This paper presents an advanced method for active power flow control by use of static phase shifting transformer. It is based on non-standard load-flow model, which enables more accurate evaluation of the relevant technical effects of phase shifting transformer installation. For solution of the power flow control problem defined, the special fast decoupled procedure is developed. The high numerical efficiency and simplicity of this procedure has been established on the example of real interconnection formed by the Electric Power System of Serbia and Montenegro, Romania, Bulgaria, Former Yugoslav Republic of Macedonia, Greece and Albania (ex Second UCTE synchronous zone).