A Novel FACTS DDSC for Power Quality Enhancement[1]

International Journal of EmergingElectric Power Systems

Volume 7, Issue 3 2006 Article 6

A Novel FACTS Based (DDSC) Compensatorfor Power-Quality Enhancement of L.V.

Distribution Feeder with a Dispersed WindGenerator

Adel M. Sharaf∗ Khaled Mohamed Abo-Al-Ez†

∗University of New Brunswick, [email protected]†University of New Brunswick, [email protected]

Copyright c©2006 The Berkeley Electronic Press. All rights reserved.

A Novel FACTS Based (DDSC) Compensatorfor Power-Quality Enhancement of L.V.

Distribution Feeder with a Dispersed WindGenerator

Adel M. Sharaf and Khaled Mohamed Abo-Al-Ez

Abstract

In a deregulated electric service environment, an effective electric transmission and distribu-tion networks are vital to the competitive environment of reliable electric service. Power qual-ity (PQ) is an item of steadily increasing concern in power transmission and distribution. Thetraditional approach to overcoming capacity and quality limitations in power transmission anddistribution in many cases is the addition of new transmission and/or generating capacity. This,however, may not be practicable or desirable in the real case, for many of reasons. From tech-nical, economical and environmental points of view, there are two important - and most of thetime combined - alternatives for building new transmission or distribution networks to enhancethe transmission system capacity, and power quality: the Flexible alternating current transmissiondevices and controllers, and the distributed generation resources near the load centers. The con-nection of distributed generation to the distribution grid may influence the stability of the powersystem, i.e. angle, frequency and voltage stability. It might also have an impact on the protec-tion selectivity, and the frequency and voltage control in the system. This paper presents a lowcost FACTS based Dynamic Distribution System Compensator (DDSC) scheme for voltage sta-bilization and power transfer and quality enhancement of the distribution feeders connected to adispersed wind generator, using MATLAB/ SimPower System simulation tool.

KEYWORDS: voltage stabilization, power quality, FACTS, distributed/dispersed resources, noveldynamic distribution system compensator (DDSC)

I. INTRODUCTION In a deregulated electric service environment, an effective electric transmission and distribution networks are vital to the competitive environment of reliable electric service [1]. Power quality (PQ) is an item of steadily increasing concern in power transmission and distribution. Since transmission services are now provided under contract, restrictions on voltage and current distortion, sags and fluctuations are coming into force at a scale hitherto unseen in many countries. Light flicker in work places as well as domestic dwellings, and energy and production outages due to poor quality of electrical grids is no longer acceptable. The traditional approach to overcoming such capacity and quality limitations in power transmission and distribution in many cases is the addition of new transmission and/or generating capacity [2, 3]. This, however, may not be practicable or desirable in the real case, for a variety of reasons. Adding of new lines and/or extending of existing substations may be too costly and time-consuming, concessions for new rights-of-way may be hard or impossible to come by, and last but not least, there may be serious obstacles in the way from an ecological point of view [4].

From technical, economical and environmental points of view, there are two important -and most of the time combined- alternatives for building new transmission or distribution networks to enhance the transmission system capacity, and power quality:

1- The Flexible AC transmission systems (FACTS) devices and controllers. 2- The distributed/Dispersed generation resources (DGR) near the load

centers. In fact the distributed generation becomes more economically viable if there is

a strong backbone of the transmission/ distribution grid. Flexible AC transmission systems (FACTS) technology opens up new opportunities for controlling power and enhancing the usable capacity of present as well as new and upgraded lines. In this paper a novel low cost Dynamic Distribution System Compensator (DDSC) is developed based on the FACTS technology to overcome the voltage stability and power transfer capability and quality of the distribution feeders connected to Distributed generation resources. II. THE FACTS DEVICES AND CONTROLLERS By the IEEE definition [1]: Flexibility of electric power transmission is the ability to accommodate changes in the electric transmission/Distribution system or operating conditions while maintaining steady state and transient margins. Flexible AC transmission systems (FACTS) are alternating current transmissions

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Sharaf and Abo-Al-Ez: A Novel FACTS DDSC for Power Quality Enhancement

Published by The Berkeley Electronic Press, 2006

systems incorporating power electronic–based and static controllers to enhance controllability and increase power transfer capability.

FACTS are designed to remove congestion constraints and to meet planners´, investors´ and operators´ goals without their having to undertake major system additions. This offers ways of attaining an increase of power transmission capacity at optimum conditions, i.e. at maximum availability, minimum transmission losses, and minimum environmental impact at minimum investment cost and time expenditure. Improving or safeguarding of power quality in transmission and distribution is the second very important driving force for the implementing of FACTS in power systems. For instance, the building of a steel plant may be an undertaking of great importance to a country or a region, offering GNP growth as well as employment. In many cases, however, where the supplying grid is weak or insufficient, this added value will also become a nuisance to many due to pollution of the grid, pollution which will spread far and wide over the grid and in the worst case become an impediment to industrial endeavor elsewhere and in any case a source of complaint. FACTS will offer remedy in such cases, by enabling confinement or neutralizing of electrical disturbances such as voltage sags and fluctuations, harmonic distortion, and phase unbalance in three-phase systems. As a useful added value, improved economy of the process or processes in question will usually also be achieved [4].

III. The DISTRIBUTED / DISPERSED GENERATION RESOURCES Distributed Renewable generation Resources (DGR) are small-scale generation technologies located near to the load. These are typically 5 MW or less. Photo-voltaic cells, micro-turbines, fuel cells, wind turbines, combustion turbines, and small synchronous generators are typical examples of the distributed resources [5]. Benefits of the (DGR) to the utility are: Maximum use of standby capacity through safe parallel operation with the utility grid, enhanced voltage stability and avoided line losses during heavy-load conditions, and Improved system load factor [5, 6]. Customer Benefits of (DGR): Reliability improvement, Power Quality (PQ) improvement, and Electricity Consumption reduction [5].

Recently, there has been great interest in the integration of dispersed generation units at the distribution level. Recent technology improvements in micro-turbines, fuel cells, wind energy and energy storage devices have provided the opportunity for dispersed generation at the distribution level. With the possibility of significant penetration of distributed generation, more studies are needed on dynamic analysis of distribution systems. The traditional distribution system differs from the transmission system in the following aspects [7]:

• It is typically radial or weakly meshed.

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International Journal of Emerging Electric Power Systems, Vol. 7 [2006], Iss. 3, Art. 6

http://www.bepress.com/ijeeps/vol7/iss3/art6

• Distribution lines usually have a larger R/X ratio. • There may be significant three-phase unbalance including unbalanced loads

and single phase or two phase lines. Distributed Renewable Energy Sources (DRES), also called distributed

generation resources (DGR), and describes smaller-scale power generation or storage located close to where the power is needed. Units can be connected directly to the consumer or to a utility’s transmission and distribution system. Distributed generation can provide standby generation, peak shaving capability, base load generation or cogeneration. Capacity ranges from one kilowatt (the approximate demand for a residential customer) to 15 megawatts to supply large commercial or medium industrial facilities. Various technologies are used for distributed generation, including wind and solar power, external combustion engines and “combined heat and power” generators. The connection of distributed generation to the grid may influence the stability of the power system, i.e. angle, frequency and voltage stability [8]-[9]. It might also have an impact on the protection selectivity, and the frequency and voltage control in the system. On the other hand, DG units have not been designed to support system stability during power system failures [8]. The applied small synchronous generators have simple exciter and governor control schemes compared to large central power generators and induction generators are not able to control the reactive power at all. (DGR) units connected via electronic power converters do not have large capabilities to control active and reactive power. The system inertia of DG units is normally low. Further more, the power generation from DG leads to a reduction of power generation from central power units and the number of online generators, spinning reserve. This results in a larger uncertainty in terms of power system stability when a major disturbance occurs [10].

IV. DESCRIPTION OF THE SYSTEM UNDER STUDY The system under study, shown in Fig.1 is composed of:

1. The distribution system feeder of 25 km with a hybrid load (Linear, Nonlinear (arc type), and motorized loads) at the end of the feeder, and four linear loads uniformly distributed along the feeder length.

2. The wind energy generator (WECS) is connected to the distribution feeder at the middle of its length.

System parameters, load, and control settings are given in the Appendix.

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Fig.1. Single line diagram of the Distribution feeder with proposed WECS interference at the

middle of the feeder.

V. THE WIND GENERATOR Wind turbines convert the kinetic energy of the wind to mechanical power. Simply stated, a wind turbine works the opposite of a fan. Instead of using electricity to make wind, a turbine uses wind to make electricity. The wind turns the blades, which spin a shaft, which connects to an induction generator and makes electricity. The electricity is sent through transmission and distribution lines to a substation, then on to homes, business and schools. Wind energy offers many advantages over conventional power production, including minimal environmental impact, reduced dependence on fossil fuels, and potential long-term income for property owners who lease land for wind farms [11]. A generic model of Wind Energy-Penetration with no Storage, Wind-Diesel (HPNSWD) system is used [12]. This technology was developed by Hydro-Quebec to reduce the cost of supplying electricity in remote northern communities [13]. The optimal wind penetration (installed wind capacity/peak electrical demand) for this system depends on the site delivery cost of fuel and available wind resource. The wind speed is assumed to be constant at 10 m/sec. the wind turbine data is given in the appendix. The wind turbine characteristics are shown in Fig.2 [14].

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Fig. 2. Characteristics of the wind turbine of the study system [14].

VI. THE NOVEL DYNAMIC DISTRIBUTION SYSTEM COMPENSATOR (DDSC) AND ITS CONTROL SCHEME The power systems of today, by and large, are mechanically switched. There is a widespread use of microelectronics, computers, and high speed communications for control and protection of the grid; however, when operating signals are sent to the power circuits, where the final control action is taken, the switching devices are mechanical and there is little high speed control. In effect, in the point view of both dynamic and steady state operation the system is really uncontrolled. The FACTS controllers have the ability to control the interrelated parameters that govern the operation of the grid including series impendence, shunt impedance, current, voltage, phase angle, and the damping of oscillations at various frequencies below the rated frequency. These constraints can not be overcome, while maintaining the required system reliability, by mechanical means without lowering the usable transmission capacity. By providing added flexibility, FACTS controllers can enable a line to carry power closer to its thermal rating. Mechanical switching needs to be supplemented by rapid response power electronics. It must be emphasized that FACTS are enabling technology, and not a

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one-on-one substitute for mechanical switches [1]. This is shown from the construction of The Novel low cost FACTS based Dynamic Distribution System Compensator (DDSC), and the design of its control scheme. Fig.3 shows the novel (DDSC) MATLAB/ SIMPOWER SYTEM block model, comprising a switched power filter that ensures voltage stability and power quality at the load bus, the distribution substation bus, and the wind generator bus.

Fig.3. MATLAB / Sim-Power System block model of the Novel FACTS (DDSC).

Fig.4 shows the proposed novel Tri-loop (PI) Proportional plus Integral, dynamic error driven sinusoidal SPWM switching controller. The dynamic controller is used to stabilize the voltage at the required key buses by regulated pulse width switching of the two ideal mechanical switches shown in Fig.3. The dynamic tri-loop error driven variable structure sliding mode controller is characterized by structural simplicity.

Fig.4.MATLAB / Sim-Power System block of the (DDSC) Controller.

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The selected fixed switching frequency fs =1/Ts is usually a function of nonlinear load dynamic variations and ranges from (300- 3000 Hz). The modulated controller parameters are usually selected for a given controller near tuned frequency in the range of (150 – 900 Hz) and with a damping factor (0.2 to 0.5) and quality factor (5-10). The tri-loop regulator uses a global error (et) consisting of the RMS load voltage, RMS load current and a dynamic current ripple loop. The three key dynamic loops play a vital role in effective dynamic voltage regulation and reactive power compensation. The scaling and time delay selection of these key loops is done using an offline guided trial and error method to insure fast response and minimize total error (et).The three regulating loops are [17, 18]:

Loop 1 – the main loop for the dynamic voltage error using the RMS voltage at the load bus; this loop is to maintain the voltage at the load bus at a reference value by modulating the admittance of the compensator.

Loop 2 – the dynamic error is using RMS dynamic load current. This loop is an auxiliary loop to compensate for any sudden electrical load excursions.

Loop 3 – the dynamic error is using the instantaneous absolute value of the load current to provide an effective dynamic tracking control to suppress any current harmonic ripples.

The Complete MATLAB/ SIMPOWER SYTEM block models of the system under study, is shown in the appendix.

VII. SIMULATION RESULTS To validate the proposed low cost (DDSC) Scheme, A MATLAB/ SimPower System Model is built for the system under study, and the simulation is performed for two cases, each case consider the system with and without the DDSC Scheme. The two cases are:

1. The Hybrid load is connected to the end of the distribution feeder, without the wind energy generator.

2. The Hybrid load is connected to the end of the distribution feeder, and the wind energy generator is inserted at the mid point of the distribution feeder.

The distribution feeder has a uniform distributed linear load, and at the end of the distribution feeder there is one nonlinear load at the beginning of the simulation: • At t= 0.1sec the distributed generation source located at the middle of the

feeder is inserted into the feeder circuit. • AT t=0.2 sec the NLL (arc type) is inserted at the end of the feeder. • At t=0.3 sec the Motorized load is inserted at the end of the feeder.

The novel FACTS (DDSC) device is used to stabilize the voltage at the key buses, and enhance the power transfer capability of the distribution feeder to

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decrease the feeder congestion problems, and improve the power quality. The simulation is applied to the system under study for 1 sec.

Case 1: The Hybrid load is connected to the end of the distribution feeder, without the wind energy generator:

1. Without FACTS - (DDSC) Scheme: The voltage, current, active power, reactive power, total appearant power, and the power factor at the Key Buses (The Distribution substation Bus, and the Hybrid load Bus) are shown in the following figures. (All parameters are per unit values).

Fig.5. Unified System dynamic response Parameters at the Distribution Substation Bus.

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Fig.6. Unified System dynamic response Parameters at the Hybrid Load Bus.

2. With FACTS- (DDSC) Scheme connected in shunt to the Hybrid load bus:

Fig.7. Unified System Parameters at the Distribution Substation Bus with the (DDSC).

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Fig.8. Unified System dynamic Response Parameters at the Hybrid Load Bus with the (DDSC).

Case 2: The Hybrid load is connected to the end of the distribution feeder, and the wind energy generator is inserted at the mid point of the distribution feeder. 1. Without FACTS- (DDSC) Scheme:

Fig.10. Unified System dynamic Response Parameters at the Distribution Substation Bus.

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Fig.11. Unified System Dynamic Response Parameters at the Hybrid Load Bus.

Fig.12. Unified System Dynamic Response Parameters at the Wind Generator Bus.

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2. With FACTS- (DDSC) Scheme connected in shunt to the Hybrid load bus, and the Wind Generator Buss:

Fig.13. Unified System dynamic Response Parameters at the Distribution Substation Bus with the (DDSC).

Fig.14. Unified System Dynamic Response Parameters at the Hybrid Load Bus with the (DDSC).

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Fig.15. Unified System Dynamic Response Parameters at the Wind Generator Bus with the (DDSC).

VIII. CONCLUSIONS

• Deregulation in the electric power system sectors, make it essential to provide reliable, secure, and stable transmission and distribution grids with integrated Distributed Renewable Wind Energy Schemes. • Power quality (PQ) is an issue of steadily increasing concern in power transmission and distribution. • The evolving technologies of Flexible AC transmission systems (FACTS), along with different Distributed/ Dispersed Generation Resources (DGR), provided technical, economical and environmental effective solution to overcome the congestion constraints and Power Quality (PQ) problems of the transmission and distribution grids. • Flexible AC transmission systems (FACTS) are alternating current transmission systems incorporating power electronic–based and static controllers to enhance controllability and increase power transfer capability. • Distributed Renewable generation Sources (DRGS) are small-scale generation technologies located near to the load being served. Thus, connected at the distribution voltage levels. • The connection of distributed generation to the grid may influence the stability of the power system, i.e. angle, frequency and voltage stability. • A generic model of the High-Penetration Wind with no Storage, Wind-Diesel (HPNSWD) system is used in this paper.

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• It must be emphasized that FACTS are enabling technology, and not a one-on-one substitute for mechanical switches. This is shown from the construction of The Novel low cost FACTS based Dynamic Distribution System Compensator (DDSC), and the design of its control scheme proposed in this paper. • The proposed novel Tri-loop (PI) Proportional plus Integral, dynamic error driven sinusoidal SPWM switching controller is used to stabilize the voltage at the required key buses by regulated pulse width switching of the two ideal mechanical switches. • the proposed low cost (DDSC) Scheme is validated using a MATLAB/ SimPower System Model built for the system under study, and the simulation is performed for two cases, each case consider the system with and without the (DDSC) Scheme. • The proposed (DDSC) FACTS based device with dynamic tri-loop controller did enhance the voltage stability at the system key buses, and improved the system’s power quality, and also increased the power transmission capacity of the distribution feeder, which will prevent any problems due to power congestion. The stability and power quality were greatly enhanced in case of the wind energy source interference at the mid-point of the distribution feeder. The following tables summarizes the results of the a MATLAB/ SimPower System simulations:

METER READINGS OF THE SYSTEM PARAMETERS AT THE KEY BUSES:

Case 1: The Hybrid load is connected to the end of the distribution feeder, without the wind energy generator:

Without the (DDSC) Scheme With the (DDSC) Scheme System Parameter at the Key Buses (in p.u)

Substation Bus Load Bus Substation Bus Load Bus Phase Voltage 0.7063 0.6544 0.9849 1.008

Current 1.526 1.249 1.384 1.077 Power Factor 0.5215 0.424 0.919 0.7737 Active Power 0.3842 0.2451 0.8858 0.594

Reactive Power 0.6151 0.5149 -0.1028 -0.2358 Total Appearant Power 0.7253 0.5702 0.8917 0.6391

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Case 2: The Hybrid load is connected to the end of the distribution feeder, and the wind energy generator is inserted at the mid point of the distribution feeder:

Without the (DDSC) Scheme With the (DDSC) Scheme System Parameter at the Key Buses (in p.u)

Substation Bus Load Bus

The Wind G. Bus

Substation Bus Load Bus

The Wind G. Bus

Phase Voltage 0.6849 0.6317 0.527 1.001 1.022 1.049 Current 1.688 1.215 0.8706 0.192 1.082 0.5703

Power Factor 0.3398 0.4242 0.9369 0.8961 0.7766 0.8555 Active Power 0.2429 0.2302 0.3299 0.7786 0.6076 0.3621

Reactive Power 0.6618 0.482 0.1125 -0.1058 -0.1861 -0.1876 Total Appearant

Power 0.705 0.5342 0.3486 0.7858 0.6355 0.4078

IX. APPENDIX 1- THE STUDY SYSTEM PARAMETERS

THE 3 PHASE A.C SOURCE

• 3 phase zero impedance programmable voltage source. • 138 kV (L-L) r.m.s, Phase = 0 degrees. • Harmonic generation:

Order n=2, Amplitude = 0.15 p.u, Phase = 35 degrees, Negative sequence. Order n= 3, Amplitude = 0.2 p.u, Phase = -25 degrees, Zero sequence.

• Base voltage = 138 kV (L-L) r.m.s.

THE HYBRID LOAD

Hybrid load is at the end of the 25 km short distribution feeder: • Linear load: 1.5 MW, 0.5 MVAR. • Squirrel cage Induction Motor Load: 50 KVA, 25 kV - (L-L) r.m.s, 60

Hz. • Non linear arc type load = 30 MW.

THE UNIFORMLY

LINEAR DISTRIBUTED LOADS ALONG THE FEEDER

• Linear load, each: 1.5 MW, 0.5 MVAR. • The short feeder: R = 0.0127 Ohm/km, L = 0.997 mH/km. • Loads Locations’ from the distribution substation: • Load 1: at 5 km • Load 2: at 10 km • Load 3: at 15 km • Load 4: at 20 km.

THE TRANSFORMER

Between the Source bus and the distribution substation bus • Step down transformer: 10 MVA 3 phase 2 winding, 138/25 kV,

Connection (∆/Yg). • R1 = R2 = 0.002 p.u • L1= L2 = 0.08 p.u

Base Power = 10 MVA, Base voltage on the secondary side = 25 kV (L-L) THE TRI-

LOOP • The gains :Kp = 100, Ki = 10; (Kp/Ki = τ1 = 0.1) • The scaling factors: γv= 1.0, γi = γripple = 0.5

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2- THE COMPLETE MATLAB/SIMPOWER SYSTEM OF THE SAMPLE STUDY SYSTEM:

Distribution feeder with proposed WECS located at the middle of the feeder MATLAB Functional- Model

CONTROLLER • Delay time = 10 ms

THE PWM SWITCHING

BLOCK

• 1 arm – two bridge pulses • αD = ton /T S/W (duty cycle ratio) ; 0 < αD< 1.0 • T S/W = 1/ f S/W ; f S/W = 2000 Hz (selected)

THE FACTS BASED (DDSC)

• 6 Pulse Diode Rectifier Bridge • 3 phase capacitors, each Cf= 120 µF • Rf = 0.5 Ω , Lf = 10 mH • Two Ideal switches : Ron = 0.001 Ω, Lon = 0.001 mH , Snubber

Resistance = 0.1 M Ω, Snubber Capacitance = infinity

THE DATA OF THE WIND

GENERATOR

3 phase Squirrel Cage Induction Generator: • 4.16 kV (L-L) r.m.s, 3.6 MVA, 60 Hz. • Stator : Rs = 0.016 p.u, Ls = 0.06 p.u • Rotor: Rr’ = 0.015 p.u, Lr’ = 0.06 p.u • Mutual Inductance Lm = 3.5 p.u • Inertia Constant = 2 , Friction Factor = 0, Pairs of poles = 2

Base Power = 3.6 MVA, Base voltage on the secondary side = 4.16 kV (L-L)

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X. REFRENCES 1. Narain G.Hingorani, Laszlo Gyungyi, “Understanding FACTS: Concepts and Technology of Flexible AC Transmission Systems”, IEEE Press, 1999. 2. Yong Zheng, and N.Chowdhury, “Expansion of Transmission Systems in a Deregulated Environment”, IEEE CCGEI 2004. 3. R.Fang, D.Hill, “A New Strategy for Transmission Expansion in Competitive Markets”, IEEE Transactions on Power Systems, Vol.18, No.1, February 2003. 4. Rolf Grünbaum, Raghuveer Sharma, and Jean-Pierre Charpentier, “Improving the efficiency and quality of AC transmission systems”, Joint World Bank / ABB Power Systems Paper, 2000. 5. http://ece.uprm.edu/~iap/PRESENTATIONS2003/DISTPOWERGENERATION.PDF. 6. http://www.energy.ca.gov/distgen/strategic/workshop_ppt/Horgan_Presentation.pt 7. Y. Zhu and K. Tomsovic, “Adaptive Power Flow Method for Distribution Systems with Dispersed Generation”, IEEE Transactions on Power Delivery, Vol. 17, No. 3, July 2002. 8. CIGRE- TF 38.01.10, “Modeling new forms of generation and storage” November 2000. 9. SUSTELNET, “Review of technical options and constraints for integration of distributed generation in electricity networks” 2002. 10. Vu Van, T., Vandenbrande, E., Soens, J., Van Dommelen, D.M., Driesen, J. and Belmans, R., "Influences of large penetration of distributed generation on N-1 safety operation", IEEE Power Engineering Society, Denver, Colorado, USA, 2004. 11. http://www.alliantenergy.com/docs/groups/public/documents/pub/p012416.hcsp 12. R. Gagnon, B. Saulnier, G. Sybille, P. Giroux; "Modeling of a Generic High-Penetration No-Storage Wind-Diesel System Using Matlab/Power System Blockset" 2002 Global Wind power Conference, April 2002, Paris, France 13. B. Saulnier, A.O. Barry, B. Dube, R. Reid, “Design and Development of a Regulation and Control System for the High-Penetration No-Storage Wind/Diesel Scheme" European Community Wind Energy Conference 88, June 1988, Herning, Denmark. 14. MATLAB SIM-POWER SYSTEMS BLOCK SET, R14 SP3. 15. Pradeep K. Nadam, Paresk C. Sen, “ Industrial Application of Sliding Mode Control”, IEEE/IAS International Conference On Industrial Automation and Control, Proceedings, 1995.

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16. Edward Y.Y. Ho, Paresk C. Sen, “Control Dynamics of Speed Drive System Using Sliding Mode Controllers with Integral Compensation”, IEEE Transactions on Industry Applications, Vol.21, NO.5, September/October 1991. 17. A. M. Sharaf and Guosheng Wang, “Wind Energy System Voltage and Energy Enhancement Using Low Cost Dynamic Capacitor Compensation Scheme”, Electrical, Electronic and Computer Engineering, 2004. ICEEC04. 2004. 18. A.M.Sharaf, and Kh.M.Abo-Al-Ez, “A FACTS based Dynamic Capacitor Scheme for Voltage Compensation and Power Quality Enhancement”, the IEEE ISIE06 Conference, Montreal, Quebec, July 2006.

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A Novel FACTS DDSC for Power Quality Enhancement[1]

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