Cheul-U Kim

A new single-phase five-level PWM inverter employing a deadbeat control scheme

A single-phase five-level PWM inverter is presented to alleviate harmonic components of the output voltage and the load current. Operational principles with switching functions are analyzed. To keep the output voltage sinusoidal and to have the high dynamic performances even in the cases of load variations and the partial magnetization in filter inductor, the deadbeat controller is designed and implemented on a prototype. The validity of the proposed inverter is verified through simulation and experiments. To assess the proposed inverter, it is compared with the conventional single-phase three-level PWM inverter under the conditions of identical supply DC voltage and switching frequency. In addition, it is compared with the five-level cascaded PWM inverter.

Multilevel PWM inverters suitable for the use of stand-alone photovoltaic power systems

This paper presents a new multilevel pulse width-modulation (PWM) inverter scheme for the use of stand-alone photovoltaic systems. It consists of a PWM inverter, an assembly of LEVEL inverters, generating staircase output voltages, and cascaded transformers. To produce high-quality output voltage waves, it synthesizes a large number of output voltage levels using cascaded transformers, which have a series-connected secondary. By a suitable selection of the secondary turn-ratio of the transformer, the amplitude of an output voltage appears at the rate of an integer to an input dc source. Operational principles and analysis are illustrated in depth. The validity of the proposed system is verified through computer-aided simulations and experimental results using prototypes generating output voltages of an 11 level and a 29 level, respectively, and their results are compared with conventional counterparts.

A novel high-performance voltage regulator for single-phase AC sources

Regulation of load voltage in single-phase applications is becoming an important issue for critical loads. This paper presents a novel high-performance single-phase voltage regulator which has a common arm between the rectifier and inverter, and adopts an appropriate switching strategy. The proposed voltage regulator employs six switches and can be implemented by only one three-phase inverter module. The proposed voltage regulator has the capability of delivering sinusoidal input current with unity power factor, good output voltage regulation, and bidirectional power flow. For these purposes, a fully digital controller is designed and implemented using a TMS320F240 digital signal processor. In addition, a novel low-cost AC capacitor is also presented. This type of capacitor requires two DC capacitors and two diodes, enabling low-cost and compact manufacturing. Consequently, the complete voltage regulator system, which is mainly suitable for an uninterruptible power supply as well as reactive or nonlinear loads, can be constructed compactly and inexpensively. Experimental results are presented to verify the feasibility of the proposed voltage regulator system.

An efficient multilevel-synthesis approach and its application to a 27-level inverter

This paper presents an efficient multilevel-synthesis scheme and its application to a 27-level inverter. In the proposed multilevel scheme, this can be realized by an array of switching devices composing full-bridge inverter modules and proper mixing of each transformer terminal voltage. The most different aspect, compared to the conventional approach, in the synthesis of the multilevel output waveform is the utilization of a combination of transformers rather than the accumulation of capacitor voltage sources. A 27-level inverter consists of three full-bridge modules and their corresponding transformers. Quasi-sinusoidal voltage waves can be generated from a suitable selection of the turns ratio of the transformer. The validity of the proposed system is verified by computer-aided simulation and experimental results using a 500-W prototype, which can generate a 110-V ac output voltage from a 12-V dc input.

ZVZCS single-stage PFC AC-to-DC half-bridge converter

A zero-voltage- and zero-current-switched single-stage AC-to-DC half-bridge converter with high power factor is presented to reduce the switching losses and to achieve sinusoidal, unity power factor input currents. The single-stage approach, which combines a boost converter used as power-factor correction with a half-bridge converter used as DC-to-DC conversion into one power stage, has a simple structure and low cost. At the same time, the switching losses could be considerably reduced, because the switches of the proposed converter are designed to be turned on at zero voltage and off at zero current. Detailed analysis and experimental results are presented on the proposed converter, which is operated at constant switching frequency and in discontinuous conduction mode.

Interface circuit for photovoltaic system based on buck-boost current-source PWM inverter

This paper presents a current-source-inverter based on a buck-boost configuration and its application for residential photovoltaic system. The proposed circuit has five switches. Among them, only one switch acts as chopping, and the other determine the polarity of output; therefore, it can reduce the switching loss. Because the input inductor current is operated on the discontinuous conduction mode, high power factor can be achieved without additional input current controller. So the overall system shows a simple structure. The operational modes are analysed in depth, and then it was verified through the experimental results using a 150 W prototype.

High-Performance Sustain Driver for Plasma Display

The sustain driver for ac plasma display should provide alternating high-voltage pulses to ignite plasma and recover the energy discharged from the intrinsic capacitance between the scanning and sustaining electrodes inside the panel. In this paper, an efficient sustain circuit that employs a voltage boost-up function is proposed to achieve faster rise-time that would be suitable for the wide use of the address-and-display-period-separated (ADS) driving method. The proposed sustain driver improves recovery efficiency, regardless of the variation of the panel capacitance. The principle of operation, features, and simulation results are given and verified on a 7.5-in-diagonal panel at a 200-kHz operating frequency based on an experimental prototype

A novel AC-PDP sustain driver based on dual resonance in sustaining mode operation

A novel sustain driver employing an energy recovery faculty is proposed for efficient driving of a plasma display panel (PDP) in the sustaining mode operation. The proposed driver uses dual resonance. One is a main resonance between an inductor and an external capacitor to produce alternative pulses and the other is a subresonance between an inductor and a panel to recover the energy consumption by the capacitive displacement current of the PDP. The operational principle and design procedure of the proposed circuit are presented with theoretical analysis. The validity of the proposed sustain driver is verified through the simulated and experimental results based on a 7.5-in diagonal panel with 200-kHz operating frequency.

Reference frame approach for torque ripple minimization of BLDCM over wide speed range including cogging torque

Torque ripple control of brushless DC motor has been the main issue of servo drive systems in which the speed fluctuation, vibration and acoustic noise should be minimized. In this paper, the novel approach to achieve ripple-free torque control with maximum efficiency based on the d-q-0 reference frame is presented. The proposed method optimizes the reference phase current waveforms including even the case of 3 phase unbalanced condition. As a result, the proposed approach provides a simple and clear way to obtain the optimal motor excitation currents. The validity and practical applications of the proposed control scheme are verified through the simulations and experimental results.

An efficient AC-PDP sustain driver employing boost-up function

The sustain driver for AC plasma display panel should provide alternating high voltage pulses to ignite plasma and recover the energy discharged from the intrinsic capacitance between the scanning and sustaining electrodes inside the panel. In this paper, an efficient sustain circuit employing boost-up function is proposed to achieve a faster rise-time in order to be suitable to widely use the address display period separated (ADS) driving method. The proposed circuit improves the recovery efficiency, regardless of the variation of the panel capacitance. The principle of operation, features, and simulated results are illustrated and verified on a 7.5-inch diagonal panel at 200 kHz operating frequency based on experimental prototype.