Control of Non-conventional Synchronous Motors

Chapter 4

Control of the Double-star Synchronous Machine Supplied by PWM Inverters ¹

4.1. Introduction

In high-power applications, such as naval propulsion, the constraints of power segmentation, reliability and safety of functioning have led to the development of specific electrical actuators created by associating machines with a high number of phases with static converters. Thus, during the 1980s, the double-star synchronous machine with two current commutators was used for the electrical propulsion systems of ships [BEN 98, KET 95, KHE 95, KOT 96]. This supply mode, with thyristor current commutators, ensured the simplicity and reliability of the electrical actuator. However the supply of the machine with pulses of currents rich in harmonics led to ripples in the electromagnetic torque. A shift of 30° between the two stars of the machine stator reduced these torque ripples [KHE 95, WER 84]. The use of the smoothing inductance necessary to manufacture the direct current (DC) source supplying the commutator, and thyristor type semi-conductor components decreased the performance of the electrical actuator in dynamic state.

Since the end of the 1990s, thanks to progress made in the field of power electronics and industrial computer science, a new power electronic converter – the double star synchronous machine – is being investigated. The supply of double star synchronous machines with PWM inverters produces sinusoidal currents in the machine windings [ABB 84, NEL 73, SIN 02] ...