【摘要】：微電網(wǎng)是一種集分布式電源、局部負(fù)荷為一體的獨(dú)立供電系統(tǒng),可以在并網(wǎng)和孤島兩種模式下運(yùn)行。孤島運(yùn)行時(shí),在并聯(lián)分布式電源之間合理分配功率是一個(gè)重要的控制目標(biāo)。由于下垂控制可實(shí)現(xiàn)無通信系統(tǒng)的功率分配,因而受到了廣泛關(guān)注。然而,傳統(tǒng)下垂控制器受到線路阻抗不匹配、局部負(fù)荷等因素影響,難以實(shí)現(xiàn)精確的功率分配控制。 因此,本文重點(diǎn)研究基于下垂控制策略的功率分配特性及其改進(jìn)方法以及平滑切換方法,具體研究?jī)?nèi)容如下： 首先,本文建立了逆變器模型；設(shè)計(jì)了電壓外環(huán)電流內(nèi)環(huán)控制器；建立了下垂控制器模型,在此基礎(chǔ)上分析了有功-頻率和無功-電壓下垂控制器的穩(wěn)定性,并進(jìn)行了仿真驗(yàn)證。 其次,本文分析了逆變器并聯(lián)系統(tǒng)的功率分配特性；研究了線路阻抗、局部負(fù)荷對(duì)功率分配的影響。 再次,本文研究了一種基于Q—U下垂特性的虛擬阻抗的控制方法,通過該控制策略消除等效輸出阻抗的偏差對(duì)無功功率的分配影響,從而改善無功功率分配特性,并進(jìn)行了仿真驗(yàn)證。 最后,本文研究了基于下垂控制的微電網(wǎng)平滑切換方法。該方法可以在不改變控制模式的情況下實(shí)現(xiàn)并網(wǎng)和孤島模式的平滑切換,仿真結(jié)果驗(yàn)證了該方法的正確性和有效性。 本文理論分析及仿真驗(yàn)證表明：虛擬阻抗可以有效彌補(bǔ)線路阻抗不匹配對(duì)無功功率分配的影響,從而改善無功分配精度�；谙麓箍刂频奈㈦娋W(wǎng)平滑切換方法由于不改變控制模式,從而降低了復(fù)雜性,提高了靈活性。該結(jié)論對(duì)基于下垂控制的功率分配策略和平滑切換方法有一定的應(yīng)用價(jià)值。
[Abstract]:Microgrid is an independent power supply system with distributed generation and local load, which can be operated in two modes: grid-connected and isolated island. The reasonable distribution of power between parallel distributed power sources is an important control objective when the island is running. Because droop control can realize power distribution of no communication system, it has been paid more and more attention. However, the traditional droop controller is affected by the line impedance mismatch and local load, so it is difficult to achieve accurate power allocation control. Therefore, this paper focuses on the power allocation characteristics based on droop control strategy and its improvement method and smooth switching method. The specific research contents are as follows: first, the inverter model is established in this paper; The voltage outer loop current inner loop controller is designed, and the sagging controller model is established, and the stability of active power frequency and reactive power voltage droop controller is analyzed and verified by simulation. Secondly, the power distribution characteristics of parallel inverter system are analyzed, and the influence of line impedance and local load on power distribution is studied. Thirdly, this paper studies a control method of virtual impedance based on Q-U droop characteristic. By using this control strategy, the influence of the deviation of equivalent output impedance on the distribution of reactive power is eliminated, so as to improve the distribution characteristics of reactive power. The simulation is also carried out. Finally, this paper studies the smooth switching method of microgrid based on droop control. The method can realize smooth switching between grid-connected and islanding mode without changing the control mode. The simulation results show that the method is correct and effective. Theoretical analysis and simulation results show that virtual impedance can effectively compensate for the effect of line impedance mismatch on reactive power distribution and improve the accuracy of reactive power distribution. Because the smooth switching method of microgrid based on droop control does not change the control mode, it reduces the complexity and improves the flexibility. This conclusion has certain application value to power allocation strategy and smooth switching method based on droop control.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TM727

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本文編號(hào)：2256254