Fault estimation with analytical cable model for MMC-HVDC in offshore applications

Reliable operation of offshore windfarms is very critical and it depends on efficient operation of each component. Underwater cable is one of key element which has less access to measurements except at both ends of the transmission. In this paper, a detailed cable model is considered to analyse the nature of fault from signatures of measurements in offshore Multi-Modular Converter High Voltage DC (MMC-HVDC) systems. The cable model representing the frequency dependent characteristics is used in this paper. The estimated model is emulated inside the controller while controller controls and gets feedback from the physical model. Both the model results are initially verified in all healthy states and all operating modes. Different abnormal conditions including short circuit and open circuit phenomenon are created on the simulated cable model and analysed. A novel method of identifying these faults with the available measurements using estimated cable model is proposed. This is further verified with the simulation results.