太阳能电池发电量实时监控系统

为了实时监控太阳能电池发电量,设计一种太阳能电池发电量实时监控系统,该系统利用单片机和霍尔电流传感器实时测量太阳能电池的输出电压、电流得到输出功率,然后经运算得到电量值送液晶显示器显示结果.实验表明:该系统测量误差小于3%,且低成本、低功耗.使其在离网光伏系统中应用广泛.     

基于嵌入式处理器STM32的抽油机井实时监控系统设计

为了解决抽油机井生产过程中的实时监控问题,本文提出了一种基于嵌入式处理器STM32的抽油机井实时监控系统设计方案,并完成系统的软硬件设计.该系统能够测量抽油机并的油压、油温、三相电流电压、功率、有功、无功、功率因数以及示功图等参数,以此来实现对抽油机井的实时监控.系统各部分与上位机使用RS485总线连接,上位机通过Modbus协议与各模块通信.该系统具有操作简便、测量准确的特点,实现了数据的实时接收和远程监控功能.     

基于CAN总线的电气火灾监控系统设计

介绍了基于CAN总线的火灾监控系统的设计方法,该监控系统可对三相电流信号以及漏电流信号进行检测,并可实时显示和报警.还可通过CAN总线进行网络通信以完成分布式远程控制和故障诊断功能.     

基于AVR单片机的太阳能发电量检测装置的设计

发电量检测是太阳能光伏发电系统的重要组成部分.本文设计了一种精度更高,功耗、成本更低的太阳能发电量检测系统.系统以AVR单片机为控制器,避免了数模转换器等引起的能量消耗并最大程度地简化了系统结构.同时引入了霍尔电流传感器,可以几乎无损耗地将电流信号转换为电压信号.实验结果表明：太阳能发电系统正常工作时,太阳能发电量能够实时显示在显示屏上,且误差率不超过5％.     

基于VB的大电流直流电源的实时监控系统

文章介绍了一种基于VB的监控系统,符合大电流直流电源的控制要求,能实现直流电压、电流的实时监控,移相脉冲模拟显示,历史数据查询以及异常报警等功能,为电源的实时监视和智能控制提供了很大的方便。     

基于组态王的分布式监控系统研制

针对校飞监控系统对自动化与信息化要求高的实际情况,研制开发了一种基于组态王的分布式监控系统,整套监控系统能对校飞设备进行实时监视、控制。该系统可以实时采集和显示设备的相关参数,并可进行事后回放,友好的界面操作系统、简易的操作环境,使系统更人性化。介绍了系统的组成、监控软件实现及其核心代码。该系统已得到成功应用,系统稳定,降低了飞行成本,提高了工作效率。     

重庆轻轨实时移动视频监控系统研究

文章给出了一种设计实时移动视频监控系统的方案。实时移动视频监控系统包括：控制中心监视子系统、车站监视子系统、车载子系统和传输子系统。文章首先从结构和功能两个方面阐述了各个子系统，然后从技术层面说明了实时移动视频监控系统的优越性。该系统在重庆轻轨中得到应用，并取得了较好的实际效果。     

基于ZigBee的油井数据传输系统研究与设计

为实现油井抽油机参数实时监控,利用ZigBee无线数据传输,实现数据的采集、存储、显示控制系统。系统以ZigBee模块为核心,前端采用压力传感器、温度传感器、电流传感器进行测量,得到的数据通过ZigBee模块以无线局域网的方式输出。接收端为手持设备,通过ZigBee模块接收并显示。该系统工作稳定,使用方便,为掌握抽油机生产状况提供极大的帮助。     

连续激光辐照硅太阳电池损伤特性的光束诱导电流表征

针对连续激光辐照硅太阳能电池的损伤特性,采用光束诱导电流(LBIC)成像方法进行表征,并对其毁伤特性进行了分析。首先采用波长为1 070 nm的连续激光聚焦在硅太阳能电池表面,诱导太阳能电池产生损伤,再通过LBIC系统扫描得到激光辐照区域的光电流分布图,进而分析太阳能电池的损伤情况。为了表征不同深度下太阳能电池的损伤情况,LBIC测量系统分别采用650 nm和980 nm波长激光作为探测光源。结果表明,1 070 nm连续激光辐照硅太阳能电池非栅线部位时,太阳能电池损伤首先发生在内部;随着功率密度的增加,在太阳能电池表面熔融前,电池内部已经产生了失效区域。当激光辐照太阳能电池栅线时,栅线会发生熔断,导致辐照位置远离电极引线一侧的光电流下降;严重时会使太阳能电池产生垂直于栅线的裂纹,使远离电极引线一侧的电池失效。该研究成果可为连续激光辐照太阳能电池损伤机理研究提供参考。     

基于Modbus的供水自动化监控系统构建

根据供水自动化监控系统的应用需求,构建了一种有效的监控系统网络的模型,系统采用Modbus协议进行远程数据传输,监控应用层与现场层能实时的进行数据交换,进而实时在线的监控自动供水系统。通过对该网络模型的构建,说明了整个系统的构成,监控软件的相关设计和开发,以及Modbus协议的实现。实践证明,本方案是一种有益的尝试,得到了良好的应用。     

Reactive power consumption in photovoltaic inverters: a novel configuration for voltage regulation in low‐voltage radial feeders with no need for central control

High photovoltaic (PV) system generation in low‐voltage feeders can cause voltage rise especially in low demand conditions. The conventional way of coping with voltage violation is disconnection of the PV systems or curtailment of the generated power. To address this issue, a novel configuration for voltage management in a radial feeder via regulated reactive power capability in PV inverters is presented. The novelty of the proposed configuration is based on the fact that all the PV inverters with the ability to consume reactive power are involved in voltage regulation without being centrally controlled. In order to apply the configuration, a reference voltage is initially estimated for each PV system, and the PV inverters are calibrated accordingly. These settings depend on the feeder topology and can be calculated by the distribution network operator with a simple power flow modelling tool. Finally, this paper presents a sensitivity analysis in order to examine how reactive power consumption in a single inverter influences PV penetration and inverter sizing at various PV topologies along the feeder. Copyright © 2014 John Wiley & Sons, Ltd.     

Flyback Inverter Controlled by Sensorless Current MPPT for Photovoltaic Power System

This paper presents a flyback inverter controlled by sensorless current maximum power point tracking (MPPT) for a small photovoltaic (PV) power system. Although the proposed system has small output power such as 300 W, a few sets of small PV power systems can be easily connected in parallel to yield higher output power. When a PV power system is constructed with a number of small power systems, the total system cost will increase and will be a matter of concern. To overcome this difficulty, this paper proposes a PV system that uses no expensive dc current sensor but utilizes the method of estimating the PV current from the PV voltage. The paper shows that the application of this novel sensorless current flyback inverter to an MPPT-operated PV system exhibits satisfactory MPPT performance similar to the one exhibited by the system with a dc current sensor as well. This paper also deals with the design method and the operation of the unique flyback inverter with center-tapped secondary winding.     

An analysis of reliability in the early stages of photovoltaic systems in Japan

In order to disseminate Photovoltaic (PV) technologies into the energy network, the cost down is not only important, but also improving the performance of the PV system is significant issues. Long‐term reliability is one of the most important issues in terms of PV system performance. Previous researches were mainly focused on the reliability of PV modules, but the PV system is composed of a power conditioner, wiring, junction box, and so on. To improve the reliability of PV systems, it is important to accumulate trouble cases focused on all components of PV system. In this paper, we aim at evaluation of the reliability for the PV system on the early stages of PV system's lifetime by using large number of Japanese PV systems' data from the field Test in Japan. New Energy and Industrial Technology Development Organization has been running the “Field test project in Japan” from 1992. In this project, PV system users have cooperated with the collection of monitoring data and reported on the information of maintenance and certain failures of PV systems for 4 years after installation of PV system. Using those reports each year of installation, we evaluated reliability of PV systems by means of parameters such as Mean Time Between Failure, Mean Time To Repair, and the suspension time of PV system. As a result, the main trouble of PV systems was related power conditioner, and a few trouble of PV module was caused by typhoon. Moreover, the trend of the failure rate before FY 2000 of installation was demonstrated as the trend of initial failure in “bathtub curve;” however, the trend of its after FY 2001 of installation was indicated as the accidental failure in “bathtub curve.” Further, the operator simply forgot to restart the power conditioner after maintenance or suspensions of PV system in many trouble cases, and the user did not notice that it had been suspended for a while. These trouble cases can be avoidable easily through the effective alarm such as error message of power conditioner systems with monitoring systems. Thereby, monitoring with the evaluation method of PV systems is one of the important technologies due to the long‐term reliability and stable operation. Copyright © 2010 John Wiley & Sons, Ltd.     

A novel power benefit prediction approach for two‐axis sun‐tracking type photovoltaic systems based on semiconductor theory

Photovoltaic (PV) systems incorporated with sun‐tracking technology have been proposed and verified to effectively increase the power harvest. However, the actual power generated from a PV module has not been investigated and compared with that analyzed from theoretical models of the PV material. This study proposes a novel method for estimating the power benefit harvested by a two‐axis sun‐tracking type (STT) PV system. The method is based on semiconductor theory and the dynamic characteristics, including maximum power point tracking of PV modules that can be integrated with the database of annual solar incidences to predict the power harvested by any STT PV system. The increment of annual energy provided by an STT PV system installed at any arbitrary latitude, compared with that by a fixed‐type system, can be accurately estimated using the proposed method. To verify the feasibility and precision performance of this method, a fixed‐type and a two‐axis STT PV system were installed at 24.92° north latitude in northern Taiwan and tested through long‐term experiments. The experimental results show that the energy increments estimated by the theoretical model and actual measurement are 19.39% and 16.74%, respectively. The results demonstrate that the proposed method is capable of predicting the power benefit harvested by an STT PV system with high accuracy. Using our method, a PV system installer can evaluate beforehand the economic benefits of different types of PV systems while taking different construction locations into consideration, thereby obtaining a better installation strategy for PV systems. Copyright © 2012 John Wiley & Sons, Ltd.     

A Single-Phase Voltage-Controlled Grid-Connected Photovoltaic System With Power Quality Conditioner Functionality

Future ancillary services provided by photovoltaic (PV) systems could facilitate their penetration in power systems. In addition, low-power PV systems can be designed to improve the power quality. This paper presents a single-phase PV system that provides grid voltage support and compensation of harmonic distortion at the point of common coupling thanks to a repetitive controller. The power provided by the PV panels is controlled by a Maximum Power Point Tracking algorithm based on the incremental conductance method specifically modified to control the phase of the PV inverter voltage. Simulation and experimental results validate the presented solution.     

Renewable Energy Systems With Photovoltaic Power Generators: Operation and Modeling

A substantial increase of photovoltaic (PV) power generators installations has taken place in recent years, due to the increasing efficiency of solar cells as well as the improvements of manufacturing technology of solar panels. These generators are both grid-connected and stand-alone applications. We present an overview of the essential research results. The paper concentrates on the operation and modeling of stand-alone power systems with PV power generators. Systems with PV array-inverter assemblies, operating in the slave-and-master modes, are discussed, and the simulation results obtained using a renewable energy power system modular simulator are presented. These results demonstrate that simulation is an essential step in the system development process and that PV power generators constitute a valuable energy source. They have the ability to balance the energy and supply good power quality. It is demonstrated that when PV array- inverters are operating in the master mode in stand-alone applications, they well perform the task of controlling the voltage and frequency of the power system. The mechanism of switching the master function between the diesel generator and the PV array-inverter assembly in a stand-alone power system is also proposed and analyzed. Finally, some experimental results on a practical system are compared to the simulation results and confirm the usefulness of the proposed approach to the development of renewable energy systems with PV power generators.     

Photovoltaic module reliability model based on field degradation studies

Crystalline silicon photovoltaic (PV) modules are often stated as being the most reliable element in PV systems. This presumable high reliability is reflected by their long power warranty periods. In agreement with these long warranty times, PV modules have a very low total number of returns, the exceptions usually being the result of catastrophic failures. Up to now, failures resulting from degradation are not typically taken into consideration because of the difficulties in measuring the power of an individual module in a system. However, lasting recent years PV systems are changing from small isolated systems to large grid‐connected power stations. In this new scenario, customers will become more sensitive to power losses and the need for a reliability model based on degradation may become of utmost importance. In this paper, a PV module reliability model based on degradation studies is presented. The main analytical functions of reliability engineering are evaluated using this model and applied to a practical case, based on state‐of‐the‐art parameters of crystalline silicon PV technology. Relevant and defensible power warranties and other reliability data are obtained with this model based on measured degradation rates and time‐dependent power variability. In the derivation of the model some assumptions are made about the future behaviour of the products—i.e. linear degradation rates—although the approach can be used for other assumed functional profiles as well. The method documented in this paper explicitly shows manufacturers how to make reasonable and sensible warranty projections. Copyright © 2008 John Wiley & Sons, Ltd.     

Parallel-Connected Solar PV System to Address Partial and Rapidly Fluctuating Shadow Conditions

Solar photovoltaic (PV) arrays in portable applications are often subject to partial shading and rapid fluctuations of shading. In the usual series-connected wiring scheme, the residual energy generated by partially shaded cells either cannot be collected (if diode bypassed) or, worse, impedes collection of power from the remaining fully illuminated cells (if not bypassed). Rapid fluctuation of the shading pattern makes maximum power point (MPP) tracking difficult; generally, there will exist multiple local MPPs, and their values will change as rapidly as does the illumination. In this paper, a portable solar PV system that effectively eliminates both of the aforementioned problems is described and proven. This system is capable of simultaneously maximizing the power generated by every PV cell in the PV panel. The proposed configuration consists of an array of parallel-connected PV cells, a low-input-voltage step-up power converter, and a simple wide bandwidth MPP tracker. Parallel-configured PV systems are compared to traditional series-configured PV systems through both hardware experiments and computer simulations in this paper. Study results demonstrate that, under complex irradiance conditions, the power generated by the new configuration is approximately twice that of the traditional configuration. The solar PV system can be widely used in many consumer applications, such as PV vests for cell phones and music players.     

Analysis Results of Output Power Loss Due to the Grid Voltage Rise in Grid-Connected Photovoltaic Power Generation Systems

This paper describes the connected photovoltaic (PV) power generation system's grid overvoltage protection function and summarizes the occurrence of the output power loss due to the grid voltage rise. Power injection from the PV system will raise the voltage at the power distribution line. A power conditioning subsystem (PCS) needs to regulate its output if the voltage becomes higher than the upper limit in order to avoid the overvoltage at the power grid. Thus, a PV system cannot generate electricity under the high grid voltage. There are 553 residential PV systems installed in Ota, Japan, for the demonstration research project of clustered PV systems. Measurement data of these 2.1-MW grid-connected PV systems are used for the analysis. Only the limited number of PV systems experienced a significant amount of output energy loss due to the high grid voltage in a particular day, whereas the other system's outputs also raise the grid voltage. The causes of this maldistribution of the output energy loss are the difference of the line impedance, the difference of the starting voltage of the PCS's grid overvoltage protection function, and the imbalance of the load in single-phase three-wire power distribution systems. The present control of the PCS successfully avoids the overvoltage on the grid but cannot share the loss.     

Attaining a 30-year photovoltaic system lifetime: The BOS issues

Failures of power conditioning systems and balance of system (BOS) components have been responsible for the majority of system downtime in virtually all of the USA's large grid-tied photovoltaic (PV) power plants. For these and future PV power plants, therefore, improvements in component reliability must be made before the design goal of a 30-year system liftime can be attained. Advances in technology can increase reliability and still reduce costs of PV modules and power conditioning systems. However, since BOS components come generally from mature technologies, increased reliability must be attained through the purchase of higher quality components.