| HVDC has the characteristics of the economy, high controllability and quick adjustability,which make it widely applied in long distance, high-capacity transmission andinterconnection of regional power grids, and gradually formed complex power systems withthe parallel operation of AC and DC transmission and multi-infeed DC systems, especially inSouth China Power Grid(CSG). Commutation failure is the most typical problems underAC/DC interactions for MIDC system. With the operation of Xiluodu and Nuozhadu HVDCproject, CSG will form a more complex MIDC system during the “Twelfth Five-year Plan”period. Some serious faults may lead to simultaneous commutation failures in all eight DClines, the commutation failure and power recovery characteristics is very important for thesafe and stable operation of power grid. Therefore, the study of commutation failure andpower recovery characteristics with detailed electromagnetic transient modeling of MIDCsystem is necessary.This paper analyzed the mechanism and the main factors affecting commutation failureand power recovery process of HVDC system firstly. Take the Nuozhadu±800kV UHVDCproject as an example, by using PSCAD/EMTDC simulation software, the influence factorson commutation failure and power recovery process are studied, included the inverter busvoltage change, theAC system strength and voltage-dependent current order limit (VDCOL).A method for quickly modeling and debugging of EMTDC aimed to solve the difficultyof the establishment of the accurate initial steady-state for large-scale AC-DC power systemelectromagnetic transient simulation is proposed. The idea through partitioning the largepower grid into several small grids and modeling and debugging each small grid separatelyimproves the modeling efficiency and model accuracy. Dynamic equivalent of the summerpeak load operation mode in the planning of2015China Southern Power Grid is taken, andthe detailed model of the equivalent power grid which includes all8HVDC transmissionsystems and500kV main network is established.The commutation failures in multi-infeed HVDC transmission systems of2015ChinaSouthern Power Grid are researched in depth by EMTDC simulation. The fault regions ofdifferent types in which faults may lead to simultaneous commutation failures in multi DClines are given, DC response characteristics and recovery process under typical faultsoccurring near converter buses in majority DC inverter stations in Guangdong power gridwere analyzed emphatically. Finally, the impact of the application of±200Mvar staticsynchronous compensator(STATCOM) in500kV Beijiao station, Shuixiang station and Mumian Station on commutation failure and recovery characteristics of multi-infeed systemare analyzed by the simulation. |
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