O. Dranga

James Cook University, Townsville, Queensland, Australia

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Publications (28)12.88 Total impact

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    ABSTRACT: The current paper is dedicated to present browser-based multimedia-rich software tools and e-learning curriculum to support the design and modeling process of power electronics circuits and to explain sometimes rather sophisticated phenomena. Two projects will be discussed. The so-called Inetele project is financed by the Leonardo da Vinci program of the European Union (EU). It is a collaborative project between numerous EU universities and institutes to develop state-of-the art curriculum in Electrical Engineering. Another cooperative project with participation of Japanese, European and Australian institutes focuses especially on developing e-learning curriculum, interactive design and modeling tools, furthermore on development of a virtual laboratory. Snapshots from these two projects will be presented.
    IEEJ Transactions on Industry Applications 01/2008;
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    [Show abstract] [Hide abstract]
    ABSTRACT: The current paper is dedicated to present browser-based multimedia-rich software tools and e-learning curriculum to support the design and modeling process of power electronics circuits and to explain sometimes rather sophisticated phenomena. Two projects will be discussed. The so-called Inetele project is financed by the Leonardo da Vinci program of the European Union(EU). It is a collaborative project between numerous EU universities and institutes to develop state-of-the art curriculum in electrical engineering. Another cooperative project with participation of Japanese, European and Australian institutes focuses especially on developing e-learning curriculum, interactive design and modeling tools, furthermore on development of a virtual laboratory. Snapshots from these two projects will be presented.
    Power Conversion Conference - Nagoya, 2007. PCC '07; 05/2007
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    ABSTRACT: The main objective of the paper is to present new browser-based, interactive software tools for modeling of various power electronics circuits. The static and dynamic operation, including the continuous and discrete time linearization of widely applied DC-DC converter cells are discussed in the first part of the paper. The second part focuses on the basics of the pulse-width-modulation and its application in one-phase sinusoidal inverters. The interactive tools provide numerous excellent opportunities for industrial and academic education. Another application field of numerous embedded interactive software components is their utilization as fast, real-time model-building tools
    Power Electronics and Motion Control Conference, 2006. EPE-PEMC 2006. 12th International; 10/2006
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    ABSTRACT: Power-factor-correction (PFC) power supplies are required to provide high input power factor and tight output voltage regulation. The usual configuration takes a two-stage cascade structure, consisting of a PFC preregulator and a dc/dc converter. Previous studies of the dynamical behaviour mainly focused on the boost PFC preregulator, assuming that it is being terminated by a resistive load. However, in practice, as the PFC preregulator is terminated by a dc/dc converter whose characteristics differ from resistive load's, the assumption of resistive load termination gives rather inaccurate information about the stability of the system. In this paper we study the complete two-stage PFC power supply and show that the interaction between the PFC stage and the dc/dc converter stage plays an important role in determining the stability of the system
    Power Electronics Specialists Conference, 2006. PESC '06. 37th IEEE; 07/2006
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    ABSTRACT: This paper describes the fast-scale bifurcation phenomena of a single-stage power-factor-correction (PFC) power supply which is a cost effective design for low-power applications. The circuit employs a cascade configuration of a boost converter and a forward converter, which share an active switch and operate in discontinuous conduction mode, to provide input PFC and tight output regulation. Main results are illustrated by "exact" circuit simulations as well as theoretical analysis based on the use of Jacobians. This work provides a convenient means of predicting stability boundaries which can facilitate the selection of practical parameter values for maintaining stable operation.
    Circuits and Systems I: Regular Papers, IEEE Transactions on 02/2006; · 2.24 Impact Factor
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    ABSTRACT: Exploiting the recent achievements of the information and communication technologies, a new e-learning initiation entitled Yoto project was launched in 2004. On longer run its most important objective is to build up and maintain an electrical engineering knowledge base, on shorter run it helps giving more and more publicity to some relevant fields, especially power electronics, drives and motion control. The multimedia rich content can be utilized in the high level academic education, in the industrial vocational trainings and also in supporting the circuit and system design specialists by fast interactive tools. This paper presents a new e-module attached to the Yoto project about the dynamic operation and modeling of dc-dc converters.
    Industrial Technology, 2005. ICIT 2005. IEEE International Conference on; 01/2006
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    H.H.C. Iu, C.K. Tse, O. Dranga
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    ABSTRACT: This paper studies a system of parallel-connected dc/dc buck converters under current-mode control. The effects of variations of the reference current are studied. It has been observed that the system exhibits low-frequency bifurcation behaviour while period-doubling at switching frequency is suppressed. Extensive simulations are used to capture the behaviour. Time-domain waveforms, stroboscopic maps and trajectories are shown. The paper reveals the drastic alteration of bifurcation behaviour of dc/dc converters due to subtle coupling.
    Circuits and Systems, 2005. ISCAS 2005. IEEE International Symposium on; 06/2005
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    H.H.C. Iu, C.K. Tse, O. Dranga
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    ABSTRACT: This paper studies a single buck converter and a system of parallel-connected dc/dc buck converters under current-mode control. The effects of variations of the reference current are studied. It has been observed that the system exhibits low-frequency bifurcation behaviour while period-doubling at switching frequency is suppressed. Extensive simulations are used to capture the behaviour. Time domain waveforms, stroboscopic maps, and trajectories are shown. The paper reveals the drastic alteration of bifurcation behaviour of dc/dc converters due to subtle coupling.
    Circuits Systems and Signal Processing 03/2005; 24(2):201-219. · 0.98 Impact Factor
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    O. Dranga, B. Buti, I. Nagy, H. Funato
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    ABSTRACT: Variable-structure piecewise-linear nonlinear dynamic feedback systems emerge frequently in power electronics. This paper is concerned with the stability analysis of these systems. Although it applies the usual well-known and widely used approach, namely, the eigenvalues of the Jacobian matrix of the Poincare´ map function belonging to a fixed point of the system to ascertain the stability, this paper offers two contributions for simplification as well that utilize the periodicity of the structure or configuration sequence and apply an alternative simpler and faster method for the determination of the Jacobian matrix. The new method works with differences of state variables rather than derivatives of the Poincare´ map function (PMF) and offers geometric interpretations for each step. The determination of the derivates of PMF is not needed. A key element is the introduction of the so-called auxiliary state vector for preserving the switching instant belonging to the periodic steady-state unchanged even after the small deviations of the system orbit around the fixed point. In addition, the application of the method is illustrated on a resonant dc-dc buck converter.
    Circuits and Systems I: Regular Papers, IEEE Transactions on 02/2005; · 2.24 Impact Factor
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    O. Dranga, C.K. Tse, Siu Chung Wong
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    ABSTRACT: Power-factor-correction (PFC) power supplies are required to provide high input power factor and tight output voltage regulation. The usual configuration takes a two-stage cascade structure, consisting of a PFC preregulator and a dc/dc converter. Previous studies of the dynamical behaviour mainly focused on the boost PFC preregulator, assuming that it is being terminated by a resistive load. However, in practice, as the PFC pre-regulator is terminated by a dc/dc converter whose characteristics differ from resistive load's, the assumption of resistive load termination gives rather inaccurate information about the stability of the system. In this paper we study the complete two-stage PFC power supply and show that the interaction between the PFC stage and the dc/dc converter stage plays an important role in determining the stability of the system.
    Circuit Theory and Design, 2005. Proceedings of the 2005 European Conference on; 01/2005
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    International Power Electronics and Motion Control Conference, EPE-PEMC 2004, Riga, Latvia; 09/2004
  • Chi K. Tse, Octavian Dranga
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    ABSTRACT: The problem of sudden loss of stability (more precisely, sudden change of operating behaviour) is frequently encountered in power electronics. A classic example is the current-mode controlled dc/dc converter which suffers from unwanted subharmonic operations when some parameters are not properly chosen. For this problem, power electronics engineers have derived an effective solution approach, known as ramp compensation, which has become the industry standard for current-mode control of dc/dc converters. In this chapter, the problem is reexamined in the light of bifurcation analysis. It is shown that such an analysis allows convenient prediction of stability boundaries and facilitates the selection of parameter values to guarantee stable operation. It also permits new phenomena to be discovered. An example is given at the end of the chapter to illustrate how some bizarre operation in a power-factor-correction (PFC) converter can be systematically explained.
    08/2004: pages 722-723;
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    ABSTRACT: The concept of a variable active-passive reactance (VAPAR), which can generate a virtual variable inductance in power circuits, including negative values, has already been proposed. Since it has found application in the power flow control of power systems, where the power flow is essentially restricted by a line inductance, the aim of the paper is to report on the stability of this virtual inductance in an RL circuit. The periodic steady-state operation of the variable-structure, piecewise-linear, nonlinear system is modeled by its Poincare map. The stability criterion employs the position of the eigenvalues of the Jacobian matrix of the Poincare map, evaluated at its fixed point. Bifurcation behaviour when varying the virtual inductance is revealed. Such an analysis allows accurate prediction of stability boundaries and facilitates the selection of parameter values to guarantee stable operation.
    Circuits and Systems, 2004. ISCAS '04. Proceedings of the 2004 International Symposium on; 06/2004
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    ABSTRACT: Since power circuits are significantly influenced by inductances, a variable active-passive reactance (VAPAR) has previously been introduced in order to generate a virtual negative inductance, which has found applications in the rapid power flow control of power systems. It is used to cancel an existing undesired inductance, since the power flow through a simple power system of two voltage buses connected by an inductive power line is essentially restricted by the line inductance. These studies also indicated that the stability of the system could be compromised by the presence of stray capacitances. The present paper aims to offer a more accurate stability assessment of this RLC configuration, estimated so far by linear approximation, by essentially ignoring the switching process within VAPAR. The normal periodic steady-state regime leads to a fixed point in the stroboscopic map used to model the variable-structure piecewise-linear nonlinear system. The stability is indicated by the eigenvalues of the Jacobian matrix of the stroboscopic map, evaluated at this fixed point. The analysis reveals bifurcation behaviour and allows accurate and convenient prediction of the stability boundary in the parameter space of the virtual negative inductance required by the application and the stray capacitance present in the power circuit.
    Power Electronics Specialists Conference, 2004. PESC 04. 2004 IEEE 35th Annual; 02/2004
  • ECU Publications. 01/2004;
  • ECU Publications. 01/2004;
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    C.K. Tse, O. Dranga, H.C.C. Iu
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    ABSTRACT: Bifurcation analysis is performed to a power-factor-correction (PFC) boost converter to examine the fast-scale instability problem. Computer simulations and analysis reveal the possibility of period-doubling for some intervals within the line cycle. The results allow convenient prediction of stability boundaries. Analytical equations and design curves are given to facilitate the selection of parameter values to guarantee stable operation.
    Circuits and Systems, 2003. ISCAS '03. Proceedings of the 2003 International Symposium on; 06/2003
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    O. Dranga, B. Buti, I. Nagy
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    ABSTRACT: This paper reports on the stability analysis of one member of a dual-channel resonant DC-DC converter family. The study is confined to the buck configuration in symmetrical operation. The output voltage of the converter is controlled by a closed loop applying constant-frequency pulsewidth modulation. The dynamic analysis reveals that a bifurcation cascade develops as a result of increasing the loop gain. The trajectory of the variable-structure piecewise-linear nonlinear system pierces through the Poincare plane at the fixed point in state space when the loop gain is small. For stability criterion the positions of the characteristic multipliers of the Jacobian matrix belonging to the Poincare map function defined around the fixed point located in the Poincare plane is applied. In addition to the stability analysis, a bifurcation diagram is developed showing the four possible states of the feedback loop: the periodic, the quasi-periodic, the subharmonic, and the chaotic states. Simulation and test results verify the theory.
    IEEE Transactions on Industrial Electronics 03/2003; · 6.50 Impact Factor
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    ABSTRACT: The aim of the paper is to investigate the bifurcation behavior of the power-factor-correction (PFC) boost converter under a conventional peak current-mode control. The converter is operated in continuous-conduction mode. The bifurcation analysis performed by computer sim- ulations reveals interesting eects of variation of some chosen parameters on the stability of the converter. The results are illustrated by time-domain waveforms, discrete-time maps and parameter plots. An analytical investigation conrms the results obtained by computer simula- tions. Such an analysis allows convenient prediction of stability boundaries and facilitates the selection of parameter values to guarantee stable operation.
    International Journal of Bifurcation and Chaos 01/2003; · 0.92 Impact Factor
  • O. Dranga, I. Nagy
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    ABSTRACT: The stability analysis of the buck member of a dual channel resonant DC-DC converter family is reported. The study is confined to the symmetrical continuous current mode. The output voltage of the converter is controlled by a feedback loop applying constant frequency PWM. The dynamic analysis applies to stability criterion the positions of the characteristic multipliers of the Jacobian matrix belonging to the Poincare map function defined around the fixed point located in the Poincare plane where the trajectory of the variable structure, piecewise linear, nonlinear system pierces through the plane. The study reveals that the process loses its stability as a result of varying the loop gain
    Industrial Electronics, 2001. Proceedings. ISIE 2001. IEEE International Symposium on; 02/2001

Publication Stats

212 Citations
12.88 Total Impact Points

Institutions

  • 2006
    • James Cook University
      Townsville, Queensland, Australia
  • 2005
    • City University of Hong Kong
      • Department of Electronic Engineering
      Kowloon, Hong Kong
    • University of Western Australia
      • School of Electrical, Electronic and Computer Engineering
      Perth, Western Australia, Australia
  • 2004–2005
    • The Hong Kong Polytechnic University
      • Department of Electronic and Information Engineering
      Hong Kong, Hong Kong
    • Utsunomiya University
      • Division of Electrical and Electronic Engineering
      Totigi, Tochigi, Japan
  • 2003
    • The University of Hong Kong
      Hong Kong, Hong Kong
  • 2000
    • Budapest University of Technology and Economics
      • Department of Automation and Applied Informatics
      Budapeŝto, Budapest, Hungary