KR100996507B1 - Solar cell generation using multi-phase step-up converter - Google Patents

Abstract

PURPOSE: A solar energy generating system is provided to reduce the heat from a step-up DC/DC converter by selectively using the step-up converter according to the generation quantity. CONSTITUTION: Two or more solar cell modules(110) convert sunlight into DC power. Two or more step-up converters(120) step up DC power outputted from two or more solar cell modules. An output monitoring unit(141) is connected to one output terminal of two or more step-up converters to monitor the size of the output of the solar energy generating system. An inverter(130) converts power outputted from two or more step-up converters. Two or more operation constant determining units determine the operation of two step-up converters according to the size of the output of the output monitoring unit.

Description

[0001] Solar power generation system using a multi-phase step-up converter [0002]

The present invention relates to a photovoltaic power generation system using a multi-phase step-up converter, and more particularly, to each of the solar cell array (array) by having a step-up type DC / DC converter to selectively drive the step-up converter according to the amount of power generated The DC / DC converter of the present invention can improve the operation efficiency of the entire solar power generation system by improving the operation efficiency of the step-up type DC / DC converter as compared with the configuration including each step-up DC / DC converter for the solar cell array of the solar cell array. To a photovoltaic power generation system using the same.

In general, photovoltaic power generation (Photovolatics) is a power generation system that converts light directly into electrical energy using a solar cell without the aid of a generator, and is a power generation system configured according to actual demand load using a solar cell.

It is composed of power converters such as solar cells, storage batteries, and inverters. When sunlight is irradiated on a solar cell in which a P-type semiconductor and an N-type semiconductor are bonded together, holes are generated in the solar cell by energy of the sunlight. ) And electrons are generated.

At this time, holes are gathered toward the P-type semiconductor and electrons are gathered toward the N-type semiconductor, and when a full position occurs, current flows. In response, the inverter converts the generated DC power into AC of commercial frequency and voltage to connect to the power system. At the same time, electrical monitoring and protection of the DC and AC side of the system.

The grid-connected photovoltaic power generation system includes a solar cell module consisting of a plurality of solar cell arrays, a DC / DC converter for boosting the voltage output from the solar cell module to a constant high-voltage DC voltage necessary for converting the voltage into a commercial voltage. , And a control module for controlling each configuration.

1 is a view showing a grid-tied photovoltaic power generation system according to the present invention. As shown in the figure, the solar power generation system according to the conventional invention has a structure in which individual boost type DC / DC converters and inverters are connected to each solar cell array.

2 is a view showing the efficiency according to the operating point of the converter when operating the grid-connected photovoltaic power generation system according to the present invention. For example, if the output of each solar cell is 10 KW, and it is composed of three solar cells and a 30 KW output solar power generation system, each of the step-up type converters in the system can be different according to the designer or the development condition, It is designed to have maximum operating efficiency at ~ 10 KW.

However, due to the characteristics of photovoltaic power generation, it has the characteristic that it can not be developed to the condition that it always operates with the design output, that is, the maximum operation efficiency. This contributes to the increase in loss of the entire power generation system. For example, if it is generating 30% of the output of each solar cell, each solar cell rated at 10kW is operated at 3kW each. Therefore, if the converter connected to each solar cell of each photovoltaic power generation system is operated separately, each converter is operated at the operating point of 3kW, there was a problem that can not operate at the optimum operating efficiency of the converter.

The present invention is to solve the above-mentioned problems of the prior art, an object of the present invention is to replace the step-up DC / DC converter that can be selectively operated by the step-up DC / DC converter that is connected to each solar cell array, respectively It is to provide a photovoltaic power generation system using a multi-phase step-up converter that can increase the power generation efficiency of the photovoltaic power generation system by configuring a grid-connected photovoltaic power generation system connected to the entire solar cell array.

The solar power generation system using the step-up converter according to the present invention includes a solar cell module 110 constituting a plurality of solar cell arrays and converting and outputting solar light to a DC power source; A step-up converter 120 for stepping up and outputting a DC power output from the solar cell module 110; An inverter 130 for converting power output from the boost converter 120; It characterized in that it comprises a; two or more operation constant determination unit for monitoring the amount of power generated by the photovoltaic power generation system 100 to select whether to operate the boost converter (120).

In the photovoltaic power generation system using the boost converter according to the present invention, the two or more operation constant determining unit is characterized by consisting of a first phase control unit, a second phase control unit, a third phase control unit.

In the photovoltaic power generation system using the step-up converter according to the present invention, the two or more operating constant determination unit, the comparison of receiving the input of the output monitoring unit 141, the signal processing only in any one of the two or more operation constant determination unit / Calculation unit is provided.

In the photovoltaic generation system using the step-up converter according to the present invention, the step-up converter 120 is composed of two or more step-up converters.

In the solar power generation system using the step-up converter according to the present invention, the at least two step-up converters are provided with a shared capacitor only in one of them.

As described in detail above, according to the solar power generation system using the boost converter according to the present invention, a boost type DC / DC converter connected to each solar cell array is replaced with a boost type DC / DC converter selectively operated. By constructing a grid-connected photovoltaic system that connects to the solar array, you can not only increase the power generation efficiency of the photovoltaic system but also selectively use a boosted DC / DC converter to suit the amount of power generated. It is possible to reduce the heat generated in the heat exchanger.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating a grid-connected photovoltaic power generation system according to the prior art.
2 is a view showing the efficiency according to the operating point of the converter when operating the grid-connected photovoltaic power generation system according to the present invention.
FIG. 3 is a simplified view of a solar power generation system using a step-up converter according to the present invention.
4 is a circuit diagram of a photovoltaic power generation system using a step-up converter according to the present invention.
5 is a diagram illustrating a control unit.
6 is a diagram illustrating a current output from a boost converter.
FIG. 7 is a diagram illustrating power generation versus converter efficiency according to operating constants determined by the first, second and third phase controllers.
8 is a view showing efficiency curves when solar cells having different power generation outputs are used.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail.

Figure 3 is a schematic view of the photovoltaic system 100 using a multi-phase boost converter according to the present invention, Figure 4 shows a specific circuit diagram of the photovoltaic system using a multi-phase boost converter according to the present invention.

FIG. 5 is a control unit 140 according to the present invention, the output monitoring unit 141 for monitoring the amount of power of the solar cell module, the amount of power measured by the output monitoring unit 141 according to the preset period of the on of the plurality of converters First, second, three-phase control unit (140a, 140b, 140c) for determining the operating constant for controlling the off, other fields for controlling the power generation in the photovoltaic power generation system to control the overall operation of the photovoltaic power generation system of the present invention (Not shown in the drawing, and is a generic structure in this field, so that detailed description thereof is omitted).

4, a solar power generation system 100 using a polyphase step-up converter according to the present invention includes a solar cell module 110, a step-up converter 120, an inverter 130, and a controller 140. Here, three solar cell modules 110 and three first, second and third phase control units 140a, 140b and 140c are mainly described, and the present invention is not limited thereto. The solar cell module may be further added by the selection of the practitioner to implement the first, second, and three phase controllers 140a, 140b, and 140c; may also be added in the same manner as the solar cell module.

In detail, the solar cell module 110 configures a plurality of solar cell arrays in parallel to output solar light, and the boost converter 120 boosts and outputs the DC power output from the solar cell module 110.

Step-up converter 120 is a booster circuit commonly used in the field and is a conventional booster type converter known in the field consisting of a switching element, such as a capacitor, a reactor and a MOSFET, a diode commonly used in the field and boosts DC As a booster, the operation principle and the boosting process thereof are known and conventional in the art, and thus detailed description thereof will be omitted.

Here, the boost converter 120 is provided to correspond to each solar cell module 110. Although not shown, if there are N solar cell modules, there are N boost converters and each of the first phase boost converters 120a, The two-phase boost converter 120b, the third-phase boost converter 102c ... (omitted) ... N-phase boost converter 120N.

In addition, as shown in FIG. 4 of the present invention, the first phase step-up converter 120a is provided with a shared capacitor C5, but only the structure in which the step-up converters 120b and 120c of the other phases share the shared capacitor C5 is illustrated. The shared capacitor C5 may be provided in the second phase boost converter 120b and the third phase boost converter 120c so that the other phase boost converter shares the shared capacitor C5.

The inverter 130 is used for power conversion of the photovoltaic power generation system 100 using the polyphase boost converter, and the operation constant determining unit 140a, 140b, 140c monitors the output of the photovoltaic power generation system 100 to boost the power. And determines whether the converter 120 operates.

Are connected to each phase converter, and the same number is provided as the number of solar cell modules increases.

In the present invention, the operation constant determining unit 140a, 140b, 140c is the first phase control unit 140a, the second phase control unit 140b, the first phase control unit 140c, which is also the first phase control unit 140a, A second phase control unit 140b, a third phase control unit 140c, ... (not shown), and an Nth phase control unit 140N. For convenience of explanation, the first phase control unit 140a, the second phase control unit 140b, and the third phase control unit 140c are collectively referred to as first, second, and three phase control units.

At the output terminal of the first phase step-up converter 120a, there is an output monitoring unit 141 for monitoring the boosted solar output size, and the first phase control unit 120a receives the output of the output monitoring unit 141 and processes the signal. / RTI > For convenience of explanation, the first and second phase control units 120a and 120c are provided with comparison / calculation units. However, the comparison / calculation unit may be provided in the second phase control unit 140b or the third phase control unit 140c have.

In the present invention, the output monitoring unit 141 determines the output of the photovoltaic module by judging the magnitude of the voltage due to the resistance partial pressure, but is not limited thereto. The magnitude of the current can be selectively used, such as a monitoring method or a method of receiving a voltage and current at the same time, and the sensing method and the circuit of the output monitoring unit 141 uses a known method in the art. It is omitted.

In addition, digitizing the sensed signal to a certain size or converting it into an appropriate analog signal to signal processing suitable for a comparator is also known and tolerated in the art and thus omits specific descriptions. The comparator that compares the magnitudes of the signals and outputs a signal for driving the switching elements of the respective voltage-rising converters is also a common circuit in the field and is a device, so that detailed description is omitted.

Referring to the photovoltaic power generation system 100 using the multi-phase step-up converter configured as described above with reference to the differences with the conventional invention as follows.

The solar power generation system 100 according to the present invention has a respective boost converter for boosting the total power generation output of a solar cell array connected in parallel unlike the conventional invention.

Each phase converter is provided with an output monitoring unit 141 to monitor the total amount of generated power at all times. The monitored power amount value is sent to the first, second, and third phase controllers 140a, 140b, and 140c to control the on / off of each boost converter 120a, 120b, and 120c.

The on / off of each boost converter 120a, 120b, 120c may be determined according to a section of a predetermined amount of power so as to maximize the boost efficiency of the converter. In this case, the setting of the power amount section may be performed by a method in which the user calculates a point in which the boosting efficiency is maximized in advance, and stores the setting value in a memory (not shown) provided in the controller 140. It is also possible to take a method of automatically setting up the maximum boosting efficiency after measuring the boosting efficiency by installing a separate sensor for each input and output of the) to obtain the ratio of the output power to the input power for a predetermined time.

In the present invention, each phase controller according to the magnitude of the reference value of the comparator of the operation constant determination unit (140a, 140b, 140c) outputs the operation signal of the switching element of the boost converter unit 120, the first, second, three-phase control unit ( 140a, 140b, 140c to be selectively operated.

For example, in the 30KW photovoltaic power generation system of the three solar cell modules, the first phase controller 140a operates when the output of the boost converter 120 is less than 1/3 of the rated output, for example, 9KW or less. So that only the first phase-up converter 120a is driven, so that only the first phase-up converter 120a operates at 9 KW.

Here, the reference value to be compared of the comparator of the first phase control unit 140a is set to a conversion reference value such as a voltage or a current corresponding to the comparison target value of 9 KW or less.

In addition, when the output of the boost converter 120 is equal to or greater than 1/3 or more than 2/3 of the rated output, for example, between 9 and 18 KW, the first phase controller 140a and the second phase controller 140b operate to operate the first phase boost converter. By driving only the 120a and the second phase boost converter 120b, the first phase boost converter 120a and the second phase boost converter 120b each share 9KW.

Here, the reference value to be compared by the comparator of the first phase control unit 140a is set to a current conversion reference value, even if the comparison target value is equal to or less than 9 KW, and the comparison target of the comparator of the second phase control unit 140b The reference value is set as a conversion reference value such as a voltage or current corresponding to the comparison target value is more than 9kw 18KW or less, so that the first and second phases are boosted by the output signals of the first and second phase controllers 140a and 140b. The converters 120a and 120b are driven.

When the output of the boost converter 120 is in the range of 2/3 or more and 3/3 of the rated output, for example, 18 kW or more and 30KW, the first phase controller 140a, the second phase controller 140b, and the third phase controller 140c Operating the first phase boost converter 120a, the second phase boost converter 120b, and the third phase boost converter 120c to operate the first phase boost converter 120a and the second phase boost converter 120b. Each of the third phase-up converters 120c shares and operates 10KW.

Here, the reference value to be compared of the comparator of the first phase control unit 140a is set to the conversion reference value of the voltage or current corresponding to the comparative value of 9 KW or less, and the comparison target of the comparator of the second phase control unit 140b The reference value to be compared is set to a conversion reference value such as a voltage or current corresponding to the comparison target value of 9 kW or more and 18 KW or less and the comparison target value of the comparator of the third phase control unit 140c is The converter 1 is set to a conversion reference value such as a voltage or a current corresponding to 18 kW or more and 30 KW or less. Thus, the output signals of the first, second and third phase control units 140a, 140b, 120b and 130c are driven.

 In addition, the present invention can operate the phase difference of the operation step-up converter controlled by the first, second and third phase control units 140a, 140b, and 140c.

This is because the efficiency of operation of the converter can be improved by operating in parallel with the phase difference for efficient operation of the step-up converter according to the amount of generated electricity (the first, second and third phase control units 140a, 140b and 140c) When the boost converter 120 is selected, the operation control unit (not shown) includes the first phase converter 120a, the second phase converter 120b, and the control signal of the first, second, and third phase controllers 140a, 140b, and 140c. If the converter to be operated is the first step-up converter 140a and the second step-up converter 140b, the operation control unit controls the first phase converter 120a and the second phase converter 120b, The switching element of the phase converter 120b is turned on and the switching element of the third phase converter 120c is turned off to control the step-up converter 120 to operate in two phases.

 That is, in the case of having N converters, the phase difference is determined as (360 ° / N), for example, in the case of three phases (360 ° / 3), each phase controls the switching elements of the boost converters to have a phase difference of 120 °.

The phase difference can be set by putting a phase difference for each phase in a triangular wave or a sawtooth wave generated by the operation control unit. It is a conventional technique in the art to control a switching element on and off by the square wave or sawtooth wave, and thus the operation principle and circuit configuration The detailed description is omitted.

As shown in FIG. 6, if three step-up converters are to be operated as shown in FIG. 6, the currents output from the step-up converter 120 are each configured to have a phase difference of 120 degrees.

Further, the currents flowing through the converters of each phase are configured such that the same currents flow. Therefore, as shown in FIG. 6, the magnitudes of the currents I _L1 , I _L2 , and I _{L3 of} each phase are all I _M , and I _L1 , I _L2, and I _L3 have a phase difference of 120 °, respectively.

FIG. 7 is a diagram showing the power generation amount versus the efficiency of the converter according to the number of converters to be operated as determined by the first, second, and third phase controllers 140a, 140b, and 140c. It is assumed that three solar cells are rated at 10 kW, and all three solar cells generate 3 kW and the generation power is 30%.

As shown in FIG. 2, when 3kW is individually driven in one phase, it is found that the driving efficiency is very low. However, when one of the boost converters 120 is driven at 9kW as shown in FIG. It can be seen that the operation efficiency is significantly increased as compared with the case where the three converters are operated at 3 kW each.

Referring to the power generation efficiency and efficiency curve of the solar cell module 110 shown in FIG. 7, when the sum of the generated power generated at the third stage is less than about 15 kW, the efficiency of the converter is maximized when operating with one step- The efficiency of the converter is maximized when the converter is operated with two step-up converters, and the efficiency of the converter is maximized when the converter is operated with three step-up converters when the converter is operated with about 25kW or more.

8 is a view showing efficiency curves when solar cells having different power generation outputs are used. In this case, it is assumed that the power generation output of each phase solar cell is 5 kW, 5 kW, and 10 kW, respectively, and operates in three phases. If a total of 20kW is generated in each phase of the solar cell, the boost converter 120 may have the maximum boosting efficiency only when it is operated in three phases as shown in FIG. 8. Therefore, it can be seen that in this case, there are three driving boost converters to be operated and each phase is operated with a phase difference of 120 °.

The step-up converter 120 according to the present invention may not operate at least one of the first phase converter 120a, the second phase converter 120b and the third phase converter 120c according to the generated power, Compared with photovoltaic systems, it is possible to reduce the heat generation of the boost converter.

In the above described exemplary embodiments of the present invention by way of example, the scope of the present invention is not limited only to this specific embodiment and those skilled in the art within the scope described in the claims of the present invention Appropriate changes will be possible.

Claims (5)

Two or more solar cell modules 110 that configure a plurality of solar cell arrays to convert and output sunlight into a DC power source;
Two or more step-up converters 120 for boosting and outputting each DC power output from the two or more solar cell modules 110;
An output monitoring unit 141 connected to an output terminal of any one of the two or more boost converters 120 to monitor the magnitude of the output of the solar power generation system;
An inverter 130 for converting power output from two or more boost converters 120;
(140a, 140b, 140c, ..., 140n.) For selecting the operation of each of the two or more step-up converters (120) according to the magnitude of the output of the output monitoring unit (141) ;
The two or more operation constant determining units 140a, 140b, 140c, ...., 140n.
Only one of the two or more operation constant determining unit is provided with a comparison / operation unit for receiving the output of the output monitoring unit 141 and processing the signal
The two or more boost converter,
A photovoltaic power generation system using a boost converter, characterized in that only one boost converter has a shared capacitor. delete delete delete delete

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