Nonlinear Analysis and Control of Interleaved Boost Converter Using Real-Time Cycle to Cycle Variable Slope Compensation

Switched-mode power converters are inherently nonlinear and piecewise smooth systems that may exhibit a series of undesirable operations that can greatly reduce the converter's efficiency and lifetime. This paper presents a nonlinear analysis technique to investigate the influence of system parameters on the stability of interleaved boost converters. In this approach, Monodromy matrix that contains all the comprehensive information of converter parameters and control loop can be employed to fully reveal and understand the inherent nonlinear dynamics of interleaved boost converters, including the interaction effect of switching operation. Thereby not only the boundary conditions but also the relationship between stability margin and the parameters given can be intuitively studied by the eigenvalues of this matrix. Furthermore, by employing the knowledge gained from this analysis, a real-Time cycle to cycle variable slope compensation method is proposed to guarantee a satisfactory performance of the converter with an extended range of stable operation. Outcomes show that systems can regain stability by applying the proposed method within a few time periods of switching cycles. The numerical and analytical results validate the theoretical analysis, and experimental results verify the effectiveness of the proposed approach

Feed-forward control method for digital power factor correction in parallel connected buck-boost converter (CCM mode)

Amongst power converters, rectifiers are needed by many devices that are connected at the distribution end of AC electrical power networks. When large capacitors are used to reduce the voltage ripple at the dc output, the line current becomes non-sinusoidal. Such non-sinusoidal line currents increase the total harmonic distortion, resulting in significant power losses within the power network. The power factor correction converter or PFC converter is a well-known alternative to generate a flat dc voltage while shaping the input current to the input ac grid voltage, emulating a resistive behavior. As the parallel connection of PFC converters is a promising way to achieve a higher power rating, questions arise on balancing the current and power over these connected converters. In this paper, based on the differential equations of a buck-boost converter, a method is obtained to compute the duty cycles of the semiconductor devices aimed at obtaining the unity power factor while balancing the current. Feed-forward algorithms are used to tune the model parameters in order to strongly reduce the input current harmonics. The proposed scheme is simulated in MATLAB and results are given showing that the proposed algorithms result in a good power factor correction

Robust Control of a Multi-phase Interleaved Boost Converter for Photovoltaic Application using µ-Synthesis Approach

The high demand of energy efficiency has led to the development power converter topologies and control system designs within the field of power electronics. Recent advances of interleaved boost converters have showed improved features between the power conversion topologies in several aspects, including power quality, efficiency, sustainability and reliability. Interleaved boost converter with multi-phase technique for PV system is an attractive area for distributed power generation. During load variation or power supply changes due to the weather changes the output voltage requires a robust control to maintain stable and perform robustness. Connecting converters in series and parallel have the advantages of modularity, scalability, reliability, distributed location of capacitors which make it favorable in industrial applications. In this dissertation, a design of µ-synthesis controller is proposed to address the design specification of multi-phase interleaved boost converter at several power applications. This thesis contributes to the ongoing research on the IBC topology by proposing the modeling, applications uses and control techniques to the stability challenges. The research proposes a new strategy of robust control applied to a non-isolated DC/DC interleaved boost converter with a high step voltage ratio as multi-phase, multi-stage which is favorable for PV applications. The proposed controller is designed based on µ-synthesis technique to approach a high regulated output voltage, better efficiency, gain a fast regulation response against disturbance and load variation with a better dynamic performance and achieve robustness. The controller has been simulated using MATLAB/Simulink software and validated through experimental results which show the effectiveness and the robustness

Single-stage, single-phase, ac–dc buck–boost converter for low-voltage applications

The suitability of a single-stage ac–dc buck–boost converter for low-voltage applications is investigated. In-depth discussion and analysis of the converter's operating principle, basic relationships that govern converter steady-state operation and details of the necessary control structures needed to comply with the grid code are provided. The validity of the proposed system is confirmed using power system computer aided design (PSCAD)/electromagnetic transients including DC (EMTDC) simulations, and is substantiated experimentally. The buck–boost converter under investigation has good dynamic performance in both buck and boost modes, and ensures near unity input power factor over the full operating range, whilst having fewer devices and passive elements than other published versions of the buck–boost converter

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

Spectral analysis of electric current in LEDs Lamps

This work presents an analysis of electric current signal in LEDs lamps. Electrical signals are measured in two circuits, one that corresponds to the commercial LEDs lamp connected to AC source and another one incorporating a control system into the LEDs lamp. Such control system works as a power factor correction (PFC) and is designed by using a boost converter and a current controller. Signals are analyzed in terms of frequency-based representations oriented to estimate the power spectral density (PSD). In this study, two approaches are used: Discrete Fourier transform and periodogram. The goal of this work is to show that more complex PSD estimation methods can provide useful information for studying the quality energy in electric power systems, which is comparable with that provided by traditional approaches. In particular, periodogram shows to be a suitable alternative exhibiting meaningful changes along its spectral power plotting when analyzing the circuit without applying PFC. As a result of this work, a set of LEDs lamps characteristics is introduced, including a novel periodicity factor

Dynamic modeling of pwm and single-switch single-stage power factor correction converters

The concept of averaging has been used extensively in the modeling of power electronic circuits to overcome their inherent time-variant nature. Among various methods, the PWM switch modeling approach is most widely accepted in the study of closed-loop stability and transient response because of its accuracy and simplicity. However, a non-ideal PWM switch model considering conduction losses is not available except for converters operating in continuous conduction mode (CCM) and under small ripple conditions. Modeling of conductor losses under large ripple conditions has not been reported in the open literature, especially when the converter operates in discontinuous conduction mode (DCM). In this dissertation, new models are developed to include conduction losses in the non-ideal PWM switch model under CCM and DCM conditions. The developed model is verified through two converter examples and the effect of conduction losses on the steady state and dynamic responses of the converter is also studied. Another major constraint of the PWM switch modeling approach is that it heavily relies on finding the three-terminal PWM switch. This requirement severely limits its application in modeling single-switch single-stage power factor correction (PFC) converters, where more complex topological structures and switching actions are often encountered. In this work, we developed a new modeling approach which extends the PWM switch concept by identifying the charging and discharging voltages applied to the inductors. The new method can be easily applied to derive large-signal models for a large group of PFC converters and the procedure is elaborated through a specific example. Finally, analytical results regarding harmonic contents and power factors of various PWM converters in PFC applications are also presented here