Adaptive nonlinear control law applied to a three-phase NPC boost rectifier operating under severe conditions

In this paper, an adaptive nonlinear control law applied to a three-phase three-level neutral-point-clamped (NPC) boost rectifier operating under severe conditions is presented. The control technique consists of applying an adaptive nonlinear control to the exact nonlinear model of the rectifier obtained in (d,q,0) reference frame. By applying a nonlinear feedback linearization technique to the nonlinear model results in a linear and decoupled model. Afterward a robust model reference adaptive control scheme is proposed for the feedback-linearized system in order to control the power factor, output and neutral point voltages. The robustness of the adaptive controllers with respect to uncertainty is then examined. The uncertainties include variations of plant parameters: decrease of boost inductor and frequency variations and also include input and output disturbances, utility single-phase collapse and load shedding. Simulation results of a 25 kW rectifier are obtained using the Power System Blockset (PSB) and Simulink/Matlab. These results show how the adaptive law updates the system parameter so that instabilities are counteracted and the robustness is guaranteed under these severe operation conditions where a low output voltage ripples and line-current THD, a small overshoot and a fast settling time are obtained.