Ignacio Gonzalez

Modulation Technique for Low Frequency Harmonic Cancellation in Auxiliary Railway Power Supplies

The auxiliary railway power supply (ARPS) is needed in order to provide low and medium voltages to the onboard systems from the catenary high voltage. The outputs of the ARPS can be dc (24 Vdc ÷100 Vdc) or ac (400 Vac). In the case of ac voltage generation, the ac output voltage is under very restrictive total harmonic distortion specifications even in the presence of nonlinear loads which draw low-frequency current harmonics. Along the present paper, a new modulation technique is proposed under the name of harmonic cancellation technique. It is based on the proper pre-distortion of the inverter output voltage in order to generate a controlled fundamental harmonic as well as a set of low-frequency harmonics which cancel out the harmonic pollution due to the nonlinear load performance. The theoretical background needed to implement the modulation technique is provided as well as the experimental validation of the proposed modulation technique through a scale-down prototype.

AUV based multi-vehicle collaboration: Salinity studies in Mar Menor coastal lagoon

Abstract An experiment with different AUVs was carried out in the Mar Menor Coastal Lagoon from October 31 to November 5 in order to measure and assess the influence of the water from the Mar Menor on the adjacent area of the Mediterranean. This was carried out as a result of the meeting held between several institutions from the Iberian Peninsula and EEUU (see Vilanova Marine Science/Robotics Meeting 2010). The experiment was to launch several AUVs at the same time in different zones of the Mediterranean and Mar Menor lagoon. AUVs took salinity data trying to do a coordinated mission during two operative days (November 3 and November 5). Others days of the experiment were used to the vehicles preparation and error correction (November 2 and November 4). This paper presents the steps followed in preparation and operative days with the set of AUVs. This paper presents also the salinity results obtained during these missions.

Feasible solutions space for the Harmonic Cancellation Technique

AC power supplies generated by means of an inverter are under very restrictive specifications regarding their AC output voltage THD, even when they are supplying both linear and nonlinear loads. The presence of the low frequency harmonic content due to nonlinear loads operation, greatly increase the THD of the AC power supply output voltage. Traditional state of the art techniques approach this problem from two main sides: filtering and fast control loops. However, the proposed technique aims to solve the aforementioned problem from a different point of view: the inverter modulation technique. Therefore, the Harmonic Cancellation Technique (HCT) has been developed. It is a modulation technique which is able to cancel out the low frequency harmonics due to the nonlinear load operation through the proper pre-distortion of the inverter output voltage. The present paper presents the limitations of the available solutions space for the proposed modulation technique. It also provides an insight of the converter design parameters which may help to enlarge the ranges of operating conditions for which HCT can be applied.