直流输电系统仿真模型与基本响应特性研究.doc

PAGE PAGE 55 直流输电系统仿真模型与基本响应特性研究 摘要 本文首先总结回顾了传统高压直流输电和新型直流输电技术的发展。然后基于CIGRE直流输电标准测试系统，解剖分析了直流输电系统主电路的建模方式和各控制环节的原理框图，最后利用Matlab/Simulink仿真平台自行搭建了直流输电系统模型。通过分别降低整流侧和逆变侧换流电压的方法，进行直流输电系统控制模式的切换测试，得出了所搭模型的稳态特性曲线图，验证了模型的正确性。 本模型增加主控极，能实现定功率控制模式和定电流控制模式的仿真，继而进行电流阶跃响应特性、功率阶跃响应特性和γ阶跃响应特性的仿真实验。在电流阶跃响应实验中，通过增大或减小PI参数，考察了控制器参数对阶跃响应动态特性和稳态特性的影响。 另外，对两侧交流系统分别进行三相短路、两相短路、两相短路接地和单相接地故障，考察了交流系统发生不同短路故障时直流输电系统各参数的响应特性，分析了对称故障和不对称故障引起响应特性的原因和特点，指出了逆变侧发生故障更容易导致换相失败。并对直流输电线路接地短路故障进行了仿真，考察了故障点过渡电阻大小对故障响应特性的影响。然后对直流线路故障时的故障清除策略进行仿真。最后指出在各种故障情况下，直流输电控制系统都能快速而准确地切换控制模式，尽可能地降低故障影响，并且使故障切除后系统能较快恢复到正常稳态运行。 [关键词] CIGRE直流输电标准测试系统；Matlab/Simulink；阶跃响应；故障响应特性 Abstract Firstly, the development of the traditional HVDC and the newly DC transmission technology are summarized in Chapter 1.Based on CIGRE HVDC Benchmark Model，this paper analyzes the modeling of the main circuit and the principle block diagram of some major control links. Then, a HVDC system simulation model is set up on the Matlab /Simulink platform. By testing for this model, a curve related to the system’s steady-state behavior is plotted and the rationality of the model is proved. Next, a series of simulations are conducted for the current step response, the power step response and the extinguish angle step response in this model. In the experiment of the current step response, the influence caused by the different PI parameters on the dynamic characteristics and the steady-state characteristics of the system is studied. Finally, the responses of the system under the different faults, including the three-phase to ground fault, the two-phase shorting, the two-phase to ground fault and the single-phase to ground fault, are tested. The reasons of the different responses resulting from the symmetrical and asymmetrical fault are discussed. It is found that the faults happening on the inverter side are more likely to lead to the commutation failure. When the grounding fault happens on the DC line, it is appeared that the values of eart