21st JUMV International Automotive Conference SCIENCE AND MOTOR VEHICLES 2007 1 MODELING AND CONTROL OF THE ENERGY SOURCES POWER INTERFACE FOR AUTOMOTIVE HYBRID ELECTRICAL SYSTEM NICU BIZON*, EMILIAN LEFTER*, MIHAI OPROESCU* *University of Pitesti, Pitesti, Romania, nbizon@upit.ro ABSTRACT. This paper presents an investigation of the dynamics phenomena in the energy sources power interface for Automotive Hybrid Electrical System (AHES). The boost converter is used into an (AHES) as power interface between the PEM-Fuel Cells (PEMFC) as primary energy source and the battery stack as energy storage device. The battery DC bus is controlled to be in the specified range. In this paper we investigate the AHES without PEMFC source. Now the energy is delivery from battery and high load pulses are sustained by ultracapacitors stack under controlled buck-boost converter. The simulation results show that the buck-boost converter behavior can be improved using a well designed control surface. The used Simulink models for the used AHES blocks and some design consideration are presented, too. KEYWORDS: Automotive, Hybrid Electrical System, ultracapacitor, buck-boost converter, hysteretic control, fuzzy control, Simulink models 1. The Automotive Hybrid Electrical System The typical Automotive Hybrid Electrical System (AHES), with PEMFC source and Energy Storage Device (ESD) – battery and ultracapacitor stack, is presented in figure 1 [1-3]. The boost converter is ideally suited for interfacing the inverter system with the PEMFCs [3-5]. Based on the load conditions, the boost stage can be commanded to draw a specific amount of current from the fuel cell with a ripple well defined by the frequency, size of the inductor, and duty ratio. Ultracapacitors stack (UCS) must be connected to the battery DC bus with a bidirectional converter [5]. In this paper we chouse a buck-boost converter witch can operate in buck mode when the voltage difference between battery DC bus and ultracapacitors stack DC bus is bigger than a high voltage reference (V_H) and in boost mode when that voltage difference in lower than low voltage reference (V_L). In buck mode the UCS is charged from battery DC bus (only from battery stack in this paper).