International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 11, November 2013) 172 Design of Multi Level Converter for Interline Power Flow Controller with Variable Inputs in SIMULINK/MATLAB M. Venkateswarareddy 1 , Dr. Bishnu Prasad Muni 2 , Ph.D , Dr. A.V.R. S. Sarma 3 , Ph.D, 1 Research Scholar(Ph.D), Electrical Engineering Dept., University college of Engineering, Osmania University, A.P India 2 Additional General Manager, Bharat Heavy Electricals Limited(R&D), BALA NAGAR, Hyderabad, India 3 Professor EE Dept., University College of Engg, Osmania University Hyderabad, India Abstract--The Interline Power Flow Controller (IPFC) a concept for the compensation and effective power flow management of multi-line transmission systems. In its general form, the IPFC employs two or more number of converters (VSC) with a common dc link, each to provide series compensation for a selected line of the transmission system. Because of the common dc link, any converter within the IPFC is able to transfer real power to any other and thereby facilitate reactive power transfer among the lines of the transmission system. Since each converter is also able to provide reactive power compensation, the IPFC is able to carry out an overall real and reactive power compensation of the total transmission system. This capability makes it possible to equalize both real and reactive power flow between the lines, transfer power from overloaded to under loaded lines, compensate against reactive voltage drops and the corresponding reactive line power, and to increase the effectiveness of the compensating system against dynamic disturbances. The paper explains the basic theory and operating characteristics of the five level inverter based IPFC with phasor diagrams, and simulated waveforms in SIMULINK/MATLAB Keywords - AC transmission, FACTS, IPFC, line compensation, 5 level inverter, power flow controller, Series compensation, VSC. Section I I. INTRODUCTION Flexible AC Transmission Systems (FACTS) based on either Voltage or Current Source converters (VSC/CSC) these can be used to control steady-state as well as dynamic/transient performance of the power system. Converter-based FACTS controllers when compared to conventional switched capacitor/reactor and thyristor - based FACTS controllers such as Static Var Compensator (SVC) and Thyristor-controlled Series Capacitor (TCSC) have the advantage of generating/absorbing reactive power without the use of ac capacitors and reactors. In addition converter-based FACTS controllers are capable of independently controlling both active and reactive power flow in the power system. Series connected converter-based FACTS controllers include Static Synchronous Series Compensator (SSSC), Unified Power Flow Controller (UPFC) and Interline Power Flow Controller (IPFC). A SSSC is a series compensator with ability to operate in active/inductive modes to improve the system stability. The IPFC includes a Static Synchronous compensator (STATCOM) and a SSSC that share a common dc-link. The IPFC consists of two or more SSSC with a common dc-link so, each SSSC contains a VSC that is in series with the transmission line through a coupling transformer, and injects a voltage with controllable magnitude and phase angle into the line. IPFCs provide independent control of reactive power of each individual line, while active power could be transferred via the dc-link between the compensated lines. Section II A. Inter line power flow controller Generally, the Interline Power Flow Controller (IPFC) is a combination of two or more independently controllable static synchronous series compensators (SSSC) which are solid-state voltage source converters which inject an almost sinusoidal voltage at variable magnitude and couples via a common DC link as shown in fig.1 Conventionally series capacitive compensation fixed thyristor controlled or SSSC based is employed to increase the transmittable real power over a given line and to balance the loading of a normally Encountered multi-line transmission system at their dc terminals and connected to the ac systems through their series coupling transformers.