Optimal Power Flow
Optimal power flow (OPF) is a fundamental tool in power system planning and operation. Prior to the restructuring of the industry, OPF was used in transmission planning, transmission-constrained economic dispatch, security re-dispatch, reactive power management, etc..
The objectives of this work is to used a simulation package and method suitable in solving the OPF problem, to give a succinct definition and function of the OPF, his objective, defined to be some quantifiable metric-typically some economic measure of system performance such as production costs or transmission losses or some system characteristic such as available transfer capability, so as his application in electrical system. The use of OPF is also outline.
The general OPF problem formulation and the careful review of different optimization methods are presented. As OPF is a generic term that describes a broad class of problems in which we seek to optimize a specific objective function while satisfying constraints dictated by operational and physical particulars of electric system, the optimization methods review here include:linear programming (LP), nonlinear programming (NLP), quadratic programming (QP), Newton's base method, interior point methods, hybrid method and the artificial intelligence method. All the methods are presented with their advantages and disadvantages in solving an OPF problem.
Considering all the proposed methods, an OPF problem is solved using the Newton's method which is well known in the area of power system and has been a standard solution algorithm for the power flow problem for decades.
Meanwhile a computer programming package is required in order to solve the problem base on power flow and power loss analysis. PSS/E, power system simulation for engineering is used in the application of Newton's method to OPF. The objectives here are the losses minimization using IEEE 11-bus system. The control variable in this thesis is tap changing transformer. Shunt capacitors is also used for reactive power compensation. And at the end the combination of tap changing transformer and shunt capacitor is used.
The simulation result is presented according to the Optimal power flow performance as compare to conventional load flow, the position and influence of tap changing, the shunt placement in the circuit in order to observe the best position for reactive power compensation in losses minimization which is the main objective of this thesis. It is to mention that the control of the tap ratio will normally not drastically reduce the system costs. In reality, tap ratio control allows control of the reactive power flow thus reducing losses. The combination of transformer taps and shunt capacitor gives us the best result for losses minimization.
Finally the use of the OPF with other important electrical power system technique, such as optimal power flow incorporating facts devices and optimal power flow solution with transient stability constraints are presented.