Utilization of supercapacitors to reduce lead acid battery stresses in UPS
Résumé
This work presents the study of the reduction in battery stresses by using supercapacitors (SC's) in a 500 kVA rated UPS. We aim at investigating the optimal SC-battery combination versus the SC's cost. This investigation is threefold; first, supercapacitors and battery models developed using Matlab/Simulink® are presented and validated. Second, the architecture and the simulation of the designed system combining the two types of storage devices are shown. The study emphasizes on UPS autonomous running for grid faults lasting few minutes, the supercapacitors supply the transient demand of power and the battery is responsible for the smoothness requirement of energy. Third, extensive simulations are carried out to determine the gain in battery RMS current, the gain in energy losses, the energy efficiency and the elimination rate of surge load power. These four performance parameters are determined by simulation and then analyzed. They reflect the potential decrease in battery stresses due to the SC's. A thorough analysis involving optimal study proposes to draw the optimal SC's number and filter constant from the variation of the aforementioned parameters versus the cost of the SC's.
Mots clés
Lead Acid Battery
Supercapacitors
Virtual storage
Power supply circuits
Optimization
Lead acid batteries
Uninterruptible Power Supply
Battery models
Elimination rate
Extensive simulations
Filter constant
Grid fault
Load power
MATLAB /simulink
Optimal combination
Performance parameters
Super capacitor
Capacitors
Cost benefit analysis
Energy dissipation
Energy efficiency