WO2015170903A1

WO2015170903A1 - Micro-converter device for photovoltaic energy generation source

Info

Publication number: WO2015170903A1
Application number: PCT/KR2015/004584
Authority: WO
Inventors: 조경호; 김정렬; 조창익
Original assignee: (주)알티에스에너지
Priority date: 2014-05-08
Filing date: 2015-05-08
Publication date: 2015-11-12
Also published as: KR101561640B1

Abstract

A micro-converter device for photovoltaic modules, according to the present invention, comprises: a plurality of micro-converters which are connected to a plurality of photovoltaic modules connected in series, and which include module controllers for measuring power of the respective corresponding photovoltaic modules and controlling output power of the corresponding photovoltaic modules according to a first duty value; and a string control unit which directly measures power of a first photovoltaic module among the plurality of photovoltaic modules, and which calculates the first duty value by using a pattern search algorithm for directly searching for an optimum duty of each photovoltaic module so as to transmit the first duty value to each module controller, on the basis of power of the photovoltaic modules received from a plurality of module controllers and the directly measured power of the first photovoltaic module. According to the present invention, a tracking of a maximum power point can simply be performed though a direct duty controlling method by pattern searching, and thus, system implementation costs can be reduced and a device can be simply implemented.

Description

Micro Converter Units for Solar Energy Sources

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micro converter device for a photovoltaic energy generating source, and more particularly to a micro converter device for directly searching for and controlling an optimum duty of each solar module.

The present invention relates to a research project carried out with the support of the Small and Medium Business Administration of Korea (Task No .: S2216876, Title: Development of Current Level Compensation Compensator (MCCU) Module Level Power Management Unit having a maximum Insertion Loss of 3% or less).

In general, photovoltaic power generation system is a pollution-free and unlimited system of converting solar energy directly into electrical energy, which has recently been spotlighted as renewable energy.

Such a photovoltaic system is essentially equipped with a photovoltaic module (PV module), and maximum power point tracking (hereinafter referred to as 'MPPT') in the central inverter to increase photovoltaic efficiency. Do this. Up to thousands of photovoltaic modules are connected to one inverter. Since the output voltage and current of one photovoltaic module is small, the voltage output from a string in which a plurality of photovoltaic modules are connected in series as the input of the inverter (increased output The output current (raised output current) from the plurality of strings connected in parallel with the voltage is supplied.

In this case, since the internal solar modules are connected in series, if the characteristics of one solar module are reduced and output less current than other modules in the vicinity, the current value of the solar modules is inferior. This causes a problem that current flows through the entire string. In addition, in a structure in which a plurality of strings are connected in parallel, a problem arises in that the whole is lowered to the lowest voltage even when the voltages of the strings do not match.

Meanwhile, in the solar module, as shown in FIG. 1, the current-voltage and power-voltage characteristic curves change as the amount of solar radiation changes.

The reason why the characteristics of a particular module in the string is deteriorated is due to shadows, dust, fallen leaves, characteristic changes due to deterioration between modules, and the like. For example, when the shadow is partially shadowed inside the string, the shadowed solar modules have a lower current value according to this characteristic curve, and the current of the entire string is determined based on the lowest current value. In addition, two or more submodules are usually connected in series in the solar module, and when one of the submodules is shadowed, the current of the entire solar module falls.

On the other hand, in recent years, by mounting a micro-converter that performs the maximum power point tracking in the unit of the solar module to compensate to some extent that the characteristics of the specific solar module is inferior. The micro-converter receives 100% of the output power of the photovoltaic module, adjusts the voltage of the photovoltaic module so that it is in the MPP (Maximum Power Point) state, and exports the power as a string. At this time, the micro-converter consumes 2 ~ 3% of energy by itself (this is called 'Insertion loss'), so the micro-converter is installed in a situation where the solar radiation is high, there is no cloud, and there is no deterioration between modules. There is a problem that the production power is lower than when not.

On the other hand, as the maximum output point tracking algorithm performed in the micro-converter, P & O (Perturbation & observation) algorithm is widely used because of its very simple operation and simple implementation. In order to implement the P & O algorithm in the micro-converter, the voltage (PV voltage) of the photovoltaic module must be changed to the target voltage determined by the P & O algorithm.In order to move the PV voltage to the target voltage, a high-speed proportional-integral controller ( Controllers (hereinafter referred to as "PI controllers"), however, hardware implementations of PI controllers add cost, and even if implemented in software, a 32-bit high-performance CPU is required. There is a problem.

The present invention is to solve the above-mentioned problems, and to provide a micro-converter device for a photovoltaic module that simplifies the maximum power point tracking by the duty direct control method by the pattern search instead of the P & O algorithm.

Photovoltaic module micro-converter device according to the characteristics of the present invention

A plurality of micro-converters connected to a plurality of solar modules connected in series, each of the micro-converters including a module controller measuring power of the corresponding solar modules and controlling output power of the corresponding solar modules according to the first duty value; And directly measuring the power of the first solar module of the plurality of solar modules, and based on the power of the solar module received from the plurality of module controllers and the power of the first measured solar module directly, And a string controller for calculating and transmitting the first duty value to each module controller using a pattern search algorithm for directly searching for an optimal duty of the solar module.

Here, the first solar module may be a solar module connected to the last of the series connected solar modules.

The plurality of micro-converters may be connected in parallel with the plurality of photovoltaic modules and compensate for power deviation by providing a bypass path to the output of the photovoltaic module when a difference in production power occurs between the corresponding photovoltaic modules. .

The micro-converter includes an inductor providing a bypass path for current deviation compensation, first and second switches installed at one end of the inductor to set a current path, and a driver for driving the first and second switches at a predetermined duty. The module controller may further include a voltage and current measurement value of the corresponding solar module to the string controller, and perform a duty cycle of the switch based on the duty value received from the string controller. Can be controlled.

The string controller may include a module voltage / current detector for detecting voltage and current of the first solar module, a string current detector for measuring string currents of the plurality of solar modules connected in series, and the module voltage / current detector. The pattern search algorithm is used based on the detected voltage and current values of the first photovoltaic module, the string current values detected by the string current detector, and the voltage and current values of the photovoltaic module transmitted by the module controller. And a string controller for calculating the first duty value and transmitting the calculated first duty value to each module controller.

The string controller changes a duty value performed in each module controller based on a reference duty value and a duty variation value as a reference for a previous pole, and among the string stage output power values calculated in one pole, After determining the higher value of the maximum value of the trial and the previous pole, the duty value at that time can be set as the new reference duty value.

Further, the string controller stores all voltage values of the photovoltaic module when the output power of the corresponding photovoltaic module is increased during an attempt to increase or decrease the duty value of each module controller, and then outputs the duty from the module voltages. Calculation can be used as a basis for a new pole.

According to the exemplary embodiment of the present invention, the maximum power point tracking can be simplified by the duty direct control method using the pattern search, thereby reducing the system implementation cost and simplifying the device implementation.

In addition, according to an embodiment of the present invention, by directly measuring the voltage and current of the photovoltaic module connected to the last of the string unit in the string controller, there is an advantage that the error and calculation amount when calculating the maximum power point is reduced.

1 is a view showing the current-voltage and power-voltage characteristics of a typical solar module when the solar radiation changes.

2 is a view showing the configuration of a cell, a sub module, and a module described in the embodiment of the present invention.

3 is a diagram illustrating an example of I-V characteristics of a cell, a submodule, and a module.

4 is a block diagram of a micro converter device for a solar module according to the first embodiment of the present invention.

5 is a view illustrating in detail the micro-converter 130 and the string control unit 140 shown in FIG.

6 is a detailed view of the string controller 143 according to the first embodiment of the present invention.

7 shows a maximum power point tracking process using the P & O algorithm.

8 illustrates a maximum power point tracking process using a GPS algorithm.

9 illustrates a maximum power point tracking process using the MGPS algorithm.

10 is a simulation result when using the MGPS algorithm according to an embodiment of the present invention.

11 is a flowchart illustrating a soft start according to an embodiment of the present invention.

12 is a flowchart illustrating a soft stop according to an embodiment of the present invention.

FIG. 13 is a configuration diagram of a photovoltaic module microconverter device according to a second embodiment of the present invention.

FIG. 14 is a diagram illustrating the micro-converter shown in FIG. 13 in more detail.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like elements throughout the specification.

Hereinafter, a micro converter device for a solar energy generation source and a control method thereof according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a diagram illustrating a configuration of a cell, a sub module, and a module described in an embodiment of the present invention, and FIG. 3 is a diagram illustrating I-V characteristics of a cell, a sub module, and a module.

According to an embodiment of the present invention, a plurality of solar cells (for example, 60 or 72) 40 are connected in series to one solar module 60. In the case of partial shadowing of multiple solar cells connected in series, all cells are limited by the output current due to the nature of the series connection. Therefore, the bypass diodes 70 are connected in parallel to each of the submodules 50 in which a predetermined number (for example, 20 or 24) cells are grouped. As a result, even in the case of partial shadows, the power generation of the photovoltaic module can be bypassed, and only the shadowed submodules can be bypassed, resulting in efficient power production.

According to the exemplary embodiment of the present invention shown in FIG. 2, 20 or 24 cells are connected in series to form one submodule, and three submodules having parallel connected bypass diodes are configured as one single module. However, the present invention is not limited thereto and may be configured by changing the number of cells constituting the submodule as necessary. For example, to reduce the number of bypass diodes, 60 cells are determined as one submodule and one module has one submodule, or 60 submodules are connected by connecting bypass diodes in each cell. It is also possible to configure as a module.

As shown in FIG. 3, since the submodule is a series of one or more cells (called unit cells) in series, the current of the submodule is equal to the current of the unit cell and the magnitude of the submodule. The voltage is equal to the sum of the magnitudes of the voltages of the plurality of unit cells. Similarly, the voltage of one module is equal to the sum of the magnitudes of the voltages of the plurality of submodules, and the current of the module is equal to the current of one submodule.

Cells, sub-modules, and modules described in the embodiments of the present invention are all solar energy generating sources. Hereinafter, for convenience of description, a module is described as an example of a solar energy generation source, but the present invention is not limited thereto. Of course, the module may be directly applied to a cell or a sub module.

As shown in FIG. 4, the micro converter device for a solar module according to the first embodiment of the present invention includes a junction box 120, a micro converter 130, and a string controller 140.

The junction box 120 is combined with the solar module 110 to serve as an interface for outputting the output of the solar module 110 to another solar module or another device.

The micro-converter 130 serves to compensate for the current deviation between the solar modules by varying the path of the current according to the difference in the production power of the solar module 110. The micro converter 130 is connected in parallel with the solar module 110, and manages a plurality of solar modules. According to the first embodiment of the present invention, when there is no mismatch of the production power between the solar modules, it operates as if there is no micro-converter, and only when there is a difference in the production power between the solar modules, By providing a bypass path to compensate for mismatched current, the problem of the cascade type micro-converter is improved.

The string controller 140 adjusts the voltage (PV voltage) of the solar module by controlling the duty cycle of the micro-converter 130 based on the production power of the solar module output from the micro-converter 130. do. Here, the string controller 140 performs control in units of strings.

In FIG. 5, the micro-converter 130 includes an inductor 131,

switches

132 and 133 installed at one end of the inductor for setting a current path, a driver 134 for driving the switch, and a module for controlling the duty cycle of the switch. Controller 135.

In FIG. 5, the inductor 131 serves to provide a bypass path for current deviation compensation, and switches 132 and 133 are installed at one end of the inductor 131 to bypass the current path (that is, through the inductor). Path or direct path between solar modules).

The driver 134 drives the

switches

132 and 133 in an on or off state under the control of the module controller 135. At this time, the switch 132 provided on the left side of the one end of the inductor 131 and the switch 133 provided on the right side of the one end of the inductor 131 operate opposite to each other.

The module controller 135 transmits the voltage and current measurement values of the solar module 110 to the string controller 140 and based on the duty cycle control data and the operation control data received from the string controller 140. The duty cycle of 132 and 133 is controlled. In addition, the module controller 135 is connected between the two photovoltaic module 110 to operate by sending the power deviation of the two modules to the output through the path inside the module controller.

Specifically, the module controller 135 determines the voltage ratio of the two solar modules 110 connected to the module controller, and is connected to the existing one in a situation in which mismatches (ie, power deviations) occur between the solar modules. Bypass the serial connection path between photovoltaic modules to the inductor path.

In FIG. 5, the module controller 135 is configured to have one-to-one correspondence to the N-1 solar modules 110, but only the last solar modules 110 and PV _N constituting the string are strings instead of the module controller 135. It is directly connected to the controller 140.

The string controller 140 directly measures the power of the solar module 110 (PV _N ) connected to the last, and the power of the remaining solar modules PV1, ... PV _N-1 is the module controller of the module. Acquire through 135. The string controller 140 may adjust the pulse width modulation (PWM) duty value of each module controller 135 by using a pattern search algorithm described below based on the power values obtained through the module controller 135. It calculates and controls each module controller 135.

In FIG. 5, the string controller 140 includes a module voltage / current detector 142 that detects the voltage and current of the solar module PV _N connected last, and a string current detector 141 that measures the string current Itot. ), The voltage and current values detected by the module voltage / current detector 142, the string current values detected by the string current detector 141, and the voltage and current of the remaining solar modules transmitted from each module controller 135. A string controller for calculating a maximum power point using a pattern search algorithm, calculating a pulse width modulation duty value of each module controller 135 based on the calculated maximum power point, and transmitting the calculated pulse width modulation duty value to each module controller 135. 133).

As shown in FIG. 6, the string controller 143 communicates with the module controller 135 to receive voltage and current measurements of the photovoltaic module 110, and transmits the photovoltaic module to the module controller 135. Communication module 143a transmitting control data for control, voltage and current values of the photovoltaic module received through the communication module 143a, and current and string currents of the photovoltaic module 110 measured directly A duty cycle to the module controller 135 according to the maximum power point tracking unit 143b and the maximum power point tracking unit 143b that calculate the maximum power point using a pattern search algorithm based on The duty controller 143c transmits a control signal to adjust the voltage of the solar module 110.

The operation of the micro-converter device according to the first embodiment of the present invention shown in Figures 4 to 6 will be described in detail.

The micro-converter device according to the first embodiment of the present invention is connected to only the last photovoltaic module 110 (PV _N ), not to receive the voltage across the high voltage string from the string controller 140.

First, the module controller 135 measures the voltage and current of the connected solar module 110, and transmits it to the string controller 143 through an internal communication module (not shown). In this case, the communication module is preferably implemented as a wireless communication module. In addition, when the module controller 135 transmits the voltage and current measurement values of the photovoltaic module 110 to the string controller 143, the module controller 135 transmits the measured values and the unique number (ID) of the corresponding photovoltaic module 110 together. It is desirable to distinguish the solar modules. Here, by assigning each unique number ID for each solar module, the string controller 143 can easily know which solar module voltage and current measurement values are received.

The communication module 143a of the string controller 143 receives voltage and current measurement values of each photovoltaic module transmitted from the plurality of module controllers 135 and transmits them to the duty controller 143c. The duty controller 143c converts the input voltage and current measurement values into corresponding digital voltage and current values, stores them in the internal memory, and transfers them to the maximum power point follower 143b.

The module current detector 142 of the string controller 140 directly measures the module voltage (V _N ) and the current (I _N ) of the photovoltaic module (110, PV _N ) connected to the last of the string unit, and the duty controller (143c). ), And the string current detector 141 detects the current I _{tot of the} entire string and delivers it to the duty controller 143c. The duty controller 143c converts the voltage and current values V _{N and} I _N and the string current values I _{tot of the} last solar module 110 and PV _N transmitted as described above into digital current values. At the same time it is stored in the transfer to the maximum power follower (143b).

At this time, the duty controller (143c) is on the basis of the current (I _tot), and the module current value (I _1, I _2, ..I _n) transmitted from the respective controller module (135) flowing through the string having each module controller The currents I _L1 , I _L2 , ..I _Ln flowing through the inductor are calculated using Equation 1 below.

Equation 1

If the current flowing through the specific inductor calculated from Equation 1 is overcurrent, the duty controller 143c performs a soft stop algorithm that temporarily exits the maximum power point following mode to prevent the overcurrent from flowing. If the current flowing through all the inductors is normal, the maximum power point tracking unit 143b calculates the maximum power point for adjusting the voltage of the solar module.

According to an embodiment of the present invention, the maximum power point tracking unit 143b uses the generalized pattern search algorithm (hereinafter referred to as 'GPS') instead of the P & O algorithm conventionally used for the maximum power point tracking. To follow.

7 shows a maximum power point tracking process using the P & O algorithm.

According to the P & O algorithm, a string controller 143, a new reference voltage (V _1, V _2, .., V _N) Duty (d _1, d _2, each module control unit 135 therefrom when the decision ... After determining, d _N-1 ), the determined duty d ₁ , d ₂ ,..., d _N-1 is transmitted wirelessly to each module controller. Then, the controller calculates the string 143 is the power (P _1, P _2, ..., P _N) receives the new voltage, the current value of the photovoltaic module, the drive over the air by the transfer duty, and the calculated According to the power increase and decrease, a new reference voltage is determined, a new duty is determined, and then a cycle of transmitting to each module controller 135 is repeated.

Therefore, this P & O algorithm can take a long time to follow the maximum power point. In addition, there is a disadvantage in that a high voltage DC / DC converter is required inside the string controller because the string voltage must be controlled.

Hereinafter, a pattern search algorithm according to an embodiment of the present invention will be described. The pattern search algorithm is used as an algorithm for obtaining an optimal solution in control engineering. In an embodiment of the present invention, each module of a photovoltaic module is applied by applying a pattern search algorithm used in control engineering. Directly search for the optimum duty performed in the controller.

As a pattern search algorithm used in an embodiment of the present invention, a generalized pattern search algorithm (called 'GPS') and a modified generalized pattern search algorithm (called 'MGPS') may be used. In addition, a combination of GPS algorithm and MGPS can be used.

The term “pattern search” described in the embodiment of the present invention may be used as a term including all combinations or modifications of GPS, MGPS, GPS, or MGPS.

8 illustrates a maximum power point tracking process using a GPS algorithm.

According to the GPS algorithm according to the embodiment of the present invention, when controlling the N solar modules, the number of module controllers 135 is (N-1) and the duty values of all the module controllers 135 are set to a certain size (duty fluctuation). Value) to increase or decrease the value of the photovoltaic module.

This is defined as a trial, and in one trial only the duty of one module controller is changed.

In the GPS algorithm according to the embodiment of the present invention, the duty and the duty variation value are defined as in Equation 2 below. Here, the duty variation value is a concept corresponding to the size of a mesh in a GPS algorithm generally used in control engineering.

Equation 2

As shown in FIG. 8, in order to find out the power change with respect to the duty value change of all the N-1 module controllers 135, a total of 2 (N-1) attempts should be made, which is one poll. It is defined as.

In this case, one poll may be expressed as in Equation 3 below.

Equation 3

Here, D _prev means a reference duty value which is a reference in the previous pole, and the duty variation value is set to a value that is increased or decreased compared to the previous pole according to whether the attempt in each pole is successful, as will be described later. Can be.

GPS algorithm according to an embodiment of the present invention, the highest value of the output power values (Ptot, k) of the string stage calculated in one pole (k th attempt in Figure 8) and the highest value of the highest value of the previous pole After the determination, the duty value at that time is set as the new reference duty value D _prev . Therefore, it can be defined as a method of changing only one duty per pole, and FIG. 8 shows an example of an internal table configuration for this. In FIG. 8, a method of determining the k th duty of one pole as a reference of the next pole is illustrated.

The pattern GPS algorithm according to an embodiment of the present invention increases the magnitude of the new duty variation value in the new pole to the previous value (e.g., twice the previous duty variation value) to speed up the maximum power point tracking. However, if there is no duty vector that produces more power than the maximum of the previous pole in a single pole, then the pole is considered to be a decreasing output pole and the new duty variation value of the new pole is maintained while maintaining the reference to the previous pole. Decreases (eg, 1/4 of the previous duty change).

In addition, according to an embodiment of the present invention, if one pole is not attempted up to 2 (N-1), but a value greater than the maximum power value of the previous pole appears in the middle, the pole is treated as a success and the next pole is prepared. Modified schemes are also possible. In addition, after the duty is calculated, an abrupt inductor current change can be prevented in advance by placing an upper limit and a lower limit on the duty value so that the duty does not deviate from a certain range.

Meanwhile, according to another exemplary embodiment of the present invention, the maximum power point may be tracked using a modified generalized pattern search algorithm (called 'MGPS').

9 illustrates a maximum power point following process using a deformation pattern search (MGPS) algorithm.

The MGPS algorithm does not seek the highest value of the output values of the string stages calculated in one pole, but rather when the output power of the solar module 110 is increased during an attempt to increase or decrease the duty value of each module controller. After storing all the voltage values of the optical module, the duty is calculated from these module voltages and used as the reference for the new pole. Therefore, MGPS can change the duty of all module controllers at the same time per pole.

That is, according to the MGPS algorithm according to an embodiment of the present invention, every attempt is to calculate the output power by sensing the output voltage and output current in the unit of the solar module, the solar module of the attempt to increase the output power of the solar module Remember the voltage. Subsequently, when setting the reference of the next pole, the reference duty is set by calculating a voltage ratio between the photovoltaic modules with respect to a voltage at which the output power of the photovoltaic module is increased.

Specifically, referring to FIG. 9, the output power P ₁ , ₁ of the solar module 110 controlled by the duty value d ₁ , ₁ performed by the first module controller of the first attempt is previously determined. The output power of the corresponding photovoltaic module 110 is increased, and the new duty value d ₁ to be used in the next pole is calculated based on the photovoltaic module voltage value V _PV1,1 .

Also, the output power P _{2, k} of the solar module 110 at the duty value d _{2, k} at the second module controller of the kth trial is equal to the output power of the previously corresponding solar module 110. Since it is increased, the new duty value d ₂ to be used in the next pole is calculated based on the photovoltaic module voltage value V _{PV2, k} at this time.

In the MGPS algorithm according to the embodiment of the present invention, as in the GPS algorithm, the magnitude of the new duty variation value in the new pole is increased from the previous value (e.g., twice the previous duty variation value) to speed up the maximum power point tracking. Let's do it. However, if there is no duty vector that produces more power than the maximum of the previous pole in a single pole, then the pole is considered to be a decreasing output pole and the new duty variation value of the new pole is maintained while maintaining the reference to the previous pole. Decreases (eg, 1/4 of the previous duty change).

Meanwhile, according to an embodiment of the present invention, an algorithm of a combination of GPS and MGPS is also possible when searching for a pattern. For example, when starting a new poll, it is also possible to perform both GPS and MGPS, and then compare the results to determine the condition of the maximum output power as the reference for the new poll.

FIG. 10 illustrates a simulation result of four solar modules using a GPS algorithm according to an exemplary embodiment of the present invention.

In the embodiment of the present invention, the initial duty values are set to 0.4, 0.4, and 0.5, respectively, and the x-axis of each graph represents the number of attempts for the duty variation, and FIGS. 10A, 10B, 10C, and 10D are shown in FIGS. The y-axis of the graph represents the solar module voltage, the output power, the solar module current, and the duty value of the module controller, respectively. In FIG. 9, when there are 4 (N = 4) solar modules, one pole has 6 (= 2 (N-1)) attempts, and through dozens of attempts (i.e., 10 or fewer poles). It can be seen that the maximum power point is stably found.

As described above, according to the solar module micro-converter device according to the first embodiment of the present invention, since the optimum duty of each solar module is directly searched and controlled by pattern search, following the maximum power point is simplified. In this way, there is no need for a PI controller, which reduces the cost of system implementation while simplifying device implementation.

On the other hand, according to the micro-converter device for a solar module according to the first embodiment of the present invention shown in Figures 4 to 6, if there is a severe mismatch between the solar modules or if the solar modules that have mismatch occurs continuously However, there is a problem that an overcurrent flows through the inductor of the module controller at the boundary with the module that is not.

In the embodiment of the present invention, as a countermeasure against such a problem, the soft start method shown in FIG.

That is, irrespective of the situation of the solar module, the first and second switches of the module controller (micro converter) are not unconditionally started with d = 0.5 as an initial value, but are initially switched off at all module controllers (S10). , Turn on the duty (d _i ) of each module controller sequentially. At this time, if the change is reduced by measuring the change in the total amount of power before and after operating the duty of the module controller (S12), the module controller is turned off (S13). On the contrary, when the total amount of power is increased, the duty of the module controller is turned on. Therefore, check if there is a module controller with overcurrent in the inductor. (S14)

If there is an inductor that has an overcurrent, check the inductor current in both directions from the adjacent module to the inductor center, and turn off the module controller with the inductor current close to zero. Check if it falls to (S15)

If the current of the inductor through which the overcurrent flows does not fall below the reference value, the module controller belonging to the inductor close to zero is next turned off. (S16, S14, S15) This operation is repeated until the overcurrent falls below the reference point.

On the other hand, according to an embodiment of the present invention, in order to solve the problem that the excessive current flows through the inductor of the module controller at the boundary between the module that is seriously mismatched between the photovoltaic module and the module that is not, during the normal operation rather than the initial operation In Fig. 12, the municipal ring soft stop function is used.

The string controller 140 periodically checks the current of the inductor, and when the current flowing through the inductor is less than the first reference level (S20), determines that there is no current deviation, and turns off the corresponding module controller. (S21) When the current flowing through the inductor is higher than the first reference level, it is determined whether the current flowing through the inductor flows at a value higher than the second reference level (that is, whether the overcurrent flows) (S22), and the current of the inductor If there is a module that flows to a value higher than the second reference level, as shown in FIG. 11, the controller of the module having the inductor current close to zero is checked by checking the inductor current in both directions from the adjacent module to the inductor. After the duty off, check whether the current of the inductor that the overcurrent flowed falls below the reference value. (S23)

As a result of this check, if the current of the inductor does not fall below the reference value, the module controller belonging to the inductor close to zero is duty-off. This operation is repeated until the overcurrent drops below the reference point.

On the other hand, the pattern search algorithm according to the embodiment of the present invention described above, the solar module micro-converter device according to the first embodiment of the present invention shown in Figures 4 to 6 (hereinafter referred to as "parallel structured micro-converter device" However, the present invention is not limited thereto, and the present invention is also applicable to a conventional series solar module micro converter device (hereinafter referred to as a 'serial structure micro converter device').

Hereinafter, a micro converter device for a solar module according to a second embodiment of the present invention will be described with reference to FIGS. 13 and 14.

As shown in FIG. 13, the micro-converter apparatus for a solar module according to the second embodiment of the present invention includes a plurality of micro-converters 230, string controllers 240, and string inverters connected one-to-one to a plurality of solar modules. 220. The plurality of micro converters 230 are connected in series. The micro-converter 230 is connected in one-to-one correspondence to the N-1 solar modules 110, but is directly connected to the string controller 240 instead of the micro-converter 230 to the last solar module 110 constituting the string. do.

As illustrated in FIG. 14, each micro-converter 230 includes an inductor 231, switches 232, 233, 234, and 235 provided at both ends of the inductor, a driver 236 for driving the switch, and a duty cycle of the switch. It includes a module controller 237 for controlling.

In FIG. 14, the driver 236 drives the

switches

232, 233, 234, and 235 in an on or off state under the control of the module controller 237. The module controller 237 transmits the voltage and current measurements of the solar module 110 to the string controller 240 and based on the duty cycle control data and the operation control data received from the string controller 240. The duty cycle of (232, 233, 234, 235) is controlled.

The string controller 240 directly measures the power of the last solar module 110 connected, and the power of the remaining solar modules is obtained through the module controller 237 of the module. The string controller 240 calculates a pulse width modulation (PWM) duty value of each module controller 237 using the GPS algorithm or the MGPS algorithm described above based on the power values obtained through the module controller 237. Thereby controlling each module controller 237.

The string inverter 230 converts the DC voltage output from the string into an AC voltage.

According to the photovoltaic module micro-converter device according to the second embodiment shown in FIGS. 14 and 15, the photovoltaic module according to the first embodiment of the present invention is similar to the photovoltaic module microconverter device by the pattern search. By directly searching for and controlling the optimal duty of, the maximum power point tracking can be simplified, and there is an advantage of simplifying device implementation while reducing system implementation cost by eliminating the need for a PI controller.

Although the embodiments of the present invention have been described above, the present invention is not limited thereto, and various other changes and modifications are possible. For example, in FIG. 14 and FIG. 14, the GPS controller or the MGPS algorithm is performed by the string controller 240, but may be independently performed by each micro converter. That is, depending on the performance of the CPU built in the communication module of the module controller of the micro-converter, GPS or MGPS may be performed in the micro converter or may be performed in the string controller.

The present invention is applied to a photovoltaic device. In particular, in order to adjust the voltage of the photovoltaic module, the string controller directly measures the power of the photovoltaic module, and based on this, it is effectively applied to a technique for calculating the maximum power point using a pattern search algorithm.

Claims

A plurality of micro-converters connected to a plurality of solar modules connected in series, each of the micro-converters including a module controller measuring power of the corresponding solar modules and controlling output power of the corresponding solar modules according to the first duty value; And

And directly measuring the power of a first solar module of the plurality of solar modules, and based on the power of the solar module received from the plurality of module controllers and the power of the first measured solar module directly. And a string controller which calculates and transmits the first duty value to each module controller using a pattern search algorithm for directly searching for an optimal duty of the optical module.
The method of claim 1,

The first photovoltaic module is a micro-converter device for a photovoltaic module that is the last photovoltaic module of the series connected photovoltaic modules.
The method of claim 1,

The plurality of micro converters are connected in parallel with the plurality of photovoltaic modules and provide a bypass path to the output of the photovoltaic module to compensate for power deviations when a difference in production power occurs between the corresponding photovoltaic modules. Micro converter unit for modules.
The method of claim 3, wherein the micro converter

Inductors provide bypass paths for current deviation compensation

First and second switches installed at one end of the inductor to set a current path, and

A driver for driving the first and second switches to a predetermined duty,

The module controller transmits the voltage and current measurement values of the corresponding solar module to the string controller, and controls the duty cycle of the switch based on the duty value received from the string controller. Device.
The method of claim 1, wherein the string controller

A module voltage / current detector for detecting voltage and current of the first solar module,

A string current detector for measuring string currents of the plurality of solar modules connected in series;

Based on the voltage and current values of the first photovoltaic module detected by the module voltage / current detector, the string current values detected by the string current detector, and the voltage and current values of the photovoltaic module transmitted by the module controller. And a string controller configured to calculate and transmit the first duty value to each module controller using the pattern search algorithm.
The method of claim 5, wherein the string controller

A communication module communicating with the module controller to receive voltage and current measurement values of the solar module and transmitting control data for controlling the solar module to the module controller;

Maximum power point for calculating the maximum power point using a pattern search algorithm based on the voltage and current value of the solar module received through the communication module and the voltage / current and string current of the first solar module directly measured Followers, and

And a duty controller for adjusting a voltage of the solar module by transmitting a duty cycle control signal to the module controller according to the maximum power point calculated by the maximum power point follower.
The method according to any one of claims 1 to 6,

The string controller

Change the duty value performed in each module controller based on the reference duty value and the duty variation value, which are the reference for the previous poll,

The microconverter device for photovoltaic module that determines the highest value among the output power values of the string stage calculated in one pole and the highest value of the previous pole value, and sets the duty value at that time as the new reference duty value. .
The method of claim 7, wherein

And said duty variation value is set to a value that is increased or decreased from the previous pole according to whether the attempt at each pole is successful.
The method according to any one of claims 1 to 6,

The string controller stores all voltage values of the photovoltaic module when the output power of the corresponding photovoltaic module is increased during an attempt to increase or decrease the duty value of each module controller, and then calculates a duty from the module voltages. Micro-converter device for photovoltaic module which sets new pole standard.
The method of claim 4, wherein

The string controller

Turn off the first switch and the second switch at the beginning of the startup, turn on the duty of each module controller sequentially, measure the change in the total amount of power before and after the duty of the module controller and measure the corresponding duty if the amount of power decreases. A micro-converter device for photovoltaic modules that is off and maintains its current duty when the amount of power increases.
The method of claim 10,

The string controller checks whether there is a module controller through which an overcurrent flows in the inductor while maintaining a current duty. If there is an inductor that has an overcurrent, the string controller checks the inductor current in both directions away from an adjacent module around the inductor. A micro-converter device for a photovoltaic module that controls the duty of the module controller by turning off the duty of the module controller having an inductor current close to that.
The method of claim 10,

The string controller periodically checks the overcurrent of the inductor during normal operation, and if there is a module in which the current of the inductor flows more than the reference, the inductor close to zero by checking the inductor current in both directions away from the adjacent module. A micro-converter device for photovoltaic modules that controls the duty of the module controller by turning off the duty of the module controller with the current.