JP2005051014A - Computation method of photovoltaic power generation simulation and computer-readable data storage medium recording computation program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a computation method for calculating a more accurate monthly temperature coefficient using an I-V curve forming method that is more accurate and has higher general-purpose so as to provide a method of computing an annual photovoltaic power generation simulation using the monthly temperature coefficient. <P>SOLUTION: The monthly temperature coefficient is calculated using insolation intensity specified on the basis of an I-V curve in a reference condition and the method of forming an I-V curve at the temperature of a solar cell, and the annual solar power generation is calculated by the use of the above coefficient. The method of forming the I-V curve can be made by two ways, one is that basic characteristic values (IL, Co, n, Rsh, and Rs) at temperatures of 25°C, b°C, and c°C are obtained, the basic characteristic values at a designated temperature are obtained through curvilinear interpolation, values are obtained through a Newton's method using the above basic characteristic values to form the I-V curve, and the other is that the points on the I-V curve in the reference condition are converted through a practical I-V curve conversion formula to form the I-V curve. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

As shown in FIG. 8, the solar cell directly converts solar light energy into electric energy. That is, an electromotive force is generated by applying a photovoltaic effect which is a kind of photoelectric effect. When light (photon) having appropriate energy is incident on the solar cell, free electrons and holes are generated. Electrons and holes that have reached the vicinity of the pn junction in the solar cell semiconductor diffuse to the n-type semiconductor side and the p-type semiconductor side, respectively, and gather at both electrode parts, so that power can be taken out and voltage and current are generated. It is.
The present invention relates to a method for accurately and simply predicting (simulating) the annual power generation amount of a solar cell using the amount of solar radiation energy incident on the light receiving surface of the solar cell actually installed. Therefore, it is related with the method of calculating the monthly temperature coefficient correctly. For that purpose, it is necessary to draw an IV curve accurately from the solar radiation intensity, the solar cell temperature, and the solar cell characteristic value. Therefore, the present invention relates to a method for creating an IV curve and a PV curve in a solar cell, a monthly temperature coefficient calculation method using this method, and a photovoltaic power generation simulation calculation method.

As an example of annual simulation calculation of solar radiation energy received by the light receiving surface of the solar cell, the commissioned work result report of New Energy Development Organization (Japan Meteorological Association: “Study on technology for developing technology for practical application of photovoltaic power generation system” Development "Basic Survey on Power Generation" (1987)). However, this report is a calculation of the solar radiation energy on the light-receiving surface (inclined surface), and is not an accurate simulation calculation up to the power generation amount of the solar cell, and there are almost no such cases.
Examples of accurate simulation calculations up to the amount of power generation include a paper published by the present inventor, namely, the Institute of Electrical Engineers of Japan (Iga et al .: “Development of a simulation program for photovoltaic power generation using the IV curve creation method”, Academic theory D115 Vol.6, 1995). The reason why there is no accurate prediction calculation up to the power generation amount is that the technology for drawing the IV curve at the specified solar radiation intensity and solar cell temperature was not well established. The inventor has invented the “practical IV curve creation method” shown in the aforementioned IEEJ paper 1 as a technique for drawing this IV curve, and has already developed a simulation calculation method of the power generation amount to which this technique is applied.
On the other hand, as a method for easily calculating the annual power generation amount, a method of summing up the annual amount by multiplying the monthly solar radiation amount (KWh) by the solar cell rated output and the temperature coefficient is often implemented by solar cell manufacturers.

In view of the current state of the prior art as described above, a more versatile and accurate IV curve creation method is used to calculate a more accurate monthly temperature coefficient, which makes it easier to calculate annual photovoltaic power generation simulations. It is something to be implemented. Conventionally, the monthly temperature coefficient is generally 0.8 in summer, 0.9 in winter, and 0.85 in spring / autumn. However, this coefficient does not reflect the effects of regional differences, individual solar cell characteristic values, installation bases, etc. that have a large effect on power generation. Therefore, this coefficient that matches the actual situation is calculated and applied.
Therefore, in the present invention, in order to calculate this coefficient more accurately, as a method for creating an IV curve at a specified solar radiation intensity and solar cell temperature, the calculation target solar cell reference state (solar radiation intensity 1 KW / m ² , solar cell The basic characteristic value (IL, Co, n, Rsh) is obtained by solving the basic characteristic equation of the solar cell using the characteristic value (Isc, Iop, Vop, Voc, Rs) of the temperature 25 ° C, and the IV curve of the reference state Apply how to create.
That is, based on the IV curve in the reference state, the IV curve at the solar radiation intensity and solar cell temperature specified by the following two methods (1) and (2) is drawn.
(1) At an insolation intensity of 1 kw / m ² , create IV curves at other temperatures (b ° C, c ° C) from IV curves at the reference temperature (a ° C = 25 ° C), and obtain basic characteristic values (IL , Co, n, RsR, Rs), obtain the basic characteristic values at the specified temperature by curve interpolation, and then create an IV curve of the specified temperature and solar radiation intensity from these basic characteristic values.
(2) Convert each point on the IV curve in the standard state to the specified temperature and solar radiation intensity using the “Practical IV curve conversion formula”.

The annual photovoltaic power generation simulation calculation method according to claim 1 is:
Monthly power generation from the solar radiation intensity calculated from the solar radiation intensity / direct ratio, solar cell installation orientation / tilt angle, etc., and the outside air temperature / wind speed / photosensitive solar radiation at the target spot. Calculate and aggregate monthly, then
A monthly temperature coefficient is calculated in advance by dividing the monthly power generation amount (KWh) by the monthly light receiving surface solar radiation amount (KWh) and the solar cell rated capacity,
In the method of calculating the monthly photovoltaic power generation amount by multiplying the monthly temperature coefficient by the monthly light receiving surface solar radiation amount (KWh) and the solar cell rated capacity,
It is characterized by using the following method in the process of calculating the solar cell power from the solar radiation intensity of the solar cell light receiving surface, the solar cell temperature, and the solar cell characteristic value.
Solar cell basic formula
I = IL-IO * {exp (q (V + RsI) / nKoT) -1}-(V + RsI) / Rsh
IO = CoT ³ exp (-qEg / nKoT)
here,
I: Output current [A] Co: Saturation current temperature coefficient V: Output voltage [V] Eg: Energy gap [eV]
IL: Photovoltaic current [A] T: Solar cell element absolute temperature [K]
IO: Saturation current [A] Ko: Boltzmann constant [J / K]
Rs: DC resistance [Ω] q: Charge amount of electrons [C]
Rsh: Parallel resistance [Ω]
n: For each of the basic characteristic values (IL, Co, n, Rsh, Rs) in the junction constant, values of a ° C., b ° C., and c ° C. are obtained, and again using the solar cell basic formula, the respective a ° C., b ° C. The basic characteristics (IL, Co, n, Rsh, Rs) at the specified temperature are obtained by interpolating the values at c ° C, and the voltage-current curve (IV curve) at the specified solar radiation intensity and solar cell temperature is obtained. The method is to create and use the method of calculating the power at the Pmax point or specified voltage on this IV curve.
The solar power generation amount simulation calculation method according to claim 2 is based on the solar radiation intensity calculated from the solar radiation amount / direct ratio of the target point, the solar cell installation direction / tilt angle, and the outside temperature / wind speed / light receiving surface solar radiation of the target point. Calculate the monthly power generation amount from the solar cell temperature calculated from
A monthly temperature coefficient is calculated in advance by dividing the monthly power generation amount (KWh) by the monthly light receiving surface solar radiation amount (KWh) and the solar cell rated capacity,
In the method of calculating the monthly photovoltaic power generation amount by multiplying the monthly temperature coefficient by the monthly light receiving surface solar radiation amount (KWh) and the solar cell rated capacity,
It is characterized by using the following method in the process of calculating the solar cell power from the solar radiation intensity of the solar cell light receiving surface, the solar cell temperature, and the solar cell characteristic value.
Create a voltage-current curve in the standard state from the solar cell characteristic values (Isc, Iop, Vop, Voc). From this voltage-current curve, convert the solar radiation and temperature into the specified solar radiation intensity and the voltage at the specified solar battery temperature. Create a current curve (IV curve)
It is characterized by using a method of obtaining the power at the Pmax point or specified voltage on this IV curve.
The solar power generation simulation calculation method according to claim 3 is: Monthly average daily solar radiation amount / monthly average direct delivery ratio, solar cell installation azimuth / tilt angle, and latitude / longitude solar declination at the target location. Calculate monthly power generation amount by month from solar cell temperature by hour calculated from solar radiation intensity and outside temperature, wind speed, light receiving surface solar radiation at the target point,
Divide the monthly power generation amount (KWh) by the solar cell light receiving surface solar radiation amount per unit area (KWh / m ² ) and the solar cell rated capacity (kw / kw / m ² ) to calculate the monthly temperature coefficient in advance. ,next,
Calculate the monthly power generation by multiplying the monthly temperature coefficient by the amount of solar radiation on the light-receiving surface (KWh / m ² ) and the rated capacity of the solar cell (kw / kw / m ² ). In the way to
It is characterized in that the following method is used in the process of calculating the solar cell power from the solar radiation intensity of the solar cell light receiving surface, the solar cell temperature, and the solar cell characteristic value.
{01} Including voltage V, current I, photovoltaic current IL at solar radiation intensity 1 kw / m ² , saturation current temperature coefficient Co, junction constant n, parallel resistance Rsh, series resistance Rs, solar cell temperature T (absolute temperature) Function: Func (V, I, IL, Co, n, Rsh, Rs, T) = IL-CoT ³ exp (-qEg / nk0T) * (exp (q * (V + Rs * I) / (n * k0 * T)) -1)-(V + Rs * I) / Rsh-I, then
{02} A function obtained by differentiating the function Func (V, I, IL, Co, n, Rsh, Rs, T) with a variable V: Dif (V, I, IL, Co, n, Rsh, Rs, T) make,
{03} Solar cell reference condition (solar cell temperature Ta (298K (ta = 25 ° C)), solar radiation intensity Ea (1kw / m ² )), short circuit current Isca, optimum current Iopa-optimum voltage Select Vopa, open voltage Voca point P1 (0, Isca), P2 (Vopa, Iopa), P3 (Voca, 0),
{04} The function Func (V, I, IL, Co, n, Rsh, Rs, T) = 0 where T is the reference state temperature Ta (298 K), the series resistance Rs is the value Rsa at the reference temperature, and Substituting the values of the points P1, P2, P3 and IL, Co, n, Rsh as unknowns: Func (0, Isca, IL, Co, n, Rsh, Rsa, Ta) = 0,
Relational expression: Func (Voca, 0, IL, Co, n, Rsh, Rsa, Ta) = 0,
Formula: Func (Vopa, Iopa, IL, Co, n, Rsh, Rsa, Ta) = 0
{05} The function Dif (V, I, IL, Co, n, Rsh, Rs, T) = 0, the reference state temperature Ta (298 K), the series resistance Rs, the value Rsa at the reference temperature, and the point Substituting the value of P2 (Vopa, Iopa) and making IL, Co, n, Rsh unknown
Create a relation: Dif (Vopa, Iopa, IL, Co, n, Rsh, Rsa, Ta) = 0, then
{06} The four relational expressions: Func (0, Isca, IL, Co, n, Rsh, Rsa, Ta) = 0, Func (Voca, 0, IL, Co, n, Rsh, Rsa, Ta) = 0 , Func (Vopa, Iopa, IL, Co, n, Rsh, Rsa, Ta) = 0, Dif (Vopa, Iopa, IL, Co, n, Rsh, Rsa, Ta) = 0 satisfying solution A (ILa, Coa , na, Rsha) is calculated by a nonlinear solution program, then
{07} The function: Substituting the solution A (ILa, Coa, na, Rsha) into IL, Co, n, Rsh with Func (V, I, IL, Co, n, Rsh, Rs, T) = 0 Then, substitute the value Rsa for the reference state temperature Ta (298K) and the series resistance Rs for T, and the relational expression of variables V and I: Func (V, I, ILa, Coa, na, Rsha, Rsa, Ta ) = 0
{08} This equation is again solved by a non-linear solution program to obtain a solution of I for V of about 40-50 points, and voltage (V) -current (I) and voltage (V) -power (P) (power) in the reference state (P) = voltage (V) x current (I)) relationship points (about 40-50 points), voltage V-current I curve (IV curve), voltage V-power P connecting these points Create a curve (PV curve), then
{09} In order to obtain the solar cell solar radiation intensity Eb (here 1 kw / m ² ), solar cell temperature Tb (absolute temperature: TbK = tb (° C.) + 273), voltage Vb, and current Ib, In the solar radiation temperature Ea (1 kw / m ² ), solar cell temperature Ta (298 K: absolute temperature: Ta = ta + 273), short circuit current Isca, series resistance Rsa, fluctuation value of the short circuit current Isc when the temperature changes by 1 ° C. Conversion formula (Va, Ia) → (Vb, Ib) where α, fluctuation value β of open circuit voltage Voc when temperature changes by 1 ° C., and curve correction factor K:
Ib = Ia + α * (tb-ta)
Vb = Va + β * (tb-ta)-Rsa * (Ib-Ia)-K * Ib * (tb-ta) is created, and each voltage-current point created in {08} above or Each point on the IV curve connecting the points is used as the Ia and Va values, and the solar radiation temperature Eb (1 kw / m ² ) and each point at the solar cell temperature Tb (K) (voltage Vb-current Ib: about 40-50 points) And create IV and PV curves connecting these points.
{10} From the IV curve created in {09} above, select any five points that are not close to each other, and these points (VQ1, IQ1), (VQ2, IQ2), (VQ3, IQ3), (VQ4, IQ4 ), (VQ5, IQ5) are substituted into variables V, I of the above relational expression: Func (V, I, IL, Co, n, Rsh, Rs, Tb) = 0, and IL, Co, n, Rsh , Rs as unknown
Relational expression: Func (VQ1, IQ1, IL, Co, n, Rsh, Rs, Tb) = 0,
Relational expression: Func (VQ2, IQ2, IL, Co, n, Rsh, Rs, Tb) = 0,
Relational expression: Func (VQ3, IQ3, IL, Co, n, Rsh, Rs, Tb) = 0,
Relational expression: Func (VQ4, IQ4, IL, Co, n, Rsh, Rs, Tb) = 0,
Relational expression: Func (VQ5, IQ5, IL, Co, n, Rsh, Rs, Tb) = 0 is created, and the solution B (ILb, Cob, nb, Rshb, Rsb) of the five relational expressions is generated by a nonlinear solution method. And then
{11} The relationship between the voltage Vc and the current Ic at the solar radiation intensity Ec (here 1 kw / m ² ) and solar cell temperature Tc (absolute temperature: Tc (K) = tc (° C.) + 273) 09},
Conversion formula (Va, Ia) → (Vc, Ic):
Ic = Ia + α * (tc-ta)
Create IV and PV curves using Vc = Va + β * (tc-ta)-Rsa * (Ic-Ia)-K * Ic * (tc-ta)
{12} Select any five points that are not close to each other on the IV curve created in {11}, and these values (VR1, IR1), (VR2, IR2), (VR3, IR3), (VR4, IR4) , (VR5, IR5) is substituted into variables V and I of the relational expression: Func (V, I, IL, Co, n, Rsh, Rs, Tc) = 0, and IL, Co, n, Rsh, Rs Is an unknown,
Relational expression: Func (VR1, IR1, IL, Co, n, Rsh, Rs, Tc) = 0,
Relational expression: Func (VR2, IR2, IL, Co, n, Rsh, Rs, Tc) = 0,
Relational expression: Func (VR3, IR3, IL, Co, n, Rsh, Rs, Tc) = 0,
Relational expression: Func (VR4, IR4, IL, Co, n, Rsh, Rs, Tc) = 0,
Relational expression: Func (VR5, IR5, IL, Co, n, Rsh, Rs, Tc) = 0
And the solution C (ILc, Coc, nc, Rshc, Rsc) of the five relational expressions is calculated by a non-linear solution program,
{13} Incorporates the specified solar radiation intensity Em and solar cell temperature tm (ie at each time of the month)
{14} The solution A (ILa, Coa, na, Rsha) of {06} at the temperature ta (25 ° C .: absolute temperature Ta (K) = ta (° C.) + 273) in the reference state, the temperature tb ( Celsius: Tb = tb + 273) {10} solution B (ILb, Cob, nb, Rshb, Rsb), temperature tc (Celsius: Tc = tc + 273), {12} solution C (ILc, Coc, nc) , Rshc, Rsc) and the input value Rsa (IL, Co, n, Rsh, Rs) are interpolated at three points, and the characteristic value M at the specified temperature tm (ILm, Com, nm, Rshm, Rsm) And then
After correction by {15} IL by irradiance Em actually measured the ^{ILm 'm = ILm × Em ÷} Ea (Ea = 1 (KW / m 2), the relationship: Func (V, I, IL , Co, n ′, Rsh, Rs, T) = 0 and IL ^′ m, Com, nm, Rshm, Rsm is substituted, and Func (V, I, IL ^′ m, Com, nm, Rshm, Rsm, Tm) = 0 Create a voltage (V) -current (I) relationship (about 40-50 points) using a nonlinear solution program, and the relationship between the voltage (V) -current (I) or the IV curve and PV curve connecting them. Create
{16} Obtain the power at the Pmax point on this IV curve or the voltage specified as a parameter. {17} Using this value as the power value for each month time, the monthly and annual total is calculated to obtain the monthly and annual power generation. It is characterized by seeking.
The photovoltaic power generation amount simulation calculation method according to claim 4 is:
Monthly average daily irradiance of the target site, monthly average direct rate, solar cell installation direction / tilt angle, monthly solar radiation intensity calculated from the longitude and latitude and solar latitude, and the outside temperature, wind speed, Calculate the amount of power generation by time from the solar cell temperature by month calculated from the solar radiation on the light-receiving surface, total the month,
Divide the monthly power generation amount (KWh) by the solar cell light receiving surface solar radiation amount per unit area (KWh / m ² ) and the solar cell rated capacity (kw / kw / m ² ) to calculate the monthly temperature coefficient in advance. ,next,
Calculate the monthly power generation by multiplying the monthly temperature coefficient by the amount of solar radiation on the light-receiving surface (KWh / m ² ) and the rated capacity of the solar cell (kw / kw / m ² ). In the way to
It is characterized in that the following method is used in the process of calculating the solar cell power from the solar radiation intensity of the solar cell light receiving surface, the solar cell temperature, and the solar cell characteristic value.
{18} Incorporates the specified solar radiation intensity Em and solar cell temperature tm (ie at each time of the month)
{19} With respect to the voltage Va−current Ia value (about 40 to 50 points) in the reference state (intensity of solar radiation 1 kw / m ² , solar cell temperature 25 ° C.) created by the above {01} to {08}, {09} Using Isca, α, β, Rsa, k, the conversion formula (Va, Ia) → (Vk, Ik):
Ik = Ia + Isca * (Em / Ea-1) + α * (tm-ta)
Vk = Va + β * (tm-ta)-Rsa * (Ik-Ia)-K * Ik * (tm-ta)
To create these voltage V-current I values or the IV curve and PV curve connecting them,
{20} Obtain power at the Pmax point on this IV curve or power at the voltage specified as a parameter, and use this value as the power value for each month's time to calculate the monthly and annual power generation. It is characterized by.
The computer-readable data storage medium storing the processing program of the photovoltaic power generation amount simulation calculation method according to claim 5 is the processing program capable of executing these methods according to claims 1, 2, 3, and 4. It is characterized by including.

The features of claims 1, 2, 3 and 4 are that the annual power generation amount can be calculated easily and accurately by using the monthly temperature coefficient.
In addition, the features of claims 1, 2, 3 and 4 are not limited to specific single crystal solar cells, and other single crystals, polycrystals, amorphous solar cells, etc., have the specified solar radiation intensity and solar cell temperature. The IV curve is versatile and can be created accurately, and the amount of power generated by the solar cell can be accurately simulated.
In addition, the features of claims 1 and 3 are the same as in claims 2 and 4, and the power generation amount of the solar cell can be calculated by simulation, and the solar radiation intensity is 1 KW / m ² at other temperatures. When characteristic values (for example, Isc, Iop, Vop, Voc, etc. at 55 ° C, etc.) are given, by using these values, the specified solar radiation intensity can be obtained even if α, β, Rs, K cannot be obtained.・ The IV curve of the solar cell temperature can be created, and the simulation calculation of the power generation can be performed.
The feature of claim 5 is that it can be read by a computer from a storage medium in which a simulation calculation program for solar radiation and power generation according to claims 1, 2, 3, and 4 is recorded. Simulation calculation is possible, and it is directly useful for a wide range of applications such as the design and operation of photovoltaic power generation systems.

Here, matters and terms relating to the present invention will be described.
First, in order to understand the overall calculation of the annual solar power generation amount, an outline of the solar power generation amount simulation calculation program already developed by the present inventors will be described (see IEEJ Paper 1). Fig. 3 shows a block diagram of the photovoltaic power generation simulation calculation program. Three subprograms: (1) (solar cell) light-receiving surface solar energy calculation subprogram, (2) solar cell (module) temperature calculation Subprogram, and (3) Solar cell output calculation subprogram.

(1) The feature of the solar energy calculation subprogram on the light-receiving surface is
-The base of calculation time includes solar cell calculation calculation described later, so that the solar radiation amount of the specified period of solar cells installed at arbitrary points, tilt / azimuth and various tracking method solar cells can be calculated accurately, 30 minutes.
-As shown in Fig. 4, the solar cell light receiving surface solar radiation amount is divided into a direct horizontal light component and a scattered light component, and the light receiving surface solar radiation intensity is calculated by a method with high calculation accuracy for each. In addition, the amount of solar radiation on the light-receiving surface of the sun is determined in a comprehensive manner including the amount of solar radiation reflected on the ground.
In order to calculate the monthly average hourly solar radiation amount from the monthly average-daily total solar radiation amount, it is obtained by a method with high calculation accuracy as shown in the following procedure (see FIG. 5).
a. Find the sunrise and sunset times on the 15th of each month.
b. A of y = a * sin (π / to * t) is determined so that the monthly average-daily total solar radiation amount becomes the area of the basic sine curve (the hatched portion in FIG. 5). However t ₀ is - the time (day entry sunrise).
c. Y = b * sin ((2π / to) * t-π / 2) + b so that the monthly average-daily total solar radiation amount is the area of the sine curve with the period doubled (the vertical hatching in FIG. 5) B of d. The value of y at each time is obtained from the equation of the basic sine curve (above b) and the sine curve having the cycle twice (above c), and the average value is used as the solar radiation intensity at each time.

(2) The characteristics of the solar cell module temperature calculation subprogram are:
・ Input the solar radiation intensity at the light receiving surface for each month average time calculated in (1) above (every 30 minutes: the same applies below), the outside temperature for each month average time calculated from the monthly average maximum outside temperature / minimum outside temperature, and the wind speed. Using the value, the solar cell (module) temperature is obtained by the multiple regression equation.

  (3) As described above, the solar cell output calculation subprogram is characterized by creating an IV curve for each month and each time based on the IV curve of a specific sun as described in the paper of the Institute of Electrical Engineers of Japan at the most. Yes. The present invention provides a general-purpose IV curve creation method that is not limited to a specific type of solar cell, and a solar cell power generation simulation calculation method using the method.

Next, terms etc. will be explained.
The temperature of the solar cell is generally referred to as “solar cell module temperature”, but is shortened in the present invention and is also referred to as “solar cell temperature”. This temperature is usually measured by a thermocouple embedded in the solar cell module. The solar cell is called by the name of cell → module → array depending on the stage of its configuration.

○ Regarding symbols used for solar cell temperature, t (° C) in lower case indicates Celsius and T (K) in upper case indicates absolute temperature. That is, T (K) = t (° C.) + 273. The capital letter T is mainly used in the solar cell basic formula, and t is used elsewhere.

○ For solar cell output and power generation amount, the product of the instantaneous generation voltage V of the solar cell and the instantaneous generation current I is called the solar cell output (unit W or KW), and the time integrated value is the power generation amount (unit wh Or kwh).

○ The basic characteristic formula of the solar cell is the following formula.
I = IL-Co * T ³ * exp (-qEg / nKoT) * (exp (q (V + RsI) / nKoT) -1)-(V + RsI) / Rsh
Here, each symbol is as follows.
I: Output current [A] Co: Saturation current temperature coefficient V: Output voltage [V] Eg: Energy gap [eV]
IL: Photovoltaic current [A] T: Solar cell element absolute temperature [K]
IO: Saturation current [A] Ko: Boltzmann constant [J / K]
Rs: DC resistance [Ω] q: Charge amount of electrons [C]
Rsh: Parallel resistance [Ω]
n: Junction constant The above formula is a theoretical formula based on the basic formula of the semiconductor. To find each point on the IV curve from this equation, move I on the left side of this equation to the right side.
Func (V, I, IL, Co, n, Rsh, Rs, T)
= IL-Co * T ³ * exp (-qEg / nKoT) * (exp q (V + RsI) / nKoT-1)-(V + RsI) / Rsh-I
The relationship between V and I is solved by a nonlinear solution program after substituting the values of basic characteristic values (IL, Co, n, Rsh, Rs). Refer to IEEJ Paper 2 (Iga: “Method of Creating IV Curve Using Voltage-Current Characteristic Equation in Light Irradiation State of Solar Cell and Its Utilization”, Electrical Engineering D116 Volume 10, No. 1996)

In the present invention, the characteristic values are properly used as follows.
The basic characteristic value is a basic characteristic in the basic formula of the solar cell.
(1) (Solar cell) Basic characteristic values: IL, Co, n, Rsh, Rs
(2) (Solar cell) Characteristic value ... Isc, Iop, Vop, Voc, α, β, Rs, K
As described above, Rs is used in both (1) and (2).

○ The conversion formula is as follows.
(1) "Practical IV curve conversion formula"
I1 = I2 + Isc (E1 / (E2) -1) + α (t1-t2)
V1 = V2 + β (t1-t2) -Rs (I1-I2) -K * I1 * (t1-t2)
(2) Inversion formula of “practical IV curve transformation formula” (inverse application)
(This is a modified version of V2 and I2 in equation (1))
I2 = I1 + Isc (E2-E1) / E2 + α (t2-t1)
V2 = V1 + β (t2-t1) -Rs (I2-I1) -K * I1 * (t2-t1)
Here, (1) and (2) are new and excellent formulas different from the commonly known formulas of JIS8913, 8914, and 8919. The equation (1) is used in Japanese Patent Application No. 6-2626 and the IEEJ Paper 1 (see FIG. 9).
Further, the symbols used in these equations are V2, I2, E2, and t2, respectively, for the voltage value, current value, solar radiation intensity, and solar cell temperature in the reference state. In addition, the voltage value, current value, solar radiation intensity, and solar cell temperature in the designated state are V1, I1, E1, and t1.
Α: Fluctuation value of Isc when temperature changes by 1 ° C (A / ° C)
β: Fluctuation value of Voc when the temperature changes by 1 ° C (V / ° C)
Rs: Module series resistance (Ω)
K: Curve correction factor (Ω)
Isc: Short circuit current
Top: Optimum current
Vop: Optimum voltage
Voc: Release voltage.
FIG. 9 shows a list of voltage-current value conversion formulas under the reference state voltage-current value and measurement-time solar radiation intensity / solar cell temperature conditions.
The lower columns (1) and (2) in FIG. 9 are “practical IV curve conversion equations”, and the right columns (3) and (4) in FIG. 9 are “practical IV curve conversion equations”. This corresponds to the inverse transformation formula of
This figure was published in IEEJ Paper 3 (Iga: “Polar Solar Radiation Meter Using a Practical IV Curve Preparation Method”, Electrotechnical D, Vol. 117, No. 10, 1997). In the author's formula, the lower column is a patent application filed in Japanese Patent Application No. 6-2626 prior to publication of the paper. In general, the leftmost or middle column formula may still be used.
FIG. 7 shows the relationship between the voltage V and the current value I of the solar cell in the state of receiving sunlight.
As shown in FIG. 7, the voltage-current value relationship curve is called an IV curve (or IV curve), and the voltage-power value relationship curve is called a PV curve (or PV curve). The voltage (Vop) at the maximum power (Pmax) is called the optimum voltage, and the current (Iop) at that time is called the optimum current.

By calculating the monthly temperature coefficient for each region, solar cell characteristic value, solar cell stand, etc. in advance by the method of claims 1, 2, 3, and 4, an accurate annual power generation amount can be easily calculated.
In addition, the following effects can be expected by the method of creating an IV curve at the specified solar radiation intensity and solar cell temperature by the IV curve creating method of claims 1, 2, 3 and 4, and calculating the amount of photovoltaic power generation by simulation.
(1) In general, not only a specific type or a specific solar cell, but also the characteristic values (Isc, Iop, Vop, Voc, Rs, α, β, K) of the solar cell are input and used. The monthly and annual power generation of the system can be calculated accurately. In other words, the amount of power generation can be accurately calculated according to the type, installation location, solar cell stand, etc. of the applied solar cell, which is useful for designing and operating an effective solar power generation system.
(2) By combining the above-mentioned “photovoltaic power generation simulation calculation program (The Institute of Electrical Engineers of Japan paper 1)” and the present invention into a system, it is possible to calculate a more accurate and accurate power generation amount. The quantity simulation calculation becomes more effective.
(3) In the simulation calculation of photovoltaic power generation, detailed and accurate calculation compared with the method of calculating the power generation amount by multiplying the calculated value of the solar radiation amount of the light receiving surface by conversion efficiency, which has been carried out in most places. Therefore, deeper and more detailed analysis is possible. That is, detailed evaluation of the effect by the parameter is also possible.
(4) The method described in (1), (2) and (3) above is used in the method of creating an IV curve for the specified solar radiation intensity and solar cell temperature in claims 1 and 3 and calculating the photovoltaic power generation by simulation. In addition, even if all the characteristic values of solar cells (Isc, Iop, Vop, Voc, α, β, Rs, K) are not available, that is, IV at a temperature other than the reference temperature (25 ° C) (eg 55 ° C) Calculation may be possible if curves, Isc, Iop, Vop, and Voc values are obtained.
In claim 5, it is easy to put a program by a photovoltaic power generation amount simulation calculation method including an IV curve creation method according to claims 1, 2, 3 and 4 into a recording medium and read and calculate by a computer when necessary. Therefore, it is widely useful for the design, construction and operation of photovoltaic power generation systems.

Next, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a flowchart for calculating the monthly temperature coefficient. Here, in the power generation amount calculation program according to the monthly average time, not only the IV curve creation method according to the present invention but also a method already developed by the present inventors may be applied. In addition, if there is publicly available data for the portion surrounded by a broken line in the figure, the data may be utilized.
FIG. 2 illustrates a “method for creating an IV curve of specified solar radiation intensity / solar cell temperature” which is one of the core parts of the photovoltaic power generation simulation calculation method of the present embodiment.
The solar cell characteristic values (Isc, Iop, Vop, Voc, α, β, Rs, K) are input at S11, the constants (Eg, Ko, e) are input at S12, and the solar cell reference state (S13) Basic characteristic values (IL, Co, n, Rsh) at solar radiation intensity 1kw / m ² and solar cell temperature 25 ° C)
I = IL-Co * T ³ exp (-qEg / nKoT) * (exp (q (V + RsI) / nKoT) -1)-(V + RSI) / Rsh
Find by solving. That is, by substituting the characteristic values (Isc, Iop, Vop, Voc) given to the basic characteristic equation, four nonlinear simultaneous equations are created and solved.
Assuming that the obtained basic characteristic values are ILa, Coa, na, and Rsha, in S14, these basic characteristic values are substituted again into the above-mentioned solar cell basic characteristic expression, and a relational expression between the voltage V and the current I is obtained. In this relational expression, the current I with respect to the voltage V is obtained by solving this characteristic expression, the relation of IV is obtained, and the IV curve of the reference state is created.

  In S15, the “practical I-V curve conversion formula” is applied to each point on the I-V curve created in S14 to obtain the I-V curve (S19) at the specified solar radiation intensity and the specified solar cell temperature.

On the other hand, in S16, the solar radiation intensity remains at 1 kw / m ² , and IV curves at temperatures other than 25 ° C. at b ° C. and c ° C. are obtained by “practical IV curve conversion formula”.
For S20, values of 5 to 8 points on the IV curve at b ° C. are used, and the basic characteristic values IL, Co, n, Rsh, and Rs are obtained by solving the basic characteristic equation. In S21, the basic characteristic value at c ° C. is similarly obtained. In S22, the basic characteristic value at the designated solar cell temperature is obtained from the basic characteristic values at 25 ° C., b ° C., and c ° C. by curve interpolation.

The basic characteristic value IL at the specified voltage obtained here is corrected for solar radiation intensity. In S23, the basic characteristic value obtained in this way is applied to the basic characteristic expression of the solar cell to obtain the relationship between the voltage V and the current I, that is, the IV curve.
FIG. 3 is a block diagram of a “photovoltaic power generation simulation calculation program” developed by the present inventor and has already been shown in IEEJ paper 1. As described above, the “method of creating an IV curve at a specified solar radiation intensity / solar cell temperature”, which is a core part of the present invention, is incorporated in the “solar cell output calculation subprogram”.

  FIG. 4 and FIG. 5 explain characteristic functions included in the “photovoltaic power generation simulation program”.

  FIG. 6 is a diagram of a data storage medium and a computer on which a “photovoltaic power generation simulation calculation program” including the present invention is recorded.

It is a flowchart of monthly temperature coefficient calculation. It is a block diagram of an IV curve creation method of specified solar radiation intensity and solar cell temperature. It is a block diagram of a photovoltaic power generation amount simulation calculation program (developed). It is a calculation flow figure of the solar cell light-receiving surface solar radiation amount. It is a solar radiation amount curve creation figure according to monthly average time. It is a figure of the data storage medium and computer which recorded the photovoltaic power generation amount simulation calculation program. It is a solar cell output characteristic curve (I-V curve, P-V curve). It is a diagram of how solar power generation works. This is the conversion formula of the voltage V-current value I at the solar radiation intensity and solar cell temperature at the time of measurement to the standard state (The Institute of Electrical Engineers of Japan: “Solar cell solarimeter using a practical IV curve creation method, Electrical theory D 117, No.10, 1997)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Computer main body 2 Keyboard 3 Mouse 4 Monitor 5 Storage medium 17 Computer

Claims (5)

Monthly power generation from the solar radiation intensity calculated from the solar radiation intensity / direct ratio, solar cell installation orientation / tilt angle, etc., and the outside air temperature / wind speed / photosensitive solar radiation at the target spot. Calculate and aggregate monthly, then
A monthly temperature coefficient is calculated in advance by dividing the monthly power generation amount (KWh) by the monthly light receiving surface solar radiation amount (KWh) and the solar cell rated capacity,
In the method of calculating the monthly photovoltaic power generation amount by multiplying the monthly temperature coefficient by the monthly light receiving surface solar radiation amount (KWh) and the solar cell rated capacity,
In the process of calculating solar cell power from the solar radiation intensity of the solar cell light receiving surface, the solar cell temperature and the solar cell characteristic value,
Solar cell basic formula
I = IL-IO * {exp (q (V + RsI) / nKoT) -1}-(V + RsI) / Rsh
IO = CoT ³ exp (-qEg / nKoT)
here,
I: Output current [A] Co: Saturation current temperature coefficient V: Output voltage [V] Eg: Energy gap [eV]
IL: Photovoltaic current [A] T: Solar cell element absolute temperature [K]
IO: Saturation current [A] Ko: Boltzmann constant [J / K]
Rs: DC resistance [Ω] q: Charge amount of electrons [C]
Rsh: Parallel resistance [Ω]
n: For each of the basic characteristic values (IL, Co, n, Rsh, Rs) in the junction constant, obtain values of a ° C., b ° C., and c ° C.,
Interpolate the values at a ° C, b ° C, and c ° C to obtain the basic characteristics (IL, Co, n, Rsh, Rs) at the specified temperature, and again use the solar cell basic formula to specify the solar radiation intensity. An annual photovoltaic power generation simulation calculation method characterized by using a method of creating a voltage-current curve (IV curve) at a solar cell temperature and obtaining power at a Pmax point or a specified voltage on the IV curve. Monthly power generation from the solar radiation intensity calculated from the solar radiation intensity / direct ratio, solar cell installation orientation / tilt angle, etc., and the outside air temperature / wind speed / photosensitive solar radiation at the target spot. Calculate and aggregate monthly, then
A monthly temperature coefficient is calculated in advance by dividing the monthly power generation amount (KWh) by the monthly light receiving surface solar radiation amount (KWh) and the solar cell rated capacity,
In the method of calculating the monthly photovoltaic power generation amount by multiplying the monthly temperature coefficient by the monthly light receiving surface solar radiation amount (KWh) and the solar cell rated capacity,
In the process of calculating solar cell power from the solar radiation intensity of the solar cell light receiving surface, the solar cell temperature and the solar cell characteristic value,
Create a voltage-current curve in the standard state from the solar cell characteristic values (Isc, Iop, Vop, Voc). From this voltage-current curve, convert the solar radiation and temperature into the specified solar radiation intensity and the voltage at the specified solar battery temperature. Create a current curve (IV curve)
An annual photovoltaic power generation simulation calculation method characterized by using a method of obtaining power at a Pmax point or a specified voltage on the IV curve. Monthly average daily solar radiation amount / monthly average direct rate, solar cell installation direction / tilt angle, longitude / latitude, solar declination calculated from the time of day, and the outside temperature / wind speed of the target point.・ Calculate the amount of power generation by time from the solar cell temperature by month calculated from the solar radiation on the light receiving surface and total the month,
Calculate the monthly temperature coefficient by dividing the monthly power generation (KWh) by the solar cell light receiving surface solar radiation (KWh / m ² ) and solar cell rated capacity (kw / kw / m ² ) per unit area, ,
Calculate the monthly power generation by multiplying the monthly temperature coefficient by the amount of solar radiation on the light-receiving surface (KWh / m ² ) and the rated capacity of the solar cell (kw / kw / m ² ). In the way to
In the process of calculating solar cell power from the solar radiation intensity of the solar cell light receiving surface, the solar cell temperature and the solar cell characteristic value,
{01} Including voltage V, current I, photovoltaic current IL at solar radiation intensity 1 kw / m ² , saturation current temperature coefficient Co, junction constant n, parallel resistance Rsh, series resistance Rs, solar cell temperature T (absolute temperature) Function: Func (V, I, IL, Co, n, Rsh, Rs, T) = IL-CoT ³ exp (-qEg / nk0T) * (exp (q * (V + Rs * I) / (n * k0 * T)) -1)-(V + Rs * I) / Rsh-I, then
{02} A function obtained by differentiating the function Func (V, I, IL, Co, n, Rsh, Rs, T) with a variable V: Dif (V, I, IL, Co, n, Rsh, Rs, T) make,
{03} Solar cell reference conditions (solar cell temperature Ta (298K (ta = 25 ° C)), solar radiation intensity Ea (1kw / m ² )), short circuit current Isca, optimum current Iopa-optimum voltage Select Vopa, open voltage Voca point P1 (0, Isca), P2 (Vopa, Iopa), P3 (Voca, 0),
{04} The function Func (V, I, IL, Co, n, Rsh, Rs, T) = 0, the solar cell temperature T, the reference state temperature Ta (298 K), the series resistance Rs, the value Rsa at the reference temperature , And the values of the points P1, P2, P3, and IL, Co, n, Rsh as an unknown relational expression: Func (0, Isca, IL, Co, n, Rsh, Rsa, Ta) = 0 ,
Relational expression: Func (Voca, 0, IL, Co, n, Rsh, Rsa, Ta) = 0,
Formula: Func (Vopa, Iopa, IL, Co, n, Rsh, Rsa, Ta) = 0
{05} The function Dif (V, I, IL, Co, n, Rsh, Rs, T) = 0, the reference state temperature Ta (298 K), the series resistance Rs, the value Rsa at the reference temperature, and the point Substituting the value of P2 (Vopa, Iopa) and making IL, Co, n, Rsh unknown
Create a relation: Dif (Vopa, Iopa, IL, Co, n, Rsh, Rsa, Ta) = 0, then
{06} The four relational expressions: Func (0, Isca, IL, Co, n, Rsh, Rsa, Ta) = 0, Func (Voca, 0, IL, Co, n, Rsh, Rsa, Ta) = 0 , Func (Vopa, Iopa, IL, Co, n, Rsh, Rsa, Ta) = 0, Dif (Vopa, Iopa, IL, Co, n, Rsh, Rsa, Ta) = 0 satisfying solution A (ILa, Coa , na, Rsha) is calculated by a nonlinear solution program, then
{07} The function: Substituting the solution A (ILa, Coa, na, Rsha) into IL, Co, n, Rsh with Func (V, I, IL, Co, n, Rsh, Rs, T) = 0 Then, substitute the value Rsa for the reference state temperature Ta (298K) and the series resistance Rs for T, and the relational expression of variables V and I: Func (V, I, ILa, Coa, na, Rsha, Rsa, Ta ) = 0
{08} This equation is again solved by a non-linear solution program to obtain a solution of I for V of about 40-50 points, and voltage (V) -current (I) and voltage (V) -power (P) (power) in the reference state (P) = voltage (V) x current (I)) relationship points (about 40-50 points), voltage V-current I curve (IV curve), voltage V-power P connecting these points Create a curve (PV curve), then
{09} In order to obtain the solar radiation intensity Eb (here 1 kw / m ² ), solar cell temperature Tb (absolute temperature: Tb (K) = tb (° C.) + 273) of the solar cell, the solar cell Solar radiation intensity Ea (1 kw / m ² ) in the standard state of the battery, short circuit current Isca, series resistance Rsa at the solar cell temperature Ta (298 K: absolute temperature: Ta = ta + 273), the short circuit current Isc when the temperature changes by 1 ° C. Conversion formula (Va, Ia) → (Vb, Ib), where the fluctuation value α of the current, the fluctuation value β of the open circuit voltage Voc when the temperature changes by 1 ° C., and the curve correction factor K:
Ib = Ia + α * (tb-ta)
Vb = Va + β * (tb-ta)-Rsa * (Ib-Ia)-K * Ib * (tb-ta) is created, and each voltage-current point created in {08} above or Each point on the IV curve connecting the ^two is used as the Ia and Va values, and the solar radiation temperature Eb (here 1 kw / m ² ), each point at the solar cell temperature Tb (K) (voltage Vb-current Ib: about 40-50 Point), create an IV curve and PV curve connecting these points, and then
{10} From the IV curve created in {09} above, select any five points that are not close to each other, and these points (VQ1, IQ1), (VQ2, IQ2), (VQ3, IQ3), (VQ4, IQ4 ), (VQ5, IQ5) are substituted into variables V, I of the above relational expression: Func (V, I, IL, Co, n, Rsh, Rs, Tb) = 0, and IL, Co, n, Rsh , Rs as unknown
Relational expression: Func (VQ1, IQ1, IL, Co, n, Rsh, Rs, Tb) = 0,
Relational expression: Func (VQ2, IQ2, IL, Co, n, Rsh, Rs, Tb) = 0,
Relational expression: Func (VQ3, IQ3, IL, Co, n, Rsh, Rs, Tb) = 0,
Relational expression: Func (VQ4, IQ4, IL, Co, n, Rsh, Rs, Tb) = 0,
Relational expression: Func (VQ5, IQ5, IL, Co, n, Rsh, Rs, Tb) = 0 is created, and the solution B (ILb, Cob, nb, Rshb, Rsb) of the five relational expressions is generated by a nonlinear solution method. And then
{11} The relationship between the voltage Vc and the current Ic at the solar radiation intensity Ec (here 1 kw / m ² ) and solar cell temperature Tc (absolute temperature: Tc (K) = tc (° C.) + 273) 09},
Conversion formula (Va, Ia) → (Vc, Ic):
Ic = Ia + α * (tc-ta)
Create IV and PV curves using Vc = Va + β * (tc-ta)-Rsa * (Ic-Ia)-K * Ic * (tc-ta)
{12} Select any five points that are not close to each other on the IV curve created in {11}, and these values (VR1, IR1), (VR2, IR2), (VR3, IR3), (VR4, IR4) , (VR5, IR5) is substituted into variables V and I of the relational expression: Func (V, I, IL, Co, n, Rsh, Rs, Tc) = 0, and IL, Co, n, Rsh, Rs Is an unknown,
Relational expression: Func (VR1, IR1, IL, Co, n, Rsh, Rs, Tc) = 0,
Relational expression: Func (VR2, IR2, IL, Co, n, Rsh, Rs, Tc) = 0,
Relational expression: Func (VR3, IR3, IL, Co, n, Rsh, Rs, Tc) = 0,
Relational expression: Func (VR4, IR4, IL, Co, n, Rsh, Rs, Tc) = 0,
Relational expression: Func (VR5, IR5, IL, Co, n, Rsh, Rs, Tc) = 0
And the solution C (ILc, Coc, nc, Rshc, Rsc) of the five relational expressions is calculated by a non-linear solution program,
{13} Incorporates the specified solar radiation intensity Em and solar cell temperature tm (ie at each time of the month)
{14} The solution A (ILa, Coa, na, Rsha) of {06} at the temperature ta (25 ° C .: absolute temperature Ta (K) = ta (° C.) + 273) in the reference state, the temperature tb ( ° C: solution B (ILb, Cob, nb, Rshb, Rsb) of {10} at Tb (K) = tb (° C) +273), solution of {12} at temperature tc (Celsius: Tc = tc + 273) C (ILc, Coc, nc, Rshc, Rsc) and input value Rsa (IL, Co, n, Rsh, Rs) are interpolated at three points, and characteristic value M (ILm, Com at specified temperature tm) is interpolated. , nm, Rshm, Rsm), then
{15} after correction by IL ^'m = ILm × Em by the specified irradiance Em a ÷ Ea (Ea = 1 (KW / m 2)) ILm, the relationship: Func (V, I, IL , Co , n, Rsh, Rs, T) = 0, substitute IL ^′ m, Com, nm, Rshm, Rsm and Func (V, I, IL ^′ m, Com, nm, Rshm, Rsm, Tm) = 0 The voltage (V) -current (I) relationship (about 40-50 points) is obtained by a nonlinear solution program, and the voltage (V) -current (I) relationship or the IV curve, PV Create a curve
{16} An annual photovoltaic power generation simulation calculation method using a method of obtaining the power at the Pmax point on the IV curve or the voltage specified as a parameter. Monthly average daily irradiance of the target site, monthly average direct rate, solar cell installation direction / tilt angle, monthly solar radiation intensity calculated from the longitude and latitude and solar latitude, and the outside temperature, wind speed, Calculate the amount of power generation by time from the solar cell temperature by month calculated from the solar radiation on the light-receiving surface, total the month,
Calculate the monthly temperature coefficient by dividing the monthly power generation (KWh) by the solar cell light receiving surface solar radiation (KWh / m ² ) and solar cell rated capacity (kw / kw / m ² ) per unit area, ,
Calculate the monthly power generation by multiplying the monthly temperature coefficient by the amount of solar radiation on the light-receiving surface (KWh / m ² ) and the rated capacity of the solar cell (kw / kw / m ² ). In the way to
In the process of calculating solar cell power from the solar radiation intensity of the solar cell light receiving surface, the solar cell temperature and the solar cell characteristic value,
{17} Incorporates the specified solar radiation intensity Em and solar cell temperature tm (ie at each time of the month)
{18} With respect to the voltage Va-current Ia value (about 40 to 50 points) in the reference state (intensity of solar radiation 1 kw / m ² , solar cell temperature 25 ° C.) prepared by {01} to {08}, {09} Using Isca, α, β, Rsa, k, the conversion formula (Va, Ia) → (Vk, Ik):
Ik = Ia + Isca * (Em / Ea-1) + α * (tm-ta)
Vk = Va + β * (tm-ta)-Rsa * (Ik-Ia)-K * Ik * (tm-ta)
To create these voltage V-current I values or the IV curve and PV curve connecting them,
{19} Method of obtaining power at the Pmax point on this IV curve or power at the voltage specified as a parameter, and using this value as the power value at the time of each month, summing the month and year to obtain the monthly and annual power generation An annual photovoltaic power generation simulation calculation method characterized by using the A computer-readable data storage medium storing a processing program for a photovoltaic power generation amount simulation calculation method according to claim 1.

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