MODELING OF IPFC WITHOUTMODELING OF IPFC WITHOUTCOMMON DC LINK FORCOMMON DC LINK FORTRANSMISSION LINESTRANSMISSION LINES

By Project Guide

M.SENTHILKUMAR Mr. V. JAYAPRAKASH

ABSTRACTABSTRACT

• The Separated Interline Power Flow Controller (S-IPFC) presented is a new concept for a FACTS device.

The S-IPFC is an adapted version of the IPFC, which eliminates the common dc link of the IPFC and enable the separate installation of the converters.

Without location constrain, more power lines can be equipped with the SIPFC, which gives more control capability of the power flow control. Instead of the common dc link,

The exchange active power between the converters is through the same actransmission line at 3rd harmonic frequency. Every converter has its own dc capacitor to

provide the dc voltage.

This paper presents the basis theory of the S-IPFC, steady-stateanalysis, primary control loop and the corresponding simulation results.

It is derived from the IPFC, and possesses all the control capability of the IPFC.

The ‘master’ converter can adjust the voltage magnitude , transmission angle, and line impedance.

The ‘slave’ converter provides the activ e power for ‘master’ converter, and at the same time adjusts its own line reactance.

The S-IPFC eliminates the common dc linkof the IPFC, which enables the long range installation of converters

and gives more flexibility for the IPFC.

INTRODUCTIONINTRODUCTION

• Power flow control becomes a big issue in nowadays power system network due to the following reasons: the aging of the equipment, the increase of distributed generations, the power marketing, etc. The conventional power flow controllers that based on copper and iron are not suitable for the future power system, because of their slow response and stepwise control. Flexible AC Transmission System (FACTS), the power electronic based power flow controllers, do not have these disadvantages and attract more and more attention from both academic and industry. Several FACTS devices, such as TCSC, TCR, STATCOM, UPFC, IPFC, have been achieved in recent decades .

IPFCIPFC

• The Interline Power Flow Controller (IPFC) addresses the problem of compensating a number of transmission lines at a given substation. Conventionally, series capacitive compensation (fixed, thyristor-controlled or SSSC-based) is employed to increase the transmittable real power over a given line and also to balance the loading of a normally encountered multiline transmission system. However, independent of their means of implementation, series reactive compensators are unable to control the reactive power flow in, and thus the proper load balancing of, the lines.

LITERATURE REVIEW LITERATURE REVIEW

• Yuan, Zhihui; de Haan, Sjoerd W.H.; and Ferreira, Braham:

• This paper presents a new concept for power flow control by distributed UPFC. The system, called distributed power flow controller (DPFC), consists of several low-power series converters and one shunt large-power converter without common dc link. Also new is that the power exchange between the shunt and series parts is through the existing transmission line at a harmonic frequency. This solution enables the DPFC to fully control all power system parameters, and it reduces the cost and increases the reliability of device at the same time.

• Yuan, Zhihui; de Haan, Sjoerd W.H.; and Ferreira, Braham:

• This paper proposes that the UPFC is the most powerful power flow controller recently, and because of the exchange of active power between the shunt and series parts, they have to be located at the same place. This paper presents a new concept to transmit power without the common dc link of the UPFC, which gives the possibility of the separated UPFC. The exchange of active power is through the existing transmission line but at a different frequency, which is independent from the fundamental frequency component. The results of steady-state analysis of the separated UPFC are also presented in this paper.

• R. Strzelecki; G. Benysek; and Z. Fedyczak:

• To improve energy quality in distribution systems, many different solutions there are implemented, for example: i) Active Power Filters (APF); ii) Unified Power Flow Controllers (UPFC); iii) Unified Power Quality Conditioners (UPQC); iv) Interline Power Flow Controllers (IPFC). Interline Power Flow Controllers are the classical series or series-parallel filters applied to given number of independent lines with common, for all lines, DC element. Their possible functions are enlarging and include power flow control between lines, reactive power compensation and distribution system stability improvement. This paper shows that using probabilistic approach to the distribution system we can considerably decrease power rating of the Parallel Active Power Filter's when it is a component of the Interline Power Flow Controller.

• Gyugyi, L.; Sen, K.K.; and Schauder, C.D.:

• The Interline Power Flow Controller (IPFC) proposed is a new concept for the compensation and effective power flow management of multi-line transmission systems. In its general form, the IPFC employs a number of inverters 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 inverter within the IPFC is able to transfer real power to any other and thereby facilitate real power transfer among the lines of the transmission system.

INTERLINE POWER FLOW CONTROLLER INTERLINE POWER FLOW CONTROLLER

BASIC PRINCIPLE AND FUNCTIONING OF IPFCBASIC PRINCIPLE AND FUNCTIONING OF IPFC

The distributed FACTS single phase The distributed FACTS single phase converter converter

METHOD FOR ACTIVE POWER EXCHANGE METHOD FOR ACTIVE POWER EXCHANGE WITHOUT COMMON DC LINKWITHOUT COMMON DC LINK

• The method for active power exchange is based on the non-sinusoidal power theory. According to Fourier analysis, a non-sinusoidal voltage and current can be expressed by the sum of sinusoidal functions in different frequencies with different amplitudes. The definition of active power is the mean value of the product of voltage and current. Since the integrals of all the cross-product of terms with different frequencies are zero, the active power can be expressed by:

• where cos On is power factor in nth harmonic frequency. Equation describes that active powers at different frequencies are isolated from each other, and the voltage or current in one frequency has no influence on other frequency component. Consequently, the apart from the fundamental active power can be exchanged through ac terminal instead of the common dc link between converters. One converter extracts active power from the fundamental frequency and injects the power back to the ac terminal at a harmonic frequency, the other converter absorbs the harmonic power and converts it to fundamental frequency back. Therefore, the converters use harmonic as media to transmit active power, and the common dc link is eliminated.

FUZZY LOGIC CONTROLLER (FLC) FUZZY LOGIC CONTROLLER (FLC)

The fuzzy logic controller involves four main stages:

•Fuzzification•Rule base•Inference mechanism•Defuzzification

Fuzzy logic controllerFuzzy logic controller

FUZZY LOGIC CONTROLLER IN S-IPFC FUZZY LOGIC CONTROLLER IN S-IPFC

• Fuzzy logic controller in S-IPFC calculates the d-axile of 3rd harmonic voltage based on the dc voltage error. The inputs to the fuzzy controller are the dc voltage reference value and measured dc voltage. This controller use Min-Max operator (Mamdani implication) and Centroid defuzzification method. The output obtained is the 3rd harmonic voltage

SOFTWARE USED SOFTWARE USED

• MATLAB – Simulink is the software used in this project. Simulink is a software package for modeling, simulating, and analyzing dynamic systems.

MATLAB/SIMULINK MODEL MATLAB/SIMULINK MODEL

Simulink model for control loop of converter Simulink model for control loop of converter AA

Simulink model for control loop of converter BSimulink model for control loop of converter B

SIMULATION RESULTSSIMULATION RESULTS

power flow in lines on source sidepower flow in lines on source side

Power flow in line 1 with fuzzy controller Power flow in line 1 with fuzzy controller in S-IPFCin S-IPFC

Power flow in line 2 with fuzzy Power flow in line 2 with fuzzy controller in S-IPFC controller in S-IPFC

CONCLUSION

• The new concept of S-IPFC is a new member of converter-based FACTS devices. It is derived from the IPFC, and possesses all the control capability of the IPFC. The S-IPFC along with the Fuzzy logic controller eliminates the common dc link of the IPFC, which enables the long range installation of converters and gives more flexibility for the IPFC. The S-IPFC can employ more converters to the system, also the shunt converter. The S-IPFC equipped with shunt converter will behave as multiple UPFCs. Every series converter is able to fully control its line parameters. The shunt converter injects 3rd harmonic frequency current to the network, to provide active power for series converters. The challenge of the S-IPFC is the voltage rating of the series converter. During high active power exchanging operation condition, the converter will inject 3rd harmonic voltage, whose amplitude may be even larger than the voltage at the fundamental frequency

• However, with the help of Distributed FACTS idea, the series voltage rating can be increased without huge amount of cost.

• The S-IPFC is a solution for power flow control in a meshed power system. It has all the advantages of converter based FACTS devices, and can employ large number of converters without location constrain and significant extra cost. Hopefully, the S-IPFC will be placed in transmission network and provide a better power flow control in the future.

REFERENCESREFERENCES• Yuan, Zhihui; de Haan, Sjoerd W.H.; and Ferreira, Braham: (2007) ‘A

New FACTS Component -Distributed Power Flow Controller (DPFC)’, 12th European Conference on Power Electronics and Applications.

• Yuan, Zhihui; de Haan, Sjoerd W.H.; and Ferreira, Braham: (2007) ‘UPFC with Eliminated Common DC Link Connection Between Shunt and Series Part’, Power Engineering Society General Meeting, 2007. Page(s):1 – 4.

• R. Strzelecki; G. Benysek; and Z. Fedyczak: (2002) ‘Interline Power Flow Controller-Probabilisitic Appoach’, Digital Object Identifier.

• Gyugyi, L.; Sen, K.K.; and Schauder, C.D.: (1999) ‘The interline power flow controller concept: a new approach to power flow management in transmission systems’, Power Delivery, IEEE Transactions.

• Hingorani .N.G, and Gyugui.L, (2000), ‘Understanding FACTS Concepts and Technology of Flexible AC Transmission System’, IEEE Press.

• Deepak Divan: (2004) ‘A distributed static series compensator system for realizing active power flow control on existing power lines’, Power Systems Conference and Exposition.

• Song, Yong Hua; and Johns, Allan T.: (1999) ‘Flexible ac transmission systems (FACTS)’, London, Institution of Electrical Engineers.

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