Yanfeng Chen

Coexisting Fast-Scale and Slow-Scale Instability in Current-Mode Controlled DC/DC Converters: Analysis, Simulation and Experimental Results

This paper investigates the coexisting fast-scale and slow-scale bifurcations in simple dc/dc converters under peak current-mode control operating in continuous conduction mode. Our focus is the boost converter as it is a representative form of dc/dc converter requiring current-mode control. Effects of varying the input voltage and some chosen parameters on the qualitative behavior of the system are studied in detail. Analysis based on a nonlinear simplified discrete-time model, which takes into account the effects of parasitics, is performed to investigate the coexistence of fast-scale and slow-scale bifurcations, and to identify the different types of bifurcation. Boundaries of stable region, slow-scale bifurcation region, fast-scale bifurcation region, coexisting fast and slow-scale bifurcation region are identified. Experimental measurements of the boost converter are provided for verification of the analytical results.

INTERACTION OF FAST-SCALE AND SLOW-SCALE BIFURCATIONS IN CURRENT-MODE CONTROLLED DC/DC CONVERTERS

This paper investigates the interaction of fast-scale and slow-scale bifurcations in the boost converter under current-mode control operating in continuous conduction mode. Effects of varying some chosen parameters on the qualitative behaviors of the system are studied in detail. Analysis is performed to identify the different types of bifurcation. Boundaries of stable region, slow-scale bifurcation region, fast-scale bifurcation region, interacting fast and slow-scale bifurcation regions are identified.

A Modeling and Analysis Method for Fractional-Order DC–DC Converters

This paper proposes a modeling and analysis method for fractional-order dc–dc converters operating in continuous conduction mode (CCM). As an example, a fractional-order boost converter is studied in detail. Instead of using fractional calculus, the method presented here uses a general state vector differential equation to describe the converter. By combining the principle of harmonic balance and equivalent small parameter method, an approximate analytical steady-state solution of the state variables could be obtained. Subsequently, the CCM-operating criterion of the converter is discussed based on the proposed method, and the appropriate parameters are provided to make sure that the fractional-order converter operates in CCM. In addition, a statistical analysis of harmonics is performed, from which the effects of fractional orders on harmonics can be observed. Moreover, numerical simulations are performed using the Adams–Bashforth–Moulton-typed predictor–corrector method and the Oustaloups-filter-based approximation method. Both the dc components and ripples of the state variables obtained from these two methods are combined with those obtained by the proposed method, and they are in good agreement. Finally, the fractional-order capacitor and inductor are designed and verified by simulations, and on the basis of which experiments of the fractional-order boost converter are carried out to further verify the proposed method.

BIFURCATION INVESTIGATION AND STABILITY ANALYSIS FOR PEAK CURRENT MODE INPUT-SERIES OUTPUT-PARALLEL DC–DC CONVERTERS

This paper investigates nonlinear bifurcation behaviors in the input-series output-parallel (ISOP) connected DC–DC converters under peak current control operating in continuous conduction mode. Cir...

A new analyzing scheme for non-integer order DC/DC converters

A new method of steady-state analysis for non-integer order DC/DC converters operating in continuous-conduction-mode (CCM) is put forward. First, the periodic and time-variant non-integer order DC/DC converter system is modeled by a nonlinear vector differential equation. Then by combining the principle of harmonic balance and equivalent small parameter method, the vector differential equation is solved, and analytical periodic steady-state solutions are obtained. The analytical results on a non-integer order Boost converter agree well with those obtained by modeling simulations using MATLAB software.

A radial basis function Neural Networks based space-vector PWM controller for voltage-fed inverter

In this paper, the basic principle of space-voltage vector PWM (SVPWM) is presented. Due to back propagation neural networks (BP) based SVPWM controller have local optimization problem and lower training rate, a radial basis function neural networks (RBF) controller based SVPWM is proposed. Using Matlab/Simulink together with Neural Network Toolbox, we develop a computer simulation program for the RBF-SVPWM Inverter. The results indicate that the RBF-SVPWM Inverter generates less current harmonic distortion than BP- SVPWM Inverter and the traditional SVPWM Inverter.

Enhanced-Boost Quasi-Z-Source Inverter With an Active Switched Z-Network

This paper proposes a new topology for an enhanced-boost quasi-Z-source inverter with an active switched Z-network. Compared to enhanced-boost quasi-Z-source inverters (EB-QZSI) with two switched impedance networks, this proposed inverter has the same high boost factor while using two fewer LC pairs and one fewer diode and only adds one switching device. In addition, current stress across switches is reduced by half, which leads to significant reduction in the conduction loss of switches and improves efficiency of the overall inverter. Moreover, the proposed inverter also draws continuous input current and maintains common ground between the source and the inverter bridge. Operation principles and comparisons with EB-QZSI are presented. Both simulation and experimental results validate theoretical analysis of the proposed inverter.

Predicting the unstable period-1 orbit (UPO-1) of DC-DC converters by extracting harmonic content

Purpose n n n n nThis study aims to predict the unstable period-1 orbit (UPO-1) of DC–DC converters and find analytical expressions to describe it. n n n n nDesign/methodology/approach n n n n nNonlinear dynamical phenomena of a peak–current–mode controlled direct current–direct current (DC–DC) Boost converter are discussed briefly first. Then fast fourier transform (FFT) analysis of state variables under different dynamic states is provided, and the characteristic of the harmonic content in different states is summarized. Following these, a scientific hypothesis on the harmonic content of the UPO-1 is presented, and the Equivalent Small Parameter method is adopted then, thus analytic-form expressions of the UPO-1 can be derived. n n n n nFindings n n n n nAccording to results of theoretical analysis, numerical simulations and experiments, this paper illustrates that, like stable period-1 orbit, the UPO-1 is also made up of the DC component and harmonics with integer times of switching frequency. n n n n nOriginality/value n n n n nThis work provides an unreported approach for extracting the UPO-1 of DC–DC converters, which is mainly based on predicting the harmonic structure information of the orbit. According to experimental parts of the work, it shows that the stabilizer can be designed easier by using the proposed method. Additionally, from a broader perspective, the results could also have implications in a wide class of forced oscillation systems.

Implementation of power factor corrector with fractional capacitor

Based on the fact that both the phase and amplitude characteristics of fractional capacitor are related to its order, the introduction of fractional capacitor will make power factor correction (PFC) more flexible compared with the one using conventional capacitor. In order to verify the PFC function with fractional capacitor, an equivalent fractional capacitor model composed of an inverter and a resistor in series is presented in this paper. As the inverter is served as a controlled voltage source, the order of the proposed fractional capacitor can be varied between 0 and 2 easily just by changing the control parameters of the inverter, and the power level of the fractional capacitor model is the same as that of the inverter, which is able to be used in high power occasion. Finally, the simulation and experimental results are provided to validate the feasibility of power factor corrector with the proposed fractional capacitor model.

An extended analytical approach for obtaining the steady-state periodic solutions of SPWM single-phase inverters

Inverters are widely applied in industrial fields. To acquire the analytical solution of sinusoidal pulse width modulation (SPWM) Single-phase inverters, a traditional harmonic balance based method is extended, in which the double Fourier transform is used to describe the nonlinear switching function of the converter. Thus the steady-state periodic solution of the inverter can be obtained by our approach. In order to test and verify the correctness of the solution obtained, comparative works are accomplished in MATLAB/Simulink. Moreover, experimental results are presented to demonstrate the high effectiveness of the proposed method.