This paper presents a comparative study of the new constant Jacobian matrix load flow method, fast decoupled load flow method and novel hybrid load flow method. A mathematical model for the new constant Jacobian matrix load flow solution method in rectangular coordinates is first presented. In this method, the usual decoupling of real and reactive power load flow equations is not done as in the case of fast decoupled load flow method. Some reasonable assumptions are made to make the matrix constant, thereby avoiding the necessity of computing the matrix in every iteration. The proposed method exhibits better Convergence Reliability (CR). Numerical results from IEEE and other system examples are presented for the comparative study of the three load flow methods for better future planning.

Load flow or power flow is an important and basic study frequently performed by the engineers for future planning, operation and control purpose. The Power System (PS) is normally represented by a set of nonlinear simultaneous algebraic equations. The researchers have presented numerous mathematical models and load flow solution methods for the solution of these nonlinear equations in the last six decades. The load flow calculations have been used to solve large PS problems using digital computers since 1956 (Ward and Hale, 1956). A brief review of the load flow solution methods for such problems can be found from Wu (1977), and Ahasn and Jalil (2005). Gauss-Seidel (GS) and Newton Raphson (NR) methods were widely used by the PS planners and research engineers for the solution of load flow problems. In the year 1974, Stott and Alsae (1974) proposed the fast decoupled load flow method, which was very well recognized and is still popular throughout the world. This method also fails to converge in certain situations (Stott, 1974; and Rao et al., 1980) explained in detail. This convergence problem has motivated researchers from time to time to look for other alternatives. A constant matrix method was proposed by Singh et al. (1984). The matrix of this method is found to be the same as the matrix of fast decoupled load flow method proposed by Stott and Alsac (1974), therefore it has a similar convergence problem. The other constant matrix method in polar coordinates has been proposed by Rao et al. (1980), wherein unlike the fast decoupled load flow method, the off-diagonal sub-matrices are not neglected. On the other hand, the usual decoupling assumptions are not taken into account, otherwise this method may be found more reliable in comparison to fast decoupled load flow method. Rao et al. (1981) have also proposed a novel hybrid load flow solution method which was found to be reliable and promising for certain ill-conditioned systems. The novel hybrid load flow method was found to be more promising for specific power flow problems, which are commonly encountered in power distribution networks. A superior method, other than the fast decoupled load flow method (Stott and Alsac, 1974) and novel hybrid load flow solution method (Rao et al., 1981), is still needed for the better future planning purpose. Thus, this paper first presents the usual load flow equations in rectangular coordinates. The constant Jacobian matrix model is used to develop the new reliable load flow method for the basic load flow study.

It is very interesting that in the proposed model, the constant matrix is found to be exactly the same as in the polar version. The presented constant Jacobian matrix load flow solution method in rectangular coordinates based on the mathematical model is illustrated with 5, 14, 26, 30, 57 and 61 bus system examples. The Convergence Reliability (CR) of the constant matrix method is also proved to be a special feature. A comparison of the constant Jacobian matrix load flow method, fast decoupled load flow and novel hybrid load flow method is presented in this paper.

Electrical and Electronics Engineering Journal, Three Load Flow Methods, Mathematical Model, Power Distribution Networks, Convergence Reliability, Power System, Jacobian Matrix Model, Jacobian Matrix Load Flow Method, Advance Computer Technique, Computer Programing, Hybrid Load Flow Solution Methods.