The application of multilevel converters for traction drive systems is being investigated. The main advantage of this kind of topology is that it can generate almost perfect current or voltage waveforms, because it is modulated by amplitude instead of pulse-width. That means that the pulsating torque generated by harmonics can be eliminated, and power losses into the machine due to harmonic currents can also be eliminated. Another advantage of this kind of drive is that the switching frequency and power rating of the semiconductors is reduced considerably. The amplitude modulation is based on a cascade of N converters scaled in a 'trinary' form (three-state 'H' converters). In the chain of N converters of each phase (N-Stage Converter), there is a 'Master converter' that manages more than 80% of the total power, and N-1 'Slave converters' that take the rest of the power (less than 20%). One important drawback of this kind of arrangement is that it needs isolated power sources for each one of the N converters, and also for each phase. This paper shows that this problem can be overcome by using isolated motor windings for each phase of the traction motor (which is easy to get in normal machines), and by using low-power high-frequency, bidirectional switching power supplies for the 'slave converters'. Simulations using PSIM (Power Electronics Simulator) have demonstrated the feasibility to build drive converters for electric vehicles using multilevel inverters. They are being compared with inverters using the conventional PWM technique. The multilevel converter used in the simulations, works with only four inverters (N=4): one Master and three Slaves. In both the cases (PWM and multilevel), the traction motors have a rating of 80 kW, and the battery pack supply is 240 Vdc. The battery pack is connected to the master converters of each phase in parallel, and to the slaves through isolated bi-directional switching power supplies.
Traction drive system for electric vehicles, using multilevel converters
Antriebssystem für Elektrofahrzeuge mit Hilfe mehrstufiger Konverter
2002
10 Seiten, 9 Bilder, 10 Quellen
Aufsatz (Konferenz)
Datenträger
Englisch
A battery-supplied traction drive for electric vehicles
British Library Conference Proceedings | 1994
|A battery-supplied traction drive for electric vehicles
Tema Archiv | 1994
|DYNAMIC PROCESSES IN THE DRIVE SYSTEM OF ELECTRIC TRACTION VEHICLES
Taylor & Francis Verlag | 1988
|