Abstract
Integration of renewable energy generations requires the transmission of bulky power over long distance, and high-voltage direct current (HVDC) transmission systems become a more preferable choice compared to conventional HVAC systems. For HVDC systems, one of the important concerns is the DC protection strategy which can significantly impact on the connected AC system performance, e.g. system frequency. The maximum loss-of-infeed for a AC network is highly dependent on the duration of the power outage, and the impacts of DC fault protection arrangements which result in different speed of power restoration on the connected AC system, on the system frequency, have not been properly understood. Different DC protection arrangements using DC disconnectors, fast and slow DC circuit breakers on frequency response of the connected AC networks are investigated. A three-terminal meshed HVDC system is studied to demonstrate system behaviour during DC faults.
Highlights
High voltage direct current (HVDC) technology has significant advantages on long-distance power transmission and renewable energy integration, e.g. low cost and higher controllability, when compared to the traditional AC power transmission technology
One major challenge for the system frequency is the decreasing system inertia with large HVDC system penetration which can lead to deteriorated frequency performance under system disturbances
In [8], a comparison of frequency response after generator outage in hybrid systems with different levels of wind penetration was carried out and the results showed that the rate of change of frequency (ROCOF) and frequency nadir became larger with the decrease of system inertia
Summary
High voltage direct current (HVDC) technology has significant advantages on long-distance power transmission and renewable energy integration, e.g. low cost and higher controllability, when compared to the traditional AC power transmission technology. One major challenge for the system frequency is the decreasing system inertia with large HVDC system penetration which can lead to deteriorated frequency performance under system disturbances. For AC network disturbances such as loss of infeed and load change, it has been indicated in [4,5,6,7] that the rate of change of frequency (ROCOF) will increase significantly when the same disturbance occurs in an AC-DC hybrid system with low inertia, compared to the systems with high inertia. In [8], a comparison of frequency response after generator outage in hybrid systems with different levels of wind penetration was carried out and the results showed that the ROCOF and frequency nadir became larger with the decrease of system inertia. The reduction of system inertia weakens the effect of primary frequency regulation provided by conventional synchronous generators which will make the system frequency performance even worse after such AC network disturbances [9, 10]
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