Guy Olivier

An AC-to-DC Converter with Improved Input Power Factor and High Power Density

A novel single-phase switch-mode rectifier (SMR) structure is proposed and analyzed. The proposed converter structure employs a synchronous front-end rectifier (SFER) stage which provides high-quality input characteristics with small input filtering. Consequently the proposed converter structure exhibits high power density and has low implementation cost.

A Novel Type of 12-Pulse Converter

A new family of ac-dc converters for low-voltage high-current applications is introduced in which a peculiar connection of the power transformers is used to ensure current sharing amongst semiconductors.

3-D computation of transformers overheating under nonlinear loads

This paper deals with a mixed analytical and numerical method to study the electromagnetic and thermal behavior of a dry type transformer under nonlinear loads. First a three-dimensional finite element method (FEM) using a magnetic scalar potential formulation is applied to compute the magnetic field in the free and iron spaces. This nonlinear FEM calculation is then combined with a mixed analytical and numerical form of the electrical circuit equation to take into account the skin and proximity effects in the rectangular windings. Then a steady state thermal FEM using the previous resultant current densities allows to characterize the temperature distribution of the transformer with nonsinusoidal currents. Finally this coupling model is applied to a 10-kVA distribution transformer to validate the effectiveness of the proposed method.

Analysis and design of single-controlled switch three-phase rectifier with unity power factor and sinusoidal input current

This paper describes a new low-cost three-phase AC-DC high-power/low-harmonic-controlled rectifier and its analysis, design, and performance. The circuit consists of a three-phase diode-bridge rectifier, followed by a boost stage containing only one switch and one boost inductor. The proposed converter is used to automatically draw sinusoidal input-current waveforms with high efficiency. This is achieved with discontinuous-input voltage to the rectifier and with a discontinuous-inductor-current mode of operation of the boost converter. By using a simplified single-phase model and symbolic analysis method, analytical equations are obtained and used for design.

A new approach for the dynamic control of unified power flow controller (UPFC)

This paper presents a new approach for the dynamic control of FACTS apparatus, such as the UPFC and the STATCOM. With the new control strategy, the capabilities of the UPFC can be exploited not only for steady state power flow control but also to improve damping and transient stability assuring a good behavior during contingencies and the protection of the equipment. To achieve optimal UPFC behavior during the dynamic phenomena, the controllable system parameters are determined on-line based on the local instantaneous voltage and current measurements. The strategy is based on the theory of instantaneous powers defined in the positive, negative and zero sequence with real and imaginary components. The power flow calculation should not involve any conventional definitions of power. The Fortescus transformation will be used to conform the relation of the instantaneous active and reactive power (p, q) with the conventional active and reactive power (P/sub 3/spl phi//, Q/sub 3/spl phi//). A complete model of the UPFC and the transmission system has been implemented in a digital simulator to demonstrate the versatility of the new control strategy. Interesting results have been obtained, which are presented in this paper.

Analysis and design of single controlled switch three phase rectifier with unity power factor and sinusoidal input current

This paper describes a new low cost three-phase AC-DC high power/low harmonic controlled rectifier and its analysis, design and performance. The circuit consists of a three-phase diode bridge rectifier followed by a boost stage containing only one switch and one boost-inductor; the proposed power converter is used to automatically draw sinusoidal input current waveforms, with high efficiency. This is achieved with discontinuous input voltage to the rectifier and with a discontinuous inductor current mode of operation of the boost power converter. By using a simplified single-phase model and symbolic analysis method, analytical equations are obtained and used for design.<<ETX>>

Adaptive feedback linearization for position control of a switched reluctance motor: analysis and simulation

The authors present an adaptive feedback linearizing scheme for position control of a switched reluctance motor (SRM). This nonlinear adaptive control structure compensates for all the nonlinearities between inputs and outputs; allows the use of a linear controller for motion tracking and improves the performance by reducing torque ripple of the SRM. First, a detailed nonlinear model of the SRM is developed, and the parameterization of the model and the electronic commutation strategy are established. The gradient algorithm is used for the adaptation law. The linearizing adaptive control is applied to a single link direct-drive manipulator. Simulation results are given to demonstrate the effectiveness of the control method.<<ETX>>

Adaptive input-output linearization of a switched reluctance motor for torque control

In this paper a nonlinear adaptive feedback linearizing torque control is designed for a fifth order model of a three phase switched reluctance motor (SRM) which includes both electrical and mechanical dynamics. This nonlinear adaptive control structure compensates for all the nonlinearities between inputs and outputs. In addition, it allows the use of a decoupling linear controller for motion tracking for one phase and stabilization for the two other phases. A validated nonlinear model of the SRM is used for system simulation. The control algorithm contains an adaptive scheme based on the parametrized model. A method based on flux observation is used to measure the instantaneous torque. Simulation results are given to demonstrate the effectiveness of the control method.<<ETX>>

Flicker Compensation in Arc Furnace Power systems Using the UPFC

This paper presents a new approach for the dynamic compensation of flicker and harmonics in arc furnace power systems based on the UPFC. An arc furnace induces different kinds of disturbances caused by the harmonics and transient over voltage during the melting of scraps. Dynamic compensation is needed to improve the efficiency of process and to mitigate the disturbances caused to the network. The arc furnace load actually looks like a voltage source of harmonics behind a series of impedance consisting of the secondary cables to the electrodes. The UPFC with series active compensation capability opposed to variations of the arc resistance and suppress voltage flicker at the source. The design and control strategy of the UPFC based on the instantaneous power calculation are detailed by this paper. A typical arc furnace and UPFC model has been implemented in digital simulator to demonstrate how the UPFC can be controlled to take care of all disturbances

Acceptable direct current in three-phase power transformers: comparative analysis

This paper presents a comparative analysis of the temperature rise in three-phase core-form and shell-form power transformers in the presence of direct current. The temperature-rise assessment is compared on the basis of direct-current injection tests in single-phase core-form transformers, with a nominal voltage rating of 735 kV and nominal power ratings of 370 MVA and 550 MVA. The theoretical analysis of the saturation of three-phase transformers in the presence of direct current is based on the study of their magnetic circuit. The principle of duality was applied to obtain equivalent electric circuits simulated using the Electromagnetic Transients Program (EMTP) and validated using experimental results.