模塊化多電平VSC-HVDC系統(tǒng)建模及控制策略研究
發(fā)布時間：2019-07-01 11:47
【摘要】：柔性直流輸電系統(tǒng)憑借著控制方式靈活,潮流反轉方便以及故障后的快速恢復性等優(yōu)點得到了快速的發(fā)展和應用。在電壓源型換流器高壓直流輸電(Voltage Sourced Converter based HVDC,VSC-HVDC)技術基礎上提出的采用模塊化多電平換流器(Modular Multilevel Converter,MMC)的柔性直流輸電技術更是有著輸電容量大,交直流側輸出波形質量高,開關損耗低,適用領域范圍廣等優(yōu)點,已成為了柔性直流輸電的代表性技術。故針對MMC-HVDC系統(tǒng)的建模及控制策略研究具有重要意義,因此,本文開展以下研究內(nèi)容,并得出以下結論。首先對MMC的拓撲結構和運行原理進行了介紹,詳細分析了MMC各相上、下橋臂電壓和電流之間的關系,建立了含開關函數(shù)的MMC高頻和低頻數(shù)學模型,并以此為基礎,引入了Park變換,完成了數(shù)學模型在三相靜止坐標系下向同步旋轉坐標系下的轉換,為MMC-HCDC控制系統(tǒng)的設計提供了理論基礎。其次對MMC-HVDC系統(tǒng)的閥層和極層控制策略進行了研究。采用載波移相正弦脈寬調制作為MMC的調制策略,并將采用排序算法的子模塊電容電壓均壓控制策略和相間環(huán)流抑制控制策略加入至載波移相正弦脈寬調制策略中,完成了MMC-HVDC系統(tǒng)的閥層控制策略設計,同時采用了雙閉環(huán)矢量控制策略作為MMC-HVDC系統(tǒng)的極層控制策略。在PSCAD/EMTDC電磁暫態(tài)仿真平臺下驗證了電容電壓均壓控制策略和相間環(huán)流控制策略的有效性以及采用雙閉環(huán)的矢量控制系統(tǒng)可以實現(xiàn)有功功率和無功功率解耦的功能,完成了MMC-HVDC系統(tǒng)控制策略的研究和控制器的設計。最后以某省級電網(wǎng)實際規(guī)劃為背景,鑒于該省存在的過剩能源無法及時消納問題,設計出提高該省電網(wǎng)外送能力的柔性直流輸電方案。由于仿真軟件的限制,對比分析了在相同條件下的MMC-HVDC系統(tǒng)和VSC-HVDC系統(tǒng)在暫態(tài)響應下的外部特性,得出在只考慮直流系統(tǒng)的外部特性時,可以應用VSC-HVDC系統(tǒng)等效成MMC-HVDC系統(tǒng)來完成提高電網(wǎng)外送能力的任務。在PSCAD/EMTDC電磁暫態(tài)仿真平臺下,將預先設計的送端交流等值電網(wǎng)并網(wǎng)點處并入柔性直流輸電系統(tǒng),針對交流系統(tǒng)和直流系統(tǒng)在不同故障下的暫態(tài)響應進行了分析,分析出不同故障對送端交流系統(tǒng)的影響,為實際工程的設計與實施提供了理論依據(jù)。
[Abstract]:Flexible HVDC system has been developed and applied rapidly because of its flexible control mode, convenient power flow reversal and rapid recovery after fault. Based on the voltage source converter HVDC (Voltage Sourced Converter based HVDC,VSC-HVDC) technology, the flexible HVDC technology based on modular multilevel converter (Modular Multilevel Converter,MMC) has become the representative technology of flexible HVDC because of its large transmission capacity, high output waveform quality on AC / DC side, low switching loss and wide range of applications. Therefore, it is of great significance to study the modeling and control strategy of MMC-HVDC system. Therefore, the following research contents are carried out in this paper, and the following conclusions are drawn. Firstly, the topological structure and operation principle of MMC are introduced, the relationship between voltage and current of upper and lower bridge arm of MMC is analyzed in detail, and the high frequency and low frequency mathematical models of MMC with switching function are established. On this basis, Park transformation is introduced, and the transformation of mathematical model from three-phase static coordinate system to synchronous rotating coordinate system is completed, which provides a theoretical basis for the design of MMC-HCDC control system. Secondly, the valve layer and pole layer control strategy of MMC-HVDC system is studied. Carrier phase-shifted sinusoidal pulse width modulation is used as the modulation strategy of MMC, and the sub-module capacitance voltage equalizing control strategy and interphase circulation suppression control strategy based on sorting algorithm are added to the carrier phase-shifted sinusoidal pulse width modulation strategy. The valve layer control strategy of MMC-HVDC system is designed. At the same time, the double closed-loop vector control strategy is used as the polar layer control strategy of MMC-HVDC system. The effectiveness of capacitance voltage equalizing control strategy and interphase circulation control strategy is verified on PSCAD/EMTDC electromagnetic transient simulation platform, and the decoupling function of active power and reactive power can be realized by using double closed loop vector control system. The control strategy of MMC-HVDC system is studied and the controller is designed. Finally, based on the actual planning of a provincial power grid, in view of the problem that the excess energy can not be absorbed in time, a flexible DC transmission scheme to improve the transmission capacity of the provincial power grid is designed. Due to the limitation of simulation software, the external characteristics of MMC-HVDC system and VSC-HVDC system under the same conditions are compared and analyzed, and it is concluded that when only the external characteristics of DC system are considered, the equivalent MMC-HVDC system of VSC-HVDC system can be used to improve the outgoing capacity of power grid. Under the PSCAD/EMTDC electromagnetic transient simulation platform, the pre-designed AC equivalent power grid at the transmission end is integrated into the flexible DC transmission system, and the transient response of the AC system and the DC system under different faults is analyzed, and the influence of different faults on the AC system at the transmission end is analyzed, which provides a theoretical basis for the design and implementation of the actual project.
【學位授予單位】：沈陽工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM721.1
本文編號：2508446
[Abstract]:Flexible HVDC system has been developed and applied rapidly because of its flexible control mode, convenient power flow reversal and rapid recovery after fault. Based on the voltage source converter HVDC (Voltage Sourced Converter based HVDC,VSC-HVDC) technology, the flexible HVDC technology based on modular multilevel converter (Modular Multilevel Converter,MMC) has become the representative technology of flexible HVDC because of its large transmission capacity, high output waveform quality on AC / DC side, low switching loss and wide range of applications. Therefore, it is of great significance to study the modeling and control strategy of MMC-HVDC system. Therefore, the following research contents are carried out in this paper, and the following conclusions are drawn. Firstly, the topological structure and operation principle of MMC are introduced, the relationship between voltage and current of upper and lower bridge arm of MMC is analyzed in detail, and the high frequency and low frequency mathematical models of MMC with switching function are established. On this basis, Park transformation is introduced, and the transformation of mathematical model from three-phase static coordinate system to synchronous rotating coordinate system is completed, which provides a theoretical basis for the design of MMC-HCDC control system. Secondly, the valve layer and pole layer control strategy of MMC-HVDC system is studied. Carrier phase-shifted sinusoidal pulse width modulation is used as the modulation strategy of MMC, and the sub-module capacitance voltage equalizing control strategy and interphase circulation suppression control strategy based on sorting algorithm are added to the carrier phase-shifted sinusoidal pulse width modulation strategy. The valve layer control strategy of MMC-HVDC system is designed. At the same time, the double closed-loop vector control strategy is used as the polar layer control strategy of MMC-HVDC system. The effectiveness of capacitance voltage equalizing control strategy and interphase circulation control strategy is verified on PSCAD/EMTDC electromagnetic transient simulation platform, and the decoupling function of active power and reactive power can be realized by using double closed loop vector control system. The control strategy of MMC-HVDC system is studied and the controller is designed. Finally, based on the actual planning of a provincial power grid, in view of the problem that the excess energy can not be absorbed in time, a flexible DC transmission scheme to improve the transmission capacity of the provincial power grid is designed. Due to the limitation of simulation software, the external characteristics of MMC-HVDC system and VSC-HVDC system under the same conditions are compared and analyzed, and it is concluded that when only the external characteristics of DC system are considered, the equivalent MMC-HVDC system of VSC-HVDC system can be used to improve the outgoing capacity of power grid. Under the PSCAD/EMTDC electromagnetic transient simulation platform, the pre-designed AC equivalent power grid at the transmission end is integrated into the flexible DC transmission system, and the transient response of the AC system and the DC system under different faults is analyzed, and the influence of different faults on the AC system at the transmission end is analyzed, which provides a theoretical basis for the design and implementation of the actual project.
【學位授予單位】：沈陽工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM721.1
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