KR20100077526A - Dc-dc convert for the photovoltaic system - Google Patents

Abstract

PURPOSE: A DC-DC converter for a photovoltaic system is provided to transit the phase of a DC-DC converter module by serially forming an inputting part and parallelly forming an outputting part. CONSTITUTION: A plurality of DC-DC converter modules(200) is serially formed. A controller(300) is received inputting voltages which correspond to DC voltages from a photovoltaic module(100), and the controller parallelly outputs outputting voltages. The outputting voltages and currents from the DC-DC converter modules are compensated by the controller, and the phase of pulse-width-modulation signal is controlled.

Description

DC-DC Converter for Photovoltaic Power Generation {DC-DC Convert for the Photovoltaic System}

The present invention relates to a DC-DC converter for photovoltaic power generation, and more particularly, inputs to a plurality of DC-DC converter modules connected in series are configured in parallel with outputs of each DC-DC converter module. It is a DC-DC converter that shifts the phase to reduce the ripple current of the output current.

Soaring demand for electricity leads to a surge in the consumption of energy resources for power generation, which leads to cost and environmental problems. Recently, due to the depletion of fossil energy, which is the main energy source, and environmental problems, development of various environmentally friendly energy sources is actively progressed. Among them, development of power generation system using solar energy, which is a clean energy source, is being actively progressed. .

1 is a view of a full-bridge DC-DC converter for photovoltaic power generation according to the prior art.

As shown in FIG. 1, a high frequency transformer T1 including a primary coil L1 and a secondary coil L2 wound at a predetermined winding ratio, and first to fourth devices connected to the primary coil L1. A full bridge circuit portion including power switches S1 to S4 and bridge diode rectifiers D1 to D4 are connected to be connected to the secondary coil L2, and the coil L3 and the capacitor C2 are connected to the rear end thereof. LC filter consisting of) is connected.

The full-bridge DC-DC converter configured as described above is used in a high frequency link type solar PCS. The full bridge DC-DC converter boosts the low variable output DC voltage of the solar cell module to a constant DC voltage of high voltage.

In the case of PV PCS according to the prior art, since a high voltage is generally transmitted from a plurality of solar modules in a solar power generation system, there is a problem that it is difficult to use a MOSFET device having a low rated voltage. The ripple current of the output current is high.

The present invention provides a DC-DC converter module constituting a full bridge topology of a zero voltage switching (ZVS) method using a MOSFET device having a low rated voltage, wherein the plurality of DC-DC converter modules are configured and It is an object of the present invention to provide a DC-DC converter capable of reducing the ripple current by controlling the phase of the output current.

In order to achieve the above technical problem, the present invention, a plurality of DC-DC converter module is configured in series, the input voltage is applied in series from the PV module in series, and outputs the output voltage in parallel, the plurality of DC- Compensating the output voltage and current from the module to the DC converter and a control unit for controlling the phase of the PWM signal, the control unit is each so that each of the output signals from the plurality of DC-DC converter module spaced apart from each other by a predetermined interval A DC-DC converter for photovoltaic power generation, characterized by shifting phases.

Preferably, two DC-DC converter modules may be configured in series, and the controller may shift the phase of one of the two output signals outputted from the two DC-DC converter modules by 90 degrees. Can be.

Further, the control unit, the voltage controller for compensating the respective output voltage based on the reference voltage; A current controller for compensating the respective output currents based on a reference current; And a PWM signal controller for shifting the phase of the output signal from each DC-DC converter module and generating respective duty signals thereto.

In addition, the DC-DC converter module may be configured in a full bridge topology of zero voltage switching (ZVS).

Preferably the DC-DC converter module, four MOSFETs consisting of a full bridge; And a transformer having a primary winding connected to the full bridge and a secondary winding connected to a rectifier configured as a bridge diode of an output terminal.

According to the present invention, when configuring a plurality of DC-DC converter module in series, the input is configured in series and the output in parallel to shift the phase of each DC-DC converter module to reduce the ripple current of the output current Can be reduced.

In a photovoltaic power converter, a plurality of DC-DC converters in a full bridge topology consisting of MOSFET devices are configured in series, so that a MOSFET device having a small rated voltage can be applied to high voltage power from a PV module.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

Figure 2 shows a schematic configuration of one embodiment of a DC-DC converter for photovoltaic power generation according to the present invention.

The DC-DC converter for photovoltaic power generation according to the present invention includes a plurality of DC-DC converter modules 200 connected to each other, and a plurality of DC-DC converter modules 200 are configured in series, such as the PV module 100. Input voltage, which is a direct current voltage, is applied in series, and output voltages are output in parallel.

In addition, the control unit 300 to compensate for the output voltage and current from the plurality of DC-DC converter module 200 and to control the phase of the PWM signal.

Here, the controller 300 shifts the phases of the plurality of output voltages and the plurality of output currents that are output in parallel from the plurality of DC-DC converter modules 200 so as to be spaced apart from each other at regular intervals, thereby providing a phase of the PWM signal. To control.

3 shows another simple embodiment according to the invention.

In the embodiment of FIG. 3, two DC-DC converter modules 200 are configured in series, and in each of the two DC-DC converter modules 200, each of the DC-DC converter modules 210 and 230 is a PV module 100. The input voltage is input in series and the output voltage is output in parallel.

In addition, the control unit 300 controls the phase of the PWM signal by shifting the phases so that the phases of the two DC-DC converter modules are spaced apart from each other.

The DC-DC converter module of the embodiment of FIG. 3 will be described in more detail with reference to the circuit diagram of FIG. 4.

As shown in FIG. 4, the DC-DC converter module in the present invention may be configured with a full bridge topology of a zero voltage switching (ZVC) method, and four MOSFETs having respective switching functions may be referred to as full bridges. Can be implemented.

In general, since the MOSFET has a low rated voltage, it is not easy to directly apply to a PV module having a large output. To improve this, in the present invention, a MOSFET is used to divide and input a voltage input from the PV module 100. Voltage from PV module 100 to DC-DC converter 200 composed of two DC-DC converter modules 210 and 230 in series Receives serially.

In addition, the primary winding of the transformer having a predetermined turns ratio is connected to the full bridge of the MOSFET for boosting, and the secondary winding is connected to a rectifier composed of a bridge diode of an output terminal. Furthermore, two DC-DC converter modules 210 are connected. 230 outputs in parallel.

In the embodiment of FIG. 4, the voltage input from the PV module 100 is V _PH , and the voltage output through the rectifier of each DC-DC converter module 210, 230 is V _C , and the entire DC-DC The output at converter 200 becomes V _DC combined with V _PH and V _C.

Although not shown in FIG. 4, since the impedance of the load applied to the output terminal and the internal impedance of each DC-DC converter module are the same, the input voltage applied to each DC-DC converter module can be kept constant.

As described above, in the present invention, a plurality of DC-DC converter modules are connected in series, and inputs are configured in parallel, and outputs are configured in parallel, and the converter is composed of MOSFETs having a low rated voltage by dividing a high voltage from a PV module by configuring the inputs in series. This enables the output to be configured in parallel to control the phase of the output current from each DC-DC converter module to reduce the ripple current. Hereinafter, the control unit of the present invention for reducing such a ripple current is Examine.

FIG. 5 shows a graph of the output when the phase of the output current is not controlled by the controller according to the present invention in the embodiment of FIG. 4.

In FIG. 4, the output currents output from the respective DC-DC converter modules 210 and 230 are I _o1 and I _o2 , respectively, and since the output stages are configured in parallel, the output currents of the entire DC-DC converter are I _o1 and I. _o2 is the sum of I _o .

The I _o1 and I _o2 of each of the output waveform and the I _o1 and I _o2 is the combined I _o of the output waveform is also appear as shown in FIG. 5, an overall output current, as shown in 5 I _o of the output waveform It can be seen that the ripple current is high.

In order to reduce such a ripple current, the present invention includes a control unit 300 for controlling the phase of the output current, Figure 6 shows a schematic configuration of the control unit.

The controller 300 includes a voltage controller 310, a current controller 320, and a PWM signal controller 330, where the voltage controller 310 is configured in parallel with the DC-DC converter 200 to be DC-DC. The output voltage of the converter 200 is fed back and compared with the reference signal to compensate for the error of the voltage. The current controller 320 is configured in series with the DC-DC converter 200 and passes through the voltage controller 310. Compensate for the error by comparing with the actual output current.

With the signal passing through the current controller 310 and the voltage controller 320, the PWM is received. In the present invention, the output signal from each DC-DC converter module 210, 230 through the PWM signal controller 330. The phases of are shifted to generate respective duty signals for them.

FIG. 7 shows a graph of an output when the phase of the output current is controlled by the controller according to the present invention in the embodiment of FIG. 4.

As shown in FIG. 7, it can be seen that the control unit 300 controls the phase of the output signals of the respective DC-DC converter modules 210 and 230 to significantly reduce the ripple current of the output current. In FIG. 4, a phase shift is performed such that output signals of two DC-DC converter modules 210 and 230 have a phase difference of 90 degrees with each other.

As described above, according to the present invention, the two DC-DC converter modules 210 and 230 are connected in series, the inputs are configured in series, and the outputs are configured in parallel so that output signals from the respective DC-DC converter modules 210 and 230 are output. When the phase shifts have 90 degree phase difference with each other, it can be seen that the ripple current is reduced by half and the frequency is doubled, thereby reducing the size of the output inductor.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments described in the present invention are not intended to limit the technical idea of the present invention but to explain, and the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

1 is a view showing a full-bridge DC-DC converter for photovoltaic power generation according to the prior art,

Figure 2 shows a schematic configuration of one embodiment of a DC-DC converter for photovoltaic power generation according to the present invention,

Figure 3 shows a schematic configuration of another embodiment of a DC-DC converter for photovoltaic power generation according to the present invention,

4 shows a circuit diagram for a DC-DC converter in the embodiment of FIG. 3,

5 shows a graph of the output current and output voltage before the phase shift in the embodiment of FIG.

6 shows a schematic configuration of a controller in the present invention,

FIG. 7 is a graph illustrating output current and output voltage after phase shift in the embodiment of FIG. 3.

<Description of Major Symbols in Drawing>

100: PV module,

200: a plurality of DC-DC converter module,

210, 230: DC-DC converter module,

300: control unit,

310: output voltage compensator,

320: output current compensator,

330: PWM signal controller.

Claims (6)

A plurality of DC-DC converter module is configured in series, receives the input voltage which is a DC voltage in series from the PV module, and outputs the output voltage in parallel, Compensating the output voltage and current from the plurality of DC-DC converter module and a control unit for controlling the phase of the PWM signal, And the control unit shifts each phase so that each of the output signals from the plurality of DC-DC converter modules is spaced apart from each other by a predetermined interval. The method of claim 1, A DC-DC converter for photovoltaic power generation, characterized in that two DC-DC converter modules are configured in series. The method of claim 2, The control unit, the DC-DC converter for photovoltaic power generation, characterized in that for shifting the phase of any one of the two output signals output from the two DC-DC converter module by 90 degrees. 4. The method according to any one of claims 1 to 3, The control unit, A voltage controller for compensating the respective output voltages based on a reference voltage; A current controller for compensating the respective output currents based on a reference current; And And a PWM signal controller for shifting the phase of the output signal from each DC-DC converter module to generate respective duty signals thereto. The method of claim 4, wherein The DC-DC converter module is a DC-DC converter for photovoltaic power generation, characterized in that configured as a full bridge topology of ZVS (Zero Voltage Switching) method. The method of claim 5, The DC-DC converter module, Four MOSFETs consisting of full bridges; And And a transformer having a primary winding connected to the full bridge and a secondary winding connected to a rectifier composed of a bridge diode of an output stage.

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