KR102515128B1 - Energy storage system including dc-dc converter and electricity providing system including the same and control method of the same - Google Patents

Abstract

Embodiments relate to an energy storage system including a DC/DC converter, a power supply system including the energy storage system, and a control method thereof.
Embodiments include a power generation device that generates electrical energy; an inverter for inverting the electrical energy into alternating current; an energy storage system receiving the electrical energy to charge a battery and supplying electrical energy to the inverter by discharging the charged electrical energy; and a DC link capacitor disposed between the inverter and the energy storage system, wherein the energy storage system includes a DC/DC converter including one or more switches and disposed between the DC link capacitor and the battery, The DC/DC converter may provide a power supply system for charging the DC voltage of the DC link capacitor to an operating voltage of the inverter by supplying a DC current to the DC link capacitor before starting a discharging operation of the battery.

Description

Energy storage system including DC-DC converter, power supply system including the same, and control method thereof

Embodiments relate to an energy storage system including a DC/DC converter, a power supply system including the energy storage system, and a control method thereof.

Electrical energy is widely used because it is easy to convert and transmit. In order to efficiently use such electric energy, an energy storage system (ESS) is used. The energy storage system receives power and charges the battery. In addition, the energy storage system supplies power by discharging the power charged in the battery when power is needed. Through this, the energy storage system can supply power flexibly.

Specifically, when the power supply system includes the energy storage system, it operates as follows. Energy storage systems discharge electrical energy stored in batteries when a load or grid is overloaded. In addition, when the load or grid is lightly loaded, the energy storage system receives power from the generator or grid and charges the battery.

In addition, when the energy storage system exists independently of the power supply system, the energy storage system receives idle power from an external power source and charges the battery. Also, when the system or load is overloaded, the energy storage system supplies power by discharging the power charged in the battery.

On the other hand, the energy storage system should initially charge (or pre-charge) the DC link voltage disposed at the inverter input terminal of the power supply system during the battery discharge mode operation to reduce the voltage difference between the battery side and the inverter side and block inrush current. In order to initially charge the DC link voltage, the power supply system receives initial charging power from a generator or grid.

However, when initial charging power is not supplied from the power generation device because there is no generated power and the supply of initial charging power is stopped in the system, the energy storage system cannot initially charge the DC link voltage.

Also, in the energy storage system, when a DC/DC converter performs power conversion, power conversion efficiency varies according to an output power ratio. In particular, DC/DC converters have a problem in that power conversion efficiency rapidly decreases below a predetermined ratio of output power, and as a result, energy storage systems have a problem in that energy supply or supply efficiency in a battery decreases.

In addition, the energy storage system charges the battery by driving a DC/DC converter when the battery is discharged. In this case, the DC/DC converter received standby power from the battery for operation. However, when the battery is completely discharged or over-discharged, the energy storage system cannot drive the DC/DC converter because it cannot receive standby power from the battery, and thus the battery has to be replaced, resulting in waste of cost and resources.

In addition, the energy storage system performs droop control to improve stability during charging or discharging of the battery. In particular, the energy storage system performs droop control according to the state of charge (SOC) of the battery. However, in order to control the droop according to the state of charge (SOC) of the battery, a communication line and a communication unit for communication with the BMS of the battery were separately required, and the speed delay of the feedback process using communication improved stability during battery charging or discharging operation. There were limits to what it could do.

Embodiments are designed to solve the problems of the prior art described above, and an object of the embodiments is to provide an energy storage system including a DC/DC converter, a power supply system including the energy storage system, and a control method thereof.

In addition, an embodiment is to provide an energy storage system including a DC/DC converter capable of initially charging a DC link voltage without a separate configuration, a power supply system including the energy storage system, and a control method thereof.

In addition, an embodiment is to provide an energy storage system including a DC/DC converter with excellent power conversion efficiency, a power supply system including the energy storage system, and a control method thereof.

In addition, an embodiment is to provide an energy storage system including a DC/DC converter capable of charging the battery without replacing the battery even when the battery is over-discharged, a power supply system including the same, and a control method thereof.

In addition, an embodiment is to provide an energy storage system including a DC/DC converter that quickly determines an operation mode of charging or discharging a battery, a power supply system including the energy storage system, and a control method thereof.

In addition, an embodiment is to provide an energy storage system including a DC/DC converter that does not require a separate communication line and communication unit for droop control during battery charging or discharging, a power supply system including the same, and a control method thereof.

In addition, an embodiment is to provide an energy storage system including a DC/DC converter capable of rapidly controlling droop when a battery is charged or discharged, a power supply system including the same, and a control method thereof.

Technical tasks to be achieved in the embodiments are not limited to the technical tasks mentioned above, and other technical tasks not mentioned can be clearly understood by those skilled in the art from the description below. There will be.

In order to solve the above technical problem, a DC / DC converter according to an embodiment includes an overcurrent protection circuit connected to a first terminal; a DC stabilization circuit connected to the second terminal; a bridge circuit unit electrically connected between the overcurrent protection circuit unit and the DC stabilization circuit unit and including a switch; a control unit controlling the bridge circuit unit; an auxiliary power supply unit generating driving power for the control unit based on the first power supplied to the second stage; and a backup power supply electrically connected between the first end and the auxiliary power supply, wherein when the first power is not supplied to the auxiliary power supply from the second end, the backup power supply supplies second power to the auxiliary power supply. can provide.

In addition, in the DC/DC converter according to the embodiment, the first power may be standby power, and the second power may be minimum power for the auxiliary power unit to generate driving power for the control unit.

In addition, in the DC/DC converter according to the embodiment, when the first power is not supplied to the auxiliary power supply unit from the second stage, a battery connected to the second stage may be in an over-discharged state.

In addition, in the DC/DC converter according to the embodiment, a DC link capacitor may be connected to the first stage.

In addition, in the DC/DC converter according to the embodiment, the backup power supply unit may provide the second power based on the power input to the first stage.

In addition, in the DC/DC converter according to the embodiment, the backup power supply unit may provide the second power based on power input from a terminal connected to an external power source.

In addition, the DC/DC converter according to the embodiment may further include a current limiting unit between the backup power supply unit and the second terminal.

In the power conversion method according to the embodiment, in the power conversion method for receiving power from a first end and providing power to a second end, the first power to an auxiliary power supply unit when the first power is supplied from the second end providing; providing second power from a backup power supply to the auxiliary power supply when the first power is not supplied from the second terminal; and generating, by the auxiliary power supply unit, driving power for a control unit based on the first power or the second power.

Effects of an energy storage system including a DC/DC converter according to an embodiment, a power supply system including the same, and a control method thereof are described below.

The embodiment may initially charge the DC link voltage without a separate configuration.

In addition, since the initial charge speed of the DC link voltage is fast in the embodiment, the battery discharge operation can be performed quickly.

In addition, the embodiment may have excellent power conversion efficiency of the DC/DC converter.

In addition, since the power conversion efficiency of the DC/DC converter is excellent in the embodiment, energy efficiency delivered during charging or discharging of the battery may be high.

In addition, the embodiment can charge the battery even if the battery is over-discharged.

In addition, the embodiment does not need to replace the battery even if the battery is over-discharged. In addition, the embodiment can quickly determine the operation mode of charging or discharging the battery.

In addition, the embodiment does not require a separate communication line and communication unit for droop control during battery charging or discharging.

In addition, the embodiment enables rapid droop control during battery charging or discharging.

Effects obtained in the examples are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the description below. will be.

The accompanying drawings are provided to aid understanding of the embodiments, and provide examples of the embodiments along with detailed descriptions. However, the technical features of the embodiments are not limited to specific drawings, and features disclosed in each drawing may be combined with each other to form a new embodiment.
1 is a diagram for explaining a schematic configuration of a power supply system according to an embodiment.
2 is a diagram for explaining an energy storage system according to an exemplary embodiment.
3 is a graph for explaining a DC voltage and a DC current of a DC link capacitor during initial charging according to an exemplary embodiment.
4 is a circuit diagram of a DC/DC converter according to an embodiment.
FIG. 5 describes an operation for initially charging a DC link capacitor by the DC/DC converter of FIG. 4 .
FIG. 6 describes an operation for initially charging a DC link capacitor by the DC/DC converter of FIG. 4 .
7 is a circuit diagram of a DC/DC converter according to another embodiment.
FIG. 8 describes an operation for initially charging a DC link capacitor by the DC/DC converter of FIG. 7 .
FIG. 9 describes an operation for initially charging a DC link capacitor by the DC/DC converter of FIG. 7 .
10 is a circuit diagram of a DC/DC converter according to another embodiment.
11 is a graph showing a power conversion ratio according to an output power ratio when an energy storage system according to an embodiment converts direct current to direct current power.
12 is a diagram illustrating a pulse width control method of a DC/DC converter of an energy storage system according to an exemplary embodiment.
13 is a diagram for explaining a signal according to output power of an energy storage system according to an exemplary embodiment.
14 is a diagram for explaining a method of initially charging a DC link capacitor of a power supply system according to an exemplary embodiment.
15 is a diagram for explaining a power supply method of an energy storage system according to an exemplary embodiment.
16 is a diagram for explaining a configuration of a converter efficiency control unit applied to an energy storage system of a power supply system according to an exemplary embodiment.
17 is a diagram for explaining a power conversion efficiency control method of a DC/DC converter of an energy storage system according to an embodiment.
18 is a diagram for explaining an energy storage system according to another embodiment.
19 is a diagram for explaining an energy storage system according to another embodiment.
20 is a diagram for explaining an energy storage system according to another embodiment.
21 is a diagram for explaining an energy storage system according to another embodiment.
22 is a diagram for explaining a power conversion method for battery charging in a DC/DC converter of an energy storage system according to an embodiment.
23 is a diagram for explaining an energy storage system according to another embodiment.
FIG. 24 is a diagram for explaining the control unit of FIG. 23 .
FIG. 25 is a diagram for explaining a droop control curve of the energy storage system of FIG. 23 .
FIG. 26 is a diagram for explaining the reference current determiner of FIG. 24 .
FIG. 27 is a diagram for explaining the current controller of FIG. 24 .
FIG. 28 is a diagram for explaining a power conversion method of the energy storage system of FIG. 23 .
FIG. 29 is a diagram for explaining a method of selecting an operation mode of FIG. 28 .
FIG. 30 is a diagram for explaining a method of determining reference power of FIG. 28 .

Hereinafter, embodiments related to the present invention will be described in more detail with reference to the drawings. The suffixes "module" and "unit" for components used in the following description are given or used together in consideration of ease of writing the specification, and do not have meanings or roles that are distinct from each other by themselves.

Advantages and features of the present invention, and methods for achieving them, will become clear with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and only the present embodiments make the disclosure of the present invention complete, and common knowledge in the art to which the present invention belongs It is provided to fully inform the holder of the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numbers designate like elements throughout the specification.

In describing the embodiments of the present invention, if it is determined that a detailed description of a known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted. In addition, terms to be described below are terms defined in consideration of functions in the embodiments of the present invention, which may vary according to the intention or custom of a user or operator. Therefore, the definition should be made based on the contents throughout this specification.

Combinations of each block in the accompanying drawings and each step in the flowchart may be performed by computer program instructions. Since these computer program instructions may be loaded into a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing equipment, the instructions executed by the processor of the computer or other programmable data processing equipment may correspond to each block of the drawing or each flowchart. This will create means for performing the functions described in the step. These computer program instructions may also be stored in a computer usable or computer readable memory that can be directed to a computer or other programmable data processing equipment to implement functionality in a particular way, such that the computer usable or computer readable memory The instructions stored in may also produce an article of manufacture containing instruction means for performing the functions described in each block of the drawing or each step of the flowchart. The computer program instructions can also be loaded on a computer or other programmable data processing equipment, so that a series of operational steps are performed on the computer or other programmable data processing equipment to create a computer-executed process to generate computer or other programmable data processing equipment. It is also possible that the instructions performing the processing equipment provide steps for executing the functions described in each block of the drawing and each step of the flow chart.

Additionally, each block or each step may represent a module, segment or portion of code that includes one or more executable instructions for executing specified logical function(s). It should also be noted that in some alternative embodiments, it is possible for the functions recited in blocks or steps to occur out of order. For example, two blocks or steps shown in succession may in fact be performed substantially concurrently, or the blocks or steps may sometimes be performed in reverse order depending on their function.

1 is a diagram for explaining a schematic configuration of a power supply system according to an embodiment.

Referring to FIG. 1 , a power supply system 1 according to an embodiment includes a power generation device 10, an energy storage system 20, an inverter 30, an AC filter 40, an AC/AC converter 50, a grid (60), a system controller 80, and a load 70.

The power generation device 10 may produce electrical energy. When the power generation device 10 is a photovoltaic power generation system, the power generation device 10 may be a solar cell array. A solar cell array is a combination of a plurality of solar cell modules. A solar cell module may be a device that converts solar energy into electric energy by connecting a plurality of solar cells in series or parallel to generate predetermined voltage and current. Accordingly, the solar cell array can absorb solar energy and convert it into electrical energy. Also, when the generator 10 is a wind power generation system, the generator 10 may be a fan that converts wind energy into electrical energy.

Meanwhile, the generator 10 is not limited thereto, and may include a tidal power generation system in addition to the photovoltaic power generation system and the wind power generation system. However, this is just an example, and the power generation device 10 is not limited to the above-mentioned types, and may include all power generation systems that generate electrical energy using renewable energy such as solar heat or geothermal heat.

Also, the power supply system 1 may supply power only through the energy storage system 20 without the power generation device 10 . In this case, the power supply system 1 may not include the generator 10 .

The inverter 30 may convert DC power into AC power. More specifically, DC power supplied by the generator 10 or DC power discharged by the energy storage system 20 may be converted into AC power.

The AC filter 40 may filter noise of power converted into AC power. Also, depending on the embodiment, the alternating current filter 40 may be omitted.

The AC/AC converter 50 converts the voltage of the noise-filtered AC power so that the AC power can be supplied to the grid 60 or the load 70, and converts the converted AC power to the grid 60 or the load ( 70) can be supplied. Also, according to embodiments, the AC/AC converter 50 may be omitted.

The system 60 is a system in which many power plants, substations, transmission and distribution lines, and loads are integrated to generate and use electric power.

The load 70 may receive electrical energy from a power generation system such as the generator 10 or the energy storage system 20 to consume power.

The energy storage system (ESS) 20 may receive electrical energy from the generator 10, charge it, and discharge the charged electrical energy according to the power supply/demand situation of the system 60 or load 70. . More specifically, when the grid 60 or the load 70 is lightly loaded, the energy storage system 20 may receive idle power from the generator 10 and charge it. When the grid 60 or the load 70 is overloaded, the energy storage system 20 may supply power to the grid 60 or the load 70 by discharging the charged power. In addition, the energy storage system 20 may be connected between the power generation device 10 and the inverter 30 so as to be electrically connected to the power generation device 10 and electrically connected to the inverter 30 .

The system controller 80 may control operations of the energy storage system 20 , the inverter 30 , and the AC/AC converter 50 . More specifically, the system controller 80 may control charging and discharging of the energy storage system 20 . When the grid 60 or the load 70 is overloaded, the system controller 80 may control the energy storage system 20 to supply power and transfer power to the grid 60 or the load 70. . When the system 60 or the load 70 is at a light load, the system control unit 80 may control an external power supply source or generator 10 to supply and transfer power to the energy storage system 20 .

Hereinafter, the energy storage system will be described in more detail.

2 is a diagram for explaining an energy storage system according to an exemplary embodiment.

Referring to FIG. 2 , an energy storage system 20 according to an embodiment may include a DC/DC converter 100, a battery 200, and a charging controller 300. Although not shown in FIG. 1 , the energy storage system 20 may be connected to the inverter 30 through the DC link capacitor 90 . That is, the DC link capacitor 90 may be disposed between the energy storage system 20 and the inverter 30 . Accordingly, the energy storage system 20 may receive the DC voltage Vdc of the DC link capacitor 90 in the charging mode and provide the DC voltage Vdc to the DC link capacitor 90 in the discharging mode.

The battery 200 may receive charging power from the DC/DC converter 100 in the charging mode and perform a charging operation by the received power. In addition, the battery 200 may output pre-stored power to the DC/DC converter 100 in the discharge mode. Also, the battery 200 may include a plurality of battery cells to perform charging and discharging operations.

The charging controller 300 may include a battery management system (BMS). The charging controller 300 may provide battery state information about the state of the battery 200 to the system controller 80 . For example, the charging control unit 300 monitors at least one of voltage, current, temperature, remaining power amount, and charging state of the battery 200, and transmits state information of the monitored battery 200 to the system control unit 80. can be conveyed In addition, the charging control unit 300 can maintain an appropriate voltage for a plurality of battery cells while charging or discharging. Also, the charging controller 300 may operate based on a control signal from the system controller 80 . Also, the charging controller 300 may control the DC/DC converter 100 according to the monitored state information of the battery 200 . Also, the charging control unit 300 may control the DC/DC converter 100 according to a charging mode or a discharging mode. More specifically, the charging controller 300 provides a charge control signal or a discharge control signal for controlling the DC/DC converter 100 to the converter controller of the DC/DC converter 100, and the DC/DC converter 100 The converter controller of may provide a PWM signal to the switch of the DC/DC converter 100 based on the charge control signal or the discharge control signal. Also, the charging controller 300 may control the DC/DC converter 100 to initially charge the DC link capacitor 90 in the discharge mode of the battery 200 . That is, the charging control unit 300 provides an initial charging control signal for controlling the DC/DC converter 100 to the converter control unit of the DC/DC converter 100, and the converter control unit of the DC/DC converter 100 initially An initial charge switch signal may be provided to the switch of the DC/DC converter 100 based on the charge control signal. Also, the charging controller 300 may control the DC/DC converter 100 to increase power conversion efficiency of the DC/DC converter 100 . More specifically, the charging control unit 300 provides a power conversion efficiency control signal capable of increasing the power conversion efficiency of the DC/DC converter 100 to the converter control unit of the DC/DC converter 100, and the DC/DC converter ( The converter controller of 100) may provide a PWM signal to the switch of the DC/DC converter 100 based on the power conversion efficiency control signal.

The DC/DC converter 100 may convert the amount of DC power that the energy storage system 20 receives in a charging mode or supplied in a discharging mode. More specifically, the DC/DC converter 100 converts the DC power provided to the DC link capacitor 90 from the generator 10 or the inverter 30 into a voltage size for charging the battery 200 to the battery ( 200) can be provided. In addition, the DC/DC converter 100 may convert the DC power provided by the battery 200 into a voltage level usable by the inverter 30 and provide the DC power to the DC link capacitor 90 .

<Initial charge of DC link capacitor>

3 is a graph for explaining a DC voltage and a DC current of a DC link capacitor during initial charging according to an exemplary embodiment.

The energy storage system 20 according to an embodiment does not require a separate configuration for initial charging of the DC link capacitor 90 for a discharge mode operation. The energy storage system 20 provides the electric energy stored in the battery 200 to the DC link capacitor 90 by the switching operation of the DC/DC converter 100 so that the DC voltage of the DC link capacitor 90 becomes the inverter 30 ) can be initially charged up to the operating voltage. More specifically, the DC/DC converter 100 may provide the DC current Idc to the DC link capacitor 90 . When the DC link capacitor 90 is provided with the DC current Idc, charges may be charged and the DC voltage Vdc may increase. During the initial charging period, the DC/DC converter 100 may initially charge the DC voltage Vdc up to an operating voltage at which the inverter 30 may perform an inverting operation. For example, as shown in FIG. 3 , during the initial charging period Ti, the DC/DC converter 100 turns on or off the switch to generate the DC current Idc of a predetermined level I1 for a plurality of periods T1, T2, and T3. , T4) can be provided. When the DC current Idc is continuously provided during the initial charging period Ti, circuit damage may occur due to a large voltage difference between the voltage of the inverter 30 and the DC/DC converter 100 . Accordingly, the DC/DC converter 100 may provide the DC current Idc to the DC link capacitor 90 for a plurality of periods. A plurality of periods in which the direct current Idc is provided may all be the same period. The present invention is not limited thereto, and as the DC voltage Vdc increases, the voltage difference between the voltage at the inverter 30 and the DC/DC converter 100 decreases, so the supply period of the DC current Idc can be gradually increased. In this case, the initial charging time can be reduced. As the DC current Idc is provided, the DC voltage Vdc increases. The DC/DC converter 100 terminates the initial charge when the DC voltage Vdc reaches the operating voltage V1 and performs a boosting operation in a discharge mode. When the DC/DC converter 100 performs a boosting operation, it may reach the second DC voltage level V2.

Also, a method of initially charging the DC/DC converter 100 may include the method of initially charging the DC link capacitor of FIG. 14 .

Hereinafter, initial charging of the DC link capacitor 90 according to a specific embodiment of the DC/DC converter 100 will be described.

4 is a circuit diagram of a DC/DC converter according to an exemplary embodiment, and FIGS. 5 and 6 describe an operation of the DC/DC converter of FIG. 4 to initially charge a DC link capacitor.

Referring to FIG. 4 , a DC/DC converter 100 according to an embodiment is a bi-directional DC/DC converter and may be an insulated converter.

The DC/DC converter 100 according to an embodiment may include a controller 130. The control unit 130 may generate a PWM signal based on a control signal provided from the charging control unit 300 and provide the PWM signal to the bridge circuit unit 120 including the switch.

The DC/DC converter 100 according to an embodiment may include an overcurrent protection circuit unit 110 . The overcurrent protection circuit unit 110 may prevent EOS or overcurrent flowing into or out of the energy storage system 20 . The overcurrent protection circuit unit 110 may be disposed between a first terminal to which the DC link capacitor 90 is connected and the bridge circuit unit 120 . In addition, the overcurrent protection circuit unit 110 may include a circuit breaker. In this case, the overcurrent protection circuit unit 110 may open between the first end and the bridge circuit unit 120 when EOS or overcurrent flows into the energy storage system 20 . Accordingly, the overcurrent protection circuit unit 110 may block the input/output of the energy storage system 20 and external current. The DC-DC converter 100 according to an embodiment may include a bridge circuit unit 120. The bridge circuit unit 120 may include a transformer (T), a first full bridge circuit 121, and a second full bridge circuit 122. In addition, the bridge circuit unit 120 is divided into a primary circuit on the left side and a secondary circuit on the right side based on the transformer T composed of the first and second coils LP and Ls, and the primary circuit is the primary circuit. Switch elements (Q1 to Q4) constituting the full bridge circuit 121 may be included. And the secondary circuit may include a DC stabilization circuit 140 composed of a second capacitor C2 and a second inductor L2, and a second full bridge circuit 122 composed of switch elements Q5 to Q8. . The DC stabilization circuit unit 140 may be connected to the second terminal to which the battery 200 is connected.

In the primary side circuit, the first coil Lp is connected between the third node N3 and the fourth node N4. And the first full bridge circuit 121 is composed of a first leg (leg) and a second leg between the first and second nodes (N1, N2), the first leg is the first and third nodes (N1, N3) and a second switch element Q2 connected between the third and second nodes N3 and N2, and the second leg includes first and fourth nodes ( It consists of a third switch element (Q3) connected between N1 and N4 and a fourth switch element (Q4) connected between the fourth and second nodes (N4, N2).

In the secondary circuit, the battery 200 and the second capacitor C2 are connected between the fifth and sixth nodes N5 and N6, and the second inductor L2 is connected to the fifth and seventh nodes N5 and N7. and the second coil Ls is connected between the tenth and ninth nodes N10 and N9. And the second full bridge circuit 122 consists of a third leg and a fourth leg between the seventh and eighth nodes (N7, N8), the third leg is between the seventh and ninth nodes (N7, N9) It is composed of a fifth switch element Q5 connected to and a sixth switch element Q6 connected between the ninth and eighth nodes N9 and N8, and the fourth leg is composed of the seventh and tenth nodes N7 and N10. It consists of a seventh switch element (Q7) connected between the ) and an eighth switch element (Q8) connected between the tenth and eighth nodes (N10, N8).

The DC-DC converter 100 according to an embodiment is a bi-directional converter, and in a step-down mode, the DC input voltage on the first and second nodes N1 and N2 is dropped to reduce the voltage to the fifth and sixth nodes. A DC output voltage is output to the nodes N5 and N6, and in a step-up mode, the DC input voltage on the fifth and sixth nodes N5 and N6 is increased to increase the voltage to the first and second nodes N1. , N2), the DC output voltage is output.

DC-DC converter 100 according to an embodiment performs a switching operation of the first full bridge circuit 121 and the second full bridge circuit 122 to initially charge the DC link capacitor 90 for the discharge mode, DC current Idc may be provided to the DC link capacitor 90 . For example, referring to FIG. 5 , the Nth (N is a natural number) DC current Idc among the plurality of DC currents Idc provided for initial charging is the seventh switch element Q7 of the second full bridge circuit 122. ) And the sixth switch element (Q6) is turned on, the fifth switch element (Q5) and the eighth switch element (Q8) are turned off, the first switch element (Q1) and the fourth switch element (Q1) of the first full bridge circuit 121 The switch element Q4 may be turned on and the second switch element Q2 and the third switch element Q3 may be turned off. Referring to FIG. 6 , among the plurality of DC currents Idc provided for initial charging, the N+1th (N is a natural number) direct current Idc is the fifth switch element Q5 of the second full bridge circuit 122. And the eighth switch element (Q8) is turned on and the sixth switch element (Q6) and the eighth switch element (Q8) are turned off, the third switch element (Q3) and the second switch of the first full bridge circuit 121 The device Q2 may be turned on and the first switch device Q1 and the fourth switch device Q4 may be turned off.

7 is a circuit diagram of a DC/DC converter according to another embodiment, and FIGS. 8 and 9 describe an operation for initially charging a DC link capacitor in the DC/DC converter of FIG. 7 .

Referring to FIG. 7 , a DC/DC converter 1100 according to another embodiment may be a bi-directional DC/DC converter and may be a non-isolated converter.

The DC/DC converter 1100 according to another embodiment may include a controller 1130. The control unit 1130 may generate a PWM signal based on a control signal provided from the charging control unit 300 and provide the PWM signal to the top switch unit 1150 including a switch or the bridge circuit unit 1120 .

A DC/DC converter 1100 according to another embodiment may include an overcurrent protection circuit unit 1110 . The overcurrent protection circuit unit 1110 may prevent EOS or overcurrent flowing into or out of the energy storage system 20 . The overcurrent protection circuit unit 1110 may be disposed between the top switch unit 1150 to which the DC link capacitor 90 is connected. In addition, the overcurrent protection circuit unit 1110 may include a circuit breaker. In this case, the overcurrent protection circuit unit 1110 may open between the first stage and the top switch unit 1150 when EOS or overcurrent flows into the energy storage system 20 . Accordingly, the overcurrent protection circuit unit 1110 may block the input/output of the energy storage system 20 and external current.

A DC/DC converter 1100 according to another embodiment may include a top switch unit 1150. The top switch unit 1150 may be disposed between the overcurrent protection circuit unit 1110 and the bridge circuit unit 1120 . Also, the top switch unit 1150 may include a thirteenth switch element Q13.

A DC/DC converter 1100 according to another embodiment may include a bridge circuit unit 1120. The bridge circuit unit 1120 may be disposed between the top switch unit 1150 and the DC stabilization circuit unit 1140 . The bridge circuit unit 1120 may include ninth to twelfth switch elements Q9 to Q12.

The DC/DC converter 1100 according to another embodiment may include a DC stabilization circuit unit 1140 . The DC stabilization circuit unit 1140 may include a 2-1 inductor L21, a 2-2 inductor L22, and a second capacitor C2. The DC stabilization circuit unit 1140 may be connected to the second terminal to which the battery 200 is connected.

The top switch unit 1150 is connected between one side of the overcurrent protection circuit unit 1110 and the eleventh node N11. The battery 200 and the second capacitor C2 are connected between the 15th and 16th nodes N15 and N16, and the 2-1 inductor L2-1 is connected to the 15th and 13th nodes N15 and N13. and the 2-2nd inductor L2-2 is connected between the 15th node and the 14th node N15 and N14. The bridge circuit unit 1120 consists of an 11th leg between the 11th and 12th nodes N11 and N12 and a 12th leg, and the 11th leg is between the 11th and 13th nodes N11 and N13. It consists of a connected 11th switch element (Q11) and a 12th switch element (Q12) connected between the 13th and 12th nodes (N13 and N12), and the twelfth leg is composed of the 11th and 14th nodes (N11 and N14) It consists of a ninth switch element (Q9) connected between the 10th switch element (Q10) connected between the fourteenth and twelfth nodes (N14, N12).

The DC-DC converter 1100 according to another embodiment is a bi-directional converter, and in a step-down mode, the DC input voltage on the DC link capacitor 90 is dropped to the 15th and 16th nodes (N15 and N16). ), the DC output voltage is output, and in the step-up mode, the DC input voltage on the 15th and 16th nodes N15 and N16 is raised to output the DC output voltage to the DC link capacitor 90. .

The DC-DC converter 1100 according to another embodiment performs a switching operation of the top switch unit 1150 and the bridge circuit unit 1120 to initially charge the DC link capacitor 90 for the discharge mode, thereby generating the DC link capacitor 90 ) can provide a direct current (Idc). For example, referring to FIG. 8 , the Nth (N is a natural number) DC current Idc among the plurality of DC currents Idc provided for initial charging is when the 11th switch element Q11 of the bridge circuit unit 1120 turns on. The ninth switch element Q9, the tenth switch element Q10, and the twelfth switch element Q12 may be turned off, and the thirteenth switch element Q13 of the top switch unit 1150 may be turned on. Referring to FIG. 9 , the N+1th (N is a natural number) DC current Idc among the plurality of DC currents Idc provided for initial charging is when the ninth switch element Q9 of the bridge circuit unit 1120 is turned on. The eleventh switch element Q11, the tenth switch element Q10, and the twelfth switch element Q12 may be turned off, and the thirteenth switch element Q13 of the top switch unit 1150 may be turned on. In addition, the thirteenth switch element Q13 of the top switch unit 1150 may be turned off while the direct current Idc for charging the gun is not provided.

10 is a circuit diagram of a DC/DC converter according to another embodiment.

Referring to FIG. 10 , the DC/DC converter of FIG. 10 is identical to the DC/DC converter of FIG. 7 according to another embodiment except for the top switch unit 2150 . Therefore, description of the same configuration as that of the DC/DC converter of FIG. 7 will be omitted.

The top switch unit 2150 according to another embodiment may include a main switch unit 2151 and an initial charge switch unit 2152. The main switch unit 2151 may include a thirteenth switch element Q13 disposed between one end of the overcurrent protection circuit unit 2110 and the eleventh node N11. The initial charge switch unit 2152 may be connected in parallel with the main switch unit 2151 . The initial charge switch unit 2152 may include a fourteenth switch element Q14 and a resistor R. One side of the fourteenth switch element Q14 may be connected to one end of the overcurrent protection circuit unit 2110 and the other side may be connected to one side of the resistor R. One side of the resistor R may be connected to the other side of the fourteenth switch element Q14 and the other side may be connected to the eleventh node N11. The resistor R has a lower level than the current flowing through the main switch unit 2151. A current of is allowed to flow through the initial charge switch unit 2152.

In the DC/DC converter 2100 according to another embodiment, when a step-down mode operation, which is a charging mode, or a stem-up mode operation, which is a discharging mode, is performed, the main switch unit 2151 is turned on/off and the initial charge switch unit 2152 can remain off. Also, in the DC/DC converter 1100, in the initial charge mode before starting the discharge mode, the main switch unit 2151 may remain off and the initial charge switch unit 2152 may be turned on/off. That is, when the DC/DC converter 2100 according to another embodiment initially charges the DC link capacitor 90, the operation of the bridge circuit 2120 is performed by the bridge circuit 1120 of the DC/DC converter 1100 of FIG. ) may be the same as the operation of

Accordingly, the energy storage system according to the embodiment may initially charge the DC link capacitor before the discharge mode operation without a separate configuration. In addition, the energy storage system according to the embodiment can gradually increase the DC current provided to the DC link capacitor, so that the initial charge speed is fast and the battery discharge operation can be performed quickly.

<Converter Efficiency Control>

11 is a graph showing a power conversion ratio according to an output power ratio when an energy storage system converts direct current to direct current power according to an embodiment, and FIG. 12 is a pulse width control method of a DC/DC converter of an energy storage system according to an embodiment. , and FIG. 13 is a diagram for explaining a signal according to output power of an energy storage system according to an exemplary embodiment.

Referring to FIG. 11 , in general, power conversion efficiency (dotted line) of a DC/DC converter rapidly decreases when an output power is less than a predetermined ratio P1 during power conversion. For example, when a DC/DC converter converts power with less than 25% of its maximum output power, its power conversion efficiency is rapidly reduced to 95% or less.

The energy storage system 20 according to an exemplary embodiment may maintain power conversion efficiency (solid line) at a predetermined efficiency even when the output power of the DC/DC converter falls below a predetermined ratio P1. For example, the DC/DC converter can maintain power conversion efficiency at 95% when converting power with less than 25% of the maximum output power. To this end, the DC/DC converter 100 may provide DC current (Idc) with high power conversion efficiency when the power conversion efficiency is less than or equal to a predetermined ratio (P1) of the maximum output power. In this case, the output power can be adjusted by controlling the pulse width of the PWM signal that controls the DC/DC converter 100 . In addition, since the DC current Idc provided below the predetermined ratio P1 of the maximum output power has a problem in that the current ripple increases as the intensity increases, the current intensity may be set to a current intensity that satisfies a predetermined ripple range. More specifically, referring to FIG. 12 , the DC/DC converter 100 may receive a PWM signal used for power conversion from the converter control unit during charging mode or discharging mode operation. The pulse width of the PWM signal may be set to the first pulse width W1 for one period Tw when the DC/DC converter 100 outputs the output power at a predetermined ratio P1 or more of the maximum output power. In this case, the intensity of the output power can be adjusted by adjusting the intensity of the direct current (Idc). In addition, the pulse width of the PWM signal may be adjusted to the second pulse width W2 for one period Tw when the DC/DC converter 100 outputs the output power less than the predetermined ratio P1 of the maximum output power. there is. In this case, the intensity of the output power may be adjusted by maintaining the intensity of the DC current (Idc) whose power conversion efficiency is higher than a predetermined efficiency and adjusting the pulse width of the PWM signal. As an example, referring to FIG. 13, (a) is a case in which the DC/DC converter 100 outputs an output power of 300W, and (b) is a case in which the DC/DC converter 100 outputs an output power of 900W. is the case In the DC/DC converters 100 of (a) and (b), the power conversion efficiency is maintained at the strength of the DC current (Idc) having a predetermined efficiency or more, and the pulse widths of the PWM signals are different from each other. That is, in the PWM signal of the DC/DC converter 100, the pulse width for outputting 900W of power is greater than the pulse width for outputting 300W of power.

Also, the method for controlling the power conversion efficiency of the DC/DC converter 100 may include the converter efficiency control method of FIGS. 15 to 17 .

Therefore, the energy storage system according to an embodiment may have excellent power conversion efficiency of a DC/DC converter. In addition, since the energy storage system according to an embodiment has excellent power conversion efficiency of a DC/DC converter, energy efficiency delivered when charging or discharging a battery may be high.

14 is a diagram for explaining a method of initially charging a DC link capacitor of a power supply system according to an exemplary embodiment.

Referring to FIG. 14 , the power supply system may include starting a battery discharge mode of the energy storage system (S1410). That is, the system controller may transmit a command signal informing the energy storage system of the discharge mode operation.

The power supply system may include determining whether the DC voltage is greater than or equal to the operating voltage (S1420). More specifically, the charging control unit of the energy storage system may determine whether the DC voltage of the DC link capacitor is greater than or equal to an operating voltage capable of performing an inverting operation of the inverter.

The power supply system may include performing a battery discharging operation when the DC voltage is equal to or higher than the operating voltage (S1430). More specifically, the DC/DC converter may perform a boosting operation to increase the DC input voltage provided from the battery and provide the DC voltage to the DC link capacitor.

The power supply system may include starting an initial charging mode when the DC voltage is less than the operating voltage (S1440).

When the initial charging mode starts, the power supply system may include providing an initial charging current to the DC link capacitor (S1450). That is, the DC/DC converter of the energy storage system may provide DC current to the DC link capacitor using electric energy of the battery. In this case, a method in which the DC/DC converter of FIGS. 3 to 10 initially charges the DC link capacitor may be used.

While the initial charging current is provided, the power supply system may include a step of determining whether the DC voltage is greater than or equal to the operating voltage (S1460). In this case, if the DC voltage is equal to or higher than the operating voltage, the DC/DC converter may terminate the initial charging mode and discharge the battery (S1430).

While the initial charging current is provided, the power supply system may include determining whether the DC current is equal to or greater than the reference current when the DC voltage is less than the operating voltage (S1470). The reference current may be a preset current. The reference current may be a current strength sufficient to charge the DC link capacitor. In addition, since the voltage difference between the inverter side and the battery side is large, the reference current may be set below a predetermined level since circuit damage due to inrush current may occur if the reference current exceeds a predetermined level. The power supply system may stop providing the initial charging current when the DC current is greater than or equal to the reference current (S1480). In this case, the switch of the DC/DC converter is turned off and no DC current is provided to the DC link capacitor. Conversely, the power supply system may continue to provide the initial charging current when the DC current is less than the reference current.

After stopping providing the initial charging current, the power supply system may include a step of determining whether the DC current is equal to or less than the set current (S1490). The set current may be a preset current. The set current may be smaller than the reference current. For example, the set current may be 0A. The power supply system may continue to stop providing the initial charging current when the DC current is not equal to or less than the set current. Conversely, the power supply system may provide the initial charging current when the DC current is less than or equal to the set current. That is, the power supply system may initially charge the DC link capacitor according to the magnitude of DC current provided to the DC link capacitor, thereby stably initial charging the DC link capacitor.

15 is a diagram for explaining a power supply method of an energy storage system according to an embodiment, and FIG. 17 is a diagram for explaining a power conversion efficiency control method of a DC/DC converter of an energy storage system according to an embodiment. 16 is a diagram for explaining a configuration of a converter efficiency controller applied to an energy storage system of a power supply system according to an embodiment.

Referring to FIG. 15 , the power supply method according to an embodiment may include operating the energy storage system in a charging mode or a discharging mode ( S1510 ).

The power supply method may include determining whether the converter efficiency is controlled (S1520). That is, the energy storage system may determine whether it is necessary to control the power conversion efficiency of the DC/DC converter. In this case, the energy storage system may determine whether the output power is less than the reference power (S1530). The output power may be power currently output by the DC/DC converter. The reference power may be output power at which the power conversion efficiency of the DC/DC converter becomes a predetermined efficiency. The reference power may be set in advance. For example, the reference power may be a power that is a predetermined ratio of the maximum output power of the DC/DC converter. For example, the reference power may be 25% of the maximum output power of the DC/DC converter.

If the output power is not less than the reference power, the charging operation or the discharging operation may be performed without controlling the converter efficiency (S1550).

When the output power is less than the reference power, the energy storage system may include a step of controlling converter efficiency (S1540).

More specifically, referring to FIG. 17 , converter efficiency control may include calculating a pulse width based on output power (S1541). More specifically, Equation 1 may be used to calculate the pulse width.

(Equation 1)

For example, a pulse width of 1 kW can be calculated by controlling converter efficiency up to 25% of the output power of a DC/DC converter having a maximum output power of 5 kW and setting a repetition period of a PWM signal to 2 ms. In this case, the pulse width of 1 kW may be 1.6 ms, which is 1 kW/(5 kW*25%)*2 ms.

Also, converter efficiency control may determine an average power value (S1542). The average power value may be calculated by the charging control unit measuring the output power value for a predetermined number of repetition cycles of the PWM signal. Thereafter, the converter efficiency control may calculate a comparison value between the output power and the average power value (S1543). That is, the comparison value may be a value obtained by subtracting the average power value from the output power. For example, referring to FIG. 16 , the energy storage system 20 may include a converter efficiency controller 500 . The converter efficiency controller 500 may be included in the charging controller 300, but is not limited thereto. The converter efficiency controller 500 may compare the output power Pdc and the average power value Pavg to calculate the power difference value Pd. Thereafter, converter efficiency control may calculate a power compensation value based on the comparison value (S1544). For example, the converter efficiency controller 500 may include a compensator 510 . Compensation unit 510 may be a PI controller. The compensator 510 may provide the input power difference value Pd as a power compensation value Pc. Thereafter, converter efficiency control may provide compensated output power by compensating the reference power with a power compensation value (S1545). For example, the converter efficiency controller 500 may provide the compensated output power Pdc* by adding the power compensation value Pc to the reference power Pref. In this case, pulse width calculation in S1541 may be calculated based on the compensated output power.

18 is a diagram for explaining an energy storage system according to another embodiment.

Referring to FIG. 18 , an energy storage system 20 according to another embodiment may include a DC/DC converter 1800, a battery 200, and a charging controller 300. Although not shown in FIG. 1 , the energy storage system 20 may be connected to the inverter 30 through the DC link capacitor 90 . That is, the DC link capacitor 90 may be disposed between the energy storage system 20 and the inverter 30 . Accordingly, the energy storage system 20 may receive the DC voltage Vdc of the DC link capacitor 90 in the charging mode and provide the DC voltage Vdc to the DC link capacitor 90 in the discharging mode. In addition, a configuration included in the DC/DC converter of the energy storage system according to another embodiment to be described later may be included in the configuration of the DC/DC converter of the energy storage system according to the embodiment of FIGS. 2 to 17 . The battery 200 may receive charging power from the DC/DC converter 1800 in the charging mode and perform a charging operation by the received power. Also, the battery 200 may output pre-stored power to the DC/DC converter 1800 in the discharge mode. Also, the battery 200 may include a plurality of battery cells to perform charging and discharging operations. Also, the battery 200 may be connected to the second terminal (Nb).

The charging controller 300 may include a battery management system (BMS). The charging controller 300 may provide battery state information about the state of the battery 200 to the system controller 80 . For example, the charging control unit 300 monitors at least one of voltage, current, temperature, remaining power amount, and charging state of the battery 200, and transmits state information of the monitored battery 200 to the system control unit 80. can be conveyed In addition, the charging control unit 300 can maintain an appropriate voltage for a plurality of battery cells while charging or discharging. Also, the charging controller 300 may operate based on a control signal from the system controller 80 . Also, the charging control unit 300 may control the DC/DC converter 1800 according to the monitored state information of the battery 200 . Also, the charging control unit 300 may control the DC/DC converter 1800 according to a charging mode or a discharging mode. More specifically, the charging controller 300 provides a charge control signal or a discharge control signal for controlling the DC/DC converter 1800 to the controller 1830 of the DC/DC converter 1800, and the DC/DC converter ( The control unit 1830 of 1800 may provide a PWM signal to the switch of the DC/DC converter 1800 based on the charge control signal or the discharge control signal. In addition, the charging control unit 300 may be driven based on the second driving power supply VCC2 provided by the auxiliary power supply unit 1850 .

The DC/DC converter 1800 may convert the amount of DC power supplied from the energy storage system 20 in a charging mode or supplied in a discharging mode. That is, the DC/DC converter 1800 may be a bidirectional DC/DC converter. More specifically, the DC/DC converter 2300 converts the DC power provided from the generator 10 or the inverter 30 to the DC link capacitor 90 into a voltage size for charging the battery 200 to the battery ( 200) can be provided. In addition, the DC/DC converter 1800 may convert the DC power provided by the battery 200 into a voltage level usable by the inverter 30 and provide the DC power to the DC link capacitor 90 .

The DC/DC converter 1800 may include an overcurrent protection circuit 1810, a bridge circuit 1820, a controller 1830, a DC stabilization circuit 1840, an auxiliary power supply 1850, and a backup power supply 1860.

The control unit 1830 may generate a PWM signal based on the control signal provided from the charging control unit 300 and provide the PWM signal to the bridge circuit unit 1820 including the switch. Also, the control unit 1830 may drive based on the first driving power VCC1 provided by the auxiliary power supply unit 1850 .

The overcurrent protection circuit unit 1810 may prevent EOS or overcurrent flowing into or out of the energy storage system 20 . The overcurrent protection circuit unit 1810 may be disposed between the first terminal Na to which the DC link capacitor 90 is connected and the bridge circuit unit 1820 . Also, the overcurrent protection circuit unit 1810 may include a circuit breaker. In this case, the overcurrent protection circuit unit 1810 may open between the first terminal Na and the bridge circuit unit 1820 when EOS or overcurrent flows into the energy storage system 20 . Accordingly, the overcurrent protection circuit unit 1810 may block the input/output of the energy storage system 20 and external current.

The bridge circuit unit 1820 may be disposed between the overcurrent protection circuit unit 1810 and the DC stabilization circuit unit 1840 and electrically connected to each component. The bridge circuit unit 1820 may drop the DC voltage of the DC power input from the overcurrent protection circuit unit 1810 in the step-down mode and output the voltage to the DC stabilization circuit unit 1840 . In addition, the bridge circuit unit 1820 may increase the voltage of the DC voltage of the DC power input from the DC stabilization circuit unit 1840 in the step-up mode and output the voltage to the overcurrent protection circuit unit 1810 . The bridge circuit 1820 may include one or more switches. For example, the bridge circuit unit 1820 may be an insulated full bridge circuit of FIG. 4 . As another example, the bridge circuit unit 1820 may be a non-isolated full bridge circuit of FIG. 7 . It is not limited thereto, and the bridge circuit unit 1820 may be configured as a half bridge circuit. The bridge circuit unit 1820 may operate based on the PWM signal of the control unit 1830.

The DC stabilization circuit unit 1840 may operate to increase the DC voltage in the step-up mode of the bridge circuit unit 1820 and decrease the DC voltage in the step-down mode. Also, the DC stabilization circuit unit 1840 may be an LC filter. The DC stabilization circuit unit 1840 may be connected to the second end Nb.

The auxiliary power supply unit 1850 may generate driving power based on the first power P1 provided to the second terminal Nb. The first power P1 provided to the second terminal Nb is based on energy stored in the battery 200 . The first power P1 may be standby power. In addition, the auxiliary power supply unit 1850 receives the second power P2 from the backup power supply unit 1860 when the first power P1 is not supplied from the second end Nb, and based on the second power P2 Thus, a driving power source can be generated. For example, when the first power P1 is not supplied from the second terminal Nb to the auxiliary power source 1850, the battery 200 connected to the second terminal Nb may be over-discharged. The second power P2 may be minimum power for generating driving power. The driving power source may be plural. The driving power includes first driving power VCC1 provided to the charging controller 300 of the energy storage system 20 and second driving power VCC2 provided to the controller 1830 of the DC/DC converter 1800. can do. The present invention is not limited thereto, and the auxiliary power supply unit 1860 may output a plurality of driving power supplies having different voltage levels as needed. More specifically, the second terminal Nb of the auxiliary power supply 1850 may be connected to the third terminal Nc disposed at the input terminal and the output unit of the backup power supply 1860 . In the auxiliary power supply 1850 , when the first power P1 is provided to the second terminal Nb, the first power P1 may be input to the third terminal Nc and then input to the input terminal. In addition, the auxiliary power supply unit 1850 outputs the second power P1 to the third terminal when the first power P1 is not supplied to the second terminal Nb and the second power P2 is supplied to the second terminal Nb. It can be input to the terminal (Nc) and input to the input terminal. Accordingly, the DC/DC converter can generate driving power even when the battery is over-discharged, and thus can perform a battery charging operation. In addition, the DC/DC converter can be charged without replacing the battery even if the battery is over-discharged.

The backup power supply unit 1860 may provide second power P2 based on power provided from the DC link capacitor 90 or the inverter 30 . More specifically, the backup power supply 1860 may be electrically connected between the first terminal Na and the auxiliary power supply 1850 . The backup power supply unit 1860 may generate second power P2 based on the third power P3 provided from the first terminal Na. In addition, the backup power supply 1860 may provide second power P2 to the auxiliary power supply 1850 when the first power P1 is not supplied to the auxiliary power supply 1850 from the second terminal Nb. For example, the backup power supply 1860 may have one end connected to the first end Na and the other end connected to the third end Nc. The backup power supply unit 1860 may provide the second power P2 to the third terminal Nc, and may provide the second power P2 to the auxiliary power supply unit 1850 at the third terminal Nc.

Thus, another embodiment can charge the battery even if the battery is over-discharged. In addition, in another embodiment, there is no need to replace the battery even if the battery is over-discharged.

19 is a diagram for explaining an energy storage system according to another embodiment.

Referring to FIG. 19 , the energy storage system according to another embodiment of FIG. 19 has the same configuration as the energy storage system of FIG. 18 except for the current limiting unit 1870 . Therefore, the same description as the energy storage system of FIG. 18 is omitted.

The energy storage system 20 according to another embodiment may include a DC/DC converter 1800 including a current limiting unit 1870 .

The current limiting unit 1870 may be disposed in the input unit of the auxiliary power supply unit 1850. For example, the current limiting unit 1870 may be disposed at the third terminal Nc. The current limiting unit 1870 may prevent power input to the auxiliary power supply unit 1850 from being reversely provided. Also, the current limiting unit 8170 may prevent the provided power from being provided to a configuration in which it should not be provided. More specifically, the current limiting unit 1870 may include a first diode D1 and a second diode D2. The first diode D1 allows the first power P1 provided from the second terminal Nb to be provided to the third terminal Nc. Also, the first diode D1 may prevent the second power P2 from being provided to the second terminal Nb. The second diode D2 allows the second power P2 provided by the backup power supply unit 1860 to be provided to the third terminal Nc. Also, the second diode D2 may prevent the first power P1 from being provided to the backup power supply 1860 .

Accordingly, in the DC/DC converter according to another embodiment, the auxiliary power unit can stably generate driving power using the current limiting unit and can prevent unwanted battery charging.

20 is a diagram for explaining an energy storage system according to another embodiment.

Referring to FIG. 20 , the energy storage system according to another embodiment of FIG. 20 has the same configuration as the energy storage system of FIG. 18 except for the DC/DC converter. Therefore, the same description as the energy storage system of FIG. 18 is omitted.

The DC/DC converter 2000 may include an overcurrent protection circuit 2010, a bridge circuit 2020, a controller 2030, a DC stabilization circuit 2040, an auxiliary power supply 2050, and a backup power supply 2060. Although not shown, the DC/DC converter 2000 may further include the current limiting unit of FIG. 19 .

The control unit 2030 may generate a PWM signal based on a control signal provided from the charging control unit 300 and provide the PWM signal to the bridge circuit unit 2020 including the switch. In addition, the control unit 2030 may drive based on the first driving power supply VCC1 provided by the auxiliary power supply unit 2050 .

The overcurrent protection circuit unit 2010 may prevent EOS or overcurrent flowing into or out of the energy storage system 20 . The overcurrent protection circuit unit 2010 may be disposed between the first terminal Na to which the DC link capacitor 90 is connected and the bridge circuit unit 2020 . In addition, the overcurrent protection circuit unit 2010 may include a circuit breaker. In this case, the overcurrent protection circuit unit 2010 may open between the first end Na and the bridge circuit unit 2020 when EOS or overcurrent flows into the energy storage system 20 . Accordingly, the overcurrent protection circuit unit 2010 may block the input/output of the energy storage system 20 and external current.

The bridge circuit unit 2020 may be disposed between the overcurrent protection circuit unit 2010 and the DC stabilization circuit unit 2040 and electrically connected to each component. The bridge circuit unit 2020 may drop the DC voltage of the DC power input from the overcurrent protection circuit unit 2010 in the step-down mode and output the voltage to the DC stabilization circuit unit 2040 . In addition, the bridge circuit unit 2020 may increase the voltage of the DC voltage of the DC power input from the DC stabilization circuit unit 2040 in the step-up mode and output the voltage to the overcurrent protection circuit unit 2010 . Bridge circuitry 2020 may include one or more switches. For example, the bridge circuit unit 2020 may be an insulated full bridge circuit of FIG. 4 . As another example, the bridge circuit unit 2020 may be a non-insulated full bridge circuit of FIG. 7 . It is not limited thereto, and the bridge circuit unit 2020 may be configured as a half bridge circuit. The bridge circuit unit 2020 may operate based on the PWM signal of the control unit 2030.

The DC stabilization circuit unit 2040 may operate to increase the DC voltage in the step-up mode of the bridge circuit unit 2020 and decrease the DC voltage in the step-down mode. Also, the DC stabilization circuit unit 2040 may be an LC filter. The DC stabilization circuit unit 2040 may be connected to the second end Nb.

The auxiliary power supply unit 2050 may generate driving power based on the first power P1 provided to the second terminal Nb. The first power P1 provided to the second terminal Nb is based on energy stored in the battery 200 . The first power P1 may be standby power. In addition, the auxiliary power supply unit 2050 receives the second power P2 from the backup power supply unit 2060 when the first power P1 is not supplied from the second terminal Nb, and based on the second power P2 Thus, a driving power source can be generated. For example, when the first power P1 is not supplied from the second terminal Nb to the auxiliary power supply 2050, the battery 200 connected to the second terminal Nb may be over-discharged. The second power P2 may be minimum power for generating driving power. The driving power may be plural. The driving power includes first driving power VCC1 provided to the charging controller 300 of the energy storage system 20 and second driving power VCC2 provided to the controller 2030 of the DC/DC converter 2000. can do. The present invention is not limited thereto, and the auxiliary power supply unit 2060 may output a plurality of driving power supplies having different voltage levels as needed. More specifically, the second terminal Nb of the auxiliary power supply unit 2050 and the output unit of the backup power supply unit 2060 may be connected to the third terminal Nc disposed at the input terminal. In the auxiliary power supply unit 2050 , when the first power P1 is provided to the second terminal Nb, the first power P1 may be input to the third terminal Nc and then input to the input unit. In addition, the auxiliary power supply unit 2050 outputs the second power P1 to the third terminal when the first power P1 is not supplied to the second terminal Nb and the second power P2 is supplied to the second terminal Nb. It can be input to the terminal Nc and input to the input unit. Accordingly, the DC/DC converter can generate driving power even when the battery is over-discharged, and thus can perform a battery charging operation. In addition, the DC/DC converter can be charged without replacing the battery even if the battery is over-discharged.

The backup power supply unit 2060 may provide second power P2 based on power provided from an external power source disposed outside the DC/DC converter 2000 . More specifically, the backup power supply 1860 may be electrically connected between the external input terminal InputE and the auxiliary power supply 2050 . The backup power supply 2060 may generate the second power P2 based on the fourth power P4 provided from the external input terminal InputE. In addition, the backup power supply 2060 may provide second power P2 to the auxiliary power supply 2050 when the first power P1 is not supplied from the second terminal Nb to the auxiliary power supply 1850. For example, the backup power supply 2060 may have one end connected to the external input terminal inputE and the other end connected to the third terminal Nc. The backup power supply unit 2060 may provide the second power P2 to the third terminal Nc, and may provide the second power P2 to the auxiliary power supply unit 2050 at the third terminal Nc.

Thus, another embodiment can charge the battery even if the battery is over-discharged. Also, according to another embodiment, there is no need to replace the battery even if the battery is over-discharged.

21 is a diagram for explaining an energy storage system according to another embodiment.

Referring to FIG. 21 , the energy storage system according to another embodiment of FIG. 21 has the same configuration as the energy storage system of FIGS. 18 and 20 except for the backup power unit and the backup power control unit. Therefore, the same description as the energy storage system of FIGS. 18 and 20 is omitted.

The backup power supply unit 2060 may provide second power P2 based on the power provided from the backup power control unit 2070 . More specifically, the backup power supply unit 1860 may be electrically connected between the backup power control unit 2070 and the auxiliary power supply unit 2050 . The backup power supply unit 2060 may generate second power P2 based on the fifth power P5 provided from the backup power control unit 2070 . In addition, the backup power supply 2060 may provide second power P2 to the auxiliary power supply 2050 when the first power P1 is not supplied from the second terminal Nb to the auxiliary power supply 1850. For example, the backup power supply unit 2060 may have one end connected to the backup power control unit 2070 and the other end connected to the third terminal Nc. The backup power supply unit 2060 may provide the second power P2 to the third terminal Nc, and may provide the second power P2 to the auxiliary power supply unit 2050 at the third terminal Nc.

A DC/DC converter of an energy storage system according to another embodiment may include a backup power control unit 2070. The backup power control unit 2070 selects any one of the power provided from the external power source and the power provided from the first terminal (Na) based on the control signal of the control unit 2030 and provides the selected power to the backup power supply unit 2060. can More specifically, the backup power control unit 2070 may be disposed between the external input terminal InputE, the first terminal Na and the backup power supply unit 2060 . The backup power controller 2070 may include a switch. For example, the controller 2030 may control the backup power controller 2070 to provide the third power P3 of the first stage Na as the fifth power P5 to the backup power source 2060 . In addition, the control unit 2030 may control the backup power control unit 2070 to provide the fourth power P4 of the external input terminal InputE as the fifth power P5 to the backup power supply unit 2060 . Thus, another embodiment can charge the battery even if the battery is over-discharged. Also, according to another embodiment, there is no need to replace the battery even if the battery is over-discharged.

22 is a diagram for explaining a power conversion method for battery charging in a DC/DC converter of an energy storage system according to an embodiment.

The power conversion method of FIG. 22 may use the DC/DC converter configuration of FIGS. 18 to 21 .

Referring to FIG. 22 , a method for converting power of a DC/DC converter according to an embodiment may include determining whether first power is supplied from a second stage (S2201). For example, in a battery discharge state, the auxiliary power unit may determine whether first power is provided from the first terminal.

The power conversion method of the DC/DC converter according to the embodiment may include providing first power when the first power is provided from a second stage to the auxiliary power supply unit ( S2202 ). That is, when the first power is supplied from the first terminal, the auxiliary power unit may receive the first power.

The power conversion method of the DC/DC converter according to the embodiment may include generating, by the auxiliary power unit, driving power of the control unit based on the first power when receiving the first power (S2203). More specifically, the auxiliary power supply may generate a plurality of driving power sources based on the first power. The auxiliary power supply unit may provide the generated driving power to a necessary component. For example, as described in FIGS. 18 to 21 , the auxiliary power supply may generate first driving power for driving the charging control unit and second driving power for driving the control unit of the DC/DC converter.

The power conversion method of the DC/DC converter according to the embodiment may include a step of providing, by the backup power supply unit, second power to the auxiliary power unit when the first power is not supplied from the second terminal in S2201 (S2204). A method of providing the second power to the auxiliary power unit by the backup power unit may be the same as the configuration in which the backup power unit provides the second power to the auxiliary power unit of FIGS. 18 to 21 .

The power conversion method of the DC/DC converter according to the embodiment may include generating driving power of the control unit based on the second power of the auxiliary power supply (S2205). More specifically, the auxiliary power supply unit may generate a plurality of driving power sources based on the second power. The auxiliary power supply unit may provide the generated driving power to a necessary component. For example, as described in FIGS. 18 to 21 , the auxiliary power supply may generate first driving power for driving the charging control unit and second driving power for driving the control unit of the DC/DC converter.

Thus, another embodiment can charge the battery even if the battery is over-discharged. Also, according to another embodiment, there is no need to replace the battery even if the battery is over-discharged.

23 is a diagram for explaining an energy storage system according to another embodiment.

Referring to FIG. 23 , an energy storage system 20 according to another embodiment may include a DC/DC converter 2300, a battery 200, and a charging controller 300. Although not shown in FIG. 1 , the energy storage system 20 may be connected to the inverter 30 through the DC link capacitor 90 . That is, the DC link capacitor 90 may be disposed between the energy storage system 20 and the inverter 30 . Accordingly, the energy storage system 20 may receive the DC voltage Vdc of the DC link capacitor 90 in the charging mode and provide the DC voltage Vdc to the DC link capacitor 90 in the discharging mode. In addition, a configuration included in the DC/DC converter of the energy storage system according to another embodiment to be described later may be included in the configuration of the DC/DC converter of the energy storage system according to the embodiment of FIGS. 2 to 22 . The battery 200 may receive charging power from the DC/DC converter 2300 in the charging mode and perform a charging operation by the received power. In addition, the battery 200 may output pre-stored power to the DC/DC converter 2300 in the discharge mode. Also, the battery 200 may include a plurality of battery cells to perform charging and discharging operations. Also, the battery 200 may be connected to the second terminal (Nb).

The charging controller 300 may include a battery management system (BMS). The charging controller 300 may provide battery state information about the state of the battery 200 to the system controller 80 . For example, the charging control unit 300 monitors at least one of voltage, current, temperature, remaining power amount, and charging state of the battery 200, and transmits state information of the monitored battery 200 to the system control unit 80. can be conveyed In addition, the charging control unit 300 can maintain an appropriate voltage for a plurality of battery cells while charging or discharging. Also, the charging controller 300 may operate based on a control signal from the system controller 80 . Also, the charging control unit 300 may control the DC/DC converter 2300 according to the monitored state information of the battery 200 . Also, the charging control unit 300 may control the DC/DC converter 2300 according to a charging mode or a discharging mode. More specifically, the charging controller 300 provides a charge control signal or a discharge control signal for controlling the DC/DC converter 2300 to the controller 2330 of the DC/DC converter 2300, and the DC/DC converter ( The controller 2330 of 2300 may provide a PWM signal to the switch of the DC/DC converter 2300 based on the charge control signal or the discharge control signal.

The DC/DC converter 2300 may convert the amount of DC power supplied from the energy storage system 20 in a charging mode or supplied in a discharging mode. That is, the DC/DC converter 2300 may be a bidirectional DC/DC converter. More specifically, the DC/DC converter 2300 converts the DC power provided from the generator 10 or the inverter 30 to the DC link capacitor 90 into a voltage size for charging the battery 200 to the battery ( 200) can be provided. In addition, the DC/DC converter 2300 may convert DC power provided by the battery 200 into a voltage level usable by the inverter 30 and provide the DC power to the DC link capacitor 90 . Also, the DC/DC converter 2300 may operate in a charging mode, a standby mode, and a discharging mode based on the voltage provided from the DC voltage link capacitor. That is, the DC/DC converter 2300 can monitor the voltage provided from the DC voltage link capacitor even without providing a control signal from the charging control unit 300 to determine whether to operate in the charging mode, standby mode, and discharging mode and operate. there is. A more detailed description of the operation of the DC/DC converter 2300 in the charging mode, the standby mode, and the discharging mode will be described later.

The DC/DC converter 2300 may include an overcurrent protection circuit 2310, a bridge circuit 2320, a controller 2330, a DC stabilization circuit 2340, an auxiliary power supply 2350, and a backup power supply 2360.

The control unit 2330 may control the bridge circuit unit 2320. For example, the control unit 2330 may generate a PWM signal based on a control signal provided from the charging control unit 300 and provide the PWM signal to the bridge circuit unit 2320 including the switch. As another example, the controller 2330 may determine an operation mode and reference power according to the magnitude of the voltage provided from the DC link capacitor 90 . In addition, the control unit 2330 may generate a PWM signal based on the determined reference power and provide the PWM signal to the bridge circuit unit 2320 including the switch. A detailed description of other examples will be given later.

The overcurrent protection circuit unit 2310 may prevent EOS or overcurrent flowing into or out of the energy storage system 20 . The overcurrent protection circuit unit 2310 may be disposed between the first terminal Na to which the DC link capacitor 90 is connected and the bridge circuit unit 2320 . In addition, the overcurrent protection circuit unit 2310 may include a circuit breaker. In this case, the overcurrent protection circuit unit 2310 may open between the first terminal Na and the bridge circuit unit 2320 when EOS or overcurrent flows into the energy storage system 20 . Accordingly, the overcurrent protection circuit unit 2310 may block the input/output of the energy storage system 20 and external current.

The bridge circuit unit 2320 may be disposed between the overcurrent protection circuit unit 2310 and the DC stabilization circuit unit 2340 and electrically connected to each component. The bridge circuit unit 2320 may drop the DC voltage of the DC power input from the overcurrent protection circuit unit 2310 in the step-down mode and output the voltage to the DC stabilization circuit unit 2340 . In addition, the bridge circuit unit 2320 may increase the voltage of the DC voltage of the DC power input from the DC stabilization circuit unit 2340 in the step-up mode and output the voltage to the overcurrent protection circuit unit 2310 . The bridge circuit 2320 may include one or more switches. For example, the bridge circuit unit 2320 may be an insulated full bridge circuit of FIG. 4 . As another example, the bridge circuit unit 2320 may be a non-isolated full bridge circuit of FIG. 7 . It is not limited thereto, and the bridge circuit unit 2320 may be configured as a half bridge circuit. The bridge circuit unit 2320 may operate based on the PWM signal of the control unit 2330.

The DC stabilization circuit unit 2340 may operate to increase the DC voltage in the step-up mode of the bridge circuit unit 2320 and decrease the DC voltage in the step-down mode. Also, the DC stabilization circuit unit 2340 may be an LC filter. The DC stabilization circuit unit 2340 may be connected to the second end Nb.

The sensing unit 2350 may sense the voltage of the first terminal Na and provide the sensed voltage to the controller 2330 . The voltage of the first terminal Na may be a DC voltage provided by the DC link capacitor 90 . Also, the sensing unit 2350 may be controlled by the controller 2330.

Thus, another embodiment can quickly determine the operating mode of charging or discharging the battery. In addition, another embodiment does not require a separate communication line and communication unit for droop control during battery charging or discharging. In addition, another embodiment enables rapid droop control during battery charging or discharging.

24 is a diagram for explaining the controller of FIG. 23, FIG. 25 is a diagram for explaining a droop control curve of the energy storage system of FIG. 23, and FIG. 26 is a diagram for explaining the reference current determiner of FIG. 24. FIG. 27 is a diagram for explaining the current controller of FIG. 24 .

Referring to FIG. 24 , a controller 2330 of a DC/DC converter 2300 according to another embodiment may include a reference power determiner 2331. The reference power determiner 2331 may determine an operation mode and reference power.

For example, the reference power determiner 2331 may determine an operation mode and reference power according to the magnitude of the voltage of the first stage. More specifically, referring to FIG. 25 , the reference power determiner 2331 may determine an operating mode and reference power based on a droop control curve according to a voltage of a first stage. In the case of the operation mode, the reference power determiner 2331 may determine the charging mode when the voltage Vdc of the first terminal is equal to or greater than the first voltage V1. The reference power determiner 2331 may determine the standby mode when the voltage Vdc of the first terminal is less than the first voltage V1 and greater than the second voltage V2. The reference power determiner 2331 may determine the discharge mode when the voltage Vdc of the first terminal is less than or equal to the second voltage V2. The first voltage V1 and the second voltage V2 may be preset voltages, but are not limited thereto, and the first voltage V1 and the second voltage V2 may be directly set by a user or using external communication. It can be. The first voltage V1 may be greater than the second voltage V2. In the case of reference power, if the operation mode is the charging mode, the reference power determination unit 2331 subtracts the first voltage V1 from the voltage Vdc of the first stage and then multiplies the charging power slope Sc to calculate the reference power. can When the operation mode is the discharge mode, the reference power determiner 2331 may calculate the reference power by subtracting the voltage Vdc of the first terminal from the second voltage V2 and then multiplying the second voltage V2 by the discharge power slope Sd. The charging power slope Sc and the discharge power slope Sd may be preset values, but are not limited thereto and may be directly set by a user or using external communication. The charging power slope Sc and the discharge power slope Sd may be different from each other, but are not limited thereto and may be equal to each other. Also, the droop control curve may include the maximum power so that the reference power may be limited to the maximum power. Specifically, the maximum power may include maximum charge power (PCMax) and maximum discharge power (PDMax). The maximum charging power (PCMax) may be a power value at which the reference power can be maximized in the charging mode. The maximum discharge power PDMax may be a power value at which the reference power can be maximized in the discharge mode.

As another example, the reference power determiner 2331 may determine an operation mode according to a battery voltage state. More specifically, the reference power determiner 2331 may operate in a charging mode when the battery voltage is higher than or equal to a predetermined voltage.

As another example, the reference power determiner 2331 may determine an operation mode and reference power according to a user's control. In this case, the user may determine the operation mode and reference power directly or through communication.

Also, the reference power determiner 2331 may determine an operation mode and reference power by selecting one example from among one example, another example, and another example.

The controller 2330 of the DC/DC converter 2300 according to another embodiment may include a reference current determiner 2332. The reference current determiner 2332 may determine the reference current based on the operation mode and the reference power determined by the reference power determiner 2331 . More specifically, referring to FIG. 26 , in case of charging mode (a), the reference current determiner 2332 may include a first reference current selector 2604 . The first reference current selector 2604 determines the reference current I_CCR determined using the droop curve according to the magnitude of the voltage of the first terminal determined by the reference power determiner 2331 and the reference current I_MCR determined according to the user's setting. ) and the reference current I_BR determined according to the battery voltage state may be selected as the reference current I_CR for generating the PWM signal, which is a switching signal. Also, in the case of charging mode (a), the reference current determiner 2332 may include a first current extractor 2601. The first current extractor 2601 divides the reference power P_CCR determined using the droop curve according to the magnitude of the voltage of the first terminal determined by the reference power determiner 2331 by the battery voltage V_B to generate the reference current I_CCR ) can be extracted. In addition, in the case of charging mode (a), the reference current determiner 2332 may include a first comparator 2602 and a PI voltage controller 2603. The first comparator 2602 may compare the preset battery reference voltage V_BR and the current battery voltage V_B and provide the battery voltage difference value V_Bd to the PI voltage controller 2603 . The PI voltage controller 2603 may provide a reference current I_BR according to PI control based on the battery voltage difference value V_Bd. In the case of the discharge mode (b), the reference current determiner 2332 may include a second reference current selector 2604 . The second reference current selector 2604 determines the reference current I_CDR determined using the droop curve according to the magnitude of the voltage of the first stage determined by the reference power determiner 2331 and the reference current I_MDR determined according to the user's setting. ) can be selected as the reference current (I_DR) for generating a PWM signal, which is a switching signal. In the case of the discharge mode (b), the reference current determiner 2332 may include a second current extractor 2605. The second current extractor 2605 divides the reference power P_CDR determined by using the droop curve according to the magnitude of the voltage of the first stage determined by the reference power determiner 2331 by the voltage V_L of the first stage as a reference The current (I_CDR) can be extracted.

The controller 2330 of the DC/DC converter 2300 according to another embodiment may include a limited power determiner 2333. The limited power determiner 2333 may limit the reference power so that the reference power does not exceed a predetermined power. More specifically, if the determined reference power is greater than the set maximum power, the limited power determiner 2333 may provide the maximum power to the current control unit 2334 as the reference power. In addition, the limited power determiner 2333 may provide the inverter limited power as reference power to the current control unit 2334 when the determined reference power is greater than the inverter limited power according to the inverter 30 . In addition, the limited power determiner 2333 may provide the battery limited power as reference power to the current control unit 2334 when the determined reference power is greater than the battery limited power according to the battery 200 .

The controller 2330 of the DC/DC converter 2300 according to another embodiment may include a current controller 2334. The current controller 2334 may generate a PWM signal that is a switching signal based on the determined reference current. More specifically, referring to FIG. 27 , in the case of charging mode (a), the current controller 2334 operates the second comparator 2701, the first PI current controller 2702, and the first PWM converter 2703. can include The second comparator 2701 may compare the reference current I_CR and the battery current I_B input to the battery 200 and provide the reference current difference value I_CRD to the first PI current controller 2702. . The first PI current controller 2702 may provide the charge control current I_CC according to the PI control to the first PWM converter 2703 based on the reference current difference value I_CRD. The first PWM conversion unit 2703 may provide a PWM signal, which is a switching signal, to the bridge circuit unit 2320 based on the charge control current I_CC. In the case of the discharge mode (b), the current controller 2334 may include a third comparator 2704, a second PI current controller 2705, and a second PWM converter 2706. The third comparator 2704 compares the reference current I_DR with the current I_L of the first stage Na input to the battery 200 and converts the reference current difference value I_DRD to the second PI current controller 2705 ) can be provided. The second PI current controller 2705 may provide the discharge control current I_DC according to the PI control to the second PWM converter 2706 based on the reference current difference value I_DRD. The second PWM conversion unit 2706 may provide a PWM signal, which is a switching signal, to the bridge circuit unit 2320 based on the discharge control current I_DC.

FIG. 28 is a diagram for explaining a power conversion method of the energy storage system of FIG. 23 .

Referring to FIG. 28 , the power conversion method of the energy storage system may include sensing a voltage of a first terminal (S2810). The first stage may refer to a node to which a DC/DC converter and a DC link capacitor are connected. A method of sensing the voltage of the first stage may follow the description of FIG. 23 .

The power conversion method of the energy storage system may include selecting an operation mode according to the level of the voltage of the first stage (S2820). The operation mode may be any one of a charging mode, a standby mode, and a discharging mode. A detailed description of S2820 follows FIG. 29 .

The power conversion method of the energy storage system may include determining reference power according to the magnitude of the voltage of the first terminal (S2830). A method of determining the reference power according to the magnitude of the voltage of the first stage may follow the descriptions of FIGS. 23 to 27 and FIG. 30 .

The power conversion method of the energy storage system may include generating a switching signal based on the determined reference power (S2840). The switching signal may control a switch operation of a bridge circuit unit operating in a charging mode or a discharging mode. A method of generating a switching signal based on the determined reference power may follow the descriptions of FIGS. 23 to 27 .

FIG. 29 is a diagram for explaining a method of selecting an operation mode of FIG. 28 .

Referring to FIG. 29 , the method of selecting an operation mode may include determining whether a voltage of a first terminal is equal to or greater than a first voltage (S2821). When the voltage of the first terminal is equal to or greater than the first voltage, a step of selecting a charging mode (S2822) may be included.

The method for selecting the operation mode may include determining whether the voltage at the first terminal is a second voltage binomial if the voltage at the first terminal is equal to or greater than the first voltage ( S2823 ). When the voltage of the second stage is equal to or less than the second voltage, a step of selecting a discharge mode (S2824) may be included. In addition, if the voltage of the second terminal is not equal to or less than the second voltage, the process may return to S2821.

FIG. 30 is a diagram for explaining a method of determining reference power of FIG. 28 .

Referring to FIG. 30 , the method of determining the reference power may include calculating the first reference power using the voltage of the first stage (S2831). A method of calculating the first reference power using the voltage of the first stage may follow the descriptions of FIGS. 23 to 25 .

The method of determining the reference power may include determining whether the first reference power exceeds the maximum power (S2832). If the first reference power exceeds the maximum power, the reference power may be determined as the maximum power (S2833).

The method of determining the reference power may include determining whether the first reference power exceeds the inverter limit power if the first reference power does not exceed the maximum power (S2834). When the first reference power exceeds the inverter limit power, the reference power may be determined as the inverter limit power (S2835).

The method of determining the reference power may include determining whether the first reference power exceeds the battery limit power if the first reference power does not exceed the inverter limit power (S2836). When the first reference power exceeds the battery limit power, the reference power may be determined as the battery limit power (S2837).

The method of determining the reference power may include determining the reference power as the first reference power when the first reference power does not exceed the battery limit power ( S2838 ).

Thus, the embodiment can quickly determine the operating mode of charging or discharging the battery. In addition, the embodiment does not require a separate communication line and communication unit for droop control during battery charging or discharging. In addition, the embodiment enables rapid droop control during battery charging or discharging. According to an embodiment of the present invention, the above-described method can be implemented as a processor-readable code in a program recording medium. Examples of media readable by the processor include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage system, etc. include

The embodiments described above are not limited to the configuration and method described above, but the embodiments may be configured by selectively combining all or part of each embodiment so that various modifications can be made.

In addition, although the above shows and describes preferred embodiments of the present invention, the present invention is not limited to the specific embodiments described above, and the technical field to which the present invention belongs without departing from the gist of the present invention claimed in the claims. Of course, various modifications are possible by those skilled in the art, and these modifications should not be individually understood from the technical spirit or perspective of the present invention.

10 power plant
20 energy storage system
30 inverter
40 ac filter
50 ac-to-ac converter
60 strains
70 load
90 DC link capacitor
100 DC/DC converter
200 battery
300 charge control

Claims (8)

an overcurrent protection circuit unit connected to a first terminal connected to the DC link capacitor;
a DC stabilization circuit connected to the second terminal connected to the battery;
a bridge circuit unit electrically connected between the overcurrent protection circuit unit and the DC stabilization circuit unit and including a switch;
a control unit controlling the bridge circuit unit;
an auxiliary power supply unit generating driving power for the control unit based on the first power provided to the second stage through the battery;
a backup power supply electrically connected between the first terminal and the auxiliary power supply;
A current limiting unit disposed between the backup power supply unit and the second stage;
When the first power is not supplied to the auxiliary power supply from the second end, the backup power supply provides second power to the auxiliary power supply through the second end based on the third power provided through the DC link capacitor. and
The current limiting unit,
a first diode disposed between the backup power supply and the second terminal; and
A second diode disposed between the battery and the second terminal;
Each of the anode terminal of the first diode and the anode terminal of the second diode is connected to the auxiliary power supply,
The first diode prevents the first power supplied through the battery from being supplied to the backup power supply while providing the second power supplied through the backup power supply to the auxiliary power supply;
The second diode prevents the first power from being supplied to the backup power supply while providing the first power supplied through the battery to the auxiliary power supply. According to claim 1,
The first power is standby power,
The second power is a DC / DC converter that is the minimum power for generating the driving power of the control unit by the auxiliary power supply unit. According to claim 1,
When the first power is not supplied from the second terminal to the auxiliary power supply unit, a battery connected to the second terminal is in an over-discharge state. delete According to claim 1,
The backup power supply unit provides the second power based on the power input to the first stage DC/DC converter. According to claim 1,
Further comprising a backup power control unit disposed between the first stage and the backup power supply unit,
The backup power control unit includes a terminal connected to an external power source and a switch selectively connected to the DC link capacitor. According to claim 6,
The backup power supply unit performs a switching operation under the control of the control unit to provide the second power based on power input from one of the external power supply and the DC link capacitor.
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