This new control approach provides an operation mode on which the module capacitor ripple of the modular multilevel converter (MMC) can be reduced to roughly 10% of conventional design. This means that the capacitance value of the converter can be reduced to 10% of original design if meeting the same design criteria. The capacitor rated current is also decreased. At the same time, the arm inductance value is also decreased to about 10% of original design. Both of the benefits can greatly reduce the cost for capacitors and inductors to about 5% or even lower as well as reduce the mechanical size of the converter. That means a great increase of the power density of the converter.
This new control approach also decouples the module capacitor ripple apart from the line frequency, which renders the MMC potential applications in variable frequency drive or other domains that require the varying of the fundamental frequency. Furthermore, the new control approach provides the capability to output high torque at the start of the motors.