KR102588520B1 - Energy storage system including dc-dc converter and electricity providing system including the same and control method of the same - Google Patents

Abstract

A converter according to an embodiment includes a first bridge circuit; second bridge circuit; a transformer connected between the first bridge circuit and the second bridge circuit; an LC circuit connected to the second bridge circuit; A sensor that senses a voltage of the first bridge circuit; and a control unit that controls the second bridge circuit according to the sensed voltage, wherein the LC circuit is connected to a battery, and the charging power and discharging power of the battery are power values in the form of a droop curve according to the sensed voltage. It is controlled by

Description

Energy storage system including a direct current to direct current converter, power supply system including the same, and control method thereof

The embodiment relates to an energy storage system including a direct current to direct current converter, a power supply system including the same, and a control method thereof.

Electrical energy is widely used because it is easy to convert and transmit. To use electrical energy efficiently, an energy storage system (ESS) is used. The energy storage system receives power and charges it to the battery. Additionally, when power is needed, the energy storage system supplies power by discharging the power charged in the battery. Through this, the energy storage system allows power to be supplied flexibly.

Specifically, when the power supply system includes an energy storage system, it operates as follows. Energy storage systems discharge electrical energy stored in batteries when the load or system is overloaded. Additionally, when the load or system is lightly loaded, the energy storage system receives power from the power generation device or system and charges the battery.

Additionally, 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. Additionally, when the system or load is overloaded, the energy storage system supplies power by discharging the power charged in the battery.

Meanwhile, the energy storage system must initially charge (or precharge) the DC link voltage placed at the inverter input terminal of the power supply system when operating in the battery discharge mode 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 received initial charging power from a power generation device or system.

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

In addition, the energy storage system's power conversion efficiency changes depending on the ratio of output power when the DC/DC converter performs power conversion. In particular, DC/DC converters have a problem in which power conversion efficiency rapidly decreases below a certain ratio of output power, and ultimately, energy storage systems have a problem in which energy supply or supply efficiency from batteries decreases.

Additionally, the energy storage system charges the battery by driving a direct current/direct current 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 fully discharged or overdischarged, the energy storage system cannot receive standby power from the battery and cannot drive the direct current/direct current converter, so the battery must be replaced, causing cost and resource waste problems.

Additionally, the energy storage system performs droop control to improve stability during battery charging or discharging operations. In particular, the energy storage system performed droop control according to the state of charge (SOC) of the battery. However, in order to control droop according to the state of charge (SOC) of the battery, a separate communication line and communication unit were needed to communicate with the battery's BMS, and the speed delay of the feedback process using communication improved stability during battery charging or discharging operation. There was a limit to what I could do.

The embodiment is designed to solve the problems of the prior art described above, and the purpose of the embodiment is to provide an energy storage system including a direct current/direct current converter, a power supply system including the same, and a control method thereof.

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

Additionally, the embodiment provides an energy storage system including a direct current/direct current converter with excellent power conversion efficiency, a power supply system including the same, and a control method thereof.

Additionally, the embodiment provides an energy storage system including a direct current/direct current converter capable of charging the battery without replacing the battery even if the battery is overdischarged, a power supply system including the same, and a control method thereof.

Additionally, the embodiment provides an energy storage system including a direct current/direct current converter that quickly determines an operation mode of charging or discharging a battery, a power supply system including the same, and a control method thereof.

Additionally, the embodiment provides an energy storage system including a direct current/direct current converter that does not require a separate communication line and communication unit for droop control when charging or discharging a battery, a power supply system including the same, and a control method thereof.

Additionally, the embodiment provides an energy storage system including a direct current/direct current converter capable of rapid droop control when charging or discharging a battery, a power supply system including the same, and a control method thereof.

The technical problems to be achieved in the embodiment are not limited to the technical problems mentioned above, and other technical problems 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 problems, a direct current/direct current converter according to an embodiment includes an overcurrent protection circuit connected to a first stage; A direct current stabilization circuit connected to the second stage; a bridge circuit electrically connected between the overcurrent protection circuit and the direct current stabilization circuit and including a switch; and a control unit that controls the bridge circuit unit, wherein the control unit can determine an operation mode and a reference power according to the level of the voltage of the first stage.

Additionally, in the DC/DC converter according to the embodiment, the control unit may provide a switching signal for controlling the switch based on the determined reference power to the bridge circuit.

Additionally, in the DC/DC converter according to the embodiment, a DC link capacitor may be connected to the first end.

In addition, in the DC/DC converter according to the embodiment, the operation mode is a charging mode when the voltage of the first stage is greater than or equal to the first voltage, and the voltage of the first stage is less than the first voltage and less than the second voltage. If it is large, it may be in standby mode, and if the voltage of the first stage is less than or equal to the second voltage, it may be in discharge mode.

In addition, in the DC/DC converter according to the embodiment, the reference power is calculated by subtracting the first voltage from the voltage of the first stage and multiplying the charging power slope when the operation mode is a charging mode, and the operation mode is In the discharge mode, it can be calculated by subtracting the voltage of the first stage from the second voltage and then multiplying it by the discharge power slope.

In addition, in the DC/DC converter according to the embodiment, the control unit generates the switching signal based on the maximum power when the determined reference power is greater than the set maximum power, and when the determined reference power is greater than the inverter limit power, the control unit generates the switching signal based on the maximum power. The switching signal may be generated based on the inverter limited power, and if the determined reference power is greater than the battery limited power, the switching signal may be generated based on the battery limited power.

A power conversion method according to an embodiment includes sensing a voltage of a first stage; selecting an operation mode according to the magnitude of the voltage of the first stage; determining a reference power according to the magnitude of the voltage of the first stage; and generating a switching signal based on the determined reference power.

The effects of an energy storage system including a direct current/direct current converter, a power supply system including the same, and a control method thereof according to an embodiment are described as follows.

The embodiment can initially charge the direct current link voltage without a separate configuration.

Additionally, in the embodiment, the initial charging speed of the direct current link voltage is fast, so the battery discharge operation can be performed quickly.

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

Additionally, in the embodiment, the power conversion efficiency of the DC/DC converter is excellent, so the energy efficiency delivered when charging or discharging the battery can be high.

Additionally, the embodiment can charge the battery even if the battery is overdischarged.

Additionally, the embodiment eliminates the need to replace the battery even if the battery is overdischarged. Additionally, the embodiment can quickly determine the operating mode of charging or discharging the battery.

Additionally, the embodiment does not require a separate communication line or communication unit for droop control when charging or discharging the battery.

Additionally, the embodiment allows rapid droop control when charging or discharging the battery.

The effects that can be 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 drawings attached below are intended to aid understanding of the embodiments and provide examples of the embodiments along with detailed descriptions. However, the technical features of the embodiment are not limited to specific drawings, and the features disclosed in each drawing may be combined to form a new embodiment.
1 is a diagram for explaining the schematic configuration of a power supply system according to an embodiment.
Figure 2 is a diagram for explaining an energy storage system according to an embodiment.
Figure 3 is a graph for explaining the DC voltage and DC current of the DC link capacitor during initial charging according to an embodiment.
Figure 4 is a circuit diagram of a direct current/direct current converter according to an embodiment.
FIG. 5 explains the operation of the DC/DC converter of FIG. 4 to initially charge the DC link capacitor.
FIG. 6 explains the operation of the DC/DC converter of FIG. 4 to initially charge the DC link capacitor.
Figure 7 is a circuit diagram of a DC/DC converter according to another embodiment.
FIG. 8 explains the operation of the DC/DC converter of FIG. 7 to initially charge the DC link capacitor.
FIG. 9 explains the operation of the DC/DC converter of FIG. 7 to initially charge the DC link capacitor.
Figure 10 is a circuit diagram of a DC/DC converter according to another embodiment.
Figure 11 is a graph showing the power conversion ratio according to the output power ratio when the energy storage system according to one embodiment converts direct current to direct current power.
FIG. 12 is a diagram illustrating a method of controlling the pulse width of a direct current/direct current converter of an energy storage system according to an embodiment.
FIG. 13 is a diagram illustrating a signal according to the output power of an energy storage system according to an embodiment.
FIG. 14 is a diagram for explaining an initial charging method of a DC link capacitor of a power supply system according to an embodiment.
Figure 15 is a diagram for explaining a method of supplying power to an energy storage system according to an embodiment.
Figure 16 is a diagram for explaining the configuration of a converter efficiency control unit applied to the energy storage system of the power supply system according to an embodiment.
FIG. 17 is a diagram for explaining a method of controlling power conversion efficiency of a direct current/direct current converter of an energy storage system according to an embodiment.
Figure 18 is a diagram for explaining an energy storage system according to another embodiment.
Figure 19 is a diagram for explaining an energy storage system according to another embodiment.
Figure 20 is a diagram for explaining an energy storage system according to another embodiment.
Figure 21 is a diagram for explaining an energy storage system according to another embodiment.
Figure 22 is a diagram for explaining a power conversion method for battery charging in a direct current/direct current converter of an energy storage system according to an embodiment.
Figure 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 the droop control curve of the energy storage system of FIG. 23.
FIG. 26 is a diagram for explaining the reference current determination unit of FIG. 24.
FIG. 27 is a diagram for explaining the current control unit of FIG. 24.
FIG. 28 is a diagram for explaining the power conversion method of the energy storage system of FIG. 23.
FIG. 29 is a diagram for explaining a method of selecting the operation mode of FIG. 28.
FIG. 30 is a diagram for explaining a method of determining the 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 “part” for components used in the following description are given or used interchangeably only for the ease of preparing the specification, and do not have distinct meanings or roles in themselves.

The advantages and features of the present invention and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. The present embodiments are merely provided to ensure that the disclosure of the present invention is complete and to provide common knowledge in the technical field to which the present invention pertains. It is provided to fully inform those who have the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

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

Combinations of each block in the attached drawings and each step in the flowchart may be performed by computer program instructions. Since these computer program instructions can be mounted on the processor of a general-purpose computer, special-purpose computer, or other programmable data processing equipment, the instructions performed through the processor of the computer or other programmable data processing equipment are included in each block of the drawing or each flow chart. This creates a means to perform the functions described in the steps. These computer program instructions may also be stored in computer-usable or computer-readable memory that can be directed to a computer or other programmable data processing equipment to implement a function in a particular manner, so that the computer-usable or computer-readable memory The instructions stored in can also produce manufactured items containing instruction means that perform the functions described in each block of the drawing or each step of the flowchart. Computer program instructions can also be mounted 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 process that is executed by the computer, thereby generating a process that is executed by the computer or other programmable data processing equipment. Instructions that perform processing equipment may also provide steps for executing functions described in each block of the drawing and each step of the flowchart.

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). Additionally, it should be noted that in some alternative embodiments it is possible for the functions mentioned in blocks or steps to occur out of order. For example, two blocks or steps shown in succession may in fact be performed substantially simultaneously, or the blocks or steps may sometimes be performed in reverse order depending on the corresponding function.

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

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

The power generation device 10 can produce electrical energy. When the power generation device 10 is a solar power generation system, the power generation device 10 may be a solar cell array. A solar cell array combines multiple solar cell modules. A solar cell module may be a device that connects a plurality of solar cells in series or parallel to convert solar energy into electrical energy and generate a predetermined voltage and current. Therefore, a solar cell array can absorb solar energy and convert it into electrical energy. Additionally, when the power generation device 10 is a wind power generation system, the power generation device 10 may be a fan that converts wind energy into electrical energy.

Meanwhile, the power generation device 10 is not limited to this, and may be configured as a tidal power generation system in addition to the solar power generation system and the wind power generation system. However, this is an example, and the power generation device 10 is not limited to the types mentioned above, and may include any power generation system that generates electric energy using renewable energy such as solar heat or geothermal heat.

Additionally, 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 power generation device 10.

The inverter 30 can convert direct current power into alternating current power. More specifically, direct current power supplied by the power generation device 10 or direct current power discharged by the energy storage system 20 can be converted into alternating current power.

The AC filter 40 can filter noise of power converted to AC power. Additionally, depending on the embodiment, the AC 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 system 60 or the load 70, and converts the converted AC power to the system 60 or the load ( 70) can be supplied. Additionally, depending on the embodiment, 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 consume electric power by receiving electric energy from a power generation system such as the power generation device 10 or an energy storage system 20 .

The energy storage system (20; ESS; Energy Storage System) receives electric energy from the power generation device 10, charges it, and can discharge the charged electric energy according to the power supply and demand situation of the system 60 or load 70. . More specifically, when the system 60 or the load 70 is lightly loaded, the energy storage system 20 can receive idle power from the power generation device 10 and charge it. When the system 60 or the load 70 is overloaded, the energy storage system 20 may supply power to the system 60 or the load 70 by discharging the charged power. Additionally, 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 the inverter 30 .

The system control unit 80 can control the operation of the energy storage system 20, the inverter 30, and the AC/AC converter 50. More specifically, the system control unit 80 can control charging and discharging of the energy storage system 20. When the system 60 or the load 70 is overloaded, the system control unit 80 can control the energy storage system 20 to supply power to deliver power to the system 60 or the load 70. . When the system 60 or the load 70 is lightly loaded, the system control unit 80 can control the external power source or power generation device 10 to supply power and transmit it to the energy storage system 20.

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

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

Referring to FIG. 2 , the energy storage system 20 according to one embodiment may include a DC/DC converter 100, a battery 200, and a charging control unit 300. Although not shown in FIG. 1, the energy storage system 20 may be connected to the inverter 30 through a direct current link capacitor 90. That is, the DC link capacitor 90 may be placed between the energy storage system 20 and the inverter 30. Accordingly, the energy storage system 20 may receive the direct current voltage (Vdc) of the direct current link capacitor 90 in the charging mode and provide the direct current voltage (Vdc) to the direct current 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 using the received power. Additionally, the battery 200 may output pre-stored power to the DC/DC converter 100 in discharge mode. Additionally, the battery 200 may include a plurality of battery cells to perform charging and discharging operations.

The charging control unit 300 may include a battery management system (BMS). The charging control unit 300 may provide battery status information about the state of the battery 200 to the system control unit 80. For example, the charging control unit 300 monitors at least one of the voltage, current, temperature, remaining power amount, and charging status of the battery 200, and sends the monitored status information of the battery 200 to the system control unit 80. It can be delivered. Additionally, the charging control unit 300 can maintain a plurality of battery cells at an appropriate voltage while charging or discharging. Additionally, the charging control unit 300 may operate based on a control signal from the system control unit 80. Additionally, the charging control unit 300 may control the DC/DC converter 100 according to the monitored status information of the battery 200. Additionally, the charging control unit 300 may control the DC/DC converter 100 according to the charging mode or discharging mode. More specifically, the charging control unit 300 provides a charging control signal or a discharging control signal for controlling the DC/DC converter 100 to the converter control unit of the DC/DC converter 100, and the DC/DC converter 100 The converter control unit may provide a PWM signal to the switch of the DC/DC converter 100 based on the charging control signal or the discharging control signal. Additionally, the charging control unit 300 may control the DC/DC converter 100 for initial charging of 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 provides the initial charging control signal for controlling the DC/DC converter 100. An initial charging switch signal may be provided to the switch of the DC/DC converter 100 based on the charging control signal. Additionally, the charging control unit 300 may control the DC/DC converter 100 to increase the power conversion efficiency of the DC/DC converter 100. More specifically, the charging control unit 300 provides a power conversion efficiency control signal that can increase 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 control unit 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 can convert the amount of DC power supplied by the energy storage system 20 in a charging mode or in a discharging mode. More specifically, the DC/DC converter 100 converts the DC power provided from the power generation device 10 or the inverter 30 to the DC link capacitor 90 into a voltage level for charging the battery 200, thereby converting the DC power to a voltage level for charging the battery 200. 200). Additionally, the DC/DC converter 100 can convert the DC power provided by the battery 200 into a voltage level that can be used by the inverter 30 and provide it to the DC link capacitor 90.

<Initial charging of DC link capacitor>

FIG. 3 is a graph illustrating the DC voltage and DC current of a DC link capacitor during initial charging according to an embodiment.

The energy storage system 20 according to one embodiment does not require a separate configuration for initial charging of the DC link capacitor 90 for 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 is transmitted to the inverter 30. ) can be initially charged up to the operating voltage. More specifically, the DC/DC converter 100 may provide a direct current (Idc) to the DC link capacitor 90. When the DC link capacitor 90 is provided with a DC current (Idc), the DC link capacitor 90 is charged and the DC voltage (Vdc) can increase. The DC/DC converter 100 can initially charge the DC voltage (Vdc) to an operating voltage at which the inverter 30 can perform inverting operations during the initial charging period. As an example, as shown in FIG. 3, during the initial charging period (Ti), the DC/DC converter 100 turns the switch on or off to generate a direct current (Idc) at a predetermined level (I1) for a plurality of periods (T1, T2, T3). , T4). If direct current (Idc) is continuously provided during the initial charging period (Ti), the problem of circuit damage may occur because the voltage difference between the voltage on the inverter 30 and the DC/DC converter 100 is large. Accordingly, the DC/DC converter 100 can provide the DC current (Idc) to the DC link capacitor 90 for a plurality of periods. The plurality of periods during which direct current (Idc) is provided may all be the same period. It is not limited to this, but as the DC voltage (Vdc) increases, the voltage difference between the voltage on the inverter 30 side and the DC/DC converter 100 decreases, so the provision period of the DC current (Idc) can be gradually increased. In this case, the initial charging time can be reduced. As direct current (Idc) is provided, direct current voltage (Vdc) increases. When the DC voltage (Vdc) reaches the operating voltage (V1), the DC/DC converter 100 ends initial charging and performs a boosting operation in discharge mode. When the DC/DC converter 100 performs a boosting operation, it can reach the second DC voltage level (V2).

Additionally, the method of initial charging of the DC/DC converter 100 may include the initial charging method of the DC link capacitor of FIG. 14.

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

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

Referring to FIG. 4, the DC/DC converter 100 according to an embodiment is a bidirectional DC/DC converter and may be an isolated converter.

The DC/DC converter 100 according to one embodiment may include a control unit 130. The control unit 130 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 120 including the switch.

The DC/DC converter 100 according to one embodiment may include an overcurrent protection circuit unit 110. The overcurrent protection circuit unit 110 can prevent EOS or overcurrent from flowing into or out of the energy storage system 20. The overcurrent protection circuit unit 110 may be disposed between the first end to which the DC link capacitor 90 is connected and the bridge circuit unit 120. Additionally, 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 stage and the bridge circuit unit 120 when EOS or overcurrent flows into the energy storage system 20. Accordingly, the overcurrent protection circuit unit 110 can block the input and 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 and a secondary circuit on the right based on the transformer (T) consisting of the first and second coils (LP, Ls), and the primary circuit is the first circuit. It may include switch elements (Q1 to Q4) constituting the full bridge circuit 121. And the secondary circuit may include a direct current stabilization circuit unit 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 direct current stabilization circuit unit 140 may be connected to the second terminal to which the battery 200 is connected.

In the primary circuit, the first coil (Lp) is connected between the third node (N3) and the fourth node (N4). And the first full bridge circuit 121 consists of a first leg and a second leg between the first and second nodes (N1, N2), and the first leg is connected to the first and third nodes (N1, It consists of a first switch element (Q1) connected between (N3) and a second switch element (Q2) connected between the third and second nodes (N3, N2), and the second leg is connected to the 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 fourth and second nodes (N4 and N2).

In the secondary circuit, the battery 200 and the second capacitor C2 are connected between the fifth and sixth nodes (N5, N6), and the second inductor (L2) is connected between the fifth and seventh nodes (N5, N7). 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), and the third leg is between the seventh and ninth nodes (N7, N9). It consists of a fifth switch element (Q5) connected to and a sixth switch element (Q6) connected between the ninth and eighth nodes (N9, N8), and the fourth leg is connected to the seventh and tenth nodes (N7, N10). ) and a seventh switch element (Q7) connected between them 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 bidirectional converter. In step down mode, the DC input voltage on the first and second nodes (N1, N2) is lowered to connect the fifth and sixth nodes (N1, N2). A direct current output voltage is output to the nodes (N5, N6), and in step up mode, the direct current input voltage on the fifth and sixth nodes (N5, N6) is raised to the first and second nodes (N1). , N2), the direct current output voltage is output.

The 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 for initial charging of the DC link capacitor 90 for the discharge mode. A direct current (Idc) can be provided to the direct current link capacitor 90. As an example, referring to FIG. 5, among the plurality of direct currents (Idc) provided for initial charging, the Nth (N is a natural number) direct current (Idc) is connected to 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, and the first switch element (Q1) and the fourth switch element (Q1) of the first full bridge circuit 121 are turned on. 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 direct currents (Idc) provided for initial charging, the N+1th (N is a natural number) direct current (Idc) is connected to the fifth switch element (Q5) of the second full bridge circuit 122. And the eighth switch element (Q8) is turned on, the sixth switch element (Q6) and the eighth switch element (Q8) are turned off, and the third switch element (Q3) and the second switch of the first full bridge circuit 121 are turned on. The element Q2 may be turned on and the first switch element Q1 and the fourth switch element Q4 may be turned off.

FIG. 7 is a circuit diagram of a DC/DC converter according to another embodiment, and FIGS. 8 and 9 illustrate the operation of the DC/DC converter of FIG. 7 to initially charge the DC link capacitor.

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

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

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

The 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. Additionally, the top switch unit 1150 may include a thirteenth switch element Q13.

The 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 direct current 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, N16), and the 2-1 inductor (L2-1) is connected between the 15th and 13th nodes (N15, N13). The 2-2 inductor (L2-2) is connected between the 15th node and the 14th node (N15, N14). The bridge circuit unit 1120 consists of an 11th leg and a 12th leg between the 11th and 12th nodes (N11, N12), and the 11th leg is between the 11th and 13th nodes (N11, N13). It consists of an 11th switch element (Q11) connected to the 12th switch element (Q12) connected between the 13th and 12th nodes (N13, N12), and the 12th leg is connected to the 11th and 14th nodes (N11, N14). It consists of a ninth switch element (Q9) connected between them and a tenth switch element (Q10) connected between the fourteenth and twelfth nodes (N14, N12).

The DC-DC converter 1100 according to another embodiment is a bidirectional converter. In step down mode, the DC input voltage on the DC link capacitor 90 is lowered to connect the 15th and 16th nodes (N15, N16). ), and in step up mode, the DC input voltage on the 15th and 16th nodes (N15, N16) is increased to output a 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 to charge the DC link capacitor 90. ) can provide direct current (Idc). As an example, referring to FIG. 8, the Nth (N is a natural number) direct current (Idc) among a plurality of direct currents (Idc) provided for initial charging is when the 11th switch element (Q11) of the bridge circuit unit 1120 is turned 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, among the plurality of direct currents (Idc) provided for initial charging, the N+1th (N is a natural number) direct current (Idc) turns on the ninth switch element (Q9) of the bridge circuit unit 1120. The 11th switch element (Q11), the 10th switch element (Q10), and the 12th switch element (Q12) may be turned off, and the 13th switch element (Q13) of the top switch unit 1150 may be turned on. Additionally, the thirteenth switch element Q13 of the top switch unit 1150 may be turned off while direct current (Idc) for charging the gun is not provided.

Figure 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 the same as the DC/DC converter according to another embodiment of FIG. 7 except for the top switch unit 2150. Therefore, description of the same configuration as 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 resistance R has a level lower than the current flowing in the main switch unit 2151. Allows current to flow through the initial charge switch unit 2152.

In the DC/DC converter 2100 according to another embodiment, when operating in a step-down mode, which is a charging mode, or a step-up mode, which is a discharging mode, the main switch unit 2151 is turned on/off and the initial charging switch unit 2152 is switched on. can remain off. Additionally, in the initial charge mode of the DC/DC converter 1100 before starting the discharge mode, the main switch unit 2151 may remain in an off state 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 unit 2120 is similar to that of the bridge circuit unit 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 can initially charge the DC link capacitor before operating in the discharge mode without separate configuration. Additionally, the energy storage system according to the embodiment can gradually increase the direct current provided to the direct current link capacitor, resulting in a fast initial charging speed and rapid battery discharging operation.

<Converter efficiency control>

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

Referring to FIG. 11, in general, the power conversion efficiency (dotted line) of a DC/DC converter drastically decreases when the output power during power conversion falls below a predetermined ratio (P1). For example, when a direct current/direct current converter converts power with less than 25% of the maximum output power, the power conversion efficiency drastically drops to less than 95%.

The energy storage system 20 according to one embodiment can maintain power conversion efficiency (solid line) at a predetermined efficiency even if the output power of the DC/DC converter is below a predetermined ratio (P1). For example, a direct current/direct current 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 can provide a direct current (Idc) with high power conversion efficiency when it is below a predetermined ratio (P1) of the maximum output power during power conversion. 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 direct current (Idc) provided below a predetermined ratio (P1) of the maximum output power has the problem of increasing current ripple as the intensity increases, it can 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 when operating in a charging mode or discharging mode from the converter control unit. The pulse width of the PWM signal may be set to the first pulse width (W1) for one cycle (Tw) when the DC/DC converter 100 outputs output power above a predetermined ratio (P1) 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 cycle (Tw) when the DC/DC converter 100 outputs output power below a predetermined ratio (P1) of the maximum output power. there is. In this case, the intensity of the output power can be adjusted by maintaining the intensity of the direct current (Idc) whose power conversion efficiency is greater than a predetermined efficiency and adjusting the pulse width of the PWM signal. As an example, referring to FIG. 13, (a) is a case where the DC/DC converter 100 outputs an output power of 300W, and (b) is a case where the DC/DC converter 100 outputs an output power of 900W. This is the case. In the DC/DC converters 100 of (a) and (b), the power conversion efficiency is maintained at an intensity of DC current (Idc) that is greater than a predetermined efficiency, and the pulse widths of the PWM signals are different from each other. That is, the pulse width of the PWM signal of the DC/DC converter 100 for outputting a power of 900W is larger than the pulse width for outputting a power of 300W.

Additionally, a method by which the DC/DC converter 100 controls power conversion efficiency may include the converter efficiency control method of FIGS. 15 to 17.

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

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

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

The power supply system may include determining whether the direct current voltage is higher than 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 higher than the operating voltage that can perform the inverting operation of the inverter.

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

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

When the power supply system starts the initial charging mode, it may include providing the initial charging current to the direct current link capacitor (S1450). In other words, the direct current/direct current converter of the energy storage system can provide direct current to the direct current link capacitor using the electric energy of the battery. In this case, the DC/DC converter of FIGS. 3 to 10 may use a method of initially charging the DC link capacitor.

While the initial charging current is provided, the power supply system may include a step (S1460) of determining whether the direct current voltage is higher than the operating voltage. In this case, if the DC voltage is higher than the operating voltage, the DC/DC converter can end the initial charging mode and perform a battery discharging operation (S1430).

While the initial charging current is provided, the power supply system may include a step (S1470) of determining whether the direct current is greater than or equal to the reference current if the direct current voltage is less than the operating voltage. The reference current may be a preset current. The reference current may be a current intensity sufficient to charge the DC link capacitor. Additionally, since the voltage difference between the inverter side and the battery side is large, the reference current may be set below a predetermined intensity because circuit damage may occur due to inrush current if the intensity is higher than the predetermined intensity. The power supply system may stop providing the initial charging current when the direct current is greater than 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 can continue to provide the initial charging current as long as the direct current is below the reference current.

After stopping provision of the initial charging current, the power supply system may include a step (S1490) of determining whether the direct current current falls below the set current. The set current may be a preset current. The set current may be smaller than the reference current. As an example, the set current may be 0A. The power supply system may continue to provide initial charging current until the direct current is below the set current. Conversely, the power supply system can provide the initial charging current when the direct current falls below the set current. In other words, the power supply system can stably initial charge the DC link capacitor by performing initial charging according to the size of the DC current provided to the DC link capacitor.

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

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

The power supply method may include determining whether it is a converter efficiency control area (S1520). In other words, the energy storage system can 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 the power currently output by the DC/DC converter. The reference power may be the output power at which the power conversion efficiency of the DC/DC converter reaches a predetermined efficiency. The reference power can be set in advance. For example, the reference power may be a power that is a predetermined ratio from the maximum output power of the DC/DC converter. As an 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, charging or discharging operations can be performed without converter efficiency control (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 the pulse width based on the output power (S1541). More specifically, pulse width calculation can use Equation 1.

(Equation 1)

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

Additionally, converter efficiency control can determine the average power value (S1542). The average power value can be calculated by the charging control unit measuring the output power value for a predetermined number of repetitions of the PWM signal. After this, the converter efficiency control can 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. As an example, referring to FIG. 16 , the energy storage system 20 may include a converter efficiency control unit 500. The converter efficiency control unit 500 may be included in the charging control unit 300, but is not limited thereto. The converter efficiency control unit 500 may calculate the power difference value (Pd) by comparing the output power (Pdc) and the average power value (Pavg). After this, the converter efficiency control can calculate the power compensation value based on the comparison value (S1544). As an example, the converter efficiency control unit 500 may include a compensation unit 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). After this, converter efficiency control can provide compensated output power by compensating the power compensation value to the reference power (S1545). As an example, the converter efficiency control unit 500 may provide the compensated output power (Pdc*) by adding the power compensation value (Pc) to the reference power (Pref). In this case, the pulse width calculation in S1541 may be calculated based on the compensated output power.

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

Referring to FIG. 18 , the energy storage system 20 according to another embodiment may include a DC/DC converter 1800, a battery 200, and a charging control unit 300. Although not shown in FIG. 1, the energy storage system 20 may be connected to the inverter 30 through a direct current link capacitor 90. That is, the DC link capacitor 90 may be placed between the energy storage system 20 and the inverter 30. Accordingly, the energy storage system 20 may receive the direct current voltage (Vdc) of the direct current link capacitor 90 in the charging mode and provide the direct current voltage (Vdc) to the direct current link capacitor 90 in the discharging mode. Additionally, the configuration included in the DC/DC converter of the energy storage system according to another embodiment to be described in the future 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 charging mode and perform a charging operation using the received power. Additionally, the battery 200 may output pre-stored power to the DC/DC converter 1800 in discharge mode. Additionally, the battery 200 may include a plurality of battery cells to perform charging and discharging operations. Additionally, the battery 200 may be connected to the second stage (Nb).

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

The DC/DC converter 1800 can convert the amount of DC power supplied by the energy storage system 20 in charging mode or in discharging mode. That is, the DC/DC converter 1800 may be a bidirectional DC/DC converter. More specifically, the direct current/direct current converter 2300 converts the direct current power provided from the power generation device 10 or the inverter 30 to the direct current link capacitor 90 into a voltage level for charging the battery 200 and converts it to a voltage level for charging the battery 200. 200). Additionally, the DC/DC converter 1800 can convert the DC power provided by the battery 200 into a voltage level that can be used by the inverter 30 and provide it to the DC link capacitor 90.

The DC/DC converter 1800 may include an overcurrent protection circuit unit 1810, a bridge circuit unit 1820, a control unit 1830, a DC stabilization circuit unit 1840, an auxiliary power supply unit 1850, and a backup power supply unit 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. Additionally, the control unit 1830 can be driven based on the first driving power source (VCC1) provided by the auxiliary power unit 1850.

The overcurrent protection circuit unit 1810 can prevent EOS or overcurrent from flowing into or out of the energy storage system 20. The overcurrent protection circuit unit 1810 may be disposed between the bridge circuit unit 1820 and the first end (Na) to which the DC link capacitor 90 is connected. Additionally, 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 stage 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 can block the input and 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 step-down mode and output the voltage drop to the DC stabilization circuit unit 1840. Additionally, the bridge circuit unit 1820 may increase 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 unit 1820 may include one or more switches. As an example, the bridge circuit unit 1820 may be the isolated full bridge circuit of FIG. 4. As another example, the bridge circuit unit 1820 may be the non-insulated full bridge circuit of FIG. 7. It is not limited to this, 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 to decrease the DC voltage in the step-down mode. Additionally, 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 stage Nb. The first power P1 provided to the second stage Nb is based on the 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 provided from the second stage Nb, and receives the second power P2 based on the second power P2. This can generate driving power. For example, when the first power P1 is not provided to the auxiliary power supply unit 1850 from the second stage Nb, the battery 200 connected to the second stage Nb may be overdischarged. The second power P2 may be the minimum power for generating driving power. There may be multiple driving power sources. The driving power includes a first driving power (VCC1) provided to the charging control unit 300 of the energy storage system 20 and a second driving power (VCC2) provided to the control unit 1830 of the DC/DC converter 1800. can do. It is not limited to this, and the auxiliary power unit 1860 may output a plurality of driving powers with different voltage levels as needed. More specifically, the second terminal (Nb) of the auxiliary power supply unit 1850 may be connected to the third terminal (Nc) disposed at the input terminal, and the output unit of the backup power supply unit 1860 may be connected. When the first power P1 is provided to the second terminal Nb, the auxiliary power supply unit 1850 may input the first power P1 to the third terminal Nc and then input the first power P1 to the input terminal. In addition, the auxiliary power unit 1850 is configured to operate the auxiliary power unit 1850 when the first power P1 is not provided to the second stage Nb and the second power P2 is provided to the second stage Nb. It can be input to the terminal (Nc) and input to the input terminal. Therefore, the DC/DC converter can generate driving power even if the battery is overdischarged, and thus can perform a charging operation of the battery. Additionally, the direct current/direct current converter allows charging without replacing the battery even if the battery is overdischarged.

The backup power supply unit 1860 may provide the second power P2 based on the power provided from the DC link capacitor 90 or the inverter 30. More specifically, the backup power supply unit 1860 may be electrically connected between the first terminal Na and the auxiliary power supply unit 1850. The backup power supply unit 1860 may generate the second power P2 based on the third power P3 provided from the first stage Na. Additionally, the backup power supply unit 1860 may provide the second power P2 to the auxiliary power supply unit 1850 when the first power P1 is not provided to the auxiliary power supply unit 1850 from the second stage Nb. As an example, one end of the backup power supply unit 1860 may be connected to the first end (Na) and the other end may be connected to the third end (Nc). The backup power supply unit 1860 may provide the second power P2 to the third stage Nc, and the second power P2 may be provided from the third stage Nc to the auxiliary power supply unit 1850.

Accordingly, another embodiment can charge the battery even if the battery is overdischarged. Additionally, in another embodiment, there is no need to replace the battery even if the battery is overdischarged.

Figure 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 that of the energy storage system in FIG. 18 is excluded.

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

The current limiting unit 1870 may be disposed at the input unit of the auxiliary power supply unit 1850. As an example, the current limiting unit 1870 may be disposed at the third stage Nc. The current limiter 1870 can prevent power input to the auxiliary power supply unit 1850 from being provided in the reverse direction. Additionally, the current limiter 8170 can prevent provided power from being provided to configurations where 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 stage (Nb) to be provided to the third stage (Nc). Additionally, the first diode D1 may prevent the second power P2 from being provided to the second stage Nb. The second diode D2 allows the second power P2 provided by the backup power unit 1860 to be provided to the third terminal Nc. Additionally, the second diode D2 can prevent the first power P1 from being provided to the backup power supply unit 1860.

Therefore, the DC/DC converter according to another embodiment uses a current limiting unit to enable the auxiliary power unit to stably generate driving power and prevent unwanted charging of the battery.

Figure 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 that of the energy storage system in FIG. 18 is excluded.

The DC/DC converter 2000 may include an overcurrent protection circuit unit 2010, a bridge circuit unit 2020, a control unit 2030, a DC stabilization circuit unit 2040, an auxiliary power supply unit 2050, and a backup power supply unit 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 the control signal provided from the charging control unit 300 and provide the PWM signal to the bridge circuit unit 2020 including the switch. Additionally, the control unit 2030 can be driven based on the first driving power source (VCC1) provided by the auxiliary power unit 2050.

The overcurrent protection circuit unit 2010 can prevent EOS or overcurrent from flowing into or out of the energy storage system 20. The overcurrent protection circuit unit 2010 may be disposed between the bridge circuit unit 2020 and the first end (Na) to which the DC link capacitor 90 is connected. Additionally, 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 stage 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 and 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 can voltage drop the DC voltage of the DC power input from the overcurrent protection circuit unit 2010 and output it to the DC stabilization circuit unit 2040 in step-down mode. Additionally, the bridge circuit unit 2020 may increase the voltage of the DC power input from the DC stabilization circuit unit 2040 and output the voltage to the overcurrent protection circuit unit 2010. The bridge circuit unit 2020 may include one or more switches. As an example, the bridge circuit unit 2020 may be the isolated full bridge circuit of FIG. 4. As another example, the bridge circuit unit 2020 may be the non-insulated full bridge circuit of FIG. 7. It is not limited to this, 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 to decrease the DC voltage in the step-down mode. Additionally, 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 stage Nb. The first power P1 provided to the second stage Nb is based on the 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 provided from the second stage Nb, and receives the second power P2 based on the second power P2. This can generate driving power. For example, when the first power P1 is not provided to the auxiliary power supply unit 2050 from the second stage Nb, the battery 200 connected to the second stage Nb may be overdischarged. The second power P2 may be the minimum power for generating driving power. There may be multiple driving power sources. The driving power includes a first driving power (VCC1) provided to the charging control unit 300 of the energy storage system 20 and a second driving power (VCC2) provided to the control unit 2030 of the DC/DC converter 2000. can do. It is not limited to this, and the auxiliary power unit 2060 may output a plurality of driving powers with different voltage levels as needed. More specifically, the second terminal (Nb) of the auxiliary power supply unit 2050 may be connected to the third terminal (Nc) disposed at the input terminal, and the output unit of the backup power supply unit 2060 may be connected. When the first power P1 is provided to the second terminal Nb, the auxiliary power supply unit 2050 may input the first power P1 to the third terminal Nc and input it to the input unit. In addition, the auxiliary power unit 2050 is configured to operate the auxiliary power unit 2050 when the first power P1 is not provided to the second stage Nb and the second power P2 is provided to the second stage Nb. It can be input to the terminal (Nc) and input to the input unit. Therefore, the DC/DC converter can generate driving power even if the battery is overdischarged, and thus can perform a charging operation of the battery. Additionally, the direct current/direct current converter allows charging without replacing the battery even if the battery is overdischarged.

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 unit 1860 may be electrically connected between the external input terminal (InputE) and the auxiliary power supply unit 2050. The backup power unit 2060 may generate the second power P2 based on the fourth power P4 provided from the external input terminal InputE. Additionally, the backup power supply unit 2060 may provide the second power P2 to the auxiliary power supply unit 2050 when the first power P1 is not provided to the auxiliary power supply unit 1850 from the second stage Nb. As an example, one end of the backup power supply unit 2060 may be connected to an external input terminal (inputE) and the other end may be connected to a third terminal (Nc). The backup power supply unit 2060 may provide the second power P2 to the third stage Nc, and the second power P2 may be provided from the third stage Nc to the auxiliary power supply unit 2050.

Accordingly, another embodiment can charge the battery even if the battery is overdischarged. Additionally, in another embodiment, there is no need to replace the battery even if the battery is overdischarged.

Figure 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. Accordingly, the same description as the energy storage system of FIGS. 18 and 20 is excluded.

The backup power supply unit 2060 may provide second power P2 based on the power provided by 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 unit 2060 may generate the second power P2 based on the fifth power P5 provided from the backup power control unit 2070. Additionally, the backup power supply unit 2060 may provide the second power P2 to the auxiliary power supply unit 2050 when the first power P1 is not provided to the auxiliary power supply unit 1850 from the second stage Nb. As an example, one end of the backup power supply unit 2060 may be connected to the backup power control unit 2070 and the other end may be connected to the third terminal (Nc). The backup power supply unit 2060 may provide the second power P2 to the third stage Nc, and the second power P2 may be provided from the third stage Nc to the auxiliary power supply unit 2050.

The DC/DC converter of the energy storage system according to another embodiment may include a backup power control unit 2070. The backup power control unit 2070 selects one of the power provided from the external power source and the power provided from the first terminal Na based on the control signal from the control unit 2030 and provides it to the backup power supply unit 2060. You 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 control unit 2070 may include a switch. As an example, the control unit 2030 may control the backup power control unit 2070 to provide the third power P3 of the first stage Na as the fifth power P5 to the backup power supply unit 2060. Additionally, 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. Accordingly, another embodiment can charge the battery even if the battery is overdischarged. Additionally, in another embodiment, there is no need to replace the battery even if the battery is overdischarged.

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

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

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

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

The power conversion method of the DC/DC converter according to the embodiment may include a step (S2203) in which the auxiliary power source generates the driving power of the control unit based on the first power when first power is received. More specifically, the auxiliary power supply unit may generate a plurality of driving power sources based on the first power. The auxiliary power unit may provide the generated driving power to necessary configurations. For example, as described in FIGS. 18 to 21 , the auxiliary power supply unit may generate a first driving power source for driving the charging control unit and a second driving power source 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 (S2204) in which the backup power supply provides second power to the auxiliary power supply if the first power is not provided from the second stage in S2201. The method of providing the second power to the auxiliary power supply by the backup power supply may be the same as the configuration in which the backup power supply provides the second power to the auxiliary power supply of FIGS. 18 to 21.

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

Accordingly, another embodiment can charge the battery even if the battery is overdischarged. Additionally, in another embodiment, there is no need to replace the battery even if the battery is overdischarged.

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

Referring to FIG. 23, the energy storage system 20 according to another embodiment may include a DC/DC converter 2300, a battery 200, and a charging control unit 300. Although not shown in FIG. 1, the energy storage system 20 may be connected to the inverter 30 through a direct current link capacitor 90. That is, the DC link capacitor 90 may be placed between the energy storage system 20 and the inverter 30. Accordingly, the energy storage system 20 may receive the direct current voltage (Vdc) of the direct current link capacitor 90 in the charging mode and provide the direct current voltage (Vdc) to the direct current link capacitor 90 in the discharging mode. Additionally, the configuration included in the DC/DC converter of the energy storage system according to another embodiment to be described in the future 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 charging mode and perform a charging operation using the received power. Additionally, the battery 200 may output pre-stored power to the DC/DC converter 2300 in discharge mode. Additionally, the battery 200 may include a plurality of battery cells to perform charging and discharging operations. Additionally, the battery 200 may be connected to the second stage (Nb).

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

The DC/DC converter 2300 can convert the amount of DC power supplied by the energy storage system 20 in charging mode or in discharging mode. That is, the DC/DC converter 2300 may be a bidirectional DC/DC converter. More specifically, the direct current/direct current converter 2300 converts the direct current power provided from the power generation device 10 or the inverter 30 to the direct current link capacitor 90 into a voltage level for charging the battery 200 and converts it to a voltage level for charging the battery 200. 200). Additionally, the DC/DC converter 2300 can convert the DC power provided by the battery 200 into a voltage level that can be used by the inverter 30 and provide it to the DC link capacitor 90. Additionally, the DC/DC converter 2300 may operate in charge mode, standby mode, and discharge mode based on the voltage provided from the DC voltage link capacitor. In other words, the DC/DC converter 2300 can determine whether to operate the charging mode, standby mode, and discharging mode by monitoring the voltage provided from the DC voltage link capacitor and operate even without providing a control signal from the charging control unit 300. there is. A more detailed description of the operation of the DC/DC converter 2300 in charging mode, standby mode, and discharging mode will be described later.

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

The control unit 2330 can control the bridge circuit unit 2320. As an 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 a switch. As another example, the control unit 2330 may determine the operation mode and reference power according to the magnitude of the voltage provided from the DC link capacitor 90. Additionally, the control unit 2330 may generate a PWM signal based on the determined reference power and provide it to the bridge circuit unit 2320 including the switch. Specific descriptions of other examples will be provided later.

The overcurrent protection circuit unit 2310 can prevent EOS or overcurrent from flowing into or out of the energy storage system 20. The overcurrent protection circuit unit 2310 may be disposed between the bridge circuit unit 2320 and the first end (Na) to which the DC link capacitor 90 is connected. Additionally, 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 stage 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 can block the input and 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 step-down mode and output the voltage drop to the DC stabilization circuit unit 2340. Additionally, the bridge circuit unit 2320 may increase 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 unit 2320 may include one or more switches. As an example, the bridge circuit unit 2320 may be the isolated full bridge circuit of FIG. 4. As another example, the bridge circuit unit 2320 may be the non-insulated full bridge circuit of FIG. 7. It is not limited to this, 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 to decrease the DC voltage in the step-down mode. Additionally, 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 end (Na) and provide the sensed voltage to the control unit 2330. The voltage of the first stage Na may be a direct current voltage provided by the direct current link capacitor 90. Additionally, the sensing unit 2350 may be controlled by the control unit 2330.

Accordingly, another embodiment can quickly determine the operating mode of charging or discharging a battery. Additionally, another embodiment does not require a separate communication line or communication unit for droop control when charging or discharging the battery. Additionally, another embodiment allows rapid droop control when charging or discharging the battery.

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

Referring to FIG. 24, the control unit 2330 of the DC/DC converter 2300 according to another embodiment may include a reference power determination unit 2331. The reference power determination unit 2331 may determine the operation mode and reference power.

As an example, the reference power determination unit 2331 may determine the 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 determination unit 2331 may determine the operation mode and reference power based on the droop control curve according to the voltage of the first stage. In the case of the operation mode, the reference power determination unit 2331 may determine the charging mode if the voltage (Vdc) of the first stage is greater than or equal to the first voltage (V1). The reference power determination unit 2331 may determine the standby mode when the voltage (Vdc) of the first stage is smaller than the first voltage (V1) and greater than the second voltage (V2). The reference power determination unit 2331 may determine the discharge mode if the voltage (Vdc) of the first stage 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 set directly by the user or through external communication. It can be. The first voltage (V1) may be greater than the second voltage (V2). In the case of the reference power, if the operation mode is the charging mode, the reference power determination unit 2331 calculates the reference power by subtracting the first voltage (V1) from the voltage (Vdc) of the first stage and then multiplying by the charging power slope (Sc). You can. If the operation mode is the discharge mode, the reference power determination unit 2331 may calculate the reference power by subtracting the voltage (Vdc) of the first stage from the second voltage (V2) and then multiplying it by the discharge power slope (Sd). The charging power slope (Sc) and the discharging power slope (Sd) may be preset values, but are not limited thereto and may be set using external communication or directly by the user. The charging power slope (Sc) and the discharging power slope (Sd) may be different from each other, but are not limited thereto and may be the same. Additionally, the droop control curve may include the maximum power so that the reference power is limited to the maximum power. Specifically, the maximum power may include maximum charging power (PCMax) and maximum discharging power (PDMax). The maximum charging power (PCMax) may be a power value at which the reference power can be maximized when the operating mode is charging mode. The maximum discharge power (PDMax) may be a power value at which the reference power can be maximized when the operation mode is discharge mode.

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

As another example, the reference power determination unit 2331 may determine the operation mode and reference power according to user control. In this case, the user can determine the operation mode and reference power directly or using communication.

Additionally, the reference power determination unit 2331 may determine the operation mode and reference power by selecting one example among one example, another example, and another example.

The control unit 2330 of the DC/DC converter 2300 according to another embodiment may include a reference current determination unit 2332. The reference current determination unit 2332 may determine the reference current based on the operation mode and reference power determined by the reference power determination unit 2331. More specifically, referring to FIG. 26 , in the case of charging mode (a), the reference current determination unit 2332 may include a first reference current selection unit 2604. The first reference current selection unit 2604 selects a reference current (I_CCR) determined using a droop curve according to the magnitude of the first stage voltage determined by the reference power determination unit 2331, and a reference current (I_MCR) determined according to the user's settings. ) and the reference current (I_BR) determined according to the battery voltage state can be selected as the reference current (I_CR) for generating the PWM signal, which is a switching signal. Additionally, in the case of charging mode (a), the reference current determination unit 2332 may include a first current extractor 2601. The first current extractor 2601 divides the reference power (P_CCR) determined using a droop curve according to the magnitude of the voltage of the first stage determined by the reference power determination unit 2331 by the battery voltage (V_B) to determine the reference current (I_CCR). ) can be extracted. Additionally, in the case of charging mode (a), the reference current determination unit 2332 may include a first comparison unit 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 a 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 discharge mode (b), the reference current determination unit 2332 may include a second reference current selection unit 2604. The second reference current selection unit 2604 selects a reference current (I_CDR) determined using a droop curve according to the magnitude of the voltage of the first stage determined by the reference power determination unit 2331 and a reference current (I_MDR) determined according to the user's settings. ) can be selected as the reference current (I_DR) for generating a PWM signal, which is a switching signal. Additionally, in the case of discharge mode (b), the reference current determination unit 2332 may include a second current extractor 2605. The second current extractor 2605 divides the reference power (P_CDR) determined using a droop curve according to the magnitude of the voltage of the first stage determined by the reference power determination unit 2331 by the voltage (V_L) of the first stage to provide a standard Current (I_CDR) can be extracted.

The control unit 2330 of the DC/DC converter 2300 according to another embodiment may include a limited power determination unit 2333. The limited power determination unit 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 determination unit 2333 may provide the maximum power as the reference power to the current control unit 2334. Additionally, if the determined reference power is greater than the inverter limited power of the inverter 30, the limited power determination unit 2333 may provide the inverter limited power as the reference power to the current control unit 2334. Additionally, if the determined reference power is greater than the battery limit power according to the battery 200, the limited power determination unit 2333 may provide the battery limited power as the reference power to the current control unit 2334.

The control unit 2330 of the DC/DC converter 2300 according to another embodiment may include a current control unit 2334. The current control unit 2334 may generate a PWM signal, which 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 control unit 2334 uses the second comparison unit 2701, the first PI current controller 2702, and the first PWM conversion unit 2703. It can be included. The second comparison unit 2701 may compare the reference current (I_CR) with the battery current (I_B) input to the battery 200 and provide a reference current difference value (I_CRD) to the first PI current controller 2702. . The first PI current controller 2702 may provide a charging control current (I_CC) according to PI control to the first PWM converter 2703 based on the reference current difference value (I_CRD). The first PWM converter 2703 may provide a PWM signal, which is a switching signal, to the bridge circuit unit 2320 based on the charging control current (I_CC). In the case of discharge mode (b), the current control unit 2334 may include a third comparison unit 2704, a second PI current controller 2705, and a second PWM converter 2706. The third comparison unit 2704 compares the reference current (I_DR) with the current (I_L) of the first stage (Na) input to the battery 200 and sets 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 a discharge control current (I_DC) according to PI control to the second PWM converter 2706 based on the reference current difference value (I_DRD). The second PWM converter 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 the 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 the voltage of the first stage (S2810). The first stage may refer to a node where a DC/DC converter and a DC link capacitor are connected. The method for sensing the voltage of the first stage can follow the description of FIG. 23.

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

The power conversion method of the energy storage system may include determining the reference power according to the magnitude of the voltage of the first stage (S2830). The method of determining the reference power according to the magnitude of the voltage of the first stage can follow the description of FIGS. 23 to 27 and the description of 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 can control the switch operation of the bridge circuit operating in charge mode or discharge 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 the operation mode of FIG. 28.

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

The method of selecting an operation mode may include determining whether the voltage of the first stage is equal to or greater than the second voltage if the voltage of the first stage is not greater than or equal to the first voltage (S2823). If the voltage of the second stage is less than or equal to the second voltage, a step of selecting a discharge mode (S2824) may be included. Additionally, if the voltage of the second stage is not less than the second voltage, it can return to S2821.

FIG. 30 is a diagram for explaining a method of determining the 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). The method of calculating the first reference power using the voltage of the first stage can 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). If the first reference power exceeds the inverter limited power, the reference power may be determined as the inverter limited 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). If the first reference power exceeds the battery limit power, the reference power may be determined to be the battery limit power (S2837).

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

Accordingly, the embodiment can quickly determine the operating mode of charging or discharging the battery. Additionally, the embodiment does not require a separate communication line or communication unit for droop control when charging or discharging the battery. Additionally, the embodiment enables rapid droop control when charging or discharging the battery. According to an embodiment of the present invention, the above-described method can be implemented as processor-readable code on a program-recorded medium. Examples of media that can be read by the processor include ROM, RAM, CD-ROM, magnetic tape, floppy disk, and optical data storage systems, and can also be implemented in the form of a carrier wave (e.g., transmission via the Internet). Includes.

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

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

10 Power generation device
20 Energy storage system
30 inverter
40 alternating current filter
50 alternating current to alternating current converter
60 strains
70 loads
90 DC Link Capacitor
100 DC/DC converter
200 batteries
300 charging control unit

Claims (20)

first bridge circuit;
second bridge circuit;
a transformer connected between the first bridge circuit and the second bridge circuit;
an LC circuit connected to the second bridge circuit;
A sensor that senses a voltage of the first bridge circuit; and
A control unit that controls the second bridge circuit based on the difference between the sensed voltage and a preset reference voltage,
The LC circuit is connected to the battery,
The charging power and discharging power of the battery are controlled by a droop curve-shaped power value according to the sensed voltage,
The control unit is a converter that supplies first power to the battery when the sensed voltage is greater than or equal to a first reference voltage. According to paragraph 1,
The LC circuit is,
an inductor connected to one end of the battery; and
A converter including a capacitor connected to one end and the other end of the battery. delete delete According to paragraph 1,
The first power is
A converter whose value is the difference between the sensed voltage and the first reference voltage multiplied by a preset charging power slope constant. According to paragraph 1,
The control unit controls the second bridge circuit to discharge second power from the battery when the sensed voltage is lower than the second reference voltage. According to clause 6,
The converter wherein the second reference voltage is smaller than the first reference voltage. In clause 7,
The second power is a value obtained by multiplying the difference between the sensed voltage and the second reference voltage by a preset slope constant. According to clause 6,
The control unit enters standby mode when the sensed voltage is less than the first reference voltage and greater than the second reference voltage. According to clause 6,
The control unit controls the second bridge circuit so that when the sensed voltage is a voltage between the first reference voltage and the second reference voltage, the power of the battery becomes 0. According to clause 10,
If the sensed voltage is greater than the third reference voltage, the control unit controls the second bridge circuit so that the first power corresponds to the product of the third reference voltage and a preset charging power slope constant,
A converter wherein the third reference voltage is greater than the first reference voltage. According to clause 10,
If the sensed voltage is less than the fourth reference voltage, the control unit controls the second bridge circuit so that the second power corresponds to the product of the fourth reference voltage and a preset charging power slope constant,
The converter wherein the fourth reference voltage is smaller than the second reference voltage. A bridge circuit electrically connected to a DC link capacitor;
an inductor and capacitor electrically connected to the bridge circuit;
A sensor that senses the voltage between the bridge circuit and the DC link capacitor; and
A control unit that controls the bridge circuit based on the difference between the sensed voltage and a preset reference voltage,
The inductor is connected to one end of the battery,
The capacitor is connected to one end and the other end of the battery,
The power of the battery unit is controlled to a droop curve-shaped power value according to the sensed voltage,
The control unit determines the power value based on a difference value between the sensed voltage and a preset reference voltage and a preset slope constant,
The control unit controls the bridge circuit to supply first power to the battery when the sensed voltage is higher than the first reference voltage. delete According to clause 13,
The first power is a DC-DC converter where the difference between the sensed voltage and the first reference voltage is multiplied by a preset charging power slope constant. According to clause 13,
The control unit controls the bridge circuit to discharge the second power from the battery when the sensed voltage is lower than the second reference voltage,
A DC-DC converter wherein the second reference voltage is smaller than the first reference voltage. According to clause 16,
The second power is a DC-DC converter where the difference between the sensed voltage and the second reference voltage is multiplied by a preset slope constant. According to clause 17,
The control unit controls the bridge circuit so that if the sensed voltage is a voltage between the first reference voltage and the second reference voltage, the power of the battery terminal is 0. According to clause 18,
If the sensed voltage is greater than the third reference voltage, the control unit controls the bridge circuit so that the first power corresponds to the product of the third reference voltage and a preset charging power slope constant,
A DC-DC converter wherein the third reference voltage is greater than the first reference voltage. According to clause 19,
If the sensed voltage is less than the fourth reference voltage, the control unit controls the bridge circuit so that the second power corresponds to the product of the fourth reference voltage and a preset charging power slope constant,
A DC-DC converter wherein the fourth reference voltage is smaller than the second reference voltage.