A New Hybrid T-type Nested Neutral Point Clamped (NNPC) Multilevel Inverter with Improved Voltage Balancing Strategy

In this paper, a new hybrid configuration of nested neutral point clamped (NNPC) inverter is suggested which generates a 9-level phase-to-neutral ac side voltage. The circuit configuration and operation principle of the introduced converter are discussed first. In the suggested topology, the regulating of the voltages of capacitors is achieved by exploiting the redundancy in switching states. On the other hand, a higher number of generated levels allows us to use the low-frequency modulation with accepted near sinusoidal output waveform. In this study, a capacitor voltage balancing strategy based on the nearest level control (NLC) algorithm is introduced. In the introduced strategy, the switching power loss is significantly reduced in comparison to the conventional high-frequency PWM techniques while the voltages of the capacitors are kept balanced with an acceptable voltage ripple. The simulation results are provided to validate the feasibility of the proposed MLI and the performance of the presented balancing method.