Voltage Balancing of the DC-Link Capacitors in Three-Level T-Type Multiphase Inverters

This paper illustrates an algorithm to balance the voltages across the DC-link capacitors of a three-level multiphase inverter feeding a star-connected load with an odd number of phases. The proposed strategy keeps the DC-link capacitors balanced in any operating condition and minimizes the low-frequency voltage oscillations, even during open-phase faults and with non-sinusoidal output currents. Finally, the paper identifies the operating region where the voltage oscillations of the DC-link capacitors can be canceled. The developed algorithm can maintain constant voltages even if the capacitors are unbalanced, and its performance is compared to that of other carrier-based algorithms. Experimental tests are carried out on a five-phase induction motor in healthy and faulty conditions.