Power supply systems, power supply methods

Abstract

The present invention provides a power supply system and power supply method that can suppress the accelerated degradation of fuel cells. [Solution] When the electrical load fluctuates, the fuel cell supplies power to the electrical load at its rated output without changing its output. The energy storage device adjusts its output to follow the fluctuations in the required power and supplies power to the electrical load. Therefore, the power supply system can supply power that corresponds to the fluctuations in the required power of the electrical load by the combined output of the fuel cell and the energy storage device.

Description

Technical Field

[0001] The present invention relates to a power supply system and a power supply method.

Background Art

[0002] The control device of the system described in Patent Document 1 causes power to be supplied to the load by discharging the storage battery until the fuel cell becomes capable of power supply after starting up. When the fuel cell becomes capable of power supply, the control device increases the output of the fuel cell. When the output of the fuel cell is greater than the load power, charging of the storage battery is performed with the differential power. When the output of the fuel cell is less than the load power, the differential power is supplemented by discharging from the storage battery.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, when the remaining capacity of the fuel cell reaches a specified value, the output value of the fuel cell is controlled to be the same as the load power. Also, when the load fluctuation value is below a threshold value, power is supplied to the load only from the output of the fuel cell. That is, the output of the fuel cell varies according to changes in the remaining capacity of the fuel cell, the load power fluctuation value, etc. When the output of the fuel cell fluctuates frequently, the fuel cell may be promoted to deteriorate.

[0005] An object of the present invention is to provide a power supply system and a power supply method capable of suppressing the promotion of deterioration of a fuel cell.

Means for Solving the Problems

[0006] According to a first aspect of the present invention, a power supply system is provided comprising a fuel cell capable of generating electricity by reacting a fuel and an oxidizer and supplying power to an electrical load, a power storage device capable of supplying power to the electrical load, and a control unit, wherein the power supply system supplies the necessary power required by the electrical load using the combined output of the fuel cell and the power storage device, wherein the control unit does not change the output of the fuel cell when the necessary power of the electrical load fluctuates while the output of the fuel cell is at a predetermined value, and the power storage device supplies power to the electrical load in accordance with the fluctuations in the necessary power of the electrical load.

[0007] The control unit adjusts the output of the energy storage device when the power requirement of the electrical load fluctuates, thereby maintaining the fuel cell output at a predetermined value. Therefore, even if the power requirement of the electrical load fluctuates, the fuel cell output does not fluctuate. Consequently, the power supply system can suppress the accelerated deterioration of the fuel cell.

[0008] According to a second aspect of the present invention, a power supply system is provided comprising a fuel cell capable of generating electricity by reacting a fuel and an oxidizer and supplying power to an electrical load, a power storage device capable of supplying power to the electrical load, and a control unit, wherein the power supply method is provided in which the power required by the electrical load is supplied by the sum of the output of the fuel cell and the output of the power storage device, wherein when the required power of the electrical load fluctuates while the output of the fuel cell is at a predetermined value, the control unit does not fluctuate the output of the fuel cell, and the power storage device supplies power to the electrical load in accordance with the fluctuations in the required power of the electrical load.Therefore, the same effects as in the first aspect are obtained. [Brief explanation of the drawing]

[0009] [Figure 1] This is a block diagram illustrating the schematic configuration of power supply system 1. [Figure 2] This is a block diagram of control circuit 4. [Figure 3] This is a flowchart of the power supply process. [Figure 4]This is a continuation of the power supply processing flowchart in Figure 3. [Figure 5] This graph shows the changes in the power requirements of electrical load 30, the output of fuel cell 8, the output of energy storage device 5, and the remaining charge of energy storage device 5. [Modes for carrying out the invention]

[0010] One embodiment of the present invention is described below. The referenced drawings are used to illustrate the technical features that the present invention may adopt. That is, the configurations, controls, etc., shown in the drawings are not intended to limit the invention to those shown, but are merely illustrative examples.

[0011] <Configuration of Power Supply System 1> Referring to Figures 1 and 2, the configuration of the power supply system 1 of this embodiment will be described. The power supply system 1 can start the fuel cell 8 and supply power to the electrical load 30. Figure 1 shows the main configuration of the power supply system 1. Switches, relays, circuit switching devices, interface circuits, drive circuits, etc., are well known and are therefore omitted.

[0012] The power supply system 1 includes a fuel cell 8. The fuel cell 8 generates electricity using hydrogen supplied from a hydrogen supply source 6. The hydrogen supply source 6 can be a hydrogen storage alloy tank, a hydrogen gas cylinder, or the like. A hydrogen storage alloy tank is a container that houses a hydrogen storage alloy that releases hydrogen through an endothermic reaction. A hydrogen gas cylinder is a container filled with gaseous hydrogen under high pressure. The fuel cell 8 may also generate electricity using fuels other than hydrogen, such as methanol, methane gas, ammonia, or bioethanol.

[0013] The power supply system 1 further includes a control circuit 4, an AC input terminal 13, an AC / DC converter 10, a DC output terminal 14, a power storage device 5, a DC / DC converter 9, and an operation panel 28. The control circuit 4 controls the power supply system 1. Specifically, the control circuit 4 controls the fuel cell 8, the power storage device 5, the DC / DC converter 9, and the hydrogen supply source 6.

[0014] As shown in Figure 2, the control circuit 4 includes a CPU 41, RAM 42, ROM 43, non-volatile memory 44, and an input / output interface 45. The CPU 41 controls the power supply system 1 and executes programs for power supply processing, which will be described later. The RAM 42 temporarily stores data necessary when executing various processes. The ROM 43 stores various programs. The non-volatile memory 44 stores various setting values ​​necessary for program execution.

[0015] The input / output interface 45 mediates the input and output of signals between the CPU 41 and the energy storage device 5, fuel cell 8, hydrogen supply source 6, DC-DC converter 9, and control panel 28. The control circuit 4 may use a dedicated circuit board that performs the power supply processing described later.

[0016] A grid power supply 20 can be connected to the AC input terminal 13. An example of a grid power supply 20 is commercial power. An AC / DC converter 10 is connected to the AC input terminal 13. The AC / DC converter 10 converts the AC voltage of the grid power supply 20 to a DC voltage. A power supply line 31 is connected to the AC / DC converter 10.

[0017] A diode 37 is placed on the power supply line 31. The diode 37 rectifies the direction of the current flowing through the power supply line 31 so that it flows from the AC / DC converter 10 towards the connection point 51. The power supply line 31 is connected to power supply lines 32 and 34 via the connection point 51. The power supply line 32 is connected to power supply lines 33 and 35 via the connection point 52.

[0018] A power storage device 5 is connected to the power supply line 35. The power supply system 1 is used with the power storage device 5 pre-charged to, for example, 100%. The grid power supply 20 is connected to the AC input terminal 13 when charging the power storage device 5. Power output from the grid power supply 20 is supplied to the power storage device 5 via power supply lines 31, 32, and 35.

[0019] In addition, the power storage device 5 supplies power to the control circuit 4 via the power supply line 36. The remaining amount of the power storage device 5 is detected by a battery remaining amount meter IC incorporated in the battery management system (BMS) board of the power storage device 5. The CPU 41 of the control circuit 4 can acquire the remaining amount of the power storage device 5 detected by the battery remaining amount meter IC from the BMS board. When it is determined that the remaining amount of the power storage device 5 is 100%, the CPU 41 opens a circuit breaker (not shown) of the power supply line 31 to stop power transmission from the system power supply 20 to the power storage device 5. If the power storage device 5 does not have a function of charging from the system power supply 20, the AC-DC converter 10 and the AC input terminal 13 may not be provided.

[0020] A DC output terminal 14 is connected to the power supply line 33. When the user supplies power from the power supply system 1 to the electrical load 30, the user connects the electrical load 30 to the DC output terminal 14. The power storage device 5 can supply power to the electrical load 30 via the power supply lines 35 and 33.

[0021] The fuel cell 8 generates electricity by reacting fuel and an oxidant. The fuel cell 8 of the present embodiment uses hydrogen supplied from a hydrogen supply source 6 as fuel and oxygen in the air as an oxidant. The fuel cell 8 outputs DC power of, for example, 1000 W as its rated output. The fuel cell 8 is connected to a DC-DC converter 9. The DC-DC converter 9 converts the power output by the fuel cell 8 into power whose voltage is stepped down or stepped up to the voltage required by the electrical load 30.

[0022] The DC-DC converter 9 is connected to the power supply line 34. The fuel cell 8 can supply power to the electrical load 30 via the power supply lines 34, 32, and 33. In addition, the fuel cell 8 can supply power to the power storage device 5 via the power supply lines 34, 32, and 35.

[0023] The power supply system 1 supplies the necessary power to the electrical load 30 through the combined output of the fuel cell 8 and the energy storage device 5. The power required by the electrical load 30 is called the required power. The required power of the electrical load 30 fluctuates depending on its usage. The power supply system 1 responds to fluctuations in the required power by having the energy storage device 5 output the difference between the output of the fuel cell 8 and the required power of the electrical load 30.

[0024] The control panel 28 includes various switches that accept input from the user for operations performed on the power supply system 1. The control panel 28 includes a power supply switch 29. The power supply switch 29 is a switch that the user uses to instruct the power supply system 1 to supply power to the electrical load 30.

[0025] <Power supply processing> Referring to Figures 3 and 4, the power supply process of the power supply system 1 will be described. When the main power switch included in the operation panel 28 is turned ON, the power supply system 1 supplies power from the energy storage device 5 to the control circuit 4. The CPU 41 of the control circuit 4 starts operating when it is supplied with power stepped down by the step-down circuit installed in the control circuit 4. The CPU 41 reads the power supply process program from the ROM 43 and executes it.

[0026] The CPU 41 determines whether the power supply switch 29 is ON or OFF (S12). If it determines that the power supply switch 29 is OFF (S12: NO), the CPU 41 returns to S12 and waits for the power supply switch 29 to be turned ON.

[0027] If the CPU 41 determines that the power supply switch 29 is ON (S12: YES), it closes the circuit breaker (not shown) on the power supply line 33. The energy storage device 5 connects to the electrical load 30 via the power supply lines 35 and 33 and supplies the necessary power to the electrical load 30 (S13). The CPU 41 determines whether the power supply switch 29 is OFF or OFF (S14). If the CPU 41 determines that the power supply switch 29 is OFF (S14: YES), it opens the circuit breaker on the power supply line 33 and returns the process to S12, waiting for the power supply switch 29 to be turned ON.

[0028] If the power supply switch 29 is determined to be ON (S14: NO), the CPU 41 determines whether the remaining charge of the energy storage device 5 is 50% or more (S16). If the remaining charge of the energy storage device 5 is determined to be 50% or more (S16: YES), the CPU 41 returns to processing S14 and continues to supply power from the energy storage device 5 to the electrical load 30. If the remaining charge of the energy storage device 5 is determined to be less than 50% (S16: NO), the CPU 41 supplies hydrogen from the hydrogen supply source 6 to the fuel cell 8.

[0029] The CPU 41 supplies the power necessary for starting the fuel cell 8 from its internal power source and starts the fuel cell 8. The power necessary for starting the fuel cell 8 may also be supplied from the energy storage device 5. The fuel cell 8 starts generating power (S21). The CPU 41 also starts timing the continuous operating time of the fuel cell 8 (S22). Continuous operating time is the time from startup until the fuel cell 8 has stopped generating power.

[0030] The CPU 41 supplies the power generated by the fuel cell 8 to the electrical load 30 (S23). The output of the fuel cell 8 is supplied to the electrical load 30 via power lines 34, 32, and 33. In addition, power line 35, which is connected to the energy storage device 5, is connected to power lines 32 and 33 at connection point 52. That is, the energy storage device 5 is connected to the electrical load 30 via power lines 35 and 33, and also connected to the fuel cell 8 via power lines 35, 32, and 34. Therefore, the total output of the fuel cell 8 and the energy storage device 5 is supplied to the electrical load 30.

[0031] If the output of fuel cell 8 is greater than or equal to the required power, the output of fuel cell 8 is supplied to the electrical load 30 via power lines 34, 32, and 33. At this time, the difference in power between the output of fuel cell 8 and the required power is branched at connection point 52 and supplied to the energy storage device 5 via power line 35. In other words, power is supplied to the electrical load 30 solely by the output of fuel cell 8. The difference in power when the output of fuel cell 8 is greater than or equal to the required power is the surplus power that the output of fuel cell 8 has compared to the required power. The energy storage device 5 is charged by this difference in power.

[0032] If the output of fuel cell 8 is less than the required power, the output of fuel cell 8 is supplied to the electrical load 30 via power lines 34, 32, and 33. At this time, the difference between the required power and the output of fuel cell 8 is supplied to the electrical load 30 from the energy storage device 5 via power lines 35 and 32. In other words, the required power to the electrical load 30 is supplied by the combined output of fuel cell 8 and energy storage device 5. The difference in power when the output of fuel cell 8 is less than the required power is the amount of power that is insufficient for fuel cell 8 to meet the required power. Energy storage device 5 discharges the difference in power.

[0033] Furthermore, if the output of fuel cell 8 and the power required by the electrical load 30 are the same, the power difference will be 0. In this case, the power required by the electrical load 30 will be supplied solely by the output of fuel cell 8. The energy storage device 5 will not be charged or discharged.

[0034] The CPU 41 determines whether the power supply switch 29 is off or not (S31). If it determines that the power supply switch 29 is on (S31: NO), the CPU 41 determines whether the hydrogen has been depleted or not (S36). Hydrogen depletion occurs when the amount of hydrogen stored in the hydrogen storage alloy tank of the hydrogen supply source 6, or the amount of hydrogen stored in the hydrogen gas cylinder, becomes 0, and the fuel cell 8 can no longer generate power. If hydrogen is depleted, the CPU 41 receives a signal from the hydrogen supply source 6 indicating that hydrogen has been depleted. If the CPU 41 does not receive a signal indicating that hydrogen has been depleted and determines that hydrogen has not been depleted (S36: NO), the CPU 41 determines whether the remaining amount in the energy storage device 5 is 0% or not (S37).

[0035] If the CPU 41 determines that the remaining charge of the energy storage device 5 is not 0% (S37: NO), it determines whether the remaining charge of the energy storage device 5 is 80% or more (S41). If the CPU 41 determines that the remaining charge of the energy storage device 5 is less than 80% (S41: NO), it determines whether the continuous operating time of the fuel cell 8 has exceeded the maximum operating time (S42). The maximum operating time is the time set to stop power generation in order to protect the fuel cell 8, assuming that the fuel cell 8 has been operating continuously since startup without stopping power generation midway. If the CPU 41 determines that the continuous operating time of the fuel cell 8 has not exceeded the maximum operating time (S42: NO), it returns to processing S31. Therefore, the total output of the fuel cell 8 and the energy storage device 5 is continuously supplied to the electrical load 30.

[0036] The output of the fuel cell 8 increases over time after power generation begins. The fuel cell stack that makes up the fuel cell 8 is a structure made up of stacked unit cells, which are the smallest power generation units. The rated output of the fuel cell 8 is the rated capacity, which is determined by the number of stacked unit cells. Therefore, once the output of the fuel cell 8 increases over time and reaches the rated output, the output of the fuel cell 8 is maintained at the rated output.

[0037] The power requirements of the electrical load 30 can fluctuate. The energy storage device 5 outputs the difference in power, and together with the output of the fuel cell 8, supplies the necessary power to the electrical load 30. Therefore, the output of the energy storage device 5 fluctuates in accordance with the fluctuations in the power requirements. That is, if the output of the fuel cell 8 is in surplus relative to the power requirements, the energy storage device 5 receives the difference in power from the fuel cell 8 and charges itself. If the output of the fuel cell 8 is insufficient relative to the power requirements, the energy storage device 5 discharges and supplies the difference in power to the electrical load 30.

[0038] As charging continues, the remaining capacity of the energy storage device 5 increases. If the CPU 41 determines that the remaining capacity of the energy storage device 5 is 80% or more (S41: YES), the CPU 41 stops supplying hydrogen from the hydrogen supply source 6 to the fuel cell 8 and stops generating power from the fuel cell 8 (S43). The CPU 41 returns to processing in S14. The energy storage device 5 is connected to the electrical load 30 via the power supply lines 35 and 33. Therefore, the energy storage device 5 supplies the necessary power to the electrical load 30.

[0039] If the CPU 41 determines that the maximum operating time has elapsed (S42: YES), it stops supplying hydrogen from the hydrogen source 6 to the fuel cell 8 and stops generating power from the fuel cell 8 (S43). The CPU 41 returns to processing S14. The energy storage device 5 supplies the necessary power to the electrical load 30.

[0040] Furthermore, if the CPU 41 determines that the hydrogen in the hydrogen supply source 6 has been depleted (S36: YES), the CPU 41 stops generating power from the fuel cell 8 (S38). The CPU 41 opens the circuit breaker on the power supply line 33 and performs termination processing to shut down the power supply system 1 (S39), thereby ending the power supply process.

[0041] If the CPU 41 determines that the remaining charge of the energy storage device 5 is 0% (S37: YES), the CPU 41 stops generating power from the fuel cell 8 (S38). The CPU 41 opens the circuit breaker on the power supply line 33 and performs termination processing to shut down the power supply system 1 (S39), thereby ending the power supply process.

[0042] If the CPU 41 determines that the power supply switch 29 is off (S31: YES), it stops supplying hydrogen from the hydrogen source 6 to the fuel cell 8 and stops the power generation of the fuel cell 8 (S32). The CPU 41 returns to processing S12 and waits for the power supply switch 29 to be turned on.

[0043] <Changes in the output of fuel cell 8 and energy storage device 5> Next, referring to the graphs shown in Figure 5, we will explain the changes in the required power of the electrical load 30, the output of the fuel cell 8, the output of the energy storage device 5, and the remaining capacity of the energy storage device 5. In the graph of Figure 5(A), the vertical axis shows the required power of the electrical load 30 [W], and the horizontal axis shows time. In the graph of Figure 5(B), the vertical axis shows the output of the fuel cell 8 [W], and the horizontal axis shows time. In the graph of Figure 5(C), the vertical axis shows the output of the energy storage device 5 [W], and the horizontal axis shows time. Note that for the output of the energy storage device 5, a positive value indicates the discharge amount, and a negative value indicates the charge amount. In the graph of Figure 5(D), the vertical axis shows the remaining capacity [%] of the energy storage device 5, and the horizontal axis shows time.

[0044] An example of the power requirements for electrical load 30 is shown in Figure 5(A). Specifically, the power requirements for electrical load 30 are 1000W at T0, and fluctuate in small increments between 700W and 1100W between T0 and T6. The power requirements increase to 1500W at T6 and decrease to 400W at T7. After that, the power requirements fluctuate significantly between 400W and 1500W between T6 and T13. The power requirements become 1000W from T13 onward.

[0045] When the power supply process is executed at T0, the remaining capacity of the energy storage device 5 is 100%, so the required power is supplied from the energy storage device 5 to the electrical load 30. From T0 to T1, the output of the energy storage device 5 fluctuates in accordance with the small fluctuations in the required power. The remaining capacity of the energy storage device 5 decreases, and at T1, it falls below 50%. Therefore, at T1, the fuel cell 8 is started, and the supply of power from the fuel cell 8 to the electrical load 30 begins. From T1 onward, the combined output of the fuel cell 8 and the energy storage device 5 is supplied to the electrical load 30.

[0046] The output of the fuel cell 8 increases towards its rated output between T1 and T3. At T2, the output of the fuel cell 8 exceeds the required power. Therefore, from T2 onward, if the output of the fuel cell 8 exceeds the required power, the surplus output of the fuel cell 8 relative to the required power is supplied to the energy storage device 5. In this case, the energy storage device 5 is charged, and its remaining capacity increases.

[0047] At T3, the fuel cell 8's output reaches its rated output. Between T3 and T4, the fuel cell 8 outputs 1000W as its rated output and supplies it to the electrical load 30. The required power fluctuates slightly between T3 and T4, but within the range of 700W to 1100W. Therefore, when the required power is less than 1000W, the energy storage device 5 is charged by being supplied with the difference between the fuel cell 8's output and the required power. Also, when the required power is 1000W or more, the energy storage device 5 discharges the difference between the fuel cell 8's output and the required power and supplies it to the electrical load 30.

[0048] At T4, the remaining charge of the energy storage device 5 will be 80% or more. The fuel cell 8 will stop generating power. The output of the fuel cell 8 will become 0. Therefore, from T4 onward, the necessary power will be supplied to the electrical load 30 from the energy storage device 5.

[0049] At T5, when the remaining charge of the energy storage device 5 falls below 50%, the fuel cell 8 is started. As the output of the fuel cell 8 increases, the output of the energy storage device 5 decreases. At T6, the output of the fuel cell 8 reaches its rated output. Also at T6, the power requirement of the electrical load 30 stops fluctuating and increases to 1500W. Therefore, the energy storage device 5 outputs 500W so that the total output with the fuel cell 8 becomes 1500W.

[0050] At T7, when the power required by the electrical load 30 falls below the rated output of the fuel cell 8, the energy storage device 5 is charged by being supplied with the difference between the output of the fuel cell 8 and the required power. Between T7 and T8, the required power remains below the rated output of the fuel cell 8, and charging of the energy storage device 5 continues. At T8, the remaining charge of the energy storage device 5 exceeds 80%, and the fuel cell 8 stops generating power. Subsequently, until T9, the required power is supplied from the energy storage device 5 to the electrical load 30. Then, at T9, when the remaining charge of the energy storage device 5 falls below 50%, the fuel cell 8 is started.

[0051] At T10, the output of fuel cell 8 reaches its rated output. Between T10 and T11, fuel cell 8 outputs power at its rated output. The power requirement of electrical load 30 fluctuates significantly within the range of 400W to 1500W. The energy storage device 5 follows the fluctuations in the power requirement of electrical load 30 and performs charging or discharging based on the power difference between the output of fuel cell 8 and the required power.

[0052] At T11, the remaining charge of the energy storage device 5 exceeds 80%, and the fuel cell 8 stops generating power. Then, the necessary power is supplied from the energy storage device 5 to the electrical load 30. At T12, the remaining charge of the energy storage device 5 falls below 50%, and the fuel cell 8 is started. Then, at T13, the output of the fuel cell 8 reaches its rated output. Between T10 and T11, power from the energy storage device 5 is supplied to the electrical load 30, and the remaining charge decreases.

[0053] From T13 onward, the power required for electrical load 30 becomes 1000W, the same as the rated output of fuel cell 8. The power difference between the output of fuel cell 8 and the required power becomes 0, and the energy storage device 5 neither charges nor discharges.

[0054] Then, at T14, the continuous operating time of fuel cell 8 exceeds the maximum operating time. Power generation by fuel cell 8 is stopped. Energy storage device 5 supplies the necessary power to the electrical load 30. Since the remaining charge of energy storage device 5 is less than 50%, fuel cell 8 is immediately started up. At T15, the output of fuel cell 8 reaches its rated output, and the necessary power to the electrical load 30 can be supplied by the output of fuel cell 8 alone.

[0055] As explained above, the power supply system 1 supplies the necessary power to the electrical load 30 by the combined output of the fuel cell 8 and the energy storage device 5. When the required power of the electrical load 30 fluctuates, the fuel cell 8 continues to operate at its rated output. The energy storage device 5 adjusts its output in accordance with the required power. Therefore, even if the required power of the electrical load 30 fluctuates, the output of the fuel cell 8 does not fluctuate. Consequently, the power supply system 1 can suppress the accelerated deterioration of the fuel cell 8.

[0056] The power supply system 1 can reduce the operating time of the fuel cell 8 by not outputting power when the remaining charge of the energy storage device 5 is 50% or more. Therefore, the power supply system 1 can suppress the accelerated deterioration of the fuel cell 8.

[0057] The power supply system 1 can supply power to the energy storage device 5 by power supply from the fuel cell 8 when the remaining charge of the energy storage device 5 is less than 80%. Therefore, the power supply system 1 can increase the amount of time when power can be supplied from the energy storage device 5 to the electrical load 30, and reduce the amount of time when the fuel cell 8 is operating. Thus, the power supply system 1 can suppress the accelerated deterioration of the fuel cell 8.

[0058] The power supply system 1 stops supplying power from the energy storage device 5 when the output of the fuel cell 8 exceeds the required power. Therefore, the power supply system 1 does not waste the output of the fuel cell 8.

[0059] Furthermore, the power supply system 1 can supply the difference between the output of the fuel cell 8 and the required power to the energy storage device 5 when the output of the fuel cell 8 is greater than or equal to the required power. In other words, the energy storage device 5 can be charged with the surplus output of the fuel cell 8. Therefore, the power supply system 1 does not waste the output of the fuel cell 8.

[0060] When the power supply system 1 starts supplying power to the electrical load 30, it supplies the necessary power to the electrical load 30 using the output of the energy storage device 5. In other words, the power supply system 1 can supply power to the electrical load 30 from the energy storage device 5, which can supply power immediately, before starting to supply power from the fuel cell 8, which takes time to start up. Therefore, the electrical load 30 can receive power immediately when it needs it.

[0061] When the power supply system 1 starts supplying power to the electrical load 30, if the remaining charge of the energy storage device 5 is less than 50%, it immediately starts the output of the fuel cell 8 in addition to the output of the energy storage device 5. This allows the power supply system 1 to maintain the supply of necessary power to the electrical load 30 by supplying power from the fuel cell 8 before the remaining charge in the energy storage device 5 runs out.

[0062] The power supply system 1 can limit the continuous operating time of the fuel cell 8 to a maximum operating time. In other words, the power supply system 1 restricts the continuous operation of the fuel cell 8. Therefore, the power supply system 1 can suppress the accelerated deterioration of the fuel cell 8.

[0063] The fuel cell 8 maintains its rated output even when the required power of the electrical load 30 fluctuates, without adjusting its output to follow the fluctuations. The power supply system 1 then provides the output necessary to follow the fluctuations from the energy storage device 5, and the combined output of the fuel cell 8 and the energy storage device 5 is used to respond to the fluctuations in required power. By maintaining its rated output, the fuel cell 8 can be driven according to predetermined operating conditions. Therefore, the power supply system 1 can suppress the deterioration of the fuel cell 8.

[0064] In the above embodiment, hydrogen is an example of the fuel of the present invention. Oxygen is an example of the oxidizer of the present invention. The CPU 41 of the control circuit 4 is an example of the control unit of the present invention. The rated output is an example of a predetermined value of the present invention. 50% is an example of a first predetermined amount of the present invention. 80% is an example of a second predetermined amount of the present invention. The maximum operating time is an example of a predetermined time of the present invention.

[0065] The present invention is not limited to the above embodiments and various modifications are possible. The power supply system 1 may function, for example, as a backup system that maintains the supply of power to the electrical load 30 in the event of a power outage. The electrical load 30 is not limited to DC voltage; the necessary power may be supplied by applying AC voltage. In this case, the output of the fuel cell 8 and the output of the energy storage device 5 can be supplied to the electrical load 30 via a DC-AC inverter.

[0066] The output voltages of the fuel cell 8 and the energy storage device 5 are merely examples and may be changed as appropriate according to the electrical load 30. The rated output energy of the fuel cell 8 is merely an example and may be changed as appropriate. The value used as the basis for the remaining capacity of the energy storage device 5 in the decision processes of S16 and S41 is merely an example and may be changed as appropriate. The energy storage device 5 may be a lead-acid battery, nickel-metal hydride battery, lithium-ion battery, NAS battery, solid-state battery, etc. The control circuit 4 may use a microcomputer, ASIC (Application Specific Integrated Circuits), FPGA (Field Programmable Gate Array), etc. as the processor instead of the CPU 41.

[0067] The fuel cell 8 and the energy storage device 5 are connected via power lines 34, 32, and 35, but the fuel cell 8 and the energy storage device 5 may also be directly connected via a DC-DC converter 9. In this case, the output of the fuel cell 8 may be connected via pass-through within the energy storage device 5, so that the output of the fuel cell 8 and the output of the energy storage device 5 are output as a total output from the energy storage device 5. Furthermore, the energy storage device 5 may be configured to allow pass-through charging of the output of the fuel cell 8.

[0068] The CPU 41 stopped generating power from the fuel cell 8 when it determined that the remaining charge of the energy storage device 5 was 50% or more, but it is not limited to this and may continue generating power from the fuel cell 8.

[0069] If multiple fuel cells 8 are provided and the power requirements of the electrical load 30 fluctuate relatively large, the number of fuel cells 8 generating power may be increased or decreased according to the increase or decrease in power requirements. Furthermore, if the power requirements of the electrical load 30 fluctuate in small increments, the energy storage device 5 may, as in this embodiment, supply the difference in power to the electrical load 30 to track the fluctuations. [Explanation of symbols]

[0070] 1. Power supply system 5. Energy storage device 8 fuel cell 30 Electrical load 41 CPU

Claims

1. A fuel cell that generates electricity by reacting fuel and an oxidizer and can supply power to an electrical load, A power storage device capable of supplying power to the aforementioned electrical load, Control unit and Equipped with, A power supply system that supplies the necessary power required by the aforementioned electrical load using the combined output of the fuel cell and the energy storage device, The control unit, When the output of the fuel cell is at a predetermined value and the required power of the electrical load fluctuates, the output of the fuel cell is not changed. The energy storage device supplies power to the electrical load in accordance with fluctuations in the required power of the electrical load. A power supply system characterized by the following.

2. The control unit, If the remaining amount of the energy storage device is equal to or greater than a first predetermined amount, the fuel cell will not output power. The power supply system according to claim 1, characterized by the following:

3. The control unit, If the remaining amount of the energy storage device is less than the second predetermined amount, the system controls the supply of the required power to the electrical load and the supply of power to the energy storage device using the output of the fuel cell. The power supply system according to claim 2, characterized by the following:

4. The control unit, If the output of the fuel cell is greater than or equal to the required power, control is performed to supply power to the electrical load using only the output of the fuel cell. The power supply system according to claim 3, characterized by the following:

5. The control unit, If the output of the fuel cell is equal to or greater than the required power, control is performed to supply the difference between the output of the fuel cell and the required power to the energy storage device. The power supply system according to claim 4, characterized by the following:

6. When starting to supply power to the electrical load, the necessary power is supplied to the electrical load by the output of the energy storage device. The power supply system according to claim 5, characterized by the following:

7. The control unit, When starting to supply power to the electrical load, if the remaining amount of the energy storage device is less than a first predetermined amount, control is performed to supply the required power to the electrical load using the output of the fuel cell and the output of the energy storage device. The power supply system according to claim 6, characterized by the following:

8. The control unit, If the continuous operating time since the start of output of the fuel cell has elapsed for a predetermined period of time, the output of the fuel cell shall be stopped. A power supply system according to any one of claims 1 to 7, characterized by the following:

9. The output of the aforementioned fuel cell must be at its rated capacity. The power supply system according to claim 8, characterized by the following:

10. A fuel cell that generates electricity by reacting fuel and an oxidizer and can supply power to an electrical load, A power storage device capable of supplying power to the aforementioned electrical load, Control unit and In a power supply system comprising the above, a power supply method is provided in which the necessary power required by the electrical load is supplied by the sum of the output of the fuel cell and the output of the energy storage device, The control unit, When the output of the fuel cell is at a predetermined value and the required power of the electrical load fluctuates, the output of the fuel cell is not changed. The energy storage device supplies power to the electrical load in accordance with fluctuations in the required power of the electrical load. A power supply method characterized by the following.

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