| With the high penetration of renewable energy and high proportion of power electronic equipment in the grid,the future power system presents new characteristics such as diversified operation modes and complicated stability mechanism,and the requirements for safe and stable operation of the power grid are also increasing.Power flow（PF）calculation is the basis of power grid security and stability analysis,and the mainstream method is Newton-Raphson（NR）method.However,the local convergence of NR makes this method sensitive to initial value selection,and unreasonable initial value will lead to non-convergence of PF calculation.When the PF diverges,it cannot be clearly determined whether the divergence is caused by the defects of NR or there is no PF solution of the system under this operating mode.Holomorphic Embedding Load Flow Method（HELM）,as a new PF calculation approach,can effectively avoid the above problems in the process of solving PF using NR.But when the existing HELM solves the PF of large-scale system,the high order of power series will easily lead to the divergence of analytical continuation and poor convergence,and the calculation redundancy of HELM is high,resulting in low efficiency.Under this research background,this paper mainly completes the following research work:Firstly,this paper proposes a new HELM based on constant values（CHELM）.Based on the solution theory of holomorphic embedding nonlinear equations,a new HELM model based on constant values is constructed on the basis of the AC PF equation of the power system under rectangular coordinates and combined with the characteristics of different types of buses.The solution strategy of dynamically updating the constant values is further proposed to realize the PF solution.Then,this paper proposes to define the priori buses of the power system.Through the prior bus voltage amplitude error,it evaluates whether the power mismatch in the process of PF calculation is close to the PF convergence threshold,and then determines whether to calculate the voltage approximation values of all buses in the power system,so as to reduce the redundancy of the traditional HELM calculation and improve the efficiency of HELM in large-scale power systems.Finally,considering the generator bus type conversion in PF calculation,two bus type conversion strategies based on HELM are proposed.The accuracy and effectiveness of the proposed method are analyzed and verified by different scales AC testing systems whose buses range from 4 to 25000,and the results of the proposed method are compared with the MATPOWER calculation based on NR method.The results show that the proposed method is independent of the initial value and can accurately and efficiently solve the PF solution of the power system.Compared with the NR and the traditional HELM,the proposed method has better PF convergence. |
