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• A weak bus identification index is derived to identify the critical bus when power flow is unsolvable. • An extended system considering new bus type is proposed to improve power flow solvability. • A weak bus identification and bus type switching based framework is established to provide adjustment measures efficiently and automatically. • The method could provide a suitable solution automatically for unsolvable power flow in a variety of scenarios, retains stable convergence and has potential in large-scale power grids. The power flow solvability is greatly challenged by the growing pressure on power grid induced by the rapid development of economy. The approaches of restoring power flow solvability should be profoundly studied. Most of adopted power flow adjustment methods are based on manual interference which require extensive human resources with inefficiency. Thus, a power flow adjustment strategy based on a weak bus identification and a new bus type conversion is proposed. A weak bus identification index is defined and expressed when power flow has no solution. We propose a novel bus type and a concept of the power shortage to restore power flow solvability. The generator action set is determined by calculating the left eigenvector of the Jacobian matrix. At last, we establish a linear programming model to determine the generator output adjustment. Numerical results are obtained in 3 test systems and an actual system in China. Compared with other methods, the proposed method is verified to have a higher success rate of restoring power flow solvability and has robustness in various scenarios. [ABSTRACT FROM AUTHOR]

• The purpose of this article is to study a power flow algorithm with strong convergence, initial value adaptability, and efficiency. • This paper proposes a two-part alternating iterative framework based on dynamic equivalent admittance. • The proposed algorithm has universality for well-and ill-conditioned systems. • The proposed method combines the convergence characteristics of the Z-bus Gauss method and Newton's method, so it is easy to implement based on existing program codes. Power flow is an extensively used tool in various operations and planning of power systems. In this paper, we propose an efficient hybrid method for solving the power flow problems in ill-conditioned power systems. This method is implemented in a framework of two-part alternating iteration. In Part I of this method, PV bus voltages are regarded as constant and PQ bus voltages are updated by the Z-bus Gauss method. In Part II of this method, PQ bus loads are equivalent to dynamic admittances, and PV bus voltage angles are updated by Newton's method. The values of PQ bus voltage magnitudes and PV bus voltage angles are passed between Part I and Part II. The proposed method is validated in well- and ill-conditioned systems and compared with several well-known power flow methods. Results show that the proposed method is robust and efficient to address the issues related with large-scale ill-conditioned power systems and it is not significantly affected by the considered initial guess. [ABSTRACT FROM AUTHOR]