本文選題：雙饋異步發(fā)電機　切入點：低電壓穿越　出處：《華中科技大學(xué)》2014年碩士論文

【摘要】：隨著自然環(huán)境的不斷惡化和不可再生能源的過度消耗，人類面臨著環(huán)境污染和能源危機等重大難題，清潔與可再生能源的發(fā)展因此備受矚目。風(fēng)能作為應(yīng)用最廣的可再生能源之一，受到了越來越廣泛的關(guān)注。近年來，風(fēng)力發(fā)電在電力能源中所占的比重越來越大，對于電網(wǎng)的影響也日益顯現(xiàn)。為此，各國都制定了相應(yīng)的并網(wǎng)準(zhǔn)則，其中一個就是低電壓穿越要求(LVRT)，即在電網(wǎng)電壓發(fā)生一定的跌落故障下，保持風(fēng)機不脫網(wǎng)運行，并為電網(wǎng)提供一定的無功支撐。雙饋感應(yīng)發(fā)電機(DFIG)所需的變流器容量小，可實現(xiàn)有功、無功獨立調(diào)節(jié)，是風(fēng)力發(fā)電的主流機型。然而，由于雙饋風(fēng)機定子與電網(wǎng)直接相連，易受電網(wǎng)電壓波動的影響，其在嚴(yán)重故障下的LVRT性能很不理想。 現(xiàn)有的LVRT方案主要分為輕微故障下改進變流器控制策略和嚴(yán)重故障下增加硬件兩種方式。增加硬件主要是在轉(zhuǎn)子側(cè)投入Crowbar電阻泄能，并封鎖變流器。Crowbar的投入會導(dǎo)致轉(zhuǎn)矩脈動并吸收無功，并且不合適的切除時刻會導(dǎo)致更嚴(yán)重的暫態(tài)過程。而改進勵磁控制策略無需增加額外的硬件，在故障期間可以對暫態(tài)過程進行一定的控制，，減小電磁振蕩和轉(zhuǎn)矩脈動�，F(xiàn)有的改進勵磁控制策略一般需要磁鏈的準(zhǔn)確觀測和相序的快速分離，不易實現(xiàn)，并且存在較大的轉(zhuǎn)矩脈動。 本文從故障下的暫態(tài)過程入手，分析了過壓、過流的機理，并從轉(zhuǎn)子側(cè)端口等效阻抗的角度，根據(jù)端口的電壓電流特性將轉(zhuǎn)子側(cè)變流器(RSC)等效成一個阻抗。本文分析了現(xiàn)有的低電壓穿越控制策略在電氣特性方面的統(tǒng)一性，并從簡單的物理原理解釋了其作用機理，從而歸納出了評判某種控制策略可行性的一個標(biāo)準(zhǔn)。根據(jù)對轉(zhuǎn)子電流需求的深入分析和楞次定律的理解，提出了一種反向電流跟蹤控制策略，并給出了合理的參數(shù)選取原則。該策略具有明確的物理意義，控制結(jié)構(gòu)簡單，而且理論上能消除轉(zhuǎn)矩脈動。 反向電流跟蹤控制策略的效果在MATLAB/Simulink(許可證號:11111-11111-02011-44270)中進行了仿真驗證。最后本文設(shè)計搭建了一套10kW雙饋風(fēng)力發(fā)電系統(tǒng)，并配備了一臺電網(wǎng)電壓跌落故障發(fā)生器，通過電網(wǎng)故障實驗驗證了本文所提出的低電壓穿越控制策略的有效性。該策略具有以下特點： 1.結(jié)構(gòu)簡單，原理清晰； 2.控制策略易于切換； 3.有效抑制轉(zhuǎn)矩脈動。 在深度故障下，保持不脫網(wǎng)運行和向電網(wǎng)發(fā)出無功是相矛盾的。因此需要考慮何時改變控制目標(biāo)，在度過了最嚴(yán)重的暫態(tài)過程之后為電網(wǎng)提供無功支撐。
[Abstract]:With the deterioration of the natural environment and the excessive consumption of non-renewable energy, mankind is faced with environmental pollution and energy crisis, so the development of clean and renewable energy has attracted much attention.As one of the most widely used renewable energy, wind energy has attracted more and more attention.In recent years, wind power plays a more and more important role in electric power, and its influence on power grid is becoming more and more obvious.For this reason, all countries have formulated the corresponding grid connection criteria, one of which is the low voltage traversing requirement (LVRTT), that is, keeping the fan running without the grid and providing certain reactive power support for the power network under the condition of a certain drop fault of the grid voltage.The converter required by doubly-fed induction generator (DFIGG) is of small capacity, can realize active power and independent regulation of reactive power, and is the mainstream model of wind power generation.However, because the stator of doubly-fed fan is directly connected to the power grid, it is easy to be affected by the voltage fluctuation of the power network, and its LVRT performance is not ideal under the serious fault.The existing LVRT schemes are mainly divided into two ways: improving converter control strategy under slight fault and adding hardware under severe fault.The main reason for increasing the hardware is to put Crowbar resistance into the rotor side and block the input of the converter .Crowbar will lead to torque ripple and absorb reactive power, and the improper cutting time will lead to more serious transient process.The improved excitation control strategy can control the transient process without adding additional hardware and reduce the electromagnetic oscillation and torque ripple.The existing improved excitation control strategy generally requires the accurate observation of flux and the fast separation of phase sequence, which is difficult to achieve, and there is a large torque ripple.In this paper, the mechanism of overvoltage and overcurrent is analyzed from the transient process of fault. From the point of view of the equivalent impedance of the rotor side port, the rotor side converter RSC is equivalent to an impedance according to the voltage and current characteristics of the port.In this paper, the unity of the existing low voltage traversing control strategy in the electric characteristic is analyzed, and the mechanism of its action is explained from the simple physical principle, and a criterion for judging the feasibility of a certain control strategy is concluded.According to the deep analysis of rotor current demand and the understanding of Lenz's law, a reverse current tracking control strategy is proposed, and the reasonable parameter selection principle is given.The strategy has clear physical meaning, simple control structure and can eliminate torque ripple theoretically.The effectiveness of the reverse current tracking control strategy is verified by simulation in MATLAB / Simulink (license number 11111-111-02011-44270).Finally, a 10kW doubly-fed wind power generation system is designed and built, and a voltage sag fault generator is equipped. The effectiveness of the proposed low-voltage traversing control strategy is verified by the power network fault experiment.The strategy has the following characteristics:1.Simple structure, clear principle;2.The control strategy is easy to switch;3.Effectively restrain torque ripple.Under the condition of deep fault, it is contradictory to keep the grid running and to issue reactive power to the power grid.Therefore, it is necessary to consider when to change the control objectives and provide reactive power support to the power network after the most severe transient process.
【學(xué)位授予單位】：華中科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TM614

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