【作者】 李广凯；

【导师】 李庚银； 赵成勇；

【作者基本信息】 华北电力大学（河北） ， 电力系统及其自动化， 2008， 博士

【摘要】 电压源换流器型直流输电(Voltage Source Converter-Based HVDC,VSC-HVDC)是一种新的直流输电技术,它具备有功无功快速独立控制、可以向远距离小功率无源网络供电、可以向系统发出无功功率、易于构成多端网络等特点。VSC-HVDC技术涉及电气技术、现代电力电子技术、自动控制理论等诸多学科领域。由于其出现和发展时间还不长,许多基础理论和相关的应用基础问题还需要深入探讨。本文针对VSC-HVDC的稳态特性、暂态特性和与传统直流输电相结合的新型输电方式以及在电网恢复中的应用几个方面进行研究,取得以下几个方面的成果。1.推导了VSC-HVDC功率传输方程的直角坐标形式,采用逆系统方法设计了基于有功、无功功率独立调节的VSC-HVDC控制系统,实现了VSC的有功、无功四象限独立、灵活调节。当实际交流系统三相交流电压不对称时,VSC传输功率会发生波动,从而影响VSC-HVDC系统的运行。根据瞬时无功功率理论,推导出了消除VSC传输功率波动需满足的输出正、负序电压间的关系式。采用不对称触发以及逆系统方法设计VSC的传输功率控制系统,消除了系统电压不对称带来的有功功率波动。分析了基于VSC-HVDC的配电网的结构、有功、无功功率运行特性,及对交流系统的调压作用。2.提出了基于SPWM控制和开关函数的VSC-HVDC系统暂态模型,分析了VSC-HVDC系统的开关特性和暂态运行机理,分析了其在负荷变化和故障时候的暂态运行原理。提出了基于能量守恒原理的VSC-HVDC系统暂态模型,分析了VSC-HVDC系统的能量变化过程和暂态运行机理,推导了VSC-HVDC整流侧换流器、逆变侧换流器及直流部分的能量平衡关系。3.结合传统HVDC技术成熟、成本低廉的优点和VSC-HVDC运行控制方式灵活的优点,提出一种新的混合直流输电(Hybrid HVDC)方式,并探讨其结构组成、技术特点、运行特性、运行机理、调节方式和调节特性,给出Hybrid HVDC的有功无功运行图。4.分析了用于电网互联的VSC-HVDC在电网大停电时的自保护问题,提出通过“软关断”策略使VSC-HVDC能够平稳退出功率输送,不发生剧烈的变化和设备的破坏,但还保持直流电压,进入热备用状态。分析了利用VSC-HVDC进行电网恢复的过电压抑制问题,提出了VSC-HVDC在一侧交流系统大停电情况下的软启动方法,避免了长线路合闸操作过电压和变压器空充过电压。基于Lyapunov稳定理论,采用基于Backstepping设计方法的VSC-HVDC控制策略应用于电网恢复,用以提高电网恢复中的稳定性。更多还原

【Abstract】 Voltage Source Converter-Based HVDC (VSC-HVDC) is a novel DC transmission technology, which is characterized by quick and independt control of active and reactive power, power supply to small isolated long distance passive load, generation of reactive power to AC system as well as the ability to make up easily multi-terminal network. VSC-HVDC technology relates to many academic fields such as electrical technology, modern power electronics technology, and automation control theory, etc. Because VSC-HVDC has emergered recently with a short period of development, many basic theories and application issues need to be investigated deeply, especially the mathmetic model, operation characteristic and mainly application questions.Aiming at the stable and dynamic characteristics of VSC-HVDC, new transmission type conjointed with tranditional HVDC technology as well as its application in power system restoration, the following results are achieved:1. The rectangular coordinate form of VSC’s power transmitting equations is deduced through coordinate transformation. By using the nonlinear control of inverse system, VSC-HVDC control system is designed based on that active and reactive power is adjusted respectively, and then the active and reactive power of VSC can be controlled in four quadrants. When three phases voltage are asymmetrical, the transmitted power of VSC fluctuates and the operation of VSC-HVDC is influenced. The power characteristic of VSC under asymmerical voltage is drawn according to instantaneous power theory. By adopting asymmetrical control scheme, the fluctuation of active power caused by asymmerical voltage is eliminated. The configuration, active and reactive power operation characteristics and its influence on AC voltage of VSC-based distribution network are also analyzed.2. The dynamic mathematic model of VSC-HVDC with SPWM control is founded and its switch characteristic and dynamic operation mechanism under changing load and fault condition are analyzed. The foundation of dynamic mathematics model of VSC-HVDC based on energy conservation principle, the analysis of the process of energy conversion and dynamic operation mechanisms, and the deduction of energy banlance relationship, are realized.3. Conventional HVDC has the advantages of mature state of art and lower cost. VSC-HVDC has the advantages of flexible operation and control and the disadvantages of high cost. Combining the advantages of the two kinds of transmissions, a novel hybrid HVDC transmission is proposed. And then its configuration, technology specialty, operation characteristic and mechanism, regulation type and characteristic as well as active and reactive power operation diagram, are discussed.4. The self-protection for VSC-HVDC used in power system network interlinkage when power system has blackout is analyzed. A“soft shut-off”control strategy is put forward, which can make VSC-HVDC quit the deliver of power and then operate as the spinning reserve power source without acute change and equipment breakage. Through discussing the overvoltage restraintion question of no-load long transmission line, the soft-startup of VSC-HVDC in the case of one side AC system has blackout is developed to avoid severe operation overvoltage of switching on the no-load long line. Based on Lyapunov stability theory, control strategy for VSC-HVDC in network restoration is designed, adopting backstepping method to improve the stability of power system restoration.更多还原