Method for controlling a wave power system by means of a control obtained by minimizing an objective function weighted and discretized by the trapezoidal rule

Patent metadata

Field	Value
Publication number	US-11111897-B2
Application number	US-201716348215-A
Country	US
Kind code	B2
Filing date	Oct 26, 2017
Priority date	Nov 9, 2016
Publication date	Sep 7, 2021
Grant date	Sep 7, 2021

Abstract

The present invention provides improvement of the operation of a wave energy system by use of a method for predictive control (COM) of the converter machine that maximizes the energy generated by considering the energy conversion efficiency (MOD ENE) and a wave prediction (PRED). Furthermore, the method according to the invention determines the optimal control by minimizing an objective function weighted and discretized by the trapezoidal rule.

First claim

The invention claimed is:

1. A method of controlling a wave energy system that converts energy of waves into electrical or hydraulic energy, the wave energy system comprising at least one mobile device that cooperates with at least one energy converter machine, and the at least one mobile device oscillates in motion with respect to the at least one energy converter machine, comprising:
a) constructing a dynamic model of the wave energy system relating velocity of the at least one mobile device to a force exerted by the waves on the at least one mobile device and to the force exerted by the at least one energy converter machine on the at least one mobile device;
b) constructing an energy model of the wave energy system relating average power generated by the at least one energy converter machine to force exerted by the at least one energy converter machine on the at least one mobile device to the velocity of the at least one mobile device and to the efficiency of the wave energy system;
c) predicting the force exerted by the waves on the at least one mobile device for a predetermined time period;
d) determining a control value of the force exerted by the at least one energy converter machine on the at least one mobile device which maximizes average power generated by the at least one energy converter machine by:
i) determining an objective function representative of the power generated by the at least one energy converter machine by use of the prediction of the force exerted by the waves on the at least one mobile device, of the dynamic model and of the energy model;
ii) discretizing the objective function by a trapezoidal rule; and
iii) weighting, in the discretized objective function, future values of control by predetermined weighting coefficients;
iv) determining the control value from the force exerted by the at least one energy converter machine on the at least one mobile device by minimizing the discretized and weighted objective function; and

e) controlling the at least one energy converter machine by use of the control value.

2. A method as claimed in claim 1 , wherein the discretized and weighted objective function J is expressed by a relationship: J=Σ j=0 N p −2 q j u a (k+ j |k)(v(k+ j |k)+v(k+j+1|k)), with q j being the weighting coefficients, u a being the force exerted by the at least one energy converter machine on the at least one mobile device, v being the velocity of the at least one mobile device and Np being a number of time steps contained in a prediction horizon and k and j being time steps.

3. A method as claimed in claim 2 , wherein the discretized and weighted objective function J is written in matrix form as:

J
=

u
e
T

⁢

Hu
e

+

2
⁢

u
e
T

⁢

f
⁡

[

x
⁡

(

k
|
k

)

w
e

]

,

with u e being a vector of the force exerted by the at least one energy converter machine on the at least one mobile device, x being the state vector of a model of the wave energy system with the at least one energy converter machine, w e being the vector of the wave force predictions, H being a weighting matrix on vector u e , f being a weighting matrix n on the current state x of a global dynamic model of the wave energy system and the vector of the wave force predictions w e and T is duration.

4. A method as claimed in claim 3 , wherein negative or zero eigenvalues of the weighting matrix H are replaced by positive eigenvalues.

5. A method as claimed in claim 1 , wherein force exerted by the waves on the at least one mobile device is predicted by at least one of measurement or estimation of the force exerted by the waves on the at least one mobile device, by using pressure detectors adjacent the at least one mobile device or force sensors between the at least one mobile device and the at least one energy converter machine.

6. A method as claimed in claim 2 , wherein force exerted by the waves on the at least one mobile device is predicted by at least one of measurement or estimation of the force exerted by the waves on the at least one mobile device, by using pressure detectors adjacent the at least one mobile device or force sensors between the at least one mobile device and the at least one energy converter machine.

7. A method as claimed in claim 3 , wherein force exerted by the waves on the at least one mobile device is predicted by at least one of measurement or estimation of the force exerted by the waves on the at least one mobile device, by using pressure detectors adjacent the at least one mobile device or force sensors between the at least one mobile device and the at least one energy converter machine.

8. A method as claimed in claim 4 , wherein force exerted by the waves on the at least one mobile device is predicted by at least one of measurement or estimation of the force exerted by the waves on the at least one mobile device, by using pressure detectors adjacent the at least one mobile device or force sensors between the at least one mobile device and the at least one energy converter machine.

9. A method as claimed in claim 1 , wherein the dynamic model of the wave energy system is written as:

{

x
.

⁡

(
t
)

=

A
c

⁢

x
⁡

Assignees

• Ifp Energies Now

Inventors

• Tona Paolino
• Nguyen Hoai-Nam

Classifications

• Y02E10/30

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

• F05B2270/20

  to optimise the performance of a machine · CPC title

• F05B2240/40

  Use of a multiplicity of similar components · CPC title

• F05B2260/84

  Modelling or simulation · CPC title

• F05B2270/1033

  Power (if explicitly mentioned) · CPC title