【摘要】：為解決分布式微源并網(wǎng)穩(wěn)定性問題,學(xué)者提出了微電網(wǎng)理論。隨著微電網(wǎng)的發(fā)展,難點(diǎn)問題層出不窮,比如微網(wǎng)在孤島運(yùn)行模式中的無功功率均分問題,以及微網(wǎng)接入不平衡負(fù)載時(shí)輸出端和公共耦合點(diǎn)(Point of Common Coupling,PCC)電壓不平衡問題。因此,研究逆變器接口控制技術(shù)解決上述問題具有重要意義。下垂控制能夠利用本地信息,對(duì)通訊要求較低,是實(shí)現(xiàn)并聯(lián)逆變器均分無功功率的重要控制方法,但是微網(wǎng)線路阻抗呈阻性導(dǎo)致逆變器輸出的有功功率和無功功率耦合,影響下垂控制分配無功功率效果,此外逆變器等效輸出阻抗的阻性分量和感性分量無法嚴(yán)格按照容量比匹配也會(huì)造成逆變器輸出的無功功率無法均分�；谔摂M阻抗無功功率均分控制方法可以解決傳統(tǒng)下垂控制無法均分無功功率問題,但是如何整定虛擬阻抗一直是個(gè)難點(diǎn)。虛擬阻抗包括虛擬電阻和虛擬電抗。針對(duì)虛擬電阻整定問題,本文提出一種虛擬負(fù)電阻的方法,通過添加同線路電阻大小相同的虛擬負(fù)電阻,抵消線路電阻產(chǎn)生的壓降;針對(duì)虛擬電抗整定問題,本文提出了一種利用逆變器輸出參數(shù)整定虛擬電抗的無功功率均分控制策略。選取線路結(jié)構(gòu)簡(jiǎn)單的逆變器作為參考逆變器,其他逆變器作為目標(biāo)逆變器。利用參考逆變器和目標(biāo)逆變器的輸出電壓、下垂系數(shù)、線路電抗來整定目標(biāo)逆變器的虛擬電抗,參考逆變器的虛擬電抗根據(jù)濾波電感進(jìn)行整定。在平衡負(fù)載和不平衡負(fù)載兩種情況中,該方法可以提高傳統(tǒng)下垂控制均分無功功率精度。針對(duì)不平衡負(fù)載條件下系統(tǒng)電壓不平衡問題,本文給出一種同時(shí)補(bǔ)償逆變器輸出端和PCC點(diǎn)電壓不平衡度協(xié)調(diào)補(bǔ)償控制策略,該方法優(yōu)先補(bǔ)償逆變器輸出端電壓,在輸出端電壓不平衡度滿足供電要求前提下,對(duì)PCC點(diǎn)電壓不平衡度進(jìn)行補(bǔ)償。此方法可同時(shí)改善逆變器輸出端和PCC點(diǎn)電壓不平衡問題。在MATLAB/Simulink軟件環(huán)境的仿真結(jié)果驗(yàn)證了上述控制策略的有效性。
[Abstract]:In order to solve the stability problem of distributed microsource grid connection, scholars put forward the theory of microgrid. With the development of microgrid, difficult problems emerge in endlessly, such as the sharing of reactive power in isolated island operation mode, and the voltage imbalance between output and common coupling point (Point of Common Coupling,PCC when microgrid is connected to unbalanced load. Therefore, it is of great significance to study the inverter interface control technology to solve the above problems. Drooping control can make use of local information and has low communication requirements. It is an important control method to realize the equal sharing of reactive power of parallel inverter, but the impedance of microgrid line is resistive, which leads to the coupling of active power and reactive power of inverter output. The effect of sag control on reactive power distribution is affected. In addition, the resistive component and inductive component of equivalent output impedance of inverter can not be matched strictly according to the capacity ratio, which will also cause the reactive power output of inverter to be unevenly divided. The method based on virtual impedance reactive power sharing control can solve the problem that traditional drooping control can not divide reactive power evenly, but how to adjust virtual impedance has always been a difficult point. Virtual impedance includes virtual resistance and virtual reactance. In order to solve the problem of virtual resistance tuning, a method of virtual negative resistance is proposed in this paper, which can offset the voltage drop caused by line resistance by adding virtual negative resistance with the same size of line resistance. In order to solve the problem of virtual reactance tuning, a reactive power sharing control strategy using inverter output parameters to adjust virtual reactance is proposed in this paper. The inverter with simple circuit structure is selected as the reference inverter and the other inverters as the target inverter. The output voltage, sag coefficient and line reactance of the reference inverter and the target inverter are used to adjust the virtual reactance of the target inverter, and the virtual reactance of the reference inverter is adjusted according to the filter inductance. In the case of balanced load and unbalanced load, this method can improve the accuracy of the traditional sag control. In order to solve the problem of system voltage imbalance under unbalanced load, this paper presents a coordinated compensation control strategy for simultaneous compensation of inverter output and PCC point voltage imbalance. This method gives priority to compensation of inverter output voltage. On the premise that the output voltage imbalance meets the requirements of power supply, the voltage imbalance of PCC point is compensated. This method can improve the voltage imbalance of inverter output and PCC at the same time. The simulation results in MATLAB/Simulink software environment verify the effectiveness of the above control strategy.
【學(xué)位授予單位】：蘭州理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TM727

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本文編號(hào)：2475177