Low THDi front-end stage under non-sinusoidal voltage

A digital controller for Boost front-end stages connected to non-sinusoidal voltage grids is presented in this work. The utility voltage is not pure sinusoidal and presents a typical harmonic distortion (THDv) lower than 5 %, fulfilling the standard limits. Traditional PFC rectifiers achieve a resistor emulator behavior, using the input voltage as reference to control de input current. Critical applications like aircraft systems must comply with very strict harmonic limits impossible to fulfill if the input voltage is distorted. The aim of this work is to present a modification in the nonlinear-carrier (NLC) control to obtain a pure sinusoidal current independently of the input voltage waveshape and therefore introducing some active filtering action in the utility. Experimental results show the agreement with the predicted low current distortion in a Boost CCM front-end stage of 1 kW, connected to a 400 Hz grid.