Isolated Chargers for EVs Incorporating Six-Phase Machines

Abstract

The paper considers two isolated solutions for fast charging of electric vehicles (EVs). The isolation is located on the grid side (off-board), while the rest of the charging apparatus is placed on-board the EV and it entirely consists of the existing power electronics components that would be otherwise used only for propulsion. Thus, substantial savings on the space, weight, and cost are achieved. The considered configurations fully incorporate either a symmetrical or an asymmetrical six-phase machine, as well as a six-phase inverter, into the charging process. Due to the nature of the connections, torque production is avoided during the charging/vehicle-to-grid (V2G) modes of operation. Thus the machines do not have to be mechanically locked, and their rotors naturally stay at standstill. Control schemes for both configurations are elaborated, and theoretical results are validated by experiments for the two configurations in both charging and V2G modes.

Multiphase machines and drives - Revisited

“…existence of additional degrees of freedom in multiphase machines are discussed in [21][22][23][24][25][26]. Most of them focus on post-fault operating strategies for motoring [21][22][23] and generating applications [24,25].…”

“…The final paper of this SS [26] addresses an entirely new application of the additional degrees of freedom offered by multiphase machines. Any attempt to fully integrate a threephase machine into a fast (three-phase) on-board battery charger for an EV, and thus re-use the propulsion components (the inverter and the machine) during the battery charging, inevitably leads to torque development.…”

“…However, if multiphase power electronics and machines are used instead of the three-phase counterparts, it becomes possible to achieve full integration without any torque production in the machine during the charging process, and thus achieve substantial savings in the space, weight and cost of the entire system. Such solutions, based on symmetrical and asymmetrical sixphase machines, are developed in [26]. The charging/vehicleto-grid modes of operation are realized without any torque production, thus enabling the rotor to stay naturally at standstill; hence the need for the mechanical rotor locking is avoided.…”

A Simple Braking Method for Six-Phase Induction Motor Drives With Unidirectional Power Flow in the Base-Speed Region

“…These components allow the post-fault operation without extra hardware, and this fault tolerance is highly appreciated in safety-critical low-power applications such as in aircraft [18][19][20] or electric vehicle actuators [21]. While this capability is known from the early research studies in multiphase drives, other innovative uses for the new degrees of freedom have also appeared in recent times [6,14,[22][23][24]. Since the braking mode of operation requires three degrees of freedom to independently regulate flux, torque and losses, an innovative use of the x-y currents is suggested in [25] to intentionally generate the losses.…”

Multidirectional power flow control among double winding six-phase induction machine winding sets

“…As already mentioned, there are several practical applications of the multiple three-phase induction machines such as, more-electric aircrafts [3][4][5] and electrical vehicles (EVs) [8][9][10][11]. In the latter application, the electrical power generation and distribution systems are expected to raise from the conventional low dc voltage to a higher dc voltage level in the near future.…”