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This paper presents new prototype of phase-shift transformer parasitic components-assisted ZVS-PWM DC-DC converter with choke input type DC smoothing filter which incorporates ZCS active power switches in series with each rectifier diode in high-frequency transformer secondary-side. This efficient DC-DC converter with a wide ZVS operation range, which is suitable for high-power applications can achieve soft-switching operation under a condition of no circulating current. Its operating principle and unique features are described. The steady-state operating characteristics of the proposed converter topology are illustrated and discussed on the basis of the simulation and some experimental results of 2 kW-40 kHz breadboard.

In this paper, a dynamic mathematical system model of an active three-phase current-source PWM power converter for power factor correction is described on the basis of instantaneous space vectors. The system formulation with the discretized value representation and its control algorithm to achieve the deadbeat responses on state variables of the low pass filter in the utility AC side of this converter are evaluated and discussed from an experimental point of view. The system response is quick and transient oscillations of both source current and capacitor voltage are suppressed effectively, though the state variable in the state feedback is only the current.

A novel zero-voltage and zero-current soft-switching PWM DC-DC converter with low voltage and current stresses is presented in this paper. A new interleaved two switch forward converter topology is developed to minimize circulating current with no additional auxiliary circuits. This converter has many advantages such as less components, better efficiency, high power density and cost effective for high power applications. The principle of operation is illustrated together with steady-state analysis. Moreover, the effectiveness of the proposed converter topology is verified by simulation and experiments.

In AC servomotor drive systems, in some cases, mechanical resonant vibration is generated according to the load conditions. In order to overcome this problem, the authors introduced a load speed feedback method, and then prevented shaft vibration. In order to compensate three control gains which are PI proportional constant, PI integral time constant and load speed feedback gain, the /spl alpha/-parameter ultimate sensitivity method (which is based on the partial model matching method) is proposed. The feature of this method is that both the response and the stability of the AC servomotor drive system are secured by setting only one parameter /spl alpha/. Moreover, a fuzzy reasoning logic algorithm is applied to compensate the parameter /spl alpha/. This proposed control strategy does not require any kind of knowledge or information on system parameter tuning techniques. In this paper, the effectiveness of this advanced autotuning control scheme in an AC servomotor system is evaluated and verified by computer simulation.

This paper presents a new approach to select the low frequency switching optimum PWM patterns in a voltage-source-fed PWM inverter for large capacity utility interactive power conditioner which is to be specified under a condition of minimized THD of output-side line voltage in order to suppress higher harmonic voltage and current components. A feasible test is implemented for utility-power source by using a trially-produced three-phase optimized PWM inverter with low-pass filter using IGBTs which is designed for high power application. It is verified that low frequency switching optimized PWM patterns are effective in minimizing higher harmonic voltage components in terms of a compact low-pass filter. Furthermore, this experimental work provides high efficient and high-power quality DC/AC converter characteristics. It is also proved that this optimum PWM pattern under a low frequency switching scheme has excellent voltage and current waveform performances as compared to voltage-fed inverters operating at various types of PWM patterns.

This paper presents a novel type of voltage-fed quasi-load resonant half-bridge IGBT inverter operating at constant frequency variable power (CFVP) regulation scheme which is more suitable and acceptable for new high-frequency high-power induction-heated (IH) cooking appliances. This application-specific high-frequency inverter using a new generation specially-designed IGBTs can efficiently operate under a principle of ZVS-PWM control strategy. The operating principle of the new inverter circuit is presented together with its power regulation characteristics on the basis of its computer-aided simulation analysis and its experimental results. The steady-state characteristics of cost effective quasi-resonant inverter developed for high-frequency IH cooking appliances such as multi-burner type IH cookers are discussed from a practical point of view.

This paper presents a two-paralleled PWM amplifier using switch-mode power current tracking technique in order to generate a gradient magnetic field in a magnetic resonance imaging (MRI) system. This circuit has 8-IGBTs at their inputs/outputs so as to realize further high-power density. A digital control scheme can minimize the current ripple and improve its control response in the gradient coils. It is proved that the proposed technique will highly enlarge the diagnostic target and improve the image quality of MRI.

This paper presents a high-frequency voltage source-fed load-resonant IGBT inverter with a series-compensated resonant inductor and a high-voltage transformer for ozone generating tube drive, which operates under a principle of the PDM (pulse density modulation) and PWM based power control strategy. The high-frequency inverter is composed of a high-voltage transformer series compensated inductor and ozone generating tube which is based on the silent principle. The state-of-the art efficiency incorporating a voltage-fed type high-frequency load resonant inverter with PDM and PWM control scheme is demonstrated, and its operating principle is described for ozone generating tube driving. It is noted that the pulse density modulated series resonant high-frequency inverter using IGBTs makes an ozone generating system simple, thus leading to improve the ozone generation efficiency. Finally, it is proved in feasible experiment and simulation that the series load-resonant inverter type ozonizer developed in this paper provides stable silent discharge characteristics over a wide output power range from 10% to 100%.

In this paper, an efficient power electronic circuit simulation approach is discussed for a digitally controlled single-phase active PFC converter system. The control circuit simulation control software used in this simulation technique can also be applied to the digital signal processor (DSP) for control implementation of a practical power factor correction power conversion circuit. This circuit simulation technique is based on a circuit equation modeled by substituting control input dependent time-varying resistors in place of active power switches and passive diodes incorporated into the active PFC converter circuit and the system treated here; one state-vector equation described by state-variables for inductors and capacitors together with an algebraic computation method to transform the matrices of the circuit equation into matrices of the state vector equation. In addition, this paper proves the effective performance of a single phase PFC converter with digital control strategy and its performance evaluation on the basis of computer-aided simulation accompanied by experimental results.

This paper presents a pulse amplitude modulated voltage source type series load resonant inverter using the latest high power SITs, which operates a load adaptive tuned frequency-tracking scheme. The zero voltage soft switching resonant inverter using application-specific SITs is demonstrated for industrial induction heating applications, which works under a little higher inverter frequency than a resonant frequency in other to achieve lossless capacitor snubber dependent soft commutation. The resonant frequency tracking control strategy is based upon load adaptive variable frequency operation. The steady-state operating characteristics of this high frequency resonant inverter with a PLL-based resonant frequency tracking control scheme are discussed and experimentally evaluated in addition to its control performance. The actual experiments of SIT series resonant inverter with a high-frequency transformer are carried out and tested under the practical short circuit condition so as to obtain the unknown design data for the protective capability of SITs, and provide the optimum snubber circuit.

This paper describes a new method to select the optimum sinewave PWM patterns of a large-capacity current source-fed active PWM AC/DC converter, its performance evaluations and a practical procedure to design a low-pass filter which is used to suppress higher harmonics flowing into the utility-grid power source. A feasible test is carried out using a 500 kVA active PWM converter which is designed and operated for unique considerations mentioned above. It is verified that these new considerations are more effective to minimize higher harmonic current components flowing into the utility-grid AC line. Furthermore, this experimental work provides highly efficient AC/DC converter characteristics under a unity power factor correction and sinewave line current shaping schemes.

In this paper, an efficient power electronic circuit simulation approach is discussed for a digitally controlled three phase active PFC converter system. The control circuit simulation software used in this simulation technique is also applied to the digital signal processor (DSP) based control implementation of a a practical power factor correction (PFC) power conversion circuit with a digital control scheme. This circuit simulation technique is based on a circuit equation modeled by substituting control input dependent time-varying resistors in place of all the power switches incorporated in the bridge arms of the three phase active PFC converter circuit and system treated here, one state-vector equation described by state-variables for inductors and capacitors, together with an algebraic computation method to transform the matrix of the circuit equation into matrix of the state vector equation. In addition, this paper proves the effectiveness of a voltage-fed three phase PFC converter with a digital control PWM strategy and its performance evaluations on the basis of computer-aided simulation results together with experimental result.

The discontinuous current mode control scheme for AC-DC converter with active power filtering function and power factor correction has widespread use for single phase input power supplies, because this control scheme has practical advantages of simple configuration and cost-effectiveness. But it has not been practically adopted for three phase input power supplies because the characteristics of conventional control scheme have some disadvantages for three phase AC mains. Thus, to improve these disadvantages, a new circuit configuration with a discontinuous current mode control scheme suitable for three phase AC mains is proposed by the authors. This paper presents an operating principle and unique features of the proposed three phase active AC/DC converter topology on the basis of simulation results.

The purpose of this study is to describe a unified simulation technique in order to research and develop digitally-controlled switching mode power converters. The computer-aided simulation procedure is based on a circuit equation modeled by time-varying resistors taking the place of the switches and the diodes, a state equation for the inductors and the capacitors, an algebraic computation method to transform the matrices of the circuit equation into the matrices of the state equation in addition to a control algorithm described and implemented by computer program. Moreover, a flexible and functional computer network environment is discussed from a view point to functionally combine the circuit simulation as well as control programming implemented for the target equipment and its debugging. Finally, as simulation examples, the inverter-fed DC-DC converter with transformer parasitic components is introduced and its experimental results are presented to verify the simulation results.

This paper presents a novel prototype of a new conceptual electromagnetic induction fluid heating appliance series capacitor-compensated load resonant high-frequency inverter with a phase-shifted PWM and power factor correction. Its operating characteristics in the steady-state are illustrated and evaluated on the basis of computer simulation and experimental results. The promising cost-effective application of this electromagnetic induction-heated fluid-heating appliances is proposed, which is more suitable for industrial, chemical and consumer utilizations from a practical point of view.

This paper describes the review of a travelling-wave type ultrasonic motor (T-USM) and a newly-proposed speed tracking controller of T-USM on the basis of computer software-based variable-gain adjustment strategy. Its speed characteristics which are effectively capable of improving speed ripple, speed regulation and speed tracking properties are feasibly demonstrated in experiments as compared with a previously-developed fuzzy-logic speed controller of a T-USM actuated servo system. It is proved that T-USM speed control scheme developed herein is practically acceptable for speed servo direct drive systems.

In this paper, a novel prototype of a zero voltage soft-switching PWM three-phase AC/DC active power converter with a new transformer-assisted quasi-resonant tank DC link (TQRDCL) is presented for power factor correction, sinewave line current shaping and constant output DC voltage regulation. The instantaneous space voltage modulated sinewave line current synthesizing scheme of this high-power factor active rectifier with an instantaneous output DC power feedback loop is implemented by digital signal processor-based software and its related hardware. The simulation results of this soft-switched active rectifier are illustrated and discussed as compared with the other resonant DC link rectifiers and hard-switched active rectifier.

This paper describes a fixed frequency resonant pole-assisted soft-switching PWM inverter-fed DC-DC high-power converter with a HV transformer-coupled stage, which operates under ZVS transition principle. The zero-voltage soft-switching operation of this practical power converter circuit using the latest IGBTs as well as its efficacy are evaluated by a trially-produced 50 kW-100 kV converter system operating at 20 kHz/30 kHz. It is proved from a practical point of view that the switching losses of IGBTs and their electrical dynamic stresses as well as EMI noise can be considerably reduced under HF switching-based phase-shift PWM control a wide load range. The structure and the circuit modeling of HV transformers and the power converter using these transformers are discussed. Simulation results are illustrated and evaluated. Power converter performances are compared with those of previously developed resonant converters.

This paper describes a feasible auto tuning method of DC brushless servomotors which introduces a fuzzy algorithm. This is basically considered as a technique to adjust two gains of a PI compensator under the principle providing an additional reference generator, an observer and fuzzy reasoning with a general-purpose speed control loop including a PI regulator. It is possible to adjust the gains so as to have an optimum level through repeating 10 or more step responses in relation to variations of load inertia and mechanical vibration in addition to control characteristic fluctuations. It is proven, on the basis of experimental results, that DC brushless servomotors can be automatically tuned to provide an optimum response if it is at a completely unstable state experimental results. >

A novel type of quasi-resonant DC link (QRDCL) three-phase voltage source inverter topology operating under a principle of HF transformer-assisted zero voltage switching (ZVS) PWM is presented. The basic operating principle of a transformer-assisted QRDCL (TQRDCL) more suitable for CVCF/UPS, power active filters and switched-mode PWM power converters is presented in this paper. Its operating characteristics are discussed and evaluated in terms of using computer-aided simulation results. An experimental inverter circuit is built and tested for CVCF/UPS systems on the basis of a hard switched PWM inverter.

This paper describes the advanced developments of the voltage-fed series load resonant high-frequency high-power inverter using static induction transistors (SITs) for industrial induction-heating and melting power supply. The load-adaptive variable frequency tuned-controller using PLL, the AC/DC converter for PAM, and protective control schemes are described from a practical viewpoint. In particular, the practical short circuit test of this SIT inverter developed induction heat treatments and is demonstrated in order to obtain the various basic data relating to switching characteristics of large capacity SITs incorporated into this inverter circuit and to design the cost-effective protective circuits of SITs in addition to their optimum snubber circuits for SIT switching-legs.

This paper is concerned with a novel control scheme for full-bridge series-resonant phase-shifted PWM inverter. This control scheme is based upon varying inverter frequency adaptively according to load circuit parameters and phase-shifted angle phi . As a result, switching losses and stresses are minimized under phase-shifted power regulation. High frequency series-resonant inverters using this control technique and static induction power devices are practically applied to a 30 kHz-500 kHz high-power induction heating and melting power supply. The trially-produced inverter breadboards using static induction transistors are successfully demonstrated and discussed from a practical point of view. Finally, zero-voltage soft-switching effects of lossless capacitive snubbers are mentioned for an inverter circuit design which is incorporated into one switching leg of the full-bridge configuration.

This paper presents a novel zero-voltage soft-switching phase-shifted PWM DC-DC full-bridge power converter using power MOSFETs which employs a tapped inductor as the output low-pass filter. By using the tapped low-pass filter inductor and saturable reactors in the rectifier stage, the freewheeling current through the transformer and its primary side circuit can be effectively minimized. In addition, the switching and conduction losses of the DC-DC power converter are substantially reduced as low as those of traditional hard-switching PWM power converters. The principle of this converter operation and analysis are illustrated and discussed. The cost effective performances of the power converter is experimentally confirmed with a 500 W 100 kHz breadboard.