Subsynchronous Oscillation Characteristics Analysis Of Direct Drive Wind Farms Connected With Power Grid And Its Control

Recent years have seen a serious threat to the power grid’s safe operation mechanism as well as restrictions on the full consumption of wind power.This new type of sub synchronous oscillation(SSO),which is brought on by the dynamic interaction between wind turbines and their power electronic controls with the AC/DC power grid,has grown to be a significant technical challenge for the power industry.A significant SSO incident caused a huge number of wind turbines to be improperly unplugged from the grid at the Hami wind power station in Xinjiang,China.This essay focuses on three main issues: modeling,analysis,and control,in response to the new stability issue of wind power SSO.The main research content and innovative work include: 1)a method for constructing a complex torque model of a direct drive wind farm based on mechanism derivation;2)Quantitative analysis method for SSO stability based on complex torque model 3)Wind turbine inverter control method for suppressing SSO.(1)A wind turbine complex torque modeling approach taking into account complete order control was presented for modeling direct drive wind farms,making it clear that only complex torque models taking into account internal and external loop control can be utilized for precise quantitative analysis of SSO.Furthermore,the direct drive wind turbine is split into a DC capacitor portion and an electrical control section for the system’s dominant oscillation mode based on the complex torque coefficient approach.The analytical formula for the damping torque in the electrical control section is developed,and a sophisticated torque model for the direct drive wind farm is given.The damping angle is used to investigate the sub synchronous oscillation mechanism in the system.(2)The stability of the system is assessed in terms of sub synchronous oscillation analysis based on the damping coefficient being smaller than 0,and the impact of the power grid’s strength,the operating environment,and the control parameters on the damping characteristics of the system is examined.The accuracy of the analysis results is confirmed by developing time-domain simulations;in order to describe the coupling impact between numerous wind farms,the complex torque model for direct drive wind farm networking that has been suggested is expanded.The operating characteristics of a single wind farm are related to both its own operating conditions and control parameters as well as the operating conditions and control parameters of other wind farms,it is noted that each wind farm is connected to the others through grid impedance.Due to the small transmission amount of wind turbine side oscillation,the traditional complex torque coefficient method and the traditional complex torque coefficient method have difficulty accurately calculating the damping coefficient,while the impedance analysis method yields a two-dimensional matrix that makes it challenging to quantify the level of system instability.The article’s suggested complex torque coefficient technique is quite useful.(3)In order to disrupt and inhibit the generation path of sub synchronous oscillation,the sub synchronous notch filter removes the sub synchronous components from the controller.The operational parameters of the sub synchronous notch filter were designed based on the frequency distribution of sub synchronous oscillation in the constructed simulation model.A sub synchronous notch filter was built into the sophisticated torque model that had already been constructed.Through electromagnetic transient simulation,the efficiency of suppressing oscillation was examined from a damping standpoint.The output d-axis current id of the grid side converter is chosen as the input signal of the extra damping controller simultaneously on the basis of the phase compensation principle.At the same time,the parameters of SSDC are tuned in accordance with the aim of damping maximization based on the improved particle swarm optimization.An extra damping controller is introduced based on the previously defined complex torque model.It is evident from the Bode diagram and electrical damping characteristic diagram that the system is currently in a stable state according to the aforementioned stability requirements.When working conditions change,power grid strength changes,and control parameters change,we study the parameter adaptability of the damping controller and verify its effectiveness through electromagnetic transient simulation.