A Review on Transformer Less UPFC

1. International Journal of Trend in International Open Access Journal International Open Access Journal | www.ijtsrd.com International Journal of Trend in Scientific Research and Development (IJTSRD) Research and Development (IJTSRD) www.ijtsrd.com ISSN No: 2456 ISSN No: 2456 - 6470 | Volume - 2 | Issue – 6 | Sep 6 | Sep – Oct 2018 A Review A Review on Transformer - Less UPFC Shaikh Mohammed Tauseef1, S. M. Kulkarni2 Shaikh Mohammed Tauseef PG Scholar PG Scholar1, Associate Professor2 Electrical Engineering, PES College of Engineering, Aurangabad, Maharashtra Department of Electrical Engineering Maharashtra, India ABSTRACT This paper is a review of an innovative technique with a new concept of transformer-less unified power flow controller (UPFC). The Transformer-less UPFC is based on two cascade multilevel inverters (CMIs), which reduce the complexity of the circuit. The construction of the conventional UPFC consists of two back-to-back inverters complexity and bulkiness which involves the transformers which are complication for isolation & attaining high power rating with required output waveforms. The proposed controller will reduce the cost and space as compared to the conventional UPFC. A multilevel configuration technique will be used to reduce the total harmonic content and thus increases the overall efficiency of the system. INTRODUCTION The control of an AC power system in real time is involved because power flow is a function of the transmission line impedance, the magnitude of the sending and receiving end voltages, and the phase angle between these voltages. In recent years, demand for electric power continued to grow hence to achieve greater flexibility and better utilization of existing systems the concept of flexible AC transmission systems or FACTS is been introduced. technology is a collection of Controllers, which can be applied individually or in coordination with others to control one or more of the interrelated system parameters. The most versatile FACTS device that can be used to achieve power flow control is the Unified power flow controllers (UPFCs). This paper is a review of an innovative technique with less unified power flow less UPFC is based on two cascade multilevel inverters (CMIs), which reduce the complexity of the circuit. The nstruction of the conventional UPFC consists of back inverters complexity and bulkiness which involves the transformers which are complication for isolation & attaining high power rating with required output osed controller will reduce the cost and space as compared to the conventional UPFC. A multilevel configuration technique will be used to reduce the total harmonic content and thus increases the overall efficiency of the system. which which results results in in Fig. 1:- The Conventional UPFC The Conventional UPFC The Unified Power Flow Controller (UPFC) concept was proposed by Gyugyi in 1991. The UPFC was time control and dynamic transmission systems, providing required to solve many of the problems facing the power delivery industry. The Unified Power Flow Controller (UPFC) concept was proposed by Gyugyi in 1991. devised for the real-time control and dynamic compensation of ac transmission systems, providing multifunctional flexibility required to solve many of the problems facing the power delivery industry. The UPFC is able to control, simultaneously or selectively, all the parameters affecting power flow in the transmission line (i.e., voltage, impedance, phase angle), and this unique capability is signified by the adjective "unified" in its name. independently control both the real and reactive power flow in the line. It proportionally increases the load capability of existing transmission lines. There are several advantages of the UPFC, but even though it suffers from the requirement of bulky zigzag transformers to interface the inverters to transmission UPFC bulky and slow responding to dynamic load changes. To overcome conventional UPFC, recently, a modular transformer less UPFC based on Cascaded Multi (CMIs) has been proposed. The control of an AC power system in real time is involved because power flow is a function of the magnitude of the sending and receiving end voltages, and the phase he UPFC is able to control, simultaneously or all the parameters affecting power flow in the transmission line (i.e., voltage, impedance, and nique capability is signified by in its name. It can also independently control both the real and reactive It proportionally increases the transmission lines. electric power has achieve greater operating flexibility and better utilization of existing power systems the concept of flexible AC transmission FACTS is been introduced. The FACTS llers, which can coordination with others advantages of the conventional to control one or more of the interrelated system The most versatile FACTS device that used to achieve power flow control is the UPFC, but even though it suffers from the zigzag transformers to interface lines, which makes the s). UPFC bulky and slow responding to dynamic load To overcome recently, a modular transformer- on Cascaded Multi-level inverters such such dra drawbacks of @ IJTSRD | Available Online @ www.ijtsrd.com www.ijtsrd.com | Volume – 2 | Issue – 6 | Sep-Oct 2018 Oct 2018 Page: 940

2. International Journal of Trend in Scientific Research and Development (IJTSRD) ISSN: 2456 International Journal of Trend in Scientific Research and Development (IJTSRD) ISSN: 2456 International Journal of Trend in Scientific Research and Development (IJTSRD) ISSN: 2456-6470 Theory of Transformer – Less UPFC The proposed transformer-less UPFC configuration is shown in Fig. 2(a), which consists of two CMIs: series CMI and shunt CMI. Advantages ?Improves voltage profile for the duration of the transient conditions in the power transmission systems. ?Low THD of output voltage ?Low switching loss. ?High efficiency. ?Independent active and reactive control over the transmission line Applications ?AC transmission, distribution electrical energy. ?Power grid. ?Transmitting electrical energy over long distances ?Electricity supply industry ?Used to couple stages of devices such as microphones Conclusion In this paper, review of a new based on a novel configuration of two CMIs was proposed. It has been discussed can achieve the same controllability as the traditional UPFC. However, the traditional UPFC consisting of two back to-back inverters requires and zigzag transformers. The new UPFC two CMIs offers several traditional UPFC, such as completely transformer and highly modular structure, efficiency, high reliability, low cost, and fast dynamic response. The new transformer therefore, very well suited for fast power flow control of wind and solar power transmission. References 1.N. G. Hingorani and L. Gyugyi, UnderStanding FACTS: concept and technology of flexible AC transmission systems. New York: IEEE Press 2000. 2.L. Gyugyi, “Unified power for flexible AC transmission systems,” IEE Proc. C Gener., Transmiss. Distrib., vol. 139,pp. 323 331, 1992. 3.H. Akagi, S. Inoue, and T. Yoshii, “Control and performance ofa transformerless cascade PWM STATCOM with star configuration,” IEEE Trans. Ind. Appl., vol. 43, no. 4, pp. 1041 2007. less UPFC configuration is s of two CMIs: Improves voltage profile for the duration of the transient conditions in the power transmission Low THD of output voltage. Independent active and reactive power flow control over the transmission line. distribution, utilization of Fig. 2(a):- The series CMI is directly connected in series with the transmission line and the shunt CMI is directly connected in parallel to the line but after the series CMI. Each CMI, as shown in Fig. 2(b) and (c), is composed of a number of cascade H-bridge bridge modules. The series CMI is directly connected in series with the transmission line and the shunt CMI is directly connected in parallel to the line but after the series Transmitting electrical energy over long distances. Electricity supply industry. amplifiers and to match microphones and record players Fig. 2(b) and (c), is bridge or half- a new transformer-less UPFC novel configuration of two CMIs was discussed that the new UPFC same controllability as the traditional nal UPFC consisting of requires bulky isolation zag transformers. The new UPFC consisting of Fig. 2(b):- advantages over the traditional UPFC, such as completely transformer-less highly modular structure, light weight, high reliability, low cost, and fast dynamic transformer-less UPFC is, therefore, very well suited for fast and distributed power flow control of wind and solar power Fig. 2(c):- Here are the unique features of the new 1.Unlike the conventional back-to- coupling, there is no transformer needed CMI-based UPFC; hence, the new UPFC can achieve low cost, light weight, small size, high efficiency, high reliability, and fast dynamic response; 2.The shunt inverter is connected after the series inverter, which is distinctively different from the traditional UPFC. Each CMI has its own dc capacitor to support dc voltage; 3.There is no active power exchange between the two CMIs and all dc capacitors are floating; 4.The new UPFC uses modular CMIs and their inherent redundancy provides greater flexibility to system design and higher reliability. system design and higher reliability. configuration: -back dc link N. G. Hingorani and L. Gyugyi, UnderStanding FACTS: concept and technology of flexible AC New York: IEEE Press, coupling, there is no transformer needed in the based UPFC; hence, the new UPFC can achieve low cost, light weight, small size, high efficiency, high reliability, and fast dynamic L. Gyugyi, “Unified power-flow control concept for flexible AC transmission systems,” IEE Proc. Transmiss. Distrib., vol. 139,pp. 323– The shunt inverter is connected after the series inverter, which is distinctively different from the aditional UPFC. Each CMI has its own dc H. Akagi, S. Inoue, and T. Yoshii, “Control and performance ofa transformerless cascade PWM STATCOM with star configuration,” IEEE Trans. Ind. Appl., vol. 43, no. 4, pp. 1041–1049,Jul./Aug. There is no active power exchange between the two CMIs and all dc capacitors are floating; The new UPFC uses modular CMIs and their inherent redundancy provides greater flexibility to @ IJTSRD | Available Online @ www.ijtsrd.com www.ijtsrd.com | Volume – 2 | Issue – 6 | Sep-Oct 2018 Oct 2018 Page: 941