VC-21-C053 -- Harmonic Mitigation Strategies in Variable Frequency Drive Applications

The demand for higher efficiency HVAC systems has led to fast adoption of energy saving modern variable frequency drives (VFDs) and motor control technology. The successful introduction of VFD controlled compressors, pumps and fans into chillers and air handlers has helped meet these demands and led to rapid deployment into data centers, hospitals, power plants and other critical cooling markets. Some benefits of variable frequency technology include i) smaller air handing packages using high-speed electrical motors and ii) higher partial load system energy efficiency, where the complete system is considered from electrical input to HVAC load. However, they also produce harmonic electric currents that lead to poor electrical power quality and equipment failure if levels are not kept low enough. Harmonics and power quality have never been more important to understand and mitigate as the adoption levels of VFD controlled HVAC equipment increase along with increasing harmonic levels.