雙饋風力發(fā)電機組低電壓穿越控制策略研究
發(fā)布時間：2018-12-20 16:24
【摘要】：隨著風電裝機容量在電網(wǎng)中的比例逐年增大,為了維護電力系統(tǒng)運行的穩(wěn)定性和安全性,電網(wǎng)制定了并網(wǎng)風力發(fā)電機組不脫網(wǎng)運行的低電壓穿越要求。雙饋風力發(fā)電機簡稱DFIG,為當今世界研究的主流風力發(fā)電機型,相比于其他機型,變頻器容量大小相對偏小、風機轉(zhuǎn)速可調(diào)節(jié)、有功功率與無功功率可實現(xiàn)解耦控制；然而,雙饋式風機的定子側(cè)直接連接電網(wǎng)側(cè),使得風電機組對電網(wǎng)故障非常敏感。 本文提出了在電網(wǎng)電壓小幅驟降時,通過控制策略來實現(xiàn)雙饋風力發(fā)電機(DFIG)的低電壓穿越能力,首先建立了DFIG在電網(wǎng)電壓驟降下的暫態(tài)勵磁精確模型,并在此基礎(chǔ)上考慮槳距角對風機的影響,建立了同時控制轉(zhuǎn)子勵磁電壓和風機槳距角的DFIG發(fā)電機四階非線性模型。基于反饋精確線性化理論,提出了非線性協(xié)調(diào)控制策略。仿真結(jié)果表明,電網(wǎng)電壓小幅驟降時,所提出的控制策略能更有效控制轉(zhuǎn)子電流,保護勵磁變頻器,抑制暫態(tài)過程中風機轉(zhuǎn)速振蕩,促進電壓恢復,維護電網(wǎng)穩(wěn)定,提高了風力發(fā)電機的運行能力和對電網(wǎng)電壓驟降的適應(yīng)性。 針對電壓大值跌落,通過加入Crowbar保護電路實現(xiàn)低電壓穿越。本文分析了雙饋風電機組的暫態(tài)短路電流的表達式和Crowbar保護電路電阻值的選��；對電壓大幅驟降時投入Crowbar電路后引起直流側(cè)過電壓問題,建立了基于反饋線性化理論的網(wǎng)側(cè)變頻器非線性控制策略。仿真表明,加入Crowbar電路能很好的抑制電流,實現(xiàn)低電壓穿越運行；網(wǎng)側(cè)非線性控制器在電壓驟降過程中能很好的抑制直流側(cè)過電壓。 由于在電網(wǎng)電壓深度跌落時,采用Crowbar電路,DFIG以異步電機方式運行,將從電網(wǎng)吸收大量無功功率。針對Crowbar電路引起的無功補償問題,本文考慮協(xié)調(diào)STATCOM補償裝置,提供動態(tài)無功電流用以保證電力系統(tǒng)的穩(wěn)定性,防止電壓進一步下降及Crowbar電路再次動作。通過仿真研究證明了：對引入了Crowbar保護的風機,協(xié)調(diào)STATCOM能解決無功補償問題,改善并網(wǎng)電能質(zhì)量,提高風電機組低電壓穿越能力。
[Abstract]:With the proportion of wind power installed capacity increasing year by year, in order to maintain the stability and security of power system, the low voltage traversing requirement of grid connected wind turbine is established. Doubly-fed wind turbine (DFIG,) is the mainstream wind turbine in the world. Compared with other types of wind turbine, the capacity of inverter is relatively small, the speed of fan can be adjusted, and the active power and reactive power can be decoupled. However, the stator side of the doubly-fed fan is directly connected to the grid side, which makes the wind turbine very sensitive to the power grid fault. In this paper, the low voltage traversing capability of doubly-fed wind turbine (DFIG) is realized by control strategy when the voltage drop is small. Firstly, the accurate transient excitation model of DFIG under voltage drop is established. On this basis, considering the influence of pitch angle on fan, the fourth order nonlinear model of DFIG generator is established, which can control both rotor excitation voltage and fan pitch angle. Based on the feedback exact linearization theory, a nonlinear coordinated control strategy is proposed. The simulation results show that the proposed control strategy can control the rotor current more effectively, protect the excitation frequency converter, suppress the oscillation of the fan speed during the transient process, promote the voltage recovery, and maintain the stability of the power network. The performance of the wind turbine is improved and the adaptability to the voltage drop of the grid is improved. For voltage drop, low voltage traversing is realized by adding Crowbar protection circuit. In this paper, the expression of transient short-circuit current of doubly-fed wind turbine and the selection of resistance of Crowbar protection circuit are analyzed. A nonlinear control strategy based on feedback linearization theory is established for DC side overvoltage caused by input of Crowbar circuit when voltage plummeted. The simulation results show that adding Crowbar circuit can restrain the current and realize the low voltage traversing operation, and the nonlinear controller on the grid side can restrain the DC side overvoltage in the process of voltage sag. Because of the Crowbar circuit and the asynchronous motor DFIG will absorb a large amount of reactive power from the power grid. To solve the problem of reactive power compensation caused by Crowbar circuit, this paper considers the coordination of STATCOM compensator to provide dynamic reactive current to ensure the stability of power system and to prevent the further drop of voltage and the reoperation of Crowbar circuit. The simulation results show that the coordinated STATCOM can solve the problem of reactive power compensation, improve the quality of grid-connected power and improve the low voltage traversing ability of wind turbine.
【學位授予單位】：廣西大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TM315
本文編號：2388240
[Abstract]:With the proportion of wind power installed capacity increasing year by year, in order to maintain the stability and security of power system, the low voltage traversing requirement of grid connected wind turbine is established. Doubly-fed wind turbine (DFIG,) is the mainstream wind turbine in the world. Compared with other types of wind turbine, the capacity of inverter is relatively small, the speed of fan can be adjusted, and the active power and reactive power can be decoupled. However, the stator side of the doubly-fed fan is directly connected to the grid side, which makes the wind turbine very sensitive to the power grid fault. In this paper, the low voltage traversing capability of doubly-fed wind turbine (DFIG) is realized by control strategy when the voltage drop is small. Firstly, the accurate transient excitation model of DFIG under voltage drop is established. On this basis, considering the influence of pitch angle on fan, the fourth order nonlinear model of DFIG generator is established, which can control both rotor excitation voltage and fan pitch angle. Based on the feedback exact linearization theory, a nonlinear coordinated control strategy is proposed. The simulation results show that the proposed control strategy can control the rotor current more effectively, protect the excitation frequency converter, suppress the oscillation of the fan speed during the transient process, promote the voltage recovery, and maintain the stability of the power network. The performance of the wind turbine is improved and the adaptability to the voltage drop of the grid is improved. For voltage drop, low voltage traversing is realized by adding Crowbar protection circuit. In this paper, the expression of transient short-circuit current of doubly-fed wind turbine and the selection of resistance of Crowbar protection circuit are analyzed. A nonlinear control strategy based on feedback linearization theory is established for DC side overvoltage caused by input of Crowbar circuit when voltage plummeted. The simulation results show that adding Crowbar circuit can restrain the current and realize the low voltage traversing operation, and the nonlinear controller on the grid side can restrain the DC side overvoltage in the process of voltage sag. Because of the Crowbar circuit and the asynchronous motor DFIG will absorb a large amount of reactive power from the power grid. To solve the problem of reactive power compensation caused by Crowbar circuit, this paper considers the coordination of STATCOM compensator to provide dynamic reactive current to ensure the stability of power system and to prevent the further drop of voltage and the reoperation of Crowbar circuit. The simulation results show that the coordinated STATCOM can solve the problem of reactive power compensation, improve the quality of grid-connected power and improve the low voltage traversing ability of wind turbine.
【學位授予單位】：廣西大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TM315
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，本文編號：2388240
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