Nonlinear synergetic control for m parallel-connected DC-DC buck converters: Droop current sharing

Abstract

In this paper we consider a general case of an m-paralleled buck converter system feeding dependent current source, which can easily represent resistive, constant current, and constant power loads. For control design, we use synergetic control theory, which is based on ideas of self-organization. The theory allows designers to derive analytical control laws for nonlinear, high-dimensional, and multi-connected systems. In the paper we derive general nonlinear PI control algorithms for the m parallel-connected DC buck converter under droop current sharing nullifying steady state current sharing error and improving voltage regulation. We study the stability of the closed loop system under different loading conditions. We clarify the choice of control law coefficients, and we show the benefits of dynamic power sharing provided by synergetic control design. The simulation results presented in the paper show good agreement with the theory.