Design and Implementation of DC-Bus System ...

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Design and Implementation of DC-Bus System Module for Parallel Integrated Sustainable Energy Conversion Systems Mahmoud M. Amin, Student Member, IEEE, and O. A. Mohammed, Fellow, IEEE

Abstract-- In this paper, a performance analysis of a highly integrated, high-performance dc-bus system module is presented. This module introduces a solution for medium & low voltage DC distribution applications. It is designed for applications requiring a single bus solution to control up to twelve DC-sources sharing same dc-bus and having same dc-voltage level. The bus is also designed to interface with various power converter modules. Moreover, it has ability for parallel integrated renewable sources connection representing DC-microgrid. A master-slave dc-bus voltage control technique for parallel wind-based synchronous generators is introduced. This technique is developed based on the voltage oriented control (VOC) algorithm for PWM converters. Test results for different disturbance conditions are carried out to validate this developed module. The proposed system is also implemented in a laboratory setup which includes two synchronous generators (250 W, 2.2 kW) each driven by a variable speed prime mover (VSPM) to emulate a wind turbine behavior, two 3-phase PWM based converters, 3-phase line inductors connected between wind generators and converters, variable resistive DC-load, and a digital signal processor (DSP TMS320F240). The experimental results confirm the validity of the developed module for parallel integrated sustainable energy conversion systems. Index Terms—DC-bus, PWM converters, Voltage oriented control, Wind energy conversion system.

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I. INTRODUCTION

ARALLEL connection of multi sustainable energy systems is one useful method for solving the high power requirements. The sustainable systems could be different kinds (wind, photovoltaic, etc), or of same kind like in wind farms. Our scope of work will focus on the same kind of renewable energy source, considering multi wind generators connected to the common dc-bus system through multi parallel power converters. Connecting modular unit systems in parallel is an efficient and reliable method of increasing the power ratings of the modular units limited by the voltage and current limits of semiconductor power switches [1], [2]. For this reason parallel converters and inverters have been a viable alternative method of satisfying system power requirements beyond the capacity of the largest modular unit system. Parallel converters and/or inverters are also used for reducing harmonics of PWM switching frequency, and increasing available output voltage and frequency [3].

This work was supported in by Florida International University, Energy Systems Research Laboratory. Mahmoud M. Amin is with Electrical and Computer Engineering Dep., FIU, W Flagler 10555 Miami, USA (e-mail: [email protected]). Prof. Osama Mohammed is with Electrical and Computer Engineering Dep., FIU, W Flagler 10555 Miami, USA (e-mail: [email protected]).

Nonetheless, in parallel connection, the technique of load sharing among multi modules is still evolving to date. For example, in PWM converters connected in parallel, it may not be easy to share the load current among converters while maintaining the desired output voltage. In [4], A sliding- mode control scheme for a uniform current distribution among dc-dc converter modules connected in parallel have been proposed. A static VAR compensator (SVC) for the voltage regulation of the three-phase induction generator IG driven directly by the variable speed dc (VSDC) motor as the wind turbine have been investigated [5]. Research interest in three-phase pulse width modulated (PWM) rectifiers (ac/dc converters) has grown rapidly over the past few years due to some of their important advantages, such as power regeneration capabilities, control of dc-bus voltage, low harmonic distortion of input currents, and high power factor (usually, near unity) [6]. Conventional thyristor phasecontrolled converters have the inherent drawbacks that the power factor decreases as the firing angle increases and that harmonics of the line current are relatively high [7]. On the other hand, Modern IGBT controlled converter modules introduces many advantages in terms of high power capability (3.3 kV, 1200 A devices are commercially available), hardswitching (150 kHz), small conduction losses (23.8W), and low harmonic distortion (3-4%) [8]. The difficulty in controlling the converters is mainly due to the nonlinearity. Many research results focusing on the control point of view have been reported [9], [10]. The design methods and the performance of the voltage and current proportional plus integral (PI) controllers, which are as usually made up of inner current control loops and an outer voltage control loop in a cascade structure, have been analyzed [9]. The cascade control structure is not so effective for the system control of which both dynamics are close to each other. Particularly, the voltage oriented control (VOC), which guarantees high dynamics and static performance via internal current control loops, has become very popular and has constantly been developed and improved [10]. It is giving the ability to control each current component (in the synchronous d-q frame) separately without any effect from the other component which improves the dynamic performance of the system. In this paper, a dc-bus system module for a parallel windbased three-phase voltage source PWM ac/dc converter is proposed with VOC strategy in the synchronous d–q frame. The proportional plus integral (PI) current controllers in d-q axes is designed and analyzed to meet the time domain specification: minimum overshot, minimum settling time and minimum steady-state error. After that a PI voltage controller is designed to accomplish the specifications of the voltage

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control loop based on the dynamics of the DC-bus. A Software Phase Locked Loop (SPLL) for phase angle detection of the generator voltage in synchronous reference frame is proposed. The dc-bus module system is designed to provide superior monitoring and control management and is highly suitable for various applications such as [photovoltaic generation (PV) systems, wind energy conversion systems (WECS), fuel cells (FCs), battery banks, hybrid electric vehicles (HEVs), adjustable speed drives (ASDs)] II. SYSTEM DESCRIPTION

Fig. 2. The developed physical dc-bus system module.

Power electronics systems are playing an important position in the overall generation system. The classical scheme of ac-dc conversions, which is normally used, is shown in Fig. 1.a. The system presents a simple solution of boost type converter with possibility to increase dc output voltage. The main drawbacks of this solution are that the diode input circuit results in a lower power factor and draw highly distorted currents from the source. Furthermore, a large size dc link capacitor is required for smoothing the dc voltage. The proposed topology is shown in Fig. 1.b. With this topology, boost converter is omitted without any change in the objectives of WECS. The advantages of the proposed system over the conventional system are that it has a simpler circuit and less complexity. Also, the small number of power stages increases efficiency when compared to the topology shown in Fig. 1. Moreover, reliability of the system is greatly improved, because the parallel multi-converter system provides redundancy. Furthermore, unity power factor operation can be achieved. The proposed system is connected to the developed dc-bus module. The bus construction is based on two bus bars with high conductivity and four supports as shown in Fig 2. It also has two digital LCD displays in order to monitor the dcbus voltage level. The module is covered by clear sheets. It contains an open frame PCB multiple output switching mode power supply (+15, -15, +5 V). A high voltage dc-bus transducer is mounted inside the module in order to read the actual bus voltage and use it for closed-loop control operation. The module has multi-access input/output comprehensive connectivity and ability for interfacing with DSP & microcontrollers. A 1000 µF/ 1000 V dc-capacitor is imbedded internally and it works as dc-bus filter.

III. SYSTEM MODELING

VOC Wind Turbine Rectifier DC-Bus Wind Turbin

SG Diode DC Boost DC-Bus Rectifier Chopper

Pout

SG

VOC Wind Turbine Rectifier

Pout

A. Model of wind turbine According to Betz theory, the mechanical power generated by a wind turbine is shown as [13]: , (1) 0.5 where ρ is the air density, R is the rotor radius of the wind turbine, and ν is the wind speed. The power coefficient Cp depends on the blade pitch angle β and the tip speed ratio λ, which is defined as the ratio between the linear blade tip speed and the wind speed as λ =Ω.R/v, where Ω is the rotor speed of the wind turbine. The output torque of the wind turbine is: , (2) 0.5 where the torque coefficient is

,

,

/ .

B. Mathematical model of voltage source PWM converter Three-phase representation for the input and output sides of the converter circuit is shown in Fig. 3 where L and R represent a line inductor mounted between the generator and the converter terminal, ega(t) the generator phase voltage and va(t) the bridge converter voltage controllable according to the demanded dc voltage level. From Fig. 3, the inductors, which are connected between the converter input terminals and the generator lines, are an integral part of this circuit. This brings current source character of input circuit and provides the boost feature of the converter. The line current ia(t) is controlled by the voltage drop across the inductance L interconnecting two voltage sources (generator and converter). The inductance voltage equals the difference between the line voltage egab(t) and the converter line voltage vab(t). When the angle between the two voltage sources, , and amplitude of converter voltage V are controlled, we indirectly control phase and amplitude of the line current. In this way, the magnitude and sign of the dc current, idc, is subject to be controlled and determine the active power conducted through converter. The reactive power could be controlled independently according to the relative phase of fundamental harmonic current i with respect to voltage e.

SG (a)

(b)

Fig. 1. (a) Conventional SG-based WECS with diode rectifier and dc boost chopper. (b) Proposed parallel SG-based WECS with VOC rectifier. Fig. 3 Three-phase power circuit for the PWM converter.

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Assuming that the generator line voltages are a three-phase balanced voltage source, they can be written by the following equation: . cos . cos . cos

2 /3 2 /3

1 1 0

0 1 1

Referring to Fig. 3, the dynamic equation for the input side of the three-phase converter system can be summarized as: _

_

_

_

(4)

where , are the generator and converter terminal line voltages, respectively, and R is the inductor internal resistance. Referring to Fig. 3, the dynamic equation for the output side of the three-phase converter system can be written as: (5) . The line voltage, the virtual line current and where the terminal voltage of the PWM converter can be transformed to a d-q synchronous reference frame using Park transformation such that [9]: 0 0

(6)

where p is the derivative operator, i.e. p=d/dt,. The relation between id, idc can be obtained through the active and reactive power relation, where the complex power, S, is the sum of the active power, P, and reactive power, Q, and is defined as: .

(7)

where the superscript * means complex conjugate. The instantaneous active and reactive power can also be obtained in the synchronous reference frame as follows: 3 2 3 2

.

.

.

.

(8)

At the balance case and UPF operation, the q component for the generator voltage and current are zero; therefore (8) can be modified to: 3 2

.

(9)

Assuming no power dissipation in the converter power switches, the converter input power is equal to the output power, thus:

(10)

Accordingly, from (9) and (10), we can write the following equation: 3 2

(3)

where VLm is the maximum amplitude of the generator line voltage. Assuming a virtual line-line currents as: , , and . In other words, let us define this transformation: 1 0 1

.

IV.

(11)

THE PROPOSED CONTROL SYSTEM 3B

The VOC PWM converter is based on coordinate transformations between the stationary abc and αβ frames to the synchronous rotating d-q reference frame, and vice versa. By controlling the converter in a synchronous d-q frame, the currents being regulated will be dc quantities which eliminate the steady state error [10]. According to the converter dynamic equations in synchronous frame, (6), there are coupling terms between these equations which degrade the dynamic performance (slow the controller transient and cause high overshoots) of the system. These terms are the coupling q current component (ωLiq) and generator voltage on the d-axis equation, ed , while coupling d current component (ωLid) and eq on the q-axis equation. The vector controller will decouple these terms, giving the ability to control each current component separately without any effect from the other component. The schematic diagram of the VOC PWM converter is shown in Fig. 4. The two current components, id and iq, could be oriented to control the converter operation via internal current control loops. Consequently, the system performance is largely depending on the quality of applied current control technique. The easiest technique is the hysteresis current control that provides a fast dynamic response [14]. However the major problem of hysteresis control is that, its average switching frequency varies with the load current, which makes the switching pattern uneven and random, thus, resulting in additional stress on switching devices. Several techniques are reported in the literature to improve the system performance [15-19]. Among presented techniques and widely used for high performance current control is the d-q synchronous controller, where the currents being regulated are DC quantities. Two current controllers are utilized as inner controllers. The first is q-current controller with reference which determines the reactive power. Figure 5 shows two SPWM converters sharing single load. It is assumed that the converters are rectifying the output voltage of two wind generator systems. It is not convenient to let each unit controlling the dc bus voltage separately without any information from the other units. A discrepancy could happen between the controllers. The Master-Slave scheme can solve this problem. One converter unit is selected to be a Master whereas the others are treated as slaves. Each of the slave unit has a self governing system, i.e., it has its inner current control feedback loop. Only the master unit has the outer dc voltage control feedback loop giving the reference 0, the unity current to the entire slave units. By setting power factor operation is achieved. The other is the d-current set by the outer dc voltage controller with reference

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controller and decides the active power flow between the wind generator and the dc bus. A. The DC link voltage control Using Proportional Integral (PI) voltage controller, the dc voltage can be regulated by choosing the dc current reference, such that: .

.

(12)

where is the desired dc voltage, , are the constant gains of the PI voltage controller. Thus, in order to find out the relationship between and , the power equation, (11), are considered such that: 2 . 3 (13) 0

Fig. 4 Schematic diagram of the overall proposed WECS control system.

_ +

PI

PI

+ + + _

S P W M

B. Software PLL for phase angle detection A precise detection of the phase angle of the generated power is highly recommended in wind energy conversion systems utilizing converter-inverter unites. A zero-voltage crossing detection method, where the zero voltage must be accurately detected each half period, can be used. However, the synchronization must be updated, not just at the zero voltage, but continuously during the whole period, because multi-zero crossing can occur with the existence of noise. The Phase Locked Loop (PLL) technique can be applied here for precise detection of the phase angle. PLL is widely used in communication engineering because of its excellent noise rejection capability [11]. A hybrid (hardware & software) PLL was introduced by Jovan [12] for synchronizing a single-phase PWM inverter (UPS) with the grid. However, this technique needs software and hardware implementations. A fully software PLL for the phase angle detection of the three-phase generator voltage is proposed herein using the d-q synchronous reference frame. Fig. 6 shows a basic block diagram of the applied PLL. The output of the voltage, is fed back to the phase controlled oscillator (VCO), frequency detector input, and comparison continues until both frequency and phase are made the same, and the phase and frequency of the VCO are in locked state with reference signal , . i.e. The second-order loop filter is commonly used as a good tradeoff of the filter performance and system stability [13]. The proportional-integral (PI) loop filter of the second order can be expressed in the form: / (14) and denote the gain parameters of the PI loop where filter. The configuration of the PLL system using the d-q components in the synchronous reference frame of the threephase input voltage is shown in Fig. 7. In Fig. 8, the response of the PLL system at 60Hz, 120V is shown. The voltage appears as dc values. + -

VCO

Loop filter

, Fig. 6 Basic PLL block diagram.

PI

Controllers

Phase detector gain

Plant

PI

S P W M

·

PI / /

·

1 ·

Current & Voltage Controllers for converter

PI Fig. 7 SPLL applied for wind generation converter. Fig. 5 Controllers and plants diagram for parallel converters sharing one DC link.

5 1

2

3 4 1) Ea (100V/div-10ms) 3) Ed (80V/div-10ms)

2) (5V/div-10ms) 4) Eq (80v/div-10ms)

(a)

(b) Fig. 8 The SPLL response. (a) Simulation. (b) Experimental.

V.

SIMULATION AND EXPERIMENTAL RESULTS 4B

In order to investigate the performance of the overall proposed system, an experimental setup for parallel wind energy conversion system is constructed and connected to a dc-load through dc-module. A prototype experimental setup is designed and implemented, including a digital signal processor (DSP TMS320F240) as the control heart of the proposed system and all the interfacing circuits to the analog power circuits. Each unit of the system is built and tested alone, and then the whole system is connected and tested. A simulation program using Simulink™ was carried out using simulation parameters shown in Table I. The SPWM presented in this paper has been used with a 5 kHz switching frequency. VOC strategy discussed in section IV is utilized in the simulation. The parameters for the synchronous machines are listed in Table II, Appendix. Fig. 9 shows the photograph of the pair of VOC rectifiers with the built-in capability of paralleling. C. Wind speed variation In order to evaluate the performance of the proposed emulator in turbulent wind speed condition, an experimental test has been carried out. Fig. 10 shows the daily average wind speed at Chicago City during 2009. Rectifier 1

Rectifier 2

The SPWM technique used in the converter simulation has been investigated. Fig. 11 shows the generator output voltages eabc, at 60 Hz with the converter terminal phase voltages vabc. The converter terminal line voltages vL_abc are shown in Fig. 12. D. DC reference change test , and the actual In Fig. 13, the reference voltage, voltage, is shown. The reference voltage set to be changed from 450V to 600V, while the corresponding generator phase current is shown in Fig. 14. The generator line currents are shown in Fig. 15.a, giving a total harmonic distortion (THD) equal to 3.98 %. The harmonic content in the generator line current is shown in Fig. 15.b. The UPF demand was investigated in Fig. 16, where the generator line current and the phase voltage are in phase. 1

2

3

1) Ea (100V/div-2.5ms) 3) Ec (100V/div-2.5ms)

2) Eb (100V/div-2.5ms)

1

1) Va (100V/div-2.5ms)

(b)

(a)

Fig. 11 Generator output voltages and converter terminal phase voltages. (a) Simulation. (b) Experimental. 1

1) Vab (100V/div-2.5ms)

(b)

(a)

Fig. 12 Converter terminal line voltages. (a) Simulation. (b) Experimental. 2

1

Fig. 9 Laboratory prototype of the 3-kW parallel WECS connected to the dcbus.

1) 2)

(200V/div-100ms) (200V/div-100ms)

(a)

(b)

Fig. 13 The converter output Reference DC voltage and Actual DC voltage. (a) Simulation. (b) Experimental.

1

1)

Fig. 10. Daily average wind speed in Chicago 2009.

(5A/div-50ms)

(b) (a) Fig. 14 The generator line current. (a) Simulation. (b) Experimental.

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(b) (a) Fig. 15 (a) the converter line currents at 60Hz generator output. (b)The harmonic spectrum for the generator current. PF=0.998

1 2 1) 2)

(100V/div-10ms) (5A/div-10ms)

(b) (a) Fig. 16 The generator phase voltage and line current showing the unity power factor at 60Hz. (a) Simulation. (b) Experimental.

(b) (a) Fig.18 Converter response under wind speed variation. (a) Falling edge response. (b) Rising edge response.

E. Load variation test The converter response under load variations is shown in Fig. 17. We started loading the DC-bus by RL=40 Ohm and at 3.2 sec load changed to be 60 Ohm. At 3.8 sec, the load returns to its initial value of 40 Ohm. From DC output voltage waveform, we can notice that the system gives a good and fast transient performance during loading change instants and returns to its reference value within 0.1 sec. Since the load resistance increases at 3.2 sec, the generator current should produce less current while the load and DC output current decreases. F. Generator voltage and frequency variation test Imitating the variation in wind speed, which leads to variation in the generator output voltage and frequency, is shown in Fig. 18. The Figure shows the converter output DC voltage under step change in the generator output voltage and frequency. Fig. 18a represents the falling response in the DC voltage with the line current and phase voltage, while Fig. 18b shows the rising response. Fig. 19 shows the efficiency curve, as the average efficiency is about 97.2% along the load range. This demonstrates the expected improvement when compared with similar works.

Fig. 17 Converter’s variables response under load step change.

Fig. 19. Efficiency versus output power curve.

VI. CONCLUSION 5B

In this paper, the main objective was to obtain a controlled dc voltage from parallel wind energy conversion systems using a flexible digitally controlled converter system. A dc-bus system module has been designed, fabricated, and implemented in order to have ability to connect multiple sources sharing same bus and having same dc voltage level. The VOC technique has been used for high-performance control operation. The synchronous frame SPLL has been proposed to give a fast detection for the phase and frequency variation resulting by the variable speed operation. The main advantages of the developed dc-bus module are: Multi-access input/output comprehensive connectivity, DSP & Microcontrollers interface, Bus voltage level monitoring & isolation, DC-bus capacitor filter. The simulation and experimental tests confirmed the effectiveness of the proposed system. The use of parallel converters provides high reliability and high power capability (6.6 kW). The generator line currents have acceptable THD with a simple control circuit (3.98%). Unity power factor operation (PF=0.998) which leads to economical utilization for the wind generator. Furthermore, the test results show a very fast transient response (0.1 sec) under different possible conditions (wind speed variation and load variation) and high efficiency due to a reduced number of components (above 96% for a wide power range). The developed bus system module verified its superiority for general industrial electronics and sustainable energy applications.

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APPENDIX TABLE I SIMULATION PARAMETERS FOR VOC VSC Symbol

Quantity

Value

fg Vdc

Generator frequency DC bus voltage

60 Hz 400 V

L R Cdc fsw Vg

Line inductor Internal resistance DC bus capacitor Switching frequency Generator output voltage

2.7 mH 0.7 Ω 1000 µf 5 kHz 120 V r.m.s

TABLE II SMALL AND LARGE SYNCHRONOUS GENERATOR PARAMETERS Symbol Po(Small) Po(Large) Vn

Quantity Output power Output power Nominal voltage,

Value 1/3 hp 3 hp 120/208 V r.m.s

n In(Small) In(Large) Vf

Nominal speed Nominal current Nominal current Field voltage

1800 rpm 1.7 A 8.7 A 125 V

REFERENCES [1] [2] [3]

[4]

[5] [6] [7] [8]

[9] [10] [11] [12] [13]

[14]

Y. Chen and K. M. Smedley, “Parallel Operation of One-Cycle Controlled Three-Phase PFC Rectifiers,” IEEE Trans. on Ind. Elect., vol. 54, no. 6, pp. 3217-3224, Dec 2007. S. K. Mazumder, “Continuous and discrete variable-structure controls for parallel three-phase boost rectifier,” IEEE Trans. Ind. Electron., vol. 52, no. 2, pp. 340–354, Apr. 2005. Mariano López, Luis García de Vicuña, Miguel Castilla, Pedro Gayà, and Oscar López , “Current Distribution Control Design for Paralleled DC/DC Converters Using Sliding-Mode Control” IEEE Trans. on Ind. Elec., vol.51, no.2, pp. 419-428, Apr. 2004. M. Malinowski, M. P. Kazmierkowski, S. Hansen, F. Blaabjerg, , and G D. Marques, “Virtual-Flux-Based Direct Power Control of Three-Phase PWM Rectifiers ,” IEEE Tran. On Ind. App., vol. 37, no. 4, Jul. /Aug. 2001. H. K¨om¨urc¨ugil, and O. K¨ukrer, “A Novel Current-Control Method for Three-Phase PWM AC/DC Voltage-Source Converters,” IEEE Tran. On Ind. Electron. , vol. 46, no. 3, June 1999. K. Sheng, B. W. Williams, and S. J. Finney, “A Review of IGBT Models,” IEEE Tran. On Power. Electron. , vol. 15, no. 6, Nov. 2000. V. Blasko and V. Kaura, “A new mathematical model and control of a three-phase ac–dc voltage source converter,” IEEE Trans. Power Electronics, vol. 12, pp. 116–123, Jan. 1997. M. Malinowski, M. P. Kazmierkowski, and A. M. Trzynadlowski, “A Comparative Study of Control Techniques for PWM Rectifiers in AC Adjustable Speed Drives,” IEEE Trans. Power Electronics, IEEE Transactions On Power Electronics, vol. 18, no. 6, Nov. 2003. Paul C. Krause, Oleg Wasynczuk, and Scott D. Sudhoff, “Analysis Of Electric Machinery and Drive Systems” Purdue University, second edition, IEEE Press, Wiley-Interscience, 2002. V. Valtchev, A. Bossche, J. Ghijselen, and J. Melkebeek, “Autonomous renewable energy conversion system” Energy conversion and management, An International Journal, vol. 43, pp. 259–275, 2002. D. W. Novotny, and T. A. Lipo, “Vector control and Dynamic of AC Drive” Copyrightby Clarendon Press Oxford University, 1996. Z. Jovan “A method of synchronizing microprocessor-controlled pulse width modulation inverter with the mains voltage” EPE, Conf. Proce., Sevilla, Spain, pp,347-350, 1995. M. M. N. Amin, and O. A. Mohammed, “Vector Oriented Control of Voltage Source PWM Inverter as a Dynamic VAR Compensator for Wind Energy Conversion System Connected to Utility Grid,” in APEC’ 2010 Conf., vol. I, pp. 1640-1650, California, USA, Feb. 2010. B. K. Bose, “Power electronics and variable frequency drives: Technology and applications” IEEE Press, Inc. 1997.

[15] M. P. Kazmierkowski, and L. Malesani, “Current control techniques for three-phase voltage-source PWM converters: a survey”, IEEE Trans. on Ind. Elect., vol. 45, no. 5, pp. 691-703, 1998. [16] D. Lee, G. Lee, and K. Lee “DC-bus voltage control of three-phase AC/DC PWM converters using feedback linearization”, IEEE Trans. on Ind. App., vol. 36, no. 3, pp. 826-833, 2000. [17] H. Song, and K. Nam “Dual current control scheme for PWM converter under unbalanced input voltage conditions” IEEE Trans. on Ind. Elect., vol. 46, no. 5, pp. 953-,Oct. 1999. [18] T. Ohnuki, O. Miyashita, P. Lataire, and G. Maggetto “Control of a three-phase PWM rectifier using estimated AC-side and DC-side voltages”, IEEE Trans. on Power Elect., vol. 14, no. 2, pp. 222-226, 1999. [19] S. Huang, and J. Wu “A control algorithm for three-phase three-wired active power filters under nonideal mains voltages” IEEE Trans. on Power Elect., vol. 14, no. 4, pp. 753-760, 1999.

BIOGRAPHIES Mahmoud M. AMIN (S’09) received the B.Sc. degree in Electrical Power & Machines engineering, and the M.S. degree in Electrical Engineering, all from Faculty of Engineering, Helwan University, Cairo, Egypt, in 2003, and 2008, respectively. He is currently a Ph.D. student (Research Assistant) in the Energy Systems Research Lab., Electrical and Computer Engineering Dep. (ECE) at Florida International University (FIU). His research interests wind energy systems, power electronics, power quality, and smart grid. He is the author of more than 15 scientific papers presented at international conferences or published in reviewed journals. He is the recipient of the IEEE Power & Energy Society (PES) Prize Paper Award at the 2010 General Meeting, as well as the 2010 Graduate Student Association (GSA)Paper Award at Florida International University. He is also a member in the DEI Academic Honor Society. Osama A. Mohammed (S'79, SM'84, F’94): Professor Mohammed received his M.S. and Ph.D. degrees in Electrical Engineering from Virginia Polytechnic Institute and State University. He has many years of teaching, curriculum development, research and industrial consulting experience. He authored and coauthored over 300 technical papers in the archival literature as well as in National and International Conference records in addition to additional numerous technical and project reports and monographs. He is author of book chapters including; Chapter 8 on direct current machines in the Standard Handbook for Electrical Engineers, 15th Edition, McGraw-Hill, 2007 and a book Chapter entitled " Optimal Design of Electromagnetic Devices: the genetic Algorithm Approach and System Optimization Strategies," in the Book entitled: Electromagnetic Optimization by Genetic Algorithms, John Wiley & Sons, 1999. Professor Mohammed specializes in Electrical Energy Systems especially in areas related to alternate and renewable energy systems. He is also interested in design optimization of electromagnetic devices, Artificial Intelligence Applications to Energy Systems as well as Electromagnetic Field Computations in Nonlinear Systems for these energy applications. He has current interest in Shipboard power systems and integrated motor drives. He is also interested in the application communication and sensor networks for the distributed control of power grids. Dr. Mohammed has been successful in obtaining a number of research contracts and grants from industries and Federal government agencies. He has a current active and funded research programs in several areas funded by the office of Naval Research and the US Department of Energy. Professor Mohammed is also interested in developing learning environments and educational techniques for Internet based delivery systems and virtual laboratories. Professor Mohammed is the recipient of the 2010 IEEE Power and Energy Society Cyrill Vinott Electromechanical Energy Conversion Award. He is an elected Fellow of IEEE and an elected Fellow of the Applied Computational Electromagnetic Society. He is Editor of IEEE Transactions on Energy Conversion, IEEE Transactions on Magnetics,

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and an Editor of COMPEL. Professor Mohammed is the current President of the Applied Computational Electromagnetic Society (ACES) He received many awards for excellence in research, teaching and service to the profession. Professor Mohammed has chaired sessions and programs in numerous International Conferences and has delivered numerous invited lectures at scientific organizations in North and South America, Europe, Asia and Africa. Professor Mohammed was the General Chair of the 2009 IEEE IEMDC conference held in Miami Florida, May 3-6 2009 and was the Editorial Board Chairman for the IEEE CEFC2010 held in Chicago, IL USA, May 9-12, 2010. Professor Mohammed was also the general chair of the IEEE CEFC 2006 held in Miami, Florida, April 30 – May 3, 2006. He was also general chair of the 19th annual Conference of the Applied Computational Electromagnetic Society ACES-2006 held in Miami, Florida March 14-17, 2006. He was the General Chairman of the 1993 COMPUMAG International Conference and was also the General Chairman of the 1996 IEEE International Conference on Intelligent Systems Applications to Power Systems (ISAP'96) as well as the General Chairman of the 1994 IEEE Southeast conference. He was the technical program chair for the IEEE CEFC conference in Milwaukee, WI, June, 2000. Dr. Mohammed also organized and taught many short courses on power systems, Electromagnetics and intelligent systems in the U.S.A and abroad. Dr. Mohammed was the Chair, Vice Chair and Technical Committee Program Chair for the IEEE PES Electric Machinery Committee. He was a member of the IEEE/Power Engineering Society Governing Board (1992-1996) and was the Chairman of the IEEE Power Engineering Society Constitution and Bylaws committee. Professor Mohammed currently serves as the International Steering Committee Chair for the IEEE International Electric Machines and Drives Conference sponsored by the IEEE Power and Energy, Industry Applications, Power Electronics and Industrial Electronics Societies. He also serves as chairman, officer or as an active member on several IEEE PES committees, sub-committees and technical working groups.