Modeling and maximum power point tracking (MPPT) method for PV array under partial shade conditions

Influenced by partial shade, PV module aging or fault, there are multiple peaks on PV array's output power–voltage (P–V) characteristic curve. Conventional maximum power point tracking (MPPT) methods are effective for single peak P–V characteristic under uniform solar irradiation, but they may fail in global MPP tracking under multi-peak P–V characteristics. Existing methods in literature for this problem are still unsatisfactory in terms of effectiveness, complexity and speed. In this paper, we first analyze the mathematical model of PV array that is suitable for simulation of complex partial shade situation. Then an adaptive MPPT (AMPPT) method is proposed, which can find real global maximum power point (MPP) for different partial shade conditions. When output characteristic of PV array varies, AMPPT will adjust tracking strategies to search for global peak area (GPA). Then it is easy for conventional MPPT to track the global MPP in GPA. Simulation and experimental results verify that the proposed AMPPT method is able to find real global MPP accurately, quickly and smoothly for complex multi-peak P–V characteristics. Comparison analysis results demonstrate that AMPPT is more effective for most shade types.     

A new test cell for the evaluation of thermo-physical performance of facades building components

How do the new building façade components work under real climatic conditions? The question is especially related to the dynamic behaviour of new and complex components such as the ventilated walls, the Phase Change Material, or others that use nano-technologies and aerogels. One of the objectives of the undergoing research activity, named Abitare Mediterraneo, is the evaluation of their thermal behaviour through the use of an outdoor test cell, in order to reproduce under the real external conditions the performance of these components, and consequently define the main thermal parameters such as the attenuation factor and the thermal inertia, characterising the component; moreover, the results will be used to write new algorithms for dynamic simulation tools allowing an appropriate evaluation of the complex behaviour of the whole building at a real scale condition. The new test cell is realised in Florence, Italy. The design starts from the study of the experience of the existing PASSYS test cells, overtaking the main weakness of the building structure and of the heat-flux sensors.     

Optimization of the investment cost of solar based grid

A new optimization method of the investment cost of a distribution grid supplied by photovoltaic (PV) sources. This method consists of determining the optimal grid cables cross sections and the optimal grid supply point (GSP) position, such that the sum of the joule losses and the cables investment costs are optimized. The determination of these parameters are performed by the programming of analytical equations using Matlab software, taking into account the influence of technical and economical requirements on the choice of the cables cross sections and the possibility of using several photovoltaic generators (PVG) with separated grids for spaced loads from a long distance, by optimizing the grouping loads combination. The obtained results show that: for a lowest global investment cost, the optimal GSP is referred to the minimum cost center (MCC), for the grid joule losses minimization, it can be in the minimum joule losses cost center (MJLCC); or in the center of the minimum investment cost of cables (CMICC) in the case of the cables investment cost minimization. The adoption of the optimal cross sections, the optimal PVGs (GSPs) number and their optimal positions achieve significant economic gains in terms of the investment cost.     

Overcoming barriers and uncertainties in the adoption of residential solar PV

In recent years decreasing hardware costs have driven down the installed price of solar photovoltaic (PV) systems and spurred adoption. However, system cost is not the only barrier faced by solar adopters. Potential adopters also face various informational barriers, leading to high indirect costs during the information search process. There is a significant gap in the literature for empirical work on solar adoption linking how the information context (installer marketing; neighbors with solar, i.e., peer effects; etc.) interacts with a potential adopter's motivations to impact decision outcomes. To address this gap we present results of a new survey on the decision-making process of residential PV adopters in northern California. The main aspects of our analysis include: salient motivating factors, information gathering process, peer effects, role of installers, and factors driving the choice of outright purchase versus third-party ownership (e.g., leasing) modes of adoption. We find that installers and neighbors play important, but often supplementary, roles throughout the decision-making process and have influence on both the decision to adopt as well as on the mode of adoption. Furthermore, expected financial returns and concerns about operations and maintenance are the main determining factors for the mode of adoption.     

Theoretical and experimental study on the application of diffuse‐reflection concentrators in PV/T solar system

In order to improve the practicability of PV/T solar system, we proposed the theory and method on the application of diffuse‐reflection concentrator in the PV/T solar system and analyzed the concentration characteristics of this proposed application. In addition, we designed experimental prototype of PV/T solar system and conducted test and analysis of the thermal and electrical characteristics of the PV/T solar system with or without a concentrator, respectively. The results showed that for the PV/T solar system with diffuse‐reflection concentrator, the amount of incident irradiance was increased by an average of 26% during test period, and the 200‐L water in the system was heated to 58 °C, which was 12 °C higher than that of PV/T solar system without diffuse‐reflection concentrator; moreover, the max output power was increased by 11%. Therefore, it is a feasible way to improve the practicability of PT/V solar system by integrating a diffuse‐reflection concentrator. Copyright © 2016 John Wiley & Sons, Ltd.     

Comparison of two PV array models for the simulation of PV systems using five different algorithms for the parameters identification

Simulation is of primal importance in the prediction of the produced power and automatic fault detection in PV grid-connected systems (PVGCS). The accuracy of simulation results depends on the models used for main components of the PV system, especially for the PV module. The present paper compares two PV array models, the five-parameter model (5PM) and the Sandia Array Performance Model (SAPM). Five different algorithms are used for estimating the unknown parameters of both PV models in order to see how they affect the accuracy of simulations in reproducing the outdoor behavior of three PVGCS. The arrays of the PVGCS are of three different PV module technologies: Crystalline silicon (c-Si), amorphous silicon (a-Si:H) and micromorph silicon (a-Si:H/μc-Si:H).The accuracy of PV module models based on the five algorithms is evaluated by means of the Route Mean Square Error (RMSE) and the Normalized Mean Absolute Error (NMAE), calculated for different weather conditions (clear sky, semi-cloudy and cloudy days). For both models considered in this study, the best accuracy is obtained from simulations using the estimated values of unknown parameters delivered by the ABC algorithm. Where, the maximum error values of RMSE and NMAE stay below 6.61% and 2.66% respectively.     

A new approach of sizing battery energy storage system for smoothing the power fluctuations of a PV/wind hybrid system

In this paper, a new approach for optimally sizing the storage system employing the battery banks for the suppression of the output power fluctuations generated in the hybrid photovoltaic/wind hybrid energy system. At first, a novel multiple averaging technique has been used to find the smoothing power that has to be supplied by the batteries for the different levels of smoothing of output power. Then the battery energy storage system is optimally sized using particle swarm optimization according to the level of smoothing power requirement, with the constraints of maintaining the battery state of charge and keeping the energy loss within the acceptable limits. Two different case studies have been presented for different locations and different sizes of the hybrid systems in this work. The results of the simulation studies and detailed discussions are presented at the end to portrait the effectiveness of the proposed method for sizing of the battery energy storage system. Copyright © 2016 John Wiley & Sons, Ltd.     

An overview of the environmental,economic, and material developments of the solar and wind sources coupled with the energy storage systems

There is a constant growth in energy consumption and consequently energy generation around the world. During the recent decades, renewable energy sources took heed of scientists and policy makers as a remedy for substituting traditional sources. Wind and photovoltaic (PV) are the least reliable sources because of their dependence on wind speed and irradiance and therefore their intermittent nature. Energy storage systems are usually coupled with these sources to increase the reliability of the hybrid system. Environmental effects are one of the biggest concerns associated with the renewable energy sources. This study summarizes the last and most important environmental and economic analysis of a grid‐connected hybrid network consisting of wind turbine, PV panels, and energy storage systems. Focusing on environmental aspects, this paper reviews land efficiency, shaded analysis of wind turbines and PV panels, greenhouse gas emission, wastes of wind turbine and PV panels' components, fossil fuel consumption, wildlife, sensitive ecosystems, health benefits, and so on. A cost analysis of the energy generated by a hybrid system has been discussed. Furthermore, this study reviews the latest technologies for materials that have been used for solar PV manufacturing. This paper can help to make a right decision considering all aspects of installing a hybrid system. Copyright © 2017 John Wiley & Sons, Ltd.     

Harmonic modelling of PV systems for probabilistic harmonic load flow studies

Probabilistic harmonic load flow (HLF) is currently enjoying renewed popularity. This is not surprising since in the near future, thousands of photovoltaic (PV) systems will be integrated into distribution systems. However, as yet, there is no model capable of explaining PV harmonic current behaviour in probabilistic HLF studies. To fill this gap, the harmonic modelling of PV systems proposed in this paper has three key points. First, it provides an effective model of the relationship between PV harmonic current emission and background harmonic voltages. Second, it statistically characterises PV harmonic currents (relative magnitude and phase angle) at different fundamental‐frequency current output intervals using historical time‐series data. In this statistical characterisation, the first fifth moments of each PV harmonic current are used to accurately approximate the raw probability density function (PDF) by means of the Legendre series. Finally, the third key point of this harmonic modelling is a method capable of determining the distribution functions of PV harmonic currents (absolute magnitude and phase angle), based on the statistical characterisation and a fundamental‐frequency probabilistic PV model. The numerical results obtained confirm the effectiveness of this PV model. Copyright © 2014 John Wiley & Sons, Ltd.     

大型并网光伏电站监控系统设计与实现

监控系统在大型光伏电站中起着至关重要的作用。在分析光伏电站监控系统功能的基础上设计了监控系统的网络和组成结构,分别讨论了升压站内设备和光伏发电设备的CIM模型,Modbus与IEC 104的映射,以及AGC/AVC控制调节流程等关键技术。运行情况表明,依照此设计和实现的监控系统运行稳定可靠,完全满足大型光伏发电的监控要求。