A CASE FOR MEDIUM VOLTAGE DIRECT CURRENT(MVDC) POWER FOR DISTRIBUTION APPLICATIONS(MVDC) POWER FOR DISTRIBUTION APPLICATIONS

IEEE-PES Power Systems Conference and Expositiony pPaper Session: Substation Innovations from Conventional Design

March 23, 2011 – Phoenix, AZ

Authors:D G R d D G K i U i it f Pitt b hDr. Gregory Reed, Dr. George Kusic – University of PittsburghDr. Jan Svensson, Dr. Zhenyuan (John) Wang – ABB Inc., R&D

Background, Motivation, and Introduction Background, Motivation, and Introduction

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A New Era of DC Power SystemsA New Era of DC Power Systems

• Corporate research centers, universities, and industry are beginning to (re)consider the premise of DC power in future g g ( ) p ptransmission and distribution system applications.

• Historically, AC has dominated the power industryW i h T l Edi d h i l f h h i i i l• Westinghouse, Tesla, Edison, and others intensely fought the initial ‘AC/DC Wars’ at the turn of 20th Century

• AC proved superior for all the right reasons at the timeH ti t d t d d ‘l ’ t ld d• However, we continue today to depend on a ‘legacy’ century-old and aging AC approach, concept, technology-base, and infrastructure

• What has changed for DC in the 21st Century?• The era of Power Electronics Technologies• Continued improvements and efficiencies in semiconductors, devices,

circuits, designs, systems, and applications scaled at all levels

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• Consumer devices, emerging resources, energy storage, and other systems operating at or supplying absolute DC power

DC Applications in Modern SocietyDC Applications in Modern Society

• Rapidly Emerging DC Applications in the 21st Century• Consumer ElectronicsConsumer Electronics

• Devices and Equipment Operated at Low-Level DC (Res/Comm)• Renewable Energy Systems

• Generation Systems Producing DC Output Power (e g Solar)Generation Systems Producing DC Output Power (e.g., Solar)• Transportation Electrification

• Electric Vehicles Powered by DCInformation Technology and the Internet• Information Technology and the Internet

• Enhancement of Energy Efficiency via DC (e.g., Data Centers)• Energy Storage Technologies

DC O d I i h h DC I i• DC Output and Integration through DC Interconnections• Transmission and Distribution Infrastructure

• High Voltage Direct Current (HVDC) Systems (i.e., Transmission)

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• What is Missing?• Medium Voltage DC (MVDC) Distribution Infrastructure

Medium Voltage DC NetworksMedium Voltage DC Networks

• MVDC Technology Development• Benefits for installations of large and small scale wind / solar g

farms, and other forms of bulk and distributed generation; as well as for DC-loads, energy storage, EV integration, etc.

• Efficiency is expected to increase due to minimized powerEfficiency is expected to increase due to minimized power conversions; but overall complexity may increase

• New technical requirements, standards, protective devices, schemes, and other concepts require development / proofschemes, and other concepts require development / proof

• R&D is necessary for evaluating the MVDC potential

• High Voltage Direct Current (HVDC) Systems• Proven benefits and merit over high voltage AC transmission

for long distance power delivery applications and recent off-shore and other generation interconnections

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• MVDC, however, is not a simple scaling of voltage level• Focused research, development, and demonstration is needed

The MVDC Distribution Network ConceptThe MVDC Distribution Network Concept

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Medium Voltage DC Network ConceptMedium Voltage DC Network Concept

Non-Synchronous Generation (Wind)

Photovoltaic Generation

Fuel CellsAC Transmission Supply

Existing AC Infrastructure FACTS

Compensation

DCACDC

DCDCDC

Future HVDC Intertie

STATCOM / SVC

DCAC

DC

DCDC DC

DCDC

HVDC / MVDC

HVDC System

DCAC

DCDC

Electric Vehicle

DC

Distribution DC Load Circuits

Electronic and

DC DC

ACDC

DCDC

DCAC

Distribution Level Storage

Electric Vehicle

Sensitive Load

Electronic and AC Loads

Future DC Industrial Facility Future DC

Data Centers Motor

Variable Frequency Drives

7Control Algorithm

MVDC Network ApplicationsMVDC Network Applications

•• Development Program Applications• Renewable energy resource integration and end-use aspects:Renewable energy resource integration and end use aspects:

• Solar energy – distributed, remote• Wind energy – distributed, off-shore, remote• Fuel cell integration• Fuel cell integration • Electric vehicle integration• Variable frequency drives supply

S iti d l t i l d l• Sensitive and electronic load supply • Data centers – supply infrastructure• Power plants – internal plant distribution systems• Greenfield industrial parks

• Energy storage interconnection and control• DC/AC power factor correction for distribution load circuitsDC/AC power factor correction for distribution load circuits• Dynamic voltage and VAR optimization• High Voltage AC and DC transmission integration

Preliminary WorkPreliminary WorkModeling, Simulation, and AnalysisModeling, Simulation, and Analysis

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Preliminary MVDC Development Preliminary MVDC Development –– Subsystem 1Subsystem 1Subsystem 1 Subsystem 1

+ - Three Level 20 kV / 460 V

Wind TurbineMOD 2 Type 575 V / 14 kV

Six Pulse Graetz

Neutral Point Clamp

Multilevel Inverter

#1 #2

20 kV / 460 VI M

10 kW

1.4 MW Supply

#1 #2 Bridge AC/DC

RectifierBidirectional AC

DC/DC Converter

CLoad

n = 5

GRID Transmission

#1 #2

69 kV / 14 kV

69 kV

Five Level Neutral Point

Clamp Multilevel I t

20 kV / 460 V

#1 #2

GRID Transmission

I M

10

69 Inverter20 kV

10 kW

Research Objectives Research Objectives –– Subsystem 1Subsystem 1Subsystem 1Subsystem 1

• Analysis conducted within the PSCAD simulation environment• Evaluating the performance of two practical topologies of a uat g t e pe o a ce o t o p act ca topo og es o

multilevel inverters which include the neutral point clamp converter and flying capacitor circuitry.

• PWM Techniques: Phase Disposition Phase Opposition• PWM Techniques: Phase Disposition, Phase Opposition Disposition, and Alternate Phase Opposition Disposition

• Total Harmonic Distortion: THD appears to be the best metric for evaluating their performance.g p

• Dynamic Performance Evaluation of Network• Wind Speed Adjustments: Average wind speed will be modeled

initially without ramp and fluctuation effects in the wind sourceinitially without ramp and fluctuation effects in the wind source.• DC Bus and Motor Faults: Analyze the effects of capacitor

balancing of the power electronic inverters and effects of motor torque and speeds.torque and speeds.

• Load Energizing: Impacts on THD distribution as certain loads are connected in and out of the circuitry.

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Preliminary MVDC Development Preliminary MVDC Development –– Subsystem 2Subsystem 2

60 0 [MVA]

Subsystem 2 Subsystem 2

#1 #2

60.0 [MVA]230.0 [kV] / 20.0 [kV]

MW MVAR

60.0 [MVA]

#1 #2

[ ]575 [V] / 20.0 [kV]

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MVAC System for Comparison MVAC System for Comparison –– Subsystem 2Subsystem 2Subsystem 2Subsystem 2

60.0 [MVA]230 0 [kV] / 20 0 [kV]

#1 #2

230.0 [kV] / 20.0 [kV]

60.0 [MVA]20.0 [kV] / 4.0 [kV]

MW MVAR#1 #2

60.0 [MVA]5.0 [kV] / 20.0 [kV]

60.0 [MVA]

#1 #2

#1 #2

[ ]20.0 [kV] / 5.0 [kV]

60.0 [MVA]575 [V] / 20.0 [kV]

#1 #2

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Factors for Factors for Comparison of MVDC/ACComparison of MVDC/AC–– Subsystem 2Subsystem 2

• Performance under the following conditions• Loss of Generation

Subsystem 2Subsystem 2

• Loss of Generation

• i.e., PV Array is lost due to a fault, how does the system react and recover from this loss?

• Dynamic Changes in Renewable Generation

• Similar to “loss of generation” but generation is not completely lost only its voltage and thus power are alteredcompletely lost, only its voltage and thus power are altered

• Switch Misfiring

• If the power electronics do not react in an ideal mannerIf the power electronics do not react in an ideal manner, how is voltage and power flow affected?

Preliminary Preliminary MVDC DevelopmentMVDC Development–– Subsystem 3Subsystem 3Subsystem 3Subsystem 3

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Research ObjectivesResearch Objectives–– Subsystem 3Subsystem 3

• DC Distribution for Future Industrial Facilities• Manufacturing/Industry

Subsystem 3Subsystem 3

• Manufacturing/Industry

• Direct DC Supply for VFDs, Industrial Automation and Electronics Equipment

• Data Centers and IT

• Direct DC Supply for Computer, UPS and Battery Systems, LED lightingLED lighting

• DC Bus Architecture

• Easily incorporates on-site solar generation and hybridEasily incorporates on-site solar generation and hybrid electrical storage options

Next Steps in MVDC DevelopmentNext Steps in MVDC Development

• Program Objectives, Goals, and Future Vision• Complete the modeling analysis and verification of all• Complete the modeling, analysis, and verification of all

subsystems of the MVDC concept• Integrate the various subsystems, resources, and loads into

one model for full scale analysisone model for full-scale analysis• Development and integration of control concepts• Establish full verification of total system concepts, including

operation and control • Model and test various improvements and enhancements for

parameter evaluation (e.g., advanced semiconductor characteristics, optimized converter designs and control, etc.)

• Scaled proto-type development and testing• Full scale deployment and demonstrationp y• Application for retrofit or green-field facility/site as a complete

DC-based network

SummarySummary

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SummarySummary

• MVDC Technology Development Benefits• Improved efficiency for renewable energy integrationImproved efficiency for renewable energy integration • Support for the continued evolution of greater penetrations of

DC-based loads and resources• Enhanced integration of energy storage systems and EVs• Enhanced integration of energy storage systems and EVs• Advancements in optimization, design, and applications of high

capacity power electronics converter technologies• Advanced semi-conductor device developments• Advanced smart grid methodology development for integrated

resource/load energy management and control• Enhancement of existing interconnecting alternating current (AC)

infrastructure• Enabled development of additional HVDC delivery infrastructurep y• Increased efficiency and lower operating losses in overall power

system delivery, generation, and end-use applications

AcknowledgmentsAcknowledgments

The Commonwealth of Pennsylvania –Dept. of Community and Economic Development, Ben Franklin Technology Development AuthorityBen Franklin Technology Development Authority

University of Pittsburgh –Electric Power Research Group Graduate Students: ect c o e esea c G oup G aduate Stude tsBrandon Grainger, Matthew Korytowski, Emmanuel Taylor

Q & AQ & A

THANK YOUTHANK YOU