Enhanced predictive control strategy for low sampling frequency in a multilevel topology

Multilevel converters are an interesting solution because they can provide reduced harmonic distortion, work in higher power systems, assembled by replaceable modules and may use a lower commutation frequency on the power switches. These devices need to be controlled where predictive control strategy has gained significant acceptance on the academic researches and on industry applications because its simplicity and fast dynamic response. This work presents a predictive control strategy oriented to control Cascaded H-Bridges to work under low sampling and switching frequencies using the PWM technique to ensure a given switching frequency. To cancel some undesired harmonics, the carrier of PWM can be phase-shifted to reduce the harmonics distortion. Furthermore, the switching function guarantees to change the state in just one leg at every sampling time and the other leg changes its value as a function of the sign of the voltage injected, which reduces the total losses on the power converter. The proposed strategy is analyzed mathematically and corroborated by simulation results.