Search

Speed and selectivity of DC fault protection are critical for High-Voltage DC (HVDC) grids and present significant technical and economic challenges. Therefore, this paper proposes a non-unit protection solution that detects and discriminates DC faults based on frequency domain analysis of the transient period of DC faults. The representation of a generic HVDC grid section and the corresponding DC-side fault signatures in the frequency domain form the basis of a generalized approach for analytically designing a protection scheme based on Wavelet Transform (WT). The proposed solution is adaptive within its design stage and offers general applicability and immunity to system changes, while the protection settings are configured for optimized performance. The scheme is validated through offline simulations in PSCAD/EMTDC and the technical feasibility of the algorithm in the real world is demonstrated through the use of real-time digital simulation (using RTDS) and Hardware-in-the-Loop (HIL) testing. Both offline and real-time simulations demonstrate that the scheme is able to detect and discriminate between internal and external faults at a significantly high speed, while remaining sensitive to high impedance faults and robust to external disturbances and outside noise. [ABSTRACT FROM AUTHOR]

In this article, a novel, learning-based method for accurate location of faults in multiterminal direct current (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, first, can reliably determine the type of fault, second, can accurately estimate the fault location (including the cases of highly resistive faults), and, third, is practically feasible. [ABSTRACT FROM AUTHOR]

High-voltage direct-current (HVDC) systems are being widely employed in various applications because of their numerous advantages such as bulk power transmission, efficient long-distance transmission, and flexible power-flow control. However, line-commutated-converter-based HVDC systems suffer from commutation failure, which is a major drawback, leading to increased device stress and interruptions in transmitted power. This paper proposes a predictive control strategy, deploying a commutation failure prevention module to mitigate the commutation failures during ac system faults. The salient feature of the proposed strategy is that it has the ability to temporarily decrease the firing angle of thyristor valves depending on the fault intensity to ensure a sufficient commutation margin. In order to validate the performance of the proposed strategy, several simulations have been conducted on the CIGRE Benchmark HVDC model using PSCAD/EMTDC software. Additionally, practical performance and feasibility of the proposed strategy are evaluated through laboratory testing, using the real-time Opal-RT hardware prototyping platform. Simulation and experimental results demonstrate that the proposed strategy can effectively inhibit the commutation failure or repetitive commutation failures under different fault types, fault impedances, and fault initiation times. [ABSTRACT FROM AUTHOR]

This paper presents a method for rapid detection of faults on voltage source converter multiterminal HVdc transmission networks using multipoint optical current sensing. The proposed method uses differential protection as a guiding principle, and is implemented using current measurements obtained from the optical current sensors distributed along the transmission line. Performance is assessed through detailed transient simulation using MATLAB/Simulink models, integrating inductive dc-line terminations, detailed dc circuit-breaker models, and a network of fiber-optic current sensors. Moreover, the feasibility and required performance of optical-based measurements is validated through laboratory testing. Simulation results demonstrate that the proposed protection algorithm can effectively, and within very short period of time, discriminate between faults on the protected line (internal faults), and those occurring on adjacent lines or busbars (external faults). Hardware tests prove that the scheme can be achieved with the existing, available sensing technology. [ABSTRACT FROM PUBLISHER]