Grid Integration and Impact of a Wave Power System

Author: Arvind Parwal; Cecilia Boström; Damir Šljivac; Uppsala Universitet; []

Keywords: ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ANN; buck-boost converter; current control; energy storage system; force control; flicker; FPGA control; grid integartion; harmonics; linear generator; PHIL; microgrid; voltage variation; wave energy; WEC; Engineering Science with specialization in Science of Electricity; Teknisk fysik med inriktning mot elektricitetslära;

Abstract: Increasing energy consumption and concern for carbon emissions has boosted the demand for renewable energy production. The focus on renewable energy has gained much attention in wind, solar, hydro and wave power generations. Wave power has great potential due to its high energy density but there are challenges as well. This thesis addresses some of the challenges involved in the grid integration of wave energy and in maintaining power quality. In this thesis a grid connection of permanent magnet linear generator (PMLG) based wave energy converter (WEC) as a renewable energy source is evaluated at the Division of Electricity, Uppsala University.The grid impact of a wave energy park in terms of flicker, voltage variations and harmonic distortion at the grid-connection point are investigated extensively. The short-term flicker level generated by the WEC and a wave energy park (WEP) related to the rated WEP power and grid impedance angle at the PCC are evaluated.In this thesis, an improved control for hybrid energy storage is presented, which enhanced the efficiency and increased the battery life while smoothing the intermittent power from the WEP. The thesis, also, contributes to resolve the problem of inertia and power balance by integrating the DC-link capacitor in the control loop which reduce the size and cost of the components at the DC-link.The work presented in the thesis has contributed for the force control of the PMLG which is predicted and controlled by regulating the stator currents of the generator. A nonlinear, neural, control is evaluated and compared to a linear, proportional-integral, control. The results from the nonlinear control show the good agreement between the referenced and the generated currents. The reduced losses enhanced the accuracy of the system.A control and grid connection system for a WEC has been designed and installed. The thesis addresses the issue of power quality in low, steady and varying power flows of compliance with the grid code requirements.

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