光伏发电系统变步长MPPT控制策略研究

光伏器件输出功率是外部环境、负载的非线性函数,为了充分发挥光伏器件的效能,最大功率点跟踪(Maximum Power Point Tracking,简称MPPT)控制应根据光伏器件的工作情况来调整占空比扰动量。现有变步长控制虽有较好的快速跟踪能力和稳态效果,但实现复杂、通用性较差。在分析光伏器件输出功率与占空比变化关系的基础上,提出一种简单的变步长MPPT控制方法。仿真和实验结果表明,该方法能够使光伏发电系统快速跟踪外部环境变化,在最大功率点处的控制效果明显优于扰动观察法,且实现简单。

户用光伏并网发电系统的研究与设计

阐述了基于数字信号处理器TMS320LF2407A的户用光伏并网发电系统的研究和设计。文中详细分析了系统的工作原理和锁相环设计,同时给出了系统的控制框图和锁相环程序流程图,并进行了样机实验。实验结果表明,并网电流波形良好,并且与电网电压同频同相,并网的功率因数为1。

自适应算法在光伏发电系统最大功率追踪中的应用

针对光伏发电系统的最大功率跟踪问题,采用自适应控制算法,在硬件电路得基础上进行了试验。结果表明,该方法能较快地跟踪太阳能的最大功率,并具有较高的跟踪精度。

后备式光伏发电系统的研究与设计

以光伏发电技术为基础,结合电力电子和微机控制等技术,研究并设计了后备式光伏发电系统。与传统的独立式光伏发电系统相比,该系统能够控制太阳能电池自动跟踪太阳光,并实现光伏电池的最大功率点跟踪(MPPT)控制和对蓄电池的充放电保护等功能。最后,建立了功率变换器以实现DC/DC,DC/AC变换。实验结果验证了该系统的可行性和实用性。

光伏发电系统中逆变器技术应用及展望

光伏阵列产生的是直流电流和电压,而许多负载都使用交流电,因此需要通过逆变器把直流电变成交流电。随着光伏发电系统(Photo Voltaic System,简称PVS)的日益推广,太阳能PVS中使用的逆变器也越来越多。如何用户对深入了解PVS中的逆变器性能及正确选用逆变器也越来越重要了。本文分类总结了用于PVS中的逆变器;分析研究了这些逆变器在PVS系统中的应用特点;展望了PVS中逆变器向高性能和智能化方向发展的趋势。

风力和太阳能光伏发电现状及发展趋势

阐述风能和太阳能是丰富清洁的可再生能源,风力发电和太阳能光伏发电是重要的后续能源,将为能源结构调整和环境保护做出巨大贡献。介绍国内外风能与太阳能资源,分析国内外风力及太阳能光伏发电现状,论述其发展趋势及需要解决的问题。针对风能与太阳能的特点,指出风力与太阳能互补发电比单一发电方式更优越,并介绍风力与太阳能光伏互补发电的研究现状及进一步发展所要做的努力。

风电/光伏发电接入电网的电压稳定及控制分析

作为典型的新能源发电方式,风电/光伏发电系统出力带有间歇性和不确定性,接入电网时容易导致电网电压不稳。因此该文从静态和动态两个方面分析了风电/光伏发电接入电网的电压稳定能力,分别提出了风电和光伏发电入网的电压控制策略,以防止电网运行受到影响,为改善电力系统能源结构提供了技术支撑。

风电光伏发电接入电网的电压稳定及控制方法

随着可持续发展观念的引入,新能源的开发与使用越来越受到人们的重视。如今,电的已经成为人们生存和发展必不可少的能源,但是传统的发电方法费时费力,污染环境,所以就出现了风电/光伏发电。但是因为风电/光伏发电具有不稳定性,所以导致了风电/光伏发电接入电网的电压也不稳定。本文通过研究风电/光伏发电接入电网的电压不稳定的原因,提出了相应的应对策略及控制方法。

一种新型的光伏逆变器控制方法

提出一种用于光伏发电系统中逆变器的直接电流跟踪控制方法,并对其工作原理进行了理论分析和实验验证。不同于现有的SPWM逆变和同步锁相控制,该方案具有控制简便、输出功率因数高、工作可靠等优点,具有推广价值。

A review on the cooling of energy conversion and storage systems using thermoelectric modules

Exploitation of sustainable energy sources requires the use of unique conversion and storage systems,such as solar panels,batteries,fuel cells,and electronic equipment.Thermal load management of these energy conversion and storage systems is one of their challenges and concerns.In this article,the thermal management of these systems using thermoelectric modules is reviewed.The results show that by choosing the right option to remove heat from the hot side of the thermoelectric modules,it will be a suitable local cooling,and the thermoelectric modules increase the power and lifespan of the system by reducing the spot temperature.Thermoelectric modules were effective in reducing panel temperature.They increase the time to reach a temperature above 50℃ in batteries by 3 to 4 times.Also,in their integration with fuel cells,they increase the power density of the fuel cell.

Short-term prediction of photovoltaic power generation based on LMD-EE-ESN with error correction

Considering the instability of the output power of photovoltaic(PV)generation system,to improve the power regulation ability of PV power during grid-connected operation,based on the quantitative analysis of meteorological conditions,a short-term prediction method of PV power based on LMD-EE-ESN with iterative error correction was proposed.Firstly,through the fuzzy clustering processing of meteorological conditions,taking the power curves of PV power generation in sunny,rainy or snowy,cloudy,and changeable weather as the reference,the local mean decomposition(LMD)was carried out respectively,and their energy entropy(EE)was taken as the meteorological characteristics.Then,the historical generation power series was decomposed by LMD algorithm,and the hierarchical prediction of the power curve was realized by echo state network(ESN)prediction algorithm combined with meteorological characteristics.Finally,the iterative error theory was applied to the correction of power prediction results.The analysis of the historical data in the PV power generation system shows that this method avoids the influence of meteorological conditions in the short-term prediction of PV output power,and improves the accuracy of power prediction on the condition of hierarchical prediction and iterative error correction.

Sixty-four-slice computed tomography in surgical strategy of portal vein cavernous transformation

AIM:To investigate the role of 64-slice computed tomography(CT) in portal vein cavernous transformation to determine surgical strategy.METHODS:The site of lesions and extent of collateral circulation in 12 pediatric cases of cavernous transformation of the portal vein with surgical treatment were analyzed.RESULTS:Eleven of 12 children had esophageal varices and were treated with lower esophageal and gastric devascularization and splenectomy,and the other case was only treated with splenectomy.There were eight cases with spontaneous spleen/stomach-renal shunt,four with Retzius vein opening,which was reserved during surgery.Three cases of lesions involving the intrahepatic portal vein(PV) were treated with living donor liver transplantation.One patient died from PV thrombosis after liver transplantation,and the rest had no significant complications.CONCLUSION:The PV,its branches and collateral circulation were clearly seen by 64-slice spiral CT angiography,which helped with preoperative surgical planning.

A Real-time Modeling of Photovoltaic Array

This paper mainly aims at the modeling problem of the photovoltaic (PV) array with a 30 kW PV grid-connected generation system. An iterative method for the time-varying parameters is proposed to model a plant of PV array. The relationship of PV cell and PV array is obtained and the solution for PV array model is unique. The PV grid-connected generation system is used to demonstrate the effectiveness of the proposed method by comparing the calculated values with the actual output of the system.

Transient Stability Assessment of Synchronous Generator in Power System with High-Penetration Photovoltaics

As photovoltaic （PV） capacity in power system increases, the capacity of synchronous generator needs to be reduced relatively. This leads to the lower system inertia and the higher generator reactance, and hence the generator transient stability may negatively be affected. In particular, the impact on the transient stability may become more serious when the considerable amounts of PV systems are disconnected simultaneously during voltage sag. In this work, the generator transient stability in the power system with significant PV penetration is assessed by a numerical simulation. In order to assess the impact from various angles, simulation parameters such as levels of PV penetration, variety of power sources （inverter or rotational machine）, and existence of LVRT capability are considered. The simulation is performed by using PSCAD/EMTDC software.

PV Power Short-Term Forecasting Model Based on the Data Gathered from Monitoring Network

The degree of accuracy in predicting the photovoltaic power generation plays an important role in appropriate allocations and economic operations of the power plants based on the generating capacity data gathered from the geographically separated photovoltaic plants through network. In this paper, a forecasting model is designed with an optimization algorithm which is developed with the combination of PSO （Particle Swarm Optimization） and BP （Back Propagation） neural network. The proposed model is further validated and the experiment results show that the predication model assures the prediction accuracy regardless the day type transitions and other relevant factors, in the proposed model, the prediction error rate is worth less than 20% in all different climatic conditions and most of the prediction error accuracy is less than 10% in sunny day, and whose precision satisfies the management requirements of the power grid companies, reflecting the significance of the proposed model in engineering applications.

Some Remarks about the Deployment of Floating PV Systems in Brazil

Floating photovoltaic systems installed in water bodies such as natural lakes or dams reservoirs, have attracted increased worldwide attention since 2011 and have already been deployed in several countries, including Japan, South Korea and USA. In Brazil, pilot-projects were announced in the reservoirs of hydroelectric power plants of Balbina （State of Amazonas） and Sobradinho （State of Bahia）. Several advantages, not necessarily valid in Brazil, are mentioned for deploying this kind of technology, such as an increase in energy generation, reduction of water losses through evaporation, low environmental impact, no occupation of land etc. In this article, several of these allegations are analyzed preliminarily under the Brazilian point of view, and relevant considerations are presented. It is concluded that the technical and economic advantages of floating photovoltaic systems are not yet clear in Brazil and that pilot projects, such as those under way, should be used to clarify several important aspects related to them.

Transient Stability Analysis of Power System with Photovoltaic Systems Installed

The impact of large-scale grid-connected PV （photovoltaics） on power system transient stability is discussed in this paper. In response to an increase of PV capacity, the capacity of conventional synchronous generator needs to be reduced relatively. This leads to the lower system inertia and the higher generator reactance, and hence, the power system transient stability may negatively be affected. In particular, the impact on the transient stability may become more serious when the considerable amounts of PV systems are disconnected simultaneously during voltage sag. In this work, the potential impact of significant PV penetration on the transient stability is assessed by a numerical simulation using PSCAD/EMTDC.

Design of hybrid damping controller based on multi-target gravitational search optimization algorithm in a multi-machine power system with high penetration of PV park

A mathematical approach was proposed to investigate the impact of high penetration of large-scale photovoltaic park(LPP) on small-signal stability of a power network and design of hybrid controller for these units.A systematic procedure was performed to obtain the complete model of a multi-machine power network including LPP.For damping of oscillations focusing on inter-area oscillatory modes,a hybrid controller for LPP was proposed.The performance of the suggested controller was tested using a 16-machine 5-area network.The results indicate that the proposed hybrid controller for LPP provides sufficient damping to the low-frequency modes of power system for a wide range of operating conditions.The method presented in this work effectively indentifies the impact of increased PV penetration and its controller on dynamic performance of multi-machine power network containing LPP.Simulation results demonstrate that the model presented can be used in designing of essential controllers for LPP.

Issues and Solutions for China's Photovoltaic Power Industry

Solar energy is an important renewable energy.Developing photovoltaic power will not only relieve the energy supply-demand contradiction and optimize the energy structure,but also help to restructure this industry.This paper analyzes the status quo and the development prospects of China's photovoltaic power industry and its existing issues,and puts forward some suggestions and solutions for its healthy and orderly development.