Abstract

In geophysical survey industry, helicopter time domain electromagnetic systems (HTEM) are used widely due to their better spatial resolution and ability to conduct surveys in difficult geographical areas. However, these systems are limited in terms of the exploration depths achieved due to the constraints on the overall weight of the system that a helicopter can safely tow. There is a scope to develop a compact yet high power system that is light in weight, fast in response and able to control high current pulses to achieve deeper exploration depths. In this thesis, a new LabVIEW based power converter is proposed and implemented to achieve flexible and faster control of the TEM system. The current control is implemented with hysteresis current control logic and a constant ON-Time current control logic. Proposed topology and current control helps to achieve the targeted fall-time (100 μs) at the end of current pulse. An optimized LabVIEW code and constant ON-Time current control scheme is implemented to achieve sampling times as low as 2 μs. The comparison of experimental results with MATLAB simulation results validates the effectiveness of the control scheme. To reduce the switching power loss in the converter, the same hard switching power converter, working with constant ON-Time current control is modified to simulate a zero current switching scheme by designing the required resonant elements.