内蒙古电网继电保护一体化整定计算系统的开发与应用

内蒙古电网原继电保护整定计算系统功能简单,没有统一的数据平台,使得中调、地调形成信息"孤岛",而且整定计算基础数据以及定值单管理不规范.针对内蒙古电网的实际情况,开发了继电保护一体化整定计算系统.该系统在中调服务器上部署数据库服务器,构建统一的数据平台,保证了数据的一致性,其功能模块包括图形建模、故障计算、整定计算、信息管理等.实际应用中,该系统实现了中调、地调的一体化联合计算功能,有效提高了继电保护整定计算的工作效率和计算精度,也为提升继电保护定值管理水平提供了有效手段.     

一种基于OPM和FBG滤波器的新型双工ROF系统

提出了一种采用光相位调制器(OPM)和光纤布 拉格光栅(FBG)滤波器实现的双向光纤无线通信(ROF)系统。在中心站,系统采用OPM和FBG滤波器产生抑制一阶边带的多边带光信号 ,而2.5Gbit/s 的下行链路信号只调制在中心光载波上同时经过光纤进行传输。在基站,未被调制的边带信 号用来重新调 制上行链路信号。建立了产生光载毫米波的理论模型,分析了光纤色散导致的相位影响,并 通过仿真实验 验证了系统的可行性。结果显示,经过60km光纤传输后,上、下行 链路信号的眼图都清晰可见,上行链 路功率代价小于0.2dB,下行链路功率代价小于1.8dB,系统具有较好的抗色散能力。     

Performance analysis of opportunistic nonregenerative relaying

Opportunistic relaying in cooperative communication depends on careful relay selection. However, the traditional centralized method used for opportunistic amplify‐and‐forward protocols requires precise measurements of channel state information at the destination. In this paper, we adopt the max–min criterion as a relay selection framework for opportunistic amplify‐and‐forward cooperative communications, which was exhaustively used for the decode‐and‐forward protocol, and offer an accurate performance analysis based on exact statistics of the local signal‐to‐noise ratios of the best relay. Furthermore, we evaluate the asymptotical performance and deduce the diversity order of our proposed scheme. Finally, we validate our analysis by showing that performance simulation results coincide with our analytical results over Rayleigh fading channels, and we compare the max–min relay selection with their centralized channel state information‐based and partial relay selection counterparts. Copyright © 2013 John Wiley & Sons, Ltd.     

Cognitive amplify‐and‐forward relay networks with beamforming under primary user power constraint over Nakagami‐m fading channels

In this paper, we analyze the performance of cognitive amplify‐and‐forward (AF) relay networks with beamforming under the peak interference power constraint of the primary user (PU). We focus on the scenario that beamforming is applied at the multi‐antenna secondary transmitter and receiver. Also, the secondary relay network operates in channel state information‐assisted AF mode, and the signals undergo independent Nakagami‐m fading. In particular, closed‐form expressions for the outage probability and symbol error rate (SER) of the considered network over Nakagami‐m fading are presented. More importantly, asymptotic closed‐form expressions for the outage probability and SER are derived. These tractable closed‐form expressions for the network performance readily enable us to evaluate and examine the impact of network parameters on the system performance. Specifically, the impact of the number of antennas, the fading severity parameters, the channel mean powers, and the peak interference power is addressed. The asymptotic analysis manifests that the peak interference power constraint imposed on the secondary relay network has no effect on the diversity gain. However, the coding gain is affected by the fading parameters of the links from the primary receiver to the secondary relay network. Copyright © 2012 John Wiley & Sons, Ltd.     

基于暂态能量的输电线路速动保护方案

利用母线杂散电容吸收高频分量的特点,构成了能准确区分区内、区外故障的速动保护方案。对输电线路保护安装处的电压、电流进行模量转换得到模量电压和模量电流,并将模量电压和电流进行Daubechies 4小波变换得到所需频段的低频信息和高频信息,利用这些信息计算得到相应频段的频谱能量,然后得到模量电压和模量电流的暂态特征,将电压和电流的暂态特征综合起来得到故障后的暂态能量,该暂态能量可用来识别故障位置。该保护方案的灵敏度不受过渡电阻、雷击、故障类型、负荷电流、系统运行方式等因素的影响。此外,由于保护的数据窗很短,电压互感器、电流互感器的传变特性对保护的性能没有影响。     

特高压输电线路负序方向纵联保护

采用数字式二阶RC低通滤波器和半波差分傅里叶算法，结合相序变换滤取负序分量，可在微机保护中实现负序方向元件，并可在故障初几毫秒内正确动作。用该方法实现的负序方向元件可正确及时地捕捉到由不对称故障发展起来的三相短路故障瞬间的不对称，故可以反映各种不对称故障和由不对称故障发展起来的三相故障。仿真试验验证了用所提出的方法实现的负序方向元件用于特高压输电线路的可行性和优越性。     

适用于发展性故障的故障分量提取算法

提出了适用于发展性故障的故障分量提取算法。该算法首先计算发展性故障发生前保护安装处的故障分量,再根据发展性故障发生前保护安装处的电流和获取的故障分量求得非故障状态网络中的支路电流;发生发展性故障后,利用保护安装处的全电流减去求得的支路电流得到发展性故障后的故障分量电流。该算法不受电网参数波动和负荷变化的影响。在IEEE 9节点系统模型基础上,BPA仿真验证了算法的正确性。     

适用于母线保护的电子互感器采样频率转换算法

在电子式互感器应用环境中,母线保护连接不同采样频率的电子式电流互感器（ECT）时,需要将原始采样频率不同的采样数据转换为同一采样频率。文中提出了时域连续有限冲激响应滤波器的概念,并以此为基础构造了连续数字低通滤波器,从电子式互感器输出的离散采样数据恢复出连续信号,重新计算出任意时刻的采样值。用含丰富谐波信号的1 000kV线路故障电流进行的计算分析表明, 4 kHz/2.4 kHz采样频率转换,该算法在数据窗长6个采样间隔（延时为0.75 ms）时,其峰值瞬时值误差均小于0.66%,精度和实时性能满足母线保护的要求。     

基于多代理系统的继电保护定值在线校核预警系统

基于多代理系统体系结构,研究并设计了继电保护定值在线校核预警系统.该系统利用代理的智能化特点,实现了对实时采集的电网信息的智能化分析,准确形成实时运行方式;利用多代理系统体系结构对分布式并行计算的良好支持,实现了校核计算的并行处理,提高了实时计算速度;利用公共对象请求代理体系结构软总线技术,以IEC 61970的公共信息模型和IEC 61850的保护功能逻辑节点相结合作为系统涉及的电力设备信息模型,提高了系统的可扩展性和开放性.实际应用表明,本系统利用代理实现多线程并行处理后,计算速度快,完全能满足在线运行需要,具有较高的实用价值.     

Decode‐and‐forward with full‐duplex relaying

This paper addresses the full‐duplex relaying. Some expressions for outage and average capacity of a two‐hop cooperative system with a full‐duplex relay are derived under an independent but not identically distributed Rayleigh fading environment. Using these expressions, we provide the performance analysis without Monte Carlo simulations. The impact of interference between the relay output and input is investigated. Copyright © 2011 John Wiley & Sons, Ltd.