A general maximum power transfer theorem

The maximum power transfer theorem provides the condition which the load resistance or impedance must satisfy for maximum power absorption from the source network. This paper reviews the conventional maximum power transfer theorem and presents a modification to the theorem by incorporating a measure of the relative importance of power transmission efficiency over power transferred to the load     

On state-space synthesis of reciprocal n-ports

The paper considers the state-space synthesis of reciprocal n-ports with a minimum number of reactive elements. After formulating the synthesis problem new procedures are given for the lossless and for the passive cases which use a directly determinable reciprocal minimal realization as starting point. The methods are presented in terms of admittance matrices and then restated for impedance, hybrid and scattering matrix synthesis.     

On impedance matching and maximum power transfer

This paper investigates the relationship between the impedance matching and the maximum power transfer problems, and presents a predictor–corrector framework for fast estimation of the maximum power transfer limit for the load increase pattern with a common scaling factor. First, a network equivalent technique is presented and a “decoupled” equivalent network is obtained for every load bus. Second, a special form of impedance matching condition is derived for the maximum power transfer problem with an unlimited load variation pattern. Though this is an unrealistic case in power systems, it might have a profound physical mechanism and lead to an interesting explanation and application for the presented equivalent technique. Third, this paper discusses the relationship between the impedance matching and the maximum power transfer problem for the load increase pattern with a common scaling factor. Finally, a predictor–corrector framework is introduced for fast estimation of the maximum power transfer limit for the load increase pattern with a common scaling factor.     

Energy-related concepts for non-linear time-varying n-ports: Passivity and losslessness

Definitions of passivity and losslessness are presented that apply to n-port networks which are not necessarily linear, time-invariant, or lumped; in fact, these definitions apply to any n-port that has an abstract dynamical system representation. For lumped, non-linear n-port networks that can be mathematically represented by a finite-order dynamical system, conditions for passivity and losslessness are formulated in terms of properties of the state equation function, the output function, etc. These conditions can be verified without solving the state equation, and can be viewed as non-linear generalizations of the well-known time-domain and frequency-domain passivity and losslessness conditions for linear time-invariant lumped n-port networks.     

Necessary and sufficient conditions for absolute stability of linear n-ports

A set of necessary and sufficient conditions is stated and proved for the absolute stability (under any passive terminations), in the ‘bibo’ sense, of a linear n-port characterized by its open-circuit impedance matrix. A more explicit set of such conditions is derived for the special case n = 3. In the process of deriving this set of conditions, some results and theorems concerning finding the zero sets of two and three parameter functions, are stated and proved. Also derived is a set of necessary and sufficient conditions for the absolute stability of two-ports characterized by the scattering parameters. Such sets have already been derived previously, but the present set is considerably simpler.     

叠加定理中功率的适用性分析

叠加定理作为线性电路中非常重要的一个定理,它是指当电路中有多个电源共同作用时,或任何1个支路电压(或电流),都可以看成是由各个电源单独作用时,在该支路产生的电压(电流)的代数和.但与电路响应有直接联系的能量问题的求解在该定理中并未直接述及,主要研究在直流电路、同频率正弦交流电路及不同频率正弦交流电路中叠加定理是否适用于功率的计算,并用Multisim软件进行仿真.从仿真结果和理论计算比较得出不同频率正弦交流电路中叠加定理适用于平均功率的计算.     

Existence of hybrid matrices for active n-ports encountered in the analysis of transistor networks

It is shown that hybrid matrices exist for certain types of active n-ports constructed using resistors and controlled sources. Furthermore, it is shown that the existence of these hybrid matrices implies that a certain well-known set of necessary and sufficient conditions, which guarantees the uniqueness of solutions to the nonlinear DC equations of transistor networks, can be simplified. Additional results are presented which show how the amount of computation required to verify these conditions can be reduced.     

On the impact of relay circuit losses in four-coil wireless power transfer systems

In wireless power transfer (WPT) systems with more than two coils, the intermediary or relay circuits are used to extend the link distance. Thus, to achieve this extension efficiently in terms of power transfer, these relay circuits must have low losses. However, there are several instances in which there are restrictions in reducing the ohmic losses in all the relay circuits of the system. This is the case of biomedical applications where commonly there are size and access restrictions since one of the circuits can be implanted and also in applications using high-temperature superconductor (HTS) coils due to the difficulty in implementing the necessary cooling system for all the coils of the system. Therefore, in these situations, the designer need to choose which relay circuit will be optimized. In this work, it is presented an analysis on the impact that losses in individual relay circuits have on efficiency, and power transfer, of typical four-coil wireless power transfer systems consisting of circuit 1 (transmitter), relay circuits 2 and 3, and circuit 4 (load). It is shown that the losses on relay circuit 2 have greater impact on efficiency, while the losses of relay circuit 3 have a greater impact on power transfer for a given condition. Practical experiments confirm the developed analysis.     

Wireless power transfer for electric vehicle at the kilohertz band

Wireless power transfer (WPT) technology has attracted considerable attention in recent years, and there have been numerous reports about this technology. This has led to ambiguity over the actual state of WPT technology for electrical vehicles (EV) in Japan. Therefore, this paper describes the WPT technology using the kilohertz band for EVs available in Japan. WPT requirement for EV, circuit topology, coil types, control method, component, foreign object detection, and dynamic charging in Japan are summarized in this study. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Total transfer capability computation for multi-area power systems

This paper presents a method for multi-area power system total transfer capability (TTC) computation. This computation takes into account the limits on the line flows, bus voltage magnitude, generator reactive power, voltage stability, as well as the loss of line contingencies. The multi-area TTC problem is solved by using a network decomposition approach based on REI-type network equivalents. Each area uses REI equivalents of external areas to compute its TTC via the continuation power flow (CPF). The choice and updating procedure for the continuation parameter employed by the CPF is implemented in a distributed but coordinated manner. The proposed method leads to potential gains in the computational efficiency with limited data exchanges between areas. The developed procedure is successfully applied to the three-area IEEE 118-bus test system. Numerical comparisons between the integrated and the proposed multi-area solutions are presented for validation.     

Modeling of transfer Characteristics for the broadband power line communication channel

This paper presents a novel approach to model the transfer function of electrical power lines for broadband power line communication. In this approach, the power line is approximated as a transmission line and the two intrinsic parameters, the characteristic impedance and the propagation constants, are derived based on the lumped-element circuit model. Using these intrinsic parameters, the transfer characteristics for a N-branch power distribution network are derived based on the scattering matrix method. Detail derivation of this line model is given in this paper. The model has been verified with practical measurements conducted on actual power networks. It is demonstrated that the model accurately determine the line characteristics under different network configuration and when different household appliances are connected.     

一种动态无线电能传输系统的线圈切换方法

阵列式动态无线电能传输系统因其运行损耗和漏磁更小、灵活性更好而被提出,其工作性能通常取决于发射阵列和接收线圈的结构。提出了一种基于LCC-S补偿拓扑的线圈切换方法,使切换时刻的互感下降和互感突变最小化以提高系统的偏移容忍度;同时,比较了应用该切换方法后,单层和双层发射阵列系统的工作性能。仿真结果显示,虽然双层发射阵列系统的切换控制更复杂,但在接收线圈与发射线圈间发生偏移时其输出功率下降更小,偏移容忍度更高。实验结果证明,该线圈切换方法在实际中有效可行。     

HEV用动力蓄电池的最大充放电性能

结合动力蓄电池在混合动力汽车(HEV)上的应用特点,分析了最大充放电性能的影响因素和描述方法,并使用车辆在城市和高速道路上的运行情况统计数据设计了新的实验程序,包括长持续期(30 s)和短持续期(10 s)两部分.对Optima D34型12 V 55 Ah VRLA电池进行的实验结果表明,长短持续期的充放电性能相差很大.对于HEV,应将长持续期和短持续期性能区分对待.     

浅谈农村配电网的无功补偿

针对农村配电网的具体状况,说明对农村配电网进行低压无功补偿的必要性及其重要意义,并提出了农村配电网无功补偿的最佳方法.最后,对农村配电网无功补偿实例进行分析,比较补偿前后的功率因数、线路输送的无功功率、线路电压损失、年线损电量.比较结果表明：对农村配电网进行无功补偿的节能降损效果非常好.     

基于广义Tellegen定理的小扰动定理在含光伏源的电力系统潮流算法中的应用研究

广义Tellegen定理与物理系统属性无关,只与物理系统所建立的数学模型有关,因而被广泛地应用于电力系统中。考虑光伏并网影响因素,将光伏系统视为PQ节点,在电流注入潮流模型的基础上,利用小扰动定理建立基于广义Tellegen定理的修正方程。利用新的修正方程,以引入光伏源的IEEE30节点测试系统为例进行潮流计算。算例分析表明,该算法的迭代次数及潮流计算速度均有所改善,同时也表明了广义Tellegen定理在含光伏源系统中同样具有重要的应用价值。     

厂用电大功角切换问题探讨

发电厂厂用电工作电源与备用电源属于同一个大电网系统,在一些特殊情况下,两者之间也会有大的功角,导致厂用电切换无法采用并联方式。针对上述问题,结合上安#5机组启动试验,对同系统厂用电大功角切换问题进行了探讨,纠正了某些厂用电切换的不正确观点,提出了合理的切换方式,并经过试验验证其合理性。     

Single variable expressions for the efficiency of a reciprocal power transfer system

The analytical expressions for the efficiency of a reciprocal power transfer system as a function of multiple parameters, that is, the elements of its impedance matrix, already exist. In this work, closed expressions for this efficiency as a function of a single parameter, that is, the extended kQ factor, are derived. This is done for three representative configurations: (i) maximum efficiency; (ii) maximum power transfer; and (iii) conjugate image set‐up. The derived formulas are useful for the design and optimization of different types of power transfer systems. Copyright © 2016 John Wiley & Sons, Ltd.