JP5814775B2 - Solar cell characteristic calculation method - Google Patents

Description

The present invention relates to a method for calculating characteristics of a solar cell . More specifically, particularly in a solar battery, reverse saturation of solar cells constituting the solar battery module from values of only a short circuit current, an open circuit voltage, an operating current, and an operating voltage described in the inspection sheet of the solar battery module The present invention relates to a method for calculating the characteristics of a solar cell, which obtains current and diode performance indexes and performs highly accurate modeling calculations on the characteristics of each solar cell .

  There is an increasing need to grasp the power generation amount of the photovoltaic power generation system with high accuracy in order to introduce the total purchase system. The solar cell modules that make up the solar power generation system have different characteristics for each solar cell module, and the characteristics fluctuate depending on the amount of solar radiation and temperature. This is very important.

  FIG. 1 (a) shows the current-voltage characteristics of the solar cell module. A current at a voltage of 0V is called a short-circuit current Isc, and a voltage at which the current becomes 0A is called an open circuit voltage Voc. FIG. 1 (b) shows power-voltage characteristics, where the point at which power is maximized is the operating point, the operating voltage for that operating point is called the maximum operating voltage Vop, and the operating current is called the maximum operating current Iop.

When constructing a solar power generation system at a power generation site, an inspection sheet for a solar cell module as shown in Fig. 2 is delivered. This inspection sheet describes the short-circuit current Isc, the open-circuit voltage Voc, the operating voltage Vop, and the operating current Iop of each solar cell module at a solar radiation intensity of 1 kW / m ² and a room temperature of 298K. Therefore, in order to grasp the characteristics of each solar cell module at the power generation site with high accuracy, the characteristics of the solar cell module with high accuracy are obtained only from the information of the short circuit current Isc, the open circuit voltage Voc, the operating voltage Vop, and the operating current Iop. It is important to develop a method to reproduce

For solar cells, I: output current [A], Is1: reverse saturation current [A], V: output voltage [V], Isc: short-circuit current [A], T: solar cell element absolute temperature [K], k : Boltzmann constant [J / K], Rs: DC resistance [Ω], q: Electron charge [C], Rsh: Shunt resistance [Ω], n1: Junction constant, p: Solar radiation intensity [kW / m ² ] The characteristic can be expressed by the equation (1) using the following parameters.
I = Isc ・ p-Is1 ・ {exp (q (V + Rs ・ I) / (n1 ・ k ・ T))} ― (V + Rs ・ I) / Rsh… (1)
Solar radiation intensity Ea (1kW / m ² ), normal temperature (Ta = 298K) Ia: Output current [A], Va: Output voltage [V], Isca: Short-circuit current [A], Rsa: Short-circuit with DC resistance [Ω] Using current temperature coefficient α [A / ℃], open circuit temperature coefficient β [V / ℃], curve correction factor K, solar radiation intensity Eb, temperature Tb, Ib: output current [A] and Vb: output voltage [V] can be calculated using Equation (2) and Equation (3).
Ib = Ia + Isca ・ (Eb / Ea-1) + α ・ (Tb-Ta)… (2)
Vb = Va + β ・ (Tb-Ta) -Rsa ・ (Ib-Ia) -K ・ Ib ・ (Tb-Ta) ... (3)
In Patent Document 1, when the solar energy determine the power generation amount at each temperature when the 1 kW / m ^2, firstly, the solar energy and 1 kW / m ^2, current solar cell temperature of 25 ° C. - determined voltage characteristics, following In addition, the power generation amount correction unit uses the correction formulas (2) and (3), which are correction formulas to correct the generated current according to the temperature, and the generated current and voltage in the current-voltage characteristic at 25 ° C correspond to the temperature. To correct it.

There exists nonpatent literature 1 as other prior art. In Non-Patent Document 1, regarding the calculation of the parameter value that determines the current-voltage characteristics in the reference state where the solar radiation energy is 1 kW / m ² and the solar cell temperature is 25 ° C., the sensitivity of the parameter with variation is obtained.
The parameter value is determined by performing fitting in the order of higher sensitivity.

JP 2003-5849 A

26th European Photovoltaic Solar Energy Conference and Exhibition p. 3364-3368

  In the method in Patent Document 1 listed above, Isc, Voc, Vop, Iop and Rs at room temperature 298K, α, β, K, or other temperatures such as room temperature 298K and other temperatures such as Isc, Voc, Vop, Iop at Tb Necessary.

In mega solar and industrial power generation sites that require tens of thousands of solar cell modules, the solar module inspection sheet has a solar radiation intensity of 1 kW / m ² , a short-circuit current Isc at room temperature of 298K, an open-circuit voltage Voc, and an operating voltage Vop. Only the operating current Iop is given. For tens of thousands of solar cell modules, it is difficult to measure Isc, Voc, Vop, Iop, Rs, and α, β, K at other temperatures. It is not realistic to set values of Isc, Voc, Vop, Iop, Rs, α, β, and K other than room temperature.

  The values of α, β, and K can be estimated from the temperature characteristics available from the solar cell module manufacturer, but the available data are the temperature characteristics related to the solar cell module located at the TYP value (standard). However, the variation of α, β, K of each solar cell module cannot be reflected in the model, and there is a drawback that the accuracy in estimating the power generation amount is lowered.

The method in Non-Patent Document 1 uses only the short-circuit current Isc, the open-circuit voltage Voc, the operating voltage Vop, and the operating current Iop at a solar radiation intensity of 1 kW / m ² and room temperature of 298K, and can be used for device variations and variations in characteristics due to solar radiation and temperature On the other hand, it is possible to develop a modeling calculation method for grasping the characteristics of a solar cell module with high accuracy. The method described in Non-Patent Document 1 performs a sensitivity calculation using the fact that the distribution of solar cell module characteristics is a normal distribution, and thus shows a distribution that does not form a normal distribution due to a mixture of crystal defects. The solar cell module has a drawback that the modeling accuracy is lowered.

Therefore, the short-circuit current Isc at a solar radiation intensity of 1 kW / m ² and room temperature of 298 K is also produced in low-cost silicon crystal solar cells with mixed crystal defects and CIGS (Copper Indium Gallium Selenide) solar cells that contain crystal defects in production. Modeling to calculate the parameters indicating the device performance using only the open-circuit voltage Voc, the operating voltage Vop, and the operating current Iop, and to grasp the characteristics of the solar cell module with high accuracy against characteristics fluctuations due to solar radiation and temperature. The challenge is to develop an arithmetic technique.

  Among the means for solving the problems according to the present application, a representative example is a solar cell, and the temperature and the amount of solar radiation are predetermined using data on the short-circuit current and open-circuit voltage of the solar cell in the reference state. And calculating a junction constant indicating the performance of the solar cell and an impurity concentration of the carrier of the solar cell on the basis of a parameter value constituting a formula of the reverse saturation current value and the predetermined reverse saturation current To do.

According to the present application, even in a silicon crystal solar cell manufactured at a low cost and mixed with crystal defects and a CIGS (Copper Indium Gallium Selenide) solar cell including crystal defects in manufacturing, the solar radiation intensity is 1 kW / m ² and the room temperature is 298 K. Using only the short-circuit current Isc, the open-circuit voltage Voc, the operating voltage Vop, and the operating current Iop, the device performance parameters are calculated to understand the characteristics of the solar cell module with high accuracy even when the characteristics change due to solar radiation and temperature. Modeling calculation techniques can be provided.

It is a figure which shows the current-voltage characteristic and power-voltage characteristic of a solar cell module. It is a figure which shows the inspection sheet | seat of the solar cell delivered to a power generation site. It is a figure which shows the whole flowchart concerning Example 1 of this invention. It is a figure which shows the detail of the calculation which calculates the junction constant which shows the performance of a solar cell, and the impurity concentration of a carrier in the flow which concerns on Example 1 of this invention. It is a figure which shows the detail of the fitting calculation in exposure conditions in the flow which concerns on Example 1 of this invention. It is a photovoltaic power generation system which concerns on Example 2 of this invention, and is the figure which used this modeling method for monitoring of MPPT (Maximum Power Point Tracking) control. It is a photovoltaic power generation system which concerns on Example 3 of this invention, and is the figure which used this modeling method for monitoring of MPPT control. It is a photovoltaic power generation system which concerns on Example 3 of this invention, and is a figure which shows the detail about the monitoring method of MPPT control. It is a solar power generation system which concerns on Example 4 of this invention, and is the figure which applied the solar cell as a thermometer and a pyranometer. It is a solar power generation system which concerns on Example 4 of this invention, and is the figure which showed the detail which calculates temperature and solar radiation from a solar cell. It is a solar power generation system which concerns on Example 5 of this invention, and is the figure which showed the modeling result of the CIS solar cell.

FIG. 3 is a flowchart of the modeling technique according to the first embodiment of the present invention. Assuming that the reverse saturation current constituting the equation (1) is Is1, Is1 is K1: impurity concentration, Ego1: band gap [eV], T: solar cell element absolute temperature [K], k: Boltzmann constant [J / K], n1: The parameters of the junction constant can be used and can be expressed by equation (4).
Is1 = K1 ・ T ³・ exp {− (Ego1 / (n1 ・ k ・ T))}… (4)
Input the solar radiation intensity Ea (1kW / m ² ), short-circuit current Isc at normal temperature (Ta = 298K), open-circuit voltage Voc, operating voltage Vop, operating current Iop of the solar cell module you want to model, and in calculation S400, Is1, K1, n1 calculation S401, fitting S402a, and shunt resistance calculation S402b are performed. Thereby, the parameter of the solar cell module in the reference state is determined.

  Next, focus on temperature characteristics. Calculation of temperature characteristics S500 can perform highly accurate temperature dependence modeling in S501 by obtaining the temperature characteristics of the open circuit voltage Voc and the reverse saturation current Is1 of each solar cell module having a large temperature coefficient. It becomes possible.

  Using the obtained temperature characteristic of the open-circuit voltage Voc and the temperature characteristic of the reverse saturation current Is1, the open-circuit voltage Voc [Tb] and the reverse saturation current Is1 [Tb] at the temperature Tb that is the exposure condition are calculated in S502a. Thereafter, in S502b, the values of the short-circuit current Isc, the operating voltage Vop, and the operating current Iop at the exposure site, Isc [Tb], Vop [Tb], and Iop [Tb] are calculated.

  Finally, fitting the series resistance Rs value that cannot be calculated along the semiconductor device in S503a, and using the obtained series resistance Rs, the shunt resistance Rsh is calculated using S503b. The parameters indicating the characteristics of the solar cell are determined, and a curve indicating the characteristics of the solar cell such as the current-voltage characteristic and the power-voltage characteristic can be obtained.

FIG. 4 shows a detailed flowchart of the reference state calculation S400. As described above, Is1, K1, and n1 are calculated in S401 using the equation (4). Using the values of the parameters constituting the normal (crystalline silicon) reverse saturation current: Is0 as a reference as reference values, calculate the reverse saturation current: Is1 of the module to be obtained. Normal reverse saturation current (of crystalline silicon): Is0, K0: Impurity concentration, Ego: Band gap [eV], T: Solar cell element absolute temperature [K], k: Boltzmann constant [J / K] , N0: The parameter of the junction constant is used and expressed as in equation (5).
Is0 = K0 ・ T ³・ exp {− (Ego / (n0 ・ k ・ Ta))}… (5)
When calculating Is1 from Equation (4) and Equation (5),
Is1 = (K1 / K0) ・ Is0 ・ exp {Ego1 / (n1 ・ k ・ Ta)} / exp {Ego / (n0 ・ k ・ Ta)}… (6)
Here, as references, Is0: 1.68 × 10 ⁻⁵ [A], K0: 0.1, Ego: 1.205 [eV], and n0: 1.8 are determined. Further, Ta = 298K and k: 1.3806503 × 10 ⁻²³ . Ego1 uses 1.205 [eV] when the modeling target is a silicon crystal system, and 1.15 to 1.20 [eV] when CIS is used.

First, provisional values of n1 and K1 are determined, and Is1 is obtained using Equation (6). Next, the solar radiation intensity Ea (1 kW / m ² ) of the solar cell module, the short-circuit current Isc at normal temperature (Ta = 298K), the open-circuit voltage Voc and the calculated Is1 are substituted into Equation (7) to obtain n1.
n1 = q− (Voc / Ncell) / (k ・ Ta) ・ {1 / ln (Isc / Is1)}… (7)
N1 obtained by the equation (7) is further substituted into the equation (6) to obtain Is1. The calculated open voltage Voc1 is obtained by substituting n1 and Is1 calculated here into equation (8).
Voc1 = ((n1 ・ k ・ Ta) / q) ・ ln (Isc / Is1)… (8)
At the end of S401, the calculated open-circuit voltage: Voc1 is compared with Voc of the inspection sheet. If Voc1> Voc, K1 = K1 + 0.0001, otherwise K1 = K1-0.0001 and the carrier impurity Adjust the density.

  The operations from the calculation of the above equation (6) to the adjustment of the impurity concentration of the carrier are repeated until each parameter value converges. In FIG. 4, as an example, it was repeated 1000 times.

  For Rs: DC resistance [Ω], as shown in S402a, fill factor calculated from the inspection sheet: FF = (Iop * Vop) / (Isc * Voc) and Iop calculated by equation (1) While comparing the fill factor using 'FF', shift the value of each parameter and adjust.

  Once Rs is obtained, the unknown parameter is only Rsh, and is calculated using equation (1) (S402b).

Using the parameters obtained from the above calculations, the solar radiation intensity obtained from Equation (1) under the conditions of 1 kW / m ² and room temperature (298 K) is the current-voltage characteristics obtained by measurement. High correlation with characteristics.

FIG. 5 shows a detailed flowchart of the temperature characteristic calculation unit S500. Pay attention to temperature characteristics. The temperature characteristics can be modeled with high accuracy by calculating the temperature characteristics of the Voc and the reverse saturation current Is of each solar cell module in S501. The temperature characteristic of the open-circuit voltage Voc is expressed as in equation (9) by differentiating equation (8) with temperature.
∂Voc / ∂T = ((n1 ・ k) / q) ・ ln (Isc / Is1) − ((k ・ T) / (q ・ Is1)) ・ (∂Is1) / (∂T)
= Voc / T − ((k ・ T) / (q ・ Is1)) ・ (∂Is1) / (∂T) ... (9)
Here, equation (4) is transformed and
∂Is1 / ∂T = 3 ・ K1 ・ T ²・ exp (− (Ego1 / k ・ T)) + ((K1 ・ T ・ Ego1) / k) exp (− (Ego1 / k ・ T)) = (3 / T + Ego1 / (k ・ T ² )) ・ Is1… (10)
Thus, the temperature characteristic of Is1: reverse saturation current is obtained. By substituting equation (10) into equation (9), the open-circuit voltage temperature characteristic as shown in equation (11) is obtained.
∂Voc / ∂T = (Voc / T) − (1 / T) ・ ((3 ・ n1 ・ k ・ T) / q + (Ego1 / q)) ... (11)
From the above, the temperature coefficient β [V / ° C.] of the open circuit voltage for each device can be obtained. By using this temperature coefficient, Voc [Tb], Is [Tb], Isc [Tb], Vop [Tb], and Iop [Tb] at the temperature Tb that is the exposure condition are calculated in S502.

From Equation (10) and Equation (11), Is1 [Tb] and Voc [Tb] when the temperature Tb is variable are obtained. By substituting into Equation (12), the short-circuit current Isc [Tb] at the temperature Tb is I want. Isc [Tb] ≒ Is1 [Tb] ・ exp ((q / (n1 ・ k ・ Tb)) ・ Voc [Tb]) ... (12)
Here, the temperature coefficient α [A / ° C.] of the short-circuit current for each device can be determined by determining the ratio between Isc and Isc [Tb] at room temperature.

Furthermore, paying attention to Vop,
Vop = ((n1 ・ k ・ T) / q) ・ ln ((Isc-Iop) / Is1) ... (13)
If Is1 is eliminated from Equation (8) and Equation (13),
(Vop−Voc) / T = ((n1 ・ k) / q) ・ ln ((Isc-Iop) / Isc) (14)
Similarly for Tb,
(Vop [Tb] −Voc [Tb]) / Tb = ((n1 ・ k) / q) ・ ln ((Isc [Tb] -Iop [Tb]) / Isc [Tb])… (15)
Here, in non-patent literature “Comparison of Photovoltaic Array Maximum Power Point Tracking Techniques” Esram Trishan, IEEE Transactions on Energy Conversion Vol.11, No2, pp.439-449, 2007, environment such as solar radiation and temperature changed Even in this case, it is described that the relationship of Iop≈j · Isc (j: constant) holds,
((n1 ・ k) / q) ・ ln ((Isc-Iop) / Isc) = ((n1 ・ k) / q) ・ ln ((Isc [Tb] -Iop [Tb]) / Isc [Tb]) … (16)
Therefore, the equation for Vop temperature change is calculated as follows.
Vop [Tb] = ((Vop−Voc) / (T)) ・ Tb + Voc [b])… (17)
In other words, the calculation in S502 is performed using Equation (12) for calculating Isc [Tb], Equation (17) for calculating Vop [Tb], and Iop≈j · Isc for calculating Iop [Tb]. The obtained constant j is multiplied by Isc [Tb].

  Since the series resistance: Rs cannot be calculated using the semiconductor device characteristics, the fitting of the series resistance: Rs is performed in S503. As with S402a in FIG. 4, the fitting method is a fill factor calculated from the inspection sheet: FF = (Iop * Vop) / (Isc * Voc) and fill using Iop ′ calculated by Expression (1) While comparing the factors: FF ', the values of each parameter are shifted and adjusted.

  Finally, similarly to S402b, in S503, Rsh is calculated using Equation (1). The current-voltage characteristics of the solar cell module obtained using Equation (1) using the parameters obtained by the above S500 calculation reproduce the current-voltage characteristics obtained by actual measurement at the exposure site with high accuracy. It becomes possible.

  FIG. 6 is a block diagram of a photovoltaic power generation system equipped with an MPPT control monitoring function according to Embodiment 2 of the present invention. The solar power generation system 1 includes a voltage detection unit 3, a current detection unit 4, a load change unit 5, and an electrical load 6.

  The load changing unit 5 is realized by a step-up chopper or the like, and varies the load by varying the conduction ratio that is the on / off ratio in the switching operation of the switching element, thereby controlling the output of the solar cell. A control signal having a certain conduction rate is generated in a control unit described as an MPPT unit, converted into PWM, and then subjected to level conversion via an isolation amplifier 7 to drive a switching element in the load fluctuation unit 5. To do.

  The voltage information and current information detected by the voltage detector 3 for detecting the output voltage of the solar cell and the current detector 4 for detecting the output current of the solar cell are converted into digital values by the AD converters ADC8 and ADC9. , Transmitted to the MPPT section. Thereby, a flow rate can be controlled, feeding back the output of a solar cell panel.

  Since the output from the solar cell array is DC, it is connected to a commercial power supply via a DC / AC inverter circuit. In the solar cell system, the inverter circuit and the commercial system power supply can be regarded as playing an electrical load role.

  A maximum power point tracking control method called a hill-climbing method that is generally used to obtain highly efficient power from a solar power generation system is used. This maximum power point tracking system is called MPPT control (Maximum Power Point Tracking).

  It is possible to determine whether or not the maximum power of the solar cell is obtained by this MPPT control by using a modeling technique. As shown in Example 1, reference state calculation S400 and temperature characteristic calculation S502 are performed to calculate parameters for each solar cell. Then, the maximum power point as a solar cell array is calculated by performing array calculation.

  The solar cell array 2 is configured by arranging units called strings in which a plurality of solar cell modules are arranged in series in parallel. Each solar cell module is provided with a bypass diode in order to prevent a reverse current from flowing when a reverse bias is applied.

  The array operation is a combination of string analysis and array analysis. When performing string analysis, since the currents flowing through the plurality of modules are common, the module voltage of each solar cell when a certain current flows is obtained from Equation (1), and the sum is obtained. When the voltage is calculated from Equation (1), an inverse function is obtained, but it can be easily obtained by applying an iterative operation such as Newton's method. When the module voltage becomes negative due to the influence of the shade on the module, the bypass diode functions, so the module voltage is considered as 0. When performing an array analysis, since the voltages related to a plurality of strings are common, the current extracted from each string when a certain voltage is applied is obtained from Equation (1) and the sum thereof is obtained.

  By comparing the maximum power obtained from the array characteristics calculated as described above with the power obtained by the MPPT control obtained by the voltage detection unit 3 and the current detection unit 4, it is possible to monitor whether the MPPT control is accurately performed. It becomes possible.

  7 and 8 are block diagrams of a photovoltaic power generation system equipped with a monitoring function for MPPT control according to Embodiment 3 of the present invention. FIG. 8 shows a calculation flow for the comparison unit 13b of FIG.

First, Is1 (Tb) is obtained using Tb detected by the thermometer 15 and Equation (11). Next, the solar radiation amount detected by the solar radiation meter 16 and the current detector 4 at a certain timing is Eb [N], the current value at the MPP is Iop [N], and the solar radiation amount detected next is Eb [N + 1 ], Assuming that the current value in MPP is Iop [N + 1], Equation (13) can be rewritten as Equation (18) and Equation (19), and the ideal voltage ratio is expressed by Equation (20). I can do it.
Vop_N = ((n1 ・ k ・ Tb) / q) ・ ln ((Isc ・ Eb [N] −Iop [N]) / Is1 (Tb)) ... (18)
Vop_N + 1 = ((n1 ・ k ・ Tb) / q) ・ ln ((Isc ・ Eb [N + 1] −Iop [N + 1]) / Is1 (Tb)) (19)
(Vop_N + 1 / Vop_N) = {ln (Isc · Eb [N + 1] −Iop [N + 1]) − ln (Is1 (Tb))} / {ln (Isc · Eb [N] −Iop [N ]) -ln (Is1 (Tb))} (20)
Here, by comparing the ratio of Vop [N + 1] and Vop [N] detected by the voltage detection unit 3 with Expression (20), it is possible to monitor whether the MPPT control is properly performed. .

  FIGS. 9 and 10 are block diagrams of a solar power generation system that can use the solar cell according to the fourth embodiment of the present invention as a solar radiation meter and a thermometer, and a calculation flow for the environment calculation unit 17 in FIG. 9 is illustrated. 10 shows.

First, by performing the procedure up to the array calculation described in the second embodiment, the short-circuit current, the open voltage, the operating voltage, and the operating current at the solar radiation intensity of 1.0 kW / m ² and the room temperature of 298 K as the array are calculated. Here, by multiplying the operating current I'op measured at the exposure site by a constant j, the short-circuit current I'sc is calculated and divided by the short-circuit current at a solar radiation intensity of 1.0 kW / m ² and an ordinary temperature of 298K. Thus, the provisional value p′0 of the solar radiation amount is calculated. The amount of solar radiation calculated here is a provisional value because it does not include temperature correction.

Next, the provisional solar radiation intensity p′0 kW / m ² as an array and the open circuit voltage Voc and the operating voltage Vop at room temperature 298 K are calculated. Here, the exposure site temperature T ′ is calculated using the operating voltage V′op, the open circuit voltage Voc, and the operating voltage Vop measured at the exposure site. The calculation formula is Formula (21) obtained by modifying Formula (11) and Formula (17).
Tz = {V'op−Voc} ・ 298 − {((3 ・ n ・ k ・ 298) / q + (Ego / q)) − Voc} ・ Ncell ・ 298
T '= Tz / {(Vop−Voc} − {((3 · n · k · 298) / q + (Ego / q)) − Voc} · Ncell (21)
Since the temperature of the exposure site is determined by this calculation, the short-circuit current at the temperature T 'is obtained from the solar radiation intensity of 1.0 kW / m ² as an array from Equations (10), (11), and (12). Thus, the actual solar radiation amount p ′ can be obtained by dividing the short-circuit current I′sc.

  FIG. 11 shows the modeling result of the CIS solar cell according to Example 5 of the present invention. S900 shows current-voltage characteristics by modeling, and s901 shows current-voltage characteristics measured at the exposure site. The current-voltage characteristic measured at the time of shipment shows a current-voltage characteristic highly correlated with s900, but a difference of s902 occurs due to the light irradiation effect of CIS. This means that by using the present invention, the influence of the light irradiation effect at the exposure site can also be quantified.

  Is1: Reverse saturation current, K1: Impurity concentration, Ego1: Band gap, T: Solar cell element absolute temperature, k: Boltzmann constant, n1: Junction constant, Ea: Solar radiation intensity, Isc, I'sc: Short-circuit current, Voc , Voc1: Release voltage, Vop: Operating voltage, Iop, Iop ': Operating current, S400, S401, S402a, S402b, S500, S501, S502a, S502b, S503a, S503b: Calculation, Tb: Temperature, Rs: Series resistance, Rsh: Shunt resistance, Is0: Reverse saturation current, Is1: Reverse saturation current, n0: Junction constant, FF, FF ': Fill factor, Eb: Solar radiation, p'0: Provisional value, α, β: Temperature coefficient 1: solar power generation system, 2: solar cell array, 3: voltage detection unit, 4: current detection unit, 5: load fluctuation unit, 6: electrical load, 7: isolation amplifier, 8: AD converter, 9: ADC, MPPT part: control part, 13b: comparison part, 15: thermometer, 16: pyranometer.

Claims (12)

The solar cell receives data on short-circuit current and open-circuit voltage of the solar cell when the temperature and the amount of solar radiation are in a reference state, and the solar cell is based on a predetermined reverse saturation current value and a parameter value constituting the predetermined reverse saturation current formula. A method for calculating characteristics of a solar cell , comprising calculating a junction constant indicating the performance of the cell and an impurity concentration of a carrier of the solar cell. The second reverse saturation current calculated using the junction constant, the second open circuit voltage calculated using the second reverse saturation current and the open circuit voltage are compared with the open circuit voltage, and the carrier The method for calculating the characteristics of a solar cell according to claim 1, wherein the value of the impurity concentration is determined. The predetermined reverse saturation current is Is0, and the parameter values constituting the predetermined reverse saturation current equation are K0: impurity concentration, Ego: band gap [eV], Ta: normal temperature 298 [K], k: Boltzmann Constant [J / K], n0: junction constant, and for the solar cell, Is1: reverse saturation current, K1: impurity concentration, Ego1: band gap [eV], n1: junction constant, Voc1: second open circuit In the case where the short-circuit current obtained from the test specification of the solar cell is Isc [A], Is1: reverse saturation current and n1: junction constant are obtained by the following equations 1 and 2 , and K1: impurity 3. The solar cell characteristic calculation method according to claim 2, wherein the concentration is fitted by comparing Voc obtained from an inspection specification of the solar cell: the open-circuit voltage and the second open-circuit voltage Voc1.
Is1 = (K1 / K0) · Is0 · exp {Ego1 / (n1 · k · Ta)} / exp {Ego / (n0 · k · Ta)} (Formula 1)
Voc1 = ((n1 ・ k ・ Ta) / q) ・ ln (Isc / Is1) (Formula 2) Applying Is1: reverse saturation current [A] at a predetermined temperature, K1: impurity concentration, n1: junction constant value to the above formulas 1 and 2 , and fitting Rs: DC resistance [Ω] The method for calculating characteristics of a solar cell according to claim 3, wherein: Applying Is1: reverse saturation current [A] at a predetermined temperature, K1: impurity concentration, n1: junction constant values to the above formulas 1 and 2 , and fitting Rs: DC resistance [Ω] The method for calculating characteristics of a solar cell according to claim 3, wherein: Using the calculated K1: impurity concentration and n1: junction constant, the temperature coefficient of the open circuit voltage and the reverse saturation current is calculated, and the short circuit current, the open circuit voltage, and the maximum power at a predetermined temperature are calculated from the obtained values. 2. The method for calculating characteristics of a solar cell according to claim 1, wherein an operating point is calculated. The calculated K1: Impurity concentration, n1: Junction constant, Is1: At a predetermined temperature, Is1: The calculated short-circuit current, open-circuit voltage, Rs at a predetermined temperature from the maximum power operating point: DC resistance [Ω], Rsh: The light irradiation effect of the solar cell is quantified by obtaining the difference between the characteristic of the solar cell and the characteristic obtained by measurement at a predetermined temperature and a predetermined solar radiation intensity obtained by calculating the shunt resistance [Ω]. The solar cell characteristic calculation method according to claim 6. Prior to the calculation,
A solar cell array configured by connecting a plurality of solar cell strings in parallel, with a solar cell string in which a plurality of solar cell modules are connected in series as one unit,
A voltage controller for controlling the operating voltage of the solar cell array;
A voltage detector that detects an output voltage of the solar cell array as control information in the voltage controller;
The solar cell characteristic calculation method according to claim 1, wherein a solar power generation system including a current detection unit that detects an output current of the solar cell array is prepared . Sun according to claim 8, wherein the comparison means for comparing the maximum power which is calculated as described in the power and claim 1 obtained from the current detector and the voltage detector under the control of the voltage control unit Battery characteristic calculation method . 10. The method for calculating the characteristics of a solar cell according to claim 9, wherein the voltage value controlled by the voltage controller is varied based on the result of the comparing means. Comparing means for calculating a voltage transfer ratio of maximum power from the current obtained from the current detection unit and Is1 at a predetermined temperature: reverse saturation current [A] and comparing the voltage ratio obtained from the voltage detection unit The method for calculating characteristics of a solar cell according to claim 8. The temperature of the solar cell is calculated from the open circuit voltage and the temperature coefficient of the reverse saturation current calculated as in claim 1, the operating voltage obtained from the voltage detector and the current detector, and the value of the operating current. The solar cell characteristic calculation method according to claim 8.

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