Stability Analysis and Stabilization Improvement of the DC Power System for Unmanned Aerial Vehicle Based on the Finite-Time Controller

In an unmanned aerial vehicle DC power system (UAV DCPS), the electric motor or point-of-load converter can be considered a constant power load (CPL) with negative impedance characteristics (NIC). This NIC can reduce system damping, causing the system to become underdamped or even unstable. To address this instability caused by NIC, we propose an adaptive finite-time controller (AFTC), which offers large-signal stability and short settling time. To comprehensively analyze the stability of AFTC, we combine the large-signal method and small-signal method. The large-signal stability of AFTC is verified using a Lyapunov function, while the bifurcation method is used to obtain the critical power of CPL, and the eigenvalue method is used to reveal the damping variation. The stability analysis results show that AFTC cannot achieve critical damping without compromising steady-state performance. Therefore, a virtual damper (VD) is introduced to enhance UAV DCPS damping and stability margin. Finally, a down-scaled prototype of UAV DCPS is built to conduct disturbance tests of AFTC. Simulation and experimental results confirm the stability analysis, and VD can push AFTC from underdamped to overdamped, offsetting the effect of NIC.