Design of a Wide-Input Single-Phase Full-Bridge Power Converter for a Free-Piston Engine

Free-piston engines are new and efficient energy conversion devices that eliminate mechanical crankshafts. A wide-input power converter was needed as an electronic crankshaft for a free-piston engine to achieve efficient power generation control. A 20 kW single-phase full-bridge power converter that can operate over a wide-input voltage range was proposed in this paper to solve this problem. A current controller was designed by discussing the current flow of the power converters in four working modes, including forward electric, reverse electric, forward generation, and reverse generation. A model that considers the parasitic inductance on the wires in the circuit and the parasitic inductance and capacitance of each pole of the insulated gate bipolar transistor (IGBT) switch was established in this paper, and the accuracy of the model was verified through simulation in MATLAB/Simulink. The main parameters of the power converter, such as the absorption resistance and capacitance of the RC absorption circuit, switching frequency, gate resistance, and DC side filtering capacitor, were optimized through the enumeration method to improve the conversion efficiency of the power converter and reduce noise. A physical model was made to verify the designed power converter. The final results show that the conversion efficiency of the power converter has reached 96.5%, and the total harmonic distortion (THD) of the input current has been reduced 1.5% to reduce noise.