Simulation Design of a Wells Turbine Overspeed Protection System for an OWC-Type Ocean Wave Power Plant Based on Speed Sensor and Soft Braking Control

Habib Alifian Achmad Firmansyah, Artono Raharjo, Tsai Chang Lee

Abstract


Oscillating Water Column (OWC) ocean wave power plants use a Wells turbine that is highly sensitive to fluctuating wave energy, making overspeed a critical operational risk. This study designs and simulates a speed-sensor-based overspeed protection system using inverter-driven soft braking control for a Wells turbine-generator system, modeled in MATLAB/Simulink. Six scenarios combining two initial overspeed conditions (1710 rpm and 1800 rpm) with three braking resistor values (90 Ω, 100 Ω, and 110 Ω) were simulated against a reference speed of 1440 rpm. Results show that the protection system activates immediately and reduces speed toward the reference in all scenarios, with response times of 7.5-10.5 s and a final error below 0.01%. The 1710 rpm scenario with a 90 Ω resistor produces the most balanced response (minimum speed 1415.96 rpm, response time 9.2 s, maximum braking torque 8.24 N.m), while for the 1800 rpm condition the 100 Ω resistor gives a more stable response. A larger braking resistor slows the response time, and a higher initial speed increases the required braking torque, angular deceleration, and braking power.

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References


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