火电直流孤岛系统频率控制策略研究

发布时间：2018-03-22 16:22

本文选题：火电直流孤岛运行　切入点：频率控制　出处：《华北电力大学(北京)》2017年博士论文　论文类型：学位论文

【摘要】：高压直流输电(HVDC)因其经济性和快速灵活、高度可控的特点,在大型能源基地向负荷中心的远距离输电中应用非常广泛。若高压直流输电运行时的送端系统主要由火电机组(群)组成而与交流主网无电气联系,则称为火电直流孤岛运行,该系统则称为直流孤岛送出系统。直流孤岛送出系统有效短路比和转动惯量小,系统承受扰动能力较弱,存在着频率稳定、过电压、次同步振荡等一系列技术问题,造成机组全停和直流闭锁的可能性大大增加,给含大量热力生产过程的火电直流孤岛运行稳定控制、系统和设备安全及工程决策带来了巨大的困难。随着我国国内大型火电基地的集中开发和远距离外送以及国际电力能源的引进,受当地电网规模、系统接入条件等因素限制,火电直流孤岛系统研究和试验的现实意义和重要性日益凸显,而国内外尚没有火电直流孤岛系统的运行经验。以往对于直流孤岛系统频率稳定的研究主要依赖于接入实际直流控制保护系统的实时仿真或采用详细直流控制保护电磁暂态模型的离线仿真,采用穷举法进行交直流故障研究从而得到该系统的实际控制效果,采用试探法进行控制系统参数的优化,因而存在耗时长、投入成本高的问题,对于控制稳定性结论和认识存在盲区,无法从定性和定量两方面真正指导工程实践。本文首先从基本物理概念出发,揭示了火电直流孤岛系统频率特性问题的物理本质,对直流输电系统、汽轮机组、伺服系统等分别进行了简化建模,降低了火电直流孤岛系频率控制闭环系统的阶数,从而建立了等效的与实际系统特性一致的火电直流孤岛系统传递函数模型,针对火电机组一次调频、直流附加控制等不同控制策略和参数配合,基于根轨迹分析进行了火电直流孤岛系统的频率稳定性研究及优化控制系统参数,揭示孤岛系统频率稳定性机理。考虑到电力系统和设备的安全性,实际运行中的火电机组和直流系统的控制复杂性,本文以±500kV呼辽直流输电工程孤岛送出系统为例,建立了反映包括送端系统各发电机组、交流线路、直流系统等实际特性的详细准确电磁暂态仿真模型,通过交直流故障仿真分析,从三个方面研究揭示火电直流孤岛系统运行的关键性问题,一是稳态或正常操作时满足电力系统稳态频率控制指标的要求,二是N-1故障等无安控措施下的火电直流孤岛系统恢复能力及频率波动范围满足机组设备等频率控制要求,三是严重故障下配合安控措施的孤岛系统频率稳定性问题,并给出了不同控制参数及配合下的火电直流孤岛系统运行条件和运行控制策略。针对直流输电工程建设发展过程产生的单台火电机组与直流系统直接配合启动的需求,考虑汽轮机组、直流系统等各方面设备的能力和安全问题,研究了二者配合启动过程中由于响应特性不同而产生的频率稳定性问题。由于火电机组并网运行时锅炉及汽轮机的限制,很难在并网时初负荷从零直接提升配合启动直流,因此论文从两方面考虑,综合解决直流启动对火电机组并网初负荷的要求:一是采取措施进一步降低直流启动功率,另一方面提高机组带初负荷的能力,并对不同汽轮机组控制器的启动效果、机组与直流配合时间等方面进行了仿真论证。本文提出的研究方法为后续直流工程建设和运行中可能出现的孤岛运行方式的选择奠定了理论基础,为未来大型火电基地的集中开发和远距离外送提供了技术依据。
[Abstract]:High voltage direct current transmission (HVDC) because of its economy and fast and flexible, highly controllable, applied to long distance transmission load center in a large energy base in a very wide range. If the end system send HVDC when operating mainly by thermal power units (Group) and no electrical connection and the communication network is called power DC islanding operation, the system is called DC system. Effective short Island sent DC Island sending system ratio and small inertia, system under disturbance ability is weak, there is a stable frequency, voltage, a series of technical problems of subsynchronous oscillation, resulting in the possibility of unit full stop and DC blocking DC power to greatly increase the island contains a large number of thermal stable operation control of the production process, decision-making system and the safety of the equipment and engineering has brought great difficulties. With the focus on the development of the domestic large-scale thermal power base in China and far From the delivery and the introduction of international power, by the local power grid scale, restricting system access conditions and other factors, practical significance and importance of the research and test of DC system of power island has become increasingly prominent, and there is no operating experience in power system. The isolated DC DC frequency stabilization for the study of the islanding system mainly depends on the line the simulation of real-time simulation of actual HVDC control and protection system access or use with DC control protection electromagnetic transient model, using exhaustive method to study fault in DC to obtain the actual effect of this system, optimize the parameters of control system using heuristics, which are time-consuming, high cost problems, for the control of stability and conclusion unable to recognize the existence of blind spots, from two aspects of qualitative and quantitative real engineering practice. This paper begins from the basic physical concepts Starting, reveals the physical essence of the frequency characteristics of DC power system islanding problem, the DC transmission system, steam turbine, servo system were simplified modeling, reduce the power system frequency control DC order Island closed loop system, and established the equivalent with the actual system characteristics consistent power DC islanding system transfer function model for a time, frequency and power units, with the additional DC control of different control strategies and parameters, root locus analysis and optimization are studied based on the frequency stability of power system islanding DC control system parameters, to reveal the frequency stability of islanding system mechanism. Considering the safety of power system and equipment, control the complexity of the actual operation of the thermal power unit and DC system, taking 500kV + Hulunbeier Liaoning HVDC Island sent system as an example, including the sending end system is established to reflect the All the generating units, the AC line, with accurate electromagnetic transient simulation model of the actual characteristics of DC system, the DC fault simulation analysis, from three aspects of key problems of power system operation of DC Island, is a power system to meet the requirements of steady steady frequency control or normal operation, the two is N-1 no fault in power system security control measures under DC Island recovery and frequency fluctuation range to meet the unit frequency control requirements, the three is the frequency stability problem with islanding system under severe faults control measures, and gives the power control system of DC island operation conditions and operation strategy of different control parameters and with single power. The unit and the DC system for DC transmission project development process directly with the needs of start, consider the steam turbine unit, DC system The ability and safety problems and other aspects of equipment, on the two with the start process due to the frequency stability problem caused by different response characteristics. Because of boiler and turbine thermal power units connected to the limit, is very difficult in the network initial load from zero start with DC Direct promotion, so this paper in two aspects, comprehensive to solve the requirements of DC starting load thermal power grid at the beginning: one is to take measures to further reduce the DC power to start, on the other hand, improve the unit load capacity with initial, and the controller of different turbine starting unit and DC effect, with time and other aspects of the simulation verification. The research method for islanding operation possible follow-up HVDC project in construction and operation choice laid a theoretical foundation for the future focus on the development of large thermal power bases and distance from outside The delivery provides a technical basis.

【学位授予单位】：华北电力大学(北京)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM712;TM732

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