Digital Closed Loop Control of a Three Port Series Resonant Converter for Electric Vehicles

With the trend towards vehicle electrification, three port DC-DC converters allow an interface between the high-voltage battery pack, a 12 V battery pack and the 48 V auxiliary loads within the electric vehicle compared to conventional two-port converters. Due to the dependence of auxiliary loads on driving behaviour and passenger input, a robust controller is essential for a three-port converter to handle dynamically changing load profiles on the loading ports. This paper presents a design procedure of a digital closed loop controller (DCLC) utilizing decoupling control for a three port series resonant converter (TPSRC). The DCLC is developed on a hardware demonstrator for the voltage mode control of the loading ports (ports 2 and 3). Delays introduced from the practical implementation of the DCLC are defined to formulate inner and outer loop frequency responses and assist in compensator design. Load stability analysis is considered to determine the admissible operating region of the designed compensators. A soft start strategy to limit inrush currents in the TPSRC is utilized. Experimental results demonstrating the DCLC under voltage reference and step load changes on the hardware demonstrator of a 6 kW TPSRC are presented.