Modular motor drives can be considered as multi‐agent systems, in which the agents can work together to reach a common goal. One agent in such a modular motor drive consists of only a subset of the machine phases and power electronic converter modules, and is equipped with a dedicated controller. When the dc‐links of the different agents are connected in series to a single voltage source, giving rise to a so‐called stacked polyphase bridges converter, the power electronic converter components can have low voltage ratings. However, a voltage balancing controller must ensure that the total dc‐link voltage is distributed evenly among the agents when working in motoring mode. The goal of this research is to propose a multi‐agent voltage balancing algorithm based on dynamic average consensus, which depends solely on local computations, local measurements, and neighbour‐to‐neighbour communication. The scalability and reliability of the modular hardware are hence extended towards the control. Simulations and experimental results on a 4 kW modular axial‐flux PMSM demonstrate the feasibility of the concept.

In this paper, high-frequency (HF) modelling of electric machines with random wound distributed windings is investigated to highlight the parameter variation due to the manufacturing. HF modelling of electric machines can be performed by impedance measurements of the stator windings. The random wound windings introduce variability in the motor model limiting parameter estimation accuracy. These parameters are the following: series resistance, main inductance, skin effect and capacitive coupling of individual turns in the windings and from the windings to the frame. By measuring the impedance of the 3-phase windings of seven consecutively produced induction motors the variability due to the random wound windings can be studied. These seven motors are then compared to one another and to an eighth motor that was produced at a different point in time. From this it is illustrated that the behavior varies even when motors were produced consecutively.