Pedro Costa

As an abundant renewable energy source, wave energy has the potential to reduce carbon emissions and diversify the energy mix. Wave energy has a comparatively low TRL compared to other renewable energy technologies. To address this issue, the industry should move towards rigorous testing, focusing on real-world testing. Utility-scale projects require significant financial resources. The use of smaller devices not intended to power the utility grid, but to test the technology and collect important data on operation and maintenance is a possible answer with a much lower cost and associated risk. This paper presents the experimental testing of the complete power-to-take-off system of a standalone floating oscillating water column equipped with a biradial turbine. The tests are conducted using the hardware that is to be assembled into the buoy. The experimental campaign includes tests, first, under steady state flow and later under variable flow conditions that mimic the sea state conditions of the buoy prototype to be deployed in the Azores, Portugal. The results are later compared with the device's numerical simulations.

Wave energy is an abundant renewable energy source with great potential to add to the energy mix and reduce carbon emissions. There are many wave energy devices, and the technology has a relatively low TRL compared to other renewable energy technologies. To address this issue, the sector should move towards intensive testing, not only in laboratories but focusing on testing in real-world conditions. Utility-scale projects involve large amounts of capital. A possible solution with a considerably lower investment is the use of small devices that, although not intended to supply the utility grid, can test the technology and at the same time collect important information on operation and maintenance, thereby reducing the associated risk. The present paper focuses on the design and simulation of the power conversion and control system for a stand-alone floating oscillating water column device equipped with a biradial turbine. This work models and analyzes the design and control of the power converter system to enable effective control of the generator, maximizing the energy output under variable flow operating conditions. Simulations are conducted to evaluate the system's behaviour under different sea states, representative of the conditions predicted for the buoy deployment in the Azores, Portugal.

This paper presents a novel analytical loss formulation to predict the efficiency of three-phase inverters using silicon carbide (SiC) metal—oxide—semiconductor field-effect transistors (MOSFETs). The proposed analytical formulation accounts for the influence of the output current harmonic distortion on the conduction losses as well as the impact of the output parasitic capacitances and the deadtime on the switching losses. The losses are formulated in balanced conditions to select suitable SiC MOFETs for the desired target efficiency. To validate the proposed methodology, a 3-phase inverter is designed to present full load efficiency in excess of 99% when built using SiC MOSFETs antiparalleled with SiC Schottky diodes selected for the specified full load efficiency. Experimental assessment of the designed inverter efficiency is compared with the expected values from the proposed analytical formulation and shown to match or exceed the predicted results for loads ranging from 40% to 100% of full load.

Matrix converters have been extensively investigated in academia over the last 3 decades. Several review works targeting matrix converter topologies, commutation strategies, modulation and control techniques have been published. However, to the best of the authors’ knowledge, a review on the potential contributions of matrix converters for applications that are shaping the electric power sector transition towards decarbonization is lacking, namely applications on smart grids, sustainable transportation and electrical drives. This paper presents an extensive literature review on the more relevant research works targeting applications of matrix converters as an enabling key technology for smart and resilient grids, sustainable transportation, and innovation in variable speed electric drives.

In this paper, a direct power predictive controller (DPPC) is derived for a current source inverter (CSI) based single stage photovoltaic (PV) system. The equations of the dynamics, including AC and DC filters, are formulated directly for the PV power and for the active and reactive power injected in the grid. Then, the prediction equations are synthesized straight for the power, and, at each time instant, the optimal switching vector that guarantees simultaneously the control of the power generated by the PV arrays, and the control of the reactive power in the connection to the grid is chosen. This approach aims to guarantee fast and accurate tracking of the power. The proposed system is then validated through simulation and experimental results, showing that the PV system is able to follow the power references, guaranteeing a fast response to a step in the power, and decoupled active and reactive power control, with minimum total harmonic distortion (<5%) of the currents injected in the grid.