Senior Design 2020 – Electrical and Computer Engineering Team 2003
Electrical and Computer Engineering Team 2003
Alex Fairfax Colin Hale Benas Kirvelevicius Sean Youngblood
Sung-Yeul Park, Christopher Johnson, Lenze Americas
Three Phase AC Regenerative Power Supply
Lenze Americas, our corporate sponsor, constructs variable speed drives in order to power three phase motors. The basic operation of a variable speed drive is to take a fixed input AC source, rectify it to an intermediate DC voltage, and then invert the DC voltage to a variable voltage and frequency, allowing the attached motor to operate at different speeds. These devices are also known as variable frequency drives, or VFDs. Our group was tasked with constructing a solution to a problem that is encountered with VFDs under a particular condition. When the motor undergoes rapid deceleration, current is fed back into the VFD thus increasing the voltage on the capacitor bank. This condition is known as regenerative energy mode, and it is useful in applications like electric automobiles for recapturing energy. However, in order to keep the capacitor bank in a VFD system from being damaged, the energy must be redirected. The most common method
used is to burn off the excess energy through a resistive load. Along with wasting energy, the system generates large amounts of heat, and the additional complexity increases overall cost.
We have designed and constructed an electrical system which removes this excess energy and returns it to the grid via a DC to three-phase AC inverter. This solution is advantageous as our system simultaneously manages the VFD capacitor bank voltage, ensuring safe operation during motor regeneration conditions, and results in a renewable energy system capable of supplying electrical power to the main grid.