An Injection Circuit Coupling Low-DC Voltage Impedance Matching System With Flexible Resonance Points for Square-Wave Voltage Power Amplifier in EM Exploration

This article focuses on reactive power compensation and impedance matching of square-wave voltages. Square-wave voltage is the operating voltage in electromagnetic method (EM) exploration. The characteristics of a square-wave voltage are very different from those of a sinusoidal voltage in the power grid. Although some papers proposed impedance matching converters for square-wave voltages, they solved the high dc voltage requirement problem. The problem is caused by square-wave voltage having multiple and variable spectral components. An impedance-matching converter with an injection circuit (IMFR) for square-wave voltage is proposed. IMFR is composed of a thyristor-controlled inductor and capacitor (TCLC) part and injection circuit coupling active H-bridge part. TCLC can be controlled to resonate at the highest energy fundamental frequency for damping the largest part of the dc voltage requirement. The use of TCLC offsets the varying fundamental frequency demand on the dc voltage. First, this article gives a joint design and optimization approach for the lowest dc voltage requirement. Second, a synergistic control method of proposed IMFR is provided implementing IMFR. Third, two groups of comparative experiments show that the proposed IMFR can enlarge the current by 11.8%–38.5%. The effect on the current increase is 4.4%–7.9% higher than using only the H-bridge of the previous method when they are operated with the same dc voltage.