Comparative Analysis of Methods of Determining of Power System Load Margins: TENR Method and Quasi-Z Load Approach

Abstract

Calculation of power system bus load margins is an important task for ensuring of steady-state stability and preventing of voltage collapse. Traditional methods, such as the continuation power flow, face the problem of Jacobian matrix singularity in the vicinity of the limit point. This paper proposes a fundamentally new approach - quasi-resistive load (Quasi-Z Load) - which reformulates the steady-state equations by representing bus power consumption as an equivalent complex impedance with a variable magnitude. A comparative analysis of the proposed approach with the TENR (Transversality Enforced Newton-Raphson) method is performed. It is shown that the Quasi-Z Load approach allows continuous calculation of the steady-state solution trajectory till to the voltage collapse point and determination of the load margin without special continuation procedures. The results are verified on test schemes.