Maximization of conversion efficiency based on global normal irradiance using hybrid concentrator photovoltaic architecture

Maximization of module conversion efficiency based on global normal irradiance (GNI) rather than direct normal irradiance (DNI) was experimentally demonstrated using a hybrid concentrator photovoltaic (CPV) architecture in which a low‐cost solar cell (a bifacial crystalline silicon cell) was integrated with a high‐efficiency concentrator solar cell (III–V triple‐junction cell) to harvest diffuse sunlight. The results of outdoor experiments showed that the low‐cost cell enhanced the generated power by factors of 1.39 and 1.63 for high‐DNI and midrange‐DNI conditions, respectively, and that the resultant GNI‐based module efficiencies were 32.7% and 25.6%, respectively. © 2016 The Authors. Progress in Photovoltaics: Research and Applications published by John Wiley & Sons Ltd.     

Spectral study and classification of worldwide locations considering several multijunction solar cell technologies

Multi‐junction solar cells are widely used in high‐concentration photovoltaic systems (HCPV) attaining the highest efficiencies in photovoltaic energy generation. This technology is more dependent on the spectral variations of the impinging Direct Normal Irradiance (DNI) than conventional photovoltaics based on silicon solar cells and consequently demands a deeper knowledge of the solar resource characteristics. This article explores the capabilities of spectral indexes, namely, spectral matching ratios (SMR), to spectrally characterize the annual irradiation reaching a particular location on the Earth and to provide the necessary information for the spectral optimization of a MJ solar cell in that location as a starting point for CPV module spectral tuning. Additionally, the relationship between such indexes and the atmosphere parameters, such as the aerosol optical depth (AOD), precipitable water (PW), and air mass (AM), is discussed using radiative transfer models such as SMARTS to generate the spectrally resolved DNI. The network of ground‐based sun and sky‐scanning radiometers AErosol RObotic NETwork (AERONET) is exploited to obtain the atmosphere parameters for a selected bunch of 34 sites worldwide. Finally, the SMR indexes are obtained for every location, and a comparative analysis is carried out for four architectures of triple junction solar cells, covering both lattice match and metamorphic technologies. The differences found among cell technologies are much less significant than among locations. Copyright © 2016 John Wiley & Sons, Ltd.     

Robust state estimator design for a solar battery charging system

This article describes a robust state estimator design for a solar battery charger where there is significant noise in the output measurements of the solar array voltage that causes degradation in the performance of the maximum power point tracking. The application of the extended Kalman filter, to the photovoltaic system, can lead to enhanced state estimation results so that a recursive solution can be obtained to achieve the most accurate estimate from the noisy signals. Additionally, as a consequence of applying the Kalman filter (KF), the immeasurable state of the inductor current can be estimated without a current sensor. The proposed controller uses the estimated solar array voltage for maximum power point tracker, and the estimated inductor current for determining the battery current controller. The methods for system modeling and design of the extended KF are presented, and the experimental results verify the validity of the proposed system.     

激光供能无人机接收端的光伏阵列重构方案

激光供能无人机是以激光作为能量载体,对无人机进行实时无线能量传输,提升无人机续航时间。由于激光束能量分布不均匀,导致光伏接收器效率低下。为提高接收器转换效率,针对全交叉连接结构优化问题,提出一种基于最小均衡差的重构方案。首先对激光高斯分布情况进行数学建模,获取光伏电池单体的辐照度。然后利用最小均衡差原则对全交叉连接结构进行优化,并对各种连接结构进行仿真。仿真结果表明:阵列重构后具有更高的输出功率、转换效率和填充因子,更低的功率损耗,且相较于重构前最大输出功率分别提升了29.13、32.25。     

基于推挽电路的光伏电池最大功率点追踪系统

太阳能光伏阵列的输出特性受外界环境因素的影响,为了使光伏阵列工作在最大功率点,因此经常在系统中加入最大功率追踪器。文中论述了一种利用推挽电路对光伏电池进行最大功率点追踪(MPPT)的控制器,以TMS320LF2407DSP为控制核心。通过Matlab仿真,结果表明控制器能够准确追踪最大功率点。     

New Maximum Power Point Tracker Using Sliding-Mode Observer for Estimation of Solar Array Current in the Grid-Connected Photovoltaic System

A new maximum power point tracker (MPPT) for a grid-connected photovoltaic system without solar array current sensor is proposed. The solar array current information is obtained from the sliding-mode observer and fed into the MPPT to generate the reference voltage. The parameter values such as capacitances can be changed up to 50% from their nominal values, and the linear observer cannot estimate the correct state values under the parameter variations and noisy environments. The structure of a sliding-mode observer is simple, but it shows the robust tracking property against modeling uncertainties and parameter variations. In this paper, the sliding-mode observer for the solar array current has been proposed to compensate for the parameter variations. The mathematical modeling and the experimental results verify the validity of the proposed method.     

Automated optimization of service coverage and base station antenna configuration in UMTS networks

Deployment and maintenance of UMTS networks involve optimizing a number of network configuration parameters in order to meet various service and performance requirements. In this article we address automated optimization of service coverage and radio base station antenna configuration. We consider three key configuration parameters: transmit power of the common pilot channel (CPICH), antenna tilt, and antenna azimuth. CPICH power greatly influences coverage. From a resource management point of view, satisfying the coverage requirement using minimum CPICH power offers several performance advantages. In particular, less CPICH power leads to less interference and higher system capacity. Optimal CPICH power, in its turn, is highly dependent on how the other two parameters, tilt and azimuth, are configured at radio base station antennas. Optimizing antenna tilt and azimuth network-wise, with the objective of minimizing the CPICH power consumption, is a challenging task. The solution approach in this article adopts automated optimization. Our optimization engine is a simulated annealing algorithm. Staring from an initial configuration, the algorithm searches effectively in the solution space of possible configurations in order to find improvements. The algorithm is computationally efficient; thus, we can optimize large networks without using excessive computing resources. We present a case study for a UMTS planning scenario in Lisbon. For this network, automated optimization saves up to 70 percent of the CPICH power used in the reference network configuration. In addition, the optimized network configuration offers significant performance improvement in terms of fewer overloaded cells and lower downlink load factor     

基于电流保护约束的光伏电源并网研究

越来越多的光伏电源以分布式的方式接入配电网,改变了配网原有的结构,给配网的电流保护带来了诸多影响.从电网侧出发,分析了光伏电源接入配网对配电网的影响,建立了基于电流保护约束的光伏电源接入模型,并在IEEE33节点配网系统上进行了算例验证,通过粒子群算法(PSO)得出了在不改变配网原有保护和电力系统安全运行条件下的分布式光伏电源的最佳接入位置和容量.研究结果为分布式光伏电源的选址和定容提供了一定的理论依据.     

Interference analysis and capacity for forward link 3G CDMA network with adaptive antennas

In code division multiple access (CDMA) systems, the capacity of forward link (FL) communication to mobile receivers is limited primarily by co‐channel interference (CCI). Adaptive antenna arrays (AAAs) that use antenna arrays along with advanced signal processing at the base station (BS) have been proposed to mitigate this limitation. For a 3G CDMA cellular network, where each BS equipped with an AAA serves mixture of voice and data users within its coverage, we study FL capacity and investigate the effects of different factors (array topology, multipath angle spread, data rate, and beamforming algorithm) on this capacity under Rayleigh fading channel. By modeling the instantaneous signal‐to‐interference power ratio received at the mobile, we derive the system outage equation that considers blocking of either desired voice or data user. Simulation results show that for the same element spacing and number of antenna elements per cell, the uniform circular array (UCA) topology results in larger capacity than the sectorized uniform linear array (ULA) topology does, and that a larger angle spread or data user rate reduces FL capacity. Copyright © 2007 John Wiley & Sons, Ltd.     

Integrated photovoltaic maximum power point tracking converter

A low-power low-cost highly efficient maximum power point tracker (MPPT) to be integrated into a photovoltaic (PV) panel is proposed. This can result in a 25% energy enhancement compared to a standard photovoltaic panel, while performing functions like battery voltage regulation and matching of the PV array with the load. Instead of using an externally connected MPPT, it is proposed to use an integrated MPPT converter as part of the PV panel. It is proposed that this integrated MPPT uses a simple controller in order to be cost effective. Furthermore, the power converter has to be very efficient, in order to transfer more energy to the load than a directly-coupled system. This is achieved by using a simple soft-switched topology. A much higher conversion efficiency at lower cost will then result, making the MPPT an affordable solution for small PV energy systems     

Novel maximum-power-point-tracking controller for photovoltaicenergy conversion system

A novel maximum-power-point-tracking (MPPT) controller for a photovoltaic (PV) energy conversion system is presented. Using the slope of power versus voltage of a PV array, the proposed MPPT controller allows the conversion system to track the maximum power point very rapidly. As opposed to conventional two-stage designs, a single-stage configuration is implemented, resulting in size and weight reduction and increased efficiency. The proposed system acts as a solar generator on sunny days, in addition to working as an active power line conditioner on rainy days. Finally, computer simulations and experimental results demonstrate the superior performance of the proposed technique     

Tracking control of high‐concentration photovoltaic systems for minimizing power losses

This paper presents three key factors that cause system mismatches and power losses in high‐concentration photovoltaic (HCPV) systems. The first factor is the I–V mismatch within a module, similar to the manufacturing mismatches in conventional photovoltaic modules. The second factor is the misalignments amongst modules, and the third factor is the tracking control. Unlike in the conventional photovoltaic systems, the second and the third factors in HCPV systems introduce larger electro‐optical mismatches due to narrow acceptance angles. We have developed a model to address these three factors. It allows an accurate estimation of power losses in HCPV systems, which enabled us to propose configurations to reduce power losses without adding additional electrical components to the system. Simulation results show that the power harvest can be increased as much as 8.5% for a system using open‐loop controls by simply increasing the number of strings at the time of calibration. Experimental test results are presented for validation. Copyright © 2012 John Wiley & Sons, Ltd.     

An excellent operating point tracker of the solar-cell power supply system

When the solar array is used as an input power source, the excellent operating point tracker is often employed to exploit more effectively the solar array as an electric power source and to obtain the maximum electric power at all times even when the light intensity and environmental temperature of the solar array are varied. Usually, the excellent operating point is determined by computing the electric power from the solar-array power supply with a microcomputer, digital signal processor, etc. However, such a method has the following problems: 1) complex control-circuit configuration; 2) high cost; and 3) low control speed. From this viewpoint, this paper proposes a new excellent operating point tracker of the solar-cell power supply system, in which inexpensive p-n junction diodes are used to generate the reference voltage of the operating point of the solar array. Using the proposed method, the high degree of the solar-array excellent point tracking performance can be obtained even when the light intensity and environmental temperature of the solar array are varied. Furthermore, this paper provides the operation principle, design-oriented analysis, etc., of the proposed solar-cell power supply system.     

A PSO‐based maximum power point tracking for photovoltaic systems under environmental and partially shaded conditions

To increase the efficiency of photovoltaic (PV) systems, maximum power point (MPP) tracking of the solar arrays is needed. Solar arrays output power depends on the solar irradiance and temperature. Also the mismatch phenomenon caused by partial shade will affect the output power of solar systems and lead to the incorrect operation of conventional MPP tracker. Under partially shaded conditions, the solar array power–current characteristic has multiple maximum. This paper presents a maximum power point tracking (MPPT) with particle swarm optimization method for PV systems under partially shaded condition. The performance of the proposed method is compared with perturb and observe (P&O), improved P&O, voltage‐based maximum power point tracking and current‐based maximum power point tracking algorithms, especially, under partially shaded condition. Simulation results confirm that proposed MPPT algorithm with high accuracy can track the peak power point under different insolation, temperature and partially shaded conditions, and it has the best performance in comparison with four mentioned MPPT algorithms. Also under rapidly changing atmospheric conditions, the P&O algorithm is diverged. Copyright © 2013 John Wiley & Sons, Ltd.     

宁夏地区风光互补发电系统容量优化配置的研究

宁夏地区每年都有充足的光照和丰富的风能,非常适合建立风电站和光电站。然而,由于风能和光照会随着季节性的变化而呈现周期性的变化,为了最大化利用光照和风能,人们开发出了风光互补发电系统。然而,这些系统由于技术不够成熟,光能和风能的转化率并不高。为此,本文确立了研究主题为宁夏地区风光互补发电系统容量优化配置。通过对资料的收集与整理,了解当前主流的算法,并在此基础上进行优化,通过对容量优化配置进行改进,使得风光互补发电系统的整体性能得到提升。实验的仿真结果显示,本文提出的改进的粒子群算法效果不错,值得推荐。     

Comparison of GA and DDE for optimizing coverage in indoor environment

This paper presents a method for determining the required number and locations of transmitting antennas to optimize wireless propagation coverage in indoor ultra‐wideband communication system. In the coverage prediction model, we use the three‐dimensional ray‐tracing technique associated to a genetic algorithm and a dynamic differential evolution for optimizing the transmitting antennas location in an indoor environment. The ray‐tracing method is employed to calculate the field strength from one or more transmitting antennas, and the optimization algorithm is used to determine the required number and locations of these antennas to achieve optimized wireless coverage in the indoor environment. The combined three‐dimensional ray‐tracing and optimization algorithm was applied in the indoor environment to find the best location of the transmitting antennas by maximizing the power in the coverage area. The use of deployments to minimize the transmitting antennas and maximize the power in the coverage area was proposed. Obtained simulation results illustrate the feasibility of using the integrated ray‐tracing and optimization method to find the optimal transmitter locations in determining the optimized coverage of a wireless network. The dynamic differential evolution has better optimization results compared with the genetic algorithm. The investigated results can help communication engineers improve their planning and design of indoor wireless communication. Copyright © 2013 John Wiley & Sons, Ltd.     

Hybrid Amplitude Control Antenna Array System for Energy Efficient W-CDMA Network with Adaptive Coverage and Capacity

This paper introduces a novel technique and mathematical formulation of two dimensional elastic footprint variations and adaptive sector configuration variations by using a hybrid adaptive amplitude control antenna array system. The antenna array system can control the elevation beam-widths from 6.84° to 13° and the azimuth beam-widths from 33° to 93° for obtaining the adaptive capacity and coverage. The work illustrates the application of the antenna array system in the energy efficient W-CDMA network. The antenna array half-power beam width variation is achieved by using the antenna array amplitude control and co-located multiple antenna array switching. The Node-Bs can adaptively switch to three, four, five, six and non uniform sector configurations with the antenna array beam width control and adaptive neighbor relations. Sector configurations will vary according to the pre-defined specific traffic loading percentages out of Node-B’s total channel capacity to reduce the energy consumption of the entire network. The paper introduces an adaptive footprint overlaps shifting technique, where the sector with less traffic load will expand its footprint towards the sector with higher traffic load and the sector with higher traffic load will shrink its footprint by maintaining a fixed footprint overlaps to improve the coverage and the capacity of the network. The footprints overlap shifting is applicable only for the active sector antennas facing each other. The results confirm that the proposed antenna array system outperforms the automatic tilt optimization and can control coverage, capacity and improve the energy efficiency of the W-CDMA network.     

Global optimization of solar thermophotovoltaic systems

In this paper, we present a theoretical model based on the detailed balance theory of solar thermophotovoltaic systems comprising multijunction photovoltaic cells, a sunlight concentrator and spectrally selective surfaces. The full system has been defined by means of 2n + 8 variables (being n the number of sub‐cells of the multijunction cell). These variables are as follows: the sunlight concentration factor, the absorber cut‐off energy, the emitter‐to‐absorber area ratio, the emitter cut‐off energy, the band‐gap energy(ies) and voltage(s) of the sub‐cells, the reflectivity of the cells' back‐side reflector, the emitter‐to‐cell and cell‐to‐cell view factors and the emitter‐to‐cell area ratio. We have used this model for carrying out a multi‐variable system optimization by means of a multidimensional direct‐search algorithm. This analysis allows to find the set of system variables whose combined effects results in the maximum overall system efficiency. From this analysis, we have seen that multijunction cells are excellent candidates to enhance the system efficiency and the electrical power density. Particularly, multijunction cells report great benefits for systems with a notable presence of optical losses, which are unavoidable in practical systems. Also, we have seen that the use of spectrally selective absorbers, rather than black‐body absorbers, allows to achieve higher system efficiencies for both lower concentration and lower emitter‐to‐absorber area ratio. Finally, we have seen that sun‐to‐electricity conversion efficiencies above 30% and electrical power densities above 50 W/cm² are achievable for this kind of systems. Copyright © 2012 John Wiley & Sons, Ltd.     

Determination of spectral variations by means of component cells useful for CPV rating and design

A methodology is presented to determine both the short‐term and the long‐term influence of the spectral variations on the performance of multi‐junction (MJ) solar cells and concentrator photovoltaic (CPV) modules. Component cells with the same optical behavior as MJ solar cells are used to characterize the spectrum. A set of parameters, namely spectral matching ratios (SMRs), is used to characterize spectrally a particular direct normal irradiance (DNI) by comparison to the reference spectrum (AM1.5D‐ASTM‐G173‐03). Furthermore, the spectrally corrected DNI for a given MJ solar cell technology is defined providing a way to estimate the losses associated to the spectral variations. The last section analyzes how the spectrum evolves throughout a year in a given place and the set of SMRs representative for that location are calculated. This information can be used to maximize the energy harvested by the MJ solar cell throughout the year. As an example, three years of data recorded in Madrid shows that losses lower than 5% are expected because of current mismatch for state‐of‐the‐art MJ solar cells. Copyright © 2015 John Wiley & Sons, Ltd.     

单相光伏发电并网的研究

针对如何提高太阳能光伏发电系统的转化效率,对具有最大功率控制的系统进行研究,提出了一种双环控制方式。并以STM32为控制器,给出了其控制方法。通过Matlab建模设计光伏输出后的控制系统,新的控制系统实现了最大功率跟踪与功率因数校正。仿真表明,该方式具有简单、控制方便、效率高的优点。并通过实物加以验证该方法的可行性,该控制策略可应用于单极式光伏并网系统最大功率点跟踪控制,且实现了系统的高效率并网运行。