Quasi-Two-Level Converter for overvoltage mitigation in medium voltage drives

This work focuses on a Quasi-Two-Level (Q2L) converter topology for medium voltage drives (MVDs). It targets applications where the drive and the motor are connected via a long cable. In such systems a dv/dt filter is usually placed between the drive and motor to increase the rise time of inverter output voltage pulses, and thereby reduce the motor terminal overvoltage. The Q2L converter allows for an intrinsic reduction in the motor terminal overvoltage by dividing the voltage transitions in the inverter output voltage waveform into multiple smaller steps. Simulation results obtained with a distributed parameter cable model are presented, which show that the Q2L converter can offer lower converter capacitor energy and reduced dv/dt filter component values for a given motor terminal overvoltage requirement compared to the 5LANPC, a conventional MVD topology, at the cost of worse WTHD and efficiency.