Voltage Stability and Control in Autonomous Electric Power Systems with Variable Frequency

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dc.contributor.authorRosado, Sebastian Pedroen
dc.contributor.committeecochairWang, Fei Freden
dc.contributor.committeecochairBoroyevich, Dushanen
dc.contributor.committeememberKohler, Werner E.en
dc.contributor.committeememberBurgos, Rolandoen
dc.contributor.committeememberLiu, Yiluen
dc.contributor.committeememberCenteno, Virgilio A.en
dc.contributor.departmentElectrical and Computer Engineeringen
dc.date.accessioned2014-03-14T20:18:37Zen
dc.date.adate2007-11-19en
dc.date.available2014-03-14T20:18:37Zen
dc.date.issued2007-09-21en
dc.date.rdate2008-11-19en
dc.date.sdate2007-11-16en
dc.description.abstractThis work focuses on the safe and stable operation of an autonomous power system interconnecting an AC source with various types of power electronic loads. The stability of these systems is a challenge due to the inherent nonlinearity of the circuits involved. Traditionally, the stability analysis in this type of power systems has been approached by means of small-signal methodology derived from the Nyquist stability criterion. The small-signal analysis combined with physical insight and the adoption of safety margins is sufficient, in many cases, to achieve a stable operation with an acceptable system performance. Nonetheless, in many cases, the margins adopted result in conservative measures and consequent system over designs. This work studies the system stability under large-perturbations by means of three different tools, namely parameter space mapping, energy functions, and time domain simulations. The developed parameters space mapping determines the region of the state and parameter space where the system operation is locally stable. In this way stability margins in terms of physical parameters can be established. Moreover, the boundaries of the identified stability region represent bifurcations of the system where typical nonlinear behavior appears. The second approach, based on the Lyapunov direct method, attempts to determine the region of attraction of an equilibrium point, defined by an operation condition. For this a Lyapunov function based on linear matrix inequalities was constructed and tested on a simplified autonomous system model. In Addition, the third approach simulates the system behavior on a computer using a detailed system model. The higher level of model detail allows identifying unstable behavior difficult to observe when simpler models are used. Because the stability of the autonomous power system is strongly associated with the characteristics of the energy source, an improved voltage controller for the generator is also presented. The generator of an autonomous power system must provide a good performance under a wide variety of regimes. Under these conditions a model based controller is a good solution because it naturally adapts to the changing requirements. To this extent a controller based on the model of a variable frequency synchronous generator has been developed and tested. The results obtained show a considerable improvement performance when compared to previous practices.en
dc.description.degreePh. D.en
dc.identifier.otheretd-11162007-141350en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-11162007-141350/en
dc.identifier.urihttp://hdl.handle.net/10919/29616en
dc.publisherVirginia Techen
dc.relation.haspartSRosado_dissertation.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectmulti-pulse transformer rectifieren
dc.subjectstand-alone power systemsen
dc.subjectsynchronous generator excitationen
dc.subjectlyapunov methodsen
dc.subjectvoltage stabilityen
dc.subjectlarge-signal stabilityen
dc.titleVoltage Stability and Control in Autonomous Electric Power Systems with Variable Frequencyen
dc.typeDissertationen
thesis.degree.disciplineElectrical and Computer Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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