【作者】 王雪丽；

【导师】 梁军；

【作者基本信息】 山东大学 ， 电力系统及其自动化， 2011， 硕士

【摘要】 由于高压直流输电系统在远距离大容量输电和非同步联网方面具有诸多优势,近几年来在我国的应用日益广泛,远距离高压直流输电工程已成为国家实施“西电东送、南北互供、全国联网”战略中投资和经营的重点。随着高压直流输电线路及其传输容量在系统中所占的比例越来越大,研究交直流系统的仿真方法和动态特性变得非常重要。在电力系统暂态仿真分析时通常有机电暂态仿真和电磁暂态仿真。在交直流系统动态特性研究中,需要根据不同研究目的选择不同的暂态仿真方法。本文首先对机电暂态仿真和电磁暂态仿真的适用范围进行了探讨。通过算例仿真揭示二者在模拟直流系统动态特性、换相失败以及交流系统暂态稳定性方面的差异,确定了进行直流系统动态特性分析、大规模交直流系统暂态稳定性分析时应采用的仿真方法。研究直流系统的动态特性应采用电磁暂态仿真。因受仿真规模和计算速度的制约,建立大规模交直流系统的完整电磁暂态仿真模型以实现直流系统动态特性的准确模拟是不现实的。对此,本文提出一种新的交流系统动态等值方法,既完整保留直流系统又大量缩减交流系统的规模。并对所提方法进行了验证,其动态等值系统能够较好地反映原系统的动态特性。在交流系统动态等值基础上,建立了交直流电力系统电磁暂态仿真模型,研究了交直流电力系统在各种故障情况下直流系统的动态特性。重点分析换流站交流母线故障后直流系统本身的动态特性,精确模拟换相失败、直流控制系统的动态调节过程以及故障后直流系统的恢复过程。仿真结果表明：逆变侧交流系统故障更容易导致直流换相失败；在控制系统的作用下,该模型直流系统能够恢复正常运行。最后,以宁东直流输电系统为例,从交流系统故障对直流系统的影响和直流系统故障对交流系统的影响,探讨了交直流系统间的相互作用和暂态稳定性问题。仿真分析表明：逆变侧交流系统故障大部分会导致直流换相失败,且换相失败时间与故障线路距离换流站电气距离密切相关；直流换相失败可能导致交流系统的电压失稳,故障切除时间、无功储备也是重要影响因素；直流单极闭锁导致受端电网有功功率缺额,但没有引发频率和暂态电压稳定问题。更多还原

【Abstract】 As HVDC systems have many advantages in long-distance bulk power transmission and non-synchronous network, in recent years they have been used widely in China. Long-distance HVDC transmission projects have become the investment and business focus in implementation of national strategy that is "west to east, north and south for each other, the national network". With the increasing proportion of HVDC transmission lines and capacities in the system, the research on simulation methods and dynamic performances of AC/DC power system becomes very important.In transient simulation analysis of AC/DC power system, there are electromechanical transient simulation and electromagnetic transient simulation. It needs select different methods for different purposes when the dynamic performances of AC/DC system are researched. This thesis firstly discusses the validity of electromechanical transient simulation and electromagnetic transient simulation. The differences between the two transient simulation methods on dynamic performance and commutation failure of DC system and transient stability of AC system are revealed by an example simulation. Then, the methods of researching dynamic performance of DC system and transient stability of large-scale AC/DC system are determined.Electromagnetic transient simulation model should be used for researching dynamic performance of DC system. Conditioned by the scale and speed of simulation, it is not realistic to establish the complete electromagnetic transient simulation model of large-scale AC/DC system and simulate accurately dynamic performance of DC system. On this, a new equivalent method is presented in this paper, which focuses on how to reserve DC system and reduce AC system while maintaining dynamic performance of AC and DC system. The original system and the equivalent system are simulated respectively. The result shows that the equivalent system can preserve the main dynamic characteristics of the original system well. Based on dynamic equivalent in AC system, electromagnetic transient simulation models of AC/DC system are set up, by which the dynamic performances of HVDC are studied under some kinds of AC system faults and DC system faults. The dynamic performances of the DC system itself are analyzed under the faults of converter station AC buses. Commutation failure and the dynamic process of DC control system and the recovery process of DC system are accurately simulated. The results show that the faults at the inverter side AC system are more likely to cause commutation failure than that at the rectifier side AC system. DC system of the model can recover normal operation state under the action of HVDC control.Finally, taking NingDong DC transmission system as an example, the interaction between AC and DC systems and the transient stability are analyzed. The simulation results show that most of the faults at the inverter side AC system will lead to commutation failure, and commutation failure time is closely related to the distance from the fault line to the converter station. Commutation failure will affect the voltage stability of AC system. In addition, fault clearing time and reactive power reserves are also important factors. The active power shortfalls in AC system near inverter station are caused by DC block, which doesn’t trigger transient frequency and voltage stability problem.更多还原