【摘要】：配電網(wǎng)中電力電子設(shè)備、電氣化鐵路等非線性負(fù)荷的大量增加,導(dǎo)致電流波形發(fā)生嚴(yán)重畸變,電能質(zhì)量問題越來越受到重視。D-STATCOM是有效提高配電網(wǎng)電能質(zhì)量的裝置,針對(duì)其補(bǔ)償容量和耐壓水平的限制,本文提出了一種基于模塊化多電平變流器(MMC)的三相四線制STATCOM。論文首先對(duì)MMC的拓?fù)浣Y(jié)構(gòu)和工作原理進(jìn)行了分析,建立了單相MMC數(shù)學(xué)模型,其功率單元可以實(shí)現(xiàn)四象限運(yùn)行。MMC可以看作一個(gè)可控電壓源,通過觸發(fā)脈沖控制開關(guān)器件的通斷,來控制上下橋臂電壓,進(jìn)而實(shí)現(xiàn)對(duì)交流側(cè)輸出電壓的控制。對(duì)于脈沖調(diào)制技術(shù),主要對(duì)CPS-SPWM和CD-SPWM進(jìn)行了對(duì)比,結(jié)果表明CPS-SPWM技術(shù)能實(shí)現(xiàn)有功功率在橋臂上各功率單元間的均衡分配,能有效提高開關(guān)等效頻率,本文亦采用了CPS-SPWM技術(shù)對(duì)脈寬進(jìn)行調(diào)制。其次,構(gòu)建了三相四線制MMC-STATCOM接入系統(tǒng)時(shí)的拓?fù)浣Y(jié)構(gòu)。分析其數(shù)學(xué)模型和工作原理可知,可以通過控制MMC-STATCOM輸出電壓的幅值和相位,就可實(shí)現(xiàn)容性和感性工況下的轉(zhuǎn)換。對(duì)于補(bǔ)償指令電流的檢測(cè),采取基于瞬時(shí)無功功率理論的ip-iq法,對(duì)于濾波器采用滑動(dòng)均值濾波算法,計(jì)算速度快,占用內(nèi)存小。還分析了交流側(cè)控制策略中直接電流法和間接電流法的原理,另外為了維持直流側(cè)電壓的穩(wěn)定,對(duì)功率單元模塊的電容電壓采用了均壓控制和均衡控制策略。當(dāng)電力系統(tǒng)在非正常狀態(tài)下時(shí),為了防止MMC-STATCOM遭受破壞,需要采取一定的保護(hù)措施。針對(duì)補(bǔ)償指令過電流情況,提出了截?cái)嘞蘖鞅Ｗo(hù)和同比例限流保護(hù)策略。最后,在Matlab/Simulink上搭建了三相四線制MMC-STATCOM模型,對(duì)諧波、無功、不對(duì)稱綜合工況進(jìn)行了仿真分析,結(jié)果表明補(bǔ)償效果良好,直流側(cè)電壓能夠穩(wěn)定在給定值附近,驗(yàn)證了控制策略的有效性。此外,還分析了加裝保護(hù)措施前后裝置輸出補(bǔ)償電流的變化情況,驗(yàn)證了保護(hù)措施的可行性。
[Abstract]:D-STATCOM is an effective device to improve the power quality of distribution network. In view of the limitation of its compensation capacity and voltage withstand level, this paper presents a new method based on modularization. Three-phase four-wire STATCOM of level converter (MMC) is presented in this paper. First, the topology and working principle of MMC are analyzed, and the mathematical model of single-phase MMC is established. The power unit of MMC can operate in four quadrants. MMC can be regarded as a controllable voltage source. By triggering the pulse to control the switching device on and off, the upper and lower arm voltage can be controlled. For the pulse modulation technology, the CPS-SPWM and CD-SPWM are compared. The results show that the CPS-SPWM technology can realize the balanced distribution of active power among the power units on the bridge arm, and can effectively improve the switching equivalent frequency. The CPS-SPWM technology is also used to modulate the pulse width. The topological structure of three-phase four-wire MMC-STATCOM is constructed.The mathematical model and working principle are analyzed.It is shown that the capacitive and inductive conversion can be realized by controlling the amplitude and phase of the output voltage of MMC-STATCOM.For the detection of compensating instruction current,the ip-iq method based on instantaneous reactive power theory is adopted. The principle of direct current method and indirect current method in AC side control strategy are also analyzed. In addition, in order to maintain the stability of DC side voltage, voltage sharing control and equalization control strategy are adopted for capacitor voltage of power unit module. In order to prevent the MMC-STATCOM from being destroyed under abnormal conditions, some protective measures should be taken. In view of the overcurrent of compensating instructions, the strategies of cut-off current-limiting protection and proportional current-limiting protection are put forward. Finally, a three-phase four-wire MMC-STATCOM model is built on Matlab/Simulink to simulate the harmonic, reactive and asymmetric conditions. The simulation results show that the compensation effect is good and the DC side voltage can be stabilized near the given value, which verifies the effectiveness of the control strategy.
【學(xué)位授予單位】：華北電力大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TM761.12

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本文編號(hào)：2227453