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Soft-switching techniques have recently been applied in the design of dc-ac converters, in order to achieve better performance, higher efficiency, and higher power density. A substantial number of new topologies for different applications has been developed, however, the amount of work that has been done in this field is not widely known. This paper is an attempt to classify the soft-switched dc-ac topologies in a simple and generic way. The topology classifications are based on the location of the resonant network (load, inverter bridge, and bus), the characteristic of switching waveforms (zero-voltage switching or zero-current switching), and the type of resonance (series or parallel). Operating principles, performance, and design limitations are discussed. Some possible industrial applications of soft-switched dc-ac converters are addressed. Index Terms - Resonant dc-ac converters, soft-switched dc-ac converters, zero-voltage switching, zero-current switching.

Power electronic converters are periodic time-variant systems, because of their switching operation. The generalized state-space averaging method is a way to model them as time independent systems, defined by a unified set of differential equations, capable of representing circuit waveforms. Therefore, it can be a convenient approach for designing controllers to be applied to switched converters. This brief shows that the generalized state-space averaging method works well only within specific converter topologies and parametric limits, where the model approximation order is not defined by the topology number of components. This point is illustrated with detailed examples from several basic dc/dc converter topologies. Index Terms - Generalized state-space averaging, power converter modeling.

In this paper methods of design and application of integrated inductor-capacitor-transformer (LCT) are presented. A generalized modeling approach is also described. On the basis of this model and by using practical data, a CAD software is developed for LCT. Several integrated LC and LCT samples were designed, built, and tested. Finally, a resonant converter, using integrated LCT, was built and tested.

The stator winding current commutation timing is the central subject of switched reluctance motor control. The direct use of coil inductance information for current commutation is introduced in this paper. The drawbacks of position-based commutation, in the presence of drifting electrical parameters, are overcome by using the instantaneous coil inductance information. Algorithms to optimize torque using this approach are also presented in this paper.

Higher torque ripple is one of the few drawbacks of switched reluctance motor (SRM) drives which otherwise possess excellent characteristics for applications in many commercial drives. This paper begins with an extensive review of torque ripple reduction methods that appear in the literature and then presents a new strategy of PWM current control for smooth operation of the drive. This method includes a current control strategy during commutation when torque ripple minimization is of utmost importance.

The bang-bang controlled capacitor coupled converter ([C.sup.3]) is described in this paper. Due to the converter's inherent commutating property, the [C.sup.3] can accommodate thyristors as well as high-power gate turn-off switches, due to zero-current switching transitions. The zero-current switching is achieved at no current stress increase, therefore, the topology is considered appropriate for high-power processing. DC and small signal ac models are derived for the bang-bang controlled [C.sup.3], a design procedure is proposed, and simulation results are discussed. Finally, oscillograms from a proof of principle prototype circuit are presented.

A new discrete position sensor elimination technique for a sinusoidally wound synchronous reluctance motor drive is presented. The proposed technique determines the rotor position at zero crossing of the phase currents. The rotor position between the zero crossings is determined by applying extrapolation. The proposed technique works well at all speeds, including zero speed. This technique can be used in both vector controlled and conventional constant Volts/Hertz type of motor controllers.

This paper reports a rotor position sensing technique for synchronous reluctance motors (SynRM's) without using any discrete position sensors. An accuracy analysis of the new indirect SynRM position sensing scheme is presented. The analysis breaks down the position error to its fundamental causes in the position sensing scheme. The same basic approach can be taken to evaluate other Synrm rotor position sensing schemes.

Switched reluctance motor (SRM) optimal control parameters, which maximize torque per ampere, are calculated using a dynamic SRM model. In order to include the effect of the magnetic nonlinearity, static torque and flux-linkage data are used in the dynamic model. The static data are generated experimentally. To recreate these control parameters, online, artificial neural networks are used. Two separate networks are trained. One is trained with the low-speed control parameters for torque control at low speed, while the other is trained with the high-speed control parameters for torque control at high speed. The speed at which the SRM makes a transition from chopping control to single-pulse operation (i.e., low-speed to high-speed operation), commonly referred to as base speed, is torque (current) dependent. A small table is maintained in the controller to identify the base speed for different torque demands. When the motor exceeds the base speed for a certain torque demand, the controller switches from the low-speed neural network to the high-speed neural network and vice versa. It is also shown that the SRM is capable of producing an extended constant-horsepower operation with this optimal control. The power factor (the energy ratio) is shown to improve in this extended speed constant-horsepower range. Simulation and experimental results are presented to demonstrate the effectiveness of the proposed control scheme. Index Terms--Electrical drives, neural network control, switched reluctance machine.

Land vehicles need their drivetrain to operate entirely in constant power in order to meet their operational constraints, such as initial acceleration and gradability, with minimum power rating. The internal combustion engine (ICE) is inappropriate for producing this torque--speed profile. Therefore, multiple gear transmission is necessary with the ICE in a vehicle. Some electric machines, if designed and controlled appropriately, are capable of producing an extended constant power range. The purpose of this paper is to investigate the capabilities of the switched reluctance motor (SRM) for electric vehicle and hybrid electric vehicle applications. This investigation will be carried out in two steps. The first step involves the machine design and the finite-element analysis to obtain the static characteristic of the motor. In the second step, the finite-element field solutions are used in the development of a nonlinear model to investigate the dynamic performance of the designed motor. Several 8-6 and 6-4 SRM geometries will be investigated. Effects of different stator and rotor pole widths and pole heights on the steady state as well as on the dynamic performance of the motor will be studied. The air gap for each motor will be made as small as manufacturally possible. The aspects of performance to be compared for each design motor are: 1) the range of the constant power operation; 2) drive efficiency in this extended constant power range; 3) the power factor in this operational range; and 4) the short time overload capability. The first performance index defines the rated power of the motor. The longer the constant power range, the lower is the power rating for the same vehicle performance. Hence, special emphasis will be given to this. In the high-speed operation of the SRM, there will be considerable phase overlapping. Hence, thicker back iron than usual might be needed to prevent the back iron from saturating. However, since flux peaking of each phase occurs at different rotor positions, the phase overlapping might not necessitate special designing of the back iron. However, the possibility of the back iron being saturated will not be neglected and will be investigated. The optimal control parameters of the SRM, which maximize the constant power range with maximum torque per ampere, will be calculated. A performance comparison will be made for this optimal operation. Simulation results of the designed SRM will be presented for vehicle acceleration. To demonstrate the capability of the SRM in producing an extended constant power range, experimental results will be presented, however, for a reduced size motor available commercially. Index Terms--Constant power range, electric vehicle, hybrid electric vehicle, switched reluctance motor drive.