KR20070014403A - A virtual simulator and method of simulation for photovoltaic array - Google Patents

Abstract

A virtual simulator and a method for simulating a photovoltaic array are provided to efficiently perform simulation for the photovoltaic array by forming the photovoltaic array simulator necessary to develop a photovoltaic array PCS(power conditioning System) with only the simple DSP(Digital Signal Processor) board. A PV(Photo Voltaic) virtual simulator(110) comprises a direct current conversion unit(110), a capacitor model unit(120), a pattern generator(130), a PV model unit(140) and a DA conversion unit(150). DC current is generated from output current/voltage of an inverter(300) in the photovoltaic array PCS. DC link voltage applied to a DC link terminal is generated by finding/integrating output current of the photovoltaic array and the current flown in a capacitor from the DC current. Solar light intensity and temperature are patterned. The output voltage of the photovoltaic array is generated from the DC link voltage, and the patterned solar light intensity and temperature. The DC link voltage and the output current of the photovoltaic array are converted into analog output, and the analog output is inputted to a voltage/current sensing unit(210) of the photovoltaic array PCS.

Description

A Virtual Simulator and Method of Simulation for Photovoltaic Array

The following drawings, which are attached in this specification, illustrate the preferred embodiments of the present invention, and together with the detailed description of the present invention which serves to further understand the technical spirit of the present invention, the present invention includes matters described in such drawings. It should not be construed as limited to.

1A is a configuration diagram of a power system using a conventional solar cell.

1B is a configuration diagram of a conventional solar cell simulator.

2 is a configuration diagram of a virtual simulation device for a solar cell and a PCS for a solar cell of the present invention.

Figure 3 is a schematic diagram showing only the virtual simulation device for a solar cell of the present invention.

Figure 4 is a configuration diagram showing the input current and voltage of the DC link stage and the output current and voltage of the inverter unit of the present invention.

5 is a characteristic diagram showing a characteristic curve according to the temperature and the irradiation amount of the solar cell module of the present invention.

6 is a flowchart of a virtual simulation apparatus for a solar cell of the present invention.

* Explanation of Codes on Major Parts of Drawings *

100: virtual simulator for solar cell

110: DC current converter 120: capacitor model unit

130: pattern generator 140: solar cell model unit

150: DA converter

The present invention relates to a virtual simulation device and a simulation method for a solar cell, and more particularly, to a low-cost and efficient solar virtual simulation device and a simulation method by configuring a solar cell simulation device which is an essential device for developing a solar cell PCS with only a simple DSP board. It is about.

Recently, due to problems of global environment, depletion of fossil energy, waste disposal of nuclear power generation, and location selection due to the construction of new power plants, research and development on new and renewable energy has been actively conducted at home and abroad. The classification of key element technologies of solar cell power generation can be said to be a convergence of comprehensive technologies consisting of peripheral device technologies.

Generally, solar cells are needed to develop PCS (Power Conditioning System) for solar cells. Solar cells are very unstable to think of a general DC power supply with constant output. In other words, the amount of power that can be extracted from the solar cell varies depending on the voltage applied to the solar cell. Therefore, in order to extract the maximum power from the solar cell, the control according to the characteristics of the solar cell should be controlled. Such a control is called the maximum power point tracking control (MPPT).

Hereinafter, a virtual simulator for solar cells according to the prior art will be described.

FIG. 1A is a configuration diagram of a power system using a conventional solar cell, and FIG. 1B is a configuration diagram of a conventional solar cell simulator.

As shown in FIG. 1A, the solar cell power supply system 10 includes a solar cell array 11, a DC terminal 12, an inverter unit 13, a sine filter 14, a transformer 15, and a DSP (Discrete). Signal Processing) control unit 16 is provided.

The solar cell power supply system 10 uses the solar cell array 11 as an input power source, and converts the generated DC power into a general commercial AC power source using a PV (Photo Voltaic) Power Conditioning System (PCS) ( 10). However, since the solar cell array 11 is expensive equipment and requires a wide accommodation space, in order to develop PV PCS, a simulator capable of simulating solar cells is essential.

Meanwhile, as shown in FIG. 1B, the conventional solar cell simulator 20 includes an AC input unit 21, a rectifier unit 22, a DC output unit 23, and a controller 24.

Here, the rectifier unit 22 uses an IGBT or a thyristor as a power device. In addition, the rectifier unit 22 is composed of a current type rectifier or a voltage type rectifier and simulates the solar cell array 11 in FIG. 1A by using the DC power generated in the rectifier unit 22 (PV) PCS ( 10) is used for the development. In addition, the power input unit 21 is a single-phase or three-phase power supply depending on the power capacity of the simulator.

However, the conventional solar cell simulator 20 has a full bridge or six-element rectifier structure when the power circuit is a single phase, and the power device is composed of an IGBT or a thyristor, which are very expensive devices, and thus, the conventional solar cell simulator 20 ) In manufacturing, there is a problem of increasing the manufacturing cost.

In addition, when the rectifier unit 22 is a current type rectifier, an inductor must be inserted into the DC output unit 23, and in the case of a voltage type rectifier, a three-phase inductor must be added to the power input unit 21. There is also a problem that the size of the conventional solar cell simulator 20 increases.

In addition, an algorithm for controlling the rectifier unit 22 and a three-phase pulse width modulation (PWM) control should be performed. Since such control is complicated, the problem of increasing the manufacturing complexity of the conventional solar cell simulator 20 is also increased. have.

In addition, the response speed is important in the simulator for solar cells, and there is a problem in that a separate circuit is added to increase the response speed.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a low cost and efficient solar cell virtual simulation device and simulation method by configuring a solar cell simulation device, which is an essential device for developing a solar cell PCS, with only a simple DSP board. It is in the air.

Many specific details are set forth in the following description and in the accompanying drawings, in order to provide a more thorough understanding of the present invention. It will be apparent to those skilled in the art that the present invention may be practiced without these specific details. In addition, detailed description of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

One aspect of the present invention for achieving the above technical problem relates to a virtual simulation device for a solar cell.

A virtual simulation device for a solar cell, comprising: a direct current converting unit for generating a direct current from an output current and a voltage of an inverter unit in a solar cell power conditioning system (PCS); A capacitor model unit configured to obtain a current flowing into the capacitor from the output current of the solar cell and the direct current and integrate the same to generate a direct current link voltage applied to the direct current link stage; A pattern generator for patterning and generating sunlight and temperature; A solar cell model unit configured to generate an output current of the solar cell from the DC link voltage generated by the capacitor model unit and the amount and temperature of the solar light patterned by the pattern generator; and the DC link voltage and the output of the solar cell And a DA (Digital Analog) converting unit for converting current into an analog output and inputting the voltage and current sensing unit of the solar cell PCS.

At this time, the inverter unit is preferably composed of a plate busbar (plate busbar).

Another aspect of the present invention for achieving the above technical problem relates to a virtual simulation method for a solar cell.

A virtual simulation method for a solar cell, comprising: a first step of generating a direct current from an output current and a voltage of an inverter unit in a solar cell power conditioning system (PCS); Obtaining a current flowing into the capacitor from the output current of the solar cell and the direct current and integrating the same to generate a direct current link voltage applied to the direct current link stage; A third step of patterning and generating sunlight amount and temperature; A fourth step of generating an output current of the solar cell from the DC link voltage generated in the second step and the amount and temperature of sunlight generated by patterning in the third step; and the DC link voltage and the output current of the solar cell. And converting the signal into an analog output and inputting the voltage and current sensing unit of the solar cell PCS.

In this case, the first step is preferably obtained by dividing the value of the input power of the DC link terminal by the value of the output voltage of the inverter unit by using the output power of the inverter unit and the input power of the DC link terminal.

In the second step, the voltage of the DC link may be obtained by subtracting the value of the DC current from the value of the output current of the solar cell to obtain the value of the current flowing into the capacitor and integrating the same.

In the fourth step, it is preferable to substitute the DC link voltage, the amount of sunlight and the temperature into a solar cell characteristic equation to obtain the solar cell output current.

On the other hand, in the third step, it is more preferable to generate the light quantity pattern and the temperature pattern by using the arbitrary waveform generation function of the pattern generator.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the virtual simulation device and simulation method for a solar cell according to the present invention.

2 is a configuration diagram of a virtual simulation device for a solar cell and a PCS for a solar cell of the present invention. 2 is a configuration diagram in which the virtual solar cell simulation apparatus 100 for solar cells and the PCS 900 for solar cells are connected, but the description of the solar cell PCS 900 is not the gist of the present invention.

First, referring to the overall flow, when the output current and voltage (I _abc , V _abc ) of the solar cell PCS 900 is input to the virtual simulator 100 for solar cells, the output of the virtual simulator 100 for solar cells is a solar cell The output voltage (V _pv ) and output current (I _pv ) of the array become.

Here, the output voltage and the output current (V _pv , I _pv ) is output through the DA converter 150 is connected to be input directly to the current and voltage sensing unit 210 of the solar cell PCS 900, in this case the output voltage And output current (V _pv , I _pv ) is not the actual voltage and current level of the solar cell, but the output current and voltage (I _abc , V _abc ) level of the PCS 900 for solar cells.

Meanwhile, if the inverter unit 300 of the solar cell PCS 900 can directly sense the DC input current I _DC by the input of the solar cell virtual simulator 200, the output current and voltage of the solar cell PCS 900 ( I _abc , V _abc ) need not be sensed.

However, in order to accommodate a large power capacity in the configuration of the inverter unit 300 is generally configured to be a plate busbar (plate busbar), so the inverter unit 300 of the solar cell PCS (900) DC input current (I _DC ) Direct sensing is not easy. At this time, even if the inverter unit 300 is not made of a plate busbar (plate busbar), the virtual simulation for the solar cell for sensing the DC input current (I _DC ) of the inverter unit 300 of the solar cell PCS (900) It is not preferable because a separate sensing device in the device 100 is required.

At this time, the actual power supply of the solar cell PCS 900 is supplied from the rectified DC power supply through the diode rectifier 500. Although the DC voltage is actually supplied from the voltage of the diode rectifier 500, when the solar cell virtual simulation apparatus 100 is connected to the solar cell PCS 900, the solar cell PCS 900 is the solar cell virtual simulation apparatus 100. Is supplied by the voltage from As a result, the solar cell PCS 900 performs the maximum power point following control (MPPT) with the voltage from the virtual simulator 100 for the solar cell.

Hereinafter, the virtual simulation apparatus 100 for solar cells will be described in detail. 3 is a configuration diagram showing only the virtual simulation device for solar cells again. The virtual simulation apparatus 100 for a solar cell includes a DC current change unit 110, a capacitor model unit 120, a pattern generator 130, a solar cell model unit 140, and a DA converter 150.

4 is a configuration diagram showing the input current and voltage of the DC link stage and the output current and voltage of the inverter unit. In this case, looking at the voltage and current relationship of FIG. 4 in detail, the DC current converter 110 generates a DC link current I _DC from the output current and voltages I _abc and V _abc of the inverter unit 300. It can be seen.

Herein, the output power P _AC of the solar cell PCS 900 and the input power P _DC of the DC link terminal 400 are as follows.

In this case, the DC link current I _DC can be obtained from the fact that the output power P _AC of the solar cell PCS 900 and the input power P _DC of the DC link terminal 400 are the same.

The capacitor model unit 120 is configured to include an integrator of the virtual simulation device 100 for solar cells. This part simulates the DC link stage 400 capacitor of the inverter unit 300. The output current I _PV of the solar cell passes through the Z converter 122 and then the DC link current I _DC of the inverter 300. By subtracting, the current (I _C ) input to the capacitor is obtained. Here, the output current I _PV of the solar cell passing through the Z converter 122 becomes a previous signal value. Current I _C input to the capacitor indicates I _cap in the figure.

After obtaining I _C as described above, the voltage (V _PV ) applied to the DC link terminal 400 is obtained by passing through the integrator 121. At this time, the operation in the integrator is as follows.

The value obtained above becomes the terminal voltage V _PV of the virtual solar cell array.

The pattern generator 130 may generate the amount and temperature of sunlight as a portion that the virtual simulation apparatus 100 for the solar cell should have. The generated solar light quantity and temperature are input to the solar cell model unit 140. In particular, since the actual solar cell is impossible to change the amount of sunlight arbitrarily, it can be simulated for the pattern of various solar light quantity and temperature by using the arbitrary waveform generation function of the pattern generator 130 in the simulator.

5 is a characteristic diagram showing a characteristic curve according to temperature and irradiation amount of a solar cell module. The upper left is the current and voltage characteristic curve according to the temperature, the upper right is the voltage and power characteristic curve according to the temperature, and the lower left is the current and voltage characteristic curve according to the solar radiation and the lower Is the voltage and power characteristic curve according to the amount of solar radiation.

The basic principle of obtaining the maximum power from the solar cell is to maintain the voltage corresponding to the maximum power point in the solar cell characteristic curve of FIG.

The solar cell model unit 140 is implemented in the art to obtain the output current (I _PV ) of the solar cell from a characteristic equation for a known solar cell. The input factor of the characteristic equation for the solar cell is the photocurrent I _Ph representing the output voltage (P _PV ), the temperature T, and the amount of solar light of the solar cell.

6 is an equivalent circuit diagram of a solar cell capable of simulating two diodes and breakthrough characteristics. The circuit diagram is summarized as follows using Kirchhoff's current law (KCL).

Where I _PV is the solar cell's current, V _PV is the solar cell's voltage, q is the charge amount, K is Planck's constant, I _Ph is the photocurrent, R _S is the series resistance, A is the ideal coefficient, and I _S1 and I _S2 are the first , The saturation current of the second diode, R _P is the parallel resistance, V _Br is the breakdown voltage, a is the correction factor, and n is the index of the avalanche breakdown.

The DA converter 150 converts the solar cell current (I _PV ) obtained from the solar cell model and the solar cell voltage (V _PV ) obtained from the capacitor model into an analog output in the DSP processor. The analog output is virtually operated as if the solar cell PCS 900 is connected to the solar cell array by directly connecting to the sensing unit 210 of the solar cell voltage and current of the solar cell PCS 900.

That is, the output voltage and voltage (I _abc , V _abc ) level of the solar cell PCS 900 is analog output of the voltage (V _PV ) of the solar cell to the solar cell voltage and current of the solar cell PCS (900) Input to the sensing unit 210.

As a result, the output current and voltage information of the solar cell can be provided to any PCS without modification of the input part of the solar cell PCS. Here, the parts of the solar cell PCS whose current and voltage sensing input ratios are different can be easily adjusted programmatically in the DSP board.

7 is a flowchart of the virtual simulator for solar cells. Specifically, step S1 is a first step of generating a DC current from the output current and the voltage of the inverter unit 300 in the solar cell PCS 900.

In addition, step S2 is a second step of generating a DC link voltage applied to the DC link stage 400 by calculating the current flowing into the capacitor from the output current of the solar cell and the DC current.

In addition, step S3 is a third step of patterning and generating the amount of sunlight and temperature.

In addition, the step S4 is a step of generating the output current (I _PV ) of the solar cell from the DC link voltage generated in the second step and the photovoltaic amount (I _Ph ) and temperature (T) generated by patterning in the third step. Four steps.

In addition, step S5 is a fifth step of converting the DC link voltage (V _PV ) and the output current (I _PV ) of the solar cell to an analog output and input to the voltage and current sensing unit 210 of the solar cell PCS.

Although the present invention has been described as a specific preferred embodiment, the present invention is not limited to the above-described embodiments, and the present invention is not limited to the above-described embodiments without departing from the gist of the present invention as claimed in the claims. Anyone with a variety of variations will be possible.

Therefore, the solar cell virtual simulation apparatus and simulation method of the present invention have the following effects.

First, it virtually simulates a solar cell using only a DSP board to virtually generate output current and voltage, thereby simplifying the hardware configuration of the solar cell PCS, thereby reducing the complexity of the conventional solar cell virtual simulator.

Second, it is possible to reduce the manufacturing cost of the conventional solar cell virtual simulation device using IGBT or thyristor by using only the DSP board, and to make it smaller than the conventional solar cell virtual simulation device by not using a rectifier.

Third, by not using IGBTs or thyristors, which are power devices, the response speed may be higher than that of the conventional virtual simulator for solar cells.

Fourth, it can be applied to any solar cell PCS because it can operate only with output current and voltage of inverter.

Claims (6)

In the virtual simulator for solar cells, DC current conversion unit for generating a DC current from the output current and voltage of the inverter unit in the solar cell PCS (Power Conditioning System); A capacitor model unit configured to obtain a current flowing into the capacitor from the output current of the solar cell and the direct current and integrate the same to generate a direct current link voltage applied to the direct current link stage; A pattern generator for patterning and generating sunlight and temperature; A solar cell model unit configured to generate an output current of the solar cell from the DC link voltage generated by the capacitor model unit and the amount and temperature of solar light generated by patterning the pattern generator; and And a DA (Digital Analog) converting unit converting the DC link voltage and the output current of the solar cell into an analog output and inputting the voltage and current sensing unit of the solar cell PCS. In the virtual simulation method for solar cells, A first step of generating a DC current from an output current and a voltage of an inverter unit in a solar cell power conditioning system (PCS); Obtaining a current flowing into the capacitor from the output current of the solar cell and the direct current and integrating the same to generate a direct current link voltage applied to the direct current link stage; A third step of patterning and generating sunlight amount and temperature; A fourth step of generating an output current of the solar cell from the DC link voltage generated in the second step and the amount and temperature of sunlight generated by patterning in the third step; and And a fifth step of converting the DC link voltage and the output current of the solar cell into an analog output and inputting them to the voltage and current sensing unit of the solar cell PCS. The method of claim 2, wherein the first step, The virtual simulation method for a solar cell, wherein the output power of the inverter unit and the input power of the DC link terminal are obtained by dividing the value of the input power of the DC link terminal by the value of the output voltage of the inverter unit. The method of claim 2, wherein the second step, Virtual voltage simulation method for a solar cell, characterized in that by subtracting the value of the direct current from the value of the output current of the solar cell to obtain the value of the current flowing into the capacitor and integrating it to obtain the voltage of the DC link. The method of claim 2, wherein the fourth step, And calculating the output current for the solar cell by substituting the DC link voltage, the amount of solar light, and the temperature into a characteristic equation for the solar cell. The method according to any one of claims 2 to 5, wherein the third step, Virtual simulation method for a solar cell, characterized in that for generating a light quantity pattern and a temperature pattern using the arbitrary waveform generation function of the pattern generator.

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