New markets need new technology

Presented at Powercon 2000 Conference, Perth, Western Australia, December 4-7, 2000

NEW MARKETS NEED NEW TECHNOLOGY Lars Weimers, Member, IEEE

Master of Science Electrical Engineer (MSEE) ABB Power Systems 771 80 Ludvika Sweden

ABSTRACT

This report describes the deregulation of the electric industry as the driving force behind the development of new markets and technologies for power transmission. The new technology, HVDC Light, is well suited to meet the new markets and its demands and the reasons for this are explained. As an example, the Directlink HVDC Light Project, connecting New South Wales and Queensland project is described. KEYWORDS

Deregulated market, HVDC Light, HVDC, extruded DCcables, Cable ploughing, Voltage source converter, Windpower, interconnections, Power Quality, Multiterminal DC. 1. INTRODUCTION Governments world-wide are increasingly using competition in the electricity industry as a means of achieving cost effective outcomes. However, while competition in the generation sector is now well established, to date the achievement of market outcomes in the provision of network services has been ignored or neglected. This situation is largely due to outdated assumptions regarding economies of scale and scope and the inevitability of loop flow. These assumptions have hindered the deployment of advanced technologies, including HVDC Light. Such technologies will greatly facilitate market-driven network services, and over time will produce the same effects in the network sector that the introduction of gas turbine and combined cycle technology has produced in the generation sector, where competition is now taken for granted. Today the deregulation of the electric industry is more global and the need of network services are increasing. This is now also the case in Australia where the first interstate transmission project, The Directlink project between New South Wales and Queensland, now is in operation. More projects are discussed and the outlook for the next coming years is good.

2. PROJECT REQUIREMENTS Deregulated projects are often built by investors looking for return on investment. This means that the projects often are motivated by business decisions and not by network conditions. This has led to new project requirements. Some of these are: · Short delivery times · Rated power up to 200 MW · Environmentally friendly solutions It is important that the time period from a project decision to commercial operation is as short as possible, say maximum 12 month. To achieve this it is necessary to develop standardized designs and to have a smooth and efficient installation and commissioning process. Furthermore the permitting, including environmental reports and network studies, can not go on for ever. The investor must know that he can get the permits in a resonable time to even consider to build the project. By nature, a big project always needs more studies and impacts the environment more than a small project, which makes a big project more risky to build. This , of course, has an impact on the financing and the willingness from the investors to build the project. Experiencies from other parts of the world has shown that a rated power of approximately 200 MW is a feasible size in many respects. The power is to small to have a negative impact on the network, should a disturbance occur, and it shouldn´t be to difficult for the investors to sign a PPA (Power Purchase Agreement) for this power level. Today, environmentally friendly solutions is a must in order to get the necessary permits. For a transmission project there are the sending and receiving stations and the overhead line or cable in between. To get a permit to build an over-head line today is almost impossible, the out-come of the process is very unsure and it will take at least a few years until a decision is reached. Using a cable for the transmission will normally not create any permitting problems and the out-come is predictable and will not take long time.

All information published in this document as provided as is without any representation or warranty of any kind either express or implied including but not limited to implied warranties for merchantability, fitness for a particular purpose or non-infrigement. Any ABB documentation may include technical inaccuracies or typographical errors. Changes and additions may be made by ABB from time to any information contained herein.

3.1 HVDC Light characteristics 8G 8VZ

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An HVDC Light converter is easy to control. The performance during steady state and transient operation makes it very attractive for the system planner as well as for the project developer. The benefits are technical, economical, environmental as well as operational. The most advantageous are the following: · Independent control of active and reactive power · Feeding of power into passive networks ( i.e. network without any generation) · Power quality control · Modular compact design, factory pre-tested · Short delivery times

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· Relocatable/Leasable · Unmanned operation Fig. 1, Principles of Pulse Width Modulation (PWM)

· Robust against grid alterations

The stations should be as compact as possible and should be designed not to have a negative impact on the environment. Audible noise and other possible disturbance factors must be adressed during the design and follow the local standards in order to get the building permits. 3. HVDC LIGHT, THE NEW TECHNOLOGY HVDC Light is a new technology for power transmission using high voltage direct current. It employs the latest in power semiconductor technology , the IGBT, and is based on Voltage Source Converters which has characteristics well suited to meet the demands from the new markets. It has a standardized design, power ratings up to 200 MW, short delivery times and is friendly to the environment. The Light concept uses extruded DC cables to transmit the power which are easy to install and the resulting magnetic field is almost reduced to zero thanks to the bipolar cable arrangement.

Fig. 2, Layout of a 65 MVA HVDC Light converter

Fig. 3, Capability chart, PQ Diagram

3.1.1 Control of active and reactive power The control makes it possible to create any phase angle or amplitude, which can be done almost instantly. This offers the possibility to control both active and reactive power independently. As a consequence, no reactive power compensation equipment is needed at the station, only an AC-filter is installed. While the transmitted active power is kept constant the reactive power controller can automatically control the voltage in the AC-network. Reactive power generation and consumption of an HVDC Light converter can be used for compensating the needs of the connected network within the rating of a converter. As the rating of the converters is based on maximum currents and voltages the reactive power capabilities of a converter can be traded against the active power capability. The combined active /reactive power capabilities can most easily be seen in a P-Q diagram (positive Q is fed to the AC network).

All information published in this document as provided as is without any representation or warranty of any kind either express or implied including but not limited to implied warranties for merchantability, fitness for a particular purpose or non-infrigement. Any ABB documentation may include technical inaccuracies or typographical errors. Changes and additions may be made by ABB from time to any information contained herein.

3.1.2 Power quality control The Light converter has s a switching frequency of 2 kHz that is 40 times faster compared to a phase commutated converter operated at 50 Hz. This offers new levels of performance regarding power quality control such as flicker and mitigation of voltage dips and sags, harmonics etc caused by disturbances in the power system. Power Quality problems are issues of priority for owners of industrial plants, grid operators as well as for the general public.

The modular design also facilities a relocation of the converters, should that be desired due to changed conditions. 3.1.4 Robust against grid alterations The fact that a Light converter can feed power into a passive network makes it very robust and can easily accommodate alterations in he AC-grid to where it is connected. This is a very valuable property in a deregulated electricity market where AC-network conditions in the future will change more frequently than in a regulated market.

In the presence of a fault which would normally lead to an AC voltage decrease the converter can be rapidly deblocked and assist with voltage support to avoid severe disturbances in local industries that are sensitive to voltage dips. The response time for a change in voltage is 50 ms i.e. for a step order change in the bus voltage the new setting is reached within 50 ms. With this speed of response HVDC Light will be able to control transients and flicker up to around 3 Hz, thereby helping to keep the AC bus voltage constant. Fig. 6, Plowing of HVDC Light cable N o com pensation SV C Light

Fig. 4, Flicker mitigation with SVC Light

3.1.3 Modular compact design, factory pre-tested Major electrical equipment is delivered in enclosures and tested at factory before shipment. This eliminates the need of any buildings and also makes the installation and commissioning faster than for a traditional converter. The heaviest piece of equipment weights about 20 tons and is transportable by truck direct to site.

4. THE CABLE SYSTEM The HVDC Light extruded cable is the outcome of a comprehensive development program, where space charge accumulation, resistivity and electrical breakdown strength were identified as the most important material properties when selecting the insulation system. The selected material gives cables with high mechanical strength, high flexibility and low weight. Extruded HVDC Light cables systems in bipolar configuration have both technical and environmental advantages. The cables are small yet robust and can be installed by plowing, making the installation fast and economical.

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Fig. 7, Data for the HVDC Light cable Fig. 5, A valve enclosure arrives to site

All information published in this document as provided as is without any representation or warranty of any kind either express or implied including but not limited to implied warranties for merchantability, fitness for a particular purpose or non-infrigement. Any ABB documentation may include technical inaccuracies or typographical errors. Changes and additions may be made by ABB from time to any information contained herein.

5. APPLICATIONS The VSCs performance and characteristics invite to many new applications and concepts which previous has not been considered due to technical and economical limitations. The major driving force is the deregulation of the electricity market, where short delivery times, flexible systems and power ranges up to 200 MW are frequency asked for. The ability of the HVDC Light concept to meet these new requirements will certainly contribute to that many new projects will be built. Some examples of applications are: · · · · ·

Connecting Windpower farms to the grid Distributed generation Multiterminal DC-grid Interconnecting networks Utilising existing Rights-Of-Way

Any number of HVDC Light converters can be connected to a DC bus with fixed polarity, and by that, a meshed DC system, with the same topology as an AC system, can be built. 5.1.3 Interconnecting networks It is well known that HVDC is well suited for connection of asynchronous as well as synchronous networks. With HVDC light these interconnections can be made smaller and still have a good economy. Due to the robustness of the VSC, the station can be placed where it is best needed irrespective to network conditions. Should there be a difference in energy prices in the networks trading is possible since we have full control of power flow between the stations.

5.1 Windpower

6. DIRECTLINK PROJECT

HVDC Light is flexible and can easily be expanded by adding new units. Wind farms are often enlarged after just a few years, or joined by new farms in adjacent locations. Many suitable wind farm areas are located remotely where the network is weak. In these cases, the size of the wind farm is often restricted by the short circuit ratio. A wind farm connection directly to the AC network requires a minimum short circuit ratio around 10 for acceptable performance. With an HVDC Light connection the short circuit ratio is not a restriction.

Directlink is a 180 MVA HVDC Light transmission scheme connecting the New South Wales and Queensland power grids. It is built by a Joint Venture between NorthPower, a state owned utility in New South Wales, Australia and Hydro Quebec International.

Wind generators absorb reactive power from the AC network for magnetization. HVDC Light can supply the reactive power to the wind generators independently of the active power it receives.

The project was given the go-ahead following the completion of an extensive feasibility study that examined the financial, engineering and environmental aspects of the project. Directlink delivers power and enables NorthPower to provide a more reliable and secure electricity supply for its customers who are currently supplied by the Queensland power system. Electricity can also be exported to the Queensland power grid if required. This is the first time in history that two State Power Grids in Australia are linked together and shows a new initiative in the national market, but also breaks new technological ground. The converter stations are based on the HVDC Light technology, which is entirely new in Australia, and the stations are connected with an underground power cable. Importantly, the cable is buried for the entire 65 km. Unlike other proposals to connect the NSW and Queensland electricity grids, Directlink does not involve any new overhead transmission lines. In addition, by using existing right-of-ways along the entire route, Directlink does not require any new right-of-ways, easements or resumptions involving private property.

Fig. 8, Windpower

5.1.2 Multiterminal DC grid One feature of the HVDC Light converter is that the polarity does not change when the power flow changes. Instead the current direction changes. This makes it easy to use a converter as a building block in a multi-terminal system.

The two HVDC Light converters stations are placed at Mullumbimby and Terranora at each end of the cable. One station consists of three (3) voltage source converters (VSC), each having a rating of 60 MVA, which is the same size and rating as the converters employed for the Gotland HVDC Light project. There are in total 6 cables, two for each pair of converters, which makes a total of 390 km of HVDC Light cable.

All information published in this document as provided as is without any representation or warranty of any kind either express or implied including but not limited to implied warranties for merchantability, fitness for a particular purpose or non-infrigement. Any ABB documentation may include technical inaccuracies or typographical errors. Changes and additions may be made by ABB from time to any information contained herein.

7. CONCLUSIONS

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Fig. 9, Directlink map

Directlink benefits from the advantages from HVDC Light, some of these are : · In order to facilitate permitting the HVDC Light cable will be installed along existing rights of way for its entire 65 km route, with a substantial portion underground. · The flow of energy over HVDC Light facilities can be precisely defined and controlled, thereby meeting NECA’s Safe Harbour Provisions. The ability to control power flow over the facility also means that the capacity rights required for fully commercial network service are readily defined. · The Voltage Source Converter terminals can act independently of each other to provide ancillary services (such as var support) in the weak networks to which Directlink connects. · The use of the HVDC Light technology will greatly reduce the Directlink construction and commissioning period. Rapid response to market conditions must be a feature of market-driven transmission projects.

It is widely recognized that the role of network services has changed as a result of the introduction of competitive power markets. HVDC Light is a DC transmission technology that has important advantages for application in competitive markets. These advantages include its modularity, standardized design leading to short delivery times, and compact stations and cables reducing environment impacts and controllability giving possibilities to match the power need and/or to control the voltage in the network. These features mean that HVDC Light facilities can be installed quickly in response to competitive market signals. 8. REFERENCES [1] Asplund, G, Eriksson, K, Svensson, K: “DC Transmission based on Voltage Source Converters”, Cigré SC14 Colloquium on HVDC and FACTS in South Africa, 1997. [2] Asplund, G, Eriksson, K, Drugge, B: “Electric power transmission to distant loads by HVDC Light”, Distribution 2000, Sydney, Australia, 1997. [3] Asplund, G, Eriksson, K, Jiang, H, Lindberg, J, Pålsson, R, Svensson, K: “DC Transmission Based on Voltage Source Converters”, Cigré Conference, Paris, France, 1998.

9. BIOGRAPHIES Lars Weimers was born in Sweden 1949 and graduated from Chalmers University of Technology in 1975 with a Masters degree in Electrical Engineering. In 1979 he joined the HVDC department at ABB in Ludvika, Sweden. He has since than held several positions in the design and marketing of HVDC.In 1994 Mr Weimers was appointed the project manager for the development of Voltage Source Converters for HVDC, called HVDC Light. He than continued as the project manager for HVDC Light projects and is currently the Project Manager for the Directlink project in Australia. Mr Weimers is a member of IEEE and has been the author or coauthor of many papers for HVDC and HVDC Light.

All information published in this document as provided as is without any representation or warranty of any kind either express or implied including but not limited to implied warranties for merchantability, fitness for a particular purpose or non-infrigement. Any ABB documentation may include technical inaccuracies or typographical errors. Changes and additions may be made by ABB from time to any information contained herein.