Gerry Moschopoulos

Single-phase single-stage power-factor-corrected converter topologies

Single-phase single-stage power-factor-corrected converter topologies are reviewed in this paper. The topologies discussed in the paper are related to ac-dc and ac-ac converters that are classified on the basis of the frequency of the input ac source, the presence of a dc-link capacitor, and the type of control used (resonant or pulsewidth modulation). The general operating principles and strengths and weaknesses of the converters, which the authors have investigated over the last decade, are discussed in detail, and their suitability in practical applications is stated. Considering practical design constraints, it is possible to effectively employ many single-stage converter topologies in a wide range of applications.

Simulation of a Wind Turbine With Doubly Fed Induction Generator by FAST and Simulink

In order to fully study the electrical, mechanical, and aerodynamic aspects of a wind turbine with a doubly fed induction generator, a detailed model that considers all these aspects must be used. A drawback of many works in the area of wind turbine simulation is that either a very simple mechanical model is used with a detailed electrical model, or vice versa. Hence, the effects of interactions between electrical and mechanical components are not accurately taken into account. In this paper, three simulation programs - TurbSim, FAST, and Simulink - are used to model the wind, mechanical and electrical parts of a wind turbine, and its controllers. Simulation results obtained from the model are used to observe the interaction of all three factors affecting the operation of a wind turbine system. For example, it is shown how an electrical disturbance can cause dangerous tower vibrations under high speed and turbulent wind conditions, which may not be feasible using a simple model of the wind and wind turbine.

A zero-voltage switched PWM boost converter with an energy feedforward auxiliary circuit

A zero-voltage-switched (ZVS) pulsewidth-modulated (PWM) boost converter with an energy feedforward auxiliary circuit is proposed in this paper. The auxiliary circuit, which is a resonant circuit consisting of a switch and passive components, ensures that the converters main switch and boost diode operate with soft switching. This converter can function with PWM control because the auxiliary resonant circuit operates for a small fraction of the switching cycle. Since the auxiliary circuit is a resonant circuit, the auxiliary switch itself has both a soft turn on and turn off, resulting in reduced switching losses and electromagnetic interference (EMI). This is unlike other proposed ZVS boost converters with auxiliary circuits where the auxiliary switch has a hard turn off. Peak switch stresses are only slightly higher than those found in a conventional PWM boost converter because part of the energy that would otherwise circulate in the auxiliary circuit and drastically increase peak switch stresses is fed to the load. In this paper, the operation of the converter is explained and analyzed, design guidelines are given, and experimental results obtained from a prototype are presented. The proposed converter is found to be about 2%-3% more efficient than the conventional PWM boost converter.

A novel zero-voltage switched PWM boost converter

A novel, zero-voltage switched (ZVS) PWM boost converter that combines soft-switching with constant frequency operation is proposed in this paper. This converter can be operated with PWM control at a fixed frequency because ZVS operation is achieved with a simple auxiliary resonant circuit that is activated for only a small fraction of the switching period and handles much less power than the main power circuit. In the paper, the modes of operation of the converter are explained and analyzed, and a set of design guidelines is developed. The feasibility of the converter is shown with results obtained from an experimental prototype.<<ETX>>

A Comparative Study of a New ZCS DC–DC Full-Bridge Boost Converter With a ZVS Active-Clamp Converter

Pulse width modulation (PWM) current-fed full-bridge dc-dc boost converters are typically used in applications where the output voltage is considerably higher than the input voltage. In this paper, a comparison is made between two converter topologies of this type-the standard zero-voltage switching (ZVS) active-clamp topology and a new zero-current switching (ZCS) topology. This paper begins with a review of the operation of the ZVS active-clamp converter and that of ZCS converters in general; the advantages and disadvantages of each approach are stated. A new ZCS-PWM current-fed dc-dc boost full-bridge converter is then introduced. The operation of the new converter is explained and analyzed, and a procedure for the design of its key components is given and demonstrated with an example. Experimental results obtained from a prototype of a ZVS active-clamp converter and the new ZCS converter are presented. Finally, a comparison of the performance of the two converters is made and conclusion based on this comparison is stated.

A Nonisolated Bidirectional ZVS-PWM Active Clamped DC–DC Converter

Power electronic converter systems for applications such as telecom, automotive, and space can have dc voltage buses that are backed up with batteries or supercapacitors. These batteries or supercapacitors are connected to the buses with bidirectional dc-dc converters that allow them to be discharged or charged, depending on the operating conditions. Bidirectional dc-dc converters may be isolated or nonisolated depending on the application. A new soft-switched bidirectional dc-dc converter will be proposed in this letter. The proposed converter can operate with soft switching, a continuous inductor current, fixed switching frequency, and the switch stresses of a conventional pulsewidth modulation converter regardless of the direction of power flow. These features are due to a very simple auxiliary active clamp circuit that is operational regardless of the direction of power flow. In the letter, the operation of the converter will be discussed and its feasibility will be confirmed with experimental results obtained from a prototype.

Analysis and design of a single stage power factor corrected full-bridge converter

A simple PWM full-bridge converter that integrates input power factor correction (PFC) with DC-DC conversion is examined in the paper. The converters operation is analyzed, and the results of the analysis are used to determine its steady-state characteristics. A design procedure for the selection of components is derived and demonstrated with an example. The feasibility of the converter and its ability to satisfy the IEC 1000-3-2 Class D requirements for electrical equipment are shown with results obtained from an experimental prototype.

Analysis and Design of a Nonisolated Bidirectional ZVS-PWM DC–DC Converter With Coupled Inductors

A new zero-voltage-switched bidirectional dc-dc converter with coupled inductors is proposed in the paper. The proposed converter can operate with a steep conversion ratio, soft switching, a continuous inductor current, and fixed switching frequency. It can also operate with the switch stresses of a conventional pulsewidth-modulation-tapped/coupled-inductor converter regardless of the direction of power flow and without any voltage spikes across the switches during turn-OFF. These features are due to a very simple auxiliary circuit that is operational regardless of the direction of power flow and absorbs energy from the leakage inductance of the coupled inductors during switch turn-OFF. In the paper, the operation and design of the converter are discussed and its feasibility is confirmed with experimental results obtained from a prototype.

A Comparative Study of Zero-Current-Transition PWM Converters

Zero-current-transition (ZCT) PWM converters are conventional PWM converters that use an active auxiliary circuit to turn off the main power switch with zero current switching. In the paper, the general operating principles behind all ZCT-PWM converters are reviewed, and the operation and properties of specific boost converters are discussed. The strengths and weaknesses of each converter are stated and a new and improved ZCT-PWM boost converter is proposed and compared with the other converters. Experimental results that confirm the superior performance of the new proposed converter are presented

Single-stage ZVS PWM full-bridge converter

A new soft-switched ac-dc single-stage pulse width modulation (PWM) full-bridge converter is proposed. The converter operates with zero-voltage switching (ZVS), fixed switching frequency, and with a continuous input current that is sinusoidal and in phase with the input voltage. This is in contrast with other ac-dc single-stage PWM full-bridge converters that are either resonant converters operating with variable switching frequency control and high conduction losses, converters whose switches cannot operate with ZVS, or converters that cannot perform power factor correction (PFC) unless the input current is discontinuous. All converter switches operate with soft-switching due to a simple auxiliary circuit that is used for only a small fraction of the switching cycle. The operation of the converter is explained and analyzed, guidelines for the design of the converter are given, and its feasibility is shown with results obtained from an experimental prototype.