Stability analysis and design of stable DC distribution systems through positive feed-forward control using a novel passivity-based stability criterion

DC distribution systems, consisting of several feedback-controlled converters integrated together to form a complex interconnected system, suffer from potential degradation of stability caused by negative incremental impedances due to the presence of constant power loads. Due to the complexity of integrated DC distribution systems, analysis and design of such systems to guarantee system stability and performance is a difficult problem. As an active technique to solve subsystem interaction problem and improve system stability, the Positive Feed-Forward (PFF) Control is proposed in combination with a novel Passivity-Based Stability Criterion. In particular, the PFF control is designed based on imposing passivity of the overall bus impedance. If passivity of the overall DC bus impedance is ensured, stability is guaranteed as well. The design formulation for the PFF controller, so that both stability and performance are guaranteed, is discussed in detail. The approach results in greatly improved stability and damping of transients on the DC bus voltage and is validated by both simulations and experimental results.