| China Southern Power Grid(CSG) has become a large-scale AC/DC hybrid power grid, with a great quantity of electric power transmitted from Yunnan and Guizhou Province to Guangdong Province. By 2030 there will be 11 high voltage direct current transmission(HVDC) systems planned to be connected to the grid in Guangdong and CSG will have characteristics of strong HVDC systems and multiple HVDC systems feeding Guangdong. As for Guangdong Power Gird, the inverter stations are with close connection. Therefore, AC faults can easily affect multiple inverter stations, causing communication failure and power blocking of more than one HVDC systems. It has been a main concern that HVDC systems recovery need larger reactive power recovering from communication failure after AC faults, which may lead to transient voltage stability problem。Researches on static stability of AC/DC system has made a great progress. However, when it comes to transient voltage issues, the current study mainly apply time-domain simulation method to analyze the influence of some control parameters of HVDC systems on transient voltage recovery, or to investigate transient voltage stability of a specific AC/DC hybrid grid and dynamic reactive power compensation. It lacks of study on HVDC system power evolvement regulation after AC faults. Principles of dynamic reactive power compensation location selection of receiving AC network also has to be further studied.This passage conducts study on building the model of HVDC system power variation regulation and dynamic reactive power compensation location selection. First of all, simulations of single-infeed systems(including CIGRE test system and Chusui HVDC system in CSG) and simple multi-infeed systems are carried out through PSCAD/EMTDC, to analyze HVDC system power variation characteristics. A time-domain series model of HVDC power recovery is proposed and applied to electromechanical transient simulation. Furthermore, an index indicating transient voltage sag is put forward for multi-infeed HVDC system to investigate voltage stability after faults occurring in the receiving network. Finally, the location selection index of dynamic reactive power compensation is proposed, and then simulations are conduct to prove the accuracy of the location selection index. |
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