Enhanced Power Sharing Transient With Droop Controllers for Multithree-Phase Synchronous Electrical Machines

This paper presents a droop-based distributed control strategy for multithree-phase machines that provides augmented controllability during power sharing transients. The proposed strategy is able to mitigate the mutual interactions among different sets of windings without controlling any subspace variable, also offering a modular and redundant design. On the contrary, in a centralized configuration, subspaces would be controlled using the vector space decomposition, but fault tolerance and reliability levels required by the stricter regulations and policies expected in future transportation systems would not be satisfied. The proposed method is analytically compared against the state-of-the-art power sharing technique and equivalent models and control design procedures have been derived and considered in the comparison. Uncontrolled power sharing transients and their effects on mutual couplings among isolated sets of windings have been compared against the proposed regulated ones. Experimental results on a 22-kW nine-phase multithree-phase synchronous machine rig validate the design procedures showing good agreement with the expected performances.

I. Introduction

The electrification of transportation systems started at the end of the 19th century. At that time, engineers already studied how to electrify many different technologies for a wide range of applications, like for example locomotives [1] and tractor ploughs [2]. Nevertheless, fossil fuel technologies superseded the electrification process during the 20th century. Only recently, thanks to many technology advancements (i.e., power electronics, renewable energy sources, storage devices, etc.), following the resolution adopted by the general assembly of the United Nations held in 1989 [3], a proper propulsion system revolution aiming at pollution reduction has been launched. Since then, multiple research projects for transportation systems, i.e., mining machines [4], [5], ships [6], [7], offshore wind turbines [8], ultrahigh-speed elevators [9], road vehicles [10], and aircraft [11]–[13], have been founded by governments, innovation centers, and companies around the world.