Describing Function Analysis of Nonlinear Decentralized Control Scheme for Modular Power Sharing

Connecting multiple power converters in series and/or parallel has significant benefits: increased reliabil-ity/reparability, reduced individual device stress, and higher operating frequency. Modular systems require a control scheme to ensure equal sharing of power, which may be centralized, distributed, or decentralized (no communication between modules at all). Decentralized control has a clear advantage as it is the most scalable and robust to single-module failure. In this paper, we analyze a nonlinear decentralized control scheme which has been shown to be suitable for modular power sharing. The non-linear control law cannot be analyzed using the common and powerful tools for linear systems. Here we use describing function analysis and phase-plane analysis to prove the non-existence of limit cycles for a single module and to examine its transient response. Further, we verify the behaviour of the controller by experimentally demonstrating the performance of the controller for a variety of control-parameters. Finally, we present experimental validation of power sharing.