EMTP simulation of SLF interrupting performance for two serially connected arcs with different arc parameters

This paper shows the calculation of SLF interrupting performance for two serially connected Mayr‐type arc models with different arc parameters by using EMTP‐ATP Models. Arc model 1, assuming an air circuit breaker, has large arc time constant and large arc power loss. Arc model 2, assuming a vacuum circuit breaker, has small arc time constant and small arc power loss. It was not possible for arc model 1 to interrupt 300 kV‐63 kA‐90% SLF by itself. However, by connecting these arc models in series, interruption became successful, even if arc model 2 was reignited at low voltage a few microseconds after current zero. These computations suggested that serial connection of the two circuit breakers with different breaking characteristics would give a totally excellent circuit breaker by making the best use of advantages of each circuit breaker. EMTP‐ATP Models were very useful in solving the arc models, which are expressed by differential equations and coupled with the electric circuit. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(4): 25–33, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10020     

A general tool for circuit analysis based on wavelet transform

This paper deals with a generalized method for the time‐domain solution of electrical networks. The aim is to explore a new technique for the numerical simulation of circuits considering linear, time‐varying and non‐linear cases. By using the wavelet transform of the electrical quantities, differentiation and integration in the time domain are replaced by matrix multiplication. Then, the classical circuit differential equations obtained by mesh‐current, node‐voltage or state variables methods are transformed in algebraic equations. The numerical efficiency of wavelets makes the method effective for a fast and reliable numerical circuit simulation. Comparisons with analytical solutions and PSPICE simulations are presented in order to evaluate the numerical characteristics of the proposed method. Copyright © 2000 John Wiley & Sons, Ltd.     

Non‐linear circuit modelling via nodal methods

We discuss in this paper several interrelated nodal methods for setting up the equations of non‐linear, lumped electrical circuits. A rather exhaustive framework is presented, aimed at surveying different approaches and terminologies in a comprehensive manner. This framework includes charge‐oriented, conventional, and hybrid systems. Special attention is paid to so‐called augmented node analysis (ANA) models, which somehow articulate the tableau and modified node analysis (MNA) approaches to non‐linear circuit modelling. We use a differential–algebraic formalism and, extending previous results proved in the MNA context, we provide index‐1 conditions for augmented systems, which are shown to be transferred to tableau models. This approach gives, in particular, precise conditions for the feasibility of certain state‐space reductions. We work with very general assumptions on device characteristics; in particular, our approach comprises a wide range of resistive devices, going beyond voltage‐controlled ones. Copyright © 2005 John Wiley & Sons, Ltd.     

A coordinated control of voltage and reactive power by heuristicmodeling and approximate reasoning

A flexible approximate reasoning approach to coordinated control of voltage and reactive power in order to enhance the voltage security of an electric power system is presented. The control strategy is expressed by simple rules, which measure the proximity of system state to certain operating conditions, and utilize linear equations to obtain the effective control models. The desired control actions are determined by considering several criteria at the same time. The procedure has been applied to a model system in order to verify its effectiveness. The simulation results show the advantages of this fuzzy modeling approach over conventional expert systems for voltage-reactive-power control     

无损耗电阻器的实现及其在电力系统中的应用

本文介绍无损耗电阻器的实现原、类别及其在电力系统中的重要用途。它可以组成：（１）新型短路电流限制器,该设备能迅速将短路电流的冲击值等限制下来,将短路故障消灭于其萌发阶段,以确保系统电器设备的安全运行,并可提高系统的稳定性;（２）它可组成新型交流断路器;（３）它更可制成新型直流高压断路器。这种直流断路器使直流输电可以形成闭式电网来运行。特别值得指出的是：该断路器竟可直接利用同级电压的交流断路器来制造     

Comparison of Switching Loss of Single‐Phase Step‐Up/Step‐Down Bidirectional Converter with Voltage‐Fed/Current‐Fed Hybrid‐Type Operation

Electric energy storage systems are very important as one of the solutions to global warming. Step‐up/step‐down characteristics are required for electric energy storage systems. In addition, such systems must have high efficiency, low cost, and small scale. Therefore, the authors proposed a single‐phase step‐up/step‐down bidirectional converter with voltage‐fed and current‐fed hybrid‐type operation. The proposed converter consists of a two‐quadrant dc–dc converter and a single‐phase voltage‐fed converter. The circuit has several advantages such as low switching loss, use of very small capacitance, and so on. In this paper, the authors compare a comparison of the switching losses with a simple analysis.     

Efficient starting point of load-flow equations

Load flow is the solution of the static operating state of an electric power transmission system and is the most frequently computer-performed power system calculation.

In this paper, an initial linear solution of the load-flow equations is developed taking into consideration the decoupling principles, i.e. the active power depends on the voltage angle and the reactive power on the voltage magnitude.

This initial decoupled linear solution is utilized as the starting point for the solution of the load-flow equations using such numerical methods as the fast linear method, Newton's decoupled method and the Gauss—Seidel method. Its performance is compared with that of the flat starting point (V = 1.0 p.u., D = 0.0 radians). The test power systems used to test its performance are these of the standard 14, 30, 57 nodes IEEE test power systems.     

A matrix pencil approach to the local stability analysis of non‐linear circuits

This paper addresses local stability issues in non‐linear circuits via matrix pencil theory. The limitations of the state–space approach in circuit modelling have led to semistate formulations, currently framed within the context of differential‐algebraic equations (DAEs). Stability results for these DAE models can be stated in terms of matrix pencils, avoiding the need for state–space reductions which are not advisable in actual circuit simulation problems. The stability results here presented are applied to electrical circuits containing non‐linear devices such as Josephson junctions or MOS transistors. Copyright © 2004 John Wiley & Sons, Ltd.     

An interval algorithm for finding all solutions of non‐linear resistive circuits

In this letter, an efficient algorithm is proposed for finding all solutions of non‐linear (not piecewise‐linear) resistive circuits. This algorithm is based on interval analysis, the dual simplex method, and the contraction methods. By numerical examples, it is shown that the proposed algorithm could find all solutions of systems of 500–700 non‐linear circuit equations in acceptable computation time. Copyright © 2004 John Wiley & Sons, Ltd.     

Torque regulation of multiphase induction motors under symmetrical fault condition

Multiphase induction motors are popular for electric ship propulsion systems because of their superior fault‐tolerant capability. In this paper, a torque regulation method for multiphase induction motors with symmetrical fault is investigated under the precondition of constant current amplitude. On the basis of parameter recalculation, the relationships between the torque, input voltage magnitude, and frequency are analyzed by using the equivalent circuit. The maximum torque and the corresponding input voltage magnitude and frequency are predicted. Finally, the developed torque regulation method is validated by experimental test on a 45‐kW prototype 15‐phase induction machine under a symmetrical 5‐phase open‐circuit condition. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Voltage Stability Analysis in Electric Power Systems by Nonlinear Programming

ABSTRACT

Voltage instability phenomena in electric power systems are characterized by a progressive lowering of receiving end voltages beyond their nominal values.Particularly, a voltage collapse occurs at a load node when the active power fed from the load reaches a maximum value. On the basis of this observation a new method for the analysis of the voltage stability in power systems is presented.The suggested approach derives the critical voltage stability conditions for the system through the solution, by non linear programming techniques, of a non linear constrained optimization problem which considers as objective function the active power demand at a prefixed load node and as constraints the active and reactive power balance equations at the system nodes and the practical operating capabilities of generators. The method proves suitable for a rigorous individualization of the factors which affect voltage instability phenomena and can advantageously be used for planning and operation of electric power systems. Two examples are presented to illustrate the validity and the usefulness of the suggested approach.     

Self-heating in a coupled thermo-electric circuit-device model

The self-heating of a coupled thermo-electric circuit-semiconductor system is modeled and numerically simulated. The system consists of semiconductor devices, an electric network with resistors, capacitors, inductors, and voltage sources, and a thermal network. The flow of the charge carriers is described by the energy-transport equations coupled to a heat equation for the lattice temperature. The electric circuit is modeled by the network equations from modified nodal analysis coupled to a thermal network describing the evolution of the temperatures in the lumped and distributed circuit elements. The three subsystems are coupled through thermo-electric, electric circuit-device, and thermal network-device interface conditions. The resulting system of nonlinear partial differential-algebraic equations is discretized in time by the 2-stage backward difference formula and in space by a mixed finite-element method. Numerical simulations of a one-dimensional ballistic diode and a frequency multiplier circuit containing a pn-junction diode illustrate the heating of the semiconductor device and circuit resistors.     

An Equalization Time Reduction Method Using a Pseudo‐Random Number Sequence for a Cell Voltage Equalization Circuit with an LC Series Circuit

When the cells of energy storage devices such as electric double‐layer capacitors are connected in series, it results in voltage imbalance in each cell because of the nonuniform properties of the individual cells. In a previous research, the authors proposed a novel cell voltage equalization circuit using an LC series circuit, and they examined the effectiveness of this circuit. However, the characteristics of the cell voltage equalization operation depend on each cell voltage difference. Therefore, the proposed circuit has a disadvantage that the equalization time tends to be longer than other cell voltage equalization circuits with a boosting circuit. This paper proposes an equalization time reduction method that uses a pseudo‐random number sequence generated by the linear congruential generators. The proposed method can reduce the average equalization time without adding any other active or passive elements. The effectiveness of the proposed method is verified through the experimental results. According to the experimental results, the proposed equalization time reduction method reduces the equalization time to 86.5% of the conventional method.     

Analysis of parasitic quantum effects in classical CMOS circuits

In the mesoscopic regime, the MOS device performance is affected by gate‐induced quantization effects leading to a loss of transconductance and threshold voltage shift and gate leakage tunnelling currents degrading the overall device performance. We discuss the expected impact of quantum effects in highly down scaled CMOS circuits. Based on 1‐d numerical simulations for transport in mesoscopic systems, we set up Spice circuit models. The Spice models rebuild the influence of quantum effects; and the functionality of classical circuit concepts can be ‘tested’ in their robustness against these effects. A few circuit examples will be given. Copyright © 2005 John Wiley & Sons, Ltd.     

基于MATLAB的高压断路器触头电寿命仿真研究

介绍了高压断路器触头电寿命仿真的意义，研究了各种短路故障对断路器电寿命的影响。采用先进的仿真软件工具MATLAB中的电力系统仿真工具箱，建立各元件的数学模型，最后组成仿真模块，对复杂电力系统断路器运行进行动态仿真。仿真结果表明，不同的短路故障形式和不同的短路故障部位对触头寿命影响很大，本研究对电力系统高压断路器的运行有积极意义。     

Hybrid DC–DC converter with high efficiency,wide ZVS range,and less output inductance

In this paper, a new soft switching direct current (DC)–DC converter with low circulating current, wide zero voltage switching range, and reduced output inductor is presented for electric vehicle or plug‐in hybrid electric vehicle battery charger application. The proposed high‐frequency link DC–DC converter includes two resonant circuits and one full‐bridge phase‐shift pulse‐width modulation circuit with shared power switches in leading and lagging legs. Series resonant converters are operated at fixed switching frequency to extend the zero voltage switching range of power switches. Passive snubber circuit using one clamp capacitor and two rectifier diodes at the secondary side is adopted to reduce the primary current of full‐bridge converter to zero during the freewheeling interval. Hence, the circulating current on the primary side is eliminated in the proposed converter. In the same time, the voltage across the output inductor is also decreased so that the output inductance can be reduced compared with the output inductance in conventional full‐bridge converter. Finally, experiments are presented for a 1.33‐kW prototype circuit converting 380 V input to an output voltage of 300–420 V/3.5 A for battery charger applications. Copyright © 2015 John Wiley & Sons, Ltd.     

Operating tests with a 6.6‐kV reduced model of rectifying‐type fault current limiter system

Fault current limiters (FCL) are extensively needed to suppress fault currents, particularly for trunk power systems heavily connected to high‐voltage transmission lines, such as the 500‐kV‐class power system which constitutes the nucleus of the electric power system. In this paper, we propose a new FCL system, consisting of solid‐state diodes, a dc coil, and a bypass ac coil, and describe the specifications of the trunk electric power system and the 6.6‐kV reduction model. Also we propose a 6.6‐kV trial model and describe an efficiency test with a short circuit generator, which we have trial produced for the new FCL system. © 2001 Scripta Technica, Electr Eng Jpn, 137(3): 29–36, 2001