Research on Buck Closed-loop Control of High-Power Electromagnetic Transmitters

The electromagnetic transmitter is a critical device in electromagnetic exploration, injecting AC signals into the ground via grounding electrodes to generate electromagnetic fields for deep-earth detection. This paper focuses on the Buck converter in the high-power power supply system of such transmitters. A synchronous Buck topology is introduced, and its basic operating principle is analyzed. Due to the inductive nature of the load, frequency variations cause changes in load impedance, resulting in large output voltage fluctuations and slow response. To address this, a mathematical model under continuous conduction mode is developed, and PI controllers for both single-loop and dual-loop structures are designed based on PWM control principles. A sliding mode controller is further introduced for the voltage outer loop. Component parameters are calculated according to design targets, and experimental comparisons of the three control strategies are conducted. Results show that the sliding mode dualloop controller outperforms traditional PI control by reducing overshoot and improving response speed, thereby achieving stable voltage regulation from $0-1000 \mathrm{~V}$ and meeting the 15 kW power requirement.