基于近似能量函数的跟网变流器并网暂态稳定评估方法OA

With the high penetration of renewable energy,grid-connected converters have become the main interface for new energy power generation to be connected to the grid.Due to the unique dynamic characteristics of grid-connected converters controlled by phase-locked loops(PLLs),traditional transient analysis methods have limitations.Therefore,this paper proposes an improved transient stability analysis method,which realizes transient stability assessment of the grid-connected system of new energy power generation units by constructing dynamic equations and approximate energy functions.Firstly,based on the structure of grid-connected system of grid-connected converters,the equations describing the dynamic behavior of the system and the energy function reflecting the energy changes of the system are established.Considering the complexity of calculating the damping term,the trapezoidal rule or ray approximation is used to simplify the damping term in the energy function.Then,by using the dynamic equations and approximate energy functions,the energy value at each time step after a fault occurs is calculated,and the stability state of the system at the corresponding time step is determined by comparing it with the preset critical energy value.Finally,the maximum time step in the stable state is taken as the target maximum fault clearing time and the transient stability of the system is evaluated accordingly.Simulation results show that this method can accurately and quickly analyze the transient stability characteristics of the grid-connected system of grid-connected converters controlled by phase-locked loops.The analysis method proposed in this paper provides a new idea for the stability research of new energy power generation units connected to the grid.