Stability Analysis Of Wind-thermal Bundling System With AC/DC Transmission And Switching Strategy

The current status of wind power development was explored,and with the rapid development of world wind power wave,wind power has broad prospects in China,especially in Xinjiang district.Examples of Zhundong HVDC project,Ha Zheng HVDC transmission project with long distance and large capacity case engineering verified its huge development potential,meanwhile it is expected that Xinjiang wind power will have a brilliant future.The specific contents of this paper are as follows:(1)The development situation of wind power in China and the similarities and differences of wind power development at home and abroad are discussed and summarized.The wind power development trend in recent years in Xinjiang is described,and some policies and regulations promulgated in " 13 th Five-Year " period are summarized.(2)DFIG and synchronous machine model are studied.The DFIG synchronous machine and the changing characteristic of power angle are analyzed,and the mechanical equivalent moment of inertia effects on the transient stability of power system angle are also studied.It can be drawn the corresponding conclusion through the model and simulation: the proportion of wind power in 30%,Wind-Thermal bundling system has good stability.(3)a flexible HVDC control strategy is proposed.By building wind power and thermal power bale delivery system model,analyzing the stability characteristics and mechanism of VSC-HVDC,it can be deduced that the main sign of system transient stability reflects the changes in the power angle,and the transmission power size has related with power angle,thus by adjusting the power angle between the wind power bus voltage and the output voltage of the converter to realize active power control.It is verified by simulation that the strategy can adjust the deviation between the actual power and the set point,and can control the active power flexibly.At the same time,it can also detect the power angle change of the system in time,and adjust it without any delay to strengthen the stability of the system.(4)AC/DC operation and pure DC operation control strategy of two different operation modes are analyzed.An control switching policy among running modes is put forward according to the changes in electrical quantities after failure,and built model to verify in the simulation platform.The research shows that the method can quickly detect the phase shift and frequency changes in time.Control strategy can be switched according to this method,at the same time the fixed frequency control after switching can maintain the system frequency stability.Fixed AC voltage can ensure the voltage stability of the AC system at the sending end.The utility model has the advantages of detecting the phase offset and the frequency changes in a timely manner,and the operation mode can be switched smoothly,and has certain feasibility and sensitivity.