基于层次聚类分场景的光伏汇聚趋势量化方法

持续功率曲线能反映长时间波动特性规律,通过研究已建设光伏集群持续功率曲线,建立预测模型揭示不同规模集群的汇聚演化规律,最终得到待建光伏集群的持续功率曲线。首先,利用层次聚类算法确定光伏集群汇聚规模的分层顺序,得到装机容量逐层递增的光伏集群,并提出汇聚效应指标验证顺序的有效性;其次,为了更好地判断和预测光伏持续功率曲线的变化趋势,对持续功率曲线进行出力场景划分;最后,为避免单一模型预测偏差,在各出力场景下,通过改进的信息熵组合预测模型掌握汇聚过程中规模演变规律,完成规划待建设集群持续功率曲线的预测。利用河北某地区实测数据仿真结果表明：验证聚类方法得到的集群分层顺序更能体现汇聚效应,并有效提高预测精度;出力场景划分准确刻画集群持续功率曲线汇聚趋势;通过模型对比表明分场景下改进信息熵组合预测模型更能精确完成待建光伏集群持续功率特性的量化分析。     

PV output power fluctuations smoothing: The MYRTE platform experience

The MYRTE platform is one of the PEPITE project applications included in the PAN-H program of the French Research National Agency, under the reference ANR-07-PANH-012. This platform consists of a photovoltaic array, a fuel cell, an electrolyzer, tanks (H₂, O₂ and H₂O), a thermal management system and electricity converters associated to various sub-systems.     

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.     

The effect of tilt angle, air pollution on performance of photovoltaic systems in Tehran

The tilt angle influences the amount of energy collected by a photovoltaic module. However, representations of these effects on the energy yield and the performance of the PV system are commonly based on the theoretical calculations, whereas there is a lack of experimental investigations. To verify the calculations, an experimental setup has been installed at the Department of Electrical and Computer Engineering, University of Tehran. Some results of this test station, from March, 1999 to January, 2000 are represented in this paper.     

基于小波和分形提取磨粒图像特征参数的研究

根据小波变换和分形理论在多尺度分析与自相似本质上的一致性,提出了一种提取磨粒图像特征参数的新方法。给出了磨粒图像的小波变换方法和小波变换近似系数的分形维数计算方法,然后对磨粒图像进行了分析,实现了磨粒图像的特征提取。结果表明：小波变换近似系数的分形维数反映了磨粒图像上磨粒尺度及数量,可以作为磨粒图像的综合特征参数。     

基于DFT的电力系统频率及谐波精确算法

频率是电力系统运行特性评估中最重要的参数之一。传统频率测量算法存在不同程度的误差,而它所带来的频谱泄露则影响谐波测量的精度。提出基于离散傅里叶变换(DFT)的改进测频算法,该算法利用相隔半个周波的3组信号数据求取2个修正系数,分别对相邻两个周波的相角进行修正,再通过其相角差求得实际频率。在此基础上,通过实时修正采样频率实现同步采样,从而精确进行谐波分析。4种不同情况的仿真实验结果表明算法具有较好的频率跟踪效果和谐波测量精度。     

A preliminary study on potential for very large-scale photovoltaic power generation (VLS-PV) system in the Gobi desert from economic and environmental viewpoints

A 100 MW very large-scale photovoltaic power generation (VLS-PV) system is designed assuming that it will be installed in the Gobi desert, which is one of the major deserts in the world. Array arrangement, array support, foundation, wiring, and so on are designed in detail. Then energy payback time (EPT), life-cycle CO₂ emission rate and generation cost of the system are estimated based on the methodology of life-cycle analysis. As a result of the estimation, 1.7 year of EPT and 12 g C/kWh of CO₂ emission rate are obtained. These show that VLS-PV in the Gobi desert would be very promising for the global energy and environmental issues. The generation cost is calculated at 8.6 cent/kWh assuming that PV module price is one US $/W and system lifetime is 30 years.     

Morlet小波在振动信号包络检测中的应用

提出了Morlet小波在振动信号包络检测中的应用方法。该方法不仅能检测出故障信号的幅值信息,而且也能检测出故障信号中的相位信息。利用该方法对轴承的故障信号进行了分析,检测到了该故障信号幅值信息和相位信息,其效果令人满意。与原Hilbert变换比较,该方法具有重要优点。     

Photovoltaic manufacturing, system design and application trend in Iran

The application of PV systems in Iran has started since 1982, when a 1710 Watt power generator was installed in Fars (south east of Iran) to supply a telecommunication site by AEG. Till 1993 more than one hundred PV systems with various capacity and purpose of use have been installed over the country. In 1993 a production line for multicrystalline silicon solar cells and modules was installed in Tehran by the ministry of Post, Telegraph and Telephone (PTT). Since then the application of photovoltaic energy is spreading in various fields in Iran. In this paper the present and future state of photovoltaic plants, solar cell fabrication technology and optimization in system design and power conditioning are reported.     

AC side harmonic and phenomena accompanying DC-injection of utility-interactive PV system

The experiments investigated phenomena related to direct contact between the DC output of a PV array and the AC power from the utility grid. The results show that the DC power flows through the distribution transformers (DC-injection) saturating their magnetic circuits. The saturation of magnetic circuits makes peak currents, incorporating a large portion of even harmonics, flow through the high-voltage side of the distribution transformer, adding the level of harmonic distortion of its exciting current. With the increase of injecting DC-current to the utility grid, peak currents at the primary side of distribution transformer increases the most, and even among the same effective (rms) values, the increase of primary side current is larger than that of the secondary side current.     

Peak-power reduction with 100 kW PV and battery combined system at Shonan Institute of Technology

The grid connected 100 kW PV and 345 kWh battery combined system introduced in 1998 at Shonan Institute of Technology has been investigated. The system, equipped with PV and large battery, has a peak cut function against the big surge in electric power consumption in summer as well as working as an emergency electric power source. The daily peak of power consumption during summer occurs at 2:00 p.m. This time does not coincide with the time of peak power generation. The use of the PV/battery combined peak cut function effectively cuts consumption by 7% during the peak consumption period.     

Day-ahead electricity price forecasting using wavelet transform combined with ARIMA and GARCH models

This paper proposes a novel price forecasting method based on wavelet transform combined with ARIMA and GARCH models. By wavelet transform, the historical price series is decomposed and reconstructed into one approximation series and some detail series. Then each subseries can be separately predicted by a suitable time series model. The final forecast is obtained by composing the forecasted results of each subseries. This proposed method is examined on Spanish and PJM electricity markets and compared with some other forecasting methods.     

Case studies of large-scale PV systems distributed around desert area of the world

To show the huge potential of PV systems, the authors have been studying the feasibility of large-scale PV plants. If a PV module cost is assumed to be 100¥/W, it gives the electricity at a cost of 7.70−13.12 ¥/kWh for a 100 MW plant size located at 6 desert sites around the world, considering the site irradiation,local labor cost, etc. for each site. In spite of the fixed, flat plate, the cost can reach a fairly low level. The station will be composed of 20 sub-units × 10 units of 500 kW optimum size sub-units.     

Determining optimum tilt angles and orientations of photovoltaic panels in Sanliurfa, Turkey

The performance of a photovoltaic (PV) panel is affected by its orientation and its tilt angle with the horizontal plane. This is because both of these parameters change the amount of solar energy received by the surface of the PV panel. A mathematical model was used to estimate the total solar radiation on the tilted PV surface, and to determine optimum tilt angles for a PV panel installed in Sanliurfa, Turkey. The optimum tilt angles were determined by searching for the values of angles for which the total radiation on the PV surface was maximum for the period studied. The study also investigated the effect of two-axis solar tracking on energy gain compared to a fixed PV panel. This study determined that the monthly optimum tilt angle for a PV panel changes throughout the year with its minimum value as 13° in June and maximum value as 61° in December. The results showed that the gains in the amount of solar radiation throughout the year received by the PV panel mounted at monthly optimum tilt angles with respect to seasonal optimum angles and tilt angel equal to latitude were 1.1% and 3.9%, respectively. Furthermore, daily average of 29.3% gain in total solar radiation results in an daily average of 34.6% gain in generated power with two-axis solar tracking compared to a south facing PV panel fixed at 14° tilt angle on a particular day in July in Sanliurfa, Turkey.     

Performance estimation of a PV water-pumping system with utilizability function

A procedure using the concept of the utilizability function for estimating the long-term performance of direct-coupled photovoltaic water-pumping systems is presented. A modified utilizability function, based on radiation statistics, is developed, and the monthly-averaged daily amount of water is simply estimated.