晶体硅光伏组件的热斑效应详解

根据晶体硅光伏组件热斑耐久试验的结果,分析太阳电池发热的原因,并设计实验寻找热斑效应影响程度与遮挡面积大小及外接负载大小的关系,最后阐述了目前利用旁路二极管减小热斑效应影响的原理及光伏电站设计运维的注意事项。     

局部阴影遮挡下大尺寸光伏组件的输出特性研究

以太阳电池尺寸为210 mm×105 mm、电路结构为并串结构的大尺寸光伏组件为例，首先分析单片太阳电池不同阴影遮挡比例时的情况，然后分析光伏组件6种不同阴影遮挡比例和18种典型阴影遮挡位置和形状对大尺寸光伏组件输出特性的影响。结果表明：随着单片太阳电池阴影遮挡比例不断增大，二极管始终未导通，但光伏组件的最大功率逐渐降低，最后降至初始功率的2/3；阴影遮挡比例对采用并串电路结构的大尺寸光伏组件的I-V特性的影响是非线性的。对于整块光伏组件而言，阴影遮挡比例越大，光伏组件的最大功率越小；在同一阴影遮挡比例下，集中阴影遮挡对光伏组件最大功率损失的影响更大。     

晶体硅光伏组件热斑失效问题研究

以不同反向漏电流等级的多晶硅太阳电池封装成的光伏组件和实际发生热斑失效的光伏组件为研究对象,通过数值模拟和实验研究的方法,对晶体硅光伏组件热斑失效的机理和规律进行理论分析与实验验证。研究结果表明:在阴影遮挡环境下被遮挡组件区域温度和太阳电池反向电流成正向相关性,即反向漏电流越大,组件温度越高;实验同时发现即使在完全无阴影遮挡的情况下,光伏组件也可能因组件封装过程中存在虚焊、空焊等接触不良连接点,形成微小间隙,引发电弧效应,从而导致严重的热斑失效。     

非均匀光照下染料敏化太阳电池组件的输出特性与功率损失

通过分析偏压条件下染料敏化太阳电池的电流电压特性,给出遮挡情况下染料敏化太阳电池组件的电学模型。模拟分析部分遮挡情况下,染料敏化太阳电池组件的输出特性和功率损失,以及反向导通时染料敏化太阳电池的负载特性。结果表明:部分遮挡情况下并联组件中被遮挡电池处于正偏压下,由于难以被击穿,能耗极小。串联组件中被遮挡电池易工作在负偏压区域而成为耗能负载,但作为负载的功率较低。     

部分遮挡条件下CIGS组件性能实验研究

由于铜铟镓硒(CIGS)组件在遮挡条件下的输出性能明显不同于晶硅组件,因此文章设计了24组遮挡实验,对不同条件下CIGS组件的输出性能进行研究。经过研究发现:当CIGS组件中全部子电池的部分区域被遮挡时,该组件的峰值输出功率损失比例与遮挡面积比例基本一致;由于CIGS组件的反向击穿电压较低,因此当该组件的部分子电池被全部遮挡时,被遮挡的子电池会被击穿导通,该组件能够向外输出功率,但峰值输出功率损失与遮挡面积不呈线性关系;当CIGS组件部分子电池的部分区域被遮挡时,Y方向遮挡尺寸对组件峰值输出功率损失的影响大于X方向。     

一种阴影情况下光伏组件输出特性的计算方法

提出了一种计算阴影遮挡情况下组件输出特性的方法。该方法首先根据流经组件的电流对被遮挡电池及其所在电池串的输出特性进行分析,在此基础上对旁路二极管的伏安特性进行理论分析,进而判定旁路二极管导通状态,从而计算出光伏组件在阴影遮挡情况下的多峰特性。经试验验证,此种方法可精确地模拟复杂遮挡情况下光伏组件的输出特性,对于各种阴影遮挡情况下的峰值点的最大误差在3%以内。该方法较传统的失配情况下基于一个电池单元并联一个保护旁路二极管的计算方法更符合实际,具有较强的实用价值。     

非均匀辐照下光伏组件旁通二极管可靠性研究

通过调研光伏组件室外运行与室内测试条件下光伏旁通二极管实际失效数据,分析光伏旁通二极管失效概率与工作温度、运行时间等的关系。通过环境箱和双极电源结合,设置高温加正向偏置、高低温循环加正向偏置、高低温循环加反向偏置、正反向偏置循环的室内测试条件,模拟典型光伏组件表面非均匀辐照分布情况下旁路二极管的工作情况并进行耐久性实验。实验结果表明:较高环境温度时,因固定遮挡引起的旁通二极管长期正向偏置情况下,光伏组件存在失效风险。     

光伏组件热斑案例失效分析与影响因素研究

通过调研实际运行光伏电站中光伏组件热斑失效数据,定义典型热斑类别,分析电池间显著温差、电池串失效、玻璃与电池碎裂等不同热斑类型的产生原因与机理。在此基础上选择不同漏电流与缺陷类型的太阳电池,封装成特定组件,实验测试并分析电池漏电流随温度的变化趋势,以及漏电流分布与电池热斑温度的相关性。并设计光伏系统模拟太阳电池失配情况,进行热斑试验,验证热斑对组件电性能输出的影响,并分析最严重热斑产生条件。     

局部阴影条件下光伏组件性能实验研究

局部阴影遮挡严重影响光伏组件的输出特性,通过光伏组件的变比例遮挡以及特定比例下变化遮挡部位的方式对上述问题开展实验研究。研究表明:光伏组件受到阴影遮挡的比例越大,输出特性越差,10%为遮挡比例的转折点,超过之后特性曲线下降斜率陡增,当组件被遮挡20%以上时,最大输出功率Pm接近于零,特性曲线已不完整。分析10%遮挡面积下不同遮挡方式对输出特性和发电量的影响,光伏组件的Pm随单体电池被遮挡比例的增加而减小,给出不同遮挡方式下组件的功率损失。     

局部遮挡时光伏阵列失配特性建模与分析

结合局部遮挡时太阳电池的等效电路,建立太阳电池发热现象的数学模型,对不同状态下太阳电池发热的主要原因进行分类分析;基于对局部遮挡时光伏组件工作特性的分析,建立以分段函数描述的光伏组件输出特性模型,最后结合实验及仿真结果分析失配引起的输出多峰值特性和热斑效应现象,提出解决太阳电池失配问题的控制方法。为改进光伏系统设计、优化光伏系统控制方法提供理论依据。     

Reliable and efficient approach for mitigating the shading effect on photovoltaic module based on Modified Artificial Bee Colony algorithm

The operation and performance of a photovoltaic system (PV) are affected by some factors such as; solar radiation, ambient temperature, PV array configuration and shadow which may be either completely or partially. The partially shadow is caused by clouds, trees due to wind, neighboring buildings and utilities. The shadow effect causes the multiple local maximum power points in the PV module voltage-power characteristics and only one Global Maximum Power Point (GMPP); additionally the shadowing causes high power loss in the shaded cells and produces hot spot. In this paper a new optimization approach based on proposed Modified Artificial Bee Colony (MABC) algorithm is used to solve a proposed constrained objective function of PV module power loss and mitigate the shading effect. The proposed MABC is compared with GA, PSO and ABC. The obtained results proved that the MABC is the most efficient algorithm in solving the objective function that mitigating the power loss in the PV module under partially shading effect.     

Experimental study of mismatch and shading effects in the I–V characteristic of a photovoltaic module

A conventional photovoltaic module has been prepared with the purpose of accessing its cells either individually or associated. Measurements of every cell and of the whole module have been performed in direct and reverse bias, with the objective of documenting the scattering in cell parameters, working point of the cells and shading effects. Several shading profiles have been tested, and the influence of the reverse characteristic of the shaded cell in module output is stressed.     

遮挡状态下光伏组件多峰输出特性的参数计算与分析

基于太阳电池正反向输出特性,建立光伏组件输出特性模型,针对遮挡状态下的多峰输出特性,提出一种模型参数计算方法,研究不同遮挡状态对I-V特性曲线和模型参数的影响作用。通过仿真和实验,分析组件中各单元所受遮挡光强和电池片遮挡数量的变化对模型参数的影响规律。研究结果表明：模型参数计算结果和基于模型参数获得的I-V特性曲线,有较高精度;所建立的组件输出特性模型和参数计算方法,对于实现光伏组件和组串的故障诊断,具有良好的工程应用前景。     

太阳电池组串热斑防治策略研究

针对太阳电池组串热斑效应,研究太阳电池组串热斑的防治策略。首先从防治成本、功率损耗、热斑温度和组串输出功率4个技术指标总结和对比了现有太阳电池组串热斑防治策略,给出了热斑防治的评估方法。然后,提出一种串入电阻的太阳电池组串热斑防治策略。该策略利用串入的电阻分担热斑电池承受的反向电压,降低了热斑电池功率损耗和温度。设计了由电压比较器、功率MOS管、三极管、分压电阻等组成的防治电路,并给出防治电路的防治原理。最后,通过仿真与实验,验证文中防治策略的效果。与传统的解决方案对比分析表明,该文所提热斑防治策略,具有热斑电池温度低、太阳电池组串输出功率大的优点。     

Artificial neural network-polar coordinated fuzzy controller based maximum power point tracking control under partially shaded conditions

The one of main causes of reducing energy yield of photovoltaic systems is partially shaded conditions. Although the conventional maximum power point tracking (MPPT) control algorithms operate well under uniform insolation, they do not operate well in non-uniform insolation. The non-uniform conditions cause multiple local maximum power points on the power?voltage curve. The conventional MPPT methods cannot distinguish between the global and local peaks. Since the global maximum power point (MPP) may change within a large voltage window and also its position depends on shading patterns, it is very difficult to recognise the global operating point under partially shaded conditions. In this paper, a novel MPPT system is proposed for partially shaded PV array using artificial neural network (ANN) and fuzzy logic with polar information controller. The ANN with three layer feed-forward is trained once for several partially shaded conditions to determine the global MPP voltage. The fuzzy logic with polar information controller uses the global MPP voltage as a reference voltage to generate the required control signal for the power converter. Another objective of this study is to determine the estimated maximum power and energy generation of PV system through the same ANN structure. The effectiveness of the proposed method is demonstrated under the experimental real-time simulation technique based dSPACE real-time interface system for different interconnected PV arrays such as series-parallel, bridge link and total cross tied configurations.     

Computer simulation of shading effects in photovoltaic arrays

A simulation of shading effects in arrays with different string configurations has been done. Simulation has been performed using as the basic unit the solar cell, modelled in direct bias by the conventional one exponential model, and in reverse bias by an equation previously validated in different types of photovoltaic cells reverse characteristics. The influence of the amount of shading, the type of reverse characteristic of the cell, the string length and the number of shaded cells has been analysed, and some recommendations are extracted.     

局部阴影条件下光伏模组特性的建模与分析

以考虑了反向雪崩击穿的光伏电池元的双二极管电路模型为基础,建立了适用于阴影效应分析的光伏模组的数学仿真模型,分析了光伏模组在局部阴影条件下I-V和P-V特性及输出能力的变化,提出了增强光伏模组抗阴影能力的方法.     

An investigation on partial shading of PV modules with different connection configurations of PV cells

Partial shading is a commonly encountered issue in a PV (photovoltaic) system. In this paper, five different connection configurations of PV cells are studied to compare their performance under the condition of partial shading. They are SS (simple series), SP (series-parallel), TCT (total-cross-tied), BL (bridge-linked) and HC (honey comb) configurations. The electric network of each connection configuration is analyzed, taking into account the nonlinear nature of PV cells, by writing the Kirchhoff’s voltage and current equations. The analysis is followed by solving the simultaneous nonlinear equations using the Newton-Raphson algorithm, which allows the I-V (current-voltage) characteristic of the module with a specific configuration in response to different types and levels of partial shading to be evaluated. Comparison of the maximum power and fill factors of the five connection configurations is then carried out. Also studied is the reverse voltage across each PV cell. It is found that in most cases, the TCT configuration has a superior performance over the other four configurations in most comparison indices.     

Photovoltaic system testing techniques and results

Over the past three years, the New Mexico Solar Energy Institute (NMSEI) has tested and collected data on eight intermediate-size flat-plate photovoltaic systems. These data are now included in a valuable database for determining component reliability and system degradation trends. The specific test techniques used by NMSEI and the reliability of photovoltaic modules revealed by this testing are described and discussed. These methods are: I-V curve plotting, operating voltage and current measurements, and shading tests. These use of I-V curve data are important in determining array peak power rating and quickly locating large system faults. Operating voltage and current measurements are used in determining the location of module level faults. Bypass diode current measurements in conjunction with intentional module shading are used for isolating module faults in intermediate-size systems and systems with inaccessible module wiring. Of the 64000 modules tested, 362 modules (0.6%) were not contributing power