Analysis And Control Strategy Research On Oscillation Traceability Of Direct Drive Wind Power Grid Connected System Under Large Disturbance

The use of back-to-back full power converters for grid connected permanent magnet direct drive wind turbines has obvious advantages in low voltage ride through,unit maintenance costs,power generation efficiency,and has gradually become one of the mainstream wind power.However,while wind power achieves maximum energy utilization and flexible output,its complex dynamic characteristics bring new challenges to the stable operation of the power grid.When a large disturbance fault occurs and fault recovery occurs in a direct drive wind power grid connected system,the interaction between control links such as wind power converters and phase-locked loops may induce oscillations in the system,posing a threat to the safe and stable operation of the power system.This article conducts research on the positioning and optimization control measures of oscillation sources in direct drive wind power grid connected systems under large disturbances.The main content and achievements include:In response to the problem of oscillation tracing in direct drive wind power grid connected systems during fault transient,this paper considers the impact of phase-locked loop dynamic process on current inner loop control,derives an approximate analytical formula for system oscillation current during fault transient,and proposes an oscillation tracing analysis method based on dynamic energy flow path.Considering current inner loop control,phase-locked loop control,and low voltage ride through control,the direct drive wind power grid connected system is divided into multiple subsystems according to different control links.Dynamic energy models of each subsystem are constructed based on system control and topology equations,and the convergence points of each energy in the dynamic energy model are defined as energy convergence points.The oscillation current analytical formula is used to analyze the energy convergence points and the energy between control links,Based on the dynamic energy accumulation value of each path throughout the fault transient process.trace the energy injected into the energy accumulation point,determine the oscillation conduction path between the control links of the external transmission system,and achieve oscillation tracing.In response to the problem of oscillation tracing in the direct drive wind power grid connected system during fault recovery.this paper considers the DC voltage outer loop control and the grid side converter d-axis inner loop control,and proposes an oscillation tracing analysis method based on dynamic energy flow path.Based on the dynamic response after the DC voltage outer loop control is re applied during the fault recovery period,a dynamic energy model is constructed.The DC voltage oscillation component is used to solve the non periodic component of the system’s dynamic energy,and the positive and negative characteristics of the non periodic component are used to determine the energy flow path,achieving oscillation tracing.A control parameter optimization strategy for direct drive wind power grid connected systems under large disturbance faults is proposed to address the issue of system dynamic response and improper parameter settings during transient and recovery periods,which pose a threat to the stable operation of the power grid.Aiming at the oscillation problem of direct drive wind power grid connected systems during fault transient and fault recovery periods,this study investigates the impact of control link parameters on system storage energy in the direct drive wind power grid connected system.Based on this,the optimization goal is to reduce the cumulative value of system total storage energy and consider the relationship between control parameters.Constraint conditions are formulated,and a constrained multi-parameter collaborative optimization model is established to optimize key control parameters,reduce the impact of oscillation on the system.