An extended DC-model for estimation of transfer capacity of power systems with phase shifting transformers

An interconnected power system is made of several areas that can exchange power through tie lines. These tie lines are equipped with Phase Shifting Transformers (PSTs) for active power flow control. In a multi-area power system operation, an operator within a control area should know the maximum power that can be imported to the area for the best possible operation of the system. AC power flow method if adopted for optimization problem in such systems complicates the process. This paper suggests a method to optimally evaluate transfer capacity (TC) of an area and to obtain optimum settings for the PSTs using an extended DC-model. The suggested model uses Bus Incidence and loop incidence matrices to derive simple linear expressions that relate the line flows to the phase shifts introduced by the PSTs. The proposed model is tested for the Standard 39-bus test system using Linear Programming technique in MATLAB.