KR20180112361A - Grid connected single-stage inverter based on cuk converter - Google Patents

Abstract

The present invention relates to a grid connected single-stage inverter based on a cuk converter, which uses a cuk converter to convert a DC voltage supplied from a renewable energy module into a full-wave rectified sinusoidal voltage, converts the half period of the voltage of the sinusoidal wave rectified though an unfolding bridge circuit part to negative polarity to output the voltage of the sinusoidal wave, and supplies it to a system power source, thereby compensating for a phase lag effect and attenuating a total harmonic distortion in a systematic disturbance environment. According to the grid connected single-stage inverter based on a cuk converter, it is possible to produce DC power with AC power at a high power density and at a low cost. Especially, it is possible to supply power to the grid power source stably even in an environment where output control is difficult due to system disturbance and right half plane zero characteristic. The grid connected single-stage inverter includes: a renewable energy module; a DC-DC converter part; an unfolding bridge circuit; and a main control part.

Description

[0001] The present invention relates to a grid-connected single-stage inverter based on-cuk converter,

[0001] The present invention relates to a cook-converter-based, grid-connected single-stage inverter for generating DC power at high power density and low cost with AC power, more particularly, The voltage of the sinusoidal wave is converted into a rectified sinusoidal wave voltage, the half period of the sinusoidal wave rectified by the unfolding bridge circuit portion is switched to negative polarity, the sinusoidal wave voltage is outputted to the system power source to compensate for the influence of phase lag, To a single-stage inverter based on a cook converter capable of attenuating whole harmonic distortion.

As is well known, a power generation system using a solar cell or a thermoelectric battery module is rapidly spreading due to the characteristics of being an environmentally friendly energy source, and research and development are being actively conducted in any field.

Inverter converts DC power generated from such renewable energy module into AC power and supplies it to grid power grid. In particular, inverter that performs power conversion according to optimum operating point for each new and renewable energy module is called micro inverter or modular inverter .

Among such modular inverters, a converter unit for converting the full-wave rectified sinusoidal power into an alternating-current power and an unfolding bridge unit for converting the converted sinusoidal power into alternating-current power are used in place of the two-stage inverter having the conventional boost converter unit and the inverter unit Single-stage inverters are gaining popularity as modular inverters with simple structure and low cost.

In recent years, modular inverters with low power and low cost have been demanded with high efficiency of solar photovoltaic cells and thermoelectric modules. In addition, a modular inverter having a larger power density is required compared with a conventional modular inverter In fact there is.

Modular single-stage inverters based on cook converters are characterized by simple structure, low cost and large power density. Such an inverter must supply power to the grid power grid, so it must have a total harmonic distortion (THD) of less than a certain level so that the output power does not impair the quality of the grid. For this purpose, an appropriate output current control method is required. Feedforward control and feedback control are mainly used as control methods.

In particular, in order to control the output current in a system disturbance environment, it is necessary to use a linear controller with a high gain. In the case of the Cook inverter, there is a sufficient phase margin (RHP: Right Half Plane) Phase margins), it is difficult to control the output current with a conventional proportional-integral controller.

A problem to be solved by the present invention is to provide a DC converter using a Cuk converter of a type including a boost converter type and a buck converter type, The voltage is converted to the full-wave rectified sinusoidal wave voltage and the half period of the voltage of the full wave rectified sinusoidal wave is switched to the negative polarity through the unfolding bridge circuit section to output the sinusoidal wave voltage to the system power source And to provide a grid-based single-stage inverter based on a cook converter capable of attenuating the total harmonic distortion rate in a system disturbance environment.

According to an aspect of the present invention, there is provided a grid-connected single-stage inverter based on a cook converter, the grid-connected single-stage inverter comprising: a renewable energy module; (V _in ) supplied from the renewable energy module to a first output voltage (V _o1 ) of a full wave rectified sinusoidal wave, and outputs the first output voltage (V _o1 ) - a dicing converter section; And a second output voltage (V _o2 ) of the sinusoidal wave by switching the odd or even-numbered period of the first output voltage (V _o1 ) output from the dish- Folding bridge circuitry; And a second output voltage V _o2 corresponding to the input voltage V _in and a corresponding input current i _in , the first output voltage V _o1 and a corresponding first output current i _o1 , And a main controller for receiving the input signal and generating a pulse width modulation signal PWM to control operation of the dictation-to-decoder converter, wherein the main controller compares a duty voltage generated internally with a triangular waveform, The pulse width modulation signal PWM having a ratio is generated.

According to the cook-converter-based single-stage inverter based on the cooker according to the present invention, the DC converter supplied from the renewable energy module is converted into the full-wave rectified sinusoidal voltage using the cook converter of the type including the boost converter type and the buck converter type Stage inverter for converting the half-period of the voltage of the full-wave rectified sine wave to negative polarity and outputting the output voltage of the sinusoidal wave to the system power supply in the unfolding bridge circuit section. Thus, a modular inverter having low cost and high power density As shown in FIG.

In addition, it solves the problem of the output current control due to the system disturbance environment and the right to the zero effect, and it is possible to stably operate the single converter based on the cook converter in the grid connection environment.

FIG. 1 is a block diagram of a cooktool converter based single-ended system interconnection inverter according to an embodiment of the present invention.
FIG. 2 is an output waveform diagram of a cookie converter-based single-ended inverter of a grid-connected type according to an embodiment of the present invention.
3 is a detailed circuit diagram of a cook-converter-based dc-to-dc converter of a grid-connected single-stage inverter according to an embodiment of the present invention.
4 is a diagram for explaining the operation of the cook-converter-based dc-to-dc converter of the grid-connected single-stage inverter according to the embodiment of the present invention.
FIG. 5 is another diagram for explaining the operation of the cook-converter based decoupling converter unit of the grid-connected single-stage inverter according to the embodiment of the present invention.
FIG. 6 is a detailed circuit diagram of an unfolding bridge circuit unit of a single-stage inverter based on a cook converter according to an embodiment of the present invention.
7 is a detailed block diagram of a main controller of a grid-based single-stage inverter based on a cook converter according to an embodiment of the present invention.
8 is a detailed block diagram of the controller of the main control unit of FIG.
9 is a conventional output voltage and current waveform using a proportional integral controller.
10 is an output voltage and current waveform using a cook-converter-based grid-connected single-stage inverter according to an embodiment of the present invention.

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

FIG. 1 is a block diagram of a cooktool converter based single-ended system interconnection inverter according to an embodiment of the present invention.

As shown in FIG. 1, the cook-converter-based single-stage inverter based on a cooker according to the present invention includes a renewable energy module 110, a DC-DC converter unit 120, an unfolding bridge a first voltage current sensing unit 160, a second voltage current sensing unit 170, and an output voltage sensing unit 180. The bridge control unit 130, the main control unit 140, the system power supply 150,

The DC-DC converter unit 120 includes a Cuk converter having a boost converter unit and a buck converter unit. The DC-DC converter 120 converts a DC input voltage V _in to the first output voltage V _o1 of the full wave rectified sinusoidal wave as shown in FIG.

The dicing-to-dither converter unit 120 may set the duty ratio of the input voltage (V _in ) to a different sinusoidal frequency for each sampling period, and output the sinusoidal wave with a full wave rectified voltage. The dictation-to-dictation converter unit 120 can perform both the operation of raising and lowering the voltage internally by using the above-described cook converter instead of using only the buck converter or the boost converter. Accordingly, the dic-decy converter unit 120 can output power having a high power density and can minimize ripple in both input and output power.

The decode-and-decode converter 120 connects the boost converter unit and the buck converter through a transformer, thereby achieving an insulation effect between the input and the output power. By reducing the duty ratio input area of the cook converter, It is possible to avoid the high duty ratio area area where the voltage change due to the duty ratio change is sensitive and to control the power so as to more easily perform the maximum power point tracking (MPPT).

3 is a detailed circuit diagram of a cook-converter-based dc-to-dc converter of a grid-connected single-stage inverter according to an embodiment of the present invention.

3, the dash-and-dia converter section 120 includes a boost converter section 121 and a buck converter section 123. The boost converter section 121 and the buck converter section 123 are connected to a transformer (122). ≪ / RTI >

Boost converter unit input voltage (V _in) connected in series between the both side terminals inductor (L1), the other terminal of the capacitor (C1), 1 primary coil of the transformer (122) (N _P) and the inductor (L1) of the input voltage And a switch element S1 connected between the other terminals of the inductor (V _in ). The switching element S1 may be implemented as a MOS transistor, and the switching element S1 is hereinafter referred to as a MOS transistor. A capacitor C2 is connected between both terminals of the MOS transistor S1.

The buck converter unit 123 includes an inductor L2 connected in series between the two terminals of the first output voltage V _o1 , a capacitor C3, a secondary coil N _S of the transformer 122, And a capacitor C4 connected between both terminals of the first output voltage _Vo1 and a diode D1 connected in reverse between the other terminal of the first output voltage _Vo1 and the other terminal of the first output voltage _Vo1 .

The cook converter unit 123 is for converting a DC power source into a full-wave rectified sinusoidal power source by inputting a different duty voltage for each sampling period, and the elements of the step-up converter in the two-stage inverter having the conventional boost converter and inverter unit It is possible to implement the device at a significantly lower value. In order to implement the cook-converter-based single-ended inverter of the grid-connected type according to the present invention and to verify the control algorithm, the device values are designed as follows.

4 and 5 are views for explaining the operation of the cook-converter-based decoupling converter unit of the grid-connected single-stage inverter according to the embodiment of the present invention.

FIG. 4 is a graphical representation of the current flow when the MOS transistor S1, which is a switch element, is turned on in the dishi-DC converter section, and FIG. 5 is a graphical representation of the current flow when the MOS transistor S1 is off Hereinafter, the operation of the dictation-to-digital converter will be described with reference to these drawings.

4, when the MOS transistor S1 is turned on by the pulse width modulation signal PWM supplied from the main control unit, the input voltage V _in is supplied only to the inductor Ll So that the current flowing through the inductor L1 is increased, whereby electric energy is accumulated in the inductor L1. This operation is similar to that of the conventional switch-on mode of the boost converter.

The electric energy charged in the capacitor C1 is transmitted to the primary coil N _P of the transformer 122 and the electric energy corresponding thereto is transmitted to the secondary coil N _S of the transformer 122. Electrical energy that has been charged into the electric energy and the capacitor (C3) transmitted to the secondary windings (N _S) of the transformer (122) is released with is transmitted to the inductor (L2) and a capacitor (C4). Therefore, the first output voltage (V _O1 ) of the DC-DC converter section 120 is equal to the voltage across the two terminals of the capacitor C3. This operation is similar to the operation of the conventional buck converter in the switch-off mode.

5, when the MOS transistor S1 is turned off by the pulse width modulation signal PWM, the electric energy stored in the inductor L1 is discharged. At this time, (V _in ) and the inductor (L 1) are the same. Accordingly, the input voltage V _in and the voltage of the inductor Ll are combined and transmitted to the capacitor C 1 and the primary coil N _P of the transformer 122. Accordingly, the voltage boosted by the turns ratio N _S / N _P of the primary coil N _P and the secondary coil N _S of the transformer 122 is transmitted from the transformer 122 to the capacitor C 3, do. This operation is similar to the operation in the switch-off mode of the conventional boost converter. Since the electric energy accumulated in the inductor L2 is discharged and charged to the capacitor C4, the amount of the output current of the DSSC 120 is reduced. This operation is similar to the operation of the switch-on mode of the buck converter.

The conventional D / A converter unit outputs the dicing voltage, whereas the D / D converter unit 120 according to the present invention outputs the full-wave rectified sine wave voltage, so that the capacitor C3 having a small capacity can be used.

The unfolding bridge circuit unit 130 converts an even-numbered (or odd-numbered) period of the voltage of the full-wave rectified sine wave outputted from the dishi-dic converter unit 120 to a negative polarity, (V _o2 ) to the system power supply 150. The second output voltage (V _o2 )

FIG. 6 is a detailed circuit diagram of an unfolding bridge circuit unit of a single-stage inverter based on a cook converter according to an embodiment of the present invention.

6, the unfolding bridge circuit unit 130 according to the present invention includes a first input terminal connected to the first output voltage V _O1 of the dish- Thyristors DR3 and DR4 connected in series between the two input terminals connected to the first output voltage V _{O1 of} the dicode-to-dither converter unit 120, the thyristors DR3 and DR4, And an inductor L3 connected between a connection node of the second output voltage V _O2 and one terminal of the second output voltage V _O2 .

6, when the system power source is positive (+), the first switching mode is set so that the thyristors DR2 and DR3 are turned on and the thyristors DR1 and DR4 are turned off, so that the odd- Is output as the second output voltage (V _O2 ) as it is. When the system power supply 150 is negative, the second switching mode is set so that the thyristors DR2 and DR3 are turned off and the thyristors DR1 and DR4 are turned on to output a sinusoidal wave voltage The even-numbered section is switched to the negative polarity. Accordingly, the second output voltage _Vo2 of the unfolding bridge circuit unit 130 is outputted in the form of a sine wave as shown in Fig. 2 (b).

For example, when the frequency of the system power supply is 60 Hz, the thyristors DR1, DR2, DR3, DR4 are switched to the first switching mode and the second switching mode correspondingly. This switching operation not only operates at a lower frequency than that of the conventional inverter but also has a feature of minimizing the switching loss by switching when the voltage and the current are '0'.

The L filter formed of the inductor L3 connected to the output terminal of the unfolding bridge circuit unit 130 serves to minimize the power ripple. The unfolding bridge circuit unit 130 according to the present invention is configured such that the unfolding bridge circuit unit 130 according to the present invention outputs a sinusoidal wave with full wave rectification in the dish- The polarity of the polarity is changed. Therefore, since the role of the L filter formed of the inductor L3 can be minimized, the capacity of the inductor L3 can be minimized. The inductor (L3) element value was designed to 190 μH in order to implement the cook-converter-based single-stage inverter based on the present invention and to verify the control algorithm.

The first voltage / current sensing unit 160 detects a voltage and a current input from the renewable energy module 110 and outputs an input voltage V _in and an input current i _in .

The second voltage / current sensing unit 170 detects the full-wave rectified voltage and current output from the dic-decy converter unit 120 and outputs a first output voltage V _o1 and a first output current i _o1 corresponding thereto, .

The output voltage sensing unit 180 detects a voltage output from the unfolding bridge circuit unit 130 and outputs a second output voltage V _o2 corresponding to the detected voltage.

The main control unit 140 controls the input voltage V _in and the input current i _{in that} are output from the first voltage current sensing unit 160 and the first output Width modulated signal PWM having a duty ratio based on the voltage V _o1 and the first output current i _o1 and the second output voltage V _o2 output from the output voltage sensing unit 180, And controls the switching operation of the MOS transistor S1 in the boost converter section. Accordingly, the DC-DC converter 120 converts the DC input voltage V _in into the first output voltage V _o1 of the sine wave and outputs the converted output voltage V _o1 . More detailed description will be given below.

7 is a detailed block diagram of a main controller of a grid-based single-stage inverter based on a cook converter according to an embodiment of the present invention.

7, the reference duty voltage generator 141, the maximum power point follower MPPT 142, the phase lock loop unit 143, the reference output current calculator 144, the first summer 145 ), A controller 146, a second summer 147, and a comparator 148.

The reference duty voltage generating unit 141 generates the reference duty voltage Vout using the input voltage V _in supplied from the first voltage current sensing unit 160 and the first output voltage V _o1 supplied from the second voltage current sensing unit 170 And outputs the reference duty voltage (V _{duty_ref} ) using the following Equation (1). The reference duty voltage V _{duty_ref} is a voltage used to convert the input voltage V _in into the first output voltage V _o1 of the full wave rectified sinusoidal wave by the _{dictation-to-dither} converter unit 120.

Where N _S / N _P is the winding ratio of the transformer.

However, when the load is an unstable system voltage, the DC-DC converter unit 120 has difficulty in generating a normal alternating current using only the reference duty voltage V _{duty_ref} . In consideration of this, the additional duty voltage (V _{duty_add} ) is further obtained through the following process.

The maximum power point tracking unit MPPT outputs the maximum power to the renewable energy module 110 based on the input voltage V _in and the input current i _in supplied from the first voltage / current sensing unit 160 (I _optimum ) required for the current to be output.

The phase lock loop unit 143 derives a final phase value that is synchronized with the second output voltage V _o2 supplied from the output voltage sensing unit 180.

Based on the output current computing unit 144 is obtained, the maximum power point current value in a sine wave at an optimum current value (i _optimum) supplied from the tracking unit (142) (A _i) to obtain the same phase as the system power supply 150 And obtains a frequency (ω _d ) synchronized at 60 Hz based on the final phase value output from the phase locked loop unit 143. The reference output current calculator 144 calculates the reference output current i _{o1_ref} using the sinusoidal current value A _i and the frequency ω _d obtained as described above and Equation (2) below.

The first summer 145 _multiplies the absolute value of the reference output current i _{o1_ref} output from the reference output current calculator 144 by the output current i _o1 output from the second voltage / current sensing unit 170, And outputs a difference current (i _diff ) corresponding thereto.

The controller 146 outputs the additional duty voltage (V _{duty_add} ) using the difference current i _diff output from the first summer 145.

8 is a detailed block diagram of the controller of the main control unit of FIG. The operation of the controller 146 will be described in detail with reference to FIG.

The repetitive learning controller 146-1 repeatedly learns the difference current i _diff to pass through a phase lead compensator 146-2 and then outputs a first additional duty voltage V _{duty_add_1} , .

The iterative learning controller 146-1 is composed of a phase preceding compensator 146-2. The half learning controller 146-1 stores all the difference currents of the same phase in the previous periods and outputs a value passed through the low pass filter (LPF) for the sum value, and outputs this value to the phase leading compensator 146- 2) to output this value in phase after a few steps. This phase leading compensator 146-2 can compensate for the right-to-zero effect of the cook-based modular inverter.

The third summer 146-3 sums the first additional duty voltage (V _{duty_add_1} ) and the difference current (i _diff ) and outputs a second additional duty voltage (V _{duty_add_2} ) accordingly.

The proportional-integral controller 146-4 proportionally integrates the second additional duty voltage (V _{duty_add_2} ) to finally output the additional duty voltage (V _{duty_add} ).

The second summer 147 sums the reference duty voltage (V _{duty_ref} ) and the additional duty voltage (V _{duty_add} ) and outputs a duty voltage (V _duty ) corresponding thereto.

The comparator 148 compares the duty voltage (V _duty ) input from the second summer 147 to the non-inverting input terminal with a triangular waveform RW input to the inverting input terminal, and outputs a pulse width And outputs a modulation signal PWM.

The comparator 148 simply compares the reference duty voltage V _{duty_ref} supplied from the reference duty voltage generator 141 with the triangular waveform RW and _outputs a pulse width modulation signal PWM ), And outputs the pulse width modulation signal PWM having the duty ratio in comparison with the duty voltage (V _duty ) obtained through the above process and the triangular waveform RW, -Decycle converter unit 120 and the unfolding bridge circuit unit 130. [0040] FIG.

In order to verify the algorithm of the grid-connected single-stage inverter based on the cook converter according to the present invention, a 400W power conversion experiment was performed using a Cook-based modular inverter in a grid-connected environment.

FIGS. 9 and 10 are graphs showing final output voltage and current waveforms of a 400 W power conversion experiment using a cook-converter-based modular inverter in a grid-connected environment.

FIG. 9 is a waveform using only a conventional linear controller, and FIG. 10 is an output current waveform having a THD (Total Harmonic Distortion) of 2.5% using the control algorithm according to the present invention.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, It is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims (17)

In a grid-connected single-stage inverter,
Renewable energy modules;
(V _in ) supplied from the renewable energy module to a first output voltage (V _o1 ) of a full wave rectified sinusoidal wave, and outputs the first output voltage (V _o1 ) - a dicing converter section;
And a second output voltage (V _o2 ) of the sinusoidal wave by switching the odd or even-numbered period of the first output voltage (V _o1 ) output from the dish- Folding bridge circuitry; And
The input voltage (V _in) and the input current (i _in), said first output voltage (V _o1) and a first output current (i _o1) and the second output voltage (V _o2) a corresponding a corresponding And a main control unit for receiving the input signal and generating a pulse width modulation signal PWM to control operation of the dictation-
The main control unit
Wherein the pulse width modulated signal (PWM) having the duty ratio is compared with a duty voltage generated inside the single-stage inverter. 2. The apparatus of claim 1, wherein the main control unit
A reference duty voltage generator for generating a reference duty voltage based on the input voltage V _in and the first output voltage V _o1 ;
A maximum power point follower for obtaining an optimum current value required for the renewable energy module to output maximum power based on the input voltage V _in and the input current i _in ;
A phase locked loop unit for deriving a final phase value to be synchronized with the second output voltage V _o2 ;
A current value of a sinusoidal wave is obtained from an optimum current value supplied from the maximum power point tracking unit, a synchronized frequency is obtained based on the final phase value, and a reference output current is obtained using the sinusoidal current value and frequency An output current calculator;
A first summing unit for obtaining a difference value between the absolute value of the reference output current and the first output current ( _io1 ) to obtain a difference current according to the difference;
A controller for outputting an additional duty voltage using the difference current;
A second adder for summing the reference duty voltage and the additional duty voltage to obtain a duty voltage corresponding thereto; And
And a comparator for comparing the duty voltage with a triangular waveform to generate and output the pulse width modulated signal having a duty ratio corresponding to the duty voltage. The apparatus as claimed in claim 2, wherein the reference output current calculation unit
Wherein the reference output current is obtained according to the following equation: " (1) "

Here, i _{o1_ref} is a reference output current, A _i is a current value of the sinusoidal wave, and ω _d is a frequency synchronized with the system power supplied from the phase lock loop unit. 3. The apparatus of claim 2, wherein the controller
An iterative learning controller that outputs a final value repeatedly learned using the difference current;
A phase predistorter compensating an output of the iterative learning controller to output a first additional duty voltage;
A third summing unit for summing the first additional duty voltage and the difference current to output a second additional duty voltage; And
And a proportional integral controller for proportionally integrating the second additional duty voltage to output an additional duty voltage. ≪ RTI ID = 0.0 > 21. < / RTI > The method of claim 1, wherein the renewable energy module
And a plurality of modules are provided to generate the DC input voltage. 2. The apparatus of claim 1, wherein the dish-
Wherein the duty ratio is set differently for each sampling period to output the first output voltage (V _o1 ). 2. The apparatus of claim 1, wherein the dish-
A boost converter for boosting the input voltage supplied from the renewable energy module and periodically accumulating the input voltage;
A buck converter unit for dropping the voltage accumulated in the boost converter unit and outputting the dropped voltage; And
And a transformer for connecting the output terminal of the boost converter section and the input terminal of the buck converter section in an insulated state. 8. The power converter according to claim 7, wherein the boost converter
A first capacitor and a first capacitor serially connected between one terminal of the input voltage and one of the taps of the primary coil of the transformer; And
And a switch element connected between a common node of the first inductor and the first capacitor and the other terminal of the input voltage. 9. The switching device according to claim 8,
Mode inverter based on a cook converter. 10. The method of claim 9,
And a second capacitor is connected between both terminals of the MOS transistor. 8. The buck converter of claim 7,
A third capacitor and a second inductor connected in series between one of the taps of the secondary coil of the transformer and one terminal of the first output voltage;
A diode connected between a common connection node of the third capacitor and the second inductor and the other terminal of the first output voltage; And
And a fourth capacitor connected between both terminals of the first output voltage. 3. The system of claim 1, wherein the fourth capacitor is connected between both terminals of the first output voltage.
The apparatus of claim 1, wherein the unfolding bridge circuitry
A first thyristor and a second thyristor serially connected between both input terminals connected to the first output voltage; And
And a third thyristor and a fourth thyristor serially connected to both input terminals connected to the first output voltage.
13. The system of claim 12, wherein the unfolding bridge circuitry
The second thyristor and the third thyristor are turned on in the positive period of the sinusoidal wave, the first thyristor and the fourth thyristor are turned off to output the full-wave rectified sinusoidal wave intact,
In the negative period, the second thyristor and the third thyristor are turned off, the first thyristor and the fourth thyristor are turned on, and the even-numbered period of the full-wave rectified sinusoidal wave is switched to negative polarity and output A single-stage inverter based on a cook converter.
13. The system of claim 12, wherein the unfolding bridge circuitry
And a L filter is further provided at the output terminal.
15. The apparatus of claim 14, wherein the L filter
And a third inductor connected between a connection node of the third and fourth thyristors and one terminal of the second output voltage, wherein the ripple of the output voltage of the sinusoidal wave is removed. Grid - connected single - stage inverter.
2. The apparatus of claim 1, wherein the main control unit
A first voltage / current sensing unit sensing the input voltage and the input current;
A second voltage / current sensing unit sensing the first output voltage and the first output current;
And an output voltage sensing unit for sensing the second output voltage, respectively.
The apparatus of claim 2, wherein the reference duty voltage generator comprises:
_Wherein the reference duty voltage (V _{duty_ref} ) is _obtained using the following equation: < EMI ID = _1.0 >

V _o1 is the first output voltage, V _in is the input voltage, and N _S / N _P is the winding ratio of the transformer provided in the dishi-decoder converter.

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