Hybrid Magnet - Field Winding Solutions for Exciters of Synchronous Generators

Abstract

The use of the classical, wound-field synchronous generator in the field of power generation, as opposed to a permanent magnet machine, is driven by the need of controlling the field winding voltage and current in such a way to guarantee a constant voltage at the generator's armature terminals. In a traditional generating set, this

An Improved Automatic Voltage Regulator for Self-Excited, Small-to-Medium Power Generating Sets equipped with Brushless Excitation Systems

“…Therefore, besides possibly improving the GS dynamic performance, a more flexible operation would enable further system improvements. In fact, when a hybrid PMs -field winding solution is envisioned for the exciter as proposed in [10], the unidirectional nature of the SCR limits the degrees of freedom of the PMs design. In other words, they have to be sized in such a way to provide an excitation level (when no current flows in the exciter field winding) which would not imply the need for negative exciter field currents at any of the operations of the main generator.…”

“…In other words, they have to be sized in such a way to provide an excitation level (when no current flows in the exciter field winding) which would not imply the need for negative exciter field currents at any of the operations of the main generator. For example, in [10], the rated no-load operation of the alternator was targeted for the PMs design. On the other hand, the implementation of a bi-directional system feeding the exciter field winding would permit to size the PMs in such a way to provide an excitation level (when no current flows in the exciter field winding) targeting any of the load operations points of the main generator.…”

“…While these solutions result in much more performing systems, however they come at the cost of increasing the overall complexity and cost. A hybrid PM -field winding exciter has been proposed in [10], which achieves an improved overall system efficiency while limiting the production costs. A significant constraint of this work was that of keeping the rest of the system unaltered, i.e.…”

“…Therefore, the magnets were designed to provide the rated voltage at the generator terminals when this operates at no-load. On the other hand, the constraint imposed in [10] limits the degrees of freedom relative to the exciter design, which can be further improved by selecting a more suitable operating point for the sizing of the PMs. In fact, when any of the generator load condition is assumed for the PM design, the unidirectional SCR is no longer sufficient and a static converter able to provide also negative current values to the exciter field coils needs to be used.…”