Energy efficiency of a 3-level shunt active power filter powered by a fuel-cell / battery DC bus with regulated duty cycles

Abstract

Introduction. Nowadays, electrical energy is indispensable in industrial, tertiary and domestic appliances. However, its efficiency is becoming affected by the presence of the disturbances that appear in the electrical networks such as harmonics, unbalance, sags/swells, flickers …etc. Indeed, the disturbances cause a decrease in the power factor and an increase in the power losses. In this paper, the harmonic disturbance is considered and a 3-level shunt active power filter powered by a hybrid fuel-cell/battery DC is applied to mitigate current harmonic components from the electrical feeder. Aim. Studying the energy efficiency of a system based on a 3-level shunt active filter powered by a hybrid fuel-cell / battery DC bus. Methodology. It is a matter of finding the suitable formulas that express the efficiency and the relative power losses according to the load factor (which is the ratio between the short-circuit active power and the load active power) and the load power factor. The DC bus energy is controlled using an energy management algorithm that contributes in generating the required reference input currents and output voltages of the fuel-cell and the battery. The DC/DC converters control circuits are performed in a closed loop by means of regulated duty cycles. Results. The simulation results carried-out under MATLAB/Simulink environment show better filtering quality if compared with the case of open loop control of the DC/DC converters and lesser differences between the fuel-cell power, the battery power and their respective reference powers. Which concerns the energy efficiency, the results demonstrate that higher efficiency and lower relative power losses can be achieved only when higher load factor and load power factor are attained. Therefore, the compensating system of the power factor is very important to improve the energy efficiency.