模块化多电平VSC-HVDC系统建模及控制策略研究
发布时间：2019-07-01 11:47
【摘要】：柔性直流输电系统凭借着控制方式灵活,潮流反转方便以及故障后的快速恢复性等优点得到了快速的发展和应用。在电压源型换流器高压直流输电(Voltage Sourced Converter based HVDC,VSC-HVDC)技术基础上提出的采用模块化多电平换流器(Modular Multilevel Converter,MMC)的柔性直流输电技术更是有着输电容量大,交直流侧输出波形质量高,开关损耗低,适用领域范围广等优点,已成为了柔性直流输电的代表性技术。故针对MMC-HVDC系统的建模及控制策略研究具有重要意义,因此,本文开展以下研究内容,并得出以下结论。首先对MMC的拓扑结构和运行原理进行了介绍,详细分析了MMC各相上、下桥臂电压和电流之间的关系,建立了含开关函数的MMC高频和低频数学模型,并以此为基础,引入了Park变换,完成了数学模型在三相静止坐标系下向同步旋转坐标系下的转换,为MMC-HCDC控制系统的设计提供了理论基础。其次对MMC-HVDC系统的阀层和极层控制策略进行了研究。采用载波移相正弦脉宽调制作为MMC的调制策略,并将采用排序算法的子模块电容电压均压控制策略和相间环流抑制控制策略加入至载波移相正弦脉宽调制策略中,完成了MMC-HVDC系统的阀层控制策略设计,同时采用了双闭环矢量控制策略作为MMC-HVDC系统的极层控制策略。在PSCAD/EMTDC电磁暂态仿真平台下验证了电容电压均压控制策略和相间环流控制策略的有效性以及采用双闭环的矢量控制系统可以实现有功功率和无功功率解耦的功能,完成了MMC-HVDC系统控制策略的研究和控制器的设计。最后以某省级电网实际规划为背景,鉴于该省存在的过剩能源无法及时消纳问题,设计出提高该省电网外送能力的柔性直流输电方案。由于仿真软件的限制,对比分析了在相同条件下的MMC-HVDC系统和VSC-HVDC系统在暂态响应下的外部特性,得出在只考虑直流系统的外部特性时,可以应用VSC-HVDC系统等效成MMC-HVDC系统来完成提高电网外送能力的任务。在PSCAD/EMTDC电磁暂态仿真平台下,将预先设计的送端交流等值电网并网点处并入柔性直流输电系统,针对交流系统和直流系统在不同故障下的暂态响应进行了分析,分析出不同故障对送端交流系统的影响,为实际工程的设计与实施提供了理论依据。
[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.
【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM721.1
本文编号：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.
【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM721.1
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