Frequency response characteristics of the unified power flow controller

The frequency response characteristics of the unified power flow controller are derived using a state variable formulation. These characteristics are shown to be functions of the UPFC parameters as well as of the operating point. The method is used to identify operating points that cause resonance problems. The analytical formulation is validated using an electromagnetic transients simulation tool. In addition, the influence of the UPFC´s control system on the frequency response characteristic is investigated using a frequency scanning procedure coupled with a time domain simulation.