Akeshi Maeda

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.

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 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.

A single-phase buck-boost AC-to-DC converter with high-quality input and output waveforms

This paper describes a new single-phase buck-boost power factor correction (PFC) converter with output-voltage-ripple-free operation. The rectifier is operated by two modulators which obtain PFC and the ripple-free operation, respectively. The modulator controls the buck-boost switch to obtain PFC. On the other hand, another modulator controls squire-value of instantaneous-inductor-current to perform the ripple-free operation. In both modulation, space or time-integral-value of the input and output currents in each modulation period is controlled directly and indirectly, respectively. Thus, modulation errors or distortions of the currents are eliminated even if the DC-inductor-current produces large ripples. The theories and combination technique of the modulators, implementation and experimental results are shown.

An Optimal Efficiency Control for Energy Saving of Ac Motor by Thyristor Voltage Controller

This paper describes a simple but effective method for energy saving of ac motors having a widely variable load. The proposed method is based on an optimal efficiency control which is operated by voltage-current pattern such as to maintain the maximum efficiency on the efficiency-output characteristics of the motor, in voltage control with thyristors. The parameters of simplified voltage-curreqt pattern can be determined approximately and reliably from the rated voltage and current of the motor. Experiments are focused on a single phase capacitor motor and a 3-phase induction motor, the optimal energy saving are proved by the proposed method.

Comparison of the characteristics between buck and buck-boost high-power-factor converters with pulse-space-modulation

The current-fed high-power-factor converters (buck and buck-boost converters) have several advantages, such as no lower-limit of the output-voltage control range and no rush-current of the input-current. However, the single-phase current-fed high-power-factor converter with PWM (pulse width modulation) produces undesirable lower order harmonics in the input-current. Thus, the PWM requires a bulky and costly inductor connected in the DC-side of the current-fed converter to reduce the DC-inductor-current ripples. To overcome the problem, the authors have proposed PSM (pulse-space-modulation). This paper describes a comparison of the characteristics (THD (total harmonic distortion of the input-current), the power factor and reducing DC-inductors inductance) between buck and buck-boost high-power-factor converters applying PSM. The buck-boost converter has many advantages over the buck converter in the input current waveform, power factor and reducing DC-inductors inductance. To illustrate the validity of the theory, experimental results obtained from a 1.2 kW setup and computer simulation results are shown.

A single-phase buck-boost PFC converter with output-voltage, ripple-reducing operation

This paper describes a new single-phase buck-boost power-factor-correction (PFC) converter with output-voltage, ripple reducing operation. The converter consists of a conventional buck-boost PFC converter and an additional switch to obtain a freewheeling mode of the dc inductor current, and is operated by two modulators. The first modulator controls the buck-boost switch to obtain PFC. The other modulator controls the square value of the instantaneous dc inductor current to perform the output-voltage-ripple-reducing operation. In the two modulations, the time integral value of the input and output currents in each modulation period are controlled directly and indirectly, respectively. Thus, modulation errors or undesirable distortions of the input current and output voltage ripple are eliminated even if the dc inductor current produces large ripple in a low-frequency range. The theories and combination techniques for the two modulators, implementation, and experimental results are described.

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.

A new single-phase high-power-factor converter with buck and buck–boost hybrid operation

In recent years, a wide variety of high-power-factor converter schemes have been proposed to solve the harmonic problem. The schemes are based on conventional boost, buck or buck-boost topology and their performance, such as output voltage control range in the boost and buck topology or efficiency in the buck boost topology are limited. To solve this, the authors propose a single-phase high-power-factor converter with a new topology obtained from a combination of buck and buck-boost topology. The power stage performs the buck and buck-boost operations by a compact single stage converter circuit while the simple controller/modulator appropriately controls the alternation of the buck and buck-boost operation and maintains a high quality input current during both the buck and buck-boost operations. The proposed scheme results in a high performance rectifier with no limitation of output voltage control range and a high efficiency. In this paper, the principle and operation of the proposed converter scheme are described in detail and the theory is confirmed through experimental results obtained from a 2[kW] prototype converter.