JP2004129337A - Uninterruptible power system - Google Patents

Abstract

An uninterruptible power supply using a fuel cell and another power storage means is provided with a system capable of stably supplying power even when a power failure occurs continuously or when a load fluctuates rapidly.
An uninterruptible power supply having a function of supplying AC power from a commercial power supply to a connected load device and storing the AC power in a power storage means such as a capacitor via a rectifying means when receiving a commercial power supply. In the event of a commercial power outage, the DC output from the power storage means is converted to AC power and supplied to the load equipment, and the fuel cell is provided, and the power supplied from the power storage means to the load equipment has reached a predetermined value. Upon detection, power is supplied to the load equipment from the fuel cell.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an uninterruptible power supply.
[0002]
[Prior art]
Uninterruptible power supplies are widely used as backup power supplies for computers and power supplies for emergency light facilities. The uninterruptible power supply mainly depends on a secondary battery for power supply at the time of a power failure. Therefore, it is necessary to select a secondary battery according to the supply power required by the load device at the time of a power failure. In particular, when the power supplied from the load device is required, it is necessary to use a large-sized and large-capacity secondary battery, and the whole uninterruptible power supply becomes large and heavy, and becomes extremely expensive. In addition, it is necessary to perform trickle charging on the secondary battery to compensate for self-discharge, and a large-capacity secondary battery requires a large amount of electric power for trickle charging and increases the running cost of the apparatus.
[0003]
It is disclosed that a fuel cell is used instead of a secondary battery in order to suppress the increase in size and weight of such a system. The uninterruptible power supply must detect the power failure of the commercial power supply and immediately supply the output from the storage means from the secondary battery to the load. It took time until the power supply of the power failure power supply started, which was inappropriate for an uninterruptible power supply.
[0004]
In order to solve such a problem, for example, Patent Document 1 discloses that a fuel cell is combined with another electric storage means such as an electric double layer capacitor or a secondary battery, and the time from the start of the power failure to the start of the start of the fuel cell is determined. From the power supply to the load.
[0005]
In the uninterruptible power supply device disclosed in Patent Literature 1, power is supplied from a power storage unit to a load at the start of a power failure, and during this time, a fuel cell start operation is performed. If the power outage time is within the discharge time from the power storage means, it is not necessary to start the fuel cell, so even if the commercial power supply has not been recovered even after the discharge time of the power storage means has reached the predetermined time. A start-up operation of the fuel cell is performed.
[0006]
In such a system, almost no power is stored in the power storage means when the fuel cell is started. When the commercial power returns, the power storage means is charged again using the commercial power. However, if the power fails again immediately after the commercial power returns, the power storage means does not accumulate the power required to supply the load for the time required to start the fuel cell, so that power cannot be continuously supplied to the load. There is a problem that.
[0007]
Further, the fuel cell is an excellent power source for constantly supplying a certain amount of electric power, but is inferior in follow-up of load fluctuation. Was stopped and the backup discharge was interrupted in some cases.
[0008]
[Patent Document 1]
JP 2000-341879 A
[Problems to be solved by the invention]
The present invention relates to an uninterruptible power supply using the above-described fuel cell and other power storage means, and a system capable of stably supplying power even when a power failure occurs continuously or when the load fluctuates rapidly. To provide.
[0010]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 of the present invention supplies AC power from a commercial power supply to a connected load device at the time of receiving commercial power supply, and also converts the AC power through a rectifier. An uninterruptible power supply device having a function of storing DC power from a power storage means and supplying AC power to a load device at the time of a commercial power outage. An uninterruptible power supply is characterized in that it detects that the power supplied to the load device from the power supply reaches a predetermined value and supplies power from the fuel cell to the load device.
[0011]
The invention according to claim 2 of the present invention, in the uninterruptible power supply according to claim 1, monitors the power supplied from the power storage means to the load device, and predicts the possible power supply time from the power storage device to the load device, It is characterized in that the fuel cell is activated at least before the activation time required for activation of the fuel cell.
[0012]
According to a third aspect of the present invention, in the uninterruptible power supply according to the first or second aspect, a part of the output of the fuel cell is stored in the power storage means.
[0013]
According to a fourth aspect of the present invention, in the uninterruptible power supply according to the first, second or third aspect, when a supply output to a load device is equal to or more than a predetermined output, the difference between the supply output and the predetermined output is stored. It is characterized by supplying from a means to a load device.
[0014]
Further, the invention according to claim 5 of the present invention is the uninterruptible power supply according to claim 1, 2, 3 or 4, further comprising means for detecting a state of charge (SOC) of the power storage means, wherein the SOC is within a predetermined range. It is characterized in that control is performed so that
[0015]
According to a sixth aspect of the present invention, in the uninterruptible power supply according to the first, second, third, fourth, or fifth aspect, a capacitor is used as power storage means.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a configuration of an uninterruptible power supply according to an embodiment of the present invention. When the commercial power is received, the AC power from the commercial power 1 is supplied to the load device 2 via the direct transmission circuit 7. On the other hand, the AC power from the commercial power supply 1 is converted into DC by the rectifier 4 and is input to the power storage 10 via the charge controller 8 to charge the power storage 10.
[0017]
Next, the operation of the uninterruptible power supply of the present invention when the commercial power supply 1 is stopped will be described. Detecting that the commercial power supply 1 has stopped, the switching means 3 is switched to convert the DC output from the power storage means 10 as necessary into voltage by the converter 16, and then to AC power by the inverter 5, and to the load equipment 2. This AC power is supplied.
[0018]
The discharge load of the power storage means 10 is detected by the load detection means 14. For example, the load can be detected using the current sensor 17. The discharge duration of the power storage means 10 is predicted by the discharge time prediction means 13 based on the discharge load of the power storage means 10. This prediction can be achieved, for example, by storing a discharge time table for each discharge load in the discharge time prediction means 13 and referring to the measured discharge load and discharge time table. Needless to say, it is preferable to provide the discharge time table with environmental temperature characteristics in order to improve prediction accuracy.
[0019]
In addition, in order to more accurately execute the prediction of the discharge time, the state of charge (hereinafter, referred to as SOC) of the power storage means is detected by the SOC detection means 9 and stored in the discharge time prediction means 13. It is preferable to use a table for each SOC as the discharge time table. The SOC detection by the SOC detection means 9 can be achieved by various methods. For example, a charge / discharge current to the power storage means 10 is detected by a current sensor (not shown) included in the SOC detection means 9, and this is integrated with time. Can be obtained.
[0020]
The discharge time T of the power storage means 10 predicted by the discharge time prediction means 13 is compared with a time t required for starting the fuel cell 11 (hereinafter referred to as a required start time), and the fuel cell 11 is started based on the result. Specifically, the fuel cell control means 12 starts the fuel cell 11 when T = t + Δt in consideration of the margin time Δt (Δt> 0). Since the fuel cell control unit 12 operates by supplying power from the power storage unit 10, the above-described discharge time prediction unit 13 predicts the discharge time in consideration of the power required for the activation.
[0021]
At this point, the DC output from the fuel cell 11 is converted into AC power via the inverter 5 and supplied to load equipment. Here, a part of the DC output of the fuel cell 11 is input to the power storage means 10 via the charge control means 8, and the SOC of the power storage means 10 is controlled to increase.
[0022]
When the commercial power supply 1 returns, the operation of the fuel cell 11 is stopped by the fuel cell control means 12. In the present invention, at this point, the SOC of power storage means 10 is maintained sufficiently high. Therefore, the fuel cell 11 can be restarted even after the commercial power supply 1 is restored and the power supply of the commercial power supply 1 is stopped again immediately after the fuel cell 11 is stopped. In the conventional configuration in which the power storage means 10 is charged only by the commercial power supply 1, if a power failure occurs immediately after the return of the commercial power supply, the fuel cell 11 cannot be restarted in the storage battery means 10; In the configuration, stable restart of the fuel cell 11 enables stable power supply.
[0023]
Further, as a preferable configuration of the present invention, the fuel cell 11 and the power storage means 10 are operated in cooperation. The load current of the fuel cell 11 is monitored by a current sensor 18, and when it is detected that the output of the fuel cell 11 exceeds a specific output capable of obtaining a stable output, the output voltage of the converter 16 is controlled to increase by the converter control means 15. The power supplied to the load device 2 is covered by the power from the fuel cell 11 and the power storage means 10.
[0024]
According to such a configuration, the shortage of power can be compensated by the power supplied from the power storage unit 10 even if the load of the load device 11 suddenly increases. In the fuel cell, when the load suddenly increases and the reaction exceeds a specific output, the reaction may be stopped. However, in the present invention, the fuel cell 11 can be operated stably to supply power stably. In addition, while the discharge from the power storage unit 10 is being performed, the charge control unit 8 stops the power supply from the fuel cell 11 to the power storage unit 10, thereby improving the efficiency of the system.
[0025]
Conversely, when there is a surplus in the output of the fuel cell 11, if the surplus power is stored in the power storage means 10, the efficiency of the system can be further improved. In order to efficiently store such surplus power, it is preferable to control the SOC of the power storage means 10 to an area where surplus power can be accepted.
[0026]
In addition, a conventionally known secondary battery such as an alkaline storage battery, a lead storage battery, and a lithium secondary battery can be used as the power storage means 10, but more preferably, a high-capacity capacitor is used as the power storage means 10. And the charging / discharging efficiency is higher than that of the secondary battery, so that the efficiency of the system can be further improved. Further, if a tank (not shown) for storing the fuel to be supplied to the fuel cell 11 is externally provided and the capacity is increased, there is an advantage that a long-time operation is possible.
[0027]
Furthermore, although the embodiment in which the AC power is output has been described as an embodiment of the present invention, it goes without saying that the configuration of the present invention can be applied to the embodiment in which a DC output is obtained. In this case, except for the inverter 5 shown in FIG. 1, the commercial power may be converted to a DC output through the rectifier 4 and then the DC power may be supplied to the load device 2 through the direct feed circuit 7 and the switching unit 3. .
[0028]
【The invention's effect】
According to the present invention, in an uninterruptible power supply device using a fuel cell and other power storage means, a system capable of efficiently and stably supplying power even when a continuous power failure occurs or when the load fluctuates rapidly. Because it can be provided, it is extremely useful industrially.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an uninterruptible power supply according to the present invention.
DESCRIPTION OF SYMBOLS 1 Commercial power supply 2 Load equipment 3 Switching means 4 Rectification means 5 Inverter 7 Direct feed circuit 8 Charge control means 9 SOC detection means 10 Power storage means 11 Fuel cell 12 Fuel cell control means 13 Discharge time prediction means 14 Load detection means 15 Converter control means 16 Converter 17 Current sensor 18 Current sensor

Claims (6)

An uninterruptible power supply having a function of supplying AC power from a commercial power supply to a connected load device and storing the AC power in a power storage unit via a rectifying unit when receiving commercial power, In the event of a power outage, the DC output from the power storage means is converted to AC power and supplied to the load device, and a fuel cell is provided, and the power supplied from the power storage device to the load device has reached a predetermined value. And an electric power is supplied from the fuel cell to the load device. The supply power from the power storage means is monitored to predict a power supply possible time from the power storage means to the load device, and the power supply possible time is at least before a start-up time required for starting the fuel cell. The uninterruptible power supply according to claim 1, wherein the power supply is activated. The uninterruptible power supply according to claim 1 or 2, wherein a part of the output of the fuel cell is stored in the power storage means. 4. The uninterruptible power supply according to claim 1, wherein a difference between the supply output and the predetermined output is supplied from the power storage unit when a supply output to the load device is equal to or more than a predetermined output. The uninterruptible power supply according to claim 1, further comprising means for detecting a state of charge (SOC) of the power storage means, and controlling the SOC to be within a predetermined range. The uninterruptible power supply according to claim 1, wherein a capacitor is used as the power storage means.

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