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The design and implementation of a small-scale solar energy conversion system is presented in this thesis. The power circuit of the PV inverter is composed of a push-pull converter and a full-bridge inverter. The inverter converts DC power generated by photovoltaic cells into AC power. This design allows flexible arrangements of various solar cells modules. The systems can supply loads and feed excess power to the grid with unit power factor when operated under grid-connected mode, or supply loads exclusively by operating in the stand-alone mode. In grid-connected mode, it is controlled to follow the variations of solar panel insolation for achieving maximum power point tracking. A 150W prototype of the conversion system is implemented, simulation and experimental results are provided to verify the performance.

The availability of high speed and high power switching devices, such as the IGBT, has opened the opportunity for an increasing number of grid-connected inverter applications that have historically been unachievable. Recently, the number of inverter applications has surged, with now the focus being on increasing the relative performance and power capability. Such applications include UPSs, dynamic voltage restorers, STATCOMs, frequency converters and distributed grid sources such as solar panels. The inverter switching frequency limits its associated bandwidth and hence performance. Every application can benefit by reduction of the extent of this limitation. While state of the art devices like IGBTs enable such applications, the onus is now on developing high bandwidth digital controllers; the ability to connect multiple devices together to achieve power scaling; and having the confidence that the applications will work with other systems on a grid.% Solutions for for improving the inverter performance, ability to scale the power and operation compliance with other grid-connected devices are sought. Constraints and limitations imposed by the hardware and traditional continuous-time derived controllers are identified. A discrete-time direct design controller is then developed specifically for digital controllers, that for the same inverter configuration, achieves twice the bandwidth of a well-tuned traditional controller. An important feature of a controller is having the configurability of being able to choose inverter bandwidth over stability margin. To provide power scaling above that of a single switching module, investigations are performed on the suitability of actively paralleling inverter modules. Both the use of the developed discrete direct design controller and the identification of potential inter-module instabilities for a particular configuration enables the application of paralleled inverters. The operation is confirmed through the application of a sixteen paralleled module inverter system. Finally, a graphical analysis technique is introduced for analysing complex grids that may include inverter systems. The graphical technique demonstrates stability constraints with a range of sources and loads, including both inverters and rotating machines, which historical analysis techniques have been unable to do.

Este trabalho apresenta o desenvolvimento de uma metodologia para a etiquetagem e qualificação de inversores para Sistemas Fotovoltaicos Conectados à Rede, com finalidade de servir de proposta de procedimento para inclusão no Regulamento de Avaliação de Conformidade de Equipamentos e Sistemas Fotovoltaicos do Programa Brasileiro de Etiquetagem. O procedimento desenvolvido avalia os inversores quanto à eficiência, qualidade de energia, proteções e informações operacionais e de instalação. / This work presents the development of a methodology for qualification and labeling of inverters for grid-connected photovoltaic systems, aiming serving as procedural proposal for inclusion in the Conformity Assessment Rules of Equipments and Photovoltaic Systems of the Brazilian Labeling Program. The developed procedure evaluates the inverters efficiency, power quality, protections and operational and installation information.

Este trabalho apresenta o desenvolvimento de uma metodologia para a etiquetagem e qualificação de inversores para Sistemas Fotovoltaicos Conectados à Rede, com finalidade de servir de proposta de procedimento para inclusão no Regulamento de Avaliação de Conformidade de Equipamentos e Sistemas Fotovoltaicos do Programa Brasileiro de Etiquetagem. O procedimento desenvolvido avalia os inversores quanto à eficiência, qualidade de energia, proteções e informações operacionais e de instalação. / This work presents the development of a methodology for qualification and labeling of inverters for grid-connected photovoltaic systems, aiming serving as procedural proposal for inclusion in the Conformity Assessment Rules of Equipments and Photovoltaic Systems of the Brazilian Labeling Program. The developed procedure evaluates the inverters efficiency, power quality, protections and operational and installation information.

Legislation about the water use in Morocco including the watering of green spaces is about to change. Indeed, the watering of green spaces will have to be made from waste water treatment plant. This report focuses on a golf course located in Agadir which is subject to the new regulation. The option studied through this paper is the desalination of salt water powered by solar energy. This paper focuses specifically on the generation of solar energy. The aim of the report is to compare the levelized cost of water express in €/m3 for three different alternatives: A) water from the drinking water plant; B) water from a reverse osmosis desalination plant driven by electricity from the national grid; C) water from a reverse osmosis desalination plant driven mainly by solar energy and some electricity from the national grid.The paper will first present the boundary conditions for the case study (part I), the technical analysis (part II-A & B) and then the economic analysis (part II-C). Part III presents the results, based on the simulation results from the software PVsyst, for both the technical and economic analysis and part IV explains the technical part in more detail.In the conclusion, the writer of the report would recommend to another in depth economic analysis in few years as the capital cost for the system with the reverse osmosis desalination plant and the photovoltaic plant is at the moment too high. However, regarding at the levelized cost of water, this case study become competitive with the other alternative. Moreover, looking at the environmental issues (water depletion, greenhouse gas emission) one could decide to take action and therefore take some economic risks.

This research investigates a low-cost generator and power electronics unit for smallscale (<10kW) wind turbines, for both standalone and grid-connected applications. The proposed system uses a high-inductance permanent magnet generator together with a switched-mode rectifier (SMR) to produce a variable magnitude output current. The high inductance characteristic allows the generator to operate as a current source, which has the following advantages over conventional low-inductance generator (voltage source) systems: it offers simple control, and avoids the need for bulky / costly energy storage elements, such as capacitors and inductors. The SMR duty-cycle is controlled in an open-loop manner such that 1) maximum power is obtained for wind speeds below rated, and 2) the output power and turbine speed is limited to safe values above rated wind speed. This topology also has the ability to extract power at low wind speeds, which is well suited to small-scale wind turbines, as there is often limited flexibility in their location and these commonly see low average wind speeds. The thesis is divided into two parts; the first part examines the use of the SMR as a DC-DC converter, for use in standalone applications. The duty-cycle is essentially kept constant, and is only varied for maximum power tracking and turbine speed / power limiting purposes. The SMR operates in to a fixed voltage source load, and has the ability to allow current and hence power to be drawn from the generator even at low wind and hence turbine speeds, making it ideal for battery charging applications. Initial dynamometer testing and limited wind-tunnel testing of a commercially available wind turbine show that turbine power can be maximised and its speed can be limited by adjusting the SMR duty-cycle in an open-loop manner. The second part of the thesis examines the use of the SMR as a DC-AC converter for grid-connected applications. The duty-cycle is now modulated sinusoidally at the mains frequency such that the SMR produces an output current that resembles a fullwave rectified sinewave that is synchronised to the mains voltage. An additional H-bridge inverter circuit and low-pass filter is used to unfold, filter and feed the sinusoidal output current in to the utility grid. Simulation and initial resistive load and preliminary grid-connected tests were used to prove the inverter concept, however, the permanent magnet generator current source is identified as non-ideal and causes unwanted harmonic distortion. The generator harmonics are analysed, and the system performance is compared with the Australian Standard THD requirement. It is concluded that the harmonics are caused by 1) the low-cost single-phase output design, 2) the use of an uncontrolled rectifier, and 3) the finite back-EMF voltage. The extent of these harmonics can be predicted based on the inverter operating conditions. A feed-forward current compensation control algorithm is investigated, and shown to be effective at removing the harmonics caused by the nonideal current source. In addition, the unipolar PWM switching scheme, and its harmonic components are analysed. The low-pass filter design is discussed, with an emphasis on power factor and THD grid requirements. A normalised filter design approach is used that shows how design aspects, such as cutoff frequency and quality factor, affect the filter performance. The filter design is shown to be a trade-off between the output current THD, power loss, and quality factor. The final chapter summarises the thesis with the design and simulation of a 1kW single-phase grid-connected inverter. The inverter is designed based on the low-pass filter and feed-forward compensation analysis, and is shown to deliver an output current to the utility grid that adheres to the Australian Standards. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1375316 / Thesis (Ph.D.) - University of Adelaide, School of Electrical and Electronic Engineering, 2009

Pakistan has been riddled with energy shortage crisis. Long hours of load shedding have caused major economic setbacks in urban areas and rural areas do not even make the cut. Some rural parts, which are connected to the grid, suffer major load shedding and so economic growth is minimal. Most energy is directed towards industrial demand; hence the domestic demand suffers and causes long hours of load shedding. To aid this supply-demand gap, microgrids can be helpful in relieving some of the domestic load on the grid. A microgrid may be more economical only as a support for the main grid in an area, depending on its configuration. Since microgrids are generally composed of renewable energy sources like wind or solar or a combination of both, the supply from just these sources may result in high intermittency. To allow uniform supply, a backup energy source or energy storage is included with the renewable sources. Sizing a microgrid for the targeted region is critical. Some major sizing factors include the availability of renewable resource, load profile of the region, land availability, grid availability, etc. For this thesis, a region near Gharo, a town in Thatta District in Sindh, Pakistan, is selected to deploy the microgrid with a wind farm and battery energy storage system. The microgrid is connected to the main feeder, which supplies grid electricity to a small town of 30 small homes, a school and a small hospital. Hourly wind speed data and an annual load profile is used to calculate the most economic size of the microgrid, depending on the energy dispatch philosophy. To find the most economical solution, this thesis incorporates a stochastic technique, known as the Particle Swarm Optimization (PSO), which is a powerful intelligence evolution algorithm for solving optimization problems. Over the years, PSO has gained popularity due to its simple structure and high performance in solving linear or non-linear objective functions with any number of constraints. In this case, the objective function to be minimized is the net present cost of the microgrid, which comprises of annual capital cost, annual operation and maintenance cost, annual replacement cost of all equipment involved and the annual net cost of buying/selling electricity from/to the grid, respectively.

Grid-connected inverters have wide application in the field of distributed generation and power quality. As the power level demanded by these applications increase, the design and performance evaluation of these converters become important. In the present work, a 50 kVA three-phase back-to-back connected inverter with output LCL filter is built to study design and performance evaluation aspects of grid-connected inverters. The first part of the work explores the split-capacitor resistive-inductive (SC-RL) passive damping scheme for the output LCL filter of a three-phase grid-connected inverter. The low losses in the SC-RL scheme makes it suitable for high power applications. The SCRL damped LCL filter is modelled using state space approach. Using this model, the power loss and damping are analysed. A method for component selection that minimizes the power loss in the damping resistors while keeping the system well damped is proposed. Analytical results show the losses to be in the range of 0.05-0.1% and the quality factor to be in the range of 2.0-2.5. These results are validated experimentally. In the second part of the work, a test method to evaluate the thermal performance of the semi-conductor devices of a three-phase grid-connected inverter is proposed. The method eliminates the need for high power sources, loads or any additional power converters for circulation of power. Only energy corresponding to the losses is consumed. The capability of the method to evaluate the thermal performance of the DC bus capacitors and the output filter components is also explored. The method can be used with different inverter configurations -three-wire or four-wire and for different PWM techniques. The method has been experimentally validated at a power level of 24kVA. In the third part of the work, the back-to-back connected inverter is programmed as a hardware grid simulator. The hardware grid simulator emulates the real-time grid and helps create grid disturbances often observed at the point of common coupling in an ac low voltage grid. A novel disturbance generation algorithm has been developed, analysed and implemented in digital controller using finite state machine model for control of the grid simulator. A wide range of disturbance conditions can be created using the developed algorithm. Experimental tests have been done on a linear purely resistive load, a non-linear diode-bridge load and a current-controlled inverter load to validate the programmed features of the grid simulator.

Este trabalho propõe um procedimento para qualificar sistemas fotovoltaicos conectados à rede, o qual possui dois focos principais: o comissionamento e a caracterização da produção de energia. Também resume alguns aspectos normativos relacionados aos sistemas fotovoltaicos, apresenta os principais parâmetros de desempenho utilizados para caracterizar um sistema fotovoltaico, propõe uma metodologia para calcular a energia injetada na rede, a qual incorpora modelos matemáticos e procedimentos de medição, tanto novos quanto convencionais, e aplica essa metodologia em um estudo de caso de um sistema fotovoltaico real. / This work proposes a procedure for qualifying grid-connected photovoltaic systems, which has two main focuses: the commissioning and the characterization of energy production. The work also summarizes some regulatory aspects related to photovoltaic systems, presents the main parameters used to characterize the performance of a photovoltaic system, proposes a methodology to calculate the energy injected into the grid, which incorporates both new and conventional mathematical models and measurement procedures, and applies this methodology to a case of study of a real photovoltaic system.