FORMATION OF Y-BUS MATRIX
AIM: To develop a program to complete 60% admittance matrix for the given system network by the method of inspection. THEORY: Bus admittance matrix is often used in power system studies in most of power system studies it is necessary to form Y-bus matrix of the system by considering certain power system parameter depending upon the type of analysis. For example in load flow analysis it is necessary to form Y-bus matrix without taking into account the generator impedance and load impedance. In short circuit analysis the generator transient reactance and transformer impedance taken in account, in addition to line data. Y-bus may be computed by inspection method only if there is no natural coupling between the line shunt admittance are added to the diagonal elements corresponding to the admittance. FORMULA USED: Yij=Yij for i=1 to n Yij= -Yij= -1/Zij Yij=Yij Where Yij= Sum of admittance connected to bus Yij= Negative admittance between buses Y11=(1/Z12)+(1/Z13)+Yc12+Yc13 =(1/(0.1+0.3j))+(1/(0.2+0.6j))+0.014j+0.01j =1.5-4.48j Y22=(1/Z21)+(1/Z23)+Yc21+Yc23 =(1/0.1+0.3j)+(1/0.15+0.5j)+0.01j+0.025j =1.55-4.81j Buses of which there are connected the half diagonal elements are affected. The equivalent circuit of changing transformer may be considering forming Y-bus matrix. The dimension of Y-bus matrix is n X n where n is the number of buses in a power system network, each bus is connected only to two other buses. So the Y-bus of the large network is high is properly not evident in small systems. But in system where there are hundreds of buses the speed is high it may be of 99% hence by applying separate technique numerical computation storage required may be drastically reduced.
Generalized [Y-bus] Each admittance Yii(i=1 to n) is called the self admittance or driving point admittance terminating on the particular box. Each half admittance term Yij (j,i = 1, 2-n, i=j)(I,1) and Yii = Yii. Yji Yij, where Yij is admittance connected between buses i and j.
FLOW CHART: START
Read number of buses(NB) number of lines(NL) and Line data
Line Number=1
From[Y-Bus]matrix using the formula Yii= Yij=Yji=-yij Yes
Increment Line Number
No Is this the last line? Yes Print the [Y-Bus] matrix
STOP Y33 = (1/Z21)+(1/Z23)+ Yc21 + Yc23 = (1/(0.2+0.6j))-(1/(0.15+0.5j))+0.014j + 0.0125j = 1.05 33j Y12 = -1/ (0.1+0.3j) = 1-3j Y23 = -1/ (0.15+0.5j) = 0.55 1.83j
ALGORITHM: Step1: Initialize Y-bus matrix that is replaced by all zero Yji = -Yij = half diagonal element. Step2: Compute Yij = Yij = diagonal element. RESULT: The program for the Y-bus formation by the method of inspection is written and the line data are given and input and output is verified using hand calculation.
FORMATION OF Y-BUS MATRIX
AIM: To develop a program to obtain bus impedance matrix Z-bus of the given power system. THEORY: Z-bus matrix is an important matrix used in different kinds of power system study such as short circuit study, load flow study etc. In short circuit analysis the generator uses transformer impedance must be taken into account. In quality analysis the two-short element are neglected by forming the z-bus matrix which is used to compute the voltage distribution factor. This can be largely obtained by reversing the y-bus formed by resection method or by analytical method. Taking inverse of the y-bus for large system in time conditioning managing modification in the system requires whole process to be repeated to voltage changes in the system. In such cases zbus computed to z-bus solving algorithm. ALGORITHM: Step 1: Read the values such as number of lines, number of buses and line data, generator data and transformer data. Step 2: Initialize y-bus matrix y-bus[i] [j] =complex. Step 3: Compute y-bus matrix by considering only line data. Step 4: Modifies the y-bus matrix by adding the transformer and the generator admittance to the respected diagonal elements for y-bus matrix. Step 5: Compute the z-bus matrix by the modified y-bus matrix. Step 6: Check the iteration by multiplying modified y-bus matrix to z-bus and check whether the resulting matrix is a unit matrix or not. Step 7: Print the z-bus matrix.
FLOW CHART: START
Read number of buses(NB) number of lines(NL) and Line data
Line Number=1
From[Y-Bus]matrix using the formula Yii= Yij=Yji=-yij Increment Line Number
Is this the last line?Yes Yes Zbus=1/Ybus
No
Print the [Y-Bus] matrix
STOP
RESULT: The program has been developed to compute the Z-bus matrix and thus result are verified by multiplying the modified Y-bus matrix and Z-bus matrix to get unit matrix.
