KR100964597B1 - Uninterrupted power supply - Google Patents

Abstract

PURPOSE: An uninterruptible power supply unit is provided to prevent the overcharging of a battery by efficiently transferring the energy from a load to an AC input power source. CONSTITUTION: A battery(130) stores the energy. A balance node(BN) is connected to an AC power source through a switch. A first power source converting circuit(120) is connected to the balance node, the battery, and a load. A first power source converting circuit controls the voltage level which is applied to a load by charging and discharging the energy of a battery. A second power source converting circuit(110) is connected to the balance node and the battery. A second power source converting circuit controls a current applied in the balance node or the load by charging and discharging the energy of a battery.

Description

Uninterruptible Power Supply {UNINTERRUPTED POWER SUPPLY}

TECHNICAL FIELD The present invention relates to power supply technology, and more particularly, to an uninterruptible power supply.

An uninterrupted power supply (UPS) is a device that provides power to a load generated from a battery or a separate auxiliary power source in an emergency such as a power failure. The uninterruptible power supply can operate during power outages, providing auxiliary power for a few seconds to hours to protect the electrical installations of the load and safely shut down.

Generally, non-powered power supplies are not limited to computer protection equipment and are used to prevent damage caused by unexpected power interruptions, severe business interruptions or data loss in data centers, telecommunications or other electrical equipment.

Uninterruptible power supplies are classified into on-line, off-line, and line interactive methods.

Among them, the on-line method converts commercial power into DC power by the converter circuit, and converts the DC power into the battery through the charging circuit and converts the AC power back into the AC power through the inverter circuit.

The off-line method outputs commercial AC power as it is, and the charging circuit charges the battery. In case of power failure, the inverter circuit is driven to output power stored in the battery.

In addition, the line interactive system converts power between the battery and the inverter circuit at all times, and converts the power with each other, and the commercial AC power is also linked together. Use the power source.

On the other hand, Silicon Controlled Rectifiers (SCRs), which are generally used as switches for uninterruptible power supplies, operate as if they were turned on for a certain period of time even if the control voltage was changed. If a sudden phase change occurs, there is a problem that the internal circuit may be short circuited and damaged.

In addition, if the power flow inside the uninterruptible power supply is not smooth while the uninterruptible power supply performs voltage regulation, the battery may be overcharged, which may cause permanent damage to the battery.

Among the embodiments, the uninterruptible power supply includes a battery, a balance node, a first conversion circuit and a second conversion circuit. The battery stores energy. The balance node is connected to an AC input power source via a switch. The first power conversion circuit is connected to the balance node, the battery and the load, and controls the voltage level applied to the load by charging and discharging the energy of the battery. The second power conversion circuit is connected to the balance node and the battery, and charges and discharges the energy of the battery to regulate the current flowing into or out of the balance node and the current flowing into or out of the load.

Among the embodiments, the uninterruptible power supply includes a switch, a first power converter, a second power converter, and a phase controller. The switch unit includes an insulated gate bipolar transistor for opening and closing an electrical connection between an AC input power source and a balance node. The first power converter is connected to the balance node, the battery, and the load, and controls the voltage level applied to the load by charging and discharging the energy of the battery. The second power converter is connected to the balance node and the battery, and charges and discharges the energy of the battery to adjust the current flowing into or out of the plurality of balance nodes and the current flowing into or out of the load. Detects a phase change of the AC input voltage, controls the switch unit according to the phase change, and controls an operation mode of the first and second power conversion units.

Among the embodiments, the power supply method includes detecting a phase change of an AC input voltage provided from an AC input power source, and between an AC input power source and a balance node according to an instantaneous phase change of the AC input voltage during power failure or recovery of power failure. Opening and closing an electrical connection of the controller, charging and discharging the energy of the battery according to the voltage level of the balance node, adjusting a voltage level applied to the load, and flowing into or out of the balance node from the AC input power. And charging and discharging the energy of the battery according to the current level to adjust the current level flowing into or out of the load from the balance node.

The description of the disclosed technique is merely an example for structural or functional explanation and the scope of the disclosed technology should not be construed as being limited by the embodiments described in the text. That is, the embodiments may be variously modified and may have various forms, and thus the scope of the disclosed technology should be understood to include equivalents capable of realizing the technical idea.

On the other hand, the meaning of the terms described in the present application should be understood as follows.

Terms such as "first" and "second" are intended to distinguish one component from another component, and the scope of rights should not be limited by these terms. For example, the first component may be named a second component, and similarly, the second component may also be named a first component.

The term “and / or” should be understood to include all combinations that can be presented from one or more related items. For example, the meaning of "first item, second item and / or third item" may be given from two or more of the first, second or third items as well as the first, second or third items. Any combination of the possible items.

When a component is referred to as being "connected" to another component, it should be understood that there may be other components in between, although it may be directly connected to the other component. On the other hand, when an element is referred to as being "directly connected" to another element, it should be understood that there are no other elements in between. On the other hand, other expressions describing the relationship between the components, such as "between" and "immediately between" or "neighboring to" and "directly neighboring to", should be interpreted as well.

Singular expressions should be understood to include plural expressions unless the context clearly indicates otherwise, and terms such as "include" or "have" refer to features, numbers, steps, operations, components, parts, or parts thereof described. It is to be understood that the combination is intended to be present, but not to exclude in advance the possibility of the presence or addition of one or more other features or numbers, steps, operations, components, parts or combinations thereof.

For each step, the identifiers (e.g., a, b, c, ...) are used for convenience of description, and the identifiers do not describe the order of the steps, and each step is clearly contextual. Unless stated in a specific order, it may occur differently from the stated order. That is, each step may occur in the same order as specified, may be performed substantially simultaneously, or may be performed in the reverse order.

All terms used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. The terms defined in the commonly used dictionary should be interpreted to coincide with the meanings in the context of the related art, and should not be interpreted as having ideal or excessively formal meanings unless clearly defined in the present application.

1 is a block diagram illustrating an uninterruptible power supply according to an embodiment of the present invention.

Referring to FIG. 1, the uninterruptible power supply device includes a battery 130, a balance node BN, a first power conversion circuit 120, and a second power conversion circuit 110. The uninterruptible power supply may further include a controller 140 and at least one switch SW1 or SW2.

The battery 130 stores energy. The balance node BN is connected to the AC input power 150 through a switch.

The first power conversion circuit 120 is connected to the balance node BN, the battery 130, and the load 160, and controls the voltage level applied to the load 160 by charging and discharging the energy of the battery 130. .

The second power conversion circuit 110 is connected to the balance node BN and the battery 130, and charges and discharges the energy of the battery 1300 to flow into or out of the balance node BN and load 160. Adjust the current flowing into or out of the furnace.

The first power conversion circuit 120 includes a first transformer circuit 121 and a first inverter 122.

The first transformer circuit 121 includes a primary winding connected in series between the balance node and the load 160 and a secondary winding inductively coupled with the primary winding.

The first inverter 122 is connected between the secondary winding of the first transformer circuit 121 and the battery 130, and in response to a control signal, converts the AC power of the first transformer circuit 121 into direct current power. The battery 130 may be provided, or the DC power of the battery 130 may be converted into AC power and provided to the first transformer circuit 121.

The second power conversion circuit 110 includes a second transformer circuit 111 and a second inverter 112.

The second transformer circuit 111 includes a primary winding connected between the balance node BN and a neutral line, and a secondary winding inductively coupled with the primary winding.

The second inverter 112 is connected to the secondary winding of the second transformer circuit 111 and, in response to a control signal, converts the AC power of the second transformer circuit 111 into DC power and provides the battery 130 to the battery 130. Alternatively, the DC power of the battery 130 is converted into AC power and provided to the second transformer circuit 111.

The controller 140 provides a control signal to the control first and second inverters 112 and 122.

2 and 3 are block diagrams illustrating the operation of the uninterruptible power supply. 2 and 3 are randomly selected and approximated values for illustrative purposes only and may differ from actual values. Hereinafter, the rated voltage of the load 160 is assumed to be 220V.

2 shows the operation of the uninterruptible power supply when the voltage of the AC input power supply 150 is higher than the rated voltage of the load 160.

Referring to FIG. 2, when the AC input voltage is 240V and the input current is 1A, the voltage drop of 20V is caused by the primary winding of the first transformer circuit 121 included in the first power conversion circuit 120. To generate a rated voltage of 220V to the load 160. In this case, considering the power flow, since 240W of power is supplied, the current may be increased instead of lowering the voltage supplied to the load 160. The second power conversion circuit 110 converts energy provided from the first power conversion circuit 120 or the battery 130 to provide a current of 0.1A to the balance node BN. That is, the voltage supplied to the load 160 by the first power conversion circuit 120 is adjusted, and surplus power is supplied from the first power conversion circuit 120 to the second power battery 130 or the second conversion circuit 110. ) Can be circulated. In addition, the second conversion circuit converts the circulated power into a current form and provides the balance node BN to adjust the current flowing from the balance node BN to the load 160.

3 shows the operation of the uninterruptible power supply when the voltage of the AC input power supply 150 is lower than the rated voltage of the load 160.

Referring to FIG. 3, when the magnitude of the AC input voltage is 200 V and the magnitude of the input current is 1.1 A, the voltage of 20 V is caused by the primary winding of the first transformer circuit 121 included in the first power conversion circuit 120. The rise may occur to supply a rated voltage of 220V to the load 160. In this case, considering the power flow, since 240W of power is supplied, the current may be reduced instead of increasing the voltage supplied to the load 160. The second power conversion circuit 110 provides a current of 0.1 A to the first power conversion circuit 120 or the battery 130 from the balance node BN. That is, the voltage supplied to the load 160 by the first power conversion circuit 120 may be adjusted, and the required power may be circulated in the direction of the second power conversion circuit 110 or the battery 130 at the balance node. In addition, the first conversion circuit 120 may adjust the provided voltage level of the load 160 by converting the circulated power in the form of voltage.

That is, the first power conversion circuit 120 adjusts the voltage drop or voltage rising level across the first transformer circuit 121 according to the voltage of the balance node BN and the rated voltage of the load 160. In addition, the second power conversion circuit 110 may adjust the current level flowing in the primary winding of the second transformer circuit 111 according to the current level flowing into or out of the balance node BN from the AC input power source 150. . This process may be performed when the control of the controller 140 and the first and second conversion circuits 110 and 120 interact. In this case, the first and second inverters 112 and 122 may be circuits for performing bidirectional DC-AC power conversion. The first and second inverters 112 and 122 may be full bridge or half bridge inverters or rectifiers including a plurality of insulated gate bipolar transistors.

4 is a block diagram illustrating an impedance relationship of the uninterruptible power supply of FIG. 1.

Referring to FIG. 4, the equivalent impedance Zs in the AC input power direction at the balance node BN may be smaller than the equivalent impedance in the load 160 direction at the balance node BN.

In other words, the balance node BN may be a node in which circulated energy is adjusted in the form of a current, and a node to which the circulated energy moves from the first power conversion circuit 120 and the battery 130 to adjust the voltage. The balance node BN may be connected closer to the AC input power side than the first transformer circuit 121 of the first power conversion circuit 120 connected in series so as to smoothly perform the electric power circulation.

The uninterruptible power supply device according to an embodiment may convert the energy of the battery 130 into AC power to be delivered to the balance node BN when the battery 130 is overcharged over an allowable range, and in this case, the AC input power direction. Since the equivalent impedance of S is smaller than the equivalent impedance in the direction of the load 160, energy may flow smoothly toward the AC input power. In the energy circulation process for controlling voltage and current, the battery 130 may be prevented from being overcharged with energy.

5 is a block diagram illustrating an operating characteristic of an uninterruptible power supply according to an embodiment.

Referring to FIG. 5, the AC input power supplies power to one or more loads 531, 532, 533 through an uninterruptible power supply. In this case, if the loads 531, 532, and 533 are inductive, such as an electric motor, regenerative energy ER may be generated according to power fluctuations. For example, if the power supply to the loads 531, 532 and 533 including the motor is momentarily interrupted, the motor will exhibit characteristics similar to the generator for a period of time and provide regenerative energy (ER) toward the uninterruptible power supply. .

Even in this case, the uninterruptible power supply device according to the embodiment of the present invention, as described above, efficiently transfers energy from the load 160 toward the AC input power source to prevent overcharging of the battery 130 and to load 160. And damage to internal circuits of the uninterruptible power supply.

6 is a block diagram illustrating an uninterruptible power supply device according to another exemplary embodiment.

The uninterruptible power supply of FIG. 6 further includes a phase controller 200 as compared to the uninterruptible power supply of FIG. 1.

The phase controller detects a phase change of the AC input voltage provided from the AC input power, and controls an operation mode of the uninterruptible power supply by controlling the electrical connection between the AC input power and the balance node BN according to the phase change.

FIG. 7 is a block diagram illustrating in detail the phase controller 200 included in the uninterruptible power supply of FIG. 6.

Referring to FIG. 7, the phase controller 200 includes an isolation amplifier circuit 210, a processor 22, an input / output unit 230, a driving driver 240, and a local power supply 250.

The isolation amplification circuit 210 receives the AC input voltage AC INPUT provided from the AC input power and the AC output voltage UPS OUTPUT of the uninterruptible power supply, and provides a phase signal PHASE SIGNAL.

The processor 220 determines a phase change of the AC input voltage AC INPUT and the AC output voltage UPS OUTPUT based on the phase signal PHASE SIGNAL, and based on the phase change and the switch open / close signal SWITCH INPUT. Phase error information (PHASE ERROR), switch status information (SWITCH STATUS) and switch control signal (SWCTRL) is provided.

The input / output unit 230 receives the switch open / close signal SWITCH INPUT and provides the switch 220 to the processor 220, and outputs switch error information (SWITCH ERROR) and switch state information (SWTCH STATUS).

The driving driver 240 provides the gate voltage GCTRL of the insulated gate bipolar transistor in response to the switch control signal SWCTRL. The driving driver 240 may provide the switch state information SWST to the processor 220.

The local power supply unit 250 generates a DC power based on an AC input voltage AC INPUT, an AC output voltage AC OUTPUT, or an AUX POWER INPUT, and generates a DC power. Supply to the unit 230 and the drive driver 240.

8A and 8B are block diagrams illustrating the operation of the automatic transfer switch at the time of power failure or recovery of power failure.

8A and 8B, an automatic transfer switch (ATS) 350 is connected to an external power supply 310 or an auxiliary power supply 320 in front of the uninterruptible power supply systems 200 and 330. The external power source 310 may be a power supply line delivered through a power transmission line, and the maintenance power source 320 may be an auxiliary power generation facility that operates in an emergency such as a power failure. 4A illustrates the operation of the automatic transfer switch 350 in the normal state, and FIG. 4B illustrates the operation of the automatic transfer switch 350 in the power failure state. That is, the automatic transfer switch 350 is connected to the external power source 310 in the normal state, but is switched when the power failure is connected to the auxiliary power source 320, and when the power failure is restored and returns to the normal state again, the external power switch ( 310).

In this case, the phases of the voltages provided by the external power supply 310 and the auxiliary power supply 320 may be different from each other. An uninterruptible power supply connected to a rear end may generate a momentary phase change during a switching operation of the automatic transfer switch 350. It may adversely affect the circuit 200, 230, or the load 340.

The phase controller 200 according to an exemplary embodiment detects a phase change of an AC input voltage provided from an external power source 310 or an auxiliary power source 320, and controls a switch connected to the phase control unit according to the detected phase change to uninterruptible power failure. Controls the operation mode of the power supply 330. Therefore, it is possible to prevent circuit damage due to instantaneous phase change.

9A to 9E are waveform diagrams illustrating a phase change of a voltage input to an uninterruptible power supply.

9A and 9B show phase changes of voltages provided from an external power supply and an auxiliary power supply, respectively. 9A and 9B, the phase of the voltage provided from the external power source and the phase of the voltage provided to the auxiliary power source may be different. In general, the problem is when the difference between the two voltage phases is relatively large. 9A and 9B show a case where there is a phase difference of 180 degrees at the time t0 at which the switching operation is performed.

9C is a waveform diagram illustrating a switching operation of a conventional uninterruptible power supply, and FIG. 5D is a waveform diagram illustrating a phase change of a voltage provided to an internal circuit of a conventional uninterruptible power supply.

Referring to FIG. 9C, when a device such as a silicon controlled rectifier is used for a conventional uninterruptible power supply switching operation, even if the control voltage of the silicon controlled rectifier is changed at time t0, the switch is turned off after a predetermined time (t1 time point). A characteristic may occur that does not turn off completely. Therefore, the operation of the switch is turned on from t0 to t1 time, which may affect the internal circuit of the uninterruptible power supply.

Referring to FIG. 9D, when the automatic switching switch performs a switching operation at time t0, when the input voltage waveform is changed from FIG. 9A to FIG. 9B, an instantaneous phase change is suddenly generated. The AC input voltage flows into the internal circuit of the uninterruptible power supply as it is not properly blocked. Therefore, the elements of the internal circuit can be shorted or permanently damaged.

9E is a waveform diagram illustrating a switching operation of a phase controller according to an exemplary embodiment of the present invention.

Referring to FIG. 9E, the phase controller detects a phase change of the AC input voltage, and when there is an instantaneous phase change as shown in FIG. 9D, controls the switching operation by using an included insulated gate bipolar transistor connected to the phase controller. When the insulated gate bipolar transistor is used as the switching element, the response characteristic can be improved.

In addition, the phase controller tracks the phase change of the AC input voltage and turns off the switch when the instantaneous phase change exceeds the allowable range in case of power failure or recovery of power failure, thereby maintaining the operation mode of the uninterruptible power supply in the power failure mode. do.

The detailed method of controlling the operation mode of the uninterruptible power supply by the phase controller may be freely modified according to embodiments. In an embodiment, as shown in FIG. 9E, the power input to the uninterruptible power supply may be cut off so that the uninterruptible power supply may be recognized as if a power failure occurs. Such a method can be applied to an existing uninterruptible power supply without adding a separate device other than a phase control unit or changing an internal configuration. Therefore, it is possible to expect a cost reduction effect because there is no need to exchange equipments on the whole.

FIG. 10 is a diagram illustrating an operation mode of an uninterruptible power supply under control of a phase controller during correction or power failure recovery.

Referring to FIG. 10, when the switch is turned off, the phase change of the AC input voltage 410 and the phase change of the AC output voltage 420 of the uninterruptible power supply are compared, and the phase change of the AC output voltage is within an allowable range. Once entered, the switch is turned on to switch the uninterruptible power supply's operating mode to normal mode. That is, even if the power failure is recovered at time t0, a sudden phase change may occur, thus maintaining the correction mode and turning on the switch at time t2 when the phase change enters the allowable range, thereby allowing the uninterruptible power supply to operate in the normal mode.

The disclosed technique may have the following effects. It is to be understood, however, that the scope of the disclosed technology is not to be construed as limited thereby, as it is not meant to imply that a particular embodiment should include all of the following effects or only the following effects.

The uninterruptible power supply apparatus according to an embodiment may convert the energy of the battery into alternating current power and deliver it to the balance node when the battery is overcharged in an allowable range or more. In this case, the energy may flow smoothly toward the alternating current input power. In the energy cycle for voltage and current regulation, the battery may be overcharged with energy, thereby preventing the battery from being damaged.

In addition, inductive loads can efficiently transfer energy from a regenerative energy load generated in accordance with power fluctuations to an AC input power source, thereby preventing overcharging of a battery and preventing damage to a load and an uninterruptible power supply internal circuit.

The uninterruptible power supply according to an exemplary embodiment may improve a response characteristic by controlling a switching operation using an insulated gate bipolar transistor.

In addition, the phase control unit included in the uninterruptible power supply unit tracks the phase change of the AC input voltage and controls the operation mode of the uninterruptible power supply unit when the instantaneous phase change exceeds the allowable range in case of power failure or recovery of the power failure. Damage can be prevented.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims It can be understood that

1 is a block diagram illustrating an uninterruptible power supply according to an embodiment of the present invention.

2 and 3 are block diagrams illustrating the operation of the uninterruptible power supply.

4 is a block diagram illustrating an impedance relationship of the uninterruptible power supply of FIG. 1.

5 is a block diagram illustrating an operating characteristic of an uninterruptible power supply according to an embodiment.

6 is a block diagram illustrating an uninterruptible power supply device according to another exemplary embodiment.

FIG. 7 is a block diagram illustrating in detail the phase controller 200 included in the uninterruptible power supply of FIG. 6.

8A and 8B are block diagrams illustrating the operation of the automatic transfer switch at the time of power failure or recovery of power failure.

9A to 9E are waveform diagrams illustrating a phase change of a voltage input to an uninterruptible power supply.

FIG. 10 is a diagram illustrating an operation mode of an uninterruptible power supply under control of a phase controller during correction or power failure recovery.

Claims (14)

A battery for storing energy; A balance node connected to an AC input power source via a switch; A first power conversion circuit connected to the balance node, the battery and the load, and configured to adjust the voltage level applied to the load by charging and discharging energy of the battery; And An uninterruptible power supply device connected to the balance node and the battery and including a second power conversion circuit configured to charge / discharge energy of the battery to regulate current flowing into or out of the balance node and current flowing into or out of a load; . The equivalent impedance of the AC input power source at the balance node is Uninterruptible power supply, characterized in that less than the equivalent impedance of the load side at the balance node. The method of claim 1, wherein the first power conversion circuit is A first transformer circuit comprising a primary winding connected in series between the balance node and the load and a secondary winding inductively coupled with the primary winding; And It is connected between the secondary side winding of the first transformer circuit and the battery, in response to a control signal, converts the AC power of the first transformer circuit into direct current power to provide to the battery, or the direct current power of the battery An uninterruptible power supply comprising: a first inverter converting into alternating current power and providing the converted power to the first transformer circuit. 4. The circuit of claim 3, wherein the first power conversion circuit is And a voltage drop or voltage rise level across the first transformer circuit in accordance with the voltage of the balance node and the rated voltage of the load. The method of claim 1, wherein the second power conversion circuit is A second transformer circuit comprising a primary winding connected between the balance node and a neutral line and a secondary winding inductively coupled with the primary winding; And Connected to the secondary winding of the second transformer circuit, in response to a control signal, converts the AC power of the second transformer circuit into direct current power to provide the battery or converts the DC power of the battery into AC power And a second inverter provided to the second transformer circuit. The method of claim 5, wherein the second power conversion circuit is And a current level flowing in the primary winding of the second transformer circuit according to a current level flowing into or out of the balance node from the AC input power. The method of claim 6, wherein the second power conversion circuit is When the battery is overcharged more than the allowable range, the uninterruptible power supply characterized in that the energy of the battery is converted into AC power and transferred to the balance node. The uninterruptible power supply of claim 6, wherein When the load is inductive, the uninterruptible power supply, characterized in that to transfer the regenerative energy generated by the power fluctuations supplied to the inductive load to the balance node. The method of claim 1, The electronic device may further include a phase controller configured to detect a phase change of the AC input voltage provided from the AC input power and control an electrical connection between the AC input power and the balance node according to the phase change to control an operation mode of the uninterruptible power supply. Uninterruptible power supply, characterized in that. The method of claim 9, wherein the phase control unit Tracking the phase change of the AC input voltage and turning off the switch when the instantaneous phase change exceeds the allowable range in case of power failure or recovery of power failure, thereby maintaining the operation mode of the uninterruptible power supply in the power failure mode. Uninterruptible power supply. The method of claim 10, wherein the phase control unit When the switch is turned off, the phase change of the AC input voltage and the phase change of the AC output voltage of the uninterruptible power supply are compared, and when the phase change of the AC output voltage falls within an allowable range, the switch is turned on. Uninterruptible power supply, characterized in that for switching the operation mode of the uninterruptible power supply to a normal mode. The method of claim 9, wherein the phase control unit An isolation amplifier circuit receiving an AC input voltage provided from the AC input power and an AC output voltage provided to the load and providing a phase signal; The phase change of the AC input voltage and the AC output voltage is determined based on the phase signal, and the phase error information, the state information of the switch and the switch control signal are provided based on the determined phase change and the switch open / close signal. A processor; An input / output unit configured to receive the switch open / close signal and provide it to the processor, and output error information of the switch and state information of the switch; A driving driver providing a driving voltage of the switch in response to the switch control signal; And And a local power supply unit configured to generate DC power based on the AC input voltage, the AC output voltage, or an auxiliary power supply, and supply the DC power to the processor, the input / output unit, and the driving driver. A switch unit including an insulated gate bipolar transistor for opening and closing an electrical connection between an AC input power source and a balance node; A first power converter connected to the balance node, a battery, and a load, and configured to adjust a voltage level applied to the load by charging and discharging energy of the battery; A second power converter connected to the balance node and the battery and configured to charge and discharge the energy of the battery to adjust current flowing into or out of the balance node and current flowing into or out of the load; And And a phase control unit for detecting a phase change of an AC input voltage, controlling the switch unit according to the phase change, and controlling an operation mode of the first and second power conversion units. delete

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