Paper presentation1
- 2. COMPLEMENTARY CONTROL OF OSCILLATING WATER COLUMN-BASED WAVE ENERGY CONVERSION PLANTS Submitted by FATHIMA RUZILA KP S8-EEE
- 3. INTRODUCTION • Energy from sea can be extracted from Tides Temperature gradient Waves Ocean currents • 1000’s of patents have been lodged world wide for harnessing wave power • The most notable one is the oscillating water column (OWC) • Two control methods are used 1) Rotational speed control 2) Airflow control through turbine
- 4. COMPONENTS OF OWC • Capture chamber: fixed structure with its bottom open to the sea Here air compresses & decompresses due to wave motion • Conical duct: Erected on the top of the chamber Power take off system is located here Consist of a Throttle valve ,Wells turbine & Doubly fed induction generator
- 5. OBJECTIVE • To improve the instantaneous power output • To improve power efficiently to a wide range of sea states • To propose a novel control scheme that allows maximizing & improving the power generated by 2 methods
- 6. CAPTURE CHAMBER Fig 1:capture chamber and ocean wave
- 7. WAVE THEORY & MODEL • Wave energy & wave motion are a time varying oscillatory phenomenon • Assume the timescales related to wave variation as: (1) short time variation of order of a few seconds (2) medium term of order of few minutes (3) long term of order of hours • To study regular and irregular waves it is necessary to take in account the spectrum of the waves
- 8. Fig 2: representative spectrum of the wave climate
- 9. WELLS TURBINE fig 3: wells turbine
- 10. • A particular axial flow turbine • Converts oscillating flow in to a unidirectional directional rotary motion • Design depends upon pressure amplitude & volume flow rate at turbine inlet • The turbine consist of 8 blades with their chord lines lying in the plane of rotation • A linear relationship exist between pressure drop & flow rate
- 11. THROTTLE CONTROL VALVE • Throttle valve is mounted in series with the turbine • Prevent pressure difference across turbine from exceeding critical value • also control input to turbine • Valve is governed by an actuator • Actuator drives the valve to desired position against a counter weight • Once in position it is held steady by electro- magnetic brakes
- 12. DOUBLY FED INDUCTION GENERATOR fig 4: system scheme
- 13. CONTROL STATEMENT • Two different control strategies coupled so as to improve the final result : Turbine rotational speed control Airflow control
- 14. TURBINE ROTATIONAL SPEED CONTROL fig 5: control scheme of RSC
- 15. • Use of RS control provides a fast response to the abrupt and short changes in turbine speed • Allows oscillations in Pg about mean value • Control block regulates the power generated by the stator to obtain the maximum allowed active power • This control strategy can be easily implemented • Since only control variable is wr
- 16. AIRFLOW CONTROL • PID control scheme compose simple & well known technique •
- 17. ADVANTAGES • Improves instantaneous power output • Improves power returned to grid & electric energy quality • Enables plant to respond efficiently to a wide range of states • The only control variable is rotational speed wr & can be easily implemented
- 18. FUTURE SCOPE • Direct supply of electrical power to grid • Combined electricity supply & coastal/harbour defense • As an integral part of a stand-alone generation system in a remote area • potential producer of pressurized seawater for a reverse osmosis desalination plant
- 19. CONCLUSION • The proposed complementary scheme successfully maximizes the power returned to the grid • Improves the quality of supply • Governs the throttle valve that modulates the airflow across the turbine