Control of Synchronous Motors

Chapter 3

Optimal Supplies and Synchronous Motors Torque Controls. Design in the d-q Reference Frame ¹

3.1. Introduction: on the controls designed in the Park d-q reference frame

The design and realization of torque control are crucial stages for the control of an electrical motor. In the case of a synchronous motor, it comes down to defining and regulating the stator current references. This explains the importance given to these questions in this book. Chapter 2 was devoted to the controls in the a-b-c reference frame, a very important case, but relatively heavy if we want to discuss it rigorously. This chapter tackles this same question in the d-q reference frame, where it is easier to design controls that are very efficient in terms of precision and dynamics. Indeed, as soon as the digital components facilitated the real time implementations of sophisticated algorithms, the synchronous motor models presented by the Park transformation became excellent tools for designing controls. The first advantage of this model is the fact that the saliency is easily taken into account, as shown by the torque expression as a function of the currents (see for example, equation [3.3] deduced from equation [1.73] in Chapter 1, section 1.5.3). Let us note however that, as educational preliminaries, we will often present the principle of the methods in the case of non-salient pole machines. Moreover, to impose the torque simply consists of regulating “direct” currents.

One of the greatest advantages ...