Showing papers by "Martin Jones published in 2015"

Onboard Integrated Battery Charger for EVs Using an Asymmetrical Nine-Phase Machine

Abstract: This paper considers an integrated onboard charger for electric vehicles that incorporates an asymmetrical nine-phase machine and an inverter into the charging process. The charging is from three-phase mains, and it employs exclusively the power electronic components that already exist on board the vehicle and that are mandatory for the propulsion. No new elements are introduced. Moreover, the charging is achieved without any hardware reconfiguration since the existing elements and their connections are not altered during the transfer from propulsion to the charging mode. Instead, the operating principle is based on additional degrees of freedom that exist in nine-phase machines. These degrees of freedom are employed to avoid electromagnetic torque production in the machine during the charging process, although currents flow through its stator windings. The configuration operates with a unity power factor and is capable of vehicle to grid (V2G) operation as well. A detailed theoretical analysis is given, and the control for the charging/V2G and propulsion modes is discussed. Theoretical analysis is validated by experiments for charging, V2G, and propulsion operating regimes.

Analytical Formulas for Phase Voltage RMS Squared and THD in PWM Multiphase Systems

Abstract: The analysis and assessment of the pulsewidth modulation (PWM) techniques is commonly based on the comparison of the total harmonic distortion (THD) results. THD is usually calculated by application of the Fourier transformation and by taking a limited number of harmonics into the consideration. In this paper, derivation of analytical formulas for the phase voltage THD is presented. The considered system is a symmetrical multiphase starconnected load, supplied from a multilevel pulsewidth-modulated voltage-source inverter (VSI, three-phase case is also covered). The solution is based on the Parseval’s theorem, which links frequency spectrum and time domain through the average power (i.e., rootmean- square (rms) squared value) of the signal. The assumption throughout the derivations is that the ratio of the switching to fundamental frequency is high. Derivations are based on the integration of the power of the PWM signal in a single switching period over the fundamental period of the signal. Only ideal sinusoidal reference voltages are analyzed, and no injection of any type is considered. Formulas for phase voltage THD for any number of phases are derived for two- and three-level cases, for themost commonly used carrier-based methods. Comparison of the analytically obtained curves with simulation and experimental results shows a high level of agreement and validates the analysis and derivations.

On the five-phase open-end winding drives performance

Abstract: Two multilevel five-phase open-end winding drive topologies are analysed and compared in this paper. The first topology consists of a five-phase machine and two two-level five-phase inverters, supplied with isolated dc-link voltages. In the second topology three-level and twolevel five-phase inverters are used to supply a five-phase machine. Variation of two dc-link's voltage ratio can lead to different overall number of phase voltage levels in both considered topologies. Dc-link voltage ratio influence on performance of drive topologies is analysed and experimental verification is provided for the four most suitable drive configurations.

Performance comparison of two four-level five-phase open-end winding drives

Abstract: Two four-level five-phase open-end winding drives are analysed in this paper, and their performances compared. The first topology consists of two two-level voltage source inverters (VSI) supplying a five-phase machine with open-end windings (OeW). The second topology comprises one three-level and one two-level VSI to supply the five-phase OeW machine. In both cases, two VSIs are supplied from isolated dc-sources, with voltages in a ratio 2∶1. As a consequence, the output phase-voltage waveforms are equivalent to those produced by a four-level five-phase VSI. The paper shows that the considered topologies exhibit significantly different operating characteristics.

An open-end winding drive with a single DC voltage source

Abstract: In this paper, a novel multiphase multilevel open-end winding (OeW) drive is presented. The topology employs one three-level and one two-level voltage source inverter (VSI) to supply a five-phase OeW machine. Three-level VSI operates with low switching frequency, while the second inverter is used to mitigate unwanted low-order harmonics. Proposed drive requires one dc source only, for three-level VSI dc-link formation, while the second inverter's dc side comprises capacitor bank only. Developed modulation strategy is capable of capacitor voltage balancing and providing constant dc-link voltage ratio. Presented results, for the dc-link voltage ratio 2:1, show that topology provides low phase voltage and phase current harmonic distortion.