承德某区域集中供热设计

本文针对区域复杂的地形环境、热源的局限性以及城市现状与未来的发展对供热的需求差别,经综合分析比较,该集中供热系统采取短期直供,待电厂具备抽汽加热能力之后改为间接供热的形式。阐述了直供中为克服地形高差大等设计难题而采取的在系统主管网上设置减压站、中继泵站等一系列安全措施。运行情况表明该系统设计是成功的。     

Joint relay selection and resource allocation in cooperative device-to-device communications

Device-to-device (D2D) communications allow proximate cellular user equipments (UEs) to communicate with each other directly under the control of base station (BS). In this paper, considering the selection relaying (SR) rule which allows a subset of potential relays to forward the source’s data to the corresponding destination, we first establish a multi-relay system model where a D2D UE can act as not only a source but also a potential relay for another D2D link, and then analyze the cooperation behaviors among selfish UEs. Next a simple strategy is proposed to deal with the relay selection problem, and then the fair and efficient resource sharing problem among cooperating D2D UEs is formulated as a bargaining game. Since the game function is non-convex, we turn to an iterative method by introducing an auxiliary function to get the proportional fair resource allocation results. The system efficiency and fairness are proved by numeral simulation results.     

A new approach for mitigating blackout risk by blocking minimum critical distance relays

Electric power systems are complex and commonly run near their operational limits. Power systems are basically designed based on the (N − 1) criterion. In these systems, total or partial blackouts are unavoidable. Cascading failures following an initial event is recognized as the main mechanism for power system blackouts. Undesirable activation of zone 3 of distance relays due to their local function has been identified as one of the major causes for propagation of cascading failures. In this paper, in order to mitigate the risk of power system blackouts, a novel approach is proposed for recognizing the critical line outages with the highest contribution in cascading failure and preventing their undesirable outage by blocking zone 3 of their distance relay. In this paper, based on the statistical activation of distance relays, a deterministic–probabilistic approach is developed for identifying the critical lines with the highest contribution in blackouts due to activation of zone 3 of their distance relays. In order to avoid interference of relay blocking with the main protection duty of distance relays, the proposed approach recognizes the minimum critical lines with the highest contribution in cascading failure for blocking zone 3 of their distance relays. The proposed approach is demonstrated on the New England 39-bus system and detailed simulation studies carried out to examine the validity and effectiveness of the proposed approach.     

Microgrids formed by renewable energy integration into power grids pose electrical protection challenges

System parameters of a microgrid change in its two operating modes primarily due to output current limitation of PWM based inverters connected with renewable energy sources. The unavailability of an appropriate protection scheme, which must be compatible with both modes of a microgrid operation, is a major problem in the implementation of a microgrid. Two important properties of the microgrid components are peer-to-peer, and plug-and-play. It means that there is no component like a master controller which is critical for the operation of a system, and a distributed-generation unit can be installed at any location in a microgrid. These properties further complicate the protection of a microgrid. This paper reports the MATLAB/SIMULINK model of a microgrid along with the models of the conventional protection schemes and renewable energy distributed-generation resources. Malfunctioning in the conventional protection schemes in islanding mode is identified and models of newly proposed protection schemes are developed. Different types of faults are simulated in all the protection zones of the system and the system parameters are analysed to identify the possible fault detection methods. Based on the simulation results, a protection scheme is recommended that can meet the protection standards such as selectivity, co-ordination and reliability.     

基于USB4751的多路信号转接器设计

本文在介绍了利用USB4751 DI/O模块和PCLD-785B继电器板构建多路信号转接器基础上,描述了开发24路电源负载调整率的自动测量系统组成框图,并针对继电器板接线示意图进行了工作原理说明,结合实际测量设计了在LabVIEW中如何实现自动控制的程序.该信号转接器已应用于实际测量工作中,克服手动测量、人工接线、手工...     

平推式硫化罐自动控制系统的研究及改进

本文根据平推式硫化罐特点，采用继电控制设计的基本原则、基本方法，通过选用时间继电器、小型通用继电器和电接点压力表组成的联锁保护装置，对硫化罐继电控制电路进行设计及技术改进来控制硫化时间，从而达到工艺要求。     

智能电表综合管理系统的研制

介绍一种由用户智能电表，中继器，近端中心分机，远端管理中心构成的智能电表综合管理系统。分析了系统近端和远端通信可选择的方式及可行性，并阐述了中继器的设计思想和系统软，硬件的主要技术。     

Relay-based critical point estimation of a process with the PID controller in the loop

The proposed procedure is implemented without breaking the loop with the controller in operation, by activating a cascade of band-pass filters in series with a relay in the inner loop and a notch filter in the outer loop. A highly accurate estimate of the critical point of a process G_p(s) is obtained in the presence of measurement noise and load disturbance. The effectiveness of the proposed procedure is illustrated using a test batch consisting of stable, integrating and unstable processes, including dead-time.