Disseny d'un convertidor MPPT per microaerogeneradors aïllats

Abstract

During last years, wind generation has experienced a great expansion due to concern about climate change, the greenhouse effect caused by air pollution and scarcity of fossil resources. In this context, research efforts on new wind generators have increased new power converters topologies and its control strategies. Much of these resources done by innovation centers are focused on high-power (>100 kW), leaving to a second place lower power applications mainly applied in isolated applications. However, these kinds of systems are really important considering a rural or isolated electrification framework. The present master’s project aims to contribute the study and development of electrical systems for micro-wind generation in off-grid systems. It has been designed an AC/DC converter with the capability of extracting the maximum power of the wind turbine. This is possible thanks to a maximum power point system based on disturbance based on perturb and observe algorithm, which does not require parameterization of the wind turbine, as usual. This last alternative involves a time and cost spending which is not justifiable in low power applications. In order to validate the converter and maximum power point search system, the present project has designed and implemented an experimental platform able of emulating real operation conditions of a wind system, too. In Chapter 3, it’s done the study of the state of art about the more relevant electrical systems of isolated low power wind applications. It has been fixed a group of needs and requirements of the electrical system, as well as a proposed power converter structure. Once the converter is proposed, Chapter 4 details its design considerations. First, the topology of Ac/DC converter is selected the chosen alternative consists in a three-phases rectifier diode bridge, a buck-boost converter and a current output filter for batteries. Then, has been chosen the design criteria and the components of the converter have been dimensioned. Then Chapter 5 develops a small-signal average model of the power converter getting the transfer functions necessary for control design. The control of the converter is managed by a "Observe & Perturbe" MPPT algorithm with fixed step followed by two cascaded PI controllers. This control allows working in a maximum power point with rectified voltage changes avoiding sudden changes in battery current. Once validated the control and the design of the converter through simulations, it has been implemented on an experimental platform for verify the prototype under various test proposed in Chapter 6. It has been also developed a wind turbine emulator able of generating a real operation environment by the wind system platform (Generator, AC/DC converter and batteries). Finally, Chapter 7 ends the work with some conclusions on the developed prototype and its design. This chapter allows extracting that the converter meets the aforementioned objectives. The system works on the maximum power point and the platform is able to emulate the operation of a wind turbine. Chapter 8 details some future work ideas to improve the current performance.