Passivity- based Control of Multilevel Cascade Inverters: High Performance with Reduced Switching Frequency

This paper approaches the control problem of (buck- type) multilevel cascade inverters. The main pursued objective is the generation of an output voltage waveform with very low harmonic distortion under reduced switching frequency operation. For developing the proposed controller a pulsewidth modulation (PWM) based design is first considered, in order to obtain a continuous time control law, to later on, using quantization arguments, modify it to achieve the reduced switching frequency. Due to its proved capacity for generating high performance circuit responses, in the high frequency step design a Passivity-based approach is followed while for the low frequency one a hysteresis type scheme is introduced. The usefulness of the scheme is validated via numerical simulations comparing the proposed scheme with a classical PWM based design.