混合双馈入直流系统接地故障特性分析及其控制保护策略研究

发布时间：2018-03-18 06:03

本文选题：电网换相换流器高压直流输电　切入点：电压源换流器高压直流输电　出处：《西南交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：电网换相换流器高压直流输电(LCC-HVDC)凭借其经济性、稳定性、快速可控性以及可实现电网异步互联等诸多优势,在我国的"西电东送"战略中起到了至关重要的作用。随着大功率全控型电力电子器件的进步和规模化可再生能源的开发,电压源换流器高压直流输电(VSC-HVDC)也得到了快速发展。近年来,由LCC-HVDC和VSC-HVDC构成的混合双馈入直流输电系统受到了越来越多的关注与研究。接地故障作为电力系统最常见的故障之一,一直是直流输电系统故障保护策略研究关注的重点。目前为止,还没有针对混合双馈入直流系统接地故障特性及其保护策略的系统研究。本文首先针对LCC-HVDC和VSC-HVDC两种直流输电系统分别建立了数学模型,设计出相应的控制策略,并仿真验证了控制策略的有效性。在此基础上,建立包含LCC-HVDC和VSC-HVDC的混合双馈入直流系统的电磁暂态系统模型。随后,选取混合双馈入直流系统中的LCC-HVDC子系统整流侧、VSC-HVDC子系统整流侧及混合双馈入直流系统逆变侧这三个主要区域作为研究对象,针对区域内的主要接地故障进行仿真分析,并对故障机理进行研究。对于混合双馈入直流系统中VSC-HVDC子系统,针对不对称接地故障导致的换相电压三相不平衡情况,设计基于VSC系统无源性及其欧拉-拉格朗日数学模型的正序、负序无源控制器。仿真结果表明,该控制器的动稳态控制特性良好。在此基础上,设计改进的定有功功率控制以保证故障状态下VSC-HVDC子系统的有功功率稳定输出。仿真结果表明,该方法有效地控制了故障电流增幅。
[Abstract]:LCC-HVDCs have many advantages, such as economy, stability, fast controllability, asynchronous interconnection and so on. It has played an important role in the strategy of "power transmission from west to east" in China. With the development of high-power fully controlled power electronic devices and the development of large-scale renewable energy, Voltage source converter (HVDC) VSC-HVDC) has also been developed rapidly. In recent years, the hybrid double-fed DC transmission system composed of LCC-HVDC and VSC-HVDC has attracted more and more attention and research. Grounding fault is one of the most common faults in power system. It has always been the focus of research on fault protection strategy of HVDC transmission system. There is no systematic research on grounding fault characteristics and protection strategy of hybrid double-fed DC system. Firstly, mathematical models of LCC-HVDC and VSC-HVDC DC transmission systems are established, and corresponding control strategies are designed. The simulation results show the effectiveness of the control strategy. Based on this, the electromagnetic transient system model of a hybrid double-fed DC system including LCC-HVDC and VSC-HVDC is established. Three main areas of LCC-HVDC subsystem rectifier side VSC-HVDC subsystem and inverter side of hybrid double-fed DC system are selected as the research object, and the main grounding faults in the region are simulated and analyzed. And the fault mechanism is studied. For the VSC-HVDC subsystem in the hybrid double-fed DC system, the three-phase voltage imbalance caused by the asymmetrical grounding fault is considered. Based on the VSC system passivity and its Euler-Lagrangian mathematical model, a positive-order and negative-sequence passive controller is designed. The simulation results show that the controller has good dynamic and steady-state control characteristics. An improved constant active power control is designed to ensure the stable output of the active power of the VSC-HVDC subsystem under the condition of failure. The simulation results show that the proposed method can effectively control the increase of the fault current.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM721.1

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