A Nonlinear Hybrid Impedance Matching Technique for Electromagnetic Exploration Transmitter With 96% Multifrequency Signal Energy Utilization

In electromagnetic exploration applications, the grounded cable and transmitting coil transducers are typical inductive loads that can cause reactive power occupation problems to power converters and limit the effective utilization of transmission signal energy. However, the existing impedance matching techniques show poor compatibility with nonlinear square voltage signals, which use multiple harmonic components to efficiently acquire geological information of multiple depths. To address these issues, a novel nonlinear hybrid impedance matching (NHIM) technique that combines a passive thyristor-controlled capacitor (TCC) and active insulated-gate bipolar transistor-controlled converter (ICC) is proposed to provide multifrequency impedance matching simultaneously under varying frequency conditions. In this article, the nonlinear matching strategy is first introduced. Then, the NHIM parameter optimal design is proposed considering the reduction of dc supply voltage requirement. After that, a cooperative control strategy is proposed, including multifrequency power calculation, impedance identification, and control reference calculation for TCC and ICC to constitute fundamental and high-frequency reactive power compensation. Finally, comparative simulations and experiments verify the cooperative design methodology of the proposed NHIM. Compared with the existing broadband matching, the proposed method ensures 12%–460% spectral amplitude enhancement and over 96% multifrequency signal energy utilization, which is a 10%–13% performance improvement over previous techniques.