Mathematical and imitation modelling of bearing currents driving machines in oil & gas equipment semiconductor transformer drives

Developing offshore hydrocarbon fields is nowadays a primary objective of power engineering. To develop hydrocarbon fields, one uses floating drilling rigs and drilling vessels, icebreakers, supply vessels, transport vessels (tankers and gas carriers), and submarine pumping complexes. When designing high-voltage electric drives with frequency converters, multiple interrelated studies are carried out using mathematical and simulation models, whereby calculation accuracy and the properties of the final product depend on the quality of such simulation. Refined mathematical models are a must if modeling and calculations are to be sufficiently accurate. Mathematical and simulation modeling of electric drives, as well as computational analysis thereof are becoming ever more relevant as engineers have to design more and more power facilities for oil-and-gas fields. We herein demonstrate an algorithm for simulation modeling of stand-alone three-level electric drive inverters, which includes analysis of such drive’s structural diagram, assumption-making, generating an equivalent electric drive diagram, describing the drive mathematically, synthesizing a modulation algorithm, and compiling simulation models. Our studies have shown the effect that resistance parameters and the inductance of motor chokes have on the output voltage quality of a stand-alone inverter. We have also studied how switching frequency of a stand-alone inverter affects distortions in the output voltage and current. We additionally give recommendations on how to select motor chokes.