KR101265707B1 - Photovoltaic power generation system include multi-inverter - Google Patents

Abstract

PURPOSE: A multi-inverter photovoltaic power generating system is provided to change the capacity of an inverter according to the amount of electric power, thereby increasing a utilization ratio. CONSTITUTION: A solar cell array includes multiple solar cell strings(120). The solar cell string is composed by multiple solar cell modules. A string optima(200) performs maximum power point tracking. An inverter(300) has multiple power converting modules. A remaining charge sensing unit senses remaining charges inside the power converting module.

Description

Photovoltaic power generation system include multi-inverter}

The present invention relates to a photovoltaic power generation system having an inverter provided with a plurality of power conversion modules, and in particular, by varying the capacity of the inverter according to the amount of power produced from the photovoltaic cell array to improve the use efficiency of the inverter, The present invention relates to a multi-inverter photovoltaic power generation system in which unlocking of the power conversion module is prevented when residual charge is detected in the conversion module.

Since the output of one solar cell currently used in solar power generation is very small, a solar cell module (PV module: Photovoltaic Module) is constructed by connecting several solar cells in order to efficiently obtain the required output . Although the power generated from one solar cell module has a larger capacity than that of a single solar cell, it can be used as a power source for a small-sized device, and the amount of power required to supply generated power to a general commercial power system is inevitable.

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.
For example, Patent Application 10-2007-9917211 (Applicant: Kiyoung Midas Co., Ltd., the name of the invention: String-based solar power control device) has a photovoltaic system generated during the operation of converting sunlight into electrical energy. Among the various loss components, the difference of intrinsic module characteristics in the production of solar cells and modules due to the level of direct / parallel connected DC power of the solar array, the difference in power generation due to the partial shade effect, the power when not grouped between modules A technique for attaching a converter that performs MPPT to a series-connected array of solar cell modules is disclosed to prevent level loss and the loss of power generated by such string mismatch.

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

As shown in FIG. 1, the 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 one 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 10A is used, the amount of power produced by the solar cell array 10A is often smaller than that of the inverter 40 and thus the inverter 40 ) Will cause a decrease in efficiency.

On the other hand, the prior art had a problem that a safety accident is likely to occur due to residual charge (charge current) even after the power is cut off when the operator unlocks the power conversion module for inspection and repair of the inverter 40. In particular, the capacitance inside the inverter 40 and the winding of the transformer are particularly dangerous because residual charge may be large.

One aspect of the present invention is to improve the use efficiency of the inverter according to the amount of power produced from the solar cell array, but multi-inverter photovoltaic power generation is prevented from unlocking the power conversion module when residual charge is detected in the power conversion module of the inverter To provide a system.

Multi-inverter photovoltaic power generation system according to an embodiment of the present invention, comprising a plurality of solar cell string consisting of a plurality of solar cell module, the solar cell array for generating power generation; and is connected to the solar cell string maximum A string optima performing power point tracking, transforming the voltage of the power generation power, and performing the maximum power point tracking by applying a plurality of different tracking methods according to the power fluctuation range of the power generation power; An inverter having an inverter body, and a plurality of power conversion modules formed on the inverter body to be selectively locked or unlocked, respectively, for converting the generated power transformed from the string optimizer into AC power and outputting the alternating current power; At least one of the plurality of power conversion modules depends on the remaining charges in the power conversion module. Therefore, the power conversion module may be locked or unlocked by the inverter body using a lock signal or a lock release signal that is selectively output.

In addition, at least one of the plurality of power conversion module, the residual charge detection unit for detecting the residual charge in the power conversion module, and receiving the detection signal of the residual charge, input of the unlocking signal of the power conversion module It characterized in that it comprises a power conversion module control unit for controlling the block to maintain the lock of the power conversion module.

In addition, at least one of the plurality of power conversion module, the signal output unit for selectively outputting the lock signal or the unlock signal of the power conversion module by the user, and the lock signal of the power conversion module in the signal output unit Or receiving and unlocking the power conversion module to lock or unlock the power conversion module, wherein the power conversion module controller further includes a power conversion module driving unit to selectively block the unlocking signal when the residual charge inside the conversion module is detected. Characterized in that.

In addition, one of the plurality of power conversion module, the switching circuit unit for driving the transistors therein to generate an AC voltage and AC current, and a transformer for boosting the AC voltage applied from the switching circuit unit to supply to a commercial power source Characterized in that is provided.

In addition, any one of the plurality of power conversion module, characterized in that the switching circuit unit for driving the transistors therein to generate an AC voltage and AC power, and a capacitance unit connected to the switching circuit unit.

In addition, the residual charge detection unit, it characterized in that for detecting the residual charge of at least one of the transformer or the capacitance unit.

The inverter may vary the number of conversion modules driven among the plurality of conversion modules according to the magnitude of the generated power.

In addition, the solar cell module is characterized in that the fixed or tracking solar cell module.

In addition, the plurality of conversion modules are characterized in that the conversion capacity is the same.

The inverter further includes a power distribution unit for distributing the generated power to the plurality of conversion modules and an inverter control unit for selecting a conversion module to be driven, wherein the inverter control unit includes the power generation unit among the plurality of conversion modules. It is characterized in that the distribution of the power distribution unit is controlled so that a conversion module having a relatively short driving time compared to other conversion modules is driven first.

The multi-inverter photovoltaic power generation system according to the embodiment of 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 has the effect of preventing the safety accident by preventing the unlocking of the power conversion module when residual charge is detected in the power conversion module 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 configuration diagram schematically 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 diagram illustrating the configuration of the string optimizer in more detail.
4 is a diagram illustrating the configuration of the string controller in more detail.
5 is a power-voltage graph illustrating a case in which the power fluctuation range is increased.
6 is a voltage-current graph with temperature and solar radiation change.
FIG. 7 is an exemplary diagram for describing the configuration and operation of the inverter of FIG. 2.
FIG. 8 is a diagram illustrating a power conversion module of the inverter illustrated in FIG. 7.
9 is a perspective view schematically showing the appearance of an inverter according to an embodiment of the present invention.
10 is a flowchart illustrating an operation of preventing unlocking of an inverter power conversion module according to an embodiment of the present invention.

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

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

As shown in FIG. 2, the photovoltaic power generation system according to the embodiment of 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 power and provides the string to the optimizer 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 power 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 optimizer 200 to supply the generated power to the string converter 230.

The string optima 200 performs the maximum power point tracking for each of the solar cell strings 120, so that the solar cell strings 120 generate the maximum power, and generate power generated from the solar cell strings 120. The voltage is converted to match the inverter input voltage and supplied to the inverter 300.

In particular, the string optimizer 200 according to an embodiment of the present invention performs a maximum power point tracking by selectively applying a power tracking algorithm according to two conditions. In detail, the string optima 200 does not significantly change the generation power, that is, when the amount of light, insolation, illuminance, the temperature of the solar cell module, the temperature around the solar cell module, and the like do not show a sudden change. In some cases, the maximum power point tracking of the generated power is performed by applying another maximum power point tracking method. In addition, the string optimizer 200 detects environmental factors affecting the power generation of the solar cell module 110 and performs the maximum power point tracking according to the detected value. To this end, the string optimizer 200 includes a string controller 210, a string converter 230, and a detector 290.

The string controller 210 controls the string converters 230 to perform the maximum power point tracking for each solar cell string 120, thereby allowing the solar cell array 100 to produce the maximum power. To this end, the string controller 210 provides a tracking control signal for tracking the maximum power point to each string converter 230.

In addition, the string controller 210 generates a control signal by reflecting the detection value from the detector 290 in the following control signal when generating the following control signal. In detail, the string controller 210 varies a control algorithm for controlling the string converter according to a first state in which the generated power is maintained at a substantially constant level and a second state requiring rapid following due to a sudden change in the generated power. Accordingly, another control signal is supplied to the string converter 230. Detailed functions and configurations of the string controller 210 will be described in detail later.

The string converter 230 is connected to each of the solar cell strings 120 constituting the solar cell array 100 and performs maximum power point tracking for each solar cell string 120 under the control of the string controller 210. To allow the solar cell array 100 to produce maximum power.

In addition, the string converter 230 boosts or decompresses the voltage of the generated power generated by each solar cell string 120 to match the input voltage of the inverter 300, and converts the transformed generated power into the inverter 300. To pass. In particular, the outputs of the string converters 230 are collected and input to the inverter 300. For this purpose, each string converter 230 converts the voltage of the generated power so that the magnitude of the output voltage is the same. To this end, the string converter 230 performs the maximum power point tracking according to the following control signal from the string controller 210, and in particular, applies a different tracking method according to the first state and the second state, thereby quickly following the Maximum power point tracking can be achieved with maximum efficiency.

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 optimizer 200. Herein, 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 detection unit 290 essentially detects the temperature of the solar light and the solar cell module 110, such as the amount of solar radiation, sunshine, illumination and the like and transmits the detection 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 optimizer 200 and converts the generated power into AC power. In particular, the inverter 300 according to the embodiment of the present invention selectively drives the plurality of power conversion modules 340 in order to increase conversion efficiency and reduce consumption and failure due to driving.

To this end, the inverter 300 includes a plurality of power conversion modules 340 for converting direct current power output from the string optimizer 200 into alternating current power, and generated power generated from the string optimizer 200. It is configured to include a distribution unit 330 for distribution to the conversion module 340. The inverter 300 determines the number and capacity of the power conversion module 340 to be operated according to the capacity of the generated power, and selects one or more of the plurality of power conversion modules 340 according to the determination result to generate the DC power generation. Convert power to AC power. The power conversion module 340 is configured to have the same conversion capacity for ease of control, exchange and production. However, it may be composed of a plurality of power conversion module 340 having a different conversion capacity, thereby not limiting the present invention.

In addition, the inverter 300, in particular, the inverter control unit 320 collects the driving time of the power conversion module 340 to select the conversion unit to be operated, and checks the collected driving time information power conversion module with a low operating time 340 is preferentially selected and driven.

Next, the configuration of the string optimizer will be described in more detail with reference to FIG. 3. 3 is a diagram illustrating the configuration of the string optimizer in more detail.

As shown in FIG. 3, the string optimizer 200 according to an embodiment of the present invention includes a string controller 210, a string converter 230, and a detector 290.

The string optimizer 200 performs maximum power point tracking and DC-DC conversion for each of the solar cell strings 120. The string optimizer 200 integrates the solar cell strings 120 having different characteristics to prevent efficiency degradation that may occur due to the maximum power point tracking. Specifically, the string optima 200 performs individual maximum power point tracking for each solar cell string 120. In addition, the string optima 200 boosts or decompresses the output voltage vs from vs1 to vsn from the solar cell string 120 along with the maximum power point tracking so as to provide direct current to the input voltage vo of the inverter 300. To convert. To this end, the string optimizer 200 includes a DC converter 231 and an mppt controller (Maximum Power Point Tracking, 233), and a fuse 251 connected between the solar cell string 120 and the DC converter 231. ), And a circuit breaker (CB) 253 connected between the DC converter 231 and the inverter 300.

The DC converter 231 converts each of the output voltages VS of the string into input voltages vo of the inverter 300. The DC converter 231 performs DC conversion under the control of the mppt controller 233. At this time, the DC converters 231 perform DC conversion so that the output voltage of the magnitude, that is, the inverter input voltage vo. As shown in FIG. 3, the outputs of the plurality of DC converters 231 are collected and supplied to the inverter 300 through the circuit breaker 253. As described above, the string optimizer 200 performs the maximum power point tracking for each string by the DC converter 231, so that the maximum power is produced in each of the solar cell strings. In addition, the string optimizer 200 transforms the output of each of the solar cell strings 120 so as to generate an output voltage having a predetermined magnitude, thereby preventing power loss due to conversion. In addition, the string optimizer 200 equalizes the magnitude of the voltage output from the DC converter 231, collects the same, and transfers the generated voltage to the inverter 300, whereby the inverter 300 converts generated power having different voltage magnitudes. This prevents any efficiency degradation that may occur and allows it to be driven with high efficiency.

Meanwhile, the mppt controller 233 controls the maximum power point tracking and DC conversion of each DC converter 231 according to the tracking control signal of the string controller 210. In particular, the present invention performs the maximum power point tracking by applying a different tracking method according to the first state and the second state. This will be described in more detail with reference to the string controller 210 below.

The string controller 210 generates a tracking control signal based on the detected value and controls each mppt controller 233 according to the tracking control signal, so that the mppt controller 233 has the maximum power for each solar cell string 120. Allows to perform point tracking and direct current conversion. The string controller 210 generates a tracking control signal according to the power detection value and the power fluctuation state as described above.

In detail, the string controller 210 may have a different method according to a power fluctuation state among a direct control method, a P & O (Perturb & Observe) method, an incremental conductance (IncCond: Incremental Conductance), and a hysterisis band method. A tracking control signal is generated by applying a tracking algorithm.

Here, briefly describing each method, the direct control method follows the power point by changing the tracking point by inputting an item contributing to the change in power generation amount such as temperature or solar radiation. For example, the direct control method is a method of calculating a proportional constant with respect to temperature or insolation in advance and applying it to generation of a follow-up control signal to search for the maximum power point according to the input proportional constant.

The PENO method increases or decreases the output voltage of the solar cell string periodically and compares the previous output with the current output to find the maximum operating point.

The incremental conductance method follows the maximum power operating point by comparing the output conductance of the solar cell string 120 with the incremental conductance. For example, the incremental conductance method reduces the tracking voltage when the output conductance is larger than the incremental conductance, increases the tracking voltage when the output conductance is smaller than the incremental conductance, and determines the maximum output point when the output conductance and the incremental conductance are the same. That's the way it is.

In addition, the hysteresis band variation control method increases the output voltage of the solar cell string 120 to the maximum power point, and then multiplies any gain by the power at the maximum power point to specify the minimum power value. In this case, two minimum power values are generated. The minimum power value is generated by increasing or decreasing the output voltage of the solar cell string 120 based on the maximum power point.

These tracking methods have their advantages and disadvantages. The direct control method is simple in configuration and allows immediate response to the detected value, but has the lowest conversion efficiency among the proposed methods. The PENO method has excellent conversion efficiency because the maximum power point is stabilized in the case of slowly changing environmental factors, but there is a disadvantage in that following control fails in case of sudden change. In addition, the incremental conductance method is capable of fast tracking even when environmental factors change rapidly, but has a disadvantage in that a large amount of cost is required for the configuration of the control device due to the complicated computation and control algorithms. In addition, the hysteresis band fluctuation control method is capable of tracking power even when at least one maximum power point occurs near the maximum power point, but has a disadvantage of causing power loss at the maximum power point.

In the present invention, the incremental conductance method or PENO method is used in the first state in which the tracking efficiency is important because the fluctuation range of the environmental element is not large, and the direct control method or the incremental conductance method or hysteresis is used in the second state in which the fluctuation range is large and requires fast tracking. Tracking is performed using the band shift control method. By applying a tracking method having different tracking characteristics according to the state, fast tracking and efficient tracking can be achieved. In particular, the execution of the tracking method may be performed by splitting the string controller 210 and the string converter 230, thereby preventing the circuit and the control method from being complicated, while achieving excellent tracking efficiency.

This will be described in more detail with reference to FIGS. 4 and 5 below.

4 is a diagram illustrating the configuration of the string controller in more detail.

The string controller 210 includes a state determination unit 211, a following range calculation unit 213, a control signal generator 215, and a following history storage unit 217.

The state determination unit 211 checks the power fluctuation range through the sensed value and the output value of the solar cell string 120, compares the checked fluctuation range with a predetermined reference fluctuation range, and determines the current state. Transfer to the following range calculation unit 213. Here, the reference variation width may be selected through any one or more of voltage change, solar radiation, and temperature change in which the following tracking method selected for power tracking in the first state fails to follow. That is, the state determination unit 211 determines the change rate of power by determining the change rate per unit time, the change rate per unit time of solar radiation, and the change rate per unit time of temperature with respect to the voltage of the generated power produced by the solar cell string 120, Through this, it is determined whether the current state is the first state or the second state. The state determination unit 211 notifies the following range calculation unit 213 of whether the current state is the first state or the second state. Here, the reference variation width may be determined by the user regardless of the tracking failure value. The state determination unit 211 continuously performs the state determination on each of the solar cell strings 120.

The following range calculating unit 213 selects a tracking method, a voltage to perform maximum power point tracking, and a current range according to the detected value from the detector 290 and the current state information determined by the state determining unit 211. The controller transmits the selected range value to the control signal generator 215. That is, the following range calculation unit 213 uses the sensed value, the current state information, and the output voltage of the solar cell string 120, so that the power generation value of the solar cell module 110 can be maximized in the current weather state. Calculate the overcurrent range. In detail, the following range calculating unit 213 selects a tracking method according to whether the current state is the first state or the second state, and follows the current tracking method by reflecting the voltage decrease, the voltage increase, the decrease width, and the increase width by the detected value. Select the voltage and current range to perform. The tracking range calculator 213 transmits the calculated tracking range to the tracking history storage unit 217 together with the detected value, and also to the control signal generator 215. The tracking range calculation unit 213 may be configured to change the current state from the first state to the second state, maintain the second state, or change the second state from the second state to the first state for tracking efficiency. The tracking range for the connected mppt controller 233 is calculated. In detail, in the case of the solar cell string 120 maintaining the first state and the mppt controller 233 connected thereto, power tracking of the high efficiency is performed by the following tracking method selected according to the first state without reflecting environmental factors. At this time, even if the reflection of the change in environmental factors is not applied, fast following can be achieved. On the other hand, if the fluctuation range is large, such as when the state is maintained in the second state or when the state is changed from the first state to the second state, the environmental element may be changed more quickly and efficiently to follow the tracking method selected in the second state. Perform the calculation of the following range of consideration. That is, the following range calculating unit 213 reduces the voltage range and the current range corresponding to the following range in consideration of the increase / decrease of the environmental element, or limits the increasing or decreasing state so that the fast following can be performed. . In addition, in the case of changing from the second state to the first state, a voltage range current of a range in which the first state following method can succeed the following state in order to apply the following tracking method specified in the first state and to prevent the following failure due to the conversion. The range and increase / decrease state are calculated and transmitted to the control signal generator 215.

The control signal generator 215 generates a control signal according to the tracking method generated by the state determining unit 211 and the following range calculating unit 213 and transmits the control signal to the mppt controller 233. Here, the control signal generator 215 may perform any one of the first and second state tracking methods, and the mppt controller 233 may perform the other tracking method.

The tracking history storage unit 217 stores the tracking range information, the detected value, and the current state information transmitted from the tracking range calculator 213, and provides the stored information at the request of the tracking range calculator 213. . The tracking history storage unit 217 records and maintains the time-sensitive detection value, the output voltage of the solar cell string, the tracking method used, the holding time of the tracking method, the efficiency, and the like for each solar cell string 120.

5 and 6 are views for explaining a tracking process according to the present invention. FIG. 5 is a power-voltage graph showing a case in which the power fluctuation range is increased, and FIG. 6 is a voltage-current graph according to temperature and solar radiation change.

Referring to FIG. 5, a graph g1 is a voltage-power graph for explaining tracking according to the first and second states. In FIG. 5, the state maintained at the points A1, A2, and B1 may be referred to as a stable first state. In addition, the state in which the maximum power point moves from A1 and A2 to B1 or vice versa may be referred to as a second state. Of course, when moving slowly from A1 to B1, the first state is regarded as the first state. However, when moving rapidly, the second state is determined.

This judgment is based on the standard fluctuation range. When the reference fluctuation range is determined as the amount of change in the output voltage per hour, when the PENO type following method is used as the following method of the first state, the voltage change width at which the PENO type fails to be set is set as the reference variable width. That is, in the case where the PENO method changes around ± 10V per second, if the tracking failure occurs, the reference variation width is determined to be less than ± 10V / s. The temperature and the amount of solar radiation of the solar cell module 110 are also calculated in the same manner. That is, the reference variation width is set to a value less than or equal to the variation width that causes the tracking failure in the first state following the output change of the solar cell string 120.

The first state and the second state are determined according to the reference variation width, and different tracking methods are selected and used according to the state. That is, when the maximum power point is varied between A1 and A2 as shown in the curve g1 and does not deviate from the reference fluctuation range of the first state tracking method, the maximum power point tracking is performed by the first state tracking method.

In addition, when the power-voltage curve suddenly changes from g1 to g2, it is out of the reference variation range of the first state tracking method, and in this process, the second state tracking method is applied to achieve maximum power point tracking. Then, as time passes, the power-voltage curve gradually changes from g2 or g2. If the amount of change is less than or equal to the reference variation width, it is regarded as the first state, and the first state following method is applied to the first state following method. Follow is made by. The change in the tracking method depends on whether there is a change value in which the tracking failure of the first state tracking method may occur as described above.

For example, in the present invention, the power fluctuation range is small in the first state, and when it gradually changes, the peak power point is stabilized so that the PENO method having good tracking efficiency is used as the first state following method, and in the second state, an incremental conductance capable of fast following is possible. Method or hysteresis band fluctuation control method can be used as the following method. Alternatively, the incremental conductance method may be used in the first state, and the hysteresis band variation control method may be applied as the following method in the second state.

On the other hand, Figure 6 is a graph showing the voltage and current curve of the solar cell string according to the temperature and solar radiation.

In the case of (a) in Figure 6 is a graph showing a case where the temperature changes when a constant, a graph form in which the voltage increases or decreases, such as C when the temperature is higher than the B curve, A when the temperature is lower.

In the case of (b), when the temperature is constant, the amount of insolation changes. When the amount of insolation increases, the voltage current curve changes in the order of c ', b', a ', and in reverse order as the amount of insolation decreases. , The current curve changes.

As described above, the string optimizer 200 according to the present invention detects environmental factors such as solar radiation, solar cell temperature, solar cell module temperature, wind speed, and humidity through the sensing unit 290, and follows the maximum power point. Applicable to

This environmental factor can be applied to the following method in the form of proportionality constant. That is, when the voltage calculated by the following method is V2 in (a), the following voltage can be calculated by multiplying the calculated voltage by the increase and decrease by the solar radiation and the increase and decrease by the temperature. In particular, the application of such environmental elements is preferably applied to a second state in which stable power generation is achieved and power fluctuation width becomes larger than the first state in which the power fluctuation range is small, making it difficult to follow.

In the second state, it is difficult to predict whether the voltage and current fluctuations will occur in the future when the power increases, or the voltage and current fluctuations will occur in the decrease of the generated electric power. Is likely to occur. Therefore, if the power range is calculated by determining whether the power is increased or decreased by the environmental factor and applying it to the tracking method, and determining the direction in which the generated power increases or decreases the generated power, the tracking becomes easier and faster. Following can be done.

In particular, by applying the environmental elements by dividing the state in this way, the excessive operation processing of the string controller 210 is reduced, and in the stable state, the output voltage and output of the solar cell string 120 by the string converter 230 By performing the maximum power point following through the current, it becomes possible to improve the following speed, following stability, and maximum power production effect.

Next, an inverter according to an embodiment of the present invention will be described in more detail with reference to FIG. 7. FIG. 7 is an exemplary diagram for describing the configuration and operation of the inverter of FIG. 2.

As shown in FIG. 7, the inverter 300 according to the embodiment of the present invention changes the number of power conversion modules 340 driven according to the amount of generated power delivered through the string optima 200. The driving efficiency of 300 is reduced, the conversion efficiency is reduced, and the aging acceleration is prevented, and the DC-AC conversion is performed in an optimal state.

The inverter 300 includes an inverter body 310, an inverter controller 320, a power distribution unit 330, and a plurality of power conversion modules 340.

The inverter body 310 forms an exterior of the inverter 300 such that the inverter control unit 320, the power distribution unit 330, and the plurality of power conversion modules 340 are mounted therein.

7 illustrates an example in which five power conversion modules 340 having the same capacity are configured. The power conversion module 340 is performed by the power distribution unit 330 operating according to the switching control of the inverter controller 320. Here, the five power conversion module 340 is formed to be selectively locked or unlocked with respect to the inverter body 310, a detailed description will be described later.

The string optimizer 200 converts the generated electric power provided from each solar cell string 120 into direct current-direct current conversion to an inverter input voltage having the same voltage. The input voltage converted as described above is collected into one and supplied to the power distribution unit 330 of the inverter 300.

The power distribution unit 330 distributes the generated power whose voltage size is converted to the inverter input voltage to the power conversion module 340, so that the power conversion module 340 converts the generated power of the DC form into the power of the AC form. To be able.

To this end, the inverter controller 320 determines the size of the generated power through the string optimizer 200 or a separate measuring instrument, and determines the number of power conversion modules 340 to be operated. For example, if the conversion capacity of each power conversion module 340 is 50KVA (or 50KW), and the magnitude of power transmitted from the string optimizer 200 is 120KVA (or 120KW), the inverter controller 320 may be driven. The number of power conversion modules 340 is determined to be three.

When the number of power conversion modules 340 to be driven is determined, the inverter controller 320 transmits a switching control signal to the power distribution unit 330 so that the power distribution unit 330 may supply power to the three power conversion modules 340. Control to configure the circuit. The power distribution unit 330 operates a power switching device such as an IGBT according to a switch control signal to connect the three power conversion modules 340 and the output lines of the string optimizer 200.

In this case, the inverter controller 320 may select not only the number of power conversion modules 340 to be driven but also the power conversion module 340 to be driven. In particular, the inverter controller 320 may be selected according to the driving time of each power conversion module 340. It is possible to do That is, the inverter controller 320 controls the driving so that the driving time of the power conversion module 340 is uniform. To this end, the inverter control unit 320 measures the driving time of each power conversion module 340, and controls the switching of the power distribution unit 330 to preferentially drive the power conversion module 340 having a low driving time.

FIG. 8 is a diagram illustrating a power conversion module of the inverter illustrated in FIG. 7, and FIG. 9 is a perspective view schematically illustrating an appearance of an inverter according to an embodiment of the present invention.

As shown in FIG. 8 and FIG. 9, the power conversion module 340 of the inverter 300 according to the embodiment of the present invention includes a switching circuit part 341, a transformer 342, a capacitor part 343, and residual charge detection. The unit 344 includes a power conversion module controller 345, a signal output unit 346, and a power conversion module driver 347.

The switching circuit unit 341 of each power conversion module 340 drives the transistors inside the switching circuit unit 341 through a signal applied from the inverter control unit 320 to generate an AC voltage and an AC current.

The switching circuit unit 341 is a switching element, for example, field effect transistors such as MOSFET (Metal-Oxide Semiconductor Field Effect Transistor) are connected in a half bridge or full bridge form to convert the input voltage input in the DC form into an AC voltage Can be.

The transformer 342 boosts the applied AC voltage and supplies the boosted commercial power supply voltage to the commercial power supply 11. To this end, the transformer 342 includes a primary coil (not shown) and a secondary coil (not shown). The primary coil is connected to each of the first and second output terminals 341A and 341B of the switching circuit unit 341, and the secondary coil is connected to the commercial power source 11. One end of the primary coil is connected to the first output terminal 341A of the switching circuit unit 341, and the other end thereof is connected to the second output terminal 341B of the switching circuit unit 341. Here, the direction of the alternating current applied to the primary coil is periodically changed according to the alternating current voltage output to the first output terminal 341A and the alternating voltage input to the second output terminal 341B. The direction of the current flowing through the primary coil changes periodically. Therefore, the commercial power source 11 current is induced to the secondary side coil. The transformer 342 boosts the input voltage according to the turns ratio of the primary coil and the secondary coil.

The capacitor portion 343 is connected in parallel to each of the first and second output terminals 341A and 341B of the switching circuit portion 341. The capacitor unit 343 may be composed of at least one capacitor 343. In order to increase the capacity of the capacitor 343 formed in the capacitor unit 343, a plurality of capacitors 343 may be used. In this case, the plurality of capacitors 343 are preferably formed in parallel.

The capacitor unit 343 may prevent the ripple of the AC voltage output to the first and second output terminals 341A and 341B of the switching circuit unit 341. That is, the capacitor unit 343 may prevent ripple caused by driving of the transistors in the switching circuit unit 341.

Residual charge detection unit 344 is a means for detecting the residual charge of the transformer 342 or the capacitor unit 343, and outputs a residual charge detection signal when the residual charge is detected in the transformer 342 or the capacitor unit 343 do.

The signal output unit 346 outputs a lock signal or an unlock signal of the power conversion module 340 to lock or unlock the power conversion module 340 by a user's selection. For example, the signal output unit 346 may output a lock release signal when an attempt is made to open the power conversion module 340 by a user's physical force or an operation of the manipulation unit. Similarly, the power conversion module may be output by the user. If no attempt is made to open 340, a lock signal may be output.

The power conversion module controller 345 blocks the lock release signal of the power conversion module 340 from the residual charge detection unit 344 to be input to the power conversion module driver 347 to maintain the lock of the power conversion module 340. Control as possible.

The power conversion module driver 347 receives the lock signal or the unlock signal of the power conversion module 340 of the signal output unit 346 to lock or unlock the power conversion module 340.

For example, the power conversion module driver 347 may be configured to include a switch and a relay, not shown. That is, the power conversion module driver 347 receives the locking signal or the unlocking signal of the power conversion module 340 of the signal output unit 346 and the power conversion module 340 receives the power through the switch and the relay. Lock or unlock with respect to 310.

10 is a flowchart illustrating an operation of preventing unlocking of an inverter power conversion module according to an embodiment of the present invention.

As shown in FIG. 10, first, the residual charge detection unit 344 determines whether residual charge is detected in the transformer 342 or the capacitor unit 343 (S100).

If residual charge is detected by the residual charge detection unit 344, the residual charge detection signal is output.

In addition, when the power conversion module controller 345 receives the residual charge detection signal, the lock release signal of the power conversion module 340 is blocked from being input to the power conversion module driver 347.

Therefore, even if the user attempts to open the power conversion module 340, the power conversion module 340 is able to maintain the locked state without opening in the inverter body 310 (S130).

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, . ≪ / RTI > Accordingly, such modifications are deemed to be within the scope of the present invention, and the scope of the present invention should be determined by the following claims.

100 ... Solar Array 110 ... Solar Module
120 ... Solar String 200 ... String Optima
210 ... string control unit 211 ... status determination unit
213 ... following range calculator 215 ... control signal generator
217 ... following history storage 230 ... string converter
231 DC converter 233 mppt controller
251 Fuse 253 Circuit Breaker
290 Detecting unit 300 Inverter
310 Inverter main unit 320 Inverter control unit
330 ... distributor 340 ... converter

Claims (10)

A solar cell array having a plurality of solar cell strings composed of a plurality of solar cell modules and producing power generation; and,
A string connected to the solar cell string to perform maximum power point tracking, transform the voltage of the generated power, and apply the plurality of different tracking methods according to the power fluctuation range of the generated power to perform the maximum power point following. Optima;
An inverter having an inverter body for forming an appearance and a plurality of power conversion modules respectively formed to be selectively locked or unlocked on the inverter body to convert and generate the generated power transformed from the string optimizer into AC power; Including;
At least one of the plurality of power conversion modules,
Residual charge detection unit for detecting the residual charge in the power conversion module,
When receiving the detection signal of the residual charge, the power conversion module control unit for controlling to maintain the lock of the power conversion module by blocking the input of the unlock signal of the power conversion module,
A signal output unit for selectively outputting a lock signal or a unlock signal of the power conversion module by a user, and receiving the lock signal or the unlock signal of the power conversion module at the signal output unit to lock the power conversion module Or unlocking the power conversion module driving unit, wherein the power conversion module control unit selectively blocks the unlocking signal when the residual charge inside the conversion module is detected by the power conversion module control unit. delete delete The method of claim 1,
In any one of the plurality of power conversion module,
A switching circuit unit which drives the transistors therein to generate an AC voltage and an AC current;
And a transformer for boosting the AC voltage applied from the switching circuit unit and supplying the AC power to the commercial power supply. The method of claim 1,
In any one of the plurality of power conversion module,
A switching circuit unit which drives the transistors therein to generate AC voltage and AC power;
And a capacitance portion connected to the switching circuit portion. delete The method of claim 1,
The inverter,
The multi-inverter photovoltaic power generation system, characterized in that for varying the number of the conversion module driven among the plurality of conversion modules according to the size of the power generation. delete delete The method of claim 1,
The inverter further includes a power distribution unit for distributing the generated power to the plurality of conversion modules, and an inverter control unit for selecting a conversion module to be driven.
The inverter control unit,
The multi-inverter photovoltaic power generation system, characterized in that for controlling the distribution of the power distribution unit so that the conversion module relatively short drive time compared to the other conversion module, the drive time of the plurality of conversion module is driven first.

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