Reliable power flow calculation with improved convergence characteristics for distribution systems

For construction of smart grid with optimal operations, analytical studies for distribution systems are important, and advanced method which is applicable to any power systems is required. Today, Newton-Raphson method is utilized for a lot of power flow analysis. However, since R/X ratios of lines are relatively high in distribution systems, it is said that the convergence characteristics of Newton-Raphson method are poor. In addition, when some bus voltages are close to the voltage stability limit in power systems, the convergence characteristics are worse. In this paper, first the convergence characteristics of conventional Newton-Raphson method is evaluated using radial distribution systems with lines of high R/X ratios. Next, the new calculation method for ill-conditioned system is proposed which is based on Newton-like method with a little devisal. In the method, admittances of load at each P-Q specified buses are embedded in Y-matrix. The effectiveness and robustness of the proposed method for distribution systems is demonstrated.