双级式单相光伏并网系统的研究与仿真

介绍了双级式单相光伏并网系统,分析了其拓扑结构。升压采用模糊推理进行最大功率点跟踪控制;双闭环控制实现了对电网电压的同频同相控制,达到了并网要求。通过MatlabR2010对系统进行了仿真,仿真结果表明逆变输出电流和电网电压同频同相,并有效地跟踪了光伏阵列的最大功率点。     

A dodging algorithm to reconfigure photovoltaic array to negate partial shading effect

The efficiency of photovoltaic (PV) power system is hampered to a large extent when it is shaded even by a fraction. The performance dwindle in PV array due to partial shading is not proportional to the volume of shading, rather it depends on pattern of shading, array configuration, and site where PV panels are installed. Total cross‐tied (TCT) is the proven scheme among all the prevailing interconnection schemes like series, parallel, series–parallel (SP), and bridge linked to negate partial shading impact. This work aims at proposing a new adaptive algorithm to reconfigure the PV array such that it evades the shading effect. Also, it suggests a unique PV panel arrangement for a familiar shading pattern by which the shading prospects are reduced considerably. The proposed work has a clear edge over the TCT method in managing shading, ruling out multiple peaks in output power curve. This technique is highly recommended for constant power loads as the output current is maintained constant, setting aside the varying atmospheric conditions, whereas other reconfiguring techniques do not address this application. The suggested topology is simulated in matlab /Simscape environment for a 3 × 3 PV array and realized in a hardware prototype where a digital signal controller Dspic30f4011 is used to impart the proposed control algorithm. Copyright © 2015 John Wiley & Sons, Ltd.     

Performance evaluation of a MPPT controller with model predictive control for a photovoltaic system

ABSTRACT

Efficiency has been a major factor in the growth of photovoltaic (PV) systems. Different control techniques have been explored to extract maximum power from PV systems under varying environmental conditions. This paper evaluates the performance of a new improved control technique known as model predictive control (MPC) in power extraction from PV systems. Exploiting the ability of MPC to predict future state of controlled variables, MPC has been implemented for tacking of maximum power point (MPP) of a PV system. Application of MPC for maximum power point tracking (MPPT) has been found to result into faster tracking of MPP under continuously varying atmospheric conditions providing an efficient system. It helps in reducing unwanted oscillations with an increase in tracking speed. A detailed step by step process of designing a model predictive controller has been discussed. Here, MPC has been applied in conjunction with conventional perturb and observe (P&O) method for controlling the dc-dc boost converter switching, harvesting maximum power from a PV array. The results of MPC controller has been compared with two widely used conventional methods of MPPT, viz. incremental conductance method and P&O method. The MPC controller scheme has been designed, implemented and tested in MATLAB/Simulink environment and has also been experimentally validated using a laboratory prototype of a PV system.     

最大功率跟踪控制在光伏系统中的应用

对最大功率跟踪控制中DC-DC变换器的原理和控制方法进行了实验研究,利用DC-DC转换电路和单片机控制系统实现最大功率点跟踪,使太阳电池始终保持最大功率输出;和普通的控制器相比增加输出功率5％～15％。     

Enhanced power quality based single phase photovoltaic distributed generation system

This article presents a novel control strategy for a 1-? 2-level grid-tie photovoltaic (PV) inverter to enhance the power quality (PQ) of a PV distributed generation (PVDG) system. The objective is to obtain the maximum benefits from the grid-tie PV inverter by introducing current harmonics as well as reactive power compensation schemes in its control strategy, thereby controlling the PV inverter to achieve multiple functions in the PVDG system such as: (1) active power flow control between the PV inverter and the grid, (2) reactive power compensation, and (3) grid current harmonics compensation. A PQ enhancement controller (PQEC) has been designed to achieve the aforementioned objectives. The issue of underutilisation of the PV inverter in nighttime has also been addressed in this article and for the optimal use of the system; the PV inverter is used as a shunt active power filter in nighttime. A prototype model of the proposed system is developed in the laboratory, to validate the effectiveness of the control scheme, and is tested with the help of the dSPACE DS1104 platform.     

光伏并网系统MPPT控制和实现方法的研究

太阳能电池阵列输出特性具有强烈的非线性,为了提高系统的整体效率,一个重要的途径就是实时调整光伏电池的工作点,进行最大功率点跟踪（maximum power pointtracker,MPPT）,使之始终工作在最大功率点附近。最大功率点跟踪方法是一个提高光伏组件效率的很有效的方法。     

On the testing,characterization, and evaluation of PV inverters and dynamic MPPT performance under real varying operating conditions

The increasing number of photovoltaic inverters that are coming on to the PV market stresses the need to carry out a dynamic characterization of these elements and their maximum power point tracking (MPPT) algorithms under real operating conditions. In order to make these conditions repeatable at the laboratory, PV array simulators are used. However, actual simulators, including the commercial simulators, recreate only a single or small set of PV array characteristic curves in which quite commonly theoretical calculations are included in order to simulate irradiance and temperature artificial variations. This is far from being a recreation of the real and long dynamic behavior of a PV array or generator. The testing and evaluation of the performance of PV inverters and MPPT algorithms has to be carried out when the PV system moves dynamically according to real operating conditions, including processes such as rapidly changing atmospheric conditions, partial shadows, dawn, and nightfall. This paper tries to contribute to the analysis of this problem by means of an electronic system that both measures the real evolution of the characteristic curves of PV arrays at outdoor operation and then recreates them at the laboratory to test PV inverters. This way the equipment can highlight the different performances of PV inverters and MPPT techniques when they operate under real operating conditions. As an example, two commercial inverters are tested and analyzed under the recreated behavior of a PV generator during 2 singular days that include processes of partial shading and fast irradiance variations. Copyright © 2007 John Wiley & Sons, Ltd.     

Solar spectral influence on the performance of photovoltaic (PV) modules under fine weather and cloudy weather conditions

The performance of photovoltaic modules is influenced by solar spectrum even under the same solar irradiance conditions. Spectral factor (SF) is a useful index indicating the ratio of available solar irradiance between actual solar spectrums and the standard AM1·5‐G spectrum. In this study, the influence of solar spectrum on photovoltaic performance in cloudy weather as well as in fine weather is quantitatively evaluated as the reciprocal of SF (SF⁻¹). In the cases of fine weather, the SF⁻¹ suggests that solar spectrum has little influence (within a few %) on the performance of pc‐Si, a‐Si:H/sc‐Si, and copper indium gallium (di)selenide modules, because of the “offset effect”. The performance of a‐Si:H modules and the top layers of a‐Si:H/µc‐Si:H modules can vary by more than ± 10% under the extreme conditions in Japan. The seasonal and locational variations in the SF⁻¹ of the bottom layers are about ± several %. A negative correlation is shown between the top and bottom layers, indicating that the performance of a‐Si:H/µc‐Si:H modules does not exceed the performance, at which the currents of the top and bottom layers are balanced, by the influence of solar spectrum. In the cases of cloudy weather, the SF⁻¹ of the pc‐Si, a‐Si:H/sc‐Si, and copper indium gallium (di)selenide modules is generally higher, suggesting favorable for performance than that in fine weather. Much higher SF⁻¹ than that in fine weather is shown by the a‐Si:H module and the top layer of the a‐Si:H/µc‐Si:H module. The SF⁻¹ of the bottom layer neither simply depend on season nor on location. Copyright © 2011 John Wiley & Sons, Ltd.     

光伏电池输出特性与最大功率点跟踪的仿真分析

根据太阳能光伏电池的等效电路特点,建立了相应的光伏电池组件的仿真模型。该模型可以实现在不同光照强度和温度下光伏组件的输出特性,在此模型基础上研究了光伏组件最大功率追踪方法(MPPT)。在众多最大功率追踪方法中,扰动法有着比较优秀的控制效果。针对最常用的最大功率点跟踪方法-扰动观察法,提出一种改进型的扰动法算法,通过仿真结果和实验证明该方法在一定程度上可解决光伏电池输出非线性的问题,有效避免跟踪偏差,提高光伏电池的输出效率,且动态响应速度快,使光伏系统具有良好的动态和稳态性能。     

Experimental energy yield in 1·5 × and 2 × PV concentrators with conventional modules

Low concentration devices along with standard (one sun) modules represent an attractive option to reduce the cost per kilowatt‐hour in photovoltaic installations. This paper deals with the energy gains obtained over a year by two of such devices: a 2 × V‐trough concentrator and a 1·5 × single flat mirror structure. The experiment was mounted on a two‐axis tracking system located in Arguedas (northern Spain). Due to various optical and electrical phenomena, the energy gain is notably lower than the geometrical concentration. We have conducted a theoretical analysis of these phenomena and quantified the energy loss associated with each. Daily and monthly energy gains show an influence of daylight clearness index on energy output. In view of this effect, and taking into account a possible increase in degradation of the photovoltaic modules due to high working temperatures and hot‐spots, the viability of these concentration devices is far from being clear. Copyright © 2007 John Wiley & Sons, Ltd.     

Developing a method and simulation model for evaluating the overall energy performance of a ventilated semi‐transparent photovoltaic double‐skin facade

A comprehensive simulation model has been developed in this paper to simulate the overall energy performance of an amorphous silicon (a‐Si) based photovoltaic double‐skin facade (PV‐DSF). The methodology and the model simulation procedure are presented in detail. To simulate the overall energy performance, the airflow network model, daylighting model, and the Sandia Array Performance Model in the EnergyPlus software were adopted to simultaneously simulate the thermal, daylighting, and dynamic power output performances of the PV‐DSF. The interaction effects between thermal, daylighting, and the power output performances of the PV‐DSF were reasonably well modeled by coupling the energy generation, heat‐transfer, and optical models. Simulation results were compared with measured data from an outdoor test facility in Hong Kong in which the PV‐DSF performance was measured. The model validation work showed that most of the simulated results agreed very well with the measured data except for a modest overestimation of heat gains in the afternoons. In particular, the root‐mean‐square error between the simulated monthly AC energy output and the measured quantity was only 2.47%. The validation results indicate that the simulation model developed in this study can accurately simulate the overall energy performance of the semi‐transparent PV‐DSF. This model can, therefore, be an effective tool for carrying out optimum design and sensitivity analyses for PV‐DSFs in different climate zones. The methodology developed in this paper also provides a useful reference and starting point for the modeling of other kinds of semi‐transparent thin‐film PV windows or facades. Copyright © 2015 John Wiley & Sons, Ltd.     

Multilayer light emitting devices with organometal halide perovskite: Polymer composite emission layer: The relationship of device performance with the compositions of emission layer and device configurations

The formation of composite layers comprising polymers such as poly(ethylene oxide) (PEO) and organometal halide perovskites (Peros) is an effective way to improve the morphology integrity of Pero films and the performance of Pero light emitting devices. Herein, we report the influences of the ratio of the organic content to inorganic content in the precursors as well as the compositions of PEO: Pero films on their morphology, crystal structure and electroluminescent property. Multilayer Pero light emitting devices show the external quantum efficiency of ca. 4.0% and power efficiency of 7.9 lm W⁻¹.     

Wireless powered underlay cognitive radio network with multiple primary transceivers: Energy constraint,node arrangement,and performance analysis

This paper considers a cognitive radio–assisted wireless information and power transfer system consisting of multipair of transceiver in primary network and 2‐hop relaying link in secondary network. In this investigation, a decoded‐and‐forward–assisted relay node and power splitting protocol are deployed to obtain ability of wireless energy transfer. The relay node harvests energy from the radio frequency signals of the secondary transmitter and primary transmitters in data transmission to the destination by reusing the licensed spectrum resource. We propose 2 policies for wireless power transfer at the relay, namely, (1) multisource power transfer and (2) single‐source power transfer. To evaluate performance under energy harvesting regime, we derive the closed‐form outage probability expressions and achievable throughput of the secondary network in delay‐limited transmission mode. In addition, we investigate the impact of various system parameters including number of primary transceivers, primary outage threshold, and position arrangement of nodes in primary transceivers on the outage performance of the proposed scheme. Furthermore, we evaluate the system energy efficiency to show trade‐off metric of energy consumption and throughput. Performance results are presented to validate our theoretical derivation and illustrate the impacts of various system parameters. An important result is that the secondary network is more beneficial than harmful from the primary interference under power constraint and reasonable node location arrangement.