Ali I. Maswood

A Novel Variable Hysteresis Band Current Control of Three-Phase Three-Level Unity PF Rectifier With Constant Switching Frequency

A Simple and novel variable hysteresis band current control technique for three-phase three-level unity power factor (PF) rectifier is proposed in this paper. The hysteresis band is controlled as variations of the rectifier input voltage and output dc link voltage to achieve constant switching frequency at any operating conditions, i.e., at rated and below and above the rated conditions. The rectifier has the characteristic of easy implementation, and draws a nearly sinusoidal current at unity input PF. Theoretical and predicted results of its analysis are verified initially through digital simulation, and confirmed by using an experimental prototype

A Unity-Power-Factor Converter Using the Synchronous-Reference-Frame-Based Hysteresis Current Control

In this paper, a high-performance unity-power-factor rectifier-inverter structure is presented. A synchronous-reference-frame-based hysteresis current control as inner loop and dc-link voltage control as outer loop are adopted for the front-end converter. With the proposed control algorithm, the converter draws high-quality sinusoidal supply currents and maintains good dc-link-voltage regulation under wide load variation, and even under unbalanced and nonsinusoidal supply voltage conditions. Theoretical results of its analysis are verified initially through digital simulation. Finally, experimental results of a 1-kVA laboratory prototype system confirm the feasibility of the proposed technique

A novel unity power factor input stage for AC drive application

In this paper, a new method of improving the input current total harmonic distortion (THD) as well as power factor of a three-phase suppressed-link rectifier-inverter is presented. This proposed method makes use of a novel controlled diode rectifier. The technique involves the use of bidirectional switches across the front-end rectifier, and a dSPACE based intelligent control algorithm. The operation of the converter is fully analyzed and design example provided. The main feature of the topology is low cost, small size, high efficiency and simplicity, and is excellent for retrofitting front-end rectifier of existing ac drives, UPS etc.

A novel suppressed-link rectifier-inverter topology with near unity power factor

This work describes a novel method in improving the input current total harmonic distortion (THD) as well as the power factor of a three-phase suppressed-link rectifier-inverter circuit. This proposed method makes use of only three bi-directional low power static switches with a relatively simple gating circuit. This paper illustrates how the proposed method is superior in reducing the input current THD of a rectifier-inverter set to about 5%, which is in line with the requirements of IEEE standard 519-1992. This is accomplished without the use of any filter or complex wave shaping techniques. A delta-modulated (DM) voltage source inverter (VSI) with proportional integrator forms the output stage of the converter. It helps to provide constant volts per hertz operation without the need for additional feedback circuitry and complexity. Moreover, this novel DM technique also helps to provide a smooth transition from the pulse width modulation (PWM) to square wave, hence allowing full utilization of the DC bus voltage.

A novel method of harmonic assessment generated by three-phase AC-DC converters under unbalanced supply conditions

A three-phase converter is fully analyzed, and the performance of the converter is evaluated under both balance and unbalanced supply situations. It is observed that the level of imbalance in the supply voltage increases the harmonic content of the input current and decreases the power factor of the converter. This situation worsens toward the lower output region of the converter. The nature of the analysis has been kept very general so that future related work can be incorporated. >

Design aspects of planar and conventional SMPS transformer: a cost benefit analysis

The intent of this paper is to design a high-frequency transformer that is to be incorporated into the DC/DC pulsewidth-modulated switch-mode power supplies by two different technical approaches: a conventional wound-coil magnetic using copper wires, and a planar magnetic with layered copper tracks on laminated printed circuit board. Comparisons will be made between the two approaches in terms of profile: mounting height and surface area, and performance: power losses and efficiency. Other indicators like temperature rise and leakage inductance that causes electromagnetic interference, and cost, materials, and process fluency are also to be looked into. A sandwiched configuration for primary and secondary windings is proposed for the planar type. Issues arising and typical phenomena encountered will be discussed in detail. Primarily, the dominating factor in performance, cost effectiveness, or circuit compactness that restrains the choice of a particular type is to be evaluated.

A switching loss study in SPWM IGBT inverter

This work discusses an exact mathematical approach of calculating the IGBT turn-on, turn-off and on-state energy losses. Instantaneous voltage and current values are studied, linearized and employed to formulate the equations needed to calculate the IGBT switching loss. The inverter employs a switching pattern commonly known as sinusoidal PWM (SPWM). With this popular switching pattern, switching losses are derived for a common 3-phase inverter. Waveforms describing each switching states are developed. Mathematical equations describing the switching waveforms are formulated. The net switching loss is compared with that of the inverter to make sense of the process of loss in an inverter.

An Efficient UPF Rectifier for a Stand-Alone Wind Energy Conversion System

In this paper, a near-unity-power-factor front-end rectifier employing two current control methods, namely, average current control and hysteresis current control, is considered. This rectifier is interfaced with a fixed-pitch wind turbine driving a permanent-magnet synchronous generator. A traditional diode-bridge rectifier without any current control is used to compare the performance with the proposed converter. Two constant wind speed conditions and a varying wind speed profile are used to study the performance of this converter for a rated stand-alone load. The parameters under study are the input power factor and total harmonic distortion of the input currents to the converter. The wind turbine generator-power electronic converter is modeled in PSIM, and the simulation results verify the efficacy of the system in delivering satisfactory performance for the conditions discussed. The efficacy of the control techniques is validated with a 1.5-kW laboratory prototype, and the experimental results are presented.

Modular-Cell Inverter Employing Reduced Flying Capacitors With Hybrid Phase-Shifted Carrier Phase-Disposition PWM

This paper proposes a new approach of modular-cell inverter with a reduced number of flying capacitors (RFCI) using hybrid carrier-based pulsewidth modulation (PWM) named as phase-shifted carrier phase-disposition PWM (PSC-PD-PWM). The novel multilevel inverter topology is designed by clamping a series of modular cell onto a low-operational-frequency cell. The proposed transformerless RFCI reduces significantly the component counts, cost, and size of the converter. The overall performances of RFCI are greatly enhanced as compared with the classical multilevel flying capacitor inverter (MFCI). Hence, a comparative analysis of the proposed RFCI is made against the classical MFCI in this paper based on seven-level output phase voltages. The feasibility of the RFCI with PSC-PD-PWM is validated through experimental results under dynamic operating conditions.

Analysis of a PWM voltage source inverter with PI controller under non-ideal conditions

Apart from the traditional pulse-width modulation (PWM) or SPWM voltage source inverters (VSI), the proposed VSI with a Proportional integral current controller (PI VSI) offers superiority. They include instantaneous current control and wave shaping, fixed inverter switching frequency independent of the output frequency resulting in only known harmonics, and free-running carrier operation. A modeling approach to proposed PI VSI is introduced. A design example of the VSI power circuitry is presented. The PI controller design is discussed. Finally the VSI load current is verified for harmonic contents and instantaneous current control capabilities, under normal, unbalanced, load outage and load short-circuit conditions.