Probabilistic Global Maximum Power Point Tracking Algorithm for Continuously Varying Partial Shading Conditions on Autonomous PV Systems

A photovoltaic (PV) string with multiple modules with bypass diodes frequently deployed on a variety of autonomous PV systems may present multiple power peaks under uneven shading. For optimal solar harvesting, there is a need for a control schema to force the PV string to operate at global maximum power point (GMPP). While a lot of tracking methods have been proposed in the literature, they are usually complex and do not fully take advantage of the available characteristics of the PV array. This work highlights how the voltage at operating point and the forward voltage of the bypass diode are considered to design a global maximum power point tracking (GMPPT) algorithm with a very limited global search phase called Fast GMPPT. This algorithm successfully tracks GMPP between 94% and 98% of the time under a theoretical evaluation. It is then compared against Perturb and Observe, Deterministic Particle Swarm Optimization, and Grey Wolf Optimization under a sequence of irradiance steps as well as a power-over-voltage characteristics profile that mimics the electrical characteristics of a PV string under varying partial shading conditions. Overall, the simulation with the sequence of irradiance steps shows that while Fast GMPPT does not have the best convergence time, it has an excellent convergence rate as well as causes the least amount of power loss during the global search phase. Experimental test under varying partial shading conditions shows that while the GMPPT proposal is simple and lightweight, it is very performant under a wide range of dynamically varying partial shading conditions and boasts the best energy efficiency (94.74%) out of the 4 tested algorithms.

Responses of photosynthetic characteristics and leaf senescence in summer maize to simultaneous stresses of waterlogging and shading

A field experiment was performed to investigate the physiological mechanism of the simultaneous stresses of waterlogging and shading on leaf photosynthetic and senescence during three growth stages of summer maize.The responses of leaf gas exchange parameters and antioxidant enzyme activities of the summer maize hybrids Denghai 605(DH605)to waterlogging(W),shading(S),and their combination(W+S)for 6 days at the third leaf stage(V3),the sixth leaf stage(V6),and the tasseling stage(VT)were recorded.Shading,waterlogging,and their combination disturbed the activities of protective enzymes and increased the contents of H2O2and O-2,accelerating leaf senescence and disordering photosynthetic characteristics.Under waterlogging,shading and their combination,leaf Pn,the photo-assimilates and grain yield was decreased.The greatest reduction for waterlogging and the combined stresses occurred at V3 and that for shading stress occurred at VT.The individual and combined stresses reduced the activities of protective enzymes and inhibited photosynthesis,reducing the accumulation of photosynthetic compounds and thereby yield.Waterlogging and the combined stresses at the V3 stage showed the greatest effect on leaf photosynthetic and senescence,followed by the V6 and VT stages.The greatest effect for shading stress occurred at VT,followed by the V6 and V3 stages,and the combined influence of shading and waterlogging was greater than that of either single stress.

女性主义翻译理论视域下Dance of the Happy Shades李玉瑶汉译本研究

Dance of the Happy Shades是加拿大作家艾丽斯·门罗的成名作,该部描写女性题材的短篇小说集历时15年完成于1968年出版,荣获加拿大最高文学奖项——总督奖。目前,我国有部分学者从图里翻译规范理论出发对Dance of the Happy Shades进行了汉译本对比研究,而从女性主义翻译理论出发的研究有待拓展。本文以李玉瑶汉译本为研究对象,从女性主义翻译理论视域出发,探讨女性译者如何在翻译中体现女性主义翻译意识,从而帮助读者进一步理解原著。

Diff erences in pigment circadian rhythmicity in greenand red-leafed tree species in the sun and shade

Light fl ux and quality are crucial factor for setting endogenous plant circadian rhythms.Evaluating the daily rhythmicity of leaf chlorophyll content is an eff ective method to monitor the plant physiological endogenous clock in response to environmental signals such as light availability/quality.Here,we used a leaf-clip sensor to monitor diurnal rhythms in the content of chlorophyll and fl avonoids such as fl avonols and anthocyanins in three green-(Ailanthus altissima,Tilia platyphyllos and Platanus×acerifolia)and two red-leafed(Acer platanoides cv.Crimson King and Prunus cerasifera var.pissardii)tree species,adapted to sun(L)or shade(S).Signifi cant diff erences in chlorophyll content(Chl)and its variations during the day were observed among treatments in all the analyzed species.S-plants had more Chl than L-plants irrespective of leaf color,and Chl variations were more distinct during the day than in L-plants.In particular,contents were lowest in the morning(9:00)and in the middle of the day(at 12:00 and 15:00),and the highest at dusk(21:00).The less evident trends in Chl variation in L-plants were attributed to a decrease in Chl content in high light,which likely masked any increases in the shaded counterparts during the afternoon.Daily fl avonol levels did not vary no notably during the day.In sun-exposed red leaves,anthocyanins partially screened mesophyll cells from incident light,and its levels were similar to the Chl dynamics in the shaded counterparts.This study provides new bases for further work on endogenous rhythms of plant pigments and improves our understanding of plant physiology in the context of day/night rhythmicity.

Decreased panicle N application alleviates the negative effects of shading on rice grain yield and grain quality

Light deficiency is a growing abiotic stress in rice production.However,few studies focus on shading effects on grain yield and quality of rice in East China.It is also essential to investigate proper nitrogen(N)application strategies that can effectively alleviate the negative impacts of light deficiency on grain yield and quality in rice.A two-year field experiment was conducted to explore the effects of shading(non-shading and shading from heading to maturity)and panicle N application(NDP,decreased panicle N rate;NMP,medium panicle N rate;NIP,increased panicle N rate)treatments on rice yield-and quality-related characteristics.Compared with non-shading,shading resulted in a 9.5-14.8%yield loss(P<0.05),mainly due to lower filled-grain percentage and grain weight.NMP and NIP had higher(P<0.05)grain yield than NDP under non-shading,and no significant difference was observed in rice grain yield among NDP,NMP,and NIP under shading.Compared with NMP and NIP,NDP achieved less yield loss under shading because of the increased filled-grain percentage and grain weight.Shading reduced leaf photosynthetic rate after heading,as well as shoot biomass weight at maturity,shoot biomass accumulation from heading to maturity,and nonstructural carbohydrate(NSC)content in the stem at maturity(P<0.05).The harvest index and NSC remobilization reserve of NDP were increased under shading.Shading decreased(P<0.05)percentages of brown rice,milled rice,head rice,and amylose content while increasing(P<0.05)chalky rice percentage,chalky area,chalky degree,and grain protein.NMP demonstrated a better milling quality under non-shading,while NDP demonstrated under shading.NDP exhibited both lower chalky rice percentage,chalky area,and chalky degree under non-shading and shading,compared with NMP and NIP.NDP under shading decreased amylose content and breakdown but increased grain protein content and setback,contributing to similar overall palatability to non-shading.Our results suggested severe grain yield and quality penalty of rice when subjected to shading after heading.NDP improved NSC remobilization,harvest index,and sink-filling efficiency and alleviated yield loss under shading.Besides,NDP would maintain rice’s milling,appearance,and cooking and eating qualities under shading.Proper N management with a decreased panicle N rate could be adopted to mitigate the negative effects of shading on rice grain yield and quality.

Maize cryptochromes 1a1 and 1a2 promote seedling photomorphogenesis and shade resistance in Zea mays and Arabidopsis

Maize growth and development are regulated by light quality,intensity and photoperiod.Cryptochromes are blue/ultraviolet-A light receptors involved in stem elongation,shade avoidance,and photoperiodic flowering.To investigate the function of cryptochrome 1(CRY1) in maize,where it is encoded by Zm CRY1,we obtained two Zm CRY1a genes(Zm CRY1a1 and Zm CRY1a2),both of which share the highest similarity with other gramineous plants,in particular rice CRY1a by phylogenetic analysis.In Arabidopsis,overexpression of Zm CRY1a genes promoted seedling de-etiolation under blue and white light,resulting in dwarfing of mature plants.In seedlings of the maize inbred line Zong 31(Zm CRY1aOE),overexpression of Zm CRY1a genes caused a reduction in the mesocotyl and first leaf sheath lengths due to down-regulation of genes influencing cell elongation.In mature transgenic maize plants,plant height,ear height,and internode length decreased in response to overexpression of Zm CRY1a genes.Expression of Zm CRY1a were insensitive to low blue light(LBL)-induced shade avoidance syndrome(SAS) in Arabidopsis and maize.This prompted us to investigate the regulatory role of the gibberellin and auxin metabolic pathways in the response of Zm CRY1a genes to LBL treatment.We confirmed a link between Zm CRY1a expression and hormonal influence on the growth and development of maize under LBL-induced SAS.These results reveal that Zm CRY1a has a relatively conservative function in regulating maize photomorphogenesis and may guide new strategies for breeding high density-tolerant maize cultivars.

A New Flower Pollination Algorithm Strategy for MPPT of Partially Shaded Photovoltaic Arrays

Photovoltaic(PV)systems utilize maximum power point tracking(MPPT)controllers to optimize power output amidst varying environmental conditions.However,the presence of multiple peaks resulting from partial shading poses a challenge to the tracking operation.Under partial shade conditions,the global maximum power point(GMPP)may be missed by most traditional maximum power point tracker.The flower pollination algorithm(FPA)and particle swarm optimization(PSO)are two examples of metaheuristic techniques that can be used to solve the issue of failing to track the GMPP.This paper discusses and resolves all issues associated with using the standard FPA method as the MPPT for PV systems.The first issue is that the initial values of pollen are determined randomly at first,which can lead to premature convergence.To minimize the convergence time and enhance the possibility of detecting the GMPP,the initial pollen values were modified so that they were near the expected peak positions.Secondly,in the modified FPA,population fitness and switch probability values both influence swapping between two-mode optimization,which may improve the flower pollination algorithm’s tracking speed.The performance of the modified flower pollination algorithm(MFPA)is assessed through a comparison with the perturb and observe(P&O)method and the standard FPA method.The simulation results reveal that under different partial shading conditions,the tracking time for MFPA is 0.24,0.24,0.22,and 0.23 s,while for FPA,it is 0.4,0.35,0.45,and 0.37 s.Additionally,the simulation results demonstrate that MFPA achieves higher MPPT efficiency in the same four partial shading conditions,with values of 99.98%,99.90%,99.93%,and 99.26%,compared to FPA with MPPT efficiencies of 99.93%,99.88%,99.91%,and 99.18%.Based on the findings from simulations,the proposed method effectively and accurately tracks the GMPP across a diverse set of environmental conditions.

橡胶树大筒苗培育方法VII.遮阴率的筛选

为了解不同遮阴环境下橡胶树(Hevea brasiliensis)大筒苗的生长及光合特性,明确大筒苗生长的适宜光照环境,以小苗芽接苗和组培苗为胚苗的橡胶树大筒苗为材料,设置5个遮阴处理:CK(全光照),S60、S70、S80和S90(分别为60%、70%、80%、90%遮阴率),观测其出圃时的生长指标和光合参数变化情况。结果表明,不同遮阴率对橡胶树大筒苗的生长、光合参数及出圃时顶蓬叶的叶面积和叶绿素相对含量均有极显著影响,且2种胚苗间差异显著。大筒苗的壮苗指数随遮阴率的增加呈现先增后降的趋势;与全光照相比,遮阴显著影响大筒苗的出圃率,但对定植成活率的影响较小;胚苗类型与遮阴处理的交互作用明显。全光照和过度遮阴(S90)均会明显抑制大筒苗的生长,不同胚苗的大筒苗最适遮阴率不同,小苗芽接苗大筒苗在S60、组培大筒苗在S80下的生长表现最好。因此,橡胶树大筒苗培育时应根据不同的胚苗类型选择适宜的遮阴措施。

耐荫谷子杂交种的创制及其耐荫生理机制研究

为解决中国大量林下土地常年撂荒、杂草丛生、病虫害严重、林果质量逐年下降的难题。本研究旨在通过开发耐荫性谷子种植资源,提高林下土地利用率及林下经济效益。研究以具有良好综合性状和潜在利用价值的谷子种质资源为材料,通过专项试验筛选出耐荫种质资源,进一步利用这些亲本材料,创制出7份耐荫不育系,4份耐荫恢复系;8个耐荫谷子杂交种。这些杂交种表现出良好的生长性能,能够在树木遮荫的环境中茁壮成长。为了深入了解耐荫谷子杂交种的生理机制,我们测定了叶片叶绿素a、叶绿素b含量及比值、根轮数等。研究结果显示,耐荫谷子杂交种具有较高的叶绿素a和叶绿素b含量(分别在2.11~2.35 mg/gFW和0.65~0.76 mg/gFW之间),较低的叶绿素a/叶绿素b比值(3.09~3.25),以及较多的根轮数(≥5)。这些生理特征有助于植物在低光环境下更有效地捕获光能、吸收营养,并增强对病虫害的抵抗力。本研究的成果不仅促进了耐荫谷子杂交种的育成,而且为林下经济提供了实践应用模式。建立了“谷子/板栗”、“谷子/核桃”、“谷子/山楂”和“谷子/中低密度生态林”4种立体套种模式,这些模式有助于提升林地的综合效益和生态价值。因此,该研究对于改善林下土地利用、促进农业多样性和生态可持续性具有重要的实践意义。

基于实测数据的高海拔大日温差地区拱上组合梁桥-无砟轨道体系温度场研究

温度作用是影响桥梁-轨道结构服役性能的重要因素之一。为探究高海拔大日温差地区拱上组合梁桥-无砟轨道体系的温度场变化规律,基于某拟建铁路上承式大跨拱桥桥址处的环境温度持续监测数据与卫星反演得到的太阳辐射数据,建立了考虑太阳辐射阴影遮挡效应的拱上组合梁桥-无砟轨道体系温度场模型,重点分析日温度变化规律和竖向温差分布规律,获得了考虑实测气温和太阳辐射逐时变化的全年日温度场;采用广义帕累托分布对竖向温差样本进行了极值分布估计,确定不同超越概率的竖向温差代表值,提出多折线形式的竖向温度梯度模式。研究结果表明,梯度相较于平原地区更为显著,无砟轨道的遮挡效应使得温度梯度分布上移,钢梁外侧腹板在冬季产生局部梯度作用;基于实测数据的温差极值估计方法考虑了环境温度和太阳辐射对结构温度场的随机影响,可为特殊地区桥梁设计阶段温度作用的计算提供参考。

广州地区耐阴爵床科植物筛选及其园林应用

爵床科Acanthaceae植物多自然分布于热带、亚热带林下,种类繁多,生活型、生态型多样,且适应性较强、栽培繁殖易、管理粗放,在气候湿热的广州地区的园林造景中具有广阔应用前景。通过对华南国家植物园及广州市代表性公园绿地中的爵床科植物的园林应用进行调查,观察记录不同种间的形态、物候及观赏特征;通过比较不同光照栽培环境下的生长发育表现,筛选出45种观赏性高、耐阴性强、可广泛应用于广州地区林缘或林下栽培的爵床科植物,并介绍其观赏特征及园林应用形式。最后,结合调查情况,建议通过加强爵床科植物种质资源发掘和利用、增加对耐阴性种质的筛选、丰富园林应用形式、优化养护管理、加大科普宣教力度等措施应对现状问题。

自适应免疫粒子群算法在光伏MPPT中的应用

光伏阵列在局部遮阴条件下,其P-U特性曲线呈多峰特性,传统的最大功率点跟踪(MPPT)算法容易陷入局部最优,而无法追踪到最大功率点。粒子群(PSO)算法适用于复杂多极值的寻优问题,因而在多峰值MPPT中得到广泛应用。针对粒子群算法寻优过程中易早熟收敛至局部最优、迭代后期收敛速度慢以及精度低等问题,提出了一种自适应免疫粒子群算法。该算法对惯性权重和学习因子进行自适应调整,并且与免疫算法相结合。仿真结果表明:该算法在静态局部遮阴以及动态局部遮阴条件下,均能追踪到最大功率点,并且收敛速度更快,精度更高,稳定性更好。

隧道火灾中细水雾降温消烟数值模拟研究

细水雾系统因其良好的控烟作用在隧道火灾中得到广泛应用。基于气溶胶动力学机理提出细水雾降温消烟数值模型,通过模拟狭长通道细水雾阻烟实验验证其有效性。为探究细水雾粒径、雾化锥角、细水雾与排烟口间距对降温消烟效果的影响规律,进一步采用该模型开展细水雾系统在大尺度隧道火灾中降温消烟效果研究。研究表明:细水雾液滴粒径越小,降温消烟效果越好,且消烟效率与粒径成反比,但当粒径小于100μm时,因液滴蒸发导致消烟效率有所降低;雾化锥角在60°时消烟效果最好,雾化锥角增大或减小都会降低细水雾系统的消烟效果;当细水雾系统与排烟系统间距较小时,由于细水雾液滴会被排烟系统抽出,导致消烟效果减弱,因此两者间距越大,消烟效果越好。

湿热地区遮阳形式对校园热环境的影响研究

受气候变暖与热岛效应影响,城市热环境正在恶化,对人居环境和居民健康造成严重威胁。校园是一种重要的教育类社区,亦受到高温威胁。改善夏季校园热环境,营造凉爽宜居校园环境,对保障师生健康、丰富户外活动、提高学习效率、节约能源等方面具有积极意义。本研究旨在探究遮阳对室外热环境的调节能力及机制。选取重庆大学校园内常见的遮阳空间(树荫遮阳、遮阳篷遮阳、亭子遮阳),对其热环境(黑球温度(Tg)、空气温度(Ta)、相对湿度(Rh)、地面温度(Ts))进行现场实测,分析不同遮阳形式对夏季校园室外热舒适(生理等效温度(PET)、通用热气候指数(UTCI))的影响程度。研究表明:遮阳可以有效阻挡太阳辐射,改善室外环境的热舒适。无遮阳空间的Ta、Tg、Ts、PET、UTCI均高于有遮阳空间;在湿热环境下,遮阳篷遮阳与亭子遮阳的热舒适优于树荫遮阳;在遮阳条件下,不同地面材质对室外热舒适的影响无明显差异;不同遮阳形式的天空可视因子(SVF)对室外热环境有明显影响,SVF对Tg、Ts、PET、UTCI的影响较大,对Ta和Rh的影响较弱。研究结果将对营造健康安全的校园热环境提供理论支撑。

基于混合粒子群算法的波浪能发电集群优化方法

对波浪能发电集群的优化控制有助于波浪能的有效利用,为此文章提出了基于混合粒子群算法的波浪能发电集群优化方法。以直驱式发电装置为研究对象,探讨其构成发电集群短期尺度下稳定状态的数学模型,由简至繁依次考虑波浪动态压力、装置间辐射影响和遮挡效应,以便更准确地模拟一定密集度的波浪能发电装置部署下的实际效果。以集群功率最大化为优化目标,根据装置运动和海域能量约束,提出混合粒子群算法求解集群的最优参数,在传统算法基础上设定自适应惯性权重并加入交叉和变异操作,以应对复杂集群方程解空间的多峰性问题。算例结果验证了所述集群优化方法的有效性,求解质量良好;同时表明波浪能发电集群规模越大,装置之间的辐射影响越复杂,遮挡效应越明显。

基于机器学习的外窗百叶外遮阳性能预测与敏感性研究

在建筑围护结构中越来越多地使用透明围护结构,会导致高能耗和光热环境不适等问题。为了解决这一问题,遮阳作为一种减少建筑的能源消耗和改善室内环境较为有效的手段被越来越多地使用。为探究百叶外遮阳参数对遮阳性能的影响程度,采用机器学习算法预测遮阳性能,利用基于机器学习的改进敏感性分析法探讨了影响遮阳性能的2类参数(建筑和遮阳)的局部和全局敏感性,确定影响最大的参数。研究结果表明:XGBoost预测热环境、能耗指标精度最高,而随机森林算法预测光环境指标效果最好。同时发现遮阳参数是影响室内热环境和建筑能耗的最重要因素,整体权重均在0.5以上;建筑参数显著影响室内采光,其权重高达0.9左右。

基于改进黏菌算法的光伏多峰值MPPT控制

针对传统最大功率点跟踪技术在局部遮阴等天气条件下存在无法追踪到全局最大功率点的问题,提出一种基于改进黏菌算法的MPPT控制。首先,对太阳电池模型及多峰值特性进行分析;其次,在黏菌算法中引入领导者策略和基于最优个体的凸透镜反向学习策略,在提高算法计算精度、收敛速度的同时克服了算法易“早熟”现象;最后,根据光伏阵列最大功率输出特性分别确定算法优化模型、初始化位置及重启机制。仿真与实验结果表明:基于改进黏菌算法的MPPT控制能快速、准确地跟踪到全局最大功率点,有效规避陷入局部最优问题,提高了光伏系统的转换效率。

基于改进LGWO-INC算法的MPPT控制研究

光伏发电阵列板在局部遮阴下会产生多个功率峰值,传统算法难以准确快速追踪光伏最大功率点(maximum power point,MPP),该文提出一种基于莱维飞行灰狼算法(Levy grey wolf optimization,LGWO)与电导增量法(incremental conductance,INC)结合的复合算法追寻MPP,莱维飞行帮助灰狼算法跳出局部最优,搜寻MPP附近时,切换电导增量算法减少系统振荡,在静态与动态局部遮阴下通过Simulink进行光伏并网仿真验证。研究结果显示,所提复合算法收敛效果快速精确,并且符合并网谐波(total harmonic distortion,THD)含量要求,可保证系统的稳定运行。

局部阴影下基于GWO-P&O混合算法的光伏最大功率点跟踪

针对局部遮阴环境下传统灰狼优化(Gray wolf optimization,GWO)算法在跟踪最大功率点时P-U特性曲线出现多峰值、后期收敛速度慢、稳态精度低等问题,结合灰狼优化算法和扰动观察法(Perturbation and observation,P&O)各自的优势,提出了基于GWO-P&O的混合优化最大功率点跟踪(Maximum power point tracking,MPPT)算法。首先,采用灰狼优化算法逐渐向光伏的全局最大功率点靠近。其次,在灰狼优化算法收敛后期引入P&O法,既保持了灰狼优化算法较高的稳态精度,又能以较快速度寻找到局部最大功率点。最后,在不同环境工况下,将所提出的GWO-P&O方法与传统GWO算法进行对比。结果表明,改进的GWO-P&O算法在保证良好稳态性能的同时,一定程度上提高了GWO算法后期跟踪最大功率时的收敛速度。

种植密度对角果期弱光胁迫油菜籽粒油脂积累的影响

角果期光照不足显著影响油菜籽粒含油量,而增加种植密度具有明显的增产效果,但其对角果期弱光胁迫下籽粒含油量的影响未见报道。本试验选用华油杂62和沣油520两个品种进行大田试验,设置3个种植密度(15×104、30×104、45×104株hm-2)和2个光照强度(透光率为100%, LT100%和花后10~35 d透光率为70%, LT70%),从籽粒碳代谢和油脂代谢角度,研究种植密度对角果期弱光胁迫下油菜籽粒含油量的影响机制。结果表明:与LT100%相比,LT70%处理下2个品种花后25 d、35 d时籽粒叶绿素含量、核酮糖-1,5-二磷酸核酮糖羧化酶(Ribulose 1,5-bisphosphate carboxylase, Rubisco)活性降低,光合速率下降,光合产物葡萄糖含量降低0.4%~27.9%;蔗糖合成酶(Sucrose synthase,SuSy)分解活性降低,导致果糖含量降低了4.8%~24.5%,减少了籽粒碳水化合物积累与转运,同时磷脂酸磷酸酯酶(Phosphatidate phosphatase, PPase)、6-磷酸葡萄糖脱氢酶(Glucose-6-phosphate dehydrogenase, G6PDH)活性降低,导致含油量降低2.1%~11.8%,油脂产量降低27.0%~35.3%。与低密度遮阴相比,高密度LT70%处理下籽粒的Rubisco、SuSy活性降幅变小,但籽粒G6PDH和PPase活性降幅变大。这些结果表明,在本试验条件下,通过增加密度可以缓解弱光对籽粒光合碳代谢的抑制,通过增加群体产量缓解弱光胁迫下产油量的损失。