Fast Energy Exchange between Fixed Supercapacitor and On-board Supercapacitor

Author Name(s): Manjusha Palandurkar, Manisha Gaikwad, Mohan Renge
Author Email: palandurkarmv@rknec.edu

Abstract

Supercapacitor (SC) is an electrical energy storage device that bridges the gap between electrolytic capacitor and rechargeable battery. It can accept and deliver charge much faster than battery as well it has a high power density. This property makes them a good choice to be used in electric vehicles like buses and cars. To recharge the on-board SC module used in electric vehicle in less time, a high amount of power is required. If this power is taken from distribution network, then high magnitude of peak current is absorbed from the supply which can create constraint on power network. To overcome this problem, on-board SC module is charged through fixed SC module which acts as energy buffers through DC- DC converters. In this paper, instead of using boost and buck converter, a double stage conversion technique is proposed for the fast energy exchange between the two energy systems with the help of MATLAB Simulink software and by experimental results.

Introduction

Day by day, the world is moving towards the eco friendly solutions. One of being them is the Electric Vehicles (EV) which is the source of zero carbon emissions. In EV, the batteries are the main energy source which provides anatomy of the vehicle. Battery stores the electrical energy in the form of electro chemical process. The batteries have been used since long time due to their electrical qualities such as higher energy density, voltage stability. The main demerit regarding the batteries is their number of charge/discharge cycles which are limited [1]. The battery life is affected if the number of charge/discharge cycles exceeds its limit. It also falls short in supplying the peak power demands by the load. To overcome the limitations of the battery, another energy storage device available is supercapacitor (SC). Supercapcitor is electrochemical double layer capacitor (ECDL) but no chemical reactions are involved during the energy storage process. Due to this, it can be charged discharged thousands of times [1]. The property of SC to provide a high power exchange makes them stand apart from the battery. Because of this property, supercapacitor module can be used as energy storage system in electric vehicles such as buses and cars. If supercapacitors, as a module, are used as main energy storage system for an electric bus, then the needed stored energy has to power the bus from the start station and to the next refilling station.

Conclusion

In this paper work, transfer of energy from fixed SC module to on-board SC module has been analysed using simulation and performing experiments. The input current is kept constant while charging on-board SC module. SC can store/deliver high amount of instantaneous power due to their high power density. This property allows a fast energy exchange between the two SC modules provided that they are interfaced with a suitable convertor. Here, the double stage convertor is used to interface both the SC modules by implementing a proper control strategy. The hardware model of double stage converter is tested on DC regulated supply instead of using fixed SC module as input. The on-board SC module gets charged in 45 sec by controlling current through the DC supply.

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