N-phase Interleaved Boost Converter with Constant Power Loads Stabilized under Large Disturbances Using a Fractional-order Nonlinear Controller*

Abstract

In DC microgrid systems, interleaved boost converters (IBCs) are widely used to boost the output voltage of renewable energy sources on the source side of a DC bus owing to their high voltage gain and low current ripple. However, because power electronic converters on the load side behave as constant power loads (CPLs) with negative impedance characteristics, their high penetration can degrade the system stability. Therefore, this article proposes a fractional-order nonlinear controller integrated with an extended nonlinear disturbance observer (ENDO) for N-phase IBCs. First, the reduced-order model of the IBC is transformed into a canonical form using the differential geometric method. Subsequently, with the ENDO, the dynamic performance can be enhanced by estimating the disturbances, and a fractional-order nonlinear sliding surface is established to avoid the singularity problem and increase control flexibility. In addition, the stability of the proposed controller is analyzed using Lyapunov's theorem. In a CPL variation test, the proposed controller exhibited a faster dynamic performance and lower tracking error than conventional controllers, with at least a 27% improvement in the integral squared error (ISE). Both simulation and experimental results demonstrated the effectiveness of the controller, which can ensure large-signal stability and improved dynamic performance in DC microgrid systems.