【作者】 王艳玲；

【导师】 韩学山；

【作者基本信息】 山东大学 ， 电力系统及其自动化， 2012， 博士

【摘要】 随着社会的发展和变迁,可耗竭资源日益枯竭,以及生态环境的日益恶化,能源使用的洁净化迫在眉睫。由此,大规模可再生能源发电并网势在必行,电力系统呈现集中与分布并存,风、光、储、水、火等多种电源并存,造成电网结构将越来越复杂,输电能力的计算也越来越复杂。这一复杂性主要体现在：(1)为挖掘现有输电元件输电能力的潜在能力,需要在动态热定值(Dynamic Thermal Rating,DTR)基础上进行在线输电元件载荷能力的定值；(2)在电网输电能力计算中需要计及各类电源的电压支撑特性,以及各类电源的调节特性；(3)分布式电源引入后电力系统运行体系由集中走向分散,其引起的潮流双向问题使输配电网难以清晰定界,从而有必要在输配电系统联合一体化分析的基础上计算电网输电能力。因此,本文在DTR热定值基础上,考虑电源的调节特性及其运行限制,基于扩展潮流对运行条件下的输电元件载荷能力在线定值和对计及分布式电源影响的电网静态输电能力计算进行了深入的研究。研究的主要内容和成果如下：(1)在DTR热定值基础上,计及电压水平及功角静稳等电力系统运行限制对线路载荷能力的影响,建立了运行条件下交流输电线路载流量在线定值模型和算法。其特点在于考虑发电机组电压调节特性,推导出基于扩展潮流的输电线路双端口诺顿变参数等值模型,并实现了系统等值参数的在线跟踪,结合历史样本,借助时间序列分析预估等值参数的变化规律,使运行条件下交流输电线路载荷能力更贴近实际。研究表明,该双端口诺顿等值模型可有机考虑互联系统中并行流对输电线路载荷能力的影响,并且通过等值参数的变化反映电磁功率的时变性。通过潮流计算验证了该模型和算法的可行性及有效性,并结合威海电网,对220KV输电线路载荷能力在线定值进行验证。(2)计及发电机组调节特性及其运行限制对电网输电能力的影响,建立了基于扩展潮流求解电网输电断面最大输电能力的最优潮流模型和算法。该模型以输电断面内所有支路的有功传输功率之和最大为目标,等式约束不再是传统潮流约束而是扩展潮流约束,扩展潮流将描述元件动态特性的微分方程加入到潮流计算中,将传统潮流方程与动态元件的状态方程联立求取其稳态解,同时解出系统中各个节点的电压、相角、各种动态元件内部的状态变量,比传统潮流计算得出了更多的信息,更加全面地描述了电力系统的模型。在该扩展潮流模型中发电机组采用双轴四阶模型,励磁器采用IEEE-I型励磁调节器,调速器采用简化了的典型调速器模型。通过基于信赖域的线性规划序列迭代法求解该最优潮流模型,并与基于传统潮流的最大输电能力求解结果相比较,由于在扩展潮流模型中考虑了调速器和励磁系统等元件调节特性对电网输电能力的影响,使计算结果更符合实际。(3)计及分布式电源引入后其引起的逆潮流问题使输配电系统难以清晰定界,建立了含分布式电源的输配电联合系统扩展潮流模型和算法。它是输配电网一体化联合分析电网输电能力的基础。在分析燃气轮机和风力发电机等典型分布式电源动态特性的基础上,推导出输配电联合系统扩展潮流模型。输配电联合电力系统规模极其庞大,其节点数和支路数比相关的输电系统大多个数量级。输配电联合系统不同区域存在网络结构、网络参数和潮流大小等方面的差异,若对联合系统进行统一的计算将无法保证计算的可靠性和收敛性。本文采用主从分解协调法的求解思路,将含分布式电源的输配电联合电力系统划分为主从系统,输电网定义为主系统,将配电网划分为若干从系统,主系统与从系统的连接点称为根节点,在输配电系统联合扩展潮流方程基础上推导出主系统扩展潮流方程与从系统扩展潮流方程,在分解过程中针对主从系统的不同特点,分别采用各自适应的算法,在分解的基础上再通过协调计算消去根节点失配量,从而实现输配电联合系统一体化潮流计算。通过算例进一步验证了由于分布式电源的存在,输配电系统间不存在发输电与用电的确定关系,从而使得对输配电系统联合计算求取计及分布式电源的电网输电能力显得尤为必要。(4)在含分布式电源的输配电系统联合扩展潮流的基础上,建立了输配电联合系统一体化连续潮流计算模型和算法。连续潮流是计算电网输电能力的重要工具,基于输配电联合系统扩展潮流的连续潮流计算,能有效求取计及分布式电源影响的电网最大输电能力。在输配电系统联合扩展潮流方程基础上,充分考虑了同步发电机及燃气轮机有功功率和转子电流约束,以及风力发电机定子电流约束,通过连续潮流分析输配电联合系统的输电能力。主从联合系统的连续潮流计算过程中采用主从分解协调法,主从系统分解进行预测校正,计算负荷增长量,主从系统协调计算消去根节点失配量,从而实现主从联合系统连续潮流计算,该处理方式对解算大系统有一定适用前景。输配电系统的联合输电能力计算考虑了输电系统和配电系统地相互影响,实现电力系统联合一体化计算,提高了计算结果的逼真性。更多还原

【Abstract】 With the social development and diversification, exhaustible resource shortage and the worsening of the ecological environment, clean energy use is imminent. Such, large-scale renewable energy generation connected to the power grid is imperative. For the power system, the concentration and distribution operation co-exist, the wind, light, reservoir, water, fire and other power co-exist, and power grid structure is more and more complex. The calculation of power transfer capability of power grid is also more and more complex. This complexity is mainly reflected as follows:(1) In order to excavate the maximum potential of the existing power transfer components, it is very necessary to online value the loadabilitiy of power transfer component based on dynamic thermal rating (DTR);(2)In the calculation of the power transfer capability of power grids, it is very essential to consider the voltage support capability of all kinds of power generators and the regulation characteristics and operational constraints of various types of power generators;(3) After the introduction of distributed power, power system from a centralized conformation into scattered conformation, the transmission and distribution network difficult to clear delimitation caused by backflow problem, it is particularly necessary to calculate the TTC based on the transmission-distribution joint systems.Therefore, this paper, in the scenarios of dynamic thermal rating, taking into account the generator units’regulation characteristics and operating restrictions, based on expanded power flow, thoroughly researches the online value of the loadability of transmission components under operation and the decision-making of the static TTC considering the influence of the distributed generators. The main works and achievements can be summarized as follows: (1) Based on the DTR technologies and taking into account voltage drop and steady-state-stability limitation, the model and algorithm of online valuing loadability under operation are established. Considering the generator units voltage regulation characteristics, the variable parameter dual-port Norton equivalent model based on expanded power flow is derived, and the online tracking of the equivalent parameters of the system is implemented. Based on the historical samples, time series method is used to analyze the variation law of the equivalent parameters to make the maximum loadability of transmission line under operation closer to the actual situation. Studies have shown that the dual-port Norton equivalence can very well reflect the effect of parallel flow on the transmission line loadability in interconnected systems, and the changes in the equivalent parameters reflect the non-linearity and time-varying properties of power systems, and by the equivalent parameters variation, the time-varying nature of the electromagnetic power is reflected. The feasibility and effectiveness of the equivalent model and the algorithm are testified by continuous power flow in IEEE-39system and are confirmed by the analysis of the loadability of Weihai220kV transmission line under operation.(2) Taking into account the generator units’voltage and frequency regulation characteristics and operating restrictions on the power transmission capability, the optimal power flow model and the corresponding algorithm based on expended power flow are established for the calculation of TTC. The objective of the model is the largest total number of active power transferred by branches of cross-section. The equality constraint of the model is no longer the traditional power flow, but the expended power flow. The expanded power flow adding the component dynamic characteristics differential equations to the power flow calculation, combining the traditional power flow equations with the state equations of the dynamic components to strike the steady-state solution, the system node voltage, phase angle, the state variables within dynamic components are solved, More information and more comprehensive description of power system model than traditional power flow, In the expanded power flow, the generators use biaxial fourth-order model, the excitations use the IEEE I-type excitation regulator model and the speed governors use the simplified typical model. The optimal power flow is solved by linear programming method based on trust region, and compared with the solution results of the total transfer capability based on the traditional power flow, due to the governor and excitation regulation characteristics considered in the expanded power flow, thus breaking the previous transfer capability assumption of constant terminal voltage of generator units to make the results more realistic.(3) Taking into account the transmission and distribution network difficult to clear delimitation caused by backflow problem after the introduction of distributed generators, the expended power flow model and algorithm of transmission-distribution joint system with distributed generators are established, which is the basis of integration TTC calculation of the transmission-distribution joint system. Based on the analysis of dynamic characteristics of distributed generators such as gas turbines and wind turbines, expanded power flow equation of transmission-distribution joint system is derived. The scale of the transmission-distribution joint system is extremely large. The number of nodes and branches of joint system is a lot more than the corresponding transmission system. The network structure, network parameters and the size of power flow are different in different regions of the joint system. Therefore, the unified calculation of joint system will not be able to assure the reliability and convergence. This paper uses the master-slave decomposition and coordination method. The transmission-distribution joint system with distributed power is divided into master-slave systems. The transmission system is defined as master system. The distribution system is divided into several slave systems. The connection nodes of master system and slave system are called as root nodes. The expanded power flow of master system and slave system is deduced based on the expanded power flow of transmission-distribution joint system. In the decomposition calculation, the master and slave system use their adaptive algorithms respectively for the different characteristics of their own. On the basis of the decomposition calculation, the coordination calculation eliminates the mismatch of root nodes, in order to achieve the integration power flow calculation of the transmission-distribution joint system. Furthermore, the transmission and distribution system do not exist the exact relationship of transmission and consumption power is determined by examples. So taking into account the distributed power, it is particularly necessary to calculate the TTC based on the transmission-distribution joint systems.(4) Based on the expanded power flow of transmission-distribution joint system with distributed generators, the integration continuous flow model and algorithm of transmission-distribution joint system are established. Continuous power flow is an important tool for TTC calculation. Continuous power flow calculation based on the expanded power flow of the transmission-distribution joint system, taking into account the influence of distributed generators, can effectively calculate the TTC of transmission system. Based on the expanded power flow of transmission-distribution joint system with distributed generators, taking full account of the synchronous generator and gas turbine active power and rotor current constraints, and the wind generator stator current constraints, the TTC is accurately analyzed by continuous power flow of the joint system. The continuous power flow of joint system is analyzed and is solved by master-slave decomposition and coordination method. The decomposition calculation is to predict, correct and compute the load growth. The coordination calculation is to eliminate the mismatches of root nodes. Such the continuous expended power flow calculation of master and slave system is achieved. The above treatment method is Applicable to solving a large system. The joint calculation, taking into account the interaction of main and slave system, realizes the integration calculation of power system and makes the results more realistic.更多还原