Adaptation of a magnetic equivalent circuit for excitation system design
The major emphasis of this research is the adaptation of a magnetic equivalent circuit model for population-based optimal design of excitation systems for wound rotor synchronous machines (WRSM), specifically for power generation. The performance of an excitation system impacts the ability of a primary WRSM to deliver high quality power in non-grid connected (islanded) applications. Specifically, there are requirements associated with delivery of fault current and responsiveness to transient loading of the primary WRSM that are contingent on the capability of the exciter system to deliver field current to the primary field winding. Optimization of the excitation system to meet these requirements is the impetus of this research. In this thesis, a mesh-based MEC interior armature WRSM model is developed, wherein the armature is rotating interior to the stationary field winding. This involves the construction of a new set of reluctance paths associated with interchanging the position of a primary field and armature. Once developed, the interior armature model is used to model the exciter of a primary WRSM. This exciter is coupled to the field winding of a 25 kWe primary WRSM via a passive diode rectifier. Two cases of hardware results are used to experimentally validate the modeling approach: open circuit results for a standalone exciter and transient load application performance for the exciter coupled to the primary WRSM. The former case shows accuracy to within 5% at steady-state while the latter shows accuracy to within 6% in dynamic operation. An optimization of a standalone exciter via genetic algorithm is presented as well.^
Steven D. Pekarek, Purdue University.