Electromagnetic Interference in Variable Frequency Drives used in Onshore Power Plants

Electric power generation in onshore drilling platforms essentially depends on diesel generators to supply the adequate voltage and current to drive high torque draw-work motors for oil extraction. These motors can be driven by DC-Drive converters if the motors are of a DC-type or using a variable frequency drive (VFD) if the motors are of AC-type. The latter is the preferred method of drive due to their capability of speed and frequency variations, low maintenance, and high throughput. However, these advantages come with a price of EMI generation at system and circuit levels that can disrupt the production and results in unacceptable downtime and revenue loss. This paper presents an investigation of the electromagnetic interference (EMI) issues generated in VFD inverters, used in onshore drilling rigs. The conducted emissions above the fundamental switching frequency of the VFD, is explained and emphasis on the CM, DM coupling paths of the conducted and radiated emissions, are identified. In addition, an EMI noise suppression method is discussed, and a proper solution is provided, to comply with the applicable EMC standards. Finally, results of conducted EMI emissions of the VFD system are reported. An EMI reduction above 20dB, across the EMC spectrum has been achieved.