MODELING AND ELIMINATION OF LOAD BUSES IN OPTIMAL POWER FLOW SOLUTIONS

ABSTRACT

This paper presents a method to solve the optimal power flow problem after eliminating load buses from the system. Loads are first modeled and reflected in the admittance matrix and then their respective buses are eliminated. The obtained model is a reduced model of the original system. The admittance matrix is of the same order as the number of voltage-controlled buses in the system. The variables of the reduced model are the voltage-controlled buses voltages, angles and active power generations. Newton Raphson method is used to calculate the variables of the reduced model while minimizing an objective function. Voltages and angles of the original system are then calculated by a direct method. These voltages are required to update load models and to check for voltage and line current violations at the eliminated portions of the network. The simulation is carried out on two systems, IEEE 118 bus test system and a 131 bus actual system. It is shown that solution time is significantly reduced when compared to the conventional optimal power flow Newton Raphson method using the original system.