Average current mode control of battery/ultracapacitor hybrid energy system & its microcontroller based implementation

Battery has good energy density but poor power density. Although it can store sufficient energy for the required driving range, but it lacks to provide the acceleration performance of the drivetrain. Since Ultracapacitors (UC) have good power density, it is used along with the battery as an auxiliary storage device to form Hybrid Energy Storage System (HESS). Battery and UC should provide the low and high frequency components of the load current demand respectively. This paper presents the Average Current Mode Control (ACMC) for frequency based load current demand arbitration between battery/UC HESS, and its microcontroller based implementation. Since the use digital platform like microcontroller would introduce sampling and computational delay in the control loop, same has been considered for controller design. An UC voltage control loop has also been designed so to keep UC sufficiently charged for providing/absorbing loads acceleration and regeneration demand.