KR102343689B1 - bidirectional DC-DC converter, and energy storage system including the same - Google Patents

Abstract

According to various embodiments, a bidirectional DC-DC converter and an energy storage system including the same are disclosed. A bidirectional DC-DC converter including first to fourth nodes and a ground node, a first inductor between the first node and the third node and a second inductor between the third node and the second node A second tapped inductor including a first tapped inductor, a third inductor between the first node and the fourth node, and a fourth inductor between the fourth node and the second node, the third node and A first switch and a first diode connected in parallel between a ground node, a second switch and a second diode connected in parallel between the second inductor and a second node, and a parallel connection between the fourth node and a ground node A bidirectional DC- comprising a third switch and a third diode, a fourth switch and a fourth diode connected in parallel between the fourth inductor and a second node, and a capacitor connected between the second node and a ground node; Disclosed are a DC converter and an energy storage system including the same.

Description

Bidirectional DC-DC converter, and energy storage system including the same

The present invention relates to a bidirectional DC-DC converter and an energy storage system including the same.

A typical bidirectional DC-DC converter operates in a unidirectional boost mode in which the voltage is stepped up (step-up) and a unidirectional buck mode in which the voltage is stepped down (step-down). Non-isolated bidirectional DC-DC converters are widely used because of their advantages over isolated bidirectional DC-DC converters in terms of the number and size of components. When the non-isolated bidirectional DC-DC converter is operated in the boost mode, if the output voltage compared to the input voltage is greatly increased, the target output voltage may not be achieved due to the limit of the step-up. Even if the target output voltage is achieved, the duty ratio becomes 0.8 to 0.9 or more, which increases the possibility of causing instability of control. As an alternative to this, an isolated bidirectional DC-DC converter has appeared, but there are problems such as an increase in the total number of parts and low efficiency because parts such as a transformer, an auxiliary inductor, and a resonance element are required.

An object of the present invention is to provide a non-isolated bidirectional DC-DC converter having control stability using a tapped inductor and an energy storage system including the same.

A bidirectional DC-DC converter according to an aspect of the present invention is a bidirectional DC-DC converter including first to fourth nodes and a ground node, wherein a first inductor between the first node and the third node and the A first tap inductor including a second inductor between a third node and the second node, a third inductor between the first node and the fourth node, and a fourth inductor between the fourth node and the second node A second tap inductor comprising: a first switch and a first diode connected in parallel between the third node and a ground node; a second switch and a second diode connected in parallel between the second inductor and a second node , a third switch and a third diode connected in parallel between the fourth node and a ground node, a fourth switch and a fourth diode connected in parallel between the fourth inductor and a second node, and the second node; It includes a capacitor connected between the ground node.

According to an example of the bidirectional DC-DC converter, when operating in the boost mode, the first switch and the third switches operate alternately (interleaved) with each other, and the second switch and the fourth switches are turned off. characterized in that

According to another example of the bidirectional DC-DC converter, the first switch is turned on when the third switch is turned off, and the third switch is turned on when the first switch is turned off. It is characterized in that it is turned on.

According to another example of the bidirectional DC-DC converter, the first tap inductor transfers stored energy to the second node when the first switch is turned off, and the second tap inductor transfers the stored energy to the second node when the third switch is turned off. It is characterized in that the stored energy is transferred to the second node.

According to another example of the bidirectional DC-DC converter, the first switch is turned off after maintaining a turn-on state while the third switch is turned on, turned off, and changed to a turn-on state.

According to another example of the bidirectional DC-DC converter, the first switch and the third switches are turned on with a duty ratio of less than 80%.

According to another example of the bidirectional DC-DC converter, the step-up ratio of the second voltage of the second node to the first voltage of the first node has a step-up ratio of any one of 6 times to 12 times.

According to another example of the bidirectional DC-DC converter, when operating in the buck mode, the second and fourth switches operate alternately (interleaved) with each other, and the first and third switches are turned off. .

According to another example of the bidirectional DC-DC converter, a DC power supply is connected between the second node and the ground node, and the first tap inductor receives energy from the DC power supply when the second switch is turned on, The second tap inductor may receive energy from the DC power source when the fourth switch is turned on.

According to another example of the bidirectional DC-DC converter, the second switch is in a turn-off state when the fourth switch is in a turn-on state, and the fourth switch is in a turn-off state when the second switch is in a turn-on state, It is characterized in that it is turned off.

According to another example of the bi-directional DC-DC converter, the second switch is turned off, the turn-on, and the turn-off state is maintained while the fourth switch is changed to the turn-off state, and is turned on. .

According to another example of the bidirectional DC-DC converter, the second and fourth switches are turned on with a duty ratio of less than 40%.

According to another example of the bidirectional DC-DC converter, the first tapped inductor includes the first inductor and the second inductor having a turns ratio of 1:N, and the bidirectional DC-DC converter increases the turns ratio so that the It is characterized by reducing the peak current in the bidirectional DC-DC converter.

An energy storage system according to an aspect of the present invention, the bidirectional DC-DC converter of any one of claims 1 to 13, a battery connected between a first node of the bidirectional DC-DC converter and a ground node, the bidirectional DC-DC converter A power conversion device for converting power between the DC link and at least one of a DC link comprising the capacitor between a second node of the DC-DC converter and the ground node, a power generation system, a grid and a load and the bidirectional DC-DC and a power conversion system including a converter and an integrated controller for controlling the power conversion device.

The bidirectional DC-DC converter according to various embodiments of the present invention can ensure control stability because a control signal having a duty ratio of 0.8 or less can be used even when operating in a boost mode in which the output voltage is 8 times the input voltage. . In addition, it can operate in a buck mode that lowers the voltage. Accordingly, the energy storage system including the bidirectional DC-DC converter according to various embodiments of the present disclosure may include a battery having a low voltage.

In addition, the bi-directional DC-DC converter according to various embodiments of the present invention has the advantages of the non-isolated bi-directional DC-DC converter, and as it operates in an interleaved manner, the maximum current can be reduced by half.

1 schematically shows a circuit diagram of a bidirectional DC-DC converter according to an embodiment of the present invention.
2 shows a control timing diagram when the bidirectional DC-DC converter operates in a boost mode according to an embodiment of the present invention.
3 to 6 show a bidirectional DC-DC converter operating in a boost mode for each section.
FIG. 7 shows a control timing diagram when the bidirectional DC-DC converter shown in FIG. 1 operates in a buck mode.
8 to 11 show a bidirectional DC-DC converter operating in a buck mode for each section.
12 schematically illustrates an energy storage system and peripheral configuration according to an embodiment.
13 is a block diagram illustrating a schematic configuration of an energy storage system according to an embodiment.

Advantages and features of the present invention, and methods for achieving them, will become apparent with reference to the detailed description in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments presented below, but may be implemented in various different forms, and should be understood to include all transformations, equivalents, and substitutes included in the spirit and scope of the present invention. do. The embodiments presented below are provided to complete the disclosure of the present invention, and to fully inform those of ordinary skill in the art to the scope of the invention. In describing the present invention, if it is determined that a detailed description of a related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof. Terms such as first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings. decide to do

1 schematically shows a circuit diagram of a bidirectional DC-DC converter according to an embodiment of the present invention.

Referring to FIG. 1 , the bidirectional DC-DC converter 100 includes first to fourth nodes N4 and a ground node GND.

A DC power is connected between the first node N1 and the ground node GND. Although the DC power source is indicated as the battery 21 in FIG. 1 , the output voltage of the rectifier circuit to which the AC voltage is applied may be a DC power source, and the inventive concept is not limited thereto. Although not shown in FIG. 1 , a capacitor may further include a capacitor connected in parallel to the DC power between the first node N1 and the ground node GND. Meanwhile, in the following description, it is assumed that the DC power connected between the first node N1 and the ground node GND is the battery 21 .

The bidirectional DC-DC converter 100 may operate in a boost mode and a buck mode. When operating in the boost mode, the bidirectional DC-DC converter 100 boosts the voltage of the first node N1 and outputs it to the second node N2. In this case, the first node N1 is an input node, and the second node N2 is an output node. When operating in the buck mode, the bidirectional DC-DC converter 100 reduces the voltage of the second node N2 and outputs it to the first node N1 . In this case, the second node N2 is an input node, and the first node N1 is an output node. The second voltage V2 of the second node N2 is higher than the level of the first voltage V1 of the first node N1 . That is, the first node N1 is a low voltage terminal, and the second node N2 is a high voltage terminal. Meanwhile, the battery 21 may be connected between the first node N1 and the ground node GND, and a DC link may be connected to the second node N2 .

According to an embodiment, the battery 21 may be connected to the first node N1 , and a load or commercial power may be connected to the second node N2 through a bidirectional inverter. When operating in the boost mode, the battery 21 connected to the first node N1 is discharged, and the discharged power may be supplied to a load connected to the second node N2 or commercial power. When operating in the buck mode, the battery 21 connected to the first node N1 is charged from the commercial power connected to the second node N2 .

The bidirectional DC-DC converter 100 includes a first tap inductor 121 and a second tap inductor 123 . The first tapped inductor 121 and the second tapped inductor 123 are inductors that have a circuit connectable tap in the middle of the existing inductor. Unlike a transformer, the purpose of 'energy storage' is not 'energy transfer'. is an inductor. The first tap inductor 121 includes a first inductor L1 and a second inductor L2 magnetically coupled with a turns ratio of 1:N, and is disposed between the first inductor L1 and the second inductor L2. A tab is formed in (the third node N3 ). The second tap inductor 123 includes a third inductor L3 and a fourth inductor L4 magnetically coupled with a turns ratio of 1:M, and is disposed between the third inductor L3 and the fourth inductor L4. A tab is formed on the

The first inductor L1 is connected between the first node N1 and the third node N3 , and the second inductor L2 is connected between the second node N2 and the third node N3 . The third inductor L3 is connected between the first node N1 and the fourth node N4 , and the fourth inductor L4 is connected between the second node N2 and the fourth node N4 .

The first to fourth inductors L1 to L4 may have the same inductance. Also, a coupling coefficient between the first inductor L3 and the second inductor L2 and a coupling coefficient between the third inductor L3 and the fourth inductor L4 may correspond to each other. However, the present invention is not limited thereto, and the inductances of the first inductor L1 and the third inductor L2 or the second inductor L2 and the fourth inductor L4 may have different values, and the first The coupling coefficient between the inductor L1 and the second inductor L2 and the coupling coefficient between the third inductor L3 and the fourth inductor L4 may also have different values. For convenience of explanation, hereinafter, the first inductor ( L1 ) and the third inductor ( L3 ), the second inductor ( L2 ), and the fourth inductor ( L4 ) have inductances corresponding to each other, and the first inductor ( L1 ) ) and the coupling coefficient between the second inductor L2 and the third inductor L3 and the fourth inductor L4 are assumed to have corresponding values.

The turns ratio between the first inductor L1 and the second inductor L2 is 1:N. N is a value of 1 or more, and as the value of N increases, the step-up ratio may also increase. The turns ratio between the first inductor L1 and the second inductor L2 may be set in consideration of the duty ratio D of the first switch S1 and the peak value of the current flowing through each inductor. Similarly, the turns ratio between the third inductor L3 and the fourth inductor L4 is 1:M. M is a value of 1 or more, and as the value of M increases, the step-up ratio may also increase. The turns ratio between the third inductor L3 and the fourth inductor L4 may be set in consideration of the duty ratio D of the third switch S3 and the peak value of the current flowing through each inductor. N and M may have values corresponding to each other, but N and M may be different values, and the scope of the present invention is not limited thereto. Hereinafter, for convenience of description, the turns ratio between the first inductor L1 and the second inductor L2 and the turns ratio between the third inductor L3 and the fourth inductor L4 have the same value as 1:2. It is assumed and explained.

The bidirectional DC-DC converter 100 includes a first switch S1 and a first diode D1, a second inductor L2 and a second connected in parallel between the third node N3 and the ground node GND. A second switch S2 and a second diode D2 connected in parallel between the node N2, a third switch S3 and a third diode D2 connected in parallel between the fourth node N4 and the ground node GND A third diode D3, a fourth switch S4 and a fourth diode D4 connected in parallel between the fourth inductor L4 and the second node N2 are included. The first diode D1 allows a current to flow from the ground node GND to the third node N3 . The second diode D2 allows a current to flow from the second inductor L2 to the second node N2, and the third diode D3 allows a current to flow from the ground node GND to the fourth node N4. , the fourth diode D4 allows a current to flow from the fourth inductor L4 to the second node N2. The first switch S1 and the first diode D1 may be implemented as a power MOSFET device having a vertical diffused MOS (MOS) structure. The second switch S2 and the second diode D2, the third switch S3 and the third diode D3, the fourth switch S4 and the fourth diode D4 may also be implemented as power MOSFET devices. have.

The bidirectional DC-DC converter 100 , 100 includes a capacitor 130 connected between the second node N2 and the ground node GND. For example, the capacitor 130 may constitute a DC link. The capacitor 130 may stabilize the second voltage V2 of the second node N2 . The capacitor 130 may have a sufficiently large capacitance (capacitance) such that the ripple voltage of the second node N2 is smaller than the level of the second voltage V2 .

2 shows a control timing diagram when the bidirectional DC-DC converter operates in a boost mode according to an embodiment of the present invention. 3 to 6 show a bidirectional DC-DC converter operating in a boost mode for each section.

Referring to FIG. 2 , when the bidirectional DC-DC converter 100 operates in the boost mode, the first switch S1 and the third switch S3 are alternately switched at each switching period Ts. . The switching period Ts is a time required to repeat the first period t0-t1, the second period t1-t2, the third period t2-t3, and the fourth period t3-t4 once. to be. The second switch S2 and the fourth switch S4 remain turned off.

Meanwhile, the first current I1 is defined as a current flowing from the first node N1 to the third node N3 through the first inductor L1, and the second current I2 is the third node N3. It is defined as the current flowing through the second inductor L2 from the to the second node N2. The third current I3 is defined as a current flowing from the first node N1 to the fourth node N4 through the third inductor L3, and the fourth current I4 is the fourth current I4 from the fourth node N4. It is defined as the current flowing through the fourth inductor L4 to the second node N2.

During the first period t0 - t1 of the switching period Ts, the first switch S1 is turned off and the third switch S3 remains turned on. During the second period t1-t2, the first switch S1 and the second switch S2 are turned on. During the third period t2-t3, the first switch S1 is turned on, and the second switch S2 is turned off. During the fourth period t3-t4, the first switch S1 and the third switch S3 are turned on.

The first period t0-t1 in which the first switch S1 is turned off and the third period t2-t3 in which the third switch S3 is turned off may have a corresponding time interval. The ratio of the time during which the first switch S1 and the third switch S3 are turned on during the switching period Ts is the duty ratio D. In the switching period Ts, the turn-off time of the first switch S1 and the turn-off time of the third switch S3 may correspond to each other, and thus the first switch S1 and the turn-off time of the third switch S3 The duty ratio D may be the same. However, the present invention is not limited thereto, and the duty ratio D of the first switch S1 and the duty ratio D of the third switch S3 may be different from each other. Hereinafter, for convenience of description, it is assumed that the duty ratios D of the first switch S1 and the third switch S3 correspond to each other.

Depending on the step-up ratio of the bidirectional DC-DC converter 100 operating in the boost mode, the first switch S1 and the third switch S3 may be turned on with a duty ratio D of less than 80%. Meanwhile, as described above, it is assumed that the turns ratio of the first inductor L1 and the second inductor L2 is 1:2, and the turns ratio of the third inductor L3 and the fourth inductor L4 is 1:2. Assume For example, when the step-up ratio is 4, the first switch S1 and the third switch S3 may be turned on with a duty ratio D of approximately 50%. When the step-up ratio is 6, the first switch S1 and the third switch S3 may be turned on with a duty ratio D of approximately 62.5%. When the step-up ratio is 8, the first switch S1 and the third switch S3 may be turned on with a duty ratio D of approximately 70%, and further, when the step-up ratio is 12, the first switch S1 and the second switch S3 3 switches S3 are turned on with a duty ratio D of approximately 79%.

Accordingly, when the step-up ratio of the bidirectional DC-DC converter 100 is 4 or more and 12 or less, the first switch S1 and the third switch S3 are turned on with a duty ratio D of 50% or more to less than 80%. can be In this case, the first switch S1 and the third switch S3 may be alternately turned off at each switching period Ts. For example, when the first switch S1 is turned off, the third switch S3 may be turned on, and when the third switch S3 is turned off, the first switch S1 may be turned on. That is, although it depends on the turns ratio, when the turns ratio is 1:2, there may not be a state in which both the first switch S1 and the third switch S3 are turned off.

The second voltage V2, which is the voltage of the capacitor 130, may be increased or decreased within the switching period Ts, but has a constant level on average after the bidirectional DC-DC converter 100 is stabilized. Therefore, in this specification, the average voltage means the average voltage during the switching period (Ts) after the bidirectional DC-DC converter 100 is stabilized.

Hereinafter, it is assumed that the bidirectional DC-DC converter 100 is stabilized and then proceeds from the first section t0-t1 to the fourth section t3-t4, and the first section t0-t1 repeats again. .

2 and 3 , in a first period t0 - t1 , the first switch S1 is turned off and the third switch S3 is turned on.

3 , the first current I1 flowing through the first inductor L1 flows to the third node N3, and the second current I2 flowing through the second inductor L2 is 3 flows through the diode D3. The third current I3 flowing through the third inductor L3 flows to the third switch S3, and the fourth current I4 flowing through the fourth inductor L4 is turned on when the third switch S3 is turned on. 0.

In the first period t0 - t1, the first current I1 and the second current I2 have the same magnitude and direction as there is no current flowing between the ground node GND and the third node N3. have The first current I1 and the second current I2 are the first inductor L1 , the third node N3 , the second inductor L2 , the second diode D2 , the capacitor 130 , and the battery 21 . ) and the first node N1. The first inductor L1 emits stored energy, and the second inductor L2 emits energy induced by magnetic coupling with the first inductor L1. The second node to which the capacitor 130 is connected, that is, the high voltage terminal, receives energy emitted by the first inductor L1 and the second inductor L2 and energy supplied by the battery 21 .

Referring to the first period t0 - t1 in the graph of the first current I1 and the second current I2 of FIG. 2 , the first current ( As I1) rapidly decreases, the second current I2 rapidly rises, and a portion of energy stored in the first inductor L1 is transferred to the magnetically coupled second inductor L2. Thereafter, the first current I1 and the second current I2 become equal and decrease with the same slope, and energy stored in the first inductor L1 and the second inductor L2 is released.

In the first period t0 - t1 , the third current I3 is the battery 21 , the first node N1 , the third inductor L3 , the fourth node N4 , the third switch S3 and the ground Cycles via node GND. The third inductor L3 stores energy supplied from the battery 21 during the first period t0 - t1. Meanwhile, energy is not stored or emitted in the fourth inductor L4 because there is no current flow.

Referring to the first section t0-t1 in the graph of the third current I3 shown in FIG. 2 , the third current I3 increases with a constant slope, and the third inductor L3 is connected to the battery 21 Energy supplied from Meanwhile, as will be described later, the constant slope is the same as the slope at which the third current I3 increases in the second period t1-t2 and the fourth period t3-t4.

2 and 4 , the first switch S1 is turned on at a first time t1, and the first switch S1 and the third switch S3 are turned on during the second period t1-t2. Keep turn on.

4, the first current I1 flowing through the first inductor L1 flows to the first switch S1, and the third current I3 flowing through the third inductor L3 is 3 flows to the switch S3. The second current I2 and the fourth current I4 are zero.

In the second period t1-t2, the first current I1 is generated by the battery 21, the second node N2, the first inductor L1, the third node N3, the first switch S1, and It is cycled through the ground node (GND). The first inductor L1 stores energy supplied by the battery 21 . Since the second inductor L2 does not flow current, energy is not stored or released.

Referring to the second period t1-t2 in the graph of the first current I1 shown in FIG. 2 , the first current I1 rapidly rises at a time t1 when the first switch S1 is turned off. and the second current I2 is rapidly reduced to zero, and energy stored in the second inductor L2 is transferred to the magnetically coupled first inductor L1. After that, the first current I1 increases with a constant slope, and energy is stored in the first inductor L1. As will be described later, the constant slope at which the first current I1 increases is the same as the slope at which the first current I1 increases in the third period t2-t3 and the fourth period t3-t4. .

The third current I3 is circulated through the battery 21 , the first node N2 , the third inductor L3 , the third switch S3 , and the ground node GND. The third inductor L3 stores energy supplied by the battery 21 . Since the fourth inductor L4 does not flow current, energy is not stored or released.

Referring to the second period t1-t2 in the graph of the third current I3 shown in FIG. 2 , during the second period t1-t2, the third current I3 increases with a constant slope, 3 Energy is stored in the inductor (L3).

2 and 5 , the third switch S3 is turned off at the second time, the first switch S1 is turned on during the third period t2-t3, and the third switch S3 ) is turned off.

The first current I1 flowing through the first inductor L1 flows to the first switch S1, and the second current I2 is 0. The first current I1 circulates through the battery 21 , the first node N1 , the first inductor L1 , the third node N3 , the first switch S1 , and the ground node GND . The first inductor L1 stores energy supplied by the battery 21 during the third period t2-t3. The second inductor L2 does not emit or store energy as there is no current flow.

Referring to the third section t2-t3 in the graph of the first current I1 shown in FIG. 2, the first current I1 increases with the same slope as the slope of the second section t1-t2, Energy is stored in the first inductor L1.

The third current I3 flowing through the third inductor L3 flows to the fourth inductor L4 through the fourth node N4. A fourth current I4 is induced in the fourth inductor L4 by magnetic coupling with the third inductor L3, and the induced fourth current I4 flows to the fourth diode D4. The third current I3 and the fourth current I4 are the same as there is no current flowing out or flowing between the fourth node N4 and the ground node GND.

The third current I3 and the fourth current are the battery 21 , the first node N1 , the third inductor L3 , the fourth node N4 , the fourth inductor L4 , and the fourth switch S4 . , is cycled through the second node N2 and the capacitor 130 . The third inductor L3 emits the stored energy during the third period t2-t3, and the fourth inductor L4 releases the energy induced by the coupling with the third inductor L3 at the second time period in the third period. It is released during (t2-t3). The high voltage terminal N2 receives energy emitted by the third inductor L3 and the fourth inductor L4 and energy supplied by the battery 21 .

Referring to the third period t2-t3 in the graph of the third current I3 and the fourth current I4 shown in FIG. 2 , the third switch S3 is turned off at a time t2 . The current I3 sharply decreases and the fourth current I4 sharply rises, and some of the energy stored in the third inductor L3 is transferred to the magnetically coupled fourth inductor L4 . Thereafter, the third current I3 and the fourth current I4 become equal and decrease with the same slope, and energy stored in the third inductor L3 and the fourth inductor L4 is released.

2 and 6 , the third switch S3 is turned on at the third time, and during the fourth period t3-t4, the first switch S1 and the third switch S3 are turned on. keep the status

The first current I1 flowing through the first inductor L1 flows to the first switch S1 , and the third current I3 flowing through the third inductor L3 flows to the third switch S3 . When the first switch S1 and the third switch S3 are turned on, the second current I2 and the fourth current I4 are zero.

The first current I1 is circulated through the battery 21 , the first node N1 , the first inductor L1 , the third node N3 , the first switch S1 , and the ground node GND . The first inductor L1 stores energy supplied by the battery 21 during the fourth period t3-t4. The second inductor L2 does not store or emit energy since there is no current flow.

Referring to the fourth period t3-t4 in the graph of the first current I1 shown in FIG. 2 , the first current I1 is the first current I1 in the third period t2-t3 It increases with the same slope as the increasing slope, and energy is stored in the first inductor L1.

The third current I3 is circulated through the battery 21 , the first node N1 , the third inductor L3 , the third switch S3 , and the ground node GND. The third inductor L3 stores energy supplied by the battery 21 during the fourth period t3-t4. The fourth inductor L4 does not store or emit energy as there is no current flow.

Referring to the fourth section t3-t4 in the graph of the third current I3 shown in FIG. 2 , the third current I3 rapidly rises at a time t3 when the third switch S3 is turned off. and the fourth current I4 sharply decreases to 0, and the energy stored in the fourth inductor L4 is transferred to the magnetically coupled third inductor L3. Thereafter, the third current I3 increases with the same slope as the slope at which the third current I3 of the second period t1-t2 increases, energy is stored in the third inductor L3, and the fourth current I3 increases. No current flows in the inductor L4.

According to an embodiment, the first inductor L1 stores the energy supplied from the battery 21 in the second section t1-t2, the third section t2-t3, and the fourth section t3-t4. do. The first inductor L1 stores a portion of the energy stored during the second period t1-t2 to the fourth period t3-t4 at the time t0 when the first switch S1 is turned off during the first period ( during t0-t1). Meanwhile, the second inductor L2 emits energy induced by the first inductor L1 during a first period t0-t1 at a time t0 when the first switch S1 is turned off, and Energy is not stored or released in the second period t1-t2, the third period t2-t3, and the fourth period t3-t4 except for the time point t1.

Also, the third inductor L3 stores energy supplied from the battery 21 in the first period t0-t1 , the second period t1-t2 , and the fourth period t3-t4 . The third inductor L3 is stored during the first period t0-t1, the second period t1-t2, and the fourth period t3-t4 when the third switch S3 is turned off at the second time. Some of the one energy is emitted during the third period (t2-t3). Meanwhile, the fourth inductor L4 emits energy induced by the third inductor L3 during the third period t2-t3 at the time t2 when the third switch S3 is turned off, and the first Energy is not stored or released in the fourth period t3-t4 except for the period t0-t1, the second period t1-t2, and the third time point t3.

According to an embodiment, the bidirectional DC-DC converter 100 may cut the peak current by half. The bidirectional DC-DC converter 100 may alternately transfer energy stored in the first tap inductor 121 and the second tap inductor 123 to the capacitor 130 . For example, the bidirectional DC-DC converter 100 transfers the energy stored in the first tap inductor 121 and the energy of the battery to the high voltage terminal in the first period t0 - t1, and then transmits the energy to the high voltage terminal in the third period ( At t2-t3), the energy stored in the second tap inductor 123 and the energy of the battery may be transferred to the high voltage terminal. That is, since the two tap inductors divide and store and release energy to be provided by one tap inductor during the switching period Ts, the bidirectional DC-DC converter 100 can reduce the peak current by half. Meanwhile, the bidirectional DC-DC converter 100 may include three or more tap inductors, and in this case, the magnitude of the peak current may be further reduced.

The bidirectional DC-DC converter 100 receives input power in a stabilized state and outputs DC power having a preset step-up ratio through the first period t0-t1 to the fourth period t3-t4. In this case, the first current I1 and the third current I3 have the same value at the start time and end time of the switching period Ts.

The bidirectional DC-DC converter 100 operating in the boost mode has a step-up ratio (V2/V1) of (1+N*D)/(1-D). The derivation of the step-up ratio (V2/V1) is omitted since it can be derived from commonly known induction circuits and circuit analysis.

According to an embodiment, in order for the bidirectional DC-DC converter 100 to operate at an 8-fold step-up ratio (V2/V1), the first switch S1 and the third switch S3 have a 70% duty ratio ( D) (assuming a turns ratio of 1:2 as described above). In this case, when the first voltage V1, which is the output voltage of the battery 21, is 50V, the bidirectional DC-DC converter 100 can output 400V, and the non-isolated DC-DC converter is boosted by 8 times. Even with the ratio, stable control is possible with a duty ratio (D) within 80%, and the peak current can be reduced by half in the interleaved method.

In addition, the bidirectional DC-DC converter 100 may further reduce the duty ratio D and the peak current by adjusting the turns ratio of the first tap inductor 121 and the second tap inductor 123 . Since the bidirectional DC-DC converter 100 has a step-up ratio (V2/V1) of (1+N*D)/(1-D), the duty ratio (D) is increased by increasing the turns ratio (increasing N). ) and peak current. For example, when N is 2, when the step-up ratio V2/V1 is 6, the duty ratio of the first switch S1 and the third switch S2 is a duty ratio D of 62.5%, and the step-up ratio D is 62.5%. When the ratio (V2/V1) is 8, it has a duty ratio D of about 79%, but when N is 4, when the step-up ratio (V2/V1) is 6, it is 50%, and the step-up ratio (V2/V1) is When the value is 8, the duty ratio D is approximately 59%. As N increases, the duty ratio D of the first switch s1 and the third switch S3 having the same step-up ratio decreases.

In addition, by adjusting the turns ratio of the first tapped inductor 121 and the second tapped inductor 123, the duty ratio D of the switch can be adjusted at the operating point of the converter, so the conduction loss of the switch and the reverse voltage recovery problem of the diode By reducing , efficiency and EMI (Elcctro-Magnetic Interference) noise can be improved.

FIG. 7 shows a control timing diagram when the bidirectional DC-DC converter shown in FIG. 1 operates in a buck mode. 8 to 11 show a bidirectional DC-DC converter operating in a buck mode for each section.

1 and 7 , the second switch S2 and the fourth switch S4 are alternately switched with each other at every switching period Ts. The first switch S1 and the third switch remain turned off during the switching period Ts.

As described above, when the bidirectional DC-DC converter 100 operates in the buck mode, the second node N2 becomes an input node and the first node N1 becomes an output node. The bidirectional DC-DC converter 100 reduces the second voltage V2 of the second node N2 to output the first voltage V1 to the first node N1 . Accordingly, the DC power supply Vs having the second voltage V2 between the second node N2 and the ground node GND is connected in parallel with the capacitor 130 . The DC power (Vs) is a commercial power or a power obtained by rectifying the commercial power. The second voltage V2 is higher than the level of the first voltage V1 .

Meanwhile, hereinafter, the first current I1 is defined as a current flowing from the third node N3 to the first node N1 through the first inductor L1, and the second current I2 is the second node It is defined as a current flowing from (N2) to the third node (N4) through the second inductor (L2). The third current I3 is defined as a current flowing from the fourth node N4 to the first node N1 through the third inductor L3, and the fourth current I4 is defined as the current flowing from the second node N2 to the second node N2. It is defined as a current flowing through the fourth inductor L4 to the fourth node N4.

The bidirectional DC-DC converter 100 operating in the buck mode may supply energy of the DC power supply Vs to the battery 21 connected to the first node N1 . That is, in the buck mode, the battery 21 may be charged by receiving energy from the DC power supply Vs.

During the first period t0 - t1 of the switching period Ts, the second switch S2 is turned off, and the fourth switch S4 is turned on. At the first time t1, the fourth switch S4 is turned off, and during the second period t1-t2, both the second switch S2 and the fourth switch S4 are turned off. At the second time t2 , the second switch S2 is turned on, the second switch S2 is turned on during the third period, and the fourth switch S4 is turned off. At the third time t3, the second switch S2 is turned off, and during the fourth period t3-t4, both the second switch S2 and the fourth switch S4 are turned off.

The duration of the third period t2-t3, which is the period in which the second switch S2 is turned on, and the duration of the first period t0-t1, the period in which the fourth switch S4 is turned on, are the same as each other. can do. That is, the duty ratio D, which is the ratio of the time during which the second switch S2 is turned on during the switching period Ts, may be the same as the duty ratio D of the fourth switch S4. Meanwhile, the present invention is not limited thereto, and the duty ratio D of the second switch S2 and the duty ratio D of the fourth switch S4 may be different from each other. For easy understanding of the present invention, it is assumed that the duty ratios D of the second switch S2 and the fourth switch S4 are equal to each other.

The bidirectional DC-DC converter 100 operating in the buck mode has a step-down ratio (V1/V2) of D/(D+N(1-D)). The derivation of the reduced-pressure ratio (V1/V2) is omitted since it can be derived from a generally known induction circuit and circuit analysis. As described above, it is assumed that the turns ratio of the first and second inductors and the turns ratio between the third and fourth inductors are 1:2.

Although it depends on the step-down ratio (V1/V2) of the bidirectional DC-DC converter 100 operating in the buck mode, when the step-down ratio is 1/4 to 1/16, the second switch S2 and the fourth switch S4 can be turned on with a duty ratio of 10% or more and less than 50%. For example, when the pressure reduction ratio is 1/4, the second switch S2 and the fourth switch S4 may be turned on at a duty ratio of 40%. When the pressure reduction ratio is 1/8, the second switch S2 and the fourth switch S4 may be turned on with a duty ratio D of approximately 22.2%. When the pressure reduction ratio is 1/16, the second switch S2 and the fourth switch S4 may be turned on with a duty ratio D of approximately 11.8%.

In this case, the second switch S2 and the fourth switch S4 may be alternately turned on at every switching period Ts. For example, when the second switch S2 is turned on, the fourth switch S4 may be turned off. When the fourth switch S4 is turned on, the second switch S2 is turned on. may be in a turned off state. That is, there may not be a state in which both the second switch S2 and the fourth switch S4 are turned on. Through this, the peak current of the bidirectional DC-DC converter 100 can be reduced by half, and ripple can be minimized.

For example, when the second voltage V2 of the DC power source Vs is 400V, in order to charge the battery having the first voltage V1 of 50V, the bidirectional DC-DC converter 100 reduces the pressure by 1/8 have rain In this case, the second switch S2 and the fourth switch S4 are controlled to be turned on at a duty ratio of approximately 22.2%, and the second switch S2 and the fourth switch S4 are turned on alternately, so that the peak current can be reduced by half.

7 and 8 , during the first period t0 - t1 , the second switch S2 is turned off and the fourth switch S4 maintains the turned on state.

As shown in FIG. 8 , the first current I1 flowing through the first inductor L1 passes through the first node N1 to the battery 21 . The third current I3 flowing through the third inductor L3 also goes to the battery 21 through the first node N1, and the fourth current I4 flowing through the fourth inductor L4 is the fourth node It flows through (N4) to the third inverter.

The first current I1 circulates through the first inductor L1 , the first node N1 , the battery 21 , the ground node GND, and the first diode D1 . The first inductor L1 emits some of the stored energy. Meanwhile, the second inductor L2 does not store or emit energy as there is no current flow.

Referring to the first section t0 - t1 in the graph of the first current I1 shown in FIG. 7 , the first current I1 is reduced with a constant slope, and the energy stored in the first inductor L1 is released do. The battery 21 is charged by transferring the energy emitted by the first inductor.

The third current I3 and the fourth current I4 are the same as there is no current flowing between the ground node GND and the fourth node N4 . The third current I3 and the fourth current I4 are the DC power source Vs, the second node N2, the fourth switch S4, the fourth inductor L4, the third node N3, and the third It circulates via the inductor L3, the first node N1, and the battery 21. The third current I3 and the fourth current I4 charge the battery 21 while storing energy in the third inductor L3 and the fourth inductor L4 . That is, the energy supplied from the DC power supply Vs is stored in the third inductor L3 and the fourth inductor L4 during the first period t0 - t1 and charges the battery 21 .

Referring to the first period t0 - t1 in the graph of the third current I3 and the fourth current I4 shown in FIG. 7 , the third The current I3 sharply decreases and the fourth current I4 sharply rises, and some of the energy stored in the third inductor L3 is transferred to the magnetically coupled fourth inductor L4 . Thereafter, the third current I3 and the fourth current I4 are the same and increase with the same slope, and energy is stored in the third inductor L3 and the fourth inductor L4 .

7 and 9 , the fourth switch S4 is turned off at a first time t1, and the second switch S2 and the fourth switch S4 are turned off during the second period t1-t2. is turned off.

As shown in FIG. 9 , the first current I1 flowing through the first inductor L1 flows into the battery 21 . The third current I3 flowing through the third inductor L3 also flows to the battery 21 .

The first current I1 is circulated through the first inductor L1 , the first node N1 , the battery 21 , the ground node GND, and the first diode D1 . The first inductor L1 emits a portion of the stored energy during the second period t1-t2. The first current I1 transfers energy emitted by the first inductor L1 to the battery 21 to charge the battery 21 . The second inductor L2 does not store or emit energy since there is no current flow.

Referring to the second period t1-t2 in the graph of the first current I1 shown in FIG. 7 , the first current I1 decreases in the first period t0-t1 in the first current I1. is reduced to the same slope as the current slope, and energy stored in the first inductor L1 is released.

The third current I3 is circulated through the third inductor L3 , the first node N1 , the battery 21 , the ground node GND, and the third diode D3 . The third inductor L3 emits a portion of the stored energy during the second period t1-t2. The battery 21 is charged by receiving the energy emitted by the third inductor L3.

Referring to the second period t1-t2 in the graph of the third current I3 and the fourth current I4 shown in FIG. 7 , the third current I3 and the fourth current I4 are displayed at a time t1 when the fourth switch S4 is turned off. The current I3 sharply increases and the fourth current I4 sharply decreases to 0, and the energy stored in the fourth inductor L4 is transferred to the magnetically coupled third inductor L3. After that, the third current I3 gradually decreases, and the energy stored in the third inductor L3 is released.

7 and 10 , the second switch S2 is turned on at the second time t2, and the second switch S2 remains turned on during the third period t2-t3, The fourth switch S4 remains turned off.

10, the first current I1 flowing through the first inductor L1 flows to the battery 21, and the second current I2 flowing through the second inductor L2 is the second node It flows through (N2) to the first inductor (L1).

The first current I1 and the second current I2 are equal to each other because there is no current flowing between the third node N3 and the ground node GND. The first current I1 and the third current I3 are the DC power supply Vs, the second node N2, the second switch S2, the second inductor L2, the third node N3, and the first It circulates via the inductor L1, the first node N1, the battery 21, and the ground node GND. The first current I1 and the third current I3 charge the battery 21 while storing energy in the first inductor L1 and the second inductor L2 . That is, the energy supplied by the DC power supply Vs is stored in the first inductor L1 and the second inductor L2 during the third period t2-t3 and charges the battery 21 .

Referring to the third period t2-t3 in the graph of the first current I1 and the second current I2 shown in FIG. 7 , the first switch S2 is turned on at a time t2. The current I1 sharply decreases, and the second current I2 sharply rises, so that a portion of the energy stored in the first inductor L1 is transferred to the magnetically coupled second inductor L2. Thereafter, the first current I1 and the second current I2 become equal and increase with the same slope, and energy is stored in the first inductor L1 and the second inductor L2.

The third current I3 circulates through the first node N1 , the battery 21 , the ground node GND, the third diode D3 , and the fourth node N4 . The third inductor L3 emits a portion of the stored energy during the third period t2-t3. The third current I3 transfers energy emitted by the third inductor L3 to the battery 21 to charge the battery 21 . That is, on the other hand, energy is not stored or emitted in the fourth inductor L4 as there is no current flow.

Referring to the third period t2-t3 in the graph of the third current I3 shown in FIG. 7 , the third current I3 decreases in the third current I3 of the second period t1-t2. is reduced to the same slope as the current slope, and the third inductor L3 emits energy.

7 and 11 , the second switch S2 is turned off at the third time t3, and the second switch S2 and the fourth switch S4 are turned off during the fourth period t3-t4. The turned off state is maintained.

11, the first current I1 flowing through the first inductor L1 flows to the battery 21, and the third current I3 flowing through the third inductor L3 is the first node It flows to the battery 21 through (N1).

The first current I1 is circulated through the first inductor L1 , the first node N1 , the battery 21 , the ground node GND, and the first diode D1 . The first inductor L1 emits a portion of the stored energy during the fourth period t3-t4. The battery 21 is charged by receiving the energy emitted by the first inductor L1. The second inductor L2 does not store or emit energy since there is no current flow.

Referring to the fourth period t3-t4 in the graph of the first current I1 and the second current I2 shown in FIG. 7 , the first current I1 at a time t3 when the second switch is turned off. ) sharply increases and the second current I2 sharply decreases to 0, and the energy stored in the second inductor L2 is transferred to the magnetically coupled first inductor L1. After that, the first current I1 is gradually decreased, and the energy stored in the first inductor L1 is released.

The third current I3 is circulated through the third inductor L3, the first node N1, the battery 21, the ground node GND, the third diode D3, and the fourth node N4. . The third inductor L3 emits a portion of the stored energy during the fourth period t3-t4. The battery 21 is charged by receiving the energy emitted by the third inductor L3. The fourth inductor L4 does not store or emit energy as there is no current flow.

Referring to the fourth section t3-t4 in the graph of the third current I3 shown in FIG. 7 , the third current I3 includes the second section t1-t2 and the third section t2-t3. of the third current I3 is reduced to the same slope as the reduced slope, and energy stored in the third inductor L3 is released.

After the bidirectional DC-DC converter 100 operating in the buck mode is stabilized, the first current I1 and the third current I3 have the same value at the start time and end time of the switching period Ts. During the first period t0-t1, the second period t1-t2, and the fourth period t3-t4 in which the energy stored by the first inductor L1 is emitted, the first current I1 has a constant slope , and the first current I1 increases with a constant slope during the third period t2-t3 in which the first inductor L1 receives energy from the DC power source Vs.

Similarly, during the second period t1-t2, the third period t2-t3, and the fourth period t3-t4 in which the energy stored by the third inductor L3 is emitted, the third current I3 is It decreases with a constant slope, and during the first period in which the third inductor L3 receives energy from the DC power source Vs, the third current I3 increases with a constant slope.

12 schematically illustrates an energy storage system and peripheral configuration according to an embodiment.

Referring to FIG. 12 , the energy storage system 1 according to the present embodiment supplies power to the load 4 in connection with the power generation system 2 and the grid system 3 . The energy storage system 1 includes a battery system 20 for storing power and a power conversion system (hereinafter referred to as 'PCS') 10 . The PCS 10 converts the power provided from the power generation system 2 , the grid 3 , and/or the battery system 20 into an appropriate form of power to the load 4 , the battery system 20 and/or the grid. (3) can be supplied.

The power generation system 2 is a system that produces electric power from an energy source. The power generation system 2 may supply power generated by power generation to the energy storage system 1 . The power generation system 2 may include, for example, at least one of a solar power generation system, a wind power generation system, and a tidal power generation system. For example, the power generation system 2 may include all power generation systems that generate power using renewable energy such as solar heat or geothermal heat. The power generation system 2 may configure a large-capacity energy system by arranging a plurality of power generation modules capable of generating power in parallel.

The grid 3 may include a power plant, a substation, a power transmission line, and the like. When the grid 3 is in a steady state, the grid 3 supplies power to the load 4 and/or the battery system 20 , or supplies power from the battery system 20 and/or the power generation system 2 . can receive When the grid 3 is in an abnormal state, power transmission between the grid 3 and the energy storage system 1 is stopped.

The load 4 may consume power produced by the power generation system 2 , power stored in the battery system 20 , and/or power supplied from the grid 3 . Electrical devices of a home or factory in which the energy storage system 1 is installed may be an example of the load 4 .

The energy storage system 1 may store the power generated by the power generation system 2 in the battery system 20 or may supply it to the system 3 . The energy storage system 1 may supply the electric power stored in the battery system 20 to the system 3 , or store the electric power supplied from the system 3 in the battery system 20 . In addition, the energy storage system 1 performs a UPS (Uninterruptible Power Supply) function when the system 3 is in an abnormal state, for example, when a power outage occurs, and the power produced by the power generation system 2 or the battery system 20 ) stored in the load (4) can be supplied.

13 is a block diagram illustrating a schematic configuration of an energy storage system according to an embodiment.

Referring to FIG. 13 , the energy storage system 1 may include a PCS 10 that converts power, a battery system 20 , a first switch 30 , and a second switch 40 . The battery system 20 may include a battery 21 and a battery manager 22 .

The PCS 10 converts the power provided from the power generation system 2 , the grid 3 , and/or the battery system 20 into an appropriate form of power to the load 4 , the battery system 20 and/or the grid. (3) can be supplied. The PCS 10 may include a power converter 11 , a DC link 12 , a bidirectional inverter 13 , a bidirectional DC-DC converter 100 , and an integrated controller 15 .

The power converter 11 may be a power converter connected between the power generation system 2 and the DC link 12 . The power converter 11 may convert the power generated by the power generation system 2 into a DC link voltage and transmit it to the DC link 12 . The power converter 11 may include, for example, a power conversion circuit such as a converter circuit, a rectifier circuit, and the like, depending on the type of the power generation system 2 . When the power generation system 2 generates DC power, the power converter 11 may include a DC-DC converter circuit for converting the DC power generated by the power generation system 2 into another DC power. When the power generation system 2 generates AC power, the power converter 11 may include a rectifying circuit for converting AC power generated by the power generation system 2 into DC power.

When the power generation system 2 is a photovoltaic power generation system, the power converter 11 tracks the maximum power point so as to obtain the maximum power generated by the power generation system 2 according to variations in insolation, temperature, etc. (Maximum Power Point) Tracking) may include an MPPT converter circuit that performs control. When there is no power generated by the power generation system 2 , the operation of the power converter 11 is stopped, so that the power consumed by the power converter 11 can be minimized or reduced.

Due to problems such as an instantaneous voltage drop in the power generation system 2 or grid 3, or a peak load generation in the load 4, the level of the DC link voltage may become unstable. However, the DC link voltage needs to be stabilized for normal operation of the bidirectional DC-DC converter 100 and the bidirectional inverter 13 . The DC link 12 may be connected between the power converter 11 , the bidirectional inverter 13 , and the bidirectional DC-DC converter 100 to keep the DC link voltage constant or substantially constant. DC link 12 may include, for example, a large capacitor. The DC link 12 may include a capacitor connected to the second node N2 of the bidirectional DC-DC converter 100 of FIG. 1 . According to another example, the DC link 12 may be connected between the second node N2 and the ground node GND of the bidirectional DC-DC converter 100 of FIG. 1 . The DC link voltage may be, for example, 400V.

The bidirectional inverter 13 may be a power conversion device connected between the DC link 12 and the first switch 30 . The bidirectional inverter 13 may convert a DC link voltage provided from at least one of the power generation system 2 and the battery system 20 into an AC voltage of the grid 3 and output it. The bidirectional inverter 13 converts the AC voltage provided from the grid 3 into a DC link voltage and outputs it to the DC link 12 in order to store the power of the grid 3 in the battery system 20 in the charging mode. can

The bidirectional inverter 13 may include a filter for removing harmonics from the AC voltage output to the grid 3 . In addition, the bidirectional inverter 13 is a phase locked loop (PLL) for synchronizing the phase of the AC voltage output from the bidirectional inverter 13 and the phase of the AC voltage of the grid 3 in order to suppress or limit the generation of reactive power. circuit may be included. Also, the bidirectional inverter 13 may perform functions such as limiting a voltage fluctuation range, improving a power factor, removing a DC component, protecting or reducing transient phenomena, and the like.

The bidirectional DC-DC converter 100 may be coupled between the DC link 12 and the battery system 20 . The bidirectional DC-DC converter 100 may DC-DC convert power stored in the battery system 20 into a DC link voltage in a discharging mode and output it to the DC link 12 . In addition, the bidirectional DC-DC converter 100 DC-DC converts the DC link voltage of the DC link 12 to a DC voltage of an appropriate voltage level (eg, a charging voltage level required by the battery system 20) in the charging mode. and output to the battery system 20 . When charging or discharging of the battery system 20 is not performed, the operation of the bidirectional DC-DC converter 100 is stopped, so that power consumption may be minimized or reduced.

The integrated controller 15 may monitor the status of the power generation system 2 , the grid 3 , the battery system 20 , and the load 4 . For example, the integrated controller 15 determines whether a power failure has occurred in the system 3, whether power is produced in the power generation system 2, the amount of power produced in the power generation system 2, the state of charge of the battery system 20, It is possible to monitor the power consumption, time, etc. of the load 4 .

The integrated controller 15 includes the power converter 11, the bi-directional inverter 13, the bi-directional DC-DC converter 100, the battery system 20, the first switch 30, and the second according to the monitoring result and a predetermined algorithm. 2 It is possible to control the operation of the switch (40).

The integrated controller 15 may control the first to fourth switches S1 to S4 of the bidirectional DC-DC converter 100 illustrated in FIG. 1 . For example, the integrated controller 15 turns off the bidirectional DC-DC converter 100 so that the first and third switches S1 and S3 alternately turn off each other, and the second and second 4 switches S2 and S4 may be turned off. The integrated controller 15 turns on the bidirectional DC-DC converter 100 so that the bidirectional DC-DC converter 100 operates in a buck mode, the second and fourth switches S2 and S4 alternately turn on each other (interleaved), and the first and third switches (S1, S3) may be turned off.

When a power outage occurs in the system 3 , the integrated controller 15 may control the power stored in the battery system 20 or the power generated in the power generation system 2 to be supplied to the load 4 . In addition, when sufficient power cannot be supplied to the load 4, the integrated controller 15 prioritizes the electrical devices of the load 4 and preferentially applies power to the high-priority electrical devices. It is also possible to control the load 4 to supply. Also, the integrated controller 15 may control charging and discharging of the battery system 20 .

The first switch 30 and the second switch 40 are connected in series between the bidirectional inverter 13 and the grid 3, and perform short-circuit and open operations under the control of the integrated controller 15 to generate a power generation system ( Controls the flow of current between 2) and the grid (3). The short-circuit and open states of the first switch 30 and the second switch 40 may be determined according to the states of the power generation system 2 , the system 3 , and the battery system 20 . Specifically, when power from at least one of the power generation system 2 and the battery system 20 is supplied to the load 4 or power from the grid 3 is supplied to the battery system 20 , the first switch (30) becomes a short circuit state. When power from at least one of the power generation system 2 and the battery system 20 is supplied to the grid 3 or power from the grid 3 is supplied to at least one of the load 4 and the battery system 20 , the second switch 40 is in a short-circuited state.

When a power outage occurs in the system 3 , the second switch 40 is in an open state and the first switch 30 is in a short-circuited state. That is, while supplying power from at least one of the power generation system 2 and the battery system 20 to the load 4 , the power supplied to the load 4 is prevented from leaking to the system 3 . In this way, by operating the energy storage system 1 as a stand alone system, a worker who works on the power line of the system 3 or the like uses the power transmitted from the power generation system 2 or the battery system 20 . To prevent electric shock accidents.

The battery system 20 may receive and store power from at least one of the power generation system 2 and the system 3 , and supply the stored power to at least one of the load 4 and the system 3 . The battery system 20 may be connected to the first node N1 of the bidirectional DC-DC converter 100 of FIG. 1 . The output voltage of the battery system 20 may be, for example, 50V.

The battery system 20 may include a battery 21 including at least one battery cell to store power, and a battery manager 22 to control and protect the battery 21 . The battery manager 22 is connected to the battery 21 and may control the overall operation of the battery system 20 according to a control command from the integrated controller 15 or an internal algorithm. For example, the battery manager 22 may perform an overcharge protection function, an overdischarge protection function, an overcurrent protection function, an overvoltage protection function, an overheat protection function, a cell balancing function, and the like.

The battery manager 22 may obtain the voltage, current, temperature, remaining power, lifespan, and state of charge (SOC) of the battery 21 . For example, the battery manager 22 may measure the cell voltage, current, and temperature of the battery 21 using sensors. The battery manager 22 may calculate the amount of power remaining, the lifespan, and the state of charge of the battery 21 based on the measured cell voltage, current, and temperature. The battery manager 22 may manage the battery 21 based on the measurement result and calculation result, and transmit the measurement result and calculation result to the integrated controller 15 . The battery manager 22 may control charging and discharging operations of the battery 21 according to a charging and discharging control command received from the integrated controller 15 .

The bidirectional DC-DC converter 100 may convert a voltage between the battery system 20 having, for example, an output voltage of 50V and a DC link 12 having, for example, a DC link voltage of 400V. Although the step-up ratio of the bidirectional DC-DC converter 100 is approximately 8 times, according to embodiments of the present invention, control stability can be secured because a control signal having a duty ratio of 80% or less can be used, and the peak voltage By lowering , stable power conversion is possible. In addition, the bidirectional DC-DC converter 100 may operate in a voltage-down buck mode. Accordingly, since the output voltage of the battery system 20 can be lowered, when a small capacity is required, the battery 21 including a small number of battery cells can be used.

The spirit of the present invention should not be limited to the above-described embodiments, and not only the claims described below, but also all scopes equivalent to or changed from these claims, fall within the scope of the spirit of the present invention. will do it

10: power conversion system
11: power converter
12: DC link
13: Bi-directional inverter
15: integrated controller
20: battery system
21: battery
22: battery management unit
100: bidirectional DC-DC converter
121: first tap inductor
L1, L2: first inductor, second inductor
123: second tap inductor
L3, L4: third inductor, fourth inductor
130: capacitor
S1, S2, S3, S4: first switch, second switch, third switch, fourth switch
D1, D2, D3, D4: first diode, second diode, third diode, fourth diode
N1, N2, N3, N4: first node, second node, third node, fourth node
GND: ground node

Claims (14)

A bidirectional DC-DC converter comprising first to fourth nodes and a ground node, comprising:
a first tap inductor including a first inductor between the first node and the third node and a second inductor between the third node and the second node;
a second tap inductor including a third inductor between the first node and the fourth node and a fourth inductor between the fourth node and the second node;
a first switch and a first diode connected in parallel between the third node and a ground node;
a second switch and a second diode connected in parallel between the second inductor and a second node;
a third switch and a third diode connected in parallel between the fourth node and a ground node;
a fourth switch and a fourth diode connected in parallel between the fourth inductor and a second node; and
a capacitor connected between the second node and a ground node; and
The second inductor and the second switch are connected in series between the third node and the second node,
A bidirectional DC-DC converter in which the fourth inductor and the fourth switch are connected in series between the fourth node and the second node. According to claim 1,
When operating in the boost mode, the first switch and the third switches operate alternately (interleaved) with each other, and the second switch and the fourth switches are turned off. 3. The method of claim 2,
When the third switch is turned off, the first switch is turned on,
Bidirectional DC-DC converter, characterized in that when the first switch is turned off, the third switch is turned on. 4. The method of claim 3,
The first tap inductor transfers the stored energy to the second node when the first switch is turned off,
wherein the second tap inductor transfers stored energy to the second node when the third switch is turned off. 4. The method of claim 3,
wherein the first switch is turned on, turned off, and turned off after maintaining the turn on state while the third switch changes to the turn on state, the turn off state, and the turn on state. 3. The method of claim 2,
The bidirectional DC-DC converter, characterized in that the first switch and the third switches are turned on at a duty ratio of 50% or more to less than 80%. 7. The method of claim 6,
Bidirectional DC-DC converter, characterized in that the step-up ratio of the second voltage of the second node to the first voltage of the first node has any one of a step-up ratio of 6 to 12 times. According to claim 1,
When operating in the buck mode, the second and fourth switches operate alternately (interleaved) with each other, and the first and third switches are turned off. 9. The method of claim 8,
When the fourth switch is turned on, the second switch is turned off,
Bidirectional DC-DC converter, characterized in that when the second switch is turned on, the fourth switch is turned off. 10. The method of claim 9,
DC power is connected between the second node and the ground node,
The first tap inductor receives energy from the DC power supply when the second switch is turned on,
The second tap inductor is a bidirectional DC-DC converter, characterized in that when the fourth switch is turned on, the energy is supplied from the DC power source. 10. The method of claim 9,
The second switch is turned off, the turn on, and the turn off state is maintained while the fourth switch changes to the turn off state, and is turned on. 9. The method of claim 8,
wherein the second and fourth switches are turned on with a duty ratio of less than 50%. According to claim 1,
The first tap inductor includes the first inductor and the second inductor having a turns ratio of 1:N,
The bidirectional DC-DC converter increases the turns ratio to decrease the peak current in the bidirectional DC-DC converter. The bidirectional DC-DC converter of any one of claims 1 to 13;
a battery connected between a first node of the bidirectional DC-DC converter and a ground node;
a DC link comprising the capacitor between a second node of the bidirectional DC-DC converter and the ground node;
a power conversion device for converting power between the DC link and at least one of a power generation system, a grid, and a load; and
and a power conversion system including an integrated controller for controlling the bidirectional DC-DC converter and the power conversion device.

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