Intelligent fault location in MTDC networks by recognising patterns in hybrid circuit breaker currents during fault clearance process

In this paper, a novel, learning-based method for accurate location of faults in MTDC networks is proposed. By assessing the DC circuit breaker currents during the fault clearance process, a pattern recognition approach is adopted from which the fault location is estimated. The implementation of the algorithm is allocated into three main stages, where similarity coefficients and weighted averaging functions (incorporating exponential kernels) are utilized. For the proposed algorithm, only a short-time window of data (equal to 6 ms) is required. The performance of the proposed method is assessed through detailed transient simulation using verified MATLAB/Simulink models. Training patterns have been retrieved by applying a series of different faults within an MTDC network. Simulation and experimental results revealed that the proposed scheme i) can reliably determine the type of fault ii) can accurately estimate the fault location (including the cases of highly resistive faults) and iii) is practically feasible

A controllable thyristor-based commutation failure inhibitor for LCC-HVDC transmission systems

Commutation failure is a serious malfunction in line-commutated high voltage direct current (HVdc) converters which is mainly caused by the inverter ac faults, and results in a temporary interruption of transmitted power and damage to the converter equipment. In this article, a controllable commutation failure inhibitor (CCFI) is developed which obviates the main drawbacks of the existing power electronic based and fault current limiting based strategies. Under normal circumstances, the developed CCFI improves the steady-state stability and the power transfer capability of the inverter ac lines, while it does not cause excessive voltage stress on the converter valves. In addition, it would reduce the risk of commutation failure occurrence, since it does not lead to any voltage drop in the commutation circuit. When a fault occurs at one of the inverter ac systems, its corresponding CCFI limits the fault current depending on the reduced extinction angle. This would not only inhibit the successive commutation failures on the HVdc converter, but also extend the lifetime of components in the inverter ac systems. The practical feasibility of the developed CCFI is assessed through laboratory testing, using a real-Time Opal-RT hardware prototyping platform. The obtained results indicate that the developed CCFI can reliably inhibit the commutation failures during various types of faults