【摘要】：風(fēng)力發(fā)電技術(shù)已成為國內(nèi)外學(xué)者研究熱點,在大電網(wǎng)三相電壓平衡時傳統(tǒng)風(fēng)電機(jī)組已實現(xiàn)并網(wǎng)發(fā)電。然而在微網(wǎng)或小型孤網(wǎng)中存在三相電壓不平衡及不對稱故障的情況,給風(fēng)電機(jī)組鎖相、并網(wǎng)發(fā)電帶來了一系列困難。針對上述問題,本文對風(fēng)電機(jī)組網(wǎng)側(cè)變流器在電網(wǎng)三相電壓不平衡及不對稱故障下的控制策略展開了深入研究。首先,對風(fēng)電機(jī)組網(wǎng)側(cè)變流器以及三相電壓不平衡電網(wǎng)建模。研究了網(wǎng)側(cè)變流器在電網(wǎng)三相電壓平衡下的數(shù)學(xué)模型,并分析了網(wǎng)側(cè)變流器穩(wěn)態(tài)運(yùn)行特性。并為進(jìn)一步研究電網(wǎng)三相電壓不平衡下網(wǎng)側(cè)變流器的運(yùn)行特性,推導(dǎo)了三相電壓不平衡下的網(wǎng)側(cè)變流器數(shù)學(xué)模型。然后,針對電網(wǎng)三相電壓不平衡直接導(dǎo)致傳統(tǒng)的網(wǎng)側(cè)變流器鎖相不準(zhǔn)確問題,對傳統(tǒng)的電網(wǎng)鎖相方法進(jìn)行了改進(jìn)�；诂F(xiàn)有的三相電壓不平衡下同步參考坐標(biāo)系的軟件鎖相方法,增加陷波器,改進(jìn)二階廣義積分器,從不平衡電網(wǎng)中提取出正負(fù)序分量,然后分別計算出正負(fù)序相位角。進(jìn)一步在MATLAB/Simulink中搭建了仿真模型,在電網(wǎng)電壓不平衡度為10%的工況下,對所提出的改進(jìn)鎖相方法進(jìn)行驗證。通過仿真結(jié)果看出,所用方法可以快速、準(zhǔn)確地提取出網(wǎng)側(cè)電壓正負(fù)序分量及相位信息。其次,由于直接功率控制策略具有算法簡單、響應(yīng)性能好等特點,在網(wǎng)側(cè)變流器中采用了直接功率控制。但傳統(tǒng)基于PI控制的空間矢量直接功率控制(SVM-DPC)無法滿足電壓不平衡下非線性系統(tǒng)的高頻開關(guān)控制,為了實現(xiàn)上述目的,提出一種基于滑模變結(jié)構(gòu)的空間矢量直接功率控制,通過內(nèi)外環(huán)的協(xié)調(diào)控制,抑制了直流母線電壓二倍頻分量,并增加了陷波器,實現(xiàn)了無功功率無差調(diào)節(jié),消除了二次諧波影響,保證了直流母線電壓穩(wěn)定。并在單相接地和兩相電流短路故障工況下,分別對傳統(tǒng)與改進(jìn)控制策略進(jìn)行仿真對比,對所改進(jìn)控制策略的正確性進(jìn)行了驗證。最后,搭建了基于DSP28335網(wǎng)側(cè)變流器硬件平臺。設(shè)計了網(wǎng)側(cè)變流器的主電路、控制電路及外圍保護(hù)電路,測試了各部分電路的正確性。利用硬件平臺中控制電路部分與RTLAB半實物仿真平臺,在不同單相負(fù)載增加工況下,對采用傳統(tǒng)基于PI控制的SVM-DPC與所提出的基于滑模變結(jié)構(gòu)的SVM-DPC的網(wǎng)側(cè)電壓、電流進(jìn)行了對比,對改進(jìn)控制策略的有效性進(jìn)行了驗證。
[Abstract]:Wind power generation technology has become a hot topic for scholars at home and abroad. When the three-phase voltage balance of large power grid, the traditional wind turbine has realized grid-connected generation. However, there are three phase voltage imbalance and asymmetric faults in microgrid or small isolated grid, which brings a series of difficulties for wind turbine to phase lock and grid connection. In order to solve the above problems, the control strategy of wind turbine grid-side converter under the unbalance and asymmetry of three-phase voltage is studied in this paper. First, the wind turbine grid side converter and three-phase voltage imbalance network are modeled. The mathematical model of grid-side converter under three-phase voltage balance is studied, and the steady-state operation characteristics of grid-side converter are analyzed. In order to further study the operation characteristics of grid-side converter under three-phase voltage imbalance, the mathematical model of grid-side converter under three-phase voltage imbalance is derived. Then, aiming at the inaccurate phase locking problem of traditional grid-side converter caused by unbalanced three-phase voltage, the traditional power grid phase-locked method is improved. Based on the existing software phase-locking method of synchronous reference coordinate system under unbalanced three-phase voltage, the notch filter is added, the second-order generalized integrator is improved, the positive and negative sequence components are extracted from the unbalanced power network, and the phase angles of positive and negative sequence are calculated respectively. Furthermore, the simulation model is built in MATLAB/Simulink, and the improved phase-locked method is verified under the condition of voltage imbalance of 10%. The simulation results show that the proposed method can extract the positive and negative sequence components and phase information of the voltage on the grid side quickly and accurately. Secondly, because the direct power control strategy has the characteristics of simple algorithm and good response performance, direct power control is used in the grid-side converter. But the traditional space vector direct power control (SVM-DPC) based on PI control can not satisfy the high frequency switching control of nonlinear system under voltage imbalance. A space vector direct power control based on sliding mode variable structure is proposed. Through the coordinated control of internal and external loop, the double frequency component of DC bus voltage is restrained, and the notch filter is added to realize reactive power reactive difference regulation. The second harmonic effect is eliminated and the DC bus voltage is stable. Under the condition of single-phase grounding and two-phase current short-circuit fault, the traditional control strategy and the improved control strategy are simulated and compared, and the correctness of the improved control strategy is verified. Finally, the hardware platform based on DSP28335 converter is built. The main circuit, control circuit and peripheral protection circuit of the grid-side converter are designed, and the correctness of each circuit is tested. Using the control circuit part of the hardware platform and the RTLAB hardware-in-the-loop simulation platform, under different single-phase load increasing conditions, the grid-side voltages of the traditional SVM-DPC based on PI control and the proposed SVM-DPC based on sliding mode variable structure are studied. Compared with the current, the effectiveness of the improved control strategy is verified.
【學(xué)位授予單位】：沈陽工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM46;TM614

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