Influence of Inherent Circuit Parameters of MVDC Grid Components During Short-Circuit Faults in Ship Power Systems

Implementing medium-voltage DC (MVDC) grids in ship power systems has many intricacies, such as larger fault currents, the inability to include conventional protection systems, etc.; however, this has not been deeply investigated. To circumvent these intricacies, it is important to understand the characteristics of MVDC grids installed in a ship power system environment. A feasible method to achieve this is to model the grid components in terms of their equivalent circuit and study their typical behaviour under fault conditions. Being a DC circuit, the steady-state grid parameters of the ship power system are predominantly resistive in nature; therefore, the pertinent circuit model approach remains theoretically adequate. Pertinent results and information gathered from such studies might provide a clear insight into the typical behaviour of MVDC grids under faults and help to resolve their diagnostic integrity. In this context, a simulation study that aims to understand the influence of inherent circuit parameters of MVDC grid components under normal and fault conditions is initiated. First, a circuit model that adequately represents a 2 MW MVDC grid is selected, and its transient and steady-state behaviours under normal and fault conditions are studied. The grid components (i.e., generator, converters, etc.) are modelled with r, l, and c parameters in such a way that the steady-state and transient nature of the grid elements are theoretically represented. Later, the influence of these circuit representations during short-circuit faults in different sections of the DC grid is studied. Pertinent results reveal that the circuit representations of grid components manifest significant impact under fault conditions and induce damped-out oscillations superimposed on grid voltage and currents. This information is essential to developing smart fault protection systems operating independently of the main grid control algorithm and might help to enhance safety features along with grid resilience and reliability.