Wave-to-Wire Power Maximization Control for All-Electric Wave Energy Converters with Non-Ideal Power Take-Off

The research presented in this paper investigates novel ways of optimizing all-electric wave energy converters for maximum wave-to-wire efficiency. In addition, a novel velocity-based controller is presented which was designed specifically for wave-to-wire efficiency maximization. In an ideal wave energy converter system, maximum efficiency in power conversion is achieved by maximizing the hydrodynamic efficiency of the floating body. However, in a real system, that involves losses at different stages from wave to grid, and the global wave-to-wire optimum differs from the hydrodynamic one. For that purpose, a full wave-to-wire wave energy converter that uses a direct-drive permanent magnet linear generator was modelled in detail. The modelling aspect included complex hydrodynamic simulations using Edinburgh Wave Systems Simulation Toolbox and the electrical modelling of the generator, controllers, power converters and the power transmission side with grid connection in MATLAB/Simulink. Three reference controllers were developed based on the previous literature: a real damping, a reactive spring damping and a velocity-based controller. All three literature-based controllers were optimized for maximum wave-to-wire efficiency for a specific wave energy resource profile. The results showed the advantage of using reactive power to bring the velocity of the point absorber and the wave excitation force in phase, which was done directly using the velocity-based controller, achieving higher efficiencies. Furthermore, it was demonstrated that maximizing hydrodynamic energy capture may not lead to maximum wave-to-wire efficiency. Finally, the controllers were also tested in random sea states, and their performance was evaluated.

THE EFFECTIVENESS OF TENS IN REDUCING THE PAIN LEVELS AMONGST WOMEN IN THE FIRST STAGE OF GIVE BIRTH

The TENS instrument is a tool as an alternative of the non-pharmacological therapies to help give birth women in dealing with pain. There are electrodes in this tool that are useful for channeling electric wave to women’s back, that it stimulates the nerves in the area pain. The signal from TENS serves to disrupt the pain signals that affect the nerves and break the pain signal, as a result reducing patients’ pain levels. The aim of the study was to find out the effectiveness of TENS towards decreasing pain levels in the first stage of labour. The study applied the quasi-experimental research method with the one group pre-test design approach. The population was women the first stage of labour, and samples were selected using the accidental sample technique, and five women participated in this study. Data were analysed using the dependent T test. The results of the study obtained TENS with a frequency of 108 Hz and a voltage of 82 Volt is safe to patients’ skin. There was not a significant effect of TENS to the level of pain with ρ-value 0.374. It can be concluded that the TENS instrument that designed in this study is ineffective in managing labor pain especially the first stage. There is a need further research to test this instrument in the laboratory, and redesign it related to the instrument size and packaging.Keywords: give birth, pain, TENS