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