New designs of low/high‐pass and mid‐pass/stop FIR digital filters

New designs of highly efficient low/high‐ and mid‐pass/stop (centre‐symmetric band‐pass/stop) FIR non‐recursive digital filters are presented. The designs are based on the modulation property of DFT, applied to the already presented MAXFLAT halfband low‐pass filters. The presented filters have explicit formulas for their tap‐coefficients, and therefore are very easy to design. They have highly smooth frequency response and wider transition regions like MAXFLAT filters. The design formulae are modified to give new classes of low/high‐ and mid‐pass/stop filters, for which, like in equiripple filters, the transition bandwidth can be reduced by increasing the size of ripple on magnitude response. It is shown, with the help of design examples, that the performance of these filters is comparable to that of equiripple filters. Copyright © 2001 John Wiley & Sons, Ltd.     

Explicit design formulas for current‐mode leap‐frog OTA‐C filters and 300 MHz CMOS seventh‐order linear phase filter

The leap‐frog (LF) configuration is an important structure in analogue filter design. Voltage‐mode LF OTA‐C filters have recently been studied in the literature; however, general explicit formulas do not exist for current‐mode LF OTA‐C filters and there is also need for current‐mode LF‐based OTA‐C structures for realization of arbitrary transmission zeros. Three current‐mode OTA‐C structures are presented, including the basic LF structure and LF filters with an input distributor or an output summer. They can realize all‐pole characteristics and functions with arbitrary transmission zeros. Explicit design formulas are derived directly from these structures for the synthesis of, respectively, all‐pole and arbitrary zero filter characteristics of up to the sixth order. The filter structures are regular and the design formulas are straightforward to use. As an illustrative example, a 300 MHz seventh‐order linear phase low‐pass filter with zeros is presented. The filter is implemented using a fully differential linear operational transconductance amplifier (OTA) based on a source degeneration topology. Simulations in a standard TSMC 0.18µm CMOS process with 2.5 V power supply have shown that the cutoff frequency of the filter ranges from 260 to 320 MHz, group delay ripple is about 4.5% over the whole tuning range, noise of the filter is 420nA/√Hz, dynamic range is 66 dB and power consumption is 200 mW. Copyright © 2008 John Wiley & Sons, Ltd.     

Transient current analysis of induction generators for wind power generating system

In this paper we present a transient current analysis of induction generators used in a wind power system before and after three‐phase fault conditions. First, the basic equations of an induction generator connected to an infinite bus are developed and then transient current analysis formulas are derived for a three‐phase fault before and after fault clearance. We also determine the initial phase angle for the three‐phase fault or the restoration phase angle of the power supply voltages and the time at which the maximum or minimum transient currents flow in the system. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(1): 38–45, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10319     

A control strategy for active filters using quasi‐instantaneous positive sequence extraction filters

A novel control strategy for active filters, employing quasi‐instantaneous positive sequence extraction of utility voltage, can be useful in harmonic polluted and/or imbalanced utility voltage. In this paper, the authors examined its transient response, its performance under the change of fundamental frequency of utility voltage and its performance under utility voltage with harmonics and unbalance. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(1): 54–65, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10307     

Log‐domain linear transformation filters revised: improved building blocks and comparison results

A method for designing high‐order log‐domain filters has already been proposed in the literature based on the concept of the classical linear transformation (LT) filters. For this purpose, a substitution table containing the log‐domain LT equivalent of each passive element has been introduced. Drawbacks of the log‐domain filter topologies derived according to this table are the following: (a) a dc offset current appears at the output of all pole filters and (b) dc instability is observed in the case of the substitution of LC resonators. In addition, an alternative technique already proposed for simulating filters with LC resonators is valid only under small‐signal conditions. In order to overcome the aforementioned problems, new log‐domain LT equivalents of a number of passive elements are introduced in this paper. The correct operation of the novel blocks has been verified through simulation results. Also, a comparison concerning the behaviour of the log‐domain LT filters and that of the filters derived according to the leapfrog and the wave methods has also been performed. Copyright © 2007 John Wiley & Sons, Ltd.     

Generation of current mode filters using NAM expansion

Systematic synthesis method to generate a family of current mode band‐pass–low‐pass circuits based on nodal admittance matrix (NAM) expansion is given. Eight equivalent circuits are obtained, five of them are new. Each of the generated circuits uses two grounded capacitors and three grounded resistors and two balanced output current conveyor (BOCCII) or two balanced output inverting current conveyor (BOICCII) or a combination of the two types. Generation of a low input impedance current mode band‐pass–low‐pass circuits based on NAM expansion results in 16 equivalent circuits. The NAM expansion is also used to generate 32 equivalent current mode universal filters using four BOCCII or BOICCII or a combination of the two types. Copyright © 2010 John Wiley & Sons, Ltd.     

Analysis of discontinuities in rectangular ducts and higher order mode excitations using TLM and FEM methods

In acoustic waveguide, it is believed that higher order modes have a dramatic effect on the behaviour of the global acoustic waves when the frequency of the source is above the cut‐off frequency of the duct. In this paper, we are going to study the influence of the discontinuities on the excitation and the propagation of higher order modes in symmetrical and non‐symmetrical ducts using theoretical analysis and numerical simulations. As for numerical simulations, transmission line matrix (TLM) method and finite element method (FEM) will be used. Moreover, we will try here to compare the two numerical methods, showing their advantages and disadvantages. The transfer functions of symmetrical and non‐symmetrical ducts will also be shown and discussed as well as numerical simulations of the acoustic pressure into the duct in three‐dimensional (3‐D) system. 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.     

Performance prediction of a hybrid‐excitation synchronous machine with axially arranged excitation poles and permanent‐magnet poles

This paper presents a method of predicting the steady‐state performance of a new hybrid‐excitation synchronous machine (HESM) theoretically. The field pole of this HESM is axially divided into two parts; one is an excitation part and the other a permanent‐magnet (PM) part. A nonlinear equivalent circuit, which can include the saliency of the rotor and the magnetic saturation due to the iron core, is derived. Based on this equivalent circuit, the steady‐state performance of the HESM is calculated, and the results are confirmed through experiments. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(2): 43–49, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20033     

高压直流输电系统直流滤波器的设计

直流滤波器是抑制高压直流输电(HVDC)直流侧谐波的最有效、最典型且应用最广泛的设施,其设计的优劣既牵涉到HVDC系统的运行性能和安全稳定性,又关系到整个系统总投资的高低。为深入研究直流滤波器的设计,首先总结了现有HVDC工程直流滤波器的配置现状,在分析直流滤波器电路结构和阻抗-频率特性的基础上,忽略电阻的影响,根据调谐点滤波器阻抗Z=0,推导了双调谐滤波器和三调谐滤波器设计的精确公式,提出了详细的参数设计方法,而公式有多组解,选取最大的串联谐振频率rω1那一组解,此时滤波器阻抗-频率特性在谐振点附近的曲线比较平坦,滤波效果最好。然后以HVDC实际工程直流滤波器参数进行验证,结果表明所提出的公式完全正确,可为直流滤波器的参数设计提供工程指导。最后以满足等效干扰电流为基本要求,对某HVDC工程的直流滤波器进行了实例设计。     

Analysis of transient surge transmission characteristics of electronic circuits due to arc discharge generated with disconnector on/off in GIS

In gas‐insulated switchgear (GIS), the arc discharge due to a disconnector on/off generates fast transient surges, which can be the cause of malfunction and damage to electronic devices such as microprocessors and AD converters, if the fast transient surge exceeds a specified level. In this paper, it is shown that the comparison and evaluation are realized between the measured results and the calculated ones of fast transient surges generated due to a disconnector on/off in 300 kV GIS by adopting the evaluation index. The calculation is carried out by applying the authors' proposed equivalent circuits using distributed constant lines in consideration of the structure of GIS and a newly developed divided‐type voltage sensor. Also, it is found by using the evaluation index that the measured results and the calculated results are in good agreement with each other. Furthermore, the cause of the occurrence of the peak of the evaluation index is clarified by analyzing the equivalent circuit. And the signal conditioning using a low‐pass filter for electronics circuits connecting the divided‐type voltage sensor is designed. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(2): 34–42, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10360     

On the realization of current transfer function using voltage amplifiers

Current transfer function is a feature of current‐mode filters. Current‐mode filters have so far been realized principally using current amplifiers and current conveyors. Some current‐mode filter architecture using operational amplifiers have also been reported. In this article it is shown that by using the principles of transposed network and nullor model for the active device, a current transfer function can be realized in a very simple way using a voltage amplifier, i.e. operational amplifier (OA). The key concept is the knowledge that each ideal (i.e. infinite gain) controlled source is exactly equivalent to a nullor. Thus, a voltage‐mode filter implemented using an ideal three terminal (output, input and ground) OA can be very easily converted to a current‐mode filter using the same OA. The principle has been illustrated by considering single‐OA‐ and multi‐OA‐based second‐order voltage‐mode filters. SPICE simulation results are provided to validate the theoretical concept. Copyright © 2006 John Wiley & Sons, Ltd.     

The Kalman filter in the context of adaptive filter theory

Model‐based adaptive algorithms are usually derived with the help of the Wiener‐Hopf equation based on empirical statistics. They are often interpreted as an extension to their model‐independent counterparts, i.e. the stochastic‐gradient based adaptive filters. As a consequence, it is generally not considered worthwhile to show the analogy between Kalman filters and adaptive filters. This article pursues just these two goals. First, it tries to remove the notion that the Kalman filter is a complicated and unnecessary detour from the subject of adaptive filtering. Second, the advantage of a deeper insight into adaptive algorithms from Kalman's viewpoint emerges from our treatment. Based on a time‐varying FIR filter model, the Kalman filter is completely derived and serves as a general framework for the special case of model‐based adaptive filters. Copyright © 2004 John Wiley & Sons, Ltd.     

Monotonic,critical monotonic,and nearly monotonic low‐pass filters designed by using the parity relation for Jacobi polynomials

A new class of continuous‐time low‐pass filter using a set of Jacobi polynomials, with all transmission zeros at infinity, is described. The Jacobi polynomial has been adapted by using the parity relation for Jacobi polynomials in order to be used as a filter approximating function. The resulting class of polynomials is referred to as a pseudo Jacobi polynomials, because they are not orthogonal. The obtained magnitude response of these filters is more general than the magnitude response of the classical ultraspherical filter, because of one additional degree of freedom available in pseudo Jacobi polynomials. This additional parameter may be used to obtain a magnitude response having either smaller passband ripples or sharper cutoff slope. Monotonic, critical monotonic, or nearly monotonic passband filter approximating functions can be also generated. It is shown that proposed pseudo Jacobi polynomial filter approximation also includes the Chebyshev filter of the first kind, the Chebyshev filter of the second kind, the Legendre filter, and many transitional filter approximations, as its special cases. Several examples are presented, and detailed formulas including the practical suggestions for their efficient implementation are also provided. The proposed nearly monotonic filter is compared with the least‐square‐monotonic filters, designed as critical monotonic, in details. The advantages of the new filters are discussed. Copyright © 2017 John Wiley & Sons, Ltd.     

Analysis of a low‐complexity change detection scheme

In many applications, for example in fault detection, it is important to discriminate between changes in system dynamics and abrupt changes in the disturbance level. A new low‐complexity change detection method based on the average behaviour of the estimated impulse response parameters of the normalized least mean‐square (NLMS) algorithm is presented. The solution includes second‐order Kalman filters based on exponential transient models for parameter convergence. Explicit formulas for time‐varying state covariances and Kalman gains are given. The receiver operating characteristics (ROC) is also computed and used for performance evaluation. The effects of the approximations in the averaging analysis that occur for high adaptation gains are handled with an experimental ROC analysis. Copyright © 2000 John Wiley & Sons, Ltd.     

Active device‐less voltage equalization charger using capacitors,diodes, and an AC power source

Conventional cell/module voltage equalizers or equalization chargers based on traditional DC‐DC converters require numerous switches or transformers as the number of series connections increases; therefore, their cost and complexity tend to increase and their reliability decreases as the number of connections increases. This paper proposes a novel voltage equalization charger that consists only of passive components such as capacitors, diodes, and a transformer. The fundamental operating principle, major features, and derivation of equivalent DC circuits are presented. A symmetrical configuration is also proposed to mitigate the RMS current flowing through energy storage cells in the charging process. Simulations and experimental charging and cycle tests were performed on series‐connected electric double‐layer capacitor modules to demonstrate the equalization performance. The experimental and simulation results were in good agreement, and the voltage imbalances were gradually eliminated as time elapsed even during charge‐discharge cycling. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 181(3): 39‐48, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21288     

Midterm stability evaluation of wide‐area power system using synchronized phasor measurements

In recent years, the PMU (Phasor Measurement Unit) has received a great deal of attention as a synchronized measurement system of power systems. Synchronized phasor angles obtained by the PMU provide valuable information for evaluating the stability of a bulk power system. The aspect of instability phenomena during midterm tends to be more complicated, and the stability analysis using the synchronized phasor measurements is effective in order to keep a complicated power system stable. This paper proposes a midterm stability evaluation method for the wide‐area power system using synchronized phasor measurements. By clustering the power system to some coherent groups, step‐out is predicted on the basis of an aggregated two‐machine equivalent power system. The midterm stability of a longitudinal power system model of Japan's 60‐Hz systems constructed by a hybrid‐type power system simulator is practically evaluated using the proposed method. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 147(1): 25–32, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10274     

Design of square‐root domain filters by substituting the passive elements of the prototype filter by their equivalents

A novel technique for designing square‐root domain (SRD) filters is introduced in this paper. The concept of the proposed method is based on the substitution of the passive elements of the corresponding prototype filter by their SRD equivalents. The signal processing performed by the proposed SRD equivalents achieves that the voltage at each terminal of the SRD equivalent is the compressed version of the voltage at the corresponding terminal of the passive element, and that the current that flows through the SRD equivalent is the same as that flows through the passive element. The main attractive characteristic of the proposed method is that a quick procedure for designing SRD filters is offered. The validity of the proposed technique was verified by studying the behaviour of a 5th‐order SRD low‐pass filter. In order to demonstrate the benefits offered by the proposed technique, a SRD leapfrog filter was also designed and its performance is compared with that of the active filter that topologically simulates the same prototype filter. Copyright © 2007 John Wiley & Sons, Ltd.