KR101401751B1 - Apparatus and method for efficiency optimization of energy using fuel battery in system - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system having a fuel cell and a secondary battery, and a charging control method thereof. The present invention relates to a system for supplying power to a system using a fuel cell unit and a secondary battery. The present invention relates to a fuel cell system for generating electricity using fuel and air, And a secondary battery for supplying power to the system. The charge state information of the secondary battery and the applied voltage information to be applied to the system are continuously monitored and the charge capacity to be applied to the secondary battery is calculated on the basis of the charge state information. And a control unit for controlling the charging voltage of the secondary battery to be supplied to the secondary battery. According to the present invention, the voltage of the secondary battery that supplies the charging power to the system is fixedly maintained at a minimum voltage for driving the system, thereby increasing the efficiency and operation efficiency of the LDO of the system.

Fuel cell, secondary battery, DC / DC converter, LDO

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a system having a fuel cell and a secondary battery,

The present invention relates to a system having a fuel cell and a secondary battery, and more particularly, to maximize efficiency of a DC / DC converter or LDO of the system, a charging voltage of the secondary battery is set to a minimum voltage And a secondary battery, and a charge control method for the fuel cell.

Conventionally, various kinds of primary batteries and secondary batteries have been used to carry small electric equipment. However, with the recent enhancement of the performance of small-sized electric apparatuses, power consumption is increased, so that it is impossible to supply sufficient energy to a small-sized and light-weight primary battery. The rechargeable battery is advantageous in that it can be repeatedly used. However, the energy that can be used for one recharge is smaller than that of the primary battery, and a separate power supply and charging device is required for charging the rechargeable battery. Since it takes several tens of minutes to several hours in general, it is inconvenient to use the secondary battery.

Conventionally, attention has been paid to a fuel cell as a solution to such a problem. This is the main reason why the fuel cell is higher in power generation efficiency than the conventional power generation system and the waste is clean. Further, the amount of energy that can be supplied per volume or weight can be increased from several times to tens of times that of a conventional primary or secondary battery, and can be continuously used by replacing only the fuel, The fuel cell system is attracting attention as a driving source of compact electrical equipment. Recently, fuel cell and secondary battery are connected in parallel to supply charging power to the system. At this time, the fuel cell is charged with the secondary battery, and the current charged in the secondary battery is used in the system. The secondary battery includes NI-Ion, NI-Cd, and NI-Mh.

However, in the conventional technology as described above, the secondary battery is charged in the fuel cell and then the power of the secondary battery is supplied to the system. However, as the secondary battery is charged more, the voltage becomes higher, If the voltage is increased, the operation efficiency of the system is lowered and the lifetime of the fuel cell system is shortened.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to provide a DC / DC converter or a LDO in a system having a fuel cell and a secondary battery, A fuel cell for controlling the charging capacity to be supplied from the fuel cell to the secondary battery, a system including the secondary battery, and a charging control method therefor.

According to an aspect of the present invention, there is provided a fuel cell system including a fuel cell unit for generating electricity using fuel and air; A secondary battery that supplies power to the system and is charged by the fuel cell unit; A controller for monitoring a charged state of the secondary battery and an amount of power required by the system to control the fuel cell unit to apply a predetermined power to the secondary battery; And a DC / DC converter for supplying power from the secondary battery to the system.

When the output power that can be supplied from the fuel cell unit to the secondary battery is equal to or greater than the maximum required power of the system, the control unit compares the lowest voltage Vmin required by the system with the comparison voltage Vmax, which is higher than the lowest voltage Vmin, The control unit controls the fuel cell unit to charge the secondary battery when the charged state of the secondary battery is equal to or lower than the lowest voltage Vmin, and when the state of charge of the secondary battery is equal to or higher than the comparison voltage Vmax, Thereby stopping charging operation of the battery.

When the output power that can be supplied from the fuel cell unit to the secondary battery is equal to or greater than the maximum required power of the system, the control unit compares the lowest voltage (Vmin) required by the system with a comparison voltage Vmax is set so that the system loads are analyzed and compensated by the system loads if the charge state of the secondary battery is between the lowest voltage Vmin and the comparison voltage Vmax, The battery unit may apply the charging power to the secondary battery.

On the other hand, the system includes a power management unit that reduces the frequency of a central processing unit (CPU) or reduces system loads by turning off unused equipment in the system .

When the output power that can be supplied from the fuel cell unit to the secondary battery is less than the maximum required power of the system, the control unit calculates the minimum voltage (Vmin) and the charging maximum voltage (Vhigh) required by the system, ) And when the state of charge of the secondary battery is present between the intermediate value (Vmid) and the charge maximum voltage (Vhigh), system loads are analyzed and compensated for by the system loads The fuel cell unit applies a charging power to the secondary battery, and controls the charging to be terminated when the charging state of the secondary battery reaches the charging maximum voltage (Vhigh) or more.

Meanwhile, when the state of charge of the secondary battery is present between the lowest voltage (Vmin) and the interim value (Vmid), the controller analyzes the system loads and analyzes the system load load is greater than the output of the fuel cell unit, the control unit drives the power management unit to make the power required by the system less than or equal to the power output from the fuel cell unit, and controls the fuel cell unit to charge the secondary battery, When the charging state of the secondary battery is equal to or higher than the charging maximum voltage (Vmax), charging ends.

According to another aspect of the present invention, there is provided a fuel cell system comprising: (A) a battery having a minimum voltage (Vmin) required by the system and Setting a comparison voltage (Vmax) higher than the lowest voltage (Vmin); (B) continuously monitoring the charged state of the secondary battery to charge the secondary battery when the charged state of the secondary battery is not more than the lowest voltage (Vmin); And (C) stopping the charging operation of the fuel cell unit when the charging state of the secondary battery is equal to or higher than the comparison voltage Vmax.

According to another aspect of the present invention, when the output power that can be supplied from the fuel cell unit to the secondary battery is equal to or greater than a maximum required power of the system, (A ') the minimum voltage (Vmin) Setting a comparison voltage (Vmax) higher than the voltage (Vmin); And (B ') continuously monitoring the state of charge of the secondary battery. When the state of charge of the secondary battery is present between the lowest voltage (Vmin) and the comparison voltage (Vmax), the system load And charging the secondary battery with the fuel cell unit by compensating for the load.

If the voltage of the secondary battery deviates from the minimum voltage Vmin and the voltage Vmax, the charging state of the secondary battery is continuously monitored. If the secondary battery is at the lowest voltage Vmin, Charging the secondary battery with the fuel cell unit; (b) stopping the charging operation of the fuel cell unit when the charging state of the secondary battery is equal to or higher than the comparison voltage (Vmax).

According to another aspect of the present invention, when the output power that can be supplied from the fuel cell unit to the secondary battery is less than the maximum required power of the system, (a ') the minimum voltage (Vmin) A maximum voltage (Vhigh), and a value (Vmid); (b ') when the state of charge of the secondary battery is present between the interim value (Vmid) and the charge maximum voltage (Vhigh), analyzing system loads and compensating for system loads thereof A step in which the fuel cell unit applies charging power to the secondary battery; And (c ') terminating the charging when the state of charge of the secondary battery is equal to or greater than the charging maximum voltage (Vhigh).

If the state of charge of the secondary battery is present outside the interim value (Vmid) and the maximum charging voltage (Vhigh) (d ') in the step (b'), (Vmin) and the intermediate value (Vmid); (e ') analyzing system loads if the condition (d') is satisfied; (f ') If the system loads are greater than the output of the fuel cell unit as a result of the analysis of the step (e'), the power management unit drives the power management unit, Or less; (g ') charging the secondary battery at the fuel cell unit; And (h ') terminating the charging when the state of charge of the secondary battery is equal to or higher than the charging maximum voltage (Vhigh).

If the condition (d ') is not satisfied, the system is terminated when the state of charge of the secondary battery is not more than the minimum voltage (Vmin) required by the system.

If the system loads are smaller than the output of the fuel cell unit as a result of the analysis of the step (e '), the step (g') is performed after the step (e ').

The following effects can be expected in the charge control apparatus and the charge control method of the system including the fuel cell and the secondary battery according to the present invention as described above.

That is, the present invention provides an advantage that the voltage output from the secondary battery to the system can be fixedly maintained by supplying the predetermined applied voltage controlled by the fuel cell unit to the secondary battery, thereby increasing the operating efficiency of the system.

It also has the advantage of being able to efficiently handle the input range voltage regulation of the DC / DC converter of the system.

Further, the present invention can more efficiently drive the fuel cell unit, and has an advantage that the life of the fuel cell stack of the fuel cell unit can be prolonged.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a fuel cell and a secondary battery system according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the internal structure of a system including a fuel cell and a secondary battery according to a specific embodiment of the present invention.

As shown, the system 100 of the present invention includes a fuel cell 110 that generates electricity using fuel and air, and supplies a predetermined output voltage to the secondary battery 120. The fuel cell unit 110 includes a fuel storage unit 111, a pump 113, a reforming unit 115, an air intake unit 117, and a fuel cell stack 119. The fuel storage unit 111 is a tank for storing chemical fuels such as methanol and petroleum, and the pump 113 pumps the fuel stored in the fuel storage unit 111. The air intake part 117 supplies external air for the chemical reaction of the fuel stored in the fuel storage part 111. The reforming unit 115 generates a reforming reaction from the fuel supplied from the fuel storage unit 111 by the pump 113 to generate a fuel gas such as hydrogen. The fuel cell stack 119 generates an electromotive force by causing an electrochemical reaction using the fuel gas supplied from the reforming unit 115 and the air supplied from the air intake unit 117.

The system 100 includes a secondary battery 120 that receives a predetermined output voltage from the fuel cell unit 110 and supplies power to the system. The secondary battery 120 may be trickle charged by the fuel cell stack 119 of the fuel cell unit 110.

The system 100 further includes a charging capacity detector 130 for continuously monitoring the charged state of the secondary battery 120 and an applied voltage detector 140 for monitoring an applied voltage to be applied to the system 100. [ .

Based on the charging state information of the secondary battery 120 monitored by the charging capacity detecting unit 130 and the applied voltage detecting unit 140 and the applied voltage information to be applied to the system, And a control unit 150 for calculating a charging capacity to be applied to the secondary battery 120 and controlling the secondary battery 120 to be charged by the electromotive force generated by the fuel cell unit 110.

At this time, the controller 150 controls the charging step differently according to the comparison result between the output power information that the fuel cell unit 110 can supply to the secondary battery 120 and the maximum required power information of the system . As a result of the comparison, three cases (CASE1, CASE2, CASE3) may occur.

CASE1 is a case where the output power that can be supplied from the fuel cell unit 110 to the secondary battery 120 is greater than a maximum required power of the system, and CASE2 is a case where the output power from the fuel cell unit 110 to the secondary battery 120 ) Is the same as the maximum required power of the system, and CASE3 is a case where the output power that can be supplied from the fuel cell unit 110 to the secondary battery 120 is smaller than the maximum required power of the system to be. The control unit 150 performs different processes according to each case (CASE1, CASE2, CASE3).

Meanwhile, in the case of CASE1 and CASE2, the controller 150 may control the fuel cell unit 110 to supply a predetermined output voltage to the secondary battery 120 by two methods. Here, the predetermined output voltage means that the voltage of the secondary battery 120 is a charging voltage corresponding to a compensation amount to be the minimum voltage required by the system. (For example, the minimum voltage of the secondary battery to be fixed = the current secondary battery voltage + the predetermined output voltage). This is because, when the output voltage of the secondary battery 120 is fixedly maintained at a minimum voltage, And the efficiency of the DC / DC converter 170 and the LDO is increased.

The first method is a method of controlling by the state of charge of the secondary battery 120. At this time, the controller 150 sets the lowest voltage Vmin required by the system and sets a comparison voltage Vmax slightly higher than the lowest voltage in consideration of the tolerance of the lowest voltage Vmin. The control unit 150 continuously accesses the voltage of the secondary battery 120 monitored by the charging capacity detecting unit 130. When the voltage of the secondary battery 120 reaches the minimum voltage Vmin, The control unit controls the fuel cell stack 119 so that the secondary battery 120 is charged. At this time, the controller 150 continuously receives the result of monitoring the charging state of the secondary battery 120 from the charging capacity detector 130, and when the voltage of the secondary battery 120 is higher than the comparison voltage Vmax), it is controlled so that the charging is stopped.

The second method is to control the system loads and the voltage balance of the secondary battery 120. At this time, the controller 150 sets the lowest voltage Vmin required by the system and sets a comparison voltage Vmax slightly higher than the lowest voltage in consideration of the tolerance of the lowest voltage Vmin. The control unit 150 continuously accesses the charged state of the secondary battery 120 monitored by the charging capacity detector 130 and determines whether the voltage of the secondary battery 120 reaches the lowest voltage Vmin, The comparison voltage Vmax. If the voltage of the secondary battery 120 is between the lowest voltage Vmin and the comparison voltage Vmax, the controller 150 senses the current of the current system through the resistance of the system, Analyzes the system load, and controls the fuel cell unit 110 to charge the secondary battery 120 by compensating for the load.

Meanwhile, in the above-described method, the voltage of the secondary battery 120 does not deviate from the minimum voltage Vmin and the voltage Vmax. However, the instantaneous error may cause the voltage of the secondary battery 120 to deviate from the minimum voltage Vmin and the voltage Vmax. When the voltage of the secondary battery 120 is equal to or higher than the comparison voltage Vmax, the control unit 150 controls the charging unit 150 to charge the secondary battery 120 when the voltage of the secondary battery 120 is lower than the lowest voltage Vmin. The charging operation (charging ON / OFF) of the fuel cell unit 110 is preferably controlled so as to be stopped. Under the control of the controller 150, the present invention can hold the output voltage of the secondary battery 120 at a minimum voltage required by the system.

On the other hand, when it is determined as CASE3, that is, when the load of the system is larger than the power output from the fuel cell unit 110 to the secondary battery 120, the controller 150 controls the power management (Power management) unit 160 to be driven.

The power management unit 160 may receive a driving signal from the controller 150 to lower the frequency of the central processing unit (CPU) or turn off an unnecessary device (off). The apparatus includes, for example, a liquid crystal display (LCD) unit, a hard disk drive, a CD ROM drive, an FDD, and the like, which are various peripheral controller chip display devices including a video controller in addition to a main CPU. By using the power management unit 160 as described above, it is possible to instantaneously make the load of the system lower than the output voltage of the fuel cell unit 110.

The present invention also includes a DC / DC converter 170 for distributing an output voltage to each device. A liquid crystal display (LCD) unit, a hard disk drive, a CD ROM drive, an FDD, and the like, which are various peripheral controller chip display devices such as a video controller.

Hereinafter, a charge control method of a fuel cell and a system including a secondary battery according to a specific embodiment of the present invention will be described in detail.

The system including the fuel cell and the secondary battery of the present invention compares the output power that can be supplied from the fuel cell unit 110 to the secondary battery 120 and the maximum power required by the system, Perform different charging steps. At this time, as a result of the comparison, three cases (CASE1, CASE2, CASE3) occur.

That is, CASE1 is a case where the output power that can be supplied from the fuel cell unit 110 to the secondary battery 120 is larger than the maximum required power of the system, and CASE2 is a case where the output power from the fuel cell unit 110 to the secondary battery 120 is equal to the maximum required power of the system, and CASE3 is a case where the output power that can be supplied from the fuel cell unit 110 to the secondary battery 120 is less than the maximum required power of the system . The control unit 150 controls the fuel cell unit 110 to supply the rechargeable battery 120 with the charging power in a different manner depending on each situation.

Hereinafter, a method of supplying the charging power according to each situation (e.g., CASE1, CASE2, CASE3) will be described in detail with reference to the drawings.

The control unit 150 may control the fuel cell unit 110 to supply a predetermined output voltage to the secondary battery 120 in two ways. The first method is a method of controlling by the voltage of the secondary battery 120, and the second method is a method of controlling by system loads and a voltage balance of the secondary battery 120. This will be described by way of example with reference to the first embodiment and the second embodiment, respectively.

FIG. 2 is a flowchart showing a charging method of a charging system using a fuel cell and a secondary battery according to the first embodiment of the present invention.

The controller 150 sets the lowest voltage Vmin required by the system and sets a comparison voltage Vmax slightly higher than the lowest voltage Vmin in consideration of the tolerance of the lowest voltage Vmin (S210).

Thereafter, the control unit 150 continuously accesses the voltage of the secondary battery 120 that is monitored by the charge determination unit 130 (S220).

When the voltage of the secondary battery 120 is lower than the minimum voltage Vmin, the controller 150 controls the fuel cell stack 119 to charge the secondary battery 120 (S240).

While the operation 240 is being performed, the controller 150 continuously receives the result of monitoring the state of charge of the secondary battery 120 from the charge capacity detector 130. When the voltage of the secondary battery 120 is equal to or higher than the comparison voltage Vmax (S250), the charging is stopped (S260).

3 is a flowchart showing a charging method of a charging system using a fuel cell and a secondary battery according to a second embodiment of the present invention.

CASE1 and CASE2, the controller 150 sets the minimum voltage Vmin required by the system as in the first embodiment and sets the lowest voltage Vmin in consideration of the tolerance of the lowest voltage Vmin, A relatively high comparison voltage Vmax is set (S310).

The controller 150 continuously accesses the charged state of the secondary battery 120 monitored by the charging capacity detector 130 (S320).

At this time, the controller 150 determines whether the voltage of the secondary battery 120 is between the minimum voltage Vmin and the comparison voltage Vmax at step S330. If it is determined in operation 330 that the voltage of the secondary battery 120 is between the minimum voltage Vmin and the comparison voltage Vmax, the system current is sensed using the resistance of the system, The system load is analyzed (S440). Thereafter, the control unit 150 compensates the corresponding load to control the fuel cell unit 110 to charge the secondary battery 120 (S350).

Meanwhile, in the above-described method, the voltage of the secondary battery 120 does not deviate from the minimum voltage Vmin and the voltage Vmax. However, due to an instantaneous error, the voltage of the secondary battery 120 may deviate from the minimum voltage Vmin and the comparison voltage Vmax. At this time, the controller 150 continuously monitors the state of charge of the secondary battery as in the first embodiment, controls the secondary battery 120 to be charged when the secondary battery 120 is at the lowest voltage Vmin or less, Control is performed so that charging is terminated when the secondary battery 120 becomes equal to or higher than the comparison voltage Vmax to control the voltage of the secondary battery to fall within the minimum voltage Vmin and the comparison voltage Vmax. Thereafter, steps 330 to 350 are continuously performed.

As described above, according to the first and second embodiments, the voltage of the secondary battery 120 can be fixedly maintained at a minimum voltage required by the system.

4 is a flowchart showing a charging method of a charging system using a fuel cell and a secondary battery according to a third embodiment of the present invention.

On the other hand, in case of CASE 3, the controller 150 sets the lowest voltage Vmin required by the system, sets the charging maximum voltage Vhigh, and sets the interim value Vmid (S410).

Then, it is determined whether the output voltage of the secondary battery 120 is between the intermediate value Vmid and the charging maximum voltage Vhigh (S420).

If it is determined that the voltage of the secondary battery is between the intermediate value Vmid and the charging maximum voltage Vhigh as a result of the determination in operation 420, the current of the system is sensed using the resistance of the system, Analyze the system load. The control unit 150 compensates for the corresponding load, and controls the fuel cell unit 110 to charge the secondary battery 120 (S430).

At this time, if the output voltage of the secondary battery 120 is equal to or greater than the charging maximum voltage Vhigh, the controller 150 controls the charging to be ended (S450).

On the other hand, if it is determined that the voltage of the secondary battery 120 does not exist between the intermediate value Vmid and the charging maximum voltage Vhigh in step 420, It is determined whether it is greater than the required minimum voltage Vmin and equal to or less than the intervening value Vmid (S460).

If it is determined in operation 460 that the output voltage of the secondary battery is greater than the minimum voltage Vmin and equal to or less than the intervening value Vmid, current, and analyzes the system load (S470).

If it is determined in operation 470 that the output of the fuel cell is smaller than the load of the system, the control unit 150 transmits a drive signal for driving the power management unit 160.

At this time, the power management unit 160 receives the driving signal, controls the frequency of the central processing unit (CPU), or controls the unnecessary device to be turned off (S490). Then, it is possible to instantaneously make the load of the system below the output of the fuel cell unit 110.

Thereafter, the resistance of the system is again used to sense the current of the system and analyze the system load.

If the output of the fuel cell unit 110 is greater than the load of the system, the control unit controls the fuel cell unit 110 to charge the secondary battery 120.

At this time, the controller 150 continuously receives the result of monitoring the state of charge of the secondary battery 120 from the charge capacity detector 130. When the voltage of the secondary battery 120 is equal to or higher than the charging maximum voltage Vhigh (S500), the charging is stopped.

If it is determined in operation 460 that the output voltage of the secondary battery 120 is greater than the minimum voltage Vmin required by the system and is not less than the value Vmid, It is determined whether the output voltage of the secondary battery 120 is less than or equal to a minimum voltage Vmin required by the system in operation S520. If the output voltage of the secondary battery 120 is less than the minimum voltage Vmin, And controls the system to be terminated.

It is to be understood that the invention is not limited to the disclosed embodiment, but is capable of many modifications and variations within the scope of the appended claims. It is self-evident.

1 is a block diagram showing an internal configuration of a system including a fuel cell and a secondary battery according to a specific embodiment of the present invention.

2 is a flowchart showing a charging method of a charging system using a fuel cell and a secondary battery according to a first embodiment of the present invention.

3 is a flowchart showing a charging method of a charging system using a fuel cell and a secondary battery according to a second embodiment of the present invention.

4 is a flowchart showing a charging method of a charging system using a fuel cell and a secondary battery according to a third embodiment of the present invention.

Description of the Related Art [0002]

110: fuel cell unit 111: fuel storage unit

113: pump 115:

117: air suction portion 119: fuel cell stack

120: secondary battery 130: charge capacity detection unit

140: applied voltage detecting unit 150:

160: Power management unit 170: DC / DC converter

Claims (13)

A fuel cell unit for generating electricity using fuel and air; A secondary battery that supplies power to the system and is charged by the fuel cell unit; A controller for monitoring a charged state of the secondary battery and an amount of power required by the system to control the fuel cell unit to apply a predetermined power to the secondary battery; And And a DC / DC converter for supplying power from the secondary battery to the system; Wherein when the output power that can be supplied from the fuel cell unit to the secondary battery is equal to or greater than a maximum required power of the system, the control unit compares the minimum voltage Vmin required by the system with a comparison voltage Vmax And when the state of charge of the secondary battery is between the lowest voltage (Vmin) and the comparison voltage (Vmax), system loads are analyzed and compensated by the system loads, Wherein the charging unit applies charging power to the secondary battery. The method according to claim 1, When the output power that can be supplied from the fuel cell unit to the secondary battery is equal to or greater than a maximum required power of the system, Wherein, (Vmin) higher than a minimum voltage (Vmin) required by the system and a comparison voltage (Vmax) higher than the lowest voltage (Vmin) are set so that when the charged state of the secondary battery is the lowest voltage Wherein the charging operation of the fuel cell unit is stopped when the charging state of the secondary battery is equal to or higher than the comparison voltage Vmax. delete The method according to claim 1, The system comprises: The system further includes a power management unit that reduces system frequency by lowering the frequency of a central processing unit (CPU) or turning off equipment not in use by the system. A fuel cell and a secondary battery. 5. The method of claim 4, When the output power that can be supplied from the fuel cell unit to the secondary battery is less than the maximum required power of the system, Wherein, The minimum voltage Vmin, the charging maximum voltage Vhigh, and the interim value Vmid required by the system are set, When the state of charge of the secondary battery is present between the middle value Vmid and the maximum charging voltage Vhigh, the system loads are analyzed and compensated for by the system loads, Wherein the controller is configured to apply a charging power to the secondary battery and control charging to end when the charging state of the secondary battery reaches the charging maximum voltage Vhigh or higher. . 6. The method of claim 5, Wherein, Wherein the system loads are analyzed when the state of charge of the secondary battery is between the minimum voltage (Vmin) and the interim value (Vmid) The power management unit drives the power management unit to make the power required by the system less than or equal to the power output from the fuel cell unit and controls the fuel cell unit to charge the secondary battery, And the charging is ended when the charging state is the charging maximum voltage (Vhigh) or more. delete When the output power that can be supplied from the fuel cell unit to the secondary battery is equal to or greater than the maximum required power of the system, (A) setting a minimum voltage (Vmin) required by the system and a comparison voltage (Vmax) higher than the minimum voltage (Vmin); And (B) continuously monitoring the state of charge of the secondary battery to analyze the system load when the state of charge of the secondary battery is between the lowest voltage (Vmin) and the comparison voltage (Vmax) And charging the secondary battery with the fuel cell unit by compensating for the corresponding load. 9. The method of claim 8, (C) continuously monitoring a state of charge of the secondary battery, and charging the secondary battery with the fuel cell unit when the secondary battery is at the lowest voltage (Vmin) or less; And (D) stopping the charging operation of the fuel cell unit when the charging state of the secondary battery is equal to or higher than the comparison voltage (Vmax). Charge control method. When the output power that can be supplied from the fuel cell unit to the secondary battery is less than the maximum required power of the system, (a ') setting a minimum voltage (Vmin) and a charging maximum voltage (Vhigh) required by the system, and a value (Vmid) between them; (b ') If the state of charge of the secondary battery is present between the above-mentioned intermediate value (Vmid) and the charging maximum voltage (Vhigh), system loads are analyzed and compensated for their system loads Applying a charging power source to the fuel cell unit; And (c ') terminating the charging when the state of charge of the secondary battery reaches the charging maximum voltage (Vhigh) or more; and terminating the charging of the secondary battery. 11. The method of claim 10, If it is determined in step (b ') that the charging state of the secondary battery is other than the interim value (Vmid) and the charging maximum voltage (Vhigh) (d ') determining whether a state of charge of the secondary battery is present between a minimum voltage (Vmin) required by the system and the interim value (Vmid); (e ') analyzing system loads if the condition (d') is satisfied; (f ') If the system loads are greater than the output of the fuel cell unit as a result of the analysis of the step (e'), the power management unit drives the power management unit ; (g ') charging the secondary battery at the fuel cell unit; And (h ') charging the secondary battery when the charging state of the secondary battery is equal to or higher than the charging maximum voltage (Vhigh); and terminating charging of the secondary battery. 12. The method of claim 11, If the condition (d ') is not satisfied, Wherein the controller controls the system to be terminated when the state of charge of the secondary battery is equal to or lower than a minimum voltage (Vmin) required by the system. 12. The method of claim 11, If the system loads are smaller than the output of the fuel cell unit as a result of the analysis of step (e '), Wherein the step (g ') is performed after the step (e').

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