JP2003133569A - Method and apparatus for evaluating output of solar battery in field - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for solving the conventional problem that an evaluation method having excellent flexibility and higher accuracy is not yet established for evaluating the output and the generation of power of a solar battery in a field, it is difficult to obtain a stable evaluation value due to a sudden change of irradiation and the spectrum of the sun light, and that the method of evaluating a Pmax operation (MPPT operation) in a field is not yet established. SOLUTION: The irradiation intensity of the sun light and I-V and P-V curves in a solar battery temperature during measurement are calculated from solar battery characteristic values and these are evaluated and compared with a voltage-current value. It is determined from the standard deviation of the output evaluation value that the irradiation intensity is stable and obtained data can be evaluated. The method for calculating a compensation coefficient for the temperature compensation of solar battery conversion efficiency has been developed. In addition, the method for verifying the effect of the Pmax operation (MPPT operation) during the interlaced operation has also been developed using the principle described above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION A solar cell, as shown in FIG.
It directly converts the light energy of the sun into electrical energy. That is, the photovoltaic effect, which is a type of photoelectric effect, is applied to generate an electromotive force. When light (photons) with appropriate energy enters the solar cell, free electrons and holes are generated. Occur. Solar cell in semiconductor
The electrons and holes reaching the vicinity of the pn junction are diffused to the n-type semiconductor side and the p-type semiconductor side, respectively, and are collected at both electrode portions, so that electric power can be taken out and voltage and current are generated. Solar cells can be roughly classified into crystalline silicon type, amorphous silicon type, and compound type. Crystalline silicon solar cell,
In particular, since the manufacturing process of a single crystal solar cell is complicated and a large amount of electric power is required, research for cost reduction is being advanced.
Recently, there are reports that the conversion efficiency of more than 20% was achieved by devising the device structure. The efficiency of polycrystalline silicon solar cells, whose manufacturing process is a little simple, is practically about 10% to 15%. Amorphous silicon-based solar cells (amorphous solar cells) are promising as low-cost solar cells because they are simple in manufacturing process, require little manufacturing energy, and require less silicon material. Further, since it can be formed as a thin film on various substrates, a wide range of application is expected. Efficiency is
It is about 10%. The present invention relates to an outdoor evaluation method / apparatus for a photovoltaic power generation system including such a solar cell. That is, the present invention relates to a method and software applied to a solar cell output / power generation amount measurement / evaluation device (commonly called "IV curve tracer") installed in the field. And the evaluation method in the interconnection operation state, software and Pmax operation in the interconnection operation state (MPPT operation ...
・ Maximum output control operation) evaluation method and software. The present invention also relates to an evaluation device including a medium in which these methods / software programs are recorded. Further, the present invention relates to a pyranometer including a signal indicating whether measurement data can be evaluated.

[0002]

2. Description of the Related Art The method of measuring and displaying the characteristics and performance of manufactured solar cells at the time of shipment is determined by JIS C8913, JIS 8914, etc. That is, the solar cell module is measured and displayed using a solar simulator. On the other hand, there is a problem that the amount of power generated by a solar cell recently installed in the field may be unexpectedly small.
On the other hand, a method for evaluating a solar cell in the field is not well established. That is, although JIS C 8919 describes the related items of solar cell evaluation in the field, it is under the conditions such as limited solar radiation intensity and solar radiation fluctuation, and when actually applied various problems are encountered. is there. For example, the evaluation value is often greatly different depending on the measurement month / day / time, and it is often difficult to evaluate due to the weather.

Conventionally, the following methods have been generally known as general methods for evaluating the output and power generation amount of a solar cell, but each has many problems. a. "I-V curve tracer" method When evaluating the output of a solar cell installed in the field, disconnect the solar cell from the interconnected operating state, connect the "I-V curve tracer", and load the equipment. I-V curve is created instantaneously by switching at high speed. And this I
-V curve as standard condition (solar radiation intensity 1kW / m2, solar cell temperature 2
To return to 5 ° C), the formula of JIS C8913 (or IEC891) is used. The maximum output (Pmax) is obtained from the I-V curve and the P-V curve in this reference state, and is evaluated by comparing with the specification value (P = Iop * Vop) given by the manufacturer. With this evaluation method, the formula for converting to the standard state is as follows. That is, the voltage value, current value, solar radiation intensity, and solar cell temperature in the standard state are V2, I2, E2, and T2, respectively.
And the measured voltage value, current value, solar radiation intensity, solar cell temperature and measured short-circuit current are V1, I1, E1, T1, respectively.
When Isc is used, conversion is performed using the following formula. I2 = I1 + Isc ((E2 / E1) -1) + α (T2-T1) ... (3 ') V2 = V1-β (T2-T1) -Rs (I2-I1) -KI2 (T2- T1) ・ ・ ・ (4 ') where α is the fluctuation value of Isc when the measured solar cell temperature fluctuates by 1 ° C [A / ° C] β: Voc when the measured solar cell temperature fluctuates by 1 ° C Fluctuation value [V / ° C] Rs: Series resistance of the measured solar cell [Ω] K: Curve correction factor [Ω / ° C] However, as described above, this formula is limited to the solar radiation intensity (80
It is applicable only in the range of 0 W or more). Moreover, although the output at each moment can be evaluated, it cannot be evaluated by the amount of electric power in the period. Furthermore, when there is a large fluctuation of solar radiation, there is a problem that the output of the pyranometer and the solar cell are conspicuously different in time, and stable evaluation is often difficult. In addition, there was a problem of influence on the output due to mismatching of the solar spectrum and wavelength sensitivity of the solar cell. Further, this method originally had a problem that the solar cell had to be disconnected from the interconnected operation and measured and evaluated.

B. Method Based on Evaluation Value (During Interconnection Operation) There is a problem that the same method as the evaluation method (method a) by the above-mentioned “IV curve tracer” can be implemented even in the interconnection operation state. A method was being sought.

C. Method Based on Solar Cell Conversion Efficiency Solar cell conversion efficiency is often used as a general method for evaluating solar cells installed in the field. Conversion efficiency
It is expressed as in equation (1), and this conversion efficiency can be used to evaluate the integrated energy value for a certain period. Solar cell conversion efficiency (%) = Solar cell power generation (kWh) ÷ Solar cell light receiving surface solar energy (kWh / m2) ÷ Solar cell area (m2) × 100 ……………………………… (1) In this expression, the solar cell temperature (also referred to as “solar cell module temperature”) that greatly affects the amount of power generated by the solar cell is not included in the expression. Therefore, the value is not generalized depending on the solar cell temperature, that is, the season and time. Even if solar cell temperature correction is applied, it is difficult to determine because the temperature coefficient of solar cell output changes depending on the solar radiation intensity and solar cell temperature. In addition, the response time of the pyranometer, fluctuations in solar radiation, operating voltage, etc. also have an effect.

As a next problem, when the photovoltaic power generation system is interconnected with the grid, the output (power generation) differs depending on the operating voltage of the solar cell, so that the photovoltaic power generation system is operated at a voltage that maximizes the output ( Pmax operation or MPPT operation) has been developed and is actually applied. However, despite the importance of assessing how well the Pmax operation is performed in the field,
The method of confirming and evaluating the operation was not established. Even in the interconnection operation in the field, when there is a rapid change in the solar radiation intensity as described above, there are various problems in mismatching the solar radiation intensity and the solar cell output.

[0007]

The problems to be solved by the present invention are as follows in view of the circumstances of the conventional techniques as described above. First, a. The method using the "IV curve tracer" will be described. As described in “Issue” above, “I-V
Voltage-current value measured by "curve tracer", that is, I
If the JIS C 8913 formula is applied to return each value on the −V curve to the standard state, it can be applied only within a limited range of solar radiation intensity, and evaluation as an integrated value for a certain period cannot be performed. Therefore, in the present invention, conversely, the characteristic values (Isc, Iop, Vop, Voc, α, β, Rs,
K) to standard condition (solar radiation intensity 1kW / m2, solar cell temperature 25)
℃) I-V curve is created, and I-V curve and P-V curve under the solar radiation temperature and solar cell temperature conditions at the time of measurement are created.
It is intended to compare and evaluate with the I-V curve and the P-V curve created by measuring with the "I-V curve tracer".
Next, there is a problem that it is difficult to obtain a stable evaluation value because there is a time difference between a rapid solar radiation fluctuation and the solar radiation intensity measured by a pyranometer and the measured solar cell output. In order to deal with this issue, we tried to judge whether or not the data is in the time zone of the condition that can be evaluated by whether the evaluation value is stable. In addition, in order to clarify the effect of the wavelength difference of sunlight on the output, we have clarified the solar spectrum and the wavelength sensitivity of the solar cell, and in order to evaluate it more accurately, we analyze the air mass (AM), dew point temperature, etc. We decided to consider the relationship.

Next, among the evaluation methods in the interconnected operation state, b.
The "method based on evaluation value" (during interconnection operation) will be described.
As an evaluation method, an IV curve in the standard state is created from the characteristic values (Isc, Iop, Vop, Voc, α, β, Rs, K) of the solar cell as in the case of a. It was examined to convert the I-V curve and PV curve at the intensity / solar cell temperature and compare / evaluate with the voltage / current / power value of the solar cell measured in the interconnected operation state.

Next, among the evaluations based on the state in which the solar cell is connected to the grid, the method of using the solar cell conversion efficiency is generally used. The temperature coefficient of the given solar cell output (solar intensity / solar cell temperature (Changes apart) cannot be accurately grasped. Therefore, the temperature coefficient for each solar cell temperature range and the solar radiation intensity of the solar cell output can be calculated by using the characteristic values (Isc, Iop,
It was considered to find it by drawing I-V curve and PV curve of various solar temperature and solar cell temperature conditions from Vop, Voc, α, β, Rs, K). The temperature coefficient calculated in this way is used to calculate and evaluate the solar cell conversion efficiency (after temperature correction) in which the solar cell conversion efficiency is accurately corrected.

As a method applying the above method to the evaluation of Pmax operation, the solar radiation intensity at the time of measurement and the solar cell temperature are measured.
It was decided to create an I-V curve and a P-V curve and compare the optimum voltage and maximum power value with the operating voltage / power for evaluation.

In any of the methods (0012, 0013, 0010) in the above-mentioned interconnection operation state, the above "I
As in the method using the −V curve tracer, there is a difference in the spectrum of sunlight depending on the measurement date and time, a rapid fluctuation in solar radiation, and a difference in the response time between the solar radiation intensity measured by the pyranometer and the measured solar cell output, so stable comparison evaluation is possible. It's hard to do. Therefore, again, we tried to judge that the data was in the time zone that can be evaluated based on whether the evaluation value is stable. In addition, in order to clarify the effect of the difference in sunlight, we tried to elucidate and accurately evaluate the solar radiation spectrum and the wavelength sensitivity of the solar cell.

[0012]

According to the solar cell output evaluation method of claim 1, the characteristic values (Isc, Iop, Vop, Voc, α,
β, Rs, K), I-V curve and PV curve in standard condition (solar radiation intensity 1kW / m2, solar cell temperature 25 ° C) are created,
Input the solar radiation intensity and solar cell temperature conditions at the time of measurement, convert to I-V curve, P-V curve in the conditions, I-V curve measured by "I-V curve tracer", and P-V curve The comparison is characterized in that the solar cell output is evaluated.

The solar cell output evaluation method according to claim 2 is a solar cell measurement value (Isc, Iop, Vop, Voc, α, β, Rs, K).
To standard condition (solar radiation intensity 1kW / m2, solar cell temperature 25 ℃)
I-V curve and P-V curve are created, converted into I-V curve and P-V curve under the solar temperature and solar cell temperature conditions at the time of measurement, and linked with the maximum output value on the P-V curve. It is characterized in that the solar cell output is evaluated by comparing with the electric power value which is the product of the voltage and current value of the solar cell terminal measured in the system operating state.

According to the solar cell output evaluation method of claim 3, with respect to the solar cell output evaluation value (measured value / calculated value) calculated at a constant interval, the average value / standard deviation (σ) of the evaluation value for a constant time period is calculated. When the calculated standard deviation (σ) is smaller than a certain value, the average value of the evaluation values is adopted as the evaluation value of the output in the time zone.

According to the solar cell output evaluation method of claim 4, for the solar cell output evaluation value (measured value / calculated value) calculated at a constant interval, an average value / standard deviation (σ) of the evaluation value for a constant time period is calculated. When the standard deviation (σ) is continuously smaller than a certain value and the solar radiation intensity is larger than the certain value and the air mass (AM) is smaller than the certain value, the average value of the evaluation values is calculated as the time. It is characterized in that it is used as an output evaluation value of the band.

The solar cell output evaluation method according to claim 5 is a solar cell output evaluation value (measured value / calculated value) as explanatory variables for solar radiation intensity (W / m2) (represented by a clear sky index), air mass (AM). ), Dew point temperature (℃) (represented by the amount of precipitable water), and made a multiple regression equation, and calculated by substituting the standard conditions (solar radiation intensity 1000 W / m2, air mass 1.5) and typical dew point temperature. The evaluation value is used as the evaluation value of the solar cell.

The solar cell output evaluation method according to claim 6 is a method for evaluating a solar cell output in an interconnected operation state, wherein the temperature coefficient calculation method when the conversion efficiency is corrected by the temperature at the time of measurement is {01}. The solar cell characteristic values (Isc, Iop, Vo
From p, Voc, α, β, Rs, K), typical solar radiation intensity (1000W / m2, 800W / m2, 50) at solar cell temperatures of 25 ℃ and 55 ℃
0V / m2, 300W / m2, etc.) I-V curve and P-V curve are created, and the solar cell maximum output (Pmax) temperature coefficient for each solar radiation intensity at {02} solar cell temperature 25 ° C and 55 ° C is calculated. Then, at {03} solar cell temperature of 25 ℃ and 55 ℃,
A quadratic regression equation with the solar radiation intensity of the temperature coefficient at the solar cell maximum output (Pmax) as an explanatory variable was created, and the solar cell temperature at the time of {04} measurement was created with the {03} solar cell temperature 25 ° C.
25 ° C obtained by {05} {04} by calculating the temperature coefficient of the solar radiation intensity at 25 ° C and 55 ° C.
It is characterized in that the temperature coefficient at the solar cell temperature at the time of measurement is obtained by continuous interpolation from the temperature coefficient of and 55 ° C.

The solar cell output evaluation method according to claim 7 is a measurement value (solar intensity, solar cell temperature, solar cell temperature, solar cell temperature, Solar cell voltage / current / power)
{06} Solar cell characteristic values (Isc, Iop, Vop, Voc, α,
β, Rs, K), I-V curve in the standard state, P-V
Create a curve and convert it to the I-V curve and PV curve of the above-mentioned solar radiation intensity and solar temperature conditions. {07} Voltage value (Vop 'at the maximum power point of the PV curve created in {06} above {06} ) To the operating voltage V ', and {08} above {0
6} Calculate the ratio of the power P '(V' * I ') at the time of measurement to the maximum power value (Pmax') of the P-V curve created in
The feature is that the operation (MPPT operation) is evaluated.

The solar cell output evaluation method according to claim 8 is an average value of measured values (solar radiation intensity, solar cell temperature, solar cell voltage / current / power) at a constant interval (1 to 10 minutes, etc.) in the interconnected operation. And the characteristic value (Is
c, Iop, Vop, Voc, α, β, Rs, K), the I-V curve and the P-V curve in the standard state are created, and the I-V curve of the average solar radiation intensity and the solar cell temperature conditions, P Convert to −V curve and calculate the ratio of the voltage V ″ of the above measured value to the voltage value (Vop ″) at the maximum power point of the P−V curve created in {10} above {09}, and {11} Calculate the ratio of the measured power P "(V" * I ") to the maximum power value (P" max) of the P-V curve created in {09} above, and perform Pmax operation (MPPT
It is characterized by carrying out an evaluation of (operation).

The solar radiation measuring system according to claim 9 takes in the signals of the short-circuit current and temperature of the solar radiation meter and the solar cell, and outputs the {12} solar cell short-circuit current (Isc ') at that temperature and the temperature of the solar cell. Calculate the short-circuit current (Isc ") corrected by the coefficient, find the ratio with the insolation intensity by the pyranometer, and calculate the standard deviation of the ratio for a fixed interval (1 to 10 minutes, etc.) for a fixed period. When the calculated value is smaller than a fixed value, the solar radiation intensity is larger than the fixed value, and the air mass (AM) is smaller than the fixed value, the evaluable time zone signal is output together with the solar radiation signal from the global pyranometer.

The evaluation method / software according to claim 10 is characterized in that the evaluation method / software according to claim 1 is included as evaluation software for the “IV curve tracer”.

According to the eleventh aspect of the present invention, there is provided a solar cell output evaluation device / system, wherein the solar cell output evaluation device / system is in an interconnected operation state.
It is characterized by utilizing the solar cell output evaluation methods and software described in 8 and 9.

Claims 1 and 2 use a general-purpose and highly accurate method to measure the I-V curve of the solar radiation intensity at the time of measurement and the solar cell temperature, and P-V.
The feature is that the curve can be calculated. Claims 3 and 4 are characterized in that data that can reliably evaluate the solar cell output can be selected. Claim 5 is characterized in that the output evaluation value is analyzed and evaluated in consideration of the sunlight spectrum when the output evaluation result varies depending on the season. Claim 6 is characterized in that the coefficient for temperature correction of the solar cell conversion efficiency is calculated universally and accurately. Claim 7 claims Pmax in the state where the solar radiation is stable.
The feature is that the effect of operation (MPPT operation) can be understood by the voltage ratio and the power ratio. Claim 8 is characterized in that the effect of the Pmax operation (MPPT operation) can be grasped by the voltage ratio and the power ratio even if the solar radiation varies to some extent. Claim 9 is characterized in that, together with the total amount of solar radiation, the solar radiation intensity is stable during the time period and a signal indicating whether or not the solar cell can be evaluated can be obtained. Claim 10 is characterized in that the evaluation of the solar cell by the "IV curve tracer" can be carried out in a more general and accurate manner. Claim 11 is characterized in that it is a device / system that can evaluate a solar cell output and Pmax operation generally and accurately even when the solar cells are in an interconnected state.

The techniques and terms relating to the present invention will now be described. ○ I-V curve and PV curve of solar cell The voltage and current at the output end of the solar cell show the characteristics shown in Fig. 11. The point at which the voltage on the IV curve showing the relationship between the voltage and the current is zero, that is, the current in the short-circuit state is called the short-circuit current Isc, and the point at which the current is zero, that is, the voltage in the open state is called the open-circuit voltage Voc. The point of maximum power on the PV curve showing the relationship between voltage and power is called maximum output Pmax, the voltage at that time is called optimum voltage Vop, and the current is called optimum current Iop. ○ I-V curve tracer The output of the solar cell changes depending on the solar radiation intensity on the solar cell light receiving surface, the temperature of the solar cell, the size of the load resistance, and the voltage at the solar cell output terminal. Therefore, accurate evaluation cannot be performed only by the conversion efficiency, which is the ratio of the solar cell output to the solar input energy to the solar cell. Therefore, by disconnecting the solar cell from the load, connecting a simulated load, and switching the value at high speed, a large amount of voltage-current or voltage-power data was obtained in a short time, and the I-V curve, P-V Create curves and then use these curves as a reference condition (solar radiation intensity 1k
I / V curve converted to W / m2 / solar cell temperature 25 ℃, PV
Create a curve. Then, this curve is compared with the characteristic values (Isc, Iop, Vop, Voc) which are the specifications of the solar cell. This is a device applied for this purpose (Fig. 9). Figure 10 shows an example of measurement results using this IV curve tracer. ○ Pmax operation (MPPT operation) As mentioned above, the solar cell output depends on the size of the load resistance.
That is, the output (power generation) differs depending on the operating voltage. Therefore, Pmax operation (MPPT operation) is the operation that always controls the voltage so that the maximum output is obtained. ○ air mass (AM) The amount of air that sunlight passes through, and if the zenith angle of the sun is θ (the angle between the vertical line on the ground and the line in the direction of the sun), approximately AM = se
It is represented by cθ. This corresponds to the distance that sunlight travels through the atmosphere and affects the solar spectrum. ○ Dew point temperature As it represents the amount of water in the air, it affects the solar spectrum. Note that the dew-point temperature represents the amount of water on the ground, and is related to the amount of water not only on the ground but also in the sky before the sunlight reaches the surface of the earth. The water content in the sky is represented by the descending water content.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. Figure 1 is a diagram illustrating the outline of the solar cell evaluation method in the field using the "I-V curve tracer", calculates the standard deviation for 10 times of the evaluation value measured and calculated every 1 minute, the Although it is determined whether the data of the period can be adopted as the evaluation target data, the data of one minute of the measurement data may be different intervals, or data measured at shorter intervals. Also, the condition of solar radiation intensity is not limited to 300 W / m2 or more. The larger the solar radiation intensity is set, the more stable the evaluation data tends to be obtained, but the number of data (evaluation target data) that can be used for evaluation tends to be limited. There is a need. Furthermore, the measurement time zone is set here from 10:00 to 14:00, but it may be from 9:00 to 15:00 in regions with relatively low latitudes, which is determined by the solar altitude and the required number of data to be evaluated. If the evaluation value of this evaluation data is within 5% throughout the year, the evaluation result can be shown by the average value of each evaluation value and its range, but if it is significantly larger than about 5%, it will depend on the solar spectrum. The analysis, that is, the analysis based on the insolation intensity for each wavelength is performed. In addition, in Fig. 1, the I-V curve of this condition from the solar cell characteristic value and the solar radiation intensity / solar cell temperature,
"Practical I-V curve conversion method" for creating PV curves
(See IEEJ paper 1 (Iga et al .: "Development of a solar power generation simulation calculation program using the IV curve creation method", Denki Theory D, Vol. 115, No. 6, (1995)). The method of using the basic equation of the solar cell (The Institute of Electrical Engineers of Japan 2 (Iga: "I-V curve creation method using voltage-current equation of solar cell under light irradiation state and its application")
D, Volume 116, No. 10, (1996))
There is also a method of creating a PV curve and calculating the power value of the maximum output (Pmax).

FIG. 2 is a diagram for explaining the outline of the method for evaluating a solar cell in the interconnected operation state. The basic flow is the same as in Figure 1.

FIG. 3 is a flow chart for calculating the output temperature coefficient of the solar cell output (Pmax) under the conditions of solar radiation intensity and solar cell temperature at the time of measurement. This temperature coefficient can also be applied to evaluation by conversion efficiency. Here, the regression equations of 25 ° C and 55 ° C are obtained, but it is not limited to these temperatures, other temperatures may be used, and the regression equation of the temperature of 3 or more points is obtained.
The measured temperature coefficient may be obtained by curve interpolation. In addition, the regression formula for each temperature is that the solar radiation intensity is 1000W / m2, 800W / m2, 500W / m
Although the Pmax value at 2, 300 W / m2 is used for the calculation, these solar radiation intensities are not limited, and may be calculated from other solar radiation intensity values. The conversion efficiency is basically based on the temperature correction for the conversion efficiency in a certain period (here, 10 minutes), but the temperature conversion is applied for a shorter period (for example, 1 minute), and the average conversion efficiency for 10 minutes. You can also ask. When the fluctuation of solar radiation is large, it is considered that the corrected conversion efficiency also has an unstable value.

FIG. 4 shows an evaluation method for Pmax operation (MPPT operation) in the interconnected operation state. In the stable state where the solar radiation fluctuation is small, both the voltage evaluation value and the electric power evaluation value are stable and constant values, but when the solar radiation fluctuation is large, the average solar radiation intensity / average solar cell at intervals of about 1 to 10 minutes is obtained. A stable evaluation of Pmax operation (MPPT operation) can be obtained by evaluating the temperature and average operating voltage.

FIG. 5 shows a system and its software capable of outputting a signal indicating whether or not it is a solar radiation signal in the evaluable time zone (that is, whether or not it is a stable solar radiation time zone) together with a signal from the pyranometer. In the figure, the standard deviation (σ) is 300 W / m2 or more as the solar radiation intensity and 10 as the measurement time zone.
Although it is set to the hour to 14:00, these values are not limited and may be values around this value depending on the situation.

FIG. 6 shows the mechanism of photovoltaic power generation, which has been outlined in "Technical field to which the invention belongs". FIG. 7 shows a method of creating an IV curve of solar radiation intensity / solar cell temperature conditions at the time of measurement from the characteristic value of the solar cell, which is the basis of the evaluation method of the present invention (The Institute of Electrical Engineers of Japan, 1). In addition, Fig. 8 shows the basic formula of the solar cell in the case of the method of using the basic formula of the solar cell, which is another method for creating the IV curve (The Institute of Electrical Engineers of Japan, 2). Figure 9 is an example of an "I-V curve tracer". Other models have almost the same functions and similar evaluation software. Fig. 10 shows the measurement status and output example by the "I-V curve tracer". FIG. 11 illustrates the I-V curve and PV curve of the solar cell which is the basis of the present invention, and is outlined in the explanation in "Means for solving the problems". Figure 12 shows the comparison and evaluation of the solar cell output under the measured solar radiation intensity and solar cell temperature conditions. The Pmax value of the PV curve between the actual measurement of the broken line and the calculated value of the solid line is compared and evaluated. In the interconnected state, the electric power indicated by x and the calculated Pmax value of the PV curve are compared and evaluated. Also, in the evaluation of Pmax operation, V "/ Vop for voltage and P (V" * I ") / Pmax for power
Evaluate with. Figure 13 shows the method of evaluating a solar cell for a certain period. It is evaluated by averaging the ratio of the measured Pmax value (output) and the calculated Pmax value (output) during that period, and by the ratio of the total value of each period. The case is shown. The latter is in some sense closer to the actual because it is weighted by the size of the output. FIG. 14 is a list of equations for converting the I-V curve in the measurement insolation intensity / solar cell temperature into the reference state. The equations used in the present invention are equations (1) and (2) obtained by modifying equations (3) and (4). Formulas (3) and (4) are JIS
As shown in Fig. 14, it is superior to equations (3) 'and (4)' used in the above.

[0031]

As the characteristics and performance of the solar cell, the values displayed by the manufacturer as the result of the factory test (shipment test) are usually used. However, we often hear reports that solar cells that are actually installed outdoors and are interconnected generate only about 70-80% of the value displayed by the manufacturer. Therefore, by developing a method and device for accurately and universally evaluating the output of solar cells in the field, if the output / power generation amount is insufficient, the cause is investigated, countermeasures are taken, and the output / power generation amount is checked. Can be increased. Therefore, this will lead to an increase in the amount of power generated by the solar cell actually installed, and a great effect can be expected. Here, the effects of the above-described evaluation methods and devices will be described. (1) Evaluation method using [I-V curve tracer] I-V curve of solar radiation intensity and solar cell temperature condition at measurement, P
The maximum power (P
Not only the max) but also the fill fater (FF) and short circuit current can be evaluated. In the present invention, the solar radiation is stable, and the solar radiation output signal and the solar cell output are evaluated using data that does not have a time lag. Therefore, stable evaluation can be carried out regardless of the season, the time, and the like. Then, the influence of the solar spectrum difference is taken into consideration so that a more accurate evaluation value can be obtained. Furthermore, since a highly reliable conversion formula / conversion method is used in the evaluation, not only the evaluation accuracy is high, but also the applicable range is wide. (2) Evaluation method during interconnected operation This evaluation method allows evaluation to be performed in the interconnected operating state without disconnecting the solar cells. In this case as well, similar to the evaluation method using the “I-V curve tracer” in (1) above, stable evaluation can be performed by using data with little solar radiation fluctuation, and a highly reliable conversion formula / conversion method is applied. Since the evaluation is performed in a stable manner, a stable and highly accurate evaluation can be generally performed. Furthermore, as described above, the evaluation can be performed in consideration of the influence of the solar spectrum difference. (3) The solar cell conversion efficiency evaluation is based on the ratio of the output energy to the input energy for a certain period of time, so a clear evaluation can be obtained and it is easy to understand. Since the temperature coefficient of the output of the solar cell used here is a value accurately obtained for each solar radiation intensity and solar cell temperature from the solar cell characteristic value, more accurate evaluation can be performed. In other words, the method based on the conversion efficiency after temperature correction can perform an evaluation that is not easily affected by the magnitude of solar radiation intensity and solar radiation fluctuation. (4) How much Pmax operation (MPPT
It is useful for investigating the cause when there is insufficient output because it can be evaluated whether it is running. This method has a feature that it can be evaluated almost unaffected by the magnitude of solar radiation intensity and fluctuation of solar radiation. (5) The pyranometer system and evaluation device / system of the present invention can be compactly constructed and are suitable for application in the field.

[0032]

[Brief description of drawings]

FIG. 1 is a flow chart of a solar cell output evaluation method in a field using an “IV curve tracer”.

FIG. 2 is a flow chart of a solar cell output evaluation method in an interconnected operation state.

FIG. 3 is a calculation flow chart of a temperature correction coefficient under a solar radiation intensity / solar cell temperature condition at the time of measurement when performing temperature correction of solar cell conversion efficiency.

FIG. 4 is a flowchart of an evaluation method of Pmax follow-up operation (MPPT operation) in an interconnected operation state.

FIG. 5 is a schematic diagram of a pyranometer system that outputs an evaluable time zone signal (evaluation availability signal).

[Fig. 6] Fig. 6 is a diagram of the mechanism of solar power generation.

FIG. 7 is a method for creating an I-V curve of the solar radiation intensity / solar cell temperature condition at the time of measurement by the “practical I-V curve creating method”.

FIG. 8 is a basic formula of a solar cell.

FIG. 9 is an example of an “IV curve tracer”.

FIG. 10 is an example of output by an “IV curve tracer”.

FIG. 11 is an IV curve and a PV curve of the solar cell.

FIG. 12 is a comparison / evaluation of the solar cell output under the measurement solar radiation intensity / solar cell temperature conditions.

FIG. 13 is a method for evaluating a solar cell for a certain period.

FIG. 14 is a list of equations for converting an I-V curve at a measurement insolation intensity / solar cell temperature into a reference state.

[Explanation of symbols]

Isc short-circuit current Iop optimum current Vop optimum voltage Voc open circuit voltage

Claims (11)

[Claims] 1. A solar cell characteristic value (Isc, Iop, Vop, Voc,
From α, β, Rs, K), create an I-V curve and PV curve in the standard condition (solar radiation intensity 1kW / m2, solar cell temperature 25 ° C), and enter the solar radiation intensity and solar cell temperature conditions during measurement. Then, convert to I-V curve and P-V curve under the conditions,
Solar cell output evaluation method characterized by evaluating solar cell output by comparing with IV curve and PV curve measured by "curve tracer" 2. A characteristic value of a solar cell (Isc, Iop, Vop, Voc,
From α, β, Rs, K), I-V curve and PV curve in standard special condition (solar radiation intensity 1kW / m2, solar cell temperature 25 ° C) are created, and the solar radiation intensity and solar cell temperature condition at the time of measurement are created. I
By converting the −V curve and the PV curve and comparing the maximum power value on the PV curve with the power value which is the product of the voltage and current value of the solar cell terminal measured in the interconnected operation state, Solar cell output evaluation method characterized by evaluating solar cell output 3. An average value / standard deviation (σ) of the output evaluation value (measured value / calculated value) of the solar cell calculated at constant intervals for a constant time, and the standard deviation (σ) is calculated. Is smaller than a constant value, the average value of the evaluation values is adopted as the evaluation value of the output in the time zone, 4. An average value / standard deviation (σ) of the output evaluation value (measured value / calculated value) of the solar cell calculated at a constant interval for a certain period of time, and the standard deviation (σ) is calculated. When the solar radiation intensity is larger than a certain value and the air mass (AM) is smaller than a certain value, the average value of the evaluation values shall be adopted as the output evaluation value for that time period. Output evaluation method characterized by 5. A solar cell output evaluation value (measured value / calculated value)
The multiple regression equation is created by taking the solar radiation intensity (W / m2) (represented by the clear sky index), air mass (AM), dew point temperature (° C) (represented by the amount of precipitable water) as explanatory variables for The solar cell output evaluation method, characterized in that the evaluation value calculated by substituting the conditions (solar radiation intensity 1000 W / m2, air mass 1.5) and the typical dew point temperature is used as the evaluation value of the solar cell. 6. A method of evaluating a solar cell output in an interconnected operation state, wherein a method of calculating a temperature coefficient when the conversion efficiency is corrected by the temperature at the time of measurement is {01} the solar cell characteristic value (Isc, Iop , Vop, Voc, α, β, Rs, K), typical solar radiation intensity (1000W / m2, at solar cell temperatures of 25 ℃ and 55 ℃)
800 W / m2, 500 W / m2, 300 W / m2, etc.) I-V curve and P-V curve are created, and the maximum solar cell output of each solar radiation intensity at {02} solar cell temperature 25 ℃ and 55 ℃ (Pmax)
And the temperature coefficient are calculated and the {03} solar cell temperature is 25 ° C and 55
Create a quadratic regression equation with the solar radiation intensity of the temperature coefficient at the solar cell maximum output (Pmax) at ℃ as an explanatory variable,
The value of the solar radiation intensity at the time of {04} measurement is entered into the regression equation for the solar cell temperatures of 25 ° C and 55 ° C created in {03}, and
Calculate the temperature coefficient of the solar radiation intensity at ℃, {05} {04}
Solar cell output evaluation method, characterized in that the temperature coefficient at the solar cell temperature at the time of measurement is obtained by linear interpolation from the temperature coefficients of 25 ° C and 55 ° C obtained in 7. The interconnected operation according to claim 3 or claim 4.
Using the measured values (solar intensity, solar cell temperature, solar cell voltage / current / power) during the time when the solar radiation fluctuations, etc. are stable, described in {06} Solar cell characteristic values (Isc, Iop, Vop, Voc ，
α, β, Rs, K), I-V curve in the standard state, P
-Create a V curve and I-in the above solar radiation intensity and solar temperature conditions
Converted to V-curve and P-V curve, {07} Voltage value (Vop ') at maximum power point of P-V curve created in {06} above
The ratio of the operating voltage V'to the electric power P '(V' * I ') at the time of measurement against the maximum output value (Pmax') of the P-V curve created in {08} above {06} And calculate Pmax
PV cell output evaluation method characterized by performing operation (MPPT operation) evaluation 8. An average value of measured values (solar radiation intensity, solar cell temperature, solar cell voltage / current / power) at fixed intervals (1 to 10 minutes, etc.) is obtained by using these values, and {09 } Characteristic value of solar cell (Isc, Iop, Vop, Voc,
α, β, Rs, K) to I-V curve in the standard state, P-
Create a V-curve and convert it to the I-V curve and PV curve of the above average solar radiation intensity and solar cell temperature conditions, {10} above {0
Calculate the ratio of the average voltage V "of the above measured values to the voltage value (Vop") at the maximum power point of the P-V curve created in 9}, and further create the PV curve created in {11} above {09}. Power P "(V" * I ") when measuring against the maximum power value (P" max) of
The output evaluation method of the solar cell, which is characterized by calculating the ratio of Pmax and performing Pmax operation (MPPT operation). 9. A short circuit current in which a short circuit current of the pyranometer and the solar cell and its temperature signal are fetched and the {12} solar cell short circuit current (Isc ') is corrected by the temperature and the temperature coefficient of the solar cell. (Isc ") is calculated, the ratio with the insolation intensity by the pyranometer is calculated, and the standard deviation of the ratio of {13} constant interval (1 to 10 minutes, etc.) for a certain period is calculated. When the solar radiation intensity is smaller than a certain value and the air mass (AM) is smaller than a certain value, the pyranometer system is characterized in that it outputs an evaluable time zone signal together with the solar radiation signal from the global pyranometer. 10. An “I-V curve tracer” including the solar cell output evaluation method and software according to claim 1. 11. A solar cell output evaluation device / system in an interconnected operation state including the solar cell output evaluation method / software according to claim 2, 3, 4, 5, 6, 7, and 8.