Modelling photovoltaic modules with neural networks using angle of incidence and clearness index

A neural network for modelling photovoltaic modules using angle of incidence and clearness index is proposed. Engineers require methods to estimate the output of a photovoltaic plant depending on meteorological conditions. Therefore, models for the grid inverter and the generator must be provided, and their outputs must be combined. The connection between both models is related to the maximum power point of the generator and how it is tracked by the inverter. That maximum power point under specific conditions of irradiance and module temperature is determined by the I–V curve of the module, which must be simulated under those conditions. Algebraic procedures were used to simulate the I–V curve. Recently, neural networks have been used for the same purpose. Previous methods only take into account the irradiance and the module temperature. The model proposed is based on neural networks, and it uses not only the irradiance and the module temperature but also the angle of incidence and the instantaneous clearness index as additional inputs. The normalised clearness replaces the standard clearness index because it allows the removal of the hourly trend found in this last index. This new model improves the results obtained with previous ones as it can distinguish amongst samples with the same solar irradiance and temperature values but with different angle of incidence and instantaneous clearness index. Results show that this model could be used to improve the accuracy of the tools used to forecast the output of photovoltaic plants. Copyright © 2014 John Wiley & Sons, Ltd.     

Effect of lithium intercalation on the photovoltaic performances of photovoltachromic cells

In the last few years, a new class of smart multifunctional photoelectrochemical devices has been attracting the interest of several academic institutions and industrial companies: photovoltachromic cells, combining the features of photoelectrochromic cells with those of dye‐sensitized solar cells. Here, we report the results of a detailed electrochemical analysis aiming at investigating the electrochemical behavior of these complex photoelectrochemical devices. In particular, we have been focused on the effect of Li⁺ ions displacement during the coloration of the electrochromic tungsten oxide on the performances of the photovoltaic unit. As we had previously observed striking differences between the performances of the barely photovoltaic mode (with the tungsten oxide in the bleached state) and the photovoltachromic mode (with the tungsten oxide in the colored state), we thus attempted to provide a reasonable physical interpretation to the observed phenomena. Copyright © 2013 John Wiley & Sons, Ltd.     

Carbon nanotube–polyaniline composites

The last decade has seen a growing interest in hybrid electrically conducting nanocomposites. This article aims to provide a detailed overview of the present status of research in carbon nanotube–polyaniline (CNT/PANI) composites, from processing to structural and property evaluations. CNT/PANI are synthesized by electrochemical and chemical processing. When chemical methods are used, the main challenge is to obtain processable CNT/PANI in the emeraldine salt (ES) form composites. Stable dispersions of ES–CNT in organic media are prepared using the post doping method, inverse emulsion polymerization, or ex situ polymerizations. On the contrary, stable water dispersions of CNT/ES are prepared using hydrophilization of a preformed CNT/ES composite, direct synthesis of micelle–CNT hybrid templates, interfacial polymerization, covalent functionalization of CNT with a water soluble polymer, or using electrostatic interactions between two oppositely charged ES and CNT aqueous colloids. Moreover, the strategies for the synthesis of ternary CNT/PANI composites incorporating noble metal nanoparticles, metal oxide, or graphene sheets are also presented and analyzed in depth. Finally, we give a review of potential applications, including chemical sensors, capacitors, fuel cells and electronic devices.     

熔体静电纺丝的工艺条件对纺丝纤维直径的影响

主要研究纺丝温度、纺丝电压、接收距离等参数对聚丙烯(PP)熔体静电纺丝纤维直径的影响。采用了只变一个参数,其它参数固定的常规实验方法。在实验条件范围内,随着纺丝温度的升高,纤维的平均直径逐渐减小,得到PP的最佳纺丝温度240℃。在固定电压的情况下,得到最佳接收距离7cm。在固定接收距离的情况下,随着电压的增加,电场中的喷射流熔体受到的电场力逐渐增大,得出最佳纺丝电压35kV。     

Development of a‐SiOx:H solar cells with very high Voc × FF product

In this study, deposition conditions for making a‐SiO_x:H are investigated systematically in order to obtain a high band gap material. We found that at given optical band gap, a‐SiO_x:H with favorable opto‐electronic properties can be obtained when deposited using low CO₂ flow rates and deposition pressures. We also found that a low radio frequency power density is required in order to limit the effect of ion bombardment on the material properties of i‐a‐SiO_x:H and thereby the solar cell performance. In addition, by decreasing the heater temperature from 300 to 200°C when making the i‐a‐SiO_x:H, the V_oc can be increased. We employed optimized p‐doped and n‐doped a‐SiO_x:H films into the p‐i‐n solar cells, and as a consequence, a high V_oc of over 1 V and high fill factor (FF) are obtained. When depositing on texture‐etched ZnO:Al substrates, a high efficiency a‐SiO_x:H single junction solar cell having a high V_oc × FF product of 0.761 (V_oc: 1.042 V, J_sc: 10.3 mA/cm², FF: 0.73, efficiency: 7.83%) was obtained. The a‐SiO_x:H solar cell shows comparable light degradation characteristics to standard a‐Si:H solar cells. Copyright © 2014 John Wiley & Sons, Ltd.     

6 kV电机四星带间隙组合式过电压保护器的选型与试验

从真空开关操作过电压导致高压电动机绝缘损坏的机理着手,分析了过电压保护器应具备的条件,确定了较常用的带串联间隙四星形过电压保护器的选型、安装、定期试验方法及注意事项。认为,避雷器额定电压的选择应不小于9.94kV;避雷器持续运行电压的选择应大于最高运行线电压即7.2kV,并小于工频放电电压值;避雷器残压值的选择应低于15.9kV;工频放电电压的选择值根据负载不同,应在9.3kV～12.48kV。     

低压电力线载波通信技术研究与应用

在详细分析了低压电力线载波通信特点的基础上,系统地阐述了电力线载波通信技术的发展概况,并针对传统的电力线载波通信技术,扩频载波通信技术以及正交频分复用技术阐述了其性能特点以及适用性。同时,结合国内电力线通信技术的发展,阐述了电力线载波通信技术应用现状。文章最后阐述了低压电力线载波通信的国内外发展现状。并提出了电力线载波通信的应用前景。     

一种单相电压凹陷检测方法及其DSP实现

动态电压恢复器（DVR）是目前解决供电电压凹陷问题的有效装置,对电压凹陷特征量的准确检测是DVR正常运行的前提。本文基于同步坐标变换及软件锁相环（SPLL）,提出了一种单相电压凹陷检测方法。该方法可以实现对单相电压凹陷幅值、起止时刻和相位跳变等特征量的动态检测。计算机仿真和DSP硬件实验表明,该方法适用于单相DVR的电压凹陷实时检测．     

碱金属热电转换器功率调节系统研究

针对碱金属热电转换器(AMTEC)的伏安特性,设计了DC/DC和DC/AC两级变换的功率调节系统.功率调节系统采用高频变压器隔离,避免了工频变压器产生的一系列问题.DC/DC变换器采用移相ZVS(零电压开关)PWM全桥变换和电压闭环控制,把AMTEC在较宽范围变动的输出电压变成稳定的直流电压.逆变器控制采用优化的特定消谐PWM技术,以滤波后总谐波含量(THD)为目标函数,计算预定开关角度.整个系统具有电压输入范围宽、转换效率高、输出波形THD低等优点.     

永磁磁阻发电机的电压控制

普通永磁同步发电机由于励磁不可调,端电压随转速或负载变化而变化,影响了供电品质.本文提出一种永磁磁阻发电机的电压控制策略,通过与发电机并联的电力电子装置,对其补偿适当励磁所需的无功电流,来保持发电机端电压的稳定.本文阐述了该发电机系统的结构、原理、电机的数学模型和电压控制方法.仿真实验证明该方法可在一定的转速和负载变化范围内保持端电压不变,补偿电流较小.