A Broadband Multi-Frequency Resonance Compensator for Frequency-Domain Electromagnetic Prospecting Transmitting System

In the frequency-domain electromagnetic (FDEM) exploration, reactive power due to transmitting coil inductance results in weak transmitting signal strength. However, traditional resonance compensation methods for controllable single-frequency or uncontrollable multi-frequency applications are poorly applicable to broadband multi-frequency detection signals in FDEM prospecting. To solve this problem, a new broadband multi-frequency resonance compensator (MFRC) is proposed in this article to adaptively compensate the load multi-frequency reactive power over a broad frequency range. Firstly, the working principle and matching performance of the proposed MFRC are mathematically introduced. On this basis, an optimal design method of the MFRC component parameters is proposed, considering practical constraints and the required frequency range. Further, a broadband adaptive control strategy for MFRC is proposed, including impedance identification, fast duty cycle calculation, and dynamic multi-frequency resonance compensation. Finally, simulation and experimental results are given to demonstrate the effectiveness of the proposed MFRC topology, parameter design, and control strategy. The results show that the detection main frequency energy can be effectively enhanced by over 54% in the 1∼4kHz transmission band using the proposed technique. Compared with conventional schemes, the proposed MFRC allows adaptive multi-frequency resonance compensation and significant expansion of matching frequency over the required broad frequency range.