Digital Control of a Bidirectional Resonant Converter for Electric Vehicle Applications with Enhanced Transient Response

This paper presents the design and implementation of a bidirectional resonant converter with enhanced dynamic response to electric vehicles (EV). The proposed system comprises an assembly of four switches, a capacitor, and an inductor on both the primary and secondary sides of the transformer. The value of C-L-L-C was calculated using the first harmonic approximation method. Moreover, the small-signal analysis method was used to design the control system and analyze the dynamic performance of the system. Closed-loop control algorithms for voltage and current loops with synchronous rectifiers (SRs) were designed and implemented on a 32-bit microcontroller (STM32G474RET6). A 70 kHz, 400 W prototype is built with a peak conversion efficiency of 95.05% using SR in the forward mode. Without SR, the peak conversion efficiency was 93.57% in the forward mode and 93.04% in the reverse mode. In the forward mode, the proposed algorithm reduced the settling time to 15 ms, in contrast to the 40 ms associated with the conventional algorithm; in the reverse mode, the proposed algorithm reduced the settling time to 10 ms, in contrast to the 15 ms associated with the conventional algorithm.