發(fā)布時(shí)間：2018-04-10 07:33

  本文選題：模塊化多電平換流器型高壓直流輸電　切入點(diǎn)：故障暫態(tài)分析　出處：《昆明理工大學(xué)》2017年碩士論文

【摘要】：伴隨著電力電子相關(guān)技術(shù)的發(fā)展,模塊化多電平換流器(MMC)作為一種新型的多電平換流器拓?fù)浣Y(jié)構(gòu),應(yīng)用于高壓直流輸電領(lǐng)域后,具有諸多優(yōu)點(diǎn),形成了柔性直流輸電的代表性技術(shù)。目前對(duì)MMC-HVDC的研究主要著重于控制設(shè)計(jì)方面,對(duì)MMC-HVDC保護(hù)和故障類仿真分析方面還需進(jìn)一步的研究。本文采用電磁暫態(tài)仿真軟件PSCAD/EMTDC搭建的MMC-HVDC仿真模型,分析了模塊化多電平柔性直流輸電系統(tǒng)整體運(yùn)行情況,MMC換流器主要的拓?fù)浣Y(jié)構(gòu)和子模塊運(yùn)行機(jī)理,以及在現(xiàn)有MMC-HVDC輸電系統(tǒng)保護(hù)策略的研究基礎(chǔ)上分析了MMC-HVDC的調(diào)制和保護(hù)策略。對(duì)目前MMC換流器中經(jīng)常采用的PWM調(diào)制策略進(jìn)行分析,對(duì)基于PWM調(diào)制策略的MMC換流器進(jìn)行仿真,仿真了不同電平數(shù)的換流器對(duì)輸出波形信號(hào)的影響,驗(yàn)證MMC換流器濾除諧波的特性。同時(shí)還對(duì)MMC-HVDC系統(tǒng)保護(hù)策略,系統(tǒng)保護(hù)范圍的劃分進(jìn)行了探討,分析了基于斷路器保護(hù)和基于換流器拓?fù)浣Y(jié)構(gòu)自清除故障能力的保護(hù)方案。研究對(duì)MMC-HVDC線路運(yùn)行方式及故障識(shí)別有重要意義。在MMC-HVDC系統(tǒng)故障特性方面,充分考慮了線路頻率阻抗特性、故障距離、過(guò)渡電阻等對(duì)故障暫態(tài)量的影響。給出了 MMC-HVDC系統(tǒng)仿真時(shí)子模塊的個(gè)數(shù)、子模塊的電容及MMC橋臂上的電抗計(jì)算過(guò)程。分析了雙極故障情況下MMC子模塊和直流線路單極接地故障下暫態(tài)電流的特性,并對(duì)系統(tǒng)直流側(cè)單極接地故障和雙極接地故障進(jìn)行了仿真分析。在MMC-HVDC仿真的過(guò)程中增加了雷擊故障,并對(duì)在MMC-HVDC系統(tǒng)中雷擊產(chǎn)生的干擾和故障進(jìn)行了仿真分析。基于此,提出了MMC-HVDC系統(tǒng)基于小波系數(shù)高低能量比的單端保護(hù)方法。在分析MMC直流側(cè)阻抗頻率特性后發(fā)現(xiàn)MMC換流器對(duì)故障信號(hào)中的高頻成分具有明顯的衰減作用,可以通過(guò)故障信號(hào)的波型特征和小波能量差異來(lái)實(shí)現(xiàn)交、直流側(cè)故障的辨識(shí),仿真驗(yàn)證該方法識(shí)別故障效果明顯且有效。
[Abstract]:With the development of power electronic correlation technology, modularized multilevel converter (MMC), as a new topology of multilevel converter, has many advantages after it is applied in the field of HVDC transmission.The representative technology of flexible direct current transmission is formed.At present, the research of MMC-HVDC mainly focuses on control design, and further research on MMC-HVDC protection and fault class simulation is needed.In this paper, the MMC-HVDC simulation model based on the electromagnetic transient simulation software PSCAD/EMTDC is used to analyze the main topology and operation mechanism of the modularized multilevel flexible DC transmission system.The modulation and protection strategies of MMC-HVDC are analyzed on the basis of the existing protection strategies of MMC-HVDC transmission system.The PWM modulation strategy which is often used in MMC converter is analyzed. The MMC converter based on PWM modulation strategy is simulated, and the influence of different level converter on the output waveform signal is simulated.Verify the characteristics of MMC converter filter harmonic.At the same time, the protection strategy of MMC-HVDC system and the division of system protection range are discussed, and the protection scheme based on circuit breaker protection and self-clearing fault capability based on converter topology is analyzed.The research is of great significance to the operation mode and fault identification of MMC-HVDC line.In the aspect of fault characteristics of MMC-HVDC system, the effects of line frequency impedance, fault distance and transition resistance on fault transient are fully considered.The number of sub-modules, the capacitance of sub-modules and the reactance calculation process of MMC bridge arm in MMC-HVDC system simulation are given.In this paper, the characteristics of transient current in MMC submodule and unipolar grounding fault of DC line are analyzed, and the DC side unipolar grounding fault and bipolar grounding fault of the system are simulated and analyzed.In the process of MMC-HVDC simulation, the lightning strike fault is added, and the interference and fault caused by lightning strike in MMC-HVDC system are simulated and analyzed.Based on this, a single-end protection method based on high-low energy ratio of wavelet coefficients for MMC-HVDC system is proposed.After analyzing the impedance frequency characteristics of MMC DC side, it is found that the MMC converter has obvious attenuation effect on the high frequency component of the fault signal. The fault identification of AC and DC side can be realized by the wave type characteristic of the fault signal and the difference of wavelet energy.Simulation results show that the method is effective and effective.
【學(xué)位授予單位】：昆明理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TM721.1

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