Yasuyuki Nishida

A predictive instantaneous-current PWM controlled rectifier with AC-side harmonic current reduction

A new single-phase bridge rectifier controlled by a predictive instantaneous-current PWM control scheme for reducing AC-side harmonic currents and improving power factor is proposed. The rectifier can operate at the unity displacement power factor and has fast response to an input signal as a current reference. The effect of the DC-side voltage ripples is taken into account. The paper describes three digital control schemes for such rectifiers and presents experimental and simulation studies on steady-state and dynamic performances of the rectifier. The effectiveness of the control schemes is confirmed by experiments and simulations. The proposed rectifier can be used for applications such as UPS systems and static VAr compensators.

Predictive instantaneous value controlled PWM inverter for UPS

A microprocessor-based pulse-width modulation (PWM) inverter (UPS) that obtains high-quality sinusoidal output voltage even under a rectifier load is proposed for uninterruptible power supplies. The proposed PWM inverter system uses a closed-loop digital feedback with a sinusoidal reference, and the PWM pattern is determined at every sampling instant. A modification that increases the maximum pulse width, which is limited by the computation time in conventional digital approaches, to provide larger output voltage and a repetitive control technique are applied to the proposed control system. A larger maximum pulse width, stable operation, high output voltage accuracy, very low output voltage distortion, and very fast response are realized.<<ETX>>

A new instantaneous-current controller for three-phase buck-boost and buck converters with PFC operation

A new instantaneous-current controller for three-phase buck-boost and buck power converters with power factor correction (PFC) operation is proposed. Based on the idea of a three-phase equivalent pulse-current-source with delta-form, the controller simply generates three-phase switching-patterns for PFC operation. Additionally, the controller employs a pulse-space-modulation technique to compensate modulation errors caused by ripples in the DC-inductor current and to reduce the size of the inductor. The modulation technique is further extended to realize a discontinuous-switching scheme to reduce switching losses. The paper describes the theory and the implementations. To show the validity of the theory, experimental waveforms, spectra and static characteristics, obtained by a 3 kW setup are introduced. Finally, conclusions are drawn and abilities and problems for future study are described.<<ETX>>

A new simple topology for three-phase buck-mode PFC rectifier

The author proposes a new and simple topology for three-phase buck-mode PFC-rectifier which obtains a very high input-power-factor, high-quality input-line-currents and a regulated output-voltage in buck-mode-range. The proposed rectifier, obtained by modifying a conventional simple topology for three-phase boost-mode PFC, employs new principal of current-synthesis and a simple and unique modulation-technique to improve the input-characteristics. In this paper, the proposed topology, principal of the current-synthesis and the modulation-technique are introduced. Then, experimental results obtained a 2 kW prototype-converter are shown to confirm the validity of the theory.

A simplified discontinuous-switching-modulation for three-phase current-fed PFC-converters and experimental study for the effects

The authors propose a new modulation scheme to obtain discontinuous switching in instantaneous current-controlled three-phase buck and buck-boost power factor correction (PFC) power converters. Since the proposed discontinuous switching modulation eliminates the switching actions which produce the highest energy dissipation in modulation period, the average switching loss is reduced by half. The loss reduction effect is analyzed theoretically and experimentally. Further, a simple scheme to generate the discontinuous switching patterns in the instantaneous current controller is introduced. The validity of the theory and applicability of the discontinuous switching modulation in practice are confirmed through experimental results obtained from 2 kW prototype power converters.

High power factor PWM rectifiers with an analog pulse-width predictor

A single-phase PWM bridge rectifier controlled by a pulse-width predictor (PWP) to operate switching devices to realize a high power factor and to reduce the AC-side current harmonics is proposed. The PWP provides instantaneous current central with either a constant frequency carrier or a piecewisely fixed multiple-frequency carrier in one source-voltage cycle. The paper describes the control schemes and implementation of analog PWPs, and performance characteristics of the rectifier. Unity displacement power factor was obtained and the AC-side current harmonics were reduced. Experimental results show the usefulness of the proposed method and applicability to rectifiers in UPS systems, etc.<<ETX>>

Three-phase buck/boost-type high-power-factor switching converter

The harmonic pollution caused by ac-to-dc converters has been of great concern. To overcome this problem, several power-factor-correction (PFC) converters have been developed and applied in recent years. However, several power converter systems, such as the motor drive system, with a wide V/F control range, uninterruptible power supply system and dc power supply system with universal input voltage range, require an ac-to-dc converter or an off-line converter (preregulator) with a wide output-voltage control range in order to be highly efficient. However, the most conventional PFC converters employ a voltage-fed or current-fed type topology and they have a lower or upper limitation of the output-voltage control range. Thus, they do not realize sufficiently high-system efficiency. On the other hand, a buck/boost converter has a wide control range of the output voltage and acts in PFC operation under an appropriate control technique. Thus, study of the possibility of using the buck/boost ac-to-dc converter with PFC and a wide output-voltage control range is important to the realization of harmonic-free and efficient power conversion systems. In this paper, the author proposes a three-phase bridge-type ac-to-dc converter system with a high input power factor and a wide output-voltage control range. The controller of the proposed system includes the following two new techniques. One is the pulse integral value modulation that compensates modulation errors in conventional pulse-width-modulation caused by dc current ripples or fluctuations of the current pulse amplitude. The other is a switching pulse pattern generator, using the idea of equivalent pulse current source for the bridge as a way to simplify the pulse pattern generation process. This paper describes the proposed converter system, the control and modulation principles, and experimental results that show the reliability and usefulness of the proposed buck/boost converter system.

Simplified predictive-instantaneous-current-control for single-phase and three-phase voltage-fed PFC converters

An analog controller-based predictive instantaneous current control scheme for single-phase and three-phase voltage-fed power factor correction (PFC) power converters are proposed in this paper. Through a modification of the original control scheme for digital controller-based single-phase power converters, a simplified analog controller-based single-phase version is obtained. On the other hand, a phase decoupling technique is developed to apply the single-phase version to three-phase power converters. By combining the single-phase analog version and the phase decoupling technique, a simple three-phase version is obtained. In this paper, theories of the analog controller version for single-phase power converters and the combined three-phase version are discussed. Further, experimental results for single-phase and three-phase power converters are shown to confirm the validity of these theories.