Method of controlling a device for converting wave energy to electrical energy

Patent metadata

Field	Value
Publication number	US-9261070-B2
Application number	US-201214008153-A
Country	US
Kind code	B2
Filing date	Mar 27, 2012
Priority date	Mar 29, 2011
Publication date	Feb 16, 2016
Grant date	Feb 16, 2016

Abstract

The invention converts wave energy into electrical energy. A device moved by wave action is coupled to an electric machine for generating electrical power and to drive the device to improve conversion of wave action into electrical power. The conversion of the wave energy is improved through real-time estimation of forces exerted by waves on a pendulum axis to estimate the force to be applied to the device by the electric machine acting as an electrical motor.

First claim

The invention claimed is:

1. A method of converting wave energy into electrical energy using a device including a moving element oscillating with respect to an electrical machine in response to waves comprising:
a) selecting a relationship expressing a position of the moving element as a function of a force exerted by the machine on the moving element as a function of wave force applied to the moving element;
b) actuating the machine to produce a given force on the moving element;
c) measuring a position of the moving element with respect to the machine over time;
d) determining a wave force using the relationship which accounts for the given force of the machine and the measured position of the moving element;
e) determining a new value of force exerted by the machine on the moving element corresponding to a force for maximizing an average electrical power generated by the machine, which depends on the wave force on a new value of the force exerted by the machine on the moving element and on a position of the moving element with respect to the machine; and
f) actuating the machine to produce the new value of force by supplying electrical energy to the machine when the force provided by the machine drives the moving element and for recovering electrical energy from the machine when the force provided by the machine resists motion of the moving element.

2. A method as claimed in claim 1 , wherein the relationship expresses an equality between a sum of forces applied to the moving element and a product of a mass of the moving element and an acceleration of the moving element.

3. A method as claimed in claim 1 , comprising:
selecting a first model expressing force exerted by the machine on the moving element as a function of time;
selecting a second model expressing wave force applied to the moving element as a function of time;
in b), setting values for parameters of the first model while the machine is actuated to produce a force given by the first model with the set parameter values;
in d), determining the parameters of the second model;
in e), determining parameters of the first model; and
in f), actuating the machine to produce a force determined by the first model with the parameters determined in e).

4. A method as claimed in claim 3 , wherein the second model comprises a sum of sinusoidal functions.

5. A method as claimed in claim 4 wherein,
In a), selecting a relationship

J
⁢

⁢

x
¨

+

μ
⁢

⁢

x
.

+

k
⁢

⁢
x

=

∑

i
=
1

P

⁢

D
i

⁢

sin
⁡

(

ω
i

⁢
t

+

φ
i

)

+
C

⁢

C=K x x+K v {dot over (x)} for the first model;

∑

i
=
1

P

⁢

⁢

D
i

⁢

sin
⁡

(

ω
i

⁢
t

+

φ
i

)

for the second model and
wherein:
x is position of the moving element with respect to the machine;
J is the inertia of the moving element;
k is the restoring force due to earth's gravity;
μ is a term modelling viscous friction of the moving element;
C is a force exerted by the motor on the moving element;
Kx and Kv are parameters;
P is an integer; and
Di is an amplitude, ωi is a frequency and φi is a phase.

6. A method as claimed in claim 5 wherein, in e), the new value of force allowing an average electrical power generated by the machine to be maximized is determined for a frequency ωi to which a greatest amplitude of Di corresponds.

7. A method as claimed in claim 5 wherein, in e), a new value of force allowing the average electrical power generated by the machine to be maximized is determined for all frequencies of ωi.

8. A method as claimed in claim 5 wherein, in a), P ranges between 10 and 100 and frequencies ωi are selected ranging between 0 and 2 Hz.

9. A method as claimed in claim 8 wherein, in e), a new value of the force allowing the average electrical power generated by the machine to be maximized is determined for all frequencies of ωi.

10. A method as claimed in claim 8 wherein, in e), the new value of force allowing an average electrical power generated by the motor to be maximized is determined for a frequency ωi to which a greatest amplitude of Di corresponds.

11. A method as claimed in claim 4 wherein, prior to a), values of J, k and μ are determined.

12. A method as claimed in claim 11 wherein, in e), the new value of force allowing an average electrical power generated by the machine to be maximized is determined for a frequency ωi to which a greatest amplitude of Di corresponds.

13. A method as claimed in claim 11 wherein, in e), a new value of force allowing the average electrical power generated by

Assignees

• Henwood Nicolas
• Malaize Jérémy
• Chauvin Jonathan
• IFP Energies Nouvelles

Inventors

• Henwood Nicolas
• Malaize Jérémy
• Chauvin Jonathan

Classifications

• F03B15/00 Primary

  Controlling (controlling in general G05 {; regulation of plants characterised by the use of siphons F03B13/086}) · CPC title

• F03B13/20

  wherein both members {, i.e. wom and rem} are movable relative to the sea bed or shore · CPC title

• Y02E10/38

  Cross-Sectional Technologies · mapped topic

• Y02E10/30

  Energy from the sea, e.g. using wave energy or salinity gradient · CPC title