本文選題：柔性多端直流輸電系統(tǒng) + 交流故障穿越控制　； 參考：《華北電力大學(xué)(北京)》2017年碩士論文

【摘要】：隨著傳輸功率和電壓等級(jí)不斷提升、新能源發(fā)電需求不斷加大,高壓柔性多端直流輸電(Multi-terminal High Voltage Direct Current transmission based on Voltage Source Converter,VSC-MTDC)在經(jīng)濟(jì)性、互連性和控制性等方面都開始顯現(xiàn)極大的優(yōu)勢(shì)。當(dāng)柔性多端直流連接的交流電網(wǎng)發(fā)生一定程度的故障時(shí),為了保持系統(tǒng)的穩(wěn)定性,直流系統(tǒng)需要具備一定的故障穿越能力。本文針對(duì)這一需求,以模塊化多電平換流器(Modular Multi-terminal Converter,MMC)柔性多端直流輸電為對(duì)象,在研究其工作原理、拓?fù)浣Y(jié)構(gòu)和數(shù)學(xué)模型的基礎(chǔ)上,分析交流系統(tǒng)側(cè)故障對(duì)系統(tǒng)的主要影響,并結(jié)合仿真分析了交流電流、有功功率和直流電壓等物理量的故障暫態(tài)特性。基于暫態(tài)分析,通過在閥級(jí)控制中增加調(diào)制比比例積分控制環(huán)節(jié)和反饋量,抑制故障時(shí)交流電流幅值的增大。通過對(duì)柔性多端直流系統(tǒng)的內(nèi)環(huán)解耦控制的改進(jìn),實(shí)現(xiàn)正負(fù)序分量單獨(dú)控制,抑制不對(duì)稱故障下交流電流的負(fù)序分量。在故障較大需要切除故障換流站時(shí),分析了電壓下垂控制特性,并與電壓裕度控制進(jìn)行了對(duì)比,對(duì)下垂控制進(jìn)一步改進(jìn),添加有功功率反饋環(huán)節(jié),使非故障換流站靈活分配功率,在較小的電壓偏差情況下迅速達(dá)到新的穩(wěn)定。在PSCAD/EMTDC仿真軟件中搭建了四端MMC-MTDC系統(tǒng)分別進(jìn)行仿真驗(yàn)證,結(jié)果表明通過控制策略的設(shè)計(jì),故障時(shí)交流側(cè)電流的幅值減小,能保持三相對(duì)稱性,在故障換流站退出運(yùn)行后電壓下垂控制特性靈活,而改進(jìn)的下垂控制使有功功率分配更合理,直流電壓偏差減小,一定程度上提高了柔性多端直流系統(tǒng)對(duì)交流系統(tǒng)側(cè)故障的穿越能力。
[Abstract]:With the continuous improvement of transmission power and voltage, the demand for new energy generation is increasing, and the high voltage flexible multi-terminal High Voltage Direct Current transmission based on Voltage Source converter VSC-MTDCs are beginning to show great advantages in economy, interconnection and control. In order to maintain the stability of the system, the DC system needs to have a certain fault traversing ability when the flexible multi-terminal DC power grid has a certain degree of failure. In this paper, the flexible multiterminal DC transmission of modular multilevel converter, Modular Multi-terminal converter, is taken as an object. On the basis of studying its working principle, topological structure and mathematical model, the main influence of AC system side fault on the system is analyzed. The fault transient characteristics of AC current, active power and DC voltage are analyzed by simulation. Based on the transient analysis, the amplitude of AC current is restrained by increasing the modulation ratio, proportional integral control and feedback in the valve level control. By improving the internal loop decoupling control of flexible multi-terminal DC system, the positive and negative sequence components are controlled separately to suppress the negative sequence components of AC current under asymmetric faults. When the fault converter station needs to be removed, the characteristics of voltage sag control are analyzed, and compared with voltage margin control, the droop control is further improved and the active power feedback link is added. The power distribution of the non-fault converter station is flexible, and the new stability can be achieved quickly under the condition of small voltage deviation. A four-terminal MMC-MTDC system is built in the PSCAD/EMTDC simulation software for simulation verification. The results show that the amplitude of AC side current decreases and the three-phase symmetry can be maintained by the design of control strategy. The voltage droop control characteristic is flexible after the fault converter station exits from operation, but the improved droop control makes the distribution of active power more reasonable, and the DC voltage deviation decreases. To some extent, the ability of flexible multi-terminal DC system to pass through AC system side faults is improved.
【學(xué)位授予單位】：華北電力大學(xué)(北京)
【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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本文編號(hào)：1814564