Novel Three-Phase Nine-Level Inverter and Its Control Strategies

In this paper, the authors propose a new three-phase, nine-level inverter with self-balancing of capacitors voltages. The proposed inverter is the result of a serial connection of the SPUC topology and the NPC converter. A single DC source is used, and each phase is made up of nine power switches and three capacitors. Two control techniques are proposed to maintain capacitors voltages at desired values, the first of which is a PWM technique ensures the self-balancing of capacitors voltages in open loop without using any filters or PI regulators, and the second is based on the hysteresis control which offers a nearly sinusoidal waveform of the load current without using any voltage sensors. The authors make use of the Matlab Simulink environment to perform the simulation of the proposed concept. The dynamics of the latter was verified against load change.