Yufei Zhou

Fast-scale instability in a PFC boost converter under average current-mode control

This paper investigates the fast-scale instability in a power-factor-correction (PFC) boost converter under a conventional average current-mode control. The converter is operated in continuous mode. Computer simulations and theoretical analysis are performed to study the effects of the time-varying input voltage under the variation of some chosen parameters on the qualitative behaviour of the system. It is found that fast-scale instability may occur during a line cycle, which can cause distortion to the line current and degrade the practical power factor. The results provide useful information for the design of PFC boost converters to avoid distortion due to fast-scale bifurcation. Copyright

APPLYING RESONANT PARAMETRIC PERTURBATION TO CONTROL CHAOS IN THE BUCK DC/DC CONVERTER WITH PHASE SHIFT AND FREQUENCY MISMATCH CONSIDERATIONS

The buck converter has been known to exhibit chaotic behavior in a wide parameter range. In this paper, the resonant parametric perturbation method is applied to control chaos in a voltage-mode controlled buck converter. In particular, the effects of phase shift and frequency mismatch in the perturbing signal are studied. It is shown that the control power can be significantly reduced if the perturbation is applied with an appropriate phase shift. Moreover, when frequency mismatch is inevitable, intermittent chaos occurs, but effective control can still be accomplished at the expense of raising the control power. Analysis, simulations and experimental measurements are presented to provide theoretical and practical evidences for the proposed control method.

Complex Intermittency in Switching Converters

Intermittent instability is commonly observed in switching power supplies during the design and development phase. It manifests as symmetrical period-doubling bifurcation in the time domain with long intermittent periods. Such intermittent operation is considered undesirable in practice and is usually avoided by appropriate adjustments of circuit parameters. This paper explores the mechanism and conditions for the emergence of intermittency in a common voltage-mode controlled buck converter. It is found that interference at frequencies near the switching frequency or its rational multiples will induce intermittent operation. The strengths and frequencies of the interfering signals determine the type and period of intermittency. The problem is analyzed by transforming the conventional parameter-bifurcation analysis to a time-bifurcation analysis. Analytical results are verified by simulations and experimental measurements.

Controlling chaos in DC/DC converters using optimal resonant parametric perturbation

The method of resonant parametric perturbation is a simple non-feedback chaos control method which is easy to implement in practice. In this paper, an optimal strategy is applied to stabilize an unstable orbit in a chaotically operating current-mode controlled buck-boost converter. Optimal values of initial phase angles are computed corresponding to minimum perturbation amplitudes. With this optimal perturbation, the converter operating in a chaotic regime can be controlled to operate in an unstable period-1 orbit that exists in the original chaotic attractor.

Modeling and simulation of Boost converter in CCM and DCM

this paper introduced the operation principle of current mode control Boost converter. The equations of two different work states were built by applying the theory of KCL and KVL. Two models working in CCM and DCM were respectively established using Matlab / Simulink and the nonlinear phenomenon of Boost converter can be observed through simulation. The results of theoretical analysis are corresponded with simulation and it can confirm these models are correctness and feasibility. It was also studied the change of these parameters impacting on the bifurcation and it can find the change of these parameters impacting on the stability of the converter. So, it can provide a reliable instruction for the stability design of Boost converter.

Complex Phenomena in SEPIC Converter Based on Sliding Mode Control

A hysteretic current-controlled SEPIC converter, which uses the sum of two inductor currents as the control variable, is discussed. The operation states of the converter are studied based on the theory of sliding mode control. The equivalent control and relative differential equations on the sliding surface are derived, based on which, the stability of equilibrium point is analysed with the calculation of eigenvalues. With numerical calculation and computer simulation, it is shown that the equilibrium point will lose the stability via a Hopf bifurcation when the current reference increases. Subsequently the converter will exhibit complex dynamical behavior including limit cycle, double limit cycle, quasi-periodicity, and chaos by increasing the current reference furthermore.

Principle of designing slope compensation in PFC Boost converter

Due to wide input fluctuation with line frequency of 50 Hz, power-factor-correction (PFC) Boost converters tend to exhibit fast-scale instability over time domain. The traditional remedy is to impose slope compensation so as to weaken or eliminate this instability. A theoretical principle on the implementation of slope compensation signal is still lacking. Empirical design will induce over compensation frequently, resulting in a large decrease of power factor. In order to tackle this issue, by constructing the discrete-time iterative map of the PFC Boost converter from the viewpoint of bifurcation control theory of nonlinear systems, consequently, the criterion of critical stability for the PFC circuit can be established. Based on this stability criterion, appropriate design of slope compensation can be achieved. Our work indicates that 3 main circuit parameters (i.e. switching cycle, output reference voltage and inductor) determine the effective amplitude design of the slope compensation signal. The results, validated by a large quantity of analytical and numerical studies, show that appropriate slope compensation can be effective in weakening (or controlling) fast-scale bifurcation while maintaining a rather high input power factor.

Intermittent chaos and subharmonics in current-mode controlled SEPIC converters

Intermittent phenomena are commonly observed in periodically driven switching power converters. This paper explores the intermittent chaos and subharmonics in a current-mode controlled SEPIC converter using a circuit model with intruding interference. The theoretical analysis and computer simulation are prensted, which indicate that the signal strength and frequency of the intruding interference are vital parameters that affect the type and the period of intermittency.

Dynamical behaviour and stability analysis in SEPIC converter based on sliding-mode control

Abstract A hysteretic current-controlled SEPIC converter, which uses the sum of two inductor currents as the control variable, is discussed. The operation states of the converter are studied based on the theory of sliding-mode control. The equivalent control and relative differential equations on the sliding surface are derived, based on which, the stability of equilibrium point is analysed with the calculation of eigen-values. With numerical calculation and computer simulation, it is shown that the equilibrium point will lose the stability via a Hopf bifurcation when the reference current increases. The other circuit parameters will make influence on the first bifurcation point of reference current. Subsequently, the converter will exhibit complex dynamical behaviour, including limit cycle, double limit cycle, quasi-periodicity and chaos, by increasing the reference current furthermore.