Converters, electrical machines and drives (CEMD)

The electrical Converters, Machines and Drives group studies the design and modelling of standard and innovative electrical machines; besides, it deals with static converters, electrical drives and their control systems.

The group has developed several applications of permanent magnet (PM) machines, with conventional and innovative windings. Among the various applications there are:

radial flux or axial-flux machines with concentrated windings (tooth-coil winding). An innovative winding has been patented, applicable to low-speed machines, which allows to get sinusoidal electro-motive-forces and limited parasitic torques. These machines can be used as generators directly driven by wind or hydro low speed turbines and in seismic vibration dampening systems in civil constructions, as bridges;
multi-modular permanent magnet synchronous generators which supply two-level converters, connected in series or in parallel among them on the dc-side. The effect of the sequential command of the converters on the torsional vibrations of the shaft is studied and some methods to avoid them are proposed;

PM machines for Motor Generator Unit (MGU) used in FormulaE;
special motors, e.g. double-rotor type (one concentric into the other) for the fluid transportation in an environment with chemical agents;
high-speed micro-motors, e.g. for dental applications.
In these cases, some industrial partnerships have been carried out.

Another field is the dielectric and electromagnetic analysis of reactors, transformers and magnetic circuits.

A third subject deals with sensorless control (without position and speed sensor) applied to doubly-fed induction machines, often used in wind energy systems. Some techniques for the implementation of the sensorless control have been analyzed and some have been proposed and experimentally tested; for example, one is based on the fifth harmonic of the grid voltage.

Another subject deals with isolated micro-grids, supplied by electronic converters among which no communication exists. The main research subjects deal with system stability, power sharing among different sources and synthetic inertia.