【作者】 李可军；

【导师】 赵建国；

【作者基本信息】 山东大学 ， 电力系统及其自动化， 2005， 博士

【摘要】 可控串联补偿(Thyristor Controlled Series Compensation,简称TCSC)是指在一个交流输电系统中应用阻抗补偿,并能通过晶闸管快速控制来实现对串联阻抗的大范围连续调节,是目前世界上应用最广泛、最成功的串联型灵活交流输电(Flexible AC Transmission System,简称FACTS)技术。利用TCSC可以用于提高输电走廊的输送能力、抑制次同步谐振、阻尼功率振荡、提高系统暂态稳定性以及动态潮流控制等,为远距离交流输电提供了很好的技术手段。在研究TCSC的动态行为及其对电力系统的影响方面,时域数字仿真发挥了巨大的作用,但是数字仿真结果的正确性和准确性与数学模型的建立和仿真方法的选取有密切关系。目前,对TCSC进行全时域数字仿真研究还存在不少困难,如时域模型的准确建立、有效的仿真方法等都有待深入研究。动态模拟是电力系统研究的基本手段之一,它区别于数值计算和数字仿真的特点就在于能够反映系统真实的物理特性。TCSC动模实验装置可以在一定程度上真实地反映实际装置的物理特性,可用于研究数学模型很难甚至无法描述的特殊现象,如氧化锌避雷器(MOV)的击穿等,而且不像现场试验那样受到系统运行条件的约束。控制系统是TCSC装置的关键,其性能的优劣直接关系到整个系统的运行效果,实验装置的控制器可以和实际工程的控制器完全一样,利用各种控制理论设计的TCSC控制装置可以在实验室首先进行试验。因此,研制实验装置并以此作为平台对TCSC的基本运行特性及其控制策略等方面的研究具有重要的理论和实际意义。为此,本文将围绕TCSC动模实验装置的设计实现与TCSC控制器分层控制策略的研究两个方面来开展研究工作。本文首先介绍了一套可控串联补偿(TCSC)动态模拟实验装置及其控制保护系统的研制开发过程。在该装置中,TCSC的各组件实现了模块化,可灵活组合并根据模拟系统不同线路长度和补偿度调整TCSC的结构参数;TCSC的控制器采用分层结构,各层控制系统完成不同的控制目标,具有通用程序员接口,可以满足对TCSC各种控制策略及其相关问题进行研究的需要。动模实验结果表明作为一个实验研究平台,该实验装置可以真实地模拟TCSC的运行特性,实现TCSC各种阻抗模式的启动、运行、停止以及各模式之间的相互转换,装置动作迅速正确、运行可靠,为各种控制策略的实验研究打下了坚实基础。更多还原

【Abstract】 Thyristor Controlled Series Compensation (TCSC) is one of the FACTS (Flexible AC Transmission System) device most widely and successfully used in practice. It can regulate the impedance smoothly in large-scale by changing the firing angle of thyristor. Because of this flexibility of line impedance, TCSC is expected to control power flow over the line, improve system stability, damp power system oscillation, mitigate sub-synchronous resonance (SSR) and enhance power transfer capability of particular transmission corridors.Because of the non-linear nature of the device, digital simulations are often used to study the dynamic characteristics of TCSC. Since the reliability and accuracy of digital simulation is heavily affected by the numerical models and algorithms used, there is a limit to digital simulation when investigating the TCSC dynamic performance.Experimental setup has physical characteristic similar to real TCSC to a large extent, and it is not restricted by system operation condition. Furthermore, it can be used to investigate complex phenomena such as the breakdown of MOV. Such phenomena are very difficult, if not impossible, to investigate using digital simulation methods. As the control system of the TCSC experimental setup could be the same as those used in the practical power system, controllers based on various theories can be tested and the performance of them can be verified before their practical application. Consequently, it is of great importance to develop experimental setup of TCSC for the investigation of its basic operation characteristics and control strategy. This dissertation is devoted to implementation of TCSC experimental device and the study on control method of TCSC.Firstly, the design and application of a set of experimental device for dynamic simulation of TCSC is described in this dissertation, which includes the main TCSC circuit, the simulated power system, the protection system and the control system. As a platform for dynamic simulation study, the components of TCSC are modularized and can be flexibly combined. In addition, the structural parameters of TCSC can beregulated according to the requirement of the simulation experiment. This device contains a capacitor bank that is divided into four sections in parallel, a metal oxide varistor (MOV) and a thyristor controlled reactor with three taps. By the combination mode of parallel capacitors in-group and reactor with different of parallel capacitors in-group and reactor with different taps, the TCSC device can keep the same series compensation level with different line length of 6ookm, 400km and 300km.Hierarchical structure is applied to the controller of this TCSC experimental device and the controllers in different layers perform different control objectives, so the research on various control strategies can be conveniently conducted. This experimental device also has general interface to investigate TCSC performance and relative problems, such as impact on relaying protection, transient stability, and sub-synchronous oscillation. The experiment results show that the physical simulation platform is an effective tool to investigate FACTS devices. It has the capability to carry out measurement, protection and control schemes in real-time. By means of appropriate control strategy the impedance can be rapidly adjusted by the presented experimental device, the switching over among different impedance modes, e.g., the inductive and capacitive modes, can be flexibly implemented.Whether the objective of the TCSC device can be implemented or not depends on its impedance control. There are many control modes for TCSC to fulfill its benefits to power system, such as transient stability control, power control, current control and so on, however, all of these control modes will be translated into impedance control mode directly or indirectly to achieve their purpose. So, the relationship between frequency impedance and firing angle is very important and the key factor of TCSC device. Some experimental studies show that the resistance of reactor and thyristor valves can influence the effective impedance characteristics of TCSC.In this dissertation, the expression between firing angle and conduction angle is ascertained considering the resistance effects of reactor and thyristor valves firstly.The result shows that the condition (3 = 71-2a is not satisfied when the resistance effects are considered and dual-solution for one firing angle are also obtained in amajority of steady operation area of TCSC. The digital simulation and the result of dynamic simulation experiment all support the existence of dual solution phenomenon This dissertation also points out that TCSC can just move along one branch of frequency impedance curve and will not step to the other one if only the firing angle is changed. Through the analysis of phasor diagram, the conduction current of thyristor is limited by quality factor and current value of the reactor branch, which is the reason causing dual-solution phenomena.TCSC can not only adjust impedance smoothly but also switch between capacitive state and inductive state quickly. The mode-switching control of TCSC is important to power system stability control and is also one of the key problems of TCSC. On the basis of modeling and simulation, a practicable mode-switching control strategy was proposed in this dissertation. By means of forced synchronization of current in thyristor branch with the line current, the mode switching from capacitive veriner mode or block mode to bypass mode can be implemented. In the switching strategy from capacitive veriner mode or Block mode to inductive veriner mode a method of allowed-section triggering was put forward. To provide synchronization signal of line current for switching control in time, a method to forecast the crossover point of the current was given. Digital simulation and experiment results show that the proposed switching strategy possesses good dynamic performance the mode switching from capacitive to inductive mode could be completed fluently and swiftly.Whether the performance of TCSC device can be implemented or not depends on its impedance control. The reason of the phenomenon is thoroughly analyzed that the robustness of traditional PID control is bad when different impedance levels are ordered to step to a same level by traditional PID control. A new nonlinear PID control method for impedance control is presented in this paper by combing the immune feedback law with conventional PID control. Based on traditional PID control structure and its immune response can be regulated according to the parameters of the controller, the IMF-PID control method is practical. The comparison of the simulation results from the proposed approach with that from traditional PID control shows that the proposed approach can quickly drive theoutput impedance to the desired level with less overshoot and possess good dynamic and static performances, so it is available.In sum, physical simulation platform is capable to support the investigation of the operation, protection and control strategy of TCSC. With more and more FACTS devices applied into power system, the experimental device of TCSC will play a important role in power system research. This dissertation discusses, analyses and resolves problems in the exploitation of TCSC experiment device, and use simulation to prove and experimental results to test the theories put forward in this dissertation. Man>’ conclusions and experimental results are of practical significance, and provide reference to TCSC operating and control.更多还原