A New Kind of Hybrid UHVDC System Dedicated for Long-Distance Power Delivery and Regional Power Grids Back-to-Back Hierarchical Interconnection

This paper proposes a hybrid UHVDC system dedicated for long-distance power transmission and back-to-back interconnection of the receiving region power grids. The receiving terminal of the UHVDC system is formed by the LCC and MMC in cascaded connection. The system combines the merits of hierarchical connection and asynchronous interconnection, which optimizes the network structure of the receiving system and makes the power distribution of the receiving region grids more flexible. The topology of the system is introduced in detail. The control strategy and the DC fault clearing strategy are proposed. Finally, the UHVDC system is built in PSCAD / EMTDC. The simulation verifies the effectiveness of the control strategy, the DC fault clearing strategy and the re-starting strategy. The results indicate that this kind of UHVDC system has a good application prospect in large-capacity long-distance power transmission to the asynchronous regional power grids.