摘要
高压直流输电技术(HVDC)具有适合于远距离、大容量输送电力等优点,近些年在我国得到了迅速的发展。HVDC系统是高度可控的非线性系统,其运行工况随时都会发生改变,扰动发生的地点、类型及严重程度具有随机性,此外,系统模型还含有未建模动态部分,这些因素使得基于直流输电系统准静态模型的常规控制器常常不能很好地满足系统的实际要求。因此,如何设计出鲁棒性更好的控制系统以改善HVDC系统的运行特性,同时提高与之相连的交流系统的运行稳定性这一课题无论在国内还是国外都是具有实际意义的,
首先,论文介绍了HVDC系统的结构、数学模型,并在此基础上,详细分析了直流输电系的主要控制和调节方式的原理及控制特性,并给出了直流输电系统基本控制和附加控制的控制原理。
其次,采用状态反馈精确线性化对高压直流输电系统进行线性化,将复杂的非线性系统综合问题转化为线性系统的综合问题,这个经过精确线性化的线性系统能够真实地反映原非线性系统。随后,将该线性系统变为一类具有含未建模动态和有界扰动的不确定性系统,并转化为Hoo标准问题,以此设计Hoo鲁棒控制器,此控制器对系统自身摄动和外部扰动具有很强的鲁棒性。在前人的工作基础上,本文结合精确线性化方法和鲁棒Hoo控制理论来设计HVDC系统基本控制器和附加控制器。
最后,以新的CIGRE HVDC标准模型为基础,利用MATLAB软件对本文所设计的基本控制器和附加控制器进行仿真验证,仿真结果表明:与非线性最优控制仿真结果相比较,这种新颖的HVDC控制器更加符合实际,可以抑制系统未建模动态和有界扰动,有效地改善系统的暂态性能,具有良好的鲁棒性。
High voltage direct current transmission technology (HVDC) is suitable for power transmissions of large capacity and with long distance, in recently years, it gets a rapid development in our country. HVDC power transmission system is a highly controllable nonlinear control system. It's operating conditions change at any time, and the location, type and severity of disturbance is stochastic, besides, the converters have unmodeled dynamics. These factors make the traditional controller for HVDC based on the classical control theory cannot meet the requirements in practice. So, It is of practical significance both at home and abroad how to design a better stability robust controller to improve its performance and enhance the operating stability o f AC system connected as well.
Firstly, This paper introduces the structure and mathematical model of HVDC system, on this basis, the paper analyzes both the principle and performance of main control accommodation mode for HVDC system, and then gives the HVDC system the control theory of based control and additional control.
Secondly, state-feedback and accurate linearization is adopted for the linearization of the nonlinear mathematic model of HVDC system. This way turns the synthesis problem of the complicated nonlinear system into the synthesis problem of simple linear system. For the nonlinear system, linear system after accurate linearization can reflect the primary nonlinear system truly. Then, this linear system will be transformed to a uncertainty system with unmodeled dynamics and bounded disturbances, and transformed into the standard Hoo problems to design the robust controller. However the Hoo controller has the strong robustness on the perturbation and the disturbance of system. This thesis is based on the work of anterior researchers and combines accurate linearization with H∞robust control to design the basic controller and additional controller.
Finally, the new CIGRE HVDC standard model is chose as the simulation model of the basic controller. This thesis Simulates the designed basic controller and additional controller in MATLAB. Comparing to the nonlinear optimization controller, the results of the simulations show that the proposed controller is effective. It has a robust dynamic performance with a strong capability of restraining unmodeled dynamics and bounded disturbances. The transient and static characteristic of HVDC system has been effectively improved with good robustness.
引文
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