求解最优潮流问题的内点半定规划法

基于内点半定规划(semi-definite programming,SDP),提出一种求解最优潮流(optimal power flow,OPF)的新方法--SDP-OPF法。该方法将非凸OPF问题等价转换为半定规划问题,然后应用原始-对偶内点法求解。根据OPF半定规划模型的特点,采用基于半定规划的稀疏技术,使存储效率和计算性能得以大幅度提高。以4节点的简单电力系统为例,展示模型等价转换的过程及如何获取原OPF问题的解。IEEE-300节点等6个标准系统的仿真计算表明：所提算法具有超线性收敛性,其计算结果与内点非线性规划的结果一致,且能保证解的全局最优性,可在多项式时间内完成,是一种应用前景广阔的方法。     

A semidefinite programming method with graph partitioning technique for optimal power flow problems

A new semidefinite programming (SDP) method with graph partitioning technique to solve optimal power flow (OPF) problems is presented in this paper. The non-convex OPF problem is converted into its convex SDP model at first, and then according to the characters of power system network, the matrix variable of SDP is re-arranged using the chordal extension of its aggregate sparsity pattern by the graph partitioning technique. A new SDP-OPF model is reformulated with the re-arranged matrix variable, and can be solved by the interior point method (IPM) for SDP. This method can reduce the consumption of computer memory and improve the computing performance significantly. Extensive numerical simulations on seven test systems with sizes up to 542 buses have shown that this new method of SDP-OPF can guarantee the global optimal solutions within the polynomial time same as the original SDP-OPF, but less CPU times and memory.     

Current‐mode filters based on current mirror arrays

A technique is proposed for obtaining current‐mode filters based on current mirror arrays that operate as unity gain current amplifiers. These amplifiers by properly driving capacitors realize active lossless integrators which are the basic active elements for the derivation of filters according to the leapfrog method. Due to the fact that both the structure of the amplifiers and the adapted method for filter design are simple, the proposed technique is attractive for filter design and implementation. A design and the implementation of two third‐order low‐pass filters are presented. The array of the amplifiers has been implemented in a 0.8 µm CMOS technology. Copyright © 2007 John Wiley & Sons, Ltd.     

Design of stable two-dimensional analogue and digital filters with applications in image processing

A method is proposed for the frequency domain design of linear two-dimensional analogue and digital filters with guaranteed stability. The technique used is based on the result that the numerator and the denominator of the input immittance of a two-variable network (which is passive and lossy) are strictly Hurwitz polynomials. One of these strictly Hurwitz polynomials is assigned to the denominator of a two-variable analogue transfer function and the network elements are then used as the variables of optimization thereby guaranteeing the stability of the analogue transfer function. The transfer function of the corresponding two-dimensional discrete (digital) filter is obtained from the analogue transfer function by the bilinear transformation. Examples illustrating the versatility of the technique in designing 2D digital filters of arbitrary order approximating a given magnitude and group delay response are presented. These filters are used to process a simple binary image. The results obtained demonstrate the importance of linear phase in image processing applications. The method presented here can be extended to the design of stable m-dimensional analogue and digital filters.     

Digital design of a power system stabilizer for a power system based on plant input mapping

This paper is concerned with the plant modeling for the digital redesign of a continuous-time power system stabilizer PSS for a single machine power system using Plant-Input-Mapping PIM method. The traditional approach has been to use the bilinear transform (Tustin’s method), but this needs small sampling intervals which gives some difficulties with modern control. The presented technique guarantees the stability for any sampling rate as well as it takes closed-loop characteristics into consideration. The proposed technique is successfully applied to the discretization of the conventional continuous time PSS for single-machine power system. For comparison studies the proposed technique is compared with conventional continuous-time PSS and Tustin’s PSS. The simulation results show that the states of the proposed digital redesign technique closely match those of the conventional continuous-time PSS. The proposed digital redesign technique guarantees stability even with relatively slow sampling rates while Tustin’s method falls when sampling interval becomes larger.     

Computer simulation of electric motor drive systems including thepower electronic network

A method for studying a combined power electronic network/variable-speed AC electric motor drive system based on a simple numerical algorithm is presented. It can be applied to any machine that can be describing using a d-q-type model. An LCI-fed synchronous motor drive in the steady state is used as an illustrative example. A simple iterative technique is used to find the initial conditions in the time domain, making use of an infinite link inductance approximation to provide the first iteration. The predicted waveforms of voltage and current for a sample operating point are compared with their experimental equivalents (measured on a 3 kVA prototype drive system), and a good level of agreement is reached. The technique is sufficiently simple to have been implemented on a personal computer     

A Computer-Aided Design Toolkit For Continuous/Discrete Systems Based On Continued Fractions

This paper presents new algorithms (1) to generate complete mathematical symbolic expressions of continued fraction expansion coefficients in the s-domain, (2) to determine their numeric values and (3) to perform continued fraction inversion in the s-domain. A software package in PASCAL and LISP to implement these algorithms is developed. In addition, a simple z-domain inversion algorithm used in the computer implementation of bilinear s-z transformation is also included in the software package. These algorithms play an important role in the analysis and synthesis of complex electrical networks and control systems. Especially, the s-domain expansion and inversion algorithms have potential applications in model simplification and system order reductions. the paper also shows that the package, as such, serves as a comprehensive computer-aided analysis and design (CAD) toolkit for both continuous and discrete systems. the software is interactive and runs on computers equipped with a PASCAL or LISP compiler. It is noted that the iterative implementation of these methods using the new continued fraction algorithms saves considerable memory space and processing time. Numerical examples and computer data are given to demonstrate the development of the new algorithms and the usefulness of the software toolkit in the CAD design of continuous and discrete systems.     

The Mechanics of the Bilinear Transformation

The effect of the bilinear transformation substitution s 1 Z = -- s- on a polynomial equation nE aizi = 0 i= 0 is formulated in matrix terms. The matrices involved are formed by very simple rules. This procedure considerably facilitates calculation of the resulting s-polynomial, and makes the bilinear transformation an attractive tool for systems analysis rather than the textbook curiosity which it has been.     

基于IEC60870-5-104规约的水电厂通信管理机设计

介绍基于WinCE系统实现IEC60870-5-104规约的水电厂通信管理机的设计.采用MOXA UC7410CE嵌入式工业计算机,通过WinCE串口编程技术、以太网编程技术、多线程编程技术实现了通信管理机通过多种规约如DL/T645、CDT、Modbus等与水电厂各种微机化设备的通信,以及与监控计算机的IEC60870-5-104规约通信.分析了IEC60870-5-104规约的帧结构和在WinCE系统中的实现方法,并给出了接收过程、发送过程的流程图.提供了一种管理多TCP客户端连接的方法,允许多个上位机同时连接通信管理机并共享数据.得益于工业级嵌入式计算机的高可靠性.使通信管理机能长期稳定运行.     

A personal computer approach to overcurrent protective devicecoordination

The personal computer offers several advantages over both manual methods and shared-computer methods for overcurrent protective device coordination. The fast graphics display of a personal computer makes it possible to achieve a practical replacement for the light table. A computerized approach to overcurrent protective device coordination is presented. A flexible, hierarchical database permits convenient storage and retrieval of any time-current-characteristic curve. An expert system is implemented through a macro language, built around simple functions. The design choices for the personal computer program are discussed and an implementation meeting the design requirements is presented     

Adequacy evaluation of a small area in a large composite powernetwork

A methodology is presented which can be used to conduct adequacy studies, considering both the continuity and the quality of power supply as failure criteria on a small area in a large power network. The technique is simple and can be used with existing computer programs to determine the adequacy performance of a power network. It also considers all credible outages that can affect the adequacy of the small area in a power system. The main disadvantage is that the efficiency of the method depends on the size of the small area as compared to the size of the entire power network. The efficiency also depends on the network topology, the type of buses in the small area, and the load-curtailment philosophy. Some of these issues are illustrated by applying the methodology to the IEEE Reliability Test System. A qualitative comparison of the proposed method with two other methods that can be used to determine the adequacy of large power networks is presented     

卫星通信系统中适用于16QAM信号的一种预失真方法

提出了一种用于卫星通信系统中由记忆功率放大器引起的16QAM信号非线性失真的高效数字自适应补偿方法。该方法使用通用记忆多项式模型和间接学习结构构造预失真系统,并使用QR分解递归最小二乘算法动态更新预失真参数。针对QR分解递归最小二乘算法不能直接更新系数矢量的问题,提出了一种称为＂权值冲洗＂的高效权值更新方法。计算机仿真结果表明该方法具有收敛速度快、系统性能稳定、补偿效果好等特点,并适合于大规模电路硬件实现。     

A New Power System Digital Harmonic Analyzer

In this paper, new digital instruments measuring power-quality indicators and harmonic analyzers are developed. A new technique for simultaneous local system frequency and amplitudes of the fundamental and higher harmonics estimation from either a voltage or current signal is presented. The structure consists of three decoupled modules: the first one for an adaptive filter of input signal, the second one for frequency estimation, and the third one for harmonic amplitude estimation. A very suitable algorithm for frequency and harmonic amplitude estimation is obtained. This technique provides accurate frequency estimates with error in the range of 0.002 Hz and amplitude estimates with error in the range of 0.03% for SNR = 60 dB in about 25 ms. The theoretical basis and practical implementation of the technique are described. To demonstrate the performance of the developed algorithm, computer simulated data records are processed. Data of the distribution power system voltage signals are also collected in the laboratory environment and are processed in a newly developed digital PC-based harmonic analyzer. It has been found that the proposed method really meets the need of offline applications. Even more, by using the parallel computation algorithms, this method should meet the need of online applications and should be more practical     

Laplace方程分域展开方法

针对电磁场分析中有限元法适应能力强,但计算量大,效率低,而解析法计算量小,但适用范围窄的各自优缺点,将有限元方法与解析方法相结合,提出了一种分域展开的半解析方法用以求解工程电磁场问题。依据龙格定理,把复杂的求解场域分割为若干形状简单的子域,在每个子域内利用本征函数构造半解析展开式逼近方程的解,然后通过子域拼接得到整个场域的解。展开式系数用配点法确定。由于采用解析展开式,逼近效率高,减少了未知数个数;同时由于是局域逼近,具有解函数形式简单,计算量小,矩阵是稀疏的,条件数小,易于求解,实施方便等优点。以二维Laplace问题为研究对象,数值算例验证了方法的有效性,表明该方法花费时间短,计算精确度高。     

Node reordering and matrix partial refactorization study

Sparse matrix operation is one of the most important areas in the study of power systems. However, its performance is greatly affected by the number of fill-ins. Excessive fill-ins can be reduced through better node reordering. A new method, dealing with the node reordering, is presented in this paper. This method considers the impacts of the locations of the fill-ins and the number of fill-ins. It is not only able to handle any noncluster problem but some cluster problems too.Partial refactorization methods update the LU factors of a matrix to reflect changes in some of its elements. The applications of partial refactorization power system problems are numerous. A new method is also presented in this paper to deal with partial refactorization problems. It does not require a path graph. The coding of the new method is very simple. It reduces the number of calculations and required computer memory storage to a minimum.Detailed discussions about the abilities of the new methods to work under a wide variety of network conditions are presented in the paper. Several examples are implemented and solved. The results are also compared with those of existing methods.     

Numerical analysis of discontinuities in a rectangular waveguide loaded with isotropic or anisotropic obstacles by means of the coupled-mode method and the mode-matching method

A hybrid method obtained as a combination of the coupled-mode method (CMM) and the mode-matching method (MMM) is developed and applied in the analysis of multiple dielectric and magnetic discontinuities in rectangular waveguides. As both are moment methods, some kind of truncation has to be carried out in the computer implementation. It is shown that selection of a different number of modes in the two methods is not necessary, unless low-permittivity meida inside the waveguide are considered. As a consequence, the procedure for slecting the number of basis functions is only done in one of the methods. Numerical examples are presented showing the behaviour of the method and the proofs of convergence. Examples are included illustrating the power of this hybrid technique, especially in relation to non-reciprocal structures containing magnetized ferrites.     

A new look at component maintenance practices and their effect on customer, station and system reliability

This paper introduces a new concept in the analysis of the effect of changes in maintenance policies on component, delivery point and bulk electric system reliability and associated costs. In the new approach several different analysis methods are combined, allowing for a comprehensive look at the effect of maintenance and reliability issues. This approach has been made possible by a development of a computer platform, which seamlessly links several complex computer programs. The concepts of the new approach and the implementation of the computer platform are presented in this paper. A numerical example illustrating implementation of these concepts is also presented.     

电站锅炉效率计算方法研究

介绍锅炉效率和各项损失计算过程中的一些改进 ,对计算方法实现了计算机的标准化编程。在计算排烟损失过程中 ,提出空气湿度的修正和采用比热的多项式计算方法。在计算锅炉散热损失中 ,采用最新西安热工研究院所得试验曲线 ,改进了锅炉效率计算方法并提高了计算精度。     

单相多极开关磁阻发电机设计及性能仿真

分析中低速开关磁阻发电机运行及控制特点，提出一种基于准线性模型的设计方案和步骤，该方法克服了类比法的盲目性。编制了计算机设计仿真程序，给出了一台样机的设计结果和仿真曲线，结果表明方法合理，具备一定的精度，能满足工程设计的要求。     

基于WAMS的电力系统受扰轨迹预测

基于相量测量单元（PMU）上传的实时功角数据,应用曲线拟合理论,提出了一种电力系统事故后功角轨迹快速预测的新方法。该方法从一个简单电力系统调速控制模型出发,推导出了功角与时间关系的数学模型,即功角随时间呈正弦衰减变化。由此提出了利用三角函数曲线拟合技术,对功角受扰轨迹进行预测。对IEEE 9节点系统与华北电网进行了仿真计算,结果验证了该方法的有效性。此外,与多项式曲线拟合法的对比分析表明,该方法优于传统的多项式曲线拟合法,具有更好的预测效果。