Integrated Solid State Transformer (I-SST) Concepts for ...file.cpss.org.cn/upload/2e507efd-47ac-43e7-ac5d... · PWM ac-ac AC Filter Converter AC Filter b a 1 V x V c V O MV LV S

Power Electronics & Power Quality Laboratory, Texas A&M University, [email protected]

Integrated Solid State Transformer (I-SST) Concepts

for Utility Interface of Power Conversion Systems

Prasad Enjeti, Electrical & Computer Engineering

Texas A&M University

http://enjeti.tamu.edu

作者授权中国电源学会发布，未经作者同意禁止转载

http://enjeti.tamu.edu/

Introduction to Texas A&M Engineering

College Station

•Founded 1876•Total 65,000 Students

•Engineering Students ~ 20,000

•14 Departments•21 Degrees•Top 10

•Growth Plan 25,000 engineering students by 2025


College of EngineeringLargest college at Texas A&M

More than 20,000 students in 14departments

3rd

8thUndergraduate Program

Departments Rankedin Top 10

Research Expenditures

7SOURCES

Student enrollment includes undergraduate and graduate students from TAMU College Station, Galveston and Qatar campuses, and Engineering Academies

2017 U.S. News & World Report Rankings of Public UniversitiesAmerican Society for Engineering Education (2016 report)

@tamuengineering | #TAMUengrengineering.tamu.edu/easa

Nationally Recognized Programs


Texas A&M Electrical & Computer Engineering



Technology for the Grid of the Future

1) Brief overview of SST / Smart Transformer approaches 2) Smart Transformers in smart-grid – advantages 3) Smart Transformers for Interconnected Microgrids4) I-SST for EV Charging Stations5) I-SST for ASDs / Compact MV-ASDs / MV Power Distribution 6) I-SST for Grid Interconnected Renewables: PV / Wind / Battery

7) Conclusion

Integrated Solid State Transformer (I-SST)



Today Today we have a radial power distribution system with 3 major objectives:1. Improve reliability i.e. faults are isolated

rapidly2.Minimize the delivery losses (not paid by the

customer)3.Deliver high quality electricity – especially

voltage magnitude

• These objectives are typically achieved via distribution management systems (DMS). One of the function of DMS is FISR, fault isolation and service restoration. FISR controls the opening and closing of circuit breaker to increase reliability.

• The other function of DMS is VVC, volt var control. VVC controls voltage control devices, such as load tap changer, voltage regulators and capacitors bank to minimize the delivery losses while maintaining a good voltage profile along feeders.作者授权中国电源学会发布，未经作者同意禁止转载

• Solar PV generation is one of the fastest growing sources of renewables

• Majority of new solar installations are being done at distribution level

Dynamic Impact of Power Electronics Intelligence at the grid edge • Jorge Ramos

Renewables on the Rise

Berkeley Lab: Installed Cost of Solar Photovoltaic Systems in the U.S. Declined Significantly in 2010 and 2011 Southern light solar

NREL: Integrating High Levels of Variable Renewable Energy into Electric Power Systems

• 30% renewable energy penetration is possible with minimal changes*

What is needed for higher levels of penetration?* NREL Power Systems Engineering Center


Tomorrow - Increased Renewable Energy Integration


Solid State Transformer Market Forecast 2017 to 2022

Solid State Transformer Market is projected to witness a compound annual growth rate of 32.09% to reach to total market value of US $487.474 million by 2022

With an increase in the use of distributed energy sources, SSTs are expected to offer better control / Enable Energy Saving / Smart Grid Functionalities


Transformer Basics

SST Concepts in Traction & Smart Grid Applications – J.W. Kolar etal, ECCE Europe 2012 作者授权中国电源学会发布，未经作者同意禁止转载

Smart Transformer – 60Hz

• Smart Transformer can respond to fluctuations within the power grid instantly acting as voltage regulators and thereby reducing energy consumption by providing optimized voltage at the point of common coupling (PCC)

• At PCC, they can control the active power exchange between the microgrid and utility

• Enhance power quality and reduce grid losses

60Hz smart transformer is a low hanging fruit

Power Electronics on LV Side



Vo = Vx + D Vy

Vo = Vx + VcD = Duty Cycle 0 < D < 1

• The output voltage (Vo) is regulated by adjusting the duty ratio (D) of the AC-AC Converter

• Voltage sag & voltage swell can be compensated

PWM ac-acConverter AC FilterAC Filter

b

a

1

Vx

Vc

VO

MV

LV

S1

S1

S2

S2Vf



PWM ac-acConverter AC FilterAC Filter

NS1

NS2

NP

VO2

VO1

VO

160 V

80 V

11 kV 120V

HV

LV

Load Voltage (Vo)

Converter Voltage

Main Sec. Voltage (Vx)

Utility Voltage


b

a

AC-ACConverter

Vy Vc

LOADVoVs

Vx

1Io

Ic

Is

Io

D

Vs: 10% THDv

Vo: 3.5% THDv


Can Correct for Steady

State Voltage

Distortions



Boost MPPTInverter

• Voltage Regulation • VAR Compensation • Power Monitoring• Energy Budgeting

Technology for the Grid of the Future – as smart at the internet 作者授权中国电源学会发布，未经作者同意禁止转载

Smart Transformer – High Frequency


Smart Transformer – High Frequency


Smart Transformers in Microgrids



Micro grid 3Total capacity=200 kW

Renewable capacity=80 kWFossil fuel capacity=120 kW

80kW

90kW Utility grid

VA=VA 0

VA’=VA’ δ 40kW

45kW


Renewable capacity=40 kWFossil Fuel capacity=60kW

120kW

50kW


Renewable capacity=150 kWFossil Fuel capacity= 50 kW

415kW

10kW


Renewable capacity=490 kWFossil Fuel capacity=10 kW

BESS+ -

100kW

155 kW



Load170 kW

Load170 kW

Load85 kW

Load425 kW

Load255 kW

20kW

470kW

30 kW

25 kW

20kW


AC-AC Full Bridge with bi-directional switches

VC’

VB’

VA’

VAB

Lf1

Cf

d1n1VAB

d3n3VCA

n3VCAd3n3VCA

1

VBC

VCA

n1

n2

n3

VA

VB

Microgrid Distribution

Voltage

Fractionally Rated

Transformer

AC-AC Converter (fractional rated) with bi-directional

switches

Medium Voltage

Transformer

Medium Voltage Microgrid Interface Point of Common

Coupling

VCLf2

d2n2VBC

Proposed five microgrid configuration with Modified Angle Droop Control

VA

VC VB

VAB

VCA

VBC

1 p.u.

- 45°

-d1 n1 VAB

d2 n2 VBC

VA’



80kW

90kW Utility grid

VA=VA 0

VA’=VA’ δ 40kW

45kW



120kW

50kW



415kW

10kW



BESS+ -

100kW

155 kW



Load170 kW

Load170 kW

Load85 kW

Load425 kW

Load255 kW

20kW

470kW

30 kW

25 kW

20kW



Smart Transformers in Microgrids σδi

δ*

Pi

δi

+- PI

Pi,desiredδi,modify

+- ++ +-Pi*

a)



80kW

90kW Utility grid

VA=VA 0

VA’=VA’ δ 40kW

45kW



120kW

50kW



415kW

10kW



BESS+ -

100kW

155 kW



Load170 kW

Load170 kW

Load85 kW

Load425 kW

Load255 kW

20kW

470kW

30 kW

25 kW

20kW

At t=0.1sec, the system load changes from 25% to 85%, after t=0.2 sec, μG5 provides 25kW, 12.1 kVAR to μG1and 30 kW, 14.5 kVAR to μG2.作者授权中国电源学会发布，未经作者同意禁止转载

Electronic TransformerMedium Frequency / High Frequency


Transformer Size is a ConcernVolume and weight of the

transformer are importantin high density urbansettings with low availablespace.

Size is also a concern inunderground installations,moving power systems suchas ships, factories, etc.


Electronic Transformer – McMurray 1968

SST Concepts in Traction & Smart Grid Applications – J.W. Kolar etal, ECCE Europe 2012

US Patent 3,517,300 June 23, 1970


Electronic Transformer – McMurray 1968

SST Concepts in Traction & Smart Grid Applications – J.W. Kolar etal, ECCE Europe 2012

US Patent 3,517,300 June 23, 1970

Fully bidirectional power flowOutput voltage regulation


Transformer Cores – Price Comparison

Price ~= USD 2000 per Metric Ton

Grain Oriented Silicon Steel Sheets

Amorphous Core Material

Nanocrystalline Core Material



Ferrite Core Material



Medium Frequency TransformerTransformerDesign

M19 Core60 Hz

M19 Core600 Hz

Metglass 600 Hz

Operating Frequency (Hz) 60 600 600

Max. Flux Density (T) 1.25 0.55 1.1

Core Dimensions (cm) 62 X 4 X 7.5 54 X 5 X 2.5 60 X 4.5 X 2.5

Number of turns (#) 250 140 180

Core Volume (L) 1.9 0.67 0.62

Core Weight (kg) 14.8 5.3 5.0

Core Loss/Mass (W/kg) 1.7 7.5 1.8

Net Core Loss (W) 25 40 9

Winding Loss (W) 20 6 8

Total Transformer Loss (W) 45 46 17

Efficiency at 1.6 kVA (%) 97.3 97.2 99.0

Cost of Core (p.u.) 1.0 0.35 1.0

Cost of Winding (p.u.) 0.4 0.13 0.2

Total Cost (p.u.) 1.4 (1pu) 0.48 (0.34) 1.2 (0.86)

Use the Cost Savings 0.66 pu to Pay for

Power Converter / Controls / Protection


Medium Frequency Transformer

• 1 kHz transformer is about ¼ the size of its 60Hz counterpart• The difference in cost can possibly fund power electronics 作者授权中国电源学会发布，未经作者同意禁止转载

Medium Frequency Transformer

• Modulated with a MF square wave (switching frequency fsw)

• AC-AC converter modulates the line frequency (fs) sine wave into ‘fsw ± fs‘ Hz andhigher frequency components

• No line frequency components in the transformer voltage

Add Enjeti / Kang / Pitel paper – from conference – 1997??


Medium Frequency TransformerRIGBTs

• For unidirectionalpower flow –Replace 4 IGBTswith 4 diodes – asshown

• No energy storagecomponents

+-

Q1

Q3

Q2

Q4

QA

QB

QC

QD

vp

Leading leg

Lagging leg

ZVS with phase-shift Modulation


Medium/High Frequency TransformerModular Concept with WBG Devices

•On the primary side several low voltage converters are staked

•All primary converter outputs are coupled to common core

•Voltage sharing on series connected converters is guaranteed

•No bulky energy storage components

•ZVS contributes to high efficiency

+-

Q1

Q3

Q2

Q4

QA

QB

QC

QD

vp

Leading leg

Lagging leg


Industrial Applications that can benefit from

Integrated – Solid State Transformer (I-SST)



vpri_b+

-

ipri_b

vpri_c+

-

ipri_c

vpri_a+

-

+

-Vo

as

bscs

Lout1

ia

ib

ic

va

vb

vc

Thre

e-Ph

ase

Inpu

t Filt

er a

b

c

Lout2

ida

idc

idb

AC-AC

AC-AC

AC-AC

+-

Q1

Q3

Q2

Q4

QA

QB

QC

QD

vp

Leading leg

Lagging leg

-500

50

-5000

500

-100

0

100

0.05 0.06 0.07 0.08 0.090

200400600

ia

Vpri_a

ida

Vrec

20 kHz Operation

6 Pulse Input current quality is poor



vpri_b+

-

ipri_b

vpri_c+

-

ipri_c

vpri_a+

-

+

-Vo

as

bscs

Lout1

ia

ib

ic

va

vb

vc

Thre

e-Ph

ase

Inpu

t Filt

er a

b

c

Lout2

ida

idc

idb

AC-AC

AC-AC

AC-AC

+-

Q1

Q3

Q2

Q4

QA

QB

QC

QD

vp

Leading leg

Lagging leg

20 kHz Operation

6 Pulse

AC-AC

+

-Vo1

n

ibia

vc

vb

va

ic

AC-AC

+

-Vo2

AC-AC

+

-Von

APF

iA3

iA2

LA

LA

LA

iA1

Input current quality is high



+-

Q1

Q3

Q2

Q4

QA

QB

QC

QD

vp

Leading leg

Lagging leg

20 kHz Operation

Open Delta

ia

ib

ic

va

vb

vc

vab

vbc

Thre

e-Ph

ase

Inpu

t Filt

er

AC-AC

vpri_ab

ipri_ab

+

-

AC-AC

vpri_ab

ipri_ab

+

-

Cout

Lout

Vo

+

-

as

bscs

vrec+

-

ida

idc

idb

Input current quality is poor作者授权中国电源学会发布，未经作者同意禁止转载


+-

Q1

Q3

Q2

Q4

QA

QB

QC

QD

vp

Leading leg

Lagging leg

20 kHz Operation

Open Delta

ia

ib

ic

va

vb

vc

vab

vbc

Thre

e-Ph

ase

Inpu

t Filt

er

AC-AC

vpri_ab

ipri_ab

+

-

AC-AC

vpri_ab

ipri_ab

+

-

Cout

Lout

Vo

+

-

as

bscs

vrec+

-

ida

idc

idb

Cout

Lout

Vo

+

-

as

bscs

vrec+

-

ida1

idc1

idb1

ia

ib

ic

va

vb

vc

Th

ree-

Ph

ase

In

pu

t F

ilte

r

AC-AC

AC-AC

AC-AC

AC-AC

AC-AC

AC-AC

vab

vab

Series Cascade for higher voltage


EV Charging Application with Integrated

Solid State Transformer


EV Charging Application – with I-SSTHV grid

ACDC

DCDC

ACDC

DCDC

Step-down Transformer

HV grid

ACDC

DCDC

DCDC

DCDC

Step-down Transformer

• AC bus architecture with step-down line frequency transformer [1],[2].

• DC bus architecture with line frequency transformer [2],[3].

• Level-3 Chargers are rated > 50kW

• Both approaches use line frequency transformer which compromise the size of the Level-3 charging station

How can we improve the power density of the system?


EV Charging Application – with I-SST

ia

L1out

Coutib

ic

va

vb

vc

Thr

ee-P

hase

Inpu

t Filt

er

vpri_ab

vpri_bc

vpri_ca

ida1

vsec1 <-15°

vsec2 <+15°

va1b1

va2b2

Vout

+

-

vrec1

+

-

vrec2

+

-

+

-

+

-

+

-

ida2

vab

L2out

vbc

vca

ipri_ab

ipri_bc

ipri_ca

a

b

c

a1

b1

c1

a2

b2

c2

Ioutidb1

idc1

idb2

idc2

vout

+

-

Utility Grid AC-AC Converter and High-Frequency Transformer (20 kHz)

12 Pulse Rectifier

12 Pulse


vab

D1 D2

D4 D3

S1

S4

S2

S3

+-vp vpri_ab

Rectification Weak DC-Link

High Frequency modulation

vab vp vpri_ab

Operation Principle

• 50% duty cycle provides maximum AC link voltage.

• Change of Duty Cycle allows output voltage regulation.

𝐷𝐷 = 0.5

𝐷𝐷 = 0.3

𝐷𝐷 = 0.15

DT1

T1

1

1

ssw𝑠𝑠𝑠𝑠𝑠𝑠 = �𝑘𝑘=1

∞1𝑘𝑘𝑘𝑘 sin 2𝑘𝑘𝑘𝑘𝐷𝐷 − sin 2𝑘𝑘𝑘𝑘

12 + 𝐷𝐷 sin 𝑘𝑘𝑘𝑘𝑠𝑠𝑡𝑡 + ⋯

… +12𝑘𝑘𝑘𝑘 1 − cos 2𝑘𝑘𝑘𝑘𝐷𝐷 + cos 𝑘𝑘2𝑘𝑘

12 + 𝐷𝐷 − cos 𝑘𝑘𝑘𝑘 cos 𝑘𝑘𝑘𝑘𝑠𝑠𝑡𝑡

40 of 19



Output Voltage Analysis

𝑠𝑠𝑑𝑑𝑑𝑑𝑑𝑑 = 𝑠𝑠𝑑𝑑 𝑘𝑘𝑡𝑡 � 𝑠𝑠𝑠𝑠𝑠𝑠

𝑣𝑣𝑟𝑟𝑟𝑟𝑟𝑟1 𝑘𝑘𝑠𝑠𝑡𝑡 = 𝑣𝑣𝑎𝑎1𝑠𝑠𝑑𝑑𝑑𝑑𝑑𝑑 + 𝑣𝑣𝑏𝑏1𝑠𝑠𝑑𝑑𝑑𝑑𝑑𝑑 + 𝑣𝑣𝑟𝑟1𝑠𝑠𝑑𝑑𝑑𝑑𝑑𝑑

𝑣𝑣𝑎𝑎1 = 2𝑉𝑉𝐿𝐿𝐿𝐿 sin 𝑘𝑘𝑡𝑡 −𝑘𝑘

12� 𝑠𝑠𝑠𝑠𝑠𝑠

𝑠𝑠𝑑𝑑(𝑘𝑘𝑡𝑡) = �𝑛𝑛=1,3,5,7…

∞4𝑛𝑛𝑘𝑘

cos𝑛𝑛𝑘𝑘6

� sin 𝑛𝑛𝑘𝑘𝑡𝑡

𝑣𝑣𝑟𝑟𝑟𝑟𝑟𝑟1 = 𝑠𝑠𝑠𝑠𝑠𝑠 � 𝑠𝑠𝑠𝑠𝑠𝑠 �3 2𝑘𝑘

𝑉𝑉𝐿𝐿𝐿𝐿 1 −�𝑛𝑛=1

∞2

36𝑛𝑛2 − 1cos 6𝑛𝑛𝑘𝑘𝑡𝑡

L1out

Cout

vpri_ab

vpri_bc

vpri_ca

ida1

vsec1 <-15°

vsec2 <+15°

va1b1

va2b2

Vout

+

-

vrec1

+

-

vrec2

+

-

+

-

+

-

+

-

ida2

L2out

ipri_ab

ipri_bc

ipri_ca

a1

b1

c1

a2

b2

c2

Ioutidb1

idc1

idb2

idc2

vout

+

-

𝑉𝑉𝑜𝑜𝑜𝑜𝑜𝑜 =12𝐷𝐷 2𝑘𝑘

𝑉𝑉𝐿𝐿𝐿𝐿

41 of 19

DT1

T1

1

1

ssw

T2

2DT2

1 ssw ssw


Input Current Analysis

ia

ib

ic

va

vb

vc

Thre

e-Ph

ase

Inpu

t Filt

ervpri_ab

vpri_ca

+

-

+

-

+

-

vab

vbc

vca

AC-AC

AC-AC

ipri_ab

ipri_bc

ipri_ca

AC-AC

a

b

c

vpri_bc

ida1

vsec1 <-15°

vsec2 <+15°

va1b1

va2b2ida2

a1

b1

c1

a2

b2

c2

idb1

idc1

idb2

idc2

𝑖𝑖𝑝𝑝𝑟𝑟𝑝𝑝_𝑎𝑎𝑏𝑏 = 𝑁𝑁𝑠𝑠1 𝑖𝑖𝑑𝑑𝑎𝑎1 + 𝑖𝑖𝑑𝑑𝑎𝑎2 − 𝑁𝑁𝑠𝑠2 𝑖𝑖𝑑𝑑𝑏𝑏2 + 𝑖𝑖𝑑𝑑𝑟𝑟2

𝑠𝑠𝑑𝑑𝑝𝑝 = �𝑛𝑛=1,3,5,7…

∞4𝐼𝐼𝑜𝑜𝑜𝑜𝑜𝑜𝑛𝑛𝑘𝑘

cos𝑛𝑛𝑘𝑘6

sin 𝑛𝑛𝑘𝑘𝑡𝑡

𝑖𝑖𝑎𝑎 = 𝑠𝑠𝑠𝑠𝑠𝑠 � 𝑖𝑖𝑝𝑝𝑟𝑟𝑝𝑝_𝑎𝑎𝑏𝑏

𝑖𝑖𝑎𝑎 = 𝑠𝑠𝑠𝑠𝑠𝑠 � 𝑠𝑠𝑠𝑠𝑠𝑠 �4 3𝐼𝐼𝑜𝑜𝑜𝑜𝑜𝑜

𝑘𝑘

sin 𝑘𝑘𝑡𝑡 +1

11sin 11𝑘𝑘𝑡𝑡 +

113

sin 13𝑘𝑘𝑡𝑡

+1

23sin 23𝑘𝑘𝑡𝑡 +

125

sin 25𝑘𝑘𝑡𝑡 + ⋯

Harmonics generated by 𝑆𝑆𝑠𝑠𝑠𝑠 do not affect input current quality because they are at high frequencies!

42 of 19


Design ExampleOperating conditions used forsimulation in PLECSGrid voltage(line-to-line rms)

480 V rms

Grid frequency 60HzOutput dcvoltage

500 V

Rated power 50 kWSwitchingFrequency

20kHz

Input Inductor 25 µHOutput Inductor 1 mHOutput Capacitor 200 µFTransformer 𝐾𝐾𝑜𝑜 0.44 𝐾𝐾𝑜𝑜 =

𝑘𝑘 � 𝑉𝑉𝑜𝑜𝑜𝑜𝑜𝑜6 2𝑉𝑉𝐿𝐿𝐿𝐿

ia

Utility Grid AC-AC Converter and High-Frequency Transformer (20 kHz) L1out

Coutib

ic

va

vb

vc

12 Pulse Rectifier

Thre

e-Ph

ase

Inpu

t Filt

er

vpri_ab

vpri_bc

vpri_ca

ida1

vsec1 <-15°

vsec2 <+15°

va1b1

va2b2

Vout

+

-

vrec1

+

-

vrec2

+

-

+

-

+

-

+

-

ida2

vab

L2out

vbc

vca

AC-AC

ipri_ab

ipri_bc

ipri_ca

AC-AC

a

b

c

a1

b1

c1

a2

b2

c2

Iout

AC-AC

idb1

idc1

idb2

idc2

vout

+

-

43 of 19

Transformer’s Gain


ia

ib

ic

va

vb

vc

Thre

e -Ph

ase

Inpu

t Filt

er

vpri_ab

vpri_ca

+

-

+

-

+

-

vab

vbc

vca

AC-AC

AC-AC

ipri_ab

ipri_bc

ipri_ca

AC-AC

a

b

c

vpri_bc

Simulation Results

× 1e4Frequency

1.96 1.98 2.00 2.020

200

400

× 1e4Frequency

0 1 2 3 4 5 6 70

200

400vpri_ab

-5000

500

-5000

500

× 1e-21.0 1.5 2.0 2.5 3.0 3.5-500

0500

vpri_bc

vpri_ca

0

50

100

Frequency0 200 400 600 800 1000

0.02 0.04 0.06 0.08 0.10 0.12-100

0

100

11th 13th

ia

ia FFT

100

100

0

100

50

0.02 0.03 0.04 0.05 0.06-400-200

0200400

ia

ia ib ic

va

0.02 0.03 0.04 0.05 0.06

-500

50

+ PIModulation AlgorithmVout

Vout

*S1S2S3S4

+

-

D

Voltage closed loop0.02 0.04 0.06 0.08 0.10 0.12 0.14

-100

0

100

0.02 0.04 0.06 0.08 0.10 0.12 0.140.00.20.4

0.02 0.04 0.06 0.08 0.10 0.12 0.14

200400600

ia

D

Vout

-5000

500

-5000

500

× 1e-22.750 2.754 2.758 2.762 2.766-500

0500

vpri_ab

vpri_bc

vpri_ca

-5000

500

-5000

500

× 1e-22.750 2.754 2.758 2.762 2.766-500

0500

vpri_ab

vpri_bc

vpri_ca

44 of 19


Experimental Prototype

DSP

AC-AC Converter

Voltage and current sensors

DC power supply

12 Pulse rectifier

Output filter

Transformer

Input Filter

• 20 kHz, 10 kW Ferrite core transformer.

• 3 independent cores. 14 x 5 x 3 cm.

• 2 kW experimental layout. • 208 VLL RMS• 500 V DC output• 20 kHz switching frequency

45 of 19


ia

L1out

Coutib

ic

va

vb

vc

Thre

e-Ph

ase

Inpu

t Filt

er

vpri_ab

vpri_bc

vpri_ca

ida1

vsec2 <+15°

va1b1

va2b2

Vout

+

-

vrec1

+

-

vrec2

+

-

+

-

+

-

+

-

ida2

vab

L2out

vbc

vca

AC-AC

ipri_ab

ipri_bc

ipri_ca

AC-AC

a

b

c

a1

b1

c1

a2

b2

c2

Iout

AC-AC

idb1

idc1

idb2

idc2

vout

+

-

Experimental Results

vpri_ab

ipri_ab

ia

11th 13th

Vout (511.7 V) Iout (3.389 A)

vpri_ab

ipri_ab

ia

Vout (299.4 V)

Iout (2.063 A)

D=0.5D=0.25

46 of 19


L1out

Cout

ida1

va1b1

va2b2

Vout

+

-

vrec1

+

-

vrec2

+

-

ida2

L2out

a1

b1

c1

a2

b2

c2

Ioutidb1

idc1

idb2

idc2

vout

+

-

ida1

ida2

va1b1

va2b2

vrec1

vrec2

vout

47 of 19


EV Charging Application – with I-SSTOpen Delta 12 pulse

vpri_ab+

-

ipri_ab

+-

Q1

Q3

Q2

Q4

Q7

Q5

Q6

Q8

vab vp

ia

ib

ic

va

vb

vc vbc

Thr

ee-P

hase

Inp

ut F

ilter

+-

Q1

Q3

Q2

Q4

Q7

Q5

Q6

Q8

vp

a1

b1c1

a2

b2c2

va1b1

va2b2

ida1

idc1

idb1

ida1

idb2

idc2

vpri_bc+

-

ipri_bc

L1out

Vout

L2out

Cout +

-

Ioutvrec1

vrec2

+

-

+

-

Three phase input

AC-AC Converter and High-Frequency Transformer (20 kHz)

12 Pulse Rectifier

+150

−150



vpri_ab+

-

ipri_ab

+-

Q1

Q3

Q2

Q4

Q7

Q5

Q6

Q8

vab vp

ia

ib

ic

va

vb

vc vbc

Thr

ee-P

hase

Inp

ut F

ilter

+-

Q1

Q3

Q2

Q4

Q7

Q5

Q6

Q8

vp

a1

b1c1

a2

b2c2

va1b1

va2b2

ida1

idc1

idb1

ida1

idb2

idc2

vpri_bc+

-

ipri_bc

L1out

Vout

L2out

Cout +

-

Ioutvrec1

vrec2

+

-

+

-

Three phase input

AC-AC Converter and High-Frequency Transformer (20 kHz)

12 Pulse Rectifier

Open Delta 12 pulse

Input current quality is high

+150

−150



High Frequency Integrated Solid State Transformer (SST) 20 kHz (N2/N1) = 1For high voltage level, series stack of AC to AC converter can be connected

in series at the primary sideMedium Voltage

Vbn

Vcn

ib LS

LS

Van LS

Idc

Q5

A

Q2

Q1 Q3

Q4 Q6

iB

+

VLoad

Three phase Selective Harmonic PWM Converter

Ld

iA

iCB

C

VAS

VBS

VCS

VAP1

VAPn

VBP1

VBPn

VCP1

VCPn

LC InputFilter

iub

iua

iucic

ia

Input Filter

IQ1

IQ2

LegA

Vin60 HZ

VOut20 kHz VC

+

SiC Bidirectional AC/AC Converter with a weak DC link

S2b

S3b

S2a

S3a

S1a

S4a

S1b

S4b

EV Charging System

Vre

c

+

HF Isolation ; ZVS operation of I-SST ; Scale to high power with WBG technology 作者授权中国电源学会发布，未经作者同意禁止转载


HF Isolation ; ZVS operation of I-SST ; Scale to high power with WBG technology

VDC for the rectification Mode

Unfiltered input current for phase “a” iUa

Van Line frequency (60 Hz)

Input voltage ; Output voltage and Input current

VBP

FFT of the VBPThe dominant freq. is

around 20 kHz

Frequency spectrum for the transformer voltage VBP, The dominant frequency is around (20 kHz)

VLoad

I PV

Q 5

A

Q 2

Q 1 Q 3

Q 4 Q 6

+

L d

B

C

I Q 1

I Q 2


in series at the primary side

Utility Grid

Vbn

Vcn

Van

iB


iA

iC

VSAVP A

iub

iua

iuc

EV Charging System

VSBVP B

VSCVP C

Vre

c

+


Adjustable Speed Drive Systemswith Integrated



MV Adjustable Speed Drive – with I-SST

Large 60Hz input transformer

• MV-ASD system (ABB) with 24-pulse diode bridge rectifier configuration and 3-level,3-phase NPC inverter作者授权中国电源学会发布，未经作者同意禁止转载

Texas A&M University - Power Electronics & Power Quality Laboratory

[email protected]

Major Factors Influencing Power Density:

• EMI Filter (~ 2.5 L); DC-Link Capacitors (~ 0.5 L); Heat Sink (~ 0.5 L)Transformer (~ 14 L) > 70%

Large 60Hzinputtransformer



[email protected]

Proposed Medium Frequency Transformer for ASDs

Utility line current



[email protected]

Experimental Results


MV Adjustable Speed Drive – with I-SST• Modular inverter cells• Multi phase input transformer• High quality input/output

waveforms• Large size & weight







AC/AC Converter and Integrated Hight Frequency Solid State Transformer

VC

+

Van VAB Pri.

SiC Bidirectional AC/AC Converter with a weak DC link

S2b

S3b

S2a

S3a

S1a

S4a

S1b

S4b

Utility Supply

Vbn

Vcn iUc

Van

GND

NS1

iUb

iUa

(+200)

iap

ibp

iac

(-200)

SWAC-AC

SWAC-AC

SWAC-AC

NPA

NPB

NPC

NS2

NS3

( 00)

18-Pulse Diode Rectifier

NPC Inverter

C

L

C

L

C

L

M

NPC Inverter

Time (s)

HF (20kHz) Transformer

HF Isolation ; ZVS operation of I-SST ; Scale to high power with WBG technology 作者授权中国电源学会发布，未经作者同意禁止转载

Grid Connected Renewableswith Integrated



Large Scale PV Plant – Centralized Inverter• PV modules wired in series/parallel to 1500V DC• Central Inverter • DC coupling of PV panels• Large size medium voltage transformer interfaces PV plant with the utility grid.

DC Collection

Source: SMA Solar Technology


PV Interface – with I-SST

500 V

500 V

DC-DC converter & Medium Frequency

Isolation Transformer

690 V ac

Cell A1

Cell A2

Cell A11

Cell B1

Cell B2

Cell B11

Cell C1

Cell C2

Cell C11

DC-AC Inverter

CPV

CPV

Cpg Csg

Cps

Medium Voltage Utility

Bus – 13 kV

a

bc

• Series stacked inverter modules.

• High quality multi-level PWM output.

• Line frequency transformer is eliminated.

• Employs standards 690 V inverters with 1700 V IGBTs .

• Suitable for MW scale applications.


PV Interface – with I-SST

Is∠ 180° Vs∠ 0°

VL= IsXs∠ 270° V1∠ δ1 °

δ

V2∠ δ2 °

Vn∠ δn °

VAO∠ δ °

n21AO VVVV +++=

Is∠ -(180-θ)° Vs∠ 0°

V1∠ δ1 °

δ

Vm∠ δm ° Vm+1∠ δm+1 °

Vn∠ δn °

VAO,1∠ δ °

VL = jXs .Is∠ -(180-θ)°

n21AO VVVV +++=

500 V

500 V

DC-DC converter & Medium Frequency

Isolation Transformer

690 V ac

Cell A1

Cell A2

Cell A11

Cell B1

Cell B2

Cell B11

Cell C1

Cell C2

Cell C11

DC-AC Inverter

CPV

CPV

Cpg Csg

Cps

Medium Voltage Utility

Bus – 13 kV

a

bc


AC – Collection Grid for Large Scale PV

Several hundred 3-phase

transformerlessinverters are

employed



AC – Collection Grid for Large Scale PV

480Vrms60 Hz Frequency

480V/20kV

Layout of Eggebek Solar Park

Sector 1

• Danfoss 3-phase 480V AC Inverters are grouped together

• Droop control is employed for power sharing

• 3-phase, 480V, 50Hz AC cables are laid in the field

• A 480V/20kV utility high turns ratio transformer is employed

• Cable size/length/cost are an issue

• No DC-circuit protection


PV Interface – with I-SSTVabc3 Phase LC

Filter3 Phase MF transformer 3 Phase to 3 Phase

Cycloconverter100 KW Inverter

+

1000V

-

100 KW Inverter

+

1000V

-

100 KW Inverter

+

1000V

-

• Medium frequency transformer isolates pvand distribution grid

• AC power collection at higher voltage / frequency

• Reduced cable ohmiclosses

• Employs 400Hz to 60Hz 3-phase AC/AC line-commutated cycloconverter.

• Increased overall efficiency by 2%

• Eliminates bulky line frequency transformer; reduces site preparation & allows for more room for pv arrays.


PV / Battery Interface – with I-SST

HF Isolation ; ZVS operation of I-SST ; Scale to high power with WBG technology

VPV

I PV

Q 5

A

Q 2

Q 1 Q 3

Q 4 Q 6+

L d

PV Plant

1.5 KV120 KW

B

C

I Q 1

I Q 2


in series at the primary side

Utility Grid

Vbn

Vcn

Van

iB


iA

iC

VSAVP A

iub

iua

iuc

PV Farm

VSBVP B

VSCVP C

Vre

c

+

VBP

FFT of the VBPThe dominant freq. is

around 20 kHz

Frequency spectrum for the transformer voltage VBP, The dominant frequency is around (20 kHz)

Unfiltered input current for phase “a”

Van Line frequency (60 Hz)

VDC for the inversion Mode (Negative value)

Inversion Mode Operation


Wind Energy Interface – with I-SST

Transformer


Wind Energy Interface – with I-SST

• Transformer size / weight / cost is an issue

• Utility transformer is sometimes located onthe top of the tower. Large size adds to thecost of the structure作者授权中国电源学会发布，未经作者同意禁止转载

Wind Energy Interface – with I-SSTSmaller sizeMF Transformer

Existing hardware


MV (13.8 KV) – Power Distribution Systems for Data Centers with transformative performance

DC Distribution for Servers (48V high current)


Thank you!!Current Ongoing

Research

• Micro-grids – PINE – Grid Edge

• HF Converters – GaN / SiC• Integrated Solid State

Transformers • Cybersecurity of Grid

Connected Power Electronics Hardware


Documents

Integrated Solid State Transformer (I-SST) Concepts for ...file.cpss.org.cn/upload/2e507efd-47ac-43e7-ac5d... · PWM ac-ac AC Filter Converter AC Filter b a 1 V x V c V O MV LV S