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This study presents a method for discriminative detection of direct current (DC) faults on voltage source converter-powered multi-terminal high-voltage direct current transmission systems using two fundamental guiding principles, namely instantaneous current-differential and travelling waves. The proposed algorithm utilises local voltage and current measurements from all transmission lines connected to a DC busbar, and current measurement from the DC side of the converter. The scheme operates at a sampling frequency of 96 kHz, which conforms with IEC 61869-9. No long distance communication is involved while measurements and signal exchange within DC substations are enabled by the utilisation of IEC 61850. Performance is assessed firstly through detailed transient simulation, using verified models of modular multi-level converters, hybrid DC circuit breakers and inductive DC-line terminations. Furthermore, practical performance and feasibility of the scheme are evaluated through laboratory testing, using the real-time Opal-RT hardware prototyping platform. Simulation and experimental results demonstrate that the proposed protection algorithm can effectively, and within a very short period of time (i.e. <1 ms), discriminate between busbar and line faults (internal faults), while remaining stable during external faults. Additionally, it has been demonstrated that IEC 61869-9 is suitable for enabling fast DC protection schemes incorporating travelling waves. [ABSTRACT FROM AUTHOR]

Offshore wind plant will play an increasingly important role in future decades if ever‐stringent requirements of energy security and low carbon emissions are to be met. Although some analyses of the DFIG impact on system stability have previously been reported, none are based on a large network representing a real system, or the large network is simply not publicly available. This paper describes one such suitable equivalent dynamic model for stability studies based on the UK transmission system. The methodology for appropriate control system design and adjustment of the parameters under different dispatch conditions is presented. Two important aspects contributing to future system stability are studied in detail, namely maximum value of the rate of change of frequency and transient stability. Following National Grid future energy scenarios, a number of detailed case studies are presented to quantify the impact of key influencing factors including the size of the largest generating unit for n−1 contingency, amount of primary system response, and frequency dependency of load. The study concludes that none of the individual factors can provide a complete solution and that careful cost benefit analysis is needed to determine the proper mix of services and reinforcements needed in the future. [ABSTRACT FROM AUTHOR]