KR102475105B1 - Solar photovotaics system having micro converters - Google Patents

Abstract

The present invention relates to a photovoltaic power generation system equipped with a micro-converter. The problem to be solved is to install a micro-converter in a photovoltaic module, and to provide auxiliary MPPT (Maximum Power Point Tracking) to increase power generation efficiency.
For example, a solar module group unit made of a serial group of solar modules connected in parallel with each other; a photovoltaic power generation inverter that is connected to the photovoltaic module group unit and performs MPPT on the photovoltaic module group unit; and micro-converters installed in each of the photovoltaic modules and performing MPPT on the photovoltaic modules in which shade occurs when shading occurs.

Description

Solar power generation system with micro converter {SOLAR PHOTOVOTAICS SYSTEM HAVING MICRO CONVERTERS}

Embodiments of the present invention relate to a photovoltaic power generation system with a micro-converter, and more specifically, a photovoltaic power generation system with a high-efficiency topology and an algorithm for following a maximum power point using a micro-converter and a micro-converter. It is about.

Conventional photovoltaic power generation systems are designed to generate power with a required capacity by arranging photovoltaic modules in series and combining the series group in parallel.

In this series/parallel structured photovoltaic power generation system, when one photovoltaic module in a series group is shaded, the total power generation loss occurs by reducing the amount of power generation of non-shaded photovoltaic modules belonging to the series group. will make

In addition, depending on the degree of shade, the shaded photovoltaic module may generate electricity, albeit insignificantly, but the power generation amount may be 0W due to the series current of the non-shaded photovoltaic module, resulting in loss.

The loss rate of this power generation loss varies according to the degree of shade of the shaded photovoltaic module, and adversely affects the overall power generation efficiency of the photovoltaic power generation system.

Publication No. 10-2008-0102885 (published date: November 26, 2008) Patent Publication No. 10-2017-0058218 (published date: May 26, 2017) Registered Patent Publication No. 10-1615747 (registration date: April 20, 2016)

In an embodiment of the present invention, a micro-converter is installed in a photovoltaic module, and a micro-converter with increased power generation efficiency is performed by performing auxiliary maximum power point tracking (MPPT) on a photovoltaic module shaded according to whether or not a shadow occurs. A solar power generation system is provided.

A photovoltaic power generation system having a micro-converter according to an embodiment of the present invention includes a photovoltaic module group unit in which series groups of photovoltaic modules are connected in parallel to each other; a photovoltaic power generation inverter that is connected to the photovoltaic module group unit and performs MPPT (Maximum Power Point Tracking) on the photovoltaic module group unit; and micro-converters installed in each of the photovoltaic modules and performing MPPT on the photovoltaic modules in which shade occurs when shading occurs.

In addition, the micro-converter may include a negative buck converter.

In addition, the micro-converter may include a first capacitor connected in parallel with the photovoltaic module; a diode connected in parallel with the first capacitor; a second capacitor connected in parallel with the diode; a switch connected between the anode terminal of the first capacitor and the anode terminal of the diode; and an inductor installed between the anode of the diode and the positive terminal of the second capacitor.

In addition, the switch does not float and maintains a turned-on state so that the micro-converter always operates in a bypass mode, but is switched to a turn-off state when shading occurs, so that the micro-converter for the shading solar module MPPT can be performed auxiliary.

In addition, the micro-converter may perform input voltage control of each of the photovoltaic modules in parallel in order to prevent the voltage of the photovoltaic module from becoming 0V.

In addition, the micro-converter may be set to have a relatively slower MPPT control cycle than the photovoltaic inverter so that control priority is given to the photovoltaic inverter.

In addition, each connected to the micro-converter may further include a gateway for transmitting the state of the micro-converter to an external server or communication terminal.

According to the present invention, a micro-converter is installed in a solar module, and a micro-converter with increased power generation efficiency is provided by performing auxiliary MPPT (Maximum Power Point Tracking) on the shaded solar module according to whether or not a shade occurs. A solar power generation system can be provided.

1 is a diagram showing the entire configuration of a photovoltaic power generation system having a micro-converter according to an embodiment of the present invention.
2 is a voltage-power graph for explaining the maximum power generation point in a solar module in which no shade occurs.
3 is a voltage-power graph for explaining the maximum power generation point in a shaded solar module.
4 is a circuit diagram showing the configuration of a negative buck converter according to an embodiment of the present invention.
FIG. 5 is a diagram showing the entire configuration of the photovoltaic power generation system in FIG. 1 to which a gateway is added for each photovoltaic module.

The terms used in this specification will be briefly described, and the present invention will be described in detail.

The terms used in the present invention have been selected from general terms that are currently widely used as much as possible while considering the functions in the present invention, but these may vary depending on the intention of a person skilled in the art or precedent, the emergence of new technologies, and the like. In addition, in a specific case, there is also a term arbitrarily selected by the applicant, and in this case, the meaning will be described in detail in the description of the invention. Therefore, the term used in the present invention should be defined based on the meaning of the term and the overall content of the present invention, not simply the name of the term.

When it is said that a certain part "includes" a certain component throughout the specification, it means that it may further include other components without excluding other components unless otherwise stated. In addition, terms such as "...unit" and "module" described in the specification mean a unit that processes at least one function or operation, which may be implemented as hardware or software or a combination of hardware and software. .

Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

1 is a diagram showing the entire configuration of a photovoltaic power generation system equipped with a micro-converter according to an embodiment of the present invention, and FIG. 2 is a voltage-power for explaining the maximum power generation point in a solar module in which no shade occurs. 3 is a voltage-power graph for explaining the maximum power generation point in a shaded solar module, and FIG. 4 is a circuit diagram showing the configuration of a negative buck converter according to an embodiment of the present invention.

Referring to FIG. 1, the photovoltaic power generation system 100 of the present invention includes a photovoltaic module group unit 110, a photovoltaic power generation inverter 120, a plurality of micro converters 130, a connection board 140, and a controller ( 150) may include at least one of them.

The photovoltaic module group unit 110 may be formed by connecting a series group of photovoltaic modules 111 in parallel with each other. More specifically, a plurality of photovoltaic modules 111 are connected in series to form a series group, and a plurality of the series groups are gathered and connected in parallel to each other to form the photovoltaic module group unit 110. .

The photovoltaic power generation inverter 120 may be connected to the photovoltaic module group unit 110 to perform Maximum Power Point Tracking (MPPT) on the photovoltaic module group unit 110 . MPPT is a method for acquiring the maximum possible power from an array of solar modules, and refers to an algorithm method of finding the maximum power point of the solar module 111 by adjusting an input voltage and maintaining the most efficient amount of power.

In a conventional photovoltaic power generation system in which a micro-converter is not installed, a photovoltaic power inverter performs MPPT of a photovoltaic module. When there is no shade in all series/parallel photovoltaic modules, the maximum power such as the P0 point shown in FIG. The point (MPP) can be found. However, when a photovoltaic inverter performs MPPT and some photovoltaic modules are shaded (here, the shadows include deviations and failures of the photovoltaic modules), point P1 shown in FIG. It does not develop to the maximum power generation point P0, which is the power generation position of the optical module, or does not develop to the maximum power generation point P0, which is the power generation position of the shaded solar module at point P2 shown in FIG. The reason is that the solar power inverter controls MPPT for all solar modules, so it finds the most efficient high point in the entire system, but individual solar modules do not generate power at the maximum power generation point.

In order to solve this problem, in the present embodiment, micro converters 130 (or optimizers or compensators) may be installed in each solar module 111 to perform individual MPPT.

However, conventional commercial micro-converters require a specific solar power inverter (PCS) to be installed, and are not compatible with general commercial inverters. This is because if the micro-converter additionally performs MPPT, power generation efficiency may rather decrease due to control instability. A manufacturer of such a micro-converter can implement a photovoltaic power generation inverter together, but in this case, the price of the photovoltaic power generation inverter inevitably rises, and there is a problem that the selection of devices is narrowed.

In this way, when a micro converter and a photovoltaic power generation inverter must be used together for MPPT, the corresponding inverter controls the input voltage without performing MPPT, and the micro converters can each perform MPPT control. In this way, a DC/DC converter must be used to perform individual MPPT of a photovoltaic module using a micro converter, and the topology must mainly use a buck converter, a boost converter, and a buck-boost converter. However, this case also has several problems.

First of all, when the micro converter is applied as a boost converter, when the photovoltaic power generation inverter stops for various reasons while the photovoltaic power generation system operates normally, the output of the micro converter rises rapidly, resulting in a very large voltage to the photovoltaic power generation inverter. There is a risk that the inverter may be damaged. In this case, when the power generation point shown in FIG. 3 is at P2, it cannot operate as a boost converter and must operate as a buck converter.

In addition, when the micro-converter is applied as a buck converter, since the output cannot be higher than the input when the solar power inverter is stopped, there is no problem that the output rises rapidly, but it is floating on the buck converter switch position. Either an isolated driver must be used to drive it, or a bootstrap gate drive must be designed. The isolated driver is expensive, and the bootstrap gate drive changes the diode to a switch and has the disadvantage of always driving the lower switch. can reduce

In addition, the buck-boost converter has advantages and disadvantages of the buck converter and the boost converter, so it is difficult to apply it to a micro converter.

In this embodiment, due to the above problems, a high-efficiency low-cost micro-converter 130 applicable to the solar power inverter 120 is applied, and the micro-converter 130 is configured under the following conditions.

The micro-converter 130 according to this embodiment does not interfere with the MPPT performance of the photovoltaic inverter 120 and does not generate power at the maximum power point due to the occurrence of shading of each photovoltaic module 111 at the maximum power point. An algorithm may be provided to assist in following. In addition, since MPPT is well performed by the photovoltaic inverter 120 when there is no shade in the photovoltaic module 111, the micro converter 130 can operate in a bypass mode. In addition, the micro-converter 120 operates only on the corresponding solar module 111 where the shade occurs to assist with MPPT, and the photovoltaic module 111 where the shade does not occur can be operated to bypass, that is, the micro-converter 120 can operate to bypass. The converter 130 may be configured to operate in a bypass mode without switching (a state in which the switch is turned on as it is). In addition, the shaded photovoltaic module 111 can track the minimum amount of power generation by preventing the voltage from becoming 0V and the amount of power generation being completely 0W by the series current of the non-shaded photovoltaic module 111. .

More specifically, the plurality of micro-converters 130 are installed in each of the solar modules 111, and when shading occurs, MPPT for the corresponding solar module 111 in which shading occurs may be performed auxiliaryly. have.

In addition, the micro-converter 130 may include a negative buck converter as shown in FIG. 4 . More specifically, referring to FIG. 4, the negative buck converter 130 includes a first capacitor C1 connected in parallel with the solar module 111, a diode D connected in parallel with the first capacitor C1, and a diode ( A second capacitor (C2) connected in parallel with D), a switch (SW) connected between the anode terminal of the first capacitor (C1) and the anode terminal of the diode (D), and the anode of the diode (D) and the second capacitor (C2) ) may include an inductor (L) installed between the positive terminals.

Here, the switch (SW) is not floating and can maintain a turned-on state, and when the solar module 111 does not have a shadow, the micro converter 130 always operates in a bypass mode, but the shadow occurs MPPT of the micro-converter 130 for the corresponding photovoltaic module 111 that is switched to the turn-off state when shaded is generated may be performed auxiliaryly. At this time, the photovoltaic power generation inverter 120 may perform the entire MPPT of the photovoltaic module group unit 110 .

The micro converter 130 may control the input voltage of each solar module 111 in parallel in order to prevent the voltage of the solar module 111 from becoming 0V.

In addition, the operation mode of the micro-converter 130 may be set so that the MPPT control cycle is relatively slower than that of the photovoltaic inverter 120 so that control priority is given to the photovoltaic inverter 120 .

When the photovoltaic inverter 120 according to this embodiment basically performs MPPT and the micro converter 130 compensates only the shaded photovoltaic module 111 as a buck converter, point P2 shown in FIG. It moves to the P0 point, and since the maximum power point of the solar module 111 shaded by the micro converter 130 is followed, the P1 shown in FIG. The point moves to the point P0 so that the maximum power of the entire system can be developed. That is, the non-shaded photovoltaic module 111 operates in a bypass (switch turned on state maintained) mode, and only the buck converter of the shaded photovoltaic module 1110 performs MPPT as an aid. can In general, since the ratio of the shaded photovoltaic module 111 is relatively low, the shaded photovoltaic module 111 can be compensated for.

In addition, a high-efficiency low-cost topology for continuous switching, which is a disadvantage of a buck converter, is applied as a negative buck converter, and at this time, the switch SW is not floating, so it can be turned on.

As an auxiliary MPPT means of the micro-converter 130 according to this embodiment, it basically operates in a bypass mode, slows down the MPPT control cycle compared to the photovoltaic inverter 120, and gives control priority to the photovoltaic inverter 120. can be granted

In addition, in order to prevent the voltage of the photovoltaic module 111 from being 0V, control the input voltage of the photovoltaic module 111 in parallel, increase MPPT estimation efficiency, and reduce the ripple current of the module. By doubling the converter, the performance can be improved by interleaving (inverting) control.

FIG. 5 is a diagram showing the entire configuration of the photovoltaic power generation system in FIG. 1 to which a gateway is added for each photovoltaic module.

The photovoltaic power generation system 100 according to this embodiment is connected to the micro converter 130 and transmits the status of the micro converter 130 to the external server unit 170 or the communication terminal unit 180. A gateway 160 may be further included. In this way, in order to collect the status of all micro-converters 130, a wireless communication function is added to each micro-converter 130 through the gateway 160, and by using this, the status information of the micro-converters 130 is provided to the manager. can be conveyed

The connection board 140 is connected to the photovoltaic module group unit 110 and/or the micro converter 130, and may be configured as a means for connecting them to the inverter 120.

The control unit 150 may be a means composed of hardware and software responsible for overall control of the photovoltaic power generation system 100 .

What has been described above is only one embodiment for implementing a photovoltaic power generation system having a micro-converter according to the present invention, and the present invention is not limited to the above embodiment, and as claimed in the following claims Anyone with ordinary knowledge in the field to which the present invention pertains without departing from the gist of the present invention will say that the technical spirit of the present invention exists to the extent that various changes can be made.

100: Solar power generation system with micro-converter
110: photovoltaic module group unit
111: solar module
120: solar power inverter
130: micro converter
C1: first capacitor
D: diode
C2: second capacitor
SW: switch
L: Inductor
140: connection board
150: control unit
160: gateway
170: server unit
180: communication terminal unit

Claims (7)

A photovoltaic module group unit formed by connecting a series group of photovoltaic modules in parallel with each other;
a photovoltaic power generation inverter that is connected to the photovoltaic module group unit and performs MPPT (Maximum Power Point Tracking) on the photovoltaic module group unit; and
It is installed in each of the photovoltaic modules, and performs MPPT on the photovoltaic modules shaded when shading occurs, and the MPPT control cycle is relatively slower than that of the photovoltaic inverter so that control priority is given to the photovoltaic inverter. A solar power generation system with a micro-converter, comprising a micro-converter set to
According to claim 1,
The micro converter,
A solar power generation system with a micro-converter, characterized in that it includes a negative buck converter.
According to claim 2,
The micro converter,
A first capacitor connected in parallel with the solar module;
a diode connected in parallel with the first capacitor;
a second capacitor connected in parallel with the diode;
a switch connected between the anode terminal of the first capacitor and the anode terminal of the diode; and
A solar power generation system with a micro-converter comprising an inductor installed between the anode of the diode and the positive terminal of the second capacitor.
According to claim 3,
The switch is
Keeping the turned-on state without floating so that the micro-converters always operate in bypass mode, but when shading occurs, the micro-converter's MPPT for the shaded solar module is auxiliaryly performed by switching to the turn-off state A solar power generation system with a micro-converter, characterized in that for.
According to claim 3,
The micro converter,
The photovoltaic power generation system having a micro converter, characterized in that performing the control of the input voltage of each of the photovoltaic modules in parallel to prevent the voltage of the photovoltaic module from being 0V.
delete According to claim 1,
The photovoltaic power generation system with a micro-converter, characterized in that it further comprises a gateway connected to the micro-converter and transmitting a state of the micro-converter to an external server or communication terminal.

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