IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 50, NO. 5, SEPTEMBER/OCTOBER 2014 3549

Validation of the Plug-and-Play AC/AC PowerElectronics Building Block (AC-PEBB) forMedium-Voltage Grid Control Applications

Amrit R. Iyer, Student Member, IEEE, Rajendra Prasad Kandula, Student Member, IEEE,Rohit Moghe, Member, IEEE, Jorge E. Hernandez, Student Member, IEEE,Frank C. Lambert, Senior Member, IEEE, and Deepak Divan, Fellow, IEEE

Abstract—As ac-to-ac power conversion becomes increasinglyimportant in applications such as grid power control and motorcontrol, demand for a plug-and-play converter has increased. Tra-ditional voltage-source-inverter-based ac-to-ac power converterssuch as the back-to-back converter require dc-link capacitorsthat limit their reliability or significantly increase their size andcost. This paper examines a plug-and-play concept for achievingac-to-ac power conversion via the direct-ac/ac power electronicbuilding block (AC-PEBB). The AC-PEBB is a compact self-contained cell requiring no intermediate energy storage. It canbe used in a variety of ac/ac power electronic applications suchas matrix converters and controllable network transformers. Thispaper details the design of an 800-V 100-A AC-PEBB prototype tobe used in a 13-kV 1-MVA application. Successful test results usingseveral AC-PEBBs in a variety of configurations are demonstratedat up to 11 kV and 600 kVA.

Index Terms—AC–AC power conversion, flexible ac transmis-sion systems, high-voltage techniques, matrix converters, phasecontrol, power control, power semiconductor switches, snubbers.

I. INTRODUCTION

AC-TO-AC power conversion is becoming important inmany utility and industrial applications. The utility grid

is a prime example, where a dramatic increase in the levelof renewable resources connected to the grid is occurring inorder to increase energy security and reduce carbon emissions.However, the spatial and temporal variability of new wind andsolar generation is poorly correlated with existing loads, leadingto the need for significant transmission investments in orderto reduce possible congestion [1], [2]. In lieu of transmissionimprovements, which are typically difficult and time consumingto negotiate and implement, dynamic grid power control can beused to enhance system utilization [2]–[5]. Important metrics

Manuscript received October 29, 2013; accepted January 23, 2014. Date ofpublication February 7, 2014; date of current version September 16, 2014.Paper 2013-PEDCC-715, presented at the 2013 IEEE Energy ConversionCongress and Exposition, Denver, CO, USA, September 16–20, and approvedfor publication in the IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS

by the Power Electronic Devices and Components Committee of the IEEE In-dustry Applications Society. This work was supported by the United States De-partment of Energy through the Advanced Research Projects Agency—Energyprogram.

The authors are with the School of Electrical and Computer Engineering,Georgia Institute of Technology, Atlanta, GA 30332 USA (e-mail: ariyer@gatech.edu; krprasad@gatech.edu; rmoghe@varentec.com; jorge.hernandez@gatech.edu; frank.lambert@neetrac.gatech.edu; deepak.divan@ece.gatech.edu).

Color versions of one or more of the figures in this paper are available onlineat http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TIA.2014.2304583

for power controllers to be used for transmission applicationsinclude high reliability, scalability to 345 kV and 200 MW,and attractive cost. Traditional solutions for grid power control,such as high-voltage dc (HVDC) lines and flexible ac trans-mission system (FACTS) devices, suffer from high cost [2],[6], high complexity [6], relatively high losses [2], [5], andrelatively low reliability; typical HVDC and FACTS devicesrealize reliability levels of 95%–98% [7]–[9], whereas the UStransmission network operates at levels in excess of 99.9%[10]. To drive adoption of power controllers among utilities, atechnology is needed that is lower in cost, higher in efficiency,easy to integrate, and does not lower single-point system relia-bility. One attractive solution that exists in the literature is thecontrollable network transformer (CNT), which adds a direct-ac/ac fractionally rated power electronics converter to a loadtap changer (LTC) transformer to achieve grid power control[11]. The fractional rating of the CNT allows for efficienciesgreater than 99%, and its integrated fail-normal bypass switchallows for enhanced reliability. The design and initial testingof an ac/ac power electronic building block (AC-PEBB) for aCNT application was previously outlined by Iyer et al. in [12].

This paper expands upon the AC-PEBB in [12], where acompact, modular, and scalable direct-ac/ac building block isexamined. Important design considerations of the AC-PEBBare explained, and experimental results are shown for a CNTapplication at 11 kV and 600 kVA using six AC-PEBB cells ina variety of configurations.

II. SCALING THE CNT WITH AC-PEBB CELLS

A. CNT Review

For a CNT with a tap ratio of 1 to n and a virtual quadraturesource (VQS)-based duty cycle of

D = K0 +K2 sin(2ωt+Φ) (1)

active and reactive power can be controlled in a two-bus system,such as in Fig. 1, according to (2) and (3), as shown in [11], i.e.,

Pout=V 2A

ωLsin δ − V 2B

ωLcos(δ +Φ)

with A=1 + n− 2K0n

1− n2, B=

nK2

1− n2(2)

Qout=V 2

ωL

(A2 − 2

3B2

)− AV 2

ωLcos δ+

BV 2

ωLsin δ. (3)

0093-9994 © 2014 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission.See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.

3550 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 50, NO. 5, SEPTEMBER/OCTOBER 2014

Fig. 1. Conceptual one-line diagram of CNT connecting two buses.

Fig. 2. (a) Schematic of the AC-PEBB cell. (b) Solid model of the AC-PEBBcell.

B. AC-PEBB Overview

The PEBB concept, explained in [13], outlines a visionfor a singular building block that can reduce the size andcost of power electronics, while facilitating easier installation,maintenance, and manufacturing. PEBB technology has beenproven useful in transmission-level VSC applications, wherethe modular multilevel converters (MMC or M2C) have beencascaded for use in HVDC power transmission [14]. For direct-ac/ac converters, an ac PEBB design has been proposed in [15];however, the topic of scaling to higher voltages for direct-acPEBBs has yet to be addressed.

The AC-PEBB described in this paper and shown in Fig. 2 isa self-contained unit that provides a plug-and-play functionalityfor ac-to-ac power conversion applications. It provides a com-pact modular building block for direct-ac/ac applications andallows series and parallel connection of cells to enable scalingto higher voltage and power levels.

An AC-PEBB cell contains four insulated-gate bipolar tran-sistors (IGBTs, or MOSFETs), forming two ac switches witha midpoint connection, as shown in Fig. 2(a). Each AC-PEBB contains all necessary gate drive, snubber, and thermalmanagement components, allowing the cell to be used as astandalone matrix or thin ac converter [16]. Through direct-ac/ac conversion via the use of VQS as outlined in [17], largedc storage elements are not needed, allowing the cell to be onlya few inches in size in each dimension, as shown in Fig. 2(b).Compactness, combined with the cell’s modularity, allows it tobe easy to manufacture, install, and replace, thus reducing bothupfront and operation and maintenance costs.

C. Scaling the AC-PEBB

Usage of the AC-PEBB at higher voltage and power levelsis accomplished via series and parallel connection of multiple

Fig. 3. Series stacking of AC-PEBBs in a CNT configuration.

Fig. 4. Parallel stacking of AC-PEBBs in a CNT configuration.

cells. For example, Figs. 3 and 4 show various forms of a CNTprototype built by series and parallel connection of AC-PEBBsto the taps of a standard 1-MVA transformer. More advancedtopologies are discussed in companion paper [18].

The major obstacles encountered when scaling the AC-PEBBto utility-scale power levels are ensuring equal voltage shar-ing between devices and providing protection from incorrectcommutation sequences. These challenges can be overcome bythe active snubber concept proposed in [19]. The half-waverectified sources connected through diodes across each devicein Fig. 2(a) are conceptual representations of the active snubbertechnology being used in the AC-PEBB.

III. REVIEW OF THE AC-PEBB

The AC-PEBB consists of five parts: the main switchingdevices, the gate drivers, the snubber circuits, the bus bars, andthe thermal management system.

IYER et al.: VALIDATION OF THE PLUG-AND-PLAY AC-PEBB FOR GRID CONTROL APPLICATIONS 3551

Fig. 5. AC-PEBB snubber board.

A. Main Device Selection

The main AC-PEBB switching devices are GeneSiC Semi-conductor’s GA100XCP12-227. These are 1200-V 100-A sili-con IGBTs with a built-in silicon carbide antiparallel diode. TheSiC diodes contained in this device have minimal reverse recov-ery and high temperature tolerances, allowing device operationat tens of kilohertz and temperatures as high as 150 ◦C. Thedevice’s 1200-V rating allows it to safely operate at voltageswith a peak of up to 800 V, corresponding to a root mean square(RMS) voltage of 565 V; a 400-V buffer is in place to accountfor voltage spikes during switching due to stray inductances.

An AC-PEBB built with these devices is capable of acting asa 56.5-kVA standalone converter. Additionally, as AC-PEBBscan operate as thin ac converters, to provide full power flowcontrol, they only need to be rated at about 10%–20% ofthe level of the asset to be augmented, depending on thecontrollability range needed. Therefore, a single AC-PEBBcomposed of these GeneSiC devices can be used to route powerflows of as high as 565 kVA. Accounting for the small sizeof GeneSiC’s devices, which are 1.3 × 1.6 inches, series andparallel stacking of GeneSiC-based AC-PEBBs has the abilityto reach transmission level powers in a compact size.

B. Snubber Board Design

The AC-PEBB snubber board, as shown in Fig. 5, consistsof four snubber circuits organized on a single PCB, which isdirectly screwed onto the IGBTs of the AC-PEBB. A hybridpassive and active snubber approach is used, as shown in Fig. 6.The passive snubber portion of the design protects the converterduring a system-level fault until external circuit breakers, re-lays, or fuses have a chance to react. The active snubber portionof the hybrid snubber, as outlined in [19], creates a half-waverectified envelope around each IGBT, providing protectionfrom internal faults, such as incorrect commutations near zerocrossings, and ensuring that equal voltage is seen across everydevice. A modified version of the buck–boost design in [19]

Fig. 6. Hybrid snubber circuit for AC-PEBB.

Fig. 7. Active snubber circuit and buck–boost control for AC-PEBB.

is employed in the AC-PEBB to control each active snubberand is schematically shown in Fig. 7. More information on theelectrical design of the snubber circuit for an 800-V 100-Aapplication can be seen in [20].

Any stray inductance in the snubber-to-IGBT path leads tovoltage spikes during snubber operation, and because the snub-ber operates during incorrect commutations or fault conditions,large currents and di/dt’s will be experienced during these situ-ations. Therefore, parasitic inductances significantly reduce theeffectiveness of the snubber circuit in limiting voltage spikes.The snubber board design in Fig. 5 places the snubber capacitor(CS), diode (DS), and varistor (MOVS) as close as possible tothe IGBTs they are protecting, thus minimizing the inductancein the snubber path and maximizing their effectiveness. Thecontrol circuitry for the snubber voltage envelope creation ismoved onto the gate drive board to reduce the overall size ofthe AC-PEBB.

C. Gate Drive Board Design

The gate drivers for the AC-PEBB are chosen to be PowerexVLA-502 modules mounted onto modified Powerex BG2A gatedrive boards. The BG2A boards are augmented with protectionand fault management circuitry, control circuitry for the AC-PEBB’s snubber circuits, and fiber optic connections to carryall signals to and from the converter’s main microcontrollerunit. If long signal wires are employed in lieu of fiber opticconnections, large amounts of switching noise induced by theconverter’s extremely high di/dt levels would compromise theintegrity of the digital control signals, even if a twisted-pairconfiguration is used. Finally, gate drive board is designed todirectly plug into the main snubber board using low-inductancebus-bar connections in order to minimize inductance in thegate–emitter path of each IGBT. Fig. 8 shows the final gatedrive board as well as the layout of its various subcircuits. Eachboard controls two IGBTs.

3552 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 50, NO. 5, SEPTEMBER/OCTOBER 2014

Fig. 8. Gate drive board for AC-PEBB.

Fig. 9. Complete AC-PEBB cell.

D. Completed Cell Specifications

The completed AC-PEBB, mounted on a heat sink, is shownin Fig. 9. Again, inductance was kept to a minimum through theuse of wide bus bars and a compact design. Spacers and 30-milNomex insulation are present to keep the various layers of theAC-PEBB electrically isolated. The entire cell is a cube that isapproximately 6 × 6 × 10 inches in size. The specifications ofthe designed AC-PEBB are summarized in Table I.

E. Thermal Management

For higher power applications, cooling is provided by a novelpassive thermal management system (PTMS), shown in Fig. 10,that is capable of supporting up to 12 cells. The PTMS involvesa main AC-PEBB heat sink feeding into an oil tank and finarray. The losses generated by the system are used to createa thermosiphon to circulate the oil between the main AC-PEBBheat sink and external fin array [21].

TABLE IAC-PEBB SPECIFICATION SUMMARY

Fig. 10. PTMS of 5 kW to 40 ◦C for up to 12 AC-PEBB cells.

With the integration of the PTMS into the AC-PEBB, the cellis able to independently operate from electrical, thermal, andmechanical points of view. Additionally, the PTMS removesthe need for fans, pumps, and other moving parts, increasingthe expected lifetime of the converter to 30 years. This lifetimeputs the AC-PEBB alongside most other utility assets in termsof robustness, increasing its commercial appeal and ease ofintegration.

IV. AC-PEBB-BASED 1-MW CNT DESIGN

A. 1-MW Test Bed Design

The AC-PEBB-based CNT laboratory prototype consists oftwo 13-kV primary, 1300-V/650-V secondary, 167-kVA trans-formers, whose primary and secondary windings are series con-nected, and a set of line inductors, as shown in Figs. 11 and 12.The two transformer sets are representative of two buses in anarbitrary power system. A set of AC-PEBBs is connected acrossone of the transformers between its +/−650-V taps, achievinga CNT configuration with a tap ratio of n = 9.5%. Currentcan be circulated between the system’s transformers withoutpower transfer occurring with the grid. Using a POWERSTAT,voltage levels on the system’s input and output voltage busesare scalable from 0 to 13650 V (RMS). For safety reasons andto limit the voltage seen by the converter’s PTMS, the centertap of the transformer of bus 1 was used as ground.

Without the AC-PEBB-based converter, both bus 1 and bus 2have the same voltage magnitude and phase, and there isno power transfer across the line. With the AC-PEBB-basedconverter, the effective voltage of bus 1 is controlled to bedifferent from bus 2, in magnitude or phase or both, to induceenergy flow on the line. Hence, the functionality of the CNTand AC-PEBBs can be demonstrated by controlling the powerbetween the two buses.

IYER et al.: VALIDATION OF THE PLUG-AND-PLAY AC-PEBB FOR GRID CONTROL APPLICATIONS 3553

Fig. 11. Two-bus system of 13 kV with an input-side LTC transformer, of tap ratio n = 9.5%, connected in a CNT configuration.

Fig. 12. Two-bus system of 13 kV, 1 MW and AC-PEBB/CNT test bed.

B. AC-PEBB Control Board Design

Fig. 13 shows the control flow diagram for the AC-PEBBcell-based CNT. Switching signals originating from a digitalsignal processor (DSP) are sent to an electrically erasableprogrammable read-only memory (EEPROM), which keepstrack of the state of the system and its switching devices. TheEEPROM is preprogrammed with switching sequences thatensure proper ac commutation of the converter and prevent anyshort circuiting of the source or open circuiting of the lineinductor current; two-level, three-level, voltage, and current-based commutation sequences have all been implemented (formore information on multilevel commutation, refer to com-panion paper [18]). The EEPROM switching signals are sent

to the converter’s gate driver circuits. Converter status, faultstatus, and switch voltage and line current measurements, usedin voltage and current commutation algorithms by the DSP, arethen collected from the converter, conditioned, and sent back tothe DSP. Communication of signals between the DSP controland the AC-PEBB occurs via fiber optic links.

V. EXPERIMENTAL RESULTS

A. Parallel Operation of Modules

With six AC-PEBB cells configured as two parallel, three-level, direct-ac/ac, the CNT was shown to be able to control600 kVA of power at a bus voltage of 8 kV and line current of

3554 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 50, NO. 5, SEPTEMBER/OCTOBER 2014

Fig. 13. Control flow for direct-ac/ac converter and CNT comprised of up to12 AC-PEBB cells.

Fig. 14. Parallel three-level direct-ac/ac converter system made up of sixAC-PEBB cells.

75 A. Fig. 14 shows the schematic representation of the AC-PEBB layout, with companion paper [18] providing more de-tails on the three-level converter topology. Fig. 15 shows thetest setup with six AC-PEBB cells mounted on the PTMS andconnected to the two-bus system.

Figs. 16–19 demonstrate the CNT’s ability to have completecontrol over the phase angle of the line current, showing correctoperation of the AC-PEBB cells. In those plots, the 8-kV (RMS)

Fig. 15. Six AC-PEBB cells connected as dual three-level converters, asshown in Fig. 14, and mounted to a custom PTMS.

Fig. 16. Real power demonstration of an 8-kV, 75-A, 600-kVA two-bussystem with a three-level CNT.

Fig. 17. Negative-real power demonstration of an 8-kV, 75-A, 600-kVA two-bus system with a three-level CNT.

line voltage is the uppermost waveform, followed by the 75-A(RMS) line current. In Fig. 16, these two waveforms are inphase; in Fig. 17, they are 180◦ out of phase; in Fig. 18, thecurrent is lagging the voltage by 90◦; and in Fig. 19, the currentis leading by 90◦. This variation of phase was done in realtime; thus, full power control is seen with operation shownin positive-real, negative-real, lagging-reactive, and leading-reactive power flow modes at 600 kVA. Power magnitudecontrol was also demonstrated, although not shown.

IYER et al.: VALIDATION OF THE PLUG-AND-PLAY AC-PEBB FOR GRID CONTROL APPLICATIONS 3555

Fig. 18. Lagging-reactive power demonstration of an 8-kV, 75-A, 600-kVAtwo-bus system with a three-level CNT.

Fig. 19. Leading-reactive power demonstration of an 8-kV, 75-A, 600-kVAtwo-bus system with a three-level CNT.

The third and fourth waveforms in Figs. 16–19 show thesynthesized converter output voltage and the voltage acrosseach of the two parallel AC-PEBB-based converters. These twowaveforms depict the 25-kHz VQS-based PWM technique usedin this experiment and show the parallel modules successfullyoperating in unison.

B. Issues With Harmonics and Resonances

Note the third-harmonic ripple seen in the waveforms inFigs. 16–19. This is a byproduct of the VQS modulationmethod, as explained in [17], and would need to be filtered outin a practical application, as demonstrated in [22]. As shownin Fig. 20, a third harmonic at 41% of the fundamental is seenon converter and bus voltages in addition to the current. Thisphenomenon was not noticeable at the lower power level testsperformed in [12] and is due to the voltage drop across theimpedance of the source and power transformers from the third-harmonic current. Filtering of the third-harmonic current as in[22] will also solve the voltage harmonic issue.

In addition to harmonics, resonances at the third harmonicwere experienced. These resonances were found to be occurringbetween the filter capacitors, i.e., CF , and input transformer

Fig. 20. Frequency spectrum of 8-kV, 75-A, 600-kVA bus voltage in a two-bus system with a three-level CNT.

stages shown in Fig. 11. The filter capacitors are necessary toprevent the 25-kHz electromagnetic interference caused by theCNT from propagating back to the source. Through experimen-tal data gathered by varying the size of the filter capacitors,the equivalent source inductance was calculated to be initially30 mH from the following equation:

Lsource =1

(3ω0)2CF

2

. (4)

By lowering the number of input transformer stages, thetap ratio of the bus transformers (from 17% to 9.5%), andthe amount of filter capacitance (from 200 to 50 μF), theresonant frequency of the system was able to be moved farenough away from 60 Hz to eliminate interference with systemoperation; without these steps, the source current drawn athigher power levels due to resonances would have overloadedthe POWERSTAT and system transformers. Higher order (5ththrough 11th) harmonics were also seen in the system, causedby the filter capacitors interacting with various smaller parasiticelements present in the system. While smaller in magnitude,these harmonics increased the number of zero-crossings forvoltage and current under certain operating conditions; spend-ing more time around zero-crossings resulted in more missedcommutations. To damp higher order harmonics, resistors RF

were placed in series with the filter capacitance values. Fig. 11shows the final configuration used for higher current and higherpower testing.

C. Converter Efficiency

With the AC-PEBB configuration in Fig. 14, the input andoutput voltages and currents of the AC-PEBB system weremeasured in order to estimate system efficiency. Table II showsthe results of this measurement at 400 kVA, where the CNTis over 99% efficient, neglecting transformer core and windinglosses. This high efficiency is mainly due to the converter’sability to gain full control range without being exposed to thefull bus voltage.

3556 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 50, NO. 5, SEPTEMBER/OCTOBER 2014

TABLE IICNT CONVERTER EFFICIENCY AT 6.7 kV, 60 A, 400 kVA

Fig. 21. Real power demonstration of an 11-kV, 15-A, 165-kVA two-bussystem with a three-level CNT.

D. High-Voltage Testing

Testing was performed at lower current and higher voltagelevels to ensure that a single AC-PEBB was able to handle itsfull voltage rating of 565 V (RMS), 800 V (peak). Fig. 21 showsthese results at 11 kV, 15 A, and 165 kVA. The fourth waveformin this figure shows an individual IGBT voltage peaking at750 V, demonstrating successful operation of the AC-PEBB atnear its rated value of 800 V. Note that at higher voltages andlower currents, the third-harmonic currents do not significantlyaffect bus voltage, as explained in Section V-B.

E. Series Operation

The series-stacking capability of AC-PEBBs was examinedby validating their voltage-sharing capabilities. Fig. 22 showssuccessful voltage sharing at a 5-kV (RMS) bus voltage, where770 V (peak) is impressed across each AC-PEBB. The purplewaveform shows an individual device voltage being held toabout 335 V (peak) by the green waveform, which is the activesnubber voltage and exactly half of the voltage across an AC-PEBB cell, demonstrating equal voltage sharing and series-stacking capabilities of the cell.

VI. CONCLUSION

This paper has outlined the construction and testing of anAC-PEBB unit built for operation at MV levels. Importantdesign considerations were highlighted, and viability of theconcept has been shown successful experimental results at upto 11-kV and 600-kVA levels and low-voltage prototyping. ThePEBB proved to be compact, easy to interconnect, and highlyefficient.

Fig. 22. Demonstration of voltage sharing between individual IGBTs in aCNT at 5 kV, 10 A, and 50 kVA.

Practical issues relating to medium-voltage ac/ac converterdesign were also examined and uncovered during the course ofthis work. Harmonic and resonance issues showed themselvesto be significantly worse at higher power levels and will be amajor challenge in any practical MV or HV application. Addi-tionally, series stacking of cells became difficult as the tuning ofeach analog active snubber circuit was cumbersome when manycells were used. A more robust active snubber control design isrecommended for true plug-and-play capability to be achieved.

ACKNOWLEDGMENT

The authors would like to thank Dr. J. Rhett Mayor,B. Loeffler, and A. Semidey of the Department of MechanicalEngineering, Georgia Institute of Technology, Atlanta, GA,USA, for their contributions to this project relating to theconstruction and thermal management of the CNTs used in thisresearch. The authors would also like to thank T. Parker and theengineers/technicians of the National Electric Energy TestingResearch and Applications Center for their assistance in theconstruction and operation of the medium-voltage test bed usedin this research.

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Amrit R. Iyer (S’11) received the B.S.E.E. de-gree from the University of Illinois at Urbana-Champaign, Champaign, IL, USA, in 2003, withan emphasis in power electronics. He is currentlyworking toward the Ph.D. degree in electrical engi-neering with the Electrical Energy Group, GeorgiaInstitute of Technology, Atlanta, GA, USA, underProf. D. Divan.

He spent several semesters working with the Illi-nois Tiny Satellite Initiative, including serving as thelead for the group’s power management team. He has

published over a dozen papers and has two patents pending in his areas ofinterest. His current research interests include power electronic converter designfor medium- and high-voltage applications and smart sensing technologies forutility applications, where his work has been sponsored by General Electric,Advanced Research Projects Agency—Energy, the National Electric EnergyTesting Research and Applications Center, and Georgia Tech’s IntelligentPower Infrastructure Consortium.

Rajendra Prasad Kandula (S’10) received theB.Tech. degree from the National Institute of Tech-nology, Nagpur, India, in 2002 and the M.Tech. de-gree from the Indian Institute of Science, Bangalore,India, in 2004. He is currently working toward thePh.D. degree at the Georgia Institute of Technology,Atlanta, GA, USA.

For three years, he was a Design Engineer withBharat Heavy Electricals Ltd. R&D, New Delhi,India, working with high-power drives and grid-connected solar inverters. His research interests in-

clude power electronics for utility applications such as active filters and powerrouters for meshed systems.

Rohit Moghe (S’07–M’12) received the B.Tech.degree in electrical engineering from the Indian Insti-tute of Technology, Roorkee, India, in 2007, and theM.S. and Ph.D. degrees from the Georgia Institute ofTechnology, Atlanta, GA, USA, in 2010 and 2012,respectively.

During May–August 2008 and 2009, he was asummer intern with the ABB U.S. Corporate Re-search Center and Siemens Energy & Automation,respectively. He is currently a Principal Engineerwith Varentec Inc., San Jose, CA, USA. His research

focuses on power electronic converters for utility applications such as VARsupport, power flow controllers, medium-voltage solid-state transformers, andenergy harvesting for wireless sensors.

Dr. Moghe was awarded the Best Undergraduate Research Award by theIndian Institute of Technology. He was one of the founding members of theEnergy Club at the Georgia Institute of Technology and served as Presidentduring 2010–2011.

Jorge E. Hernandez (S’10) received the B.S. degreein electrical engineering from the Technological Uni-versity of Panama, Panama City, Panama, in 2006and the M.S. degree in electrical engineering fromthe Georgia Institute of Technology, Atlanta, GA,USA, in 2009. He is currently working toward thePh.D. degree in the School of Electrical and Com-puter Engineering, Georgia Institute of Technology.

From January to July 2007, he was a Research En-gineer with the Technological University of Panama,overseeing renewable integration projects for rural

communities. His research interests include power electronics for utility ap-plications, and power system operation/control and electricity markets, undercurrent practices and under scenarios with high wind and electric vehiclepenetration.

Frank C. Lambert (S’70–M’73–SM’87) receivedthe B.S. and M.S. degrees in electrical engineeringfrom the Georgia Institute of Technology, Atlanta,GA, USA.

He is currently the Associate Director of the Na-tional Electric Energy Testing Research and Applica-tions Center, Georgia Institute of Technology. He isresponsible for interfacing with the members of theNational Electric Energy Testing Research and Appli-cations Center to develop and conduct research proj-ects dealing with transmission and distribution issues.

For 22 years, he was with Georgia Power Company, engaged in transmission/distribution system design, construction, operation, maintenance, and automation.

Mr. Lambert participates in the IEEE Power and Energy Society DistributionSubcommittee and the PES Switchgear Committee and is serving on the PESGoverning Board as the Vice President for Chapters.

Deepak Divan (S’78–M’78–SM’91–F’98) receivedthe B.Tech. degree from the Indian Institute ofTechnology, Kanpur, India, in 1975 and the M.Sc.and Ph.D. degrees from the University of Calgary,Calgary, AB, Canada, in 1979 and 1983, respectively.

He is the President and CTO of Varentec Inc.,San Jose, CA, USA, which is a company fundedby the green-tech venture capital firm Khosla Ven-tures, providing innovative solutions to achieve asmart and dynamically controllable grid. He has over35 years of experience in industry and academia

in the areas of power electronics applied to utility and industrial systems,with Varentec being his third entrepreneurial venture. From 2004 to 2011,he was a Professor of electrical and computer engineering and the Found-ing Director of the Intelligent Power Infrastructure Consortium with theGeorgia Institute of Technology, Atlanta, GA, USA. Prior to that, he ledSoft Switching Technologies as Founder and CEO. He was also a Pro-fessor of electrical engineering with the University of Wisconsin–Madison,Madison, WI, USA. He has over 250 papers and 50 issued and pending patents.He combines unique perspectives on the changing landscape of the Transmis-sion and Distribution grid and the need for a transition to dynamic grid control,including advanced power electronics solutions. His research interests includedynamic grid control, sustainable energy, and advanced power electronics.

Dr. Divan was a recipient of the 2006 IEEE Newell Award and is a pastPresident of the IEEE Power Electronics Society.