PWM block method for control of ultracapacitor based bidirectional DC/DC backup system

This paper presents the design of a DC/DC power supply which provides energy backup to critical loads in case of momentary power main failures. This paper proposes a switch control of bidirectional converter based on PWM block method. PWM block method ensures smooth, seam less transition between charging and discharging operating modes using ultracapacitor stack as the energy source. The paper also proposes a accurate method for identification of the operating modes which is key to the switch control. The advantages of switch control using PWM block method when compared to unified control strategy which employs same control structure for charging and discharging in bidirectional converter is presented. The proposed control strategy has been verified in simulations and experimentation and the mode identification algorithm proposed here is found to be work well.