WO2013094839A1 - Multi-inverter photovoltaic power generation system - Google Patents

Abstract

The present invention relates to a multi-inverter photovoltaic power generation system to improve usage efficiency of inverters by varying the inverter capacity on the basis of amount of energy generated from a photovoltaic array, the multi-inverter photovoltaic power generation system comprising: a photovoltaic array, provided with a plurality of photovoltaic strings formed by connecting a plurality of photovoltaic modules, for generating power; a string optima for controlling maximum power point tracking for each of the plurality of photovoltaic strings, and for converting, into an output voltage of uniform size, the generated voltage of generated power output by each of the plurality of photovoltaic strings; and an inverter which is provided with a plurality of conversion units for converting the generated power transformed by the string optima into alternating current and outputting same and for converting the generated power, and a distribution unit for distributing the generated power to the plurality of conversion units, and which varies the number of conversion units in operation from among the plurality of conversion units on the basis of amount of power generated.

Description

Multi inverter solar power system

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar power generation system having an inverter provided with a plurality of change units. In particular, the multi-inverter solar system improves the use efficiency of the inverter by varying the capacity of the inverter according to the amount of power produced from the solar cell array. The present invention relates to a photovoltaic system.

Since the output of one solar cell currently used in photovoltaic power generation is very small, in order to efficiently obtain the required output, several solar cells are connected to form a PV module (PV module: Photovaltaic Module). . The power generated from one solar cell module has a larger capacity than one solar cell, but can be used as a power source for a small device, and the amount of power is too small to supply power to a general commercial power system.

For this reason, if you want to connect the power system to transmit the generated power, connect several solar cell modules into one group, or connect these groups in parallel to form a PV array. And to ensure the voltage and power required for power transmission. In order to secure such voltage and power, it is common to configure a string by connecting solar cell modules in series and to configure a solar cell array using a plurality of strings as a group.

1 is a configuration diagram schematically showing a conventional photovoltaic device.

Referring to FIG. 1, a conventional photovoltaic device connects a plurality of photovoltaic modules 10 in series to form one string 20, and connects the strings 20 in parallel to each other. It consists of the array 10A. Then, by collecting the output from the solar cell array 10A and supplying the output to the inverter, the DC power is converted into AC power and supplied to the power system.

The conventional photovoltaic device determines the capacity of the inverter 40 in consideration of the maximum generation amount of the solar cell array 10A. That is, the capacity of the inverter 40 is determined to have a capacity equal to or greater than the amount of power produced when the amount of power generation of the solar cell array 10A is maximum. However, when the inverter 40 having the same capacity as the maximum production power of the solar cell array is used, the amount of power produced by the solar cell array is often smaller than that of the inverter 40, resulting in a decrease in efficiency of the inverter 40. There is a problem.

Accordingly, an object of the present invention is to provide a multi-inverter photovoltaic power generation system to vary the capacity of the inverter according to the amount of power produced from the photovoltaic cell array, thereby improving the use efficiency of the inverter.

In addition, another object of the present invention is to perform the maximum power tracking for each string of the solar cell, to achieve the maximum power production, and to apply the environmental factors in the maximum power following the multi-inverter to achieve fast and efficient maximum power tracking It is to provide a solar power system.

A solar cell array having a plurality of solar cell strings configured to be connected to a plurality of solar cell modules and producing power generation; A string optimizer for performing maximum power point tracking control of each of the plurality of solar cell strings and converting a generation voltage of the generated power output from each of the plurality of solar cell strings into an output voltage having the same magnitude; And a plurality of converters for converting and generating the generated power transformed from the string optima into AC power, for converting the generated power, and for distributing the generated power to the plurality of converters. And an inverter configured to vary the number of converters driven among the plurality of converters according to the magnitude of the generated power.

The plurality of converters have the same converting capacity.

The inverter further includes an inverter control unit, wherein the inverter control unit distributes the distribution of the power distribution unit so that a conversion unit having a relatively short driving time compared to other conversion units, which is operated for the generation power, is preferentially driven among the plurality of conversion units. To control.

The string optimizer is connected to each of the plurality of solar cell strings to convert the power generation voltage into the output voltage and perform the maximum power point following control; A detector configured to generate a detection value including an environmental element that changes the amount of power generation of the solar cell module, the generation voltage, and the output voltage; And a controller configured to generate a power following control signal for each of the string controllers using the sensed values.

The environmental element includes any one or more of the amount of sunshine, the temperature of the region in which the solar cell module is installed, the temperature of the solar cell module surface, the air volume, the wind speed, and the humidity.

The output voltage is variable.

The string controller includes a converter for boosting or reducing the input voltage from the solar cell string; A fuse connected between the solar cell string and the converter; A circuit breaker connected to an output terminal of the converter; And an MPP controller for generating a control signal for the boosting or depressurizing of the converter.

The control unit may include a tracking range calculator configured to calculate a tracking range value including a current or voltage range at which maximum power point tracking is to be performed based on the detected value; A control signal generation unit for generating a maximum power point following control time signal by the tracking range value, the input voltage, and the output voltage from the tracking range calculator; And a tracking history storage unit storing the tracking range value in correspondence with the detection value.

The following range calculating unit divides the daily power generation time of the solar cell module into a plurality of time sections, and calculates a basic following range of each of the time sections.

The following range calculating unit calculates the following range by reflecting an expected range of power generation change due to the environmental element detection value in the basic following range.

The following range calculating unit omits power tracking for the excess of the generated voltage and the output voltage when the generated voltage and the output voltage temporarily exceed the maximum following range expected in the time section.

The solar cell string is a stationary or tracking solar cell module.

The multi-inverter photovoltaic power generation system according to the present invention can vary the capacity of the inverter according to the amount of power produced from the solar cell array, thereby improving the use efficiency of the inverter.

In addition, the multi-inverter photovoltaic power generation system according to the present invention performs the maximum power tracking for each string of the solar cell, to achieve the maximum power production, and to apply the environmental factors in the maximum power tracking, the fast and efficient maximum power tracking It is possible to make it happen.

1 is a schematic view showing a conventional photovoltaic device.

2 is an exemplary view showing the configuration of a photovoltaic power generation system according to the present invention.

3 is a configuration example showing the configuration of the string optima in more detail.

4 is a diagram illustrating a configuration of a control unit of the string optima in more detail.

5 is an exemplary view for explaining a tracking range calculation according to temperature and illuminance among environmental factors.

6 is an exemplary diagram for describing power tracking over time.

7 is an exemplary view for explaining a method of storing and using tracking history information.

8 is an exemplary view for explaining the configuration and operation of the inverter of FIG.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. In the accompanying drawings, it should be noted that the same reference numerals are used in the drawings to designate the same configuration in other drawings as much as possible. In addition, in describing the present invention, when it is determined that a detailed description of a related known function or known configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. And certain features shown in the drawings are enlarged or reduced or simplified for ease of description, the drawings and their components are not necessarily drawn to scale. However, those skilled in the art will readily understand these details.

2 is an exemplary view showing the configuration of a photovoltaic power generation system according to the present invention.

Referring to FIG. 2, the photovoltaic power generation system according to the present invention includes a solar cell array 100, a string optima 200, and an inverter 300.

The solar cell array 100 converts sunlight into electric power and provides it to the string optima 200. To this end, the solar cell array 100 is composed of a plurality of solar cell string 120, each solar cell string 120 is configured by connecting a plurality of solar cell module 110 in series. Each of the solar cell strings 120 configured in the solar cell array 100 may have a different generation capacity for each string, and different solar cell strings 120 may be configured with different solar cell modules. In addition, the solar cell modules 110 included in the same solar cell string 120 may have different capacities, power generation voltages, and operation methods. Specifically, one solar cell string 120 may be configured by connecting a plurality of solar cell modules having a power generation of 5 kw in series, and the other solar cell string 120 includes a plurality of solar cell modules 110 having a generating power of 3 kw. It can be configured by serial connection. Also, one string may be configured as a fixed solar cell module to which the solar cell module 110 is fixed, and the other string may be configured as a tracking type such that the direction and angle of the solar cell module 110 are changed along the sun. . In addition, each of the solar cell strings 120 is connected to the string converter 230 of the string optima 200 to supply the generated power to the string converter 230.

The string optimizer 200 converts the power supplied from each solar cell string 120 into DC-DC, converts the power supplied to a voltage corresponding to the input voltage of the inverter 300, and supplies the converted voltage. To this end, the string optimizer 200 performs DC-DC conversion by the maximum power point following control, and reflects the change in power generation amount in the environmental element at the maximum power point following control.

To this end, the string optima 200 is a string control device 220 and environmental elements and string control to perform DC-DC conversion and maximum power point tracking for the voltage of the generated power supplied from each solar cell string 120 And a controller 210 for generating a control signal for controlling the string controller 220 by using the input / output voltage to the device 220 as a sensed value.

The controller 210 generates a control signal for individually controlling the plurality of string controllers 220. In particular, the controller 210 performs power tracking for each string based on each input voltage and output voltage transmitted to the string controller 220, and transfers the control signal generated by the string controller to the string controller 220. do. In particular, the controller 210 performs power tracking according to environmental information transmitted from the sensor 130.

In more detail, the controller 210 may apply different tracking ranges according to environmental information such as the solar radiation amount of a location where the solar cell module 110 or the solar cell string 120 is installed, the temperature of the installation location, the temperature of the panel, and the time. The power point is followed and a control signal is generated accordingly and transmitted to the string controller 220. This control method will be described in more detail with reference to the other drawings below.

The string controller 220 converts the current flow voltage supplied from the solar cell string 120 into an input DC voltage of the inverter 301, and performs the conversion under the control of the controller 210.

In particular, the string controller 220 transmits an input voltage input from the solar cell string 120 to the string controller 220 and an output voltage value output from the inverter after the change to the controller 210. Detailed configuration and operation of the string control device 220 will be described in more detail with reference to the drawings below.

The detector 290 detects environmental factors affecting the amount of power generation of the solar cell array 100, generates a sensed value, and transmits the generated sensed value to the string controller 210 of the string optima 200. Here, the environmental factors may have a direct influence on the amount of power generation, such as solar radiation, sunshine, illuminance, temperature of the solar cell module 110, temperature of the solar cell module 110 or the solar cell string 120, wind direction, wind speed, and humidity. In addition, the solar cell module 110 includes an element that may cause a change in power generation, such as the temperature or the presence of an obstacle. In addition, the detector 290 essentially detects the temperature of the solar light and the solar cell module 110 such as solar radiation, sunshine, and illuminance, and transmits the detected result to the string controller 210. To this end, the sensing unit 290 includes a plurality of sensing sensors.

The inverter 300 receives the generated power converted to have the same voltage size by the string optima 200 and converts the generated power into AC power. In particular, the inverter 300 of the present invention selectively drives the plurality of converters 330 in order to increase conversion efficiency and reduce consumption and failure due to driving. To this end, the inverter 300 includes a plurality of converters 330 for converting DC power output from the string optima 200 into AC power, and generating power generated from the string optima 200 and outputting a plurality of converters ( It is configured to include a distribution unit 320 for distributing to 330. The inverter 300 determines the number and capacity of the converter 300 to be operated according to the capacity of the generated power, and selects one or more of the plurality of converters 330 according to the determination result to generate the generated power that is DC power. Convert to AC power. The conversion unit 300 is configured to have the same conversion capacity for ease of control, exchange and production. However, it may be composed of a plurality of conversion unit 320 having a different conversion capacity, thereby not limiting the present invention. In addition, the inverter 300, in particular, the inverter control unit 310 collects the driving time of the converter 330 to select the converter to be operated, and confirms the collected drive time information, the converter 330 with less running time. ) Is selected and driven first.

3 is a diagram illustrating the configuration of the string optima in more detail.

Referring to FIG. 3, the string optima 200 is relayed by the fuse 211 between the string controller 220 and the solar cell string 120. The fuse 211 is automatically cut when the overvoltage, overcurrent of the solar cell string 120 serves to protect the circuit. In addition, a circuit breaker 212 is installed at the output terminal of the string optima 200 to disconnect the inverter 300 from the string optima 200 when an abnormality occurs in the solar cell string 120 or the string optima 200. .

Each of the string controllers 220 is connected to the solar cell string 120 through a fuse 211, and converts a voltage of power supplied from the solar cell string 120 into an input voltage of the inverter 300. The MPT controller 221 controls the converter 222 to output the maximum power according to the control signal of the converter 222 and the controller 210. To this end, the control unit 21 of the string control device is connected to the mpp controller 221 of each string control device 220.

An input voltage input to each of the string controllers 220 and an output voltage output from each of the string controllers 220 are measured by the MPPT controller 221 and transmitted to the controller 210, or the controller 210 is each string. The voltage value may be directly received from the voltage detector installed at the input / output terminal of the control device 220. However, this does not limit the present invention.

4 is a diagram illustrating a configuration of the control unit of the string optima in more detail.

Referring to FIG. 4, the control unit includes a sensing unit 211, a following range calculation unit 310, a following history storage unit 320, and a control signal generator 330.

The sensing unit 211 detects information for generating a control signal and transmits the information to the following range calculating unit 310. To this end, the detector 211 includes an input voltage detector 301, an output voltage detector 302, and a sensor 130. The input voltage detector 301 detects a voltage of input power input to the string optima 220. The output voltage detector 302 detects a voltage of power output from the string optima 220. The input voltage detector 301 and the output voltage detector 302 detects the input voltage and the output voltage of each of the plurality of string control devices 220 in real time and transmits them to the following range calculator 310. The sensor 130 detects environmental factors affecting the solar cell array 100 and transmits the detection result to the following range calculation unit 310. Environmental elements sensed by the sensor 130 are the amount of light, illuminance of the sunlight irradiated to the solar cell array 100, the temperature, humidity of the region where the solar cell array 100 is installed, the surface temperature of each solar cell module 110 In addition, any factor that can cause a change in generation can be measured.

The following range calculator 310 selects a voltage and a current range to perform maximum power estimation according to the detection result of the detector 211, and transmits the selected range value to the control signal generator 330. That is, the tracking range calculation unit 310 determines the magnitude of the power supplied from the solar cell string 120 according to the input voltage and the output voltage from the detection unit 211 and the information detected by the sensor 130. In addition, the power generation value of the solar cell module 110 according to the current weather conditions to calculate the maximum voltage and current range.

In particular, in this calculation, the following range calculation unit 310 calculates the following range by reflecting the time information and the date or the seasonal information in the information previously input or accumulated according to the operation. In addition, the following range calculating unit 310 transmits the input voltage and the output voltage to the control signal generator 330, and transmits the calculated tracking range information to the control signal generator 330 and the following history storage unit 320. Will be delivered to The following ranges generated by the following range calculation unit 310 are generated separately for each of the solar cell strings 120.

Operation of the tracking range calculator 310 and the string optima 200 having the same will be described in more detail with reference to FIGS. 5 and subsequent drawings.

The tracking history storage unit 320 stores the tracking range information transmitted from the tracking range calculation unit 310 together with the environmental element information detected by the detection unit 211, and stored at the request of the tracking range calculation unit 310. Provide information. In particular, the tracking history storage unit 320 records and maintains changes in input voltage, output voltage, and maximum power according to environmental factors for each time zone, season, and weather condition.

The control signal generator 330 controls a power conversion rate of the MPP controller 222 by using the input voltage and output voltage values and the calculated tracking range values transmitted through the tracking range calculator 310. It generates and delivers to the epitaxial controller 222.

5 is an exemplary view for explaining a calculation of a tracking range according to temperature and illuminance among environmental factors.

Referring to FIG. 5, (a) is a graph showing the output voltage and current relationship of the solar cell string according to the temperature, and (b) is a graph showing the output voltage and current relationship of the solar cell string according to the illuminance.

In (a), when the illuminance is constant, if the temperature is lowered, the magnitude of the voltage produced from the solar cell string becomes smaller, and thus, the overall production power becomes smaller. (a) is a graph of voltage and current when C is at a lower temperature than A. Even if the current has a relatively constant value, the magnitude of the voltage is small and the maximum power is reduced.

Similarly, if the illuminance changes when the other conditions are constant in (b), the values of the output voltages (V: Va to Vc) and the output currents (I: Ia to Ic) change as shown through A 'to C'. The maximum power changes.

Therefore, the string optima 200 of the present invention, in particular, the following range calculation unit 310 selects a voltage and a current range at which the maximum power point is to be formed according to an environmental element detected by the sensing unit 211, and selects the selected voltage and current. The tracking range value calculated so that the maximum power point tracking can be controlled within the range is transmitted to the control signal generator 330. As a result, the MPP controller 221 performs power tracking at a voltage and current value at which maximum power tracking can be achieved within a short time, thereby improving power generation efficiency by the solar cell.

Specifically, the temperature, in particular, the temperature of the surface of the solar cell module having a direct influence on power generation has a feature that changes slowly over time as long as there is no influence of other environmental factors. However, in the case of winter, the temperature of the surface of the solar cell module may be drastically reduced by the wind. That is, in FIG. 5A, the maximum power point may be formed in the range 1 (P1), and the temperature may drop rapidly, thereby forming the maximum power point in the range 2 (P2). In this case, the conventional control apparatus performs the maximum power tracking to the range 2 (P2) by varying the voltage and current corresponding to the range 1 (P1), thereby increasing the time required. In particular, when the temperature recovers at a rapid rate after a temporary drop in temperature, disturbance occurs in following the maximum power, and it takes considerable time until the accurate follow.

However, if the tracking range is selected according to the temperature change and power tracking is performed in the corresponding range as in the present invention, fast tracking becomes possible, thereby minimizing waste of generated power.

6 is an exemplary diagram for describing power tracking over time.

6 (a) is a diagram showing division of power generation time by time zone, and (b) shows a change in output voltage and output current of a solar cell string according to time division.

Referring to FIG. 6, the most important factors in photovoltaic power generation are the presence and the amount of light for power generation. This amount of light does not remain constant until the sun rises and changes over time. In particular, in the case of winter, even when the maximum amount of light before and after noon it is often difficult to generate the maximum power. In particular, during winter, at the same time of winter, when the sun goes down, the amount of sunshine changes rapidly. As the graph of (a) proceeds clockwise, the voltage and current graph of (b) changes in the direction (x1) in which the output increases. In (a), the graph of (b) changes in the direction y1 where the output decreases after passing the sections b5 and b6 which are maximum output time points.

When power tracking is simply performed based on the output voltage and the input voltage in these time periods and seasons, it is difficult to produce the maximum power even when the maximum power tracking is performed. In particular, when the weather and temperature changes relatively rapidly, such as in the winter or the rainy season, it is more difficult to follow the maximum power, which leads to a loss of power generation.

Therefore, in the present invention, the generation time is divided (B1 to B10) for each time zone to approximate the maximum power following range, and the following range is selected for each range to generate a control signal for controlling the MPP controller 221. .

Specifically, assuming that (a) is a partition of the winter development time zone, the amount of sunshine changes rapidly in the first compartment (b1), the second compartment (b2) and the ninth compartment (b9), and the tenth compartment (b10). Fast maximum power tracking becomes difficult. However, at this time, the tracking range is calculated by comparing the amount of sunshine and the predetermined division and the voltage and current range, and when the power tracking is performed within the calculated tracking range, the speed and efficiency of the maximum power point tracking can be improved. do. In particular, by selecting a basic following range for each time zone, applying the power generation reduction rate according to temperature and the power generation reduction rate according to insolation amount to the selected basic following range, recalculate the following range and perform maximum power point following accordingly. Environmental factors can be applied to the power point following range.

In addition, the calculation of the power generation reduction rate is stored along with the weather conditions at the time of measurement, the amount of power generation, and the maximum power point information to be formed, and then used as a basis for speeding up the maximum power point following a similar environment. It becomes possible.

That is, if the output voltage and the output current change according to time zones as shown in (b), instead of proceeding from the maximum power point before the change, the previous maximum power point in the following range of the section corresponding to the corresponding time zone is used. The maximum power point tracking is performed in the following close range, and thus the time required for the maximum power point following can be saved, thereby maintaining the power generation efficiency at a higher level than in the related art.

As shown in (b), when there is a change in time according to time zones, even if a temporary temperature change or climate change occurs, the maximum change in time can be achieved by applying a decrease in power generation efficiency and change in following range to climate change according to time zones. The power point can be searched.

7 is an exemplary view for explaining a method of storing and using tracking history information.

Referring to FIG. 7, the solar cell string 120 may display an output graph as shown in FIG. 7A at a specific time. At this time, the maximum output tracking range on the V-I graph is P11. The tracking range calculating unit 310 selects a tracking range so that power tracking is performed near the voltage Vp and current Ip points when there is no change in the environmental element, and the control signal generator 330 converts the converter input into the selected tracking range. By performing power tracking by reflecting the output voltage, the solar cell string 120 operates to produce maximum power. In addition, the condition that the maximum power point tracking is performed, the voltage, current value, ambient temperature, panel temperature, sunshine amount, time, wind speed, and wind direction information of the maximum power following range are stored in the following history storage unit 330, and then power by similar conditions. It is used as information to confirm the following range when following.

As such, (a) when the environmental factor is changed while performing the maximum power tracking by the graph, the graph itself for the maximum power tracking may be changed. For example, in the case of a small range of temperature change and sunshine change, the maximum power point tracking can be achieved through the graph of (a), but when a large temperature change occurs or the amount of sunshine changes, The VI graph also changes significantly.

In this case, as described above, performing the maximum output point following only the feedback of the input / output voltage takes a long time, and leads to a decrease in the efficiency of the power generation system until stable following and maximum power production are achieved.

Therefore, in the present invention, by adding an environmental element to such an element, the maximum power point tracking can be controlled in a short time.

This state is shown in (b). In the case of (b), the V-I graph is changed due to the change in the temperature and the amount of sunshine of the solar cell string 120 in which power tracking is performed by the graph of (a). In this case, the maximum power point is changed from that formed in the range of P11 to the range of P12. Such a change in the V-I graph can be followed by the input voltage and the output voltage as in the prior art. However, as in the present invention, a faster response can be expected by applying a change in environmental factors, a change in output rate, or a change in the V-I graph.

For example, when the amount of sunshine and temperature change as shown in the graph of (b), the following range can be selected by reflecting only the amount of sunshine and the changed temperature. However, when reflecting the environmental factors in the estimated range as in the present invention, it is possible to follow the change in the V-I graph by predicting the temperature change of the panel according to the ambient temperature. Moreover, even in winter, even when the solar cell module is heated by sunlight, the temperature of the solar panel is changed according to the temperature and wind speed of the location where the solar cell is installed, and has a direct influence on the power production. In this case, the expected tracking range may be approximated in advance by identifying and applying similar factors from previous tracking information stored in the tracking history storage unit 330, and the input and output voltages of the solar cell string 120 are changed. By applying the input and output voltage values to the expected tracking range, it is easy to find the voltage and current range for the maximum power point tracking.

Furthermore, as mentioned in the description of FIG. 6, the string optima 200 of the present invention divides the generation time into several steps and performs power tracking by reflecting the environmental elements and the converter input / output voltage in the following range represented by each time section. do.

Follow-up using the basic follow-up range by visual section can predict seasonal and climatic factors at the time of development through environmental factors such as accumulated generation time zone and temperature. It becomes easy. In addition, when seasonal environmental factors have a great impact on power generation, such as winter, following time zone divisions favors maximum power point tracking.

In the case of the maximum power point tracking, the tracking is performed by a constantly changing voltage or current, and a large change in the temporary voltage or current may occur. In this case, when following the change in voltage or current, the efficiency is reduced in following after the temporary change is released. However, if you divide the time and limit the following range in consideration of the seasonal factors to which the time belongs, it will not follow large fluctuations in voltage and current that occur during a short time, thereby preventing power generation efficiency from falling. Will be. In addition, it is easy to determine the following direction by estimating whether the voltage or the current rises or falls according to the time zone division, and reflects the environmental factors and the converter input / output voltage, thereby enabling the rapid response to the maximum power point tracking. Moreover, environmental factors involved in such development are sorted and approached according to time division and seasonal division according to time division, and used for selecting a range of tracking, which enables fast following by using algorithm that is not very complicated compared to the existing one.

FIG. 8 is an exemplary diagram for describing the configuration and operation of the inverter of FIG. 2.

Referring to FIG. 8, as described above, the inverter 300 of the present invention includes an inverter control unit 310, a power distribution unit 320, and a conversion unit 330.

Inverter 300 of the present invention by varying the number of the conversion unit 330 is driven according to the amount of generated power delivered through the string optima 200, the drive efficiency of the inverter 300, conversion efficiency is lowered, aging acceleration The DC-AC conversion is performed in an optimal state.

8 shows an example in which five converters 330 having the same capacitance are configured. The converter 330 performs an operation by the power distribution unit 320 operating according to the switching control of the inverter controller 310.

Specifically, the string optima 200 converts the generated power provided from each solar cell string 120 into direct current-direct current conversion and converts the generated power into an inverter input voltage having the same voltage. As illustrated in FIG. 8, the converted input voltage is collected into one and supplied to the power distribution unit 320 of the inverter 300.

The distribution unit 320 distributes the generated power whose voltage size is converted to the inverter input voltage to the conversion unit 330, so that the conversion unit 330 can convert the generated power of the direct current form into the power of the alternating current. do.

To this end, the inverter controller 330 determines the magnitude of the generated power through the string optima 200 or a separate measuring instrument, and determines the number of converters 330 to be operated. For example, if the conversion capacity of each converter 330 is 50KVA (or 50KW), and the magnitude of power transmitted from the string optima 200 is 120KVA (or 120KW), the inverter controller 310 may convert the drive to be driven. The number of units 330 is determined to be three.

When the number of converters 330 to be driven is determined, the inverter controller 310 transmits a switching control signal to the power distribution unit 320 so that the power distribution unit 320 can supply power to the three conversion units 330. Control to configure the circuit. The power distribution unit 320 operates a power switching device such as an IGBT according to a switch control signal so that the three converters 330 and the output lines of the string optima 200 are connected.

In this case, the inverter controller 310 may select not only the number of converters 330 to be driven but also the converters 330 to be driven, and in particular, may be selected according to the driving time of each converter 330. Do. That is, the inverter controller 310 controls the driving so that the driving time of the converter 330 becomes uniform. To this end, the inverter control unit 310 measures the driving time of each converter 330, and controls the switching of the power distribution unit 320 to drive the converter 330 having a low driving time first.

Although illustrated and described in the specific embodiments to illustrate the technical spirit of the present invention, the present invention is not limited to the same configuration and operation as the specific embodiment as described above, within the limits that various modifications do not depart from the scope of the invention It can be carried out in. Therefore, such modifications should also be regarded as belonging to the scope of the present invention, and the scope of the present invention should be determined by the claims below.

According to the present invention, one inverter is composed of a plurality of converters, and the inverters are driven by varying the number of converters driven according to the amount of generated power. Through this, the present invention can prevent the efficiency degradation that may occur by performing the power conversion by the inverter having a conversion capacity larger or smaller than the generated power amount, it can be described the increase in the amount of power produced as a result.

In particular, the present invention is installed in place of the inverter configured in the existing photovoltaic power generation system, it is possible to increase the amount of power generation through the improvement of the efficiency of the existing facility and to reduce the reinstallation cost according to the use of the existing facility.

In addition, the present invention, unlike the conventional photovoltaic power generation system by configuring a plurality of converters, even if a failure occurs in any one of the converter it is possible to continuously operate the power generation system, as a result can increase the total amount of power generated. .

Claims (12)

A solar cell array having a plurality of solar cell strings configured to be connected to a plurality of solar cell modules and producing power generation; A string optimizer for performing maximum power point tracking control of each of the plurality of solar cell strings and converting a generation voltage of the generated power output from each of the plurality of solar cell strings into an output voltage having the same magnitude; And And a plurality of converters for converting and generating the generated power transformed from the string optima into AC power, for converting the generated power, and for distributing the generated power to the plurality of converters. And an inverter configured to vary the number of converters driven among the plurality of converters according to the magnitude of the generated power. The method of claim 1, The plurality of converters multi-inverter photovoltaic power generation system, characterized in that the conversion capacity is the same. The method of claim 1, The inverter further includes an inverter control unit, The inverter controller is configured to control the distribution of the power distribution unit so that the driving unit of the plurality of conversion unit is driven for the generation power is relatively shorter than the other conversion unit is driven first. Power generation system. The method of claim 1, The string optima is A string controller connected to each of the plurality of solar cell strings to convert the power generation voltage into the output voltage and perform the maximum power point following control; A detector configured to generate a detection value including an environmental element that changes the amount of generation of the solar cell module, the generation voltage, and the output voltage; And And a controller configured to generate a power following control signal for each of the string controllers using the sensed values. The method of claim 4, wherein The environmental factor is Multi-inverter photovoltaic power generation system comprising any one or more of the amount of sunshine, the temperature of the region in which the solar cell module is installed, the temperature of the solar cell module surface, the air flow rate, wind speed and humidity. The method of claim 5, The output voltage is a multi-inverter photovoltaic power generation system, characterized in that the variable. The method of claim 6, The string control device A converter for boosting or reducing the input voltage from the solar cell string; A fuse connected between the solar cell string and the converter; A circuit breaker connected to an output terminal of the converter; And And an MPP controller for generating a control signal for the boosting or decompressing of the converter. The method of claim 7, wherein The control unit A tracking range calculator configured to calculate a tracking range value including a current or voltage range at which maximum power point tracking is to be performed based on the detected value; A control signal generation unit for generating a maximum power point following control time signal by the tracking range value, the input voltage, and the output voltage from the tracking range calculator; And And a tracking history storage unit for storing the tracking range value in correspondence with the detected value. The method of claim 8, The following range calculation unit Multi-inverter photovoltaic power generation system characterized in that to divide the daily power generation time of the solar cell module into a plurality of time sections, and calculate the basic following range of each of the time sections. The method of claim 9, The following range calculation unit Multi-inverter photovoltaic power generation system characterized in that for calculating the following range by reflecting the expected range of power generation change by the environmental element detection value in the basic following range. The method of claim 8, The following range calculation unit And if the generation voltage and the output voltage temporarily exceed the maximum following range expected in the time section, power tracking for the excess of the generation voltage and the output voltage is omitted. The method of claim 10, The solar cell string is Multi-inverter photovoltaic power generation system, characterized in that the fixed or tracking solar cell module.

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