Date of Award

4-2017

Document Type

Thesis

Degree Name

Master of Science in Electrical Engineering (MSEE)

Department

Electrical Engineering

First Advisor

Dr. Addy Wahyudie

Second Advisor

Dr. Hussain Shareef

Third Advisor

Dr. John Ringwood

Abstract

This thesis discusses the wave energy potential of the Indian Ocean on the south coast of Central Java Island, where no previous known similar study has been conducted. A control technique that involves a dynamic electrical model was established. The following objectives were achieved. The first was to determine the ideal location to implement wave energy conversion (WEC), and the second objective was to simulate the significant wave height by using the novel control method.

To achieve these goals, the following steps and procedures were implemented. Wave energy assessment was conducted for the Indian Ocean on the south coast of Central Java Island, Indonesia. Results are analyzed with MIKE 21 Spectral Wave by adopting a 10-year hindcast spectral wave model. The model was developed by incorporating wind data from the European Centre for Medium-Range Weather Forecasts with a 0.125° spatial interval and an hourly time resolution. The model was validated with buoy observation data provided by Badan Pengkajian dan Penerapan Teknologi or Agency for the Assessment and Application of Technology, Indonesia. The buoy is located at a longitude of 110.547° and a latitude of −8.1364° and provides monthly data on significant wave height and wave period at an hourly data interval (June 2014). Validation showed that the model result matches the data, and the average error is approximately 0.042%. Time domain monthly analysis revealed that the minimum mean wave power appeared in December, January, and February, whereas the maximum mean wave power occurred in July, August, and September with a value of more than 10 kW/m during the dry season in Indonesia. The dominant significant wave height was between 1 and 2 m. The spatial analysis provided six coordinate points in Penyu Bay and Yogyakarta Coast as candidates for WEC location; the 10-year mean wave power was approximately 13–16 kW/m, and the distance from the coast was less than 350 m.

Furthermore, modeling and a control strategy for WECs were discussed. The heaving point absorber from Uppsala University was adopted. The control objective of the proposed method was to maximize the captured mechanical power under the constraint of the maximum control force. The proposed method comprised high-level and low-level controllers. The high-level controller produced the optimum reference in terms of reference velocity to satisfy the control objective. The low-level controller tracked the reference and provided robustness against model uncertainties. The low-level controller was designed before the high-level controller. The main controller in the low-level controller is a proportional–integral–derivative controller. This controller was designed with 𝐻 theory, and the genetic algorithm was utilized to solve the infinity norm of the robustness problem. The high-level controller was designed by using the obtained dynamic of the feedback control system in the low-level controller with the mechanical model of WECs. Simulation studies were also conducted. Results of nominal and perturbation cases and those of monochromatic and polychromatic sea states were compared.

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