Retrofitting Industrial Machinery Driving Large Inertia Loads to Increase the Efficiency and Power Quality in Industrial Grids

Providing regenerative braking to Variable Frequency drives (VFD) with a diode-bridge front-end is usually achieved by replacing this stage with an active one, e.g., IGBT+diodes. However, the high peak power due to braking of large inertia rotating loads may require active front-end oversizing, increasing the protection limits, and the power term in the electric bill will remain relatively high. Both issues can be addressed by storing the braking power and injecting the recovered energy as demanded during soft starting. This work presents such an energy recovery system and focuses on the grid interface realization.