Solutions for Smart and Super Grids with HVDC and FACTS

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Technical article ■ Authors: M. Claus, D. Retzmann, D. Sörangr, K. Uecker Solutions for Smart and Super Grids with HVDC and FACTS

Answers for energy. Content

0. Abstract 3

I. Introduction 3

II. HVDC and FACTS Technologies 3 A HVDC Developments 4 B FACTS Developments 5

III. Security and Sustainability of Power Supply with HVDC and FACTS 5 A Neptune HVDC Project – USA 5 B Basslink HVDC – Australia 6 C Prospects of HVDC in India 6 D Prospects of HVDC in China 7 E HVDC and FACTS in parallel Operation 8 F Prospects of VSC HVDC 9

IV. Conclusions 9

V. References 12

2 17th Conference of the Electric Power Supply Industry 27 - 31 October 2008

Solutions for Smart and Super Grids with HVDC and FACTS M. Claus, D. Retzmann1, D. Sörangr, K. Uecker Siemens AG Erlangen, Germany [email protected]

Abstract— Deregulation and privatization are posing new grid of the future must be secure, cost-effective and challenges to high-voltage transmission systems. High-voltage environmentally compatible [2]. The combination of these power electronics, such as HVDC (High Voltage Direct Current) three tasks can be tackled with the help of ideas, intelligent and FACTS (Flexible AC Transmission Systems), provide the solutions as well as innovative technologies. The combination necessary features to avoid technical problems in heavily loaded of these three tasks can be solved with the help of ideas, power systems; they increase the transmission capacity and system stability very efficiently and assist in preventing intelligent solutions as well as innovative technologies. cascading disturbances. Environmental constraints, such as Innovative solutions with HVDC and FACTS have the energy saving, loss minimization and CO2 reduction, will also potential to cope with the new challenges. By means of Power play an increasingly more important role. The loading of existing Electronics, they provide features which are necessary to power systems will further increase which will lead to avoid technical problems in the power systems, they increase bottlenecks and reliability problems. Therefore, the strategies for the transmission capacity and system stability very efficiently the development of large power systems go clearly in the and help prevent cascading disturbances. direction of Smart Grids, consisting of AC/DC interconnections The vision and enhancement strategy for the future and point-to-point bulk power transmission “highways” (Super electricity networks are, for example, depicted in the program Grid Solutions). FACTS technology is also an important part of this strategy. These hybrid systems offer significant advantages for “SmartGrids”, which was developed within the European in terms of technology, economics and system security. They Technology Platform. Features of a future Smart Grid such as reduce transmission costs as well as help bypass heavily loaded this can be outlined as follows: flexible, accessible, reliable AC systems. and economic. Smart Grids will help achieve a sustainable development. Keywords-- HVDC, FACTS, Bulk Power Transmission, Security, II. HVDC AND FACTS TECHNOLOGIES Sustainability, Micro Grid, Smart Grid, Super Grid In the second half of the last century, high power HVDC I. INTRODUCTION transmission technology was introduced, offering new The electric power supply is essential for life of a society, dimensions for long distance transmission. This development like the blood in the body. Without power supply there are started with the transmission of power in a range of less than a devastating consequences for daily life. However, hundred MW and was continuously increased. deregulation and privatization are posing new challenges to Transmission ratings of 3 GW over large distances with the transmission systems. System elements are going to be only one bipolar DC line are state-of-the-art in many grids loaded up to their thermal limits, and wide-area power trading today. Now, there are ways of transmitting up to 6 GW and with fast varying load patterns will contribute to an increasing more over large distances with only one bipolar DC congestion [1, 2]. transmission system. The first project in the world at a DC In addition to this, the dramatic global climate voltage of +/- 800 kV is the Yunnan-Guang project in China developments call for changes in the way electricity is with a power transmission capacity of 5,000 MW. Further supplied. Environmental constraints, such as loss projects with similar or even higher ratings in China, India and other countries are going to follow. minimization and CO2 reduction, will play an increasingly important role. Consequently, we have to deal with an area of FACTS, based on power electronics, was developed to conflicts between reliability of supply, environmental improve the performance of weak AC Systems and to make sustainability as well as economic efficiency [3, 4]. The power long distance AC transmission feasible. Moreover, FACTS can help solve technical problems in the interconnected power

3 systems. FACTS are applicable both in a parallel connection which is highly important for the future is its integration into (SVC, Static VAR Compensator – STATCOM, Static the complex interconnected AC system (Fig. 1c). The reasons Synchronous Compensator), in a series connection (FSC, for these hybrid solutions are basically lower transmission Fixed Series Compensation - TCSC/TPSC, Thyristor costs as well as the possibility of bypassing heavily loaded AC Controlled/Protected Series Compensation - S³C, Solid-State systems. Series Compensator), or as a combination of both (UPFC, Typical configurations of HVDC are depicted in Fig. 2. Unified Power Flow Controller - CSC, Convertible Static HVDC VSC is the preferred technology for connecting Compensator) to control load flow and to improve dynamic islanded grids, such as offshore wind farms, to the power conditions. Rating of SVCs can go up to 800 MVAr; the system [1, 11-16]. This technology provides the “Black-Start” world’s biggest FACTS project with series compensation feature by means of self-commutated voltage-sourced (TCSC/FSC) is at Purnea and Gorakhpur in India at a total converters [8]. Voltage-sourced converters do not need any rating of 1.7 GVAr. “driving” system voltage; they can build up a 3-phase AC By means of these DC and AC Ultra High Power voltage via the DC voltage at the cable end, supplied from the transmission technologies, the “Smart Grid”, consisting of a converter at the main grid. number of highly flexible “Micro Grids” will turn into a Siemens uses an innovative Modular Multilevel Converter “Super Grid” with Bulk Power Energy Highways, fully (MMC) technology for HVDC VSC with low switching suitable for a secure and sustainable access to huge renewable frequencies, referred to as HVDC PLUS [14-16]. energy resources such as hydro, solar and wind [1].

HVDC – High-Voltage DC Transmission: It makes P flow A. HVDC Developments In general, for transmission distances above 600 km, DC z HVDC “Classic” with 500 kV – up to 4,000 MW transmission is more economical than AC transmission z HVDC “Bulk” with 800 kV – for 5,000 MW up to 7,200 MW (≥ 1000 MW). Power transmission of up to 600 - 800 MW z HVDC VSC (Voltage-Sourced Converter) over distances of about 300 km has already been achieved z HVDC can be combined with FACTS 800 kV for minimal Line with submarine cables, and cable transmission lengths of up to z V-Control included Transmission Losses

approx. 1,000 km are at the planning stage. Due to these HVDC-LDT – Long-Distance Transmission developments, HVDC became a mature and reliable technology. B2B – The Short Link During the development of HVDC, different kinds of Back-to-Back Station Submarine Cable Transmission Long-Distance OHL Transmission applications were carried out. They are shown schematically AC AC AC AC AC AC in Fig. 1. DC Line DC Cable

Can be Fig. 2: HVDC Configurations and Technologies connected to long AC a) Lines The major benefit of the HVDC, both B2B and LDT, is its incorporated ability of fault-current blocking which serves as an automatic firewall for Blackout prevention in case of cascading events, which is not possible with synchronous AC b) links [10-13], ref. to Fig. 3.

Fault-Current a) Back-to-Back Solution Blocking b) HVDC Long Distance Transmission V1 V2 c) c) Integration of HVDC into the AC System Hybrid Solution G ~ P G ~ I1 I2 Fig. 1: Options of HVDC Interconnections Slow Functions Q1 α and γ Q2 Slow Functions The first commercial applications were cable transmissions, “Classic” “Classic” for AC cable transmission over more than 80-120 km is onlyL and C L and C only technically not feasible due to reactive power limitations. Fast Functions Then, long distance HVDC transmissions with overhead lines Benefits of The Firewall HVDC in a were built as they are more economical than transmissions for Blackout with AC lines [5]. To interconnect systems operating at synchronous Power & Voltage Control Prevention different frequencies, Back-to-Back (B2B) schemes were AC System Fault-Current Blocking applied. B2B converters can also be connected to long AC lines (Fig. 1a). A further application of HVDC transmission Fig. 3: Benefits of HVDC - it makes Power flow

4 B. FACTS Developments In Fig. 5, the impact of series compensation on power Since the 1960s, Flexible AC Transmission Systems have transmission and system stability is explained and Fig. 6 been evolving to a mature technology with high power ratings depicts the increase in voltage quality by means of shunt [6, 7, 9]. The technology, proven in various applications, compensation with SVC (or STATCOM). became first-rate, highly reliable one. State-of-the-art SVC applications with containerized Fig. 4 shows the basic configurations of FACTS. solutions - including a new, very fast 48 hrs containerized SVC refurbishment technology - and advanced indoor FACTS – Flexible AC Transmission Systems: Support of Power Flow technologies provide additional benefits for the user. z SVC – Static Var Compensator (The Standard of Shunt Compensation) III. SECURITY AND SUSTAINABILITY OF POWER z STATCOM – Static Synchr. Compensator, with VSC) SUPPLY WITH HVDC AND FACTS z FSC – Fixed Series Compensation and SCCL for z TCSC – Thyristor Controlled Series Compensation Short-Circuit After the 2003 Blackout in the United States, new projects z TPSC – Thyristor Protected Series Compensation Current Limitation are gradually coming up in order to enhance the system z UPFC – Unified Power Flow Controller (with VSC) security. SVC / STATCOM FSC UPFC A. Neptune HVDC Project – USA AC AC AC AC AC AC One example is the Neptune HVDC project. The task given by Neptune Regional Transmission System LLC (RTS) in Fairfield, Connecticut, was to construct an HVDC TCSC/TPSC/ TPSC transmission link between Sayreville, New Jersey and Long Island, New York. As new overhead lines can not be built in Fig. 4: Transmission Solutions with FACTS this densely populated area, power should be brought directly to Long Island by HVDC cable transmission, bypassing the P AC sub-transmission network. For various reasons, V , δ V , δ V1 1 V2 2 environmental protection in particular, it was decided not to I build a new power plant on Long Island near the city in order G ~ G ~ to cover the power demand of Long Island with its districts XC X Queens and Brooklyn, which is particularly high in summer. V L The Neptune HVDC interconnection is an environmentally Series Compensation V C V compatible, cost-effective solution which will help meet these 2 V 2 V 1 future needs. The low-loss power transmission provides P = sin δ V V access to various energy resources, including renewable ones. X - XC 1 2 The interconnection is carried out via a combination of δ δ δ δ δ submarine and subterranean cable directly to the network of where V1 = V2 , = 1 - 2 without Compensation Nassau County which borders on the city area of New York. with Compensation Benefits Neptune RTS was established to develop and commercially Reduction in Transmission Angle Increase in Transmission Capacity operate power supply projects in the United States. By delivering a complete package of supply, installation, service and operation from one single source, the seamless coverage Fig. 5: FACTS - Influence of Series Compensation on Power Transmission of the customer’s needs was provided. The availability of this combined expertise fulfills the prerequisites for financing these kinds of complex supply projects through the free Load investment market. 230 kV - 300 km Grid System Conditions: Siemens and Neptune RTS were developing the project a) Heavy Load over three years to prepare it for implementation. In addition b) Light Load V to providing technological expertise, studies, and engineering V1 2 c) Outage of 1 Line SVC (at full Load) services, substantial support was given to the customer during d) Load Rejection the project’s approval process. at Bus 2 a) b) c) d) In Fig. 7a, highlights of this innovative project typical of 1.2 the future integration of HVDC into a complex synchronous 1.1 without SVC AC system are depicted.

V2 with SVC During trial operation, 2 weeks ahead of schedule, Neptune 1.0 V2N (var. Slope) HVDC proved its Blackout prevention capability in a very th 0.9 , 2007, a Blackout occurred in The maximal Voltage Control impressive way. On June 27 Range depends on: QSVC/SCP * New York City. Over 380,000 people were without electricity 0.8 in Manhattan and Bronx for up to one hour, subway came to a * SCP = Short-Circuit Power (System MVA) standstill and traffic lights were out of operation. In this Fig. 6: FACTS - Improvement in Voltage Profile with SVC

5 situation, Neptune HVDC successfully supported the power 2005 supply of Long Island and due to this, 700,000 households could be saved there, ref. to Fig. 7b.

Ed Stern, President of Neptune RTS: “High-Voltage Direct Current Transmission will play an increasingly important Role, especially as it becomes necessary to tap Energy Reserves whose Sources are far away from the Point of Consumption” Benefits Clean & Low Cost Energy over Long Distance – suitable Safe and reliable Customer: Neptune RTS of HVDC for Peak-Load Demand Power Supply for End User: Long Island Power Authority Megacities : Firewall (LIPA) Improvement of Power Quality for Blackout Location: New Jersey: Sayreville Prevention Long Island: Duffy Avenue Improvement of local Project Infrastructures Development: NTP-Date: 07/2005 Atlantic Ocean PAC: 07/2007 Hydro Plants for: Supplier: Consortium ¾ Base Load and Siemens / Prysmian Transmission: Sea Cable – 500 kV ¾ Energy Storage Power Rating: 600/660 MW monopolar Transmission Dist.: 82 km DC Sea Cable 23 km Land Cable

“flexible”

Plus Wind Fig. 7a: Highlights of Neptune HVDC Project - USA Power Benefits of HVDC: ¾ Clean Energy ¾ CO2 Reduction Neptune HVDC: 660 MW Full Power Delivery “fuzzy” ¾ Cost Reduction in Trial Operation – 2 Weeks ahead of Schedule Covering Base and Peak-Load Demands Blackout in New Neptune HVDC York City – June successfully Fig. 8: Basslink HVDC – Sustainability of a 27, 2007 supported Long Island’s Power “Smart” and flexible Grid Supply – 700,000 Households Both Victoria and Tasmania profit from the inter-

New Jersey: Sayreville could be saved connection of their networks: During times of peak load, Tasmania delivers “green

Long Island: Duffy Avenue energy” from its hydro power stations to Victoria, while 385,000 People without Electricity in Tasmania can cover its base load demands from the grid of Manhattan and Bronx: Subway broke Victoria during dry sea-sons when water reservoirs are not down, Traffic Lights out of Operation sufficiently filled. Furthermore, the island of Tasmania – up to 1 hour Power Outage receives access to the power market of the Australian continent. Tasmania intends to install additional wind farms to Fig. 7b: Benefits of Neptune HVDC Project for increase its share in regenerative energy production. The Blackout Prevention figure shows that hydro power is perfectly suitable to be supplemented with the rather “fuzzy” wind energy – in terms of base load as well as through its ability to store energy for B. Basslink HVDC – Australia peak load demands. So far, the DC-link can do much more to Fig. 8 gives an overview of the Basslink project in reduce CO2 by the combined use of regenerative energies. Australia, which transmits electric power from wind- and hydro sources very cost-efficiently from George Town in C. Prospects of HVDC in India Tasmania to Loy Yang in Victoria and the same way back. The HVDC East-South interconnection in India This happens by means of HVDC via a combination of (commercial operation in 2003) uses both advantages, the submarine cable (with 295 km the longest submarine cable in avoidance of transmission of additional power through the AC the world up to now), subterranean cables (8 km for reasons of system and the interconnection of power areas which can not landscape protection) and overhead lines over a total be operated synchronously. A view of the HVDC northern transmission distance of 370 km. The nominal power is terminal in the state of Orissa is given in Fig. 9. 500 MW at a DC Voltage of 400 kV and a current of 1,250 A. In April 2006, Powergrid Corporation of India decided to The overload capacity of the transmission system is 600 MW increase the transmission capacity of the East-South DC during 10 hours per day. transmission from 2,000 MW to 2,500 MW. As the upgrade is now completed, it is possible to make maximum use of the system’s overload capacity. To increase the capacity of the

6 link, the experts have developed a solution known as Relative double-circuit 400 kV AC transmission line, this HVDC Aging Indication and Load Factor Limitation (RAI & LFL). transmission link improves transmission efficiency so that With their help it is possible to utilize the overload capacity of 688,000 tons of CO2 will be saved, ref. to Fig. 10. the system more effectively without having to install As the head of the consortium, Siemens has overall additional thyristors. responsibility for the project, including the design of the HVDC transmission system, and will deliver the main core components. The company will also take over the transport functions, construction work, installation and start-up. Part- ner BHEL is supplying transformers for one of the two converter stations as well as switchgear components. The new long-distance HVDC transmission link is the second system built by Siemens in India. 2500 MW D. Prospects of HVDC in China RAI & LFL: full Use of Overload Capacity – In China, the 3,000 MW +/- 500 kV bipolar Gui-Guang without additional HVDC system (Fig. 11) with a transmission distance of Thyristors 980 km was build to increase the transmission capacity from 2007 west to east. It is integrated into the large AC interconnected system. In the same system there is also an already existing 2003 2000 MW DC Station Talcher – State of Orissa HVDC scheme Tian-Guang in operation. Both DC systems operate in parallel with an AC transmission in this grid.

Fig. 9: Site View of Indian East-South Interconnector – DC Station Talcher

Furthermore, in March 2007, Siemens and its consortium partner Bharat Heavy Electricals Ltd (BHEL) were awarded an order by Power Grid Corporation of India Ltd, New Delhi, to construct a new HVDC transmission. The purpose of the new HVDC transmission system is to strengthen the power supply to the growing region around New Delhi. The system is scheduled to go into service in November 2009. This is the fourth long-distance HVDC transmission link in India.

2009 DC versus AC 2004

*2,500 2,500 MW MW 800 km 2 x 3-ph AC 400 kV India

1 x +/- 500 kV View of the Thyristor-Module

Example of HVDC 1,450 km … too long for 400 kV AC Rating: 3000 MW Ballia-Bhiwadi: Voltage: ± 500 kV 2,500 MW Reduction in CO2: Contract: Nov. 1, 2001 Project completedterminated 6 Months 688,000 tons p.a. 2003 / 2007 ahead of Schedule by Sept. 2004 through 37 % less Thyristor: 5" LTT with integrated Transmission Overvoltage Protection Losses at*

Fig. 10: Sustainability of Transmission in India - Fig. 11: Highlights of the Gui-Guang I HVDC East-South Interconnector and Ballia-Bhiwadi Transmission Project

The power transmission system is to transport electrical In addition to this, Fixed Series Compensation (FSC) and energy with low loss from Ballia in the east of Uttar Pradesh Thyristor Controlled Series Compensation were used in the province to Bhiwadi, approx. 800 km away in the province of system. Due to long transmission distances, the system Rajasthan near New Delhi. In comparison with a conventional experiences severe power oscillations after faults, close to the stability limits. With its ability to damp power oscillations,

7 HVDC plays an important role for reliable operation of the Siems substation near the landing point of the Baltic Cable system. HVDC were unforeseen right-of-way restrictions in the At the beginning of January 2008, after successful neighboring area, where an initially planned new tie-line to completion of the test phase, Siemens commissioned a third the strong 400 kV network for connection of the HVDC was +/- 500 kV DC link Guizhou-Guangdong II in the same area. denied. Therefore, with the reduced voltage of the existing Additional 3,000 MW of electric power now flow from network of 110 kV, only a limited power transfer ( 450 MW) hydroelectric and coal-fired power plants in western China with the DC-link was possible since its commissioning in over 1,225 kilometers to the urban and industrial centers of 1994, in order to avoid repetitive HVDC commutation failures Guangdong. Siemens built the Guigang I and II HVDC and voltage problems in the grid. In an initial step towards systems together with Chinese partners on behalf of the China grid access improvement, an additional transformer for Southern Power Grid Company, a state-owned energy power connecting the 400 kV HVDC AC bus to the 110 kV bus was supply company in Guangzhou. installed. In June 2007, China Southern Power Grid placed an order HVDC and FACTS in to Siemens and its Chinese partners to construct a high- parallel Operation voltage DC transmission (HVDC) system between the province of Yunnan in the southwest of China and the province of Guangdong on the south coast of the country. The system will be the first in the world to transmit electricity at a DC voltage of +/- 800 kV with a power transmission capacity of 5,000 MW. Fig. 12 gives an overview of this innovative project in China Southern Power Grid. HVDC: Power Increase –from 450 MW to 600 MW Reduction in CO : 2 634,000 tons p.a. Commercial Operation: ¾ 2009 – Pole 1 1,418 Km ¾ 2010 – Pole 2 5,000 MW +/- 800 kV DC Source:

Fig. 13: SVC Siems, Germany - Support of HVDC Baltic Cable Yunnan-Guangdong Finally, in 2004, with the new SVC, equipped with a fast

coordinated control, the HVDC could fully increase its

transmission capacity up to the design rating of 600 MW. In Reduction in CO2 versus local Power Supply with Energy-Mix addition to this measure, a new cable to the 220 kV grid was 32.9 m tons p.a. –by using Hydro Energyand HVDC for Transmission installed to increase the system strength with regard to power

increase of the HVDC system. Fig. 12: World’s first 800 kV UHV DC – in China

Southern Power Grid SVC - Essential for enhanced Grid

Access of the HVDC The additional electric power from Yunnan is intended to

supply the rapidly growing industrial region of the Pearl River

delta in the province of Guangdong and the megacities of

Guangzhou and Shenzhen. In the future, the electricity The Solution

generated by several hydro-electric power plants will be

transported from Yunnan via 1,400 km to Guangzhou over

this long-distance HVDC link. This HVDC link will save the

CO emissions of more than 30 million tons a year. This 2 corresponds to the amount of harmful gases which would be

produced otherwise, for example due to the construction of

additional conventional fossil power plants in the province of The Problem – no Right of Way for 400 kV

Guangdong to serve the regional grid. AC Grid Access of Baltic Cable HVDC 2004

E. HVDC and FACTS in parallel Operation Fig. 14: Siems – the first HV SVC in the German Grid In Figs. 13-14, an innovative FACTS application with SVC in combination with HVDC for transmission enhancement in The enhanced grid access of the HVDC can save an amount Germany is shown. of 634,000 tons of CO2 emissions p.a. through the import of This project is the first high voltage FACTS controller in more hydro power from Nordel to Germany. In Fig. 14, a the German network. The reason for the SVC installation at view of the Siems SVC in Germany is depicted.

8 F. Prospects of VSC HVDC Today, the major electric supply for the City of San In September, 2007, Siemens secured an order to supply Francisco is coming from the south side of the San Francisco two converter stations for a new submarine HVDC peninsula. The city relies mainly on AC grids which run along transmission link in the Bay of San Francisco. The HVDC the lower part of the bay. With the new HVDC PLUS PLUS system will transmit up to 400 megawatts at a DC interconnection link, power flows directly into the center of voltage of +/- 200 kV. This is the first order for the innovative San Francisco and closes the loop of the already existing HVDC PLUS technology. The order was placed by Trans Bay “Greater Bay Area” transmission. This will increase the Cable LLC, based in San Francisco, and a wholly-owned system security. subsidiary of the project developer Babcock & Brown. A As the consortium leader, Siemens was awarded a turnkey project overview is given in Fig. 15. contract which comprises the converter stations for the HVDC PLUS system, including engineering, design, manufacturing, a) installation and commissioning of the HVDC transmission Energy Exchange 2010 system. The design fulfills all requirements which have to be by Sea Cable considered for the electric components as well as for all ~ = = ~ = = No Increase in buildings in a highly seismic active zone such as San

~ = = Short-Circuit Power = Francisco. ~

= The consortium partner Prysmian will supply and install the submarine cables. The DC cables will be buried in a safe corridor separate from any existing AC cables. = =

~ = = ~ = = ~ Due to the DC transmission link, the building of additional new power plants in the City of San Francisco may be Elimination of Transmission Bottlenecks postponed or even avoided. The link will reduce grid = = congestion in the East Bay and it will also boost the overall ~ P = 400 MW, security and reliability of the power system. ± 200 kV DC The new link provides tremendous benefits for power Cable Q = +/- 170-300 MVAr Dynamic Voltage Support transmission. It will help increase sustainability and security of transmission systems significantly. b) ••Converter:Converter: ModularModular MultilevelMultilevel HVDCHVDC PLUSPLUS ConverterConverter As an example, a significant reduction in transmission ••RatedRated Power:Power: 400400 MWMW @@ ACAC TerminalTerminal receivingreceiving EndEnd constraints by using HVDC PLUS for the Trans Bay Cable ••DCDC Voltage:Voltage: ±± 200 200 kVkV Project is depicted in Fig. 16. ••SubmarineSubmarine Cable:Cable: ExtrudedExtruded InsulationInsulation DCDC CableCable

Transmission Constraints after TBC PG&E PG&E Potrero San Pittsburg Substation Francisco Pittsburg Substation Trans Bay Cable < 1 mile1 mile 53 miles 1 mile < 3 miles Transmission Constraints before TBC San Francisco – San Pablo – Suisun Bays

AC AC Cables Cables 115 kV AC/DC AC/DC 230 kV Substation Converter Submarine Converter Substation Significant Station DC Cables Station Improvements

Fig. 15: Trans Bay Cable, USA – World’s 1st VSC HVDC Project with Advanced MMC- HVDC PLUS makes it feasible Technology and +/- 200 kV XLPE DC Cable a) Geographic Map and System Requirements Fig. 16: Benefits of HVDC PLUS for Trans Bay Cable Project b) Siemens Converter Stations and Prysmian Cable Technologies IV. CONCLUSIONS From March, 2010, the 55 mile (88 kilometers) long HVDC In conclusion to the previous sections, Table 1 summarizes the PLUS system will transmit electric power from the converter impact of FACTS and HVDC on load flow, stability and station in Pittsburg to the converter station in San Francisco, voltage quality when using different devices. Evaluation is providing a dedicated connection between the East Bay and based on a large number of studies and experiences from San Francisco. Main advantages of the new HVDC PLUS link projects. For comparison, mechanically switched devices are improved network security and reliability due to grid (MSC/R) are included in the table. enhancement, voltage support and reduction in system losses.

9 Impact on System Performance Principle Devices Scheme Voltage Load Flow Stability Quality Variation of the FSC Line (Fixed Series z zzz z Impedance: Compensation) Series TPSC (Thyristor z zzz z Compensation Protected Series Compensation) TCSC (Thyristor zz zzz z Controlled Series Compensation)

MSC/R (Mechanically { z zz Switched Capacitor / Influence: * Voltage Reactor) Control: SVC { zz zzz { no or low Shunt (Static Var Compensator) z small Compensation STATCOM ** { zz zzz zz medium (Static Synchronous zzz strong Compensator) HVDC – B2B, LDT * Based on Studies Load-Flow zzz zzz z zz HVDC PLUS – VSC & practical Control Experience UPFC zz zzz zzz (Unified Power Flow Controller) ** = SVC PLUS

Table 1: FACTS & HVDC – Overview of Functions & “Ranking”

System G

System System System System System System E A B C D F

The Result: LargeLarge System System Interconnections Interconnections,, with with HVDC HVDC…… and FACTS

Step 3 HVDC – Long-Distance DC Transmission

Step 2 HVDC B2B –viaAC Lines

Step 1 High-Voltage AC Transmission & FACTS

DC is a Stability Booster and “Countermeasures”

“Firewall” against “Blackout” against large

Blackouts A “Super Grid” – “Smart” & Strong

Fig. 17: Hybrid System Interconnections – “Supergrid” with HVDC and FACTS

10 “Micro Grid” “Smart Grid” “Super Grid”

C C G G C

C C C C C C C C C C C C C CACA C C CA C C CA C C C C C C C C C C C C C C G C C C C G C C C C C C C C

C CA C C CA C

C C C C CA = Cell Agent C C C C C C Storage G +=S C Cell G Generation G Virtual Power Plant AC DC Bulk Power AC/DC Energy Highway Fig. 18: Prospects of Grid Developments Based on these evaluations, Fig. 17 shows the stepwise [4][3] M.DENA Luther, Study U. Radtke,Part 1, “Betrieb “Energiewirtschaftliche und Planung von PlanungNetzen mitfür hoher die interconnection of a number of grids by using AC lines, DC NetzintegrationWindenergieeinspeisung”, von Windenergie ETG Kongr in ess,Deutschland October an23-24, Land 2001,und OffshoreNuremberg, bis Germanyzum Jahr 2020”, February 24, 2005, Cologne, Germany Back-to-Back systems, DC long distance transmissions and [5][4] “EconomicM. Luther, U.Assessment Radtke, “Betriebof HVDC und Links”, Planung CIGRE von NetzenBrochure mit Nr.186 hoher FACTS for strengthening the AC lines. These integrated (FinalWindenergieeinspeisung”, Report of WG14-20) ETG Kongress, October 23-24, 2001, hybrid AC/DC systems provide significant advantages in [6] N.G.Nuremberg, Hingorani, Germany “Flexible AC Transmission”, IEEE Spectrum, pp. 40- terms of technology, economics as well as system security. [5] 45,“Economic April 1993 Assessment of HVDC Links”, CIGRE Brochure Nr.186 [7] “FACTS Overview”, IEEE and CIGRE, Catalog Nr. 95 TP 108 They reduce transmission costs and help bypass heavily (Final Report of WG14-20) [8][6] WorkingN.G. Hingorani, Group B4-WG“Flexible 37 AC CIGRE, Transmission”, “VSC Transmission”, IEEE Spectrum, May pp.2004 40- loaded AC systems. With these DC and AC Ultra High Power [9] L.45, Kirschner, April 1993 D. Retzmann, G. Thumm, “Benefits of FACTS for Power transmission technologies, the “Smart Grid”, consisting of a [7] System“FACTS Enhancement”, Overview”, IEEE IEEE/PES and CIGRE, T & CatalogD Conference, Nr. 95 TPAugust 108 14-18, number of highly flexible “Micro Grids” will turn into a [8] 2005,Working Dalian, Group China B4-WG 37 CIGRE, “VSC Transmission”, May 2004 [10] G. Beck, D. Povh, D. Retzmann, E. Teltsch, “Global Blackouts – “Super Grid” with Bulk Power Energy Highways, fully [9] L. Kirschner, D. Retzmann, G. Thumm, “Benefits of FACTS for Power SystemLessons Enhancement”,Learned”, Power- IEEE/PES Gen Europe T &, June D Conference, 28-30, 2005, August Milan, 14-18, Italy suitable for a secure and sustainable access to huge renewable [11] G.2005, Beck, Dalian, D. ChinaPovh, D. Retzmann, E. Teltsch, “Use of HVDCand energy resources such as hydro, solar and wind, as indicated [10] FACTSG. Beck, for D. Power Povh, SystemD. Retzmann, Interconnection E. Teltsch, and “GlobalGrid Enhancement”, Blackouts – in Fig. 18. This approach is an important step in the direction Power-GenLessons Learned”, Middle Power- East, January Gen Europe 30 –, JuneFebruary 28-30, 1, 2005,2006, Milan, Abu Dhabi, Italy United Arab Emirates of environmental sustainability of power supply [2, 16]: [11] G. Beck, D. Povh, D. Retzmann, E. Teltsch, “Use of HVDCand [12] FACTSW. Breuer, for D.Power Povh, System D. Retzmann Interconnection, E. Teltsch, and Grid “Trends Enhancement”, for future transmission technologies with HVDC and FACTS can Power-GenHVDC Applications”, Middle East, 16th January CEPSI, 30 November– February 6-10,1, 2006, 2006, Abu Mumbai, Dhabi, effectively help reduce transmission losses and CO2 emissions. UnitedIndia Arab Emirates [12][13] W.G. Beck,Breuer, W. D. Breuer,D. Povh, Povh,D.D. Retzmann Retzmann,, E. Teltsch,“Use of “Trends FACTS forforSystem future HVDC Applications”, 16th CEPSI, November 6-10, 2006, Mumbai, India [13] G. Beck, W. Breuer,D. Povh,D. Retzmann, “Use of FACTS for System Performance Improvement”, 16th CEPSI, November 6-10, 2006, Mumbai, India [14] J. M. Pérez de Andrés, J. Dorn, D. Retzmann, D. Soerangr, A. Zenkner, “Prospects of VSC Converters for Transmission System Enhancement”; V. REFERENCES PowerGrid Europe 2007, June 26-28, Madrid, Spain [1] D. Povh*, D. Retzmann*, J. Kreusel**, “Integrated AC/DC [15] J. Dorn, H. Huang, D. Retzmann, “Novel Voltage-Sourced Converters Transmission Systems – Benefits of Power Electronics for Security and for HVDC and FACTS Applications”, Cigre Symposium,November 1- Sustainability of Power Supply”. PSCC 2008, Glasgow, July 14-17, 4, 2007, Osaka, Japan 2008. Survey Paper 2, * part 1 and ** part 2 [16] W. Breuer,D. Povh, D. Retzmann, Ch. Urbanke, M. Weinhold, [2] “European Technology Platform SmartGrids – Vision and Strategy for “Prospects of Smart Grid Technologies for a Sustainable and Secure Europe’s ElectricityNetworks of the Future”, 2006, Luxembourg, Power Supply”,The 20TH World Energy Congress, November 11-15, Belgium 2007, Rome, Italy

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