JP2017152278A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system in which electric power assigned as for high-voltage auxiliary machines except an air pump can be increased.SOLUTION: An FC system includes: an air pump for supplying air to a cathode of a fuel cell; a high voltage battery for driving the air pump; a temperature sensor for detecting temperature of the high voltage battery; a fuel cell control device for controlling a fuel cell auxiliary machine such as the air pump; and an energy management device for controlling charge/discharge or the like of the high voltage battery. The energy management device sets buffers 132, 134 to an upper/lower-limit value within a charge/discharge limit range 130 of the high-voltage battery. The energy management device sets smaller buffers 150, 152 as the temperature detected by the temperature sensor is lower. The fuel cell control device reduces a change rate of the number of revolution of the air pump as the temperature detected by the temperature sensor is lower.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a fuel cell system that controls a pump that supplies an oxidant gas to a fuel cell according to the temperature of a power storage device.

  Patent Document 1 discloses a fuel cell system (fuel cell vehicle) in which high-voltage auxiliary machines are connected between a battery and a DC / DC converter. Auxiliary machines include a step-down converter that steps down the voltage of a fuel cell or a high voltage battery and applies it to a low voltage auxiliary machine, an air pump (air compressor) that supplies air to the fuel cell, and the like.

  By the way, the battery has a power range that can be charged and discharged in accordance with SOC (State Of Charge), and charging and discharging are limited within this power range. Hereinafter, this power range is referred to as a charge / discharge limit range. If the battery is used beyond this range, it will be overcharged / overdischarged, possibly leading to deterioration / failure of the battery.

  In the configuration of the fuel cell system disclosed in Patent Document 1, when the power consumption of the air pump changes greatly, for example, when the vehicle is decelerated / accelerated, there is a possibility that the battery is overcharged / overdischarged. In order to prevent overcharge / overdischarge of the battery, it is only necessary to set buffers before the upper and lower limits of the charge / discharge limit range of the battery. In this configuration, the power of both buffers is allocated as the usage of the air pump, and the power between both buffers is allocated as the usage of the high-voltage auxiliary machine other than the air pump. However, since it is impossible to predict when the power of the air pump will increase, it is necessary to set the buffer at all times.

International Publication No. 2011/013213 Pamphlet

  The battery charge / discharge limit range decreases as the temperature decreases from room temperature. For this reason, when the buffer is set at the low temperature in the same manner as at the normal temperature, the range between the two buffers is reduced, and the power allocated for the use of the high-voltage auxiliary machine other than the air pump is reduced. In particular, since the turbo-type air pump requires less power in a steady state, the difference from the power required for acceleration is large, and a large buffer is required. Then, the electric power allocated as the usage of the high voltage auxiliary machine other than the air pump is further reduced. In this state, since the use of the battery for the high voltage auxiliary machine other than the air pump is limited, it is necessary to increase the power generation amount of the fuel cell, which causes a deterioration in fuel consumption. In addition, the degree of freedom in energy management is small and undesirable. A large battery has a large capacity and a wide charge / discharge limit range, but there are problems in terms of installation flexibility and cost.

  The present invention has been made in consideration of such problems, and an object of the present invention is to provide a fuel cell system capable of increasing the power allocated as a high-voltage auxiliary device other than the air pump.

  The present invention consumes power supplied from a fuel cell that generates power using a fuel gas and an oxidant gas, a power storage device that is charged and discharged within a chargeable / dischargeable power range, and power supplied from the fuel cell and the power storage device. A load and an auxiliary device for supplying electric power to the power storage device, a pump included in the auxiliary device for supplying the oxidant gas to the fuel cell, power generation of the fuel cell and the power storage device while controlling the pump And a control device that controls charging / discharging, the fuel cell system further comprising temperature grasping means for grasping a temperature of the power storage device, wherein the control device has a lower temperature grasped by the temperature grasping means. The change rate of the rotation speed of the pump is reduced.

  According to the above configuration, the lower the temperature of the power storage device, the lower the rate of change of the rotation speed of the pump. The buffer can be made small. As a result, it becomes possible to allocate the power of the power storage device to the high voltage auxiliary machine other than the pump, and the degree of freedom in energy management is improved.

  In the present invention, the control device calculates a target power required for the fuel cell, calculates a target flow rate of the oxidant gas according to the target power, and performs a target rotation of the pump according to the target flow rate. When the power generation of the fuel cell is controlled by calculating the number and controlling the pump based on the target rotational speed, and the change rate of the rotational speed of the pump is reduced, the change rate of the target power is calculated. It may be small.

  According to the above configuration, when the change rate of the rotation speed of the pump is reduced, the change rate of the target power required for the fuel cell is reduced, so that the power generation amount of the fuel cell does not fluctuate rapidly. For this reason, overcharge / overdischarge of the power storage device can be suppressed.

  In the present invention, the control device calculates a target power required for the fuel cell, calculates a target flow rate of the oxidant gas according to the target power, and performs a target rotation of the pump according to the target flow rate. By calculating the number and controlling the pump based on the target rotational speed, the power generation of the fuel cell is controlled, and the rate of increase of the target flow rate is reduced when the rate of change in the rotational speed of the pump is reduced. It may be small.

  Normally, when the target flow rate of the pump is increased rapidly, the target pressure of the pump is also increased rapidly. At this time, if the rate of increase in the rotational speed of the pump is reduced, the calculated target flow rate and target pressure are not achieved. In this case, pressure feedback control for increasing the cathode pressure is executed, and the back pressure valve for adjusting the pressure of the oxidant gas is throttled. As a result, the flow rate of the oxidant gas may further decrease, and the power generation amount of the fuel cell may decrease. According to the above configuration, when the change rate of the rotation speed of the pump is reduced, the increase rate of the target flow rate is reduced, so that a rapid increase in the target pressure can be suppressed. As a result, the back pressure valve is not excessively throttled, and the flow rate can be prevented from further decreasing.

  In the present invention, the control device may limit the target pressure of the oxidant gas to a predetermined pressure or less according to the target flow rate or the actual flow rate of the oxidant gas supplied to the fuel cell. .

  According to the above configuration, since the target pressure of the oxidant gas is limited to a predetermined pressure or less, the back pressure valve for adjusting the pressure of the oxidant gas can be prevented from being excessively throttled in a state where the flow rate is small. It can suppress that a flow rate falls further.

  In the present invention, the apparatus further includes a pressure sensor for detecting the pressure of the oxidant gas, and the control device performs pressure control for setting the pressure of the oxidant gas to a predetermined pressure based on the pressure detected by the pressure sensor. At the same time, the pressure control may be limited according to the target flow rate or the actual flow rate of the oxidant gas supplied to the fuel cell.

  According to the above configuration, the back pressure valve that adjusts the pressure of the oxidant gas in a state where the flow rate is low is provided in order to limit the pressure control for setting the pressure of the oxidant gas to a predetermined pressure based on the pressure detected by the pressure sensor. It is possible to prevent excessive throttling, and to further reduce the flow rate.

  In this invention, the said control apparatus sets a buffer to the upper and lower limit value of the said electric power range of the said electrical storage apparatus, allocates the electric power for the said buffer as a usage-amount of the said pump, and uses electric power other than the said buffer for the other than the said pump When the charge rate of the power storage device is controlled and the change rate of the rotation speed of the pump is reduced, the buffer is made smaller as the temperature grasped by the temperature grasping means is lower. Also good.

  With the above configuration, since the buffer is made small, it becomes possible to allocate the power of the power storage device to a high voltage auxiliary machine other than the pump, and the degree of freedom in energy management is improved.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to allocate the electric power of an electrical storage apparatus to high voltage auxiliary machines other than a pump, and the freedom degree of energy management improves.

FIG. 1 is an overall configuration diagram of a fuel cell system according to the present embodiment. FIG. 2 is a block diagram of an electric power system included in the fuel cell system. FIG. 3A is an explanatory diagram for explaining the estimated power value and actual power consumption during acceleration, and FIG. 3B is an explanatory diagram for explaining the estimated power value and actual power consumption during deceleration. FIG. 4 is an explanatory diagram for explaining the charge / discharge limit range of the battery. FIG. 5 is an explanatory diagram for explaining power distribution. FIG. 6 is a characteristic diagram of a battery temperature-charge / discharge limit range. FIG. 7 is an explanatory diagram for explaining a comparative example in which the buffer is made constant. FIG. 8 is a characteristic diagram of the rotational speed increase rate-ΔAP power of the air pump. FIG. 9 is an explanatory diagram for explaining the present embodiment in which the buffer is changed according to the temperature. FIG. 10 is a flowchart of processing performed in the FC system.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings by way of preferred embodiments.

[1 Overall configuration of fuel cell system 12]
The configuration of the fuel cell system 12 (also referred to as the FC system 12) will be described with reference to FIG. As a basic device configuration of the FC system 12 according to the present embodiment, a known device can be used. For example, the configuration disclosed in Japanese Patent Application Laid-Open No. 2016-12480 can be used. In the present specification, the description will focus on the configuration related to the features of the invention, and the description (and illustration) of the known configuration will be omitted, or only a brief description (and illustration) will be given. In the present embodiment, a fuel cell vehicle 10 (also simply referred to as a vehicle 10) on which the FC system 12 is mounted is assumed.

  The FC system 12 mounted on the vehicle 10 includes a fuel cell 14 (also referred to as FC 14), a hydrogen supply system 16, an air supply system 18, a cooling system 20, an electric power system 22, and an ECU 24. Moreover, the opening sensor 32 which detects the opening degree (operation amount) of the accelerator pedal 30 is provided.

  The FC 14 has a structure in which fuel cells formed by sandwiching a solid polymer electrolyte membrane between an anode electrode and a cathode electrode are stacked. Hydrogen gas as fuel gas is supplied to the anode electrode side through the anode flow path 34, and air as oxidant gas is supplied to the cathode electrode side through the cathode flow path 36. Hydrogen gas and oxygen in the air react to generate water and generate electric power.

[1.1 Hydrogen supply system 16]
The hydrogen supply system 16 supplies hydrogen gas to the FC 14 via the hydrogen supply flow path 16S, and discharges the anode off-gas generated in the FC 14 via the gas discharge flow path 16D. The hydrogen supply channel 16S and the gas discharge channel 16D communicate with the anode channel 34.

[1.2 Air supply system 18]
The air supply system 18 supplies air to the FC 14 via the air supply flow path 18S, and discharges the cathode off gas generated in the FC 14 via the gas discharge flow path 18D. As the air supply flow path 18S, a pipe 40a, an air pump 42, a pipe 40b, a humidifier 44, and a pipe 40c are provided in this order from the upstream side (suction port side). The downstream pipe 40c communicates with the cathode flow path 36 of the FC14. As the gas discharge flow path 18D, a pipe 46a, a humidifier 44, a pipe 46b, a back pressure valve 48, and a pipe 46c are provided in this order from the upstream side (FC 14 side). The upstream pipe 46a communicates with the cathode flow path 36 of the FC14. The piping 40 b and the piping 40 c of the air supply flow path 18 </ b> S are connected by a piping 56 that bypasses the humidifier 44. The pipe 56 is provided with a valve 58. A pressure sensor 64 is provided in the pipe 46b. A flow sensor 66 is provided in the pipe 40b.

  The air pump 42 pressure-feeds external air sucked through the pipe 40a to the cathode flow path 36 of the FC 14 through the pipe 40b, the humidifier 44, the pipe 40c, and the like. The humidifier 44 humidifies the air supplied from the air pump 42 by using the cathode off gas discharged from the FC 14. The back pressure valve 48 adjusts the pressure of the cathode flow path 36 of the FC 14 by adjusting the opening of the valve in accordance with a control signal output from the ECU 24. The air pump 42, the back pressure valve 48, and the valve 58 are controlled by the ECU 24, respectively. The pressure value detected by the pressure sensor 64 is output to the ECU 24, and the opening degree of the back pressure valve 48 is controlled so that this pressure value becomes a predetermined pressure. The actual air flow value detected by the flow sensor 66 is output to the ECU 24.

[1.3 Cooling system 20]
The cooling system 20 supplies the refrigerant to the FC 14 via the refrigerant supply passage 20S and collects the refrigerant from the FC 14 via the refrigerant discharge passage 20D. The refrigerant circulates between the cooling system 20 and the FC 14, absorbs heat at the FC 14, and dissipates heat at the cooling system 20.

[1.4 Electric power system 22]
The power system 22 will be described with reference to FIG. The FC 14 is connected to a traction motor 76 (also referred to as TRC 76) via an FC contactor 70, a boost converter 72 (also referred to as FCVCU (Voltage Control Unit) 72), and an inverter 74 (also referred to as MOTPDU (Power Drive Unit) 74). The The high voltage battery 78 (also referred to as BAT 78) is connected to the TRC 76 via a BAT contactor 80 and a step-up / down converter 82 (also referred to as BATVCU 82). FCVCU 72 and BATVCU 82 are connected to TRC 76 in parallel on the secondary side 2S. Various high voltage auxiliary machines such as an air pump 42, an air conditioner 84 (also referred to as A / C 84), a heater 86, and a step-down converter 88 (also referred to as DC / DC 88) are connected in parallel to the primary side 1Sb of the BATVCU 82. .

  The FC contactor 70 switches between cutoff and connection between the FC 14 and the primary side 1Sf of the FCVCU 72 in accordance with an opening / closing signal output from the ECU 24. The FCVCU 72 is a voltage adjusting device including a chopper circuit, and boosts the voltage of the primary side 1Sf in accordance with the control signal of the ECU 24 and applies it to the secondary side 2S. The MOTPDU 74 has a three-phase bridge configuration, converts the DC voltage of the secondary side 2S into an AC voltage, and controls the TRC 76 in accordance with a target rotation speed control signal output from the ECU 24. During regeneration, the MOTPDU 74 functions as a converter, and converts the AC voltage generated by the TRC 76 into a DC voltage. MOTPDU 74 and TRC 76 are so-called loads. The TRC 76 is driven by the power of the FC 14 and / or BAT 78, and functions as a generator during regeneration. The TRC 76 is provided with a motor rotation speed sensor 90. The motor rotation speed sensor 90 detects the rotation speed of the TRC 76 and outputs a rotation speed signal to the ECU 24.

  The BAT 78 discharges the shortage of the power generation amount of the FC 14 with respect to the actual power consumption during power running, and charges the excess of the power generation amount of the FC 14 and the load with respect to the actual power consumption during regeneration. The SOC of the BAT 78 is monitored by the ECU 24. The BAT 78 is provided with a temperature sensor 92. The temperature sensor 92 detects the temperature of the BAT 78 and outputs a temperature signal to the ECU 24. The BAT contactor 80 switches between disconnection and connection between the BAT 78 and the primary side 1Sb of the BATVCU 82 in accordance with an opening / closing signal output from the ECU 24. The BATVCU 82 is a voltage adjusting device including a chopper circuit. In accordance with a control signal output from the ECU 24, the voltage of the primary side 1Sb is boosted and applied to the secondary side 2S during power running, and the secondary side 2S is regenerated. The voltage is stepped down and applied to the primary side 1Sb.

  The air pump 42 also included in the air supply system 18 (FIG. 1) is connected to the primary side 1Sb of the BATVCU 82 via an air pump PDU 94 (also referred to as A / PPDU 94). The A / PPDU 94 includes a three-phase bridge type inverter, converts the DC voltage of the primary side 1Sb into an AC voltage, and controls the air pump 42 in accordance with a target rotation speed control signal output from the ECU 24. A pump rotation speed sensor 96 (also referred to as an A / P rotation speed sensor 96) detects the rotation speed of the air pump 42 and outputs a rotation speed signal to the ECU 24.

[1.5 ECU24]
The ECU 24 will be described with reference to FIGS. 1 and 2. The ECU 24 includes an energy management ECU 100 (also referred to as an EM ECU 100) and an FC ECU 102. Each of the ECUs 100 and 102 is a computer including a microcomputer, such as a CPU, ROM (including EEPROM), RAM, and other input / output devices such as an A / D converter and a D / A converter, a timer as a timer, and the like. Have Each of the ECUs 100 and 102 functions as various function realization units (function realization means) such as a control unit, a calculation unit, and a processing unit by the CPU reading and executing a program recorded in the ROM. Each ECU 100, 102 may be composed of only one ECU or a plurality of ECUs.

  The EMECU 100 is configured to calculate the target power and buffer width (see [2.2] and [2.5] below) of the FC 14 and to perform energy management (EM) of the FC system 12. Further, the EMECU 100 is configured to output the target power of the FC 14 to the FC ECU 102 as a current command value.

  The FC ECU 102 reads and executes a program recorded in the ROM by the CPU, whereby a flow rate / pressure calculation unit 104, a rotation speed calculation unit 106, a power estimation unit 108, a pump power calculation unit 110, a change rate limiting unit 112, a gas It functions as the control unit 114 and the power system control unit 116.

  The flow rate / pressure calculation unit 104 is configured to calculate a target flow rate / pressure of the air pump 42. The rotation speed calculation unit 106 is configured to calculate a target rotation speed of the air pump 42 necessary for obtaining a target flow rate. The power estimation unit 108 is configured to calculate a power estimation value (see [2.1] below). The pump power calculation unit 110 is configured to calculate the power consumption upper limit value or the regenerative power upper limit value of the air pump 42. The change rate limiting unit 112 is configured to calculate the rotation speed of the air pump 42 with the change rate limited.

  The gas control unit 114 is configured to perform gas control of the hydrogen supply system 16 and the air supply system 18. Here, the gas control unit 114 is configured to feedback control the back pressure valve 48 in accordance with the detection value of the pressure sensor 64 and the target pressure.

  The power system control unit 116 controls the power system 22 (FC contactor 70, FCVCU 72, MOTPDU 74, BAT contactor 80, BATVCU 82, air pump 42, high voltage auxiliary devices 84, 86, 88) based on the energy management performed by the EMECU 100. Configured to control. Furthermore, the power system control unit 116 is configured to control the BATVCU 82 so that the charge / discharge of the BAT 78 does not exceed the charge / discharge limit range.

  The ECUs 100 and 102 are communicably connected to the hydrogen supply system 16, the air supply system 18, the cooling system 20, and the power system 22 via a signal line 120. Then, the program stored in the ROM is executed. For example, sensor detection values of the opening degree sensor 32, the pressure sensor 64, the flow rate sensor 66, the temperature sensor 92, the A / P rotational speed sensor 96, the FC14 voltage, current, Each device is controlled by detecting the voltage, current, rotation speed, TRC 76 voltage, current, rotation speed, BAT 78 voltage, current, temperature, SOC, secondary side 2S voltage, current, and the like of the air pump 42.

[2 Energy management of fuel cell system 12]
Here, regarding energy management (EM) performed by the EMECU 100, background technologies related to the present embodiment will be described in the following [2.1] to [2.4], and features of the present embodiment will be described in the following [2.5]. ] Will be described.

[2.1 Difference between estimated power of air pump 42 and actual power consumption]
In the vehicle 10 equipped with the FC system 12, the power generation amount (target power) required for the FC 14 is calculated at very short time intervals. At this time, the following calculation is performed. That is, the electric power required for the air pump 42 is calculated in order to realize the flow rate and pressure ratio of the air pump 42 at that time (ratio of suction side pressure and discharge side pressure of the air pump 42). This power is referred to as “power estimation value”. The estimated power value is obtained from, for example, a power calculation map with the flow rate and pressure ratio as inputs. As shown in FIG. 3A, generally, when the vehicle 10 is accelerated, the actual power consumption (solid line) actually consumed is larger than the estimated power value (dotted line) calculated at each moment. As shown in FIG. 3B, when the vehicle 10 is decelerated, the actual power consumption (solid line) actually consumed is generally smaller than the estimated power value (dotted line) calculated at each moment. In the present specification, the difference between the actual power consumption and the power estimation value (= actual power consumption−power estimation value) is referred to as “ΔAP”.

  The amount of power generated by the FC 14 is set by estimating the power of the entire FC system 12 including the estimated power value of the air pump 42 (see [2.3] below). For this reason, when ΔAP increases, the power generation amount of FC 14 is insufficient or exceeded. Insufficient power is compensated by discharging BAT 78, and excess power is stored by charging BAT 78.

[2.2 Charge / Discharge Limit Range 130 of BAT78]
As shown in FIG. 4, the BAT 78 has a charge / discharge limit range 130 defined by a charge upper limit UL and a discharge lower limit LL. When charging exceeds the charging upper limit value UL, overcharging occurs, and when discharging exceeds the discharging lower limit value LL, over discharging occurs. Use of the battery in a range exceeding the charge upper limit value UL and the discharge lower limit value LL is prohibited, and the BAT 78 is used to charge and discharge within the charge / discharge limit range 130. As a matter of course, the larger the SOC, the larger the power width that can be discharged in the charge / discharge restriction range 130, and the smaller the SOC, the larger the power width that can be charged in the charge / discharge restriction range 130.

  A deceleration-side buffer 132 is set in the charge / discharge restriction range 130 before the charge upper limit value UL, and an acceleration-side buffer 134 is set in the charge / discharge restriction range 130 before the discharge lower limit value LL. The acceleration-side buffer 134 is set to such a size that ΔAP generated when the vehicle 10 is accelerated does not exceed. The deceleration-side buffer 132 is set to a size that does not exceed ΔAP that occurs when the vehicle 10 decelerates. In other words, the electric power of the acceleration side buffer 134 and the deceleration side buffer 132 is allocated as the usage of the air pump 42. The electric power in the range other than the acceleration side buffer 134 and the deceleration side buffer 132 is allocated as a use amount other than the air pump 42. This range is referred to as an EM control range 136.

[2.3 FC14 and BAT78 power distribution]
With reference to FIG. 5, power distribution during acceleration of the vehicle 10 or normal travel will be described. FIG. 5 shows an example of power distribution when the SOC of the BAT 78 is about 50%, that is, the chargeable amount and the dischargeable amount of the BAT78 are about the same. In the vehicle 10 equipped with the FC system 12, the power generation amount (target power) required for the FC 14 is calculated. In general, the following processing is performed.

  First, the estimated power value of the air pump 42 described in [2.1] is calculated. Here, the estimated power value is referred to as estimated power 140. Further, the required power consumption 142 required for maintaining the current state of the FC system 12 such as a high voltage auxiliary machine (A / C 84, heater 86, DC / DC 88), TRC 76, etc. other than the air pump 42 is calculated. It is necessary to cover the estimated power 140 and the required power consumption 142 with the power generation of the FC 14 and the assist amount of the BAT 78. The FC system 12 sets the power generation amount 144 of the FC 14 on the assumption that the power in the discharge side range 146 (also referred to as the EM discharge range 146) of the EM control range 136 is used as the assist amount 146 a of the BAT 78. . That is, the power generation amount 144 of the FC 14 and the assist amount 146a of the BAT 78 are set so that the sum of the estimated power 140 and the required power consumption 142 is substantially equal to the sum of the power generation amount 144 of the FC 14 and the assist amount 146a of the BAT 78. Then, during actual acceleration or normal travel, the power consumption of each device is controlled so that the assist amount 146a of the BAT 78 is within the EM control range 136, that is, within the EM discharge range 146. If the assist amount 146a is within the EM discharge range 146, even if ΔAP during acceleration (= actual power consumption−power estimation value) becomes maximum, the ΔAP can be absorbed by the buffer 134 on the acceleration side. For this reason, the discharge amount of the BAT 78 does not exceed the discharge lower limit value LL.

[2.4 Relationship Between Temperature and Charge / Discharge Limit Range 130]
The charge / discharge limit range 130 of the BAT 78 described in [2.2] above varies depending on the temperature. As shown in FIG. 6, the charge / discharge restriction range 130 becomes smaller as the temperature of the BAT 78 becomes lower from normal temperature (0 ° C. in FIG. 6). That is, as shown in FIG. 7, the charge / discharge limit range 130 ′ at the low temperature is smaller than the charge / discharge limit range 130 at the normal temperature. When the same buffers 132 and 134 as those at normal temperature are set at low temperatures, the ratio of the buffers 132 and 134 in the charge / discharge restriction range 130 ′ increases, and the EM control range 136 ′ allocated to devices other than the air pump 42 decreases.

  Here, further explanation will be given by taking the acceleration of the vehicle 10 as an example. As indicated by the rotational speed increase rate-ΔAP power characteristic (referred to as characteristic A) in FIG. 8, ΔAP (= actual power consumption-power estimated value) of the air pump 42 increases as the rotational speed increase rate of the air pump 42 increases. That is, ΔAP increases as the depression rate of the accelerator pedal 30 increases. The characteristic A is determined by the air pump 42, and the temperature is not related. For this reason, it is usually necessary to set the buffer 134 according to the maximum value of the characteristic A regardless of the temperature of the BAT 78. In FIG. 8, ΔAP becomes the maximum value W1 at the rotation speed increase rate R1, and therefore the buffer 134 corresponding to the maximum value W1 is necessary. Then, the EM discharge range 146 ′ that can be used other than the air pump 42 at the time of discharge becomes small.

[2.5 Description of Embodiment]
According to the present embodiment, the EM discharge range 146 ′ (EM control range 136 ′) can be widened even when the BAT 78 is in a low temperature environment. That is, in the present embodiment, the rotation speed change rate of the air pump 42 is reduced as the temperature of the BAT 78 is lowered. An example will be described with reference to FIGS. It is assumed that the accelerator pedal 30 is stepped in the same manner in two states of normal temperature (above a predetermined temperature: for example, 0 ° C. or more) and low temperature (below the predetermined temperature: for example, less than 0 ° C.). The rate of increase in the rotation speed of the air pump 42 is not suppressed at room temperature. At this time, as shown in FIG. 8, the rotational speed increase rate can be increased to R1, which is the maximum value. For this reason, as shown in FIG. 9, a buffer 134 corresponding to ΔAP = W1 generated when the rotation speed increase rate is R1 is set. On the other hand, when the temperature is low, the rate of increase in the rotation speed of the air pump 42 is made smaller than that at normal temperature. At this time, as shown in FIG. 8, the rotational speed increase rate is limited to R2 smaller than R1 which is the maximum value. For this reason, as shown in FIG. 9, a buffer 152 corresponding to ΔAP = W2 (<W1) generated when the rotation speed increase rate is R2 is set. Then, the EM discharge range 158 that can be used other than the air pump 42 during the discharge of the BAT 78 is larger than the EM discharge range 146 ′ when the buffer 134 is set.

  The same applies when the vehicle 10 is decelerated. In this embodiment, the rotation reduction rate of the air pump 42 is not suppressed at room temperature. On the other hand, when the temperature is low, the rotation reduction rate of the air pump 42 is made smaller than that at room temperature. Then, the EM charging range 156 becomes larger than the EM charging range 148 ′ when the buffer 132 is set.

  Thus, according to the present embodiment, the lower the temperature of the BAT 78, the smaller the rate of change of the rotation speed of the air pump 42. Then, the change width of the power consumption of the air pump 42 becomes small. As a result, the buffers 150 and 152 can be reduced. That is, the EM control range 154 at a low temperature is larger than the EM control range 136 ′ when the rate of change in the rotation speed of the air pump 42 is not reduced. For this reason, the electric power of BAT78 which can be used other than the air pump 42 can be increased, and the electric power generation of FC14 can be suppressed. In addition, the degree of freedom of energy management is expanded.

[3 Processing of FC system 12]
[3.1 Processing Example 1]
The processing performed in the FC system 12 will be described with reference to FIGS. 1 and 2 as appropriate, using the flowchart shown in FIG.

  In step S1, the ECU 24 monitors the operating status of each device and acquires various information by receiving detection signals from various sensors.

  In step S2, EMECU 100 sets a buffer corresponding to the temperature to charge upper limit UL and discharge lower limit LL of charge / discharge limit range 130 of BAT 78. For example, as shown in FIG. 9, when the BAT 78 is at a low temperature (for example, less than 0 ° C.), the buffers 150 and 152 whose width decreases as the temperature of the BAT 78 decreases are set. On the other hand, when the BAT 78 is at room temperature (for example, 0 ° C. or higher), the buffers 132 and 134 having a certain width are set.

  In step S3, the EMECU 100 calculates the power generation amount required for the FC 14, that is, the target power, based on the acquired information. At this time, the power estimation value previously calculated by the power estimation unit 108 of the FC ECU 102 is fed back to the EMECU 100. The EMECU 100 calculates the power that can be charged and discharged from the BAT 78 based on the estimated power value and the widths of the buffers 150 and 152, and determines the power consumption and regenerative power that can be allocated to the load and the high voltage auxiliary machine. Then, the EMECU 100 calculates the target power of the FC 14 so that the total power generated / consumed in the FC system 12 becomes plus or minus zero. For example, when the vehicle 10 is accelerated, the target power is calculated according to the procedure described in [2.3] above. The target power is output to the FC ECU 102 as a current command value.

  In step S4, the flow rate / pressure calculation unit 104 calculates the target flow rate / pressure of the air pump 42 required to obtain the target power of the FC 14 based on the current command value.

  In step S5, the rotation speed calculation unit 106 obtains a target flow rate using the target flow rate / pressure calculated by the flow rate / pressure calculation unit 104 and the detection value of the A / P rotation speed sensor 96 of the air pump 42. The target rotational speed of the air pump 42 necessary for the calculation is calculated.

  In step S6, the power estimation unit 108 calculates a power estimation value (see [2.1] below) using the target flow rate / pressure calculated by the flow rate / pressure calculation unit 104. The calculated power estimation value is fed back to the EMECU 100 for the next calculation of the target power.

  In step S7, the pump power calculation unit 110 uses the power estimation value calculated by the power estimation unit 108 and the normal power consumption upper and lower limit values of the air pump 42, or the power consumption upper limit value of the air pump 42 at that time or Calculate the regenerative power upper limit. The normal power consumption upper limit value is the rated value of the air pump 42. The normal lower limit value of power consumption is the power required for the air pump 42 in order for the FC 14 to generate the minimum required power even when the vehicle 10 is at fault or the like.

  In step S8, the change rate limiting unit 112 determines the widths of the buffers 150 and 152 set by the EMECU 100, the target rotation number calculated by the rotation number calculation unit 106, and the estimated power value calculated by the power estimation unit 108. Is used to calculate the target rotational speed with a limited change rate. For example, the change rate of the target rotational speed is decreased as the widths of the buffers 150 and 152 are smaller, that is, the BAT 78 is lower in temperature. More specifically, the rate of change from the rotational speed at that time to the target rotational speed calculated this time is decreased as the BAT 78 is at a lower temperature. That is, the fluctuation range per hour of the target rotation speed is reduced. In this way, the power consumption or regenerative power of the air pump 42 does not exceed the buffers 150 and 152. As a result of this process, the target rotational speed after the change rate is limited becomes smaller than the target rotational speed when the change rate is not limited. On the other hand, when the constant buffers 132 and 134 are set, they are used as they are without decreasing the change rate of the target rotational speed.

  In step S9, the power system control unit 116 controls the power system 22 so that the charge / discharge amount of the BAT 78 does not exceed the charge upper limit value UL and the discharge lower limit value LL. At this time, the power system control unit 116 controls the air pump 42 via the A / PPDU 94 based on the target rotational speed calculated by the change rate limiting unit 112. The power system control unit 116 controls the power of the air pump 42 within the range of the power consumption upper limit value calculated by the pump power calculation unit 110 or the regenerative power upper limit value.

  In step S 10, the gas control unit 114 performs feedback control of the back pressure valve 48 while monitoring the pressure value detected by the pressure sensor 64 in order to set the cathode pressure to the target pressure calculated by the flow rate / pressure calculation unit 104. I do.

[3.2 Processing Example 2]
In step S3 of Processing Example 1, the EMECU 100 calculates the target power of the FC 14, but at this time, the target power can be limited according to the temperature. For example, when the BAT 78 is at a low temperature (for example, less than 0 ° C.), the change rate of the target power is decreased as the temperature is lower. More specifically, the rate of change from the target power calculated last time to the target power calculated this time is decreased as the BAT 78 is at a lower temperature. That is, the fluctuation range per hour of the target power is reduced. As an example, the change rate is reduced by multiplying the target power by a coefficient m (0 <m <1) corresponding to the temperature. On the other hand, when the BAT 78 is at room temperature (0 ° C. or higher), it is used as it is without reducing the target power change rate.

  According to the processing example 2, when the change rate of the rotation speed of the air pump 42 is reduced, the change rate of the target power required for the FC 14 is reduced, so that the power generation amount of the FC 14 does not change rapidly. For this reason, overcharge / overdischarge of the BAT 78 can be suppressed.

[3.3 Processing Example 3]
In step S4 of the processing examples 1 and 2, the flow rate / pressure calculation unit 104 calculates the target flow rate of the air pump 42. At this time, it is also possible to limit the target flow rate according to the temperature. For example, when the BAT 78 is at a low temperature (for example, less than 0 ° C.), the increase rate of the target flow rate is decreased as the temperature is lower. More specifically, the rate of increase from the current air flow rate to the target flow rate calculated this time is made smaller as the BAT 78 is lower in temperature. That is, the fluctuation range per hour of the target flow rate is reduced. As an example, the change rate is reduced by multiplying the target power by a coefficient n (0 <n <1) corresponding to the temperature. On the other hand, when BAT78 is normal temperature (0 degreeC or more), it uses as it is, without making the raise rate of target flow volume small.

  Normally, when the target flow rate of the air pump 42 is increased rapidly, the target pressure of the air pump 42 is also increased rapidly. At this time, if the rate of increase in the rotational speed of the air pump 42 is reduced, the calculated target flow rate and target pressure are not obtained. In this case, pressure feedback control for increasing the cathode pressure is executed, and the back pressure valve 48 for adjusting the air pressure is throttled. As a result, the air flow rate may further decrease, and the power generation amount of the FC 14 may decrease. According to the process example 3, when the rate of increase in the rotation speed of the air pump 42 is reduced, the rate of increase in the target flow rate is reduced, so that a rapid increase in the target pressure can be suppressed. As a result, the back pressure valve 48 is not excessively throttled, and it is possible to suppress the flow rate from further decreasing.

  By the way, in the processing example 3, while the increase rate of the target flow rate is limited, the decrease rate is not limited. This is because the behavior of the vehicle 10 is not affected even if the reduction rate is not limited.

[3.4 Processing Example 4]
In step S4 of Processing Example 3, the flow rate / pressure calculation unit 104 calculates the target pressure of the air pump 42. At this time, it is also possible to limit the target pressure according to the calculated target flow rate. . For example, when the target flow rate is less than a predetermined flow rate, the target pressure is set to a predetermined pressure or less. The predetermined pressure may be a constant value or a value that decreases as the flow rate decreases. Normally, the gas control unit 114 throttles the back pressure valve 48 when a high target pressure is set. If the back pressure valve 48 is throttled while the flow rate is low, the flow rate is further reduced and the target flow rate cannot be obtained. As in this processing example 4, when the target flow rate is less than the predetermined flow rate, the target pressure is set to be equal to or lower than the predetermined pressure, thereby suppressing an excessive decrease in the flow rate. Note that the target pressure may be limited according to the actual flow rate detected by the flow rate sensor 66 instead of the target flow rate.

  According to the processing example 4, since the target air pressure is limited to a predetermined pressure or less, it is possible to prevent the back pressure valve 48 that adjusts the air pressure from being excessively throttled in a state where the flow rate is small. Further reduction can be suppressed.

[3.5 Processing Example 5]
In step S4 of processing example 3, the EMECU 100 calculates the target pressure of the FC 14, but at this time, it is also possible to limit the pressure feedback control according to the target flow rate. For example, the pressure feedback control is temporarily stopped. When the flow rate decreases, the pressure detected by the pressure sensor 64 decreases. When the pressure feedback control is continued, the gas control unit 114 throttles the back pressure valve 48 in order to increase the pressure. Then, the flow rate is further reduced, and the target flow rate cannot be obtained. As in the present processing example 5, when the target flow rate is less than the predetermined flow rate, excessive reduction in the flow rate can be suppressed by temporarily stopping the pressure feedback control. The pressure feedback control may be limited according to the actual flow rate detected by the flow rate sensor 66 instead of the target flow rate.

  According to the above configuration, the pressure feedback control for setting the air pressure to a predetermined pressure based on the pressure detected by the pressure sensor 64 is limited, so that the back pressure valve 48 for adjusting the air pressure is excessive in a state where the flow rate is small. It is possible to prevent the flow rate from being squeezed, and to further reduce the flow rate.

[4 Other Embodiments]
In the above embodiment, the rate of change in the rotational speed of the air pump 42 is reduced in order to solve the problem that the charge / discharge restriction range 130 is narrowed when the temperature of the BAT 78 is lower than room temperature. On the other hand, even when the temperature of the BAT 78 becomes higher than room temperature, the charge / discharge restriction range 130 may be narrowed. For this reason, you may utilize the said embodiment, when the temperature of BAT78 becomes higher than normal temperature.

[5 Summary of this embodiment]
The FC system 12 includes a fuel cell 14 that generates power using hydrogen gas (fuel gas) and air (oxidant gas), a BAT 78 (power storage device) that charges and discharges within the charge / discharge restriction range 130, and the fuel cell 14 and BAT 78. The ECU 24 controls the power generation of the fuel cell 14 and the charging / discharging of the BAT 78 while controlling the air pump 42 and the load such as the TRC 76 that consumes the power supplied from the power supply and supplies power to the BAT 78 and the air pump 42. Device). The FC system 12 further includes a temperature sensor 92 (temperature grasping means) that detects (obtains) the temperature of the BAT 78. The ECU 24 (FC ECU 102) reduces the rate of change of the rotation speed of the air pump 42 as the temperature detected by the temperature sensor 92 is lower.

  The ECU 24 (EMECU 100) sets the buffers 132 and 134 to the upper and lower limit values of the charge / discharge restriction range 130 of the BAT 78, allocates the power for the buffers 132 and 134 as the usage of the air pump 42, and sets the power other than the buffers 132 and 134 minutes. Is used as a part for use other than the air pump 42, and charging / discharging of the BAT 78 is controlled. The ECU 24 (EMECU 100) sets smaller buffers 150 and 152 as the temperature detected by the temperature sensor 92 is lower when the rate of change in the rotational speed of the air pump 42 is reduced.

  According to the FC system 12, the lower the temperature of the BAT 78, the smaller the rate of change of the rotation speed of the air pump 42, so that the fluctuation range of the power consumption of the air pump 42 can be reduced. It is possible to reduce the buffer to be set. As a result, it becomes possible to allocate the power of the BAT 78 to a high-voltage auxiliary machine other than the air pump 42, and the degree of freedom in energy management is improved.

  As shown in FIG. 2, in the above embodiment, the A / PPDU 94 is provided on the primary side 1Sb of the BATVCU 82, but may be provided at other positions. For example, it may be provided on the secondary side 2S.

  Moreover, in the said embodiment, although the temperature of BAT78 is grasped | ascertained with the temperature sensor 92, when the outside of a vehicle is low temperature and a soak continues, you may make it consider that the temperature of BAT78 is low temperature.

DESCRIPTION OF SYMBOLS 10 ... Vehicle 12 ... FC system 14 ... Fuel cell (FC) 18 ... Air supply system 22 ... Electric power system 24 ... ECU
42 ... Air pump 48 ... Back pressure valve 78 ... High voltage battery (BAT) 92 ... Temperature sensor (temperature grasping means)
94 ... A / PPDU 100 ... EMECU
DESCRIPTION OF SYMBOLS 102 ... FCECU 104 ... Flow rate / pressure calculating part 106 ... Rotation speed calculating part 108 ... Current estimation part 110 ... Pump power calculating part 112 ... Change rate limiting part 114 ... Gas control part 116 ... Power system control part

Claims (6)

A fuel cell that generates power using fuel gas and oxidant gas;
A power storage device that charges and discharges within a chargeable / dischargeable power range;
A load and an auxiliary machine that consumes power supplied from the fuel cell and the power storage device and supplies power to the power storage device;
A pump included in the auxiliary machine for supplying the oxidant gas to the fuel cell;
A control device for controlling power generation of the fuel cell and charge / discharge of the power storage device while controlling the pump;
A fuel cell system comprising:
A temperature grasping means for grasping the temperature of the power storage device;
The fuel cell system, wherein the control device reduces the rate of change of the rotation speed of the pump as the temperature grasped by the temperature grasping means is lower. The fuel cell system according to claim 1, wherein
The controller is
The target power required for the fuel cell is calculated, the target flow rate of the oxidant gas according to the target power is calculated, the target rotational speed of the pump according to the target flow rate is calculated, and the target rotational speed Controlling the power generation of the fuel cell by controlling the pump based on
The fuel cell system, wherein the change rate of the target power is reduced when the change rate of the rotation speed of the pump is reduced. The fuel cell system according to claim 1 or 2,
The controller is
The target power required for the fuel cell is calculated, the target flow rate of the oxidant gas according to the target power is calculated, the target rotational speed of the pump according to the target flow rate is calculated, and the target rotational speed Controlling the power generation of the fuel cell by controlling the pump based on
The fuel cell system, wherein the rate of increase of the target flow rate is reduced when the change rate of the rotation speed of the pump is reduced. The fuel cell system according to claim 3, wherein
The controller is
The fuel cell system, wherein the target pressure of the oxidant gas is limited to a predetermined pressure or less according to the target flow rate or the actual flow rate of the oxidant gas supplied to the fuel cell. The fuel cell system according to claim 3, wherein
A pressure sensor for detecting the pressure of the oxidant gas;
The controller is
While performing pressure control to make the pressure of the oxidant gas a predetermined pressure based on the pressure detected by the pressure sensor,
The fuel cell system, wherein the pressure control is limited according to the target flow rate or an actual flow rate of the oxidant gas supplied to the fuel cell. The fuel cell system according to any one of claims 1 to 5,
The controller is
The buffer is set to the upper and lower limit values of the power range of the power storage device, the power for the buffer is allocated as the usage of the pump, and the power other than the buffer is allocated as the usage other than the pump. Control the charge and discharge of the device,
When the rate of change of the rotation speed of the pump is reduced, the buffer is made smaller as the temperature grasped by the temperature grasping means is lower.

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