A Hybrid Ultra‐High Voltage DC Transformer With Digital Twin‐Driven Operation and Control

In the context of large‐scale renewable energy transmission, to enhance the economic efficiency and operational flexibility of the ultra‐high voltage DC transformer (UHVDCT), a hybrid UHVDCT with digital twin (DT)‐driven operation and control is introduced. The proposed UHVDCT adopts a parallel configuration of high‐capacity line commutated converters (LCCs) and low‐capacity modular multilevel converters (MMCs) at the ultra‐high voltage (UHV) side, and MMCs at the high voltage (HV) side. Relying on the real‐time mapping and online analysis capabilities of the DT, the LCCs at the UHV side (UHV–LCCs) transmit the total active power flow of the UHV side by controlling it. The MMCs at the UHV side (UHV–MMCs) operate in V/f control mode, with their reference signals generated by the DT in the virtual space. Their primary function is to establish a stable voltage and frequency reference for the internal AC links of the UHVDCT. Adopting constant DC voltage and improved reactive power control mode coordinated by the DT, MMCs at the HV side (HV–MMCs) can maintain their DC voltage and the UHVDCT's dynamic reactive power balance. By integrating the merits of LCC and MMC and leveraging DT technology, the proposed UHVDCT cuts the MMC capacity requirement for lower cost, ensures stable performance, and enhances its economic and engineering viability.