Multiobjective Particle Swarm Optimization for the optimal design of photovoltaic grid-connected systems

Particle Swarm Optimization (PSO) is a highly efficient evolutionary optimization algorithm. In this paper a multiobjective optimization algorithm based on PSO applied to the optimal design of photovoltaic grid-connected systems (PVGCSs) is presented. The proposed methodology intends to suggest the optimal number of system devices and the optimal PV module installation details, such that the economic and environmental benefits achieved during the system’s operational lifetime period are both maximized. The objective function describing the economic benefit of the proposed optimization process is the lifetime system’s total net profit which is calculated according to the method of the Net Present Value (NPV). The second objective function, which corresponds to the environmental benefit, equals to the pollutant gas emissions avoided due to the use of the PVGCS. The optimization’s decision variables are the optimal number of the PV modules, the PV modules optimal tilt angle, the optimal placement of the PV modules within the available installation area and the optimal distribution of the PV modules among the DC/AC converters.     

An economic analysis comparison of stationary and dual-axis tracking grid-connected photovoltaic systems in the US Upper Midwest

This paper presents an economic analysis of stationary and dual-axis tracking photovoltaic (PV) systems installed in the US Upper Midwest in terms of life-cycle costs, payback period, internal rate of return, and the incremental cost of solar energy. The first-year performance and energy savings were experimentally found along with documented initial cost. Future PV performance, savings, and operating and maintenance costs were estimated over 25-year assumed life. Under the given assumptions and discount rates, the life-cycle savings were found to be negative. Neither system was found to have payback periods less than the assumed system life. The lifetime average incremental costs of energy generated by the stationary and dual-axis tracking systems were estimated to be $0.31 and $0.37 per kWh generated, respectively. Economic analyses of different scenarios, each having a unique set of assumptions for costs and metering, showed a potential for economic feasibility under certain conditions when compared to alternative investments with assumed yields.     

光伏并网逆变器鲁棒控制器设计

针对光伏并网逆变器模型参数未知和外界干扰问题,文章运用自适应Backstepping与耗散性理论相结合的方法进行非线性控制器设计,文章设计的每个环节都符合耗散性要求,所得控制器既能保证闭环系统稳定,又具有一定的扰动抑制能力,同时自适应环节对未知参数进行实时估计。通过自控理论可知,文章的控制方法能保证系统内所有状态变量一致有界且渐近稳定;仿真结果表明,所设计的控制器能够增强系统的抗干扰能力,提高系统的鲁棒性。     

分布式光伏逆变器的优化设计研究

文章对两级单相光伏逆变器元件及控制策略进行优化配置,提出一种光伏逆变器无直流电压传感器控制策略。该控制策略利用逆变器中直流链电压与正弦脉宽调制信号,电压与占空比的对应关系,把传统控制中需要测量和直接控制的电量,通过控制器产生的中间信号来进行间接控制,既消除测量采样电路窜入的电磁干扰又不增加计算量,在确保实现光伏电源最大功率发电和电能逆变功能基础上降低了建设成本。最后在MATLAB下仿真,仿真结果证明所提控制策略的正确性与可行性。     

Reliability of large-scale grid-connected photovoltaic systems

This paper presents a method for assessing the reliability of large-scale grid-connected photovoltaic systems. Fault tree and probability analysis are used to compute the reliability equation and the developed model is applied on military-standard data and on data taken from scientific literature.The method provides a tool useful to single out the different impacts that the large number of components belonging to the photovoltaic field and the BOS (Balance of System) chain have on system overall reliability, hence granting the possibility to design and implement more effective monitoring/diagnostic strategies and maintenance plans.     

Emissions reduction data for grid-connected photovoltaic power systems

This study measured the pollutant emission reduction potential of 29 photovoltaic (PV) systems installed on residential and commercial building rooftops across the US from 1993 through 1997. The US Environmental Protection Agency (EPA) and 21 electric power companies sponsored the project. This article presents results of analyses of each PV system’s ability to offset electric utility power plant emissions of sulfur dioxide (SO₂), nitrogen oxides (NO_x), and carbon dioxide (CO₂). Each PV system’s performance was monitored and compared with hour-by-hour operating characteristics of the participating electric utilities in order to determine pollution offsets. The monthly mean and standard deviation offset are given for each pollutant, along with the coefficient of variation.     

Optimal sizing of array and inverter for grid-connected photovoltaic systems

Optimum PV/inverter sizing ratios for grid-connected PV systems in selected European locations were determined in terms of total system output, system output per specific cost of a system, system output per annualised specific cost of a system, PV surface orientation, inclination, tracking system, inverter characteristics, insolation and PV/inverter cost ratio. Maximum total system output was determined for horizontal, vertical and 45° inclined surfaces for a low efficiency inverter for sizing ratios of 1.5, 1.8 and 1.3, respectively; and for a medium efficiency inverter with sizing ratios of 1.4, 1.5 and 1.2. PV surface orientation and inclination have little impact on the performance of a high efficiency inverter. For different PV tracking systems and for different inverter characteristics, the optimum sizing ratio varied from 1.1 to 1.3. The PV/inverter cost ratio and the PV and inverter lifetimes have significant impact on the optimum PV/inverter sizing ratio. A correlation relating optimum sizing ratio and PV/inverter cost ratio has been developed; the correlation coefficients were found to be functions of insolation and inverter type. The impact of PV/inverter sizing ratio on PV array performance was less when PV array has a much higher cost than the inverter. The optimum sizing ratio for PV/inverter cost ratio of 6 and low efficiency inverter system varied from 1.4 to 1.2 for low to high insolation sites. For a high efficiency inverter system, the corresponding variation was from 1.3 to 1.1.     

光伏并网逆变器辅助电源的设计

采用光伏并网技术的太阳能发电已成为目前发展最快、应用面最广的太阳能利用方式之一.文章介绍了光伏并网系统中逆变器辅助电源的工作原理,这种辅助电源是由TOPSwitch芯片组成的高频开关电源,它降低了辅助电源的生产成本,简化了电路,提高了整个电路板的电磁兼容性,具有较高的使用价值.     

Assesment of grid-connected photovoltaic systems in the Kuwaiti climate

Grid-connected photovoltaic (PV) systems is one of the most promising applications of PV systems. Till now, no detailed studies have been carried out to assess the potential of grid-connected systems in Kuwait. This work investigates the feasibility of implementing grid-connected PV systems in the Kuwaiti climate. The proposed system consists of crystalline solar modules mounted on the building roof and an inverter to convert PV dc output to ac voltage. The building receives electricity from both the PV array and the utility grid. In this system, the load is the total electrical energy consumption in the building.The objective of this work is to examine the performance as well as the economic feasibility of grid-connected PV systems in the Kuwaiti climate. A program is written to evaluate the performance as well as the economic feasibility of such systems in Kuwait. The input to the program is the weather data for Kuwait, time dependent building loads, as well as the utility rates for Kuwait. Weather data generator subroutine included in the program is used to generate hourly weather conditions from the monthly average values of daily radiation on horizontal surface, and ambient temperature available for Kuwait. The five-parameter PV model, which is applicable to both crystalline and amorphous PV modules, is used to determine the performance of the solar modules used in this study.The transient simulation program ( ) is used to link the components of the grid-connected PV system together. The inverter efficiency is represented as a linear function of input power. In this case, it is assumed that the AC output from the system will never be greater than the building load. Electricity tariffs will have an important impact on the cost-effectiveness of the system studied. The tariff used for electric utility is a flat rate per unit kWh of electrical energy. Simulations of the proposed system were carried out over the academic year.The building examined in this study is a flat roof building with a single story. The building roof area is large enough so that the PV arrays can be spaced widely to minimize shading losses. Different array slopes, and azimuth angles were studied to maximize the annual energy generated by the PV modules. Finally, the economic feasibility of grid-connected PV systems in Kuwait are examined.     

The performance and economical analysis of grid-connected photovoltaic systems in Daegu,Korea

The distribution of the photovoltaic systems is faced with technological and economic problems, and the businesses and corporations feel burdened by the photovoltaic system’s dubious economic value and high construction costs. Thus, not too many enterprises or private citizens have been participating in the business of installing photovoltaic systems. Moreover, because of lack of skills in integrating engineering and architectural design, they are experiencing difficulties even in using the technologies that have already been developed and available for application. To provide the basic information and specific data required for making the guidelines for developing photovoltaic technologies, this paper evaluates the system types, the actual state of operation, and performance of the two photovoltaic systems that are installed in Kiemyung University’s Osan Building and Dongho Elementary School in Daegu Metropolitan City.     

Modeling and simulation of grid-connected photovoltaic energy conversion systems

Solar power generation using PV (photovoltaic) technology is a key but still evolving technology with the fastest growing renewable-based market worldwide in the last decade. In this sector with tremendous potential for energy security and economic development, grid-connected PV systems are becoming today the most important application of solar PV generation. Based on this trend, PV system designers require an accurate and reliable tool in order to predict the dynamic performance of grid-tied PV systems at any operating conditions. This will allow evaluating the impact of PV generation on the electricity grids. This paper presents a detailed characterization of the performance and dynamic behavior of a grid-connected PV energy conversion system. To this aim, a flexible and accurate PV simulation and evaluation tool (called PVSET 1.0) is developed. The PV system is modeled, simulated and validated under the MATLAB/Simulink environment. The accuracy of simulation results has been verified using a 250 Wp PV experimental set-up.     

Performance analysis of a grid-connected photovoltaic system

Grid-connected photovoltaic systems are required to introduce photovoltaic solar energy into urban areas. To analyze these systems, a 2.0 kW_p power system has been installed at the University of Málaga, Spain. The array power output was estimated by using measured I–V curves for the installed modules with minimization of mismatch losses. The supplied grid energy and main performances are described. The effects on system yield of threshold-inverter and coupling losses of the inverter to the grid have been studied. During 1997, the system supplied 2678 kWh to the grid, i.e. the mean daily output, was 7.4 kWh. The annual performance ratio was 64.5% and the optimal value 67.9%.     

并网光伏电站关键部件的运行性能分析

简要概述了50kW大型并网光伏电站的系统构成；通过一段时间的运行，对该电站的一些关键部件进行性能评价。分析结果表明：电站的光伏组件设计合理，并网逆变器具有较高的转换效率。     

Tables for the estimation of the internal rate of return of photovoltaic grid-connected systems

A continuous decrease trend in PV costs together with a wide variety of supporting measures have turned photovoltaic grid-connected systems (PVGCS) into a profitable investment when some economic conditions are met. The internal rate of return (IRR) is a meaningful parameter for prospective owners of these PV systems. Nevertheless, this parameter has to be estimated by means of non-analytical methods. This paper presents some easy-to-use tables addressed to estimate the IRR avoiding cumbersome calculations, which is an attractive feature for owners, marketers and designers. Firstly, current and near-term costs of PVGCS are reviewed, together with some financial incentives available at present. This introduces the economic scenario, where the tables are to be used. A short introduction to the economic analysis of these systems provides a solid ground to eventually present the tables intended to the estimation of the IRR. Lastly, three examples demonstrate the use of the tables.     

The internal rate of return of photovoltaic grid-connected systems: A comprehensive sensitivity analysis

At present, photovoltaic grid-connected systems (PVGCS) are experiencing a formidable market growth. This is mainly due to a continuous downward trend in PV cost together with some government support programmes launched by many developed countries. However, government bodies and prospective owners/investors are concerned with how changes in existing economic factors – financial incentives and main economic parameters of the PVGCS – that configure a given scenario may affect the profitability of the investment in these systems. Consequently, not only is a mere estimate of the economic profitability in a specific moment required, but also how this profitability may vary according to changes in the existing scenario. In order to enlighten decision-makers and prospective owners/investors of PVGCS, a sensitivity analysis of the internal rate of return (IRR) to some economic factors has been carried out. Three different scenarios have been assumed to represent the three top geographical markets for PV: the Euro area, the USA and Japan. The results obtained in this analysis provide clear evidence that annual loan interest, normalised initial investment subsidy, normalised annual PV electricity yield, PV electricity unitary price and normalised initial investment are ordered from the lowest to the highest impact on the IRR. A short and broad analysis concerning the taxation impact is also provided.     

An approach to the selection of the inverter for architecturally integrated photovoltaic grid-connected systems

An optimal compromise between energy efficiency and aesthetics for PV in the built environment sometimes requires to divide the PV field into sections with different orientation and tile each, which are connected to a single inverter. From the experience and data collected through a year of monitoring the 2-Kwp photovoltaic grid-connected system installed on the flat roof of the High Technical School of the University of Jaen, some charts are presented to help architects, engineers and installers to select the most suitable inverter for two specific architectural solutions addressed to integrating PV in buildings. However, charts for other sites, climates and architectural designs can be easily obtained.     

并网光伏发电项目的LCOE分析

围绕并网光伏发电系统的度电成本/平准化电力成本(LCOE)水平进行了分析讨论。针对LCOE的评估依据和测算方法,提出一种适用于我国光伏发电项目的 LCOE评估模型。利用该模型对影响LCOE的几个典型因素进行了敏感性分析;测算了我国光伏发电项目的 LCOE水平;预测了光伏发电项目的 LCOE发展。     

Sizing optimisation of stand-alone photovoltaic generators for irrigation water pumping systems

This paper mainly presents an efficient non-conventional direct method for sizing optimisation of stand-alone photovoltaic (PV) generators for supplying AC-motor-based irrigation pumping systems. The efficiencies of various elements comprising a PV pumping system and the effects of PV-array tilt are taken into account. The strong impact of the tilt angle on the optimal sizing of a PV generator is demonstrated. Extensive analysis of the meteorological conditions of the study site is performed. An appropriate solar correlation model for the design site is determined. The optimality of the determined capacity and tilt angle for a PV generator is evaluated by calculating several optimality indicators. The proposed method is compared with the Kenna and Gillett method and the RETScreen method for suggesting the nominal power for PV generators. The results show the capability and accuracy of the proposed method in optimally sizing stand-alone PV generators for irrigation water pumping systems.     

Optimal sizing of solar array and inverter in grid-connected photovoltaic systems

A new analytical approach is presented for finding the optimum ratio of photovoltaic array capacity to rated inverter input capacity in grid-connected photovoltaic systems. At optimum, the sizing ratio ranges from close to 1 for high insolation sites to well above 2 for low insolation conditions depending also on inverter characteristics and component costs. The sizing is more critical in low insolation conditions and the improvement of the economic performance thus obtained may be up to 20% compared to an inverter capacity equal to the PV-array. The optimum region is quite flat and up to ±20% deviations from the optimum point typically cause less than 2% losses. The analytical method coincides well with detailed numerical simulations for several locations (latitudes 33–60°N) and PV-array orientations used in the verification.     

Generating capacity adequacy evaluation of large-scale,grid-connected photovoltaic systems

Large-scale, grid-connected photovoltaic systems have become an essential part of modern electric power distribution systems. In this paper, a novel approach based on the Markov method has been proposed to investigate the effects of large-scale, grid-connected photovoltaic systems on the reliability of bulk power systems. The proposed method serves as an applicable tool to estimate performance (e.g., energy yield and capacity) as well as reliability indices. The Markov method framework has been incorporated with the multi-state models to develop energy states of the photovoltaic systems in order to quantify the effects of the photovoltaic systems on the power system adequacy. Such analysis assists planners to make adequate decisions based on the economical expectations as well as to ensure the recovery of the investment costs over time. The failure states of the components of photovoltaic systems have been considered to evaluate the sensitivity analysis and the adequacy indices including loss of load expectation, and expected energy not supplied. Moreover, the impacts of transitions between failures on the reliability calculations as well as on the long- term operation of the photovoltaic systems have been illustrated. Simulation results on the Roy Billinton test system has been shown to illustrate the procedure of the proposed frame work and evaluate the reliability benefits of using large-scale, grid-connected photovoltaic system on the bulk electric power systems. The proposed method can be easily extended to estimate the operating and maintenance costs for the financial planning of the photovoltaic system projects.