Damping Analysis And Control Strategy Research Of Power System With High Proportion Of Hydropower And Wind Power Acces

In recent years,ultra-low frequency oscillation has occurred many times in power systems with high proportion of hydropower at home and abroad,which seriously threatens the safe and stable operation of the system.With the wide application of DC transmission,asynchronous networking and other technologies and the large-scale integration of new energy sources such as wind power,the grid structure and damping characteristics of the power system have changed,and the system will face more serious ultra-low frequency oscillation risks.Therefore,it is of great significance to carry out research on ultra-low frequency oscillation in hydropower high proportion power system with wind power access.Firstly,in this paper,the turbine governing system model and the doubly-fed wind turbine shafting system model are modeled in detail.The damping torque method is used to analyze the turbine governing system and the doubly-fed wind turbine shafting system.It is revealed that the ultra-low frequency oscillation of the hydropower system and the doublyfed wind turbine shafting oscillation are caused by the negative damping effect caused by insufficient system damping.Then,based on the derived damping torque coefficient expression,the influence of water hammer effect time constant and governor PID parameters on the damping characteristics of the speed control system is studied.Based on the mechanism analysis,a combined control strategy of additional damping and grey wolf optimization(GWO)is proposed.The proposed strategy increases the damping torque coefficient of the speed control system and improves the damping characteristics of the system.Based on the MATLAB / Simulink simulation platform,the system simulation model with turbine is built,and the ultra-low frequency oscillation phenomenon is reproduced in the system.Through simulation experiments,compared with the series correction control strategy and the particle swarm optimization(PSO)algorithm parameter setting strategy,the effectiveness of the proposed control strategy to suppress the ultra-low frequency oscillation of the system is verified.Finally,the expression of the electrical damping torque of the doubly-fed wind turbine shaft system is derived.Based on this expression,the damping characteristics of the doublyfed wind turbine system are studied,and the specific reasons for the negative damping effect of the doubly-fed wind turbine are analyzed.Through the MATLAB / Simulink simulation platform,the single-machine and multi-machine system models with doubly-fed wind turbine access are built.The simulation experiments under different wind turbine operating parameters and different wind power penetration rates show that wind power has a weak support for the stability of the power grid and weakens the damping of the system in the low frequency band and ultra-low frequency band.After being incorporated into the highproportion hydropower system,the risk of ultra-low frequency oscillation of the system is increased,and the operating environment of the power system will be deteriorated with the increase of wind power penetration rate.Based on the above analysis,an additional damping control strategy for the rotor side of the doubly-fed wind turbine is proposed.The effectiveness of the proposed control strategy to improve the system damping characteristics and reduce the risk of ultra-low frequency oscillation is verified in the single-machine model and multi-machine model with doubly-fed wind turbine access.