KR20200141836A - Power converting apparatus and photovoltaic module including the same - Google Patents

Abstract

The present invention relates to a power conversion device and a photovoltaic module having the same. According to an embodiment of the present invention, the power conversion device comprises: an inverter having a first leg including a first switching element and a second switching element connected in series with each other and a second leg including a third switching element and a fourth switching element connected in series with each other and converting DC power into AC power; and a control unit controlling the inverter. The control unit performs asynchronous pulse width variable control that switching frequencies of the first leg and the second leg of the inverter are different from each other and controls the switching element in the second leg to be turned off, and the first switching element or the second switching element to be switched at time of zero crossing of an inverter output voltage. Accordingly, the quality of the output AC power may be improved.

Description

Power converting apparatus, and a photovoltaic module including the same

The present invention relates to a power conversion device, and to a solar module having the same, and more particularly, to a power conversion device capable of improving the quality of the output AC power, and a solar module having the same.

The power conversion device is a device capable of converting the level of an input power source or converting an input DC power source into an AC power source.

Recently, in order to reduce energy, research on power conversion devices has been actively conducted.

Such a power conversion device may be used in various electric devices, and in particular, may be used in an energy supply device for supplying renewable energy.

As the energy supply device, for example, a wind power generator, a tidal power generator, and a solar module may be exemplified.

Meanwhile, in order to convert input DC power into AC power through the power conversion device, switching of a switching element in the power conversion device is performed. At this time, the total harmonic distortion (THD) increases due to switching loss, conduction loss, etc. of the switching element, resulting in a problem that the quality of the output AC power is deteriorated.

Accordingly, in the power conversion device, various methods for preventing the quality of AC power from deteriorating have been studied.

An object of the present invention is to provide a power conversion device capable of improving the quality of output AC power, and a solar module having the same.

Another object of the present invention is to provide a power conversion device capable of improving current distortion of an AC power output while performing asynchronous pulse width variable control, and a solar module having the same.

Still another object of the present invention is to provide a power conversion device capable of performing power factor control while performing asynchronous pulse width variable control, and a solar module having the same.

A power conversion device according to an embodiment of the present invention for achieving the above object, and a solar module including the same, includes a first leg including a first switching element and a second switching element connected in series with each other, and a series connection with each other. And a second leg including a third switching element and a fourth switching element, and includes an inverter for converting DC power into AC power, and a control unit for controlling the inverter, and the control unit includes a first leg and a first leg of the inverter. Asynchronous pulse width variable control with different switching frequencies of the two legs is performed, and at the time of zero crossing of the inverter output voltage, the switching element in the second leg is turned off, and the first switching element or the second switching element is controlled to switch.

On the other hand, the control unit performs asynchronous pulse width variable control in which the switching frequencies of the first leg and the second leg of the inverter are different, and at a zero crossing time when the inverter output voltage changes from positive polarity to negative polarity, the switching element in the second leg Is off, and the first switching element or the second switching element can be controlled to switch.

Meanwhile, the control unit may control the inverter to perform the reflux mode during a period between a first point in time when the fourth switching element is turned off and a second point in time when the third switching element is turned on.

Meanwhile, the controller may control the first switching element or the second switching element to switch during a period between a first point in time when the fourth switching element is turned off and a second point in time when the third switching element is turned on.

On the other hand, when the current output from the inverter is ground, the first switching element is turned on during the period between the first point in time when the fourth switching element is turned off and the second point in which the third switching element is turned on. Can be controlled to switch.

Meanwhile, when the current output from the inverter is ground, the control unit may control the first current path to be formed through a diode element connected in parallel to the first switching element and the third switching element.

Meanwhile, when the current output from the inverter is ground, the controller may control the second switching element to be turned off at a first time point.

On the other hand, the control unit controls the second switching element to switch during a period between the first point in time when the fourth switching element is turned off and the second point in time when the third switching element is turned on, when the current output from the inverter is in the leading phase. can do.

On the other hand, when the current output from the inverter is a fast phase, the controller may control the formation of the second current path through the second switching element and the diode element connected in parallel to the fourth switching element.

Meanwhile, when the current output from the inverter is a fast phase, the controller may control the first switching element to be turned on and switched at a second time point.

Meanwhile, the controller may control the switching frequency of the first switching element and the second switching element in the first leg to be greater than the switching frequency of the third switching element and the fourth switching element in the second leg.

Meanwhile, the control unit may control the switching frequency of the third switching element and the fourth switching element in the second leg to be the same as the normal frequency.

On the other hand, the control unit, during a period between the first point in time when the fourth switching element is turned off and the second point in time when the third switching element is turned on, the switching frequency of the first switching element or the second It can be controlled to be greater than the switching frequency of the 3 switching element and the fourth switching element.

On the other hand, the power conversion device according to an embodiment of the present invention, and a solar module having the same, further includes an output voltage detector for detecting an output voltage output from the inverter, and an output current detector for detecting an output current output from the inverter. Can include.

Meanwhile, the control unit may calculate a power factor based on the output voltage and the output current.

Meanwhile, the control unit may vary the switching frequency of the first switching element and the second switching element in the first leg according to the calculated power factor.

On the other hand, the control unit determines the switching timing of the first switching element or the second switching element in a period between the first point in time when the fourth switching element is turned off and the second point in time when the third switching element is turned on, according to the calculated power factor. It can be variable.

A power conversion device according to an embodiment of the present invention, and a solar module having the same, may further include a converter that converts the level of the input DC power, and a DC terminal capacitor that stores the DC power output from the converter. .

On the other hand, the converter includes a full bridge switching unit that performs switching for DC power, a transformer whose input is connected to the output of the full bridge switching unit, a synchronous rectification unit connected to the output side of the transformer, and a synchronous rectification unit connected between the transformer and the synchronous rectification unit. , A resonant capacitor and a resonant inductor may be provided.

Meanwhile, the control unit may change the switching frequency of the full bridge switching unit based on the input voltage of the converter or the voltage of the dc terminal capacitor.

On the other hand, the control unit calculates reactive power based on the inverter output current and outputs a current command value based on the calculated reactive power, and a voltage command value that generates a voltage command value based on the current command value from the reactive power calculation unit. It may include a generator and a switching control signal output unit for outputting a switching control signal based on a variable pulse width based on the voltage command value.

A power conversion device according to another embodiment of the present invention for achieving the above object, and a solar module including the same, includes a first leg including a first switching element and a second switching element connected in series with each other, and in series with each other. It has a second leg including a third switching element and a fourth switching element to be connected, and includes an inverter that converts DC power into AC power, and a control unit that controls the inverter, and the control unit comprises: a first leg of the inverter and Asynchronous pulse width variable control with a different switching frequency of the second leg is performed, and during the period between the first time point when the fourth switching element is turned off and the second time point at which the third switching element is turned on, the inverter performs the reflux mode. Can be controlled.

Meanwhile, the controller may control the power supply mode to be performed in which current flows through the switching element in the inverter before and after the reflux mode.

A power conversion device according to another embodiment of the present invention for achieving the above object, and a solar module including the same, includes a first leg including a first switching element and a second switching element connected in series with each other, A second leg including a third switching element and a fourth switching element connected in series, and an inverter for converting DC power into AC power, and a control unit for controlling the inverter, and the control unit includes a first leg of the inverter Asynchronous pulse width variable control with different switching frequencies of the second leg and the second leg is performed, and the switching frequency of the second leg is between the first time point when the fourth switching element is turned off and the second time point at which the third switching element is turned on. Is controlled to be higher than the switching frequency of the second leg before the first time point.

A power conversion device according to an embodiment of the present invention, and a solar module including the same, includes a first leg including a first switching element and a second switching element connected in series with each other, a third switching element connected in series with each other, and And a second leg including a fourth switching element, and an inverter for converting DC power into AC power, and a control unit for controlling the inverter, wherein the control unit includes a switching frequency of the first leg and the second leg of the inverter Another asynchronous pulse width variable control is performed, and at the time of zero crossing of the inverter output voltage, the switching element in the second leg is turned off, and the first switching element or the second switching element is controlled to switch. Accordingly, it is possible to improve the quality of the output AC power. In particular, it is possible to improve the current distortion of the AC power output while performing asynchronous pulse width variable control. In addition, it is possible to perform power factor control while performing asynchronous pulse width variable control.

On the other hand, the control unit performs asynchronous pulse width variable control in which the switching frequencies of the first leg and the second leg of the inverter are different, and at a zero crossing time when the inverter output voltage changes from positive polarity to negative polarity, the switching element in the second leg Is off, and the first switching element or the second switching element can be controlled to switch. Accordingly, it is possible to improve the current distortion of the output AC power source while performing asynchronous pulse width variable control.

Meanwhile, the control unit may control the inverter to perform the reflux mode during a period between a first point in time when the fourth switching element is turned off and a second point in time when the third switching element is turned on. Accordingly, it is possible to improve the current distortion of the output AC power source while performing asynchronous pulse width variable control.

Meanwhile, the controller may control the first switching element or the second switching element to switch during a period between a first point in time when the fourth switching element is turned off and a second point in time when the third switching element is turned on. Accordingly, it is possible to improve the current distortion of the output AC power source while performing asynchronous pulse width variable control.

On the other hand, when the current output from the inverter is ground, the first switching element is turned on during the period between the first point in time when the fourth switching element is turned off and the second point in which the third switching element is turned on. Can be controlled to switch. Accordingly, it is possible to improve the current distortion of the output AC power by performing power factor control while performing asynchronous pulse width variable control.

Meanwhile, when the current output from the inverter is ground, the control unit may control the first current path to be formed through a diode element connected in parallel to the first switching element and the third switching element. Accordingly, it is possible to improve the current distortion of the output AC power by performing power factor control while performing asynchronous pulse width variable control.

Meanwhile, when the current output from the inverter is ground, the controller may control the second switching element to be turned off at a first time point. Accordingly, it is possible to improve the current distortion of the output AC power by performing power factor control while performing asynchronous pulse width variable control.

On the other hand, the control unit controls the second switching element to switch during a period between the first point in time when the fourth switching element is turned off and the second point in time when the third switching element is turned on, when the current output from the inverter is in the leading phase. can do. Accordingly, it is possible to improve the current distortion of the output AC power by performing power factor control while performing asynchronous pulse width variable control.

On the other hand, when the current output from the inverter is a fast phase, the controller may control the formation of the second current path through the second switching element and the diode element connected in parallel to the fourth switching element.

Meanwhile, when the current output from the inverter is a fast phase, the controller may control the first switching element to be turned on and switched at a second time point. Accordingly, it is possible to improve the current distortion of the output AC power by performing power factor control while performing asynchronous pulse width variable control.

Meanwhile, the controller may control the switching frequency of the first switching element and the second switching element in the first leg to be greater than the switching frequency of the third switching element and the fourth switching element in the second leg. Accordingly, it is possible to improve the current distortion of the output AC power source while performing asynchronous pulse width variable control.

Meanwhile, the control unit may control the switching frequency of the third switching element and the fourth switching element in the second leg to be the same as the normal frequency. Accordingly, it is possible to improve the current distortion of the output AC power source while performing asynchronous pulse width variable control.

On the other hand, the control unit, during a period between the first point in time when the fourth switching element is turned off and the second point in time when the third switching element is turned on, the switching frequency of the first switching element or the second It can be controlled to be greater than the switching frequency of the 3 switching element and the fourth switching element. Accordingly, it is possible to improve the current distortion of the output AC power source while performing asynchronous pulse width variable control.

A power conversion device according to an embodiment of the present invention, and a solar module having the same, further include an output voltage detector for detecting an output voltage output from the inverter, and an output current detector for detecting an output current output from the inverter. I can. Accordingly, it is possible to perform power factor control while performing asynchronous pulse width variable control.

Meanwhile, the control unit may calculate a power factor based on the output voltage and the output current. Accordingly, it is possible to perform power factor control while performing asynchronous pulse width variable control.

Meanwhile, the control unit may vary the switching frequency of the first switching element and the second switching element in the first leg according to the calculated power factor. Accordingly, it is possible to perform power factor control while performing asynchronous pulse width variable control.

On the other hand, the control unit determines the switching timing of the first switching element or the second switching element in a period between the first point in time when the fourth switching element is turned off and the second point in time when the third switching element is turned on, according to the calculated power factor. It can be variable. Accordingly, it is possible to perform power factor control while performing asynchronous pulse width variable control.

On the other hand, the converter includes a full bridge switching unit that performs switching for DC power, a transformer whose input is connected to the output of the full bridge switching unit, a synchronous rectification unit connected to the output side of the transformer, and a synchronous rectification unit connected between the transformer and the synchronous rectification unit. , A resonant capacitor and a resonant inductor may be provided. Accordingly, it is possible to perform high-voltage, high-efficiency power conversion through the converter.

Meanwhile, the control unit may change the switching frequency of the full bridge switching unit based on the input voltage of the converter or the voltage of the dc terminal capacitor. Accordingly, it is possible to perform high-voltage, high-efficiency power conversion through the converter.

On the other hand, the control unit calculates reactive power based on the inverter output current and outputs a current command value based on the calculated reactive power, and a voltage command value that generates a voltage command value based on the current command value from the reactive power calculation unit. It may include a generator and a switching control signal output unit for outputting a switching control signal based on a variable pulse width based on the voltage command value. Accordingly, it is possible to improve the current distortion of the output AC power source while performing asynchronous pulse width variable control.

On the other hand, a power conversion device according to another embodiment of the present invention, and a solar module including the same, includes a first leg including a first switching element and a second switching element connected in series with each other, and a third It has a second leg including a switching element and a fourth switching element, and includes an inverter that converts DC power into AC power, and a control unit that controls the inverter, and the control unit comprises: a first leg and a second leg of the inverter. Asynchronous pulse width variable control with different switching frequencies is performed, and during a period between a first point in time when the fourth switching element is turned off and a second point in which the third switching element is turned on, the inverter may control to perform the reflux mode. . Accordingly, it is possible to improve the quality of the output AC power. In particular, it is possible to improve the current distortion of the AC power output while performing asynchronous pulse width variable control. In addition, it is possible to perform power factor control while performing asynchronous pulse width variable control.

Meanwhile, the controller may control the power supply mode to be performed in which current flows through the switching element in the inverter before and after the reflux mode. Accordingly, it is possible to improve the current distortion of the output AC power source while performing asynchronous pulse width variable control.

Meanwhile, a power conversion device according to another embodiment of the present invention, and a solar module including the same, include a first leg including a first switching element and a second switching element connected in series, and a first leg connected in series with each other. A second leg including a third switching element and a fourth switching element, and an inverter for converting DC power into AC power, and a control unit for controlling the inverter, wherein the control unit includes a first leg and a second leg of the inverter. Asynchronous pulse width variable control having a different switching frequency of is performed, and during a period between a first point in time when the fourth switching element is turned off and a second point in which the third switching element is turned on, the switching frequency of the second leg is first It can be controlled to be higher than the switching frequency of the second leg before the time point. Accordingly, it is possible to improve the quality of the output AC power. In particular, it is possible to improve the current distortion of the output AC power supply while performing asynchronous pulse width variable control. In addition, it is possible to perform power factor control while performing asynchronous pulse width variable control.

1A is a view showing an example of a solar system including a solar module according to an embodiment of the present invention.
1B is a view showing another example of a solar system including a solar module according to an embodiment of the present invention.
2 is a diagram showing a circuit diagram of an interior of a junction box in the solar module of FIG. 1A or 1B.
3A to 3D are views referenced for explanation of a power conversion device related to the present invention.
4 is a circuit diagram of a power conversion device according to an embodiment of the present invention.
5A to 7C are views referenced for explanation of the power conversion device of FIG. 4.
8 is an example of an internal block diagram of the control unit of FIG. 4.
9 is another example of a circuit diagram of a power conversion device according to an embodiment of the present invention.
10 to 12 are diagrams referenced for explanation of the power conversion device of FIG. 9.
13 is a flowchart illustrating a method of operating a solar module according to an embodiment of the present invention.
14 is an exploded perspective view of the solar cell module of FIG. 1A or 1B.

In this specification, a method for reducing the ripple of the input current input to the converter in the solar module is proposed.

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

The suffixes "module" and "unit" for the constituent elements used in the following description are given in consideration of only the ease of writing in the present specification, and do not impart a particularly important meaning or role by themselves. Therefore, the "module" and "unit" may be used interchangeably with each other.

1A is a view showing an example of a solar system including a solar module according to an embodiment of the present invention.

Referring to the drawings, a solar system 10a according to an embodiment of the present invention may include a solar module 50 and a gateway 80.

The solar module 50 is integrally provided with a junction box 200 including a solar cell module 100 and a power conversion device (500 in FIG. 2) that converts and outputs DC power from the solar cell module. can do.

In the drawings, the junction box 200 is attached to the rear surface of the solar cell module 100, but is not limited thereto. The junction box 200 may be provided separately from the solar cell module 100.

Meanwhile, a cable (oln) for supplying the AC power output from the junction box 200 to the grid may be electrically connected to the output terminal of the junction box 200.

Meanwhile, the gateway 80 may be located between the junction box 200 and the grid 90.

Meanwhile, the gateway 80 may detect an AC current io and an AC voltage vo flowing through the cable oln and output from the solar module 50.

Meanwhile, the gateway 80 may output a power factor adjustment signal for power factor adjustment based on a phase difference between the AC current io and the AC voltage vo output from the solar module 50.

To this end, the gateway 80 and the solar module 50 may perform power line communication (PLC communication), or the like, using a cable 323.

Meanwhile, the power conversion device (500 in FIG. 2) in the solar module 50 may convert DC power output from the solar cell module 100 into AC power and output it.

To this end, a converter (530 of FIG. 2) and an inverter (540 of FIG. 2) may be provided in the power conversion device (500 of FIG. 2) in the solar module 50.

Meanwhile, the power conversion device (500 in FIG. 2) may be referred to as a micro inverter. Accordingly, the micro inverter may include a converter (530 in FIG. 2) and an inverter (540 in FIG. 2).

On the other hand, the inverter (540 in FIG. 2) includes a first leg including a first switching element and a second switching element connected in series with each other, and a second switching element including a third switching element and a fourth switching element connected in series with each other. Legs can be provided. At this time, the first leg and the second leg are connected in parallel.

On the other hand, in the present invention, in order to improve the quality of the output AC power, the inverter 540 performs asynchronous pulse width variable control with different switching frequencies of the first leg and the second leg, and the inverter At the time of zero crossing of the output voltage, the switching elements SW3 and SW4 in the second leg are turned off, and the first switching element SW1 or the second switching element SW2 switches. Accordingly, it is possible to improve the current distortion of the output AC power source while performing asynchronous pulse width variable control. In addition, it is possible to perform power factor control while performing asynchronous pulse width variable control.

Next, FIG. 1B is a diagram showing another example of a solar system including a solar module according to an embodiment of the present invention.

Referring to the drawings, a solar system 10b according to an embodiment of the present invention may include a plurality of solar modules 50a, 50b, ..., 50n, and a gateway 80.

The photovoltaic system 10b of FIG. 1B differs from the photovoltaic system 10a of FIG. 1A in that a plurality of photovoltaic modules 50a, 50b, ..., 50n are connected in parallel with each other.

Each of the plurality of photovoltaic modules 50a, 50b, ..., 50n is a circuit for converting and outputting power by converting DC power from each photovoltaic module 100a, 100b, ..., 100n, and a solar cell module Junction boxes 200a, 200b, ..., 200n including elements may be provided.

In the drawings, each junction box (200a, 200b, ..., 200n) is shown to be attached to the rear surface of each solar cell module (100a, 100b, ..., 100n), but is not limited thereto. Each junction box (200a, 200b, ..., 200n) may be provided separately from each of the solar cell modules (100a, 100b, ..., 100n).

On the other hand, cables 31a, 31b, ..., oln for supplying the AC power output from each junction box 200a, 200b, ..., 200n to the grid, each junction box 200a, 200b,. .., 200n) can be electrically connected to the output terminal.

Meanwhile, the inverter 540 in each power conversion device 500 in the plurality of photovoltaic modules 50a, 50b, ..., 50n of FIG. 1B is output AC power as described above in the description of FIG. 1A. To improve the quality of, asynchronous pulse width variable control with different switching frequencies of the first leg and the second leg is performed, and at the point of zero crossing of the inverter output voltage, in the second leg The switching elements SW3 and SW4 are turned off, and the first switching element SW1 or the second switching element SW2 switches. Accordingly, it is possible to improve the current distortion of the output AC power source while performing asynchronous pulse width variable control. In addition, it is possible to perform power factor control while performing asynchronous pulse width variable control.

2 is a diagram showing a circuit diagram of an interior of a junction box in the solar module of FIG. 1A or 1B.

Referring to the drawings, the junction box 200 may convert DC power from the solar cell module 100 and output the converted power.

In particular, in relation to the present invention, the junction box 200 may include a power conversion device 500 for outputting AC power.

To this end, the power conversion device 500 may include a converter 530, an inverter 540, and a control unit 550 for controlling the converter 530.

In addition, the power conversion device 500 may further include a bypass diode unit 510 for bypass, a capacitor unit 520 for storing DC power, and a filter unit 570 for filtering the output AC power. I can.

Meanwhile, the power conversion device 500 may further include a communication unit 580 for communicating with an external gateway 80.

Meanwhile, the power conversion device 500 includes an input current detector (A), an input voltage detector (B), a converter output current detector (C), a converter output voltage detector (D), an inverter output current detector (E), and an inverter output. A voltage detector (F) may be further provided.

Meanwhile, the controller 550 may control the converter 530, the inverter 540, and the communication unit 580.

The bypass diode unit 510 may include bypass diodes Dc, Db, and Da respectively disposed between the first to fourth conductive lines (not shown) of the solar cell module 100. . 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, and Da receive photovoltaic direct current power from the solar cell module 100, in particular, from the first to fourth conductive lines (not shown) in the solar cell module 100. In addition, the bypass diodes Dc, Db, and Da may be bypassed when a reverse voltage is generated from DC power from at least one of the first to fourth conductive lines (not shown).

Meanwhile, DC power passing through the bypass diode unit 510 may be input to the capacitor unit 520.

The capacitor unit 520 may store an input DC power input through the solar cell module 100 and the bypass diode unit 510.

On the other hand, in the drawing, the capacitor unit 520 is illustrated as having a plurality of capacitors (Ca, Cb, Cc) connected in parallel to each other. It is also possible to be connected to the stage. Alternatively, the capacitor unit 520 may have only one capacitor.

The converter 530 may convert the level of the input voltage from the solar cell module 100 through the bypass diode unit 510 and the capacitor unit 520.

In particular, the converter 530 may perform power conversion using DC power stored in the capacitor unit 520.

Meanwhile, switching elements in the converter 530 may be turned on/off based on a converter switching control signal from the controller 550. Accordingly, the level-converted DC power may be output.

The inverter 540 may convert DC power converted by the converter 530 into AC power.

In the drawing, a full-bridge inverter is illustrated. That is, the upper and lower arm switching elements (SW1, SW3) and lower arm switching elements (SW2, SW4) that are connected in series with each other become a pair, and a total of two pairs of upper and lower arm switching elements are parallel to each other (SW1, SW2, SW3, SW4). Leads to Diodes D1 to D4 may be connected in reverse parallel to each of the switching elements SW1 to SW4.

The switching elements SW1 to SW4 in the inverter 540 may be turned on/off based on an inverter switching control signal from the controller 550. Accordingly, AC power having a predetermined frequency can be output. Preferably, it is desirable to have the same frequency (about 60Hz or 50Hz) as the alternating current frequency of the grid.

Meanwhile, the capacitor C may be disposed between the converter 530 and the inverter 540.

The capacitor C may store the level-converted DC power of the converter 530. Meanwhile, both ends of the capacitor C may be referred to as a dc terminal, and accordingly, the capacitor C may be referred to as a dc terminal capacitor.

Meanwhile, the input current detection unit A may detect an input current ic1 supplied from the solar cell module 100 to the capacitor unit 520.

Meanwhile, the input voltage detector B may detect an input voltage Vc1 supplied from the solar cell module 100 to the capacitor unit 520. Here, the input voltage Vc1 may be the same as the voltage stored at both ends of the capacitor unit 520.

The detected 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) detects the output current (ic2) output from the converter 530, that is, the dc end current, and the converter output voltage detection unit (D) is the output voltage output from the converter 530 (vc2), that is, detects the dc voltage. The detected output current ic2 and output voltage vc2 may be input to the control unit 550.

Meanwhile, the inverter output current detection unit E detects the current ic3 output from the inverter 540, and the inverter output voltage detection unit F detects the voltage vc3 output from the inverter 540. The detected current ic3 and voltage vc3 are input to the control unit 550.

Meanwhile, the controller 550 may output a control signal for controlling the switching elements of the converter 530. In particular, the control unit 550 is applied to at least one of the detected input current (ic1), input voltage (vc1), output current (ic2), output voltage (vc2), output current (ic3), or output voltage (vc3). Based on this, the turn-on timing signals of the switching elements in the converter 530 may be output.

Meanwhile, the controller 550 may output an inverter control signal or an inverter switching control signal Sic that controls each of the switching elements SW1 to SW4 of the inverter 540. In particular, the control unit 550 is applied to at least one of the detected input current (ic1), input voltage (vc1), output current (ic2), output voltage (vc2), output current (ic3), or output voltage (vc3). Based on this, a turn-on timing signal of each of the switching elements SW1 to SW4 of the inverter 540 may be output.

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

Meanwhile, the communication unit 580 may communicate with the gateway 80.

For example, the communication unit 580 may exchange data with the gateway 80 through power line communication.

Meanwhile, the communication unit 580 may transmit current information, voltage information, power information, and the like of the solar module 50 to the gateway 80.

Meanwhile, the filter unit 570 may be disposed at the output terminal of the inverter 540.

In addition, the filter unit 570 includes a plurality of passive elements, and based on at least some of the plurality of passive elements, the phase difference between the AC current io and the AC voltage vo output from the inverter 540 Can be used to adjust.

3A to 3D are views referenced for explanation of a power conversion device related to the present invention.

First, Figure 3a illustrates a circuit diagram of a power conversion device (500x) related to the present invention.

Referring to the drawings, the power conversion device 500x of FIG. 3A may include an inverter 540 and a control unit 550 that controls the inverter 540.

The inverter 540 includes a first leg including a first switching element SW1 and a second switching element SW2 connected in series, a third switching element SW3 and a fourth switching element SW3 connected in series with each other. A second leg including the switching element SW4 may be provided. At this time, the first leg and the second leg are connected in parallel with each other.

Meanwhile, in order to improve the output current quality, asynchronous pulse width variable control in which switching frequencies of the first leg and the second leg are different may be performed.

3B is a diagram referred to for explaining asynchronous pulse width variable control.

Referring to the drawing, during the Pd4 period before the Tzcx time point corresponding to the zero crossing point Zcx where the output voltage waveform Vgx output from the inverter 540 changes from positive polarity to negative polarity, the first leg The first switching element SW1 and the second switching element SW2 perform high-speed switching, and the third switching element SW3 and the fourth switching element SW4 of the second leg perform low-speed switching. I can.

Similarly, during the Pd3 period after the point Tzcx corresponding to the zero crossing point Zcx, the first switching element SW1 and the second switching element SW2 of the first leg perform high-speed switching, and , The third switching element SW3 and the fourth switching element SW4 of the second leg may perform low-speed switching.

Referring to FIG. 3B, during the Pdx period including the zero crossing point Zcx, all of the first to fourth switching elements SW1 to SW4 in the inverter 540 are not switched and are turned off. This Pdx interval may be referred to as a dead time interval.

The Pdx section may exist to reduce switching loss of the first to fourth switching elements SW1 to SW4.

Meanwhile, as shown in FIG. 3C, the current Igxa output from the inverter 540 is lagging behind the output voltage Vgxa. In the case of ground, the inverter 540 In the vicinity of the zero crossing point of the voltage Vgxa output from, a current peak Pka may occur due to a current discontinuity or the like.

On the other hand, as shown in FIG. 3D, when the current Igxb output from the inverter 540 is ahead of the output voltage Vgxb, and is a true phase, due to the dead time period of the Pdx section of FIG. 3B, the inverter 540 In the vicinity of the zero crossing point of the output voltage Vgxb, a current peak Pkb due to current discontinuity or the like may occur.

In the present invention, a method for improving current quality by reducing current peaks, which may occur during variable control of the asynchronous pulse width of the inverter 540, is proposed. This will be described with reference to FIG. 4 below.

4 is a circuit diagram of a power conversion device according to an embodiment of the present invention, and FIGS. 5A to 7C are views referenced for explanation of the power conversion device of FIG. 4.

Referring to FIG. 4, a power conversion device 500 according to an embodiment of the present invention may include an inverter 540, a control unit 550 for controlling the inverter 540, and a filter unit 570.

The inverter 540 includes a first leg including a first switching element SW1 and a second switching element SW2 connected in series, a third switching element SW3 and a fourth switching element SW3 connected in series with each other. A second leg including the switching element SW4 may be provided. At this time, the first leg and the second leg are connected in parallel with each other.

On the other hand, according to an embodiment of the present invention, the controller 550 performs asynchronous pulse width variable control of the inverter 540 having different switching frequencies of the first leg and the second leg, and the inverter output At the zero crossing point of the voltage, the switching elements SW3 and SW4 in the second leg are turned off, and the first switching element SW1 or the second switching element SW2 is controlled to switch.

On the other hand, the control unit 550, the first switching element (SW1) and the first switching element (SW1) in the first leg (Lega) than the switching frequency of the third switching element (SW3) and the fourth switching element (SW4) in the second leg. 2 The switching frequency of the switching element SW2 can be controlled to be larger.

Meanwhile, the controller 550 may control the switching frequency of the third switching element SW3 and the fourth switching element SW4 in the second leg to be the same as the normal frequency.

For example, the switching frequency of the first leg is a high-speed switching frequency, and may be several KHz to several hundreds KHz higher than the grid frequency of 50 Hz or 60 Hz.

Meanwhile, the switching frequency of the second leg is a magnetic flux switching frequency, and may be a system frequency of 50 Hz or 60 Hz.

On the other hand, according to an embodiment of the present invention, while performing asynchronous pulse width variable control, the peak current generated by turning off the switching elements SW1 to SW4 of the inverter 540 near the zero crossing point of the inverter output voltage, etc. To prevent this, the switching elements SW3 and SW4 in the second leg are turned off, and the first switching element SW1 or the second switching element SW2 is controlled to switch.

Accordingly, it is possible to improve the quality of the output AC power. In particular, it is possible to improve the current distortion of the output AC power supply while performing asynchronous pulse width variable control. In addition, it is possible to perform power factor control while performing asynchronous pulse width variable control.

On the other hand, the controller 550 performs asynchronous pulse width variable control in which the switching frequencies of the first leg and the second leg of the inverter 540 are different, and the inverter output voltage is changed from positive polarity to negative polarity. At the changing zero crossing time (Tzca of FIGS. 5A and 5B or Tzcb of FIGS. 6A and 6B), the switching elements SW3 and SW4 in the second leg are turned off, and the first switching element SW1 or the first 2 It is possible to control the switching element SW2 to switch. Accordingly, it is possible to improve the current distortion of the output AC power source while performing asynchronous pulse width variable control.

On the other hand, the controller 550 allows the inverter 540 to perform the reflux mode during a period between the first point in time when the fourth switching element SW4 is turned off and the second point in time when the third switching element SW3 is turned on. Can be controlled. Accordingly, it is possible to improve the current distortion of the output AC power source while performing asynchronous pulse width variable control.

Meanwhile, the control unit 550 includes the first switching element SW1 or the second switching element SW1 during a period between a first point in time when the fourth switching element SW4 is turned off and a second point in which the third switching element SW3 is turned on. The switching element SW2 may be controlled to switch. Accordingly, it is possible to improve the current distortion of the output AC power source while performing asynchronous pulse width variable control.

The filter unit 570 may include an inductor La and a capacitor Ca disposed at the output terminal of the inverter 530.

Accordingly, by implementing the filter unit 570 in an asymmetric form in consideration of the inverter 540 operated by asynchronous pulse width variable control, it is possible to reduce the common mode voltage at the output terminal of the inverter 540. In addition, it is possible to reduce the total harmonic distortion factor (THD) of the output current.

5A illustrates a case in which the current Igxa output from the inverter 540 is slower than the voltage Vgxa.

Meanwhile, as shown in the drawing, the output voltage Vgxa output from the inverter 540 may cross zero at Zca. In particular, the point Zca corresponds to a point in time when the output voltage Vgxa output from the inverter 540 has a voltage of positive polarity and then changes to a voltage of negative polarity.

The inverter output voltage detection unit F may detect the voltage vc3 output from the inverter 540, and the control unit 550 is, in particular, a zero crossing point Zca among the voltage vc3 output from the inverter 540. ) Can be detected.

5B is a diagram illustrating switching waveforms of switching elements of the inverter 540 when the current output from the inverter 540 is ground.

Referring to the drawing, when the current output from the inverter 540 is ground, as shown in FIG. 5B, the controller 550 performs a third switching from a first time Taa when the fourth switching element SW4 is turned off. During the period Pda between the second time point Tbb in which the device SW3 is turned on, the first switching device SW1 may be turned on and then switched.

In the drawing, the first switching element SW1 is turned on at a point in time Ta1 during the period Pda between the first point in time Taa and the second point in time Tbb when the third switching element SW3 is turned on. Illustrate what to do.

According to this, compared to the conventional 3b, during the Pda period in which the switching in the inverter 540 is not performed, the first switching element SW1 is turned on and switched.

On the other hand, during the Pd4a and Pd3a periods corresponding to the power supply mode for outputting AC power to the outside, a current path is formed through the switching element that is turned on according to the switching of each switching element.

And, during the Pda period, the reflux mode is performed, and the first switching element SW1 and the diode element D3 connected in parallel to the third switching element SW3 as shown in FIG. 5C or 5D are used. A current path (path1) may be formed.

That is, as shown in FIG. 5A, when the current output from the inverter 540 is ground, the controller 550 is a diode element D3 connected in parallel to the first switching element SW1 and the third switching element SW3. Through ), it is possible to control so that the first current path path1 is formed.

Accordingly, power factor control is performed while performing asynchronous pulse width variable control, and as shown in FIG. 5E, current distortion of the output AC power can be improved. In particular, it is possible to improve the current distortion of the output AC power supply during the Pda period.

5E illustrates that the peak current is removed from the waveform of the ground current Iga and the voltage waveform Vga, thereby improving current quality and voltage quality.

Meanwhile, when the current output from the inverter 540 is ground, the controller 550 may control the second switching element SW2 to be turned off at the first time point Taa. Accordingly, it is possible to improve the current distortion of the output AC power by performing power factor control while performing asynchronous pulse width variable control.

On the other hand, the control unit 550, during the period Pda between the first time point Taa in which the fourth switching element SW4 is turned off and the second time point Tbb in which the third switching element SW3 is turned on, The switching frequency of the 1 switching element SW1 or the second switching element SW2 is controlled to be greater than the switching frequency of the third switching element SW3 and the fourth switching element SW4 in the second leg. can do. Accordingly, it is possible to improve the current distortion of the output AC power source while performing asynchronous pulse width variable control.

On the other hand, the power conversion device 500 according to the embodiment of the present invention, as shown in Figure 2, the output voltage detector (F) for detecting the output voltage (Vc3) output from the inverter 540, the inverter ( The output current detector E for detecting the output current Ic3 output from 540 may be further included. Accordingly, it is possible to perform power factor control while performing asynchronous pulse width variable control.

Meanwhile, the controller 550 may calculate a power factor based on the output voltage and the output current. Accordingly, it is possible to perform power factor control while performing asynchronous pulse width variable control.

For example, the control unit 550 may perform power factor adjustment for adjusting a power factor between a voltage output from the inverter 540 and a current during the Pd4a and Pd3a periods.

Specifically, during the Pd4a period, the fourth switching element SW4 is turned on, the third switching element SW3 is turned off, and the first switching element SW1 and the second switching element SW2 are alternately switched.

Meanwhile, during the Pd3a period, the fourth switching element SW4 is turned off, the third switching element SW3 is turned on, and the first switching element SW1 and the second switching element SW2 are alternately switched.

Meanwhile, the controller 550 may perform power factor adjustment for adjusting a power factor between a voltage output from the inverter 540 and a current during the Pda period.

Meanwhile, the controller 550 may vary the switching frequencies of the first switching element SW1 and the second switching element SW2 in the first leg according to the calculated power factor. Accordingly, it is possible to perform power factor control while performing asynchronous pulse width variable control.

On the other hand, the control unit 550, according to the calculated power factor, a section between the first point Taa of the fourth switching element (SW4) is turned off to the second point (Tbb) of the third switching element (SW3) is turned on Among (Pda), the switching timing of the first switching element SW1 or the second switching element SW2 can be varied.

For example, as the calculated power factor decreases, the control unit 550 may control the switching timing of the first switching element SW1 or the second switching element SW2, Ta1, to be closer to Taa. Accordingly, it is possible to improve the current distortion of the output AC power by performing power factor control while performing asynchronous pulse width variable control.

FIG. 6A illustrates a case in which the current Igba output from the inverter 540 is leading to the voltage Vgba.

Meanwhile, as shown in the drawing, the output voltage Vgba output from the inverter 540 may be zero-crossed at Zcb. In particular, the point Zcb corresponds to a point in time when the output voltage Vgba output from the inverter 540 has a voltage of positive polarity and then changes to a voltage of negative polarity.

The inverter output voltage detection unit F may detect the voltage vc3 output from the inverter 540, and the control unit 550 is, in particular, a zero crossing point Zcb among the voltages vc3 output from the inverter 540. ) Can be detected.

FIG. 6B is a diagram illustrating switching waveforms of switching elements of the inverter 540 when the current output from the inverter 540 is a true phase.

Referring to the drawing, when the current output from the inverter 540 is a true phase, as shown in FIG. 6B, the controller 550 performs a third switching from a first time Tba when the fourth switching element SW4 is turned off. During the period Pdb between the second time point Tbb in which the element SW3 is turned on, the second switching element SW2 may be turned on and controlled to switch.

In the drawing, the second switching element SW2 continues to switch from the first point in time Tba to the point in time Tb1 in the period Pdb between the second point in time Tbb when the third switching element SW3 is turned on. Illustrate.

Accordingly, compared with the conventional 3b, the second switching element SW2 is switched during the Pdb period in which the switching in the inverter 540 is not performed.

Meanwhile, during the Pd4b and Pd3b periods corresponding to the power supply mode for outputting AC power to the outside, a current path is formed through the switching element that is turned on according to the switching of each switching element.

And, during the Pdb period, the reflux mode is performed, and the second switching element SW2 and the diode element D4 connected in parallel to the fourth switching element SW4, as shown in FIG. 6C or 6D, A current path (path2) may be formed.

That is, as shown in FIG. 6A, when the current output from the inverter 540 is a true phase, the controller 550 is a diode element D4 connected in parallel to the second switching element SW2 and the fourth switching element SW4. Through ), it is possible to control to form a second current path (path2).

Accordingly, power factor control is performed while performing asynchronous pulse width variable control, so that current distortion of the output AC power can be improved as shown in FIG. 6E. In particular, it is possible to improve the current distortion of the output AC power during the Pdb period.

6E illustrates that the peak current is removed from the waveform of the leading current Igb and the voltage waveform Vgb, so that the current quality and the voltage quality are improved.

Meanwhile, when the current output from the inverter 540 is a fast state, the controller 550 may control the first switching element SW1 to be turned on and switched at the second time point Tbb. Accordingly, it is possible to improve the current distortion of the output AC power by performing power factor control while performing asynchronous pulse width variable control.

On the other hand, the control unit 550 is, during the period Pdb between the first time point Tba when the fourth switching element SW4 is turned off and the second time point Tbb when the third switching element SW3 is turned on. The switching frequency of the 1 switching element SW1 or the second switching element SW2 is controlled to be greater than the switching frequency of the third switching element SW3 and the fourth switching element SW4 in the second leg. can do. Accordingly, it is possible to improve the current distortion of the output AC power source while performing asynchronous pulse width variable control.

Meanwhile, the controller 550 may calculate a power factor based on the output voltage from the output voltage detection unit F and the output current from the output current detection unit E. Accordingly, it is possible to perform power factor control while performing asynchronous pulse width variable control.

For example, the control unit 550 may perform power factor adjustment to adjust a power factor between a voltage and a current output from the inverter 540 during the Pd4b and Pd3b periods.

Specifically, during the Pd4b period, the fourth switching element SW4 is turned on, the third switching element SW3 is turned off, and the first switching element SW1 and the second switching element SW2 are alternately switched.

Meanwhile, during the Pd3b period, the fourth switching element SW4 is turned off, the third switching element SW3 is turned on, and the first switching element SW1 and the second switching element SW2 are alternately switched.

Meanwhile, the controller 550 may perform power factor adjustment for adjusting a power factor between a voltage output from the inverter 540 and a current during the Pdb period.

Meanwhile, the controller 550 may vary the switching frequencies of the first switching element SW1 and the second switching element SW2 in the first leg according to the calculated power factor. Accordingly, it is possible to perform power factor control while performing asynchronous pulse width variable control.

On the other hand, the control unit 550 is a section between the first time point Tba when the fourth switching element SW4 is turned off and the second time point Tbb when the third switching element SW3 is turned on, according to the calculated power factor. Among (Pdb), the switching timing of the first switching element SW1 or the second switching element SW2 can be varied.

For example, as the calculated power factor decreases, the controller 550 may control the turn-off timing of the first switching element SW1 or the second switching element SW2, Tb1, to be closer to Tbb. Accordingly, it is possible to improve the current distortion of the output AC power by performing power factor control while performing asynchronous pulse width variable control.

7A to 7C are diagrams showing a method of operating a power conversion device according to an embodiment of the present invention.

Referring to FIG. 7A, a power conversion device 500 according to an embodiment of the present invention may include an inverter 540 and a filter unit 570, and current and voltage output from the inverter 540 are filter units. Through 570, it may be output to an external grid.

7B is a diagram illustrating a zero crossing point Zc of a voltage output from the inverter 540.

The control unit 550 may control power factor control to be performed in a period Pdc including the zero crossing point Zc of the inverter output voltage, and to perform high-speed switching in the vicinity of the zero crossing Zc of the inverter output voltage. .

In particular, the controller 550 performs asynchronous pulse width variable control in which switching frequencies of the first leg and the second leg of the inverter 540 are different, and the fourth switching element SW4 is turned off. During the period between the first time point (Taa in FIG. 5A) and the second time point Tab at which the third switching element SW3 is turned on, the switching frequency of the second leg is before the first time point Taa. It can be controlled to be higher than the switching frequency of the second leg (legb) of.

That is, as shown in FIG. 7C, during the Pma section before the first point in time Taa and the Pmb section after the second point in time Tab, the control unit 550 is configured with a first leg and a second leg of the inverter 540. Asynchronous pulse widths with different switching frequencies of the legs can be variable and controlled.

At this time, the switching frequency of the first leg may be between several KHz and several hundred KHz, and the switching frequency of the second leg may be a system frequency.

Meanwhile, the control unit 550 performs power factor control during the period Po1 including the zero crossing point Tzc, and the switching frequency of the second leg is the Pma period before the first point Taa. , It may be controlled to be higher than the switching frequency during the Pmb period after the second point in time Tab.

For example, the controller 550 may control the switching frequency of the second leg to be between several KHz and several hundred KHz during the period Po1 including the zero crossing time Tzc. Accordingly, it is possible to improve the current distortion of the output AC power.

In addition, during the period Po1 including the zero crossing point Tzc, it is possible to form a bidirectional current path in the direction of the inverter as well as the system direction.

8 is an example of an internal block diagram of the control unit of FIG. 4.

Referring to the drawings, the control unit 550 may include a reactive power calculation unit 810, a voltage command value generation unit 811, and a switching control signal output unit 850.

The reactive power calculation unit 810 may calculate reactive power based on the output current Ig of the inverter 540 from the output current detection unit E, and may output a current command value based on the calculated reactive power. Accordingly, the reactive power calculation unit 810 may be referred to as a current command value generation unit.

Meanwhile, the reactive power calculating unit 810 calculates reactive power based on the power factor command value PFref and the output current Ig of the inverter 540, and based on the calculated reactive power, the d-axis current command value Idref Can be printed.

The voltage command value generation unit 811 may include a d-axis voltage command value generation unit 812 and a q-axis voltage command value generation unit 811.

The q-axis voltage command value generation unit 811 may generate a q-axis voltage command value Vqref based on the input q-axis current command value Iqref.

The d-axis voltage command value generator 812 may generate the d-axis voltage command value Vdref based on the input d-axis current command value Idref.

The control unit 550 may further include a phase detection unit 822, a zero crossing detection unit 824, a conversion unit 820, and the like.

The phase detection unit 822 may detect a phase difference θ between the output voltage and the output current based on the output voltage and the output current from the output voltage detection unit F and the output current detection unit E. .

The zero crossing detection unit 824 may detect the zero crossing point based on the output voltage from the output voltage detection unit F.

The converter 820 may output a voltage command value Vref based on the input q-axis voltage command value Vqref, d-axis voltage command value Vdref, and phase difference θ.

Next, the switching control signal output unit 850 may output the inverter switching control signal Sic based on the voltage command value Vref.

Meanwhile, in relation to an embodiment of the present invention, the switching control signal output unit 850 may output an inverter switching control signal Sic based on a voltage command value Vref and a zero crossing point.

Specifically, the switching control signal output unit 850 performs asynchronous pulse width variable control in which the switching frequencies of the first leg and the second leg of the inverter 540 are different, and the inverter output voltage is zero. At the time of crossing, the switching elements SW3 and SW4 in the second leg are turned off, and the first switching element SW1 or the second switching element SW2 transmits an inverter switching control signal Sic for switching. Can be printed.

On the other hand, the switching control signal output unit 850, during the period (Pda) including the zero crossing point of the inverter output voltage, as shown in Figure 5b, the switching elements (SW3, SW4) in the second leg (legb) is turned off. , The first switching element SW1 or the second switching element SW2 may output an inverter switching control signal Sic for switching.

Meanwhile, the switching control signal output unit 850 includes switching frequencies of the first leg and the second leg during the period PD4a before the zero crossing point of the inverter output voltage and the period Pd3a thereafter. Is different, it is possible to output the inverter switching control signal (Sic).

Accordingly, it is possible to improve the quality of the output AC power. In particular, it is possible to improve the current distortion of the output AC power supply while performing asynchronous pulse width variable control. In addition, it is possible to perform power factor control while performing asynchronous pulse width variable control.

9 is a circuit diagram of a power conversion device in a photovoltaic module according to an embodiment of the present invention, and FIGS. 10 to 12 are views referenced for explanation of the power conversion device of FIG. 9.

Referring to the drawings, a converter 530 according to an embodiment of the present invention includes a full bridge switching unit 532 for switching DC power, and a transformer whose input side is connected to the output terminal of the full bridge switching unit 532 536, a synchronous rectification unit 538 connected to the output side of the transformer 536, and a resonance capacitor Cr and a resonance inductor Lr connected between the transformer 536 and the synchronous rectification unit 538. I can.

Especially. By resonance by the resonance capacitor Cr, the resonance inductor Lr, and the transformer 536, the ripple of the input current can be reduced.

On the other hand, by the resonance capacitor (Cr) and the resonance inductor (Lr), each switching element (Q1 ~ Q4) in the full bridge switching unit 532, to perform zero voltage switching (ZVS), zero current switching (ZCS). I can.

As shown in the drawing, the full-bridge switching unit 532 includes fifth to sixth switching elements Q1 and Q2 connected in parallel with each other, and fifth to sixth switching elements Q1 and Q2 respectively connected in series. The seventh to eighth switching elements Q3 and Q4 may be provided.

In addition, a first node n1 between the fifth switching element Q1 and the sixth switching element Q2, and a second node between the seventh switching element Q3 and the eighth switching element Q4 ( Between n2), the input sides (na, nb) of the transformer 536 may be connected.

Meanwhile, the inverter 570 may include first and second switching elements SW1 and SW2 connected in series with each other, and third and fourth switching elements SW3 and SW4 connected in series with each other.

Through a fifth node (n5) between the first switching element (SW1) and the second switching element (SW2), and a sixth node (n6) between the third switching element (SW3) and the fourth switching element (SW4) , AC power can be output.

Meanwhile, as shown in the drawing, the synchronous rectifying unit 538 includes a ninth switching element S1 and a tenth switching element S2 connected in series with each other, and a first capacitor C1 and a second capacitor connected in series with each other. (C2) may be included.

In this case, the ninth switching element S1, the tenth switching element S2, and the first capacitor C1 and the second capacitor C2 may be connected in parallel with each other.

Between the third node (n3) between the ninth switching element (S1) and the tenth switching element (S2) and the fourth node (n4) between the first capacitor (C1) and the second capacitor (C2), The output side of the transformer 536 may be connected.

Meanwhile, since the synchronous rectifying unit 538 is implemented in the form of a half bridge, it may be referred to as a half bridge switching unit.

Meanwhile, since the synchronous rectifier 538 amplifies and outputs the input voltage twice, it may be referred to as a voltage doubler.

Meanwhile, the controller 550 may control the converter 530 and the inverter 570 together.

In particular, the control unit 550 may output a control signal Sfb to the full bridge switching unit 532 in the converter 530 for controlling the maximum power point tracking.

Meanwhile, the control unit 550 may output a control signal Shb to the synchronous rectification unit 538 to control the synchronous rectification unit 538.

Meanwhile, the controller 550 may output a control signal Sic to the inverter 540 for controlling the inverter 540.

Meanwhile, the controller 550 may vary the switching frequency of the full bridge switching unit 532 based on the input voltage of the converter 530 or the voltage of the dc terminal capacitor C.

Specifically, the controller 550 may control the full bridge switching unit 532 to operate in a buck mode or a boost mode according to the voltage level of the dc terminal capacitor C.

Meanwhile, the controller 550 controls the full bridge switching unit 532 to operate in the buck mode when the voltage of the dc terminal capacitor C is higher than the target voltage, and the voltage of the dc terminal capacitor C is the target voltage If less than that, the synchronous rectification unit 538, which is a half-bridge switching unit, may be controlled to operate in a boost mode.

On the other hand, the control unit 550, when the voltage of the dc terminal capacitor (C) is greater than the target voltage, the full bridge switching unit 532 operates in the buck mode, the full bridge switching unit 532 is the first switching frequency 10 1/Tsa = Fsa), and when the voltage of the dc terminal capacitor C is less than the target voltage, the synchronous rectification unit 538, which is a half bridge switching unit, operates in a boost mode, and a full bridge switching unit 532 ), and the synchronous rectification unit 538 may be controlled to operate at a second switching frequency (1/Tsb=Fsb in FIG. 11) lower than the first switching frequency (1/Tsa=Fsa in FIG. 10).

On the other hand, it is preferable that the switching frequency of the full bridge switching unit 532 is greater than the system frequency.

For example, the first switching frequency may be 135 kHz, but the second switching frequency may be 90 kHz. Accordingly, since high-speed switching is performed, the circuit elements in the converter 530 can be miniaturized. In particular, the transformer 536 can be downsized.

Meanwhile, the controller 550 may control the voltage ripple of the dc terminal capacitor C to be reduced through a buck mode or a boost mode.

On the other hand, the control unit 550, some of the plurality of switching elements (SW1 ~ SW4) in the inverter 540 performs switching according to the third switching frequency, another part, a fourth switching frequency higher than the third switching frequency It can be controlled to perform switching according to.

That is, the control unit 550 may perform asynchronous pulse width variable control on the inverter 540.

At this time, since the third switching frequency corresponds to the grid frequency and the fourth switching frequency is higher than the grid frequency, the inverter 540 can perform high-speed switching, and accordingly, the miniaturization of circuit elements in the power conversion device Becomes possible. Accordingly, it is possible to downsize the power conversion device.

Meanwhile, the controller 550 controls the fifth and sixth switching elements SW1 and SW2 to operate at a fourth switching frequency, and controls the seventh and eighth switching elements SW3 and SW4 to It can be controlled to operate at the switching frequency.

Meanwhile, the controller 550 controls the fifth switching element SW1 and the sixth switching element SW2 to perform switching by pulse width variable control while the seventh switching element SW3 is on, and 8 While the switching element SW4 is turned on, the sixth switching element SW2 and the fifth switching element SW1 may be controlled to perform switching by pulse width variable control.

On the other hand, some (SW3, SW4) of the plurality of switching elements (SW1 to SW4) in the inverter 540 and the other part (SW1, SW2) of the plurality of switching elements (SW1 to SW4) are different types of switching elements Can be

Meanwhile, some of the plurality of switching elements SW1 to SW4 in the inverter 540 (SW1, SW2) are, for example, switching elements for performing high-speed switching, such as a gallium nitride (GaN) transistor or a silicon carbide A (SiC) transistor may be included, and accordingly, reverse recovery loss during high-speed switching can be reduced.

Meanwhile, some of the plurality of switching elements SW1 to SW4 in the inverter 540 (SW3 and SW4) include, for example, a switching element that performs low-speed switching, a metal oxide semiconductor field effect transistor (MOSFET). I can.

10 is a diagram referenced to describe a case in which the full bridge switching unit 532 operates in a buck mode.

Referring to the drawings, (a) of FIG. 10 shows a voltage waveform Vdca at the dc end, which is the voltage of the capacitor C at the dc end.

FIG. 10B illustrates switching control signals SQ1 and SQ4 applied to gates of the fifth and eighth switching elements Q1 and Q4.

FIG. 10C illustrates switching control signals SQ2 and SQ3 applied to gates of the sixth switching element Q2 and the seventh switching element Q3.

10D illustrates the voltage waveform VQ4 and the current waveform IQ4 at both ends of the eighth switching element Q4.

In the case of the buck mode, the fifth switching element Q1 and the eighth switching element Q4, the sixth switching element Q2 and the seventh switching element Q3 in the full bridge switching unit 532 are alternately turned on. It is not, and may be partially overlapped by a phase shift, as shown in the figure.

That is, the phase difference between the fifth switching element Q1 and the eighth switching element Q4 is not fixed at 180 degrees, but a phase or turn-on timing may be changed by a phase shift.

In the drawing, it is illustrated that the phase difference between the fifth switching element Q1 and the eighth switching element Q4 is DLa.

Meanwhile, in the case of the buck mode, the control unit 550 may operate the full bridge switching unit 532 at a maximum switching frequency and may vary the phase difference DLa of the switching elements in the full bridge switching unit 532.

On the other hand, the control unit 550, the voltage of the dc terminal capacitor (C) is greater than the target voltage, and the greater the difference between the voltage of the dc terminal capacitor (C) and the target voltage, the more the switching element in the full bridge switching unit 532 The phase difference DLa can be controlled to increase.

In particular, the control unit 550, so that the larger the difference between the voltage of the dc terminal capacitor C and the target voltage, the larger the phase difference DLa between the fifth switching element Q1 and the eighth switching element Q4. Can be controlled.

Meanwhile, in the case of the buck mode, in the case of the buck mode, the turn-on timing of the fourth and third switching elements Q4 and Q3 in the full bridge switching unit 532 is determined by the first and second switching elements Q1 and Q2. ) Can be controlled to be delayed than the turn-on timing. Accordingly, it is possible to vary the dc terminal voltage (Vdc).

For example, when the first and fourth switching elements Q1 and Q4 are turned on, current flows, so that the resonance capacitor Cr and the resonance inductor Lr resonate.

Thereafter, when the eighth switching element Q4 is turned off and the seventh switching element Q3 is turned on, the current flowing through the transformer 536 falls to ground (GND) or zero, and the converter In 530, the converter may operate in a discontinuous mode (DCM Dis Continue Mode) and the secondary-side switch may operate ZCS Zero Current Switching.

Meanwhile, the switching elements Q9 and Q10 in the synchronous rectifying unit 537 may be switched in synchronization with the first and second switching elements Q1 and Q2 in the full bridge switching unit 532.

Meanwhile, the controller 550 may control the turn-on timing delay to increase as the voltage of the dc terminal capacitor C is greater than or equal to the target voltage and the difference between the voltage of the dc terminal capacitor C and the target voltage increases.

Accordingly, a difference between the voltage of the dc terminal capacitor C and the target voltage may be reduced, and as a result, a dc terminal voltage waveform Vdca having less ripple as shown in FIG. 10A may be output.

Meanwhile, zero voltage turn-on switching (705a, 705b) of the switching element in the full bridge switching unit 532 is performed at a time point Ta and a time point Tb, and zero voltage turn-off switching (705a, 705b) is performed. Therefore, it becomes possible to convert high-efficiency and high-voltage power.

Meanwhile, in the case of the buck mode, in the case of the buck mode, the turn-on timing of the fourth and third switching elements Q4 and Q3 in the full bridge switching unit 532 is determined by the first and second switching elements Q1 and Q2. ) Can be controlled to be delayed than the turn-on timing. Accordingly, it is possible to vary the dc terminal voltage (Vdc).

For example, when the first and fourth switching elements Q1 and Q4 are turned on, current flows, so that the resonance capacitor Cr and the resonance inductor Lr resonate.

Thereafter, when the eighth switching element Q4 is turned off and the seventh switching element Q3 is turned on, the current flowing through the transformer 536 falls to ground (GND) or zero, and the converter In 530, the converter may operate in a discontinuous mode (DCM Dis Continue Mode) and the secondary-side switch may operate ZCS Zero Current Switching.

Meanwhile, the switching elements S1 and S2 in the synchronous rectifying unit 537 may be switched in synchronization with the first and second switching elements Q1 and Q2 in the full bridge switching unit 532.

Meanwhile, the controller 550 may control the turn-on timing delay to increase as the voltage of the dc terminal capacitor C is greater than or equal to the target voltage and the difference between the voltage of the dc terminal capacitor C and the target voltage increases.

Accordingly, a difference between the voltage of the dc terminal capacitor C and the target voltage may be reduced, and as a result, a dc terminal voltage waveform Vdca having less ripple as shown in FIG. 10A may be output.

Meanwhile, zero voltage turn-on switching (705a, 705b) of the switching element in the full bridge switching unit 532 is performed at a time point Ta and a time point Tb, and zero voltage turn-off switching (705a, 705b) is performed. Therefore, it becomes possible to convert high-efficiency and high-voltage power.

11 is a diagram referred to for describing a case in which the synchronous rectifier 537 operates in a boost mode.

Referring to the drawings, (a) of FIG. 11 shows the dc end voltage waveform Vdcb, which is the voltage of the dc end capacitor C.

11B illustrates switching control signals SQ1 and SQ4 applied to the gates of the fifth and eighth switching elements Q1 and Q4.

11C illustrates switching control signals SQ2 and SQ3 applied to the gates of the sixth switching element Q2 and the seventh switching element Q3.

11D illustrates switching control signals SS1 and SS2 applied to the gates of the ninth switching element S1 and the tenth switching element S10 in the synchronous rectifying unit 537.

11E illustrates the voltage waveform VQ4 at both ends of the eighth switching element Q4 and the current waveform IQ4.

Meanwhile, in the case of the boost mode, the control unit 550 includes the fifth switching element Q1 and the eighth switching element in the full bridge switching unit 532 as shown in FIGS. 11(b) and 11(c). Q4), the sixth switching element (Q2) and the seventh switching element (Q3) may be controlled to be turned on alternately.

Meanwhile, in the case of the boost mode, the control unit 550 may operate the full bridge switching unit 532 at the minimum switching frequency and may change the turn-on duty of the switching element in the synchronous rectification unit 538. In FIG. 11D, DLb is illustrated as a turn-on duty.

For example, while the fifth switching element Q1 and the eighth switching element Q4, the sixth switching element Q2 and the seventh switching element Q3 are alternately turned on, the synchronous rectifying unit 538 While the duty of the ninth switching element S1 and the tenth switching element S2 is varied, they are turned on.

Meanwhile, while the ninth switching element S1 and the tenth switching element S2 in the synchronous rectifier 537 are turned on, energy is charged in the resonance inductor Lr. Thereby, boosting is performed.

Meanwhile, as the voltage of the dc terminal capacitor C is less than the target voltage, and the difference between the voltage of the dc terminal capacitor C and the target voltage increases, the ninth switching element in the synchronous rectifier 538 ( S1) and the turn-on duty DLb of the tenth switching element S2 may be controlled to increase.

Meanwhile, the controller 550 turns on the switching element in the synchronous rectifier 538 as the voltage of the dc terminal capacitor C is less than the target voltage and the difference between the voltage of the dc terminal capacitor C and the target voltage increases. It can be controlled to increase the duty.

Accordingly, a difference between the voltage of the dc terminal capacitor C and the target voltage may be reduced, and as a result, a dc terminal voltage waveform Vdca having less ripple as shown in FIG. 11A may be output.

Meanwhile, zero voltage turn-on switching 715a and 715b of the switching element in the full bridge switching unit 532 is performed at the time T1 and T2, and the zero voltage turn-off switching 715a and 715b is performed. Therefore, it becomes possible to convert high-efficiency and high-voltage power.

12 is a diagram showing an internal block diagram of the control unit 550 in the power conversion device 500 of the present invention.

Referring to the drawing, the control unit 550 receives an input voltage Vc1 from the input voltage detection unit B and a dc terminal voltage Vdc from the dc voltage detection unit D, and a full bridge switching unit 532 ) Can be controlled to operate in buck mode or boost mode.

In particular, the controller 550 may control the full bridge switching unit 532 to operate in the buck mode or the synchronous rectifier 538 to operate in the boost mode according to the voltage level of the dc terminal capacitor C.

Specifically, the control unit 550, when the voltage of the DC terminal capacitor (C) is higher than the target voltage, the full bridge switching unit 532 operates in the buck mode, the full bridge switching unit 532 and the synchronous rectification unit 538 Is controlled to operate at the first switching frequency, and when the voltage of the dc terminal capacitor C is less than the target voltage, the synchronous rectification unit 538 operates in the boost mode, and the full bridge switching unit 532 and the synchronous rectification unit 538 May be controlled to operate at a second switching frequency lower than the first switching frequency.

Meanwhile, the control unit 550 includes a ripple compensator 910 for compensating the ripple of the dc terminal capacitor C based on the detected dc terminal voltage and a target voltage, and a full bridge switching unit ( A pulse width variable controller 920 for controlling a pulse width in the switching element 532 may be included.

For example, the ripple compensator 910 may determine that the ripple is larger as the difference between the detected dc terminal voltage and the target voltage increases, and compensate for the ripple so that the ripple decreases.

On the other hand, the pulse width variable controller 920, based on the compensated ripple, the phase shift value of the full bridge switching unit 532 in the buck mode or the turn-on duty of the switching element in the synchronous rectifier 538 in the boost mode Can be set.

Accordingly, the control unit 550 outputs the control signal Sfb to the full bridge switching unit 532 in the converter 530 and, for control of the synchronous rectification unit 538, the control signal ( Shb) can be output.

Meanwhile, the controller 550 may control the full bridge switching unit 532 to operate in a buck mode or a boost mode according to the voltage level of the input voltage Vc1 or Vpv.

Specifically, the control unit 550, when the voltage of the input voltage (Vc1 or Vpv) is greater than or equal to the reference voltage, the full bridge switching unit 532 operates in the buck mode, the full bridge switching unit 532 and the synchronous rectification unit 538 ) Is controlled to operate at the first switching frequency, and when the voltage of the input voltage Vc1 or Vpv is less than the reference voltage, the synchronous rectification unit 538 operates in the boost mode, and the full bridge switching unit 532 and the synchronous rectification unit ( 538) may be controlled to operate at a second switching frequency lower than the first switching frequency.

13 is a flowchart illustrating a method of operating a solar module according to an embodiment of the present invention.

Referring to the drawing, the input voltage detection unit (B) and the dc terminal voltage detection unit (D) in the converter 530 detects the input voltage (Vc1) and the dc terminal voltage (Vdc), respectively (S1010).

Next, the controller 550 receives the input voltage Vc1 from the input voltage detector B and the dc voltage Vdc from the dc voltage detector D, selects a switching frequency (S1020), It may be determined whether the full bridge switching unit 532 operates in the buck mode (S1025).

For example, when the voltage of the dc terminal capacitor C is equal to or greater than the target voltage, the controller 550 may control the full bridge switching unit 532 to perform the buck mode (S1030). In this case, the switching frequencies of the full bridge switching unit 532 and the synchronous rectification unit 538 that is a half bridge switching unit may be a first switching frequency (eg, 135 kHz).

As another example, when the voltage of the dc terminal capacitor C is less than the target voltage, the controller 550 may control the synchronous rectifier 538 to perform the boost mode (S1035). At this time, the switching frequency of the full bridge switching unit 532 and the synchronous rectification unit 538, which is a half bridge switching unit, is a second switching frequency (eg, 90Khz) lower than the first switching frequency (eg, 135 kHz). I can.

Meanwhile, operations for the buck mode and the boost mode will be omitted with reference to the descriptions of FIGS. 9 to 12.

Next, the controller 550 calculates a phase shift of the full bridge switching unit 532 or a turn-on duty of the synchronous rectifier 538 according to the buck mode or the boost mode (S1040).

Further, the control unit 550 outputs a control signal Sfb to the full bridge switching unit 532 in the converter 530 based on the calculated phase shift or the calculated duty, and controls the synchronous rectification unit 538. For this purpose, the control signal Shb may be output to the synchronous rectification unit 538.

Accordingly, the ripple of the dc terminal voltage decreases, and thus, a film capacitor, not an electrolytic capacitor having a large capacity, can be used as the dc terminal capacitor C. Therefore, the dc terminal capacitor C can be downsized.

14 is an exploded perspective view of the solar cell module of FIG. 1A or 1B.

Referring to FIG. 14, the solar cell module 100 of FIG. 2 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 and upper surfaces of the plurality of solar cells 130, the rear substrate 110 and the second 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 tandem solar cell, It may be a dye-sensitized type or CdTe, CIGS type solar cell, thin film solar cell, or the like.

The solar cell 130 is formed as 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 first conductivity type silicon substrate, 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 antireflection film including at least one opening exposing a partial surface of the second conductive type semiconductor layer and formed on the second conductive type semiconductor layer, and a front electrode contacting a partial surface of the second conductive type semiconductor layer exposed through at least one opening; , It may include a rear electrode formed on the rear surface of the silicon substrate.

Each solar cell 130 may be electrically connected in series or in parallel or in series and 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 form the solar cell string 140.

Accordingly, as described with reference to FIG. 2, six strings 140a, 140b, 140c, 140d, 140e, and 140f are formed, and each string may include 10 solar cells.

The rear substrate 110, as a back sheet, has waterproof, insulating, and UV-blocking functions, and may be a TPT (Tedlar/PET/Tedlar) type, but is not limited thereto. In addition, although the rear substrate 110 is shown in a rectangular shape in FIG. 4, it may be manufactured in various shapes such as a circular shape or a semi-circular shape according to an 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 formed, and on the first sealing material 120, a plurality of solar cells 130 They can be located adjacent to each other to achieve.

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

Here, the first sealing material 120 and the second sealing material 150 allow the elements of the solar cell to be chemically bonded. The first sealing material 120 and the second sealing material 150 may be various examples such as an ethylene vinyl acetate (EVA) film.

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

The power conversion device according to the present invention, and the solar module having the same, are not limited to the configuration and method of the embodiments described as described above, but the embodiments are each embodiment so that various modifications can be made. All or some of them may be selectively combined and configured.

In addition, although the 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 claimed in the claims. In addition, 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 (20)

A first leg including a first switching element and a second switching element connected in series with each other, and a second leg including a third switching element and a fourth switching element connected in series with each other, and a DC power supply as an AC power source. Inverter to convert;
Including; a control unit for controlling the inverter,
The control unit,
Asynchronous pulse width variable control is performed in which the switching frequency of the first leg and the second leg of the inverter are different from each other, and at a zero crossing point of the inverter output voltage, the switching element in the second leg is turned off, and the first Power conversion device, characterized in that for controlling the switching element or the second switching element to switch. The method of claim 1,
The control unit,
And controlling the inverter to perform a reflux mode during a period between a first time point in which the fourth switching element is turned off and a second time point in which the third switching element is turned on. The method of claim 1,
The control unit,
Power conversion, characterized in that controlling the first switching element or the second switching element to switch during a period between a first point in time when the fourth switching element is turned off and a second point in which the third switching element is turned on Device. The method of claim 3,
The control unit,
When the current output from the inverter is ground, the first switching element is turned on during a period between a first point in time when the fourth switching element is turned off and a second point in which the third switching element is turned on to switch Power conversion device, characterized in that to control so as to. The method of claim 3,
The control unit,
When the current output from the inverter is ground, a first current path is controlled to be formed through the first switching element and a diode element connected in parallel to the third switching element. The method of claim 3,
The control unit,
When the current output from the inverter is ground, the second switching element is controlled to be turned off at the first time point. The method of claim 3,
The control unit,
When the current output from the inverter is in the leading phase, controlling the second switching element to switch during a period between a first point in time when the fourth switching element is turned off and a second point in time when the third switching element is turned on. Power conversion device, characterized in that. The method of claim 3,
The control unit,
When the current output from the inverter is in a forward phase, the second switching element and a diode element connected in parallel to the fourth switching element are used to control the formation of a second current path. The method of claim 3,
The control unit,
When the current output from the inverter is in a leading phase, the first switching element is turned on and controlled to switch at the second time point. The method of claim 1,
The control unit,
Power, characterized in that the switching frequency of the first switching element and the second switching element in the first leg is greater than that of the third switching element and the fourth switching element in the second leg Inverter. The method of claim 1,
The control unit,
During a period between a first point in time when the fourth switching element is turned off and a second point in which the third switching element is turned on, the switching frequency of the first switching element or the second switching element is the Power conversion device, characterized in that the control to be greater than the switching frequency of the third switching element and the fourth switching element. The method of claim 1,
An output voltage detector detecting an output voltage output from the inverter;
Further comprising an output current detection unit for detecting the output current output from the inverter,
The control unit,
And calculating a power factor based on the output voltage and the output current. The method of claim 12,
The control unit,
And varying switching frequencies of the first and second switching elements in the first leg according to the calculated power factor. The method of claim 12,
The control unit,
According to the calculated power factor, the switching timing of the first switching element or the second switching element during a period between a first point in time when the fourth switching element is turned off and a second point in which the third switching element is turned on Power conversion device, characterized in that variable. The method of claim 1,
A converter that converts the level of the input DC power;
Further comprising a; DC terminal capacitor for storing the DC power output from the converter,
The converter,
A full bridge switching unit for switching the DC power supply;
A transformer having an input side connected to the output terminal of the full bridge switching unit;
A synchronous rectifying unit connected to the output side of the transformer;
A resonant capacitor and a resonant inductor connected between the transformer and the synchronous rectification unit, and
The control unit,
A power conversion device, characterized in that the switching frequency of the full bridge switching unit is varied based on the input voltage of the converter or the voltage of the dc terminal capacitor. The method of claim 1,
The control unit,
A reactive power calculation unit that calculates reactive power based on the inverter output current and outputs a current command value based on the calculated reactive power;
A voltage command value generation unit that generates a voltage command value based on the current command value from the reactive power calculation unit;
And a switching control signal output unit for outputting a switching control signal based on a variable pulse width based on the voltage command value. A first leg including a first switching element and a second switching element connected in series with each other, and a second leg including a third switching element and a fourth switching element connected in series with each other, and a DC power supply as an AC power source. Inverter to convert;
Including; a control unit for controlling the inverter,
The control unit,
Asynchronous pulse width variable control in which the switching frequencies of the first leg and the second leg of the inverter are different from each other, and between a first point in time when the fourth switching element is turned off and a second point in which the third switching element is turned on During the period of, the inverter controls to perform the reflux mode. The method of claim 17,
The control unit,
Before and after the reflux mode, the power conversion device, characterized in that for controlling to perform a power supply mode in which a current flows through a switching element in the inverter. A first leg including a first switching element and a second switching element connected in series with each other, and a second leg including a third switching element and a fourth switching element connected in series with each other, and a DC power supply as an AC power source. Inverter to convert;
Including; a control unit for controlling the inverter,
The control unit,
Asynchronous pulse width variable control in which the switching frequencies of the first leg and the second leg of the inverter are different from each other, and between a first point in time when the fourth switching element is turned off and a second point in which the third switching element is turned on During the period of, the switching frequency of the second leg is controlled to be higher than the switching frequency of the second leg before the first time point. A solar module comprising the power conversion device of any one of claims 1 to 19.

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