Decentralized Resilient H∞ Load Frequency Control for Cyber-Physical Power Systems Under DoS Attacks

This paper designs a decentralized resilient H_∞ load frequency control (LFC) scheme for multi-area cyber-physical power systems (CPPSs). Under the network-based control framework, the sampled measurements are transmitted through the communication networks, which may be attacked by energy-limited denial-of-service (DoS) attacks with a characterization of the maximum count of continuous data losses (resilience index). Each area is controlled in a decentralized mode, and the impacts on one area from other areas via their interconnections are regarded as the additional load disturbance of this area. Then, the closed-loop LFC system of each area under DoS attacks is modeled as an aperiodic sampled-data control system with external disturbances. Under this modeling, a decentralized resilient H_∞ scheme is presented to design the state-feedback controllers with guaranteed H_∞ performance and resilience index based on a novel transmission interval-dependent loop functional method. When given the controllers, the proposed scheme can obtain a less conservative H_∞ performance and resilience index that the LFC system can tolerate. The effectiveness of the proposed LFC scheme is evaluated on a one-area CPPS and two three-area CPPSs under DoS attacks.      

消失模EPS模型材料表征及性能的研究

为了探究消失模EPS模型的表面粗糙度影响因素、应力应变特征以及消失模EPS模型材料的热解规律和内部胞腔结构形态,达到降低消失模铸件的表面粗糙度,科学制定消失模工艺过程的控制参数,选择适合消失模工艺的合金材料,控制铸件内碳化物残留量,提高消失模铸件的表面质量和力学性能.本文采用激光粒度分析仪对用于消失模EPS产品模型成形的原始珠粒和预发珠粒的球形度、宽长比、凸度、颗粒度频度分布、颗粒度累积分布进行了测试分析,借助白光干涉分析仪对EPS原始珠粒、预发珠粒和EPS泡沫产品模型的表面粗糙度进行观察,运用热重差热仪分析了EPS原始珠粒和预发珠粒的热解特性,测试了EPS模型的准静态三维应变空序曲线和径向形貌的特征,并探讨了优化消失模成形工艺的可行性.研究表明:相较于消失模EPS原始珠粒,预发珠粒具有球形度高、粒径频度分散、表面粗糙度值高、化学失重温度区间狭窄的特点.常温常压下消失模EPS模型具有良好的塑性和适当的强度,其韧性断口呈现密集的胞腔组织结构.     

印尼小电网过激磁保护设置的分析及处理

以印尼一电厂过激磁保护提前动作引起全岛电网瘫痪事故为例。通过分析发变组过激磁保护原理,发现在调试过程中应注意的问题和运行过程中适度调整定值,使不仅满足《大型发电机变压器继电保护整定与计算导则》和厂家要求,且考虑电网单机大、电网容量小海外特殊环境,兼顾"保网"和"保厂",以满足电网稳定、电厂安全生产及投资回报。     

Bacteria foraging optimization algorithm based load frequency controller for interconnected power system

Social foraging behavior of Escherichia coli bacteria has recently been explored to develop a novel algorithm for distributed optimization and control. The Bacterial Foraging Optimization Algorithm (BFOA), as it is called now, is currently gaining popularity in the community of researchers, for its effectiveness in solving certain difficult real world optimization problems. This paper proposes BFOA based Load Frequency Control (LFC) for the suppression of oscillations in power system. A two area non-reheat thermal system is considered to be equipped with proportional plus integral (PI) controllers. BFOA is employed to search for optimal controller parameters by minimizing the time domain objective function. The performance of the proposed controller has been evaluated with the performance of the conventional PI controller and PI controller tuned by genetic algorithm (GA) in order to demonstrate the superior efficiency of the proposed BFOA in tuning PI controller. Simulation results emphasis on the better performance of the optimized PI controller based on BFOA in compare to optimized PI controller based on GA and conventional one over wide range of operating conditions, and system parameters variations.     

消失模铸造局部稀土多元合金化研究

消失模铸造时,为了满足铸件局部特殊性能要求,在铸件模样局部加入合金元素同时加入稀土元素。铸件成形后,合金元素与稀土元素同时溶入了铸件相对应部位。试验证明,铸件局部合金化可以改善消失模铸件的局部特殊性能。     

消失模铸造涂料透气性研究

为了解决消失模铸造件气孔问题,研究了黄麻纤维对消失模铸造涂料透气性的影响.加入质量分数0.2%黄麻纤维时,涂料透气性由未加黄麻纤维时的2.1 cm4/(g·min)上升为5.8～6.3cm4/(g·min);加入质量分数0.5%黄麻纤维时,涂料透气性为9.8～10.6cm4/(g·min).结果表明,消失模铸造涂料的透气性可通过黄麻纤维的加入量调节.     

Age-of-information-aware PI controller for load frequency control

Open communication system in modern power systems brings concern about information staleness which may cause power system frequency instability. The information staleness is often characterized by communication delay. However, communication delay is a packet-centered metric and cannot refect the requirement of information freshness for load frequency control (LFC). This paper introduces the age of information (AoI), which is more compre-hensive and informative than the conventional communication delay modeling method. An LFC controller and com-munication are integrated into the design for LFC performance improvement. An AoI-aware LFC model is formulated frst, and considering each allowable update period of the smart sensor, diferent AoI-aware PI controllers are then designed according to the exponential decay rate. The right AoI-aware controller and update period are selected according to the degree of frequency fuctuation of the power system. Case studies are carried out on one-area and two-area power systems. The results show the superior performance of the AoI-aware controllers in comparison to the delay-dependent controllers.