Evaluation of advanced fuzzy logic PSS on analog network simulatorand actual installation on hydro generators

This paper presents the experimental evaluation of an advanced fuzzy logic PSS on the analog network simulator at the Research Laboratory of Kyushu Electric Power Co., Inc. The proposed power system stabilizer (PSS) is set up by using a personal computer with A/D and D/A conversion interfaces. The personal computer based PSS was set on the analog network simulator to evaluate the effectiveness of the advanced fuzzy logic control scheme, and to provide sufficient data for the actual installation of the proposed PSS on hydro-units in the Kyushu Electric Power System. This paper also describes the actual installation of the proposed PSS on hydro-units in the Kyushu Electric Power System for the long term evaluation of the proposed PSS using its prototypes     

Enhancement mode InP MISFET's with sulfide passivation andphoto-CVD grown P3N5 gate insulators

High performance enhancement mode InP MISFET's have been successfully fabricated by using the sulfide passivation for lower interface states and with photo-CVD grown P₃N₅ film used as gate insulator. The MISFET's thus fabricated exhibited exhibited pinch-off behavior with essentially no hysteresis. Furthermore the device showed a superior stability of drain current. Specifically under the gate bias of 2 V for 10⁴ seconds the room temperature drain current was shown to reduce from the initial value merely by 2.9% at the drain voltage of 4 V. The effective electron mobility and extrinsic transconductance are found to be about 2300 cm ²/V·s and 2.7 mS/mm, respectively. The capacitance-voltage characteristics of the sulfide passivated InP MIS diodes show little hysteresis and the minimum density of interface trap states as low as 2.6×10¹⁴/cm² eV has been attained     

Solution and applications of the Lyapunov equation for controlsystems

Recent advances in control systems analysis and design have implied new uses for the Lyapunov equation of the form AX+XA^T+Q=0. Implementation requirements for the incorporation of the use of Lyapunov equations in practical design, however, point out the need for a set of specialized numerical procedures. This special set of numerical procedures must efficiently solve large, sparse Lyapunov equations, solve sets of Lyapunov equations that differ only in the coefficient matrix Q, and provide good low rank estimates of the Lyapunov equation solution X in the case where low rank approximations are applicable. Discussions of the motivations for the solution of these problems and of candidate solution approaches are provided     

Transient behavior of subthreshold characteristics of fullydepleted SOI MOSFETs

It has been found that the subthreshold currents of fully depleted silicon-on-insulator (SOI) MOSFETs show a transient behavior under certain front-gate and back-gate voltage conditions. The cause of this anomaly is explained, and applications for the phenomenon are pointed out. Particularly, a simple way to measure the silicon film thickness is suggested     

Highly compact AC-AC converter achieving a high voltage transferratio

This paper reports a new, highly integrated modular design approach for pulsewidth-modulation AC-AC converters based on a modular phase-bank structure. Novel high-power 3-in-1 integrated bi-directional power modules (IBPM) rated at 1200-V AC and 150 A and the 3-to-1 phase bank circuits have been successfully developed, fabricated and tested. This enables the modularity design of the multiphase converter systems and reduces the critical parasitic inductance. A theoretical analysis of the IBPM's silicon utilization for this new breed of direct power converters has been outlined. A lab prototype at medium power level has been successfully designed, implemented, and tested with good results. A nearly 460-VRMS out voltage at a 1:0.955 voltage transfer ratio, which, perhaps, is the highest performance reported so far in the literature, has been achieved by the novel two-side modulation control system. The converter-fed AC motor system is able to operate over the 0-240 Hz range with inherent regenerative capability and four-quadrant operation. Potential industrial applications are also briefly highlighted in this paper     

Modeling of multilevel converters

In this paper, the imbricated cells multilevel converters are studied and modeled from a control viewpoint. These converters make use of several switches connected in a series, which allows using switches with reduced voltage ratings; these low voltage switches have lower conduction losses and can switch at higher frequency. In addition to this feature common to all converters using series connected switches, the control signals of multilevel converters can be phase shifted to increase the apparent switching frequency and improve the dynamic performances of the whole converter. It is shown that a multilevel inverter leg, composed of p pairs of switches and p-1 capacitors, forms a multivariable nonlinear system that cannot be properly modeled by standard methods such as state-space averaging. The transient behavior of this system depends on the current harmonics and their phase shift with the different control signals. A specific model is detailed, studied, and used to illustrate the properties of these converters. In particular, the natural balancing of the voltage across the switches is demonstrated and the time constants involved in this process are determined     

Development of maraging steel compositions intended for quenching from the liquid state

A. A. Baikov Institute of Metallurgy, Moscow. Ulyanovsk Polytechnic Institute. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 22–25, April, 1992.     

A new method of excitation control based on fuzzy set theory

The synthesis of the structure of the power system stabiliser (PSS) and its parametrization are based entirely on methods of linear system theory. Thus the desired effect of the PSS is limited to a bounded area around one system operating point. The use of a controller based on fuzzy set theory introduces an event controlled excitation of the synchronous machine taking into account the power system operation. The desired response of the fuzzy controller is given by a set of rules which are obtained from the limits of the voltage regulator and the undesired performance of the conventional excitation control. A fuzzy controller has been developed for which simulation results are provided. These results support the concept of a fuzzy controller for the purpose of excitation control. They show that a well designed fuzzy controller is superior to a fast excitation control with an additional PSS     

Two-level optimal output feedback stabilizer design

The paper addresses the design of two-level power system stabilizers using an optimal reduced order model whose state variables are torque angles and speeds. The reduced order model retains their physical meaning and is used to design a two-level linear feedback controller that takes into account the realities and constraints of electrical power systems. The two-level control strategy is used, and a global control signal is generated from the output variables to minimize the effect of interactions. The effectiveness of this controller is evaluated and a multimachine system is given as an example to illustrate the advantages of the proposed method. Responses of the system with a two-level scheme and an optimal reduced order scheme are included for comparative analysis.