【摘要】：隨著新能源的開發(fā)和利用,分布式發(fā)電系統(tǒng)受到廣泛關(guān)注。在分布式發(fā)電系統(tǒng)中并網(wǎng)逆變器具有重要作用,其性能直接影響系統(tǒng)輸出電能的質(zhì)量。在并網(wǎng)逆變器的各種電流控制方法中,重復(fù)控制因其較高的控制精度成為研究熱點(diǎn)。本文以并網(wǎng)逆變器為研究對象,對重復(fù)控制器的控制結(jié)構(gòu)、設(shè)計方法以及應(yīng)對電網(wǎng)頻率變化的改進(jìn)等問題進(jìn)行了深入的研究。對于重復(fù)控制結(jié)構(gòu),首先討論了重復(fù)控制單獨(dú)作用于系統(tǒng)時不穩(wěn)定的原因,說明了重復(fù)控制中前向通道對于系統(tǒng)穩(wěn)定性的意義。其次,在傳統(tǒng)重復(fù)控制與PI控制的復(fù)合控制中,詳細(xì)分析了重復(fù)控制與PI控制串聯(lián)結(jié)構(gòu)和并聯(lián)結(jié)構(gòu)的頻率特性,指出并聯(lián)結(jié)構(gòu)在幅頻特性中存在的缺陷。在串聯(lián)結(jié)構(gòu)下的重復(fù)控制的內(nèi)模、補(bǔ)償器、增益系數(shù)等參數(shù),根據(jù)系統(tǒng)的穩(wěn)定性條件分析不同參數(shù)設(shè)計的利弊,得到更優(yōu)的參數(shù)設(shè)計方法。最后,分析了電網(wǎng)頻率變化對重復(fù)控制性能的影響,并介紹基于分?jǐn)?shù)階理論的頻率自適應(yīng)重復(fù)控制方法。借鑒了諧振控制中應(yīng)對電網(wǎng)頻率變化所采用的準(zhǔn)諧振控制的思想,基于重復(fù)控制與諧振控制之間的數(shù)學(xué)關(guān)系而提出了選取較小內(nèi)模系數(shù)的改進(jìn)方法,有效提高了重復(fù)控制器的諧振帶寬,能夠應(yīng)對電網(wǎng)頻率變化的問題。對于內(nèi)模系數(shù)減小導(dǎo)致重復(fù)控制增益較低的問題,在對系統(tǒng)各個環(huán)節(jié)對于重復(fù)控制穩(wěn)定性影響分析的基礎(chǔ)上,整理得到了一種更優(yōu)的重復(fù)控制器參數(shù)設(shè)計流程,提高了重復(fù)控制在諧波頻率處的增益。最后,對并網(wǎng)逆變器的重復(fù)控制參數(shù)設(shè)計及改進(jìn)方法進(jìn)行了仿真和實(shí)驗(yàn)驗(yàn)證,結(jié)果表明:以重復(fù)控制與PI控制串聯(lián)結(jié)構(gòu)為基礎(chǔ)的傳統(tǒng)重復(fù)控制能夠具有較高的控制精度,但受電網(wǎng)頻率波動的影響較大,而改進(jìn)內(nèi)模的重復(fù)控制可以較好的適應(yīng)電網(wǎng)頻率變化,同時也具有很好的跟蹤性能。
[Abstract]:With the development and utilization of new energy, distributed power generation system has received extensive attention. Grid-connected inverter plays an important role in distributed power generation system, and its performance directly affects the quality of output power. Among all kinds of current control methods of grid-connected inverter, repetitive control has become a research focus because of its high control accuracy. In this paper, the control structure of repetitive controller, the design method and the improvement of power grid frequency change are deeply studied with the grid-connected inverter as the research object. For the repetitive control structure, the causes of instability when repetitive control acts on the system alone are discussed, and the significance of forward channel for system stability in repetitive control is explained. Secondly, in the compound control of traditional repetitive control and PI control, the frequency characteristics of series structure and parallel structure of repetitive control and PI control are analyzed in detail, and the defects of parallel structure in amplitude-frequency characteristics are pointed out. According to the stability conditions of the system, the advantages and disadvantages of different parameter design are analyzed, and a better parameter design method is obtained according to the internal model, compensator, gain coefficient and other parameters of repeated control in series structure. Finally, the influence of power grid frequency change on repetitive control performance is analyzed, and the frequency adaptive repetitive control method based on fractional order theory is introduced. Based on the idea of quasi-resonance control used in resonant control to cope with the frequency change of power grid, an improved method for selecting smaller internal model coefficient is proposed based on the mathematical relationship between repetitive control and resonant control. The resonant bandwidth of the repetitive controller is effectively improved and the problem of power grid frequency change can be dealt with. For the problem of low repetitive control gain caused by the decrease of internal model coefficient, based on the analysis of the influence of each link of the system on the stability of repetitive control, a better parameter design flow of repetitive controller is obtained. The gain of repetitive control at harmonic frequency is improved. Finally, the design of repetitive control parameters and the improved method of grid-connected inverter are simulated and verified by experiments. The results show that the traditional repetitive control based on repetitive control and PI control series structure can have high control accuracy. However, it is greatly affected by the frequency fluctuation of the power grid, and the repeated control of the improved internal model can better adapt to the frequency change of the power grid, and also has a good tracking performance.
【學(xué)位授予單位】：南京航空航天大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：TM464

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