Digital-Analog Hybrid Simulation of Southwest Planning Power Grid with Multi-HVDC Concentrated Delivery

Security and stability operation of multi-HVDC concentrated delivery power grid in southwest China is related to the reliable transmission of large hydropower bases, safety working of Southwest main power network and Tibet power system, and power supply to East and Central China. Digital-analog hybrid simulation-- EMT model of large-scale power grid with physical control and protection devices has obvious advantages in studying the interaction between AC and DC. Based on the new generation of UHVAC/DC hybrid simulation platform in State Grid Simulation Center, a detailed EMT real-time simulation model of Southwest power grid in 2025 level year with voltage level of 110kV and above is built. In this model, 9 located HVDCs are simulated with 3 physical controllers and 6 digital control systems. Detailed simulation is carried out for the faults near the five DC transmission terminals in the centralized area. The AC and DC response in the process of faults and recovery are studied, and also the influence of commutation failure of one DC project on other DC systems. The results shows that AC faults in Panxi area doesn not have a serious impact on the concentrated DCs in the region. However, for the commutation failure of one DC circuit, the commutation failure of adjacent DC may occur at the same time due to the increase of sending terminal voltage.