Allowable bus impedance region for MVDC distribution systems and stabilizing controller design using positive feed-forward control

摘要

Advances in switching power electronic converter technology have brought about a resurgence of interest in the use of DC power distribution systems for a variety of applications. However, the notional power electronic based DC distribution system is a complex and extensively interconnected system consisting of multiple power converters. A number of system-level challenges related to stability arise due to interaction among multiple converter subsystems. The recently proposed Passivity Based Stability Criterion (PBSC) coupled with active damping by a Positive Feed-Forward (PFF) control technique has successfully been demonstrated to provide meaningful stability analysis and stabilizing controller design via the insertion of active damping impedances. However, the PBSC provides no explicit indication of the relative stability and damping of the system under study. This paper establishes an Allowable Impedance Region concept in the s-plane to relate the magnitude of the system bus impedance Nyquist contour to the expected dynamic performance of the system. The proposed method allows for the system designer to better understand the performance of the system while evaluating for passivity. This analysis technique provides information such that an appropriate damping impedance for insertion into the system bus via PFF control may be easily identified from an analytic model of the system (“White-box” design) or from measurements performed via impedance identification techniques (“Black-box” design), thus ensuring the passivity of the system and guaranteeing stability and desired dynamic performance.