Dynamic load compensation and stabilization in bilinear AC/DC rectifiers under unknown load conditions and disturbances

Control of three-phase AC/DC converters faces significant challenges due to exogenous disturbances and dynamic resistive load variations, often leading to voltage instability. This paper addresses the control of such bilinear and underactuated systems by proposing a nonlinear Lyapunov-based adaptive controller that ensures output voltage regulation and near-unity power factor operation by enforcing sinusoidal input currents in phase with the source voltages. The approach guarantees almost global asymptotic stability while mitigating the effects of uncertainties and disturbances. The control design is carried out in the $d$-$q$ rotating reference frame and integrates a Space Vector Pulse Width Modulation (SVPWM) strategy to allocate control actions to the converter switches. Additionally, a feedforward-enhanced PI (PI+FF) controller, a Sliding Mode Control (SMC) scheme, and a state-of-the-art nonlinear controller are implemented for comparison. A detailed qualitative and quantitative performance assessment is conducted. Simulation results in a Software-In-the-Loop (SIL) environment using a PSpice-based model validate the superior robustness and tracking capabilities of the proposed approach under realistic operating conditions with variable loads and external perturbations.