Since the Gezhouba–Nanqiao Project, the number of HVDC transmission lines, converter stations, and transmission distances in China’s highvoltage direct current (HVDC) power transmission systems have increased sharply. Accordingly, the overvoltage fault rate in AC/DC transmission systems has also risen. Especially in regions such as Hubei Province, Shanghai, and Guangdong Province, which host multiple HVDC systems, the complexity of the AC/DC grid results in more intricate faultcausing factors. However, the simulation of largescale AC/DC grids has mainly been applied to the development and verification of control strategies and power flow analysis. During modeling, extensive equivalent processing is often adopted, with many primary equipment simplified or even omitted, making it impossible to obtain actual overvoltage conditions on the equipment.

To meet the practical needs of onsite overvoltage analysis and guiding fault maintenance, engineers from KeLiang leveraged the existing grid fundamental data resources of Hubei Province to establish an electromagnetic transient simulation model of the Hubei AC/DC power grid. Based on the actual requirements for onsite equipment fault analysis and grid recovery maintenance, and combined with the HyperSim and RTLAB software/hardware simulation platforms, a full primary equipment model of the AC/DC grid was built, covering entire converter stations, nearby substations, and surrounding local areas. This enabled complete primary equipment modeling beforehand and postevent electromagnetic transient fault simulation across a wide network region. The model has been applied in actual engineering commissioning and fault analysis. Its reliability has been verified through practical engineering tests, and it has been used to guide grid overvoltagerelated fault diagnosis and transformer DC bias impact analysis, with simulation results aligning with engineering reality.

After two years of cooperation and joint development, the technical collaboration project between KeLiang and the Hubei Electric Power Research Institute has now been successfully accepted. The acceptance expert panel listened to the project report, observed the performance demonstration of the testing setup, and conducted inquiries. After thorough discussion, the panel concluded that the submitted acceptance documentation was complete and standardized, meeting the project acceptance requirements. The project was smoothly accepted and received high praise.

The system is currently applied to equipment fault analysis in the Hubei power grid, having effectively supported onsite grid equipment fault analysis more than ten times. The implementation of this project has effectively bolstered the operation and maintenance of the Hubei power grid, enhanced the capability to respond to equipment faults, optimized the security and stability defense system of the Hubei grid, and raised the intelligence level of comprehensive coordinated security and stability defense, delivering significant economic and social benefits.

HyperSim is a largescale realtime digital simulation & testing system for power systems, serving as an electromagnetic transient simulation and analysis tool for hybrid AC/DC power systems. The system employs EMTP algorithms, can perform realtime electromagnetic transient simulation for largescale power systems with over 10,000 nodes, and offers high simulation accuracy (time step below 50 microseconds), excellent visualization, support for online parameter adjustment, automated testing functions, and test report generation.

By joining forces with KeLiang based on the powerful HyperSim platform, Hubei Electric Power Research Institute tackled multiple technical challenges, achieved mechanistic research on AC/DC grid fault diagnosis and grid recovery, and provided solid data support for grid security operation and maintenance.