KR102272675B1 - Photovoltaic module - Google Patents

Abstract

The present invention relates to a solar module. The photovoltaic module according to an embodiment of the present invention, the photovoltaic module includes a solar cell module including a plurality of solar cells, is attached to the rear surface of the solar cell module, and converts DC power supplied from the solar cell module into AC power. Containing a junction box having a power conversion module for converting and outputting, the power conversion module, at least one bypass diode receiving the DC power from the solar cell module, and converting the DC power from the bypass diode, , a converter unit including at least three interleaving converters, a capacitor for storing a voltage output from the converter unit, and an inverter unit for outputting AC power using the voltage stored in the capacitor. Thereby, it becomes possible to output an AC power supply stably.

Description

Photovoltaic module

The present invention relates to a solar module, and more particularly, to a solar module capable of stably outputting AC power.

Recently, as existing energy resources such as oil and coal are expected to be depleted, interest in alternative energy to replace them is increasing. Among them, a solar cell is spotlighted as a next-generation battery that directly converts solar energy into electrical energy using a semiconductor device.

Meanwhile, the photovoltaic module refers to a state in which solar cells for photovoltaic power generation are connected in series or in parallel, and the photovoltaic module may include a junction box for collecting electricity generated by the solar cells.

An object of the present invention is to provide a solar module capable of stably outputting AC power.

A photovoltaic module according to an embodiment of the present invention for achieving the above object is a solar cell module including a plurality of solar cells, is attached to the rear surface of the solar cell module, and converts DC power supplied from the solar cell module to AC power. and a junction box having a power conversion module that converts and outputs to , wherein the power conversion module includes at least one bypass diode that receives DC power from the solar cell module, and converts the DC power from the bypass diode into power. and a converter unit including at least three interleaving converters, a capacitor for storing a voltage output from the converter unit, and an inverter unit for outputting AC power using the voltage stored in the capacitor.

According to an embodiment of the present invention, in the solar module, a junction box including a converter unit including at least three interleaving converters and a power conversion module including an inverter unit is attached to the rear surface of the solar cell module. Accordingly, it is possible to stably output AC power directly from the solar module.

In particular, since the converter unit includes at least three interleaving converters, it is possible to reduce the size of circuit elements, in particular, an inductor and a transformer, in the converter unit while outputting high-output AC power. Accordingly, the thickness of the junction box becomes smaller than the thickness of the frame of the solar cell module.

On the other hand, by the interleaving operation of at least three interleaving converters, the ripple (ripple) of the input current and the output current of the converter unit is reduced, therefore, there is an advantage that the capacity and size of the circuit element in the power conversion module is reduced.

Meanwhile, according to an embodiment of the present invention, the converter unit outputs the pseudo DC power, and for this purpose, the switching frequency of the interleaving converter may be varied. Accordingly, it is possible to output a pseudo DC power supply closer to a sine wave.

Meanwhile, the interleaving converter may vary the switching frequency of the switching element in response to the duty change of the switching element. In particular, it is possible to operate the switching element in crm mode. Accordingly, zero voltage switching of the switching element is possible, and the power conversion efficiency of the converter unit is improved.

On the other hand, it is possible to vary the phase difference for the operation period of at least three interleaving converters, in this case, it is possible to prevent an instantaneous output decrease due to the switching frequency change.

In addition, by sequentially restoring the phase difference to the reference phase difference after the switching frequency is varied, it is possible to prevent output current distortion and also to prevent output degradation of the interleaving converter.

1 is an example of a configuration diagram of a solar system according to an embodiment of the present invention.
2 is a front view of a solar module according to an embodiment of the present invention.
3 is a rear view of the solar module of FIG. 2 .
4 is an exploded perspective view of the solar cell module of FIG. 2 .
FIG. 5 is an example of a bypass diode configuration of the solar module of FIG. 2 .
6 is an example of a block diagram of a power conversion module inside the junction box of FIG.
7A is an example of an internal circuit diagram of the power conversion module of FIG.
7A is an example of an internal circuit diagram of the power conversion module of FIG.
Figure 7b is another example of the internal circuit diagram of the power conversion module of Figure 6.
8A and 8B are diagrams for explaining an operating method of the power conversion module of FIG. 6 .
9A to 9B are diagrams referenced to explain the operation of the tap inductor converter of FIG. 7A.
10A and 10B are diagrams referenced for explaining that the converter unit of FIG. 6 outputs a pseudo DC power using the input power.
11 to 12 are diagrams referenced to explain a switching frequency variation according to a switching mode of a switching element.
13 illustrates a case in which the switching frequency is variable and the phase difference is fixed in three interleaving converters.
14 illustrates a case in which the switching frequency and the phase difference are varied in three interleaving converters.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

The suffixes "module" and "part" for the components used in the following description are given simply in consideration of the ease of writing the present specification, and do not give a particularly important meaning or role by themselves. Accordingly, the terms “module” and “unit” may be used interchangeably.

1 is an example of a configuration diagram of a solar system according to an embodiment of the present invention.

Referring to the drawings, the photovoltaic system 10 of FIG. 1 may include a plurality of photovoltaic modules 50a, 50b, ..., 50n.

Each solar module (50a, 50b, ..., 50n) is provided with a plurality of solar cells, each solar cell module (100a, 1000b, ..., 100n) for generating DC power, and each solar cell A junction box 200a that is attached to the back of the modules 100a, 1000b, ..., 100n and converts DC power from each solar cell module 100a, 1000b, ..., 100n into AC power and outputs it , 200b, ..., 200n) may be provided.

At this time, the junction box (200a, 200b, ..., 200n) is a power conversion module (FIG. 6) that converts DC power from each solar cell module (100a, 1000b, ..., 100n) into AC power and outputs it. 700) can be provided.

The power conversion module (700 in FIG. 6) may include, on one circuit board, bypass diodes (Da, Db, Dc), a converter unit (530 in FIG. 6), and an inverter unit (540 in FIG. 6) have. Such a power conversion module (700 in FIG. 6) may be called a micro-inverter.

On the other hand, in the embodiment of the present invention, a plurality of solar modules (50a, 50b, ..., 50n), each solar cell module (100a, 1000b, ..., 100n) and the junction box (200a, 200b) , ..., 200n) can directly output AC power, so it may be called a solar AC module.

On the other hand, according to this configuration, by attaching a micro-inverter that outputs AC power to each solar cell module 100a, 1000b, ..., 100n, even if the output of any one of the solar cell modules is low, a plurality of The photovoltaic modules 50a, 50b, ..., 50n are connected in parallel to each other, and it is possible to supply AC power generated by the grid (grid).

In addition, unlike the string method in which a plurality of photovoltaic modules (50a, 50b, ..., 50n) are connected in series with each other, they generate and output AC power independently of each other and are connected in parallel, so that the AC power of other solar modules Regardless of the output, it is possible to stably output AC power to the system.

Meanwhile, in an embodiment of the present invention, the converter unit ( 530 in FIG. 6 ) may include a plurality of interleaving converters so that an AC power output of approximately 290W to 330W is possible. In particular, it is preferable that at least three converters perform the interleaving operation.

In particular, since the volume of the inductor and the transformer used in the converter unit ( 530 of FIG. 6 ) is large, when the size of the inductor and the transformer is reduced, the capacity may be reduced, so that desired power may not be output.

For example, when using two interleaving converters, for the above-described 290W to 330W AC power output, a considerable size of an inductor, a transformer, and the like are required. As the size of the inductor and the transformer increases, the thickness of the junction box should be increased, and the thickness of the junction box may be greater than the thickness of the frame of the solar cell module 20 .

In order to solve this point, it is assumed that three or more interleaving converters are used in the embodiment of the present invention. According to this, for the above-mentioned 290W to 330W AC power output, a smaller, sized inductor, a transformer, etc. can be used, and accordingly, the thickness of the junction box is smaller than the thickness of the frame 105 of the solar cell module. can get This will be described in detail below with reference to FIG. 6 .

2 is a front view of a solar module according to an embodiment of the present invention, FIG. 3 is a rear view of the solar module of FIG. 2, and FIG. 4 is an exploded perspective view of the solar cell module of FIG.

2 to 4 , the solar module 50 according to the embodiment of the present invention includes a solar cell module 100 and a junction box 200 positioned on one surface of the solar cell module 100 . . In addition, the solar module 50 may further include a heat dissipation member (not shown) disposed between the solar cell module 100 and the junction box 200 .

First, the solar cell module 100 may include a plurality of solar cells 130 . In addition, the first sealing material 120 and the second sealing material 150 located on the lower surface and upper surface of the plurality of solar cells 130 , the rear substrate 110 and the second sealing material located on the lower surface of the first sealing material 120 . A front substrate 160 positioned on the upper surface of the sealing material 150 may be further included.

First, the solar cell 130 is a semiconductor device that converts solar energy into electrical energy, and includes a silicon solar cell, a compound semiconductor solar cell, and a stacked solar cell. It may be a tandem solar cell, a dye-sensitized or CdTe, CIGS-type solar cell.

The solar cell 130 is formed of a light-receiving surface on which sunlight is incident and a rear surface opposite to the light-receiving surface. For example, the solar cell 130 includes a silicon substrate of a first conductivity type, a second conductivity type semiconductor layer formed on the silicon substrate and having a conductivity type opposite to the first conductivity type, and a second conductivity type semiconductor layer. an anti-reflection film formed on the second conductivity-type semiconductor layer and including at least one opening exposing a partial surface of the semiconductor layer, and a front electrode contacting the partial surface of the second conductivity type semiconductor layer exposed through the at least one opening; , may include a rear electrode formed on the rear surface of the silicon substrate.

Each solar cell 130 may be electrically connected in series, parallel, or series-parallel. Specifically, the plurality of solar cells 130 may be electrically connected by the ribbon 133 . The ribbon 133 may be bonded to a front electrode formed on the light receiving surface of the solar cell 130 and a rear electrode current collecting electrode formed on the rear surface of another adjacent solar cell 130 .

In the drawing, the ribbon 133 is formed in two rows, and the solar cells 130 are connected in a line by the ribbon 133 to illustrate that the solar cell string 140 is formed. As a result, six strings 140a, 140b, 140c, 140d, 140e, and 140f are formed, and each string includes 10 solar cells. Contrary to the drawings, various modifications are possible.

Meanwhile, each solar cell string may be electrically connected by a bus ribbon. FIG. 2 shows the first solar cell string 140a and the second solar cell string 140b by bus ribbons 145a, 145c, and 145e disposed under the solar cell module 100, respectively, according to the third embodiment. The battery string 140c and the fourth solar cell string 140d are electrically connected to the fifth solar cell string 140e and the sixth solar cell string 140f. In addition, in FIG. 2 , the second solar cell string 140b and the third solar cell string 140c are respectively formed by the bus ribbons 145b and 145d disposed on the solar cell module 100 according to the fourth aspect. The battery string 140d and the fifth solar cell string 140e are electrically connected to each other.

Meanwhile, the ribbon connected to the first string, the bus ribbons 145b and 145d, and the ribbon connected to the fourth string are electrically connected to the first to fourth conductive lines 135a, 135b, 135c, and 135d, respectively. , first to fourth conductive lines 135a, 135b, 135c, and 135d are connected to bypass diodes (Da, Db, and Dc in FIG. 6 ) in the junction box 200 disposed on the rear surface of the solar cell module 100 , and connected In the drawing, the first to fourth conductive lines 135a , 135b , 135c , and 135d extend to the rear surface of the solar cell module 100 through the opening formed on the solar cell module 100 .

On the other hand, the junction box 200 is preferably disposed more adjacent to the end of the conductive line extends from both ends of the solar cell module 100 .

In FIGS. 2 and 3 , the first to fourth conductive lines 135a , 135b , 135c and 135d extend from the upper portion of the solar cell module 100 to the rear surface of the solar cell module 100 , so the junction box 200 ) exemplifies that the solar cell module 100 is positioned at the top of the rear surface. Thereby, the length of the conductive line can be reduced, so that power loss can be reduced.

The rear substrate 110, as a back sheet, functions to waterproof, insulate, and block ultraviolet rays, and may be of a Tedlar/PET/Tedlar (TPT) type, but is not limited thereto. In addition, although the rear substrate 110 is illustrated in a rectangular shape in FIG. 4 , it may be manufactured in various shapes such as a circular shape or a semi-circular shape depending on the environment in which the solar cell module 100 is installed.

On the other hand, on the rear substrate 110, the first sealing material 120 may be attached to the same size as the rear substrate 110, and a plurality of solar cells 130 on the first sealing material 120 to generate several heat. They may be located adjacent to each other to achieve this.

The second encapsulant 150 may be positioned on the solar cell 130 and bonded to the first encapsulant 120 by lamination.

Here, the first sealing material 120 and the second sealing material 150 allow each element of the solar cell to be chemically combined. Various examples of the first sealing material 120 and the second sealing material 150 are possible, such as an ethylene vinyl acetate (EVA) film.

Meanwhile, the front substrate 160 is positioned on the second sealing material 150 to transmit sunlight, and is preferably made of tempered glass to protect the solar cell 130 from external impact. In addition, in order to prevent reflection of sunlight and increase the transmittance of sunlight, it is more preferable that the glass is low iron tempered glass containing less iron.

The junction box 200 is attached to the rear surface of the solar cell module 100 , and may convert power using DC power supplied from the solar cell module 100 . Specifically, the junction box 200 may include a power conversion module 700 that converts DC power into AC power and outputs the converted power.

The power conversion module 700 may include bypass diodes Da, Db, Dc, a converter unit (530 in FIG. 6 ), and an inverter unit (540 in FIG. 6 ) on one circuit board. Such a power conversion module 700 may be referred to as a micro-inverter.

Meanwhile, in the junction box 200 , in order to prevent moisture penetration of circuit elements, a coating for preventing moisture penetration may be performed on the inside of the junction box using silicon or the like.

On the other hand, an opening (not shown) is formed in the junction box 200 so that the above-described first to fourth conductive lines 135a, 135b, 135c and 135d bypass diodes (Da, Db, and Dc) can be connected.

On the other hand, one side of the junction box 200, the AC output cable 38 for outputting the power-converted AC power to the outside may be connected.

Meanwhile, the solar module 50 may include a frame 105 for fixing the outer part of the solar cell module 10 . Meanwhile, it is preferable that the thickness of the junction box 200 is smaller than the thickness of the frame 105 so that the junction box 200 does not protrude from the rear surface.

FIG. 5 is an example of a bypass diode configuration of the solar module of FIG. 2 .

Referring to the drawings, the bypass diodes Da, Db, and Dc may be connected to the six solar cell strings 140a, 140b, 140c, 140d, 140e, and 140f. Specifically, the first bypass diode Da is connected between the first solar cell string and the first bus ribbon 145a, and is formed in the first solar cell string 140a or the second solar cell string 140b. When the reverse voltage is generated, the first solar cell string 140a and the second solar cell string 140b are bypassed.

For example, when a voltage of about 0.6V generated in a normal solar cell is generated, the potential of the cathode electrode is about 12V (=0.6V*20) compared to the potential of the anode electrode of the first bypass diode Da become higher That is, the first bypass diode Da performs a normal operation rather than a bypass.

On the other hand, when a hot spot occurs due to shading or foreign matter being attached to any solar cell of the first solar cell string 140a, the voltage generated in any one solar cell is about 0.6V. A reverse voltage (approximately -15V) is generated, not the voltage of Accordingly, the potential of the anode electrode of the first bypass diode Da is approximately 15V higher than that of the cathode electrode, and the first bypass diode Da performs a bypass operation. Accordingly, the voltage generated by the solar cells in the first solar cell string 140a and the second solar cell string 140b is not supplied to the junction box 200 . In this way, when a reverse voltage generated in some solar cells is generated, by bypassing, it is possible to prevent the destruction of the solar cell or the like. In addition, it is possible to supply the generated DC power except for the hotspot area.

Next, the second bypass diode Db is connected between the first bus ribbon 145a and the second bus ribbon 145b in the third solar cell string 140c or the fourth solar cell string 140d. When the reverse voltage is generated, the third solar cell string 140c and the fourth solar cell string 140d are bypassed.

Next, the third bypass diode Dc is connected between the first solar cell string and the first bus ribbon 145a, and is reversed in the first solar cell string 140a or the second solar cell string 140b. When the voltage is generated, the first solar cell string and the second solar cell string are bypassed.

Meanwhile, unlike FIG. 5 , it is also possible to connect six bypass diodes to correspond to six solar cell strings, and various other modifications are possible.

6 is an example of a block diagram of a power conversion module inside the junction box of FIG.

Referring to the drawings, the power conversion module 700 inside the junction box may include a bypass diode unit 510 , a converter unit 530 , a capacitor C1 , an inverter unit 540 , and a control unit 550 . have.

The bypass diode unit 510 includes bypass diodes Dc, Db, Da respectively disposed between the first to fourth conductive lines 135a, 135b, 135c, and 135d of the solar cell module 100 . can be provided. At this time, the number of bypass diodes is one or more, and it is preferable that one is smaller than the number of conductive lines.

The bypass diodes Dc, Db, Da are, from the solar cell module 50, in particular, from the first to fourth conductive lines 135a, 135b, 135c, and 135d in the solar cell module 50, solar direct current. receive power input. In addition, the bypass diodes Dc, Db, and Da can be bypassed when a reverse voltage is generated from the DC power source from at least one of the first to fourth conductive lines 135a, 135b, 135c, and 135d. have.

Meanwhile, the input power Vpv passing through the bypass diode unit 510 is input to the converter unit 530 .

The converter unit 530 converts the input power Vpv output from the bypass diode unit 510 . Meanwhile, the converter unit 530 may be referred to as a first power conversion unit.

For example, the converter unit 530 may convert the DC input power Vpv into a pseudo DC voltage as shown in FIG. 8A . Accordingly, the pseudo DC power may be stored in the capacitor C1. Meanwhile, both ends of the dc terminal capacitor C1 may be referred to as a dc terminal, and the capacitor C1 may be referred to as a dc terminal capacitor.

As another example, as shown in FIG. 8A , the converter unit 530 may boost the DC input power Vpv and convert it into DC power. Accordingly, the boosted DC power may be stored in the dc terminal capacitor C1.

The inverter unit 540 may convert the DC power stored in the DC terminal capacitor C1 into AC power. Meanwhile, the inverter unit 540 may be referred to as a second power conversion unit.

For example, the inverter unit 540 may convert the pseudo dc voltage converted by the converter unit 530 into AC power.

As another example, the inverter unit 540 may convert the DC power boosted by the converter unit 530 into AC power.

Meanwhile, the converter unit 530 preferably includes a plurality of interleaving converters for pseudo dc voltage conversion or step-up and forward power conversion.

In particular, in the embodiment of the present invention, it is assumed that the converter unit 530 includes three or more interleaving converters.

The figure illustrates that n converters 610a, 610b, ... 610n are connected in parallel to each other. The energy conversion capacities of the n converters 610a, 610b, ... 610n may be the same.

The current by the DC input power supply (Vpv) decreases to 1/N in the n converters 610a, 610b, ... 610n, and at the output terminals of the n converters 610a, 610b, ... 610n, The output currents of each converter are summed into one.

Meanwhile, the n converters 610a, 610b, ... 610n perform an interleaving operation, and the current phase of each of the n converters 610a, 610b, ... 610n is +(360°/N) compared to the reference phase. ), -(360°/N) or close to it while maintaining a phase delay.

As such, when the n converters are interleaved, the ripple of the input current and the output current of the converter unit 530 is reduced, and thus, the capacity and size of the circuit elements in the power conversion module 700 are reduced. There are advantages.

Meanwhile, as described above, when two interleaving converters are used, for the above-described 290W to 330W AC power output, a considerable size of an inductor, a transformer, and the like are required. As the size of the inductor and the transformer increases, the thickness of the junction box should be increased, and the thickness of the junction box may be greater than the thickness of the frame 105 of the solar cell module.

In order to solve this point, it is assumed that three or more interleaving converters are used in the embodiment of the present invention. According to this, for the above-mentioned 290W to 330W AC power output, a smaller, sized inductor, a transformer, etc. can be used, and accordingly, the thickness of the junction box is smaller than the thickness of the frame 105 of the solar cell module. can get

Meanwhile, as the interleaving converter, a tap inductor converter, a flyback converter, or the like may be used.

7A is an example of an internal circuit diagram of the power conversion module of FIG.

Referring to the drawings, the power conversion module 700 is a bypass diode unit 510 , a converter unit 530 , a dc stage capacitor C1 , an inverter unit 540 , a control unit 550 , and a filter unit 560 . ) may be included.

7A illustrates a tapped inductor converter as an interleaving converter. In the drawing, it is exemplified that the converter unit 530 includes first to third tap inductor converters 611a, 611b, ... 611c.

The bypass diode unit 510 includes first to fourth conductive lines 135a, 135b, 135c, and 135d respectively disposed between the a node, the b node, the c node, and the d node, respectively. and a third bypass diode Da, Db, and Dc.

The converter unit 530 may perform power conversion by using the DC power Vpv output from the bypass diode unit 510 .

In particular, the first tap inductor converter to the third tap inductor converter 611a, 611b, ... 611c respectively output the DC power converted by the interleaving operation to the dc terminal capacitor C1.

Among them, the first tap inductor converter 611a is connected to the tap inductor T1, the switching element S1 connected between the tap inductor T1 and the ground terminal, and the output terminal of the tap inductor, a diode performing one-way conduction. (D1). On the other hand, between the output terminal of the diode D1, that is, the cathode and the ground terminal, the dc terminal capacitor C1 is connected.

Specifically, the switching element S1 may be connected between the tap of the tap inductor T and the ground terminal. And, the output terminal (secondary side) of the tap inductor T is connected to the anode of the diode D1, and between the cathode of the diode D1 and the ground terminal, the dc terminal capacitor C1 is connected. do.

Meanwhile, the primary side and the secondary side of the tap inductor T have opposite polarities. Meanwhile, the tap inductor T may be referred to as a switching transformer.

Meanwhile, the primary side and the secondary side of the tap inductor T are connected to each other as shown in the drawing. Accordingly, the tapped inductor converter may be a non-isolated type converter.

On the other hand, when the three tap inductor converters 611a, 611b, and 611c are connected in parallel as shown in the figure and driven in an interleaving method, the input current components are branched in parallel, so each tap inductor converter 611a, The ripple of the current component output through 611b and 611c is reduced.

On the other hand, each of the tap inductor converters 611a, 611b, and 611c can operate adaptively in response to the power requirement of the output AC power.

For example, when the power requirement is approximately 90W to 130W, only the first converter 611a operates, or when the power requirement is approximately 190W to 230W, only the first and second converters 611a, 611b operate, or When the required value is approximately 290W to 330W, all of the first to third interleaving converters 611a, 611b, and 611c may operate. That is, each of the tap inductor converters 611a, 611b, and 611c may selectively operate. Such a selective operation may be controlled by the controller 550 .

The inverter unit 540 converts the DC power level converted by the converter unit 530 into AC power. In the drawing, a full-bridge inverter is illustrated. That is, each of the upper-arm switching elements (Sa, Sb) and the lower-arm switching elements (S'a, S'b) connected in series with each other becomes a pair, and a total of two pairs of upper and lower arm switching elements are parallel to each other (Sa&S'a, Sb&S'b). A diode is connected in antiparallel to each of the switching elements Sa, S'a, Sb, and S'b.

The switching elements in the inverter unit 540 are turned on/off based on the inverter switching control signal from the control unit 550 . Thereby, the AC power supply which has a predetermined frequency comes to be output. Preferably, it has a frequency equal to the alternating frequency of the grid (approximately 60 Hz or 50 Hz).

The filter unit 560 performs lowpass filtering in order to smooth the AC power output from the inverter unit 540 . To this end, in the drawings, the inductors Lf1 and Lf2 are exemplified, but various examples are possible.

On the other hand, the converter input current detection unit (A) senses the input current (ic1) input to the converter unit (530), the converter input voltage detection unit (B), the input voltage ( vc1) is detected. The sensed input current ic1 and input voltage vc1 may be input to the controller 550 .

On the other hand, the converter output current detection unit (C), the output current (ic2) output from the converter unit (530), that is, the dc terminal current is sensed, the converter output voltage detection unit (D), the converter unit (530) The output voltage vc2, that is, the dc terminal voltage is sensed. The sensed output current ic2 and output voltage vc2 may be input to the controller 550 .

On the other hand, the inverter output current detection unit (E) detects the current (ic3) output from the inverter unit (540), the inverter output voltage detection unit (F), the voltage (vc3) output from the inverter unit (540) to detect The sensed current ic3 and voltage vc3 are input to the controller 550 .

Meanwhile, the control unit 550 may output a control signal for controlling the switching element S1 of the converter unit 530 of FIG. 7 . In particular, the control unit 550, the sensed input current (ic1), input voltage (vc1), output current (ic2), output voltage (vc2), output current (ic3), or at least one of the output voltage (vc3) Based on this, the turn-on timing signal of the switching element S1 in the converter unit 530 may be output.

Meanwhile, the control unit 550 may output an inverter control signal for controlling each of the switching elements Sa, S'a, Sb, and S'b of the inverter unit 540 . In particular, the control unit 550, the sensed input current (ic1), input voltage (vc1), output current (ic2), output voltage (vc2), output current (ic3), or at least one of the output voltage (vc3) Based on this, the turn-on timing signal of each of the switching elements Sa, S'a, Sb, and S'b of the inverter unit 540 may be output.

Meanwhile, the control unit 550 may control the converter unit 530 to calculate a maximum power point for the solar cell module 100 and, accordingly, output a DC power corresponding to the maximum power.

Figure 7b is another example of the internal circuit diagram of the power conversion module of Figure 6.

The power conversion module 700 of FIG. 7b is the same as the power conversion module 700 of FIG. 7a , a bypass diode unit 510 , a converter unit 530 , a dc terminal capacitor C1, an inverter unit 540 . , a control unit 550 , and a filter unit 560 may be included.

However, FIG. 7b illustrates a flyback converter as an interleaving converter in the converter unit 530 . In the figure, the converter unit 530 illustrates that the first flyback converter to the third flyback converter (612a, 612b, ... 612c) is provided.

In particular, the first flyback converter to the third flyback converter (612a, 612b, ... 612c) is, unlike the tap inductor converter of the non-isolated type, as an insulating type, by the interleaving operation, respectively, the converted DC power output to the dc terminal capacitor (C1).

Of these, the first flyback converter (612a) is connected to the secondary side of the transformer (T11), the switching element (S11) connected between the primary side and the ground terminal of the transformer (T11), the transformer (T11), one-way conduction and a diode D11 that performs On the other hand, between the output terminal of the diode D11, that is, the cathode and the ground terminal, the dc terminal capacitor C1 is connected. Meanwhile, the primary side and the secondary side of the transformer T11 have opposite polarities.

8A and 8B are diagrams illustrating an operation method of the power conversion module of FIG. 6 .

First, referring to FIG. 8A , the converter unit 530 of the power conversion module 700 according to an embodiment of the present invention converts DC power from the solar cell module 100 into pseudo DC voltage. can be converted

As shown in Fig. 7a, when the converter unit 530 is a tap inductor converter, or when the converter unit 530 is a flyback converter as shown in Fig. 7b, by switching on/off of the switching element S1 or S11, full-wave rectification is performed. It can be converted to a pseudo dc voltage, having the same envelope as the DC power supply. Accordingly, the pseudo DC power may be stored in the capacitor C1.

Meanwhile, the inverter 540 receives a pseudo dc voltage, performs a switching operation, and outputs it as an AC power. Specifically, a pseudo dc voltage having the same envelope as the full-wave rectified DC power may be converted into AC power having + and - and output. In particular, it can be output by converting the AC power corresponding to the system frequency.

Next, referring to FIG. 8B , the converter unit 530 of the power conversion module 700 according to an embodiment of the present invention converts the DC power from the solar cell module 100 to a level, and specifically boosts the voltage, It can be converted to a boosted DC power supply.

As shown in Fig. 7a, when the converter unit 530 is a tap inductor converter or, as shown in Fig. 7b, the converter unit 530 is a flyback converter, by switching on/off of the switching element S1 or S11, the DC power supply ( Vp) can be converted into a boosted DC power supply. Accordingly, the boosted DC power may be stored in the capacitor C1.

The inverter 540 receives the boosted DC power, performs a switching operation, and outputs the AC power. In particular, it can be output by converting the AC power corresponding to the system frequency.

9A to 9B are diagrams referenced to explain the operation of the tap inductor converter of FIG. 7A.

Briefly describing the operation of the first tap inductor converter 611a, when the switching element S1 is turned on, as shown in FIG. 9A , the input voltage Vpv, the primary side of the tap inductor T1, and A closed loop is formed through the switching element S1, and the first current I1 flows through the closed loop. At this time, since the secondary side of the tap inductor T1 has a polarity opposite to that of the primary side, the diode D1 does not conduct and is turned off. Accordingly, energy by the input voltage Ppv is stored in the primary side of the tap inductor T1.

Next, when the switching element S1 is turned off, as shown in FIG. 9B , the input voltage Vpv, the primary side and the secondary side of the tap inductor T1, and the diode D1, and the capacitor C1 A closed loop is formed through the , and the second current I2 flows through the closed loop. That is, since the secondary side of the tap inductor T1 has the opposite polarity to the primary side, the diode D1 conducts. Accordingly, the input voltage Ppv and energy stored in the primary and secondary sides of the tap inductor T1 may be stored in the capacitor C1 through the diode D1.

As described above, the converter unit 530 can output a pseudo DC power supply or a high-efficiency, high-voltage DC power supply by using the input voltage Ppv and energy stored in the primary side and the secondary side of the tap inductor T1. .

10A and 10B are diagrams referenced for explaining that the converter unit of FIG. 6 outputs a pseudo DC power using the input power.

Referring to FIGS. 6 and 10A , the first to third interleaving converters 610a , 610b , and 610c in the converter unit 530 use a DC input power source Vpv to output pseudo DC power.

Specifically, the converter unit 530 outputs a pseudo DC power having a peak value of approximately 330V using DC power of approximately 32V to 36V from the solar cell module 100 .

To this end, the controller 550 determines the duty of the switching elements of the first to third interleaving converters 610a, 610b, and 610c based on the detected input power Vpv and the detected output power Vdc. decide

In particular, as the input voltage Vpv decreases, the duty of the switching elements of the first to third interleaving converters 610a, 610b, and 610c increases. As the input voltage Vpv increases, the duty of the switching elements decreases. .

On the other hand, as the target output power Vdc is lower, the duty of the switching elements of the first to third interleaving converters 610a, 610b, and 610c is reduced. As the target output power Vdc is higher, the duty of the switching elements is reduced. is getting bigger For example, when the target output power Vdc has a peak value of approximately 330V, the duty of the switching element may be greatest.

Fig. 10A exemplifies a pseudo DC power supply waveform Vslv output by such a duty variable, and this pseudo DC power supply waveform exemplifies following a target sine waveform Vsin.

Meanwhile, in the present invention, the switching frequency of the converter unit 530 is varied so that the pseudo DC power supply waveform Vslo more accurately follows the full-wave rectification waveform Vsin.

As shown in FIG. 10B , when the switching frequency of the converter unit 530 is fixed, the error ΔE2 between the pseudo DC power supply waveform Vslf and the target sine waveform Vsin is the converter unit 530 in FIG. 10A . It becomes larger than the error ΔE1 between the pseudo DC power supply waveform Vslv and the target sine waveform Vsin when the switching frequency of is changed.

In the present invention, in order to reduce such an error, the switching frequency of the converter unit 530 is varied. That is, the switching frequencies of the switching elements of the first to third interleaving converters 610a, 610b, and 610c are varied.

As the change rate of the target sine waveform Vsin increases, the controller 550 may control the switching frequency of the converter 530 to increase and the change rate of the target sine waveform Vsin to decrease.

10A illustrates that the switching period is set to Ta in the rising section of the target sinusoidal waveform Vsin, and the switching period is set to Tb smaller than Ta in the peak section of the target sinusoidal waveform Vsin. That is, the switching frequency corresponding to the switching period Ta is higher than the switching frequency corresponding to the switching period Tb. Thereby, the error ?E1 between the pseudo DC power supply waveform Vslv and the target sine waveform Vsin can be reduced.

On the other hand, it is also possible to describe the switching frequency variation of FIG. 10A as a switching mode technique of a switching device. For this, refer to FIGS. 11 to 12 .

11 to 12 are diagrams referenced to explain a switching frequency variation according to a switching mode of a switching element.

First, FIG. 11A illustrates an example of a duty waveform diagram of a switching element of an interleaving converter. Referring to the drawing, in a first switching period Tf1, a switching element is turned on for a first duty1, and then turned off, during a second duty2 within a second switching period Tf2. The switching element is turned on, and then turned off. In the drawing, it is exemplified that the first duty (duty1) is greater than the second duty (duty2).

Meanwhile, FIG. 11( a ) illustrates that the switching cycle of the interleaving converter is fixed and DCM (Discontinuous Conduction Mode) is applied as the switching mode.

When the switching period of the interleaving converter is fixed and dcm is applied as the switching mode, a current waveform Idcm flowing through the switching element as shown in FIG. 11B may be exemplified. As the switching element is turned on, the current flowing through the switching element increases, and as the switching element is turned off, the current decreases.

11C illustrates an actual current waveform flowing through the switching element of the interleaving converter according to dcm, and FIG. 11D illustrates the switching voltage across the switching element of the interleaving converter according to dcm.

Meanwhile, after the switching element is turned off and before the next switching period is performed, a resonance period 1105 in the interleaving converter may occur. At this time, when the switching element is operated by dcm, a section 1107 in which the switching voltage across the switching element does not become 0 occurs. Accordingly, since zero voltage switching (ZVS) for the switching element is not performed, the efficiency of the interleaving converter is deteriorated.

In the present invention, in order to solve this point, a critical conduction mode (CRM) mode, not dcm, is used as the switching mode. CRM may also be referred to as a BCM (boundary conduction mode) mode or a TM (transition mode) mode.

CRM means a mode in which a switching cycle starts whenever the current flowing through the switching element becomes 0 after the switching element of the interleaving converter is turned off. Accordingly, in CRM, the switching period may be varied according to the duty of the switching period.

12A illustrates an example of a duty waveform diagram of a switching element of an interleaving converter. Referring to the drawing, in the first switching period Tfa, the switching element is turned on for a first duty 1, thereafter turned off, and during the second duty 2 within the second switching period Tfb. The switching element is turned on, and then turned off. In the drawing, it is exemplified that the first duty (duty1) is greater than the second duty (duty2).

Meanwhile, FIG. 12( a ) illustrates that CRM having a variable switching frequency is applied to the switching mode as the switching period of the interleaving converter is varied according to the variation of the duty.

As the switching mode, when CRM having a variable switching frequency is applied, a current waveform Icrm flowing through the switching element may be exemplified as shown in FIG. 12B . As the switching element is turned on, the current flowing through the switching element increases, and as the switching element is turned off, the current decreases. And, when the current flowing through the switching element becomes 0, that is, when there is a zero crossing, a new switching period starts.

Fig. 12(c) illustrates an actual current waveform flowing through the switching element of the interleaving converter according to crm, and Fig. 12(d) illustrates the switching voltage across the switching element of the interleaving converter according to crm.

Meanwhile, after the switching element is turned off, a resonance period 1105 in the interleaving converter may occur. At this time, when the switching element is operated by crm, the time when the current of the switching element becomes 0 is determined, that is, at the time of zero crossing, the switching element is activated despite the resonance period 1105 being generated. can turn on. That is, a new switching period may be started. Accordingly, zero voltage switching (ZVS) can be performed on the switching element, and the efficiency of the interleaving converter is improved.

Accordingly, in the present invention, the switching frequency of the switching element of the interleaving converter is varied based on crm.

Meanwhile, as shown in FIG. 6 , when three interleaving converters 610a, 610b, and 610c are used, the first to third interleaving converters 610a, 610b, and 610c operate with a phase difference, respectively.

At this time, in a state in which the switching frequency variable is applied, for the operation period of the first to third interleaving converters 610a, 610b, and 610c, when a constant phase difference, for example, 120° is set, the switching period becomes In this case, there may be a problem in that the output power is lowered. This will be described with reference to FIGS. 13 and 14 .

13 illustrates a case in which the switching frequency is variable and the phase difference is fixed in three interleaving converters 610a, 610b, and 610c.

Referring to the drawing, it can be seen that the switching period is fixed to 3Tv from time 0 to 9Tv, and the phase difference between the phases of the three interleaving converters 610a, 610b, and 610c (phase a, phase b, phase c) is Tv. have.

At the next time point 9Tv, it is exemplified that the switching period is variable, so that the switching period is increased three times to 9Tv. In this case, the first interleaving converter operates during the 3TV period after 3Tv compared to the previous switching period, but the second interleaving converter considers the variable duty (3Tv) of the first interleaving converter, compared to the previous switching period, After 5Tv, it operates during the 3TV section. The third interleaving converter is also operated during the 3TV period after 7Tv compared to the previous switching period in consideration of the variable duty (3Tv) of the second interleaving converter.

At this time, the phase difference between the first interleaving converter to the third interleaving converter is fixed at 120 degrees, respectively, despite the change in the switching period. That is, after the first interleaving converter operates, the second interleaving converter and the third interleaving converter operate after the 3TV period and after the 6TV period, respectively.

In the switching period variable sections 1310 and 1320 , the power output by the second interleaving converter and the third interleaving converter is reduced compared to the first interleaving converter. Accordingly, the output current or output voltage of the converter unit 530 is momentarily decreased.

In order to solve this problem, in the embodiment of the present invention, when the switching period is changed in the plurality of interleaving converters, in order to solve the output imbalance between the interleaving converters, the phases for the operation sections of the plurality of interleaving converters are varied. This will be described with reference to FIG. 14 .

14 illustrates a case in which the switching frequency and the phase difference are varied in three interleaving converters 610a, 610b, and 610c.

Referring to the drawing, it can be seen that the switching period is fixed to 3Tv from time 0 to 9Tv, and the phase difference between the phases of the three interleaving converters 610a, 610b, and 610c (phase a, phase b, phase c) is Tv. have.

Next, it is exemplified that at the time point 9Tv, the switching period is changed, so that the switching period is increased three times to 9Tv. In this case, the first interleaving converter operates for a 3TV period after 3Tv compared to the previous switching period, and in the switching period variable period 1410, the second interleaving converter 3Tv after the switching period variable time of 9Tv, It operates during the 3TV period, and the third interleaving converter may operate during the 3TV period 6Tv later than the 9Tv, which is the switching period variable timing.

That is, unlike FIG. 13 , the controller 550 varies the phase difference between the first interleaving converter to the third interleaving converter in response to the changed period. According to the drawing, the phase difference between the first interleaving converter and the second interleaving converter and the phase difference between the second interleaving converter and the third interleaving converter vary from 120 degrees to 40 degrees.

When the switching period is increased, the controller 550 may change the phase so that the phase difference between the interleaving converters is reduced. Similarly, when the switching period is reduced, the phase may be varied so that the phase difference between each interleaving converter increases, for example, from 120 degrees to 130 degrees, or the like.

Meanwhile, when the switching period is increased, the controller 550 may change the phase so that a region in which the phases of the operation sections between the interleaving converters overlap occurs, particularly to increase. The figure illustrates that the operation period between the first interleaving converter and the second interleaving converter overlaps during a period of approximately 2TV.

On the other hand, after the switching period variable, at the time point 18Tv, the first interleaving converter operates for 3TV period compared to the previous switching period, after 9Tv, but the second interleaving converter, compared to the previous switching period, after 9.1Tv, 3TV period is operated during the period, and the third interleaving converter may also operate during the 3TV period after 9.1Tv compared to the previous switching period.

After the variable period, the controller 550 may sequentially vary the phase difference so that the phase difference in each converter approaches the reference phase difference. According to the figure, after the time point 18Tv, it can be seen that the phase difference between the first interleaving converter and the second interleaving converter and the phase difference between the second interleaving converter and the third interleaving converter increase from 40 degrees to approximately 41 degrees. have.

In this way, by sequentially bringing the phase difference closer to the original reference phase difference of 120 degrees again, current distortion can be prevented, and the above-described output degradation of the second interleaving converter and the third interleaving converter can also be prevented. .

On the other hand, this phase change is effective only when at least three interleaving converters are performed, and when two interleaving converters are used, it is preferable to have a fixed phase of 180 degrees as shown in FIG. 12 .

On the other hand, in FIGS. 10A to 14 , the switching frequency variable and the phase variable are applicable to the converter unit 530 . In particular, as shown in FIG. 7A , the converter unit 530 is a tap inductor converter, or as shown in FIG. 7B . Likewise, it is applicable when the converter unit 530 is a flyback converter.

In the solar module according to the present invention, the configuration and method of the embodiments described above are not limitedly applicable, but all or part of each embodiment is selectively combined so that various modifications can be made. may be configured.

In addition, although preferred embodiments of the present invention have been illustrated and described above, the present invention is not limited to the specific embodiments described above, and the technical field to which the present invention belongs without departing from the gist of the present invention as claimed in the claims Various modifications are possible by those of ordinary skill in the art, and these modifications should not be individually understood from the technical spirit or prospect of the present invention.

Claims (16)

a solar cell module including a plurality of solar cells;
and a junction box attached to the rear surface of the solar cell module and having a power conversion module that converts DC power supplied from the solar cell module to AC power and outputs it;
The power conversion module,
at least one bypass diode receiving the DC power from the solar cell module;
a converter unit that converts the DC power from the bypass diode into power and includes at least three interleaving converters;
a capacitor for storing the voltage output from the converter unit;
an inverter unit for outputting the AC power by using the voltage stored in the capacitor;
a control unit for controlling the operation of the converter unit and the inverter unit;
The control unit is
varying the switching period of the at least three interleaving converters,
In response to the change in the switching period, the phase difference for the operation period between the at least three interleaving converters is varied,
When the switching period is changed and the switching period is increased, the phase difference for the operation period between the at least three interleaving converters is controlled to decrease,
After the increase of the switching period, the phase difference for the operation period between the at least three interleaving converters, so as to reach a reference phase difference, the solar module, characterized in that the control so that the phase difference is sequentially increased. delete According to claim 1,
The power conversion module,
an input voltage detection unit detecting an input voltage input to the converter unit;
an input current detection unit detecting an input current input to the converter unit;
a dc terminal voltage detection unit detecting a voltage input to the capacitor;
Further comprising; an output voltage detection unit for detecting the output voltage output from the inverter unit;
The control unit is
Controlling the switching operation of the converter unit based on the detected input voltage, input current, and dc terminal voltage, and controlling the switching operation of the inverter unit based on the detected dc terminal voltage and output voltage Solar modules. According to claim 1,
The converter unit,
power conversion of the DC power from the bypass diode to output a pseudo DC power;
The inverter unit,
A photovoltaic module, characterized in that the pseudo DC power is converted into power to output the AC power. According to claim 1,
The power conversion module,
The photovoltaic module further comprising; a filter unit for filtering and outputting the AC power from the inverter unit. delete According to claim 1,
The control unit is
The photovoltaic module, characterized in that controlling the switching frequency of the at least three interleaving converters to increase as the waveform change rate of the target sine wave with respect to the pseudo DC power output from the converter unit increases. According to claim 1,
The control unit is
After the switching element of the interleaving converter is turned on and off, when the current or voltage flowing through the switching element becomes zero crossing, the switching element is turned on again. delete delete According to claim 1,
The control unit is
After the switching period is varied, the phase difference for the operation period between the at least three interleaving converters is varied so that the phase difference for the operation period between the at least three interleaving converters approaches the reference phase difference sequentially solar module. According to claim 1,
The control unit is
When the switching period is increased, the photovoltaic module, characterized in that increasing the overlap area of the operation period between the at least three interleaving converters. According to claim 1,
The solar cell module,
and a frame for fixing the outer part of the solar cell module,
The thickness of the junction box is a solar module, characterized in that smaller than the thickness of the frame. According to claim 1,
The control unit is
Solar module, characterized in that selectively operating at least one of the at least three interleaving converters. According to claim 1,
The interleaving converter,
Solar module comprising a tap inductor converter. According to claim 1,
The interleaving converter,
Solar module comprising a flyback converter.

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