Theoretical and experimental research on a single-stage Boost-LLC converter and its sliding mode control applied to electric ships

• Electric vessels are increasingly being utilized in a wide range of applications. • AC-DC converters are components within the integrated energy systems of ships. • The Boost-LLC converter is commonly used in integrated energy systems. • The proposed novel control strategy can achieve exceptional input characteristics. With increasing shortage of traditional energy sources, ship power systems are being upgraded to utilize new energy sources, rendering distributed power-generation systems essential. AC-DC converters are essential components of these systems. A frequency-conversion control (PFM)-based single-stage AC-DC resonant circuit results in a high bus voltage and large variation range. Conversely, a hybrid control strategy (APWM-PFM)-based single-stage AC-DC converter exhibits poor input characteristics, limited bandwidth, and challenging parameter design when stabilizing the bus voltage. To address these problems, a control strategy based on sliding-mode variable duty cycle control with input voltage feedforward is proposed. When the output current is stabilized, the bus voltage is stabilized within a certain range, and excellent input characteristics are obtained. The working principle and control strategy of the single-stage boost LC converter are analyzed in detail. Finally, a prototype is built to verify theoretical the analysis. Experimental results are essential for understanding the application of SCM control systems. This current experimental research shows that the proposed control strategy enables soft-switching of all switches and zero-current switching of side diodes. Additionally, the system exhibits good performance and input characteristics, with a power factor of ≥0.994, total harmonic distortion <10 %, and maximum efficiency of 94.8 % under a rated load within an input voltage range of 90–135 V.