QuickSun 830 A module solar simulator . Study of mini PV modules

QS830A module solar simulator is applied to measure electrical parameters of standard PV modules based on mono/polycrystalline silicon solar cells, large format photovoltaic (PV) modules 150 cm x 220 cm, with effective measurements time of 2 ms / 4 ms, flush pulse duration 3 ms / 10 ms (one flash tube / two flash tubes), and non-uniformity less than 2%. In order to comply with the Class AAA tolerances of the standard IEC 60904-9 Edition 2.0 of QuickSun 830A simulators (Endeas Oy, Finland), proprietary optical system behind the light source filament has been developed for filtering spectrum and improving irradiance nonuniformity simultaneously. Non-uniformity parameter for 14% of total modules testing area, i.e. 0.65 m2, will be appointed in this work.


Introduction
Quick Sun 830A simulator, Endeas Oy, Finland, placed at University of Rzeszow was horizontally installed and instructions for constructing a corresponding flash tunnel were supplied with the simulators.A flash tunnel gives better access to the flash head e.g. for changing the flash tube.A test surface with fixed test sensor positions covering the nominal test area of each simulator is a ground and basic part in order to perform fluent and reproducible irradiance non-uniformity measurements.After changing the xenon flash lamp (light source) such tests must be obligatorily performed.Non-uniformity measurements, normally, must be provided minimum once per half year with testing at our Renewable Energy Sources laboratory at the Center for Innovation and Transfer of Natural Science and Engineering Knowledge of the University of Rzeszow (we are testing more than 300 modules per month).At a factory conditions testing capacity for QS830A is 90 measurements per hour.All information about parameters and measurement accuracies are presented on the producer site [1,2].Presented here are investigations that were done during non-uniformity tests of QS 830A.Uniformity tests were always provided after changing the flush tube.
The goal of that research was to show that even if the condition for uniformity QS830A class A is not satisfied for whole testing area, we can distinguish a smaller area that meets class A requirements for inhomogeneity of light intensity, i.e. 2.28 m 2 , 2.20 m 2 , 1.14 m 2 , 0.65 m 2 .The reduced area is perfectly suited for the certification tests of mini photovoltaic's modules.Measurements are made under standard test conditions (STC): 1000 W/m 2 , 25°C, AM1.5G presented in [3][4][5][6].Current, voltage and temperature measurement accuracies are calibrated and verified to comply with IEC 60904-1 Edition 2.0 specifications [3].Irradiance measurement accuracy was factory calibrated but final calibration of QS830A was performed at Renewable Sources Laboratory by applying the two certified reference Si modules monocrystalline and   In accordance with international standards for determining the parameter of the light intensity, in accordance with the generally accepted formula [5,[7][8][9] common for any type of module testers, we checked the correctness of calculations of the area we study: where E max QS is the maximum value of light intensity, E min QS -the minimum value of light intensity.Results of non-uniformity performer for each of 88 average I-V characteristics is equal to 2.64%, shown at row two of Table 3.As we can see, the system software analyzed result is the same as presented in Figure 2, equal to 2.67% (see: first row of Table 3).Both results are in very good agreement, but the condition of non-uniformity for QS830A class AAA solar module tester is not met, because it must be less than 2%.

Results of I SC [A] measurements with isotherms of U OC [V], I SC [A], U MP -voltage at maximum power point [V], I MP -current at maximum power point [A], MPP [W] and η [%]
were show in Figure 3.
Only for I SC and η isolated lines we can observe ideal accordance of them with light intensity spatial distribution onto whole tested screen [10].The highest values of light intensity, as we can notice, are placed in the field corresponding to the four upper rows (rows from 1 st to 4 th ).Such area is responsible for deterioration of the homogenous distribution of light intensity.

Non-uniformity parameter after testing screen reduction
Further discussion for all investigated tested areas will be provided, for convenience, in mini tables similar to the Table 3. Please pay attention to the information given in the lower index of the ΔE QS830, X x Y, which determines the dimensions of the considered test field, marked with different coloured rectangles in Table 4.
i) The non-uniformity condition for QS830A for the limited screen area, after exclusion of the mentioned four upper rows area, i.e. 0.825 m x 1.58 m equal to 1.31 m 2 from total screen area 3.59 m 2 a matrix 8 columns x 7 rows (area 2.28 m 2 ), marked with a blue rectangle in Table 2 was designated.The non-uniformity condition of QS830A for the new reduced tested area 8 columns x 7 rows (2.28 m 2 ) is real and is equal to 1.24%.ΔE QS830A, X x Y of QS830A for a three smaller than matrix 8 columns x 11 rows areas: ii) 6 x 9 (2.20 m 2 ), iii) 4 x 7 (1.14 m 2 ), and iiii) 4 x 4 (0.65 m 2 ) is presented below.

Table. 4. I SC [A]
average distribution of uniformity c-Si cell with marked three fields of 6 columns x 10 rows, 4 columns x 7 rows and 4 columns x 4 rows.Both mini areas exhibit a very good non-uniformity of light intensity parameter.We can measure the small photovoltaic modules on both of these limited separate areas of the test screen, assuring that the non-uniformity condition for module simulator Class AAA is met.

Conclusions
In the considered case, when after replacing the simulator light source -xenon lamp, for the entire measurement screen the condition of non-uniformity is not met.Before analyzing the repetition of the inhomogeneity tests it is worthwhile to carefully and particularly analyze the matrix of spatial distribution of light intensity.If the largest contribution to exceeding the admissible value of inhomogeneity defining a simulator Class A contributes to the upper row of the test field, it is enough to eliminate the field of recognition from the measurement area and analyze the data again.After changing the flush pulse lamp the entire 1.58 m x 2.27 m size field does not meet the condition of non-uniformity for a Class A QS830A simulator.However, the reduced area of 1.185 m x 1.857 m and the smaller fields considered in this work are already fulfilled.All of the smaller considered areas are perfectly fulfilling the non-uniformity condition for the QS830A Class AAA simulator.The heterogeneity improvement of the test field compared with the next reduction by individual rows and columns in its area are shown in Table 5.

Figure 2
Figure 2 shows matrix of non-uniformity measured with help of uniformity c-Si sensor M2 No. NPPS 31292 on the left, and a graphic distribution of illumination automatically generated by the QS830A software on the right.This distribution is obtained on the basis of the short-circuit current I SC [A] distribution, as it was mentioned previously.

Fig. 2 .
Fig. 2. Distribution of light intensity distribution resulting from simulator software obtained on the basis of the short-circuit current I SC [A] distribution.

E3SFig. 3 .
Fig. 3. Spatial distribution of light intensity on the area 8 column x 11 rows experimentally obtained from I-V characteristics of uniformity cell and putted on them isolated lines of a) U OC [V], b) I SC [A], c) U MP [V], d) I MP [A], e) MPP [V], f) η [%].

Fig. 4 .
Fig. 4. Spatial distribution of light intensity on the area 8 column x 7 rows experimentally obtained from I-V characteristics of uniformity cell [10].

Table 1 .
Matrix of the simulator's maximum tested field, 8 columns x11 rows with segments numbering.

Table 2 .
I SC[A]average distribution of uniformity c-Si cell on whole tested screen with marked area of 8 columns x 7 rows.

Table 3 .
Results of calculation of non-uniformity parameter of QS830A performed on the basis of software intensity light distribution and distribution done on the basis of I-V characteristics for uniformity cell.

maxQS [A] E minQS [A] ΔE QS830A [1/1] (ΔE QS830A ± d(ΔE QS830A )) [%]
After reduction of the investigated testing area to the violet rectangle visible in Table4, i.e. after removing the two first top rows, first left and last right columns, we can calculate the non-uniformity condition corresponding to that reduced area.In this way we can get the largest but reduced testing area dimension 6 columns on 9 rows, i.e. area 2.20m 2 .After re-limiting the violet PV module testing area up to smaller one, i.e. after rejection two left and two right external columns, next first top row and the last bottom row, we will get matrix 4 column x 7 rows (1.14m 2 ) area marked with a green rectangle in Table4.After re-limiting green testing area, i.e. after exclusion of the two top rows and last bottom row we achieved the 4 columns x 4 rows (0.65m 2 ) area marked with a red rectangle in Table4, the smallest area investigated at this paper.