Stability Study and Nonlinear Analysis of DC-DC Power Converters with Constant Power Loads at the Fast Timescale

Rapidly growing distributed renewable networks make an increasing demand for various types of power converters to feed different loads. Power converters with constant power load (CPL) are one typical configuration that can degrade the stability of the power conversion system due to the negative impedance characteristic. This article presents a nonlinear analysis method using the developed complete-cycle solution matrix method by transforming the original linear time-variant system into a summation of segmented linear time-invariant systems. Thus, the stability of the nonlinear system can be studied using a series of the corresponding state transition matrix and saltation matrix. As this derived matrix contains all the comprehensive information relating to the system's stability, the influence of the CPL to system's fast-Timescale stability in both continuous conduction mode and the discontinuous conduction mode can be fully investigated and analyzed. The phenomena of the fast-Timescale instability around switching frequency for power converters with a CPL are observed and investigated numerically. Finally, experimental results have proven the analysis and verified the effectiveness of the developed method.