Research On Small-signal Angle Stability For Wind-PV-thermal-bundled Power Transmitted By AC/DC From A Weak AC Network

In the northwest of our country,with the development of wind power and photovoltaic(PV)and multiple HVDC project putting into operation,the stability characteristics of the northwest power grid is undergoing profound changes and the characteristics of local weak sending system is becoming more obvious.At the same time,because of the objective reality of our country,whose energy resources and energy demand is reverse distribution,all of wind power and PV as well as thermal need to be transmitted to the load center over a long distance.The interaction of the wind-PV-thermal power transmitted by AC/DC system is more complex.This paper researches on the small signal angle stability of the wind-PV-thermal-bundled power transmitted by AC/DC from a weak sending system.Firstly,the simplified dynamic models of the system are established,including DFIG,PV and DC transmission system,and the control strategies of the models are designed.Based on the dynamic models,the Linearized model can be derived.Secondly,based on the method of eigenvalue analysis of the system state matrix,the factors that influence the small signal angle stability of the wind-PV-thermal-bundled power transmitted by AC/DC from a weak sending system are explored,including the electrical distance betw een the power source of the sending system,the length of ac/dc power line,the proportion of the ac/dc transmission capacity and the capacity of the three kinds of power source.Thirdly,in order to improve the damping of the system,PSS is attached to th e active control of the DFIG and the PV as well as the constant current control of the rectifier,and the PSSs parameters are designed by artificial fish swarm algorithm respectively.Simulation results show that the PSS of the DFIG and PV as well as DC system can improve the damping of the system.Lastly,in order to eliminate adverse effects between the several PSSs,the parameters of the several PSS are designed simultaneously by artificial fish swarm algorithm,which is proved to be effective.