KS4 HVDC Status 2014-finalAndersen Power Electronic Solutions Ltd October 2014 PowerCon 2014 Chengdu...

Andersen Power Electronic Solutions Ltd

October 2014 PowerCon 2014 Chengdu 1

Status of HVDC Transmission and Progress towards HVDC Grids

Presented by Bjarne Andersen

(Past Chairman of Cigre SC B4)

Andersen Power Electronic Solutions [email protected]



Presentation Contents

• Line Commutated Converters (LCC)• Voltage Sourced Converters (VSC)• HVDC Grids



Line Commutated Converter (LCC) HVDC

• LCC HVDC was commercially introduced in 1954 and now uses thyristors.

• They depend on good quality ac voltage for commutation and can suffer commutation failures during system disturbances.

• LCC HVDC cannot provide power to a network without synchronous generation or compensators.

• LCC HVDC absorbs reactive power which is typically provided by switchable ac harmonic filters.



LCC HVDC -2

• The total rating of in-service LCC HVDC is currently >225GW.

• LCC HVDC is used mainly for bulk power transmission and interconnections.

• LCC HVDC uses overhead dc lines and/or dc cables or no transmission line (Back to Back).

• 2 multi-terminal schemes in service, two ±800kVdc schemes in construction in India,

• The largest voltage and power LCC HVDC scheme in service is rated at ±800kVdc, 8000MW.



North-East Agra, India, Multi-terminal, ±800kVdc

Single Line Diagram of North-East Agra, India Multi-terminal ±800kVdc, 6000MW, HVDC scheme

Courtesy of ABB



LCC HVDC -Examples

•

Fulong converter station of the Xiangjiaba-Shanghai, China ±800kVdc , 7200MW HVDC scheme

Courtesy of ABB



LCC HVDC -Examples

•

±800kVdc Thyristor Valves, China Courtesy of Siemens



LCC HVDC -Examples

±800kVdc Transformer for 6,000MW Champa-Kurukshetra, IndiaCourtesy of Alstom Grid



The Need for ±1100kVdc LCC HVDC

±800kVdcCourtesy of China EPRI

The power resources in Tibet The power resources in Tibet (hydro) and Xinjiang (Coal) are (hydro) and Xinjiang (Coal) are up to 160GW (110GW hydro up to 160GW (110GW hydro power & 50GW coal power )power & 50GW coal power )

Load centers are in Central Load centers are in Central and Eastern Chinaand Eastern China

Line losses of a 2500km line Line losses of a 2500km line are up to 10% for are up to 10% for ±±800kV 800kV UHVDC and 4% for UHVDC and 4% for ±±1100kV 1100kV UHVDC under same DC UHVDC under same DC current (5kA)current (5kA)

UHVDC is required due to highUHVDC is required due to highpower power transfer over ltransfer over long ong distancedistance



±1100kV LCC HVDC

• ±1100kV HVDC is being developed in China and also by European Manufactures.

• The power capacity can be 11GW with an ultimate target of 14GW.

• ±1100kV HVDC is suitable for bulk energy transport over very long distance (2000km).

• It will require very strong and robust ac networks to withstand the loss of power transfer due to ac and dc faults.



±1100kV LCC HVDC Challenges

• Dielectric design, including voltage stress control of insulation systems.

• Optimum surge arrester design essential to reduce clearances to achieve minimu OHL and converter housing (8.5m clearance at 0m, 9.6m at 2000m).

• Increased length of dc wall bushings by 7.5m compared to 800kVdc.

• Transformer weight and dimension exceed transport dimensions



1100kVdc equipment

Courtesy of ABB



Site assembly and testing of Transformer

Courtesy of China EPRI

HV valve hall to be converted for on-site assembly

Internal layout modified according to function requirement

Total space: 246m*128m, Production capability: 2 units per month



Voltage Sourced Converters (VSC)

• First commercial VSC HVDC scheme was commissioned in 1999.

• 16 schemes total 3,400MW in service, 12,000MW under construction, of which 6,400MW are for offshore wind.

• Highest pole to pole voltage today ±320kVdc.• Highest pole to ground voltage is 525kVdc.• Highest rating in service is 500MW, Highest under construction is 1000MW.

• Higher voltage and rating are considered to be easily achievable.



Voltage Sourced Converters (VSC)

• VSC HVDC uses IGBTs, are self-commutating and can operate with passive networks.

• VSC HVDC does not suffer commutation failures.• Active and Reactive Power are independently controllable.• VSC HVDC is easy to integrate in ac networks • No switchable ac harmonic filters, smaller footprint than LCC

HVDC.• Constant DC Voltage polarity, easier for multi-terminal

schemes.• The power loss of multi-level converters is a little higher than

for LCC HVDC (1.0% compared to 0.75%)• The technology is new- actual reliability and availability not yet

established.


VSC HVDC Examples

Chengdu 2014 HVDC Status 17

Valhal Converter station - Norway, 78MW, 150kVdcCourtesy of ABB


VSC HVDC Examples


Gerus Converter station - Namibia, 350MW, 0/350kVdcCourtesy of ABB


VSC HVDC Examples


Woodland Converter station - Ireland, 500MW, ±200 kVdcCourtesy of ABB



VSC HVDC -Examples

±800kVdc Transformer for 6,000MW Champa-Kurukshetra, IndiaCourtesy of Alstom Grid

INELFE, France - Spain, 2 x 1000 MW, ±320kVdcCourtesy of Siemens



VSC HVDC -Examples

Borwin 2, North Sea, 800MW, ±320kVdcCourtesy of Siemens



Why HVDC Grids?

• More and more HVDC schemes are being built for long distance transmission and interconnections.

• Consideration is being given to convert ac lines to HVDC to increase transmission capacity.

• Providing point to point HVDC systems with an alternative route for power flow can increase the reliability and availability of the energy system.



HVDC schemes in Great Britain (GB)

Slide Courtesy of SSE




GB National HVDC Centre




HVDC Schemes in India

±800kVdcCourtesy of China EPRI



Proposed New HVDC Corridors in Germany

Slide Courtesy of Siemens



HVDC in China



Nan’ao VSC MTDC Project

Slide Courtesy of SEPRI, China



Potential next MTDC application in China

Slide Courtesy of SEPRI, China

MTDC system combining LCC HVDC (rectifier end) with VSC HVDC (inverter end)



Why HVDC Grids?

Because of the growing number of HVDC schemes and with many of the terminals for these in close proximity the idea of a HVDC Grid was born.

An HVDC Grid is defined in Cigre as an HVDC system consisting of at least three converter stations and at least one mesh formed by transmission lines.



Multi-terminal or HVDC Grid?

Multi-terminal

HVDC Grid



European HVDC Grids being discussed

• Several HVDC Grids have been proposed and are being investigated in Europe.

• The purpose of all of these are to increase utilisation of renewable energy.

• Projects include:- The European SuperGrid- The North Sea Grid- The MedGrid- Desertec



Feasibility of DC Grids

CIGRE WF B4.52 set up in 2008 to investigate feasibility of HVDC Grids. Technical Brochure No 533 presents the results, concluding:

- There are no insurmountable technical obstacles to building HVDC Grids.

- HVDC Grids would provide a highly controlled overlay on AC grids, for the transmission of renewable energy and sharing of energy storage.

- Special protection is needed in case of dc side faults to identify the faulty elements and disconnect the fault, before the dc grid collapses.

- A Grid Code covering operational and performance aspects of HVDC Grids is necessary.



Technical Challenges of the DC Grid

CIGRE WF B4.52 set up in 2008 to investigate feasibility of HVDC Grids. Technical Brochure No 533 identifies that HVDC Grids are feasible, but the following issues have to be resolved:

- The protection and fault clearance of the HVDC Grid. - Functional control strategies for the HVDC Grid. - Development of Central Co-ordinating Controllers. - Modelling tools and generic converter models. - Selection of preferred DC Voltages for HVDC grids. - Development of Grid codes for HVDC Grids. - Development of benchmark tests for converter stations. - Development of efficient DC/DC converters.



Cigre SC B4 WGs in the area of HVDC Grids

• WG B4.56 - Guidelines for the preparation of “connection agreements” or “Grid Codes” for HVDC grids.

• WG B4.57 - Guide for the development of models for HVDC converters in a HVDC grid.

• WG B4.58 - Devices for load flow control and methodologies for direct voltage control in a meshed HVDC Grid.

• JWG B4/B5.59 - Control and Protection of HVDC Grids. • WG B4.60 - Designing HVDC Grids for Optimal Reliability and

Availability performance.• JWG B4/C1.65: Recommended dc voltages for HVDC grids. • JWG A3/B4.34: Technical requirements and specifications of

state-of- the-art DC Switching Equipment.


What Types of HVDC grids?

• Converter Design VSC or LCC?- Both are potentially possible

• Converter arrangement: Bipolar, Monopolar, Balanced Monopolar, or a mixture?

- This is a decision to be taken by the HVDC Grid Developer

• Earth Return Arrangements provided or not?- The earthing strategy depends on the converter arrangement. It

has a major impact on the performance during faults to ground within the HVDC Grid.

• Converter Topology Full Bridge or Half Bridge?- Both can be used, and the optimum solution may be decided

based on functional requirements.




Will HVDC Grids be Implemented? - Against

• Some of the issues delaying European HVDC Grids include:– The magnitude of the investment which will be needed whilst

European economies are only slowly emerging from a recession.– Fragmented ownership of the existing HVDC schemes (i.e. many

TSOs).– Uncertainty resulting from energy policies which in many EU

countries are relatively short term.– Political issues associated with an HVDC Grid potentially

covering many different countries, (including non-European) which may have different energy policies and security concerns.

– The fact that an actual HVDC grid has not yet been built, even though the technical experts agree that there would be no insurmountable difficulties.



Will HVDC Grids be Implemented? - For

• For:• Much lobbying from European manufacturers.• Desire in Europe to increase the amount of renewable

energy, but this require additional electrical transmission.

• Public opposition to new AC OHL in Europe.• High political interest in Europe.• New manufacturers of HVDC systems will increase

competition and lower prices.• An HVDC Grid is being considered in China!



Will HVDC Grids be Implemented? Conclusion

• Developing a completely new transmission system combining ac and dc systems is a large and time-consuming task.

• Cigre SC B4 WGs will lay foundations but more work is needed:• HVDC Grid Developer need to develop the functional

specifications/grid codes for HVDC Grid equipment (converters, dc switchgear, cables, over head lines, communications, signals,etc).

• Manufacturers need to develop new economical equipment such as fast dc breakers and dc/dc converter.

• Advantage should be taken of the experience gained during the development and evolution of the existing AC networks

• The presenter’s personal opinion is that the implementation of an European HVDC Grids is likely to commence within the next coupleof decades.

• It is likely that the first HVDC Grid will be built in China!



Any Questions?

[email protected]

For more information visit:http://b4.cigre.org/Publications/Documents-related-to-the-development-

of-HVDC-Grids

KS4 HVDC Status 2014-finalAndersen Power Electronic Solutions Ltd October 2014 PowerCon 2014 Chengdu...

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Transcript of KS4 HVDC Status 2014-finalAndersen Power Electronic Solutions Ltd October 2014 PowerCon 2014 Chengdu...