  The main challenge in using the Modular Multilevel Converter-based
constant-torque variable-speed motor drives is increased sub-module capacitor
voltage ripples (SM-CVR) at lowfundamental frequency operation, due to the
inverse relationship between SM-CVR and operating frequency. To address this
issue, a variable slope trapezoidal circulating current (CC) is injected along
with square wave common-mode voltage (CMV). Compared to sinusoidal CC and
sinusoidal CMV injection, the proposed injection technique can reduce the peak
of the CC in the range of 0% to 50%, resulting in lesser device stress and
improved efficiency. Simulation results of the proposed technique are
presented, and they are further compared with the existing injection techniques
to show the superiority
