Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.580698
Title: Analysis and control of nonlinear characteristics in DC/DC converters
Author: Imrayed, Otman Musa
Awarding Body: University of Newcastle Upon Tyne
Current Institution: University of Newcastle upon Tyne
Date of Award: 2012
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Abstract:
Nonlinear behaviour has been observed in DC/DC converters for the last two decades. Generally, it has been reported that under variation of a system parameter the stability of these systems may be lost via two types of bifurcations, namely a fast-scale and a slow-scale bifurcation. The study of converter dynamical behaviour is important to investigate its stability and to design appropriate controllers in order to avoid these undesirable behaviours. Conventionally, converter designers ignore the discontinuities introduced by the switching operation and use a linear model whose variables are the average values of circuit currents and voltages. Converter components and parameters are then chosen to guarantee stable behaviour and to avoid any operating regions in which the converter is likely to exhibit anyone of the possible unstable (nonlinear) behaviours. As a result, converter components are significantly oversized giving a larger, heavier, less efficient, and more expensive product than could be achieved by the appropriate application of nonlinear control methods. Recently, an alternative method based on the concept of the Monodromy matrix had been used to investigate the stability of the nominal periodic orbit of the DC/DC converters including switching effects. The system's transition matrix over one complete cycle is composed of the matrices over the linear segments for the ON and OFF periods, and those across the switching events, called the Jump or Saltation matrices (whose elements are functions of the parameters of the converter circuit and their time derivatives). When the eigenvalues of the Monodromy matrix goes out the unit circle, a suitable control signal is applied to push the eigenvalues of the matrix into the unit circle and thus maintain stability. This method is applied to investigate typical and exotic nonlinear phenomenon that occurs in the DC-DC boost converter operating under cascade current control. The Monodromy matrix is used to analysis the occurrence of periodic, quasiperiodic, and saturation behaviour. It shows that all those instabilities can coexist for the same parameter value, and there can be complex interactions between them. This analysis shows that an abrupt exit to saturation mode can be triggered by a torus-torus collision. This thesis also reported for the first time, the observation of three frequencies quasiperiodic behaviour in a power electronic system.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.580698  DOI: Not available
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