Rightsizing Generators Through Harmonic Mitigation Realizes Energy, Emissions, and Infrastructure Reductions

Abstract

Sizing prime and backup generator packages for nonlinear loads (such as adjustable speed drives (ASDs), solid-state uninterruptible power system, dc drives, and other SCR loads and even single phase loads, such as computer systems, ballasted lighting, and other power electronic loads) is not a simple process. Including the effects of the nonlinear load harmonics is essential to properly sizing generator capacity. Incorrectly calculating the harmonic current contribution can result in significantly undersizing the generator leading to brownout conditions, overloading of the generator, nuisance tripping, misoperation of the automatic voltage regulator, generator failures, and load equipment damage through elevated voltage distortion. However, oversizing the generator to accommodate the nonlinear load current harmonics will result in increased initial installation costs, much higher fuel and operating costs due to poor operating efficiencies and higher emissions. In an oil pipeline islanded pumping application, the problems experienced with the adjustable speed drive operation on a 200 hp pump led to the generator being significantly upsized. Not until harmonic mitigation was finally considered though, did the ASD and generator operate without issues. Computer simulations were used to demonstrate how the application of a passive wide spectrum harmonic filter would reduce the ASD harmonic currents to eliminate the voltage distortion and allow the operator to retrofit the installation with a more properly sized generator that provided energy/fuel savings and emissions reduction while maintaining good power quality.