http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

The aim of this paper is to present a review of current control techniques for three-phase voltage-source pulsewidth modulated converters. Various techniques, different in concept, have been described in two main groups: linear and nonlinear. The first includes proportional integral (stationary and synchronous) and state feedback controllers, and predictive techniques with constant switching frequency. The second comprises bang-bang (hysteresis, delta modulation) controllers and predictive controllers with on-line optimization. New trends in current control-neural networks and fuzzy-logic-based controllers-are discussed, as well. Selected oscillograms accompany the presentation in order to illustrate properties of the described controller groups.

Current control techniques for three-phase voltage-source PWM converters: a survey

The authors present the design and control of a nonconventional converter with a peak power of 3.6 MVA and a bandwidth ranging from DC values up to 10 kHz for nuclear-fusion experiments. The novel control technique is based on a comparison between the current reference and the load current, through a hysteresis comparator system. The required voltage waveforms have been obtained in two specified frequency ranges, with a strictly unified control over the whole bandwidth range. The conditions on the maximum phase shift and the maximum switching frequency required have all been fulfilled. Excellent results obtained by digital simulation confirm the validity of the proposed control scheme. The converter described here has been studied and designed for an experiment that has recently been proposed within the framework of the JET (Joint European Torus) project. >

A non conventional power converter for plasma stabilization

A comparison of envelope elimination and restoration (EER) and envelope tracking (ET) is discussed and a "hybrid" wideband EER power amplifier (PA) for the WLAN 802.11g system is proposed. A 60% efficiency (the output envelope signal power/input dc power) DC-20-MHz wideband envelope amplifier is designed for wideband EER and wideband ET (WBET) applications. A design method is developed to optimize the efficiency of the envelope amplifier for a given peak-to-average ratio and average slew rate of the envelope signal. An experimental "hybrid" Class-E EER system shows an overall efficiency (modulated RF output power/envelope amplifier dc input power) of 36% and power-added efficiency (the modulated RF output power/envelope amplifier dc input power plus RF input power) of 28% for a WLAN 802.11g signal at 19-dBm (80 mW) output power at 2.4 GHz. Digital predistortion, time alignment, and memory effect mitigation are implemented. The measured 3% error vector magnitude exceeds the 802.11g specification for 5% for a 54-Mb/s modulation signal

An Improved Power-Added Efficiency 19-dBm Hybrid Envelope Elimination and Restoration Power Amplifier for 802.11g WLAN Applications

A hysteresis control method for three-phase current-controlled voltage-source PWM inverters is presented. The method minimizes interference among phases, thus allowing phase-locked loop (PLL) control of the modulation frequency of inverter switches. The control theory is discussed, and the controller implementation is described. Design criteria are also given. The results of experimental tests show excellent static and dynamic performance. >

A novel hysteresis control method for current-controlled voltage-source PWM inverters with constant modulation frequency

Hysteresis current controllers having fixed bands are used in inverters of high-performance AC drives. The switching frequency of such controllers varies over the fundamental period of the modulating signal. The maximum switching frequency (MSF) of these controllers is high. To limit the MSF within the limit of inverter switches, fixed carrier lockouts are usually incorporated. The incorporation of carrier lockouts causes current distortion, and load currents do not confine within the predetermined band. In this paper, two new controllers are proposed. One is a mixed-mode controller of sinusoidal band added to a fixed band, and the other is an equidistant-band current controller, performances of the proposed controllers are compared with the performances of the conventional fixed-band and sinusoidal-band controllers.

Variable-band hysteresis current controllers for PWM voltage-source inverters

An analysis is presented of a voltage source delta modulation (DM) inverter. The delta modulation method provides several advantageous characteristics over commonly used sine modulation process. It is relatively easy to implement and provides low harmonics at the inverter output. The inherent features of the delta modulation also provide control of ratio of voltage to frequency and commutation numbers of an inverter without much complexity in control circuit. These and other features of DM inverters are investigated theoretically and verified experimentally. Successful implementation of DM techniques in three-phase inverters are reported.

Performance Analysis of Delta Modulated PWM Inverters

The integrator in the modulator of delta PWM inverters acts as a filter to estimate the input reference signal from the output waveform for comparison purposes. The use of a tuned filter allows the online variation of filter cutoff frequency and ensures minimization of desired harmonics from the output of the inverter. This method is particularly suitable for delta-modulated inverters used in variable-frequency applications. The modulator's harmonic performance has been studied using a windowed discrete Fourier transform. The theoretical results were verified experimentally. The significance of the modulator lies in its simplicity, versatility, and ease of online harmonic minimization, which is achieved without predetermination of the switching points. >

Harmonic minimization in delta modulated inverters using tuned filters

Two new topologies of single-phase AC-DC converter using Buck and Buck-Boost conversion with low input current THD and high input power factor are proposed. Instead of using a single phase rectifier followed by a boost DC-DC converter, or using a bridge rectifier with two diodes and two switches, the rectifier's input is chopped at high frequency during positive and negative cycles by a single bi-directional switch to get step-up/step-down ac-dc conversion. Total Harmonic Distortion (THD) of the input current of the proposed circuit with small input current filter is low. Input power factor and the efficiency of conversion of the circuit are high. No additional control is required to achieve the advantages.

Input switched single phase buck and buck-boost AC-DC converter with improved power quality

An analysis and implementation of delta modulation (DM) technique in the control of AC-DC converters are presented in this paper. The DM technique offers advantages of easy implementation, continuous converter voltage control, and a direct control on the line harmonics. A simple model of the delta modulator is proposed to predict switching frequency, identify dominant harmonics, and determine switching points of the converter waveforms. Results of parametric variations of the modulator and performances of the single and three phase DM converters are reported. Experimental results of the single and three phase DM AC-DC converters validate the analytical results. >

Mohammad Ali Choudhury

Papers

Variable-band hysteresis current controllers for PWM voltage-source inverters

Performance Analysis of Delta Modulated PWM Inverters

Harmonic minimization in delta modulated inverters using tuned filters

Input switched single phase buck and buck-boost AC-DC converter with improved power quality

Analysis of delta PWM static AC-DC converters