A Composite Nonlinear Control Scheme for Stabilizing DC-Link Voltage of Rectifier-Based Airborne Power Systems

With the rapid development of more electric aircraft (MEA) technology, more and more tightly regulated loads are characterized by constant power loads (CPLs) in airborne power systems (APSs). Due to the negative impedance and nonlinear characteristics of CPLs, the DC-link voltage fluctuation caused by the large penetration of CPLs will be amplified, which may even lead to the APS collapse. To alleviate the problem, this paper proposes a composite nonlinear control method to stabilize the DC-link voltage in rectifier-based APSs. The extended nonlinear disturbance observer (ENDO) technique can rapidly and accurately estimate the disturbances, which increases the system's dynamic performance. The backstepping control law is designed to stabilize the DC-link voltage in the sense of a large signal. The original averaged nonlinear model of the three-phase rectifier is transformed to the linear Brunovsky's form to simplify the design of the proposed control strategy, and a strict stability analysis is carried out to show the large-signal stability of the closed-loop regulated system. In addition to the DC-link voltage control, the power factor control is also considered in this paper, and these two control principles are decoupled to eliminate their mutual influence. Finally, some simulation results are carried out to prove the effectiveness of the proposed strategy.