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In this paper, we propose the use of the electrochemical impedance spectroscopy technique for state diagnosis of electric double-layer ultracapacitors. Ultracapacitors under investigation are Maxwell BCAP 0350 and they were stressed in several ways for our study. The analyzed stress conditions include accelerated aging tests, overvoltage, and over temperature tests. Chemical and physical effects on supercapacitor materials are pointed out through a morphologic analysis implemented by means of an environmental scanning electron microscope and a chemical composition analysis obtained by means of an energy dispersive spectrometer. Consequent degradation effects are described in terms of frequency behavior of equivalent circuital parameters.

In this paper, the application of a cascaded multilevel inverter as a dynamic voltage restorer (DVR) is investigated. Two discontinuous multilevel space vector modulation (SVM) techniques are implemented for DVR control and are shown to reduce inverter switching losses while maintaining virtually the same harmonic performance as the conventional multilevel SVM at a high number of levels. This paper also presents a mathematical relationship for computing the distortion at the point of common coupling (PCC) as a function of the distortion of the DVR. This enables the selection of the number of levels required for a certain application. An extended sag duration support compared to the two-level DVR is another advantage of the DVR with a cascaded multilevel inverter. The common-mode voltage (CMV) at the PCC has been evaluated for the three SVM techniques (the conventional multilevel SVM and the two discontinuous SVM), presenting a lower CMV for the second discontinuous SVM. A design example is presented for an 11-kV 5-MVA DVR multilevel cascaded inverter for up to 17 levels, employing the conventional multilevel SVM and the two discontinuous SVM techniques. Scopus

The conversion efficiency of three way catalytic converters is mainly defined by the temperature range wherein they are operating. Traditionally, ignition retard has been used to reduce the light-off time of the catalyst. This is however associated with a fuel penalty. With increasing vehicle electrification, electrically heating facilities present an alternative, especially for hybrid vehicles. Nevertheless, system complexity of hybrid vehicles prevents engineers to evaluate possible heating technologies and their corresponding fuel penalty with respect to traditional solutions. This paper evaluates the application of an electrically heated catalyst on a hybrid vehicle equipped with a Natural Gas (NG) engine. The effect of heating power on light-off time and fuel penalty is determined, using analysis techniques emerging from integrated powertrain control. By means of a case study, the importance of an integral approach is explained by comparing the fuel penalty and conversion efficiency improvement of electric heating with that of ignition retard. In this process, a mix of simulation and test data were combined, forming the foundations for future control developments of a suitable light-off strategy. © 2010 Institut français du pétrole.