利用改进数位演算法和经验模态分解的电力系统低频振荡信号瞬时参数的提取

为分析电力系统低频振荡的动态特性,需要提取低频振荡信号的瞬时参数,而电力系统低频振荡信号为非线性时变复合信号,因此参数提取前需要对其进行振荡模态分解。首先结合最小平方误差法提出了改进数位演算方法,以提高信号参数的提取精度;其次应用经验模态分解法对低频振荡信号进行模态分解,确定有效振荡模态;最后根据提取参数可分析电力系统低频振荡的动态特性。算例结果验证了该方法的有效性。     

A grid for tomorrow

The Chinese government plans to establish ultra-high voltage (UHV) systems to transmit an additional 250 GW of electricity by 2020. The plan includes prioritizing the development of 60 GW of hydropower in the western part of China. To transport power from the west to the eastern and southern industrial centers in Shanghai and Guangdong, the government intends to utilize UHV 800 kV DC for bulk power transmission and UHV 800-1000 kV AC for interconnecting the regional AC networks in the east and south. With the national UHV grid, the government hopes to address the present status of imbalance between electricity supply and demand. The UHV grid also aims to promote electricity trading between different regions over different scales, optimizing the utilization of energy sources within large areas, meeting the requirements of economic development and creating competitive national energy markets     

Flexible investment decisions in the European interconnected transmission system

Investment decisions in the power transmission system are vulnerable to substantial long-term uncertainties. Especially, in large interconnected power systems like in Europe, the impact of different influencing factors on the decision-making process is hard to estimate. In the presented approach, stochastic simulations incorporate uncertainties like the development of fuel costs and demand growth. The resulting operation plan of the available power plants and the respective utilization of the transmission network are obtained by calculating the (least-cost) optimal power flow. The performance of possible network upgrades in uncertain scenarios is evaluated by applying a real options approach based on Monte Carlo simulations. The focus of the presented work is on the strategic flexibility that FACTS devices can offer in order to appropriately cope with the uncertain development of the future. A case study for the cross-border connection between Germany and the Netherlands shows the applicability and practicability of the presented approach.     

感应滤波技术应用于工业定制电力系统的运行经验分析

介绍了感应滤波技术在实际工业定制电力系统中的运行经验.给出了感应滤波的单相等值电路并介绍了其基本的工作原理和技术特点,分析了感应滤波技术的滤波优势;针对某实际运行的基于感应滤波的工业定制电力系统,给出了一次设备的主电路拓扑以及所采用的主要技术参数和技术特性.对工业定制电力系统的电能质量进行了详细的现场测试.测试结果表明...     

负荷模型不确定性对电力系统动态仿真的影响

为解决蒙特卡洛模拟法仿真次数过多、消耗时间过长等缺点,采用一种新的不确定分析方法--概率分配法(probabilistic collocation method,PCM),定量分析动态负荷所占比例的不确定性对动态仿真及稳定的影响裕度。新英格兰 10机 39节点系统的仿真分析验证该方法在电力系统动态仿真中的实用性和有效性。仿真分析显示离故障点较近且负荷较重的节点,其动态负荷所占比例的不确定影响最大;某些距故障点较远但负荷较重的节点,其不确定性对暂态稳定仍有较大的影响。对电力系统的动态仿真结果表明PCM方法可直接在输出响应与指定参数间建立多项式关系,仅用参数的概率密度函数及少量仿真便可快速估计出响应的概率分布,从而对响应进行不确定性分析。     

基于改进希尔伯特-黄变换算法的电力系统低频振荡分析

作为一种非线性时变信号处理方法,希尔伯特-黄变换(Hilbert-Huang transform,HHT)已经被应用到电力系统低频振荡的分析中.分析经验模态分解(empirical mode decomposition,EMD)过程中存在的端点效应和模态混叠现象.针对EMD分解过程中的端点效应问题,通过4种端点延拓方法的比较,得出适合电力系统低频振荡信号分析的延拓方法.在介绍频率偏差法基本原理和适用范围的基础上,提出利用频率偏差法来解决EMD分解中存在的模态混叠现象,并建立基于极值点对称延拓和频率偏差原理的改进HHT算法.测试信号和仿真算例证明频率偏差法可有效地解决信号在EMD分解过程中的模态混叠现象,扩大了HHT在低频振荡信号分析中的应用范围.     

Dynamic output-feedback wide area damping control of HVDC transmission considering signal time-varying delay for stability enhancement of interconnected power systems

In this paper, an output-feedback-type wide area damping control (WADC) strategy is presented as a supplementary control of high-voltage direct current (HVDC) transmission to enhance thestability of large-scale interconnected power systems. This strategy can effectively suppress the varying-delay effects of wide area signal on the damping performance. A discrete-time system model that considers the varying-delay feature of wide area signal is established, then a dynamic output-feedback (DOF) type WADC is formulated by employing a new stabilization analysis method based on Lyapunov function. All the solutions of controller design problems are converted into the framework of linear matrix inequalities (LMIs). Compared to the conventional design method, the varying-delay of wide area signal is involved during each step of controller design, which is advantage to eliminate the effects of signal varying-delay on damping performance. Both the four-machine two-area test system and the sixteen-machine five-area interconnected system are used to validate the control concept and the designed controller.     

基于改进局部均值分解的低频振荡参数提取

针对电力系统低频振荡非线性时变的特点,提出了一种基于改进局部均值分解(local mean decomposition,LMD)的电力系统低频振荡信号分析方法。利用改进的局部均值分解,电力系统中的单一多模态测量信号可以分解为一组乘积函数(product function,PF)分量的和。每个PF分量可以表示为一个调幅(amplitude modulated,AM)信号和一个调频(frequency modulated,FM)信号的乘积。其中,AM信号可以近似当作相应振荡模态的瞬时幅值,并由此计算阻尼信息;FM信号可以通过直接正交和插值相结合的综合方法,计算PF的瞬时频率。数值仿真和实际测量信号的计算结果证明了所提方法的有效性和可行性。