A Modular Speed-Drooped System for High Reliability Integrated Modular Motor Drives

Future transportation challenges include a considerable reduction in pollutant emissions at a time when significant increase in demand is predicted. One of the enabling solutions is the electrification of transport systems as this should lead to improved operability, fuel savings, emission reduction, and maintenance. While state-of-the-art technology has demonstrable benefits there needs to be considerable advancement to meet future transportation affordability and emission targets. Primarily, electrical drives need an improved power density, an increased reliability, and a reduced specific cost. For this reason, integrated modular motor drives (IMMDs) present an attractive solution. Modularity leads to redundancy and easier integration. This paper presents a novel speed-drooped control system applied to motors fed by modular paralleled converters. This control technique allows precise speed regulation and power sharing among different segments showing improved fault tolerance and reliability. The design procedure and the power sharing dynamic have been presented and analyzed by means of MATLAB/Simulink and validated in a 3-kW experimental rig, showing good agreement with the expected performances.

I. Introduction

Nowadays, most three-phase motors are supplied by a conventional three-phase motor drive [1]. Next generation drives should provide greater reliability, robustness, and competitiveness on the global market of propulsion systems. A segmented machine is one of the possible solutions to increase fault tolerance, giving the chance to redesign the drive concept, providing the power in a modular and integrated way. Integrated modular motor drives (IMMDs) are the result of this process of innovation suitable for applications requiring high efficiency and power density [2], [3]. Redesign of the drive with the power electronics building block (PEBB) [4] in mind is not just a simple physical redistribution of the components into the housing to save space and wire length, but it is a chance to investigate new possible features and, therefore, new market opportunities. At the moment, higher cost is the main issue preventing their diffusion into the market, but the flexibility and functionalities introduced by IMMD systems is expected to reduce the payback time in the near future; indeed, due to their modularity, on a large-scale economy the costs of the IMMD will be cut down [1].