Multilevel STATCOMs – a new converter topology that opens up the market

Simon Sinsel, Siemens AG, Germany

Ian Ramsay, Siemens Inc., NC, USA

Key Messages

• We describe three multilevel STATCOM installations in Chile, Australia and the US.

• Each multilevel STATCOM fulfills a different primary electrical performance requirement – dynamic voltage support, load balancing and flicker reduction.

• Secondary features of the multilevel STATCOM technology favor its application on these projects – modularity, low interaction with the network in terms of harmonics and the low amount of primary equipment.

Source: Siemens AG

Agenda

Multilevel STATCOM Topology Overview

Case 1: Reactive Power Support for Increased Transmission Capacity

Case 2: Dynamic Load Balancing for Railway Applications

Case 3: Flicker Reduction

Conclusion

Multilevel STATCOM Topology Overview

Modul #1

Modul #2

Modul #3

Modul #4

Modul #n

Modul #n-1

Modul #n-2

Modul #n-3

Terminal A Terminal B

• Multilevel STATCOM is built by Power Modules connected in series. The required

output determines the number of modules.

• The sum of all power module output voltages form the terminal voltage.

• The reactive power output is controlled via the amplitude of the converter voltage.

Source: Siemens AG

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Reactive Power Support for Increased Transmission Capacity Diego de Almagro, Chile

Taltal

Carrera

Pinto

Diego de Almagro

SVC PLUSCardones

Maitencillo

Initial situation

• Trip on one of three Cardones – Maitencillo circuits led to voltage instability in northern transmission region.

• Dynamic voltage recovery criteria could only be fulfilled by limiting load on Cardones – Maitencillo lines to 340 MW.

• Increased power demand and relatively high generation cost in northern region provided incentive to increase transmission capacity on the corridor.

Grid schematic with installed multilevel STATCOM; Source: TRANSELEC

Reactive Power Support for Increased Transmission Capacity Diego de Almagro, Chile

Taltal

Carrera

Pinto

Diego de Almagro

SVC PLUSCardones

Maitencillo

Primary Project Requirement

• Increase of reactive power supply in the northern region to

(1) comply with grid code and

(2) increase load limitation from the southern grid region.

Additional Project Requirements

• Design, supply and commissioning within 15 months.

• Increased level of redundancy beneficial.

Grid schematic with installed multilevel STATCOM; Source: TRANSELEC

Reactive Power Support for Increased Transmission Capacity Diego de Almagro, Chile

220 kV

14 kV

±50 Mvar

100 MVA

±50 Mvar +40 Mvar

Results

• Compliance to required grid code criteria.

• Increased level of redundancy due to twin configuration.

• Installation increased transmission capacity through Cardones – Maitencillo from 340 to 420 MW.

SLD of installed multilevel STATCOM; Source: Siemens AG

-0.5-1.0 0.5 Iprim [pu]

Vprim [pu]

capacitive inductive

0.5

1.0

1.0

continuous operation

Multilevel STATCOM

time limited operation

Multilevel STATCOM

continuous operation

conventional SVC

time limited operation

conventional SVC

Source: Siemens AG

Reactive Power Support for Increased Transmission Capacity Diego de Almagro, Chile

Multilevel STATCOM installation at Diego de Almagro Substation; Source: Siemens AG

Dynamic Load Balancing for Railway Applications Wycarbah, Duaringa & Bluff, Australia

Initial situation

• Projected substantial increase of coal export via railway from Central Queensland to coast for export.

• Increased use of induction motor locomotives instead of DC and diesel-electric locomotives.

• Due to both drivers, potential non-compliance to grid code limitations for positive and negative sequence voltage.

FS FSTrSC

SVC SVCSVC

Railway electrification scheme prior to upgrade Source: Powerlink Queensland

Dynamic Load Balancing for Railway Applications Wycarbah, Duaringa & Bluff, Australia

Primary Project Requirement

• Installation of additional parallel compensation devices at three sites.

Additional Project Requirements

• Low interaction with the grid in terms of harmonics.

• Electrical similarity between all three sites beneficial.

132 kV Feeder

30/40 MVA

132/50 kV

±100 Mvar

Feeder

Catenary

Auto

Transformers

100 MVA

132/30 kV

Filter Filter

Tx2Tx1

Schematic feeder station with installed multilevel STATCOM Source: Powerlink Queensland

Dynamic Load Balancing for Railway Applications Wycarbah, Duaringa & Bluff, Australia

00 A

20 A

40 A

60 A

80 A

100 A

120 A

140 A

160 A

00

:00

:01

00

:43

:41

01

:27

:21

02

:11

:01

02

:54

:41

03

:38

:21

04

:22

:01

05

:05

:41

05

:49

:21

06

:33

:01

07

:16

:41

08

:00

:21

08

:44

:01

09

:27

:41

10

:11

:21

10

:55

:01

11

:38

:41

12

:22

:21

13

:06

:01

13

:49

:41

14

:33

:21

15

:17

:01

16

:00

:41

16

:44

:21

17

:28

:01

18

:11

:41

18

:55

:21

19

:39

:01

20

:22

:41

21

:06

:21

21

:50

:01

22

:33

:41

23

:17

:21

Tx 1

Tx 2

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

00

:00

:01

00

:42

:31

01

:25

:01

02

:07

:31

02

:50

:01

03

:32

:31

04

:15

:01

04

:57

:31

05

:40

:01

06

:22

:31

07

:05

:01

07

:47

:31

08

:30

:01

09

:12

:31

09

:55

:01

10

:37

:31

11

:20

:01

12

:02

:31

12

:45

:01

13

:27

:31

14

:10

:01

14

:52

:31

15

:35

:01

16

:17

:31

17

:00

:01

17

:42

:31

18

:25

:01

19

:07

:31

19

:50

:01

20

:32

:31

21

:15

:01

21

:57

:31

22

:40

:01

23

:22

:31

NPS (in %)

Results

• Significant reduction of NPS.

• Compliance to required grid code criteria for negative and positive phase sequence and harmonics.

• Synergy potential in project delivery, operation and maintenance due to same configuration.

STATCOM in service

STATCOM out of service

Comparison of NPS with multilevel STATCOM in service and out of service Source: Powerlink Queensland

Dynamic Load Balancing for Railway Applications Wycarbah, Duaringa & Bluff, Australia

Multilevel STATCOM installation at Wycarbah Feeder Station; Source: Siemens AG

Flicker Reduction CMC Steel, TX, USA

15 kV Electric Arc Furnace Busbar

STATCOM

±45 Mvar

STATCOM

±45 MvarFilter Filter

Initial situation

• CMC Steel Texas operates an 80 MVA AC Electric Arc Furnace on a 15 kV busbar.

• Existing STATCOM was not able to reduce the flicker to required value of Pst < 0.8 on the 138 kV PCC.

• Grid code compliance only possible with a flicker reduction factor higher than four.

SLD of multilevel STATCOM directly connected to Arc Furnace Busbar Source: Siemens AG

Flicker Reduction CMC Steel, TX, USA

Results

• Significant reduction of Flicker.

• Flicker performance of multilevel STATCOM higher compared to conventional Thyristor-based SVC (Factor 4 vs. factor 2).

Flicker comparison of 1st generation STATCOM and multilevel STATCOM Source: CMC Steel

Flicker Reduction CMC Steel, TX, USA

Multilevel STATCOM installation at CMC Steel, Tx; Source: CMC Steel

Conclusion

• We described three multilevel STATCOM installations in Chile, Australia and the US.

• Each multilevel STATCOM fulfills a different primary electrical performance requirement – dynamic voltage support, load balancing and flicker reduction.

• Secondary features of the multilevel STATCOM technology favor its application on these projects – modularity, low interaction with the network in terms of harmonics and the low amount of primary equipment.

Source: Siemens AG

Thank You!

For questions, comments & discussions please contact:

Simon Sinsel

simon.sinsel@siemens.com

Siemens AG, Germany

Ian Ramsay

ian.ramsay@siemens.com

Siemens Energy Inc., NC, USA

Source: Siemens AG

References

• V. Hild, L. Kirschner, G. Pilz, L. Peuther and B. Gemmell, "The best of both – Combining STATCOM with conventional thyristor based Static Var Compensator technology", unpublished, presented at the EPRI Conference, Palo Alto, CA, 2013.

• M. Pereira, D. Retzmann, J. Lottes, M. Wiesinger and G. Wong, “SVC PLUS: An MMC STATCOM for Network and Grid Access Applications” presented at IEEE PowerTech, Trondheim, 2011.

• A. Handschick, A.J. Hernandes, F. Schettler, B. Strobl, “Voltage Control in Offshore Wind Farms Using Switched Compensation Elements (MSCs, MSRs) Together with the Reactive Power Capability of the Wind Turbine Generators” unpublished, Erlangen, 2010.

• A. Janke, R. Memisevic and G. Pilz, “Queensland Railways Upgrade Project”, SCB4 Colloquiu, CIGRE, Paris, 2011.