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Inductive contactless energy transfer systems with multiple mobile loads are very complex systems. Main challenges of these systems are to propose a suitable architecture and to design their power components. These challenges are particularly more noticeable in residential areas where various types of consumers (loads) are expected. This paper introduces a new architecture and design guidelines for a high-frequency resonant transformer operating with frequency modulation. The design process includes the effects of 1) the resonant frequency, 2) the magnetizing inductance, and 3) the characteristic impedance. The excellent performance of the designed system is validated by simulation results., Peer Reviewed, Postprint (published version)

This paper explores new techniques to reduce the conducted EMI generated by switched power converters operating in multiconverter arrangement. These techniques are based in the combined application of interleaving and the modulation of some characteristics of the switching patterns. The effectiveness of such methods in terms of EMI reduction is theoreticaly developed and experimentally validated in a four channel parallel buck converter operating in closed loop. The technique that provides the best attenuation results is identified. Finally, undesired sideeffects produced by these techniques, such as an increase in the output voltage ripple, are evaluated., Peer Reviewed, Postprint (published version)

En el presente artículo se analizan diferentes técnicas para la reducción de las EMI generadas por sistemas multiconvertidor con conexión en paralelo. La reducción de las perturbaciones generadas se logra por medio de la combinación de dos técnicas: interleaving y modulación en frecuencia de las señales de control del sistema multiconvertidor (SFM). Cada una de las técnica planteadas son validadas de manera experimental sobre un sistema multiconvertidor formado por cuatro convertidores Buck conectados en paralelo, identificando la técnica que proporciona mejores resultados desde el punto de vista de la atenuación de las EMI generadas. Por último, se ha prestado especial atención a los posibles efectos no deseados producidos por estas técnicas. Por esta razón, se ha evaluado tambíen la influencia de cada una de las técnicas propuestas sobre la amplitud del rizado de la tensión de salida., Postprint (published version)

This paper presents a modulation scheme in order to reduce conducted Electromagnetic Interference (EMI) generated by modular power converters with parallel topology. The proposed scheme is based on a combination of interleaving and Switching Frequency Modulation (SFM) techniques. The objective of this modulation scheme is to cancel certain harmonics of EMI and to reduce the amplitude of the remaining harmonics. The proposed scheme has been implemented in a field programmable gate array and a four channel parallel buck converter has been used in order to verify it. A significant EMI reduction has been obtained in comparison to use the interleaving and Switching Frequency Modulation separately., Peer Reviewed, Postprint (published version)

This paper proposes a new three-phase positive sequence detector. The scheme is based on a stationary reference frame and a Moving Average Filter (MAF) that guarantees the complete cancellation of harmonics and grid imbalances. The performance of the MAF is mathematically analyzed and a proper selection of the optimal filter’s window width is realized. The proposed detector operates in open loop and there is no PI controller to be tuned. Thus, the dynamic response and simplicity is improved compared to other solutions. Performance of the proposed detector is verified through simulation and experiment. It shows very good performance under extreme grid voltage conditions, allowing fast detection of the grid voltage positive sequence (within one grid voltage cycle)., Postprint (published version)

This paper contributes to the conducted EMI reduction generated by switched power converters operating in multiconverter arrangement. The EMI reduction is achieved by means of the combination of two techniques: interleaving and switching frequency modulation. The effectiveness of such methods in terms of EMI reduction is experimentally validated in a four channel parallel buck converter. The technique that provides the best attenuation results is identified. Finally, special attention has been paid to possible undesired side-effects produced by these techniques. For this reason the converter efficiency and output voltage ripple are evaluated., Peer Reviewed, Preprint

This thesis presents the design and simulation of a digital frequency demodulator applied to a Michelson interferometer-based scanning laser vibrometer. The laser vibrometer is a velocity transducer that produces frequency-modulated signals that have traditionally been optically or electronically frequency shifted from baseband to an intermediate frequency. This shifting produces a narrow band modulation that may be demodulated with standard analog frequency demodulators. This thesis proposes replacing these traditional optics or electronic circuits with a digital frequency demodulator. The optics of a laser vibrometer can be constructed such that a near-perfect baseband quadrature representation is available for the frequency modulation. It will be seen that this representation is well suited for use by a digital frequency demodulator. This thesis applies the arctangent-type digital frequency demodulator to a laser vibrometer and demonstrates its superiority over other digital demodulation techniques. In addition some specialized signal processing to handle the special case of sine-dwell vibration tests is presented.

This document focuses on the dynamics of nonlinear oscillatory systems involving widely spaced frequencies. First, experiments on the forced oscillations of a cantilever beam with a circular cross-section are presented. The beam is excited near its fifth natural frequency but sustained large-amplitude oscillations of the first mode accompanied by modulated oscillations of the fifth mode occur. Thus, energy is transferred from the fifth to the first mode of the beam, whose natural frequencies are roughly in the ratio of 60:1. Some simple two-degree-of-freedom systems are studied in an effort to explain the strong nonlinear coupling between modes with widely spaced frequencies. In these systems, the coupling is found to give rise to some novel phenomena including static displacements or sustained oscillations of the low-frequency mode in response to a high-frequency excitation. The possibility that resonances may occur between a high-frequency excitation and a single low-frequency mode is then investigated. A single-degree-of-freedom oscillator driven at a frequency much higher than its natural frequency is analyzed. It is found that, if the excitation is modulated, resonant excitation of the oscillator may occur.

The effect of PWM frequency modulation on power supply conducted EM! noise emission is investigated. Significant reduction of emission is possible with PWM frequency modulation scheme. A forward converter is used to verify the effectiveness of the scheme. A guidance of parameter selection for noise reduction is given.