DC / DC converter and control method thereof

Abstract

According to an embodiment, the power supply control device can have an input unit that receives a required power value and a reference voltage value from the inverter and receives a link voltage value from the DC link capacitor, and a control unit that calculates a slope of a droop control curve based on the reference voltage value and the required power value, calculates an output power value by substituting a difference between the link voltage value and the reference voltage value for the slope, and calculates a target current value based on the output power value.

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a DC / DC converter and a control method thereof. [Background technology]

[0002] Electric energy is widely used because it is easy to convert and transmit. To use this electric energy efficiently, an energy storage system (ESS) is used. An energy storage system receives power and charges a battery. When power is needed, the energy storage system discharges the charged power from the battery to supply power. In this way, the energy storage system allows for a constant supply of power.

[0003] Specifically, when the power supply system includes an energy storage system, it operates as follows: When the load or the grid is overloaded, the energy storage system discharges the electrical energy stored in the battery, and when the load or the grid is lightly loaded, the energy storage system receives power from the power generation device or the grid and charges the battery.

[0004] In addition, when an energy storage system exists independently of the power supply system, the energy storage system receives idle power from an external power supply source to charge the battery, and when the grid or load is overloaded, the energy storage system discharges the charged power from the battery to supply power.

[0005] Such energy storage systems perform droop control to improve stability during battery charging or discharging. In particular, energy storage systems perform droop control according to the battery's state of charge (SOC). However, existing droop control methods have the drawback of only changing the operating point of the DC / DC converter along the specified droop curve because the charge / discharge voltage and droop curve are fixed. Furthermore, because the power output is fixed to zero during the idle period, there is a problem of no response occurring during voltage drops or increases. Another problem is that discharging and idle operation are impossible when the link voltage is within the charging voltage period, charging and idle operation are impossible when the link voltage is within the discharging voltage period, and charging and discharge are impossible during the idle period. Summary of the Invention [Problem to be solved by the invention]

[0006] The technical problem to be solved by the present invention is to provide a DC / DC converter and a control method thereof that can actively change the droop control curve and the operating point.

[0007] Another object of the present invention is to provide a DC / DC converter and a control method thereof that can be matched with inverters from various manufacturers having different operating ranges, thereby improving compatibility and control safety. [Means for solving the problem]

[0008] According to an embodiment, a DC / DC converter control method is provided, which includes the steps of: inputting a required power value from an inverter; inputting a reference voltage value from the inverter; calculating a slope of a droop control curve based on the reference voltage value and the required power value; inputting a link voltage value from a DC link capacitor; calculating an output power value by substituting a difference between the link voltage value and the reference voltage value for the slope; and calculating a target current value based on the output power value.

[0009] The step of calculating the slope of the droop control curve may include the steps of calculating a right slope based on a reference voltage value and calculating a left slope based on the reference voltage value.

[0010] The step of calculating the right slope can calculate the right slope of the droop control curve with the reference voltage value and the required power value as the operating point by the following Equation 1:

[0011] <Formula 1>

number

[0012] In Equation 1, Slope1 is the right-hand slope of the droop control curve based on the reference voltage value, and P H,Limit is the maximum charging power value, and V H,Limit is the maximum charging power start voltage value, and P set is the required power input from the inverter, and V ref is the reference voltage value input from the inverter.

[0013] The step of calculating the left slope can calculate the left slope of the droop control curve with the reference voltage value and the required power value as the operating point by the following Equation 2:

[0014] <Formula 2>

number

[0015] In Equation 2, Slope2 is the left slope of the droop control curve based on the reference voltage value, and P L,Limit is the maximum discharge power value, and V L,Limit is the maximum discharge power starting voltage value, and P set is the required power input from the inverter, and V ref is the reference voltage value input from the inverter.

[0016] The method may further include outputting a target current value to the battery.

[0017] According to an embodiment, the power supply control device can have an input unit that receives a required power value and a reference voltage value from the inverter and a link voltage value from the DC link capacitor, and a control unit that calculates a slope of a droop control curve based on the reference voltage value and the required power value, calculates an output power value by substituting the difference between the link voltage value and the reference voltage value for the slope, and calculates a target current value based on the output power value. [Effects of the Invention]

[0018] The DC / DC converter and its control method of the present invention can change the operating point of the DC / DC converter.

[0019] In addition, delays caused by physical voltage fluctuations when changing modes can be eliminated.

[0020] In addition, charging, discharging, and idle operation are possible across the entire operating voltage range.

[0021] Also, the response stability against voltage fluctuations can be improved over the entire range of the operating voltage. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a diagram illustrating a schematic configuration of a power supply system according to an embodiment; [Figure 2] FIG. 1 is a diagram illustrating an energy storage system according to an embodiment. [Figure 3] FIG. 1 is a diagram illustrating a DC / DC converter according to an embodiment. [Figure 4] 1 is a block diagram of a control system according to an embodiment. [Figure 5] FIG. 2 is a diagram illustrating a control unit according to an embodiment. [Figure 6] FIG. 4 is a diagram illustrating a droop control curve of the energy storage system according to the embodiment. [Figure 7]FIG. 10 is a diagram showing a voltage-power plane for explaining an operating region of a control unit according to an embodiment. [Figure 8] FIG. 10 is a diagram showing a voltage-power plane for explaining an operating region of a control unit according to an embodiment. [Figure 9] FIG. 10 is a diagram showing a voltage-power plane for explaining an operating region of a control unit according to an embodiment. [Figure 10] FIG. 10 is a diagram showing a voltage-power plane for explaining an operating region of a control unit according to an embodiment. [Figure 11] 3 is an operation flowchart of a DC / DC converter control method according to an embodiment. [Figure 12] FIG. 10 is a diagram illustrating the benefits of the expanded operating range for the proposed droop control compared to existing droop controls. DETAILED DESCRIPTION OF THE INVENTION

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0024] However, the technical concept of the present invention is not limited to the described embodiments, but may be embodied in various different forms, and one or more of the components of the embodiments may be selectively combined or substituted within the scope of the technical concept of the present invention.

[0025] Furthermore, unless otherwise clearly defined and described, terms (including technical and scientific terms) used in the embodiments of the present invention may be interpreted in a way that would be commonly understood by a person of ordinary skill in the art to which the present invention belongs, and commonly used terms, such as dictionary-defined terms, may be interpreted in light of the contextual meaning of the relevant art.

[0026] Furthermore, the terms used in the embodiments of the present invention are intended to explain the embodiments and are not intended to limit the present invention.

[0027] In this specification, the singular can also include the plural unless otherwise specified in the context, and when it is stated as "A and (and) at least one (or one or more) of B and C," it can include one or more of all possible combinations of A, B, and C.

[0028] Furthermore, in describing components of embodiments of the present invention, terms such as first, second, A, B, (a), (b), etc. may be used.

[0029] Such terms are used merely to distinguish a component from other components, and do not limit the essence, order, or sequence of the components.

[0030] Furthermore, when a component is described as being "coupled," "coupled," or "connected" to another component, it can include not only cases where the component is directly coupled, coupled, or connected to the other component, but also cases where the component is "coupled," "coupled," or "connected" by yet another component between the component and the other component.

[0031] Furthermore, when something is described as being formed or disposed "above or below" a component, "above" or "below" refers not only to the case where two components are in direct contact with each other, but also to the case where one or more other components are formed or disposed between the two components. Furthermore, when something is expressed as "above or below," it can mean not only the upper direction but also the lower direction based on one component.

[0032] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings, and the same or corresponding components will be given the same reference numerals regardless of the drawing numbers, and redundant description thereof will be omitted.

[0033] Fig. 1 is a diagram illustrating a schematic configuration of a power supply system according to an embodiment. Referring to Fig. 1, the power supply system 1 according to the embodiment may include a power generation device 10, an energy storage system 20, an inverter 30, an AC filter 40, an AC / AC converter 50, a grid 60, a system control unit 80, and a load 70.

[0034] The power generation device 10 can generate electrical energy. When the power generation device 10 is a solar power generation system, the power generation device 10 can be a solar cell array. A solar cell array is a combination of multiple solar cell modules. A solar cell module can be a device that connects multiple solar cells in series or parallel to convert solar energy into electrical energy and generate a predetermined voltage and current. Therefore, the solar cell array can absorb solar energy and convert it into electrical energy.

[0035] Furthermore, when the power generating device 10 is a wind power generating system, the power generating device 10 may be a fan that converts wind energy into electrical energy.

[0036] Meanwhile, the power generation device 10 is not limited thereto and may be configured as a tidal power generation system in addition to the solar power generation system and wind power generation system. However, this is merely an example, and the power generation device 10 is not limited to the above-mentioned types and may include any power generation system that generates electric energy using renewable energy such as solar heat or geothermal heat.

[0037] Also, the power supply system 1 can supply power only through the energy storage system 20 without the power generation device 10.

[0038] In this case, the power supply system 1 does not need to include the power generation device 10.

[0039] The inverter 30 can convert DC power into AC power. More specifically, the inverter 30 can convert DC power supplied by the power generation device 10 or DC power discharged by the energy storage system 20 into AC power.

[0040] The AC filter 40 can filter noise from the power converted into AC power, and the AC filter 40 can be omitted depending on the embodiment.

[0041] The AC / AC converter 50 converts the voltage magnitude of the noise-filtered AC power so that the AC power can be supplied to the grid 60 or the load 70, and supplies the converted AC power to the grid 60 or the load 70. Depending on the embodiment, the AC / AC converter 50 may be omitted.

[0042] The grid 60 is a system in which many power plants, substations, transmission and distribution lines, and loads are integrated to generate and utilize electric power.

[0043] The load 70 can receive electrical energy from a power generation system such as the power generation device 10 or the energy storage system 20 and consume (consume) the power.

[0044] The energy storage system (20; ESS; Energy Storage System) can be charged by receiving electrical energy from the power generation device 10 and can discharge the charged electrical energy depending on the power supply and demand situation of the grid 60 or the load 70. More specifically, when the grid 60 or the load 70 is lightly loaded, the energy storage system 20 can be charged by receiving idle power from the power generation device 10. When the grid 60 or the load 70 is overloaded, the energy storage system 20 can discharge the charged power to supply power to the grid 60 or the load 70. In addition, the energy storage system 20 can be electrically connected to the power generation device 10 and can be connected between the power generation device 10 and the inverter 30 so as to be electrically connected to the inverter 30.

[0045] The system control unit 80 can control the operations of the energy storage system 20, the inverter 30, and the AC / AC converter 50. More specifically, the system control unit 80 can control the charging and discharging of the energy storage system 20. When the grid 60 or the load 70 is overloaded, the system control unit 80 can control the energy storage system 20 to supply power and transfer the power to the grid 60 or the load 70. When the grid 60 or the load 70 is lightly loaded, the system control unit 80 can control the external power supply source or the power generation device 10 to supply power and transfer the power to the energy storage system 20.

[0046] FIG. 2 is a diagram illustrating an energy storage system according to an embodiment.

[0047] 2, the energy storage system 20 according to the embodiment may include a DC / DC converter 100, a battery 200, and a charge control unit 300. The energy storage system 20 may be connected to the inverter 30 through a DC link capacitor 90. That is, the DC link capacitor 90 may be disposed between the energy storage system 20 and the inverter 30. Thus, the energy storage system 20 may receive a DC voltage Vdc (input) of the DC link capacitor 90 in a charge mode and provide the DC voltage Vdc to the DC link capacitor 90 in a discharge mode.

[0048] In a charging mode, the battery 200 receives charging power from the DC / DC converter 100 and can perform a charging operation using the received power. In a discharging mode, the battery 200 can output pre-stored power to the DC / DC converter 100. In addition, the battery 200 can include a number of battery cells for performing charging and discharging operations.

[0049] The charge control unit 300 may include a battery management system (BMS). The charge control unit 300 may provide battery status information regarding the status of the battery 200 to the system control unit 80. For example, the charge control unit 300 may monitor at least one of the voltage, current, temperature, remaining energy, and charge state of the battery 200 and transmit the monitored status information of the battery 200 to the system control unit 80. The charge control unit 300 may also ensure that a number of battery cells maintain an appropriate voltage while charging or discharging. The charge control unit 300 may also operate based on a control signal from the system control unit 80. The charge control unit 300 may also control the DC / DC converter 100 according to the monitored status information of the battery 200. The charge control unit 300 may also control the DC / DC converter 100 according to a charge mode or a discharge mode. More specifically, the charge control unit 300 provides a charge control signal or a discharge 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 may provide a PWM signal to a switch of the DC / DC converter 100 based on the charge control signal or the discharge control signal. The charge control unit 300 may also control the DC / DC converter 100 for initial charging of the DC link capacitor 90 in a discharge mode of the battery 200. That is, the charge control unit 300 provides an initial charge 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 may provide an initial charge switch signal to a switch of the DC / DC converter 100 based on the initial charge control signal. The charge control unit 300 may also 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 to the converter control unit of the DC / DC converter 100, which can increase the power conversion efficiency of the DC / DC converter 100, and the converter control unit of the DC / DC converter 100 can provide a PWM signal to the switch of the DC / DC converter 100 based on the power conversion efficiency control signal.

[0050] The DC / DC converter 100 can convert the magnitude of DC power supplied in a charging mode or a discharging mode by the energy storage system 20. More specifically, the DC / DC converter 100 can convert DC power provided from the power generation device 10 or the inverter 30 to the DC link capacitor 90 into a voltage magnitude for charging the battery 200 and provide the converted voltage to the battery 200. The DC / DC converter 100 can also convert DC power provided from the battery 200 into a voltage magnitude usable by the inverter 30 and provide the converted voltage to the DC link capacitor 90.

[0051] FIG. 3 is a diagram illustrating a DC / DC converter according to an embodiment.

[0052] 3, the DC / DC converter 100 can convert the magnitude of DC power supplied by the energy storage system 20 in a charging mode or a discharging mode. That is, the DC / DC converter 100 can be a bidirectional DC / DC converter. More specifically, the DC / DC converter 100 can convert DC power provided from the power generation device 10 or the inverter 30 to a DC link capacitor 90 into a voltage magnitude for charging the battery 200 and provide the converted voltage to the battery 200. The DC / DC converter 100 can also convert DC power provided by the battery 200 into a voltage magnitude usable by the inverter 30 and provide the converted voltage to the DC link capacitor 90. The DC / DC converter 100 can also operate in a charging mode, an idle operation mode, or a discharging mode based on the voltage provided by the DC link capacitor 90. That is, the DC / DC converter 100 can monitor the voltage provided by the DC link capacitor 90 and determine whether to operate in the charging mode, idle operation mode, or discharge mode without receiving a control signal from the charging control unit 300.

[0053] The DC / DC converter 100 may include an overcurrent protection circuit unit 110 , a bridge circuit unit 120 , a control unit 130 , a DC stabilization circuit unit 140 and a sensing unit 150 .

[0054] The control unit 130 may control the bridge circuit unit 120. As an example, the control unit 130 may generate a PWM signal based on a control signal provided from the charging control unit 300 and provide the PWM signal to the bridge circuit unit 120 including the switch. As another example, the control unit 130 may determine an operation mode and an output power according to the magnitude of the voltage provided across the DC link capacitor 90. Furthermore, the control unit 130 may generate a PWM signal based on the determined output power and provide the PWM signal to the bridge circuit unit 120 including the switch. Other examples will be described in detail below.

[0055] 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 can be disposed between the first stage Na, to which the DC link capacitor 90 is connected, and the bridge circuit unit 120. The overcurrent protection circuit unit 110 can also include a circuit breaker. In this case, the overcurrent protection circuit unit 110 can open the first stage Na and the bridge circuit unit 120 when EOS or overcurrent flows into the energy storage system 20. As a result, the overcurrent protection circuit unit 110 can block input and output of external current to / from the energy storage system 20.

[0056] The bridge circuit unit 120 may be disposed between the overcurrent protection circuit unit 110 and the DC stabilizing circuit unit 140 and electrically connected to each component. In a step-down mode, the bridge circuit unit 120 may reduce the DC voltage of the DC power input from the overcurrent protection circuit unit 110 and output the reduced voltage to the DC stabilizing circuit unit 140. In a step-up mode, the bridge circuit unit 120 may increase the DC voltage of the DC power input from the DC stabilizing circuit unit 140 and output the increased voltage to the overcurrent protection circuit unit 110. The bridge circuit unit 120 may include one or more switches. For example, the bridge circuit unit 120 may be an isolated full-bridge circuit. For another example, the bridge circuit unit 120 may be a non-isolated full-bridge circuit. Without being limited thereto, the bridge circuit unit 120 may be a half-bridge circuit. The bridge circuit unit 120 may be operated based on a PWM signal from the control unit 130.

[0057] The DC stabilizing circuit unit 140 may operate to increase the DC voltage in the step-up mode of the bridge circuit unit 120 and to decrease the DC voltage in the step-down mode. The DC stabilizing circuit unit 140 may also be an LC filter. The DC stabilizing circuit unit 140 may be connected to the second stage Nb.

[0058] The sensing unit 150 may sense the voltage of the first stage Na and provide the sensed voltage to the control unit 130. The voltage of the first stage Na may be a DC voltage provided by the DC link capacitor 90. The sensing unit 150 may be controlled by the control unit 130.

[0059] Therefore, in yet another embodiment, the operating mode of the battery for charging or discharging can be quickly determined. Also, in yet another embodiment, a separate communication line and communication unit are not required for droop control during charging or discharging of the battery. Also, in yet another embodiment, quick droop control during charging or discharging of the battery is possible.

[0060] 4 and 5 are diagrams illustrating a control unit according to the embodiment, FIG. 6 is a diagram illustrating a droop control curve of the energy storage system according to the embodiment, and FIG. 7 is a diagram illustrating a target current of FIG. Calculation 8 is a diagram illustrating the current control unit of FIG. 5. FIG.

[0061] Referring to Figures 4 and 5, the control unit 130 of the DC / DC converter 100 of the embodiment may include an input unit 131, an operation mode determination unit 132, a slope calculation unit 133, an output power value calculation unit 134, a target current calculation unit 135, and a current control unit 136.

[0062] The input unit 131 can receive the required power value and the reference voltage value from the inverter, and can receive the link voltage value from the DC link capacitor.

[0063] The operation mode determination unit 132 may determine the operation mode based on the required power value and reference voltage value input from the inverter. More specifically, when the control unit 130 receives the required power value and reference voltage value, it sets a new operation point, and the operation mode determination unit 132 may set the operation mode based on the newly set operation point. For example, the operation mode determination unit 132 may calculate a threshold voltage for determining whether the charge or discharge mode is selected based on the reference voltage value and the required power value, and determine the operation mode based on the threshold voltage. The operation mode determination unit 132 may set a voltage value corresponding to the operation point as the critical voltage and determine the region to the right of the critical voltage as the charge region and the region to the left of the critical voltage as the discharge region. That is, the input unit 131 and the operation mode determination unit 132 may receive the inverter operation region from the inverter and set and determine the operation range. Furthermore, the control unit 130 may receive the link voltage and the required power value from the inverter, and may determine and output the charge or discharge operation mode based on the link voltage and the required power value.

[0064] For example, the control unit 130 may calculate a new slope of the droop control curve based on the newly set operating point, and the operation mode determination unit 132 may compare a subsequently input link voltage value with the operating point to determine the charge mode, discharge mode, or idle operation mode. For example, the operation mode determination unit 132 may determine the charge mode if the link voltage value is equal to or greater than a reference voltage value. Alternatively, the operation mode determination unit 132 may determine the discharge mode if the link voltage value is equal to or less than the reference voltage value. Alternatively, the operation mode determination unit 132 may determine the idle mode if the link voltage value is equal to the reference voltage value. FIG. 6 illustrates a case in which the inverter's required power value is 0 [W] and the corresponding reference voltage value is set to a default. However, as will be described later, the DC / DC converter 100 according to the embodiment sets a new operating point when the inverter inputs the required power value and the reference voltage value, and the operation mode determination unit 132 sets the operation mode according to the newly set operating point.

[0065] 6, the droop control curve may include a maximum power, and the output power may be limited to the maximum power. Specifically, the maximum power may include a maximum charge power (PCMax) and a maximum discharge power (PDMax). The maximum charge power (PCMax) may be a power value at which the output power can be maximized when the operating mode is the charge mode. The maximum discharge power (PDMax) may be a power value at which the output power can be maximized when the operating mode is the discharge mode.

[0066] Furthermore, the operation mode determination unit 132 can determine the operation mode depending on the voltage state of the battery 200. More specifically, the operation mode determination unit 132 can operate in the charging mode if the voltage of the battery 200 is equal to or higher than a predetermined voltage.

[0067] As yet another example, the operation mode determination unit 132 may determine the operation mode and the output power under the control of a user, in which case the user may determine the operation mode and the output power directly or through communication.

[0068] Also, for example, the operation mode determination unit 132 can select one of the other example and the further other example to determine the operation mode and the output power.

[0069] The slope calculation unit 133 can calculate the slope of the droop control curve based on the reference voltage value and the required power value. The slope calculation unit 133 can calculate the right slope based on the reference voltage value, and can calculate the left slope based on the reference voltage value.

[0070] The slope calculation unit 133 can calculate the right slope of the droop control curve with the reference voltage value as the operating point using the following equation 1.

[0071] <Formula 1>

number

[0072] In Equation 1, Slope1 is the right-hand slope of the droop control curve based on the reference voltage value, and P H,Limit is the maximum charging power value, and V H,Limit is the maximum charging power start voltage value, and P set is the required power input from the inverter, and V ref is the reference voltage value input from the inverter.

[0073] Moreover, the gradient calculation unit 133 can calculate the left gradient using the reference voltage value as the operating point using the following equation 2.

[0074] <Formula 2>

number

[0075] In Equation 2, Slope2 is the left slope of the droop control curve based on the reference voltage value, and P L,Limit is the maximum discharge power value, and V L,Limit is the maximum discharge power starting voltage value, and P set is the required power input from the inverter, and V ref is the reference voltage value input from the inverter.

[0076] In an embodiment, the right slope of the droop control curve may be the charging power slope, and the left slope may be the discharging power slope. The charging power slope and the discharging power slope may be different from each other, but are not limited thereto, and may be the same.

[0077] The output power value calculation unit 134 can calculate the output power value by substituting the difference between the link voltage value and the reference voltage value for the slope. The output power value calculation unit 134 can perform duty value compensation using the target current generation value and the feedback current. In the discharge mode, the output power value calculation unit 134 can calculate the output power value by integrating the difference obtained by subtracting the reference voltage value from the link voltage value with the left slope of the droop control curve. Alternatively, in the charge mode, the output power value calculation unit 134 can calculate the output power value by integrating the difference obtained by subtracting the link voltage value from the reference voltage value with the right slope of the droop control curve. Furthermore, the output power value calculation unit 134 can generate a current command by reflecting the target power value in a droop control curve newly generated based on the calculated slope. That is, a power command based on the link voltage can be generated, and a current command can be generated by mutually compensating the inverter's required power value and the power command value based on the reference voltage value. Target current Calculation The unit 135 can determine the target current based on the determined operation mode and output power. Calculation The unit 135 can determine the final duty using the basic duty value and the current compensation duty value according to the input / output voltage. Calculation The unit 135 can receive the operation mode output and switch the current command according to the mode.

[0078] The current control unit 136 can output a target current value to the battery. The current control unit 136 includes a charge current control unit 1361, a discharge current control unit 1363, and an idle control unit 1362, and each of the control units 1361 to 1363 can operate according to the output operation mode. The current control unit 136 can generate a PWM signal, which is a switching signal, based on the determined target current.

[0079] 7 is a diagram illustrating a voltage-power plane for explaining an operating region of a control unit according to an embodiment. Referring to FIG. 7, the control unit according to the embodiment sets a new operating point when a required power value and a reference voltage value are input from the inverter, and calculates the slope of the droop control curve based on the newly set operating point. The calculated slope is reflected in the droop control curve, generating a new droop control curve. The control unit can then calculate the output power and target current by substituting the link voltage value into the new droop control curve.

[0080] FIG. 8 is a diagram illustrating a voltage-power plane for explaining the operating region of the control unit according to the embodiment.

[0081] 8, the controller may receive a required power value of 0 [W] from the inverter, and the input unit may receive a link voltage value of 400 [V] from the DC link capacitor.

[0082] The control unit can calculate the right-side slope and left-side slope of the droop control curve based on the input required power value and the reference voltage value. In this embodiment, since the required power value is input as 0 [W], the slope of the droop control curve can be calculated as the initial setting of 350.

[0083] Next, the control unit calculates the difference between the reference voltage value 410 [V], which is a setting value, and the link voltage value 400 [V], and can calculate the output power value by substituting the calculated difference into the previously calculated slope and adding it to the required power value. The control unit can calculate the output power value by substituting the difference into the left slope when in the discharging mode, and can calculate the output power value by substituting the difference into the right slope when in the charging mode. In the embodiment, the control unit can calculate the output power value -3500 [W] by adding the value obtained by substituting the difference into the calculated slope, -3500 [W], and the required power value 0 [W].

[0084] Next, the control unit can calculate the target current value by dividing the output power value by the battery voltage. In the embodiment, the control unit can calculate the target current value -35 [A] by dividing the output power value -3500 [W] by the battery voltage 100 [V].

[0085] FIG. 9 is a diagram illustrating a voltage-power plane for explaining the operating region of the control unit according to the embodiment.

[0086] 9, the input unit may receive a required power value of −4500 [W] from the inverter, and a link voltage value of 425 [V] from the DC link capacitor.

[0087] The control unit can calculate the right-side slope and left-side slope of the droop control curve based on the input required power value and the reference voltage value of 425 V. In this embodiment, the operating point is changed based on the required power value and the reference voltage value, and the left-side slope of the droop control curve can be changed from the initial setting of 350 to 71.42 based on the changed operating point.

[0088] Next, the control unit calculates the difference between the reference voltage value 425 [V], which is a setting value, and the link voltage value 425 [V], and can calculate the output power value by substituting the calculated difference for the previously calculated slope and adding it to the required power value. The control unit can calculate the output power value by substituting the difference for the left slope in the discharging mode, and can calculate the output power value by substituting the difference for the right slope in the charging mode. In the embodiment, the control unit can calculate the output power value -4500 [W] by adding the value 0 [W] obtained by substituting the difference for the calculated slope and the required power value -4500 [W].

[0089] Next, the control unit can calculate the target current value by dividing the output power value by the battery voltage. In the embodiment, the control unit can calculate the target current value -45 [A] by dividing the output power value -4500 [W] by the battery voltage 100 [V].

[0090] The control unit can output the calculated target current value to the battery.

[0091] As described above, the DC / DC converter according to the embodiment receives a required power value from the inverter, calculates a new slope of the droop control curve, and calculates a current output to the battery according to the droop control curve reflecting the newly calculated slope, thereby changing the operating point of the DC / DC converter. In addition, the DC / DC converter can respond quickly without physical voltage fluctuations and can perform charging, discharging, and idle operation in all operating sections.

[0092] FIG. 10 is a diagram showing a voltage-power plane for explaining the operating region of the control unit according to the embodiment.

[0093] 10, the input unit may receive a required power value of −4500 [W] from the inverter, and a link voltage value of 425 [V] from the DC link capacitor.

[0094] The control unit can calculate the right-side slope and left-side slope of the droop control curve based on the input required power value and the reference voltage value of 395 V. In this embodiment, the operating point is changed based on the required power value and the reference voltage value, and the left-side slope of the droop control curve can be changed from the initial setting of 350 to 100 based on the changed operating point.

[0095] Next, the control unit calculates the difference between the reference voltage value 395 [V], which is a setting value, and the link voltage value 425 [V], and can calculate the output power value by substituting the calculated difference into the previously calculated slope and adding it to the required power value. The control unit can calculate the output power value by substituting the difference into the left slope when in discharging mode, and can calculate the output power value by substituting the difference into the right slope when in charging mode. In this embodiment, the control unit can calculate the output power value of -1500 [W] by substituting the difference 30 [V] into the calculated slope 100 to obtain a value of 3000 [W] and adding this to the required power value of -4500 [W].

[0096] Next, the control unit can calculate the target current value by dividing the output power value by the battery voltage. In the embodiment, the control unit can calculate the target current value -15 [A] by dividing the output power value -1500 [W] by the battery voltage 100 [V].

[0097] The control unit can output the calculated target current value to the battery.

[0098] As described above, the DC / DC converter according to the embodiment receives a required power value from the inverter, calculates a new slope of the droop control curve, and calculates a current output to the battery according to the droop control curve reflecting the newly calculated slope, thereby changing the operating point of the DC / DC converter. In addition, the DC / DC converter can respond quickly without physical voltage fluctuations and can perform charging, discharging, and idle operation in all operating sections.

[0099] 11 is a flowchart illustrating an operation of a DC / DC converter control method according to an embodiment. Referring to FIG. 11, first, a required power value may be input from an inverter to an input unit (S1101).

[0100] Next, the input unit may receive a reference voltage value from the inverter (S1102).

[0101] Next, the operation mode determination unit can calculate a critical voltage for determining the charge or discharge mode based on the reference voltage value and the required power value (S1103).

[0102] Next, the control unit can calculate the gradient of the droop control curve based on the reference voltage value and the required power value, with the critical voltage at the center (S1104).

[0103] Next, the input unit may receive a link voltage value from the DC link capacitor (S1105).

[0104] Next, the control unit can calculate the output power value by substituting the difference between the link voltage value and the reference voltage value into the slope (S1106).

[0105] Next, the control unit can calculate a target current value based on the output power value (S1107).

[0106] Next, the control unit can output the target current value to the battery (S1108).

[0107] FIG. 12 is a diagram illustrating the advantage of the expanded operating range for the proposed droop control compared to the existing droop control.

[0108] 12, in the case of the conventional DC / DC converter, the charge voltage and discharge voltage are fixed for each inverter, and therefore the charge operation region and the discharge operation region are limited to a predetermined range. In contrast, in the case of the DC / DC converter according to the embodiment, a droop control curve is newly calculated and applied in real time according to the operating point, so that it can be matched with inverters from various manufacturers having different operating regions, thereby improving compatibility and control safety.

[0109] The term "module" used in this embodiment refers to software or hardware components such as a field-programmable gate array (FPGA) or an ASIC, and the "module" performs a certain function. However, the term "module" is not limited to software or hardware. The "module" may be configured to reside on an addressable storage medium or to execute one or more processors. Thus, by way of example, the term "module" includes components such as software components, object-oriented software components, class components, and task components, as well as processes, functions, attributes, procedures, subroutines, program code segments, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The components and functions provided within the "modules" may be combined into fewer components and "modules" or further separated into additional components and "modules." Furthermore, the components and "modules" may be embodied to execute one or more CPUs within a device or a security multimedia card.

[0110] While the present invention has been described above with reference to preferred embodiments, those skilled in the art will appreciate that various modifications and variations of the present invention may be made without departing from the spirit and scope of the present invention as set forth in the following claims.

Claims

1. a stage in which a required power value is input from an inverter; inputting a reference voltage value from the inverter; calculating a slope of a droop control curve based on the reference voltage value and the required power value; calculating a critical voltage for determining whether the charging or discharging mode is performed based on the reference voltage value and the required power value; receiving a link voltage value from a DC link capacitor; calculating an output power value by substituting a difference between the link voltage value and the reference voltage value into the slope; and calculating a target current value based on the output power value.

2. The step of calculating the slope of the droop control curve comprises: calculating a right slope based on the reference voltage value; 2. The DC / DC converter control method according to claim 1, further comprising the step of: calculating a left-side gradient using the reference voltage value as a reference.

3. The step of calculating the right slope includes calculating the right slope of a droop control curve having the reference voltage value and the required power value as operating points according to the following Equation 1: <Formula 1> [Equation 1] In the above formula 1, Slope 1 is the right-hand slope of the droop control curve based on the reference voltage value, and P H,Limit is the maximum charging power value, and V H,Limit is the maximum charging power start voltage value, and P set is the required power value input from the inverter, and V ref 3. The DC / DC converter control method according to claim 2, wherein: is a reference voltage value input from an inverter.

4. The step of calculating the left slope includes calculating the left slope of a droop control curve having the reference voltage value and the required power value as operating points according to the following Equation 2: <Formula 2> [Equation 2] In the above formula 2, Slope 2 is the left slope of the droop control curve based on the reference voltage value, and P L,Limit is the maximum discharge power value, and V L,Limit is the maximum discharge power starting voltage value, and P set is the required power value input from the inverter, and V ref 4. The DC / DC converter control method according to claim 2, wherein the reference voltage value is input from the inverter.

5. 5. The DC / DC converter control method according to claim 1, further comprising the step of outputting the target current value to a battery.

6. an input unit to which a required power value and a reference voltage value are input from the inverter and a link voltage value is input from the DC link capacitor; a control unit that calculates a slope of a droop control curve based on the reference voltage value and the required power value, calculates an output power value by substituting a difference between the link voltage value and the reference voltage value into the slope, and calculates a target current value based on the output power value.

7. 7. The DC / DC converter according to claim 6, wherein the control unit calculates a right-side gradient using the reference voltage value as a reference, and calculates a left-side gradient using the reference voltage value as a reference.

8. The control unit calculates a right-side slope of a droop control curve having the reference voltage value and the required power value as operating points using the following Equation 3: <Formula 3> [Equation 3] In the above formula 3, Slope 1 is the right-hand slope of the droop control curve based on the reference voltage value, and P H,Limit is the maximum charging power value, and V H,Limit is the maximum charging power start voltage value, and P set is the required power value input from the inverter, and V ref 8. The DC / DC converter according to claim 7, wherein: is a reference voltage value input from the inverter.

9. The control unit calculates a left-side slope of a droop control curve having the reference voltage value and the required power value as operating points using the following Equation 4: <Formula 4> [Equation 4] In the above formula 4, Slope 2 is the left slope of the droop control curve based on the reference voltage value, and P L,Limit is the maximum discharge power value, and V L,Limit is the maximum discharge power starting voltage value, and P set is the required power value input from the inverter, and V ref 9. The DC / DC converter according to claim 7, wherein: is a reference voltage value input from an inverter.

10. 10. The DC / DC converter according to claim 6, wherein the control unit outputs the target current value to a battery.

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