KR102165788B1 - Uninterruptible power supply system including energy storage device - Google Patents

Abstract

The present invention relates to an uninterruptible power supply system including an energy storage device. In the uninterruptible power supply system of the present invention, in the uninterruptible power supply system connected to the grid, a first converter for converting the AC voltage of the grid to a DC voltage, connected in series with the first converter, and output from the first converter A second converter converting a DC voltage into an AC voltage and transferring it to a first load, a battery electrically connected to a node between the first converter and the second converter to perform charging and discharging, and between the battery and the node A UPS that is connected to and converts the magnitude of the DC voltage across both ends, wherein the third converter provides power stored in the battery to the node when the voltage of the node is lower than a predetermined threshold voltage. Operates in mode.

Description

Uninterruptible power supply system including an energy storage device TECHNICAL FIELD [0002] Uninterruptible power supply system including energy storage device TECHNICAL FIELD

The present invention relates to an uninterruptible power supply system including an energy storage device, and more particularly, to an uninterruptible power supply system that improves the response speed of the energy storage device in case of an accident and simplifies the relationship between commands.

The uninterruptible power supply system (Energy Storage System) is a system that increases energy efficiency by storing generated power in each linked system including power plants, substations, and transmission lines, and then selectively and efficiently using the power when it is needed.

If the uninterruptible power supply system equalizes the electric load that fluctuates over time and season and improves the overall load ratio, the unit cost of power generation can be lowered and the investment and operating costs required for power facility expansion can be reduced. You can save.

This uninterruptible power supply system is installed and used in power generation, transmission and distribution, and customers in the power system, and frequency regulation, generator output stabilization using renewable energy, peak shaving, and load leveling ), it is used as an emergency power supply.

The uninterruptible power supply system is largely divided into physical energy storage and chemical energy storage according to the storage method. Physical energy storage includes methods using pumped water power generation, compressed air storage, and flywheel, and chemical energy storage includes methods using lithium ion batteries, lead acid batteries, and Nas batteries.

Meanwhile, such an uninterruptible power supply system includes a host controller that controls each component, and a programmable logic controller (PLC) communicates with each component to determine a current operating state. The PLC controls all sequence operations of the uninterruptible power supply system, and commands each component to perform the operation according to each situation. The PLC and each component communicate through wireless or wired communication.

The uninterruptible power supply system uses a method in which a PLC and each component are connected through communication. As the circuit becomes complicated and the number of components increases, the connection complexity increases and performance is limited.

Specifically, as the complexity of the communication connection in the uninterruptible power supply system increases, interference with the communication signal occurs, thereby increasing the probability that an error may occur during operation, and the uninterruptible power supply mode (Uninterruptible Power Supply; There was a problem in that the operation for the following UPS) was slow.

The present invention provides an uninterruptible power supply by actively determining whether the UPS mode is operated in the DC-DC converter of the energy storage device before receiving the command from the PLC, thereby simplifying the relationship between the fast response speed and control and command in case of an accident. An object of the present invention is to provide an uninterruptible power supply system that performs a structure and operation method that can be used.

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention that are not mentioned can be understood by the following description, and will be more clearly understood by examples of the present invention. In addition, it will be easily understood that the objects and advantages of the present invention can be realized by the means shown in the claims and combinations thereof.

In order to solve such a problem, the uninterruptible power supply system of the present invention, in the uninterruptible power supply system connected to the grid, a first converter for converting the AC voltage of the grid to a DC voltage, and is connected in series with the first converter. , A second converter converting the DC voltage output from the first converter into an AC voltage and transferring it to a first load, a battery that is electrically connected to a node between the first converter and the second converter to perform charging and discharging, And a third converter connected between the battery and the node and configured to convert a magnitude of a DC voltage applied across both ends, wherein the third converter provides the node to the node when the voltage of the node is lower than a predetermined threshold voltage. It operates in a UPS mode that provides the power stored in the battery.

In addition, information on an operation state is received from the first to third converters, and a command for an operation mode of the third converter is generated based on the operation states of the first and second converters, It may further include a PLC to deliver.

In addition, the first reaction unit time for determining an operation mode based on the sensing voltage of the node in the third converter is a second reaction unit time for updating a command for the operation mode of the third converter in the PLC. Can be smaller than

Further, the third converter may accumulate the first reaction unit time to calculate an operation time, and when the operation time is less than the second reaction unit time, the third converter may maintain an operation mode.

In addition, when receiving a command for an operation mode from the PLC, the third converter may operate in an operation mode according to the received command.

In addition, when receiving a command for a charging operation from the PLC, the third converter may operate in a hold mode or a charge mode according to a voltage level of the battery.

In addition, when the voltage of the node is greater than a predetermined threshold voltage, the third converter may operate in different ways according to the voltage level of the battery.

In addition, when the battery is at a first level in a fully charged state, the third converter operates in a hold mode, and when the battery is smaller than the first level, the third converter charges the battery. It can operate in charge mode.

In addition, when the battery is a region between the first level and a second level smaller than the first level, the third converter charges the battery in a first manner, and the battery is charged with the second level and the second level. In the case of an area between the third levels smaller than the second level, the third converter may charge the battery in a second method different from the first method.

In addition, the third converter may operate in the UPS mode when the voltage level of the battery is greater than a predetermined minimum battery voltage level.

According to the present invention as described above, the uninterruptible power supply system of the present invention secures a fast response speed in case of an accident by actively supplying the uninterruptible power from the DC-DC converter of the energy storage device before receiving a command from the PLC. The relationship between control and command can be simplified.

Specifically, by simplifying the operation control algorithm of the Dc-DC converter included in the energy storage device of the uninterruptible power supply system of the present invention, it is possible to improve the response speed of the energy storage device in case of an accident, and to connect communication between each component. It is possible to reduce the probability of communication errors by reducing the complexity of the system, thereby improving the stability of the uninterruptible power supply system. In addition, maintenance and management of the uninterruptible power supply system becomes easy, and various resources and costs required to manage the system can be reduced.

In addition to the above-described effects, specific effects of the present invention will be described together while describing specific details for carrying out the present invention.

1 is a block circuit diagram illustrating an uninterruptible power supply system according to some embodiments of the present invention.
2 is a diagram for describing an operation of an uninterruptible power supply system in a normal mode according to some embodiments of the present invention.
3 is a diagram illustrating an operation in a charging mode of an uninterruptible power supply system according to some embodiments of the present invention.
4 is a diagram for explaining the operation in the UPS mode of the uninterruptible power supply system according to some embodiments of the present invention.
5 is a flowchart illustrating an operation algorithm of a DC-DC converter included in an uninterruptible power supply system according to some embodiments of the present invention.
6 is a graph illustrating a charging method of a battery included in an energy storage device of an uninterruptible power supply system according to some embodiments of the present invention.
7 is a graph for explaining a voltage of a node connected to one end of a DC-DC converter included in an uninterruptible power supply system according to some embodiments of the present invention.
8 is a flowchart illustrating an operation algorithm of a DC-DC converter included in an uninterruptible power supply system according to some other embodiments of the present invention.

The above-described objects, features, and advantages will be described later in detail with reference to the accompanying drawings, and accordingly, one of ordinary skill in the art to which the present invention pertains will be able to easily implement the technical idea of the present invention. In describing the present invention, if it is determined that a detailed description of known technologies related to the present invention may unnecessarily obscure the subject matter of the present invention, a detailed description will be omitted. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to indicate the same or similar elements.

Hereinafter, an uninterruptible power supply system including an energy storage device according to some embodiments of the present invention will be described with reference to FIGS. 1 to 8.

1 is a block circuit diagram showing an uninterruptible power supply system according to a first embodiment of the present invention.

Referring to Figure 1, the uninterruptible power supply system according to the first embodiment of the present invention is a system (AC GRID) 110, a first converter 120, a second converter 130, a first load 135, And an energy storage device 200. In addition, it may further include a PLC (300) for controlling each component of the uninterruptible power supply system.

Specifically, the grid (AC GRID) 110 provides an AC voltage to the first converter 120 through the switch AC_CB1.

The first converter 120 includes an AC-DC converter that converts an AC voltage provided by the system 110 into a DC voltage. In this case, the first converter 120 includes an AC-DC Insulated Gate Bipolar Mode Transistor (IGBT) type converter, but the present invention is not limited thereto.

A switch AC_CB2 may be disposed between the first converter 120 and the system 110. The switch AC_CB2 may electrically connect or disconnect the AC voltage transmission line. The first converter 120 and the switch AC_CB2 may be controlled by a command of the PLC 300.

The second converter 130 is connected in series with the first converter 120 and may convert the DC voltage provided by the first converter 120 into an AC voltage and transfer it to the first load 135. In this case, the second converter 130 includes a DC-AC IGBT type converter, but the present invention is not limited thereto.

A plurality of switches DC_CB1 and DC_CB2 may be disposed between the second converter 130 and the first converter 120. The plurality of switches DC_CB1 and DC_CB2 may electrically connect or disconnect the DC voltage transmission line. Likewise, the second converter 130 and the plurality of switches DC_CB1 and DC_CB2 may be controlled by a command from the PLC 300.

The first load 135 may be various electronic devices and facilities that consume power.

The energy storage device 200 may be directly connected between the first converter 120 and the second converter 130. At this time, the energy storage device 200 measures the voltage of the node N1 between the first converter 120 and the second converter 130 before receiving the command from the PLC 300, so that the voltage of the node N1 When the voltage is lower than the reference voltage, power of the battery 220 may be automatically transferred to the second converter 130. A detailed description of this will be described later.

The energy storage device 200 may include a third converter 210 and a battery 220. In this case, only one battery 220 is shown on the drawing, but the present invention is not limited thereto, and may include a plurality of battery cells, or may be a battery structure connected in parallel, series, or series parallel. The battery 220 may be charged by receiving power from the system 110 or may provide stored power to the first load 135.

The third converter 210 is located between the node N1 between the first converter 120 and the second converter 130 and the battery 220, and has both ends so that the battery 220 outputs or receives a constant power. It is possible to convert the magnitude of the DC voltage applied to. In this case, the second converter 130 includes a DC-DC IGBT type converter, but the present invention is not limited thereto.

Also, the third converter 210 may operate as a bidirectional converter. Thus, the charging/discharging circuit of the third converter 210 may be integrated into one configuration. When the third converter 210 does not operate in the'UPS mode', the battery 220 may be charged, and the third converter 210 automatically determines the state of charge (SOC) of the battery 220. Can be managed. However, the present invention is not limited thereto.

Although only one energy storage device 200 is included in the uninterruptible power supply system in the drawing, the present invention is not limited thereto, and a plurality of energy storage devices 200 may be included. In this case, the plurality of energy storage devices 200 may be connected to the same node in parallel or connected to each other in series.

When the first converter 120 operates normally, the third converter 210 of the energy storage device 200 turns off the switch DC_CB3 located between the nodes N1. The state of the energy storage device 200 may include a'Stop mode', a'Standby mode', and a'Hold mode'.

Specifically, the'Stop mode' means stopping all operations. The'standby mode' refers to a state in which the energy storage device 200 is in standby without performing voltage monitoring on the node N1. 'Hold ode' refers to a state in which the energy storage device 200 is in standby while performing voltage monitoring on the node N1, contrary to the'standby mode'. In this case, when the voltage of the node N1 is lowered, the energy storage device 200 may be switched to a'UPS mode' and operate.

In addition, when the state of charge (SOC) of the battery 220 is lower than a preset value, the energy storage device 200 charges the battery 220 by turning on the switch DC_CB3. The state of the energy storage device 200 is referred to as a'charge mode'.

However, the present invention is not limited thereto, and the energy storage device 200 operates in a'charging mode' immediately according to the voltage Vdc of the node N1 regardless of the voltage level Vbat of the battery 220. A'constant charging method' can be used.

Further, the energy storage device 200 may detect an abnormal operation of the system 110 or the first converter 120 by monitoring the voltage level of the node N1 in real time. In this case, the energy storage device 200 turns on the switch DC_CB3 to deliver the power stored in the battery 220 to the first load 135. The state of the energy storage device 200 is referred to as'UPS mode'.

A detailed description of the operation algorithm of the energy storage device 200 will be described later with reference to FIG. 5.

The PLC 300 may receive the operating states of the first converter 120, the second converter 130, and the third converter 210, and control the operation of the uninterruptible power supply system based on this.

Specifically, the PLC 300 determines the operation mode of the energy storage device 200 using the received operation states of the first converter 120, the second converter 130, and the third converter 210, and It is possible to control the operation of the uninterruptible power supply system as a basis. For example, when it is determined that the operation state of the first converter 120 is a failure, the PLC 300 determines the operation mode of the energy storage device 200 as the UPS mode, and resets the first converter 120. I can. In addition, the PLC 300 may stop the uninterruptible power supply system for safety when it is determined that the operation state of the second converter 130 is a failure. However, this is only an example, and the present invention is not limited thereto.

The PLC 300 may communicate wirelessly or wiredly with each component included in the uninterruptible power supply system. For example, the PLC 300 includes a first converter 120, a second converter 130, and a third converter 210 of the uninterruptible power supply system, and RS 485, CAN, Transmission Control Protocol (TCP)/Internet Protocol) and user datagram protocol (UDP). However, the present invention is not limited thereto.

In addition, the PLC 300 may control the operation of each component included in the uninterruptible power supply system based on the operation mode of the energy storage device 200. For example, the PLC 300 controls the operation of the first converter 120, the second converter 130, and the third converter 210, and switches AC_CB1, AC_CB2, DC_CB1, included in the uninterruptible power supply system, DC_CB2) operation can be controlled. However, the present invention is not limited thereto.

2 is a diagram for describing an operation of an uninterruptible power supply system in a normal mode according to some embodiments of the present invention. 3 is a diagram illustrating an operation in a charging mode of an uninterruptible power supply system according to some embodiments of the present invention. 4 is a diagram for explaining the operation in the UPS mode of the uninterruptible power supply system according to some embodiments of the present invention.

Referring to FIG. 2, FIG. 2 shows that the uninterruptible power supply system according to some embodiments of the present invention operates in a'normal mode'. In this'normal mode', the energy storage device 200 may operate in the'Stop mode','Standby mode', and'Hold mode' described above.

In this case, the AC voltage of the system 110 is converted into a DC voltage by the first converter 120. Subsequently, the DC voltage, which is the output of the first converter 120, is transmitted to the second converter 130, converted into an AC voltage, and transmitted to the first load 135.

At this time, the energy storage device 200 is separated from the node N1. Specifically, the energy storage device 200 compares the voltage (Vdc) of the node N1 with a predetermined limit voltage (Vdc_limit), and when the voltage (Vdc) of the node N1 is greater than the limit voltage (Vdc_limit), electrical Is separated by In this case, the energy storage device 200 may operate in a'charge mode' when receiving a charging command from the PLC 300 or when the voltage level Vbat of the battery 220 is not in a fully charged state. However, the present invention is not limited thereto.

Referring to FIG. 3, FIG. 3 shows that the uninterruptible power supply system according to some embodiments of the present invention operates in a'charging mode'. The energy storage device 200 receives a charging command from the PLC 300 in the'normal mode' state, or checks the voltage level (Vbat) of the battery 220, and when the battery 220 is not in a fully charged state, the'charge mode' Can be operated as'.

Further, in an embodiment of the present invention, when the voltage level Vbat of the battery 220 is less than a predetermined voltage level, the energy storage device 200 may operate in a'charging mode'. A detailed description of this will be described later with reference to FIGS. 5 and 7.

When the energy storage device 200 operates in the'charging mode', the energy storage device 200 is electrically connected to the node N1. In this case, the third converter 210 charges the battery 220 by converting the power of the node N1 and transferring the power to the battery 220.

Subsequently, when the voltage level Vbat of the battery 220 becomes the same as the buffer voltage level, the energy storage device 200 stops the'charging mode'.

However, the present invention is not limited thereto, and the energy storage device 200 operates in a'charging mode' immediately according to the voltage Vdc of the node N1 regardless of the voltage level Vbat of the battery 220. A'constant charging method' can be used.

Referring to FIG. 4, FIG. 4 shows that the uninterruptible power supply system according to some embodiments of the present invention operates in the'UPS mode'.

In this case, the energy storage device 200 is connected to the node N1 and the first converter 120 is separated from the node N1. Specifically, when an abnormality occurs in the first converter 120 and the power of the system 110 is not properly transmitted, the voltage Vdc of the node N1 is lowered.

In this case, the energy storage device 200 may operate to maintain the voltage Vdc of the node N1 at a certain level, and accordingly, may deliver a certain power to the first load 135.

For example, the energy storage device 200 compares the voltage Vdc of the node N1 with a predetermined limit voltage Vdc_limit, and the voltage Vdc of the node N1 is less than the limit voltage Vdc_limit , Is electrically connected to the node N1.

At this time, the PLC 300 checks the operation mode of the energy storage device 200 and, when the operation mode of the energy storage device 200 is operated in the'UPS mode', switches AC_CB2 on both sides of the first converter 120 , DC_CB1) can be turned off. However, the present invention is not limited thereto, and the energy storage device 200 may directly turn off the switches AC_CB2 and DC_CB1 on both sides of the first converter 120.

Through this, the energy storage device 200 may continuously deliver a certain amount of power to the first load 135.

Hereinafter, an operation algorithm of the third converter 210, which is a DC-DC converter included in the energy storage device 200, will be described in detail.

5 is a flowchart illustrating an operation algorithm of a DC-DC converter included in an uninterruptible power supply system according to some embodiments of the present invention. 6 is a graph illustrating a charging method of a battery included in an energy storage device of an uninterruptible power supply system according to some embodiments of the present invention.

Referring to FIG. 5, in the third converter 210 of the energy storage device 200 according to some embodiments of the present invention, first, the energy storage device 200 operates in a'hold mode' by default.

Subsequently, the voltage Vdc of the node N1 is compared with a predetermined limit voltage Vdc_limit (S110).

Subsequently, when the voltage Vdc of the node N1 is less than the predetermined limit voltage Vdc_limit, the third converter 210 determines whether the voltage level Vbat of the battery 220 is greater than the minimum voltage level Vbat_Min. It is determined (S120). As a cause of the voltage Vdc of the node N1 being lowered, for example, there may be a failure of the first converter 120 or an unstable voltage of the system 110.

Subsequently, when the voltage level (Vbat) of the battery 220 is less than the minimum voltage level (Vbat_Min), the battery 220 means a state that is not sufficient to provide power to the node N1 or the load 135, In this case, step S110 is repeatedly performed.

On the other hand, when the voltage level Vbat of the battery 220 is greater than the minimum voltage level Vbat_Min, the third converter 210 operates in the'UPS mode' in which the battery 220 is discharged (S130). . In this case, the third converter 210 may transmit a command notifying that the energy storage device 200 operates in the'UPS mode' to the PLC 300. However, since the response unit time at which the command is transmitted from the third converter 210 to the PLC 300 is longer than the response unit time for the operation of the third converter 210, the third converter 210 Before receiving the command for the operation mode, it can be actively operated first.

Subsequently, the third converter 210 senses the voltage of the node and accumulates the first reaction unit time for determining the operation mode based on this, and calculates the operation time T, and the operation time is determined by the PLC 300. 3 It is determined whether or not it is greater than the second response unit time (eg, delay time) for updating the command for the operation mode of the converter 210 (S140).

If the operation time T for the'UPS mode' of the third converter 210 is less than the second reaction unit time (eg, delay time), the third converter 210 is S120 Steps to S140 are repeated. That is, the third converter 210 may continue to operate in the'UPS mode'.

On the other hand, when the operation time (T) for the'UPS mode' of the third converter 210 is greater than the second response unit time (eg, delay time), the third converter 210 It is determined whether a command to operate in the'UPS mode' is received from the 300 (S150).

If the third converter 210 receives a command to operate in the'UPS mode' from the PLC 300, the third converter 210 repeats steps S120 to S150. In this case, the third converter 210 may continue to operate in the'UPS mode'.

In step S150, even though the voltage (Vdc) of the node (N1) and the predetermined limit voltage (Vdc_limit) have fallen below the third converter 210, the PLC 300 does not operate in the'UPS mode' by itself. It means that the command to force the operation in the'UPS mode' is transmitted. Through this, the uninterruptible power supply system of the present invention can implement a secondary safety device for supplying the uninterruptible power.

On the other hand, when the third converter 210 receives a command from the PLC 300 to operate in an operation mode other than the'UPS mode', the third converter 210 operates in the operation mode of the command, or It returns to step S110.

Conversely, when the voltage Vdc of the node N1 is greater than the limit voltage Vdc_limit, the third converter 210 operates in a'charging mode' in which the battery 220 is charged.

Subsequently, the third converter 210 checks the voltage level Vbat of the battery 220 and operates in different ways according to the voltage level Vbat (S170).

6, when the voltage level Vbat of the battery 220 is the overvoltage limit (hereinafter referred to as OVL), the third converter 210 operates in a'hold mode' (S172). ).

In contrast, when the voltage level Vbat of the battery 220 is in the second region 2, that is, the voltage level Vbat is less than the buffer voltage level OVL and is less than the reference voltage level Voltage max. In large cases, the third converter 210 charges the battery 220 in a'CV mode' (S174).

On the other hand, when the voltage level (Vbat) of the battery 220 is in the first region (Region 1), that is, less than the reference voltage level (Voltage max) and greater than the lowest voltage level (Under Voltage Limit; hereinafter UVL) , The third converter 210 charges the battery 220 in a'CC mode' different from the'CV mode' (S176). Here, the'CV mode' and the'CC mode' are related to the conventional technology, so detailed information will be omitted.

In addition, in FIG. 6, the minimum voltage level UVL is shown to be different from the minimum voltage level Vbat_Min, but the present invention is not limited thereto, and the minimum voltage level UVL and the minimum voltage level Vbat_Min may be the same. I can.

7 is a graph for explaining a voltage of a node connected to one end of a DC-DC converter included in an uninterruptible power supply system according to some embodiments of the present invention.

Referring to FIG. 7, a change in voltage Vdc at a node N1 of an uninterruptible power supply system according to some embodiments of the present invention is shown.

The third converter 210 of the present invention operates through the algorithm described with reference to FIGS. 5 and 6, and the voltage Vdc of the node N1 is maintained higher than the limit voltage Vdc_limit in a normal state.

However, when some of the components included in the uninterruptible power supply system fail or do not operate normally, the voltage Vdc of the node N1 may be lowered.

At this time, when the voltage Vdc of the node N1 becomes smaller than the predetermined limit voltage Vdc_limit, the third converter 210 operates in the'UPS mode', and the power stored in the battery 220 is transferred to the node ( N1).

The operation reaction speed of the third converter 210 corresponds to section A and may operate at a reaction speed of about 5 msec or less.

Subsequently, the third converter 210 operates in the'UPS mode' until the voltage Vdc of the node N1 becomes higher than the limit voltage Vdc_limit and returns to the normal range, which corresponds to the B section. Section B may be less than about 20 msec, but the present invention is not limited thereto.

Through this, the energy storage device 200 included in the uninterruptible power supply system of the present invention can provide uninterruptible power by actively switching an operation mode without receiving an operation command from the PLC 300.

That is, the third converter 210 of the energy storage device 200 of the present invention does not receive a command from the PLC 300 and actively determines whether the UPS mode is operated and supplies uninterruptible power, thereby providing a fast response speed in case of an accident. It is possible to secure and simplify the data exchange received from the PLC (300).

Through this, the operation control algorithm for the third converter 210 of the uninterruptible power supply system of the present invention is simplified, and thus, when an error occurs in the uninterruptible power supply system, the response speed of the energy storage device 200 is improved. I can make it. In addition, it is possible to reduce the communication error probability by reducing the complexity of communication connection between components of the uninterruptible power supply system, and improve the stability of the uninterruptible power supply system.

8 is a flowchart illustrating an operation algorithm of a DC-DC converter included in an uninterruptible power supply system according to some other embodiments of the present invention. For convenience of description, hereinafter, redundant descriptions of the same matters as those of the above-described embodiment will be omitted, and differences will be mainly described.

Referring to FIG. 8, an operation algorithm of a DC-DC converter included in the uninterruptible power supply system according to some other embodiments of the present invention is similar to the algorithm described with reference to FIG. 5.

Specifically, steps S210 to S250 of the algorithm of the uninterruptible power supply system according to some other embodiments of the present invention operate substantially the same as steps S110 to S150 of FIG. 5.

However, in the algorithm of the uninterruptible power supply system according to some other embodiments of the present invention, if the voltage (Vdc) of the node N1 is greater than the limit voltage (Vdc_limit) in step S210, the'charging mode' from the PLC 300 It is determined whether a command for is received (S260).

If a command for a'charging mode' is not received from the PLC 300, the third converter 210 operates in a'hold mode' (S272).

On the other hand, when a command for a'charging mode' is received from the PLC 300, the third converter 210 operates in a'charging mode' in which the battery 220 is charged.

Subsequently, the third converter 210 checks the voltage level Vbat of the battery 220 and operates in different ways according to the voltage level Vbat (S270).

If the voltage level Vbat of the battery 220 is an Over Voltage Limit (hereinafter OVL), the third converter 210 operates in a'hold mode' (S272).

In contrast, when the voltage level Vbat of the battery 220 is in the second region 2, that is, the voltage level Vbat is less than the buffer voltage level OVL and is less than the reference voltage level Voltage max. In a large case, the third converter 210 charges the battery 220 in a'CV mode' (S274).

On the other hand, when the voltage level (Vbat) of the battery 220 is in the first region (Region 1), that is, less than the reference voltage level (Voltage max) and greater than the lowest voltage level (Under Voltage Limit; hereinafter UVL) , The third converter 210 charges the battery 220 in a'CC mode' different from the'CV mode' (S276).

Through this, in the uninterruptible power supply system of the present invention, the third converter 210 of the energy storage device 200 actively determines whether the UPS mode is operated without receiving a command from the PLC 300 to supply uninterruptible power. By doing so, it is possible to secure a fast response speed in case of an accident and to simplify data exchange received from the PLC (300).

Through this, the operation control algorithm for the third converter 210 of the uninterruptible power supply system of the present invention is simplified, and thus, when an error occurs in the uninterruptible power supply system, the response speed of the energy storage device 200 is improved. I can make it. In addition, it is possible to reduce the communication error probability by reducing the complexity of communication connection between components of the uninterruptible power supply system, and improve the stability of the uninterruptible power supply system.

The above-described present invention is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those of ordinary skill in the technical field to which the present invention belongs. Is not limited by

110: system 120: first converter
130: second converter 135: first load
200: energy storage device 210: third converter
220: battery 300: PLC

Claims (10)

In the uninterruptible power supply system connected to the grid,
A first converter converting the AC voltage of the system into a DC voltage;
A second converter connected in series with the first converter and converting the DC voltage output from the first converter into an AC voltage and transferring the converted DC voltage to a first load;
A battery electrically connected to a node between the first converter and the second converter to perform charging and discharging; And
A third converter connected between the battery and the node and configured to convert a magnitude of a DC voltage applied across both ends thereof,
The third converter,
Operating in a UPS mode that provides power stored in the battery to the node when the voltage is lower than a predetermined threshold voltage by measuring a voltage of a node between the first converter and the second converter in real time
Uninterruptible power supply system.
The method of claim 1,
Receives information on the operation state from the first to third converters, generates a command for the operation mode of the third converter based on the operation state of the first and second converters, and transmits it to the third converter. Including PLC
Uninterruptible power supply system.
The method of claim 2,
The first reaction unit time for determining the operation mode based on the sensing voltage of the node in the third converter is less than the second reaction unit time for updating a command for the operation mode of the third converter in the PLC.
Uninterruptible power supply system.
The method of claim 3,
The third converter accumulates the first reaction unit time to calculate an operation time, and when the operation time is less than the second reaction unit time, maintains an operation mode of the third converter.
Uninterruptible power supply system.
The method of claim 2,
The third converter, when receiving a command for an operation mode from the PLC, operates in an operation mode according to the received command.
Uninterruptible power supply system.
The method of claim 2,
When receiving a command for a charging operation from the PLC, the third converter operates in a hold mode or a charge mode according to the voltage level of the battery.
Uninterruptible power supply system.
The method of claim 1,
When the voltage of the node is greater than a predetermined threshold voltage, the third converter operates in a different manner according to the voltage level of the battery.
Uninterruptible power supply system.
The method of claim 7,
When the battery is at the first level in a fully charged state, the third converter operates in a hold mode,
When the battery is less than the first level, the third converter operates in a charge mode for charging the battery.
Uninterruptible power supply system.
The method of claim 8,
When the battery is a region between the first level and a second level smaller than the first level, the third converter charges the battery in a first manner,
When the battery is a region between the second level and a third level smaller than the second level, the third converter charges the battery in a second method different from the first method.
Uninterruptible power supply system.
The method of claim 1,
The third converter operates in the UPS mode when the voltage level of the battery is greater than a predetermined battery minimum voltage level.
Uninterruptible power supply system.

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