Adaptive nonlinear control of a three-phase three-level neutral point clamped rectifier

This paper presents a control strategy for a three-phase three-level neutral-point-clamped boost rectifier, which consists of applying an adaptive nonlinear control. The exact nonlinear multiple-input multiple-output state space model of the rectifier was obtained in the (d,q,0) reference frame using the power balance between the input and output sides. Applying a change of coordinates and nonlinear feedback linearization technique to the nonlinear model results in a linear and decoupled model, a robust model-based reference adaptive control scheme is proposed for the feedback-linearized system in order to control line-currents, output and neutral point voltages and also to reduce the influence of the parameter uncertainty. This control uses a 3 kHz pulse width modulator. Computer simulations based on the use of Power System Blockset and Simulink/Matlab verify the robustness of the proposed control law in balanced output load conditions. The line-current THD and output voltage ripples are very low.