Design and implementation of PI controller for the hybrid energy system

The energy storage (e.g. battery)is a key issue for traction applications like electric vehicles (EVs) or hybrid electric vehicles (HEVs). Battery for EVs/HEVs must provide higher power and energy density, smaller size, a longer cycle-life and a lower cost. In general, battery lacks power as required by EVs, fortunately that can be provided by capacitors. That necessitates development of a hybrid energy storage system (HESS) using a battery with higher energy density and capacitor with higher power. Moreover, in order to achieve a better drive range and improve performance of the motor, a better control mechanism is also vital for the DC to DC power converters which are used in these vehicles. In this paper, a proportional integral (PI) controller will be designed and implemented for the HESS system to provide power demand, and recharge the HESS based on its state of charge. The boost converter, and buck-boost converter will be connected to selected high energy density lithium-ion battery (LIB), and high rate ultra-capacitor (UC), respectively, to create the parallel topology that will be used in our paper. Furthermore, the control strategies will be verified and compared against the traditional HESS under operating conditions useful for HEV / EV applications.