Method of controlling the energy generation of a plant for the exploitation of the wave motion

Abstract

The invention concerns a method (1000,2000,3000) for controlling a plant (30) for the generation of electrical energy through the exploitation of the wave motion (54) in a body of water. The plant (30) comprises at least one generation module (34) adapted to convert kinetic energy associated with the wave motion (54) into electrical energy by means of a movable element (62) adapted to move due to the action of the wave motion (54) and a generator element (66) adapted to convert the movement of the movable element into electrical energy, at least one sensor (72) adapted to provide a measurement indicative of the wave motion (54) with respect to an element of the plant (30). The method comprises the steps of acquiring a plurality of measurements, calculating a damping coefficient associated with the conversion of motion into electrical energy of the generator element (66), and regulating the operation of the generator element (66) so as to impose the calculated damping coefficient.

Description

[0001] METHOD OF CONTROLLING THE ENERGY GENERATION OF A PLANT FOR THE EXPLOITATION OF THE WAVE MOTION

[0002] TECHNICAL FIELD

[0003] The present invention refers to the sector of the plants for the production of electrical energy from renewable sources, in particular offshore plants for the exploitation of the wave motion.

[0004] BACKGROUND

[0005] In the field of renewable electrical energy production, solutions are known for the exploitation of energy sources available in open sea, in particular wave motion. These plants exploit the alternating motion of the waves through buoys or other floating bodies immersed in water. The motion of the buoys, originated by the waves, is transmitted to mechanical members that are configured so as to operate generators adapted to producing electrical energy.

[0006] Such energy production plants, albeit appreciated, are not without disadvantages.

[0007] First of all, the plants intended for the energy exploitation of the wave motion are designed in such a way as to overcome the oscillatory nature of the wave motion itself, in order to confer continuity to the rotary motion of the electric generators. This result is sought through complex mechanical and / or pneumatic type energy transmission and / or storage equipment. The complexity of the plants therefore results in high construction and management costs and poor reliability of the plants, especially in view of the inevitable exposure to the weather.

[0008] In addition, the exploitation of the wave motion, whose characteristics are by nature extremely variable, poses a problem of optimization of the generators. The sizing of the electrical generators is usually operated on the basis of the characteristics of the wave motion (amplitude and frequency) that are statistically more likely for the position of the plant. This sizing, however, leads to the generator working for the vast majority of its operating life in a sub-optimal regime.

[0009] Finally, the generation plants fixed on the seabed suffer from the problem linked to the presence of tides. In determining the design excursion of the buoys, in fact, one cannot limit oneself to considering only the amplitude of the waves on a statistical basis, but it is necessary to also consider the variation in the average level of the sea that follows the tidal cycle. In doing so, very long excursions for buoys are obtained, with the consequent complication of the mechanisms for collecting and transferring motion. For example, international application WO 2017 / 189455 describes a system for the production of electrical energy from wave motion known in the art suffering from the disadvantages reported above.

[0010] The need is therefore felt for a new type of plant for the generation of electrical energy starting from the exploitation of the wave motion.

[0011] SCOPE AND SUMMARY OF THE INVENTION

[0012] The scope of the present invention is therefore to overcome the drawbacks highlighted above in relation to the prior art.

[0013] In particular, a task of the present invention is to make available a method for controlling a plant for the exploitation of the wave motion that has a simple structure and that is therefore economical and reliable.

[0014] Furthermore, a task of the present invention is to make available a method for controlling a plant for the exploitation of the wave motion whose generator is controlled to easily adapt, in a dynamic way, to the characteristics of the wave motion, so as to work for as long as possible at an optimal regime.

[0015] These and other objects and tasks of the present invention are achieved by a plant in accordance with claim 1. Further characteristics are identified in the dependent claims. All appended claims form an integral part of the present disclosure.

[0016] The invention concerns a method for controlling a plant for the exploitation of the wave motion (associated with a body of water). The plant of the invention comprises at least one generation module - adapted to convert kinetic energy associated with the wave motion (for example, the kinetic energy associated with the variation of the level of the body of water) into electrical energy by means of a movable element adapted to move under the action of the wave motion, and of a generator element adapted to convert the movement of the movable element into electrical energy - and at least one sensor - adapted to provide a measurement indicative of the wave motion (for example, an information on the current level of the body of water) with respect to an element of the plant. Further, the at least one generation module is coupled to a platform. Preferably, although not in a limiting manner, the movable element has a cylindrical body and has a surface of contact with the body of water - i.e. seawater - which is substantially circular.

[0017] The method comprises the steps of acquiring a plurality of measurements, calculating a damping coefficient associated with the conversion of movement into electrical energy of the generator element - where the damping coefficient depends on a desired value of the energy converted by the generation module as a function of the plurality of measurements provided by the sensor and regulating the operation of the generator element so as to impose the calculated damping coefficient.

[0018] Advantageously, the method comprises the step of acquiring at least one of: a mechanical power transferred to the generator element, an electrical power generated by the generator element, a position of the movable element, and a position of the platform with respect to an average level of the sea.

[0019] In addition, the step of calculating a damping coefficient comprises:

[0020] - calculating an average damping coefficient according to the formula: where V\h.(a) is an observation frequency window, where n is a radius of a surface of contact with the body of water of the movable element, g is the acceleration of gravity, Mb is the mass of the movable element, Xb is a measurement provided by the sensor, p is the density of the body of water,

[0021] - determining an error value corresponding to the difference between the calculated damping coefficient and the average damping coefficient, and

[0022] - using the error value as a feedback value to calculate a new damping coefficient.

[0023] Thanks to the method according to the present invention a particularly efficient control of the plant is obtained. In particular, the regulation of the damping coefficient allows the resistant force - associated with the energy conversion work of the generation module - to be adapted to the current state of the wave motion. This avoids situations in which the resistant force is excessively strong or weak with respect to the wave motion, conditions that cause a limitation or, at the limit, prevent the conversion of energy. Furthermore, the method is implementable through a plurality of instructions effectively executable by control devices - e.g., microcontrollers, microprocessors, FPGAs, ASICs, etc. - having limited hardware resources. Similarly, multiple instances of the method may be executed by a control device in order to control a plurality of generation modules.

[0024] In one embodiment, the damping coefficient is calculated so as to obtain a maximum energy absorption as a function of the plurality of measurements provided by the sensor.

[0025] In this case, the movable element is preferably cylindrical in shape, and the damping coefficient is preferably calculated so as to verify the formula: where n is the radius of the movable element, g is the acceleration of gravity, Mb is the mass of the movable element, xmis a measurement provided by the sensor, p is the density of the body of water, W(t) is a wave motion observation time window.

[0026] Preferably, the wave motion observation time window is configured to have a duration of about one second.

[0027] Thanks to the method according to these embodiments, it is possible to determine the maximum energy absorbed by the wave motion thanks to the information alone provided by the sensor, thereby obtaining a simple, robust and efficient operation.

[0028] In one embodiment, the steps of calculating an average damping coefficient, determining an error value, and using the error value as a feedback value are performed by at least one artificial intelligence algorithm.

[0029] Advantageously, although not in a limiting manner, the observation frequency window corresponds to a further observation time window is configured to have a duration greater than the duration of the observation time window, preferably the further time window has a duration approximately equal to a multiple of the duration of the observation time window, even more preferably the further time window has a duration approximately equal to two or three times the duration of the observation time window.

[0030] Thanks to the method according to the embodiments just described, it is possible to finely regulate the operation of the plant in order to compensate for non-idealities due to environmental factors, wear of the components, etc. in a simple and effective way using the wave motion information provided by the sensor.

[0031] In one embodiment, the generation module comprises:

[0032] - a guide channel that develops vertically, fixed with respect to the platform;

[0033] - a rod slidable along the channel;

[0034] - a buoy fixed to the lower end of the rod;

[0035] - a circuit.

[0036] The rod comprises a plurality of magnets or electrical windings and the channel comprises, respectively, a plurality of electrical windings or of magnets, the circuit comprising said electrical windings. The rod and buoy assembly corresponds to the movable element and the circuit corresponds to the generator element of the generation module.

[0037] In this case, the step of regulating the operation of the generator element so as to impose the calculated damping coefficient comprises regulating the absorption of electrical energy through the electrical windings so as to generate a force resistant to the sliding of the rod in the channel that is proportional to the calculated damping coefficient.

[0038] Preferably, the circuit comprises an absorption sub-circuit comprising the electrical windings and a switch element.

[0039] In this case, the step of regulating the absorption of electrical energy through the electrical windings comprises controlling the switch element with a pulse width modulation signal as a function of the calculated damping coefficient.

[0040] Advantageously, although not in a limiting manner, the generator module comprises a float free to slide in a vertical direction within a maximum available stroke comprised between two opposite end-of-strokes: an upper end-of-stroke and a lower end-of-stroke.

[0041] In this case, the step of acquiring a plurality of measurements indicative of the wave motion with respect to an element of the plant comprises measuring a position of a portion of the float with respect to an element of the plant.

[0042] The method according to the embodiments is adapted to optimizing the operation of the plant so that the movement of the rod-buoy assembly allows to reliably obtain an energy conversion substantially corresponding to the maximum convertible energy based on the current wave motion.

[0043] Further features, aims and advantages of the present invention will become more evident from the description of the accompanying drawings.

[0044] BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The invention will be described below with reference to some examples, provided for explanatory and non-limiting purposes, and illustrated in the attached drawings. These drawings illustrate different aspects and embodiments of the present invention and reference numerals illustrating structures, components, materials and / or similar elements in different drawings are indicated by similar reference numerals, where appropriate. Moreover, for clarity of illustration, certain references may not be repeated in all drawings.

[0046] Figure 1 shows a side view of a plant in accordance with the invention, in a high tide operating configuration; figure 2 shows a side view of the plant of figure 1, in a low tide operating configuration; figure 3 shows an enlarged view of the detail indicated with III in figure 1; figure 4 shows a reverse plan view (from bottom to top) of a plant in accordance with the invention; figure 5 shows a side view of a single element of the plant of figure 1, wherein the buoy is at the bottom dead centre; figure 6 shows a view similar to that of figure 5, wherein the buoy is located in an intermediate position between the bottom dead centre and the top dead centre; figure 7 shows a view similar to that of figure 5, in which the buoy is at the top dead centre; figure 8 shows an axonometric view of the element of figure 5; figure 9 shows an enlarged view of the detail indicated with IX in figure 8; figure 10 shows an axonometric view of the element of figure 7; figure 11 shows an enlarged view of the detail indicated with XI in figure 10; figure 12 shows a view similar to that of figure 5, in which the secondary float is at its own top dead centre; figure 13 shows an enlarged view of the detail indicated with XIII in figure 12; figure 14 shows a view of the element of the figure, wherein the secondary float is at its own bottom dead centre; figure 15 shows an enlarged view of the detail indicated with XV in figure 14; figure 16 is a side view of the section made along the trace XVI-XVI of figure 12; figure 17 shows an enlarged view of the detail indicated with XVII in figure 16; figure 18 shows a view of the section made along the trace XVIII-XVIII of figure 14; figure 19 shows a block diagram of the plant of the invention; figure 20 is a diagram of a control circuit adapted to controlling the operation of one or more elements of the plant; figure 21 illustrates a flowchart of a data processing method performed by a control unit of the plant according to an embodiment of the present invention; figure 22 illustrates a flowchart of a method for maximizing energy absorption, or conversion, performed by the control unit of the plant according to an embodiment of the present invention, and figure 23 illustrates a flowchart of a method for regulating the height of the generation modules performed by the control unit of the plant according to an embodiment of the present invention.

[0047] DETAILED DESCRIPTION OF THE INVENTION

[0048] While the invention is susceptible to various modifications and alternative constructions, certain preferred embodiments are shown in the drawings and are described hereinbelow in detail. It must in any case be understood that there is no intention to limit the invention to the specific embodiment illustrated, but, on the contrary, the invention intends covering all the modifications, alternative and equivalent constructions that fall within the scope of the invention as defined in the claims.

[0049] The description deals in detail with the peculiar aspects and the technical characteristics of the invention, while the aspects and the technical characteristics per se known can only be hinted at. In these respects, the foregoing remains valid with reference to the prior art.

[0050] The use of "for example", "etc.", "or" indicates non-exclusive alternatives without limitation, unless otherwise indicated. The use of "comprises" and "includes" means "comprises or includes, but not limited to", unless otherwise indicated.

[0051] The plant of the invention is intended to operate in the presence of acceleration of gravity g. Based on the acceleration of gravity g, the vertical direction and the horizontal directions are defined uniquely. Similarly, with respect to the acceleration of gravity g, the terms "high", "upper", "above" and similar are defined with respect to the terms "low", "lower", "below" and similar.

[0052] In the following discussion, the expressions "open sea" or also off-shore will be used. These expressions are used for brevity of exposure and should not be construed in a limiting sense. In other words, "open sea" can mean a position in the sea itself or in the ocean, but also in a different body of water such as a lake, a lagoon or a river. Furthermore, these expressions are intended to identify a position in a body of water in which a wave motion adapted to the production of energy in the manners described in greater detail below can be found.

[0053] The invention concerns a plant 30 for the generation of electrical energy through the exploitation of the wave motion at sea. The plant 30 of the invention comprises:

[0054] - a bearing structure 32 comprising an emerged part and an immersed part,

[0055] - at least one generation module 34 comprising:

[0056] - a platform 36 constrained to the bearing structure 32 and flanked to the emerged part; - a guide channel 38 that develops vertically, fixed with respect to the platform 36;

[0057] - a rod 40 slidable along the channel 38; and

[0058] - a buoy 42 fixed to the lower end of the rod 40.

[0059] Furthermore, the rod 40 comprises a plurality of magnets 44 or of electrical windings 46 and the channel 38 comprises, respectively, a plurality of electrical windings 46 or of magnets 44.

[0060] Preferably, the bearing structure 32 comprises a main pillar 48 that develops in a substantially vertical direction. In other words, the design orientation provides that the axis of the main pillar 48 is arranged vertically. However, in some embodiments, the main pillar 48 may be at least partially movable about the design position, for example in floating embodiments (not shown). In these cases it is therefore possible that in use the axis of the main pillar 48 oscillates around the vertical and that the vertical orientation can be considered as the average position. In accordance with these embodiments where the bearing structure 32 is floating, it is preferably anchored to the seabed 50 or otherwise constrained so that it can remain in its predefined position and not be displaced by currents or by winds.

[0061] In accordance with some embodiments, the immersed part of the bearing structure 32 extends up to the seabed 50 and is anchored thereto. Preferably, in the case where the bearing structure 32 comprises a main pillar 48 (as in the example shown in figures 1 and 2), the main pillar 48 penetrates the seabed 50 for a length equal to a relevant portion of its overall length, for example for a length greater than about a quarter of its overall length. In this way, the main pillar 48 represents a structure firmly constrained to the ground and can validly counteract the action of currents and / or of winds that tend to displace the plant 30 from its predefined position.

[0062] As mentioned above, the bearing structure 32 comprises an emerged part, i.e. a part that in use rises above the level of the sea 52, and an immersed part, which in use is placed below the level of the sea 52. The distinction between the emerged part and the immersed part of the bearing structure 32 must be considered in an ideal design condition. In fact, as the skilled person can well understand, the level of the sea 52 varies constantly because it is subject to the motion of the waves and to the motion of the tides. For this reason, the line of demarcation between the emerged part and the immersed part of the bearing structure 32 will constantly vary in practice and can only be defined at the time of design, based on the average level of the sea 52 in the position where the bearing structure 32 is intended. For example, figures 1 and 2 schematically report the average level of the sea 52 (horizontally) and a design amplitude of the local wave motion 54 (in the form of a sinusoid); more in particular, figure 1 reports the average level of the sea 52 in a condition of high tide, while figure 2 reports the average level of the sea 52 in a condition of low tide. The wave motion 54 of equal amplitude is therefore translated vertically between the condition of figure 1 and that of figure 2.

[0063] The design amplitude of the local wave motion 54 may for example represent the maximum amplitude that is statistically detected at that specific position in a predetermined period of time. However, as the skilled person can well understand, it is possible that, following exceptional events such as anomalous waves, tsunamis or storms of particular intensity, the level of the sea 52 changes significantly. In these cases, especially if the bearing structure 32 is of the type anchored to the seabed 50, it is possible that also the part over sea level of the bearing structure 32 is temporarily submerged or, vice versa, that the immersed part may emerge at least partially.

[0064] In some embodiments, the plant 30 comprises a storage containing batteries configured to store at least part of the electrical energy produced by the plant 30. In accordance with some embodiments, the batteries are configured to store a significant part, preferably all, of the electrical energy produced by the plant 30.

[0065] Preferably, the battery storage is housed inside the bearing structure 32 and develops at least partially in the immersed part. Preferably, the battery storage develops mainly in the immersed part in such a way as to lower the overall centre of mass of the plant 30. Keeping the centre of mass as low as possible, preferably below the level of the sea 52, helps to provide stability to the plant 30.

[0066] A particularly advantageous embodiment of the battery storage is described in international patent application PCT / IB2023 / 054587. This solution allows to maximize the density of batteries per unit of volume. The battery storage in fact comprises a movable structure configured to allow the movement of the batteries along the main pillar 48 and to make them transit near a station for the operator. In this way, the gaps and passages that would be necessary to allow the operator to walk through the storage to reach each battery can be avoided within the main pillar 48. In accordance with PCT / IB2023 / 054587 solution, for example for control or maintenance needs, the operator can reach each battery simply by staying at his / her station and operating the movable structure.

[0067] Preferably the plant 30 of the invention comprises a plurality of generation modules 34. The platform 36 of each generation module 34, constrained to the bearing structure 32, extends to the side of the emerged part of the bearing structure 32, so as to remain at a predetermined level above the average level of the sea 52. Advantageously the platforms 36 of the plurality of generation modules 34 are brought closer and joined together.

[0068] Preferably, in each generation module 34, the platform 36 has a greater plan extension than the buoy 42 below. In this way, by placing side-by-side each other the platforms 36 of a plurality of generation modules 34, any interference during the movement of the buoys 42 that are adjacent to one another is avoided. The buoys 42, in fact, thanks to the structure that will be better described below, are constrained to move linearly vertically, thus being constantly included, in a plan view, within their own platform 36. The buoys 42 of generation modules 34 that are adjacent to one another are therefore completely independent of each other in the vertical translation movement.

[0069] In accordance with some embodiments, the platform 36 has, in a plan view, a shape of the so-called "tile" type, that is, a shape that, when side by side with other shapes identical to it, allows the plane to be completely covered without interruptions and without overlaps. This covering of the plane, in itself well known, is called tessellation. In accordance with some embodiments, the platform 36 has, in a plan view, a polygonal shape. For example, the platform 36 may have a hexagonal shape, as in the embodiments shown in the accompanying figures 4, 8, and 10.

[0070] Preferably, the bearing structure 32 comprises one or more terraces 58 having the same shape and the same dimensions as the platforms 36 of the generation modules 34. In this way it is possible for each terrace 58 to be flanked by the platforms 36 of the generation modules 34, completely covering the plane without interruptions and without overlaps. Consider for example the embodiment shown in figure 4 in which the main pillar 48 is surrounded by a terrace 58 having the same hexagonal shape as the platforms 36.

[0071] Preferably, the plurality of platforms 36 of the generation modules 34, and possibly the terrace 58 of the bearing structure 32, when they are side by side and joined to each other, define a slab 60 having an extension mainly in the horizontal plane. Preferably the upper surface of the slab 60 is walkable, i.e. it is configured to allow the walking of one or more operators who can thus walk along the slab 60, for example during installation or maintenance operations.

[0072] As mentioned above, a guide channel 38 extends from each platform 36. The channel 38 is fixed with respect to the platform 36, so as to maintain a substantially vertical development. Preferably, as for example in the embodiments shown in the attached figures, the channel 38 is held in position with respect to its platform 36 by means of bracing arranged according to different planes; in this way great rigidity is given to the structure formed by the channel 38 and by the platform 36 which, in the context of the present discussion, is considered rigid.

[0073] The rod 40, which, at its lower end, supports the buoy 42 is housed along the channel 38. The union of the rod 40 and of the buoy 42 forms a rod-buoy assembly 62 which, in the context of this discussion, neglecting the deformations thereof, is considered rigid. The rod-buoy assembly 62 is free to slide along the direction of the channel 38 (i.e. in the vertical direction) within a maximum available stroke comprised between two opposite end-of-strokes: an upper end-of-stroke and a lower end-of- stroke. In normal operation of the plant 30, the actual stroke of the buoy 42 (comprised between the top dead centre TDC and the bottom dead centre BDC) is preferably comprised within the maximum available stroke. Preferably the generation module 34 comprises a first sensor 64 configured to detect the position Xb of the rod-buoy assembly 62 with respect to the platform 36.

[0074] As mentioned above, the rod 40 comprises a plurality of magnets 44 or of electrical windings 46 and the channel 38 comprises, respectively, a plurality of electrical windings 46 or of magnets 44. Preferably the magnets 44 are permanent magnets. In this way a linear electric machine is obtained, in particular a linear generator 66, wherein the channel 38 forms the fixed part (or stator) and the rod 40 forms the movable part (or slider).

[0075] Preferably in the linear generator 66 the rod 40 comprises the magnets 44 and the channel 38 comprises the electrical windings 46. In fact, the electrical windings 46 must be connected by cables to a network for the collection of the energy produced and for the control of the same electrical windings 46 (as will be described later). Therefore, it is advantageous to mount the electrical windings 46 on the stator, so that the connection cables do not affect the dynamics of the rod-buoy assembly 62 and are not subjected to cyclical deformations. On the contrary, in case permanent magnets 44 are employed, no connection is required for the slider which therefore remains completely free in its movement.

[0076] As the skilled person can well understand, the opposite embodiment of the linear generator 66, in which the rod 40 comprises the electrical windings 46 and the channel 38 comprises the magnets 44, although possible, is usually disadvantageous.

[0077] As mentioned above, the electrical windings 46 are connected by cables to a network for collecting the electrical energy produced. Preferably along the line of connection of each linear generator 66 to the collection network there are arranged a tool configured to measure instant by instant the current produced by the linear generator 66 (e.g. an ammeter), and a tool configured to measure instant by instant the voltage produced by the linear generator 66 (e.g. a voltmeter).

[0078] As the skilled person can well understand, substantially three types of forces act on the motion of each rod-buoy assembly 62. A first type of force, which pushes the rod-buoy assembly 62 upwards, is the buoyancy force and depends on the volume of the buoy 42 which, instant by instant, is immersed in the water. A second type of force, which pushes the rod-buoy assembly 62 downwards, is the weight force which is constant and is defined during the design by the mass of the assembly 62 itself. A third type of force opposes the motion, in whatever direction it is directed, and in addition to the frictional forces (which for the sake of simplicity are neglected) comprises the forces of electromagnetic nature linked to the production of electrical energy.

[0079] Preferably, the structure of the rod-buoy assembly 62 determines a substantial asymmetry in the operation of the linear generator 66. In fact, from the Applicant's studies, it has emerged that it is advantageous to limit the apparent density of the rodbuoy assembly 62 (i.e. the ratio between the mass of the rod-buoy assembly 62 and the volume of the buoy 42), thus obtaining that the buoyancy force can be much greater than the weight force. Consequently, with this type of configuration, the linear generator 66 is able to produce much more electrical energy during the ascent step of the rod-buoy assembly 62 than it is able to produce during the descent step.

[0080] As the skilled person can easily understand, the extent of the braking force deriving from the generation of electrical energy by the linear generator 66, depends on the wiring diagram of the electrical windings 46. In accordance with some embodiments of the plant 30, the wiring diagram of the electrical windings 46 is not fixed but is reconfigurable according to needs. In this regard, the plant 30 preferably comprises a control unit 68 configured to control the absorbed power using a control procedure based on pulse width modulation (or PWM). Advantageously, the control unit 68 is configured to control the absorption of energy through the electrical windings 46 based on a pre-loaded logic aimed at optimizing the production of electrical energy by the linear generator 66. An example of the optimization logic that may be employed by the control unit 68 is provided below.

[0081] Preferably, the control unit 68 finds space inside the emerged part of the bearing structure 32 so that it is protected from bad weather and external agents.

[0082] Preferably, the plant 30 of the invention comprises at least one auxiliary float 70 configured to detect the variations in the level of the sea 52. Preferably, the auxiliary float 70 is configured to follow the variations in the level of the sea 52 and the plant 30 comprises a second sensor 72 configured to detect the position of the auxiliary float 70 with respect to another element of the plant 30 itself.

[0083] For example, the auxiliary float 70, arranged so as to be partially immersed in water, may comprise a rod 74 which extends vertically upwards and whose upper end cooperates with the second sensor 72 configured to detect its position. The auxiliary float 70 is free to slide in the vertical direction within a maximum available stroke comprised between two opposite end-of-strokes: an upper end-of-stroke and a lower end-of-stroke. In normal operation of the plant 30, the actual stroke of the auxiliary float 70 (comprised between the top dead centre TDC and the bottom dead centre BDC) is preferably comprised within the maximum stroke available.

[0084] As the skilled person can well understand, the auxiliary float 70, as described above, is configured so as to freely follow the variations of the level of the sea 52, unlike what happens for the rod-buoy assembly 62. In fact, although the buoy 42 tends by its nature to follow the variations in the level of the sea 52, the dynamics of the rod-buoy assembly 62 is strongly influenced by the amount of kinetic energy absorbed in the production of electrical energy by the linear generator 66. In general, therefore, the rodbuoy assemblies 62 of the plant 30 only partially follow the variations in the level of the sea 52 and do so with a variable delay and / or phase shift. The auxiliary float 70 is not part of any electric machine and is therefore subject only to the buoyancy force and to the inertia forces deriving from its own mass. For the purposes of this discussion, it can in fact be considered that the other forces, typically the frictional forces, are negligible. Therefore, it can be considered that the motion of the auxiliary float 70 constantly provides information on the variation of the level of the sea 52. In other words, it is possible to reconstruct the level of the sea 52 as a function of the kinematics (of the motion) of the auxiliary float 70.

[0085] In accordance with some embodiments, such as those depicted in the accompanying figures, the auxiliary float 70 is housed within a rod-buoy assembly 62. More particularly, the auxiliary float 70 is housed in a seat obtained inside the buoy 42 and the bar 74 is housed in a longitudinal seat obtained inside the rod 40 which therefore assumes a tubular structure. This particular arrangement allows the auxiliary float 70 to be constrained and protected at the same time. More particularly, the described structure allows to effectively constrain the auxiliary float 70 in such a way that it can translate only in a vertical direction, within the rod-buoy assembly 62, in turn constrained to the same translation. Furthermore, the fact that the auxiliary float 70 is housed within the rod-buoy assembly 62 protects it from the effects of external agents (such as winds, currents and the waves themselves) that can generate forces having horizontal components. The fact that the auxiliary float 70 is protected by these horizontal components allows it to be made with a simple and light structure, with obvious advantages in dynamic terms.

[0086] Preferably the plant 30 comprises a plurality of auxiliary floats 70; advantageously, each generation module 34 comprises its own auxiliary float 70. Preferably a secondary float is housed within each rod-buoy assembly 62.

[0087] In the configuration described above, while the first sensor 64 detects the position Xb of the rod-buoy assembly 62 with respect to the platform 36, the second sensor 72 may be configured so as to detect the position Axmof the auxiliary float 70 with respect to the rod-buoy assembly 62. In this case, by combining the signals of the two sensors it is possible to also determine the position xmof the auxiliary float 70 with respect to the platform 36.

[0088] As mentioned above, the control unit 68 is adapted to control the operation of the plant 30 in order to optimize the production of electrical energy.

[0089] In an embodiment provided with the control unit 68, the latter is adapted to controlling each of the linear generators 66 so as to change the respective absorption of electrical energy by means of a dedicated circuit - comprising one or more triacs and / or mosfet transistors and controlled by means of a control signal that regulates the duty cycle thereof. In other words, a PWM diagram is used to control energy absorption.

[0090] A circuit diagram of a management circuit 100 of the linear generators 66 is illustrated in figure 20. The management circuit 100 comprises an absorption and modulation sub-circuit 101, a storage and distribution sub-circuit 102 and a control subcircuit 103.

[0091] In particular, the absorption and modulation sub-circuit 101 comprises an inductor LI corresponding to the inductance of the electric windings 46 of one of the linear generators 66. The inductor LI is in series with a switching element, a triac Tl in the example considered, and with a diode bridge Pl. The switch LI, the triac Tl and the diode bridge Pl form a mesh of the sub-circuit 101. In addition, a resistor R1 in series with a modulation element, an opto-triac O1 in the example of figure 20, forms a modulation branch of the sub-circuit 101. In detail, a first terminal of the inductor LI, a first terminal of the resistor R1 are connected to a node of the sub-circuit 101 to which a gate terminal of the triac Tl is also connected, while a second terminal of the resistor R1 is connected to a first main terminal of the opto-triac Ol, while a second main terminal of the opto-triac Ol is connected to the gate terminal of the triac Tl. Otherwise, the gate terminals of the opto-triac Ol - i.e., anode and cathode of the photodiode comprised in the opto-triac Ol, are connected to modulation terminals pwm+ and pwm- of a control module M3 comprised in the control sub-circuit 103, for example the control unit 68. A second terminal of the inductor LI is connected to a first input terminal of the diode bridge Pl, while a second gate terminal of the triac Tl is connected to a second input terminal of the diode bridge Pl. Finally, the two output terminals of the diode bridge Pl are connected to opposite terminals of a storage capacitor Cl of the sub-circuit 101. Furthermore, the output terminals of the diode bridge Pl are connected to the connected storage and distribution sub-circuit 102 and to respective input terminals gen+ and gen- of the control module M3 of the sub-circuit 103. The sub-circuit 102 comprises elements necessary to regulate, store and deliver electrical energy provided by the sub-circuit 1 to a load. In detail, the sub-circuit 102 comprises an ammeter A2 connected to a first output terminal of the diode bridge Pl and to a first terminal of the capacitor Cl. The ammeter A2 is connected to a first input terminal of a voltage regulator, a DC / DC step up converter S2 in the example of figure 20, while a second output terminal of the diode bridge Pl and a second terminal of the capacitor Cl are connected to a second input terminal of the DC / DC step up converter S2. A pair of output terminals of the DC / DC step up converter S2 are connected to opposite ends of an accumulator element B2, to a pair of power supply terminals bat+ and bat- of the control module M3, and to a pair of input terminals of a direct current- to-alternating current converter, for example an inverter 12. Finally, a pair of output terminals is connected to the terminals of a load Z2.

[0092] The sub-circuit 103 comprises the already mentioned control module M3. In addition to the above connections, the control module M3 receives a measurement signal from the ammeter A2 comprised in the sub-circuit 102. In particular, the ammeter A2 provides a measurement signal indicative of an intensity of the electric current flowing between the node to which the diode bridge Pl and the first terminal of the capacitor Cl are connected, to the input terminal of the DC / DC step up converter S2.

[0093] The circuit 100 is able to optimize the energy absorption by one or more linear generators 66 controlled by the control unit 68 over a wide range of variations of the wave motion, from mild wave motion to intense wave motion.

[0094] In particular, the DC / DC step up converter S2 decouples the voltage present on the linear generator 66 from the voltage applied on the batteries. This allows power to be absorbed as soon as the circuit reaches the minimum working voltage of the DC / DC converter step up S2 - for example, in one embodiment a DC / DC converter step up S2 with a minimum working voltage equal to about 3 V and maximum working voltage equal to about of 70 V is used. Thanks to the DC / DC converter step up S2 it is therefore possible to absorb electrical power in a wide range of voltages, i.e. produced through wave motion conditions that are very different from one another. In an alternative embodiment, the maximum working voltage is in the order of hundreds of Volts, for example comprised between about 200V and about 300V so as to be adapted to powering inverters used commercially in systems comprising photovoltaic panels.

[0095] Power modulation is instead carried out by means of the triac T1 placed in series with the inductor LI corresponding to the inductance of the electrical windings 46. By controlling the duty cycle of the triac T1 it is possible to modulate the power absorbed by the linear generator 66 and thus optimize the power absorbed by the wave motion through the plant 30 according to the embodiments of the present invention. The triac T1 guarantees electrical conduction until the voltage at the terminals is reversed and is able to withstand the high interruption currents generated during operation of the circuit 100.

[0096] Preferably, the collection of information useful for controlling the power absorption of the plant is carried out through analogue interfaces and appropriate tools. For example, the voltages at multiple nodes of the circuit 100 are measured. Advantageously, although not in a limiting manner, analogue interfaces are provided for measuring the voltages of the nodes of the circuit and the voltages higher than the nominal voltages of the interfaces are specially scaled using resistive splitters - so as to obtain signals compatible with the analogue interfaces, which usually work with voltages in the range 0 - 10V. Furthermore, the ammeter A2 measures the current downstream of each rectifier - i.e. the assembly comprising the diode bridge Pl and preferably the capacitor Cl. The measurement provided by the ammeter A2 is used for the calculation of the absorbed power.

[0097] The data thus collected are used as feedback for the absorption control managed by the control unit that performs one or more optimization logics. In one embodiment, the optimization logics comprise a data processing method 1000 described below, of which figure 21 is a flowchart.

[0098] The control unit 68 receives (step 1001) the following measurements for each j-th generation module 34j of the plant 30:

[0099] Axm- vertical position of the auxiliary float 70 with respect to its rod-buoy assembly 62;

[0100] Axb". vertical position of the rod-buoy assembly 62 with respect to its platform 36;

[0101] Xp. vertical position of the platform 36 with respect to the bearing structure 32 and adjustable through the movement system 76

[0102] If. current produced by the corresponding linear generator 66; and

[0103] Vf. voltage produced by the corresponding linear generator 66.

[0104] Preferably, such measurements are acquired with a period of the order of milliseconds. Each pair of position measurements Axmand Axb is used to calculate (1002) the absolute position 70 of the auxiliary float 70 with respect to a fixed reference. For example, the fixed reference is a portion of the bearing structure 32. In a nonlimiting embodiment, the reference element is a portion, indicated by reference 32A in figure 3, of the bearing structure 32 at one end of the bearing structure 32 itself - that is, a top of the bearing structure 32 of the plant 30. In other words, for each generation module 34 it is calculated:

[0105] Xb = Ax +Xp. (vertical) position of the rod-buoy assembly 62 with respect to the top of the bearing structure 32.

[0106] Xm= Axm+ Axb + xpvertical position of the auxiliary float 70 with respect to the top of the bearing structure 32.

[0107] Ultimately, for each generation module 34 a sequence of positions Xb and xmover time is obtained. These sequences are transformed (1003) by means of a Fast Fourier Transform - or FFT - performed on a variable time window - preferably, variable as a function of the average period of the predominant wave motion 54 (described in detail below). In this way, the spectral components of the motion of the generation modules 34 are determined.

[0108] Furthermore, the power Pj, delivered by each linear generator 66j of the plant 30, is calculated (1004) on the basis of the measurements of the voltage Vj and of the current Ij of the corresponding linear generator 66j.

[0109] The optimization logics applied by the control unit 68 comprise a method 2000 for maximizing the absorption, or conversion, of energy, of which figure 21 is a flowchart.

[0110] In the example considered, the method 2000 is based on a model of the dynamic systems rod-buoy assembly 62 and auxiliary float 70 defined as described below - where an auxiliary float 70 of cylindrical shape has been considered, in accordance with the embodiments of the attached figures 14, 16 and 18.

[0111] The equation of the motion of the auxiliary float 70 can be defined as: where: rmis the radius of the auxiliary float 70, g is the acceleration of gravity, Mm is the mass of the auxiliary float 70, xmis the position of the auxiliary float 70, p is the density of water, and

[0112] F(t) is the trend of the water level, variable as a function of the wave motion 54 at the point where the auxiliary float 70 is located.

[0113] As will be evident, here the trend of the water level, or simply the trend of the level, indicates a position of the water surface with respect to a reference element of the plant 30, the corresponding platform 36 in the example considered.

[0114] The term -gpr2mF(t) is the forcing of the system, i.e. the force acting on the system due to the action of the wave motion 54.

[0115] The physical characteristics of the elements of the generation module 34 (e.g., rmand Mm), the physical parameters (e.g., g and p) as well as numerical coefficients and temporary variables are preferably stored in a memory element (not illustrated) of the control unit 68.

[0116] Note that equation (1) can be used in plants with auxiliary float 70, with a shape other than cylindrical, by appropriately modifying the term -gpr2x(t) as a function of the shape of the alternative auxiliary float 70.

[0117] In equation (1), the mechanical frictions of the system are considered negligible, as the auxiliary float 70 is not associated with substantial loads - there is substantially a negligible friction between the auxiliary float 70 and the longitudinal seat obtained inside the rod 40 that acts as a guide for the auxiliary float 70.

[0118] The equation of the motion (1) can be written in the space of the pulsations a as: where 5(a) is an impulse function (or Dirac delta).

[0119] Starting from equation (2) it is possible to define the trend of the level F(a) of water as a function of the pulsation a as:

[0120] The level variation F(a) defined by formula (3) is used by a method 3000 for regulating the height of the generation modules 34 of the plant 30 described below.

[0121] The rod-buoy assembly 62, with respect to the auxiliary float 70, is subject to a damping linked to a resistant force F(t) associated with the linear generator 66. The equation of the motion for the rod-buoy assembly 62 can be defined as: where: n is the radius of the rod-buoy assembly 62, g is the acceleration of gravity,

[0122] Mb is the mass of the rod-buoy assembly 62,

[0123] Xb is the position of the rod-buoy assembly 62, p is the density of water, and kxb'(t) corresponds to the resistant force F(t), with k corresponding to a damping coefficient of the linear generator 66.

[0124] In the example of equation (1), we considered a rod-buoy assembly 62 having a development of a rotation solid with radius n, thus having a surface of contact with the sea which is substantially circular. In any case, equation (1) can be used in plants with auxiliary float 70, with a shape other than cylindrical, by appropriately modifying the term -gpr2x(t) as a function of the shape of the alternative auxiliary float 70, in particular its surface of contact with the body of water.

[0125] Also in this case, the data necessary for calculating the models used during the execution of the method 3000 are stored in the memory element (not illustrated) of the control unit 68.

[0126] In the space of the pulsations, equation (4) corresponds to:

[0127] Furthermore, the kinetic power transferred to the linear generator 66 - considering that, for the intrinsic geometry of the system, the speed is always substantially parallel to the resistant force F exerted by the wave motion 54 - can be expressed as follows:

[0128] Consequently, the energy absorbed in a generic time interval T corresponds to:

[0129] Considering that x'b(t)2is real and therefore x'b(t)2= | x'b(t) |2and by applying Parseval's theorem the energy absorbed in the time interval T corresponds to: Using the level variation definition F(co) of formula (3) in the equation of motion of the rod-buoy assembly 62 of formula (4) it is possible to solve equation (4) for Xb(a), obtaining:

[0130] Considering the fact that a5(a) = 0, equation (9) can be rewritten to define k | icoxb(a) |2as follows:

[0131] Consequently, the absorbed energy E is defined as:

[0132] Formula (13) is a representation of the energy absorbed by the linear generator 66 as a function of only the motion measured by the auxiliary float 70. In other words, the energy is defined as a function of the level of the sea determined by the wave motion, i.e. the vertical component (amplitude) of the wave motion and by the mechanical characteristics of the rod-buoy assembly 62. The absorbed energy E defined by formula (13) is used by the absorption maximization method 2000 described below. In other words, equation (13) describes the model used to control the generator modules 34.

[0133] The method 2000 adapts the operation of the generator modules 34 so that the trajectory followed by each rod-buoy assembly 62 is such as to maximize the absorption of energy from the wave motion 54.

[0134] In particular, the method 2000 uses the position xmof the auxiliary float 70 of each generation module 34 of the plant 30 in a respective instance of the formula (13) of the absorbed energy E (step 2001). Each instance of formula (13) is solved to identify the maximum of the absorbed energy value E as a function of the damping coefficient k of the linear generator 66 of the corresponding generation module (step 2002). In other words, the stationary points of the formula of the absorbed energy E are identified by numerically solving in k the equation:

[0135] The damping coefficient k calculated with formula (15) represents a theoretical value under ideal conditions; however, a plurality of external factors, i.e. disturbances, affect the operation of the plant and lead to having an effective damping coefficient kedifferent from the damping coefficient k calculated.

[0136] Advantageously, although not in a limiting manner, the control logics of the control unit 68 utilize a discrete definition of formula (15) calculated as described below.

[0137] The numerical implementation of the algorithm considers the discretization of the measured quantities. In particular, the acquired measurements, i.e. the samples concerning the measured quantities, are carried out at predefined time intervals, the control algorithm is cyclically repeated every time a predetermined number of samples is acquired in a limited time interval. As described in step 1003, an FFT is performed on the sequence of measurements, i.e. on a set of acquired samples. The result is a discrete vector of coefficients. The limitation of the sample acquisitions in a time interval corresponds, for example, to the introduction of a window function W with a high logical value in the time interval in which the measurements are acquired and with a low logical value in the remaining instants of time. In one embodiment, by acquiring samples for a time interval of 1 s, the relative window function W corresponds to a rectangular function in the range from 0 to 1 s.

[0138] In particular, formula (15) is rewritten as: where Wi indicates the window function corresponding to the time interval of sample acquisition and the symbol * indicates the conjugate complex. Finally, 16 is discreetly rewritten as: which can be solved by means of numerical methods known and not described here for sake of brevity.

[0139] Accordingly, a correction is made to the damping coefficient k calculated in the previous step (step 2003). In the embodiment considered, the correction of the damping coefficient k is performed by a machine learning (ML) algorithm implemented by the control unit 68. Preferably, the ML algorithm receives as input the calculated damping coefficient k and one or more of: the mechanical power transferred to the linear generator 66 calculated by means of formula (6), the electrical power generated by the linear generator 66 - calculated as the product between voltage and current provided in output from the linear generator 66, the positions Xb and xmof the two elements 62 and 70, and the level of the platform 36 with respect to the average level of the sea 52, and provides in output a correct damping coefficient k.

[0140] In one embodiment, the ML algorithm is based on a neural network - or NN, acronym for Neural Network. Preferably, the NN is of the "Long Short Term Memory" type, which allows the effect of learning of the NN to be limited over time. This allows to guarantee a correct operation of the plant 30 in the face of transient phenomena, or sea conditions, which entail unpredictable effects on the rod-buoy assembly 62 and on the auxiliary float 70, as well as periodic (seasonal) or sudden variations of the sea conditions. In fact, these transient phenomena or sea conditions can produce different results on the plant 30 with the same measurement of the auxiliary float 70.

[0141] In one embodiment, the ML algorithm is trained by providing the above indicated input parameters of a training dataset and the feedback parameter Ak calculated as described below. The effective damping coefficient keis calculated by solving formula (5), and the pulsation is then averaged to obtain an average value <k> of the effective damping coefficient ke. The averaging operation is performed by using a time window defined by an appropriate window function W2(a)

[0142] The average value <k> is discretely redefined as:

[0143] Based on formula (19), the error value is calculated:

[0144] Ak — ktheoretical ~<'k'>, (20) which is used as a feedback value during the training of the NN algorithm.

[0145] Once the correct damping coefficient k has been calculated, the processing unit 68 generates a control signal which is transmitted to the linear generator 66 of the corresponding generator module 34 (step 2004).

[0146] In general, the window function Wi used in formula 16 and the window function 2 are different, although nothing prohibits the use of a single window function. For example, the feedback given by the calculation of the average value <k>, i.e. the method 2000, is preferably performed every 2 or 3 iterations of the method 1000. In one embodiment, the acquisition of the measurements is performed every second and corresponds to the first window function Wi while the calculation of the average value <k> is performed once every 2 -3 seconds and corresponds to the second window function 2. Optionally, the window functions Wi and / or 2 provide for a time overlapping between the groups of samples acquired and analysed periodically. In this case, it is preferably defined to have a window function that has an increasing function in the overlapping zone between the samples (e.g., such as an erf function or an appropriately scaled arcsin function). In this way, a time consistency among the samples is maintained and any variations in measurements between one cycle of execution of the method and the other are smoothed.

[0147] Preferably, the window functions Wi and / or W2 are selected as a function of the acquisition frequency and of the number of samples acquired. The sampling frequency of the measurements is, in general, an intrinsic characteristic of the measurement system used - for example, it is determined by the scanning frequency of the ports of the control unit 68 (e.g., a microcontroller or a PLC). The number of measurements, i.e. samples, acquired is instead selected by the control logics and is calibrated so as to control the plant 30 only once sufficient data are available to determine useful information on the state of the plant 30 and / or the wave motion to which the plant 30 is subject. According to Nyquist's theorem the frequency resolution of our data sequence transform is of the order of

[0148] In order for the plant 30 to function optimally, a good resolution on the predominant frequency of the wave motion is required. For example, it is preferable to maintain at least an order of magnitude of difference between the Af value defined in formula (21) and the predominant frequency of the wave motion

[0149] To ensure optimal window function Wi and / or 2 it is possible to dynamically vary the number of samples acquired nsstarting from an initial number to then reach and chase the predominant frequency of the wave motion. The number of samples and the acquisition frequency define the sizes of the window functions Wi and / or 2. Advantageously, although not in limiting manner, a maximum and minimum number of samples is set to guarantee the correct operation of the control logics. This functionality, on the one hand, avoids excessive expansion of the execution times and limits the maximum computational load of methods 100 and 2000, on the other hand, it guarantees the acquisition of a minimum amount of data that are still useful for controlling the plant 30.

[0150] In summary, the control unit 68 controls the circuit 100 - through the opto-triac O1 and the triac T1 - to regulate the absorption of the electric windings 46 - corresponding to the inductor LI - so as to exhibit the damping coefficient determined by the method 2000. In this way it is possible to control the energy converted by the linear generator 66 by absorbing a desired amount of energy, as much as possible in the example described here, in the current conditions of wave motion 54 through a PWM regulation.

[0151] In one embodiment, the control unit 68 is adapted to manage an incomplete wave motion of operation. When, due to the presence of high waves, the reaching of the top dead centre by the rod-buoy assembly 62 is detected in a relevant manner - for example, beyond a time limit period or with a frequency greater than a threshold frequency, the control unit 68 generates the control signal so as to increase the absorption of the linear generator 66, thereby reducing the movement speed of the rodbuoy assembly 62 and, therefore, decreasing the risk of damage to the generation module 34 and to the plant 30 as a whole. This incomplete wave management takes over the method 2000, when the triggering condition occurs - i.e., the top dead centre is reached by the rod-buoy assembly 62.

[0152] In accordance with some embodiments, the plant 30 of the invention also comprises movement means 76 for displacing the generation modules 34 in a vertical direction. In the event that the bearing structure 32 is fixed on the seabed 50, the average level of the sea 52 may undergo considerable variations due to the motion of the tides; compare in this regard figure 1 (which schematically represents the plant 30 in a high tide condition) and figure 2 (which schematically represents the plant 30 in a low tide condition). If the generation modules 34 were fixed with respect to the bearing structure 32, in order to enable the rod-buoy assemblies 62 to follow the wave motion 54 in all statistically relevant conditions, the buoys 42 should have a very long useful stroke. Visually, the useful stroke of the buoys 42 should extend at least from the crest of the waves of figure 1 to the valleys of the waves of figure 2. Such a useful stroke would imply great disadvantages. In fact, the greater the length of the rods 40, the more they are deformable due to the bending moments generated by the horizontal components of the forces to which they are exposed. Furthermore, the longer useful stroke length implies a greater number of permanent magnets 44 and of electrical windings 46, with a consequent increase in the mass of the rod-buoy assembly 62 and an increase in the overall costs of the linear generator 66.

[0153] The arrangement of the movement means 76 allows instead to size the useful stroke of the buoys 42 on the only amplitude of the statistically relevant wave motion 54, regardless of the average level of the sea 52. The variations in the average level of the sea 52 due to the tides are instead compensated for by the action of the movement means 76 through the displacement in the vertical direction of the generation modules 34.

[0154] Preferably, the plant 30 comprises a third sensor 78 configured to detect the position xpof each platform 36 of the generation modules 34 with respect to the bearing structure 32 of the plant 30 itself - preferably, with respect to a reference portion of the bearing structure 32. In this case, by combining the signals of the first sensor 64, the second sensor 72 and the third sensor 78, it is possible to determine the positions of each rod-buoy assembly 62 and each auxiliary float 70, with respect to the bearing structure 32.

[0155] In the solution shown in figures 1 and 2, the bearing structure 32 comprises a main pillar 48 supporting a slab 60 formed by joining the platforms 36 of a plurality of generation modules 34. The slab 60 is slidable along the main pillar 48 and can be raised and lowered through the movement means 76. In the specific embodiment, the slab 60 is hung by chains and the movement means 76 comprise one or more motorized winches configured to wind or unwind the chains (see figure 3).

[0156] Preferably, the control unit 68 is configured to control the movement means 76 in accordance with a pre-loaded logic; for example, the control unit 68 can be configured to control the motorized winches so as to position, instant by instant, the slab 60 at a correct height above the average level of the sea 52. A correct height of the slab 60 can be defined, for example, as the one allowing each rod-buoy assembly 62, under design conditions of wave motion 54, to move vertically without reaching either the upper end-of-stroke or the lower end-of-stroke. The slab 60 connected to the main structure through the movement means 76 allows the height of the generation modules 34 to be regulated with respect to the level of the sea 52.

[0157] An example of the positioning logic employed by the control unit 68 is the height regulation method 3000 provided below, of which figure 22 is a flowchart. Substantially, the method 3000 is adapted to positioning the slab 60 of the plant so that the average water level, i.e. the sea surface, remains substantially at the slab 60 and, therefore, at the centre of the working range of the strokes of the rod-buoy assemblies 62. In other words, the position of the slab 60 is regulated with respect to the average level of the sea surface to ensure a desired excursion of the rod-buoy assemblies 62. In the example considered, the method 3000 receives in input the position xmof each auxiliary float 70 of the plant 30 which is determined thanks to the measurements of the sensors 64, 72 and 78 (step 3001). For each position xmit is verified whether a limit value is reached or exceeded (decision step 3002). For example, it is verified whether a maximum end-of-stroke position of the auxiliary float 70 is reached or whether the end-of-stroke position is maintained for a period of time longer than a time limit period. In the affirmative case (output branch Y of step 3002), the position of the slab 60 is varied, by actuating the movement means 76, so as to guarantee a minimum safety distance between the level of the current wave motion and the slab 60 (step 3003).

[0158] In the negative case (output branch N of step 3002), it is not necessary to perform a safety displacement of the slab. In addition, the average position value xm(a) I a>=o of the floats 70 of the plant 30 with respect to the top of the bearing structure 32 (step 3004) is calculated, and the maximum amplitude A of water is also determined as a function of the wave motion 54 (step 3005). In the embodiment considered, the water level trend F(a) is used to determine the maximum amplitude A. In particular, the maximum amplitude A reachable by the wave motion once its harmonic components F(co) are known is calculated by means of the formula:

[0159] In other words, the maximum amplitude A corresponds to the sum of the amplitudes of the individual harmonic components of the wave motion. In other words, the maximum amplitude A represents the maximum amplitude that can be reached by a wave under current wave motion conditions 54 - that is, when the harmonic components of the level trend F(co) come to be phased with each other.

[0160] Subsequently, the average position value xm(a) I a>=o and the water level trend F(a) are filtered by means of respective moving average filters (step 3006). As a result, a filtered average position value xm(a) I a>=o - defined with respect to the selected reference element of the plant 30, i.e. the top of the structure 32 - and a filtered maximum amplitude value A, reachable by water under current wave motion conditions, are obtained.

[0161] The control unit 68 verifies whether the maximum amplitude A exceeds at least one limit value, for example an upper limit value (decision step 3007). In the embodiment, the limit value of the amplitude A is defined as the maximum amplitude value A such that the sum of the maximum amplitude A and of the average level xm(co) | a>=o is greater than the current position of the slab 60 with respect to the top of the structure 32. When an exceedance of the maximum amplitude limit value A (output branch N of decision step 3007) is not identified, the position of the slab 60 is not modified. More preferably, it is verified whether the slab is in a position substantially equal to the average level xm(a) I a>=o plus a predetermined operating offset value Offo, i.e. xm(co) | a>=o+Offo (decision step 3008). For example, the operating offset value Offo is selected as a function of the stroke of the rod-buoy assembly 62. Preferably, the operating offset value Offo is a positive or negative real value selected so that the slab results in a position equal to half the stroke of the rod-buoy assembly 62, i.e. so that the rod can slide upwards and downwards by a length equal to half the stroke under the current wave motion conditions 54.

[0162] In the affirmative case (output branch Y of step 3008), the position of the slab is not modified (step 3009) and the method is reiterated at the next measurement acquisition. Otherwise (branch N of step 3008), the movement means 76 are actuated in order to bring the slab 60 into the desired position (step 3010) - that is, substantially equal to xm(a) I a>=o+Offo and the method is reiterated at the next measurement acquisition.

[0163] On the other hand, when the maximum amplitude A is reached (output branch Y of step 3007), a displacement of the slab 60 is calculated such as to bring it to a position above the water level defined by the sum of the maximum amplitude and of the average value, i.e. A + xm(a) |ffl=o (step 3011). In the considered embodiment, the position of the slab 60 is substantially equal to the sum of the maximum amplitude and of the average value plus a first predefined safety offset value Off si, i.e. A + xm(a) I <u=o + Offsi. For example, the offset value Offsi is a positive or negative real value selected so as to guarantee the maximum excursion of the rod-buoy assemblies 62 with the current maximum amplitude of the wave motion 54.

[0164] In addition or alternatively, the method 3000 comprises determining upper and lower limit values corresponding to amplitude values of the wave motion 54 whereby the rod-buoy assemblies 62 reach and maintain the top dead centre or the bottom dead centre in the current position of the slab 60 and of the average position value xm(a) I a>=o of the body of water - for a time greater than a time limit period or with a frequency greater than a threshold frequency. In such a case, the position of the slab 60 is modified so that the stay of the rod-buoy assemblies 62 in dead centres during operation is minimized.

[0165] Optionally, the method 3000 comprises limiting a maximum movement of the slab 60 at each iteration of the correction method 3000 to prevent continuous and excessive movements of the slab. In the embodiment considered, it is verified whether the sum of the maximum amplitude and of the average value, i.e. A + xm(a) 10=o, exceeds a limit value AX that coincides with the level of the slab 60 with respect to the top of the structure 32 (decision step 3012). In the negative case (output branch N of step 3012), the movement means 76 are actuated to bring the slab 60 into the calculated position (step 3013) - i.e. the position calculated at step 3011 i.e. A + xm(a) I 0=0. Otherwise (output branch Y of step 3012), the movement means 76 are actuated to displace the slab 60 from a current position to a new position equal to the position given by the sum of the maximum wave amplitude, the average value, and a second predefined safety offset Offsi - preferably, although not in a limiting manner - different from the first offset value Offsl -, i.e. A + xm(a) I 0=0 + Oj^s2 (step 3014). This ensures that the platform remains above the level of the sea 52.

[0166] Subsequently, the method 3000 is reiterated at the next measurement acquisition.

[0167] In one embodiment, the regulation of the position of the slab 60 is carried out by means of an ML algorithm, for example an NN of the type described above. In this case, the ML algorithm is trained with a dataset, which comprises groups of data, each of which includes the maximum and minimum positions reached by the rod-buoy assemblies 62 measured in a respective condition of wave motion 54 and of a respective position of the slab 60 during the measurement of the positions of the rod-buoy assemblies 62.

[0168] As will be apparent to the skilled person, the method 3000 can be applied to the entire slab 60 of the plant 30 or to the individual platforms 36 of the plant 30, in the event that movement means 76 capable of individually displacing one or more platforms 36 are provided.

[0169] The method 3000 is preferably performed in parallel with the method 2000 as long as the plant is operational. However, there is nothing to prevent the application of different activation and operation schemes of the methods 2000 and 3000. More generally, in the embodiments in which the plant 30 is provided with the control unit 68, the latter preferably implements, although not in a limiting manner, at least one among the method 1000, the method 2000 and the method 3000.

[0170] As the person skilled can well understand, the invention overcomes the drawbacks highlighted above in relation to the known technique.

[0171] In particular, the invention makes available a plant 30 for the exploitation of the wave motion 54 that has a simple structure and that is therefore economical and reliable. In particular, the structure of the generation modules 34 and of the respective linear generators 66 is particularly simple.

[0172] In addition, the invention makes available a plant 30 for the exploitation of the wave motion 54 whose generator can easily adapt, in a dynamic way, to the characteristics of the wave motion 54, so as to work for as long as possible at an optimal regime. The plant 30 of the invention allows in fact to vary the characteristics of the linear generators 66 in order to maximize the production of electrical energy. Finally, the invention makes available a plant 30 for the exploitation of the wave motion 54 that allows to keep the excursion of the buoys 42 contained within desired levels and which can, at the same time, adapt to the variation of the average level of the sea 52 due to the tides.

[0173] In conclusion, all the details can be replaced by other technically equivalent elements; the characteristics described in relation to a specific embodiment can also be used in the other embodiments; the materials used, as well as the contingent shapes and dimensions, can be any according to the specific implementation needs without leaving the scope of protection of the following claims.

Claims

CLAIMS1. Method (1000,2000,3000) for controlling a plant (30) for the generation of electrical energy through the exploitation of the wave motion (54) in a body of water, comprising:- at least one generation module (34) adapted to convert kinetic energy associated with the wave motion (54) into electrical energy by means of a movable element (62) adapted to move due to the action of the wave motion (54) and a generator element (66) adapted to convert the movement of the movable element into electrical energy,- at least one sensor (72) adapted to provide at least one measurement indicative of the wave motion (54) with respect to an element of the plant (30), the method comprising the steps of:- acquiring a plurality of measurements,- calculating a damping coefficient associated with the conversion of movement into electrical energy of the generator element (66), where the damping coefficient depends on a desired value of the energy converted by the generation module (34) as a function of the at least one measurement provided by the sensor (72), and- regulating the operation of the generator element (66) so as to impose the calculated damping coefficient, characterized in that the at least one generation module (34) is coupled to a platform (36), and characterised by comprising the step of:- acquiring, by means of the at least one sensor (72), at least one measurement between: a mechanical power transferred to the generator element (66), an electrical power generated by the generator element (66), a position of the movable element (62), and a position of the platform (36) relative to an average level of the sea (52), and in that the step of calculating a damping coefficient comprises:- calculating the average damping coefficient according to the formula:where W2(a) is an observation frequency window, where n is the radius of a surface of contact with the body of water of the movable element (62) with which it comes into contact with the wave motion, g is the acceleration of gravity, Mb is the mass of the movable element, Xb is the at least one measurement provided by the sensor (72), p is the density of the body of water,- determining an error value corresponding to the difference between the calculated damping coefficient and the average damping coefficient,- using the error value as a feedback value to calculate a new uaiiiping coefficient.

2. Method (1000,2000,3000) according to claim 1, wherein the damping coefficient is calculated so as to obtain a maximum energy absorption as a function of the plurality of measurements provided by the sensor.

3. Method (1000,2000,3000) according to claim 2, wherein the movable element (62) has a cylindrical shape, and wherein the damping coefficient is calculated so as to verify the formula:where n is the radius of the movable element (62), g is the acceleration of gravity, Mb is the mass of the movable element, xmis a measurement provided by the sensor (72), p is the density of the body of water, W(t) is a wave motion observation time window.

4. Method (1000,2000,3000) according to claim 3, wherein the wave motion observation time window is configured to have a duration of about one second.

5. Method (1000,2000,3000) according to any one of the preceding claims, wherein the steps of calculating an average damping coefficient, determining an error value, and using the error value as a feedback value are performed by at least one artificial intelligence algorithm.

6. Method (1000,2000,3000) according to claim 2, wherein the observation frequency window corresponds to a further observation time window is configured to have a duration greater than the duration of the observation time window, preferably the further time window has a duration approximately equal to a multiple of the duration of the observation time window, even more preferably the further time window has a duration approximately equal to two or three times the duration of the observation time window.

7. Method (1000,2000,3000) according to any one of the preceding claims, wherein the generation module (34) comprises:- a guide channel (38) that develops vertically, fixed with respect to the platform (36);- a rod (40) slidable along the channel (38);- a buoy (42) fixed to the lower end of the rod (40);- a circuit (100), and wherein the rod (40) comprises a plurality of magnets (44) or of electrical windings (46) and the channel (38) comprises, respectively, a plurality of electrical windings (46) or of magnets (44), the circuit (100) comprising said electrical windings (46), and wherein the rod (40) and buoy (42) assembly corresponds to the movable element (62) and the circuit (100) corresponds to the generator element (66) of the generation module (34), wherein the step of regulating the operation of the generator element (66) so as to impose the calculated damping coefficient comprises:- regulating the absorption of electrical energy through the electrical windings (46) so as to generate a force resistant to the sliding of the rod (40) in the channel (38) proportional to the calculated damping coefficient.

8. Method (1000,2000,3000) according to any one of the preceding claims, wherein the circuit comprises an absorption sub-circuit (101) comprising the electrical windings (46) and a switch element (Tl), and wherein the step of regulating the absorption of electrical energy through the electrical windings (46) comprises controlling the switch element with a pulse width modulation (PWM) signal as a function of the calculated damping coefficient.

9. Method (1000,2000,3000) according to any one of the preceding claims, wherein the generator module (34) comprises a float (70) free to slide in vertical direction within a maximum available stroke comprised between two opposite end-of- strokes: an upper end-of-stroke and a lower end-of-stroke, and wherein the step of acquiring a plurality of measurements indicative of the wave motion (54) with respect to an element of the plant (30) comprises measuring a position of a portion of the float with respect to an element of the plant (30).

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