Probability of failure of overloaded lines in cascading failures

Power grids are vulnerable to cascading failures, as shown by previous blackouts or major system disturbances. Line outages due to overload are often the main contributors to the cascading failures leading to these undesired situations. Indeed, the more a line is overloaded, the larger is its sagging, and hence the probability that it will be tripped. It is necessary to quantify in a realistic way the probability of trip as a function of the load in order to compute a good estimation of the frequency of dangerous cascading outages. Several models were proposed for this purpose, but none of them is backed up by empirical evidence or detailed analysis. This paper studies factors that could affect the probability of trip as a function of load, and it computes this probability for two different test systems using a temperature simulation based methodology, called dynamic PRA level-I analysis. This paper then compares existing modelings of this probability to these results. This comparison shows that all modelings used in the literature are not always convenient. We finally propose a simple model that can be adopted in probabilistic risk assessment of cascading failures.     

热工控制系统电源设计现状及改进方案

介绍了江西省火力发电厂热工电源的设计现状，分析了其设计原理，存在不足，并提出了改进措施。     

Advanced control algorithms for steam temperature regulation of thermal power plants

A model-based controller (Dynamic Matrix Control) and an intelligent controller (Fuzzy Logic Control) have been designed and implemented for steam temperature regulation of a 300 MW thermal power plant. The temperature regulation is considered the most demanded control loop in the steam generation process. Both proposed controllers Dynamic Matrix Controller (DMC) and Fuzzy Logic Controller (FLC) were applied to regulate superheated and reheated steam temperature. The results show that the FLC controller has a better performance than advanced model-based controller, such as DMC or a conventional PID controller. The main benefits are the reduction of the overshoot and the tighter regulation of the steam temperatures. FLC controllers can achieve good result for complex nonlinear processes with dynamic variation or with long delay times.     

干式变压器允许过载时间的计算

提出了干式变压器热时间常数和允许过载时间的计算方法,给出了运用Excel的计算实例.     

基于有功无功联合调整的动态潮流

提出了一种新型潮流算法,可同时考虑无功功率的区域平衡以及系统负荷变化所产生的净加速功率,并通过有功和无功的联合调整以获得更合理的潮流结果。计算过程取消了常规潮流算法定义的节点类型,使所有节点均参加有功和无功迭代,避免了人为确定节点类型对潮流分布的不良影响。最后通过IEEE30节点系统将所提算法与常规潮流算法、动态潮流算法进行了比较,结果表明所提算法能够改善系统的有功和无功功率分布。     

甘肃酒泉风电出力特性分析

甘肃酒泉风电基地是中国乃至世界规划建设的第1个10 GW风电示范基地,开创了风电大规模集中开发、超远距离输送的先河.文中利用甘肃酒泉地区实际测风资料和调度能量管理系统(EMS)实际运行数据,全面分析了酒泉地区的风资源特性,研究了风电机组、风电场、风电场群和风电基地的出力特性,比较了不同时间尺度下风电出力特性的不同特点,得出如下大规模风电基地的出力特性:在长时间尺度下相关性明显,在短时间尺度下互补性明显.文中还根据大规模风电的出力特性分析了其对电网稳定和调频、调峰的影响.     

葛洲坝电站侧的电力系统稳定的计算机监控系统

电站侧的电力系统稳定监控系统，可以作为电站计算机监控系统（ＳＣＡＤＡ）的一个功能来设计，它与电站的继电保护配合，在不增加计算机系统及继电保护硬件和软件复杂性的情况下，实现电力系统稳定的计算机监控。目前大型电站基本上均设置了计算机监控系统，这种设计方案将有助于加速电力系统稳定监控自动化的实现，并使电站自动监控系统更趋合理。     

基于不确定多属性决策理论的电网连锁故障模式搜索方法

针对电网的连锁故障,提出了一种基于不确定多属性决策理论的优先排序直接搜索法.根据引发线路原发性故障的各种因素结合系统当前运行状况及历史统计数据形成决策属性表,运用基于离差最大化的多属性决策方法对可能发生的线路故障进行排序,依据排序结果及设定的门槛值进行电网连锁故障模式的搜索.搜索过程中,综合历史统计数据与系统当前状况对可能的继电保护动作行为进行排序,根据该排序结果继续搜索.搜索过程中考虑了自动装置的动作,交替进行潮流和稳定计算,以快速搜索出较易发生且后果严重的电网连锁故障模式.该方法避免了通过重复抽样来确定不确定因素造成计算时间的浪费;同时,将历史数据与当前条件相结合,运用合理的决策方法决定搜索过程的排序,保证了搜索的合理性.对WSCC-9系统进行的算例分析表明该方法具有良好的应用前景.     

雅可比矩阵趋于奇异时潮流方程解与电压静稳裕度

本从电压静态稳定性观点对系统电压静稳临界点进行了研究。中用简单系统得出的结论很好地解释了多机系统中雅可比矩阵趋于奇异时的潮流方程解，并指出就有名值表示的储备系数而言，本定义的无功功率静稳储备系数比用电压和有功功率表示的静稳储备系数更直观，物理意义更明确。     

南方互联电网发展的概念思考

本文针对南方互联电网自１９９３年建立和运行以来遇到的问题，结合电网发展，提出宏观性的概念思考。以开发我国西南部水力资源为出发点，从互联电网整体着想，在发展过程中不断完善和加强电网建设，以优化电源布局和加强网架结构，达到西电东送的战略目标，实现四省（区）经济共同发展，本文还对本网与全国联网问题作了粗略探讨。     

复杂电网连锁故障模型评述

在复杂电网中,由微小扰动触发的电力系统连锁故障会导致电网大面积崩溃的灾难性后果,对连锁故障的理论建模是研究复杂网络连锁故障的基础和关键.文章在探讨电网连锁故障机理的基础上,分别从电力系统角度和复杂网络理论角度介绍和评述了已有电网连锁故障模型,分析了预防和控制连锁故障的几种可行方法,指出在进行连锁故障的预防分析时,对网络脆弱性的分析与评估是关键,而对故障传播的控制,多智能体系统可能是一条有效途径;并指出了今后值得注意的几个研究方向.     

基于直流电源的树脂浇注干式变压器热时间常数及负载特性研究

利用直流电源下树脂浇注绕组电阻可以由电压和电流比值直接实时求得的特性,对树脂浇注干式变压器的热时间常数和绕组最终平均温升与负载率的关系进行了研究。     

电力系统连锁故障的关联模型

分析了目前电力系统连锁故障模型的不足,并根据连锁故障的特征,提出了连锁故障的关联模型。该模型通过定义连锁故障环节和环节之间的关联度函数,来描述连锁故障过程中各故障元件之间的相关性,并通过分析关联度函数的影响因素,确定不同因素组合下,关联度函数的具体形式。电力系统连锁故障关联模型不仅能实时反映连锁故障环节之间的相关性,而且能快速预测连锁故障的发展方向,并提供故障过程中的影响因素分析,为连锁故障的预防和控制决策提供参考依据。最后,以IEEE 39节点系统和实际电网为例,验证了该模型对电力系统连锁故障分析的正确性和有效性。     

无功补偿装置的故障分析与计算方法

通过分析无功补偿装置出现的异常现象,提出了电容器选型的计算方法。     

无功补偿装置的故障分析与计算方法

通过分析无功补偿装置出现的异常现象,提出了电容器选型的计算方法。     

Stabilizing control of power system using fuzzy control

This paper presents an application of fuzzy control to enhance power system stability. The proposed control consists of the controller for large disturbance (FU 1), the fuzzy controller for small disturbance (FU 2), and the fuzzy judgment mechanism (FU 3). FU 1 is determined based on the fuzzy controller [FU 1(F)] is determined according to the control rules and its input signals, i.e., speed deviation and acceleration at every sampling time of the machine. FU 2 consists of two controllers, namely, FU 2-ω and FU 2-P; FU 2-ω has the same mechanism as FU 1, while the output signal of FU 2-P is determined according to the rules together with the change of error of electrical power and terminal voltage. To obtain the optimal desired control signal during both the large and the small disturbances, the operations of FU 1 and FU 2 are judged by FU 3, where the magnitude of speed deviation is chosen as its input signal. The determined control signal is fed to AVR of the machine. The implementation of the proposed control is simple due to the small amount of calculations and required data. The effectiveness of the proposed control is demonstrated by the one-machine infinite-bus system model and very good system performance is obtained throughout all the simulations.     

我国未来同步电网构建研究

在对我国同步电网现状分析的基础上,结合我国特高压电网发展规划情况,提出了“十二五”初期和2020年前后我国同步电网构建方案。对华北一华中一华东特高压同步电网的合理性、技术可行性以及电网综合效益进行了分析。     

南方互联电网安全稳定控制系统的配置、功能及作用

本文详细说明了南方互联电网安全稳定控制系统的配置和功能，并结合现阶段南方互联电网的运行情况阐述了安全稳定控制系统在南方互联电网中的作用及存在的问题．     

南方电网无功电压运行特性的分析与探讨

介绍了电压失稳的主要形式;根据南方电网无功电压的运行情况,分析电网无功电压的薄弱区域。提出优化无功潮流、提高电网电压稳定性的4种有效措施(如合理规划网架和安排运行方式、合理配置无功补偿设备、制定无功优化控制措施和合理配置电网低压减载装置)。文章指出,为满足电网无功按电压分层分区合理分配,提高系统电压质量,南方电网必须抓紧开展无功优化的研究工作,建立电网电压稳定性分析模型,优化电网无功补偿配置方案和电压调整控制策略,不采用自动电压调整装置。     

A modified approach to transient stability enhancement with fast valving and braking resistor applications

Fast valving and braking resistor are two important members of the family of the discrete supplementary controllers (DISCOS). Both of these are very effective and economic means of transient stability enhancement under extreme contingencies. Being stationed at the similar end of a power system the two schemes carry a very good potential of an effective coordination. Such a coordinated control is helpful not only in obtaining an improved gain in stability, but also in overcoming the limitations and avoiding excessive duty on the part of an individual controller. In this work, a detailed study has been carried out to evaluate the scope and limitations of fast valving and dynamic braking resistor controls in enhancing the transient stability of power systems. Improvements have been suggested over the conventional schemes of control so as to improve their adaptability under different conditions of fault and loading or with different types of generating units.