Yongtao Yao

Analysis of Buck-Boost Converters for Fuel Cell Electric Vehicles

For the power converters of fuel cell electric vehicles, there is a great need for less component stress, smaller component size and higher efficiency. The paper presents a typical configuration of FCEV powertrains, and proposes a novel buck-boost cascaded topology for high power applications. It offers better performance compared with the single-switch buck-boost converters, such as buck-boost, CUK, Zeta, SEPIC circuit. Also, the operating principles and the parameters of the buck-boost cascaded converter are analyzed. The simulation results show that the converter has excellent electrical characteristics, and is suitable for FCEV applications.

A Generalized Model of Nonisolated Multiphase DC–DC Converter Based on Novel Switching Period Averaging Method

The continuously innovated topologies of the nonisolated multiphase dc-dc converter (NMDC) demand generalized and flexible models for the controller design. However, the increased phase number, coupling of inductors, stray circuit parameters, and asymmetric problems make the modeling work difficult. In this paper, a novel switching period averaging method aiming to simplify the modeling process is proposed. The method takes full advantage of the linear characteristic of the circuit differential equations to find out the relationship between averaged state variables and switch duty cycles. Then, the generalized model applicable to several different topologies of the NMDC is derived. The analytical solutions of steady-state model, dynamic model in both time and frequency domain are all approached. In order to verify the results, a MATLAB/Simulink model and the corresponding experimental prototype of a four-phase boost converter with two groups of two-phase coupled inductors are built. Both results coincide with the theoretical derivation, which indicates the effectiveness of the proposed method. Finally, a design process of the H∞ controller for the NMDC is presented to show the application of this model.

Low-Pass Filters Design and Simulation for the Control Circuit of DC/DC Converters

For conducted interference in the control circuit of the DC/DC converter used in FCEV, the second order Butterwoth and Chebyshev active low-pass filters and their circuit configurations are analyzed and discussed in this article. The article presents the process of their network realization and simulates them with Matlab. Furthermore, an advanced second-order active low-pass filter is designed in this article for occasions that need a large time constant in practice.

Study on the Parameter Optimization of Soft-switching DC/DC Converters with the Response Surface Methodology, a SPICE Model, and a Genetic Algorithm

The application of soft-switching techniques is increasing in the DC/DC converter area. It is important to design soft-switching parameters to ensure the converter operates properly and efficiently. An optimized design method is presented in this paper. The objective function is the total power loss of a converter, while the variables are soft-switching parameters and the constraints are the electrical requirements for soft-switching. Firstly, a response surface methodology (RSM) model with a high precision is built, and the rough optimized parameters can be obtained with the help of a genetic algorithm (GA) in the solution space determined by the constraints. Secondly, a re-optimization is conducted with a SPICE model and a GA, and accurate optimized parameters can be obtained. Simulation and experiment results show that the proposed method performs well in terms of a wide adaptability, efficiency, and global optimization.

Design of current observer based on generalized model of Multiphase Boost Converter

Multiphase Boost Converter (MBC) is widely applied in DC systems such as fuel cells and super capacitors. However complexity of MBC system limits its performance and application. In this paper, generalized model of MBC which can deal with topological innovations and non-ideal factors is reviewed. Based on this model, controllability and observability features of MBC is analyzed. It is concluded that MBC is always controllable and as long as MBC parameters are asymmetric, observable conditions are always satisfied. Then full order observer for MBC is designed, so costly current sensors of each phase can be eliminated. Finally, MBC model is verified by simulation and experiment, and observer performance is examined by circuit simulation.