A new nonlinear control of an active rectifier for variable speed generating units

This paper deals with a newly conceived (state-feedback) nonlinear control strategy for an active rectifier that is supplied by a Permanent Magnet Synchronous Generator (PMSG). The aim of the proposed control strategy is properly regulate the DC-link voltage within a wide range of system operating conditions by: (i) taking into account a sufficiently rich model, in which the classical simplification – imposing to the DC voltage dynamics a relative degree equal to two – is avoided (so that the input power is not assumed to supply instantaneously the sum of load power and charging rate of the capacitor energy, with the resistance loss and the switching device loss being neglected); (ii) resorting to neither input–output linearizing strategies (involving the DC-link voltage regulation error) that lead to unstable regulation dynamics nor to simplifying design assumptions that overlook derivatives of intermediate reference signals; (iii) avoiding the computational-effort-requirements of Model Predictive Control (MPC) techniques. Simulation and Hardware in the loop (HIL) results illustrate the effectiveness of the proposed control – exhibiting a rather simple structure while guaranteeing local exponential stability for the resulting error system – in terms of Total Harmonic Distortion (THD) and controller response to load and DC voltage reference steps: high band-width and good steady-state waveforms are achieved. Robustness issues and control adaptiveness with respect to uncertain model parameters are also finally addressed.