Bidirectional Converter Efficiency Improvement: A Design Method and Control Strategy for Wide Voltage Range Based on Matrix Transformer

ABSTRACT Isolated bidirectional resonant converters play a crucial role in the domain of power electronics, particularly in the context of rapid charging and discharging applications for electric vehicles (EVs). However, in many instances, the demand for rapid charging results in increased charging current and larger converter volume, thereby reducing the efficiency and power density of the converters. This paper presents a novel analysis and design methodology of a converter employing sensorless synchronous rectification and applies a multi‐segment linearization analysis method to resonant converters, which is simpler than time‐domain analysis and more accurate than first harmonic approximation (FHA). This analysis provides a theoretical foundation for the implementation of synchronous rectification. It employs a hybrid control strategy of phase angle and frequency to regulate the switching on inverter and rectifier sides, significantly enhancing converter efficiency and broadening the gain range. A matrix transformer configuration is utilized to optimize thermal performance and enhance power density. Based on the proposed theory, the design of a 30 kW 660–860 V input to 250–500 V with 75 A max output prototype is discussed. The design outcomes indicate that employing synchronous rectification and matrix transformer with 10 PQ3548 cores, the converter can achieve a high power density of 8 kW/L (131 W/in) and peak efficiency of 98.4.