Novel Torque Ripple Minimization Control For 25 MW Variable Speed Drive System Fed By Multilevel Voltage Source Inverter

Special Paperpg. 193-200Continuous improvements in the power rating and switching characteristics of power semiconductor devices have enabled the use of power electronics converters in high power variable speed drives (VSDs). These multimegawatt drives are needed for driving large capacity compressors in liquefied natural gas (LNG) plants. However, the generated harmonics and their associated torque ripples may result in serious drawback in the application of VSDs in the oil and gas industry. The torque ripples may lead to torsional vibrations that may in turn cause damage to the load-motor coupling. To overcome these drawbacks, a new speed control technique, which is based on a synchronized pulse width modulation (PWM) control method, is proposed. A 25 MW five level VSD system was developed to verify the new approach using two experimental tests, namely, back-to-back, and full load tests. The tests validated the feasibility of the proposed method in reducing the torsional vibration