A Dynamically Adaptive Rising-Edge Shifting Frequency PWM Implemented MPFT Technique for Portable EV Charger Development

Abstract

For EV charging applications, performance of LLC resonance half-bridge is greatly influenced by non-linear variations in battery parameters. This has a significant impact on charging efficiency and system reliability. For efficient operation, all FETs must operate with zero voltage switching (ZVS). Additionally, converter must operate with minimum circulation of reactive power among all active and passive devices. To deal with this issue, this paper proposes hybrid modulation scheme for LLC resonating converter. It is designed with coordinated utilization of both frequency modulation and rising edge shift (RES) modulation. Modulation scheme modifies pulse width dynamically and control rising edge with amount of power processing. This provides right choice of switching frequency and intermediated DC link range, which reduces switching losses in MOSFET and conduction body diode losses. Additionally, active hybrid DC link tracking reduces limit of maximum switching frequency and ensures a limited amount of reactive energy to facilitate ZVS operation. Combined approach provides maximum power factor tracking (MPFT) for wide voltage operation of charger. For this, a 500W system is designed with single phase Vienna rectifier for power factor correction (PFC) and half bridge LLC converter as a DC-DC isolated stage. It is designed for 160V-240V AC over 41-60V charging voltage.