A model-based controller for the cascade h-bridge multilevel converter used as a shunt active filter

This paper presents the modeling and control processes of the cascade h-bridge multilevel converter used as a shunt active filter. The single-phase five-level topology is studied, however, it can be easily scaled to more levels. Based on the model, a controller is proposed to compensate harmonic distortion and reactive power due to a nonlinear load which is equivalent to guarantee a current tracking of the line current towards a reference proportional to the line voltage. Simultaneously, the controller guarantees the regulation and balance of the capacitors voltages. The transformation of the model in terms of the sum and the difference of the squares of the capacitors voltages is crucial for our developments. Moreover, it is shown that, while the current tracking problem and the regulation problem depend on the sum of the injected voltages, the balance depends on the difference between them