Mitigation of low and high frequency harmonics in variable speed AC drives used in oil rigs

Modern AC drives have been extensively used in the Oil and Gas industry, because of their advantages over the DC drives, in terms of speed variation, low maintenance, frequency variation, and high torque throughput. However, significant low frequency harmonics and conducted EMI can be generated at the point of common coupling (PCC). This later can have a dramatic impact on the power factor and consequently impede the proper operation of the entire Rig power plant. This paper first investigates the harmonics generation at low frequency and the conducted EMI at the PCC of the AC drives system used in oil rigs. In addition, a custom-made solution is provided to mitigate these anomalies, by designing a combined active EMI and harmonic filter using new digital control technique. A scaled down test rig prototype is constructed to verify the feasibility of the proposed solution. Finally, simulation results are presented to show the performance of the proposed solution.