KR20120125447A - DC/DC converter and electric generating system using solar cell having the same - Google Patents

Abstract

PURPOSE: A DC/DC converting apparatus and a solar battery generating system including the same are provided to reduce voltage stress of a convertor switching apparatus by controlling operation of a snubber switch according to a voltage level. CONSTITUTION: A converter controlling unit(360a) outputs a converter control signal to a converter in order to convert an output voltage to a DC voltage. An inverter controlling unit outputs an inverter control signal to an inverter in order to covert a DC voltage to an AC voltage. A snubber controlling unit(360c) outputs a snubber control signal in order to clamp a voltage of the converter switching unit. A controlling unit controls an operation of a snubber switch(222a) in order to detect a phase of a power system(222a).

Description

DC / DC converter and solar cell power generation system including the same {DC / DC converter and electric generating system using solar cell having the same}

The present invention relates to a DC / DC converter and a solar cell power generation system including the same, and more particularly, to a DC / DC converter for generating electricity using sunlight and a solar cell power generation system including the same.

In recent years, as the demand for power surges, the expansion of the power infrastructure has emerged as a very important problem. In the case of such a power demand, the power load used in a certain season and a certain time period increases rapidly, causing a shortage of standby power at all times, and causing an accident such as a power failure.

Accordingly, in order to prevent the occurrence of the above problems, various attempts have been made, such as expanding the power infrastructure and limiting the use thereof. One of them is an infinite clean energy source and a solar cell (PV) having advantages in line with domestic semiconductor technology. The method using) is attracting attention.

On the other hand, in the power generation system using the solar cell, a power converter is mounted on the rear of the plurality of solar cell modules, and each power converter is configured to control the operation of the DC / DC converter, the DC / AC converter, and the converters. It is configured to include a control device.

Among these, the DC / DC converter includes a snubber device for clamping a voltage spike generated from the switching device, and the snubber device operates when the switching device is turned off to reduce the voltage across the switching device. Clamp the voltage spikes.

However, the conventional snubber device has a problem in that switching loss and conduction loss of the snubber device are increased because the snubber device operates in a low voltage section which is not significantly affected by voltage spikes.

For this reason, there arises a problem that the overall efficiency of the solar cell power generation system is lowered.

United States Patent Application Publication US20080093112 (published April 24, 2008)

The idea of the present invention is to control the operation of the snubber switch according to the voltage level applied to the converter switching element to reduce the switching loss and conduction loss and increase the efficiency of the solar cell power generation system and an aspect comprising the same It is to provide a battery power generation system.

To this end, a solar cell power generation system according to an embodiment of the present invention converts an output voltage generated in a solar cell into a DC voltage, and a DC / DC converter having a converter switching element; A snubber device having a snubber switch for clamping a voltage across the converter switching element; And controlling the operation of the snubber switch by detecting a phase of the power system to be fed back, and determining whether the detected power system phase falls within a reference phase section in a time condition when the snubber switch is turned on. Device; includes.

Here, the control device includes: a phase detector for detecting a phase of the power system; A time detector detecting a time condition for turning on the snubber switch; A comparison unit to determine whether a phase of the detected power system belongs to a reference phase section under a time condition during which the snubber switch is turned on; And a snubber signal generator configured to turn on the snubber switch when the phase of the power system is present within the reference phase section in the determination result.

In this case, the snubber signal generation unit may turn off the snubber switch when the phase of the power system does not exist within the reference phase section.

The comparator may detect a voltage applied to the converter switching element by using the voltage of the power system, compare the voltage applied to the detected converter switching element with a predetermined reference voltage, and apply the voltage to the converter switching element. The reference phase section may be set by using the phase of the power system at a point greater than the predetermined reference voltage, and it may be determined whether the phase of the power system belongs to the reference phase section.

In this case, the comparator may calculate the voltage applied to the converter switching element by using the voltage of the power system, the maximum current value of the converter switching element and the current variation value of the converter switching element.

In this case, the comparator calculates the maximum current value of the converter switching element using Equation 1 below.

[ Equation 1 ]

Where i _{pri, peak} is the maximum current value of the converter switching element, n is the number of turns of the primary and secondary coils of the transformer, i _{out, peak} is the maximum current value of the power system, and Duty is the flow rate of the converter switching element. .

In addition, the comparison unit calculates a current variation value of the converter switching element by using Equation 2 below.

& Quot; (2 ) & quot ;

Here, Jm is the current variation value of the converter switching element SW, Ro is the leakage inductance and the equivalent impedance of the capacitor of the converter switching element, Vin is the input voltage and VFB is the voltage output from the transformer.

In addition, the comparator calculates a voltage applied to the converter switching element by using Equation 3 below.

& Quot; (3 ) & quot ;

Here, Vsw and spike are voltages applied to the converter switching element SW, and Vgrid is voltages of the power system.

A DC / DC conversion apparatus for performing DC / DC conversion using a switching element according to an embodiment of the present invention includes a transformer having a secondary coil for inducing energy from a primary coil receiving a primary current; A snubber circuit having a snubber switch for clamping a voltage across the switching element; A phase detector detecting a phase of a power system fed back; And a snubber controller configured to control an operation of the snubber switch by determining whether a phase of the detected power system belongs to a reference phase section in a time condition when the snubber switch is turned on.

Here, the snubber controller may include: a time detector configured to detect a time condition for turning on the snubber switch; A comparison unit to determine whether a phase of the detected power system belongs to a reference phase section under a time condition during which the snubber switch is turned on; And a snubber signal generator configured to turn on the snubber switch when the phase of the power system is present within the reference phase section in the determination result.

In this case, the snubber signal generation unit may turn off the snubber switch when the phase of the power system does not exist within the reference phase section.

The comparator may detect a voltage applied to the converter switching element by using the voltage of the power system, compare the voltage applied to the detected converter switching element with a predetermined reference voltage, and apply the voltage to the converter switching element. The reference phase section may be set by using the phase of the power system at a point greater than the predetermined reference voltage, and it may be determined whether the phase of the power system belongs to the reference phase section.

In this case, the comparator may calculate the voltage applied to the converter switching element by using the voltage of the power system, the maximum current value of the converter switching element and the current variation value of the converter switching element.

In this case, the comparator may calculate the voltage applied to the converter switching element by using Equation 1, Equation 2, and Equation 3.

In this case, the snubber circuit includes a snubber capacitor having one end connected to the snubber switch and the other end connected to the drain of the switching element.

In addition, the snubber switch has a drain connected to the positive input terminal and a source connected to the drain of the switching element.

As described above, according to the DC / DC conversion device and the solar cell power generation system including the same according to an embodiment of the present invention, switching loss and conduction loss by controlling the operation of the snubber switch according to the voltage level applied to the converter switching element. There is an advantage to reduce.

That is, when the voltage applied to the converter switching element is higher than the reference voltage, the snubber switch is turned on. If the voltage applied to the converter switching element is not higher than the reference voltage, the snubber switch is turned off to reduce switching loss and conduction loss. There is an advantage to reduce.

In addition, by controlling the operation of the snubber switch in the manner described above, it is possible to reduce the voltage stress applied to both ends of the converter switching element.

In addition, there is an advantage that can easily reduce the switching loss and conduction loss of the solar cell power generation system without a separate detector or sensor.

Therefore, it creates an effect that can increase the overall efficiency of the solar cell power generation system.

1 is an overall configuration diagram of a solar cell power generation system according to an embodiment of the present invention.
FIG. 2 is a configuration diagram of the power converter shown in FIG. 1.
3 is a configuration diagram of the converter shown in FIG. 2.
4A to 4F are signal waveform diagrams of the converter shown in FIG. 2.
5 is a configuration diagram illustrating an example of the control device illustrated in FIG. 2.
6A and 6B are voltage waveform diagrams of a converter without using a snubber device or with use of a general snubber device.
6C is a voltage waveform diagram of a converter according to the use of a snubber device according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram showing the configuration of a first embodiment of the present invention; Fig. In the present description, the same reference numerals refer to the same configuration, and additional descriptions may be omitted for the purpose of understanding the present invention to those skilled in the art.

As used herein, unless an element is referred to as being 'direct' in connection, combination, or placement with other elements, it is to be understood that not only are there forms of being 'directly connected, They may also be present in the form of being connected, bonded or disposed.

It should be noted that, even though a singular expression is described in this specification, it can be used as a concept representing the entire constitution unless it is contrary to, or obviously different from, or inconsistent with the concept of the invention. It is to be understood that the description of 'comprising', 'having', 'comprising', 'comprising', etc., in this specification includes the possibility of the presence or addition of one or more other components or combinations thereof.

The drawings referred to in this specification are examples for describing embodiments of the present invention, and shapes, sizes, thicknesses, and the like may be exaggerated for effective description of technical features.

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

1 shows an overall configuration diagram of a solar cell power generation system according to an embodiment of the present invention.

As shown in FIG. 1, the solar cell power generation system 1 largely converts power generated by the solar cells 100: 100a to 100n and the solar cells 100, and applies the power to the power system 300. It consists of a converter 200 (200a-200n) and a power system 300 (Grid).

Here, the solar cell 100 is divided into the time when there is sunlight, such as daytime and the time without sunlight, such as night, so that the solar power generation is performed at the time of solar light to generate effective PV power by solar power generation, If solar power generation is not carried out, it does not produce valid PV power.

As described above, since solar power generation is not performed regularly depending on the presence or absence of solar light, the maximum power point tracking (MPPT: Maximum Power Point) tracks the maximum power point among the power generated by the solar cell 100. Tracking should be controlled to generate maximum power.

FIG. 2 shows a configuration diagram of the power converter shown in FIG. 1.

Referring to FIG. 2, the power converter 200 converts an output voltage VPV generated from the solar cell 100 into a DC voltage VDC in the form of a pulse 220, hereinafter, a converter ( DC / AC converter (240, hereinafter referred to as inverter) for converting a pulsed DC voltage (VDC) into an AC voltage (Vac) and applying it to the power system 300) The operation of the converter 220 and the inverter 240 is controlled based on the output voltage VPV of the battery 100, the output current IPV of the solar cell 100, and the voltage Vgrid of the power system 300. It is configured to include a control device 260.

Converter 220 is a means for converting the output voltage (VPV) generated in the solar cell 100 to a full-wave rectified sinusoidal DC voltage (VDC), the DC voltage (VDC) is approximately of the power system 300 It can have twice the frequency.

The converter 220 includes a flyback converter, a buck-boost converter, a push-pull converter, a half-bridge converter, a full-bridge converter, and the like. It can be used, of course, a converter of a modified form based on the converter can also be used.

FIG. 3 is a configuration diagram of the converter shown in FIG. 2. In an embodiment of the present invention, a flyback converter will be described as an example.

The flyback converter 220 illustrated in FIG. 3 includes a converter switching element SW, a transformer T, a snubber device 222, a rectifier diode D1, and an output capacitor C1.

The converter switching element SW is a means for supplying a primary voltage, which is an input voltage, to the transformer T by performing a pulse width modulation (PWM) operation according to the converter control signal PWM_sw output from the control device 260. It is composed of a MOS field-effect transistor, and a drain is connected to the transformer T and a source is connected to the ground GND.

The transformer (T) is a means for converting the primary voltage into the secondary voltage according to the turns ratio of the primary coil (Lpr) and the secondary coil (Lse), equivalently connected in parallel to the primary coil (Lpr) and magnetic The magnetization inductor Lm showing the magnetization of the magnetic core and the leakage inductor Llkg positioned on the primary current Ipr path by the leakage of the magnetic flux of the transformer T are determined. Include.

The snubber device 222 is a means for clamping the voltage across the converter switching element SW (that is, the drain-source voltage Vds of the converter switching element SW). 222a and snubber capacitor 222b.

Here, the snubber switch 222a has a drain connected to the positive input terminal, a source is connected to one end of the snubber capacitor 222b, and the snubber capacitor 222b is the snubber switch 222a. One end is connected to the source of the other end and the other end is connected to the drain of the converter switching element (SW).

In addition, the snubber switch 222a is turned on in response to the snubber control signal P_snb output from the control device 260 during the turn-off operation of the converter switching element SW so as to be connected to both ends of the converter switching element SW. The voltage applied to both ends of the converter switching element SW is clamped by charging the applied voltage to the snubber capacitor 222b.

4A to 4F are signal waveform diagrams of the converter shown in FIG. 2.

The operation of the snubber device 222 will be described in more detail with reference to FIGS. 4A to 4F.

As shown in FIG. 4A, when the converter switching element SW is turned on, the voltage applied to the converter switching element SW becomes equal to the input voltage applied to the flyback converter 220.

However, when the converter switching element SW is turned off, the secondary voltage of the transformer T (that is, the voltage output from the flyback converter 220) is applied to the magnetization inductor Lm, and thus the magnetization inductor Lm. The current flows as shown in FIG. 4B.

And, as shown in Figure 4c, due to the resonance of the input voltage, the voltage of the magnetizing inductor (Lm), the leakage inductor (Llkg) and the capacitor (C_sw) of the converter switching element (SW) at both ends of the converter switching element (SW) The sum of the voltage spikes is applied, and a current as shown in FIG. 4D flows.

As such, in order to limit the excessive voltage applied to the converter switching element SW, as illustrated in FIG. 4E, the snubber switch 222a is turned off and a predetermined time before the turn on operation. Turn on.

Then, the energy accumulated in the leakage inductor Llkg is charged by the capacitor C_sw of the converter switching element SW, and charged by the snubber capacitor 222b so that the current as shown in FIG. 4F is applied to the snubber capacitor 222b. Through the above-described process, the voltage applied to the converter switching device SW can be reduced.

Rectifier diode D1 rectifies the secondary voltage from transformer T, and output capacitor C1 smoothes the voltage through rectifier diode D1.

FIG. 5 shows a configuration diagram according to an example of the control device shown in FIG. 2.

As shown in FIG. 5, the control device (reference numeral 260 of FIG. 2) largely converts the output voltage VPV generated from the solar cell 100 to the DC voltage VDC of the same phase. Converter control unit 360a for generating and outputting low converter control signal PWM_sw and inverter control signal PWM_q1 to inverter 240 to convert DC voltage VDC output from converter 220 to AC voltage Vac. An inverter controller 260b generating and outputting PWM_q4 and a snubber controller 360c generating and outputting a snubber control signal P_snb to clamp the voltage applied to the converter switching element SW.

At this time, the control device (reference numeral 260 of FIG. 2) detects the phase of the power system to be fed back, and in the time condition in which the snubber switch 222a is turned on, the detected phase of the power system belongs to the reference phase section. It determines whether or not to control the operation of the snubber switch (222a).

The converter controller 360a includes an MPPT controller 361a, a current controller 362a, a phase detector 363a, a sine value calculator 364a, a calculator 365a, and a converter signal generator 366a.

The MPPT control unit 361a is based on the output voltage (VPV) and output current (IPV) information of the solar cell 100 to maintain the power conversion and maximum output of the inverter 240 (MPPT: Maximum Power Point) Tracking to generate a reference current (IPV *), and delivers it to the current controller 362a.

The current controller 362a calculates and outputs a DC current command value Io * according to a difference value between the output current IPV and the reference current IPV * of the solar cell 100.

The phase detector 363a detects the phase angle of the power system 300, and the sine value calculator 364a amplifies the difference between the predetermined reference frequency and the output frequency of the inverter 240 with a preset gain to obtain a frequency difference. The amplification value is calculated, and a sine value is output by adding the calculated frequency difference amplification value and the phase angle of the power system 300 detected by the phase detector 363a. In addition, the output of the phase detector 363a is provided to the comparator 364c.

The calculating part 365a includes a multiplier 365a1, and multiplies the sine value output from the sine value calculator 364a by the DC current command value Io * output by the current control part 362a to output the current command value ( Print Iout *).

The converter signal generator 366a generates and outputs the converter control signal PWM_sw using the output current command value Iout *.

The inverter signal generator 363b generates and outputs the first to fourth inverter control signals PWM_q1 to PWM_q4 to control the first to fourth inverter switching elements Q1 to Q4.

The snubber controller 360c is a means for controlling the operation of the snubber switch 222a according to the voltage level applied to the converter switching element SW. The snubber controller 360c includes a time detector 362c, a comparator 364c, and a snubber signal generator. 336c.

The time detector 362c detects the turn-on time of the snubber switch 222a by using the voltage Vgrid of the power system 300 and the voltage VPV generated by the solar cell 100.

In more detail, the snubber switch 222a has the turn-on time of the converter switching element SW because the converter switching element SW is turned off and must be turned on in a section before the turn-on operation. The turn off time may be used to detect a time when the snubber switch 222a is turned on.

The comparator 364c compares whether the phase of the power system 300 belongs to a predetermined reference phase section.

When the snubber signal generator 366c is the time when the snubber switch 222a is turned on, and the phase of the power system 300 is within a predetermined reference phase section in the comparison result of the comparator 364c, The nover switch 222a may be turned on. In addition, the snubber signal generator 366c generates a snubber control signal P_snb for turning off the snubber switch 222a when the phase of the power system 300 does not exist within a predetermined reference phase section. Output

The time detector 362c uses the voltage Vgrid of the power system 300 and the voltage VPV generated by the solar cell 100 to perform the turn-on operation of the snubber switch 222a (that is, the snubber). Operating conditions of the switch 222a).

In more detail, the magnitude of the voltage applied to both ends of the converter switching element SW is determined using the instantaneous value of the voltage Vgrid of the power system 300 and the voltage VPV generated by the solar cell 100. The operating conditions of the snubber switch 222a may be detected using the same.

That is, the snubber switch 222a has the turn-on time or the turn-off time of the converter switching element SW because the converter switching element SW is turned off and must be turned on in a section before the turn-on operation. The time for which the snubber switch 222a is turned on may be detected by using the.

Hereinafter, the configuration of the comparison unit 364c will be described in detail.

The comparator 364c detects a voltage applied to the converter switching element SW using the voltage of the power system 300.

At this time, the comparator 364c compares the voltage Vgrid of the power system 300, the maximum current value i _{pri , peak of the} converter switching element SW, and the current variation value Jm of the converter switching element SW. The voltage Vds applied to the converter switching element SW may be calculated.

To this end, the comparator 364c calculates the maximum current value i _{pri , peak of the} converter switching element SW and the current variation value Jm of the converter switching element SW, respectively.

First, the comparator 364c calculates the maximum current value i _{pri , peak} of the converter switching element SW using Equation 1 below.

Where i _{pri and peak} are the maximum current values of the converter switching element, n is the turn ratio of the primary and secondary coils of the transformer, i _{out , peak} are the maximum current value and duty of the power system and the current flow rate of the converter switching element. .

In addition, the comparator 364c calculates the current variation value Jm of the converter switching element SW by using Equation 2 below.

Here, Jm is the current variation value of the converter switching element SW, Ro is the leakage inductance and the equivalent impedance of the capacitor of the converter switching element, Vin is the input voltage and VFB is the voltage output from the transformer.

After calculating the maximum current value (i _{pri , peak} ) of the converter switching element (SW) and the current variation value (Jm) of the converter switching element (SW) through the above [Equation 1] and [Equation 2], the comparison The unit 364c calculates the voltage Vds applied to the converter switching element SW by using Equation 3 below.

Here, Vsw and spike are voltages applied to the converter switching element SW, and Vgrid is voltages of the power system.

Accordingly, the comparator 364c compares the calculated voltage Vds applied to the converter switching element SW with the reference voltage Vref.

In this case, the comparator 364c sets a reference phase section by using the phase of the power system 300 at the time when the voltage Vds applied to the converter switching element SW is greater than the predetermined reference voltage Vref. Accordingly, the comparator 364c may determine whether the phase of the power system belongs to the reference phase section.

For example, the reference phase is a range from the phase of the power system 300 at a point in time when the voltage Vds applied to the converter switching element SW is greater than the predetermined reference voltage Vref to a symmetrical range based on the phase value corresponding to the peak value. It can be set as an interval. In the reference phase section, the operation of the snubber switch 222a is controlled according to a time condition for turn-on operation detected by the time detector 362c without additionally calculating the voltage Vds applied to the converter switching element SW. The snubber control signal P_snb may be output.

When the reference phase interval is out of the set range, the comparator 364c includes the voltage Vgrid of the power system 300, the maximum current value i _{pri , peak of the} converter switching element SW, and the converter switching element SW. The voltage Vds applied to the converter switching element SW is calculated using the current variation value Jm, and the voltage applied to the converter switching element SW under the time condition at which the snubber switch 222a is turned on ( The snubber control signal P_snb controlling the operation of the snubber switch 222a may be output according to the result of comparing and comparing Vds) with the reference voltage Vref.

If the snubber switch 222a is not a time condition in which the snubber switch 222a is turned on when it is out of the set reference phase section, it is necessary to output a snubber control signal P_snb that controls the operation of the snubber switch 222a. There is no.

6A and 6B are voltage waveform diagrams of a converter without using a snubber device or using a general snubber device, and FIG. 6C is a voltage waveform diagram of a converter according to the use of a snubber device according to an embodiment of the present invention. As will be described in more detail with reference to Figures 6a to 6c.

When the snubber device is not used as shown in FIG. 6A, the converter switching element is increased because the voltage applied to the converter switching element SW is higher than the reference voltage Vref in the high voltage section (t2, t4 section) within the system frequency. (SW) could not be operated.

Therefore, in order to solve this problem, as shown in FIG. 6B, the voltage applied to the converter switching element SW in the entire region within the system frequency is controlled to be lower than the reference voltage Vref using the general snubber device. Since the snubber switch 222a operates over the entire section (t1 to t5 section), a problem of efficiency deterioration due to the loss of the snubber switch 222a occurs.

Therefore, in order to improve the problem of FIG. 6A and to solve the problem of efficiency reduction according to FIG. 6B, in one embodiment of the present invention, as shown in FIG. 6C, the voltage applied to the converter switching element SW is lower than the reference voltage. In the low voltage section (t1, t3, t5 section) within the system frequency, the snubber switch 222a is turned off, and the high voltage section (t2, t4 section within the system frequency at which the voltage applied to the converter switching element SW is higher than the reference voltage. ), The converter switching element SW can be operated in all sections within the system frequency by outputting the snubber control signal P_snb for turning on the snubber switch 222a, and the low voltage sections t1 and t3 in the system frequency. In the t5 section, the snubber switch 222a is not operated, so that the switching loss and the conduction loss of the snubber switch 222a occurring during this period can be improved.

The foregoing embodiments and accompanying drawings are not intended to limit the scope of the present invention but to illustrate the present invention in order to facilitate understanding of the present invention by those skilled in the art. Embodiments in accordance with various combinations of the above-described configurations can also be implemented by those skilled in the art from the foregoing detailed description. Accordingly, various embodiments of the invention may be embodied in various forms without departing from the essential characteristics thereof, and the scope of the invention should be construed in accordance with the invention as set forth in the appended claims. Alternatives, and equivalents by those skilled in the art.

222. Snubber device 222a. Snubber switch
222b. Snubber Condenser 360c. Snubber control unit
362c. Time detector 364c. Snubber signal generator
364c1. Detector 364c11. First operator
364c12. Second operator 364c2. Motion controller

Claims (15)

A DC / DC converter converting an output voltage generated in the solar cell into a direct current voltage and having a converter switching element;
A snubber device having a snubber switch for clamping a voltage across the converter switching element; And
A control device that detects a phase of a power system to be fed back and determines whether a phase of the detected power system belongs to a reference phase section in a time condition when the snubber switch is turned on, thereby controlling the operation of the snubber switch. Solar cell power generation system comprising;
The method according to claim 1,
The control device,
A phase detector for detecting a phase of the power system;
A time detector detecting a time condition for turning on the snubber switch;
A comparison unit to determine whether a phase of the detected power system belongs to a reference phase section under a time condition during which the snubber switch is turned on; And
And a snubber signal generator configured to turn on the snubber switch when the phase of the power system exists within the reference phase section in the determination result.
The method according to claim 2,
The snubber signal generator,
And turning off the snubber switch if the phase of the power system is not within the reference phase section.
The method according to claim 2,
Wherein,
The voltage applied to the converter switching element is detected using the voltage of the power system, the voltage applied to the detected converter switching element is compared with a predetermined reference voltage, and the voltage applied to the converter switching element is greater than the predetermined reference voltage. And setting the reference phase section by using the phase of the power system at a large time point, and determining whether the phase of the power system belongs to the reference phase section.
The method of claim 4,
The comparing unit calculates a voltage applied to the converter switching element by using the voltage of the power system, the maximum current value of the converter switching element and the current variation value of the converter switching element.
The method according to claim 5,
Wherein,
A solar cell power generation system for calculating the maximum current value of the converter switching device using the following [Equation 1].
[ Equation 1 ]

Where i _{pri, peak} is the maximum current value of the converter switching element, n is the ratio of the number of turns of the primary and secondary coils of the transformer, i _{out, peak} is the maximum current value of the power system and Duty is the flow rate of the converter switching element.
The method according to claim 5 or 6,
Wherein,
A solar cell power generation system that calculates a current variation value of the converter switching element by using Equation 2 below.
& Quot; (2 ) & quot ;

Where Jm is the current variation value of the converter switching element SW, Ro is the leakage inductance and the equivalent impedance of the capacitor of the converter switching element, Vin is the input voltage and VFB is the voltage output from the transformer.
The method of claim 7,
Wherein,
A solar cell power generation system that calculates a voltage applied to the converter switching element by using Equation 3 below.
& Quot; (3 ) & quot ;

Here, Vsw, spike is the voltage applied to the converter switching element (SW), Vgrid is the voltage of the power system.
In the DC / DC converter for performing a DC / DC conversion by using a switching element,
A transformer having a secondary coil that induces energy from the primary coil receiving the primary current;
A snubber circuit having a snubber switch for clamping a voltage across the switching element;
A phase detector detecting a phase of a power system fed back; And
And a snubber controller configured to control an operation of the snubber switch by determining whether a phase of the detected power system belongs to a reference phase section in a time condition when the snubber switch is turned on. .
The method according to claim 9,
The snubber controller is:
A time detector detecting a time condition for turning on the snubber switch;
A comparison unit to determine whether a phase of the detected power system belongs to a reference phase section under a time condition during which the snubber switch is turned on; And
And a snubber signal generator configured to turn on the snubber switch when the phase of the power system exists within the reference phase section in the determination result.
The method of claim 10,
Wherein,
The voltage applied to the converter switching element is detected using the voltage of the power system, the voltage applied to the detected converter switching element is compared with a predetermined reference voltage, and the voltage applied to the converter switching element is greater than the predetermined reference voltage. And setting the reference phase section using the phase of the power system at a large time point, and determining whether the phase of the power system belongs to the reference phase section.
The method of claim 11,
And the comparing unit calculates a voltage applied to the converter switching element by using a voltage of the power system, a maximum current value of the converter switching element, and a current variation value of the converter switching element.
The method of claim 12,
The comparator calculates the voltage applied to the converter switching element by using the following Equation 1, Equation 2 and Equation 3 below.
[ Equation 1 ]

& Quot; (2 ) & quot ;

& Quot; (3 ) & quot ;

Where i _{pri and peak} are the maximum current values of the converter switching element, n is the number of turns of the primary and secondary coils of the transformer, i _{out , peak} are the maximum current value and duty of the power system and the flow rate of the converter switching element. ,
Jm is the current fluctuation value of the converter switching element (SW), Ro is the leakage inductance and the equivalent impedance of the capacitor of the converter switching element, Vin is the input voltage and VFB is the voltage output from the transformer,
Vsw, spike is the voltage across the converter switching element (SW), Vgrid is the voltage of the power system.
The method according to claim 9,
The snubber circuit,
And a snubber capacitor having one end connected to the snubber switch and the other end connected to a drain of the switching element.
The method according to claim 9,
The snubber switch,
A DC / DC conversion device having a drain connected to a positive input terminal and a source connected to a drain of the switching device.

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