PHASE CO-ORDINATE BOND GRAPH ANALYSIS OF MULTIPORT ENERGY SYSTEMS

PhDThe analysis of unbalanced power system problems using the method of phase co-ordinates by which the phase quantities are preserved has obvious practical advantages over the transformation methods requiring the phase quantities to be substituted by, for example, symmetrical component and d-q quantities. Since the physical identity of the system is maintained in the phase frame of reference, the matematical models of the system can be subjected to actual operating constraints enabling a unified approach to be adopted in the study of both symmetrical and unsymmetrical conditions. In this thesis the bond graph techniques are used to model power system components in terms of their phase co-ordinates. The bond graph structure, which is based on energy continuity and power balance, classifies system and sub-systems, with respect to the number of energy ports through which energy or power is exchanged with the environment as well as in terms of the particular internal energy transformations involved. The use of bond graphs for the analysis of non-linear electromagnetic systems has resulted in the evolution of a uniform diagramatic structure which, represents in a single diagram the basic field properties such as the magneto-motive force and the flux linkages together with the conjugate circuit power variables, voltage and current. As an extension of this ideal the general n-port electromagnetic and electrostatic field systems are derived in bond graph notations. A very desirable feature of this method of presentation is that there exists a one-to-one-correspondence between the bond graph and a computation structure which may be used for the purpose of simulation by either analogue or digital computers. The general n-port electromagnetic and electrostatic field systems form the basis for the effective modelling of power system components such as rotating machines, transformers and transmission lines. In the investigations of earth faults, these models are simplified in accordance with the need of the particular study but are sufficiently accurate representations to allow predictions on the overall system behaviours. The bond graph approach is ideally suited to expedite the modelling of dynamic interacting energy systems and when used in conjunction with the computation structure can provide the simulation technique required to model accurately the non-linear behaviours of multiport electromechanical energy converters. The effects of magnetic saturation in synchronous generators are presented in detail.Institut Teknologi Kebangsaan, Malaysi

NASA Tech Briefs, March 1993

Topics include: Computer-Aided Design and Engineering; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences

Performance enhancement of steady-state Markov analysis for cognitive radio networks via channel reservation

Cognitive radio wireless networks CRNs have been considered as an efficient communication paradigm to the utilization of scarce spectrum. The main purpose of channel reservation of dynamic spectrum access (DSA) is to access these idle channels intelligently which are specialized for primary users (PUS) to be used by unlicensed users temporarily, which are called secondary users (SUS) without causing critical interference to the licensed userâs activity. In this paper, continuous-time Markov chain paradigm is improved via channel reservation to show the best usage of the radio spectrum bands, and the transition matrix are deduced for the proposed model. Moreover, the probability state vector is proved by performing steady state analysis. The deduced expressions of the suggested model are illustrated in the numerical results section. Keywords: Cognitive radio networks, Dynamic spectrum access, Channel reservation, Continuous-time Markov chain, Steady-state analysi