Solid-state switch-mode rectification converters have reached a matured level for improving power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input AC mains and precisely regulated DC output in buck, boost, buck-boost and multilevel modes with unidirectional and bidirectional power flow. This paper deals with a comprehensive review of improved power quality converters (IPQCs) configurations, control approaches, design features, selection of components, other related considerations, and their suitability and selection for specific applications. It is targeted to provide a wide spectrum on the status of IPQC technology to researchers, designers and application engineers working on switched-mode AC-DC converters. A classified list of more than 450 research publications on the state of art of IPQC is also given for a quick reference.

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A review of single-phase improved power quality AC-DC converters

Predictive control is a very wide class of controllers that have found rather recent application in the control of power converters. Research on this topic has been increased in the last years due to the possibilities of today's microprocessors used for the control. This paper presents the application of different predictive control methods to power electronics and drives. A simple classification of the most important types of predictive control is introduced, and each one of them is explained including some application examples. Predictive control presents several advantages that make it suitable for the control of power converters and drives. The different control schemes and applications presented in this paper illustrate the effectiveness and flexibility of predictive control.

Predictive Control in Power Electronics and Drives

The use of an inverter with an output LC filter allows for generation of output sinusoidal voltages with low harmonic distortion, suitable for uninterruptible power supply systems. However, the controller design becomes more difficult. This paper presents a new and simple control scheme using predictive control for a two-level converter. The controller uses the model of the system to predict, on each sampling interval, the behavior of the output voltage for each possible switching state. Then, a cost function is used as a criterion for selecting the switching state that will be applied during the next sampling interval. In addition, an observer is used for load-current estimation, enhancing the behavior of the proposed controller without increasing the number of current sensors. Experimental results under linear and nonlinear load conditions, with a 5.5-kW prototype, are presented, verifying the feasibility and good performance of the proposed control scheme.

Model Predictive Control of an Inverter With Output $LC$ Filter for UPS Applications

In this paper, we present a predictive control algorithm that uses a state-space model. Based on classical control theory, an exact discrete-time model of an induction machine with time-varying components is developed improving the accuracy of state prediction. A torque and stator flux magnitude control algorithm evaluates a cost function for each switching state available in a two-level inverter. The voltage vector with the lowest torque and stator flux magnitude errors is selected to be applied in the next sampling interval. A high degree of flexibility is obtained with the proposed control technique due to the online optimization algorithm, where system nonlinearities and restrictions can be included. Experimental results for a 4-kW induction machine are presented to validate the proposed state-space model and control algorithm.

Predictive Torque Control of Induction Machines Based on State-Space Models

This paper presents a new control scheme for an active front-end rectifier using model-based predictive control. The control strategy minimizes a cost function, which represents the desired behavior of the converter. Future values of currents and power are predicted using a discrete-time model. The active and reactive powers are directly controlled by selecting the optimal switching state. The main advantages of this method are that there is no need of linear current controllers, coordinates transformations or modulators. The rectifier operates with sinusoidal input currents and unity power factor. Simulation and experimental results are presented to verify the performance of the proposed power control scheme.

Direct Power Control of an AFE Using Predictive Control

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

A new rectifier controlled by predictive instantaneous-current PWM control schemes for reducing AC-side harmonic currents in consideration of the DC-side voltage ripple is proposed. Unity power factor is also obtained. The paper describes three control schemes for a single-phase rectifier, and experimental and simulation studies of rectifier performance. The effectiveness of the control schemes is confirmed by experiments and simulations. The rectifier can be used in applications such as UPS systems and static VAr compensators. >

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. >

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

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

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.

http://ieeexplore.ieee.org/iel4/5337/14583/00665825.pdf

Akeshi Maeda

Papers

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

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

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

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

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