根据光伏(photovoltaic,PV)系统输出电压-功率(U-P)曲线在最大功率点(maximum power point,MPP)两侧斜率变化的规律有所不同,MPP左侧曲线变化舒缓,右侧相对陡直的特点,在光伏最大功率点跟踪(maximum power point tracking,MPPT)控制方...根据光伏(photovoltaic,PV)系统输出电压-功率(U-P)曲线在最大功率点(maximum power point,MPP)两侧斜率变化的规律有所不同,MPP左侧曲线变化舒缓,右侧相对陡直的特点,在光伏最大功率点跟踪(maximum power point tracking,MPPT)控制方法的研究基础之上,结合现有一些变步长电导增量法,提出了一种在MPP左侧利用指数函数来调整跟踪电压步长;在MPP右侧利用对数函数来调整跟踪电压步长的分段式变步长电导增量优化算法。仿真实验结果表明该方法良好地实现了对光伏系统最大功率点的跟踪,有效地降低了跟踪过程中MPP附近由步长振荡引起的功率损耗,提高了PV系统的功率输出效率。展开更多
In order to evaluate the effect of deficit irrigation at various growth stages on wheat growth and yield, a field experiment was conducted in the 2008-2009 growing season based on the completely randomized block with ...In order to evaluate the effect of deficit irrigation at various growth stages on wheat growth and yield, a field experiment was conducted in the 2008-2009 growing season based on the completely randomized block with four replications at the experimental farm of the College of Agriculture, Shiraz University, Shiraz, Iran, located at Badjgah. Treatments involved 13 irrigation regimes which applied in stem elongation, heading and grain filling growth stages. The highest seed yield （4,333 kg-ha-1） and the lowest ones （1,377 kg＇hal） were obtained from T1 （100% field capacity （FC） in all growth stages） and T13 （50% FC in all growth stages）, respectively. With limitation in water amount seed yield was diminished, but this trend was not significant at T4 （100%, 100% and 50% FC） and TI 1 （100%, 100% and 75~/0 FC）. Stepwise regression results revealed that, seed number per spike had the largest contribution （partial R2 = 0.72） in seed yield variation. Also at TI, T4, and TI 1 treatments （well water treatments） as well as TI3 （sever stress） head number m2 contribute most in seed yield determination （partial R2 = 0.96）. It can be concluded that water shortage during the grain filling period and its allocation to the other consecutive crop, can increase crop production in southern regions of Iran.展开更多
文摘根据光伏(photovoltaic,PV)系统输出电压-功率(U-P)曲线在最大功率点(maximum power point,MPP)两侧斜率变化的规律有所不同,MPP左侧曲线变化舒缓,右侧相对陡直的特点,在光伏最大功率点跟踪(maximum power point tracking,MPPT)控制方法的研究基础之上,结合现有一些变步长电导增量法,提出了一种在MPP左侧利用指数函数来调整跟踪电压步长;在MPP右侧利用对数函数来调整跟踪电压步长的分段式变步长电导增量优化算法。仿真实验结果表明该方法良好地实现了对光伏系统最大功率点的跟踪,有效地降低了跟踪过程中MPP附近由步长振荡引起的功率损耗,提高了PV系统的功率输出效率。
文摘In order to evaluate the effect of deficit irrigation at various growth stages on wheat growth and yield, a field experiment was conducted in the 2008-2009 growing season based on the completely randomized block with four replications at the experimental farm of the College of Agriculture, Shiraz University, Shiraz, Iran, located at Badjgah. Treatments involved 13 irrigation regimes which applied in stem elongation, heading and grain filling growth stages. The highest seed yield （4,333 kg-ha-1） and the lowest ones （1,377 kg＇hal） were obtained from T1 （100% field capacity （FC） in all growth stages） and T13 （50% FC in all growth stages）, respectively. With limitation in water amount seed yield was diminished, but this trend was not significant at T4 （100%, 100% and 50% FC） and TI 1 （100%, 100% and 75~/0 FC）. Stepwise regression results revealed that, seed number per spike had the largest contribution （partial R2 = 0.72） in seed yield variation. Also at TI, T4, and TI 1 treatments （well water treatments） as well as TI3 （sever stress） head number m2 contribute most in seed yield determination （partial R2 = 0.96）. It can be concluded that water shortage during the grain filling period and its allocation to the other consecutive crop, can increase crop production in southern regions of Iran.
