A Hybrid Cascaded Transmission System Suitable for Large-scale New Energy Long-distance Island Transmission

In order to meet the collection and long-distance transmission of large-scale wind power, photovoltaic and other new energy sources in Northwest China, this paper proposes a sending-end hybrid cascade transmission system suitable for stable transmission of large-scale wind power bases. Firstly, the topology and operation characteristics of the sending-end hybrid cascaded transmission system are introduced. This system has a double-layer structure. The high-voltage valve group adopts the grid commutation converter, and the low-voltage valve group adopts the modular multilevel converter, which can realize the access and stable delivery of large-scale wind power bases. Then, the coordinated control strategy of LCC and MMC is introduced, and a coordinated start-up strategy suitable for large-scale wind power base access is proposed. Aiming at the output fluctuation of wind power base, the maximum transmission power of LCC and MMC converters is analyzed respectively. And the adaptive distribution control strategy of valve group power is designed for the system to ensure the stable and reliable operation of the system. Finally, the simulation model of the sending-end hybrid cascaded transmission system is built in PSCAD / EMTDC to verify the effectiveness of the control strategy.