KR20150085413A - Photovoltaic module - Google Patents

Abstract

The present invention relates to a photovoltaic module. According to an embodiment of the present invention, the photovoltaic module includes a solar cell module equipped with a plurality of solar cells; a junction box installed in a rear of the solar cell module to convert a DC power supplied from the solar cell module to an AC power; and a power conversion module composed of at least one bypass diode which receives DC power from the solar cell module; a converter unit comprising at least three interleaving converters which converts DC power from the bypass diode; a capacitor which stores the output power from the converter; and an inverter which outputs the AC power using a voltage stored in the capacitor. Therefore, a reliable AC power can be outputted.

Description

{PHOTOVOLTAIC MODULE}

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

With the recent depletion of existing energy sources such as oil and coal, interest in alternative energy to replace them is increasing. Among them, solar cells are attracting attention as a next-generation battery that converts solar energy directly into electrical energy using semiconductor devices.

On the other hand, the photovoltaic module means that solar cells for solar power generation are connected in series or parallel, and the photovoltaic module can include a junction box for collecting the electricity produced by the solar cell.

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

According to an aspect of the present invention, there is provided a solar module including: a solar cell module including a plurality of solar cells; a solar cell module mounted on a rear surface of the solar cell module, The power conversion module includes at least one bypass diode for receiving a DC power from the solar cell module, and a power conversion module for converting the DC power from the bypass diode into a power conversion A converter unit including at least three interleaved converters, a capacitor for storing a voltage output from the converter unit, and an inverter unit for outputting AC power using a voltage stored in the capacitor.

According to the embodiment of the present invention, the solar module is attached to the back surface of the solar cell module, the junction box including the power conversion module including the converter portion including the at least three interleaved converters and the inverter portion. As a result, it is possible to stably output the AC power directly from the solar module.

Particularly, since the converter section includes at least three interleaved converters, it is possible to reduce the size of the circuit elements in the converter section, particularly, the inductor and the transformer while outputting the 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, the interleaving operation of at least three interleaving converters reduces the ripple of the input current and the output current of the converter section, thereby reducing the capacity and size of the circuit elements in the power conversion module.

Meanwhile, according to the embodiment of the present invention, the converter unit outputs pseudo DC power, and for this, the switching frequency of the interleaving converter can be varied. As a result, it is possible to output a pseudo DC power source closer to a sine wave.

On the other hand, the interleaving converter can vary the switching frequency of the switching element in accordance with the duty of the switching element. In particular, the switching element can be operated in the crm mode. According to this, the zero voltage switching to the switching element becomes possible, and the power conversion efficiency of the converter part is improved.

On the other hand, it is possible to vary the phase difference with respect to the operation period of at least three interleaved converters. In this case, it is possible to prevent instantaneous output degradation due to the variable switching frequency.

By sequentially restoring the phase difference to the reference phase difference after the switching frequency variable, the output current distortion can be prevented and the output of the interleaving converter can be prevented from being lowered.

1 is an example of a configuration diagram of a solar photovoltaic 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.
5 is an example of a bypass diode configuration of the solar module of FIG.
FIG. 6 is an example of a block diagram of the power conversion module in the junction box of FIG. 2. 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.
7B is another example of the internal circuit diagram of the power conversion module of FIG.
8A and 8B are diagrams illustrating an operation method of the power conversion module of FIG.
Figs. 9A to 9B are views for explaining the operation of the tapped inductor converter of Fig. 7A.
FIGS. 10A and 10B are diagrams for explaining output of a pseudo direct current power source using an input power source in the converter unit of FIG. 6;
11 to 12 are diagrams referred to explain the switching frequency variation according to the switching mode of the switching element.
Fig. 13 illustrates a case where the switching frequency is variable and the phase difference is fixed in three interleaved converters.
Fig. 14 illustrates a case where the switching frequency is variable and the phase difference is variable in three interleaved converters.

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

The suffix "module" and " part "for components used in the following description are given merely for convenience of description, and do not give special significance or role in themselves. Accordingly, the terms "module" and "part" may be used interchangeably.

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

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

Each of the solar cell modules 50a, 50b, ..., 50n includes a plurality of solar cells, and each of the solar cell modules 100a, 1000b, ..., 100n that generates a DC power, The junction box 200a (100a, 1000b, ..., 100n) is attached to the back surface of the modules 100a, 1000b, ..., 100n and converts direct current power from each of the solar cell modules 100a, , 200b, ..., 200n.

At this time, the junction boxes 200a, 200b, ..., 200n include a power conversion module (see FIG. 6 (a)) for converting DC power from each of the solar cell modules 100a, 1000b, Of 700).

The power conversion module (700 of FIG. 6) may include bypass diodes (Da, Db, Dc), a converter section (530 of FIG. 6), and an inverter section (540 of FIG. 6) have. Such a power conversion module (700 of FIG. 6) may be called a microinverter.

The solar cell modules 100a, 1000b, ..., 100n and the junction boxes 200a, 200b, ..., 100n are connected to the plurality of solar modules 50a, 50b, ..., 50n in the embodiment of the present invention, , ..., 200n), it can be called a solar photovoltaic module.

According to this configuration, by attaching a micro inverter for outputting AC power to each of the solar cell modules 100a, 1000b, ..., 100n, even if the output of any one of the solar cell modules is lowered, The photovoltaic modules 50a, 50b, ..., 50n are connected in parallel to each other to supply AC power generated by the grid (grid).

Unlike the string type in which a plurality of solar modules 50a, 50b, ..., 50n are connected in series, AC power is generated and output independently of each other, and is connected in parallel. Therefore, The AC power can be output to the system stably regardless of the output.

On the other hand, in the 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 290 W to 330 W is possible. In particular, it is desirable that at least three converters perform an interleaving operation.

Particularly, since the inductors and transformers used in the converter unit (530 of FIG. 6) are large in volume, when the size of the inductor, the transformer, and the like is reduced, the capacity becomes small, and desired power may not be output.

For example, in the case of using two interleaved converters, a size of an inductor of a considerable size, a transformer or the like is required for the AC power output of 290 W to 330 W described above. As the size of the inductor, the transformer, and the like increases, the thickness of the junction box must be increased, and the thickness of the junction box may be larger than the thickness of the frame of the solar cell module 20.

To solve this problem, in the embodiment of the present invention, three or more interleaving converters are used. According to this, a small-sized inductor, a transformer, or the like can be used for the AC power output of 290 W to 330 W. Thus, when the junction box is smaller in thickness than the frame 105 of the solar cell module . This will be described in detail with reference to FIG. 6 and the following figures.

FIG. 2 is a front view of the solar module according to the 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 module of FIG.

2 to 4, a solar module 50 according to an embodiment of the present invention includes a solar cell module 100 and a junction box 200 located on one side of the solar cell module 100 . The solar module 50 may further include a heat dissipating 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. The first sealing material 120 and the second sealing material 150 located on the lower surface and the upper surface of the plurality of solar cells 130 and the rear substrate 110 and the second sealing material 120 located on the lower surfaces of the first sealing material 120, And may further include a front substrate 160 positioned on the top surface of the sealing member 150.

First, the solar cell 130 is a semiconductor device that converts solar energy into electrical energy. The solar cell 130 includes a silicon solar cell, a compound semiconductor solar cell, A tandem solar cell, a dye-sensitized solar cell, or a CdTe or CIGS type solar cell.

The solar cell 130 is formed of a light receiving surface on which solar light 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 that of the first conductivity type, An antireflection film formed on the second conductive type semiconductor layer and having at least one opening exposing a part of the surface of the second conductive type semiconductor layer; And 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, a plurality of solar cells 130 can be electrically connected by a ribbon 133. [ The ribbon 133 may be bonded to the front electrode formed on the light receiving surface of the solar cell 130 and the rear electrode collecting electrode formed on the rear surface of another adjacent solar cell 130. [

In the figure, it is illustrated that the ribbon 133 is formed in two lines, and the solar cell 130 is connected in series by the ribbon 133 to form the solar cell string 140. By this, six strings 140a, 140b, 140c, 140d, 140e and 140f are formed, and each string includes ten solar cells. Unlike the drawings, various modifications are possible.

On the other hand, each solar cell string can be electrically connected by a bus ribbon. 2 is a sectional view showing the first solar cell string 140a and the second solar cell string 140b by the bus ribbons 145a, 145c and 145e disposed at the lower part of the solar cell module 100, The battery string 140c and the fourth solar cell string 140d illustrate that the fifth solar cell string 140e and the sixth solar cell string 140f are electrically connected. 2 shows the second solar cell string 140b and the third solar cell string 140c respectively by the bus ribbons 145b and 145d disposed on the upper part of the solar cell module 100, And that the battery string 140d and the fifth solar cell string 140e are electrically connected.

On the other hand, 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 through fourth conductive lines 135a, 135b, 135c, and 135d, respectively The 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 arranged on the back surface of the solar cell module 100, Respectively. In the drawing, the first through fourth conductive lines 135a, 135b, 135c, and 135d extend through the openings formed on the solar cell module 100 to the back surface of the solar cell module 100. FIG.

It is preferable that the junction box 200 is disposed closer to an end of the solar cell module 100 where the conductive lines extend.

2 and 3, since the first to fourth conductive lines 135a, 135b, 135c, and 135d extend from the top of the solar cell module 100 to the back surface of the solar cell module 100, ) Is located at the upper part of the back surface of the solar cell module 100. FIG. Thereby, the length of the conductive line can be reduced, and the power loss can be reduced.

The back substrate 110 may be, but is not limited to, a TPT (Tedlar / PET / Tedlar) type having a waterproof, insulating and ultraviolet shielding function as a back sheet. Although the rear substrate 110 is shown as a rectangular shape in FIG. 4, the rear substrate 110 may be formed in various shapes such as a circular shape and a semicircular shape according to the environment in which the solar cell module 100 is installed.

The first sealing member 120 may be attached to the rear substrate 110 to have the same size as the rear substrate 110 and a plurality of solar cells 130 may be formed on the first sealing member 120 And can be positioned adjacent to each other so as to achieve the same.

The second sealing member 150 may be positioned on the solar cell 130 and may be laminated to the first sealing member 120.

Here, the first sealant 120 and the second sealant 150 allow each element of the solar cell to chemically bond. The first sealing material 120 and the second sealing material 150 can be various examples such as an ethylene vinyl acetate (EVA) film.

On the other hand, the front substrate 160 is preferably placed on the second sealing material 150 so as to transmit sunlight, and is preferably made of tempered glass in order to protect the solar cell 130 from an external impact or the like. Further, it is more preferable to use a low-iron-content tempered glass containing a small amount of iron in order to prevent the reflection of sunlight and increase the transmittance of sunlight.

The junction box 200 is mounted on the back surface of the solar cell module 100 and can be power-converted using the DC power supplied from the solar cell module 100. Specifically, the junction box 200 may include a power conversion module 700 that converts a DC power source to an AC power source and outputs the AC power.

The power conversion module 700 may include bypass diodes Da, Db, and Dc, a converter unit 530, and an inverter unit 540 on one circuit board. The power conversion module 700 may be called a microinverter.

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

An opening (not shown) is formed in the junction box 200 so that the first to fourth conductive lines 135a, 135b, 135c and 135d are connected to bypass diodes (Da, Db, Dc).

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

Meanwhile, the solar module 50 may include a frame 105 for fixing the outer frame of the solar cell module 10. On the other hand, 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 back surface.

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

Referring to the drawings, bypass diodes Da, Db, and Dc may be connected corresponding to 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 connected to 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 approximately 0.6 V generated in a normal solar cell is generated, the potential of the cathode electrode is approximately 12 V (= 0.6 V * 20), as compared with the potential of the anode electrode of the first bypass diode Da Lt; / RTI > That is, the first bypass diode Da operates normally, not bypass.

On the other hand, when a hot spot occurs due to shading or foreign matter adhering to any solar cell of the first solar cell string 140a, the voltage generated in any one solar cell is approximately 0.6V (About -15 V), rather than a voltage of about < / RTI > Accordingly, the potential of the anode electrode of the first bypass diode Da becomes higher by about 15 V than that of the cathode electrode, and the first bypass diode Da performs the bypass operation. Therefore, the voltage generated in the solar cell 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, it is possible to prevent destruction of the solar cell or the like by bypassing. In addition, except for the hotspot area, it is possible to supply the generated DC power.

Next, the second bypass diode Db is connected between the first bus ribbon 145a and the second bus ribbon 145b, and is connected to 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 connected to 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.

On the other hand, unlike FIG. 5, six bypass diodes can be connected corresponding to six solar cell strings, and various other modifications are possible.

FIG. 6 is an example of a block diagram of the power conversion module in the junction box of FIG. 2. FIG.

Referring to the drawing, a power conversion module 700 in a junction box may include a bypass diode 510, a converter 530, a capacitor C1, an inverter 540, and a controller 550 have.

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

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

On the other hand, the input power supply Vpv via the bypass diode 510 is input to the converter unit 530.

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

For example, the converter unit 530 can be converted into a pseudo DC voltage with the DC input power supply Vpv as shown in FIG. 8A. Accordingly, the pseudo DC power can be stored in the capacitor C1. Both ends of the dc short capacitor C1 may be referred to as a dc stage, and the capacitor C1 may be referred to as a dc short capacitor.

As another example, the converter unit 530 can boost the DC input power supply Vpv and convert it to DC power as shown in FIG. 8A. Accordingly, the boosted DC power can be stored in the dc-stage capacitor C1.

The inverter unit 540 can convert the DC power stored in the dc-stage capacitor C1 into the AC power. On the other hand, the inverter unit 540 may be called a second power conversion unit.

For example, the inverter unit 540 can convert the pseudo dc voltage converted in the converter unit 530 to AC power.

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

On the other hand, the converter unit 530 preferably includes a plurality of interleaving converters for pseudo DC voltage conversion or step-up DC power supply conversion.

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

In the figure, 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 becomes 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 the respective converters are combined into one.

The current phase of each of the n converters 610a, 610b, ... 610n is interleaved with a reference phase contrast of + 360 ° / N (610a, 610b, ... 610n) ), - (360 [deg.] / N) or close to the phase delay.

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

On the other hand, as described above, when two interleaving converters are used, a size of an inductor of a considerable size, a transformer or the like is required for the AC power output of 290 W to 330 W described above. The larger the size of the inductor, the transformer, etc., the greater the thickness of the junction box, and the thickness of the junction box may be larger than the thickness of the frame 105 of the solar cell module.

To solve this problem, in the embodiment of the present invention, three or more interleaving converters are used. According to this, a small-sized inductor, a transformer, or the like can be used for the AC power output of 290 W to 330 W. Thus, the junction box is smaller in thickness than the frame 105 of the solar cell module .

On the other hand, as the interleaving converter, a tap inductor converter, a flyback converter, or the like can be used.

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

The power conversion module 700 includes a bypass diode 510, a converter 530, a dc capacitor C1, an inverter 540, a controller 550, and a filter 560 ).

7A illustrates a tapped inductor converter with an interleaved converter. In the figure, the converter section 530 includes a first tap inductor converter to third tap inductor converters 611a, 611b, ..., 611c.

The bypass diode section 510 is connected to the first to fourth conductive lines 135a, 135b, 135c and 135d arranged between the respective angles of the a-node, b-node, c- And third bypass diodes Da, Db, and Dc.

The converter unit 530 can perform power conversion using the DC power supply Vpv output from the bypass diode unit 510. [

Specifically, the first to third tab inductor converters 611a, 611b, ..., 611c output the converted DC power to the dc-stage capacitor C1 by the interleaving operation.

The first tap inductor converter 611a includes a tap inductor T1, a switching element S1 connected between the tap inductor T1 and the ground terminal, a diode connected to the output terminal of the tap inductor, (D1). On the other hand, a dc short capacitor C1 is connected between the output terminal of the diode D1, that is, between the cathode and the ground terminal.

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

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

On the other hand, the primary side and the secondary side of the tap inductor T are connected to each other as shown in the drawing. Thereby, the tap inductor converter can be a non-insulated type converter.

On the other hand, when the three tap inductor converters 611a, 611b, and 611c are connected in parallel to each other and driven by an interleaving method, the input current components are branched in parallel. Therefore, each of the tap inductor converters 611a, 611b, and 611c, the ripples of the current components output through the transistors 611a, 611b, and 611c are reduced.

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

For example, when only the first converter 611a operates, or when the power required value is approximately 190W to 230W, only the first and second converters 611a and 611b operate or the power If the required value is approximately 290 W to 330 W, both of the first to third interleaved converters 611a, 611b, and 611c may operate. That is, each of the tapped inductor converters 611a, 611b, and 611c can selectively operate. This optional operation can be controlled by the control unit 550. [

The inverter unit 540 converts the level-converted DC power from the converter unit 530 into AC power. In the drawing, a full-bridge inverter is illustrated. Namely, the upper and lower arm switching elements Sa and Sb connected in series to each other and the lower arm switching elements S'a and S'b are paired, and two pairs of upper and lower arm switching elements are connected in parallel to each other (Sa & Sb & S'b). Diodes are connected in anti-parallel to each switching element Sa, S'a, Sb, S'b.

The switching elements in the inverter unit 540 perform a turn-on / off operation based on an inverter switching control signal from the control unit 550. [ As a result, AC power having a predetermined frequency is output. Preferably, it has a frequency (approximately 60 Hz or 50 Hz) that is equal to the alternating frequency of the grid.

The filter unit 560 performs smooth understanding of the AC power output from the inverter unit 540 and performs low pass filtering. To this end, in the figure, the inductors Lf1 and Lf2 are exemplified, but various examples are possible.

The converter input current sensing unit A senses the input current ic1 input to the converter unit 530 and the converter input voltage sensing unit B senses the input voltage ic1 input to the converter unit 530 vc1. The sensed input current ic1 and the input voltage vc1 may be input to the control unit 550. [

Meanwhile, the converter output current sensing unit C senses the output current ic2 output from the converter unit 530, that is, the dc step current, and the converter output voltage sensing unit D receives the output current ic2 from the converter unit 530 And detects the output voltage vc2, i.e., the dc voltage. The sensed output current ic2 and the output voltage vc2 may be input to the control unit 550. [

The inverter output current sensing unit E senses the current ic3 output from the inverter unit 540 and the inverter output voltage sensing unit F outputs the voltage vc3 output from the inverter unit 540, Lt; / RTI > The detected current ic3 and the voltage vc3 are input to the control unit 550. [

On the other hand, the control unit 550 can output a control signal for controlling the switching element S1 of the converter unit 530 in Fig. In particular, the control unit 550 controls the control unit 550 so that the output voltage vc2 is at least one of the detected input current ic1, the input voltage vc1, the output current ic2, the output voltage vc2, the output current ic3, On timing signal of the switching element S1 in the converter unit 530 can be output.

The control unit 550 may also output an inverter control signal for controlling each of the switching elements Sa, S'a, Sb, S'b of the inverter unit 540. In particular, the control unit 550 controls the control unit 550 so that the output voltage vc2 is at least one of the detected input current ic1, the input voltage vc1, the output current ic2, the output voltage vc2, the output current ic3, On timing signals of the respective switching elements Sa, S'a, Sb, S'b of the inverter unit 540 can be outputted based on the above-described signals.

On the other hand, the control unit 550 can control the converter unit 530 to calculate the maximum power point for the solar cell module 100 and output the DC power corresponding to the maximum power.

7B is another example of the internal circuit diagram of the power conversion module of FIG.

The power conversion module 700 of FIG. 7B includes a bypass diode 510, a converter 530, a dc capacitor C1, an inverter 540, A control unit 550, and a filter unit 560.

7B illustrates a flyback converter as an interleaving converter in the converter unit 530. In FIG. In the figure, it is exemplified that the converter section 530 includes first to third flyback converters 612a, 612b, ..., 612c.

In particular, the first flyback converter to the third flyback converters 612a, 612b, ..., 612c are of an insulation type, unlike the non-insulation type tap inductor converter, and outputs it to the dc-stage capacitor C1.

The first flyback converter 612a includes a transformer T11, a switching element S11 connected between the primary side and the ground terminal of the transformer T11, and a secondary side connected to the secondary side of the transformer T11, And a diode D11 for performing the operation. On the other hand, the dc short capacitor C1 is connected between the output terminal of the diode D11, that is, between the cathode and the ground terminal. On the other hand, 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.

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

7A, when the converter section 530 is a tapped inductor converter, or when the converter section 530 is a flyback converter as shown in Fig. 7B, by switching on / off of the switching element S1 or S11, It can be converted into a pseudo DC voltage having an envelope like a DC power supply. Accordingly, the pseudo DC power can be stored in the capacitor C1.

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

8B, the converter unit 530 of the power conversion module 700 according to the embodiment of the present invention level-converts the DC power from the solar cell module 100, specifically boosts the DC power, It can be converted into a boosted DC power source.

7A, when the converter section 530 is a tapped inductor converter, or when the converter section 530 is a flyback converter as shown in FIG. 7B, the switching power supply is turned on / off by switching on / off of the switching element S1 or S11 Vp) can be converted to the boosted DC power. Accordingly, the boosted DC power can 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 converted into AC power corresponding to the grid frequency and output.

Figs. 9A to 9B are views for explaining the operation of the tapped inductor converter of Fig. 7A.

9A, when the switching element S1 is turned on, the input voltage Vpv, the primary side of the tap inductor T1, and the secondary side of the first inductor A closed loop is formed through the switching element S1, and the first current I1 flows on 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 can not be turned on and is turned off. As a result, the energy due to the input voltage Ppv is stored in the primary side of the tapped inductor T1.

Next, when the switching element S1 is turned off, the input voltage Vpv, the primary side, the secondary side, and the diode D1 of the tap inductor T1, and the capacitor C1, And a second current I2 flows on 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 becomes conductive. Accordingly, the input voltage Ppv, the energy stored in the primary side and the secondary side of the tap inductor T1 can be stored in the capacitor C1 via the diode D1.

As described above, the converter section 530 can output a pseudo direct current power source or a high efficiency and high voltage direct current power source by using the input voltage Ppv and the energy stored in the primary side and the secondary side of the tapped inductor Tl .

FIGS. 10A and 10B are diagrams for explaining output of a pseudo direct current power source using an input power source in the converter unit of FIG. 6;

6 and 10A, the first to third interleaved converters 610a, 610b, and 610c in the converter unit 530 output a pseudo direct current power source using a DC input power source Vpv.

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

The control unit 550 controls the duty ratio of the switching elements of the first to third interleaved converters 610a, 610b, and 610c based on the detected input power supply Vpv and the detected output power supply Vdc .

In particular, the lower the input voltage Vpv, the greater the duty of the switching elements of the first through third interleaved converters 610a, 610b, 610c, and the higher the input voltage Vpv, the smaller the duty of the switching element .

On the other hand, the lower the target output power supply Vdc, the smaller the duty of the switching elements of the first to third interleaved converters 610a, 610b, and 610c, and the higher the target output power supply Vdc, . For example, when the target output power supply Vdc is about 330 V, which is the peak value, the duty of the switching element can be greatest.

In Fig. 10A, the pseudo DC power supply waveform Vslv to be outputted is exemplified by such a duty variable, and this pseudo DC power supply waveform exemplifies that it follows the target sine waveform Vsin.

On the other hand, in the present invention, the switching frequency of the converter section 530 is varied so that the pseudo DC power supply waveform Vslo more accurately follows the full-wave rectified waveform Vsin.

The error DELTA E2 between the pseudo direct current power source waveform Vslf and the target sine waveform Vsin when the switching frequency of the converter section 530 is fixed is smaller than the error DELTA E2 between the pseudo direct current power source waveform Vslf and the target sine waveform Vsin, Becomes larger than the error DELTA E1 between the pseudo direct current power supply waveform Vslv and the target sine waveform Vsin when the switching frequency of the pseudo direct current power supply Vslv is varied.

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

The control unit 550 can control so that the switching frequency of the converter unit 530 increases as the rate of change of the target sinusoidal waveform Vsin increases and the rate of change of the target sinusoidal waveform Vsin decreases.

10A, the switching period is set to Ta in the rising section of the target sinusoidal waveform Vsin, and the peak period of the target sinusoidal waveform Vsin is set to be Tb in which the switching period is smaller than Ta. That is, it is illustrated that the switching frequency corresponding to the switching period Ta is higher than the switching frequency corresponding to the switching period Tb. This makes it possible to reduce the error DELTA E1 between the pseudo DC power supply waveform Vslv and the target sine waveform Vsin.

On the other hand, for the switching frequency variable of FIG. 10A, it is also possible to describe the switching mode technique of the switching device. See FIG. 11 to FIG. 12 for this.

11 to 12 are diagrams referred to explain the switching frequency variation according to the switching mode of the switching element.

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

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

When the switching period of the interleaving converter is fixed and the dcm is applied in the switching mode, the current waveform Idcm flowing in the switching element as shown in Fig. 11 (b) can be illustrated. As the switching element turns on, the current flowing through the switching element increases, and the current decreases as the switching element turns off.

Fig. 11 (c) illustrates the actual current waveform flowing through the switching element of the interleaved converter according to the dcm, and Fig. 11 (d) illustrates the switching voltage across the switching element of the interleaved converter according to the dcm.

On the other hand, after the switching element is turned off, 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 the dcm, a section 1107 in which the switching voltage across the switching element does not become zero occurs. Therefore, the zero voltage switching (ZVS) for the switching element can not be performed and the efficiency of the interleaving converter is lowered.

In order to solve this problem, in the present invention, a critical conduction mode (CRM) mode is used instead of the dcm in the switching mode. The CRM may be referred to as a boundary conduction mode (BCM) mode or a transition mode (TM) mode.

CRM means a mode in which a switching cycle starts every time the current flowing through the switching element becomes zero after the switching element of the interleaving converter is turned off. Accordingly, the CRM can be changed in the switching cycle according to the duty of the switching cycle.

12 (a) illustrates an example of a duty waveform diagram of a switching element of an interleaving converter. Referring to the drawings, a switching element is turned on and then turned off during a first duty cycle (duty1) in a first switching cycle Tfa, and during a second duty cycle (duty2) in a second switching cycle Tfb The switching element is turned on, and then turned off. In the figure, it is exemplified that the first duty (duty1) is larger than the second duty (duty2).

On the other hand, FIG. 12 (a) illustrates that a CRM in which a switching frequency is variable in a switching mode is applied as the switching cycle of the interleaving converter is varied as the duty varies.

In the switching mode, when the CRM in which the switching frequency is variable is applied, the current waveform Icrm flowing in the switching element as shown in Fig. 12B can be exemplified. As the switching element turns on, the current flowing through the switching element increases, and the current decreases as the switching element turns off. Then, when the current flowing through the switching element becomes 0, that is, when zero crossing occurs, a new switching period starts.

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

On the other hand, after the switching element is turned off, the resonance period 1105 in the interleaving converter may occur. At this time, when the switching element is operated by crm, the time point at which the current of the switching element becomes 0 is determined, that is, at the time of zero crossing, regardless of the generation of the resonance period 1105, It can turn on. That is, a new switching period can be started. Thereby, 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.

6, when three interleaving converters 610a, 610b, and 610c are used, the first to third interleaved converters 610a, 610b, and 610c operate with phase differences, respectively.

At this time, when the switching frequency is set to a constant phase difference, for example, 120 °, for the operating intervals of the first to third interleaved converters 610a, 610b, and 610c, The output power may be lowered. This will be described with reference to Figs. 13 and 14. Fig.

13 illustrates a case where the switching frequency variable and the phase difference are fixed in the three interleaved converters 610a, 610b, and 610c.

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

At the next time point 9Tv, it is exemplified that the switching period is variable and the switching period is increased three times by 9Tv. In this case, the first interleaved converter operates for 3TV intervals, after 3Tv versus the previous switching period, while the second interleaved converter takes into account the variable duty (3Tv) of the first interleaved converter, After 5Tv, it will operate for 3TV sections. The third interleaved converter also operates for 3TV intervals, after 7Tv compared to the previous switching period, taking into account the variable duty (3Tv) of the second interleaved converter.

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

In this switching period variation section 1310 and 1320, the power output by the second interleaving converter and the third interleaving converter is reduced as compared with the first interleaving converter. Accordingly, the output current of the converter unit 530, or the output voltage, is momentarily lowered.

In order to solve this problem, in the embodiment of the present invention, in the plurality of interleaving converters, in order to eliminate the output unbalance between the interleaving converters when the switching period is variable, the phases of the plurality of interleaving converters with respect to the operating period are varied. This will be described with reference to FIG.

Fig. 14 illustrates a case where the switching frequency is variable and the phase difference is variable in three interleaved converters 610a, 610b, and 610c.

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

Next, at the time point 9Tv, it is exemplified that the switching period is variable, and the switching period is increased three times by 9Tv. In this case, the first interleaved converter operates for 3TV intervals after 3Tv, compared to the previous switching period, and in the switching period variable interval 1410, the second interleaved converter, after 3Tv, And the third interleaved converter may operate for 3TV periods after 6Tv than 9Tv, which is a switching period variable time point.

That is, unlike FIG. 13, the controller 550 varies the phase difference between the first interleaving converter and the third interleaving converter in response to the variable period. According to the figure, the phase difference between the first interleaved converter and the second interleaved converter, and the phase difference between the second interleaved converter and the third interleaved converter are varied from 120 degrees to 40 degrees.

 The control unit 550 can vary the phase so that the phase difference between the respective interleaving converters is reduced when the switching period is increased. Similarly, if the switching period is reduced, the phase can be varied so that the phase difference between each interleaving converter increases, e.g., from 120 to 130 degrees.

On the other hand, the control unit 550 can vary the phase so that, in the case where the switching period is increased, an area in which the phases of the operation intervals between the respective interleaving converters are superposed, particularly, is increased. In the figure, it is illustrated that the operating intervals between the first interleaving converter and the second interleaving converter are overlapped for about 2 TV periods.

On the other hand, after the switching cycle variable, the first interleaved converter operates for 3TV intervals after 9Tv compared to the previous switching period, at a time point of 18Tv, while the second interleaved converter, after 9.1Tv before the previous switching period, And the third interleaved converter can also operate for 3TV intervals, after 9.1Tv versus the previous switching period.

The control unit 550 can vary the phase difference such that the phase difference in each converter is close to the reference phase difference sequentially after the variable period. According to the figure, it can be seen that after the time point 18 Tv, the phase difference between the first interleaved converter and the second interleaved converter and the phase difference between the second interleaved converter and the third interleaved converter increase by about 41 degrees at 40 degrees have.

In this manner, by causing the phase difference to approach 120 degrees, which is the original reference phase difference, in sequence, it is possible to prevent the current distortion and also to prevent the above-described output drop of the second interleaved converter and the third interleaved converter .

On the other hand, this phase variable 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.

10A to 14 are applicable to the converter section 530, and in particular, as shown in FIG. 7A, the converter section 530 may be a tapped inductor converter, or alternatively, as shown in FIGS. 7B and 7B, The present invention is applicable to the case where the converter section 530 is a flyback converter.

It is to be understood that the invention is not to be limited in its application to the details of construction and the manner in which the above described embodiments of the invention are put into practice, .

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the present invention.

Claims (16)

A solar cell module comprising a plurality of solar cells;
And a junction box attached to a back surface of the solar cell module and having a power conversion module for converting a DC power supplied from the solar cell module into an AC power and outputting the AC power,
The power conversion module includes:
At least one bypass diode receiving the DC power from the solar cell module;
A converter unit for converting the DC power from the bypass diode into electric power and including at least three interleaved converters;
A capacitor for storing a voltage output from the converter; And
And an inverter unit for outputting the AC power using a voltage stored in the capacitor. The method according to claim 1,
The power conversion module includes:
And a control unit for controlling operations of the converter unit and the inverter unit. The method according to claim 1,
The power conversion module includes:
An input voltage detector for detecting an input voltage input to the converter;
An input current detector for detecting an input current input to the converter;
A dc voltage detection unit detecting a voltage input to the capacitor;
An output voltage detector for detecting an output voltage output from the inverter; And
And a control unit for controlling the switching operation of the converter unit based on the detected input voltage, the input current, and the dc step voltage, and controlling the switching operation of the inverter unit based on the detected dc step voltage and the output voltage Wherein the solar module comprises a solar cell module. The method according to claim 1,
The converter unit includes:
DC power from the bypass diode to output a pseudo DC power source,
The inverter unit includes:
And the pseudo direct current power is subjected to power conversion to output the alternating current power. The method according to claim 1,
The power conversion module includes:
And a filter unit for filtering and outputting the AC power from the inverter unit. 3. The method of claim 2,
Wherein,
Wherein the switching frequency of the at least three interleaved converters is varied. The method according to claim 6,
Wherein,
And controls the switching frequency of the at least three interleaved converters to become larger as the waveform change rate of the target sinusoidal wave with respect to the pseudo DC power supply output from the converter section increases. 3. The method of claim 2,
Wherein,
Wherein the switching element of the interleaving converter turns on the switching element again when the current or voltage flowing in the switching element becomes zero-crossing after the switching element is turned on and off. 3. The method of claim 2,
Wherein,
A switching period of the at least three interleaved converters,
Wherein the phase difference for the operating interval between the at least three interleaved converters is varied after the switching period variation. 10. The method of claim 9,
Wherein,
Wherein the phase difference for the operating interval between the at least three interleaved converters is smaller than the phase difference for the operating interval between the at least three interleaved converters before the switching period increase, And the phase difference between the interleaved converters and the interleaved converters is varied. 10. The method of claim 9,
Wherein,
The phase difference between the operating intervals of the at least three interleaved converters is varied such that the phase difference with respect to the operating interval between the at least three interleaved converters sequentially approaches the reference phase difference after the switching cycle variable. Photovoltaic modules. 10. The method of claim 9,
Wherein,
And increases the overlap region of the operating interval between the at least three interleaved converters when the switching period is increased. The method according to claim 1,
In the solar cell module,
And a frame for fixing an outer frame portion of the solar cell module,
Wherein a thickness of the junction box is smaller than a thickness of the frame. 3. The method of claim 2,
Wherein,
And selectively operates at least one of said at least three interleaved converters. The method according to claim 1,
The interleaving converter includes:
Tapped inductor < / RTI > converter. The method according to claim 1,
The interleaving converter includes:
And a flyback converter.

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