N-R Method using Rectangular Coordinates: N-R method can be applied to power flow problems in a number of ways, the most common being those using:ġ. Newton-Raphson Method Applied to Power Flow Problem: The (Δx 1, Δx 2, Δx 3,……….,Δx n) becomes smaller and smaller with every iteration and finally the iteration process is stopped when (Δx 1, Δx 2, Δx 3,……….,Δ x n) are lesser than pre-specified values. Repeating the process of iterations, with these values, we get yet better estimated values. Solution of the matrix equation provides (Δx 0 1, Δx 0 2, Δx 0 3,……….,Δx 0 n) and the better estimates of the solution are given by –
The solution of the equations needs calculation of left hand vector B which is the difference of the specified quantities and calculated quantities at (x 0 1, x 0 2, x 0 3,…,x 0 n). Where J is the square matrix of the partial derivatives on the RHS and is known as Jacobian matrix. In vector from above equation can be written as – Linearizing all the equations and arranging them in matrix form, we have: In fact it is this assumption that requires the initial solution to be close to the final solution. Partial derivatives of second and higher order are neglected according to N-R method.
#POWER WORLD SIMULATOR USES WHAT METHOD SERIES#
Δx n 0 be the corrections, which on being added to the initial assumed values, give the actual solution.Įxpanding these equations in Taylor’s series around the initial guess, we have – A flat voltage profile, i.e., V i = (1.0 + j 0) for i = 1, 2, 3 … n except the slack bus has been found to be satisfactory for almost all practical systems. The noteworthy point is that the initial solution for the nonlinear equations should not be very far from the actual solution, otherwise, there are chances of the solution diverging rather than converging and it may not be possible to have a solution whatever the computer time taken.Īt first glance it may appear to be a great drawback for the N-R method but the problem of initial guess for a power system is not at all difficult. The zero subscript defining the zero th iteration in the process of solving the above nonlinear Eq. The solution of above nonlinear equations is started with an approximate solution –
These are related by the set of nonlinear equations: Let the unknown variables be (x 1, x 2, x 3 …, x n) and the specified quantities (y 1, y 2, y 3, …, y n). The process of iteration is continued till the difference in the specified and calculated values of P, Q and V are within the given permissible limit.īefore explaining the application of N-R method to the power flow problems, it is useful to review this method in its general form.
The difference between the specified and calculated values is used to determine the correction of bus voltages.
These voltages are used to compute active power P at every bus except the swing bus and also reactive power Q wherever reactive power is specified. The drawbacks of this method are difficult solution technique, more calculations involved in each iteration resulting in large computer time per iteration and the large requirement of computer memory but the last drawback has been overcome through a compact storage scheme.Ĭonvergence can be considerably speeded up by performing the first iteration through the G-S method and using the values of voltages so obtained for starting the N-R iterations.