UNIT II
      POWER FLOW ANALYSIS 
   BUS CLASSIFICATION
   1.Slack bus or Reference bus or Swing bus:
      |V| and δ are specified. P and Q are un specified, and to be 
    calculated.
   2.Generator bus or PV bus or Voltage controlled bus:
      P and |V| are specified. Q and δ are un specified, and to be 
    calculated 
   3.Load bus or PQ bus:
      P and Q are specified. |V| and δ are un specified, and to be 
    calculated 
     ITERATIVE METHOD
               n
         I   Y V
          p    pq q
               q1
        S P  jQ V *I
          p     p       p     P  p
         P  jQ         n
          p       p      Y V
              *         pq q
            V          q1
             P
     The above Load flow equations are non linear and
      can be solved by following iterative methods.
     1.Gauss seidal method
     2.Newton Raphson method
     3.Fast Decoupled method 
      GAUSS SEIDAL METHOD
            For load bus calculate |V| and δ from V k+1 equation 
                                                                      p
                              1  P  jQ            p1                 n           
                 V k1             p        p  Y V k1  Y V k
                    p       Y        (V k)*              pq q                pq q
                              pp       P           q1              qp1          
             For generator bus calculate Q from Q K+1 equation 
                                                                    P
                                               p1               n            
                 Q k1  1*Im(V k)*                Y V k1         Y V k 
                   p                  P        pq q             pq q 
                                               q1              qp           
                                                                               
                                           k+1
          •     Check Qp,cal                     with the limits of Qp
          •     If Q           k+1 lies within the limits bus p remains as PV bus 
                        p,cal
                otherwise it will change to load bus
          •     Calculate δ for PV bus from V k+1 equation
          •                                                                          p
                Acceleration factor α can be used for faster convergence
          •     Calculate change in bus-p voltage
                                                       V k1 V k1  V k
                                                              p               p               p
          •     If |ΔV             |< ε, find slack bus power otherwise increase 
                             max
                the iteration count (k) S                                        S
          •     Slack bus power=                                 G  L