KR101550368B1 - Solar photovoltaic power generation system and method for controlling connection of solar cell array - Google Patents

Solar photovoltaic power generation system and method for controlling connection of solar cell array Download PDF

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KR101550368B1
KR101550368B1 KR1020150054675A KR20150054675A KR101550368B1 KR 101550368 B1 KR101550368 B1 KR 101550368B1 KR 1020150054675 A KR1020150054675 A KR 1020150054675A KR 20150054675 A KR20150054675 A KR 20150054675A KR 101550368 B1 KR101550368 B1 KR 101550368B1
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South Korea
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solar cell
voltage
cell group
level
switch
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KR1020150054675A
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Korean (ko)
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박재동
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(주)에너지와공조
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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02SGENERATION OF ELECTRIC POWER BY CONVERSION OF INFRA-RED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
    • H02S50/00Monitoring or testing of PV systems, e.g. load balancing or fault identification
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/165Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • GPHYSICS
    • G05CONTROLLING; REGULATING
    • G05FSYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F1/00Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
    • G05F1/66Regulating electric power
    • G05F1/67Regulating electric power to the maximum power available from a generator, e.g. from solar cell
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES; ELECTRIC SOLID STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H01L31/00Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus peculiar to the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus peculiar to the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/042PV modules or arrays of single PV cells
    • H01L31/05Electrical interconnection means between PV cells inside the PV module, e.g. series connection of PV cells
    • H01L31/0504Electrical interconnection means between PV cells inside the PV module, e.g. series connection of PV cells specially adapted for series or parallel connection of solar cells in a module
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00Energy generation through renewable energy sources
    • Y02E10/50Photovoltaic [PV] energy

Abstract

A solar cell array including a plurality of solar cell groups formed by connecting respective rows of a plurality of solar cell panels arranged in a matrix form in series, Based on the output voltage of one solar cell group or the output voltage of a plurality of solar cell groups connected in series to each other so as to fall within an allowable input voltage range of a PCS (Power Conditioning System) Off of a switch array including a plurality of switches for opening / closing a connection between a group and a PCS and a plurality of switches for opening / closing a serial connection between two neighboring solar cell groups, thereby actively coping with weather changes The solar power generation amount can be greatly improved.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic power generation system,

The present invention relates to a photovoltaic power generation system for producing electrical energy suitable for a load from solar energy and a method for controlling connection of a solar cell array.

1 is a block diagram of a conventional conventional solar power generation system. 1, a conventional general photovoltaic power generation system includes a solar cell array 110 in which a plurality of solar cell panels are connected in series and in parallel with each other, And a PCS (Power Conditioning System) 120 for converting power into electric power. This is referred to as the " Central PCS " method in which one PCS processes the entire output of the solar cell array 110 and is widely used for large-capacity generation of 10 kW or more. On the other hand, there is a "String PCS" method in which a PCS is independently installed for each group of a plurality of solar panels connected in series, and a "Multi-string PCS" method in which the "String PCS" method and the "Central PCS" method are mixed.

The "String PCS" method and the "Multi-string PCS" method are required for several converters and inverters for large-scale power generation, and thus are mainly used for small-capacity power generation due to high manufacturing cost. The "Central PCS" system as shown in Fig. 1 is widely used even when applied to large-capacity power generation because the manufacturing cost is low. However, although the "Central PCS" method is designed to be optimized for solar AM (air mass), it is difficult to actively cope with weather changes such as solar radiation, temperature, etc., have. Particularly, because of the range of the input voltage convertible by the PCS 120, that is, the limit of the allowable input voltage range of the PCS 120, solar power generation may not be smoothly performed according to the weather change.

Korean Patent Registration No. 10-1236953 discloses a module controller which is installed for each unit module corresponding to a solar panel and controls the X-axis connection and the Y-axis connection between the solar panels and the module controller which controls the Y- Two inverters are presented. However, each module controller is composed of a current transformer, a transformer for meters, an X-axis switch, a Y-axis switch, and a microprocessor. In addition to the number of module controllers required for the number of solar panels, two inverters are required, high. In addition, due to the complexity of the structure, various failure factors are latent and the operation reliability of the photovoltaic system is low. Accordingly, the above-described patent technology is hardly applied to practical industrial sites.

And to provide a photovoltaic power generation system capable of drastically improving solar power generation by actively coping with weather changes by a simple circuit that can be realized with a very small number of devices. It is also an object of the present invention to provide a method for controlling the connection of solar cell arrays of such solar power generation systems. The present invention is not limited to the above-described technical problems, and another technical problem may be derived from the following description.

A solar cell system according to an aspect of the present invention includes: a solar cell array including a plurality of solar cell groups formed by serially connecting respective rows of a plurality of solar cell panels arranged in a matrix; A PCS (Power Conditioning System) for converting power output from the solar cell array into power suitable for a load; A voltage detector for detecting a level of an output voltage of each solar cell group; A switch array including a plurality of switches for opening / closing a connection between each solar cell group and the PCS, and a plurality of switches for opening / closing a serial connection between two neighboring solar cell groups; And based on the output voltage of one solar cell group or the output voltage of each solar cell group detected by the voltage detector such that an output voltage of a plurality of solar cell groups connected in series to each other falls within an allowable input voltage range of the PCS And controlling the on / off of each switch of the switch array.

Wherein the controller is configured to control the switch connected to the solar cell group having a level corresponding to the output voltage range of the allowable input voltage range of the PCS among the plurality of solar cells, And turns on a switch for opening and closing a serial connection between adjacent solar cell groups for switches connected to the solar cell group having a level corresponding to an output voltage range out of the allowable input voltage range of the PCS.

Wherein a level of an output voltage of each solar cell group is a first level corresponding to a voltage range belonging to an allowable input voltage range of the PCS, a maximum voltage of an allowable input voltage range of the PCS, A second level corresponding to a voltage range exceeding the minimum voltage of the allowable input voltage range of the PCS while exceeding the potential difference and a second level corresponding to a voltage lower than a potential difference between the maximum voltage of the allowable input voltage range of the PCS and the maximum output voltage of each solar cell group And the third level corresponding to the interval.

Wherein the controller opens and closes a connection between a positive terminal of one of the solar cell groups and a positive input terminal of the PCS if the level of the output voltage of any one of the plurality of solar cell groups is the first level A switch for turning on a switch for turning on and off a connection between a negative terminal of the one solar cell group and a negative input terminal of the PCS and for connecting the negative terminal of the one solar cell group to the adjacent one of the solar cell groups The switch for opening and closing the series connection between the anode terminals of the solar cell group can be turned off.

Wherein when the level of the output voltage of any one of the plurality of solar cell groups is at the second level, the controller determines that the negative terminal of any one of the plurality of solar cell groups and the solar cell group adjacent to any one of the solar cell groups The switch for opening and closing the series connection between the positive terminals of the battery group can be turned on or off according to the level of the output voltage of the solar cell group adjacent to any of the solar cell groups.

 Wherein when the level of the output voltage of any one of the plurality of solar cell groups is the third level, the controller determines that the negative terminal of any one of the solar cell groups and the solar cell group adjacent to any one of the solar cell groups The switch for opening and closing the series connection between the positive terminals of the battery group can be turned on.

A first switch for opening / closing a connection between a positive terminal of one of the solar cell groups and a positive input terminal of the PCS, and a controller for opening / closing the connection between the negative terminal of the one solar cell group and the negative input terminal of the PCS, And a third switch for opening and closing a series connection between the anode terminal of one of the solar cell groups and the anode terminal of the solar cell group adjacent to the one solar cell group together The first switch, the second switch, and the third switch are turned on in sequence, and when at least two of the first switch, the second switch, and the third switch are to be turned off together, , The second switch, and the first switch in this order.

Wherein the voltage detector detects the level of the output voltage of each solar cell group by dividing the output voltage of each of the solar cell groups and comparing the plurality of divided voltages with a reference voltage, And may be any one of a plurality of voltages divided from a highest voltage of at least one level among a plurality of levels of the outputable voltage. Wherein the voltage detector comprises: a plurality of resistors for dividing an output voltage of each solar cell group; And a plurality of OP-amplifiers that generate a potential indicating a level of an output voltage of each of the solar cell groups by comparing a plurality of voltages divided by the plurality of resistors and the reference voltage.

The controller outputs a signal indicative of connection information between the solar cell groups of the solar cell array, and the PCS converts the DC power output from the solar cell array into DC power having a voltage of a different magnitude; An MPPE (Maximum Power Point Estimator) for estimating a maximum power point of the solar cell array based on connection information between solar cell groups of the solar cell array represented by the signal output from the controller; And an MPPT (Maximum Power Point Tracker) that tracks the maximum power point of the solar cell array by periodically increasing or decreasing the output voltage of the DC / DC converter, starting from a pointing voltage for reaching a maximum power point estimated by the MPPE, . ≪ / RTI >

The MPPT stops the increase / decrease of the output voltage of the DC / DC converter when the maximum power point estimated by the MPPE is changed, and starts the output voltage of the DC / DC converter from the indicated voltage for reaching the changed maximum power point The maximum power point of the solar cell array can be tracked by periodically increasing or decreasing the power. If the magnitude of the estimated power corresponding to the maximum power point estimated by the MPPE is smaller than the threshold value, the PCS determines that the DC power of the DC / DC converter is lowered in proportion to the difference between the magnitude of the estimated power and the threshold value And an inverter for converting the AC power into AC power having a voltage.

According to another aspect of the present invention, there is provided a method of controlling connection of a solar cell array including a plurality of solar cell groups formed by connecting each row of a plurality of solar cell panels arranged in a matrix in series, Receiving a signal indicating a level of an output voltage of the battery group; Determining a level of an output voltage of the one solar cell group based on the received signal; Turning off a switch for opening and closing a serial connection between a negative terminal of one of the solar cell groups and a positive terminal of a solar cell group adjacent to the one solar cell group if the determined level is the first level; A switch for opening and closing a series connection between a negative terminal of one of the solar cell groups and a positive terminal of the neighboring solar cell group is turned on and off according to the level of the output voltage of the neighboring solar cell group Turning on or off; And turning on a switch for opening and closing a serial connection between the anode terminal of one of the solar cell groups and the anode terminal of the neighboring solar cell group if the determined level is the third level.

An output voltage of one solar cell group of the solar cell array including a plurality of solar cell groups formed by connecting the respective rows of the plurality of solar cell panels arranged in a matrix form in series or a plurality of solar cell groups A plurality of switches for opening / closing a connection between each solar cell group and a PCS (Power Conditioning System) so that the output voltage falls within an allowable input voltage range of PCS, and a plurality of switches for opening / closing a serial connection between two neighboring solar cell groups The amount of photovoltaic power generation can be greatly improved by actively coping with the weather change only by controlling a very small number of switches as compared with a method of opening / closing the connection between solar panels by controlling on / off of each switch of the included switch array. Accordingly, the production cost of the photovoltaic power generation system which can actively cope with the weather change and can greatly improve the photovoltaic power generation is not only low, but also can be actively coped with the weather change by the simple switching circuit, The operation reliability of the photovoltaic system is very high.

In particular, the output of each solar cell group having a much smaller amount of data than the output voltage of each solar cell panel, such that the output voltage of one solar cell group or the output voltage of a plurality of solar cell groups connected in series to each other falls within the allowable input voltage range of PCS Off of each switch of the switch array 40 can be controlled at a high speed by controlling ON / OFF of each switch of the switch array based on the level of the voltage, Can be greatly improved. Also, since the amount of data of the output voltage of each solar cell group is small, the output voltage of one solar cell group or the output of a plurality of solar cell groups connected in series to each other Since the voltage can be within the allowable input voltage range of the PCS, it is possible to provide a photovoltaic power generation system that responds in real time to weather changes.

1 is a block diagram of a conventional conventional solar power generation system.
2 is a configuration diagram of a photovoltaic power generation system according to an embodiment of the present invention.
3 is a circuit diagram of the voltage detector 30 shown in Fig.
FIG. 4 is a diagram showing various implementations of the switch array 40 shown in FIG.
5 is a diagram showing an on / off table of each switch of the switch array 40 shown in FIG.
Fig. 6 is a configuration diagram of the PCS 20 shown in Fig.
7 is a flowchart of a method of controlling the connection of the solar cell array 10 according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The embodiments of the present invention can be applied to a solar power generation system that can actively cope with weather changes by a simple circuit that can be implemented with a very small number of elements and can greatly improve the solar power generation amount and the connection of the solar cell array of such a solar power generation system To a control method. In the following, a direct current may simply be referred to as "DC ", or an alternating current may be abbreviated as" AC ".

2 is a configuration diagram of a photovoltaic power generation system according to an embodiment of the present invention. 2, the solar power generation system according to the present embodiment includes a solar cell array 10, a PCS (Power Conditioning System) 20, a voltage detector 30, a switch array 40, and a controller 50, . Hereinafter, only the configuration related to the connection of the solar cell panel will be described in order to prevent the characteristics of the present embodiment from being blurred. It will be understood by those skilled in the art that the solar power generation system according to the present embodiment may further include other components in addition to the components described below. For example, the photovoltaic generation system according to the present embodiment may be provided with a component for protecting the photovoltaic generation system from system accidents. In Fig. 2, power lines and power terminals are indicated by solid lines to distinguish between power and signals, and signal lines and signal terminals are indicated by dashed lines. Other drawings are likewise displayed.

The solar cell array 10 is composed of a plurality of solar cell groups formed by connecting respective rows of a plurality of solar cell panels arranged in a matrix form in series. As shown in FIG. 2, the plurality of solar cell panels P (1, 1) to P (M, N) are arranged in an M x N-dimensional matrix form having M rows and N columns. Each solar cell panel is composed of a plurality of solar cells connected in series, parallel, or series-parallel. That is, the solar cell array 10 is composed of M x N solar cell panels arranged in an M x N matrix, and each column of the solar cell array 10 is connected in series and each column connected in series Each solar cell group.

M solar cell panels belonging to a row of N solar cell arrays 10 are connected in series to form N solar cell groups. For example, the solar cell group G (1) comprises solar cells P (1, 1) to P (M, 1) corresponding to the first column connected in series. Similarly, the solar cell group G (2) is constituted by serially connecting the solar cell panels P (1, 2) to P (M, 2) corresponding to the second column. That is, the solar cell group G (n) is constituted by serially connecting the solar cell panels P (1, n) to P (M, n) corresponding to the nth row.

The PCS 20 is connected to the output terminal of the solar cell array 10 to convert the power output from the solar cell array 10 into power suitable for the load 60. [ A solar cell is a device that converts light energy of sunlight into electric energy, and generates DC power, so that DC is outputted from the solar cell array 10. Since the load 60 such as household appliances and lighting equipment in the house is driven by the AC power, the AC power is mainly supplied to the load 60. [ The photovoltaic power generation system is independent from the commercial power system according to its operation mode, and is connected to the stand-alone system that supplies only the output power of the photovoltaic power generation system to the load (60), the solar power generation system and the commercial power system, And grid-connected systems that supply power. Since this commercial power is AC power, AC power is similarly supplied to the load 60. [

On the other hand, DC power may be supplied to the load 60 if the load 60 is driven by DC power. The stand-alone system generally has a battery to provide stable power to the load 60, and the power output from the stand-alone system is stored in the battery. The load 60 is driven by the electric power stored in the battery. Since the power stored in the battery is DC power, the DC power is similarly supplied to the battery. The output voltage and the output current of the solar cell array 10 may be different from the rated voltage and the rated current of the load 60. [ Accordingly, the PCS 20 can convert the magnitude of the output voltage of the solar cell array 10 and the magnitude of the output current into the magnitude of the rated voltage of the load 60 and the magnitude of the rated current. That is, the PCS 20 may convert DC power output from the solar cell array 10 into AC power suitable for the load 60, and may convert the DC power output from the solar cell array 10 into the load 60 It may be converted into a suitable DC power.

The PCS 20 of the photovoltaic power generation system is different from a general-purpose inverter for converting a direct current into an alternating current or a general-purpose DC / DC converter for converting a direct current of a certain voltage into a direct current of a different voltage, A function of tracking the point so that the maximum power can always be output from the solar cell array 10, and a function of protecting the photovoltaic generation system from system accidents.

The voltage detector 30 detects the level of the output voltage of each solar cell group of the solar cell array 10. [ The level of the output voltage of each solar cell group is detected in a state in which the electrical connection with the other solar cell group, the PCS 20, is broken. More specifically, the voltage detector 30 divides the output voltage of each solar cell group of the solar cell array 10 and compares the thus divided voltages and the reference voltage, Level can be detected. Here, the reference voltage is any one of a plurality of voltages divided from the highest voltage of at least one level among a plurality of levels obtained by dividing the range of the outputable voltage of each solar cell group.

The present embodiment divides the range of voltage that can be output by each solar cell group of the solar cell array 10 into several voltage sections and sets the voltage sections to different levels. As described below, the controller 50 can greatly reduce the amount of calculations by processing various output voltages of the solar cell group by processing the output voltage of each solar cell group based on this level. As a result, the control of the switch array 40 as described below can be performed at high speed.

3 is a circuit diagram of the voltage detector 30 shown in Fig. Referring to FIG. 3, the voltage detector 30 shown in FIG. 2 includes a plurality of resistors for dividing an output voltage of each solar cell group of the solar cell array 10, a plurality of voltages divided by a plurality of resistors, A plurality of OP-amplifiers for generating a potential indicating the level of the output voltage of each solar cell group by comparing the voltages, and a plurality of OP-amplifiers for applying voltages to nodes between the output terminals of the plurality of OP-amplifiers and the input terminals of the controller 50 And a plurality of resistors for generating a plurality of signals representing levels of output voltages of the respective solar cell groups.

In this way, the voltage detector 30 can detect the level of the output voltage of each solar cell group by generating a plurality of signals indicating the level of the output voltage of each solar cell group through the above-described operation. Meanwhile, one circuit as shown in FIG. 3 may be installed separately for each solar cell group to detect only the output voltage level of one solar cell group, and one circuit may detect the output voltage May be sequentially detected. In the former case, the voltage detector 30 can be implemented with only a few circuit elements, which is economical and can take a considerable time to detect the level of the output voltage of all the solar cell groups. In the latter case, The production cost may be considerable, but the level of the output voltage of all the solar cell groups can be detected at a time.

For example, if the allowable input voltage range of the PCS 20 is 600V to 1500V and the range of the output voltage of the solar cell group is 100V to 1200V, the range of the output voltage of each solar cell group is 100V to 1200V, 300V, 300V to 600V, and 600V to 1200V, respectively. The voltage range 600V to 1200V (strictly, the range exceeding 600V but 1200V or less) corresponds to the voltage range belonging to the allowable input voltage range 600V to 1500V of the PCS 20 and is set to the level 1. A voltage range of 300 V to 600 V (strictly 600 V or less exceeding 300 V) is a potential difference between the maximum voltage 1500 V of the allowable input voltage range of the PCS 20 and the maximum output voltage 1200 V of each solar cell group of the solar cell array 10 Which is the minimum voltage of the allowable input voltage range of the PCS 20 and not more than 600 V, and is set to the level 2. A voltage range of 100 V to 300 V (strictly, a range exceeding 100 V but less than 300 V) is a potential difference between the maximum voltage 1500 V of the allowable input voltage range of the PCS 20 and the maximum output voltage 1200 V of each solar cell group of the solar cell array 10 And is set to the level 3.

As described above, in order to divide the range of voltage that can be output by each solar cell group into three voltage sections and to distinguish the three voltage sections by three levels, three resistances R1, R2, Amplifiers U1 and U2 are used to generate the potential indicating the level of the output voltage of each solar cell group and two resistors are used for generation of the signal indicating the level of the output voltage of the solar cell array 10. [ R4, and R5 are used. Those skilled in the art will appreciate that the resistance values of the three resistors R1, R2, and R3 can be variously varied according to the permissible input voltage range of the PCS 20 and the range of voltages that each solar cell group can output By designing, it is possible to set various lengths of the voltage section of each level and by using more number of resistors and OP-amplifiers to increase the resolution of the level of the output voltage of each solar cell group, It can be appreciated that the range can be divided into a greater number of levels.

One end of the three resistors R1, R2 and R3 connected in series are connected to the positive output terminal + G (n) of one solar cell group G (n) and the other end of the three resistors R1, R2, n (n). Accordingly, the output voltage of the solar cell group G (n) is divided into three resistances R1, R2, and R3. For example, if the output voltage of the solar cell group G (n) is 300V and the resistance values of the three resistors R1, R2, and R3 are the same, the three resistors R1, R2, and R3 are divided by 100V. Since the cathode output terminal -G (n) of the solar cell group G (n) corresponds to the ground, it takes 100V for the resistor R3, 200V for the resistor R2, and 300V for the resistor R1.

The node between resistor R1 and resistor R2 is connected to the non-inverting (+) input terminal of OP-amplifier U1 and the node between resistor R2 and resistor R3 is connected to the non-inverting (+) input terminal of OP- have. Thus, a voltage (for example, 200 V) equal to the voltage applied to the resistor R 2 is applied to the non-inverting (+) input terminal of the OP-amplifier U 1 and a voltage (for example, 100 V) - applied to the non-inverting (+) input terminal of amplifier U2. The reference voltage Vr is applied to the inverting (-) input terminal of the OP-amplifier U1 and the inverting (-) input terminal of the OP-amplifier U2. Here, the reference voltage Vr is a reference voltage for discriminating the level of the output voltage of the solar cell group G (n) from the level 1 to the level 3, and when the highest voltage 600V of the level 2 is divided, The voltage applied to the resistor R2 becomes 200V when the voltage is applied and the highest voltage of the level 3 is 300V.

Thus, when the voltage across the resistor R2 is higher than the reference voltage Vr, the output terminal of the OP-amplifier U1 has a higher potential than the ground (potential 0). If the voltage across the resistor R2 is equal to the reference voltage Vr, And the output terminal of the OP-amplifier U1 has a lower potential than the ground when the voltage across the resistor R2 is lower than the reference voltage Vr. Similarly, when the voltage across the resistor R3 is higher than the reference voltage Vr, the output terminal of the OP-amplifier U2 has a higher potential than the ground, and if the voltage across the resistor R3 is equal to the reference voltage Vr, If the voltage across the resistor R3 is lower than the reference voltage Vr, the output terminal of the OP-amplifier U2 has a lower potential than the ground. The potentials of the output terminals of the two OP-amplifiers U1 and U2 indicate the level of the output voltage of the solar cell array 10. [

Vcc is applied to one end of the resistor R4 and the other end is connected to a node between the output terminal of the OP-amplifier U1 and the input terminal A of the controller 50. [ Accordingly, when the potential of the output terminal of the OP-amplifier U1 is higher than the ground potential, a high signal having the potential Vcc flows into the input terminal A of the controller 50. [ When the potential of the output terminal of the OP-amplifier U1 is equal to or lower than the ground, a low signal having a ground potential flows into the input terminal A of the controller 50. Similarly, Vcc is applied to one end of the resistor R5, and the other end is connected to a node between the output terminal of the OP-amplifier U2 and the input terminal B of the controller 50. [ Accordingly, when the potential of the output terminal of the OP-amplifier U2 is higher than the ground potential, a high signal having the potential Vcc flows through the input terminal B of the controller 50. [ When the potential of the output terminal of the OP-amplifier U2 is equal to or lower than the ground, a low signal having the ground potential flows into the input terminal B of the controller 50. [ In this way, the voltage detector 30 can detect the level of the output voltage of each solar cell group by generating two signals input to the two input terminals A and B of the controller 50. Hereinafter, a signal input to the input terminal A of the controller 50 may be referred to as an "A signal " and a signal input to the input terminal B may be referred to as a" B signal ".

The switch array 40 includes a plurality of switches S (n, 1) and S (n, 2) for opening and closing the connection between each solar cell group G (n) and the PCS 20 under the control of the controller 50, (N, 3) for opening and closing the serial connection between each solar cell group G (n) and the solar cell group G (n + 1) adjacent to each solar cell group under the control of the control unit 50 . Here, n = 1 to N, and N is the total number of solar cell groups constituting the solar cell array 10. [ In order to prevent the difficulty in understanding the present embodiment due to a large number of codes appearing in the description of this embodiment, the same code S (n, 1) is used for the signal for controlling the switch S (n, 1) . The same reference numerals are also used for the switches S (n, 2) and S (n, 3).

2, the switch S (n, 1) is provided between the positive input terminal of the PCS 20 and the positive output terminal of the solar cell group G (n) and outputs the signal S (n, 1), the connection between the positive input terminal of the PCS 20 and the positive output terminal of the solar cell group G (n) is opened or closed. The switch S (n, 2) is provided between the negative output terminal of the solar cell group G (n) and the negative input terminal of the PCS 20, And the connection between the negative output terminal of the group G (n) and the negative input terminal of the PCS 20 is opened or closed. The switch S (n, 3) is provided between the negative output terminal of the solar cell group G (n) and the positive output terminal of the solar cell group G (n + 1) , The connection between the anode output terminal of the solar cell group G (n) and the anode output terminal of the solar cell group G (n + 1) is opened or closed.

FIG. 4 is a diagram showing various implementations of the switch array 40 shown in FIG. 4A shows a circuit in which switches S (n, 1), S (n, 2) and S (n, 3) of the switch array 40 are each implemented by a TRIAC (triode AC switch) . Since TRIAC has two thyristors connected in antiparallel, current flows bidirectionally. It is suitable for large power, and it is precisely turned off at the timing of current zero. Accordingly, TRIAC shown in FIG. 4 is preferably applied to each switch of the switch array 40. In FIG. 4 (b), a metal oxide silicon field effect transistor (MOSFET) is used as a switching element of the TRIAC, which is advantageous for high-speed switching.

Based on the level of the output voltage of each solar cell group detected by the voltage detector 30 so that the output voltage of the solar cell array 10 falls within the allowable input voltage range of the PCS 20, (On / off) of each switch of the switch 40. The controller 50 may be implemented as a microcomputer or the like. The amount of solar energy actually irradiated to each solar cell of the solar cell array 10 changes instantaneously due to cloud movement due to the weather change and shadows due to the passage of time. Accordingly, some of the solar cell groups of the solar cell array 10 may be lower in power generation amount than other solar cell groups. For example, a solar cell group partially or wholly covered by the shadow of the surrounding obstacle is significantly lower in power generation amount than other solar cell groups irradiated with sunlight as a whole.

The solar cell array 10 is generally installed in a place where there is no obstacle, but an obstacle can be inevitably installed around the solar cell array 10 after the solar cell array 10 is installed. On the other hand, the phenomenon of solar cell cloaking due to cloud shadows necessarily occurs due to weather changes. As described above, since the DC / DC converter 21 of the PCS 20 is implemented as a buck-boost converter, the PCS 20 according to the present embodiment provides a very wide allowable input voltage range. However, due to the limitations of the voltage conversion range of the transformer of the PCS 20, the rated voltage of the circuit elements, etc., the allowable input voltage range of the PCS 20 can not be infinitely expanded and has a specific range. Accordingly, the output voltage of the solar cell group whose power generation amount is reduced due to the shadow of the surrounding obstacle, cloud, etc., may not be within the allowable input voltage range of the PCS 20. [

The conventional photovoltaic generation system shown in FIG. 1 includes a photovoltaic group for outputting a voltage outside the allowable input voltage range of the PCS 20 and a photovoltaic group for outputting a voltage belonging to the allowable input voltage range of the PCS 20 Since they are connected in parallel with each other, if some of the solar cell groups are covered by certain shadows, the voltage mismatch problem between the solar cell groups becomes serious. In the worst case, the output voltage of the normal solar cell group is also lowered due to the solar cell group whose power generation amount is decreased, and the power of the solar cell array 10 is deviated from the allowable input voltage range of the PCS 20, It may not be converted. Of course, the entire solar cell array 10 can be covered by shadows such as surrounding obstacles and clouds. In this case, the output voltages of all the solar cell groups are out of the allowable input voltage range of the PCS 20, so that the entire power of the solar cell array 10 is not converted by the PCS 20. [

According to this embodiment, the ON / OFF states of the respective switches of the switch array 40 are controlled so that the output voltage of one solar cell group or the output voltage of a plurality of solar cell groups connected in series to each other falls within an allowable input voltage range of the PCS 20. [ Off is controlled based on the level of the output voltage of each solar cell group, the power generation amount of the solar cell array 10 is prevented from being lowered due to the voltage mismatch between the solar cell groups, and the inoperative state of the PCS 20 is prevented . In particular, by adopting a method of opening and closing the connection between each solar cell group and the PCS 20 and opening and closing the serial connection between two neighboring solar cell groups, a very small number of switches The production cost of the photovoltaic power generation system is not only low but also the operation of the photovoltaic power generation system is very reliable because there is no cause of trouble because the photovoltaic system can actively cope with the weather change by a simple switching circuit.

More specifically, the controller 50 controls the switches connected to the solar cell groups of the level corresponding to the output voltage range within the allowable input voltage range of the PCS 20 among the plurality of solar cell groups of the solar cell array 10 The switch for turning on and off the series connection between neighboring solar cell groups is turned off and the switches connected to the solar cell group at the level corresponding to the output voltage range exceeding the allowable input voltage range of the PCS 20 are turned off Turn on the switch to open and close the series connection between the solar cell groups. As described above, the solar cell group having the level corresponding to the output voltage range within the allowable input voltage range of the PCS 20 is individually connected to the PCS 20, and the output voltage The output voltage of one solar cell group or the output voltage of a plurality of solar cell groups connected in series to each other may be connected to the PCS 20 through a series connection with a neighboring solar cell group And falls within the allowable input voltage range of the PCS 20 almost uniformly. As a result, the voltage mismatch between the solar cell groups is minimized, and the output power of the solar cell array 10 can be greatly improved.

5 is a diagram showing an on / off table of each switch of the switch array 40 shown in FIG. The controller 50 turns on or off each switch of the switch array 40 according to the table shown in Fig. 5, when both the A signal and the B signal output from the voltage detector 30 for any of the N solar cell groups G (n) of the solar cell array 10 are high On or off of all switches S (n, 1), S (n, 2), and S (n, 3) connected to the solar cell group G (n) is specified. When both the A signal and the B signal output from the voltage detector 30 to any of the N solar cell groups G (n) of the solar cell array 10 are low, the solar cell group G only the ON or OFF of the switch S (n, 3) connected to the switch S (n) is specified. The ON or OFF of the switches connected to the solar cell group G (n) in other cases is determined by the position of the solar cell group G (n) among the plurality of solar cell groups connected in series with each other and the position of the solar cell group G ) Of the solar cell group G (n + 1) adjacent to the solar cell group G (n + 1).

The controller 50 determines whether the A signal and the B signal output from the voltage detector 30 for any one of the N solar cell groups G (n) of the solar cell array 10 are high, that is, When the level of the output voltage of the battery group G (n) is level 1, the switch S (n, 1) for opening and closing the connection between the positive terminal of the solar cell group G (n) and the positive input terminal of the PCS 20 is turned on The switch S (n, 2) for opening and closing the connection between the negative terminal of the solar cell group G (n) and the negative input terminal of the PCS 20 is turned on and the negative terminal of the solar cell group G (n) 3) for opening and closing the series connection between the positive terminals of the solar cell group G (n + 1) adjacent to the solar cell group G (n + 1). Thus, the solar cell group G (n) is individually connected to the PCS 20. As described above, when the level of the output voltage of the solar cell group G (n) is level 1, since the output voltage of the solar cell group G (n) belongs to the allowable input voltage range of the PCS 20, The battery group G (n) may be individually connected to the PCS 20. [

The output voltages of most solar cell groups fall within the allowable input voltage range of PCS 20 unless the entire solar cell array 10 is covered by shadows such as surrounding obstacles or clouds. In this case, since several solar cell groups are individually connected to the PCS 20, a plurality of solar cell groups are connected in parallel and connected to the PCS 20. Hereinafter, a case where the solar cell group G (n) is individually connected to the PCS 20 can be expressed as a case where the solar cell group G (n) is connected to the PCS 20 in parallel. That is, when the level of the output voltage of the solar cell group G (n) is level 1, the solar cell group G (n) is connected to the PCS 20 in parallel.

If the A signal outputted from the voltage detector 30 is high and the B signal is low for any solar cell group G (n) of N solar cell groups of the solar cell array 10, that is, If the level of the output voltage of the solar cell group G (n) is level 2, the anode terminal of the solar cell group G (n) and the anode terminal of the solar cell group G (n + 1) (N, 3) for opening and closing the serial connection between the solar cell group G (n) and the solar cell group G (n + 1) according to the level of the output voltage of the solar cell group G Accordingly, the solar cell group G (n) may be connected to the PCS 20 in parallel or may be connected to the PCS 20 after being connected in series with the neighboring solar cell group G (n + 1). On the other hand, when the problem of voltage mismatch between the solar cell groups is intensified due to the connection of the solar cell group G (n) in parallel to the PCS 20 and the generation amount of the solar cell array 10 is remarkably decreased, the solar cell group G The output voltage of the solar cell group G (n) influences the output voltage of the other solar cell group by turning off all the switches S (n, 1), S (n, 2), S .

In the above example, the level of the output voltage of the solar cell group G (n) is the level 2 corresponding to the voltage section 300V to 600V and the level of the output voltage of the neighboring solar cell group G (n + 1) If the solar cell group G (n) and the solar cell group G (n + 1) are connected in series, the serial connection voltage between the solar cell group G (n) and the solar cell group G The permissible input voltage range of the PCS 20 may deviate from 600V to 1500V, and the switch S (n, 3) is turned off. On the other hand, when the level of the output voltage of the solar cell group G (n) corresponds to the level 2 corresponding to the voltage section 300V to 600V and the level of the output voltage of the neighboring solar cell group G (n + 1) corresponds to the voltage section 300V to 600V The solar cell group G (n) and the solar cell group G (n + 1) are connected in series when the solar cell group G (n) and the solar cell group G ) Belongs to the allowable input voltage range 600V to 1500V of the PCS 20, and the switch S (n, 3) is turned on.

Thus, when the output voltage level of the solar cell group G (n) is level 2 and the output voltage level of the solar cell group G (n + 1) is level 1, the switch S (n, 3) is turned off, When the level of the output voltage of the group G (n) is level 2 and the level of the output voltage of the solar cell group G (n + 1) is the level 2 or 3, the switch S (n, 3) is turned on. The on / off of the switch S (n, 1) and the on / off of the switch S (n, 2) according to the turn-off of the switch S (n, 3) As described above. The on / off of the switch S (n, 1) and the on / off of the switch S (n, 2) according to the turning on of the switch S (n, 3) As described below.

 If the A signal and the B signal output from the voltage detector 30 for any one of the N solar cell groups G (n) of the solar cell array 10 are both low, that is, When the level of the output voltage of the battery group G (n) is level 3, the anode terminal of the solar cell group G (n) and the anode terminal of the solar cell group G (n + 1) The switch S (n, 3) for opening and closing the serial connection is turned on. Accordingly, the solar cell group G (n) is connected to the PCS 20 after being connected in series with the neighboring solar cell group G (n + 1). As described above, when the output voltage level of the solar cell group G (n) is level 3, even when the output voltage level of the neighboring solar cell group G (n + 1) is level 1, and the series connection voltage of the solar cell group G (n + 1) and the solar cell group G (n + 1) belong to the allowable input voltage range of the PCS 20, They can be connected in series.

A switch S (n, 1) for opening and closing the connection between the positive terminal of the solar cell group G (n) and the positive input terminal of the PCS 20 and the negative terminal of the solar cell group G (n) The switches S (n, 2) for opening and closing the connections between the terminals are controlled differently according to the position of the solar cell group G (n) among the plurality of solar cell groups connected in series to each other as follows. The controller 50 turns on a switch for opening and closing the connection between the anode terminal of the solar cell group and the anode input terminal of the PCS 20 for the first solar cell group among the plurality of solar cell groups connected in series The switch for closing the connection between the negative terminal of the first solar cell group and the negative input terminal of the PCS 20 is turned off.

In addition, the controller 50 turns off the switch for opening and closing the connection between the anode terminal of the solar cell group and the anode input terminal of the PCS 20 for the last solar cell group among a plurality of solar cell groups connected in series to each other And turns on the switch for opening and closing the connection between the negative terminal of the solar cell group and the negative input terminal of the PCS 20. [ In addition, the controller 50 turns off the switch for opening / closing the connection between the anode terminal of the solar cell group and the anode input terminal of the PCS 20 for the solar cell group located in the middle among the plurality of solar cell groups connected in series to each other And turns off the switch for opening and closing the connection between the negative terminal of the solar cell group and the negative input terminal of the PCS 20.

The controller 50 includes a switch S (n, 1) for opening and closing the connection between the positive terminal of the solar cell group G (n) and the positive input terminal of the PCS 20, a negative terminal of the solar cell group G (n) A switch S (n, 2) for opening and closing the connection between the negative input terminals of the solar cell group G (n) and the negative terminal of the solar cell group G (n) The switch S (n, 1), the switch S (n, 2), and the switch S (n, 3) for turning on at least two of the switches S (N, 3) and the switch S (n, 3) when turning on at least two of the switches S (n, 1), S , 2), and the switch S (n, 1).

If the switch S (n, 3) is turned on last or the switch S (n, 3) is not turned off for the first time, the output of the solar cell groups changes from low voltage to a normal voltage or changes from a normal voltage to a low voltage An overvoltage may be applied to the PCS 20 at an instant. In this embodiment, the three switches S (n, 1), S (n, 2), and S (n, 3) connected to each solar cell group in the order described above are turned on or off, Can be prevented from being damaged.

The controller 50 generates a GC (group connection) signal indicating the connection information between the solar cell groups of the solar cell array 10 when the switches of the switch array 40 are turned on / off as described above, 20. When turning on / off each switch of the switch array 40 is completed, it is possible to know which solar cell groups are connected in parallel and which solar cell groups are connected in series. The controller 50 can generate binary data representing connection information between such solar cell groups, convert "1" in binary data into a high interval, and convert "0" into a low interval to generate a GC signal.

The solar cell has a characteristic in which the output changes non-linearly depending on the solar radiation amount, the temperature, and the load variation at the place where the solar cell is installed. The characteristic of this solar cell is expressed by the VI characteristic curve. In order to maximize the power generation efficiency of the solar cell by paying attention to the output characteristic of the solar cell, the solar cell operating point MPPT (Maximum Power Point Tracking) technology is widely used. Several algorithms have been developed to implement MPPT, and Perturbation and Observation (P & O) and IncCond (Incremental Conductance) algorithms are widely used.

The P & O algorithm measures the output power and the output voltage of the solar cell array 10 and tracks the maximum power point of the solar cell array 10 in order to gradually increase or decrease the operating voltage of the solar cell array 10 periodically The solar cell array 10 measures the change of the output power of the solar cell array 10 and continuously corrects the operating point of the solar cell array 10 in the direction in which the output power of the solar cell array 10 is increased, To track the operating point of the solar cell array 10 capable of outputting power. The P & O algorithm is most widely used because it is easy to implement, but it is insensitive to changes in the surrounding environment, and it takes some time to reach the maximum power point of the solar cell array 10.

The IncCond algorithm samples the change in current of the solar cell array 10 by comparing the output conductance of the solar cell array 10 with the incremental conductance to track the maximum power point of the solar cell array 10, 10 by setting the operating point of the solar cell array 10 whose slope is 0 by changing the slope of the PV characteristic curve to the maximum power point of the solar cell array 10 10 track the operating point of the solar cell array 10 capable of outputting the maximum power. IncCond algorithm is sensitive to environmental changes and can quickly reach the maximum power point of the solar cell array 10, but it requires a large amount of calculation and is not easy to implement.

Fig. 6 is a configuration diagram of the PCS 20 shown in Fig. Referring to FIG. 6, the PCS 20 shown in FIG. 1 includes a DC / DC converter 21, an MPPE (Maximum Power Point Estimator) 22, an MPPT (Maximum Power Point Tracker) 23, ). In order to solve the disadvantage of the P & O algorithm as described above, the present embodiment uses the maximum power point of the solar cell array 10 estimated based on the connection information between the solar cell groups of the solar cell array 10 as a starting point, The time required for reaching the maximum power point of the solar cell array 10 can be greatly reduced, and as a result, the power generation efficiency of the solar cell array 10 can be maximized. The power generation efficiency of the solar cell array 10 is lowered because the solar cell array 10 operates at a power point other than the maximum power point until the maximum power point of the solar cell array 10 is reached. The period in which the power generation efficiency of the array 10 is low can be minimized.

The DC / DC converter 21 converts the DC power output from the solar cell array 10 into DC power having a voltage different from the output voltage of the solar cell array 10 under the control of the MPPT 23. [ That is, the DC / DC converter 21 converts the DC power output from the solar cell array 10 into DC power having the voltage indicated by the MPPT 23. According to the present embodiment, the DC / DC converter 21 is implemented as a buck-boost converter capable of both voltage up conversion and voltage down conversion in order to widen the allowable input voltage range of the PCS 20 . As described above, the present embodiment can overcome the limit of the allowable input voltage range of the conventional inverter disclosed in Korean Patent No. 10-1236953 by implementing the DC / DC converter 21 as a buck-boost converter. As a result, it is not necessary to use a plurality of inverters unlike the conventional technology, so that the manufacturing cost can be reduced, and the power consumption due to the simultaneous use of several inverters can be reduced.

The PWM signal indicating the instruction voltage for reaching the maximum power point tracked by the MPPT 23 is output from the MPPT 23. The DC / DC converter 21 converts the DC power output from the solar cell array 10 into the DC power having the voltage indicated by the MPPT 23 in accordance with the PWM signal output from the MPPT 23. When the duty ratio of the PWM signal is increased, the output voltage of the DC / DC converter 21 is increased and the potential difference between the PCS 20 and the load 60 is increased. Thus, the current drawn from the solar cell array 10 . As a result, the input voltage of the DC / DC converter 21, that is, the operating voltage of the solar cell array 10, becomes low. Conversely, if the duty ratio of the PWM signal is reduced, the output voltage of the DC / DC converter 21 becomes lower, and the potential difference between the PCS 20 and the load 60 decreases, . As a result, the input voltage of the DC / DC converter 21, that is, the operating voltage of the solar cell array 10, becomes high. In this manner, the solar cell array 10 operates at the maximum power point tracked by the MPPT 23 in accordance with the PWM signal output from the MPPT 23.

The MPPE 22 estimates the maximum power point of the solar cell array 10 based on the connection information between the solar cell groups of the solar cell array 10 indicated by the GC signal outputted from the controller 50. [ More specifically, the MPPE 22 determines the wiring structure between the solar cell groups from the connection information between the solar cell groups of the solar cell array 10, and from the wiring structure between the solar cell groups thus determined, The VI characteristic curve of the solar cell array 10 under the average condition of the solar cell array 10 is calculated. Next, the MPPE 22 estimates the maximum power point of the solar cell array 10 from the VI characteristic curve of the solar cell array 10, and outputs the MPP signal indicating the maximum power point of the solar cell array 10 thus estimated To the MPPT (23).

Here, the V-I characteristic curve of the solar cell array 10 can be determined according to the wiring structure between the solar cell groups under the average condition such as the average solar radiation amount and the average temperature in the place where the solar cell array 10 is installed. The output voltage and the output current of the solar cell array 10 may vary depending on how many solar cell groups are connected in series and how many solar cell groups are connected in parallel. Accordingly, when the wiring structure between the solar cell groups and the operating conditions of the solar cell array 10 are determined, the V-I characteristic curve of the solar cell array 10 can be determined. Meanwhile, a database mapping the connection information between the solar cell groups of the solar cell array 10 and the V-I characteristic curve of the solar cell array 10 may be constructed. The MPPE 22 may calculate the V-I characteristic curve of the solar cell array 10 directly from the connection information between the solar cell groups of the solar cell array 10 using this database.

The MPPT 23 periodically increases or decreases the output voltage of the DC / DC converter 21, starting from the pointing voltage for reaching the maximum power point estimated by the MPPE 22, ≪ / RTI > More specifically, the MPPT 23 calculates a pointing voltage for reaching the maximum power point indicated by the MPP signal output from the MPPT 23, generates a PWM signal indicating the calculated pointing voltage, DC converter. Thus, the output voltage of the DC / DC converter 21 becomes the indicated voltage indicated by the PWM signal. Next, the MPPT 23 compares the output voltage of the DC / DC converter 21 with the unit voltage (for example, the power supply voltage Vout) in the direction in which the output power of the PCS 20 indicated by the TP (total power) And outputs the generated command voltage to the DC / DC converter 21. The DC / DC converter 21 outputs the command voltage to the DC / DC converter 21,

The MPPT 23 stops the increase and decrease of the output voltage of the DC / DC converter 21 when the maximum power point estimated by the MPPE 22 changes and outputs the output voltage of the DC / DC converter 21 to the thus- The maximum power point of the solar cell array 10 is tracked by periodically increasing or decreasing starting from the pointing voltage for reaching the solar cell array 10. When the wiring structure between the solar cell groups is changed, the V-I characteristic curve of the solar cell array 10 is changed and the maximum power point of the solar cell array 10 is changed. It takes a considerable time to reach the maximum power point of the solar cell array 10 changed in this way by increasing or decreasing the output voltage of the DC / DC converter 21 periodically as much as the unit voltage. In this embodiment, in order to immediately reach the maximum power point of the solar cell array 10 thus modified, the MPPT 23 stops the increase / decrease of the output voltage of the DC / DC converter 21, The DC / DC converter 21 periodically increases or decreases the output voltage of the DC / DC converter 21 in a state in which the output voltage of the DC / DC converter 21 is leaned to a pointing voltage for reaching the changed maximum power point.

The inverter 24 converts the DC power of the DC / DC converter 21 into AC power. According to the present embodiment, in order to increase the efficiency of the PCS 20, the inverter 24 calculates the maximum power point estimated by the MPPE 22, that is, the maximum power point indicated by the MPP signal output from the MPPT 23 If the magnitude of the estimated power is smaller than the threshold value, the DC power of the DC / DC converter 21 is converted into the AC power having a voltage that is lowered in proportion to the difference between the magnitude of the estimated power and the threshold value. The output power of the solar cell array 10 can be estimated from the maximum power point estimated by the MPPE 22 since the maximum power point estimated by the MPPE 22 is determined according to the wiring structure between the solar cell groups . On the other hand, the performance of the load 60 such as an LED (light emitting diode) depends on the magnitude of the current rather than the magnitude of the voltage input thereto. For example, the brightness of the LED is proportional to the magnitude of the current input to it. Since power is a product of voltage and current, lowering the voltage increases the current. By lowering the voltage when the output power of the solar cell array 10 is low, the brightness of the LED can be improved under the same power condition and the power consumption of the load 60 can be reduced.

7 is a flowchart of a method of controlling the connection of the solar cell array 10 according to an embodiment of the present invention. Referring to Fig. 7, the method of controlling the connection of the solar cell array 10 according to the present embodiment is constituted by the following steps, and is performed by the controller 50 shown in Fig. Therefore, the contents described above with respect to the controller 50 shown in FIG. 2 apply to the method of controlling the connection of the solar cell array 10 shown in FIG. 7, even if omitted below.

In step 71, the controller 50 turns off all the switches of the switch array 40 and receives the A signal and the B signal indicating the level of the output voltage of each solar cell group from the voltage detector 30. [ In step 72, the controller 50 determines the level of the output voltage of each solar cell group based on the A signal and the B signal received in step 71. [ The controller 50 determines the level of the output voltage of the solar cell group G (n) to be "1" when the A signal and the B signal of any solar cell group G (n) are both high, The level of the output voltage of the solar cell group G (n) is determined as "2 ", and when the A signal and the B signal are both low, the level of the output voltage of the solar cell group G do. In this embodiment, since the total number of solar cell groups is N, n = 1 to N.

In step 73, the controller 50 sets the identification number "n" of the solar cell group G (n) to one. When the identification number "n" of the solar cell group G (n) is 1, the steps described below are performed for the leftmost solar cell group G (1) As the identification number "n" of the battery group G (n) increases, the steps described below are performed for each solar cell group in the order from left to right. If the level of the output voltage of the solar cell group G (n) is "1" in step 74, the controller 50 proceeds to step 75. If it is "2 &

In step 75, the controller 50 controls the switch S (n, 1) for opening and closing the connection between the positive terminal of the solar cell group G (n) and the positive input terminal of the PCS 20, The switch S (n, 2) for opening and closing the connection between the cathode terminal of the PCS 20 and the cathode input terminal of the PCS 20 is turned on and the anode terminal of the solar cell group G (n) (n) is connected to the PCS 20 in parallel by turning off the switch S (n, 3) for opening and closing the series connection between the positive terminal of the solar cell group G (n +

The controller 50 controls the switch S (n) to open and close the series connection between the anode terminal of the solar cell group G (n) and the anode terminal of the solar cell group G (n + 1) adjacent to the solar cell group G (n + 1) to the level of the output voltage of the solar cell group G (n + 1) by turning on or off the output voltage of the solar cell group G (n + 1) according to the level of the output voltage of the solar cell group G Accordingly, the solar cell group G (n) is connected to the PCS 20 in parallel or connected to the neighboring solar cell group G (n + 1) in series. When the solar cell group G (n) is connected in series with the solar cell group G (n + 1), the solar cell group G (n) is driven in accordance with the level of the output voltages of the plurality of solar cell groups adjacent to the solar cell group G n are connected to the PCS 20 after being connected in series with at least one neighboring solar cell group.

In the above example, since the level 2 of the output voltage of the solar cell group G (n) corresponds to 300V to 600V, the solar cell group G (n) can be connected in series with solar cell groups of up to three levels 3. That is, depending on the level of the output voltages of the three solar cell groups G (n + 1) to G (n + 3) adjacent to the solar cell group G (n), the solar cell group G And connected to the PCS 20 after being connected in series with up to three solar cell groups. (N, 1), S (n, 2) and S (n, 3) connected to the solar cell group G (n) are turned off according to the characteristics of the solar cell array 10, .

The controller 50 turns on the switch S (n, 1) for opening and closing the connection between the positive terminal of the solar cell group G (n) and the positive input terminal of the PCS 20 in step 77, The switch S (n, 2) for opening and closing the connection between the negative terminal and the negative input terminal of the PCS 20 is turned off and the negative terminal of the solar cell group G (n) The solar cell group G (n) is connected in series with the neighboring solar cell group G (n + 1) by turning on the switch S (n, 3) for opening and closing the series connection between the positive terminals of G . The solar cell group G (n) is connected to the PCS 20 in series with at least one neighboring solar cell group according to the level of the output voltage of a plurality of solar cell groups neighboring the solar cell group G (n) .

In the example described above, the level 3 of the output voltage of the solar cell group corresponds to 100V to 300V, so that the solar cell group G (n) can be connected in series with up to four level 3 solar cell groups. That is, depending on the level of the output voltages of the four solar cell groups G (n + 1) to G (n + 4) adjacent to the solar cell group G (n), the solar cell group G And connected to the PCS 20 after being connected in series with up to four solar cell groups.

In step 78, the controller 50 adds the identification number " n "of the solar cell group G (n) to the identification number " Set a new value of "n". If the value of the identification number "n" of the newly set solar cell group G (n) is not greater than N in step 79, the controller 50 returns to step 74. If the value is greater than N, do. When the new value of the identification number "n" of the photovoltaic group G (n) is N, there are no adjacent photovoltaic groups and the number of neighboring photovoltaic groups is insufficient. If the allowable input voltage range of the PCS 20 can not be satisfied, steps 74 to 77 may be performed based on only the remaining solar cell group, or all switches connected to the remaining solar cell groups may be turned off.

For example, when the current value of the identification number "n" of the solar cell group G (n) is 1, steps 74 to 77 are performed for the solar cell group G (1) The number of the "connection number" is two and the new value of the identification number "n" of the solar cell group G (n) is three if one solar cell group G (2) is connected in series to the battery group G (1). In this case, steps 74 to 77 are performed on the solar cell group G (3). If the solar cell group G (1) is connected in parallel to the PCS 20, the "number of connections" is one and the new value of the identification number "n" of the solar cell group G (n) is two. In this case, steps 74 to 77 are performed on the solar cell group G (2).

The method as shown in Fig. 7 is performed periodically by the controller 50, so that the solar power generation system can actively cope with the weather change. According to the present embodiment, the controller 50 can turn on / off each switch of the switch array 40 at a high speed based on the level of the output voltage of each solar cell group having a much smaller amount of data than the output voltage of each solar cell panel So that it is possible to cope with a change in the weather quickly and greatly improve the power generation amount of the solar cell array 10. [ Also, since the amount of data of the output voltage of each solar cell group is small, the output voltage of one solar cell group or the output of a plurality of solar cell groups connected in series to each other Since the voltage can be within the allowable input voltage range of the PCS, it is possible to provide a photovoltaic power generation system that responds in real time to weather changes. In addition, it is possible to maximize the amount of power generated by the solar cell array 10 under the same weather conditions by following the maximum power point on the basis of the connection information between the groups of solar cells changed as described above.

The present invention has been described above with reference to preferred embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

10 ... solar array
20 ... PCS
30 ... voltage detector
40 ... switch array
50 ... controller
21 ... DC / DC converter
22 ... MPPE
23 ... MPPT
24 ... Inverter

Claims (13)

1. A solar cell array comprising: a solar cell array including a plurality of solar cell groups formed by serially connecting respective rows of a plurality of solar cell panels arranged in a matrix form;
A PCS (Power Conditioning System) for converting power output from the solar cell array into power suitable for a load;
A voltage detector for detecting a level of an output voltage of each solar cell group;
A switch array including a plurality of switches for opening / closing a connection between each solar cell group and the PCS, and a plurality of switches for opening / closing a serial connection between two neighboring solar cell groups; And
Based on a level of an output voltage of each solar cell group detected by the voltage detector such that an output voltage of one solar cell group or an output voltage of a plurality of solar cell groups connected in series to each other falls within an allowable input voltage range of the PCS And a controller for controlling ON / OFF of each switch of the switch array,
Wherein a level of an output voltage of each solar cell group is a first level corresponding to a voltage range belonging to an allowable input voltage range of the PCS, a maximum voltage of an allowable input voltage range of the PCS, A second level corresponding to a voltage range exceeding the minimum voltage of the allowable input voltage range of the PCS while exceeding the potential difference and a second level corresponding to a voltage lower than a potential difference between the maximum voltage of the allowable input voltage range of the PCS and the maximum output voltage of each solar cell group And the second level corresponds to one of the first level and the third level.
The method according to claim 1,
Wherein the controller is configured to control the switch connected to the solar cell group having a level corresponding to the output voltage range of the allowable input voltage range of the PCS among the plurality of solar cells, And turns on a switch for opening and closing a series connection between the neighboring solar cell groups for switches connected to the solar cell group having a level corresponding to an output voltage range out of the allowable input voltage range of the PCS Solar power generation system.
delete
The method according to claim 1,
Wherein the controller opens and closes a connection between a positive terminal of one of the solar cell groups and a positive input terminal of the PCS if the level of the output voltage of any one of the plurality of solar cell groups is the first level A switch for turning on a switch for turning on and off a connection between a negative terminal of the one solar cell group and a negative input terminal of the PCS and for connecting the negative terminal of the one solar cell group to the adjacent one of the solar cell groups And the switch for turning off the series connection between the positive terminals of the solar cell group is turned off.
The method according to claim 1,
Wherein when the level of the output voltage of any one of the plurality of solar cell groups is at the second level, the controller determines that the negative terminal of any one of the plurality of solar cell groups and the solar cell group adjacent to any one of the solar cell groups Wherein the switch for opening and closing the series connection between the positive terminals of the battery group is turned on or off according to the level of the output voltage of the solar cell group adjacent to any one of the solar cell groups.
The method according to claim 1,
Wherein when the level of the output voltage of any one of the plurality of solar cell groups is the third level, the controller determines that the negative terminal of any one of the solar cell groups and the solar cell group adjacent to any one of the solar cell groups And turns on a switch for opening and closing the series connection between the positive terminals of the battery group.
The method according to claim 1,
A first switch for opening / closing a connection between a positive terminal of one of the solar cell groups and a positive input terminal of the PCS, and a controller for opening / closing the connection between the negative terminal of the one solar cell group and the negative input terminal of the PCS, And a third switch for opening and closing a series connection between the anode terminal of one of the solar cell groups and the anode terminal of the solar cell group adjacent to the one solar cell group together The first switch, the second switch, and the third switch are turned on in sequence, and when at least two of the first switch, the second switch, and the third switch are to be turned off together, , The second switch, and the first switch in this order.
The method according to claim 1,
Wherein the voltage detector divides an output voltage of each of the solar cell groups and compares the plurality of divided voltages with a reference voltage to detect the level of the output voltage of each solar cell group,
Wherein the reference voltage is any one of a plurality of voltages divided from a highest voltage of at least one level among a plurality of levels of voltages that can be output by the respective solar cell groups.
9. The method of claim 8,
The voltage detector
A plurality of resistors dividing the output voltage of each solar cell group; And
And a plurality of OP-amplifiers for generating a potential indicating a level of an output voltage of each of the solar cell groups by comparing a plurality of voltages divided by the plurality of resistors and the reference voltage.
The method according to claim 1,
Wherein the controller outputs a signal indicating connection information between the solar cell groups of the solar cell array,
The PCS
A DC / DC converter for converting DC power output from the solar cell array into DC power having a voltage of a different magnitude;
An MPPE (Maximum Power Point Estimator) for estimating a maximum power point of the solar cell array based on connection information between solar cell groups of the solar cell array represented by the signal output from the controller; And
An MPPT (Maximum Power Point Tracker) that tracks the maximum power point of the solar cell array by periodically increasing or decreasing the output voltage of the DC / DC converter starting from a pointing voltage for reaching a maximum power point estimated by the MPPE Including photovoltaic systems.
11. The method of claim 10,
The MPPT stops the increase / decrease of the output voltage of the DC / DC converter when the maximum power point estimated by the MPPE is changed, and starts the output voltage of the DC / DC converter from the indicated voltage for reaching the changed maximum power point Wherein the maximum power point of the solar cell array is tracked by periodically increasing or decreasing the maximum power point of the solar cell array.
12. The method of claim 11,
If the magnitude of the estimated power corresponding to the maximum power point estimated by the MPPE is smaller than the threshold value, the PCS determines that the DC power of the DC / DC converter is lowered in proportion to the difference between the magnitude of the estimated power and the threshold value Further comprising an inverter for converting the AC power into AC power having a voltage.
1. A method for controlling connection of a solar cell array including a plurality of solar cell groups formed by connecting each row of a plurality of solar cell panels arranged in a matrix form in series,
The method comprising: receiving a signal indicative of a level of an output voltage of any one of the solar cell groups;
Determining a level of an output voltage of the one solar cell group based on the received signal;
Turning off a switch for opening and closing a serial connection between a negative terminal of one of the solar cell groups and a positive terminal of a solar cell group adjacent to the one solar cell group if the determined level is the first level;
A switch for opening and closing a series connection between a negative terminal of one of the solar cell groups and a positive terminal of the neighboring solar cell group is turned on and off according to the level of the output voltage of the neighboring solar cell group Turning on or off; And
And turning on a switch for opening and closing a serial connection between the anode terminal of one of the solar cell groups and the anode terminal of the neighboring solar cell group if the determined level is the third level How to.
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KR101614926B1 (en) * 2015-11-17 2016-04-22 주식회사 제이에스파워 System for solar energy generation
KR101779055B1 (en) * 2016-08-31 2017-09-18 남부대학교 산학협력단 String power converter system for Condensing type solar cell module
KR20190069045A (en) * 2017-12-11 2019-06-19 주식회사 이노썬 Apparatus of conversion control of combine box using the input power
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KR101135990B1 (en) * 2012-01-05 2012-04-12 (주)에이스파워텍 Solar photovoltaic generating system using variable array
JP2015012116A (en) * 2013-06-28 2015-01-19 株式会社明電舎 Serial/parallel combination determination method of photovoltaic power generation module

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KR101614926B1 (en) * 2015-11-17 2016-04-22 주식회사 제이에스파워 System for solar energy generation
KR101779055B1 (en) * 2016-08-31 2017-09-18 남부대학교 산학협력단 String power converter system for Condensing type solar cell module
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