JP5543625B2 - Wave power generator and control method thereof - Google Patents

Description

  The present invention relates to a wave power generation apparatus that generates energy by extracting energy from waves by the movement of a float floating on the sea, and a control method therefor.

  Conventionally, as a wave power generation device, there is one that floats on the sea surface or in the sea (see, for example, Patent Document 1). FIG. 9 shows an example of a conventional wave power generator. This wave power generation device 1X has a column 2X moored by an anchor 31 and a mooring line 32 installed on the seabed, and a float 3X floating on the sea surface 10 due to buoyancy. The float 3X is configured to move up and down relatively with respect to the support column 2X under the force of waves (see arrows).

  The wave power generator 1X has a frame 5X for transmitting the movement of the float 3X to a generator (not shown) installed in the support column 2X. Furthermore, in order to adjust the position of the wave power generation device 1X in the sea in the vertical direction, a buoyancy adjustment unit 33 may be provided. The conventional float 3X is a point object shape such as a dish shape or a cylindrical shape with the support column 2X as a central axis, and specifically has an annular shape (ring shape). Here, W indicates a wave, F indicates an upstream side where the wave W arrives, and R indicates a downstream side opposite to the side where the wave W arrives.

  In FIG. 10, the schematic diagram of the cross section of the wave power generator 1X is shown. The wave power generation device 1X includes a generator (hereinafter referred to as a motor) 4 installed inside the support column 2X, and a frame 5X configured to extend upward from the float 3X and then to be inserted into the support column 2X. ing. The frame 5X, the rack 6 formed in a part of the frame 5X, and the pinion 4 installed in the motor 4 form a power transmission mechanism that transmits the kinetic energy of the float 3X to the motor 4.

  Next, the operation of the wave power generator 1X will be described. First, the strut 2X of the wave power generation device 1X is substantially fixed to the seabed by an anchor 31 or the like, and is configured not to be affected by waves. The float 3X that receives the wave moves up and down with respect to the substantially fixed column 2X. The wave power generation device 1 </ b> X transmits the kinetic energy of the float 3 </ b> X as a rotational force to the motor 4 through the power transmission mechanism (the frame body 5 </ b> X, the rack 6, and the pinion 7) to generate power. With this configuration, the wave power generation device 1 </ b> X can generate energy by extracting energy from the waves that move up and down the sea surface 10.

  However, the conventional wave power generator 1X has a problem that the power generation efficiency is low. The power generation efficiency of the wave power generator 1X is about 20% at the maximum. This is because the wave power generator 1X collects only a part of the energy of the wave (incident wave) colliding with the float 3X. Most of the remaining energy of the incident wave becomes a wave (reflected wave) generated by the collision with the float 3X and a wave (transmitted wave) formed behind the float 3X, and does not contribute to power generation. Therefore, it has been difficult to improve the power generation efficiency of the wave power generation device 1X.

JP 2007-518024 A

The present invention has been made in view of the above problems, and an object of the present invention is to provide a wave power generation apparatus with improved power generation efficiency and a control method thereof in a wave power generation apparatus that extracts power from waves and generates power. For the purpose.

  In order to achieve the above object, a wave power generation device according to the present invention is a wave power generation device including a support, a float that moves relative to the support, and a generator that generates power by the movement of the float. The wave power generator includes a wave sensor for measuring a waveform, a position sensor for measuring the position of the float with respect to the support, a drive mechanism for applying an external force to the float, and a control device for controlling the drive mechanism. And the control device calculates a speed at which the float should be controlled from the values of the wave sensor and the position sensor, and controls the drive mechanism so that the float has the calculated speed. It is characterized by that.

  With this configuration, the power generation efficiency of the wave power generation device can be improved. This actively controls the float according to the oscillation of the wave, and prevents or suppresses the wave (transmitted wave) generated on the downstream side of the float and the wave (reflected wave) generated on the upstream side of the float due to reflection. Because it can.

  In the above-described wave power generation device, the back surface of the float on the downstream side opposite to the wave arrival side has the same or similar shape as the locus of movement of the float.

  With this configuration, the power generation efficiency of the wave power generation device can be improved. This is because the shape of the back surface of the float is formed to be the same or similar to the movement direction of the float, so that the float can reduce the resistance of water generated by the movement. . Therefore, generation of waves (transmitted waves) formed on the downstream side of the float can be prevented or suppressed, and the energy can be recovered as kinetic energy of the float.

  In the above-described wave power generation device, the wave power generation device includes the support column having a longitudinal direction in the vertical direction and the float that moves up and down along the support column, and the float has a wave arrival side. It is characterized in that the angle formed by the back surface and the bottom surface on the opposite downstream side is smaller than 90 degrees. With this configuration, the same effects as described above can be obtained.

  In the above-described wave power generation device, the support column having a longitudinal direction in a horizontal direction, and the float that rotates about the support column as a central axis, the float being on a downstream side opposite to a wave arrival side, A part of the back surface and the bottom surface is formed in a cylindrical shape having the central axis as the support column. With this configuration, the same effects as described above can be obtained.

  In order to achieve the above object, a method for controlling a wave power generation device according to the present invention comprises a column moored in the sea, a float that moves relative to the column, and a generator that generates electricity by the movement of the float. The float is configured such that the back surface on the downstream side opposite to the wave arrival side has the same or similar shape as the locus of movement of the float, and The wave power generation apparatus includes a wave sensor that measures a waveform, a position sensor that measures a position of the float with respect to the support, a drive mechanism that applies an external force to the float, and a control device that controls the drive mechanism. A method of controlling a power generation device, wherein the wave sensor calculates an average water level of a sea surface from a measured waveform and measures the position of the wave with respect to the average water level, and the position sensor A measurement step for measuring the position of the float with respect to the measurement, a calculation step for calculating a speed to be controlled of the float from the measured position of the float and the position of the wave, and a speed at which the float is to be controlled. As described above, a float control step of applying an external force by the driving device is provided. With this configuration, the same effects as described above can be obtained.

  The wave power generation device according to the present invention can provide a wave power generation device with improved power generation efficiency and a control method thereof.

It is the schematic of the cross section of the wave power generator of embodiment which concerns on this invention. 1 is a schematic plan view of a wave power generator according to an embodiment of the present invention. It is the schematic of the cross section of the wave power generator of different embodiment which concerns on this invention. It is the schematic of the wave power generator of different embodiment which concerns on this invention. It is the schematic which showed the structure of the wave power generator of different embodiment which concerns on this invention. It is the figure which showed the control flow of the wave power generator of different embodiment which concerns on this invention. It is the schematic of the wave power generator of different embodiment which concerns on this invention. It is the schematic of the side and plane of the wave power generator of different embodiment which concerns on this invention. It is the schematic of the conventional wave power generator. It is the schematic of the cross section of the conventional wave power generator.

  Hereinafter, a wave power generator according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of a cross section of a wave power generator 1 according to an embodiment of the present invention. The wave power generator 1 includes a support 2 moored in the sea, a float 3 that moves relative to the support 2, and a generator (hereinafter referred to as a motor) 4 that generates electricity by the movement of the float 3. Specifically, the wave power generation device 1 includes a support column 2 having a longitudinal direction in the vertical direction and a float 3 that moves up and down along the support column 2. Here, the float 3 has a downstream side R (left side in FIG. 1) opposite to the side on which the wave W arrives, compared to the volume of the upstream side F (right side in FIG. 1) where the wave W arrives around the support column 2. It is comprised so that the volume of may become small. Further, the rear surface 8 on the downstream side R of the float 3 is configured to have the same shape as the locus of movement of the float 3 indicated by an arrow. That is, since the float 3 moves up and down in the vertical direction, the back surface 8 is configured to be a plane parallel to the vertical direction. With this configuration, when the float 3 moves up and down, generation of a wave (transmitted wave) transmitted to the downstream side R via the back surface 8 can be suppressed. This is because the back surface 8 hardly performs work on the water as the float 3 moves up and down.

  The wave power generator 1 is a power transmission mechanism that transmits the kinetic energy of the float 3 to the motor 4, and includes a frame 5, a rack 6 formed in a part of the frame 5, and a pinion 7 installed on the motor 4. However, the present invention is not limited to this configuration. The power transmission mechanism and the generator 4 may have a configuration in which energy is extracted from the vertical movement of the float 3 including power generation by electromagnetic induction, adoption of a piezoelectric element, and the like. In addition to being moored at the sea, the support 2 can be fixed to the quay or directly fixed to the seabed.

  In FIG. 2, the schematic of the plane of the wave power generator 1 is shown. The float 3 is formed so that the volume on the upstream side F is larger than the downstream side R with respect to a center line (two-dot chain line) C passing through the center of the support column 3 in plan view. Specifically, it is configured to have a shape obtained by cutting a part of an annular shape (ring shape). The shape of the float 3 is not limited to the above configuration. For example, as shown by a broken line, it may be a quadrangular float 30 protruding to the upstream side F in plan view. That is, the float 3 of the wave power generation device 1 may be a float formed so that the volume on the upstream side F is larger than that on the downstream side R. As the volume difference between the upstream side F and the downstream side R in the float increases, the generation of waves (transmitted waves) transmitted to the downstream side R can be suppressed (see the sea surface 10 in FIG. 1).

  Note that the directions of the upstream side F and the downstream side R where the wave W arrives are determined for each sea area (point) where the wave power generation device 1 is installed. The traveling direction of the wave W is determined within a certain range for each point. In particular, when the land is close, the wave W travels toward the land.

  With the above configuration, the wave power generation device 1 can improve power generation efficiency. This is because a wave (transmitted wave) generated on the downstream side R as the float 3 moves up and down can be prevented or suppressed. The conventional float 3X (see FIGS. 9 and 10) moves up and down in response to the energy of the incident wave on the upstream side F, and forms a transmitted wave on the downstream side R by this vertical movement. The wave power generation device 1 can improve the power generation efficiency because it can recover the energy conventionally consumed for forming the transmitted wave as electric power.

  In FIG. 3, the schematic of the cross section of 1 A of wave power generators of different embodiment of this invention is shown. This wave power generator 1A includes a position sensor 13 that measures the relative position of the float 3A in the vertical direction z with respect to the support column 2 or the average water level WL, a wave sensor 14 that measures the waveform of the wave W that collides with the float 3, and a float 3 includes a drive mechanism (hereinafter referred to as a motor) 4 that applies an external force to 3, and a control device 11 that controls the drive mechanism 4. The control device 11 is connected to the position sensor 13, the wave sensor 14, and the drive mechanism 4 by the signal line 12 or wirelessly.

  Here, the drive mechanism 4 desirably uses the generator (motor) shown in FIG. 1 as it is, but may be newly installed. Moreover, the wave sensor 14 should just measure the relative position of the wave with respect to the support | pillar 2, or the relative position of the wave with respect to the average water level WL calculated from the waveform. Specifically, a known measuring device such as a pressure sensor, an ultrasonic sensor, or a water pressure gauge can be used. When a pressure sensor is used as the wave sensor 14, the wave sensor 14 is placed at a position below the water surface of the float 3A. When an ultrasonic sensor is used, the wave sensor 14 is above the water surface of the float 3A. Install in position. Furthermore, the float 3A has a shape that does not have a volume on the downstream side R. In this case, it is desirable that the float 3 </ b> A is configured to be movable with respect to the support column 2 without being separated, for example, by installing a guide or the like. This is to prevent the frame body 5 from being deformed by an external force such as a moment.

  Further, the angle formed between the back surface 8 and the bottom surface 9 of the float 3A is configured to be a wedge shape smaller than 90 degrees, desirably smaller than 60 degrees, and more desirably smaller than 45 degrees. Configure. This is because, with this configuration, the back surface 8 and the bottom surface 9 of the float 3A can suppress drag generated against water when the float 3A moves up and down.

  Next, control of the wave power generator 1A will be described. FIG. 4 shows a schematic diagram when the control preconditions are set. The control of the wave power generation device 1A aims to prevent the generation of the reflected wave 21 and the transmitted wave 22 by actively controlling the float 3A with respect to the incident wave 20 by the drive mechanism (motor) 4. That is, the wave power generation device 1A can extract all of the energy of the incident wave 20 as the recovered energy 23 and use it for power generation. That is, the power generation efficiency is set to 100%.

Hereinafter, mathematical formulas used for control will be described. In FIG. 4, when the incident wave 20 is η _i , the reflected wave 21 is η _r , and the respective wave amplitudes are a _i and a _r , they can be expressed by the following equation (1).

Here, assuming that the position of the float 3A is x = 0, the equation (2) is obtained.

Next, let us consider a condition (complete absorption condition) in which the incident wave 20 is absorbed and the reflected wave 21 is simultaneously zeroed by the vertical movement of the float 3A. First, when the float 3A is shaken in a state where there is no wave, the wave amplitude a with respect to the amplitude e of the float 3A can be expressed by an amplitude ratio of Expression (3).

That is, it can be expressed in the form of equation (4).

From the above, when the vertical movement operation of the float 3A is divided into an operation of setting the reflected wave 21 to zero and an operation of absorbing the incident wave 20, the equation (5) is obtained.

Here, the speed when controlling the vertical movement of the float 3A is in the form of equation (6).

Further, the general expression of the velocity potential is in the form of Expression (7).

Here, Cn is a constant determined by the boundary condition. Also,

  The first term on the right side of Equation (7) represents a reflected wave made of a float, and the second term represents an incident wave that is incident on the float and is to be absorbed. The third and fourth terms represent a standing wave having a maximum amplitude and an infinitely long wavelength on the front surface of the float.

Next, considering the water surface shape at the front surface of the float, the wave height η _{x = 0} can be expressed by Equation (9).

Here, the following formulas (10), (4), and (5) are applied to the formula (9) to obtain the formula (11).

Further, equation (12) is created in the same manner from equation (6).

The above equation (11) and equation (12) are added to obtain equation (13).

Here, the following formula (14) is put into the formula (13) and rearranged to obtain the formula (15).

Here, since the wave generated by the float is desirably zero, the equation (16) is applied to the equation (15) to obtain the equation (17).

Here, since the frequency range of the wave does not vary so much from experience, constants K _A and K _C defined by Expression (18) are used, and Expression (17) is transformed into Expression (19).

Here, ω represents frequency, and A bar represents wave-making efficiency. The wave-making efficiency indicates how many units the wave moves when the float is moved by one unit. Z indicates the relative position of the float 3A in the vertical direction with respect to the average water level WL, and this value is measured by the position sensor 13. Furthermore, η _{x = 0} indicates a waveform in front of the float, that is, a relative position in the vertical direction of the wave with respect to the average water level WL, and this value is measured by a wave sensor 14 such as a pressure type. From the above calculation formula, Formula (19), which is a control formula for controlling the wave power generation device, can be obtained. The average water level WL is a value that changes due to the influence of tides. Further, z and η _{x = 0} may be values of the relative position in the vertical direction of the float 3A with respect to the pillar 2 that is apparently fixed, and the relative position in the vertical direction of the wave with respect to the pillar 2. By this calculation, the values of z and η _{x = 0} can be easily determined, and the control can be simplified.

Next, control of the wave power generator will be described. FIG. 5 shows an outline of the configuration of the wave power generator 1A, and FIG. 6 shows a control flow. First, the wave sensor 14 that measures the waveform calculates the average water level WL of the sea surface from the time series data, the position sensor 13 measures the relative position z of the float 3A in the vertical direction with respect to the average water level WL, and the wave sensor 14 floats. The relative wave height η _{x = 0} with respect to the average water level WL at the position (x = 0) as the reference of 3A is measured (measurement step S02). The measured relative position z and wave height η _{x = 0} are sent to the control device 11. The control device 11 calculates the speed z ′ at which the float is to be controlled by the equation (19) using the position z and the wave height η _{x = 0} as parameters (calculation step S03).

Thereafter, the control device 11 outputs the calculated speed z ′ as a speed command to the drive mechanism (motor) 4 (speed command step S04). The motor 4 applies an external force to the float 3A via a power transmission mechanism such as a rack and pinion so that the relative speed of the float 3A with respect to the average water level WL is z ′ (float control step S05). The position of the float given the speed by the external force is measured again (feedback control S06). That is, the movement speed of the float 3A is sequentially controlled according to changes in the position z of the float 3A and the wave height η. The motor 4 is configured to generate power from wave energy recovered through the float while applying an external force to the float 3A.

  With the above configuration, the following operational effects can be obtained. First, the power generation efficiency of the wave power generation device can be dramatically improved. This is because the float can be actively controlled so that the reflected wave and the transmitted wave are not formed.

  Second, float control can be simplified. This is because the float is controlled at the speed z ′ as shown in the equation (19). That is, since the magnitude of the mechanical resistance or the like of the wave power generator is smaller than the external force output from the motor, it is not necessary to consider it, so that the control can be simplified. On the other hand, for example, the control can be performed by the force applied to the float, but in this case, it is necessary to consider the weight of the float, the inertial force, and the like, which complicates the control.

  Here, the above-described control can obtain a certain effect even in the wave power generation device (see FIGS. 9 and 10) having the same float shape as the conventional one. That is, even when the float has a volume larger than a certain value on the downstream side R, the above-described control can suppress the generation of transmitted waves by a certain amount.

In order to further simplify the control of the float, the control equation may be in the form of equation (20).

Expression (20) is obtained by deleting the K _c term in Expression (19). This can be eliminated because the K _c term is usually small enough. In this case, since the position sensor 13 is not required, the manufacturing cost of the wave power generation device can be reduced. Further, when the position sensor 13 breaks down at sea or the like, the control may be switched to the control according to the equation (20). With this configuration, the wave power generation device can perform efficient power generation until immediately before repairing the position sensor 13.

  Here, the wave targeted by the wave power generation device is, for example, a wave having an energy of about 15 kW per 1 m width in a direction perpendicular to the traveling direction of the wave and a period of about 7 to 8 seconds. It is. For this wave, for example, the amount of power generated when a wave power generation device having a float with a width of 10 m is 150 kw, assuming that the energy recovery efficiency is 100%.

  FIG. 7 shows a schematic diagram when setting control preconditions different from those in FIG. In the control of the wave power generation device 1B, the float 3B is actively controlled by the drive mechanism (motor) 4 with respect to the incident wave 20, and the generation amounts of the reflected wave 21 and the transmitted wave 22 are respectively controlled with respect to the incident wave. It aims at controlling so that it may become about 25%. That is, the wave power generation device 1B can extract 50% of the energy of the incident wave 20 as the recovered energy 23 and use it for power generation. That is, the power generation efficiency is set to 50%.

Hereinafter, mathematical formulas used for control will be described. In FIG. 7, when the incident wave 20 is η _i , the reflected wave 21 is η _r , the respective wave amplitudes are a _i and a _r , and the incident wave 20 and the reflected wave are transported in the same manner, the following equation (21) , (22), (23).

When a calculation similar to the calculation performed in the description of FIG. 4 is performed, the following control expression (24) can be finally obtained.

  With the above configuration, the power generation efficiency of the wave power generation device can be improved. This is because the float 3B can be actively controlled so as to suppress the formation of reflected waves and transmitted waves. Further, compared with the case described with reference to FIG. 4, the speed for controlling the float 3B is about 1/3. Therefore, the output required for the drive device (motor) can be reduced.

As described above, in order to further simplify the control of the float, the control equation (24) may be changed to the equation (25).

Expression (25) is obtained by deleting the K _c term in Expression (24). This can be eliminated because the K _c term is usually small enough. In this case, since the position sensor 13 is not required, the manufacturing cost of the wave power generation device can be reduced.

  FIG. 8 shows an outline of a side surface and a plane of a wave power generation device 1C according to another embodiment of the present invention. This wave power generation device 1C has a support column 2C having a longitudinal direction in the horizontal direction and a float 3C that rotates in the vertical direction about the support column 2C as a central axis. Further, a part of the back surface 8C and the bottom surface 9C on the downstream side R of the float 3C is configured to have the same or similar shape as the locus of movement of the float 3C indicated by an arrow. That is, since the float 3C rotates around the support column 2C, a part of the back surface 8C and the bottom surface 9C is configured to have a curved surface (cylindrical shape) centering on the support column 2C. With this configuration, when the float 3C rotates and swings, generation of waves (transmitted waves) transmitted to the downstream side R via part of the back surface 8C and the bottom surface 9C can be suppressed. This is because part of the back surface 8C and the bottom surface 9C hardly performs work on the water as the float 3C rotates.

  In addition, the float 3C is configured such that the volume on the downstream side R is smaller than the volume on the upstream side F with the center line C of the support column 2C as the center, as described above. The wave power generation device 1C can employ any of the above-described control expressions (19), (20), (24), and (25) for controlling the float 3C.

DESCRIPTION OF SYMBOLS 1 Wave power generator 2 Support | pillar 3 Float 4 Generator, drive device, motor 5 Frame 8 Back surface 9 Bottom surface 11 Control device 13 Position sensor 14 Wave sensor 20 Incident wave 21 Reflected wave 22 Transmitted wave C Center line F Upstream side R Downstream Side W wave

Claims (3)

A wave power generation device having a support, a float that moves with respect to the support, and a generator that generates electric power by the movement of the float, the wave power generation device including a wave sensor that measures a waveform, and the In the wave power generation device having a position sensor that measures the position of the float, a drive mechanism that applies an external force to the float, and a control device that controls the drive mechanism,
The control device calculates a speed z ′ at which the float should be controlled from values of the wave sensor and the position sensor, and controls the drive mechanism so that the float has the calculated speed z ′. Have
The wave power generation device according to claim 1, wherein the control device has a configuration for determining a speed z ′ of the float to be controlled by Equation (19) or Equation (24).

Here, K _A is a constant obtained by dividing the frequency ω by the wave-making efficiency A bar, K _C is a constant equal to C bar determined by the boundary condition, and z is a relative position in the vertical direction of the float with respect to the average water level WL. Η _{x = 0} indicates the relative position of the wave in the vertical direction with respect to the average water level WL. 2. The control device according to claim 1, wherein the control device has a configuration in which a speed z ′ to be controlled of the float is determined by Equation 20 or Equation 25 instead of Equation 19 or Equation 24. Wave power generator.

A wave power generation apparatus having a propeller moored in the sea, a float that moves relative to the prop, and a generator that generates electric power by the movement of the float;
In addition, the wave power generator includes a wave sensor that measures a waveform, a position sensor that measures the position of the float with respect to the support, a drive mechanism that applies an external force to the float, and a control device that controls the drive mechanism. A method for controlling a wave power generation device having
The wave sensor calculates an average water level WL of the sea surface from the measured waveform, measures the wave position η _{x = 0} with respect to the average water level WL, and the position sensor measures the position z of the float with respect to the column. Measuring steps;
A calculation step of calculating a speed z ′ to be controlled of the float from the measured position z of the float and the position η _{x = 0 of the} wave according to (Equation 19) or (Equation 24);
A control method for a wave power generation apparatus, comprising: a float control step of applying an external force by the driving device so that the float has a speed z ′ to be controlled.

Here, K _A is a constant obtained by dividing the frequency ω by the wave-making efficiency A bar, K _C is a constant equal to C bar determined by the boundary condition, and z is a relative position in the vertical direction of the float with respect to the average water level WL. Η _{x = 0} indicates the relative position of the wave in the vertical direction with respect to the average water level WL.

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