本文關(guān)鍵詞：基于模塊化多電平的柔性直流輸電控制策略研究　出處：《西南交通大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 柔性直流輸電 模塊化多電平換流器 均壓控制 環(huán)流抑制 無差拍

【摘要】：模塊化多電平換流器(MMC)是近年來提出的應(yīng)用于VSC-HVDC的新型拓?fù)浣Y(jié)構(gòu)。與傳統(tǒng)VSC-HVDC采用的兩電平、三電平換流器拓?fù)浣Y(jié)構(gòu)相比,MMC不僅具有其原有優(yōu)點(diǎn),而且采用的是模塊化設(shè)計(jì)。針對(duì)不同的電壓等級(jí)場(chǎng)合,可通過調(diào)節(jié)串聯(lián)的子模塊數(shù)來改變輸出電平的大小。在電平數(shù)很大的情況下,不但使子模塊的開關(guān)頻率得到下降,而且大大降低輸出諧波的大小而無需交流濾波器,十分適用于VSC-HVDC系統(tǒng)。 本文對(duì)模塊化多電平換流器的拓?fù)浣Y(jié)構(gòu)及工作原理進(jìn)行了詳細(xì)分析。從橋臂能量平衡的角度推導(dǎo)分析了子模塊電容電壓不平衡的原因。定義了平均開關(guān)狀態(tài),對(duì)子模塊直流電容電流及橋臂電壓波動(dòng)原理進(jìn)行了分析,得到了相間二倍頻環(huán)流產(chǎn)生的原因以及表達(dá)式。設(shè)計(jì)了結(jié)合排序法的最近電平調(diào)制策略實(shí)現(xiàn)子模塊電容電壓的均衡控制,并進(jìn)行了仿真驗(yàn)證。對(duì)橋臂電流及環(huán)流進(jìn)行了傅里葉分析,通過其頻譜圖驗(yàn)證了對(duì)橋臂電流中環(huán)流大小及組成成分的分析。設(shè)計(jì)了疊加了三相橋臂能量均分控制分量的基于載波移相的均壓調(diào)制策略,該策略在實(shí)現(xiàn)子模塊均壓控制的同時(shí)有效的抑制了環(huán)流。通過交流側(cè)單相接地故障仿真,驗(yàn)證了采用三相橋臂能量均分控制比單相橋臂能量均分控制具有更好的抗干擾能力。對(duì)比了采用最近電平調(diào)制和載波移相調(diào)制策略下MMC電平數(shù)及控制器頻率與MMC輸出電壓諧波含量的關(guān)系。 分別建立了MMC-HVDC在三相靜止坐標(biāo)系及dq旋轉(zhuǎn)坐標(biāo)系下的數(shù)學(xué)模型,并在dq坐標(biāo)系下對(duì)直接電流控制器的外環(huán)及內(nèi)環(huán)控制器進(jìn)行了設(shè)計(jì)。利用PSCAD仿真軟件,建立了兩端21電平的MMC-HVDC仿真模型,仿真驗(yàn)證了控制器具有良好的解耦特性及快速的動(dòng)態(tài)響應(yīng)能力。 根據(jù)MMC-HVDC數(shù)學(xué)模型的特點(diǎn)以及無差拍控制在數(shù)字控制中的優(yōu)點(diǎn),對(duì)MMC-HVDC系統(tǒng)換流站的數(shù)學(xué)模型進(jìn)行離散化,設(shè)計(jì)了在三相靜止坐標(biāo)系下的無差拍解耦控制策略。仿真驗(yàn)證該策略在具有良好的解耦特性及快速的動(dòng)態(tài)響應(yīng)特性的同時(shí),由于減少了控制器的坐標(biāo)變換次數(shù)及PI調(diào)節(jié)環(huán)節(jié),控制器的運(yùn)算量及復(fù)雜程度得到降低,便于數(shù)字控制器的設(shè)計(jì)與實(shí)現(xiàn)。 根據(jù)多端MMC-HVDC的連接方式和控制原則,分析了主從控制策略和結(jié)合直流電壓偏差的主從控制策略各自的原理和優(yōu)劣,在PSCAD中搭建21電平的三端MMC-HVDC仿真模型,對(duì)兩種控制策略進(jìn)行了仿真,仿真結(jié)果表明了結(jié)合直流電壓偏差的主從控制策略無需高速通信就能實(shí)現(xiàn)換流站模式的切換,提高了多端MMC-HVDC的靈活性和可靠性,應(yīng)用范圍更廣。
[Abstract]:Modular multilevel converter (MMC) is a new topology proposed in recent years. Based on VSC-HVDC and traditional VSC-HVDC with two level, three level converter topology is compared, MMC not only has its original advantages, and modular design. According to the voltage level of different occasions, by the number of sub modules in series regulate the output voltage levels change size. In the case of a large number of level, not only the switch frequency of sub modules are decreased, and greatly reduce the size of output harmonic without AC filter, which is suitable for VSC-HVDC system.
The topological structure and working principle of the modular multilevel converter is analyzed in detail. From the viewpoint of energy balance arm is analyzed by reason of the sub module capacitor voltage unbalance. The definition of average switching state, sub module and DC capacitor current bridge arm voltage fluctuation principle is analyzed, and two reasons double circulation and expression are designed. The nearest level modulation strategy with sorting method to achieve a balanced control sub module capacitor voltage, and the simulation is conducted. The bridge arm current and circulation are analyzed by Fourier analysis, the spectrum analysis is verified on the bridge arm current flows in the size and composition of the design. The superposition of the three-phase bridge voltage was based on arm carrier phase shift modulation strategy of equipartition of energy control components, at the same time, the strategy of pressure control on module implementation effectively Circulation. Through the AC single phase to ground fault simulation, verified by the three-phase bridge arm of equipartition of energy control than the single-phase bridge arm of equipartition of energy control has better anti-jamming ability. Compared with the relationship between MMC level and MMC controller frequency and harmonic content of the output voltage of the nearest level modulation and carrier phase shift modulation strategy.
The mathematical model in three-phase static coordinate and DQ coordinates of MMC-HVDC were established, and in the DQ coordinates of the outer ring and the inner loop controller of direct current controller was designed. By using PSCAD simulation software, the simulation model was established in MMC-HVDC at 21 level, the simulation shows that the controller has good decoupling property and fast dynamic response.
According to the characteristics of the MMC-HVDC mathematical model and deadbeat control advantages in digital control system, the mathematical model of MMC-HVDC converter is discretized, designed in three-phase coordinates deadbeat decoupling control strategy. The simulation results show that the strategy has good decoupling characteristics and fast dynamic response characteristics at the same time because of the reduced number of coordinate transformation, and the PI controller control link, controller and the complexity of computation is reduced, the design and Implementation for digital controller.
According to the connection mode and control principle of multi terminal MMC-HVDC, analysis of the master-slave control strategy and combined DC voltage deviation of the master-slave control strategy principle and their quality, builds the simulation model of three terminal MMC-HVDC 21 level in PSCAD, the two control strategies are simulated, the simulation results show that the combination of master-slave DC voltage error control no communication can realize switching mode converter, improve the flexibility and reliability of multi terminal MMC-HVDC, a wider range of applications.

【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)】：TM721.1

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