A new tool for dynamic security assessment of power systems

This paper describes a new tool for dynamic security assessment of power systems, in which two technologies are combined: the EEAC method and time-domain simulations. Details of the structure and functionalities of the tool are discussed. The applications of the tool are illustrated with a realistic power-system model as an example. The results show that both fast computation speed and reliable performance are achieved.     

A dynamic state estimator for power system dynamic security assessment

A global modularized dynamic state estimator is formulated to provide the data which will be required for future dynamic security assessment and dynamic security enhancement applications. The dynamic state estimator is global because it is capable of estimating small and large dynamic fluctuations in voltage angle and frequency for an entire area. The dynamic state estimator is composed of the sum of the static state estimate, obtained by using present hardware and algorithms and a modularized dynamic state estimate based on a linearized classical transient stability model with a stochastic load model. This dynamic state estimate component is modularized to (1) eliminate the need to measure or model external system generation and (2) to permit a reduction in computation requirements for (a) updating the linearized power system dynamic model and (b) for computing the state estimate. The modularization, which is accomplished by decoupling the linearized dynamic model for each subregion by measuring the power injections on lines connecting the subregion to the rest of the power system, causes the dynamic state estimate to be locally referenced. A global referencing procedure is proposed and discussed. A linearized stochastic model for the Michigan Electric Coordinated System is developed to illustrate the procedures proposed for developing the stochastic load model and determining the constant gain approximation for the governor turbine energy system dynamics. A summary of results on the performance of the Kalman state estimator is presented.     

Congestion management in dynamic security constrained open power markets

The greatest challenge facing deregulated and unbundled electricity supply industry is the operation of the grid in a non-discriminatory and equitable manner. Transmission pricing and congestion management have been at the center of the debate over facilitating greater competition of electric power generation. This paper studies dynamic security constrained congestion management in an unbundled electric power system. It is possible to reschedule the real power generation along with curtailment of real power loads/transactions to make the system dynamically secure after a fault. A conceptually reasonable and computationally feasible approach for the solution of this problem has been developed for a system with a mix of pool and contract dispatches.     

A grid computing based approach for the power system dynamic security assessment

This paper addresses the problem of parallel dynamic security assessment applications from static homogeneous cluster environment to dynamic heterogeneous grid environment. Functional parallelism and data parallelism are supported by each of the message passing interface model and TCP/IP model. To consider the differences in heterogeneous computing resources and complexity of large-scale power system communities, a kernel-based multilevel algorithm is proposed for network partitioning. Since the bottleneck in distributed computation is low speed network communication, a bi-level latency exploitation technique is introduced for numerically solving system differential equations. The proposed grid-based implementation includes the core simulation engine, grid computing middleware, a Python interface and Python front-end utilities. Tests for a 39-bus network, a 4000-bus network and a 10,000-bus network are reported, and the results of these experiments demonstrate that the proposed scheme is able to execute the distributed simulations on computational grid infrastructure and provide efficient parallelism.     

面向对象的安全风险评估系统设计与开发

为提高通信保密系统安全风险评估的智能化水平,在论述通信保密系统安全风险评估的特点及其评估方法的基础上,设计并开发了面向对象的安全风险评估系统.针对系统需求分析与系统工具选择开展研究,给出了安全风险评估系统的总体结构,从系统工作流程和原理、系统概念模型框架、评估方法模型库的实现和管理、工程设计要求及系统实现步骤等5个方面进行了系统详细设计.     

网络安全综合评价方法的研究及应用

网络安全是一复杂的系统工程,为了对网络安全进行综合评价,采用管理理论中较为成熟的德尔菲法,对影响网络安全的各种因素及目前常用的安全防范措施进行了深入研究,确立了网络安全综合评价指标体系,建立了层次分析法安全评价模型.在理论研究基础上设计并初步实现了网络安全综合评价支持系统软件.研究结果表明,这一模型能有效地对网络安全等级进行综合评价.     

Implementation and experimental studies of an adaptive self-optimizing power system stabilizer

This paper describes the implementation and experimental studies of an adaptive self-optimizing pole shifting power system stabilizer. Using an Intel iSBC386/21 single-board computer, the adaptive power system stabilizer has been tested on a physical model of a single-machine infinite-bus power system. Under different operating conditions and disturbances, the behavior of the proposed adaptive stabilizer was investigated. Comparison has also been made to a digital-type conventional fixed-parameter power system stabilizer. Results of the experimental studies show that the proposed adaptive stabilizer outperforms the conventional stabilizer.     

机载电源在线监测系统的研制

机载电源的供电质量对飞机的安全飞行和机载用电设备的正常工作至关重要。在电子试验机试飞环境中,各机载用电设备处于不同的工作状态,可能会影响机载电源的供电质量,因此,需要对试飞中的机载电源进行持续的在线监测,评估其供电质量。针对此,研制了一种机载电源在线监测系统,对115V/400Hz三相交流、28V直流电源的多工作特性参数进行持续的在线监测。该系统基于高性能专用计算机和高速同步数据采集卡,对机载电源电压和电流进行实时采集,采用相关数据处理算法,对多工作特性参数进行快速实时运算,并显示和存储,并对异常工作点的电压、电流进行录波,以便后期分析。该系统在某型电子试验机上进行了实验,监测结果实时、准确,对机载电源提高可靠性和故障分析定位具有重要的意义。     

A decision tree-based on-line preventive control strategy for power system transient instability prevention

Maintaining transient stability is a basic requirement for secure power system operations. Preventive control deals with modifying the system operating point to withstand probable contingencies. In this article, a decision tree (DT)-based on-line preventive control strategy is proposed for transient instability prevention of power systems. Given a stability database, a distance-based feature estimation algorithm is first applied to identify the critical generators, which are then used as features to develop a DT. By interpreting the splitting rules of DT, preventive control is realised by formulating the rules in a standard optimal power flow model and solving it. The proposed method is transparent in control mechanism, on-line computation compatible and convenient to deal with multi-contingency. The effectiveness and efficiency of the method has been verified on New England 10-machine 39-bus test system.     

Analysis of dynamic voltage collapse mechanism for a three-bus power system

The phenomenon of voltage collapse is reconstructed based on a three-bus power system with dynamic on-load tap-changers (OLTC). Utilizing nonlinear stability techniques, the monotonic fall of bus voltages is derived from instability of the dynamic system. The exact stability region of the system is constructed which demonstrates the concept of voltage stability region as a tool for the prevention of voltage collapse.     

Simulation of an adaptive artificial neural network for power system security enhancement including control action

This paper presents a new method for enhancing power system security, including a remedial action, using an artificial neural network (ANN) technique. The deregulation of electricity markets is still an essential requirement of modern power systems, which require the operation of an independent system driven by economic considerations. Power flow and contingency analyses usually take a few seconds to suggest a control action. Such delay could result in issues that affect system security. This study aims to find a significant control action that alleviates the bus voltage violation of a power system and to develop an automatic data knowledge generation method for the adaptive ANN. The developed method is proved to be a steady-state security assessment tool for supplying possible control actions to mitigate an insecure situation resulting from credible contingency. The proposed algorithm is successfully tested on the IEEE 9-bus and 39-bus test systems. A comparison of the results of the proposed algorithm with those of other conventional methods reveals that an ANN can accurately and instantaneously provide the required amounts of generation re-dispatch and load shedding in megawatts.     

Influence of angle control on the dynamic behaviour of power systems

Angle stability problems are well known in almost every power system in the form of transient instability or undamped system oscillations. Unlike the frequency stability problems, angle stability has not yet been treated as a control problem, due to limitations in measurements, communication and power equipment. However, new technologies employing satellites, optical fibres and power electronics have overcome these physical problems. The report demonstrates how equipment using power electronics for fast angle control can give a single line the characteristics of a multiple-line interconnection. Further, it is shown how this can completely change the dynamic behaviour of a power system, and in the ideal case even eliminates oscillations following small disturbances. The use of angle control to give DC links the desired properties of AC links is also described.     

网络数据动态传输与存储安全自动监测系统设计

为了提高网络数据动态传输与存储安全自动监测能力,进行监测系统优化设计,提出基于负载均衡调度和嵌入式总线传输控制的网络数据动态传输与存储安全自动监测系统设计方法。构建网络数据动态传输的信道均衡调度模型,采用随机线性均衡控制方法进行网络数据动态传输与存储过程中的信道自适应调度,提取网络数据动态传输过程中的模糊关联规则,采用自适应的链路转发控制方法进行网络数据动态传输与存储的安全监测和负载均衡调度。在嵌入式总线协议下进行网络数据动态传输与存储安全自动监测系统的软件开发设计。仿真结果表明,采用该方法进行网络数据动态传输与存储安全自动监测的稳定性较好,自适应控制能力较强,降低了网络数据动态传输的误比特率。     

数据库安全在电力信息系统等级保护中的应用

简述了数据库安全,详细介绍了电力信息系统对数据库安全的要求,并介绍了在电力信息系统中用到的保障数据库安全的具体措施。     

Integration of a security type system into a program logic

Type systems and program logics are often thought to be at opposing ends of the spectrum of formal software analyses. In this paper we show that a flow-sensitive type system ensuring non-interference in a simple while-language can be expressed through specialised rules of a program logic. In our framework, the structure of non-interference proofs resembles the corresponding derivations in a state-of-the-art security type system, meaning that the algorithmic version of the type system can be used as a proof procedure for the logic. We argue that this is important for obtaining uniform proof certificates in a proof-carrying code framework. We discuss in which cases the interleaving of approximative and precise reasoning allows us to deal with delimited information release. Finally, we present ideas on how our results can be extended to encompass features of realistic programming languages such as Java.     

考虑参数不确定性的转子系统瞬态动平衡研究

针对含不确定性参数的转子系统,提出了一种基于区间数学、泰勒展开和摄动理论的转子瞬态响应区间分析法.该方法求解不确定性问题时无需不确定参数的具体概率分布,适用于一般性工程分析.利用转子瞬态响应信息对一弹性支承双盘转子进行瞬态动平衡.将不确定性引入动平衡过程,分析了不同不确定性水平下不确定性参数对瞬态动平衡效率的影响.研究结果表明,该方法能有效分析转子不确定性瞬态响应,随着不确定水平增大,转子动平衡效率大幅降低.     

信息系统安全评估的交互式群决策模型及实现

在分析信息系统安全方案评估方法缺陷的基础上,提出一种多轮交互式评估方法,以解决结构化较差和不完全信息的信息系统安全评估中多人决策问题。每个群成员对方案属性两两比较得到的转换为评价矩阵,通过多轮交互过程评价、选择、排序逐步形成群体理想解,最终得到群体一致的各方案的最终群体排序,并通过实例验证了方法的有效性和可行性,为信息系统安全方案的选优提供了一种有效的方法。     

安防系统弱点评估算法的可视化实现

对安全防范系统（SPS）而言,弱点评估是系统效能评估的重要组成部分。现有的弱点评估算法普遍使用的入侵序列图（ASD）模型,在准确性、可靠性和直观性上存在一定的缺陷。对现有的弱点评估算法进行改进。提出用二维地图替代入侵序列图进行系统建模;引入广义的启发式搜索算法,以满足动态效能评估的实时性要求;添加防护元件的灵敏度分析模块,使系统在进行定期维护与升级时能获得最高的成本-效益。提出的算法已经通过编程实现,并用得到的VVA-SPS（Visualized Effectiveness Assessment of Security and Protection Systems）程序针对不同防护对象进行了算法的有效性验证。     

Implementation of Web-based dynamic assessment in facilitating junior high school students to learn mathematics

This research adopts the Graduated Prompting Assessment Module of the WATA system (GPAM-WATA) and applies it to the remedial teaching of junior high school mathematics. The theoretical basis of the development of GPAM-WATA is the idea of ‘graduated prompt approach’ proposed by Campione and Brown, 1985, Campione and Brown, 1987. In GPAM-WATA, when examinees fail to answer items correctly, they obtain instructional prompts (IPs) in a graduated way. This research developed the contents of IPs based on the mathematical problem-solving theory of Mayer (1992, pp. 458–460). A quasi-experimental design was adopted. Ninety-six junior high school seventh graders from three different classes participated in this research. The three classes were randomly divided into the GPAM-WATA group (n = 31), the N-WBT group (n = 31) and the PPT group (n = 34). All students received traditional mathematics instruction from the same teacher. After traditional mathematics instruction, all students took the pre-test of the summative assessment. The students in the three different groups then respectively received remedial teaching in the form of GPAM-WATA, normal Web-based test (N-WBT), and paper-and-pencil test (PPT). After the remedial teaching, all students took the post-test of the summative assessment. The results indicate that compared with other groups, performing remedial teaching using GPAM-WATA has significantly better effectiveness. Moreover, it is found that the IPs in GPAM-WATA are effective in remedial teaching for not only those students most lacking in different types of mathematical problem-solving knowledge but also all the other students.     

A nonlinear robust HVDC control for a parallel AC/DC power system

In this paper, a parallel AC/DC power system is investigated, and a nonlinear robust controller is proposed to improve transient stability of the power system and to damp out any prolonged oscillation after a fault is cleared. Lyapunov's direct method is used to synthesize the control, and asymptotic stability of the closed loop system and improved dynamic performance are shown by both theoretical proof and simulation results.