Sliding mode control and Unit Power Factor applied to embarked supercapacitors for electrical train traction

The use of supercapacitors (SCs) in embedded system is quite suitable because of their appropriate characteristics in term of high power capacitance, low serial resistance and their response time. The supercapacitor is a regular capacitor but with the exception that it offers very high capacitance in a small package. Rather than a battery, the supercapacitor energy storage is by means of static charge not by an electro-chemical process. There are three types of electrode materials suitable for the supercapacitor. They are: high surface area activated carbons, metal oxide and conducting polymers. The high surface electrode material, also called Double Layer Capacitor. It stores the energy in the double layer formed near the carbon electrode surface. The electrolyte may be aqueous or organic. The aqueous variety offers low internal resistance but limits the voltage to one volt. In contrast, the organic electrolyte allows 2.5 volts of charge, but the internal resistance is higher. To operate at higher voltages, supercapacitors are connected in series. On a string of more than three capacitors, voltage balancing is required to prevent any cell from reaching over-voltage. This paper deals with the conception of an embedded power source using supercapacitors which are charged by means of Unit Power Factor (UPF) electronic converter. These supercapacitors ensure the power supply of an electrical network miniature rail of 150W by using sliding mode principle control. The operating principle of this device and some simulation results obtained under Saber software and experimental results are presented.