held at the upper limit limit BU. On the other hand, at C or higher in FIG. 3A, the FC power generation amount is increased in proportion to the motor required power. The motor required power M is realized by the FC power generation amount and the battery discharge amount. That is, the power distributor 15 shown in FIG. 1 distributes the motor required power to the required power to the fuel cell and the assist required power in the assist mode, and when the assist required power is larger than the upper limit BU (assist power upper limit). The difference between the requested assist power and the assist power upper limit is subtracted from the requested assist power and added to the requested fuel cell power. Thereby, the upper limit of assist power can be observed. In addition, by covering the portion exceeding the upper limit with the electric power from the fuel cell, it is possible to prevent the drivability from being lowered.

  Incidentally, the FC power generation amount may be set to 0 because the FC efficiency is lower than the battery efficiency between the BCs in FIG. In this case, the operation of auxiliary equipment such as an air pump is stopped. However, when the operation of the auxiliary machine is resumed at the point C even though the motor required output is increasing linearly, the sound and vibration of the auxiliary machine suddenly increase, giving the driver a sense of incongruity. Become. Therefore, it is desirable to increase the amount of FC power generation between the BCs in proportion to the required motor power. That is, the power distributor 15 shown in FIG. 1 increases the fuel cell required power as the assist required power approaches the upper limit BU. As a result, the operating sound of the air pump during the assist mode can be changed according to the required motor power, and the driver's uncomfortable feeling can be reduced to improve the merchantability. However, it is desirable that the slope of the FC power generation amount between the BCs is smaller than the slope of the battery discharge amount shown in FIG. Thereby, battery power with high efficiency can be used preferentially between BCs.

(How to determine the upper limit)
Next, a method for determining the upper limit of the FC power generation amount described above will be described.
FIG. 4 is an explanatory diagram of the relationship between the remaining battery capacity (SOC) and FC efficiency and the upper limit. In the first reference embodiment, the upper limit of the FC power generation amount is determined based on the SOC and the FC efficiency. As shown in the graph of FIG. 4A, the upper limit is set higher as the FC efficiency is higher, and the upper limit is set lower as the FC efficiency is lower. It is considered that the higher the FC efficiency, the wider the range where the FC efficiency exceeds the battery efficiency. Therefore, the upper limit is set higher to widen the range of the fuel cell follow-up mode. Thereby, the system can be operated efficiently.

  Also, the upper limit is set lower as the SOC is higher, and the upper limit is set higher as the SOC is lower. When the SOC is high, it is considered that the amount of charge by regenerative power generation of the motor is increased. In this case, the expected amount of regenerative power C2 indicated by b3 in FIG. 2B increases, and the proportion of FC power C1 decreases. Along with this, the charging loss shown in b4, the FC loss shown in b5, and the like are reduced, and the battery efficiency (b1 / b5) is improved. As a result, it is considered that the range in which the battery efficiency exceeds the FC efficiency is widened. Therefore, the range of the assist mode is expanded by setting the upper limit lower as the SOC is higher (that is, as the regeneration expected value is larger). Thus, since the magnitude of the SOC reflects whether or not the operating state can be expected to be regenerated, it is possible to accurately obtain the expected future regeneration value.

When the SOC is extremely high, the upper limit is made extremely low to positively discharge the battery. When the SOC is extremely low, the upper limit is made extremely high and FC power generation is actively performed. When the FC power generation amount exceeds the motor required power, the battery is charged with the FC power.
On the other hand, for the lower limit, similarly, the lower limit is set lower as the SOC is higher, and the lower limit is set higher as the SOC is lower. This is because when the SOC is low, it is necessary to charge the battery by increasing the FC power generation amount.

(FC power generation calculator)
FIG. 5 is a schematic configuration diagram of the FC power generation amount calculator. The operation mode switching unit 40 shown in FIG. 1 includes an FC power generation amount calculator 65 shown in FIG. The FC power generation amount calculator 65 includes a zero limiter 68, an upper / lower limit control unit 70, and an upper limit release control unit 80.
The zero limiter 68 outputs 0 when the motor required power is 0 or minus, and outputs the motor required power as it is when it is plus.

  The upper / lower limit control unit 70 includes an upper limit map (see FIG. 4) 72, a lower limit map 74, and an upper / lower limiter 76. The maps 72 and 74 calculate upper and lower limit values using the input FC efficiency and SOC, and output them to the upper and lower limiter 76. The upper / lower limiter 76 outputs the upper / lower limit value when the input motor required power is outside the upper / lower limit limit, and outputs the motor required power value as it is when it is inside the upper / lower limit limit.

  The upper limit release control unit 80 includes a zero limiter 82 and an FC power generation increase map. The upper limit release control unit 80 first subtracts the output value of the upper and lower limiter 76 from the output value of the zero limiter 68 to obtain the difference between the two. The zero limiter 82 outputs 0 when the difference becomes 0 or minus, and outputs the difference as it is when it becomes plus. The FC power generation increase map 84 obtains an increase in FC power generation using the input difference. This increase corresponds to S in FIG. Then, by adding the obtained increase to the output value of the upper / lower limiter 76, the FC power generation amount can be obtained.

(Control method of fuel cell system)
Based on the above, a control method of the fuel cell system shown in FIG. 1 will be described.
FIG. 6 is a flowchart of a control method of the fuel cell system. In S10, the SOC of the battery 20 is calculated, and in S12, the FC efficiency is calculated. The calculation of the FC efficiency is performed using information such as the power consumption of the auxiliary machine 14 in addition to the power generation amount and fuel gas consumption in the fuel cell 10. In S14, the motor required power calculation unit 44 calculates the motor required power. Calculation of the required motor power is performed using information such as the opening degree of the accelerator pedal 42 and the operating state of the motor 30.

Next, the upper limit of the FC power generation amount is calculated in S16, and the lower limit is calculated in S18. Here, the upper and lower limit is calculated by performing a map search shown in FIG. 4 using the calculated FC efficiency and SOC. Thereby, the range (between AB in FIG. 3A) in which the fuel cell system is operated in the fuel cell follow-up mode is determined.
Next, in S28, the distribution of FC power and battery power (assist ratio by battery power) is determined within a range where the fuel cell system is operated in the assist mode. Here, the ratio of the slope of the FC power generation amount between BCs in FIG. 3A and the slope of the battery discharge amount in FIG.
The above processing is continued until the ignition switch is turned off (S29).

As described above in detail, the fuel cell system according to the first reference embodiment shown in FIG. 1 calculates the regenerative expectation value representing how much charge by the regenerative electric power when charging the battery 20 can be expected When the expected regeneration value calculation unit and the motor required power are less than the upper limit, the fuel cell follow mode is selected to follow the power supply from the fuel cell 10 to the motor required output, and the motor required power is greater than or equal to the upper limit An operation mode switching unit 40 that selects an assist mode for assisting power supply from the fuel cell 10 to the motor 30 by the discharge power of the battery. The operation mode switching unit 40 increases the upper limit limit as the expected regeneration value increases. Is set to be low.

  In this way, by changing the mode switching threshold according to the expected regeneration value, it is possible to take into account the loss that will occur during battery charging in the future, and to switch the operation mode at an efficient timing. In particular, when the expected regeneration value is large, the loss that occurs when the battery is charged in the future becomes small. Therefore, the system can be operated efficiently by setting the upper limit low to widen the assist mode range.

(Second Embodiment)
Next, a fuel cell system according to a second embodiment will be described. In the first reference embodiment, the expected regeneration value is obtained based on the SOC and the upper limit is set. In the second embodiment, the expected regeneration value is obtained based on the ratio of the accumulated regeneration power value to the motor required power integration value. It is different in setting. Note that detailed description of portions having the same configuration as the first reference embodiment is omitted.

  FIG. 7 is a block diagram of a fuel cell system according to the second embodiment. The expected regeneration value calculation unit 50 in the second embodiment includes a motor request power integration unit 54 that calculates an integrated value of motor request power based on the motor request power information from the motor request power calculation unit 44, and a motor PDU 32. A regenerative power integration unit 52 that calculates an integrated value of regenerative power based on the regenerative power information is provided. The regenerative expected value calculation unit 50 calculates a ratio (hereinafter referred to as “regeneration recovery rate”) between the regenerative power integrated value and the motor required power integrated value as the regenerative expected value.

  In the second embodiment, the upper limit of the FC power generation amount is determined based on the regeneration recovery rate and the FC efficiency. Specifically, the upper limit is set lower as the regeneration recovery rate is higher, and the upper limit is set higher as the regeneration recovery rate is lower. It is considered that the amount of charge by regenerative power generation of the motor increases as the ratio of the regenerative power integration value to the motor required power integration value increases. In this case, the expected amount of regenerative power C2 indicated by b3 in FIG. 2B increases, and the proportion of FC power C1 decreases. Along with this, the charging loss shown in b4, the FC loss shown in b5, and the like are reduced, and the battery efficiency (b1 / b5) is improved. Therefore, the range of the assist mode is expanded by setting the upper limit lower as the regeneration recovery rate is higher (that is, as the regeneration expected value is larger).

  If the upper limit changes rapidly, the rotation speed of the air pump changes abruptly, giving the driver a feeling of strangeness. Therefore, the expected regeneration value calculation unit 50 shown in FIG. 7 suppresses sudden changes in the regeneration recovery rate and FC efficiency by means of a smoothing filter. As the smoothing filter, it is possible to use a moving average, a first-order delay, or the like. Thereby, it is possible to suppress a rapid change in the air pump speed by suppressing a rapid change in the upper limit. Thereby, a driver | operator's uncomfortable feeling can be reduced and merchantability can be improved.

FIG. 8 is a flowchart of the control method of the fuel cell system according to the second embodiment. The SOC is calculated in S10, the FC efficiency is calculated in S12, and the motor required power is calculated in S14. In S15a, the regenerative power integrated value is calculated, in S15b, the motor required power integrated value is calculated, and in S15c, the regenerative recovery rate is calculated.
Next, the upper limit of the FC power generation amount is calculated in S16, and the lower limit is calculated in S18. Here, the upper and lower limit is calculated using the calculated regenerative recovery rate and FC efficiency. Next, in S28, the distribution of the FC power and the battery power is determined within a range where the fuel cell system is operated in the assist mode.

As described in detail above, the fuel cell system according to the second embodiment shown in FIG. 7 includes the motor required power integration unit 54 that calculates the integrated value of the motor required power, and the regenerative power that calculates the integrated value of the regenerative power. The regenerative expected value calculation unit 50 is configured such that the regenerated expected value is the ratio of the regenerative power integrated value to the motor required power integrated value (regeneration recovery rate).
The battery SOC varies depending on various factors other than the regenerative power, but since the regenerative recovery rate indicates the actual regeneration value up to now, the expected future regeneration value can be obtained with extremely high accuracy. As a result, the operation mode can be accurately switched at an efficient timing.

(Third embodiment)
Next, a fuel cell system according to a third embodiment will be described. In the third embodiment, in the case other than the assist mode, the supply of assist power to the motor is stopped by stopping the operation of the converter. Note that detailed description of portions having the same configuration as the first reference embodiment is omitted.

  FIG. 9 is a block diagram of a fuel cell system according to the third embodiment. In the third embodiment, a DC / DC converter 62 is provided between the battery 20 and the motor 30. The DC / DC converter 62 boosts the voltage supplied from the battery 20 to the motor 30. Further, in a mode other than the assist mode, a DC / DC converter stop means 60 for stopping the operation of the DC / DC converter 62 and stopping the supply of assist power to the motor 30 is provided. Note that it is desirable to configure the DC / DC converter stop means 60 so that the operation of the DC / DC converter 62 can be stopped even when the assist power is below a predetermined value. In this case, a current voltmeter (assist power detection means) 64 for detecting the assist power is provided.

FIG. 10 is a flowchart of the control method of the fuel cell system according to the third embodiment.
S10 to S18 are the same as in the first reference embodiment. In S20, it is determined whether the fuel cell following mode is set. If the determination in S20 is No (in the assist mode), distribution of FC power and battery power is determined in S28. If the determination in S20 is Yes (in the fuel cell follow-up mode), it is determined in S22 whether the charge / discharge power of the battery is small. If the determination in S22 is Yes, a DC / DC converter off command is output in S24.

As described in detail above, the fuel cell system according to the third embodiment shown in FIG. 9 includes the DC / DC converter 62 that boosts the assist power supplied from the battery 20 to the motor 30, and the DC in the case other than the assist mode. / Converter stop means 60 for stopping the operation of the DC converter 62 and stopping the supply of assist power to the motor 30.
In general, a loss occurs in the DC / DC converter 62 when assist power is supplied from the battery 20, and the efficiency of the DC / DC converter 62 decreases as the assist output decreases. On the other hand, in the third embodiment, when the assist power is not supplied from the battery 20, the operation of the DC / DC converter 62 is stopped, so that loss in the DC / DC converter 62 can be prevented.

In addition, this invention is not restricted to embodiment mentioned above and a reference form .
For example, although the FC power generation amount or the battery discharge amount is increased in proportion to the motor required power in the embodiment and the reference mode , the FC power generation amount or the battery discharge amount may be increased in a relationship other than the proportionality. In addition to using the required motor power as a reference, the fuel cell system required power such as (1) required motor power + auxiliary machine power consumption, (2) required motor power + auxiliary machine power consumption + battery charge request, etc. Thus, the FC power generation amount or the battery discharge amount may be determined. Moreover, although the lower limit of the FC power generation amount is set in the embodiment and the reference embodiment, it is not always necessary to set the lower limit.

It is a block diagram of the fuel cell system concerning the 1st reference form. (A) is explanatory drawing of FC efficiency, (b) is explanatory drawing of battery efficiency. (A) is a graph which shows the relationship between motor request electric power and FC electric power generation amount, (b) is a graph which shows the relationship between motor request electric power and battery discharge amount. It is explanatory drawing of the relationship between a battery remaining capacity (SOC) and FC efficiency, and the upper limit of FC electric power generation amount. It is a schematic block diagram of FC electric power generation amount calculator. It is a flowchart of the control method of the fuel cell system which concerns on a 1st reference form. It is a block diagram of the fuel cell system concerning a 2nd embodiment. It is a flowchart of the control method of the fuel cell system which concerns on 2nd Embodiment. It is a block diagram of the fuel cell system concerning a 3rd embodiment. It is a flowchart of the control method of the fuel cell system which concerns on 3rd Embodiment.

Explanation of symbols

  FU ... Upper limit 10 ... Fuel cell 14 ... Air pump 15 ... Power distributor (power distribution means) 20 ... Battery (power storage means) 30 ... Motor 40 ... Operation mode switching section (operation mode switching means) 44 ... Motor required power calculation section (Fuel cell system required power calculation means) 50 ... Regenerative expected value calculation section (Regeneration expected value calculation means) 52 ... Regenerative power integration section (Regenerative power integration means) 54 ... Motor required power integration section (Fuel cell system required power integration means) 60 ... DC / DC converter stop means (converter stop means) 62 ... DC / DC converter (converter) 101 ... Fuel cell system

Claims (9)

A fuel cell that generates electricity by supplying reaction gas with an air pump;
A motor driven by power supply from the fuel cell or power storage device, and
The power storage device is a fuel cell system that is charged by electric power of the fuel cell and regenerative electric power from the motor,
Fuel cell system required power calculating means for calculating required power for operating the fuel cell system;
Regenerative expectation value calculating means for calculating a regenerative expectation value indicating how much regenerative power can be expected when charging the power storage device;
When said fuel cell system required power is less than a predetermined power value, the fuel cell and select system fuel cell tracking mode to follow the power supply from the fuel cell to the request output, the fuel cell system power requirements predetermined An operation mode switching unit that selects an assist mode for assisting power supply from the fuel cell to the fuel cell system with the discharge power of the power storage device when the power value is equal to or greater than
Fuel cell system required power integrating means for calculating an integrated value of the fuel cell system required power;
Regenerative power integration means for calculating an integrated value of the regenerative power , and
The regenerative expected value calculation means sets the ratio of the regenerated power integrated value in the fuel cell system required power integrated value as the regenerative expected value,
The fuel cell system, wherein the operation mode switching unit sets the predetermined power value lower as the expected regeneration value increases. A fuel cell power generation efficiency calculating means for calculating the power generation efficiency of the fuel cell;
2. The fuel cell system according to claim 1, wherein the operation mode switching unit sets the predetermined power value larger as power generation efficiency of the fuel cell increases. 2. The fuel cell system according to claim 1 , wherein the regenerative expected value calculation means suppresses a sudden change in a ratio between the fuel cell system required power integrated value and the regenerative power integrated value by a smoothing filter. The fuel cell system according to claim 2 , wherein the fuel cell power generation efficiency calculation unit suppresses a rapid change in the fuel cell power generation efficiency by a smoothing filter. Comprises a power distribution means for distributing the fuel cell system required power to the assist mode to the assistance request power to the required power and the power storage device to the fuel cell,
The power distribution means subtracts a difference between the assist request power and the assist power upper limit from the assist request power and adds the difference to the fuel cell request power when the assist request power is larger than an assist power upper limit. The fuel cell system according to any one of claims 1 to 4 , wherein the fuel cell system is characterized. 6. The fuel cell system according to claim 5 , wherein the power distribution unit increases the fuel cell required power as the assist required power approaches the assist power upper limit. A converter that boosts assist power supplied from the power storage device to the motor;
In a case other than the assist mode, converter stop means for stopping the operation of the converter and stopping the supply of the assist power to the motor;
The fuel cell system according to any one of claims 1 to 6 , further comprising: A converter that boosts assist power from the power storage device to the motor;
Assist power detection means for detecting the assist power,
When the assist power is less than or equal to a predetermined value, converter stop means for stopping the operation of the converter and stopping the supply of the assist power to the motor;
The fuel cell system according to any one of claims 1 to 6 , further comprising:   A generator,
  A motor driven by power supply from the generator or power storage device,
  The power storage device is a generator system that is charged by electric power of the generator and regenerative electric power from the motor,
  Generator system required power calculating means for calculating required power for operating the generator system;
  Regenerative expectation value calculating means for calculating a regenerative expectation value indicating how much regenerative power can be expected when charging the power storage device;
  When the generator system required power is less than a predetermined power value, a generator follow-up mode is selected in which power supply from the generator follows the generator system required output, and the generator system required power is the predetermined power value. When the power value is greater than or equal to the power value, an operation mode switching unit that selects an assist mode for assisting power supply from the generator to the generator system by the discharge power of the power storage device;
  Generator system required power integrating means for calculating an integrated value of the generator system required power; and
  Regenerative power integration means for calculating an integrated value of the regenerative power, and
  The regeneration expected value calculation means sets the ratio of the regeneration power integrated value in the generator system required power integrated value as the regeneration expected value,
  The generator mode characterized in that the operation mode switching unit sets the predetermined power value low as the regeneration expected value increases.

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