nedo's approach to hvdc power transmission technology · latest trends in japan...

NEDO's Approach to HVDC Power Transmission Technology

Hiroshi Kato

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Director General, Smart Community DepartmentNew Energy and Industrial Technology Development Organization(NEDO)

June 4, 2019

Contents

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1. Basic informationDC vs ACDC voltage classesApplication of LVDC, MVDC, and HVDC

2. Topics from around the worldDevelopment by major overseas manufacturersTrends in EuropeTrends in ChinaTrends in the Americas and AsiaInternational conference topics

3. Latest trends in JapanHokkaido-Honshu HVDC link

4. NEDO’s approachNext Generation Offshore HVDC System R&D Project

5. Future issues

New Energy and Industrial Technology Development Organization(NEDO)

1. Basic informationDC vs AC

3

1882 Succeeded in DC transmission1884 Advocated AC transmission1896 Succeeded in long-distance AC transmission

--- AC as the world standard

Nikola Tesla

VS

Direct current (DC) and alternating current (AC) were invented in the late 19th century, and AC became the world standard for electricity because it offered a simpler way of converting between voltage levels.With the recent advancement of power electronics technology (DC-DC conversion rate ≥ 90%) and wider adoption of solar PV, DC is attracting global attention.

New Energy and Industrial Technology Development Organization(NEDO)Thomas Edison

1. Basic informationDC voltage classes

4

Source: IEC Technology Report ”LVDC : electricity for the 21st century”

HVDC

MVDC

LVDCLow Voltage Direct Current

High Voltage Direct Current

Middle Voltage Direct Current

Major use: long-distance transmission

Major use: data centers

Major use: EVs, electronic devices


1. Basic informationApplication of MVDC and LVDC

5

Factors promoting the use of MVDC and LVDC:• Wider adoption of solar PV and batteries• Popularization of DC-powered electricity-consuming devices (TV sets, air conditioners, etc.)

In limited areas such as buildings and microgrids, using DC without DC-AC conversion can be more energy efficient depending on the combination of devices installed.

Source: Five minute guide ti DC Power (ARUP)New Energy and Industrial Technology Development Organization(NEDO)

1. Basic informationApplication of HVDC

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HVDC can be more cost effective than HVAC depending on the transmission distanceBreak even distance of DC

✓ overhead transmission line: ≥800 km✓ submarine cable: ≥ 50 km

Source: Analysing the costs of High Voltage Direct Current (HVDC) transmission (August 6, 2014)

Highly cost effective long-distance transmission

Since renewable energy sources are often located at a distance from load centers, HVDC projects are underway in many countries.


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1. Basic informationHVDC transmission methods

• Separate excitation is adopted widely, while self excitation is gaining researchers’ attention• Self excitation

- High controllability leading to flexible power flow control- Enables black start and reactive power supply- Suitable for applications that require connection to weak power systems (e.g. remote islands, offshore wind plants), and/or flexible flow control to maintain grid stability

Item Separate excitation Self excitationBlack start Impossible PossibleInterconnection with AC power systems

Limited to strong AC power systems Virtually no limitations

Filter Large filter needed Small filter needed(no filter needed in some cases)

Multi-terminalization process and operation

Complicated Simple

Converter loss Small Less smallTransmission capacity expansion

Possible Possible (enabled by the recent advancement of semiconductor technology)


2. Topics from around the worldHVDC development by major manufacturers

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(self excitation)

Source: ABB websites

(separate excitation)


2. Topics from around the worldHVDC development by major manufacturers

9Source: Websites of Siemens and GE

self excitation

separate excitation

self excitation

separate excitation


2. Topics from around the worldTrends in Europe

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• European countries are carrying out DC transmission projects against the backdrop of offshore wind power growth, electricity market integration, and uneven power supply and demand.

Source: Five minute guide ti DC Power (ARUP)


2. Topics from around the worldTrends in Europe

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Country/region Project name Total budget 2014 2015 2016 2017 2018 2019 2020

EUApprox. 62.8M€(FP7)

EUApprox. 42M€(Horizon2020)

Oct 2014 – Sep 2018

Jan 2016 – Dec 2019

Source: Siemens websitehttp://www.siemens.com/press/en/feature/2016/energymanagement/2016-04-ultranet.php?content[]=EM

ULTRANET SuedLinkClassification Project name Supported by

Two-terminal DC

Inter-connection

ULTRANET PCI (EU’s projects of common interest)

SuedLinkBEST GRID(Intelligent Energy Europe Programme)

Multi-terminal

R&D

Best Paths FP7

PROMOTioN Horizon 2020

Source: TenneT websitehttps://www.tennet.eu/de/unser-netz/onshore-projekte-deutschland/suedlink/


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2. Topics from around the worldTrends in Europe (Best Paths)


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HVDC project using self excited AC/DC converters for multi-terminalizationHVDC has been adopted to strengthen Germany’s North-South interconnection(North: offshore wind plants, South: large factories)In addition, R&D for changing two-terminal DC lines into three-terminal are also being conducted in Best Paths Demo#2.

2. Topics from around the worldTrends in Europe (ULTRANET)

https://www.transnetbw.de/de/ultranetNew Energy and Industrial Technology Development Organization(NEDO)

2. Topics from around the worldTrends in China

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• China is accelerating HVDC adoption to strengthen its transmission system between potential sites for renewable power generation and densely populated areas.

Source: The Economist, Daily chart, Jan 16th 2017, China powers ahead with a new direct-current infrastructurehttps://www.economist.com/graphic-detail/2017/01/16/china-powers-ahead-with-a-new-direct-current-infrastructure



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> 20%

10% - 20%

Source: Clean Energy Consumption Plan (2018-2020)

Abandoned solar power rate by province/city in 2017

0% - 10%

> 30%

15% - 30%

5% - 15%

0% - 5%

Source: The 13th Renewable Energy Development Five Year Plan (2016-2020)

• Even if a power system has ample wind, solar, and hydro power generating capacity, the power cannot be used without enough transmission capacity. Such opportunity loss, called “abandoned” power, is a big problem with renewable energy in addition to the high development cost.

Abandoned wind power rate by province/city in 2017


Xinjiang

Heilongjiang

Jilin

Liaoning

Xizang

Sichuan

YunnanGuangxi Guangdong

Fujian

Hubei

Hunan

Inner Mongolia

NingxiaQinghai

HebeiShanxi

Henan

Anhui

Zhejiang

JiangsuShanxi

Guizhou

Chongqing Shanghai

Beijing

Tianjin

Hainan

Xinjiang

Heilongjiang

Jilin

Liaoning

Xizang

Sichuan

YunnanGuangxi Guangdong

Fujian

Hubei

Hunan

Inner Mongolia

NingxiaQinghai

HebeiShanxi

Henan

Anhui

Zhejiang

JiangsuShanxi

Guizhou

Chongqing Shanghai

Beijing

Tianjin

Hainan

Jiangxi Jiangxi


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• China’s abandoned wind power rate rose to 17% in 2016, but then dropped to 12% in 2017• China has been trying to reduce the rate by maintaining power networks, promoting energy

storage, and adjusting the locations of renewable power generation plants• The government aims to reduce the abandoned wind power rate to 5% by 2020

Amount and rate of abandoned wind in China

12,300

20,800

16,200 12,600

33,900

49,700

41,900

21,000

16%17%

11%

8%

15%

17%

12%

5%

0%

2%

4%

6%

8%

10%

12%

14%

16%

18%

-

10,000

20,000

30,000

40,000

50,000

60,000

2011 2012 2013 2014 2015 2016 2017 2020末目標

棄風量 (GWh) 全国棄風率平均

Source: National Energy Administration’s data on abandoned wind power 2011-2015 and Clean Energy Consumption Plan (2018-2020)

(GWh)

goal

Amount of abandoned wind power (GWh)

Average rate of abandoned wind power


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2. Topics from around the worldTrends in China (Zhangbei)

• A multi-terminal DC transmission project is underway in Zhangbei, Hebei Province.

Source: ABB website Created based on the data from ABB website

Commissioning year

2019

Power rating 1,500 MW

# of stations in grid

4

# of poles/station

2

AC voltage 230 kV (Kangbao)

DC voltage ±500 kV

Length of DC overhead line

DC-grid total length 648 km


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2. Topics from around the worldTrends in the Americas and Asia

Region Comment Major HVDC project

North America

USA : HVDC for interconnection of domestic networks and offshore wind power plants

Canada: HVDC for interconnection of island networks Atlantic Wind Connection

Asia HVDC applied in India, South Korea, and the PhilippinesIndia conducting a project that involves multi-terminal DC planning

South America Separately excited HVDC applied in Brazil

• DC transmission projects are planned in these regions as well• Many studies on multi-terminal DC transmission are presented in academic conferences

Source (figures): Adlantic Wind Connection websiteNew Energy and Industrial Technology Development Organization(NEDO)

2. Topics from around the worldInternational conference topics (CIGRE2018)

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HVDC was one of the hot topics at CIGRE 2018, addressed in two of the four workshops held separately from the keynotes and Study Committees’ group discussions.Three major trends:i. Interoperability (IOP) and standardization efforts in Europe, expecting the realization

of offshore DC transmission through the North Seaii. Development of systems for ultra high voltage transmission using overhead lines in

China, Brazil, and India (800 kV or 1,100 kV, often called UHV in China) iii. Improvement of DC cable performance (e.g. deep-sea DC cables)


North Sea Wind Power Hub: TenneT and its project partners are planning to build a big artificial island on Dogger Bank, a large sandbank in a shallow (15-36 m) area of the North Sea. It will be completed around 2050 and serve as a hub for WFs and interconnectors.

2. Topics from around the worldInternational conference topics (standardization)

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Workshop by CIGRE B4 and CENELEC “System aspects of HVDC grids”Bimonthly meetings have been held since April 2013 to draft European HVDC standardsRegular members: 16 manufacturers (including ABB, GE, Siemens), 19 utilities (including ENTSO-E, RTE, Tennet), 12 universities, and four companies (DNV and others)

• Drafting standards for HVDC systems involves defining the requirements specifications for AC/DC converter stations, DC switching stations, DC/DC converter stations, DC power flow controllers, and DC transmission lines. The members have also discussed topologies, controller levels and system state determination methods.

• The draft standards will be proposed to IEC.

* CENELEC: Comité Européen de Normalisation ElectrotechniqueCENELEC is a European standards organization responsible for standardization in the electrotechnicalengineering field. CENELEC consists of about 30 European member countries and it can apply fast-track procedures to the existing IEC standards to omit some of the required procedures.


3. Topics in JapanHokkaido-Honshu HVDC link

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• A new HVDC link between Hokkaido (the northernmost of Japan’s four main islands) and Honshu (the largest of the four) was built by HEPCO and started operation in March 2019. It will reinforce power supply and promote renewable energy integration in Hokkaido, and contribute to increased internal energy trading.

Highlights of the New HVDC link• Self excited DC transmission

- Able to transmit electricity during ACpower failure

• Power cable installed through the underseaSeikan tunnel

Source: NEDO translates based on HEPCO’s websitehttps://www.hepco.co.jp/energy/distribution_eq/north_reinforcement.html

Existing link (0.6 million kW)

Conversion station

Substation

New HVDC link

New HVDC link operating since

March 2019

0.6 million kW transmission capability

always available

0.3 million kW transmission capacityduring maintenance


Seikan-tunnel

Imabetsu C/S

Hokuto C/S

(0.3 million kW)

(maintenance)0.3

million kW 0.3

million kW

Existing link

0.3million kW

(maintena-nce)0.3

million kW Existing link

0.3million kW

Existing link


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Need to introduce large-scale offshore wind farms (WFs) to explore wind power potential

Wider adoption of Wider adoption of renewable energy

Ensuring stable energy supply Paris Agreement

Source: Long-term Energy Supply and Demand Outlook (METI, July 2015)

Japan’s power supply demand structure for FY 2030

Renewable energy should be adopted more widely to ensure stable energy supply and reduce GHG emissionsRenewable energy should be adopted continuously toward 2030 and beyond to facilitate early realization of the 2030 goals of the Long-term Energy Supply and Demand OutlookWind power can be economically feasible if developed on a large scale – many countries accelerating deploymentSince there is limited onshore wind potential in Japan, it is essential to focus on introducing offshore wind power

Wind power(onshore/offshore)

Energy policy implementation

GHG emissions reduction

4. NEDO’s Next Generation Offshore HVDC System R&D ProjectBackground (political significance)

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Estimated offshore wind power potential in Japan based

on wind development criteria*: about 1,380 million kW

Distributed along the coastal strip

(The farther offshore, the deeper the water)

Mostly located away from large load areas

- Approximately 70% located along the coast of Hokkaido,

Tohoku, and Kyushu regions

Source: Created by NEDO based on Report on Basic Information on Renewable Energy Zoning for FY 2013 (MOE, August 2014)

Long distance

Long distance

Offshore WF potential

Large loads

*Indicating problems with the existing transmission system

Category Item Development NOT allowed if:

Natural conditions

Wind speed < 6.5 m/s

Distance to the coast > 30 km

Sea depth > 200 m

*Wind power development criteria

4. NEDO’s Next Generation Offshore HVDC System R&D ProjectBackground (technical significance)


offshore wind power potential


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Deploy WFs by building multiple-terminal offshore DC transmission systems that connect multipleoffshore WFs to the existing large power systems and loads and transmit power efficientlyEnsure multi-vendor compatibility to involve multiple manufacturers in system building to allow forstep-by-step introduction and expansion of multiple-terminal DC transmission systems

Power system problems found in the regions with much wind potential (Hokkaido, Tohoku, andKyushu); lack of spare capacity, frequency fluctuationLarge-scale offshore WFs to be built along the coastal strip, not spread on large shoals as in Europe

Newly introduced DC transmission system in Japan: Multi-terminal

Current transmission systems in Europe: 2-terminal




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AC AC

AC AC

AC

DC

DC

DCDC

Conventional DC transmission (2-terminal)

Multi-terminal DC transmission (3-terminal)

AdvantagesReliable: bypass transmission in case of line troubleEfficient: more efficient system building than multiple two-terminal systemsExtensible

ChallengesEntire system control- Need to control each converter and power flowFault detection and isolation- Need a protection system that quickly isolates a faulty line from the othersConnection for system extension- Need a unified interface


To develop a highly reliable, low-cost, multi-vendor compatible multiple-terminal DC transmission

system and underlying technologies with one of the world’s largest transmission capacity

(voltage: ±500 kV, capacity: 1 GW)

To establish fundamental technology to accelerate adoption and integration of large-scale offshore WFs

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Offshore substation

Onshore

converter

station

Offshore converter

station

Offshore substation

Onshore

converter

station

Offshore converter

stationOnshore

substation

Onshore

converter

station

HVACHVDCDC circuit breaker (DCCB)

Power grid

Onshore substation

Onshore substation

±500 kV, 1 GW

4. NEDO’s Next Generation Offshore HVDC System R&D ProjectProject objectives


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4. NEDO’s Next Generation Offshore HVDC System R&D ProjectR&D subjects and details

R&D Subject I: System development

Plan and design economically feasible wind power collection and transmission systems to prepare for the deployment of large-scale offshore WFs in Japanese watersDevelop a model for analyzing multiple-terminal DC transmission systems and conducted model analysis to establish methods of controlling and protecting self-excited DC transmission systemsDiscuss standard specifications to ensure interoperability of different manufacturers’ self-excited AC/DC converters, which will be essential in multi-terminal DC transmission systems control

Target

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4. NEDO’s Next Generation Offshore HVDC System R&D ProjectR&D subjects and details

R&D Subject II: Underlying technologies

Develop DC breakers (1) that will help to realize a highly-reliable, low-cost multiple-terminal offshore DC transmission system, and cable joints (2), cable installation techniques (3) and offshore WF platform (4) that are more cost efficient than their conventional counterparts

1

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• Developed an analysis model for three-terminal DC transmission systems in preparation for domestic WF deployment, performed simulations with the model, and confirmed that there will be no problem with the power quality

• Drafted standard specifications for protection and control of offshore DC transmission based on the results of different manufacturers’ components connection tests conducted by project participants (Hitachi, Toshiba Energy Systems and Solutions)- The draft standards are currently under discussion with IEC

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Standard specifications (draft)

4. NEDO’s Next Generation Offshore HVDC System R&D ProjectI. System development results

• Circuit breaking is more difficult in DC than in AC because the voltage does not fall to zero• Conventional DC breakers flow the current constantly through semiconductors to ensure

interruption capabilities, causing power loss• A new interruption principle was introduced to solve the problem• The new principle has contributed to minimizing the power loss at ordinary times and

achieving one of the world’s fastest interruption speeds (3 m/s)

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4. NEDO’s Next Generation Offshore HVDC System R&D ProjectII. Underlying technology development: DC breaker

Mechanical contact

Semiconductor circuit

Commutation circuit

At ordinary times, the current flows through the mechanical contact -> extremely small lossOne of the world’s fastest interruption speeds achieved through instantaneous control of the semiconductor circuit, the commutation circuit, and the mechanical contact

Ordinary current pathIllustration of the newly developed circuit breaker structure


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4. NEDO’s Next Generation Offshore HVDC System R&D ProjectII. Underlying technology development: compatible branch joints

Development of cost effective cable joints and best installation methodsDevelopment of branch joints compatible with other companies’

Proposing a method that uses compatible branch joints to install an additional offshore WF in a system where multiple offshore WFs are linked by a MT-HVDC system to reduce costs.Developed a prototype ending box-gas (EB-G) for a 525 kV DC cable that can connect joints of other companies’ and verified its basic capabilities.

EB-G Performance Test

Circuit EB-G Cable


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4. NEDO’s Next Generation Offshore HVDC System R&D ProjectII. Underlying technology development: cable installation techniques

• Developed cable installation techniques and tools optimized for offshore wind power generation

Development of techniques for submarine cable-bringing installation Installing submarine cables up to the turbine without cable protection works by divers

will reduce time and costs. Development of techniques for submarine cable bundle installation

Generally, long submarine cables are installed one by one, but installing two or three cables at once (bundle installation) costs lower.

Development of techniques for automatic installation of submarine cable protection Installing protection tubes to submarine cables on boardwill speed cable laying. A 1/10 3D model was developed to test automatic protection tube installation as well as continuous cable laying.

1/10 protection tube installation pass line model


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4. NEDO’s Next Generation Offshore HVDC System R&D ProjectII. Underlying technology development: offshore wind turbine platform

• Different types of offshore wind turbine platforms were compared, and assessment of vulnerability to earthquakes and high-waves was carried out.Through the comparison, cost advantages of each suction foundation were confirmed.Using a centrifugal force model, horizontal loading tests were carried out to analyze performance assessment of offshore turbine platforms during an earthquake and high waves.

Suction Foundation Results of horizontal loading tests

• A simulation model of an offshore WF consists of 50 wind turbines connected in series was developed. Using the model, basic characteristics of the system were learned.


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4. NEDO’s Next Generation Offshore HVDC System R&D ProjectAchievements

• Cost advantages of a model developed using achievements of underlying technology development as well as installation sites and transmission routes for offshore WFs set a during system development stage were analyzed.

• The cost advantages are still being calculated, but the cost is likely to be cut by 20 % compared to AC transmission.

Image of offshore power network o

WFLand Connection Point

Land Connection Point


1500MW

1500MW

10km

270km

230km

95km

155km

FukushimaOnshore substation

500MW

500MW

500MW

500MW

500MW

500MW

500MW

500MW

500MW

1500MW

Targets for cost advantage analysis

KanagawaOnshore substation

FukushimaOnshoreC/S

KanagawaOnshoreC/S

FukushimaOffshoreC/S

ChibaOffshoreC/S

KanagawaOffshoreC/S

145km

270km

：

：

：

：

10km

85km

10km

Fukushima

Kanagawa Chiba

Offchore C/SOnshore C/SOnshore substationCable route

Legend

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• The project is scheduled to complete by the end of fiscal year 2019. Currently, the feasibility and the costs of MT-HVDC systems under an ideal environment are being analyzed using calculators; however, actual MT-HVDC systems must be developed for actual operation.

NEDO will continue to seek best mix of DC and AC in view of introduction and expansion of offshore wind farms in the future.

5. Future issues


Thank you for your attention.

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