ALLOCATION OF GENERATION PLANTS THAT GIVES MINIMUM LOSSES FOR IRAQI SUPER GRID NETWORK

The main goal of this work is to determine optimal location for placing generating plants in the Iraqi National Super Grid which gives minimum total losses in the system. A package build under Matlab was used to allocate optimal placement of generating sets, calculating active and reactive power for these generators, .calculating system minimum losses, and determine the effect of varying the output of the generators used on losses reduction.


INTRODUCTION
Electric power systems designed with generating units that are widely scattered and interconnected by long transmission lines may suffer significant losses.The losses depend on the line resistance and currents and are usually referred to as thermal losses.While the line resistances are fixed, the currents are a complex function of the system topology and the location of generation and load.Proper placement of generation units will reduce losses also free available capacity for transmission of power and reduce equipment stress, while improper placement may actually increase system losses.In this work an algorithm was applied to determine the best placement of new units for the Iraqi super grid network in order to maximize power available and minimize losses on the system for a given load (William 2002).

Mathematical representation of the problem:
The main objective is to find the partial derivatives (sensitivity) of active power loss with respect to active and reactive power injected at all buses except slack bus.

  
Where [SEN] is the sensitivity factor.The results of sensitivity vector   SEN are used as an indicator to the efficiency of the system to reduce losses in case of installing generation units or shunt capacitors at these buses (samir2007).
The following matrix [D] is the partial derivative of real losses with respect to voltage magnitude at load buses and voltage angles at all buses except slack bus.

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The mathematical analysis needs also Jacobian matrix   Jac which is used in power flow problem, then: Where   J is the Jacobian matrix of Newton-Raphson load flow.
The following matrix represents derivative of active power losses w.r.t generation voltages: Where   f  represent the sensitivity of losses w.r.t control variables (Manadur 1981).
Where   H represents the second partial derivative for loss P w.r.t control variables.
  u    Optimum, where  opt.= 0.001, then loss P represents minimum losses in the system.Otherwise control variables have to be developed as follows: Where P sen = partial derivative of real losses with respect to real power injected at load buses.
Q sen = partial derivative of real losses with respect to reactive power injected at load Buses (Manadur 1981).
Table1: The load & Generation of the Iraqi National Super Grid System (400 kV)

Results and Discussion
The values of dPloss/dPi which represents the efficiency to reduce system power losses with respect to real power injecting at the buses except the slack bus, were tabulated in Table3.
High negative partial derivative at any bus means that the system has high efficiency to reduce active power losses when injecting active power in that bus.On the other hand positive partial derivative for example at buses (3, 5, and 2) means that system power losses increase in case of injecting real power in these buses.The best buses to accept injecting active power are those with

Figure2: maximum real power loss reduction
The optimal power injection at all buses is obtained by adding in steps small real power (U) equal to (5 Mw) in each step at the buses with the negative partial derivative of power losses with respect to real injection power (sensitivity) as shown before in Table3.
The addition of active power to each bus is stopped when sensitivity at that bus becomes zero or positive, the overall addition is stopped when sensitivity in all buses becomes zero or positive, at the same time this process must satisfy the constraints including reactive power limits of the generators as shown in Table5 where the load bus voltage limit is pulse minus 0.05.

CONTROL OF ACTIVE POWER AT GENERATION BUSES:
Optimal power generation for the present six generators in INSG, were calculated using procedure similar to that implemented for the other buses.Generation at each bus is increased by (10 Mw) at each step until the sensitivity at the bus becomes zero or positive, i.e. the system losses start to increase.Table6 show active power generation at each generation bus which gives minimum losses equal to (25.95 Mw) with optimal losses reduction equal to (30.96 %).

. Abood Allocation of Generation Plants that gives Minimum S. S. Mustafa Losses for Iraqi Super Grid Network 3733
high negative partial derivative.Table4 and Fig.2show the values of active power injection at each load bus, which gives maximum real power loss reduction.Injecting real power at bus 9 (BGE) A.A

A.A. Abood Allocation of Generation Plants that gives Minimum S. S. Mustafa Losses for Iraqi Super Grid Network 3733
The injection of180,200,210and 300 Mw at the buses 7,8,9,11 respectively which are the best buses according to Table3, gives total system losses equal to 21.824 Mw.Total system losses according to Table4 is equal to 37.592 So: Loss Reduction =