Modular Multilevel Converter - Technology & Principles - Siemens

1 10-2009 Power Transmission DivisionE T PS SL/Re

Title in English


Title in English

Modular Multilevel Converter –Technology & Principles

Dietmar Retzmann

Power Transmission Division

© Siemens AG 2009Energy Sector


Source: National Transmission Grid Study; U.S. DOE 5/2002 – “Preview”

System Enhancement necessary !

Source: ITC 8/2003 – “Blackout”

The US Blackout 2003:Congestion, Overloadsand Loop Flows

Problems only in thesynchronously interconnected Systems

* PTDF = Power Transfer Distribution Factor

*

If Power Flow exceeds the Design Criteria: Blackout

PTD3333

E T PS SL/Re

10-2009


Power-Flow Control – with FACTS and HVDC

Voltage Source Injection:

XX

Series Compensation

VV11 VV22

Parallel Compensation

PPACAC ==FACTS

VSCVSC11 or PSTPST22

∼∼

+

… Support of Power Flow

sin (sin (δδ 11 -- δδ 22)

1 Voltage-Sourced Converter

2 Phase-Shifting Transformer

Transmission Angle

PPDCDC

Power Transmission DivisionPower Transmission Division44

E T PS SL/Re

10-2009 E T PS SL/Re10-2009Each of these Parameters can be used for Load-Flow Control and Power Oscillation Damping

G ~ G ~

PPACAC

,, δδ 22,, δδ 11 XXVV11 VV22

HVDC… makes P flow


Control Features of FACTS and HVDC

a)

b)

~

~

G ~

Loads

G ~

Loads

Loads

Loads

G ~

G ~

G ~

PP


a) FACTS: Voltage / Load-Flow Control (one Direction only) & PODb) HVDC Back-to-Back or Long-Distance Transmission:

Voltage / Bidirectional Power-Flow Control, f-Control & POD

FACTS “Classic”

FACTS VSC

∼=

∼=

“Classic”

or VSC

∼∼

+/+/-- PP


HVDC – High-Voltage DC Transmission: It makes P flow

HVDC-LDT – Long-Distance Transmission

HVDC “Classic” with 500 kV – up to 4,000 MW*

HVDC “Bulk” with 800 kV – for 5,000 MW* up to 7,200 MW**

HVDC PLUS (Voltage-Sourced Converter – VSC)

HVDC can be combined with FACTS

V-Control included

Advanced Power Transmission Systems

B2B – The Short Link

Back-to-Back Station

AC AC

DC Cable

AC AC

Submarine Cable Transmission

800 kV for minimal LineTransmission Losses

Long-Distance OHL Transmission

DC Line

AC AC

* LTT = Light-Triggered Thyristor – up to 4 kA ** ETT = Electrically-Triggered Thyristor – up to 4.5 kA


FACTS – Flexible AC Transmission Systems: Support of Power FlowSVC – Static Var Compensator* (The Standard of Shunt Compensation)SVC PLUS (= STATCOM – Static Synchr. Compensator, with VSC) FSC – Fixed Series Compensation TCSC – Thyristor Controlled Series Compensation*TPSC – Thyristor Protected Series Compensation**GPFC – Grid Power Flow Controller* (FACTS-B2B)UPFC – Unified Power Flow Controller (with VSC)

TCSC/TPSC

FSC

ACAC

/ TPSC

/ STATCOMSVC

ACAC

Advanced Power Transmission Systems

GPFC/UPFC

AC AC

/ UPFC

* with LT Thyristors** with special High

Power LT Thyristors

and SCCL **for Short-Circuit Current Limitation

LTT = Light-Triggered Thyristor


LCC, LCC, CSC CSC &&VVSCSC

8 Power Transmission DivisionE T PS SL/Re

Trends in Converter Technologies

10-2009


Pellet of LT Thyristor

Pellet ofGTO / IGCT

IGBT:

IGCT = Insulated Gate Commutated Thyristor

IGBT = Insulated Gate Bipolar Transistor

LTT = Light-triggered Thyristor

GTO = Gate Turn-Off Thyristor

High-Power Semiconductors

Chips / Module


Structure of an IGBT Module (3.3kV – 1,200A)

10 Power Transmission DivisionE T PS SL/Re10-2009Source: Infineon

11 10-2009 Power Transmission DivisionE T PS SL/Re Power Transmission Division

Classification of Converters:A. Line-Commutated Converters

Current Sourced, e.g. HVDC; use of Reactor for keeping the DC Current constant (L is the “Smoothing” Element)

Voltage Sourced – e.g. for Drive Systems, Custom Power and Traction Supplies; use of Capacitor for keeping the DC Voltage constant (C is the “Smoothing” Element)

Features: robust Technology, low Losses, high Ratings (up to > 7 GW for new HVDC Schemes in Asia)

“Synergies” with FACTS, SVC: in some way, TCR is “CurrentSourced”, TSC is “Voltage Sourced” (but no DC Energy Storage)

Switching Frequency is defined by the System Frequency

Converter Technologies – LCC“Turn-On” Capability only, System Frequency is the “Driver” Thyristors

11111111

E T PS SL/Re

10-2009 E T PS SL/Re10-2009

Source: Cigré Task Force B4.43.02 – Future Ratings and Topologies of Power Electronic Systems


B. Self-Commutated Converters (GTO, IGBT, IGCT etc.)Voltage-Sourced ConvertersThe “popular” Solution: 2 or 3-Level ConfigurationMultilevel Converters

Diode clamped“Flying” CapacitorsSubmodules

Series Connected H-Bridge Cells, Chain LinksResonant Converters

Current-Sourced Converters

Matrix Converters

Combinations of Technologies

High SwitchingFrequencies up to several kHz possible, however, with an Increase in Losses

Power Transmission Division

Classification of Converters contd.:

12121212

E T PS SL/Re

10-2009 E T PS SL/Re10-2009

Source: Cigré Task Force B4.43.02 – Future Ratings and Topologies of Power Electronic Systems

13 10-2009 Power Transmission DivisionE T PS SL/Re10-2009 E T PS SL/Re

Semiconductor Losses increase with high Switching Frequencies

kV

v (t), i (t)

t

kA

V = VD + RD x I

PL = v (t) x i (t)

Semiconductor Equivalent

PL = small

PL = very high

I ≈ 0

RDVDi(t)

v(t)

The “Switch” has to absorb a significant Amount of the total Losses

PL ≈ 0

Power Transmission Division10-2009 E T PS SL/ReSchematic Drawing for Turn-On13131313

E T PS SL/Re

10-2009


Use of Power Electronics for HVDC & FACTSTransient Performance and Losses

More Dynamics for better Power Quality:Use of Power Electronic Circuits for Controlling P, V & QParallel and/or Series Connection of ConvertersFast AC/DC and DC/AC Conversion

Transition from “slow” to “fast”

Switching Frequency

On-Off Transition 20 - 80 ms

Depending on Solution

GTO / IGCT

< 500 Hz

IGBT> 1000 Hz1-2 %

Losses

14141414

E T PS SL/Re

10-2009

50/60 Hz

ThyristorThyristor

The Solution for Bulk Power Transmission

2-6 %


The Evolution of VSC and PLUS Technology

15 Power Transmission Division

Power Electronic Devices:

IGBT in PP IGBT ModuleGTO / IGCT

E T PS SL/Re10-2009

Topologies: Two-Level Three-Level Multilevel


Power Quality for AC & DC Systems

16 E T PS SL/Re10-2009 Power Transmission Division

HVDCHVDCwithwith VSCVSC ––

HVDCHVDC PLUSPLUS


HVDC “Classic” versus HVDC PLUS

~= =

~

AC Grid 1 AC Grid 2

G ~G ~G ~G ~

C

AG G

E

CC

E

PDC PDC

Power Reversal by

CurrentVoltage only Enables the Use of XLPE Cables

Use of MI Cables only

DC+

- +

- +

-


HVDC PLUS – Typical P/Q Diagram

1818

E T PS SL/Re

10-2009 E T PS SL/Re10-2009Power Transmission Division

The Reactive Power can be controlled at any Value between the red and blue Curve

-1.00

-0.75

-0.50

-0.25

0.00

0.25

0.50

0.75

1.00

-1.25 -1.00 -0.75 -0.50 -0.25 0.00 0.25 0.50 0.75 1.00 1.25

P [p.u.]

Q [p

.u.]

Rectifier Inverter

“Over-excited”

“Under-excited”

(capacitive)

(inductive)

Example of a P/Q Design Specification

Current Limit

Voltage Limit


HVDC “Classic” – Generic P/Q Diagram

Rectifier Inverter

“Over-excited”

“Under-excited”

The Reactive Power is defined by both red and blue Curves. It is a Function of Active Power and AC-Voltage

(capacitive)

(inductive)

Typically, Reactive Power Consumption of HVDC Classic is Q = 0.5 Pd

-0.15

-0.10

-0.05

0.00

0.05

0.10

0.15

-1.25 -1.00 -0.75 -0.50 -0.25 0.00 0.25 0.50 0.75 1.00 1.25

P [p.u]

Q [p

.u.]



General Features of VSC* Technology


Grid Access for weak AC Networks

Multiterminal easier with 4-Quadrant Capability

Independent Control of Active and Reactive Power

Supply of passive Networks and Black-Start Capability

Low Space Requirements

VSC Technology makes it feasible

* VSC: Voltage-Sourced Converter

HVDC PLUS offers additional Benefits

High dynamic Performance


Benefits of HVDC PLUS

Low Switching Frequency

Reduction in Losses

Less Stresses

In Comparison with 2 and 3-Level Converter Technologies

… with Advanced VSC Technology

Siemens uses MMC Technology(Modular Multilevel Converter)

~

=

=

~

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=

21212121

E T PS SL/Re

10-2009 PTDClean Energy to and from Platforms & Islands …


HVDC PLUS with MMC – Basic Scheme


PM 1

PM 2

PM n

PM 1

PM 2

PM n

PM 1

PM 2

PM n

PM 1

PM 2

PM n

PM 1

PM 2

PM n

PM 1

PM 2

PM n

ud

Phase Unit

Vd

10-2009

IGBT2D2

D1IGBT1

Power Module (PM)

Power Electronics

Converter Arm


The Result: MMC – a perfect Voltage Generation

23 Power Transmission Division

VConv.

- Vd /2

0

+Vd /2

AC and DC Voltages controlled by Converter Arm Voltages:

VAC

10-2009 E T PS SL/Re


MMC – AC & DC Converter Currents ...

24 Power Transmission Division10-2009 E T PS SL/Re

… controlled by Voltage Sources

25 10-2009 Power Transmission DivisionE T PS SL/Re25 Power Transmission DivisionE T PS SL/Re

VDC + 200 kV

VDC - 200 kV

PLOTS : Graphs

1.000 1.010 1.020

-250 -200 -150 -100 -50

0 50

100 150 200 250

U [k

V]

+Ud -Ud US1 US2 US3

-2.00

-1.50

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

I [kA

]

is1 is2 is3

-1.50

-1.25

-1.00

-0.75

-0.50

-0.25

0.00

0.25

0.50

0.75

I [kA

]

i1p i2p i3p i1n i2n i3n

AC Converter Voltages

Currents at the AC Terminals

Six Converter Arm Currents

Obviously, no AC Filters required

Results of Computer Simulation: 400 MW with 200 Power Modules per Converter Arm

10-2009

26 10-2009 Power Transmission DivisionE T PS SL/Re26 Power Transmission DivisionE T PS SL/Re

Power Module

PLUSCONTROL

High-Speed Bypass Switch

MMC – Redundant Power Module Design

10-2009

Phase Unit

Single Module Failure


Fully suitable for DC OHL Application:Line-to-Line Fault – a crucial Issue


Phase Unit

PLUSCONTROL

Power Module

Protective Thyristor Switch

10-2009


HVDC PLUS – The Advanced MMC Technology


Some more Views of a 400 MW Converter

10-2009


Control and Protection:System Hierarchy Win-TDC with PLUSCONTROL

I/O Unit

Measuring

I/O Unit

CCSPLUSCONTROL

MMS nMMS 1

Remote HMISCADA InterfaceLocal HMI SIMATIC WinCC

I/O Level

C&P Level

Operator Level

RCI

SIMATIC TDC

Switchgear & Auxiliaries Voltages & Currents Converter – Power Module Electronics

Current Control System

DC ControlP ControlQ Control

30 10-2009 Power Transmission DivisionE T PS SL/Re30 Power Transmission DivisionE T PS SL/Re10-2009

PLUSCONTROL – Main Tasks: Current Control & Module Management

Individual Switching of Power Modules

Power Module Charge Balancing

Calculation of required Converter Arm Voltages

Control of Active and Reactive Power

Current & Voltage Balancing Control

Power Module Monitoring

1

2

n

SIMATIC TDCC&P System

SIMATIC TDCMeasuring System


HVDC PLUS – Modular Multilevel VSC

Faculty of Electrical Engineering and Information Technology – Prof. Dr. St. Bernet31 10-2009 Power Transmission DivisionE T PS SL/Re

“Off“ State “On“ State

Source:PM = Power Module – “Marquardt” Circuit

PM PM

Upper IGBT: offLower IGBT: on

Upper IGBT: onLower IGBT: off



VDC/2

vUM(t)

off

PM4

on

PM5

on

PM6

on

PM7

onoffoffoffVDC/2

PM8PM3PM2PM1vUM

vUM = VDC/2

t

VDC/4

-VDC/4

-VDC/2

vC = VDC/nCellnCell = 4

Phase Unit States and Voltages – for n = 4

Source:

PM8

PM1

PM2

PM3

PM4

PM5

PM6

PM7




VDC/2

vUM(t)

on

PM4

on

PM5

on

PM6

on

PM7

offoffoffoffVDC/4

PM8PM3PM2PM1vUM

vUM = VDC/4

t

VDC/4

-VDC/4

-VDC/2

Source:

PM8

PM1

PM2

PM3

PM4

PM5

PM6

PM7



Source:


VDC/2

vUM(t)

on

PM4

on

PM5

on

PM6

off

PM7

offonoffoff0V

PM8PM3PM2PM1vUM

vUM = 0V

t

VDC/4

-VDC/4

-VDC/2

PM8

PM1

PM2

PM3

PM4

PM5

PM6

PM7



Source:


VDC/2

vUM(t)

on

PM4

on

PM5

off

PM6

off

PM7

offononoff-VDC/4

PM8PM3PM2PM1vUM

vUM = -VDC/4

t

VDC/4

-VDC/4

-VDC/2

PM8

PM1

PM2

PM3

PM4

PM5

PM6

PM7



Source:


VDC/2

vUM(t)

on

PM4

off

PM5

off

PM6

off

PM7

offononon-VDC/2

PM8PM3PM2PM1vUM

vUM = -VDC/2

t

VDC/4

-VDC/4

-VDC/2

PM8

PM1

PM2

PM3

PM4

PM5

PM6

PM7


Features and Benefits of MMC Topology


Low Switching Frequency of Semiconductors

Low Generation of Harmonics

High Modularity in Hardware and Software

Use of well-proven Standard Components

Sinus shaped AC Voltages and Currents

Easy Scalability

Reduced Number of Primary Components

Low Rate of Voltage and Current Rise

Low Converter Station Losses *

No Filters required

High Flexibility, economical from low to high Power Ratings

High Availability of State-of-the-Art Components Use of standard AC

TransformersLow Engineering Efforts,

Power Range up to 1,000 MWHigh Reliability, low

Maintenance Requirements

Robust System

* close to 1 % – per Station

10-2009


Benefits of HVDC PLUS


HVDC PLUS

HVDC “Classic”

Example 400 MW

Space Saving

10-2009


SVC PLUS®

The Advanced STATCOMInnovation Meets Experience

39 Power Transmission DivisionE T PS SL/Re10-2009


General Features of VSC* FACTS


Grid Access for Wind Farms and Renewables

Elimination of Voltage Fluctuations and Flicker

Low Space Requirements

VSC Technology makes it feasible

High dynamic Performance

* VSC: Voltage-Sourced Converter

SVC PLUS offers additional Benefits


SVC PLUS – a wide Range of Configuration Possibilities


Containerized Solutions:SVC PLUS S: +/- 25 MVArSVC PLUS M: +/- 35 MVArSVC PLUS L: +/- 50 MVAr

Open Rack Solution (Building):SVC PLUS C: +/-100 MVAr

SVC PLUS Hybrid (Option):MSR (Mechanically Switched Reactors)

MSC (Mechanically Switched Capacitors)

HV

LV

MSR MSC

8 kV – 36 kV

SVC PLUS+/-25 ... +/ -200 MVAr

Up to 4 parallel L-Units: +/- 200 MVAr


SVC PLUS – A View of the Technology

Cooling System Converter Control & Protection


SVC PLUS – a highly flexible System


Siemens uses MMC Technology(Modular Multilevel Converter)

Low Generation of Harmonics

Low Level of HF-Noise

Low Switching Losses

No Snubbers required


SVC PLUS: HMI, local and remote Control

Power Transmission DivisionE T PS SL/Re10-2009

Local: WinCC, PC

Remote: SCADA Interface

44

External Devices

SVC PLUS

External Devices


SVC PLUS: Converter, Control and Protection

Power Transmission Division45 E T PS SL/Re10-2009


SVC PLUS: Advanced Control System


SIMATIC TDCPlant CoordinationReference ValuesMeasurements

PLUSCONTROLCurrent ControlConverter Coordination

GIB on Power ModuleCapacitor ProtectionPiloting of IGBT DriversDC Voltage Measurement


Space Requirements – Example of +/- 50 MVAr:SVC PLUS L versus SVC “Classic”


Space Saving


SVC PLUS: Example of Factory Acceptance Tests – Nuremberg, Germany



Single Line Diagram of SVC PLUS in Comparison with SVC “Classic“


SVC PLUSSVC PLUSSVC “Classic”SVC “Classic” SVC PLUSSVC “Classic”

Variable Impedance Controlled Voltage Source

STATCOM = Static Synchronous Compensator – with Multilevel


SVC PLUS – the Operation Principle


H H

H H

H H

L1

L2

L3

vconv 12

vconv 23

vconv 31

i12

i23

i31

i1

i2

i3

L

L

L

AC Equivalent

Xfmrs, Lines Loads

VSC

Electronic Generatorfor Reactive PowerVSC =

Voltage Stabilization

51 10-2009 Power Transmission DivisionE T PS SL/Re51 Power Transmission DivisionE T PS SL/Re10-2009

Power Module 1 Power Module 2 Power Module 3 Power Module 4 Power Module n

vconv 12

Lv 12conv 12v

iconv 12

SVC PLUS – Modular Multilevel Converter

Conv 12Conv 12

SVC Voltage v12


SVC PLUS: The Power Module


IGBTs

Bypass Switch

GIB (Gate-Interface Board)

DC Storage Capacitor


From Power Module to Converter –the Multilevel Voltage Generation


Power Module with DC Capacitor

vv


States and Current Paths of a Power Module in the MMC Topology – an Advanced Solution


ON ON

OFF OFF

C uDC

ON OFF

OFF ON

C VDC+ VDC

Capacitor charging/discharging

Capacitor bypassed“Off“ State

“On“ State


off

S2’

on

S3

off

S3’

off

S4

onononoffVdc/2

S4’S2S1

’S1Vph

12ph dcV V=

Vdc/2

-Vdc/2

vph

Vdc/4

-Vdc/4

dc

S1

S’1 S’

2

S3

S’3

S4

S’4

Vph

Vdc /4

Vdc /4

S2

Source: S. Bernet, T. Meynard, R. Jakob, T. Brückner, B. McGrath, “Tutorial Multi-Level Converters”, in Proc. IEEE-PESC Tutorials, 2004, Aachen, Germany

Configuration of 5-Level H-Bridge VSC


14ph dcV V=

Vdc/2

-Vdc/2

Vdc/4

-Vdc/4

dcvph

Vph

S1

S’1

S3

S’3

S’2

S4

S’4

S2

Vdc /4

Vdc /4

off

S2’

on

S3

off

S3’

off

S4

ononoffVdc/4

S4’S2S1

’S1Vph


on



off

S2’

on

S3

off

S3’

on

S4

offonoffon0

S4’S2S1

’S1Vph

0ph dcV V=

Vdc/2

-Vdc/2

Vdc/4

-Vdc/4

Vdcvph

Vph

S1

S’1

S’3

S’2

S4

S’4

S2

S3

Vdc /4

Vdc /4




on

S2’

on

S3

off

S3’

on

S4

offoffoffon-Vdc/4

S4’S2S1

’S1Vph

14ph dcV V= −

Vdc/2

-Vdc/2

Vdc/4

-Vdc/4

vph

Vph

S1

S’1

S3

S’3

S’2

S4

S’4

S2

Vdc /4

Vdc /4




on

S2’

off

S3

on

S3’

on

S4

offoffoffon-Vdc/2

S4’S2S1

’S1Vph

Vph

S1

S’1

S3

S’3

S’2

S4

S’4

S2

Vdc /4

Vdc /4

-Vdc/2-Vdc/4

Vdc/2Vdc/4

vph

14ph dcV V= −2




on

S2’

on

S3

off

S3’

on

S4

offoffoffon-Vdc/4

S4’S2S1

’S1Vph

14ph dcV V= −

Vdc/2

-Vdc/2

Vdc/4

-Vdc/4

vph

Vph

S1

S’1

S3

S’3

S’2

S4

S’4

S2

Vdc /4

Vdc /4




Harmonics of SVC PLUS in Comparison with SVC “Classic”



SVC PLUS: V/I Diagram – Current Source


Capacitive Current Inductive Current

STATCOM:Current-SourceCharacteristics

Jump next Page (SVC “Classic”)


SVC “Classic”: Examples of V/I Diagrams

ISVC (QSVC)

VSVC


1.0

Voltage Control Mode

• w/o slope

• with slope

• w/o Slope• with Slope

Reactive Power Control Mode

1.8

1.1

VSVC

ISVC

SVC: Impedance Characteristics




0.25 0.25


SVC PLUS versus SVC “Classic” –Loss Characteristics


0,0

0,5

1,0

1,5

-1 -0,5 0 0,5 1Q in pu

P in

%

SVC PLUS SVC Classic

capacitive inductive


SVC PLUS – Control Features


SVC PLUS – Standard Control FunctionsVoltage ControlReactive Power Control Control of up to 4 External Devices

SVC PLUS – The Control OptionsPower Oscillation DampingVoltage Unbalance ControlCos φ ControlFlicker Control

SVC PLUS – Internal ControlsAdaptive Gain ControlDC ControlTransformer Overload ControlOver & Undervoltage Strategies


The Advanced SVC PLUS Solution


Source: UCTE Interim Report 10-27-2003Rating: up to +/- 200 MVAr

8 Systems in 4 Transmission Projects:

Dynamic Voltage Support

2009 - 2011


Intelligent Solutions for Power Transmission

with with HVDCHVDC & &

FACTSFACTS fromfrom

HVDC HVDC PLUSPLUSandand SVCSVC PLUSPLUS

Now available –with VSC PLUS Technology

SiemensSiemens

… and the Lights will keep shining !


Intelligent Solutions for Power Transmission

SustainabilitySustainability &&

SecuritySecurity

Thank You for your Attention !

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