Calculating the shading reduction coefficient of photovoltaic system efficiency using the anisotropic sky scattering model

The front-row shading reduction coefficient is a key parameter used to calculate the system efficiency of a photovoltaic (PV) power station. Based on the Hay anisotropic sky scattering model, the variation rule of solar radiation intensity on the surface of the PV array during the shaded period is simulated, combined with the voltage–current characteristics of the PV modules, and the shadow occlusion operating mode of the PV array is modeled. A method for calculating the loss coefficient of front shadow occlusion based on the division of the PV cell string unit and Hay anisotropic sky scattering model is proposed. This algorithm can accurately evaluate the degree of influence of the PV array layout, wiring mode, array spacing, PV module specifications, and solar radiation on PV power station system efficiency. It provides a basis for optimizing the PV array layout, reducing system loss, and improving PV system efficiency.     

双面组件光伏电站最优容配比的研究

通过对采用双面光伏组件的光伏电站(以下简称"双面组件光伏电站")系统效率损失进行分析,发现在光伏组件-逆变器容配比(下文简称"容配比")变化的情况下,逆变器过载损失对此类光伏电站发电量的影响最大。提出了双面组件光伏电站容配比的优化方法,并以太阳能资源Ⅰ、Ⅱ、Ⅲ类地区的典型城市为例,进行了不同容配比和背景反射率下双面组件光伏电站发电量的模拟,通过分析各种情况下双面组件光伏电站的内部收益率(internal rate of return,iRR),得到了太阳能资源Ⅰ、Ⅱ、Ⅲ类地区双面组件光伏电站在不同背景反射率下典型的最优容配比。     

Performance enhancement of partially shaded solar PV array using novel shade dispersion technique

Solar photo voltaic array (SPVA) generates a smaller amount of power than the standard rating of the panel due to the partial shading effect. Since the modules of the arrays receive different solar irradiations, the P-V characteristics of photovoltaic (PV) arrays contain multiple peaks or local peaks. This paper presents an innovative method (magic square) in order to increase the generated power by configuring the modules of a shaded photovoltaic array. In this approach, the physical location of the modules in the total cross tied (TCT) connected in the solar PV array is rearranged based on the magic square arrangement pattern. This connection is done without altering any electrical configurations of the modules in the PV array. This method can distribute the shading effect over the entire PVarray, without concentrating on any row of modules and can achieve global peaks. For different types of shading patterns, the output power of the solar PV array with the proposed magic square configuration is compared with the traditional configurations and the performance is calculated. This paper presents a new reconfiguration technique for solar PV arrays, which increases the PV power under different shading conditions. The proposed technique facilitates the distribution of the effect of shading over the entire array, thereby, reducing the mismatch losses caused by partial shading. The theoretical calculations are tested through simulations in Matlab/ Simulink to validate the results. A comparison of power loss for different types of topologies under different types of shading patterns for a 4×4 array is also explained.     

串并联太阳能电池弧形光伏组件的发电性能研究

将弧形光伏组件安装在建筑和汽车上获取电能,已受到人们越来越多的关注。为获得更高的输出功率,有必要研究由互连太阳能电池组成的、电流不匹配的弧形光伏组件的特性。研究重点关注由串并联太阳能电池组成的弧形光伏组件的发电性能,设计了不同曲率的非平面微型光伏模块,并通过测量获取光伏模块的参数。与平面光伏模块相比,弧形光伏模块的发电量较小。此外,利用二极管模型分析了光伏模块的特性,说明并联比串联功率高的原因。最后研究了实际应用中太阳能电池的互连问题。结果表明,在理想模型下并联能获取更多电能,但大尺寸的光伏模块会产生更大电流,可能会在实际运行中产生额外损耗。因此,在实际应用中设计弧形光伏组件时也应考虑太阳能电池的互连。     

一种多功能光伏发电系统的可行性研究

通过在光伏组件的背面连接了一个热电转换模块,形成一个光伏一热电混合模块,从而将光伏组件工作过程中产生的废热转换成电能的同时又降低了光伏组件的温度,进而提高了光电转换效率。将光伏一热电模块与百叶有效结合,从而实现了室内采光、通风及节约空间等多种功能。同时,为了提高光伏组件的入射太阳辐射,引入了可调节的抛物型双面聚焦板,减少了太阳能电池板的面积,从而减少了太阳能发电的成本。     

Spatial and orientational distribution of cracks in crystalline photovoltaic modules generated by mechanical load tests

Cracks in crystalline silicon solar cells influence the photovoltaic (PV) module power output in accelerated aging tests. A detailed insight into the formation of cracks offers the potential to optimize the PV module design in order to reduce the risk of power degradation in its lifetime. In this paper we present a statistical analysis on the crack formation in 27 crystalline silicon PV modules caused by a standard mechanical load test according to IEC 61215 10.16. The criticality of cracks depends strongly on the crack orientation, therefore we analyze both the spatial distribution of cracks and its dependence on the orientation of the cracks in the tested PV modules. We find that 50% of the damaged cells are cracked parallel to the busbars, which is a crack orientation with high potential impact on the power output of the PV module. A simplified numerical analysis is used to give an explanation for the statistical data and we propose a strategy for the reduction of the crack criticality.     

基于S-V特性分析的晶硅光伏组件阴影遮障诊断

针对广泛使用的晶硅光伏组件,通过Simulink建立太阳电池双二极管精确仿真模型,对实际应用中最常见的光伏组件阴影遮挡故障进行多种工况的仿真验证。根据I-V曲线拐点、台阶、曲线下积分面积（S）下降的特征,提出一种基于S-V曲线特性的光伏组件阴影遮挡故障的在线诊断方法。该方法建立S-V曲线,根据S-V曲线分叉点位置可判断光伏组件遮挡情况,通过整体积分面积进而判断遮挡比例。对温度、辐照度进行折算,使该方法在全工况下适用。结合光伏组件功率优化器验证该诊断方法有较高的准确率,并且可准确地判断阴影遮挡面积,具有很高的实际应用价值。     

Impact of environment factors on solar cell parameters of a-Si∥μc-Si photovoltaic modules

The behavior of amorphous silicon∥micro crystalline silicon (a-Si∥μc-Si) tandem-type photovoltaic (PV) module is complex because the output current is limited by the lower current component cell. Also, the outdoor behaviors are not fully understood. The impact of environment factors on solar cell parameters of a-Si∥μc-Si PV module was quantitatively analyzed and the module was compared with other silicon-based PV modules (single crystalline silicon (sc-Si) and amorphous silicon (a-Si)). The contour maps of solar cell parameters were constructed as a function of irradiance and module temperature. The contour map of a-Si∥μc-Si PV modules is similar to that of a-Si modules. The results imply that output characteristics of a-Si∥μc-Si PV modules are mainly influenced by the a-Si top cell. Furthermore, the efficiency of a-Si∥μc-Si PV modules was compared other solar cell parameters and the contour map of efficiency is similar to that of fill factor.     

户外光伏组件背板外层材料的老化研究

针对在户外运行了6年的光伏组件背板外层材料进行了老化测试研究。将光伏组件背板外层材料划分为3个不同的分析测试区域,即太阳电池中心区域、太阳电池边缘区域及光伏组件边缘区域,通过外层材料的厚度、反射率、光泽度、耐磨性、表面微观形貌等参数评估户外光伏组件背板外层材料的老化程度。研究表明,不同分析测试区域的光伏组件背板外层材料的老化程度不同,光伏组件边缘区域的背板外层材料的老化程度最轻,太阳电池中心区域的背板外层材料的老化程度最严重。分析数据与分析结果可为户外光伏电站中光伏组件的后期运维、修复、回收等方面提供有意义的参考。     

Photovoltaic fault detection using a parameter based model

Photovoltaic (PV) modules convert part of incident solar energy into electrical energy for commercial applications, with the rest being transferred to heat energy. The modelling of PV modules plays an important role in the fault diagnosis of a PV array. The object of this paper is to develop a parameter based model of a PV module. This model is sequentially coupled with an electrical model and energy balance equation. In order to establish the parameter based model, key parameters including the total effective solar energy, total heat exchange coefficient and ambient temperature are calculated from two working points on PV module along with the corresponding temperature from a thermal camera. Using the developed model, a fault diagnosis method based on the model is illustrated. Finally, model validation is carried out by the experiments.     

An investigation of mismatch losses in solar photovoltaic cell networks

Solar photovoltaic (PV) arrays in field conditions deliver lower power than the array rating. In this paper, the sensitivity of solar cell parameters in the variation of available power from the array is investigated. The parameters characteristic of aging and fresh cells used in prototype field systems have been used for computation of reduction in the available power. It is found that in series string the fractional power loss would increase from 2% to 12% with aging of solar cells. However, this fractional power loss may be reduced to 0.4–2.4% by an appropriate series-paralleling.     

光伏电站中光伏组件串联数的优化设计

目前在光伏电站设计中,光伏组件串联数的计算广泛使用GB 50797-2012或IEC 62548-2016中的计算方式,假定在极端环境低温的情况下对光伏组串的开路电压、最大功率点电压等进行计算,进而确定光伏组件成串数量,即光伏组件串联数。但随着对光伏电站度电成本的要求日益严苛,上述对于计算光伏电站的光伏组件串联数的要求已经偏于保守。最新版的IEC 62738-2018中不再要求采用极端环境低温进行计算,而是允许在数据足够充分的情况下采用限制在日照时间内的年平均最低环境温度进行计算。基于此,依据近期国际超大型项目中光伏电站光伏组件串联数的计算经验,进一步提出了以大量气象数据为基础来预测最低环境温度与太阳辐照度的关系,并在此基础上联合计算光伏组串的开路电压与最大功率点电压,从而确定光伏电站的光伏组件串联数的计算方法。以中东地区某光伏发电项目为例对该优化方法进行验证,计算得到的光伏组件串联数比采用GB 50797-2012或IEC 62548-2016计算时得到的结果多2~4块,结果显示,该优化方法可以显著节省光伏电站的投资,并降低度电成本。     

Forecasting photovoltaic array power production subject to mismatch losses

The development of photovoltaic (PV) energy throughout the world this last decade has brought to light the presence of module mismatch losses in most PV applications. Such power losses, mainly occasioned by partial shading of arrays and differences in PV modules, can be reduced by changing module interconnections of a solar array. This paper presents a novel method to forecast existing PV array production in diverse environmental conditions. In this approach, field measurement data is used to identify module parameters once and for all. The proposed method simulates PV arrays with adaptable module interconnection schemes in order to reduce mismatch losses. The model has been validated by experimental results taken on a 2.2 kW_p plant, with three different interconnection schemes, which show reliable power production forecast precision in both partially shaded and normal operating conditions. Field measurements show interest in using alternative plant configurations in PV systems for decreasing module mismatch losses.     

Impact of uneven shading and bypass diodes on energy extraction characteristics of solar photovoltaic modules and arrays

Solar photovoltaic (PV) energy is becoming an increasingly important part of the world's renewable energy. In order for effective energy extraction from a solar PV system, this paper investigates I–V and P–V characteristics of solar PV modules and arrays. The paper particularly focuses on I–V and P–V characteristics of PV modules and arrays under uneven shading conditions, and considers both the physics and electrical characteristics of a solar PV system in the model development. The article examines how different bypass diode arrangements could affect maximum power extraction characteristics of a solar PV module or array. It is found in this article that under uneven shading conditions, solar PV cells may perform in very different ways and a solar PV system may exhibit multiple peaks in its P–V characteristics. The study of this article also shows that the arrangement of largely distributed bypass diodes within a PV module could effectively improve efficiency and maximum power point tracking strategies for energy conversion of solar PV systems.     

阴影遮挡下光伏组件横竖向放置对发电量的影响

为了提高阴影遮挡时光伏组件的发电量,针对横、竖向放置时光伏组件相互遮挡产生的功率损失,建立了光伏组件在阴影遮挡情况下的数学模型,考虑了光伏组件并联旁路二极管的影响,仿真模拟了阴影遮挡下横、竖向放置时光伏组件的输出特性,进而以某地100kW光伏阵列为例,计算了光伏组件在不同摆放方式、不同倾角与间距下的辐射量、年发电量、阴影损失及年平均效率,为光伏电站的初步设计提供了一定的参考价值。     

A SIMPLIFIED METHOD FOR DETERMINING THE AVAILABLE POWER AND ENERGY OF A PHOTOVOLTAIC ARRAY

A practical method of calculating the power and energy capabilities of a PV array source is presented in this paper. The method is based on power flow relationships with average values for constants and actural measurements of key variables, solar irradiance and module temperature on an hourly basis or other discrete time intervals. Included in this paper is an example for a PV plant and a simple procedure for constructing and validating the math model

The method is applicable to any PV array configuration which is operating normally, i.e., when no PV modules are bypassed by the shunt diodes. The array can comprise one or more PV modules. The accuracy of this method is dependent upon proper selection of the values of various constants in the math model as well as how well the model has been validated. The calculation and display of maximum power capability in real-time have been implemented in several PV plants. Some of them have found it to be very useful for operation, maintenance, performance analysis, and energy utilization improvement purposes.     

Effects of mismatch losses in photovoltaic arrays

Experimental and modeling results on the effects of mismatch losses in photovoltaic arrays are presented. Field tests conducted on each of the 192 modules are used to describe the variation in the properties of production run photovoltaic modules. Module specific estimates of a five-parameter module model are obtained by nonlinear regression. Mathematical models of four-module parallel string and series block photovoltaic array performance based on the five-parameter module model are developed and used to evaluate the variation in maximum output power and mismatch loss of arrays with random module orderings. Module maximum output power averaged 14% below the nameplate rating and exhibited a coefficient of variation of 2.1%. Mismatch losses were very small, never exceeding 0.53%. No differences between parallel string and series block arrays in array maximum output power were observed.     

Identifying the parameters of different configurations of photovoltaic models based on recent artificial ecosystem-based optimization approach

Identifying accurate and precise photovoltaic models' parameters is the primary gate in providing a proper PV system design simulate its real behavior. Therefore, this article proposed a new approach based on a recent meta-heuristic algorithm of artificial ecosystem-based optimization (AEO) to identify the optimal parameters of PV cell and module models. Various PV models are considered in this work as single diode (SD), double diode (DD), and triple diode (TD)-based circuits. The analysis is performed on which are R.T.C. France silicon solar cell, FSM-25 PV module, and Canadian-Solar-(CS6P-240P) multi-crystalline solar panel with the aid of experimental data under different operating conditions. Moreover, Lambert form is employed to validate the constructed model. Furthermore, comparative analysis with Harris hawks optimizer (HHO), gray wolf optimizer (GWO), and salp swarm algorithm (SSA) is performed. Additionally, statistical analysis using the Wilcoxon signed rank test is implemented across the three series of experiments for all employed optimizers. The obtained results confirmed the competence of the proposed approach in identifying the PV cell and modules equivalent circuits' parameters.     

Performance of low series-resistance interconnections on the polycrystalline solar cells

The performance of four ribbons of lead SnAgPb (SAP) and lead-free SnAgCu (SAC) photovoltaic (PV) ribbons in patterned (pat-) and high-conductivity (con-) types soldered on silicon solar cells are investigated by electron characteristics and microstructure analyses. The electrical performances of the solar strings were characterized before and after the soldering process by a solar flasher, and strings with commercial ribbons of lead and lead-free are compared. In general, lead ribbon solar strings show lower power loss value than lead-free counterparts. And the commercial lead and lead-free ribbon strings show highest power loss around 6.66%-10.65% of all the solar strings. Furthermore, the power losses for patterned lead (pat-SAP) and lead-free (pat-SAC) solar string are 3.93% and 5.51%, respectively, implying that a patterned structure should improve the soldering process and result in lower power loss. Yet, significant low output power loss values are detected in the solar strings which are soldered with high-conductivity ribbons. It is estimated that the power loss for high-conductivity lead (con-SAP) and lead-free (con-SAC) solar strings are 3.89% and 4.43%, respectively. And a similar condition was revealed when the solder materials were practically interconnected the solar cells in PV modules. According to the microstructure analyses, the low power loss of con-SAP solar string should be due to the good electrical performance in low series resistance (R_s) and high shunt resistance (R_sh), thus resulting in a high fill factor of the solar device.     

A power-rating model for crystalline silicon PV modules

A model for the performance of generic crystalline silicon photovoltaic (PV) modules is proposed. The model represents the output power of the module as a function of module temperature and in-plane irradiance, with a number of coefficients to be determined by fitting to measured performance data from indoor or outdoor measurements. The model has been validated using data from 3 different modules characterized through extensive measurements in outdoor conditions over several seasons. The model was then applied to indoor measurement data for 18 different PV modules to investigate the variability in modeled output from different module types. It was found that for a Central European climate the modeled output of the 18 modules varies with a standard deviation (SD) of 1.22%, but that the between-module variation is higher at low irradiance (SD of 3.8%). The variability between modules of different types is thus smaller than the uncertainty normally found in the total solar irradiation per year for a given site. We conclude that the model can therefore be used for generalized estimates of PV performance with only a relatively small impact on the overall uncertainty of such estimates resulting from different module types.