Abstract
The main concept of unified power flow controller(UPFC) is based on back to back connection of two inverters witha common capacitor dc link. This capacitor brings about severaldisadvantages such as affecting the reliability of UPFC. Thispaper proposes a new topology for UPFC based on matrixconverter. This configuration is combination of nine 4-quadrantswitches and not any storage element. Main advantages ofproposed topology are reduction of number of switches, low costand size of UPFC. This operation of UPFC is tested andsimulated on a single machine infinite bus (SMIB) using spacevector modulation (SVM) technique. The UPFC is supposed to beoperated on automatic power flow control mode.
Index Terms-- Matrix Converter, UPFC, FACTS Devices,SVM.
I. INTRODUCTION
In recent years, due to economics' and environmentproblems, build of new power planet and transmission linebecome more difficult. Hence, it is advisable to enhance thepower transfer capability of the existing transmission lines upto thermal limit instead of constructing new one. Simultaneouswith develop of semiconductor technology, the flexible actransmission systems (FACTS) devices is proposed byHingorani [1]. The main aim of FACTS devices is rapidcompensation and enhancement of flexibility of power lineparameter. Some of the main FACTS controllers are static varcompensator (SVC), thyristor control series capacitor (GCSC),static synchronous compensator (STATCOM) and staticsynchronous series compensator (SSSC). But, due toconfiguration, these controllers are not able to control theactive and reactive power, separately. At the 90's decade,Gyugyi [2] proposed a multi objective compensator by thename of UPFC that is able to control and compensate eachthree significant parameters of transmission line, which areamplitude and phase of bus voltage and reactance of line, tocontrol active and reactive power flow, separately. The UPFCis combination of STATCOM and SSSC which are connectedback to back via a common dc page link [2]. There is a large dccapacitor in the dc page link that connects two voltage sourceinverter (VSI) to each other. The main role of dc capacitor isthe control of power exchange between series and shuntterminals of UPFC. The cost and physical size of UPFC depends on rating of this dc page link capacitor bank, considerably.Also, this capacitor has shorter life when compared to an accapacitor of same rating, which limits the life and reliability ofVSI's, too [3].To overcome this problem, indirect matrix converter (IMC)topology is used instead of UPFC's common topology [4, 5].This topology removes dc capacitor from UPFC configuration,but it’s main problem is fictitious dc page link voltage control.In this context only one work has been reported [6] wherethe matrix converter is placed in series with the transmissionline which leads to the entire power being flowed throwmatrix converter so requires high power devices. The ability tolink two regions with different frequencies, said by authors, isthe advantage of series placement of matrix converter withtransmission line, but this is a rare case in power system.Moreover, the mentioned construction in [6] may carry highcurrents flows from converter during faulty condition.In this paper an effort has been taken to replace the newconfiguration of UPFC based on matrix converter instead ofcommon configuration. The matrix converter is placed shuntwith transmission line and plays variable voltage source rolethat injected series with transmission line.


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