KR20220102434A - Solar photovotaics system having micro converters - Google Patents

Abstract

The present invention relates to a photovoltaic generation system having a micro converter. An objective of the present invention is to install micro converters on photovoltaic modules and perform supplementary maximum power point tracking (MPPT) on a photovoltaic module with a shadow in accordance with shadow creation status to increase power generation efficiency. According to one embodiment of the present invention, the photovoltaic generation system having a micro converter comprises: a photovoltaic module group unit consisting of series groups of photovoltaic modules connected in parallel with each other; a photovoltaic generation inverter connected to the photovoltaic module group unit to perform MPPT on the photovoltaic module group unit; and micro converters installed on the photovoltaic modules, and performing MPPT on a photovoltaic module with a shadow when the shadow is created.

Description

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

An embodiment of the present invention relates to a photovoltaic power generation system having a micro-converter, and more specifically, a photovoltaic power generation system having an algorithm for tracking the maximum power point using a micro-converter and a micro-converter in a high-efficiency topology is about

The conventional photovoltaic power generation system is designed to generate power with a required capacity by arranging photovoltaic modules in series and combining the series groups in parallel.

In this series/parallel structure of solar power generation system, if one photovoltaic module in the series group is shaded, the amount of power generated by the non-shaded photovoltaic module belonging to the series group is reduced, resulting in overall power generation loss. will make it

In addition, depending on the degree of shading, the shaded photovoltaic module may generate electricity even slightly, but the amount of power generated by the series current of the photovoltaic module without shading may be 0W, resulting in loss.

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

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

An embodiment of the present invention installs a micro-converter in a photovoltaic module and performs auxiliary Maximum Power Point Tracking (MPPT) on the photovoltaic module in which the shadow is generated depending on whether or not the shadow occurs, thereby increasing the power generation efficiency. 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 a series group of photovoltaic modules are connected in parallel to each other; a solar power inverter connected to the photovoltaic module group unit to perform MPPT (Maximum Power Point Tracking) for the photovoltaic module group unit; and a micro-converter installed in each of the photovoltaic modules and performing MPPT on the photovoltaic module in which the shadow is generated when a shadow is generated.

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 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 positive terminal of the first capacitor and the anode terminal of the diode; and an inductor installed between the anode of the diode and the anode terminal of the second capacitor.

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

In addition, the micro-converter may perform input voltage control of each of the solar modules in parallel to prevent the voltage of the solar module from being 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, it may further include a gateway for transmitting the state of the micro-converter connected to each of the micro-converter to an external server or communication terminal.

According to the present invention, a micro-converter is installed in a photovoltaic module, and an auxiliary MPPT (Maximum Power Point Tracking) is performed for the photovoltaic module in which the shadow is generated according to whether or not a shadow is generated. A solar power system may be provided.

1 is a view showing the overall 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 the solar module in which no shading occurs.
3 is a voltage-power graph for explaining the maximum power generation point in the solar module in which the shade occurs.
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 view showing the overall configuration of a solar power generation system in which a gateway for each solar module is added in FIG. 1 .

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 as currently widely used general terms as possible while considering the functions in the present invention, but these may vary depending on the intention or precedent of a person skilled in the art, the emergence of new technology, and the like. In addition, in a specific case, there is a term arbitrarily selected by the applicant, and in this case, the meaning will be described in detail in the description of the corresponding 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, rather than the name of a simple term.

In the entire specification, when a part "includes" a certain component, it means that other components may be further included, rather than 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, the embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the embodiments of the present invention. However, the present invention may be embodied in several 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 view showing the overall configuration of a photovoltaic power generation system having 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 photovoltaic module without shading. It is a graph, and FIG. 3 is a voltage-power graph for explaining the maximum power generation point in the photovoltaic module in which the shade occurs, 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 inverter 120 , a plurality of micro-converters 130 , a connection board 140 , and a control unit ( 150) may include at least one of.

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 form the photovoltaic module group unit 110 . .

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

In the conventional photovoltaic power generation system in which the micro-converter is not installed, the photovoltaic inverter performs MPPT of the photovoltaic module, and when there is no shadow in the entire series/parallel photovoltaic module, the maximum power such as the point P0 shown in FIG. 2 The point (MPP) can be found. However, when the photovoltaic inverter performs MPPT, if some photovoltaic modules have shading (where shading includes deviation and failure of photovoltaic modules), point P1 shown in FIG. 2 is the sun without shading. Power cannot be generated to the maximum power generation point P0, which is the power generation position of the optical module, or the point P2 shown in FIG. 3 does not generate power to the maximum power generation point P0, which is the power generation location of the photovoltaic module in which the shade is generated. The reason is that the photovoltaic inverter controls the MPPT for all photovoltaic modules, so it finds the most efficient high point in the whole system, but each individual photovoltaic module does not generate power at the maximum power point.

In order to solve this problem, in the present embodiment, each micro-converter 130 (or an optimizer, a compensator) is installed in the photovoltaic module 111 to perform individual MPPT.

However, the existing commercial micro-converter requires a specific photovoltaic inverter (PCS) to be installed, and it is not compatible with general commercial inverters. This is because, if the micro-converter additionally performs MPPT, power generation efficiency may be reduced due to instability of control. The manufacturers of such micro-converters can implement a solar power inverter together. In this case, the price of the solar power inverter has to increase, and there is a problem in that the range of device selection is narrowed.

As such, when a micro-converter and a photovoltaic inverter must be used together for MPPT, the inverter does not perform MPPT, but controls the input voltage, and each micro-converter can perform MPPT control. As such, DC/DC converters must be used to perform individual MPPT of solar modules using micro-converters, and the topology of the topology is mainly to use Buck converters, Boost converters, and Buck-Boost converters. However, this case also poses several problems.

First of all, when the micro-converter is applied as a boost converter, when the photovoltaic power generation inverter is stopped for various reasons while the photovoltaic power generation system is operating normally, the output of the micro-converter rises sharply, resulting in a very large voltage to the photovoltaic power 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 rapidly rises, 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 insulated driver is expensive, and the Bootstrap Gate Drive changes the diode to a switch, and the lower switch has to be driven all the time. can be reduced.

In addition, since the buck-boost converter has advantages and disadvantages of the buck converter and the boost converter, it is difficult to apply 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 may be configured with the following conditions.

The micro-converter 130 according to this embodiment does not interfere with the MPPT performance of the photovoltaic inverter 120, and when the power is not generated at the maximum power point due to the shading of each photovoltaic module 111, the maximum power point An algorithm may be provided to assist in following the . In addition, since MPPT is well performed by the photovoltaic inverter 120 when no shading occurs in the photovoltaic module 111 , the microconverter 130 may operate in a bypass mode. In addition, the micro-converter 120 operates only on the corresponding photovoltaic module 111 in which the shading occurs to perform MPPT auxiliary, and the photovoltaic module 111 in which the shading does not occur may operate to bypass, that is, The converter 130 may be configured to operate in a bypass mode in which no switching is performed (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 being 0V to 0W by the series current of the photovoltaic module 111 where the shadowing has not occurred. .

More specifically, a plurality of micro-converters 130 are respectively installed in the photovoltaic module 111, and when a shadow occurs, MPPT can be performed auxiliary to the corresponding photovoltaic module 111 in which the shadow is generated. have.

In addition, the micro-converter 130 may include a negative buck converter (negative buck converter) as shown in FIG. 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 positive 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, so it can maintain a turned-on state, and when no shading occurs in the solar module 111 , the micro-converter 130 operates in the normal bypass mode, respectively, but the shading is generated. When switched to the turn-off state, the MPPT of the micro-converter 130 for the corresponding photovoltaic module 111 in which the shadow is generated may be performed auxiliary. At this time, the photovoltaic inverter 120 may perform the overall MPPT of the photovoltaic module group unit 110 .

The micro-converter 130 may control the input voltage of each of the photovoltaic modules 111 in parallel in order to prevent the voltage of the photovoltaic module 111 from being 0V.

In addition, the micro-converter 130 may be set to an operation mode such 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 .

The photovoltaic inverter 120 according to this embodiment basically performs MPPT, and the micro-converter 130 is a Buck converter and compensates only the shaded photovoltaic module 111. The point P2 shown in FIG. 3 is Since the maximum power point of the photovoltaic module 111 that moves to the point P0 and is shaded by the micro-converter 130 is followed, P1 shown in FIG. 2 by the photovoltaic inverter 120 performing the entire MPPT The point can move to point P0 to generate the maximum power of the entire system. That is, the photovoltaic module 111 in which the shade is not generated operates in a bypass (switch turned on state) mode, and only the Buck converter of the photovoltaic module 1110 in which the shadow is generated performs MPPT as an auxiliary. can In general, since the proportion of the photovoltaic module 111 in which the shadow is generated is relatively low, the photovoltaic module 111 in which the shadow is generated can be compensated.

In addition, a high-efficiency and low-cost topology for continuous switching, which is a disadvantage of the buck converter, is applied as a negative buck converter.

As an auxiliary MPPT means of the micro-converter 130 according to this embodiment, it basically operates in the bypass mode, makes the MPPT control cycle slower than the solar power inverter 120 , and gives the solar power inverter 120 control priority. can be given

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

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

The photovoltaic power generation system 100 according to this embodiment is each connected to the micro-converter 130 and transmits the state of the micro-converter 130 to the external server unit 170 or the communication terminal unit 180. It may further include a gateway 160 . In this way, in order to collect the states of all micro-converters 130, a wireless communication function is added to each micro-converter 130 through the gateway 160, and the state information of the micro-converter 130 is provided to the administrator using this. can transmit

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 in which hardware and software responsible for overall control of the solar power generation system 100 are configured.

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, but as claimed in the claims below. Without departing from the gist of the present invention, it will be said that the technical spirit of the present invention exists to the extent that various modifications can be made by anyone with ordinary knowledge in the field to which the invention pertains.

100: solar power system with micro-converter
110: solar 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: junction panel
150: control unit
160: gateway
170: server unit
180: communication terminal unit

Claims (7)

A photovoltaic module group unit consisting of a series group of photovoltaic modules connected to each other in parallel;
a solar power inverter connected to the photovoltaic module group unit to perform MPPT (Maximum Power Point Tracking) for the photovoltaic module group unit; and
A photovoltaic power generation system having a micro-converter, comprising a micro-converter that is installed in each of the photovoltaic modules and performs MPPT on the photovoltaic module in which the shadow is generated when a shadow occurs.
The method of claim 1,
The micro-converter is
A solar power system with a micro-converter, characterized in that it comprises a negative buck converter.
3. The method of claim 2,
The micro-converter is
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 positive terminal of the first capacitor and the anode terminal of the diode; and
A photovoltaic power generation system having a micro-converter comprising an inductor installed between the anode of the diode and the anode terminal of the second capacitor.
4. The method of claim 3,
The switch is
By maintaining the turn-on state without floating, the micro-converter operates in the normal bypass mode, but is switched to the turn-off state when shading occurs so that the MPPT of the micro-converter for the shading solar module is performed auxiliary. A photovoltaic power generation system having a micro-converter, characterized in that.
4. The method of claim 3,
The micro-converter is
In order to prevent the voltage of the photovoltaic module from being 0V, the photovoltaic power generation system having a micro-converter, characterized in that the input voltage control of each of the photovoltaic modules is controlled in parallel.
The method of claim 1,
The micro-converter is
A photovoltaic power generation system having a micro-converter, characterized in that the MPPT control cycle is set to be relatively slower than that of the photovoltaic inverter so that control priority is given to the photovoltaic power inverter.
The method of claim 1,
Photovoltaic power generation system having a micro-converter further comprising a gateway connected to the micro-converter, respectively, for transmitting the state of the micro-converter to an external server or communication terminal.

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