Showing papers by "Martin Jones published in 2019"

A Novel Synthetic Loading Method for Multiple Three-Phase Winding Electric Machines

Abstract: This paper develops a version of the synthetic loading method, suitable for the testing of multiphase machines with multiple three-phase distributed windings. The method is at first discussed in general terms for a structure with k three-phase stator windings (i.e., total number of phases is n = 3 k ). Subsequent detailed development is described for a dual three-phase (six-phase) stator winding configuration. With a control architecture that allows the use of half of the three-phase windings as a motor and the other half as a generator, the machine (and/or the converter) can be tested under full rated power without the need for any mechanical load. Moreover, the power consumed from the grid is in essence equal only to the total losses of the system. Modeling, based on the double d-q approach, and the control layout that includes full cross-coupling decoupling are described for a permanent magnet (PM) synchronous machine. An experimental test rig with a double three-phase PM machine of 150 kW rating is detailed and the samples of experimental results are provided to verity the theoretical considerations.

Control of a Symmetrical Nine-phase PMSM with Highly Non-Sinusoidal Back-Electromotive Force Using Third harmonic Current Injection

Abstract: This paper investigates an enhanced field-oriented control method for a two-pole surface permanent magnet synchronous machine (PMSM) with a symmetrical nine-phase winding configuration and a single neutral point. Magnets on the rotor are shortened, reducing cost of the machine, but cause production of highly non-sinusoidal back-electromotive force (EMF). FFT analysis of the EMF reveals a high third harmonic component, which is almost equal in magnitude to the fundamental. By investigating possible torque improvements using FEM software simulations, it was shown previously that, if controlled under optimal third harmonic current injection, the electromagnetic torque of the studied PMSM can be improved by up to 36%. The optimal current harmonic injection ratio between the fundamental and the third harmonic is determined first in this paper, using the maximum torque-per-ampere method (MTPA). An enhanced high-performance field-oriented control (FOC) algorithm to control a nine-phase non-sinusoidal back-EMF PM synchronous machine is devised next. The developed improved control algorithm is verified using simulation studies and further validated using an experimental prototype.

Arbitrary d–q current sharing in three-phase winding sets of multi-phase machines

Abstract: This study proposes a technique for arbitrary current sharing between winding sets of any multiple three-phase machine by using a decoupled control in two-dimensional orthogonal vector space decomposition subspaces. With ability to arbitrarily set the d–q currents in all winding sets, both active and reactive power of each winding set can be arbitrarily set as well. Normally, this behaviour requires machine model in multi-stator variables where control implementation may be challenging due to the cross-coupling between winding set variables. On the contrary, in this study, the correlation between multi-stator and the vector space decomposition modelling has been used so that benefits of both modelling approaches are fully utilised: a decoupled control feature thanks to vector space decomposition and an ability to individually control winding set currents, a feature of the multi-stator modelling approach.

Space vector PWM algorithm for a three-level asymmetrical six-phase motor drive

Abstract: A space vector pulse-width modulation (SVPWM) algorithm for a three-level asymmetrical six-phase drive based on vector space decomposition (VSD) approach is presented in this paper. A modification in zero plane of the transformation matrix is proposed in order to meet the requirement that the realisation of sinusoidal output phase voltages can be obtained through the chosen output leg voltage space vectors. Furthermore, a method of choosing the switching sequences based on all possible one-level transitions of the leg voltages, i.e. a permutation method, is introduced. The algorithm is then validated experimentally and obtained results show that the developed method successfully achieves the desired fundamental phase voltage, although low order harmonics are present due to uncompensated inverter dead time. Last but not least, the performance of the proposed SVPWM algorithm is compared to several carrier-based PWM algorithms including in-phase disposition with ‘double min-max injection’ (PD-DI). This is a little known type of injection, which is verified to obtain identical performance as the presented multilevel algorithm.

Dc-link voltage stability analysis technique for hybrid five-phase open-end winding drives

Abstract: The dc-link voltage stability for a hybrid five-phase open-end winding (OeW) drive operating under carrier-based pulse-width modulation is studied. The drive consists of a five-phase induction machine, supplied using one three-level and one two-level voltage source inverter. This configuration is analysed for the case of isolated dc-link rails, while the dc-link voltage ratio is considered as an additional degree of freedom. It is demonstrated that different dc-link voltage ratios lead to the different overall number of voltage levels across stator windings. Modulation strategies are investigated and their performances are analysed from the dc-link voltages stability point of view. An analytical method for dc-link voltage stability analysis is presented. Results show that the four-level configuration always leads to stable dc-link voltages, regardless of the modulation strategy. On the other hand, if the six-level configuration is combined with modulation strategies that lead to optimal harmonic performance, not all dc-link capacitor voltages will be in the balance depending on the operating conditions.