variable adj. 1.易变的,变化无常的,无定的 (opp. constant, steady)。 2.可变的,能变的;变换的。 3.【数学】变量的;【天文学】变光的;【生物学】变异的。 Prices are variable according to the exchanges. 物价跟着汇率变动。 a man of variable character 反复无常的人。 a rod of variable length (伸缩)如意棒。 a word of variable construction 可以作种种解释的词。 variable capital 可变资本。 a variable budget 临时预算。 n. 1.易变的东西。 2.【数学】变量,变数,变项,变元 (opp. constant);【天文学】变星 (=variable star);【航海】(方向不定的)变风,不定风 (opp. trade wind); 〔pl.〕 (贸易风带中的)变风带。 adv. -ably ,-ness n.
The resulting instance is not added as an object within the page s hierarchical server control tree ; it is instead treated as a non - user interface variable declaration . the 不将得到的实例作为一个对象添加到页的分层服务器控件树中,而将其作为非用户界面( ui )变量声明来对待。
First , variable speed constant frequency wind energy convertion theory is described in this paper , then presents a review on the development of wind turbines control and the main types of generator and static converters used to interface variable speed wind turbines to the electric grid . then discuss main circuit constructure and advantage of direct drive wind energy conversion system and introduce pitch - control method for wind power traction and electric power stability . simply aerodynamic characteristic of the turbine is analysised and permanent magnet synchnonous generator math model is established . to convert the variable frequency electricity into utility grid , back to back four - quadrant pwm - vsi is used and three typies of control strategy is presented to capture the maximum wind energy and transmit energy . then simulation is implemented to test the control strategy . in the following chapter a simple ac - dc - ac converter with a dc - dc boosting chopper is proposed to transmit the wind energy into electricity energy and two control strategy is presented 建立了永磁电机和变流器的数学模型,针对双pwm变频器的特点提出了三种控制策略对变流器进行控制,通过变流器交-直-交的变换,将发电机发出的变频变幅值交流电转化为可用的恒定频率的交流电,通过pwm调治能使其输出功率因数为一,并且该控制系统功率因数为可调,能在特殊情况下同电网交换一定的无功功率,并通过对变流器的控制实现了最大风能俘获的功能。最后采用matlab / simulink进行了仿真,取得了良好的仿真效果。在风力发电系统中,采用先进的最大功率俘获算法,能有效的从风中获得最大的能量。