1,388 research outputs found
Coexisting fast-scale and slow-scale instability in current-mode controlled DC/DC converters : analysis, simulation and experimental results
Author name used in this publication: Chi K. Tse2008-2009 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Dynamics and stability issues of a single-inductor dual-switching DC-DC converter
A single-inductor two-input two-output power electronic dc–dc converter can be used to regulate two generally nonsymmetric
positive and negative outputs by means of a pulsewidth modulation with a double voltage feedback. This paper studies the dynamic behavior of this system. First, the operation modes and the steady-state properties of the converter are addressed, and, then, a stability analysis that includes both the power stage and
control parameters is carried out. Different bifurcations are determined from the averaged model and from the discrete-time model.
The Routh–Hurwitz criterion is used to obtain the stability regions of the averaged (slow-scale) dynamics in the design parameter
space, and a discrete-time approach is used to obtain more accurate results and to detect possible (fast-scale) subharmonic oscillations.
Experimental measurements were taken from a system prototype to confirm the analytical results and numerical simulations.
Some possible nonsmooth bifurcations due to the change in the switching patterns are also illustrated.Postprint (published version
Stability analysis of two-stage PFC power supplies
Author name used in this publication: Chi K. TseRefereed conference paper2005-2006 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe
Using Nyquist or Nyquist-Like Plot to Predict Three Typical Instabilities in DC-DC Converters
By transforming an exact stability condition, a new Nyquist-like plot is
proposed to predict occurrences of three typical instabilities in DC-DC
converters. The three instabilities are saddle-node bifurcation (coexistence of
multiple solutions), period-doubling bifurcation (subharmonic oscillation), and
Neimark bifurcation (quasi-periodic oscillation). In a single plot, it
accurately predicts whether an instability occurs and what type the instability
is. The plot is equivalent to the Nyquist plot, and it is a useful design tool
to avoid these instabilities. Nine examples are used to illustrate the accuracy
of this new plot to predict instabilities in the buck or boost converter with
fixed or variable switching frequency.Comment: Submitted to an IEEE journal in 201
Stability analysis and control of DC-DC converters using nonlinear methodologies
PhD ThesisSwitched mode DC-DC converters exhibit a variety of complex behaviours in power
electronics systems, such as sudden changes in operating region, bifurcation and
chaotic operation. These unexpected random-like behaviours lead the converter to
function outside of the normal periodic operation, increasing the potential to generate
electromagnetic interference degrading conversion efficiency and in the worst-case
scenario a loss of control leading to catastrophic failure.
The rapidly growing market for switched mode power DC-DC converters demands
more functionality at lower cost. In order to achieve this, DC-DC converters must
operate reliably at all load conditions including boundary conditions. Over the last
decade researchers have focused on these boundary conditions as well as nonlinear
phenomena in power switching converters, leading to different theoretical and
analytical approaches. However, the most interesting results are based on abstract
mathematical forms, which cannot be directly applied to the design of practical
systems for industrial applications.
In this thesis, an analytic methodology for DC-DC converters is used to fully
determine the inherent nonlinear dynamics. System stability can be indicated by the
derived Monodromy matrix which includes comprehensive information concerning
converter parameters and the control loop. This methodology can be applied in
further stability analysis, such as of the influence of parasitic parameters or the effect
of constant power load, and can furthermore be extended to interleaved operating
converters to study the interaction effect of switching operations. From this analysis,
advanced control algorithms are also developed to guarantee the satisfactory
performance of the converter, avoiding nonlinear behaviours such as fast- and slowscale
bifurcations. The numerical and analytical results validate the theoretical
analysis, and experimental results with an interleaved boost converter verify the
effectiveness of the proposed approach.Engineering and Physical Sciences
Research Council (EPSRC), China Scholarship Council (CSC), and school of
Electrical and Electronic Engineerin
Sampled-Data and Harmonic Balance Analyses of Average Current-Mode Controlled Buck Converter
Dynamics and stability of average current-mode control of buck converters are
analyzed by sampled-data and harmonic balance analyses. An exact sampled-data
model is derived. A new continuous-time model "lifted" from the sampled-data
model is also derived, and has frequency response matched with experimental
data reported previously. Orbital stability is studied and it is found
unrelated to the ripple size of the current-loop compensator output. An
unstable window of the current-loop compensator pole is found by simulations,
and it can be accurately predicted by sampled-data and harmonic balance
analyses. A new S plot accurately predicting the subharmonic oscillation is
proposed. The S plot assists pole assignment and shows the required ramp slope
to avoid instability.Comment: Submitted to International Journal of Circuit Theory and Applications
on August 9, 2011; Manuscript ID: CTA-11-016
Analysis of an On-Line Stability Monitoring Approach for DC Microgrid Power Converters
An online approach to evaluate and monitor the stability margins of dc microgrid power converters is presented in this paper. The discussed online stability monitoring technique is based on the Middlebrook's loop-gain measurement technique, adapted to the digitally controlled power converters. In this approach, a perturbation is injected into a specific digital control loop of the converter and after measuring the loop gain, its crossover frequency and phase margin are continuously evaluated and monitored. The complete analytical derivation of the model, as well as detailed design aspects, are reported. In addition, the presence of multiple power converters connected to the same dc bus, all having the stability monitoring unit, is also investigated. An experimental microgrid prototype is implemented and considered to validate the theoretical analysis and simulation results, and to evaluate the effectiveness of the digital implementation of the technique for different control loops. The obtained results confirm the expected performance of the stability monitoring tool in steady-state and transient operating conditions. The proposed method can be extended to generic control loops in power converters operating in dc microgrids
Advances in Control of Power Electronic Converters
This book proposes a list of contributions in the field of control of power electronics converters for different topologies: DC-DC, DC-AC and AC-DC. It particularly focuses on the use of different advanced control techniques with the aim of improving the performances, flexibility and efficiency in the context of several operation conditions. Sliding mode control, fuzzy logic based control, dead time compensation and optimal linear control are among the techniques developed in the special issue. Simulation and experimental results are provided by the authors to validate the proposed control strategies
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