Mechanism of Overvoltage and Strategies of Overvoltage Suppression for UHVDC Systems Powered by Renewable Energy

The majority of renewable energy in China is located in the northwest area, including Xinjiang, Tibet, Nei Monggol and Qinghai province. However, it is critical to deliver this massive amount renewable power to the east side of China due to the imbalance of population. In addition, global energy interconnection has become increasingly popular. As an effective solution, ultra-high voltage direct current transmission systems (UHVDC) can easily achieve asynchronous grid interconnection, as well as a balanced distribution of renewable energy. This paper presents an approach to encounter overvoltage suppression by new UHVDC control strategies, as well as installing controllable lightning arrester. Validation is performed on real-time digital simulator (RTDS) by using the real data from Zhalute-Qingzhou ± 800 kV UHVDC project. The results show presented approach of overvoltage suppression can reduce the level of overvoltage from sending end by up to 15% when AC system fault happens at the receiving end.