Multi-agent control scheme for power distribution in a multi-three-phase motor drive fed by a stacked polyphase bridges converter

A multi-three-phase machine can be seen as a multi-agent system. An agent consists of a three-phase winding set of the multi-three-phase machine, fed by a dedicated three-phase power electronic converter, and steered by means of a dedicated three-phase controller. The series connection of all the three-phase power electronic converters to a single dc power source creates a so-called stacked polyphase bridges converter, and allows for the use of power electronic components with low voltage rating. A major advantage of a multi-three-phase drive is its power sharing capability: not all the agents must contribute equally to the torque demand. A major disadvantage of a stacked polyphase bridges converter, on the other hand, is its inherent instability in motoring mode. The goal of this paper is therefore to propose a multi-agent control strategy that exploits the power sharing capability of the multi-three-phase drive, and simultaneously ensures a stable distribution of the total dc-bus voltage over the agents, even if the agents are not identical. The multi-agent control strategy is in complete accordance with the modularity of the hardware: only local measurements, local computations, and neighbor-to-neighbor communication are required, without the interference of a central or master controller. The control strategy is validated on a 4 kW multi-three-phase axial-flux PMSM working in motoring mode, by means of both simulations and experiments.