An investigation into voltage control approaches on an example distribution feeder to increase PV penetration

Solar power has become an increasing electricity resource in Australia’s electrical energy in recent years. The increase is due to the decrease in the cost of solar Photovoltaic (PV) systems and incentives provided by the Federal Government’s “Renewable Energy Target” scheme to offset carbon emissions. The existing electrical grid infrastructure was not originally designed to face high penetration levels of PV systems, so the growing embedded PV penetration levels has aroused various technical challenges and one of the key challenges is voltage rise. In order to provide methods to reduce technical barriers for achieving high penetration levels in Australian electricity networks, several approaches are studied in this report. The methods are studied with respect to prosumer (the combination of producer and consumer) aspect, utility aspect and a combination of these two aspects. The simulations were carried out using DIgSILENT PowerFactory software. Where possible, all designs and specifications are undertaken in accordance and in compliance with relevant standards and Western Power requirements and guidelines. Three prosumers’ methods which can be implemented in individual inverters are studied in chapter 6. They can be used to keep the voltage within the defined limits when the PV generation is 5kW/house, which is its assumed maximum value. But these technologies need to be upgraded to be more effective since the PV generation keeps climbing in Australian distribution networks. The utilities’ methods with additional devices implemented in the network are discussed in chapter 7. These control methods can effectively and efficiently control the voltage rise problem but one disadvantage is that they are all expensive and are not economically viable options. The combination of utilities’ method and prosumers’ method are introduced in this report as well. A recommendation for future studies that could be a continuation of this topic is provided at the end of the thesis report

Wave Energy Report On The Electrical Aspects Of The Edinburgh University Wave Energy Device

In our offer of services there were no formalised Terms of Reference given, although the object of our participation was: - "To assist the ETSU Wave Power Programme by providing consultant services to Edinburgh University, the latter acting under an Agreement with the Secretary of State for Energy". By mutual agreement with ETSU and the Edinburgh Wave Power Team, the objectives of our investigations were: - a. To examine theoretical electrical concepts. b. To determine whether a.c. or d.c. electrical transmission is appropriate. c. To determine the specification of electrical generation equipment. d. To minimise the cost of generation and transmission plant. e. To make recommendations on transmission lines and cables. f. To produce an overall scheme for generation and transmission of electrical power, including an estimate of the cost thereof. The concept of installing generators, switchgear, transformers and cables out in the most exposed area of our coast line may be regarded as adventurous and perhaps this is the reason why SCOPA have been asked to work with the Edinburgh University Wave Energy Team on this project. We are proud that we are accepted as part of the team because it is refreshing to work with people anxious to overcome problems and reluctant to give up a promising concept when faced with apparent difficulty. At the same time we have come to respect the tenacious search for practical solutions to problems which is one of the main characteristics of the members of the team. It is with a sense of some surprise that we have found ourselves able to present a scheme for the generation and transmission of electrical energy from the Edinburgh 'Salter Duck' devices to the Scottish grid system which uses conventional ideas albeit in a manner not hitherto associated with the Wave Power Project. Of course there are a number of problems with the 'Duck' scheme, and, on our conventional assessment, it is relatively expensive; but we now believe it is possible, and promising. Certain problems common to wave power devices were identified during the investigations described in this report. We feel that this report would be incomplete without describing such problems, and accordingly have included these in the last Section (9) of this report. This report is confined to the technical and cost aspects of generating electrical power at sea on board the ducks, and delivering this power to the Scottish Transmission Grid System. The optimisation of hydraulic drives within the ducks, and the design of coupling arrangements between ducks is still proceeding. Arrangement of the electrical system has had to proceed on the basis of a specified duck design, which has a specific output. For reasons explained in the text of our report we consider the term "Wave Energy device" more appropriate than "Wave Power device". Henceforth the term "Energy" is used in preference to the term "Power" to describe the device

Offshore Electrical Networks and Grid Integration of Wave Energy Converter Arrays - Techno-economic Optimisation of Array Electrical Networks, Power Quality Assessment, and Irish Market Perspectives

Wave energy is an emerging industry and faces many challenges before commercial wave energy converter (WEC) arrays are installed. One of these challenges is the grid integration of WEC arrays. This includes offshore electrical networks, grid compliance, and access to electrical markets. This must be achieved in a technically viable manner and also at an acceptable cost. As electrical networks are expected to make up a large proportion of the overall WEC array CAPEX, perhaps up to 25%, this area is critical to the long term competitiveness of wave energy. The objectives of this thesis are to develop technically and economically acceptable electrical network designs for WEC arrays, evaluate voltage flicker issues for WEC arrays and develop design tools to analyse same, and evaluate the market scale for wave energy in Ireland, considering electrical integration issues in both the domestic and export markets. This thesis presents the optimum design for WEC array electrical networks. By building from the industry state of the art, including offshore wind experience, a comprehensive techno-economic optimisation process is undertaken. This includes optimising the key electrical interfaces between the WEC and the array electrical network, optimising the array network configuration, assessing efficiency of the network, and demonstrating that the network can be achieved at a cost which will allow competitiveness. Some challenges to the economics of WEC array electrical networks and some strategies for improving the economics are presented in this research also. The results provide timely guidance to WEC and WEC array developers. This research also demonstrates the critical link between voltage flicker emissions from WECs and the primary resource, i.e. ocean waves. Some practical assessment tools for the evaluation of this power quality issue are shown to assist in quantifying the problem. Also the full flicker performance of a candidate WEC is assessed helping characterise this link further. In this thesis both the domestic and export markets for Ireland’s wave energy resource are assessed as, although Ireland has an enviable wave energy resource, it is unclear where the market for this resource lies. This analysis shows that the medium term market for wave energy in Ireland is an export market. Also, although technically feasible, there is an additional cost for export transmission which must be considered in evaluating export markets. Some of the critical grid integration issues have been evaluated and addressed in this thesis. Future work is recommended in the areas of weather risk to cable installation at high energy wave sites, evaluating the benefits of shared electrical infrastructure across a range of renewable projects, designing offshore substations for WEC arrays, and quantifying the benefits of the addition of wave energy to the Irish renewable energy mix

The Application of Superconducting Technologies in Future Electrical Power Systems

Growing power demand in countries such as the UK can often result in increased power losses and voltage control problems within distribution networks. Mitigation of these issues in distribution networks is challenging when conventional power conductors and transformers are considered. There are several methods that may reduce losses in distribution networks, such as carefully sited and operated distributed generation (DG) and distributed control techniques. Since High Temperature Superconductor (HTS) cables exhibit zero resistance when cooled to the boiling point of liquid nitrogen (77Keliven), they have the potential to be used to address these issues in distribution networks. This thesis has investigated the impact of HTS cables and HTS transformers on power losses, voltage changes, fault levels and DG on an existing section of the UK distribution network and compares this with one utilising conventional cables and lines. This study has been accomplished using IPSA. Also, another piece of work calculates in terms of the power losses in HTS cables and HTS transformers including the power needs of their refrigeration systems. This has then been compared these to power losses incurred in conventional distribution and transmission networks. Furthermore, the thesis introduces the comparison costs of HTS cables and HTS transformers with conventional cables and transformers and considers future projected costs for HTS cables and transformers. This information has been used to enable a techno economic evaluation of the potential of future alternative superconductor network design. A method for reactive power sharing in an AC superconductor distribution network, including various DGs, has also been proposal. In addition, this thesis has demonstrated the possibility of increasing the ability of electrical distribution networks to deliver high power densities to critical urban areas, whilst avoiding the need for heavy network reinforcement and additional assets. These studies en achieves using IPSA and Matlab software. Finally, research of work was carried out to investigate the practical effects of installing superconductor equipment and identify novel network designs that make the best use of the attributes of superconducting network assets in terms of lower power losses, lower capital cost and a lower risk level than existing conventional distribution network designs. In 2013, the total cost of the future 33kV superconductor distribution network design would be £842.1M higher than that of the present conventional distribution network design. However, by 2030 the future 33kV superconductor network design will be £16.86 M lower than the present conventional network design. Consequently, these results show that using HTS assets in large distribution network design, operating at different voltage levels could save millions of pounds in the future

Grid integration of distributed renewable energy sources: a network planning perspective

Includes bibliographical references.With the drive for cleaner energy, Independent power producers (IPP’s) have to find suitable potential land sites that meet their renewable project needs and that prove to be technically feasible to integrate into the nearest distribution electrical infrastructure. Project feasibility for utility grid connection can in certain instances be directed to a specific area due to resource availability and existing electrical plant capability. This invariability leads to multiple establishments of renewable energy plants in the same geographic location. Distribution substations and high voltage (HV) lines in the South African National utility, Eskom, are planned and constructed based on simulation models derived from power system models built in DIgSILENT Powerfactory analysis software. For a Network Planning Engineer, planning for this integration can be become quite complex in a multi-machine scenario as above. This dissertation provides network planning criteria that a planning engineer in the utility can successfully use to plan for this integration. Three sets of criteria are established. With the inclusion of widespread distributed generation in close proximity of each other, sharing the same grid electrical infrastructure, a critical path of HV electrical elements exists, which the effects of the combined generation control. The first set of planning criteria is derived from the analysis of locating this critical path. This is determined by means of using iterative programming and calculations. Grid voltage stability is one the most important factors in determining the feasibility of generator grid integration. The voltage stability effects of the Eskom Distribution network to which these generating plants connect to, are analysed and tabulated results established. This will enable the utility to determine the location of a specific size of renewable plant, just by knowing the grid strength and not going into detail voltage stability studies. For the second set of planning criteria three sets of network range strengths are identified with corresponding ratios of grid strengths to generator short circuit current contributions. Successfully integrating DG to the grid also has many technical and cost solutions of network configurations. The third set of planning criteria identifies four generic network configurations and the building blocks of physically costing the engineering integration. Solar density maps provide an indication of proposed MW output in a particular area. In this research, solar density maps are used to identify the maximum connecting generation to the electrical grid in feasible geographic areas. The results derived from this study enable the planning engineer and/or developer to better plan the optimal location of a PV project wrt the chosen geographic area of KZN. This study case may be extended to other technologies leading to a more concise framework of network planning for renewable project integration