Comparative analysis of multiple-loops linear and non-linear control schemes applied to a three-phase three-switch three-level rectifier

This work presents a comparative evaluation of two a major drawback, namely a time-varying switching frequency, multiple-loops duty-cycle-based control schemes applied to a which may reduce, in the one hand, the reliability of the three-phase three-switch three-level boost-type rectifier. The control laws are both elaborated on the basis of a state-space averaged model of the converter, expressed in the synchronous rotating frame. On the one hand, a control scheme that uses linear regulators is designed by using the small-signal transfer functions of the converter´s model, which was linearized on the neighborhood of a suitable steady-state operating point. On the other hand, a nonlinear control scheme that uses the input-output feedback linearization approach is also designed in order to satisfy same requirements as for the linear control system. For comparison purpose, both control schemes are implemented numerically using the Simulink tool of Matlab, and simulation experiments are carried out in order to test and verify the tracking and regulation performance of each control law, as well as their robustness towards load or mains source disturbance. For the same operating conditions, the performance of the two control laws are analyzed and compared in terms of line currents total harmonic distortion (THD) and DC voltage regulation.