Novel Power Electronics Topologies, Control and Methods for Harvesting Renewable Energy in Different Applications




Fernandez, Daniel Ray

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The growing market for renewable energy technologies has resulted in rapid growth for power electronics topologies and control methods. Most of the renewable energy technologies produce DC power and hence power electronics and control are required to convert the DC voltage from renewable energy into AC power to connect to the grid. Inverters and mainly voltage source inverters (VSIs) are used for this conversion. Conventionally, classical linear control methods for example, proportional integral (PI) controllers are usually used for controlling VSIs as they have the ability to eliminate the steady state error but they can be slow and have limited bandwidth and poor disturbance rejection. In this thesis, a new feedback control method for nonlinear, grid-connected VSIs will be discussed. Specifically, a L-infinity robust control, which is calculated through a convex optimization problem based on LMIs (Linear Matrix Inequalities) and BMIs (Bi-Linear Matrix Inequalities). The study presents the nonlinear differential algebraic equations of the network, linearizes it under an operating point and uses the linearized model of the converter to compute, a L-infinity feedback control. The control algorithm is validated with Matlab/Simulink simulations under nominal conditions, disturbances and parameters uncertainties.

Furthermore, for DC grid applications, there is a demand for high step-up, non-isolated DC/DC converters. The available solutions for high gain DC-DC converters use either a transformer or a cascade of boost converters. Both solutions have distinct disadvantages, such as, increased losses, reduced efficiency, and EMI problems. In this thesis, a new type of switched capacitor (SC) DC-DC converter is presented. The proposed converter has a high DC conversion ratio, line/load regulation, fault (current) interruption capability, and either no or very small DC capacitance in the converter output side. The basic concept of the proposed SC DC-DC converter is to charge capacitors in parallel and discharge them in series, which is similar to the traditional SC DC-DC converter based on the concept of Marx generator. The proposed SC DC-DC converter consists of two parts, boost DC-DC and buck DC-DC converter parts. The thesis will present the converter development and simulation verification in Matlab/Simulink. In addition to large renewable energy sources like photovoltaic and wind energy, there is an immense amount of renewable energy sources available on the roadways such as mechanical pressure and heat. In this thesis, we explore advanced energy-harvesting and composite nanomaterials, combined with the implementation of efficient power conditioning and delivery circuits, to deliver innovative, practically viable smart charging solutions for future electric vehicles. This was achieved by implementing a novel wireless power system where (a) nanomaterials-powered light-emitting diodes (LEDs) as the energy transmitter, are embedded under the road, and (b) thin-film photovoltaic (PV) solar panels as the energy receiver, are placed under each vehicle. A lab-scale prototype was developed to testify the proposed mechanism of illuminative charging (i.e., "light" couples pavement and vehicle as a wireless energy transfer medium).


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Electrical and Computer Engineering