The doubly fed permanent magnet synchronous machine as a highly efficient drive system for constant speed applications

In this paper, a highly efficient drive system for applications with a constant rotational speed will be presented. For this a doubly fed permanent magnet synchronous machine (DFPMSM) will be used as motor/ generator. Since permanent magnet synchronous machines (PMSM) don´t work stable at the electrical grid without the usage of additional components such as damper windings or a damping mechanical load, they are typically controlled by an inverter. These additive arrangements cause losses. However, the alternative usage of an inverter in the power class of the PMSM results in switching and conduction losses as well. For these reasons, the aim is to reduce those losses to a minimum without impairing the stability of the drive system. Respecting that it is restricted to constant speed applications only, the DFPMSM is such an optimized drive concept. The stator of the DFPMSM is fed by two energy sources: first by the electrical grid and second by a low power inverter, compared with the power class of the electrical machine. In this contribution, the focus is on the serious connected DFPMSM (SC-DFPMSM).