JP5765260B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system that supplies power generated by a fuel cell to a load.

  A fuel cell constituting a fuel cell system directly converts energy released in an oxidation reaction into electric energy by oxidizing fuel by an electrochemical process. This fuel cell has a membrane-electrode assembly in which both side surfaces of a polymer electrolyte membrane for selectively transporting hydrogen ions are sandwiched by a pair of electrodes made of a porous material. Each of the pair of electrodes is mainly composed of a carbon powder carrying a platinum-based metal catalyst, and is formed on the surface of the catalyst layer in contact with the polymer electrolyte membrane and a gas having both air permeability and electronic conductivity. And a diffusion layer.

  In addition, the fuel cell system includes a power storage device such as a battery capable of storing a part of the power generated by the fuel cell, and loads both the power generated by the fuel cell and the power generated by the discharge of the power storage device. Generally, it is possible to provide a configuration that can supply to

  In the fuel cell system having such a configuration, for example, when the required power from the load is large, most of the power can be covered by the power generated by the fuel cell. On the other hand, when the required power from the load is small, power is supplied to the load while storing the surplus power generated by the fuel cell in the power storage device, or the power generation of the fuel cell is temporarily reduced or suspended to the load. Most of the power supply can be performed by discharging the power storage device. As described above, it is possible to operate the fuel cell system with high efficiency while simultaneously using the power storage and discharge of the power storage device.

  The following Patent Document 1 focuses on the fact that the power generation efficiency of the fuel cell is low when the generated power is increased and is high when the generated power is decreased, and further increases the operating efficiency of the fuel cell system in cooperation with the power storage device. Such a driving method is described. Specifically, when increasing the power output from the fuel cell system as the required power of the load increases, the increase in the generated power from the fuel cell is suppressed, and the shortage is covered by the discharge of the power storage device. ing. On the other hand, when the power output from the fuel cell system is reduced as the required power of the load decreases, the decrease in the generated power from the fuel cell is suppressed, and the surplus is stored in the power storage device.

  That is, power generation is suppressed when the power generation efficiency of the fuel cell is low, and power generation is promoted when the power generation efficiency is high. By performing the cooperation between the fuel cell and the power storage device in this way, the average operation efficiency of the fuel cell system is further improved.

JP 2008-186655 A

  The operation method of the fuel cell system described in Patent Document 1 emphasizes only the power generation efficiency of the fuel cell, and does not consider the state of the power storage device. That is, although the power that can be stored in the power storage device is finite, the operation is performed without considering the amount of stored power (SOC). As a result, the SOC becomes 100% depending on the change in the required power from the load. It may become impossible to store any more power. In this case, when the required power from the load is reduced, the reduction in the generated power of the fuel cell cannot be suppressed as described above, so that the operation efficiency of the fuel cell system is lowered.

  Conversely, the SOC may become 0% depending on the change in the required power from the load. In that case, when the required power from the load increases, the increase in the power generated by the fuel cell cannot be suppressed, and the operating efficiency of the fuel cell system will also decrease.

  Furthermore, since the operating method of the fuel cell system described in Patent Document 1 can vary in a wide range from 0% to 100%, the burden on the power storage device is large, and the power storage device deteriorates in a short period of time. There was also a problem that it would end up.

  The present invention has been made in view of such problems, and its object is to suppress the fluctuation range of the amount of electricity stored in the power storage device while improving the power generation efficiency of the fuel cell, and to suppress deterioration of the power storage device. It is an object of the present invention to provide a fuel cell system.

  In order to solve the above problems, a fuel cell system according to the present invention provides a required power for detecting the required power in a fuel cell system that outputs generated power from the fuel cell to the load based on the required power from the load. Detection means; control means for controlling the generated power; a power storage device connected in parallel to the fuel cell with respect to the load for storing and discharging; and a storage amount detection means for detecting a storage amount of the power storage device. The control device suppresses an increase in the generated power when the required power increases when the stored power amount is greater than a predetermined first stored power amount, and the stored power amount is When the amount of stored electricity is less than one storage amount, the storage amount adjustment control is performed to suppress a fluctuation range of the stored amount of electricity by suppressing a decrease in the generated power when the required power decreases. It is.

  In the present invention, when the required power from the load increases, the increase in the generated power from the fuel cell is suppressed, while when the required power decreases, the decrease in the generated power from the fuel cell is suppressed. Thereby, the operation efficiency of the fuel cell system can be improved. On the other hand, in the present invention, the increase in the generated power when the required power from the load is increased and the decrease in the generated power when the required power is decreased are not always performed, but the amount of power stored in the power storage device is reduced. Based on.

  Specifically, the increase in the generated power when the required power from the load increases is suppressed only when the power storage amount of the power storage device is larger than the predetermined first power storage amount. As a result of suppressing the increase in the generated power, the amount of power stored in the power storage device decreases to make up for the shortage with respect to the required power, and approaches the first power storage amount. Further, only when the amount of power stored in the power storage device is smaller than the predetermined first power storage amount, the reduction of the generated power when the required power from the load is reduced is suppressed. As a result of suppressing the decrease in the generated power, a surplus with respect to the required power is stored, so the amount of power stored in the power storage device increases and approaches the first power storage amount.

  Thus, in order to control the power storage amount of the power storage device to approach the first power storage amount as the generated power changes, the above control constitutes a power storage amount adjustment control that suppresses the fluctuation range of the power storage amount. . In the present invention, as a result of suppressing the fluctuation range of the storage amount by the storage amount adjustment control, the burden on the storage device is reduced, and the deterioration of the storage device can be suppressed.

  Furthermore, the amount of electricity stored in the electricity storage device is suppressed from reaching 0% or 100% by the above-described amount adjustment control of electricity. For this reason, the control which suppresses the increase in the output from a fuel cell, and the control which suppresses the decrease in the output from a fuel cell can always be made into an executable state.

  In the fuel cell system according to the present invention, as the difference between the storage amount and the first storage amount increases, the control device increases a suppression amount of the generated power when the required power increases. It is also preferable to perform control so that as the difference between the first power storage amount and the power storage amount increases, the suppression amount of the decrease in the generated power when the required power decreases is increased.

  In this preferable aspect, the control device performs control so that the amount of suppression of increase in generated power when the required power increases as the difference between the charged amount and the first charged amount increases, Control is performed such that the greater the difference from the amount of stored electricity, the greater the amount of suppression of reduction in generated power when the required power is reduced.

  The larger the difference between the amount of electricity stored in the electricity storage device and the first amount of electricity stored, the greater the amount of suppression of the increase in generated power when the required power increases. The power discharged from the device increases. For this reason, the amount of decrease in the charged amount is increased, and the charged amount can be made closer to the first charged amount.

  In addition, as the difference between the first power storage amount and the power storage amount of the power storage device is larger, the amount of surplus power stored in the power storage device is controlled to increase the amount of suppression of the decrease in generated power when the required power decreases. Becomes larger. For this reason, the amount of increase in the charged amount is increased, and the charged amount can be made closer to the first charged amount.

  That is, according to this preferable aspect, more appropriate storage amount adjustment control can be performed according to the storage amount of the power storage device, and the fluctuation range of the storage amount can be further suppressed.

  Further, in the fuel cell system according to the present invention, the control means feeds the generated power while feeding back a deviation between the charged amount and the first charged amount so that the charged amount converges to the first charged amount. It is also preferable to control.

  According to the power storage amount adjustment control described above, control is performed such that the power storage amount of the power storage device approaches the first power storage amount only when the required power from the load fluctuates. Therefore, in a situation where there is little variation in the required power from the load, a certain deviation may remain between the charged amount and the first charged amount.

  In this preferable aspect, the control means controls the generated power while feeding back the deviation between the charged amount and the first charged amount so that the charged amount converges to the first charged amount. As a result, even in a situation where there is little fluctuation in the required power from the load, the amount of electricity stored in the power storage device can be controlled to converge to the first electricity storage amount, and the fluctuation range of the electricity storage amount can be further suppressed.

  In the fuel cell system according to the present invention, it is also preferable that the control device performs a leveling process for suppressing fluctuations in the generated power.

  In a fuel cell, a phenomenon is known in which the power generation performance is lowered due to fluctuations in the output voltage. As the output voltage fluctuates, a part of the catalyst carried on the electrode of the fuel cell elutes and the effective area of the catalyst decreases. It is known that the decrease in power generation performance becomes more significant as the fluctuation range of the output voltage is larger and as the number of fluctuations of the output voltage is larger.

  In this preferred embodiment, the control device performs a leveling process that suppresses fluctuations in the generated power. Since the fluctuation of the generated power is suppressed by the leveling process, the fluctuation of the output voltage of the fuel cell is also suppressed. As a result, it is possible to suppress deterioration of the power generation performance of the fuel cell while suppressing deterioration of the power storage device by the storage amount adjustment control.

  In the fuel cell system according to the present invention, the control device does not perform the storage amount adjustment control when the storage amount is below a predetermined second storage amount that is smaller than the first storage amount. It is also preferable.

  In a situation where the amount of power stored in the power storage device is decreasing, there is little power that can be supplied to the load by discharging the power storage device. For this reason, power storage amount adjustment control cannot be performed appropriately, and the power output from the fuel cell system may be reduced. In addition, even when performing a leveling process that suppresses fluctuations in the generated power from the fuel cell, the difference between the leveled generated power and the required power cannot be compensated for by the discharge of the power storage device. You may not be able to do it.

  In this preferable aspect, the control device does not perform the power storage amount adjustment control when the power storage amount is below a predetermined second power storage amount that is smaller than the first power storage amount. Thereby, in the situation where the amount of electricity stored in the electricity storage device is decreasing, neither the amount adjustment control nor the leveling process is performed, and the output from the fuel cell system can be maintained by the generated power from the fuel cell.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell system which can suppress the fluctuation range of the electrical storage amount of an electrical storage apparatus, and can suppress degradation of an electrical storage apparatus, improving the electric power generation efficiency of a fuel cell can be provided.

It is the figure which showed the system configuration | structure of the fuel cell vehicle carrying the fuel cell system which is one Embodiment of this invention. 2 is a graph showing a change with time of power generated by the fuel cell in the fuel cell system shown in FIG. 1. 2 is a graph showing a change with time of power generated by the fuel cell in the fuel cell system shown in FIG. 1. It is a control block diagram which shows the control performed in the fuel cell system shown in FIG. It is a control block diagram which shows the control performed in the fuel cell system shown in FIG. It is a figure showing the gain map in the control block diagram shown in FIG. It is a control block diagram which shows the control performed in the fuel cell system shown in FIG. 2 is a flowchart showing control performed in the fuel cell system shown in FIG. 1.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same constituent elements in the drawings will be denoted by the same reference numerals as much as possible, and redundant description will be omitted.

  FIG. 1 is a diagram showing a system configuration of a fuel cell vehicle equipped with a fuel cell system 10 according to an embodiment of the present invention. The fuel cell system 10 functions as an in-vehicle power supply system mounted on a fuel cell vehicle. The fuel cell stack 20 generates electric power by receiving supply of reaction gas (fuel gas, oxidant gas), and oxidant gas. An oxidant gas supply system 30 (oxidant gas supply means) for supplying the air to the fuel cell stack 20 and a fuel gas supply system 40 (fuel for supplying hydrogen gas as fuel gas to the fuel cell stack 20) Gas supply means), a power system 50 for controlling charge / discharge of power, and a controller 60 (control means) for overall control of the entire system.

  The fuel cell stack 20 is a solid polymer electrolyte cell stack formed by stacking a large number of cells in series. In the fuel cell stack 20, the oxidation reaction of the formula (1) occurs at the anode electrode, and the reduction reaction of the equation (2) occurs at the cathode electrode. In the fuel cell stack 20 as a whole, the electromotive reaction of the formula (3) occurs.

H2 → 2H ++ 2e- (1)
(1/2) O2 + 2H ++ 2e-> H2O (2)
H2 + (1/2) O2 → H2O (3)

  A voltage sensor 71 for detecting the output terminal voltage (stack voltage Vc) of the fuel cell stack 20 and a current sensor 72 for detecting the output current (stack current) are attached to the fuel cell stack 20.

  The oxidant gas supply system 30 has an oxidant gas passage 33 through which the oxidant gas supplied to the cathode electrode of the fuel cell stack 20 flows and an oxidant off gas passage 34 through which the oxidant off-gas discharged from the fuel cell stack 20 flows. doing. The oxidant gas passage 33 has an air compressor 32 that takes in the oxidant gas from the atmosphere via the filter 31, a humidifier 35 for humidifying the oxidant gas pressurized by the air compressor 32, and a fuel cell stack. A shutoff valve A1 for shutting off the oxidant gas supply to 20 is provided. In the oxidizing off gas passage 34, a shutoff valve A2 for shutting off the oxidizing off gas discharge from the fuel cell stack 20, a back pressure adjusting valve A3 for adjusting the oxidizing gas supply pressure, and an oxidizing gas (dry gas). And a humidifier 35 for exchanging moisture between the gas and the oxidizing off gas (wet gas).

  The fuel gas supply system 40 includes a fuel gas supply source 41, a fuel gas passage 43 through which fuel gas supplied from the fuel gas supply source 41 to the anode electrode of the fuel cell stack 20 flows, and fuel discharged from the fuel cell stack 20. A circulation passage 44 for returning off-gas to the fuel gas passage 43, a circulation pump 45 for pressure-feeding the fuel off-gas in the circulation passage 44 to the fuel gas passage 43, and an exhaust / drain passage 46 branched and connected to the circulation passage 44 Have.

  The fuel gas supply source 41 is composed of, for example, a high-pressure hydrogen tank or a hydrogen storage alloy, and stores high-pressure (for example, 35 MPa to 70 MPa) hydrogen gas. When the shut-off valve H1 is opened, the fuel gas flows out from the fuel gas supply source 41 into the fuel gas passage 43. The fuel gas is decompressed to about 200 kPa, for example, by the regulator H2 and the injector 42, and supplied to the fuel cell stack 20.

  The fuel gas supply source 41 includes a reformer that generates a hydrogen-rich reformed gas from a hydrocarbon-based fuel, and a high-pressure gas tank that stores the reformed gas generated by the reformer in a high-pressure state. It may be configured.

  In the fuel gas passage 43, a shutoff valve H1 for shutting off or allowing the supply of the fuel gas from the fuel gas supply source 41, a regulator H2 for adjusting the pressure of the fuel gas, and a fuel gas supply to the fuel cell stack 20 An injector 42 for controlling the amount, a shutoff valve H3 for shutting off the supply of fuel gas to the fuel cell stack 20, and a pressure sensor 74 are provided.

  The regulator H2 is a device that regulates the upstream side pressure (primary pressure) to a preset secondary pressure, and includes, for example, a mechanical pressure reducing valve that reduces the primary pressure. The mechanical pressure reducing valve has a housing in which a back pressure chamber and a pressure adjusting chamber are formed with a diaphragm therebetween, and the primary pressure is reduced to a predetermined pressure in the pressure adjusting chamber by the back pressure in the back pressure chamber. It has a configuration for the next pressure. By arranging the regulator H2 upstream of the injector 42, the upstream pressure of the injector 42 can be effectively reduced. For this reason, the design freedom of the mechanical structure (a valve body, a housing, a flow path, a drive device, etc.) of the injector 42 can be increased. Further, since the upstream pressure of the injector 42 can be reduced, it is possible to prevent the valve body of the injector 42 from becoming difficult to move due to an increase in the differential pressure between the upstream pressure and the downstream pressure of the injector 42. be able to. Therefore, it is possible to widen the adjustable pressure width of the downstream pressure of the injector 42 and to suppress a decrease in responsiveness of the injector 42.

  The injector 42 is an electromagnetically driven on-off valve capable of adjusting the gas flow rate and gas pressure by driving the valve body directly at a predetermined driving cycle with an electromagnetic driving force and separating it from the valve seat. The injector 42 includes a valve seat having an injection hole for injecting gaseous fuel such as fuel gas, a nozzle body for supplying and guiding the gaseous fuel to the injection hole, and an axial direction (gas flow direction) with respect to the nozzle body. And a valve body that is slidably accommodated and opens and closes the injection hole.

  In the present embodiment, the valve element of the injector 42 is driven by a solenoid that is an electromagnetic drive device, and the opening area of the injection hole can be switched in two stages by turning on and off the pulsed excitation current supplied to the solenoid. it can. By controlling the gas injection time and gas injection timing of the injector 42 by the control signal output from the controller 60, the flow rate and pressure of the fuel gas are controlled with high accuracy. The injector 42 directly opens and closes the valve (valve body and valve seat) with an electromagnetic driving force, and has a high responsiveness because its driving cycle can be controlled to a highly responsive region. The injector 42 changes its downstream area by changing at least one of the opening area (opening) and the opening time of the valve provided in the gas flow path of the injector 42 in order to supply the required gas flow rate downstream. The gas flow rate (or hydrogen molar concentration) supplied to the side is adjusted.

  The circulation passage 44 is connected to a shutoff valve H4 for shutting off the fuel off-gas discharge from the fuel cell stack 20 and an exhaust drainage passage 46 branched from the circulation passage 44. An exhaust / drain valve H5 is disposed in the exhaust / drain passage 46. The exhaust / drain valve H <b> 5 is operated according to a command from the controller 60, thereby discharging the fuel off-gas containing impurities in the circulation passage 44 and moisture to the outside. By opening the exhaust / drain valve H5, the concentration of impurities in the fuel off-gas in the circulation passage 44 decreases, and the hydrogen concentration in the fuel off-gas circulating in the circulation system can be increased.

  The fuel off-gas discharged through the exhaust / drain valve H5 is mixed with the oxidizing off-gas flowing through the oxidizing off-gas passage 34 and diluted by a diluter (not shown). The circulation pump 45 circulates and supplies the fuel off gas in the circulation system to the fuel cell stack 20 by driving the motor.

  The power system 50 includes a DC / DC converter 51, a battery 52, a traction inverter 53, a traction motor 54, and auxiliary machinery 55. The fuel cell system 10 is configured as a parallel hybrid system in which a DC / DC converter 51 and a traction inverter 53 are connected to the fuel cell stack 20 in parallel. The DC / DC converter 51 boosts the DC voltage supplied from the battery 52 and outputs it to the traction inverter 53, and the DC power generated by the fuel cell stack 20, or the regenerative power collected by the traction motor 54 by regenerative braking. And a function of charging the battery 52 by stepping down the voltage. The charge / discharge of the battery 52 is controlled by these functions of the DC / DC converter 51. Further, the operation point (output voltage, output current) of the fuel cell stack 20 is controlled by voltage conversion control by the DC / DC converter 51.

  The battery 52 functions as a surplus power storage source, a regenerative energy storage source during regenerative braking, and an energy buffer during load fluctuations associated with acceleration or deceleration of the fuel cell vehicle. As the battery 52, for example, a secondary battery such as a nickel / cadmium storage battery, a nickel / hydrogen storage battery, or a lithium secondary battery is suitable. An SOC sensor 73 for detecting SOC (State of charge) is attached to the battery 52.

  The traction inverter 53 is, for example, a PWM inverter driven by a pulse width modulation method, and converts a DC voltage output from the fuel cell stack 20 or the battery 52 into a three-phase AC voltage in accordance with a control command from the controller 60. The rotational torque of the traction motor 54 is controlled. The traction motor 54 is a three-phase AC motor, for example, and constitutes a power source of the fuel cell vehicle.

  Auxiliary machines 55 are motors (for example, power sources such as pumps) arranged in each part in the fuel cell system 10, inverters for driving these motors, and various on-vehicle auxiliary machines. (For example, an air compressor, an injector, a cooling water circulation pump, a radiator, etc.) is a general term.

  The controller 60 is a computer system including a CPU, a ROM, a RAM, and an input / output interface, and controls each part of the fuel cell system 10. For example, when the controller 60 detects that the state of the ignition switch IG is ON, the controller 60 starts the operation of the fuel cell system 10 and is output from the accelerator opening signal ACC output from the accelerator sensor or the vehicle speed sensor. The required power from the load is obtained based on the vehicle speed signal VV and the like. That is, the controller 60 has a function as required power detection means for detecting required power. The required power from the load is the total value of the vehicle running power and the auxiliary machine power.

  Here, the auxiliary power is the power consumed by auxiliary equipment such as a humidifier, an air compressor, a hydrogen pump, and a cooling water circulation pump. That is, in the fuel cell system 10 of the present embodiment, the traction motor 54 and the auxiliary machine, which are power sources of the fuel cell vehicle, correspond to a load that receives power supply from the fuel cell system 10.

  Then, the controller 60 determines the distribution of the output power of each of the fuel cell stack 20 and the battery 52, and the oxidant gas supply system 30 and the fuel so that the generated power FP of the fuel cell stack 20 matches the target power. The operating point (output voltage, output current) of the fuel cell stack 20 is controlled by controlling the gas supply system 40 and the DC / DC converter 51 to adjust the output voltage of the fuel cell stack 20. Further, the controller 60 outputs, for example, each of the U-phase, V-phase, and W-phase AC voltage command values to the traction inverter 53 as a switching command so as to obtain a target torque corresponding to the accelerator opening, The output torque of the motor 54 and the rotation speed are controlled.

  In the fuel cell system 10 of the present embodiment, as described above, the control by the controller 60 is performed so that the power supplied (output) from the fuel cell system 10 to the load changes according to the change in the required power RP from the load. Is done. The time change of the required power RP, the generated power FP of the fuel cell stack 20, and the system power SP actually supplied from the fuel cell system 10 to the load will be described with reference to FIGS.

  FIG. 2 shows the generated power FP when the required power RP from the load changes in a situation where the SOC of the battery 52 is less than 50%, which is the target storage amount TSOC (first storage amount) that is the target value. And it is a graph which shows the time change of system electric power SP. FIG. 2 shows a time change when the required power RP decreases from W0 to W1 at time t1, and then the required power RP decreases from W1 to W0 at time t2.

  When the required power RP increases from W0 to W1 at time t1, the controller 60 immediately increases the generated power FP of the fuel cell stack 20 to W1. That is, the power output of the fuel cell system 10 is controlled so that the required power RP is entirely covered by the generated power FP. For this reason, the generated power FP and the system power SP are equal from the time t1 to the time t2.

  Subsequently, when the required power RP decreases from W1 to W0 at time t2, the controller 60 decreases the generated power FP of the fuel cell stack 20 to W0. At this time, the control is performed so as not to immediately decrease to W0 but to suppress the decrease in the generated power FP and to reduce the decrease rate. At this time, a surplus is generated in the generated power FP, but the surplus is stored in the battery 52. As a result, the system power SP supplied from the fuel cell system 10 to the load immediately decreases to W0.

  At time t2, since the generated power FP of the fuel cell stack 20 so far was large, the proton conductivity of the polymer electrolyte membrane has been improved, and the fuel cell stack 20 is generating power with high power generation efficiency. It has become. It is known that the proton conductivity of the polymer electrolyte membrane does not decrease immediately even if the generated power FP of the fuel cell stack 20 is decreased thereafter, but decreases with a certain delay. That is, the power generation efficiency is high when the generated power FP of the fuel cell stack 20 is reduced.

  Therefore, in the present embodiment, as described above, even after time t2 when the system power SP decreases, the generated power FP in the fuel cell stack 20 is not immediately decreased, so that the power generation is performed with high power generation efficiency. We are using. Since the surplus of the generated power FP at this time is stored in the battery 52, the SOC of the battery 52 can be brought close to the target storage amount TSOC of 50%. Note that the target power storage amount TSOC is not limited to 50%, and is appropriately set according to the type and configuration of the battery 52. Generally, it is set in the range of 40% to 80%.

  On the other hand, at time t1, the generated electric power FP of the fuel cell stack 20 so far has been small, so the proton conductivity of the polymer electrolyte membrane is reduced, and the fuel cell stack 20 is generating power with low power generation efficiency. It is in a state. It is known that the proton conductivity of the polymer electrolyte membrane does not increase immediately even if the generated power FP of the fuel cell stack 20 is increased thereafter, but increases with a certain delay. That is, when the generated power FP of the fuel cell stack 20 is increased, the power generation efficiency is low.

  For this reason, it is desirable from the viewpoint of power generation efficiency of the fuel cell stack 20 that the generated power FP of the fuel cell stack 20 is not immediately increased after time t1 and the shortage is compensated by discharge from the battery 52. However, in that case, the SOC of the battery 52 is further reduced. If the SOC further decreases from a state where the SOC is less than the target power storage amount TSOC of 50%, the burden on the battery 52 increases and the battery 52 deteriorates in a short period of time. Therefore, in the present embodiment, as shown in FIG. 2, in the situation where the SOC of the battery 52 is less than 50%, which is the target charged amount TSOC (first charged amount), the generated power FP is immediately increased at time t1. That is, the generated power FP of the fuel cell stack 20 is controlled while taking into consideration both the SOC variation of the battery 52 and the power generation efficiency of the fuel cell stack 20.

  FIG. 3 shows the state of the generated power FP and the system power SP when the required power RP from the load changes in a situation where the SOC of the battery 52 is larger than 50%, which is the target power storage amount TSOC (first power storage amount). It is a graph which shows a time change. FIG. 3 shows a time change when the required power RP decreases from W1 to W0 at time t4 after the required power RP increases from W0 to W1 at time t3.

  Unlike the case of FIG. 2, when the required power RP increases from W0 to W1 at time t3, the controller 60 does not immediately increase the generated power FP of the fuel cell stack 20 to W1, but suppresses the increase in the generated power FP, Control the increase rate to be gradual. At this time, the generated power FP alone is less than the required power RP, but the shortage is compensated by the discharge from the battery 52. As a result, the system power SP supplied from the fuel cell system 10 to the load immediately increases to W1.

  At time t3, since the generated power FP of the fuel cell stack 20 until then was small, the proton conductivity of the polymer electrolyte membrane was lowered, and the fuel cell stack 20 was generating power with low power generation efficiency. It has become. It is known that the proton conductivity of the polymer electrolyte membrane does not increase immediately even if the generated power FP of the fuel cell stack 20 is increased thereafter, but increases with a certain delay. That is, when the generated power FP of the fuel cell stack 20 is increased, the power generation efficiency is low.

  Therefore, in the present embodiment, as described above, even after the time t3 when the system power SP increases, the power generation FP in the fuel cell stack 20 is not immediately increased, thereby suppressing power generation in a state where the power generation efficiency is low. Yes. Since the shortage of the generated power FP at this time is compensated by the discharge of the battery 52, the SOC of the battery 52 is reduced, and the SOC can be brought close to 50% that is the target charged amount TSOC.

  On the other hand, when the required power RP decreases from W1 to W0 at time t4, the controller 60 immediately decreases the generated power FP of the fuel cell stack 20 to W0. That is, the power output of the fuel cell system 10 is controlled so that the surplus of the generated power FP does not occur.

  At time t4, since the generated power FP of the fuel cell stack 20 so far was large, the proton conductivity of the polymer electrolyte membrane has been improved, and the fuel cell stack 20 is generating power with high power generation efficiency. It has become. It is known that the proton conductivity of the polymer electrolyte membrane does not decrease immediately even if the generated power FP of the fuel cell stack 20 is decreased thereafter, but decreases with a certain delay. That is, the power generation efficiency is high when the generated power FP of the fuel cell stack 20 is reduced.

  Therefore, it is desirable from the viewpoint of power generation efficiency of the fuel cell stack 20 that the generated power FP of the fuel cell stack 20 is not immediately decreased after time t4 and the surplus is stored in the battery 52. However, in that case, the SOC of the battery 52 further increases. If the SOC further increases from the situation where the SOC is greater than the target power storage amount TSOC of 50%, the burden on the battery 52 increases and the battery 52 deteriorates in a short period of time. Therefore, in the present embodiment, as shown in FIG. 3, in a situation where the SOC of the battery 52 is larger than 50%, which is the target charged amount TSOC (first charged amount), the generated power FP is immediately reduced at time t4. That is, the generated power FP of the fuel cell stack 20 is controlled while taking into consideration both the SOC variation of the battery 52 and the power generation efficiency of the fuel cell stack 20.

  As described above, in the fuel cell system 10 according to the present embodiment, when the required power RP from the load increases, the increase in the generated power FP from the fuel cell stack 20 is suppressed, while the decrease in the required power RP. In some cases, a decrease in the generated power FP from the fuel cell stack 20 is suppressed. Thereby, the operation efficiency of the fuel cell system 10 is improved. On the other hand, in the fuel cell system 10 according to the present embodiment, the suppression of the increase in the generated power FP when the required power RP from the load increases and the suppression of the decrease in the generated power FP when the required power RP decreases are always performed. This is not based on the SOC of the battery 52. In order to control the SOC of the battery 52 so as to approach 50%, which is the target storage amount TSOC, with the change in the generated power FP, the above control constitutes a storage amount adjustment control that suppresses the fluctuation range of the SOC.

  In this embodiment, the fluctuation range of the SOC is suppressed by the power storage amount adjustment control, so that the burden on the battery 52 is reduced and the deterioration of the battery 52 is suppressed. Further, by suppressing the fluctuation range of the SOC, there is an advantage that the capacity of the battery 52 can be reduced and the battery 52 can be reduced in size.

  Furthermore, the SOC of the battery 52 is suppressed from reaching 0% or 100% by the power storage amount adjustment control. For this reason, the control which suppresses the increase of the above-mentioned generated electric power FP and the control which suppresses the reduction | decrease in the generated electric power FP are always executable.

  Next, the specific contents of the power storage amount adjustment control described above will be described in more detail with reference to FIGS. 4, 5, and 6. FIG. 4 is a control block diagram showing the contents performed by the controller 60, and shows processing for controlling the generated power FP based on the required power RP and the SOC.

  As shown in FIG. 4, the controller 60 generates a generated power command value SFP, which is a control command value of the generated power FP, based on the required power RP, the SOC of the battery 52, and the target charged amount TSOC that is the target value of SOC. decide. The controller 60 controls the flow rate of the fuel gas and the DC / DC converter 51 so that the generated power FP matches the generated power command value SFP.

  In FIG. 4, the control block CT1 receives input of the required power RP and the SOC and determines how to change the generated power FP. The control block CT1 outputs a temporary command value SFP0 as a temporary value of the generated power command value SFP. Specific processing of the control block CT1 will be described later.

  The SOC of the battery 52 is set with a target charged amount TSOC (first charged amount) as its target value. The controller 60 calculates the deviation between the SOC and the target charged amount TSOC (reference numeral SM2) and inputs it to the PID control block P1. The PID control block P1 is a control block that calculates a necessary addition amount with respect to the generated power command value SFP with normal PID in order to set the deviation to zero.

  For example, when the SOC is lower than the target power storage amount TSOC, the PID control block P1 calculates an addition to the generated power command value SFP necessary to compensate for this shortage, and the controller 60 calculates the addition. It is added to the temporary command value SFP0 (symbol SM1). As a result, the generated power command value SFP increases accordingly, and the generated power FP also increases accordingly. Therefore, the increased power compensates for the shortage of SOC, and the SOC approaches the target charged amount TSOC. In addition, since the internal processing of the PID control block P1 includes the integral term (I), it is suppressed that a steady deviation is generated between the SOC and the target charged amount TSOC.

  That is, the controller 60 controls the generated power FP while feeding back the deviation between the SOC and the target charged amount TSOC so that the SOC converges to the target charged amount TSOC. Thus, the SOC of the battery 52 is controlled so as to converge to the target charged amount TSOC even in a situation where the required power RP from the load is small, and the fluctuation range of the SOC is further suppressed.

  Next, specific processing of the control block CT1 will be described with reference to FIG. FIG. 5 is a control block diagram showing the contents performed by the controller 60, and shows the specific processing performed inside the control block CT1 shown in FIG. As described above, the control block CT1 is a control block that receives the input of the required power RP and the SOC and determines how to change the generated power FP. The controller 60 calculates the generated power command value SFP by adding the addition calculated by the PID control block P1 to the temporary command value SFP0 output by the control block CT1.

  The basic processing in the control block CT1 is to calculate a deviation between the input required power RP and the current temporary command value SFP0 (reference numeral SM3), multiply this by a gain (gain PG or gain MG), and output it. The power provisional command value SFP0 is calculated. However, it is characterized in that by providing the saturators PST and MST, different gains (gain PG and gain MG, respectively) are multiplied when the deviation between the required power RP and the temporary command value SFP0 is positive and negative. Is.

  The saturator PST is a control block that passes a signal only when the deviation is positive, that is, when the required power RP is larger than the temporary command value SFP0, and outputs 0 at other times. The saturator MST is a control block that passes a signal only when the deviation is negative, that is, when the required power RP is smaller than the temporary command value SFP0, and outputs 0 at other times. Therefore, when the required power RP is larger than the temporary command value SFP0, the gain PG is multiplied by the deviation between the two, and when the required power RP is smaller than the temporary command value SFP0, the gain is gained with respect to both the deviations. MG is multiplied.

  Here, the gain PG and the gain MG are not fixed values, and the values are changed by the SOC of the battery 52. Specifically, the value is determined with reference to the gain map shown in FIG.

  FIG. 6 is a diagram illustrating a gain map PGM that defines the relationship between the SOC and the gain PG, and a gain map MGM that defines the relationship between the SOC and the gain MG. As shown in FIG. 6, the gain map PGM has a constant value G0 when the SOC is 50% or less, which is the target charged amount TSOC. On the other hand, when the SOC exceeds 50%, which is the target power storage amount TSOC, the value is set to gradually decrease as the SOC increases.

  On the other hand, the gain map MGM has a constant value G0 when the SOC is 50% or more, which is the target storage amount TSOC. On the other hand, when the SOC falls below 50%, which is the target power storage amount TSOC, the value is set to gradually decrease as the SOC decreases.

  In the fuel cell system 10 according to the present embodiment, as a result of the gain map PGM and the gain map MGM being set as described above in the controller 60, the power storage amount adjustment control already described is performed, and the change in the required power RP The corresponding change in the generated power FP is as shown in FIGS.

  That is, when the required power RP increases, the deviation between the required power RP and the temporary command value SFP0 becomes positive. At this time, the gain PG multiplied by the deviation becomes a high value (G0) when the SOC is smaller than the target charged amount TSOC, so the temporary command value SFP0 immediately increases. As a result, the generated power FP immediately increases (from time t1 to time t2 in FIG. 2). On the other hand, when the SOC is larger than the target charged amount TSOC, the value of the gain PG decreases as the SOC increases. Therefore, the increase in the temporary command value SFP0 is suppressed. As a result, the increase in the generated power FP is suppressed, and the increasing speed of the generated power FP becomes slow (from time t3 to time t4 in FIG. 3).

  Further, when the required power RP decreases, the deviation between the required power RP and the temporary command value SFP0 becomes negative. At this time, the gain MG multiplied by the deviation becomes a high value (G0) when the SOC is larger than the target charged amount TSOC, and therefore the temporary command value SFP0 immediately decreases. As a result, the generated power FP decreases immediately (after time t4 in FIG. 3). On the other hand, when the SOC is smaller than the target charged amount TSOC, the gain MG decreases as the SOC decreases, and thus the decrease in the temporary command value SFP0 is suppressed. As a result, the decrease in the generated power FP is suppressed, and the decrease rate of the generated power FP becomes slow (after time t2 in FIG. 2).

  Thus, in the present embodiment, by having the gain maps PGM and MGM set so that the gain changes according to the SOC, the storage amount adjustment control as shown in FIGS. 2 and 3 is realized. Yes.

  According to the gain map PGM, the greater the difference between the SOC of the battery 52 and the target charged amount TSOC (the greater the SOC), the greater the amount of suppression of the increase in the generated power FP when the required power RP increases. In order to control, the electric power discharged from the battery 52 is increased in order to compensate for the shortage with respect to the required power RP. For this reason, the amount of decrease in the SOC increases, and the SOC can be brought closer to the target charged amount TSOC.

  Further, according to the gain map MGM, the greater the difference between the target charged amount TSOC and the SOC of the battery 52 (the smaller the SOC), the greater the amount of suppression of the decrease in the generated power FP when the required power RP decreases. Thus, the surplus power stored in the battery 52 is increased. For this reason, the increase amount of SOC becomes large, and it is possible to bring the SOC closer to the target power storage amount TSOC.

  Returning to FIG. 5 again, the control block CT1 multiplies the deviation between the required power RP and the provisional command value SFP0 by a gain (PG or MG), and then performs an integration process (symbol ITG). Is used to calculate the provisional command value SFP0. By performing the integration process, the temporary command value SFP0 is suppressed from rapidly changing. As a result, since fluctuations in the generated power FP are also suppressed, the integration process corresponds to a leveling process that suppresses fluctuations in the generated power FP.

  The leveling process suppresses fluctuations in the generated power FP and suppresses fluctuations in the stack voltage Vc. That is, in the fuel cell system 10 according to the present embodiment, the deterioration of the power generation performance of the fuel cell stack 20 is also suppressed while the deterioration of the battery 52 is suppressed by the storage amount adjustment control.

  The leveling process is not limited to the integration process as described above, and various methods can be employed. For example, the required power RP may not be input directly to the control block CT1, but may be input to the control block CT1 after performing a moving average process.

  Next, the control of the fuel cell system 10 performed when the SOC decreases and the output performance of the battery 52 decreases will be described. In a situation where the SOC of the battery 52 is lowered, there is little power that can be supplied to the load by discharging the battery 52. For this reason, the power storage amount adjustment control described so far cannot be appropriately performed, and the power output (system power SP) from the fuel cell system 10 may be reduced. Further, even when performing the leveling process that suppresses fluctuations in the generated power FP, the difference between the leveled generated power FP and the required power RP cannot be compensated for by the discharge of the battery 52, and the leveling process is appropriately performed. It may not be possible.

  For this reason, the fuel cell system 10 according to the present embodiment includes a switch SW1 that switches between execution and stop of the storage amount adjustment control and the leveling process. FIG. 7 is a control block diagram showing control performed in the fuel cell system 10. As apparent from FIG. 7, when the switch SW1 is ON, the control performed by the controller 60 is the same as that shown in the control block diagrams of FIGS. Both leveling processes are executed.

  On the other hand, when the switch SW1 is OFF in FIG. 7, neither the storage amount adjustment control nor the leveling process is executed. In this case, the generated power command value SFP is obtained by adding the required power RP and the output value of the PID control block P1 (symbol SM6). For this reason, neither reduction in the power generation efficiency of the fuel cell stack 20 nor fluctuation of the stack voltage Vc is suppressed, and the recovery of the SOC of the battery 52 is prioritized.

  Switching of the switch SW1 shown in FIG. 7 will be described with reference to FIG. FIG. 8 is a flowchart showing the control performed by the controller 60, and shows the contents of the control in which the controller 60 switches the switch SW1 based on the SOC. The series of processing shown in FIG. 8 is repeatedly executed by the controller 60 every time a predetermined time elapses during operation of the fuel cell system 10.

  First, in step S01, it is determined whether the SOC of the battery 52 has decreased. Specifically, the controller 60 stores a lower limit storage amount LSOC (for example, 20%) that is lower than the target storage amount TSOC (50% in the present embodiment), and the SOC is equal to or greater than the lower limit storage amount LSOC. It is determined whether or not.

  When the SOC is equal to or higher than the lower limit storage amount LSOC, the controller 60 determines that the storage amount adjustment control and the leveling process can be performed, and switches the switch SW1 to ON (step S02). On the other hand, when the SOC is lower than the lower limit storage amount LSOC, the controller 60 determines that the storage amount adjustment control and the leveling process cannot be performed, and switches the switch SW1 to OFF (step S03).

  Since the control shown in FIG. 10 is always repeatedly executed during operation of the fuel cell system 10, if the SOC becomes equal to or higher than the lower limit storage amount LSOC, the switch SW1 is turned on at that time. If the SOC is lower than the lower limit storage amount LSOC, the switch SW1 is turned OFF at that time.

  As a result of the control as described above, in the fuel cell system 10 according to the present embodiment, the controller 60 falls below a predetermined lower limit storage amount LSOC (second storage amount) where the SOC is lower than the target storage amount TSOC. If it is, the power storage amount adjustment control is not performed. Thereby, in the situation where the amount of electricity stored in the electricity storage device is decreasing, neither the amount adjustment control nor the leveling process is performed, and the output from the fuel cell system 10 can be maintained by the generated power FP.

  The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. In other words, those specific examples that have been appropriately modified by those skilled in the art are also included in the scope of the present invention as long as they have the characteristics of the present invention. For example, the elements included in each of the specific examples described above and their arrangement, materials, conditions, shapes, sizes, and the like are not limited to those illustrated, but can be changed as appropriate. Moreover, each element with which each embodiment mentioned above is provided can be combined as long as technically possible, and the combination of these is also included in the scope of the present invention as long as it includes the features of the present invention.

10: Fuel cell system 20: Fuel cell stack 30: Oxidant gas supply system 31: Filter 32: Air compressor 33: Oxidant gas passage 34: Oxidation off-gas passage 35: Humidifier 40: Fuel gas supply system 41: Fuel gas supply Source 42: Injector 43: Fuel gas passage 44: Circulation passage 45: Circulation pump 46: Exhaust drain passage 50: Electric power system 51: DC / DC converter 52: Battery 53: Traction inverter 54: Traction motor 55: Auxiliary machinery 60: Controller 71: Voltage sensor 72: Current sensor 73: SOC sensor 74: Pressure sensor A2: Shut-off valve A3: Back pressure adjustment valve ACC: Accelerator opening signal VV: Vehicle speed signal FP: Generated power H1: Shut-off valve H2: Regulator H3: Shut-off valve H4: Shut-off valve H5: Exhaust drain valve IG: Igni Switch PG, MG: Gain PGM, MGM: Gain map PST, MST: Saturator RP: Required power SP: System power SFP: Generated power command value SFP0: Temporary command value SW1: Switch TSOC: Target energy storage LSOC: Lower limit energy storage Vc: Stack voltage

Claims (4)

In the fuel cell system for outputting the generated power from the fuel cell to the load based on the required power from the load,
Requested power detection means for detecting the required power;
A control device for controlling the generated power;
A power storage device connected in parallel to the fuel cell with respect to the load for performing power storage and discharge;
A storage amount detection means for detecting a storage amount of the power storage device;
With
The controller is
If the amount of stored electricity is greater than a predetermined first stored amount of electricity, suppress the increase in the generated power when the required power increases,
When the amount of stored electricity is less than the first stored amount of electricity, by suppressing the decrease in the generated power when the required power is reduced,
There rows storage amount adjustment control of suppressing the fluctuation width of the charged amount, further, on the basis of a predetermined value which varies by the storage amount and the required power, leveling processing for calculating the provisional command value by performing an integration process The fuel cell system characterized by performing . The controller is
As the difference between the amount of stored electricity and the first amount of stored electricity is larger, the amount of suppression of increase in the generated power when the required power is increased is controlled,
The control is performed such that as the difference between the first power storage amount and the power storage amount increases, the amount of suppression of the decrease in the generated power when the required power decreases is increased. Fuel cell system. The control device controls the generated power while feeding back a deviation between the storage amount and the first storage amount so that the storage amount converges to the first storage amount. The fuel cell system according to claim 1 or 2. The control device does not perform the storage amount adjustment control when the storage amount is below a predetermined second storage amount that is smaller than the first storage amount. 4. The fuel cell system according to any one of 3 .

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