Browsing by Author "Valle, Rodolfo Lacerda"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    Low-frequency underwater wireless power transfer : maximum efficiency tracking strategy.
    (2020) Lopes, Israel Filipe; Valle, Rodolfo Lacerda; Fogli, Gabriel Azevedo; Ferreira, André Augusto; Barbosa, Pedro Gomes
    This paper proposes a strategy to improve the efficiency of a low-frequency Wireless Power Transfer (WPT) system used to charge the battery of an Autonomous Underwater Vehicle (AUV) through an Inductive Power Transfer (IPT). The IPT system uses a Split-Core Transformer (SCT) to transfer power from the docking base to the AUV, without electric contact. Under gap variation, the efficiency is changed because the variation of SCT parameters. Therefore, the input frequency is changed in order to improve the efficiency of the system trough the Maximum Efficiency Point Tracking algorithm (MEPT) without communication between primary and secondary sides. Experimental results are presented to validate the theoretical analysis and to demonstrate the behaviour of the transformer under different values of gap and excitation frequency.
  • No Thumbnail Available
    Item
    Simple and effective digital control of a variable-speed low inductance BLDC motor drive.
    (2020) Valle, Rodolfo Lacerda; Almeida, Pedro Machado de; Fogli, Gabriel Azevedo; Ferreira, André Augusto; Barbosa, Pedro Gomes
    This paper presents a simple digital control applied to a low inductance 5 kW/48 V three-phase brushless DC motor. Controlling the VSI as a full-bridge converter allowed the use of unipolar switching strategy, increasing the output equivalent frequency up to 100 kHz. The aforementioned strategy has made it possible to control the three-phase currents using a single deadbeat controller without a back-EMF feed-forward compensation. Stability analysis is performed to show that the proposed current control presents good transient response under reasonable parametric variations, as well as zero steady-state error. Precise regulation with no overshoot was obtained using an IP controller to regulate the motor speed. Experimental results are presented to validate the theoretical analysis and to compare with a conventional PI compensator and a predictive controller.
  • No Thumbnail Available
    Item
    A simple dead-time compensation strategy for grid-connected voltagesourced converters semiconductor switches.
    (2019) Fogli, Gabriel Azevedo; Valle, Rodolfo Lacerda; Almeida, Pedro Machado de; Barbosa, Pedro Gomes
    This paper presents a simple strategy to compensate the distorted currents synthesized by a grid-connected voltage source converter due to dead-time, turn-on and turn-off time delays of the semiconductor switches. The algorithm consider only the polarity of the fundamental component of the currents flowing through the converter terminals and the values of the time delays and voltage drops supplied by the manufacturers to the semiconductors devices. The presented compensation belongs to the group classified as average value compensation technique methodology since it does not change the pulse pattern of the converter's semiconductor switches. A simplified mathematical description of the effects caused by these unwanted time delays is presented and used to derive a correction factor to be added, in real time, to the converter output controller in order to compensate for its terminal voltages. The asymptotic stability and robustness of the proposed methodology is investigated redrawing the converter current controllers, designed in dq-reference frame, as proportional-resonant ones, in the abc coordinates, and adding the effect of the compensating signal in the feedback loop using the concept of describing function. In addition, the minimum value of the DC bus voltage necessary is also evaluated to ensure the operation of the converter in the linear modulation region when the compensation algorithm is active. Experimental results are presented to validate the theoretical analysis and to demonstrate the effectiveness of the proposed strategy for three different operation conditions of a grid-connected converter: (i) active power injection; (ii) active power consumption and (iii) reactive power support.