Modeling of multi-converter facts (flexible alternating current transmission systems)

Multi-converter FACTS devices can increase control flexibility of power systems by providing independent and simultaneous control of multi-power system parameters. In this thesis, the following multi-converter FACTS devices are modeled and analyzed at transmission level: Generalized Unified Power Flow Controller (GUPFC), Interline Power Flow Controller (IPFC), and Back-to-Back Static Synchronous Compensator (BtB-STATCOM). The steady-state PSCAD models of these devices are proposed for power flow studies without requiring programming coding. A quasi multi-pulse voltage source converter with low harmonic content is designed for converter-level modeling of the aforementioned devices. The magnitude and the phase angle of the voltage of the designed converter are controlled efficiently despite triggering the power semiconductors at fundamental system frequency. The dynamic control characteristics of GUPFC, IPFC, and BtB-STATCOM are extensively studied and analyzed using the developed PSCAD based converter-level models in various test power systems. A novel fuzzy-rule based control scheme for IPFC to decouple real and reactive power flow control loops is designed and tested through miscellaneous and comparative simulation studies. Using converter-level models of these devices, transient stability studies of the power systems are also addressed in this thesis. A novel self-tuning fuzzy damping controller for GUPFC is designed to damp synchronous generator oscillations and to increase speed stability of induction generators which are located in a wind farm. The same controller is adapted for IPFC to suppress inter-area mode of oscillations.