KR101408855B1 - Micro convertor device using photovoltaic module and control method thereof - Google Patents

Abstract

Provided are a micro-converter device for a photovoltaic module and a method of controlling the same, capable of coping with the overcurrent of an inductor by minimizing insertion loss. The micro-converter device for the photovoltaic module includes a micro-converter interworking with a junction box included in the photovoltaic module to compensate for a current difference between photovoltaic modules by changing a current path according to a difference between power generated by the photovoltaic modules; and a string controller for adjusting voltage of the photovoltaic module by controlling a duty cycle of the micro-converter based on the power generated by the photovoltaic modules output from the micro-converter. Two micro-converters are realized in one box and installed in every two modules to adjust the voltage of the photovoltaic module, so that the number of the micro-converter boxes can be minimized. In addition, if the overcurrent flows through the inductor, an action for the overcurrent may be taken in real time.

Description

TECHNICAL FIELD [0001] The present invention relates to a photovoltaic module,

The present invention relates to a micro converter for a photovoltaic module, and more particularly, to a micro converter for a photovoltaic module, which is capable of minimizing insertion loss and coping with an overcurrent flowing through the inductor. And a control method thereof.

Generally, a photovoltaic power generation system is a system that converts pollution-free and indefinite solar energy directly into electrical energy, and has recently attracted attention as a renewable energy.

The photovoltaic power generation system is equipped with a photovoltaic module (PV module), and the maximum power point tracking (MPPT) is performed in the central inverter in order to increase the solar power generation efficiency. There are thousands of solar modules connected to a single inverter. Because the output voltage and current of one solar module is small, the voltage is increased in string units until it is connected to the inverter, and the strings are connected in parallel And the current is increased.

In this case, since the internal solar modules are connected in series, the characteristic of one module is lowered and the current flows to the current value of the module when the current is lower than the other modules. In addition, in a structure in which a plurality of strings are connected in parallel, there arises a problem that the total voltage is lowered to the lowest voltage even when the voltages of the strings do not coincide with each other. These phenomena are not very effective even if the maximum power point tracking is performed in the central inverter.

Here, the characteristics of a specific module inside the string are inevitably degraded due to various characteristics such as shadows, dust, leaves, and degradation between modules.

2. Description of the Related Art In recent years, micro-converters that perform maximum power point tracking in units of modules have been commercialized, and to some extent compensate for the degradation of characteristics of specific modules.

On the other hand, as shown in FIG. 1, the current-voltage and power-voltage characteristic curves of the solar module are changed as the solar radiation amount of the sunlight changes.

Therefore, when the shadow is partially shaded inside the string, the current value of the shadow photovoltaic module is decreased according to the characteristic curve, and the current of the entire string is determined based on the lowest current value.

On the other hand, three submodules are usually connected in series inside the solar module, and if one of the submodules is shadowed, the current of the entire solar module is reduced.

2 is a block diagram of a micro converter system in which an MPPT device and a DC / DC converter are installed in a solar module in such a serial structure (cascade method).

Here, reference numeral 10 denotes one solar module, 11 denotes a junction box (J / B), and 12 denotes a micro-converter corresponding one-to-one with the junction box 11.

The micro-converter 12 receives 100% of the output power of the solar module 10, adjusts the voltage of the solar module to be in the MPP state, and outputs the power to the string. At this time, the microconverter 12 consumes about 2 to 3% of its own energy. Therefore, in a situation where the solar radiation is high, there is no cloud, and there is no deterioration between the modules, the production power is lower than when the microconverter is not mounted, which is called insertion loss.

On the other hand, a conventional technique for a photovoltaic device using a micro converter is disclosed in the following Patent Document 1: Korean Registered Patent Registration No. 10-1245827 (published on March 20, 2013).

In order to improve the energy efficiency and the cost reduction in the solar power generation system field, the above-mentioned Patent Document 1 has a micro inverter converter in each solar module (PV module), and in the micro inverter converter, / Respond to situation factors, perform power / environmental monitoring.

Korean Registered Patent Registration No. 10-1245827 (Announced on March 20, 2013)

However, in the above conventional techniques, a micro converter is used to prevent the degradation of the characteristics of a specific module. In this case, since the micro converter is installed per module, the system price is increased.

In addition, when the solar radiation amount is good and the module is uniform, the microconverter consumes energy unnecessarily, resulting in insertion loss which decreases the production power.

SUMMARY OF THE INVENTION An object of the present invention is to provide a microconverter device for a solar module and a control method thereof for minimizing insertion loss and coping with an overcurrent flowing through an inductor will be.

Another object of the present invention is to provide a microconverter device for a solar module and a control method thereof for minimizing the installation number of the microconverter mounted to increase the output efficiency and lowering the installation cost of the solar power generation system.

In order to achieve the above object, a microconverter device for a solar cell module according to the present invention is interlocked with a junction box provided in a solar cell module, and a current path is varied according to a difference in production power of the solar cell module A micro converter for compensating a current deviation between the solar modules; And a string controller for controlling the duty cycle of the micro-converter based on the output power of the solar module output from the micro-converter to adjust the voltage of the solar module.

The microconverter is connected to the solar module in parallel.

The microconverter is characterized in that a current path of a plurality of solar modules is varied.

The microconverter is characterized in that it only processes differences in the production power of adjacent solar modules.

The microconverter is configured separately from the junction box.

The microconverter may be integrated with the junction box.

The microconverter is implemented in units of submodules in the solar module.

The micro-converter may include an inductor for current deviation compensation; And a switch provided at one end of the inductor to set a current path.

In this case, two switches are provided at one end of the inductor, and the switches operate in opposite directions.

The microcontroller transmits the voltage and current measurement values of the solar module to the string controller, receives the duty cycle control data and the operation control data transmitted from the string controller, and controls the duty cycle of the switch based on the received duty cycle control data and the operation control data. And a module controller for controlling the module.

The microcontroller includes a driver for driving the switch to the on or off state under the control of the module controller.

The junction box provided in the solar module transmits the electric power generated from the solar module to a junction box coupled to another solar module in a serial structure.

Wherein the string controller includes a DC-DC converter that allows the solar module to maintain the maximum power point tracking.

The string controller includes a communication module that communicates with the micro-converter to receive voltage and current measurement values of the solar module, and transmits control data to the micro-converter.

The string controller includes a maximum power point calculating unit for calculating a maximum power point based on voltage and current values of each solar module received through the communication module.

The string controller may further include a duty controller for adjusting a voltage of the solar module by transmitting a duty cycle control signal to the micro-converter according to a maximum power point calculated by the maximum power point calculator.

The duty controller compares the voltage and current values of the respective solar modules with a reference value to determine shut-down and over-current. In shut-down mode, the duty controller transmits shutdown data to the micro- And removing it.

The duty controller compares the voltage and current values of the respective solar modules with a reference value. If the voltage and current values of the solar modules are determined to be overcurrent, the duty controller increases the total voltage while maintaining the duty cycle of the micro- And the remaining module adjusts the duty to increase the voltage so as to reduce the current of the inductor.

According to an aspect of the present invention, there is provided a method of controlling a micro-converter device for a solar module, the method comprising: (a) measuring a voltage and a current of the solar module in a micro- Reporting to the controller; (b) requesting the string controller to change the duty cycle if the measured current is a preset maximum value; (c) changing the duty cycle of the switch based on the received duty cycle from the string controller.

According to another aspect of the present invention, there is provided a method of controlling a micro-converter device for a solar module, the method comprising the steps of: (a) controlling a micro- Up; (b) following the maximum power point based on the voltage and current of the photovoltaic module transmitted from the wake-up microconverter, generating a duty cycle according to the following maximum power point, and transmitting the duty cycle to the microconverter; (c) confirming whether the current of the photovoltaic module received is an overcurrent, raising the total voltage in the case of an overcurrent, lowering the voltage of the photovoltaic module and raising the voltage of the remaining module to lower the current of the inductor; (d) searching the voltage and current of the photovoltaic module to send shut-down data to the micro-converter to shut down the micro-converter when in a shut-down mode.

According to the present invention, insertion loss can be minimized, and an overcurrent can be coped with even when an inductor is overcurrented.

In addition, according to the present invention, it is possible to minimize the installation number of the micro-converters installed to increase the output efficiency and to lower the installation cost of the solar power generation system.

FIG. 1 is a current-voltage and power-voltage characteristic curve diagram of a general solar module in the case of a change in irradiation dose,
2 is a configuration diagram of a microconverter device applied to a conventional photovoltaic power generation system,
3 is a configuration diagram of a micro-converter device for a solar module according to a preferred embodiment of the present invention,
Fig. 4 is a cable connection diagram of Fig. 3,
Fig. 5 is a block diagram of an embodiment of the micro-converter of Fig. 3,
FIG. 6 is a block diagram of an embodiment of the string controller of FIG. 3;
FIG. 7 is a block diagram of a micro-converter device for a solar module in which a junction box and a micro-converter are integrated in the present invention.
8 is a configuration diagram of a micro-converter device for a solar module in sub-module units according to the present invention,
Fig. 9 is a configuration diagram of a micro-converter device for a stand-alone solar module in sub-module units according to the present invention,
10 is a simulation result of a micro-converter device for a solar module according to the present invention,
11 is a diagram showing an example of a module current pattern when an overcurrent flows through an inductor in the present invention,
12 is a flowchart illustrating a control process in a module controller of a method for controlling a micro-converter device for a solar module according to the present invention.
13 is a flowchart showing a control process in a string controller in a method of controlling a micro-converter device for a solar module according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a microconverter device for a solar module according to a preferred embodiment of the present invention and a control method thereof will be described in detail with reference to the accompanying drawings.

3 is a configuration diagram of a micro-converter device for a solar module according to a preferred embodiment of the present invention.

3, the micro-converter device for a solar module according to the present invention includes a solar module 110, a junction box 120, a micro-converter 130, and a string controller 140 do.

The junction box 120 is coupled to the solar module 110 and serves as an interface for outputting the output of the solar module 110 to another solar module or other device.

The micro-converter (PMU) 130 varies the current path according to the difference in the production power of the solar module 110 to compensate for the current deviation between the solar modules.

The micro-converter 130 is connected in parallel with the solar module 110 and controls a plurality of solar modules. Here, the micro-converter 130 may be formed separately from the junction box 120. [

, d3,

); 태양광 모듈의 전압 및 전류 측정값을 상기 스트링 제어기(140)에 전송하고, 상기 스트링 제어기(140)로부터 전송된 듀티 사이클(Duty sycle) 제어데이터와 동작 제어 데이터를 수신하고, 이를 기초로 상기 스위치(d4,

, d3,

)의 듀티 사이클을 제어하는 모듈 제어기(131); 상기 모듈 제어기(131)의 제어에 따라 상기 스위치(d4,

, d3,

)를 온(on) 또는 오프(off) 상태로 구동시키기 위한 드라이버(Driver)(132)(133)를 포함한다. 여기서 인덕터의 일단 좌측에 설치된 스위치(d4, d3)와 상기 인덕터의 일단 우측에 설치된 스위치(

,

)는 상호 반대로 동작한다.As shown in FIG. 5, the micro-converter 130 includes inductors L3 and L4 for current deviation compensation; Switches (d4, d5) provided at one ends of the inductors (L3, L4)

, d3,

); Transmits the voltage and current measurement values of the solar module to the string controller 140, receives the duty cycle control data and operation control data transmitted from the string controller 140, (d4,

, d3,

A module controller 131 for controlling the duty cycle of the duty cycle; Under the control of the module controller 131, the switches d4,

, d3,

(Driver) 132 (133) for driving the liquid crystal display panel (not shown) to the on or off state. Here, the switches d4 and d3 provided on the left side of one end of the inductor and the switches d4 and d3 provided on the right side of the inductor

,

) Operate in opposite directions.

The string controller 140 controls the duty cycle of the micro-converter 130 based on the output power of the solar module output from the micro-converter 130 to adjust the voltage of the solar module do. Here, the string controller 140 performs control on a string basis.

As shown in FIG. 6, the string controller 140 communicates with the micro-converter 130 to receive voltage and current measurement values of the solar module, and transmits control data to the micro-converter 130 A communication module 141; A maximum power point calculating unit 142 for calculating a maximum power point MPP based on the voltage and current values of the solar modules received through the communication module 141; And a duty controller 143 for adjusting the voltage of the solar module by transmitting a duty cycle control signal to the micro-converter 130 according to the maximum power point calculated by the maximum power point calculator 142.

The duty controller 143 preferably compares the voltage and current values of the respective photovoltaic modules with a reference value to determine whether shut-down or over-current is present. In the shut-down mode, the duty controller 143 controls the micro- shutdown data is transmitted to remove insertion loss. More preferably, the duty controller 143 compares the voltage and current values of the respective solar modules with the reference value. If it is determined that the voltage and current values are over current, the duty controller 143 raises the total voltage while maintaining the duty cycle of the micro- The voltage of the shaded module is lowered and the voltage of the remaining module is raised to lower the inductor current.

Here, the string controller 140 communicates with all micro-converters in units of strings to collect information (voltage, current), and controls all the micro-converters simultaneously based on the collected information. For convenience of explanation, Only the control of one micro-converter 130 will be described.

In addition, the string controller 140 is equipped with a dc-to-dc converter to adjust the voltage so that the solar module maintains maximum power point tracking.

In the microconverter device for a solar module according to the present invention, the output of the solar module 110 is connected in series, and the microcomputer 130 is connected in parallel with the solar module 110 to be. In this structure, the photovoltaic module 110 operates as if there is no microconverter 130, and the microconverter 130 changes the path of the photovoltaic module output only when there is a difference in the production power between the photovoltaic modules By compensating for the mismatched current, the problems of existing cascades are improved.

For example, all PV modules in a string are delivering the best power under the same conditions, so that if the currents are equal to each other, the microconverters enter shut-down mode without power handling, minimizing insertion loss. In addition, when there is a difference in the power output between the photovoltaic modules in the string, the microconverters create a new current path and process it.

This will be described in detail as follows.

First, as shown in FIG. 4, the micro-converter device for a solar module according to the present invention is a form in which one micro-converter 13 is coupled for each of two solar modules (for example, PV 5 and PV 4). This reduces the number of microconverters compared to the conventional cascade method.

The module controller 131 provided in the micro-converter 130 measures voltage and current of each solar module and transmits it to the string controller 140 through an internal communication module (not shown). At this time, the communication module is preferably implemented as a wireless communication module. In addition, when the module controller 131 transmits the voltage and current measurement values of the photovoltaic module to the string controller 140, the module controller 131 transmits the measured values and the ID number of the corresponding photovoltaic module together to identify the photovoltaic module do. Here, the string controller 140 can recognize the voltage and current of the solar module, which are easily measured voltage and current measured values, by assigning unique IDs to the solar modules.

The communication module 141 of the string controller 140 receives the voltage and current measurement values of the respective solar modules output from the plurality of micro converters, and transmits the voltage and current measurement values to the duty controller 143. The duty controller 143 converts the input voltage and current measurement values into a corresponding digital voltage and current value, stores the converted voltage and current value in the internal memory, and transmits the same to the maximum power point calculating unit 142.

The maximum power point calculating unit 142 calculates a change amount of the digital measured voltage, and then follows the maximum power point based on the calculated change amount. Here, it is preferable that the maximum power point follow-up method, which is conventionally performed in a solar power generation facility, is adopted as it is. The following maximum power point is transmitted to the duty controller 143.

In addition, the duty controller 143 compares the current values of the respective modules to determine the shut-down mode of the photovoltaic module when the voltage and current measurement values for the respective solar modules are input, extracts the difference, And determines whether the photovoltaic module is in the shut-down mode. Here, the shut-down mode condition is that all the solar modules have the same current value due to the same environmental conditions, in which case they shut down the DC-DC converter of all micro-converters and continuously monitor the voltage, current Observe the value and return to normal mode when current fluctuation occurs.

As a result of the determination, in the shut-down mode, micro-converter operation control data (shut-down data) is generated and transmitted to the micro-converter 130 via the communication module 141. At this time, the operation control data is transmitted to substantially all of the micro-converters.

, d3,

)도 모두 오프 상태가 되어 동작을 하지 않게 된다. 즉, 태양광 모듈이 정상상태이면 마이크로 컨버터의 동작을 셧-다운 모드로 동작시켜, 삽입 손실을 최소화하게 된다.The module controller 131 in the micro-converter 130 receives and analyzes the operation control data. If the operation control data is a shut-down data, the driver 132 (133) is turned off, only the communication module and the voltage / current sensor module for communicating with the string controller 140 operate, - The dc converter operates in a shut-down state. When the driving of the drivers 132 and 133 is off, the switches d4,

, d3,

) Are all turned off and the operation is not performed. That is, if the solar module is in a normal state, the operation of the microconverter is operated in a shut-down mode to minimize the insertion loss.

The duty controller 143 of the string controller 140 searches the voltage and current values measured by the respective solar modules and calculates a maximum power point calculation unit 142 to generate a duty cycle for voltage adjustment of each photovoltaic module based on the maximum power point.

Here, the relational expression for duty cycle generation is as follows.

Where L represents the inductor, d represents the duty cycle, and v represents the measured voltage measured in the photovoltaic module.

When the duty cycle corresponding to the difference in output power between the solar modules is generated through the above-described relational expression, the duty cycle is transmitted to the micro-converter 130 through the communication module 141.

)는 오프가 되고, 이와는 반대로 스위치(d4)가 오프되면 스위치(

)는 온 상태로 동작한다.The module controller 131 in the micro-converter 130 receives the duty cycle and drives the drivers 132 and 133 according to the received duty cycle to operate the switches at the ends of the inductors L3 and L4. At this time, the two switches at one end of the inductor operate opposite to each other in normal operation. That is, when the switch d4 is turned on, the switch

The switch d4 is turned off. On the other hand, when the switch d4 is turned off,

Operate in the ON state.

The operation of these switches and the inductor changes the output path of the power line output from each solar module. As the output power path is changed, the voltage of the solar module is adjusted optimally and compensation is performed according to the output power deviation of the solar module.

In the first embodiment of the present invention, the microconverter is constructed separately from the junction box. In this case, a photovoltaic power generation system is implemented by adding a microconverter to an already installed photovoltaic module.

Meanwhile, when the solar power generation system is installed for the first time, the microconverter and the junction box are integrally implemented as another embodiment of the present invention.

For example, as shown in FIG. 7, a micro-converter is built in the junction box 220 interlocked with the solar module 210 so that the micro-converter and the junction box are integrated. In this case, the overall operation is the same as that of the embodiment shown in FIG. Here, it is preferable to embed the string controller 231 in the first junction box 230 of the string. In the remaining junction box, communication with the string controller 231 is performed, while in the shut-down mode, And when the difference in output power between the solar modules occurs, the solar modules operate in a state of adjusting the voltage of the solar modules according to the duty cycle. In addition, the output power difference between the solar modules is so severe that when the overcurrent flows through a specific inductor, it operates in a mode of reducing the overcurrent.

, d21,

, d22,

)가 구비된다.As another embodiment of the present invention, a plurality of cells 311 to 313 built in one solar module 310 and a micro-converter 320 may be coupled in a serial-parallel state to implement a solar power generation apparatus It is possible. In general, one photovoltaic module has three submodules (cells) connected in series and the output terminal is shown in the form of four ribbons. Thus, four ribbon-shaped output terminals are coupled to the junction box integrated micro-converter 320. In order to couple the four output terminals, the micro-converter 320 has two switches d20 and d21 at both ends of the three inductors L20, L21 and L22 and three inductors L20, L21 and L22,

, d21,

, d22,

.

Each switch control method is performed in the same manner as the first embodiment of the present invention. When the sub-module micro-converter is implemented as described above, it is possible to improve the performance of the photovoltaic power generation facility which can increase the efficiency as compared with the micro-converter of the solar module unit. In this case, since the number of the microconverters is increased as compared with the photovoltaic module unit, the cost may increase. Therefore, it is desirable for the designer of the photovoltaic module generation facility to design the photovoltaic power generation facility.

As another embodiment of the present invention, a micro-converter may be implemented as a stand-alone unit in units of sub-modules as shown in FIG. Here, reference numerals 411 to 413 denote sub-modules, and reference numeral 420 denotes a micro-converter. According to this structure, the micro-converter 420 operates only between the sub-modules 411 to 413 inside the solar module. Therefore, it looks like a typical cascade microconverter from the outside. This structure is improved by submodule-based operation compared to cascade module by solar module, and the cable can be easily combined like a cascade structure.

FIG. 10 is a diagram illustrating a simulation result of a micro-converter device for a solar module according to the present invention. When the shadows are applied to some solar modules in the string, the values of the currents flowing through the solar modules are calculated. It is the result of shadows on two adjacent solar modules when 8A is produced in a normal solar module and 6A in a shaded module. When the microconverter according to the present invention is not applied to such a structure, a current of 6 A flows, but when the microconverter device according to the present invention is applied, a current of 7.33 A flows. It can be seen from the experimental results that the microconverter device according to the present invention improves the efficiency in the solar power generation facility.

12 is a flowchart illustrating a method of controlling a micro-converter device for a photovoltaic module according to the present invention in a module controller installed in a micro-converter.

) 및 전류(

)를 측정하여 스트링 제어기에 보고하는 단계(S11); (b) 상기 측정한 전류가 미리 설정된 최대치(max)일 경우 듀티 사이클(

) 변경을 상기 스트링 제어기에 요청하는 단계(S12 ~ S13); (c) 상기 스트링 제어기로부터 변경된 듀티 사이클 수신시 이를 기초로 스위치의 듀티 사이클을 변경하는 단계(S14 ~ S15); 상기 스트링 제어기로부터 새로운 명령이 수신될 경우 해당 명령에 따라 제어 동작을 수행하는 단계(S16 ~ S17)를 포함한다.As shown in FIG. 12, a method for controlling a micro converter device for a solar module according to the present invention includes the steps of: (a) controlling a voltage of a solar module

) And current (

(S11) of reporting to the string controller; (b) duty cycle when the measured current is a preset maximum value (max)

) Requesting the string controller to change (S12 to S13); (c) changing the duty cycle of the switch based on the modified duty cycle received from the string controller (S14 to S15); And performing a control operation according to the command when a new command is received from the string controller (S16 to S17).

A method of controlling the micro-converter device for a solar module according to the present invention will now be described.

) 및 전류(

)를 측정하여 스트링 제어기에 보고한다.First, in step S11, the module controller in the micro-converter converts the voltage of the solar module

) And current (

) And reports it to the string controller.

)와 미리 설정된 최대치(max)를 비교하여, 상기 인덕터별 전류가 상기 최대치 이상일 경우, 단계 S13으로 이동하여 상기 스트링 제어기에 듀티 사이클(

) 변경을 요청한다. 또 다른 실시예로서 마이크로 컨버터가 인덕터 전류(

)를 측정하지 않고 스트링 제어기가 이를 계산해서 특정 인덕터에 과전류가 흐름을 판단하고 듀티 사이클 변경 명령이 필요할 경우 각 마이크로 인버터에 명령을 전송할 수 있다.In step S12, the measured inductor current (

) And a preset maximum value (max). If the inductor-by-inductor current exceeds the maximum value, the process proceeds to step S13, where a duty cycle

). As yet another embodiment,

), The string controller can calculate this to determine the overcurrent flow in a particular inductor and send a command to each micro-inverter if a duty cycle change command is needed.

Thereafter, in step S14, it is checked whether a modified duty cycle is received from the string controller. If a modified duty cycle is received, the process proceeds to step S15 where the duty cycle of the switch is changed based on the changed duty cycle.

If a new command is received from the string controller as in step S16 while the switch is operated with the received duty cycle or a new duty cycle is not received, the process moves to step S17 and performs an operation according to the command. Where the new instructions may vary and may be, for example, a micro-converter shut-down command.

FIG. 13 is a flowchart illustrating a process of controlling a micro-converter in a string controller in a method of controlling a micro-converter device for a solar module according to the present invention.

As shown in FIG. 13, a method of controlling a micro-converter device for a solar module according to the present invention includes the steps of (a) controlling a micro-converter for adjusting an output path of a solar module, Step S21; (b) following the maximum power point based on the voltage and current of the photovoltaic module transmitted from the wake-up microconverter, generating a duty cycle according to the following maximum power point, and transmitting the duty cycle to the microconverter S22, S23); (c) calculating the current of the received photovoltaic module to check whether an overcurrent flows; if the current is overcurrent, increase the total voltage to lower the current of the inductor, lower the voltage of the module whose output power is decreased, A step (S24 to S26) of calculating a new duty cycle in the upward direction and transmitting a duty value to the micro-converter; (d) searching for the voltage and current of the photovoltaic module and sending shut-down data to the micro-converter to shut down the micro-converter in a shut-down mode (S27 to S28).

A method of controlling the micro-converter device for a solar module according to the present invention will be described in detail below.

), 전류(

)를 수신한다.First, in a step S21, a string controller for controlling a microconverter adjusting an output path of a solar module wakes up a specific microconverter, and the voltage of the solar module transmitted from the wake-up microconverter

), Current (

).

)을 생성하여 상기 마이크로 컨버터에 전송한다.After the above process is performed for all the solar modules (S22), the maximum power point is followed (MPPT) based on the received voltage in step S23, and the duty cycle

) And transmits it to the micro-converter.

On the other hand, when some neighboring solar modules in the string are shadowed, an overcurrent can flow in the inductor in the microconverter adjacent to the string. In this way, countermeasures for overcurrents exceeding the rated current are required for a specific inductor.

For this purpose, the current of each inductor is calculated by the following equation at step S24.

Here, the inductor current can be calculated by a string controller. However, it is also possible to directly measure the inductor current by each micro converter and transmit it to a string controller through a communication module.

Next, in step S25, it is determined whether the current of the inductor calculated above is equal to or greater than a predetermined maximum value. If the current of the inductor is equal to or larger than the maximum value, control proceeds to step S26 to reduce the current of the inductor .

When an overcurrent flows through a specific inductor, the string controller can cope with various policies. The simplest way is to shut-off all micro-converters, or alternatively, only shut off micro-converters with inductors that have detected an over-current.

의 전류는

에 의해서 결정됨을 알 수 있다.In another method, when the above expression (2)

The current of

. ≪ / RTI >

Therefore, since the string controller knows these values, it is possible to predict whether the current of the inductor flows over the rated value. When the voltage exceeds the rated value, the duty cycle of each module controller is left as it is, If the voltage of the module is raised slightly in the Voc direction, the current in the inductor can be reduced because the current flows less. In this case, as another embodiment, the voltage of the module having a low module current may be lowered to further flow the current, and the voltage of the remaining modules may be increased as in the previous method to make the current flow smaller. In this case, The duty cycle of each module changes according to the value, so it must be transferred to the microconverter.

11 shows a pattern of the photovoltaic module current when an overcurrent flows through the inductor. In other words, when an overcurrent flows through a specific inductor, some solar modules show sharper shadows and less current. When the overcurrent flows to the inductor from this, it is possible to know the photovoltaic module that caused the inductor.

Next, in step S27, it is determined whether the currents of all the photovoltaic modules are in the same shut-down mode. If all the photovoltaic modules are in the shut-down mode, the process goes to step S28 to shut down the micro- And send shut-down data to the converter. This shut-down data allows the microconverter to operate in shut-down mode, thereby minimizing insertion loss.

Although the present invention has been described in detail with reference to the above embodiments, it is needless to say that the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the spirit of the present invention.

The present invention is applied to a photovoltaic device. In particular, the number of micro-converter boxes for adjusting the voltage of a solar module can be minimized and effectively applied to a photovoltaic device for coping with an overcurrent flowing through the inductor.

110 ... Solar modules
120 ... Junction box
130 ... Micro converter
131 ... Module controller
132, 133 ... driver
140 ... String controller
141 ... Communication module
142 ... The maximum power point calculation unit
143 ... Duty controller
150 ... Bidirectional DC-DC converter

Claims (20)

A micro converter interlocked with a junction box provided in the solar module and compensating for a current deviation between the solar modules by varying a current path according to a difference in production power of the solar module;
And a string controller for controlling a voltage of the solar module by controlling a duty cycle of the micro-converter based on the output power of the solar module output from the micro-converter.
The micro-converter device for a solar module according to claim 1, wherein the micro-converter is connected in parallel with the solar module.
The micro-converter device for a solar module according to claim 1, wherein the micro-converter has one micro-converter to vary a current path of a plurality of solar modules.
The micro-converter device for a solar module according to claim 1, wherein the micro-converter processes only differences in production power of adjacent solar modules.
The micro-converter device for a solar module according to claim 1, wherein the micro-converter is configured separately from the junction box.
The micro-converter device for a solar module according to claim 1, wherein the micro-converter is integrated with the junction box.
The micro-converter device for a solar module according to claim 1, wherein the micro-converter is implemented in units of sub-modules in the solar module.
The microcontroller of claim 1, wherein the micro-converter comprises: an inductor for current deviation compensation; And a switch provided at one end of the inductor to set a current path.
9. The micro-converter device for a solar module according to claim 8, wherein two switches are provided at one end of the inductor and operate in opposite directions.
The microcontroller according to claim 8, wherein the micro-converter transmits voltage and current measurement values of the solar module to the string controller, receives duty cycle control data and operation control data transmitted from the string controller, And a module controller that controls the duty cycle or operates in a shut-down mode.
11. The micro-converter device for a solar module according to claim 10, wherein the micro-converter includes a driver for driving the switch to the on or off state under the control of the module controller.
The micro-converter device for a solar module according to claim 1, wherein the junction box transfers power generated from the solar module to a junction box coupled to another solar module in a serial structure.
The micro-converter device of claim 1, wherein the micro-converter includes a DC-DC converter in the string converter to maintain the solar module tracking the maximum power point.
2. The solar module of claim 1, wherein the string controller comprises a communication module for communicating with the micro-converter to receive voltage and current measurements of the solar module and to transmit control data to the micro- / RTI >
15. The solar module according to claim 14, wherein the string controller includes a maximum power point calculating unit for calculating a maximum power point based on a voltage and a current value of each solar module received through the communication module. Converter device.
16. The apparatus of claim 15, wherein the string controller further comprises a duty controller for adjusting a voltage of the solar module by transmitting a duty cycle control signal to the micro-converter according to a maximum power point calculated by the maximum power point calculator Wherein the photovoltaic module is a photovoltaic module.
The duty controller according to claim 16, wherein the duty controller compares a voltage and a current value of each of the solar modules with a reference value to determine whether shut-down or over-current is present, and transmits shutdown data to the micro- Thereby to eliminate the insertion loss.
The duty controller according to claim 16, wherein the duty controller compares the voltage and current values of the respective solar modules with a reference value, and if it is determined to be an overcurrent, increases the total voltage while maintaining the duty cycle of the micro- Wherein the voltage of the shaded module is lowered and the remaining module adjusts the duty so as to increase the voltage so as to reduce the current of the inductor.
delete (a) waking up a particular micro-converter in a string controller controlling a micro-converter that adjusts the output path of the solar module;
(b) following the maximum power point based on the voltage of the photovoltaic module transmitted from the wake-up microconverter, generating a duty cycle according to the following maximum power point, and transmitting the duty cycle to the microconverter;
(c) It is checked whether the inductor current of each photovoltaic module is an overcurrent from the current of the received photovoltaic module and the string current directly measured. If it is an overcurrent, the total voltage is increased to lower the inductor current, Transmitting a duty value to the micro-converter by calculating a new duty cycle in a direction of lowering the voltage of the module and raising the voltage of the remaining module;
(d) retrieving the voltage and current of the solar module and sending shut-down data to the micro-converter to shut down the micro-converter when in a shut-down mode. Control method of microconverter device for module.

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