KR20210096488A - Grid-connected energy storage system - Google Patents

Abstract

The present invention relates to an energy storage system that reduces a ripple component in the system by controlling any two phases of a power switching element in an interleaved manner during a grid-connected operation through a three-phase power switching element. The grid-connected energy storage system according to one embodiment of the present invention comprises: a grid outputting a three-phase AC voltage through a three-phase output terminal; a load connected in parallel to the three-phase output terminal to receive a three-phase AC voltage applied to the three-phase output terminal; a three-phase power switching element converting a DC voltage output from a DC voltage source into a three-phase AC voltage and outputting the three-phase AC voltage to the three-phase output terminal or converting the three-phase AC voltage output from the grid into a DC voltage and providing the DC voltage to the DC voltage source; and a control unit connecting any two phases of the output terminal among the three-phase output terminal and controlling the three-phase power switching element to operate as an interleaved converter.

Description

Grid-connected energy storage system {GRID-CONNECTED ENERGY STORAGE SYSTEM}

The present invention relates to an energy storage system that reduces a ripple component in a system by controlling a power switching element of any two phases in an interleaved manner during a grid-connected operation through a three-phase power switching element.

An energy storage system is a device that stores power supplied from a grid or supplies the stored power to a grid and/or a load. For example, the energy storage system is operated to output constant power to a system and/or a load by adding or subtracting power stored in a DC generator or a battery.

To this end, basically, the energy storage system includes a DC voltage source, a grid, a load, a power converter for converting electric power moving between them, and a controller for controlling the power converter.

Hereinafter, the structure of the conventional energy storage system and its problems will be described with reference to FIGS. 1, 2A, and 2B.

1 is a circuit diagram illustrating a conventional grid-connected energy storage system, and FIGS. 2A and 2B are waveform diagrams for explaining a grid-connected operation of the energy storage system illustrated in FIG. 1 .

Referring to FIG. 1 , the conventional energy storage system 10 includes a DC voltage source (not shown), a DC link capacitor (C _{DC ) for storing a DC voltage (V DC} ) output from the DC voltage source, and a three-phase power switching device (S1). , S1', S2, S2', S3, S3'), the grid connected to each output terminal (L1, L2, N) of the three-phase power switching element (S1, S1', S2, S2', S3, S3') ( V _AC ) and the load (Load; Load 1, Load 2) and each output terminal (L1, L2, N) and the grid ( _VAC ) to selectively connect the cutoff switch (S) is included.

When an abnormality occurs in the grid (V _AC ), the cut-off switch (S) is opened and the three-phase power switching elements (S1, S1', S2, S2', S3, S3') _{convert the DC voltage (V DC} ) to each provided to the load. On the other hand, when the grid ( _VAC ) is in a normal state, the cut-off switch (S) is closed and the three-phase power switching elements (S1, S1', S2, S2', S3, S3') convert the _{DC voltage (V DC ) to} It is provided to the grid (V _AC ) and/or each load, or _{the AC voltage output from the grid (VAC} ) is converted and provided to a DC voltage source.

However, referring to Figure 2a, the conventional energy storage system 10 when operating in conjunction with the _{grid (VAC ) in a normal state, to supply power to the grid (VAC} ) and / or a three-phase power switching element ( S1, S1', S2, S2', S3, S3') of the pair of power switching elements connected to any one of the lag is not operated. More specifically, the energy storage system 10 does not operate the pair of power switching elements S2 and S2' provided in the lag connected to the neutral point N.

Accordingly, referring to FIG. 2B , the AC current i2 is not output from the neutral terminal N and the AC current i1 is output only from one active terminal N1, and the AC current output from the active terminal N1 is outputted. (i1) may include a ripple component according to the power conversion operation of the three-phase power switching elements (S1, S1', S2, S2', S3, S3'). In addition, the current icap output from the DC link capacitor C _DC may also include a ripple component according to the power conversion operation of the three-phase power switching elements S1, S1', S2, S2', S3, S3'. there is.

This ripple component adversely affects the system and the load connected to the system and increases the Total Harmonic Distortion (THD), which lowers the overall system stability.

Accordingly, there is a need for a method for reducing the ripple component, and in particular, a method for reducing the ripple component using a pair of power switching elements not used in the conventional grid-connected operation is required.

An object of the present invention is to provide a grid-connected energy storage system that reduces a ripple component in the system by controlling the power switching elements of any two phases in an interleaved manner during a grid-connected operation through a three-phase power switching element.

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention not mentioned may be understood by the following description, and will be more clearly understood by the examples of the present invention. Moreover, it will be readily apparent that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

The present invention reduces the ripple component in the system by connecting the output terminals of any two phases of the three-phase output terminals during the grid-connected operation and allowing two pairs of power switching elements connected to the output terminals of the two phases to operate as an interleaved converter can do it

The present invention can lower the harmonic distortion in the system by reducing the ripple component in the system by controlling the power switching elements of any two phases in an interleaved manner during grid-connected operation through the three-phase power switching element, and thus the system stability can be improved. can

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

1 is a circuit diagram showing a conventional grid-connected energy storage system.
2A and 2B are waveform diagrams for explaining a grid-connected operation of the energy storage system shown in FIG. 1;
3 is a circuit diagram illustrating an example of a grid-connected energy storage system of the present invention.
4 is a circuit diagram showing another example of the grid-connected energy storage system of the present invention.
5 is a waveform diagram illustrating an operation state of a power switching device controlled in an interleaved manner during a grid-connected operation of the energy storage system of the present invention.
FIG. 6 is a diagram illustrating an enlarged waveform diagram of A shown in FIG. 5 by way of example;
7 is a view for explaining a reduced ripple component when the power switching element operates in an interleaved manner.

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

In this specification, the first, second, etc. are used to describe various components, but these components are not limited by these terms. These terms are only used to distinguish one component from other components, and unless otherwise stated, the first component may be the second component, of course.

In addition, in the present specification, when it is described that a certain element is "connected", "coupled" or "connected" to another element, the elements may be directly connected or connected to each other, but there is another element between each element. It should be understood that elements may be “interposed,” or that each element may be “connected,” “coupled,” or “connected to,” through another element.

Also, as used herein, the singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as "consisting of" or "comprising" should not be construed as necessarily including all of the various components or various steps described in the specification, some of which components or some steps are It should be construed that it may not include, or may further include additional components or steps.

In addition, in the present specification, when "A and / or B" is said, it means A, B or A and B unless otherwise stated, and when said "C to D", it is Unless otherwise specified, it means C or more and D or less

The present invention relates to an energy storage system that reduces a ripple component in a system by controlling a power switching element of any two phases in an interleaved manner during a grid-connected operation through a three-phase power switching element.

Hereinafter, a grid-connected energy storage system (hereinafter referred to as an energy storage system) according to an embodiment of the present invention will be described in detail with reference to the drawings.

3 is a circuit diagram illustrating an example of the grid-connected energy storage system of the present invention, and FIG. 4 is a circuit diagram illustrating another example of the grid-connected energy storage system of the present invention.

5 is a waveform diagram illustrating an operation state of a power switching device controlled in an interleaved manner during a grid-connected operation of the energy storage system of the present invention.

FIG. 6 is a diagram illustrating an enlarged waveform diagram of A shown in FIG. 5 by way of example. In addition, FIG. 7 is a view for explaining a reduced ripple component when the power switching device operates in an interleaved manner.

An energy storage system (ESS, 100) of the present invention is _{a device that stores power supplied from a system (VAC} ) or supplies the stored power to a system ( _VAC ) and/or a load. _{For example, the energy storage system 100 may be operated to output constant power to the grid (V AC} ) and/or a load by adding or subtracting power stored in a DC power generator or a battery.

To this end, the energy storage system 100 includes a DC voltage source (not shown), a grid ( _VAC ), a load (Load), a power converter for converting power moving between them, and a controller (not shown) for controlling the power converter ) may be a system including

Referring to FIG. 3 , the grid V _AC may output a three-phase AC voltage through a three-phase output terminal. Hereinafter, when three phases are divided into three phases for convenience of description, they are expressed as ordinal numbers such as 1st to 3rd. For example, it is assumed that the first to third output terminals are included in the three-phase output terminal.

The load may be connected in parallel to the three-phase output terminal to receive a three-phase AC voltage applied to the three-phase output terminal. The load is a load operated by being applied with an AC voltage, and may be, for example, an induction motor.

The load can be operated by receiving the line voltage applied to the three-phase output terminal. More specifically, the grid ( _VAC ) may output an AC voltage through the first to third output terminals, any two output terminals of the first to third output terminals are live terminals (L1, L2), The other output terminal may be a neutral terminal (N). At this time, the load may operate by being applied with an inter-line voltage between each of the active terminals L1 and L2 and the neutral terminal N.

The magnitude of the line-to-line voltage between each of the active terminals L1 and L2 and the neutral terminal N may be the same or different from each other. _{More specifically, when the grid (VAC} ) connected to the three-phase output terminal is implemented as a single AC voltage source, the magnitude of the line-to-line voltage between each active terminal (L1, L2) and the neutral terminal (N) may be the same. On the other hand, when the grid ( _VAC ) connected to the three-phase output terminal is implemented with a plurality of AC voltage sources, the magnitude of the line voltage between each of the active terminals (L1, L2) and the neutral terminal (N) may be different.

Referring to FIG. 3 as an example, the system ( _VAC ) is connected between the first active terminal (L1) and the neutral terminal (N) of the three-phase output terminal, the first AC voltage source (Vac1) outputting the first AC voltage and , a second AC voltage source Vac2 connected between the second active terminal L2 and the neutral terminal N among the three-phase output terminals to output a second AC voltage. At this time, since the first AC voltage source Vac1 and the second AC voltage source Vac2 independently supply voltage, the magnitude of the first AC voltage and the magnitude of the second AC voltage may be different.

In this structure, the load may operate according to the magnitude of the first AC voltage applied between the first active terminal (L1) and the neutral terminal (N), and between the second active terminal (L2) and the neutral terminal (N). It may operate according to the magnitude of the applied second AC voltage. In addition, the load may operate according to the sum of the magnitude of the first AC voltage applied between the first active terminal L1 and the second active terminal L2 and the magnitude of the second AC voltage.

For example, when the first and second AC voltage sources Vac1 and Vac2 each output 120 [V], the load may operate by receiving 120 [V], or by receiving 240 [V] to operate. may be

Meanwhile, the magnitude of the voltage supplied to the load may be the same or different from each other. More specifically, when a single load is connected to the three-phase output terminal, the magnitude of the AC voltage supplied to the load may be the same. On the other hand, when a plurality of loads are connected to the three-phase output terminal, the magnitude of the AC voltage supplied to each load may be different.

Referring to FIG. 3 as an example, the load is connected between the first active terminal L1 and the neutral terminal N to receive the first AC voltage, the first load (Load 1), and the second active terminal (L2) and a second load (Load 2) connected between the neutral terminal (N) and receiving the second AC voltage. As described above, since the magnitudes of the first AC voltage and the second AC voltage may be different, the magnitudes of the AC voltages provided to each of the loads Load 1 and Load 2 may also be different.

For example, the loads may include first and second loads (Load 1 and Load 2) operating at 120 [V], respectively, and the first and second loads (Load 1 and Load 2) are the first active loads. 120 [V] output between the terminal (L1) and the neutral terminal (N) and between the second active terminal (L2) and the neutral terminal (N) may be respectively supplied to operate. Alternatively, the load may be implemented as a single load operating at 240 [V], in this case, the load is 240 [V] output between the first active terminal (L1) and the second active terminal (L2) It can be supplied and operated.

Referring back to FIG. 3 , the energy storage system 100 may include three-phase power switching devices S1 , S1 ′, S2 , S2 ′, S3 , and S3 ′ as a power converter. The three-phase power switching device may be connected to a DC voltage source _{to convert a DC voltage (V DC} ) output from the DC voltage source into an AC voltage.

More specifically, the three-phase power switching device converts a DC voltage (V _DC ) output from a DC voltage source into a three-phase AC voltage and outputs it to a three-phase output terminal or converts a three-phase AC voltage output from a grid (V _AC ) to a DC voltage can be converted to a DC voltage source.

The DC voltage source may be a battery capable of charging and discharging, or may be a renewable energy source (eg, a solar power module) that produces a _{DC voltage (V DC ).} The three-phase power switching device may be connected to an output terminal of the DC voltage source _{to convert a DC voltage (V DC} ) output from the DC voltage source into an AC voltage.

Meanwhile, as shown in FIG. 3 , the DC voltage source may output _{a DC voltage V DC} of a certain magnitude through the _{DC link capacitor C DC .} Specifically, the DC link capacitor C _DC may be connected in parallel to the output terminal of the DC voltage source _{to store the DC voltage V DC} output from the DC voltage source in a predetermined size. At this time, the three-phase power switching device may convert the DC voltage (V _DC) is stored in the DC link capacitor (C _DC) to a three-phase AC voltage.

The three-phase power switching device may include an upper arm and a lower arm switching device provided as a pair in each of the first to third legs leg1, leg2, and leg3 for power conversion.

Referring to FIG. 3 , the three-phase power switching device may include a first upper arm switching device S1 and a first lower arm switching device S1′ provided as a pair on the first lag. In addition, the three-phase power switching device may include a second upper arm switching device S2 and a second lower arm switching device S2′ provided as a pair on the second lag. In addition, the three-phase power switching element may include a third upper-arm switching element S3 and a third lower-arm switching element S3' provided as a pair on the third lag.

These switching devices may be implemented as devices that are turned on or off according to a control signal provided by a control unit, for example, a metal oxide semiconductor FET (MOSFET), an insulated gate bipolar transistor (IGBT), or the like.

The first upper-arm and first lower-arm switching elements S1, S1' may be connected through a first output terminal, and the second upper-arm and second lower-arm switching elements S2, S2' may be connected through a second output terminal, The third upper-arm and third lower-arm switching elements S3 and S3' may be connected through a third output terminal.

Accordingly, the upper-arm and lower-arm switching elements S1, S1', S2, S2', S3, and S3' provided in each lag control the DC voltage (V _DC ) _{output from the DC link capacitor (C DC ).} The voltage V _DC may be converted into an AC voltage, and the converted AC voltage may be output through each output terminal.

When the AC voltage is normally supplied from the grid (V _AC ) (hereinafter, the grid steady state), the three-phase power switching element may _{convert the DC voltage (V DC} ) into a three-phase AC voltage and output it to the three-phase output terminal. The three-phase AC voltage output to the three-phase output terminal _{may be supplied to the grid (VAC} ) or may be supplied to a load.

Through this process, the power stored in the DC voltage source may be reduced. For example, if the DC voltage source is a battery, the battery may be discharged through the above-described process, and if the DC voltage source is a renewable energy source, power generated from the renewable energy source may be supplied _{to the grid (VAC) through the above-described process.} there is.

Conversely, the three-phase power switching device may _{convert the three-phase AC voltage output from the grid (VAC} ) into a DC voltage and provide it to the DC voltage source. In other words, the three-phase power switching device may _{convert the AC voltage into a DC voltage by inversely converting the DC voltage (V DC} ) into an AC voltage, and may provide the converted DC voltage to a DC voltage source. .

Through this process, the power stored in the DC voltage source may be increased. For example, when the DC voltage source is a battery, the battery may be charged through the above-described process.

According to the power conversion operation of the three-phase power switching device described above, a ripple component may occur in the AC voltage applied to the inside of the system, particularly, the output terminal. This ripple component is therefore adversely affected to a load connected to the grid (V _AC) and the grid (V _AC), the present invention can include output inductors (L1, L2) connected to the output stage for the reduction of the ripple component.

Referring back to FIG. 3 , output terminal inductors L1 and L2 may be provided at at least two output terminals among the three-phase output terminals. For example, the output terminal inductors L1 and L2 may be provided at the first active terminal L1 and the neutral terminal N. Since the AC voltage applied to the second active terminal L2 is determined by the AC voltage applied to the first active terminal L1 and the neutral terminal N, the output terminal is connected to the second active terminal L2 in order to reduce device cost. The inductors L1 and L2 may not be provided.

The three-phase AC voltage may be stabilized by the output terminal inductors L1 and L2 provided at the two output terminals, and the ripple component may be partially reduced due to the improvement of the waveform.

_{On the other hand, when the AC voltage is abnormally supplied from the grid (VAC} ) due to factors such as power failure, surge voltage generation, etc. (hereinafter, grid abnormal state), the energy storage system 100 continues to connect with the _{grid (VAC ).} If so, a system failure may occur.

In order to prevent this, at least two of the three-phase output terminals may be provided with a cut-off switch (S) for cutting off the connection with the _{grid (VAC).}

Referring to FIG. 3 as an example, the cut-off switch S may be provided at the first active end L1 and the second active end L2. When the cut-off switch S provided in each of the active terminals L1 and L2 is opened, no current flows in the first active terminal L1 and the second active terminal L2, and the three-phase power switching element and the grid (V _AC) ) is an open circuit, so no current flows through the neutral terminal (N).

This cut-off switch (S) may be controlled by the control unit. Specifically, the control unit may open the shut-off switch (S) when the state of the system (V _AC) system results (V _AC) monitoring the state of the system is determined as an abnormal state.

When the connection with the grid ( _VAC ) is cut off, only the load is connected to the output terminal, and the three-phase power switching device may discharge and convert power stored in the DC voltage source under the control of the control unit to provide the load to the load. Accordingly, the load can operate normally even in a system abnormal state.

On the other hand, as described above, the DC voltage source constituting the energy storage system 100 is charged and discharged in the normal state of the system.

In order to suppress the generation of such a ripple component, the controller may connect the output terminals of any two phases of the three-phase output terminals in a system normal state, and control the three-phase power switching device to operate as an interleaved converter.

As previously described with reference to FIGS. 1, 2A and 2B , the conventional energy storage system 10 is a lag (specifically, a lag connected to the neutral point N) when operating in conjunction with the _{grid (VAC).} ) does not use the switching element provided in the On the other hand, the energy storage system 100 of the present invention connects the output terminals of any two phases among the three-phase output terminals when operating in conjunction _{with the grid (VAC) in the grid normal state, and then the switching elements S1 and S1 provided in all lags.} ', S2, S2', S3, S3'), it is possible to control the three-phase power switching device to operate in an interleaved manner.

Meanwhile, the above-described output terminal inductors L1 and L2 may be provided at any one of the first and second active terminals L1 and L2 constituting the three-phase output terminal and the neutral terminal N, respectively. At this time, when controlling the three-phase power switching device in an interleaved manner, the controller may connect two output terminals provided with the output terminal inductors L1 and L2.

Referring to FIG. 3 as an example, the output terminal inductors L1 and L2 may be provided in the first active terminal L1 and the neutral terminal N, respectively, and in this case, the controller controls the first active terminal L1 and the neutral terminal. After connecting terminal (N), it is possible to control the three-phase power switching device to operate in an interleaved manner.

Accordingly, after the ripple component is reduced through the interleaved method to be described later, _{the AC voltage output to the grid V AC} is additionally stabilized by the output terminal inductors L1 and L2, so that the ripple component included in the AC voltage is further reduced can be

The control unit may control the relay R to selectively connect the two output terminals.

To this end, the first output terminal of the three-phase output terminal may be provided with a relay R for connecting the first output _{terminal and the system V AC or connecting the first output terminal and the second output terminal.}

Referring to FIG. 3 , the first output terminal may be the neutral terminal (N) and the second output terminal may be the first active terminal (L1). A single relay (R) can be controlled in two states. In either state, the relay (R) _{disconnects the neutral point (N) and the grid (V AC} ) and makes the neutral point (N) first active. Can be connected to stage (L1). In another state, the relay (R) may disconnect the neutral terminal (N) and the first active terminal (L1) and connect the neutral terminal (N) to the system ( _VAC ).

In the system abnormal state, the control unit may open the cut-off switch (S) and control the relay (R) to _{connect the neutral terminal (N) to the system (VAC} ). Then, the control unit may control the three-phase power switching element to provide the power stored in the DC voltage source to the load.

On the other hand, in the system normal state, the control unit may close the cut-off switch (S) and control the relay (R) to connect the neutral terminal (N) to the first active terminal (L1). Subsequently, the controller may control the three-phase power switching element to charge the DC voltage source with power or discharge the power stored in the DC voltage source.

Meanwhile, the control unit may control the plurality of relays R1 and R2 to selectively connect the two output terminals.

For this purpose, between the first output end and a system (V _AC) between there may be provided with a first relay (R1) connecting the first output terminal and a system (V _AC), the first output terminal and second output terminal, the first and A second relay R2 for connecting the second output terminal may be provided.

Referring to FIG. 4 , the first output terminal may be the neutral terminal (N) and the second output terminal may be the first active terminal (L1). The first relay R1 may be controlled in a closed state and an open state. In the closed state, the first relay R1 may _{connect the neutral point N and the grid (V AC} ), and in the open state, the first relay R1 (R1) can cut the connection between the neutral point (N) and the grid ( _{VAC ).}

The second relay R2 may also be controlled in a closed state and an open state. In the closed state, the second relay R2 may connect the neutral terminal N and the first output terminal, and in the open state, the second relay R2 ) may block the connection between the neutral terminal (N) and the first output terminal.

In the system abnormal state, the control unit opens the cut-off switch (S), controls the first relay (R1) to the closed state, and controls the second relay (R2) to the open state, whereby the neutral terminal (N) and the first active terminal (L1) can be disconnected and the neutral point (N) and grid ( _VAC ) can be connected. Then, the control unit may control the three-phase power switching element to provide the power stored in the DC voltage source to the load.

On the other hand, in the system normal state, the control unit closes the cut-off switch (S), controls the first relay (R1) to the open state, and controls the second relay (R2) to the closed state, thereby reducing the neutral point (N) and the system ( V _AC ) may be separated and the neutral terminal (N) and the first active terminal (L1) may be connected. Subsequently, the controller may control the three-phase power switching element to charge the DC voltage source with power or discharge the power stored in the DC voltage source.

Hereinafter, a method for the control unit to control the three-phase power switching device in an interleaved manner in a system steady state will be described.

The controller may control the three-phase power switching device to operate as an interleaved converter by controlling the two pairs of power switching devices that output an AC voltage to each of the output terminals of the two connected phases to operate with a phase difference of half a cycle.

Meanwhile, for convenience of explanation, it is assumed that the output terminals of two phases connected among the three-phase output terminals are the neutral terminal N and the first active terminal L1 as shown in FIGS. 3 and 4 .

Referring to FIG. 5 , the controller may operate the first phase-arm switching element S1 according to the phase of the AC voltage output from the _{grid VAC.} Specifically, the control member the magnitude of the AC voltage output from the grid (V _AC) can be turned on and controls the first Sangam switching element (S1) when positive, the magnitude of the AC voltage output from the grid (V _AC) negative When the first phase-arm switching element (S1) can be controlled to turn off.

On the other hand, since the first lower-arm switching element S1' operates complementary to the first upper-arm switching element S1, when the first upper-arm switching element S1 is turned on, the first lower-arm switching element S1' is turned on is turned off, and when the first upper-arm switching element S1 is turned off, the first lower-arm switching element S1' may be turned on.

While performing a control operation for the first upper-arm switching element (S1), the control unit is the second upper-arm and second lower-arm switching elements (S2, S2') for outputting an AC voltage to the neutral terminal (N), the first active terminal The third upper-arm and third lower-arm switching elements S3 and S3' outputting the AC voltage to L1 may be controlled to be turned on and off with a phase difference of half a cycle.

In other words, the controller may delay the phase of the AC voltage output from the third lag by half a cycle slower than the phase of the AC voltage output from the second lag.

Referring to FIG. 6 , the controller controls the duty ratios of the second and third upper-arm switching elements S2 and S3 according to the target output while controlling the second and third upper-arm switching elements S2 and S3. can be operated according to the reference cycle.

In this case, the controller may control the second phase-arm switching element S2 and the third phase-arm switching element S3 to operate with a phase difference of half a cycle. For example, the controller may delay the operating phase of the third upper-arm switching element S3 by 180, which is a half of the operating phase of the second upper-arm switching element S2, for example, half of 360 degrees.

Referring to FIGS. 3 and 7 together, a first AC current iL1 may flow through the first output terminal and a second AC current iL2 may flow through the neutral terminal N according to the above-described control. Meanwhile, by the interleaved control, the ripple component included in the first AC current iL1 and the ripple component included in the second AC current iL2 may have the same magnitude and opposite sign.

In this so when such an interleaved control is to be performed first output terminal and a neutral stage (N) is connected by a relay (R), the grid (V _AC) current (hereinafter, the grid current (igrid)) to be outputted to the first It may be the sum of the alternating current iL1 and the second alternating current iL2.

As described above, since the first AC current iL1 and the second AC current iL2 each include ripple components having the same magnitude and opposite sign, when these two are added together, the first AC current iL1 and the second AC current iL1 Ripple components included in the alternating current iL2 may cancel each other out.

Accordingly, as shown in FIG. 7 , the grid current igrid in which the first alternating current iL1 and the second alternating current iL2 are added may include only a ripple component of a very low level.

When the ripple component included in the grid current (grid) is reduced, the Total Harmonic Distortion (THD) in the system can be lowered, so that the system stability can be improved.

In addition, a ripple component included in the current icap output from _{the DC link capacitor C DC} of FIG. 3 may also be reduced by the above-described interleaved control. This may increase the lifetime of the DC link capacitor (C _DC ), thereby prolonging the life of the system.

As described above, the present invention has been described with reference to the illustrated drawings, but the present invention is not limited by the embodiments and drawings disclosed in the present specification. It is obvious that variations can be made. In addition, although the effects according to the configuration of the present invention are not explicitly described and described while describing the embodiments of the present invention, it is natural that the effects predictable by the configuration should also be recognized.

Claims (11)

a system that outputs a three-phase AC voltage through a three-phase output terminal;
a load connected in parallel to the three-phase output terminal to receive a three-phase AC voltage applied to the three-phase output terminal;
a three-phase power switching device that converts a DC voltage output from a DC voltage source into a three-phase AC voltage and outputs it to the three-phase output terminal or converts a three-phase AC voltage output from the system into a DC voltage and provides the converted DC voltage to the DC voltage source; and
and a control unit that connects the output terminals of any two phases of the three-phase output terminals and controls the three-phase power switching device to operate as an interleaved converter.
Grid-tied energy storage system.
According to claim 1,
The system is
a first AC voltage source connected between a first active terminal and a neutral terminal of the three-phase output terminal to output a first AC voltage;
and a second AC voltage source connected between a second active terminal of the three-phase output terminal and the neutral terminal to output a second AC voltage.
A grid-connected energy storage system.
3. The method of claim 2,
the load is
a first load connected between the first active terminal and the neutral terminal to receive the first AC voltage;
and a second load connected between the second active terminal and the neutral terminal to receive the second AC voltage.
A grid-connected energy storage system.
According to claim 1,
The DC voltage output from the DC voltage source is stored in a DC link capacitor connected in parallel with the DC voltage source,
The three-phase power switching device converts the DC voltage stored in the DC link capacitor into a three-phase AC voltage.
A grid-connected energy storage system.
According to claim 1,
At least two of the three-phase output terminals are provided with an output terminal inductor.
A grid-connected energy storage system.
According to claim 1,
At least two of the three-phase output terminals are provided with a cut-off switch for cutting off the connection with the system.
A grid-connected energy storage system.
According to claim 1,
An output terminal inductor is provided at any one of the first and second active terminals and the neutral terminal constituting the three-phase output terminal,
The control unit connects the two output terminals provided with the output terminal inductor.
A grid-connected energy storage system.
According to claim 1,
The three-phase power switching device includes an upper arm and a lower arm switching device provided as a pair in each of the first to third lags,
The upper-arm and lower-arm switching elements provided as a pair in each of the first to third lags output alternating voltages of the first to third phases, respectively.
A grid-connected energy storage system.
According to claim 1,
A relay connecting the first output terminal and the system or connecting the first output terminal and the second output terminal is provided at a first output terminal of the three-phase output terminal;
The control unit controls the relay to connect the first and second output terminals
A grid-connected energy storage system.
According to claim 1,
The three-phase output stage includes a first and a second output stage,
A first relay connecting the first output terminal and the system is provided between the first output terminal and the system,
A second relay connecting the first and second output terminals is provided between the first output terminal and the second output terminal;
The control unit blocks the connection between the first output terminal and the system by controlling the first and second relays, and connects the first and second output terminals
A grid-connected energy storage system.
According to claim 1,
the control unit
Controls the two pairs of power switching devices that output AC voltage to each of the output terminals of the two connected phases to operate with a phase difference of half a cycle.
A grid-connected energy storage system.

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