KR20150033882A - Control system and Control method of Uninterruptible Power Supply using Lithium-ion Battery - Google Patents

Abstract

The present invention relates to a system for controlling an uninterruptible power supply using a lithium-ion battery and, more particularly, to a system for controlling an uninterruptible power supply to supply AC energy, which is supplied from an AC power source, to a load at a constant voltage through the uninterruptible power supply provided between the AC power source and the load. The system for controlling an uninterruptible power supply using a lithium-ion battery comprises: an energy storage device connected to a first node between an AC power source and a load and consisting of a lithium-ion battery to supply a voltage to the load; and a switching unit connected between the first node and the energy storage device and controlling the voltage supplied from the AC power source to the energy storage device and the voltage supplied from the energy storage device to the load.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control system for an uninterruptible power supply using a lithium ion battery,

The present invention relates to a control system for an uninterruptible power supply using a lithium ion battery and a control method thereof, and more particularly, to an uninterruptible power supply that immediately supplies power in an emergency, (SOC, State Of charge) of the ion battery, it is possible to efficiently supply the stable power to the load while effectively preventing overcharge and overdischarge of the energy reservoir.

Power supplies for communication, broadcasting, hospitals, and facilities require high stability and reliability, and often do not allow short interruptions. To meet this demand, power is backed up using an uninterruptible power supply (UPS). In other words, the uninterruptible power supply is a device that supplies stable power to the load in case of power failure or momentary power instability. A typical example of a current uninterruptible power supply used as an energy storage device is a secondary lead-acid battery.

This secondary lead-acid battery has the advantage of high energy density of 20 ~ 120 Wh / kg, but it has a low output density of 50 ~ 250 W / kg and a low cycle life characteristic of 500. Accordingly, the uninterruptible power supply using the secondary lead-acid battery has excellent characteristics for long-time power supply due to its high energy density, but has a problem of regular maintenance and repair costs due to its low life characteristics.

Accordingly, in recent years, lithium-ion batteries have been applied to energy storage devices of uninterruptible power supplies.

However, since the lithium ion battery has characteristics different from those of the secondary lead-acid battery, there is a high risk of explosion due to overcharging or overdischarge in connection with the lithium ion battery without changing the structure of the conventional uninterruptible power supply.

The present invention addresses the difficulty of providing a lithium ion battery as an energy storage device without changing the structure of the uninterruptible power supply unit due to the risk of explosion due to overcharge or overdischarge.

European Patent No. 0739075 ("Prior Art 1") discloses an uninterruptible power supply having an overcurrent protection function. Prior art 1 uses a battery as an energy storage device, and due to the use of a battery There is no mention at all of how to overcome the low life that occurs.

European Registered Patent No. 0739075 (Registered Mar. 3, 1999)

SUMMARY OF THE INVENTION The present invention has been made to overcome the above problems, and it is an object of the present invention to provide an uninterruptible power supply which immediately supplies power in an emergency, efficiently connecting a lithium- , State Of charge), which effectively prevents overcharge and overdischarge of the energy storage device, efficiently reduces the volume of the uninterruptible power supply, stores the large capacity, and stably supplies power to the load. And to provide a control system of the same.

According to an aspect of the present invention, there is provided a control system for an uninterruptible power supply using a lithium ion battery, the system comprising: an uninterruptible power supply unit provided between an ac power source and a load; A control system for an uninterruptible power supply apparatus that supplies AC energy to a load at a constant voltage, the control system comprising: a first energy storage unit connected to a first node between the AC power source and the load, And a switching unit which is connected between the first node and the energy storage element and controls a voltage supplied to the energy storage unit from the AC power supply and a voltage supplied to the load from the energy storage unit Do.

Wherein the switching unit comprises a first switch connected between the first node and both ends (+) of the energy reservoir, a second switch, a third switch, a resistor and a diode, Wherein the second switch is connected in series with the first node and a second node on both ends of the energy storage, the resistor is connected between the first switch and the first node, Wherein the diode is connected in parallel with a third node across the energy reservoir and the first node to prevent reverse current flow from the load to the energy reservoir, Is preferably connected between the diode and the first node.

Wherein the switching unit closes the first switch and opens the second switch and the third switch for a predetermined time when the energy store is first connected to the uninterruptible power supply using the lithium ion battery, It is preferable to match the voltage between the energy storage element and the inverter of the uninterruptible power supply.

Wherein the switching unit closes the third switch and opens the first switch and the second switch according to a state of charge of the energy store, And supplies the voltage to the load through the energy reservoir.

Wherein the switching unit closes the second switch and opens the first switch and the third switch in accordance with a state of charge (SOC) of the energy store, ) To charge the energy reservoir, while providing a voltage from the ac power source to the load.

A control method of an uninterruptible power supply using a lithium ion battery according to the present invention is a control method of an uninterruptible power supply using a lithium ion battery, wherein AC power supplied from an AC power source is supplied to a load at a constant voltage through control of a switching unit comprising a first switch, A method of controlling an uninterruptible power supply using a lithium ion battery, the method comprising: closing the first switch; opening the second switch and the third switch to provide a voltage to the load; An initial connection step of matching the voltage between the energy storage device, which is a lithium ion battery, and the inverter of the uninterruptible power supply; A first determination step of determining whether a state of charge (SOC) of the energy store is equal to or greater than a predetermined first set value; A second determining step of determining whether the charged state of the energy reservoir is equal to or less than a predetermined second set value when the charging state of the energy reservoir is not equal to or greater than the first set value according to a result of the determination of the first determination step; A third determination step of determining whether the voltage is supplied to the load through the energy reservoir when the charge state of the energy reservoir is equal to or less than the second set value according to the determination result of the second determination step; A fourth determination step of determining whether the charged state of the energy reservoir is equal to or less than a predetermined third set value when the voltage is supplied to the load through the energy reservoir according to the determination result of the third determination step; Wherein when the state of charge of the energy reservoir is equal to or less than the third set value, the second switch is closed and the first switch and the third switch are opened according to a result of the fourth determination, An overdischarge prevention step of charging the energy reservoir while supplying a voltage from the AC power source to the load; .

Wherein when the state of charge of the energy reservoir is equal to or greater than the first set value, the third switch is closed and the first switch and the second switch are opened according to the determination result of the first determination step, And an overcharge prevention step of supplying a voltage to the load through the energy reservoir.

And when the state of charge of the energy reservoir is not equal to or less than the second set value, the second switch is closed and the first switch and the third switch are opened and an overdischarge prevention step of charging the energy reservoir while supplying a voltage from the AC power source to the load.

Wherein when the voltage is not supplied to the load through the energy reservoir according to the determination result of the third determination step, the second switch is closed and the first switch and the third switch are opened, And an overdischarge prevention step of charging the energy reservoir while supplying a voltage from the AC power source to the load.

And when the charge state of the energy reservoir is not equal to or less than the third set value, the third switch is closed and the first switch and the second switch are opened and an overcharge preventing step of supplying a voltage to the load through the energy reservoir.

According to the control system of the uninterruptible power supply apparatus using the lithium ion battery and the control method thereof, the uninterruptible power supply apparatus provided between the alternating current power source and the load for immediately supplying power in case of emergency, It is possible to effectively reduce the volume of the uninterruptible power supply unit by connecting the lithium ion battery rather than the secondary lead-acid battery.

In addition, according to the state of charge (SOC) of the lithium ion battery, it is possible to efficiently supply power to the load by storing a large amount of power while effectively preventing overcharge and overdischarge of the energy reservoir.

Further, when a plurality of energy storage elements are constituted, it is possible to easily control own cell balancing and charging states.

FIG. 1 is a schematic diagram of a control system for an uninterruptible power supply using a lithium ion battery according to an embodiment of the present invention. Referring to FIG.
2 is a detailed block diagram of a switching unit of a control system of an uninterruptible power supply using a lithium ion battery according to an embodiment of the present invention.
3 is a first exemplary operation of a switching unit of a control system of an uninterruptible power supply unit using a lithium ion battery according to an embodiment of the present invention.
4 is a second exemplary operation of a switching unit of a control system for an uninterruptible power supply using a lithium ion battery according to an embodiment of the present invention.
5 is a view illustrating a third example of the operation of the switching unit of the control system of the uninterruptible power supply unit using the lithium ion battery according to the embodiment of the present invention.
6 is a flowchart illustrating a method of controlling an uninterruptible power supply using a lithium ion battery according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a control system and method for controlling an uninterruptible power supply using a lithium ion battery according to the present invention will be described in detail with reference to the accompanying drawings. The following drawings are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the following drawings, but may be embodied in other forms. Also, throughout the specification, like reference numerals designate like elements.

Hereinafter, the technical and scientific terms used herein will be understood by those skilled in the art without departing from the scope of the present invention. Descriptions of known functions and configurations that may be unnecessarily blurred are omitted.

In addition, a system refers to a collection of components, including devices, mechanisms, and means that are organized and regularly interact to perform the required function.

The uninterruptible power supply unit normally supplies AC power to the load through a commercial AC power source, a power conversion device, a distortion correction circuit, etc. In addition, by connecting an energy storage device to the output of the rectifier device and operating the energy storage device, So that power can be supplied to the load through the inverter without interruption.

That is, the control system and method for controlling the uninterruptible power supply using the lithium ion battery according to an embodiment of the present invention is a system and method for controlling the uninterruptible power supply using an uninterruptible power supply capable of supplying a constant voltage to the load (20) A control system and a control method for enabling an energy reservoir composed of a lithium ion battery to be safely connected to a power supply unit (UPS).

FIG. 1 is a simplified diagram illustrating a configuration of a control system for an uninterruptible power supply using a lithium ion battery according to an embodiment of the present invention. Referring to FIG. 1, a configuration of a control system for an uninterruptible power supply using a lithium ion battery according to an embodiment of the present invention will be described in detail.

The control system of the uninterruptible power supply using the lithium ion battery according to the embodiment of the present invention is provided with the switching unit 40 in the uninterruptible power supply unit provided between the AC power source 10 and the load 20, The AC power supplied from the power source 10 is stably supplied to the load 20 at a constant voltage and at the same time the switching power is supplied to the switching unit 20 so that the overcharge and overdischarge of the energy storage device 30, (40).

1, a control system for an uninterruptible power supply using a lithium ion battery includes an AC power source 10, a load 20, a converter 1, an inverter 2, a fixed switch 3, (30) and a switching unit (40).

To learn more about each configuration,

The converter 1 is connected to the AC power source 10 and converts AC energy supplied from the AC power source to DC power and transfers the DC power converted into the inverter 2 or the energy storage device 30,

The inverter 2 is connected to the converter 1 and converts the received direct current power into an alternating current power of a constant voltage and a constant frequency and transfers it to the load 20,

The fixed switch 3 can switch the load 20 so that power is supplied from the energy storage element 30 to prevent malfunction and shutdown of the load 20 when an accident occurs in the inverter 2. [

The energy storage element 30 is connected to the first node 50 between the AC power supply 10 and the load 20 and when the voltage supplied to the load 20 from the AC power supply 10 is out of the allowable voltage range The power supply from the AC power source 10 to the load 20 is not smoothly performed due to any emergency situation or the AC power supply of the constant voltage and the constant frequency due to the accident occurrence of the inverter 2 The voltage can be supplied to the load 20. In this case,

At this time, the energy storage element 30 of the present invention may be constituted by a lithium ion battery.

Lithium ion batteries are more expensive than conventional lead-acid batteries, but they are 4 to 5 times smaller in volume and have higher space utilization, less temperature sensitivity than secondary lead-acid batteries, and greater storage capacity.

Accordingly, when the operating cycle of the UPS is taken into consideration, the secondary battery has superior economy and performance.

However, lithium ion batteries are highly likely to explode when overcharged and are very dangerous in the event of an explosion. Therefore, in order to connect a lithium ion battery to an uninterruptible power supply unit connected to a conventional secondary lead-acid battery, However,

The present invention can solve this problem by providing the switching unit 40.

To be more specific,

The switching unit 40 is connected between the first node 50 and the energy storage element 30 and generates a voltage to be supplied to the energy storage element 30 from the AC power supply 10 and a voltage It is possible to control the voltage supplied to the battery 20.

2, the switching unit 40 includes a first switch 41, a second switch 42, and a third switch 42 connected between the first node 50 and the both ends (+) of the energy storage element 30, A third switch 43, a diode 44, and a resistor 45. [

The first switch 41 is connected in series with the second node 60, which is both ends of the energy storage element 30, and the first node 50,

The resistor 45 is connected between the first switch 41 and the first node 50,

The second switch 42 is connected in parallel with the second node 60 and the first node 50 at both ends of the energy storage element 30,

The diode 44 is connected in parallel with the third node 70 and the first node 50 at both ends of the energy storage element 30 to prevent reverse current from the load 20 to the energy storage element 30,

The third switch 43 may be connected between the diode 44 and the first node 50.

The control system of the uninterruptible power supply using the lithium ion battery according to the embodiment of the present invention can easily overcharge the energy storage element 30 composed of the lithium ion battery by using the switching unit 40, And it is possible to easily control its own cell balancing or charge state of the energy storage device itself even if a plurality of energy storage devices are provided.

In addition, by connecting the diode 44 in parallel with the first node 50, there is an advantage that a potential difference can be created to improve the turn-on speed of the diode 44 when a voltage accident occurs.

3, when the energy storage element 30 is first connected to the uninterruptible power supply or when it is reconnected after maintenance,

The first switch 41 is closed for a predetermined time and the second switch 42 and the third switch 43 are opened to disconnect the energy storage element 30 and the inverter 2 of the uninterruptible power supply unit The voltage can be matched.

In this case, the predetermined time is a time of 1 second to 10 seconds, and after the voltage matching of the energy storage element 30 is completed, the next operation is overlapped and continuous operation is continued.

In addition, the control of the switching unit 40 may be performed in a battery management system (BMS).

Thereafter, the state of charge (SOC) of the lithium ion battery, which is the energy storage element 30, is received from the battery management system,

In order to prevent overcharging of the energy storage element 30, it may be possible to provide a voltage to the load 20 via the energy storage element 30,

In addition, in order to prevent overdischarge of the energy storage element 30, the AC power supply 10 may supply the load 20 and the energy storage element 30 with a voltage at the same time.

More specifically,

4, when the charging state of the energy storage element 30 received from the battery management system is fully charged,

The third switch 43 is closed and the first switch 41 and the second switch 42 are opened to supply the voltage to the load 20 through the energy storage element 30 . The risk of overcharging of the energy storage element 30 can be prevented in advance.

At this time, the operation of connecting the third switch 43 of the switching unit 40 and opening the first switch 41 and the second switch 42 to prevent the overcharge of the energy storage element 30, The first switch 41 is connected for a predetermined time and the second switch and the third switch are opened in order to match the voltage between the energy storage element 30 and the inverter 2, have.

In addition, as described above, the control of the switching unit 40 may be performed in a battery management system (BMS).

5, when the charging state of the energy storage element 30 received from the battery management system is in an over-discharge state,

While the second switch 42 is closed and the first switch 41 and the third switch 43 are opened to supply the voltage from the AC power supply 10 to the load 20, (30). Thus, overdischarge of the energy storage element 30 can be quickly prevented.

At this time, the operation of connecting the second switch 42 of the switching unit 40 and opening the first switch 41 and the third switch 43 to prevent overdischarge of the energy storage element 30 , The operation of connecting the first switch 41 and opening the second switch and the third switch for a predetermined time in order to match the voltage between the energy storage element 30 and the inverter 2, 30 and the third switch 43 of the switching unit 40 and open the first switch 41 and the second switch 42 to prevent overcharging of the first and second switches 30 and 30 .

In addition, as described above, the control of the switching unit 40 may be performed in a battery management system (BMS).

6 is a flowchart illustrating steps of a method for controlling an uninterruptible power supply using a lithium ion battery according to an embodiment of the present invention. Referring to FIG. 6, a method of controlling an uninterruptible power supply using a lithium ion battery according to an embodiment of the present invention will be described in detail.

A method of controlling an uninterruptible power supply using a lithium ion battery according to an embodiment of the present invention includes a switching unit 40 in an uninterruptible power supply unit provided between an AC power source 10 and a load 20, The AC power supplied from the power source 10 is stably supplied to the load 20 at a constant voltage and at the same time the switching power is supplied to the switching unit 20 so that the overcharge and overdischarge of the energy storage device 30, (40).

6, the control method of the uninterruptible power supply unit using the lithium ion battery may include a first connecting step S100, a first determining step S200, a second determining step S300, a third determining step S400, , A fourth determination step (S500), an overdischarge prevention step (S600), and an overcharge prevention step (S700).

To learn more about each step,

The initial connection step (S100) is performed when the energy storage element (30) is initially connected to the uninterruptible power supply, or reconnected after maintenance,

The first switch 41 is closed for a predetermined time and the second switch 42 and the third switch 43 are opened to disconnect the energy storage element 30 and the inverter 2 of the uninterruptible power supply unit The voltage can be matched.

The first determination step S200 may determine whether the state of charge (SOC) of the energy storage device 30 in the battery management system is equal to or greater than a preset first preset value.

In this case, the first set value means a charge value at which the energy storage element 30 is in a buffered state or in a buffered state to supply a voltage to the load 20.

According to the determination result of the first determination step S200, when the state of charge of the energy storage element 30 is equal to or greater than the first set value, the overcharge prevention step S700 may be performed.

The overcharge protection step S700 may be performed by closing the third switch 43 and opening the first switch 41 and the second switch 42 to open the lithium storage battery 30 through the lithium ion battery And the voltage is supplied to the load 20.

In this way, overcharge of the energy storage element 30 can be prevented and a constant voltage can be continuously supplied to the load 20.

The second determining step S300 is a step of determining whether or not the charged state of the energy storage element 30 is equal to or less than the first set value according to a result of the first determining step S200,

It can be determined again whether the state of charge of the energy storage element 30 is equal to or less than the preset second set value.

In this case, the second set value means an unstable intermediate state in which the charged state of the energy storage element 30 is neither a buffer state nor a discharge state.

That is, since it means a charging state in which a voltage is supplied to the load 20 or the charging can be performed by the AC power supply 10 in accordance with the additional judgment, the second setting value can be arbitrarily manipulated by the user.

In the third determination step (S400), when the state of charge of the energy storage element (30) is equal to or lower than the second set value in accordance with the determination result of the second determination step (S300)

It is possible to judge whether a voltage is being supplied to the load 20 through the energy storage element 30 at present.

If the state of charge of the energy storage element 30 is not equal to or less than the second set value, that is, exceeds the second set value, according to the result of the second determination step S300, S600).

The over-discharge preventing step S600 is a step of closing the second switch 42 and opening the first switch 41 and the third switch 43 to disconnect the AC power source 10 from the AC power source 10 to the load 20 And at the same time, the energy storage element 30 can be charged.

Thus, overdischarge of the energy storage element 30 can be prevented.

In the fourth determination step S500, when the voltage is supplied to the load 20 through the energy storage element 30 according to the determination result of the third determination step S400,

At this time, it is possible to determine whether the charging state of the energy storage element 30 is equal to or less than a preset third set value.

At this time, the third set value means a state in which the charging state of the energy storage element 30 is close to the discharge, and the supply of the voltage to the load 20 is dangerous.

When the voltage is not supplied to the load 20 through the energy storage element 30 according to the determination result of the third determination step (S400), the energy storage element 30 applies a voltage to the current load 20 Since the state of charge is not equal to the second set value and there is a risk of overdischarge, the overdischarge prevention step S600 is performed in order to prevent this.

That is, while the second switch 42 is closed and the first switch 41 and the third switch 43 are opened to supply the voltage from the AC power supply 10 to the load 20, The storage element 30 is charged.

If the state of charge of the energy storage element 30 is equal to or less than the third set value, that is, if the state of charge of the current energy storage element 30 is close to the discharge state according to the result of the fourth determination step S500 , The lithium ion battery is protected from over discharge by performing the over discharge preventing step S600 immediately.

On the contrary, if the state of charge of the energy storage element 30 is not less than the third set value, that is, exceeds the third set value, according to the result of the fourth determination step S500, S700).

In other words, although the charged state of the energy storage element 30 is not a buffer state, the voltage is continuously supplied to the load 20, and since the current state is not a state close to the discharge, That is, the voltage can be supplied to the load 20 immediately before reaching the third set value.

That is, in other words, the control system for the uninterruptible power supply apparatus using the lithium ion battery and the control method thereof according to the present invention is characterized in that the uninterruptible power supply apparatus and the energy storage element 30 (SOC) of the lithium ion battery, which is the energy storage element 30 composed of the lithium ion battery, through the control of the switching unit 40, Accordingly, overcharge and overdischarge of the energy storage element 30 can be efficiently controlled.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, And various modifications and changes may be made thereto by those skilled in the art to which the present invention pertains.

Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .

1: Converter
2: Inverter
3: Fixed switch
10: AC power source
20: Load
30: Energy storage element
40:
41: first switch 42: second switch
43: third switch 44: diode
45: Resistor
50: First node
60: second node
70: Third node

Claims (10)

A control system for an uninterruptible power supply apparatus which supplies AC power supplied from an AC power source through an uninterruptible power supply unit provided between an AC power source and a load at a constant voltage to the load,
An energy storage element connected to a first node between the AC power source and the load, the energy storage element comprising a lithium ion battery for providing a voltage to the load; And
A switching unit connected between the first node and the energy storage element, for controlling a voltage supplied to the energy storage from the AC power supply and a voltage supplied from the energy storage element to the load;
A control system for an uninterruptible power supply using a lithium ion battery including a battery.
The method according to claim 1,
The switching unit
A first switch connected between the first node and both ends (+) of the energy reservoir, a second switch, a third switch, a resistor and a diode,
Wherein the first switch is connected in series with a second node, both ends of the energy reservoir, and the first node,
The resistor being connected between the first switch and the first node,
The second switch being connected in parallel with a second node, both ends of the energy reservoir, and the first node,
Wherein the diode is connected in parallel with a third node, both ends of the energy reservoir, to the first node to prevent reverse current flow from the load to the energy reservoir,
And the third switch is connected between the diode and the first node. The control system of the uninterruptible power supply using the lithium ion battery.
3. The method of claim 2,
The switching unit
When the energy reservoir is first connected to the uninterruptible power supply using the lithium ion battery,
The first switch is closed for a predetermined time and the second switch and the third switch are opened to match the voltage between the energy storage element and the inverter of the uninterruptible power supply. Control system for uninterruptible power supply using lithium ion battery.
3. The method of claim 2,
The switching unit
When the energy reservoir is fully charged,
Wherein the third switch is closed and the first switch and the second switch are opened to supply a voltage to the load through the energy reservoir. Control system.
3. The method of claim 2,
The switching unit
When the energy store is overdischarged,
And the energy storage device is charged while providing the voltage from the AC power source to the load by closing the second switch and opening the first switch and the third switch. Control System for Uninterruptible Power System Using.
A control method of an uninterruptible power supply using a lithium ion battery in which AC energy supplied from an AC power source is supplied to a load at a constant voltage through control of a switching unit including a first switch, a second switch and a third switch,
An energy storage device, which is a lithium ion battery that closes the first switch, opens the second switch and the third switch to provide a voltage to the load, and an inverter of the uninterruptible power supply, An initial connection step of matching the voltages between the electrodes;
A first determination step of determining whether a state of charge (SOC) of the energy store is equal to or greater than a predetermined first set value;
When the charge state of the energy reservoir is not equal to or greater than the first set value according to the determination result of the first determination step,
A second determination step of determining whether the charged state of the energy reservoir is lower than a predetermined second set value;
When the state of charge of the energy reservoir is equal to or less than the second set value in accordance with the determination result of the second determination step,
A third determination step of determining whether the voltage is supplied to the load through the energy reservoir;
When the voltage is supplied to the load through the energy reservoir according to the determination result of the third determination step,
A fourth determination step of determining whether the charged state of the energy reservoir is lower than a predetermined third set value;
When the charge state of the energy reservoir is equal to or less than the third set value according to the determination result of the fourth determination step,
An overdischarge preventing step of closing the second switch and opening the first switch and the third switch to charge the energy reservoir while providing a voltage from the AC power source to the load;
And a control unit for controlling the uninterruptible power supply using the lithium ion battery.
The method according to claim 6,
When the state of charge of the energy reservoir is equal to or greater than the first set value in accordance with the determination result of the first determination step,
An overcharge prevention step of closing the third switch and opening the first switch and the second switch to supply a voltage to the load through the energy reservoir;
And a control unit for controlling the uninterruptible power supply using the lithium ion battery.
The method according to claim 6,
When the charge state of the energy reservoir is not equal to or less than the second set value according to the determination result of the second determination step,
An overdischarge preventing step of closing the second switch and opening the first switch and the third switch to charge the energy reservoir while providing a voltage from the AC power source to the load;
And a control unit for controlling the uninterruptible power supply using the lithium ion battery.
The method according to claim 6,
When the voltage is not supplied to the load through the energy reservoir according to the determination result of the third determination step,
An overdischarge preventing step of closing the second switch and opening the first switch and the third switch to charge the energy reservoir while providing a voltage from the AC power source to the load;
And a control unit for controlling the uninterruptible power supply using the lithium ion battery.
The method according to claim 6,
When the charging state of the energy reservoir is not equal to or less than the third set value according to the determination result of the fourth determination step,
An overcharge prevention step of closing the third switch and opening the first switch and the second switch to supply a voltage to the load through the energy reservoir;
And a control unit for controlling the uninterruptible power supply using the lithium ion battery.

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