EE 451 
       Load Flow Analysis (LFA) 
    LFA is performed for: 
     1- Power system planning 
     2- Operational planning 
     3- System operation and control 
     4- Economic dispatching 
    Data obtained to identify the following: 
     1- Normal operation mode (day to day …etc.) 
     2- Contingency analysis 
     3- Outage security assessment 
     4- Optimal dispatch 
     5- Stability investigations 
                                                  Power Flow Problem 
            Consider a typical power system network, shown by its typical 
            single line diagram: 
                                   1                                                                  Load 4 
                               Load 6                           Load 5                                     2    Load 2 
                                                                                                                     
            Analysis  of  positive  sequence  network  is  performed  due  to 
            balance nature.  
            Types of buses 
                i-      Generation buses   
                  (active power (MW)) & voltage magnitude |V| 
            ii-   Load buses  (P(MW), Q (MVAR) & power factor) 
            iii-  Slack or swing bus  
                       1- Acts as a reference for voltage measured 
                       2- Supplies system losses 
         To have the following: 
                                                                                  
                                                                             
          
         Requirements: 
         P, Q (MW, MVAR), V (bus voltages) & P (power balance) 
          
          
    Network model Formulation: 
    Network modeling is necessary in order to solve the load flow 
    problem. 
    Line model, Generators, Loads (-ve generators), Transformers 
    …etc 
    At ith bus, net complex power injected into the bus: 
    S = P + j Q = (P  – P ) + (Q  – Q ) 
     i  i   i  Gi  Di   Gi Di
     
    Basic consideration: 
    [V] = [Z] [I]  Mesh 
    [I] = [Y] [V]  Nodal