Modeling of the Phase Shift plus Duty Cycle Controlled Half Bridge DC to DC Converter

Abstract:
This paper deals with the dynamic modeling of phase-shift modulated (PSM) dc-dc converters using state space averaging technique. The dual half bridge (DHB) isolated bidirectional dc-dc converter is chosen to describe the method. The state-space averaging is widely used for modeling and analysis of dc-dc converters however the transformer series inductance current in PSM converters is an ac state and conventional cycle-averaging techniques will result in the removal of this state and its effects. The previously proposed techniques either simply remove this state and get a reduced order model or are too complex to be applied in many cases. The proposed method gives an effective and straightforward full order modeling technique even for converters with higher order containing more energy storage elements like half bridges or the converters with hybrid modulation techniques where duty cycle is not fixed at 50%. The large signal and small signal state space presentations are parametrically derived and presented. The large signal model order is reduced without loss of information using derived matrix properties. Analysis results are compared with a precisely simulated converter. The parameters from an already implemented bidirectional boost dual half bridge (DHB) converter were used to confirm the validity of the new method.