Synergetic Control of a 3-Φ Buck-Boost Current DC-Link EV Charger Considering Wide Output Range and Irregular Mains Conditions

Abstract

A wide output voltage range EV charger employing a three-phase (3-Φ) buck-type current source rectifier (CSR)-stage and a series-connected boost-type DC/DC-stage is introduced. The system employs a novel control structure, enabling robust operation even under heavily unbalanced 3-Φ mains conditions. It is verified how the proposed concept achieves PFC operation while regulating the output voltage in a wide range, which requires both buck and boost functionality. This includes a synergetically combined control of the 3-Φ CSR input stage and of the subsequent DC/DC output stage. In this context, a variable DC-link current control strategy referred to as 2/3-PWM is implemented, which allows to switch only two out of the three phases of the CSR-stage. Moreover, seamless transitions between the different operating modes and modulation schemes are demonstrated for different output voltage regions. Finally, the performance of the proposed synergetic control structure is comprehensively validated with closed-loop circuit simulations, focusing on buck-boost operation and on irregular 3-Φ mains conditions, including harmonics distortion, phase loss (phase open-circuit or phase zero-voltage faults), and voltage spikes.