Stability analysis of an all-electric ship MVDC Power Distribution System using a novel Passivity-Based Stability Criterion

The present paper describes a recently proposed Passivity-Based Stability Criterion (PBSC) and demonstrates its usefulness and applicability to the stability analysis of the MVDC Power Distribution System for the All-Electric Ship. The criterion is based on imposing passivity of the overall DC bus impedance. If passivity of the bus impedance is ensured, stability is guaranteed as well. The PBSC, in contrast with existing stability criteria, such as the Middlebrook criterion and its extensions, which are based on the minor loop gain concept, i.e. an impedance ratio at a given interface, offers several advantages: reduction of artificial design conservativeness, insensitivity to component grouping, applicability to multi-converter systems and to systems in which the power flow direction changes, for example as a result of system reconfiguration. Moreover, the criterion can be used in conjunction with an active method to improve system stability, called the Positive Feed-Forward (PFF) control, for the design of virtual damping networks. By designing the virtual impedance so that the bus impedance passivity condition is met, the approach results in greatly improved stability and damping of transients on the DC bus voltage. Simulation validation is performed using a switching-model DC power distribution system.