Comparison between unipolar and bipolar single phase grid-connected inverters for PV applications

An inverter is essential for the interfacing of photovoltaic panels with the AC network. There are many possible inverter topologies and inverter switching schemes and each one will have its own relative advantages and disadvantages. Efficiency and output current distortion are two important factors governing the choice of inverter system. In this paper, it is argued that current controlled inverters offer significant advantages from the point of view of minimisation of current distortion. Two inverter switching strategies are explored in detail. These are the unipolar current controlled inverter and the bipolar current controlled inverter. With respect to low frequency distortion, previously published works provide theoretical arguments in favour of bipolar switching. On the other hand it has also been argued that the unipolar switched inverter offers reduced switching losses and generates less EMI. On efficiency grounds, it appears that the unipolar switched inverter has an advantage. However, experimental results presented in this paper show that the level of low frequency current distortion in the unipolar switched inverter is such that it can only comply with Australian Standard 4777.2 above a minimum output current. On the other hand it is shown that at the same current levels bipolar switching results in reduced low frequency harmonics

Comparison between unipolar and bipolar single phase grid-connected inverters for PV applications

An inverter is essential for the interfacing of photovoltaic panels with the AC network. There are many possible inverter topologies and inverter switching schemes and each one will have its own relative advantages and disadvantages. Efficiency and output current distortion are two important factors governing the choice of inverter system. In this paper, it is argued that current controlled inverters offer significant advantages from the point of view of minimisation of current distortion. Two inverter switching strategies are explored in detail. These are the unipolar current controlled inverter and the bipolar current controlled inverter. With respect to low frequency distortion, previously published works provide theoretical arguments in favour of bipolar switching. On the other hand it has also been argued that the unipolar switched inverter offers reduced switching losses and generates less EMI. On efficiency grounds, it appears that the unipolar switched inverter has an advantage. However, experimental results presented in this paper show that the level of low frequency current distortion in the unipolar switched inverter is such that it can only comply with Australian Standard 4777.2 above a minimum output current. On the other hand it is shown that at the same current levels bipolar switching results in reduced low frequency harmonics

Consulting Project 2018/19: Manufacturing process of superconducting magnets: Analysis of manufacturing chain technologies for market-oriented industries. Report

An international consortium of more than 150 organisations worldwide is studying the feasibility of future particle collider scenarios to expand our understanding of the inner workings of the Universe. The core of this Future Circular Collider (FCC) study, hosted by CERN, an international organisation near Geneva (Switzerland), is a 100 km long circular particle collider infrastructure that extends CERN's current accelerator complex. As a first step, an intensity frontier electron-positron collider is assumed. The ultimate goal is to build a proton collider with an energy seven times larger than the Large Hadron Collider (LHC). Such a machine has to be built with novel superconductive magnet technology. Since it takes decades for such technology to reach industrial maturity levels, R&D has already started. The superconducting magnet system is considered the major cost driver for construction of such a proton collider. A good cost-benefit balance for industrial suppliers is considered an important factor for the funding of such a project. Aim The aim of this investigation was to identify the industrial impact potentials of the key processes needed for the manufacturing of novel high-field superconducting magnets and to find innovative additional applications for these technologies outside the particle-accelerator domain. Suppliers and manufacturing partners of CERN would benefit if the know-how could be used for other markets and to improve their internal efficiency and competitivity on the world-market. Eventually, being more cost-effective in the manufacturing and being able to leverage further markets on a long-time scale will also reduce the cost for each step in the manufacturing chain and ultimately lead to lower costs for the superconducting magnet system of a future high-energy particle collider. Method The project is carried out by means of the Technology Competence Leveraging method, which has been pioneered by the Vienna University of economics and business in Austria. It aims to find new application fields for the three most promising technologies required to manufacture novel high-field superconducting magnets. This is achieved by gathering information from user-communities, conducting interviews with experts in different industries and brainstorming for new out-of-the-box ideas. The most valuable application fields were evaluated according to their Benefit Relevance and Strategic Fit. During the process, 71 interviews with experts have been carried out, through which 38 new application fields were found with credible impacts beyond particle accelerator projects. They relate to manufacturing "superconducting Rutherford cables" (15), "thermal treatment" (10) and "vacuum impregnation with novel epoxy" (13). Superconducting magnet manufacturing technologies for market-oriented industries Report. Results: A short description of all application fields that were classified as "high potential" can be found here: Superconducting Rutherford cable * Aircraft charging: Commercial airplanes only spend around 45 minutes on the ground at a time to load and unload passengers. For future electric aircraft this time window would be to small to charge using conventional cables. The superconducting Rutherford cable could charge an electric plane fast and efficiently. * Electricity distribution in hybrid-electric aircraft: On a shorter time scale, hybrid-electric aircraft is an appealing ecological technology with economic advantages. In this case, electricity for the electric engines is produced by a generator. Cables with high current densities are needed inside the aircraft to distribute the energy. The superconducting Rutherford cable could be a candidate for this task. * Compact and efficient electricity generators: Using the superconducting Rutherford cable, small and light engines and generators can be constructed. One end-use example is for instance the generation of electricity using highly-efficient wind turbines. Thermal treatment: Heat treatment is needed during the production of superconducting magnet coils. In this processing step, the raw materials are reacted to form the superconductor. This processing step is used for certain lowtemperature superconductors as well as for certain high-temperature superconductors. * Scrap metal recycling: Using a large-scale oven with very accurate temperature stabilisation over long time periods, melting points of different metals can be selected. This leads to more efficient recycling of scrap metal. It also permits a higher degrees of process automation and quality management. * Thermal treatment of aluminium: Thermal treatment of aluminium comprises technologies like tempering and hardening. The goal of this technique is to change the characteristics of aluminium and alloys containing aluminium. End-use applications include for instance the automotive and aerospace industry, where such exact treatment is necessary. Vacuum impregnation * Waste treatmnent companies currently face challenges because new legislation require more leak-tight containers. Novel epoxy resin developed for superconducting magnets in particle colliders also needs to withstand high radiation levels. Therefore, this technology can be useful in the process of managing highly-activated radioactive waste

Evaluation of the Use of Superconducting 380 kV Cable

This study describes the design of superconducting cables for use in the 380 kV three-phase network and explains general aspects of the use of such cables in the extra-high voltage grid. It compares the superconducting technology with other line technologies under many different criteria

Evaluation of the Use of Superconducting 380 kV Cable

Diese Studie führt eine Auslegung von supraleitenden Kabeln für die Anwendung im 380-kV-Drehstromnetz durch und erläutert allgemeine Aspekte des Einsatzes solcher Kabel im Höchstspannungsnetz. Dabei vergleicht sie die Supraleitungstechnologie unter vielen verschiedenen Kriterien mit anderen Leitungstechnologien

Survey and documentation of emerging technologies for the Satellite Power System (SPS)

The genesis of the solar power satellite (SPS) concept is reviewed historically and the original assumptions and guidelines which led to development of the SPS reference system design concept are discussed. Some guidelines are applicable to almost any SPS design, but others can be changed, leading to new and perhaps preferable systems. In order to stimulate new SPS concepts and to facilitate comparative assessment of emerging SPS technologies, one useful approach is to break the overall system into functional parts. The system functions which must be performed by any SPS concept and the interrelations between them are discussed and a systematic framework is presented for assessing the wide variety of system concepts and subsystem technologies which have been proposed. About 80 alternative SPS technologies are reviewed

Summary Report Comparing High Voltage Overhead and Underground Transmission Infrastructure

This report summarises the findings of an independent systematic literature review of high voltage overhead and underground transmission infrastructure, which was undertaken by The University of Queensland and Curtin University. This is the summary report for the study which is complemented by more detailed reports provided separately in Chapters 1 to 8 which cover the themes and cases studies in more detail