variable adj. 1.易變的,變化無常的,無定的 (opp. constant, steady)。 2.可變的,能變的;變換的。 3.【數(shù)學(xué)】變量的;【天文學(xué)】變光的;【生物學(xué)】變異的。 Prices are variable according to the exchanges. 物價(jià)跟著匯率變動(dòng)。 a man of variable character 反復(fù)無常的人。 a rod of variable length (伸縮)如意棒。 a word of variable construction 可以作種種解釋的詞。 variable capital 可變資本。 a variable budget 臨時(shí)預(yù)算。 n. 1.易變的東西。 2.【數(shù)學(xué)】變量,變數(shù),變項(xiàng),變?cè)?(opp. constant);【天文學(xué)】變星 (=variable star);【航?!?方向不定的)變風(fēng),不定風(fēng) (opp. trade wind); 〔pl.〕 (貿(mào)易風(fēng)帶中的)變風(fēng)帶。 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 不將得到的實(shí)例作為一個(gè)對(duì)象添加到頁的分層服務(wù)器控件樹中,而將其作為非用戶界面( ui )變量聲明來對(duì)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 建立了永磁電機(jī)和變流器的數(shù)學(xué)模型,針對(duì)雙pwm變頻器的特點(diǎn)提出了三種控制策略對(duì)變流器進(jìn)行控制,通過變流器交-直-交的變換,將發(fā)電機(jī)發(fā)出的變頻變幅值交流電轉(zhuǎn)化為可用的恒定頻率的交流電,通過pwm調(diào)治能使其輸出功率因數(shù)為一,并且該控制系統(tǒng)功率因數(shù)為可調(diào),能在特殊情況下同電網(wǎng)交換一定的無功功率,并通過對(duì)變流器的控制實(shí)現(xiàn)了最大風(fēng)能俘獲的功能。最后采用matlab / simulink進(jìn)行了仿真,取得了良好的仿真效果。在風(fēng)力發(fā)電系統(tǒng)中,采用先進(jìn)的最大功率俘獲算法,能有效的從風(fēng)中獲得最大的能量。