Design and Development of LVDC Cables

Abstract

The current energy systems with the mix of renewable and conventional sources are already working on their maximum capacity in order to meet the existing demand. In the near future to meet the burgeoning demand, the future electrical power system would be a mix of both AC and DC systems coexisting with each other. With the fast paced development of smart grids, decentralised system and micro grids, there is an increasing interest in the LVDC (Low Voltage Direct Current) distribution. Also there is increase in the loads in the residential and commercial sector side that require DC supply inherently. To tap in and realise the potential of the LVDC distribution systems, it requires the appropriate infrastructures to be developed that supports its assimilation faster. This thesis “The Design and development of LVDC cable” is a step forward in realising the potential that DC has in the LV distribution side. This research is done in collaboration between TU Delft and the Prysmian Group.

To begin with, two LVDC statespace based dynamic distribution system model namely: a neighbourhood distribution system and a ship distribution system are formed. The LVDC cables are incorporated as lines into these models. The sensitivity and stability analyses are performed by varying each of the active parameters individually, the influence that each of the active parameter has on node voltages, line currents and the stability of the system are studied and the trend is absorbed through this analysis. This analysis is set to be performed in both distribution systems under monopolar and bipolar configuration.

Subsequently, the short circuit analysis i.e the pole to pole and pole to neutral fault analysis is also performed on both the neighbourhood and ship distribution system. Here the cable’s active parameters that are expected to have an influence on the system performance and the line current during short circuit are taken into consideration. These active parameters are varied throughout this analysis and the resulting plots are further analysed to study their influence. These active parameters are cable resistance, cable inductance, cable capacitance, and cable length. The observations are tabulated for each of the active parameters individually. The generated results from this study would support in better assessment of cable’s active parameters influence on the short circuit current and designing the LVDC cables.

The accuracy of the dynamic model are validated by breaking the distribution system model into smaller sections and forthcoming results are compared to get the model accuracy. Finally based on the results from the sensitivity stability and short circuit analyses the optimal characteristics of the LVDC cables is formulated.