基于Boost电路的光伏发电MPPT控制系统仿真研究

基于光伏电池输出特性及MPPT控制原理的分析,研究了基于Boost电路的光伏发电MPPT控制系统的模型,并分析了该模型中各子模块的工作原理,并应用Simulink软件搭建了整个系统的仿真模型。以光伏阵列STP0950S-36为例,仿真验证了所研究的MPPT控制系统能很好地实现最大功率跟踪,并能快速响应外界环境的变化,有效提高光伏发电的效率。     

Correlation between ultrafast transient photomodulation spectroscopy and organic photovoltaic solar cell efficiency based on RR-P3HT/PCBM blends

Ultrafast transient spectroscopy was applied to various films of regio-regular polythiophene (RR-P3HT, donor-D) and C₆₀ derivative (PCBM, acceptor-A) blends, in conjunction with organic photovoltaic (OPV) solar cell fabrication and evaluation based on the same blends, for investigating the existence of a correlation between the device efficiency and the transient photophysics characteristics. For our transient spectroscopy measurements we used the ps pump–probe transient photomodulation (PM) technique having a unique probe spectral range in the mid-IR (0.25–1.05 eV). We found that the transient PM spectra contain photoinduced absorption bands of excitons in the donor polymer, charge transfer excitons (CTE) at the D–A interfaces, and free polarons. We compared the relative density of photogenerated CTE in D–A blends having various D–A weight ratio with the photocurrent density of fabricated solar cells based on the same blends. We found that the dissociation of CTE into free charges correlates well with the optoelectronic measurements of the corresponding solar cell. The more efficient CTE dissociation occurs in films having the optimum D–A weight ratio (which is 1.2:1 for the P3HT/PCBM system) that shows the highest OPV power conversion efficiency; this is due to the lowest CTE binding energy for this blend that results from the most suitable D- and A- grain sizes. We also show that the exciton lifetime is the shortest for the optimum blend, and this helps boosting the device efficiency by reducing energy loss.     

Characteristics of large‐scale nanohole arrays for thin‐silicon photovoltaics

Nanostructured crystalline silicon is promising for thin‐silicon photovoltaic devices because of reduced material usage and wafer quality constraint. This paper presents the optical and photovoltaic characteristics of silicon nanohole (SiNH) arrays fabricated using polystyrene nanosphere lithography and reactive‐ion etching (RIE) techniques for large‐area processes. A post‐RIE damage removal etching is subsequently introduced to mitigate the surface recombination issues and also suppress the surface reflection due to modifications in the nanohole sidewall profile, resulting in a 19% increase in the power conversion efficiency. We show that the damage removal etching treatment can effectively recover the carrier lifetime and dark current–voltage characteristics of SiNH solar cells to resemble the planar counterpart without RIE damages. Furthermore, the reflectance spectra exhibit broadband and omnidirectional anti‐reflective properties, where an AM1.5 G spectrum‐weighted reflectance achieves 4.7% for SiNH arrays. Finally, a three‐dimensional optical modeling has also been established to investigate the dimension and wafer thickness dependence of light absorption. We conclude that the SiNH arrays reveal great potential for efficient light harvesting in thin‐silicon photovoltaics with a 95% material reduction compared to a typical cell thickness of 200 µm. Copyright © 2012 John Wiley & Sons, Ltd.     

Solar cell efficiency tables (version 43)

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined, and new entries since July 2013 are reviewed. Copyright © 2013 John Wiley & Sons, Ltd.     

Improved Morphology and Efficiency of Polymer Solar Cells by Processing Donor–Acceptor Copolymer Additives

A novel wide‐bandgap conjugated polymer PBTA‐FPh based on benzodithiophene‐alt‐benzo[1,2,3]triazole as the main chain and a polar pentafluorothiophenyl (FPh) group in the side chain has been designed and synthesized. In comparison to the pristine polymer PBTA‐BO that consists of nonpolar alkyl side chains, the resulting PBTA‐FPh exhibits less pronounced aggregation while possessing analogous optical and electrochemical bandgaps. Contact angle measurements demonstrate that the surface energy can be enhanced by incorporating FPh moiety, leading to a better miscibility of PBTA‐BO with PC₇₁BM in the presence of a certain amount of PBTA‐FPh. The photoactive layer of PBTA‐BO:PC₇₁BM:PBTA‐FPh with weight ratio of 1:1.2:0.02% exhibits a percolated network with the fibrous features, as revealed by transmission electron microscopy measurements. Of particular interest is the significantly improved photovoltaic performances of polymer solar cell devices for which the power conversion efficiency is enhanced from 6.46% for the control device to 7.91% for device processed with PBTA‐FPh as the polymeric additive. These observations indicate that introducing donor–acceptor type of polymeric additive comprising of polar groups in the side chain can be a promising strategy for the fabrication of high‐performance polymer solar cells.     

单相光伏发电并网的研究

针对如何提高太阳能光伏发电系统的转化效率,对具有最大功率控制的系统进行研究,提出了一种双环控制方式。并以STM32为控制器,给出了其控制方法。通过Matlab建模设计光伏输出后的控制系统,新的控制系统实现了最大功率跟踪与功率因数校正。仿真表明,该方式具有简单、控制方便、效率高的优点。并通过实物加以验证该方法的可行性,该控制策略可应用于单极式光伏并网系统最大功率点跟踪控制,且实现了系统的高效率并网运行。     

Influence of hydrogenation on the dark current mechanism of HgCdTe photovoltaic detectors

The influence of hydrogenation on the dark current mechanism of HgCdTe photovoltaic detectors is studied.The hydrogenation is achieved by exposing samples to a H_2/Ar plasma atmosphere that was produced during a reactive ion etching process. A set of variable-area photomask was specially designed to evaluate the hydrogenation effect.It was found that the current-voltage characteristics were gradually improved when detectors were hydrogenated by different areas. The fitting results of experimental results at reverse bias conditions sustained that the improvement of current-voltage curves was due to the suppression of trap assisted tunneling current and the enhancement of minority lifetime in the depletion region. It was also found that the dominative forward current was gradually converted from a generation-recombination current to a diffusion current with the enlargement of the hydrogenation area, which was infered from the ideality factors by abstraction of forward resistance-voltage curves of different detectors.     

分布式光伏电源对配电网电压波动的影响研究

分布式光伏电源接入配电网后导致电压波动加剧等问题,限制了光伏发电的快速发展。文章从理论角度分析得到光伏功率波动水平以及光伏电源接入点短路容量大小是影响配电网电压波动大小的主要因素;考虑到未来光伏容量不断增加,光伏功率波动水平必将不断提高,因此增大接入点短路容量是降低电压波动实现大量分布式光伏电源接入配电网最为可行的方法,而配电网采用环网结构能增大接入点短路容量;最后在PSCAD/EMTDC中搭建了完整的光伏电源系统以及IEEE13节点模型,仿真验证了配电网采用环网结构增大短路容量能有效削弱光伏电源对配电网电压波动的影响,为分布式光伏的良好发展奠定基础。     

Modeling of Nonlinear Magnetizing Characteristics of Pole Transformer for Analyzing Islanding Prevention of Photovoltaic System

With increasing penetration of distributed generators such as photovoltaic (PV) systems in distribution systems, it is very important to quickly detect islanding caused by power system faults in order to assure electrical safety. We have developed a nonlinear magnetizing characteristics model of pole transformers for use in analyzing islanding prevention in PV systems. Basic experiments on the islanding detection were performed for verification of the proposed model. Analytical results obtained by the proposed model agreed well with experimental results.     

Regional forecasts of photovoltaic power generation according to different data availability scenarios: a study of four methods

The development of methods to forecast photovoltaic (PV) power generation regionally is of utmost importance to support the spread of such power systems in current power grids. The objective of this study is to propose and to evaluate methods to forecast regional PV power 1 day ahead of time and to compare their performances. Four forecast methods were regarded, of which two are new ones proposed in this study. Together, they characterize a set of forecast methods that can be applied in different scenarios regarding availability of data and infrastructure to make the forecasts. The forecast methods were based on the use of support vector regression and weather prediction data. Evaluations were performed for 1 year of hourly forecasts using data of 273 PV systems installed in two adjacent regions in Japan, Kanto, and Chubu. The results show the importance of selecting the proper forecast method regarding the region characteristics. For Chubu, the region with a variety of weather conditions, the forecast methods based on single systems' forecasts and the one based on stratified sampling provided the best results. In this case, the best annual normalized root mean square error (RMSE) and mean absolute error (MAE) were 0.25 and 0.15 kWh/kWh_avg, respectively. For Kanto, with homogeneous weather conditions, the four methods performed similarly. In this case, the lowest annual forecast errors were 0.33 kWh/kWh_avg for the normalized RMSE and 0.202 kWh/kWh_avg for the normalized MAE. Copyright © 2014 John Wiley & Sons, Ltd.