Control design for multisource systems based on DC/DC converters duty cycle value

Purpose The purpose of this paper is to describe a two-level hierarchical control strategy for electrical energy transfers in multisource renewable energy systems. The aim of the control design is to perform the energy transfers, according to the sources power variations and the load characteristics. Design/methodology/approach - The controller determines the operating mode of the multisource renewable energy system and the power ratio provided by each source to satisfy the load demand. The study is based on an accurate model of the DC/DC converters coupled on the DC bus. The performance, of the controller is compared with the usual method based on the measurements of the system variables with sensors (solar radiation, shaft speed, voltages, and currents). Findings - The proposed method does not need extra sensors to measure the available power for each source. Research limitations/implications - The method is developed for an hybrid system with two sources (photovoltaic and lead-acid battery bank) and specific zero voltage switch full-bridge isolated buck DC/DC power converters but can easily extended to more sources and other classes of DC/DC converters. Practical implications - The method is assessed through computer simulations using a simple comprehensive model. An experimental device is also developed by the GREAH Research Group of University Le Havre (France). The GREAH also participates to a technologic centre with similar topology on the site of Fecamp (France). Social implications - The proposed autonomous control schema is suitable to control hybrid systems with several energy sources in remote areas. Originality/value - The main contributions of this work are first to introduce a two stages controller and second to use the duty cycle value of the power converters as decision criteria to switch off/on the sources.