JP7484607B2 - Water current power generation device - Google Patents

Description

This disclosure relates to a water current power generation device.

There is a power generation device that has a generator inside a pressure-resistant vessel (base) that can float underwater. For example, Patent Document 1 describes a twin-engine power generation device that has a pair of turbine blades (turbines) that rotate when exposed to a water flow, and receives the rotational driving force of the turbine blades to generate electricity using a generator inside the pressure-resistant vessel.

JP 2014-534375 A

In a twin-engine power generating system, a pair of turbines rotate in opposite directions, so that the counter torque caused by the rotation of one turbine and the counter torque caused by the rotation of the other turbine cancel each other out. This prevents biased rotational force from acting on the base, and maintains a constant attitude of the base. For this reason, if the balance of the counter torques of the pair of turbines is lost due to, for example, a malfunction of one of the turbines, a biased rotational force may act on the base, disrupting the attitude of the base. Disturbance in the attitude of the base may cause problems in the operation of the power generating system.

The present disclosure aims to provide a water current power generation device that can stabilize the posture of the base body.

A water current power generation device according to one aspect of the present disclosure includes a base floating in water, a first turbine connected to a first generator mounted on the base and rotated by the water current, a second turbine connected to a second generator mounted on the base and rotated by the water current, and a control unit that controls the rotation of the first turbine and the second turbine. The control unit executes an adjustment process to adjust the rotational force acting on the base in an unbalanced state in which the balance between the first counter torque associated with the rotation of the first turbine and the second counter torque associated with the rotation of the second turbine is lost, and in the adjustment process, the rotation speed of either the first turbine or the second turbine is adjusted so as to balance the first counter torque, the second counter torque, and the restoring force corresponding to the change in the attitude of the base caused by the unbalance between the first counter torque and the second counter torque.

In this water current power generation device, in an unbalanced state, the control unit executes an adjustment process to adjust the rotational force acting on the base body. In this adjustment process, the rotation speed of either the first turbine or the second turbine is adjusted so that the first counter torque, the second counter torque, and the restoring force are balanced. This adjusts the first counter torque or the second counter torque so that the rotational forces acting on the base body cancel each other out, preventing a biased rotational force from continuing to act on the base body. This makes it possible to prevent the base body's posture from becoming too disturbed, thereby stabilizing the posture of the base body.

The control unit may perform an adjustment process by treating a state in which the tilt angle of the base about the roll direction changes over time as an unbalanced state. When the balance between the first counter torque and the second counter torque is lost, the change over time in the tilt angle about the roll direction is likely to be particularly large. Therefore, by performing an adjustment process by treating this state as an unbalanced state, it is possible to effectively prevent the posture of the base from becoming more unstable.

The adjustment process includes a process of identifying the first turbine or the second turbine to be adjusted in rotation speed, and the process of identifying the first turbine or the second turbine rotating in a direction opposite to the rotation direction of the base may be identified as the target. In an unbalanced state, a differential torque (rotational force) between the first counter torque and the second counter torque acts on the base. As a result, the tilt angle of the base around an axis parallel to the axis of rotation changes over time. For example, the first counter torque generated by the rotation of the first turbine is a rotational force opposite to the rotation direction of the first turbine. The first counter torque rotates the base in a direction opposite to the rotation direction of the first turbine. On the other hand, the second counter torque generated by the rotation of the second turbine is a rotational force opposite to the rotation direction of the second turbine. The second counter torque rotates the base in a direction opposite to the rotation direction of the second turbine. In other words, it is possible to know which of the first counter torque and the second counter torque is the cause of the unbalance, according to the rotation direction of the base. Therefore, by adjusting the rotation speed of the first turbine or the second turbine, which rotates in the opposite direction to the rotation direction of the base body, the larger of the first and second counter torques is adjusted, making it easier to balance the first and second counter torques and the restoring force.

The control unit may further include a sensor that acquires information regarding the posture of the base, and may start the adjustment process when it determines, based on the information acquired by the sensor, that the tilt angle of the base about the roll direction is equal to or greater than a threshold value. In this configuration, even in an unbalanced state, the adjustment process can be omitted if the tilt angle of the base about the roll direction is smaller than the threshold value. Therefore, it is possible to efficiently prevent the posture of the base from becoming disturbed.

The control unit may adjust the rotation speed of the first turbine by adjusting the pitch angle of the blades of the first turbine, or adjust the rotation speed of the second turbine by adjusting the pitch angle of the blades of the second turbine. In this case, it is easy to adjust the rotation speed of the first turbine or the rotation speed of the second turbine.

According to this disclosure, the posture of the base body can be stabilized.

FIG. 1 is a diagram showing a schematic configuration of a water current power generation device according to an embodiment. 2(a) and 2(b) are diagrams showing a schematic configuration of the devices provided in the power generation pod shown in FIG. 3A and 3B are diagrams for explaining the attitude of the base body. FIG. 4 is a block diagram showing the functional configuration of the controller. FIG. 5 is a diagram for explaining the attitude of the base body during control. FIG. 6 is a flowchart showing the procedure of the attitude control process. FIG. 7 is a flowchart showing the procedure of the rotational force adjustment process. FIG. 8 is a diagram for explaining the attitude of the base body after control.

An embodiment will be described below with reference to the drawings. In the description of the drawings, identical or corresponding elements are given the same reference numerals, and duplicate descriptions may be omitted. In the following, "upstream" and "downstream" are used based on the flow of water. Furthermore, "front" refers to the upstream side of the water flow, and "rear" refers to the downstream side of the water flow.

[Water current power generation device]
The water current power generation device according to this embodiment will be described with reference to Fig. 1. The water current power generation device 1 shown in Fig. 1 is a submersible floating power generation device that generates power by utilizing a water current FW. Hereinafter, the "water current power generation device 1" will be referred to as the "power generation device 1". The power generation device 1 is used, for example, when installed in the ocean and generates power using ocean currents. The power generation device 1 includes a base 2, turbines 3A, 3B, generators 4A, 4B, and a controller 10 (control unit) that controls the rotation of the turbines 3A, 3B.

The base 2 has a pair of power generation pods 21A, 21B as pods, and a beam 22. The power generation pods 21A, 21B are floats that can float in water. The power generation pods 21A, 21B are, for example, cylindrical in shape. A generator 4A (first generator) is mounted inside the power generation pod 21A. A generator 4B (second generator) is mounted inside the power generation pod 21B. The power generation pods 21A, 21B are, for example, arranged at a distance to the left and right. The power generation pods 21A, 21B are connected by a beam 22. The beam 22 is, for example, a rectangular plate-like body arranged horizontally.

The power generation pods 21A and 21B are connected to a sinker 5 placed on the bottom of the water via a mooring line 6. The sinker 5 may be, for example, a friction-type sinker or other sinker. The mooring line 6 may be connected to an anchor fixed to the bottom of the water instead of the sinker 5. The anchor may be a pile-type anchor, a suction-type anchor, or other anchor. The lower end of the mooring line 6 is connected to the sinker 5, and the upper end of the mooring line 6 is connected to the power generation pods 21A and 21B. The upper ends of the mooring lines 6 are connected to the power generation pods 21A and 21B, for example. The upper ends of the mooring lines 6 may be connected to the beam 22 instead of the power generation pods 21A and 21B.

Cables 7 are connected to the power generation pods 21A and 21B. The cables 7 include a power transmission cable for transmitting the power generated by the generators 4A and 4B, and a communication cable for communicating with onshore facilities (not shown). The cables 7 extend from the generators 4A and 4B along the mooring lines 6 toward the sinker 5, and also extend from the mooring lines 6 along the bottom of the water toward the onshore facilities.

The turbines 3A and 3B are turbines for generating electricity. The turbines 3A and 3B are configured to rotate when they receive a water flow. The turbine 3A (first turbine) is provided at the rear of the power generation pod 21A. The turbine 3B (second turbine) is provided at the rear of the power generation pod 21B. In this embodiment, the turbines 3A and 3B are so-called downwind type turbines. The turbines 3A and 3B may be upwind type turbines. Please also refer to FIG. 2 below. FIGS. 2(a) and 2(b) are diagrams showing the schematic configuration of the equipment provided in the power generation pod shown in FIG. 1.

The turbine 3A is connected to the generator 4A. The turbine 3A has a hub 31A and a plurality of blades 32A. The hub 31A is rotatably arranged around an axis along the front-rear direction of the power generation pod 21A. Specifically, the hub 31A is attached to the rotating shaft 41 of the generator 4A. The hub 31A rotates integrally with the rotating shaft 41. The blades 32A are wing members that receive the water flow FW and generate a rotational force. The blades 32A are arranged radially on the outer periphery of the hub 31A. In FIG. 2(a), two blades 32A are arranged on the hub 31A, but three or more blades 32A may be arranged on the hub 31A.

The turbine 3B is connected to the generator 4B. The turbine 3B has a hub 31B and a plurality of blades 32B. The hub 31B is rotatably arranged around an axis along the front-rear direction of the power generation pod 21B. Specifically, the hub 31B is attached to the rotating shaft 41 of the generator 4B. The hub 31B rotates integrally with the rotating shaft 41. The blades 32B are wing members that receive the water flow FW and generate a rotational force. The blades 32B are arranged radially on the outer periphery of the hub 31B. In FIG. 2(b), two blades 32B are arranged on the hub 31B, but three or more blades 32B may be arranged on the hub 31B.

The generator 4A is a device that converts the kinetic energy of the rotation of the turbine 3A into electrical energy, and generates electricity by receiving the rotational force of the turbine 3A. The generator 4B is a device that converts the kinetic energy of the rotation of the turbine 3B into electrical energy, and generates electricity by receiving the rotational force of the turbine 3B. A power conditioner may be connected to the generators 4A and 4B. The generators 4A and 4B output generated power to the power conditioner. The power conditioner can adjust the generated power of the generators 4A and 4B and control the power generation operation. The generated power is adjusted by converting the generated power, which is AC power, into DC power, and then converting the DC power into AC power so that it has the desired frequency. A high-voltage power receiving unit may be connected to the power conditioner. The high-voltage power receiving unit transforms the AC power output from the power conditioner.

2(a) and 2(b), the power generation device 1 further includes a sensor 23 and a rotation adjustment unit 24. The sensor 23 acquires information about the attitude of the base 2. The information about the attitude of the base is, for example, the amount of change per unit time in the tilt angle of the attitude of the base 2, i.e., the angular velocity. The sensor 23 is, for example, a gyro sensor. The sensor 23 detects the angular velocities of the base 2 in the roll direction, pitch direction, and yaw direction. The sensor 23 outputs the detected angular velocities in each direction to the controller 10 as needed. The sensor 23 may be provided inside either one of the power generation pods 21A and 21B, or the sensor 23 may be provided inside both of the power generation pods 21A and 21B.

The rotation adjustment unit 24 adjusts the rotation speed of the turbines 3A and 3B. The rotation adjustment unit 24 has pitch adjustment mechanisms 25A and 25B. The pitch adjustment mechanism 25A adjusts the pitch angle of the blades 32A to adjust the rotation speed of the turbine 3A. The pitch adjustment mechanism 25B adjusts the pitch angle of the blades 32B to adjust the rotation speed of the turbine 3B. In other words, in the power generation device 1, the pitch angles of the blades 32A and 32B are variable.

The pitch adjustment mechanism 25A is provided inside the power generation pod 21A. The pitch adjustment mechanism 25B is provided inside the power generation pod 21B. Each of the pitch adjustment mechanisms 25A and 25B includes, for example, a hydraulic drive device 26 and a blade shaft 27. More specifically, a blade shaft 27 is provided at the base end of each of the blades 32A and 32B. The drive device 26 is connected to the blade shaft 27. The drive device 26 is mounted, for example, in the hubs 31A and 31B. The drive device 26 includes, for example, a gear mechanism. A known mechanism can be used as the drive device 26. The drive device 26 is controlled by the controller 10 to rotate the blade shaft 27 and adjust the pitch angle of the blades 32A and 32B to any angle. The drive method of the blade shaft 27 does not have to be hydraulic, and may be an electric drive method using an electric motor or the like.

Next, the attitude of the base body 2 will be described. FIG. 3 is a diagram for explaining the attitude of the base body. FIG. 3(a) is a diagram showing the attitude of the base body 2 when both the turbines 3A and 3B described above are operating normally. For ease of understanding, in FIG. 3, the center of buoyancy BC and center of gravity GC of the base body 2 are illustrated outside the base body 2, but the center of buoyancy BC is the center of buoyancy B acting on the base body 2, and the center of gravity GC is the center of gravity of the base body 2. When both the turbines 3A and 3B are operating normally, the pitch of the blade 32A and the pitch of the blade 32B are opposite to each other. As a result, the turbines 3A and 3B rotate in opposite directions by receiving the water flow FW. As shown in FIG. 3(a), the turbine 3A rotates in a counterclockwise rotation direction RA when viewed from upstream, and the turbine 3B rotates in a counterclockwise rotation direction RB when viewed from upstream.

At this time, counter torques MA and MB act on the base body 2 as the turbines 3A and 3B rotate. The counter torque MA (first counter torque) associated with the rotation of the turbine 3A is a rotational force in the opposite direction to the rotation direction RA, and the counter torque MB (second counter torque) associated with the rotation of the turbine 3B is a rotational force in the opposite direction to the rotation direction RB. The pitch angles of the blades 32A and 32B are controlled so that the counter torques MA and MB are equal to each other. This cancels out the counter torques MA and MB, stabilizing the posture of the base body 2. Specifically, the straight line L1 passing through the rotation axis of the turbine 3A and the rotation axis of the turbine 3B is aligned horizontally, and the straight line L2 passing through the center of buoyancy BC and center of gravity GC of the base body 2 is aligned vertically, stabilizing the posture. The base body 2 floats in the water in this substantially horizontal posture. Alternatively, turbine 3A may rotate clockwise when viewed from the upstream side, and turbine 3B may rotate counterclockwise when viewed from the upstream side.

Here, due to equipment failure or some external force, one of the turbines 3A and 3B may not operate normally, causing the balance of the counter torques MA and MB to be lost. When the balance of the counter torques MA and MB is lost, the posture of the base 2 changes. Examples of a state in which the balance of the counter torques MA and MB is lost include a case in which the rotation of one of the turbines 3A and 3B is locked, or a case in which the pitch angle of one of the blades 32A and 32B cannot be controlled. Examples of a case in which the pitch angle of the blades 32A and 32B cannot be controlled include a case in which the pitch angle of the blades 32A and 32B cannot be changed, or a case in which the blades 32A and 32B are in a free-running state. FIG. 3B is a diagram showing the posture of the base 2 in a state in which the balance of the counter torques MA and MB is lost. In the example of FIG. 3B, the blade 32A is in a free-running state, and the blade 32B is in a normal state.

When blade 32A enters a free-running state, it becomes difficult for blade 32A to generate rotational force even when it receives water flow FW, and the rotation of turbine 3A weakens or stops. As a result, counter torque MA becomes 0 or an extremely small value, and a discrepancy occurs in the magnitude of counter torques MA and MB. A rotational force equivalent to this discrepancy in the magnitude of counter torques MA and MB acts on base 2, causing base 2 to tilt around the roll direction. In other words, the posture of base 2 becomes disturbed. When base 2 tilts around the roll direction, tilt around the yaw direction of base 2 may also occur.

[controller]
The controller 10 is configured to execute control for stabilizing the attitude of the base body 2 when the attitude of the base body 2 is disturbed as shown in FIG. 3B. FIG. 4 is a block diagram showing the functional configuration of the controller. Hereinafter, the functional configuration will be referred to as a "functional module". As shown in FIG. 4, the controller 10 has a tilt angle acquisition unit 11, a determination unit 12, and an adjustment unit 13 as functional modules. The adjustment unit 13 includes a specification unit 14, a pitch control unit 15, and an angular velocity acquisition unit 16. These functional modules are merely a division of the functions of the controller 10 into a plurality of modules for convenience, and do not necessarily mean that the hardware constituting the controller 10 is divided into such modules. Each functional module may be realized by executing a program, or may be realized by a dedicated electric circuit (e.g., a logic circuit) or an integrated circuit (ASIC: Application Specific Integrated Circuit) that integrates the same.

The tilt angle acquisition unit 11 acquires information regarding the attitude of the base body 2. FIG. 5 is a diagram for explaining the attitude of the base body 2 during control by the controller. For ease of understanding, in FIG. 5 as well, the center of buoyancy BC and center of gravity GC of the base body 2 are illustrated outside the base body 2, as in FIG. 3. The tilt angle acquisition unit 11 is connected to the sensor 23 and acquires information output from the sensor 23 at any time. The tilt angle acquisition unit 11 acquires the tilt angle θ of the base body 2 around the roll direction based on the information acquired from the sensor 23. In this embodiment, the tilt angle acquisition unit 11 acquires the integral value of the angular velocity ω output from the sensor 23 over time as the tilt angle θ. The tilt angle acquisition unit 11 transmits the acquired tilt angle θ to the determination unit 12.

The determination unit 12 determines whether or not to start control by the adjustment unit 13 based on the tilt angle θ received from the tilt angle acquisition unit 11. Specifically, when the determination unit 12 determines that the tilt angle θ is equal to or greater than a threshold value, it determines to start control by the adjustment unit 13. The threshold value is, for example, a preset tolerance value. As an example, a critical value at which the base body 2 can be maintained in a state where it does not rotate once is set as the threshold value. When the determination unit 12 determines to start control by the adjustment unit 13 based on the tilt angle θ, it transmits a signal to the adjustment unit 13 to start control and the tilt angle θ.

The adjustment unit 13 executes an adjustment process to adjust the rotational force acting on the base body 2 in an unbalanced state. An unbalanced state is a state in which the balance between the anti-torques MA and MB is lost. Specifically, in the adjustment process, the adjustment unit 13 determines that the unbalanced state is a state in which the tilt angle θ of the base body 2 about the roll direction is changing over time. For example, as described below, the adjustment unit 13 determines whether the unbalanced state has been resolved based on whether the tilt angle θ of the base body 2 about the roll direction is changing over time. In this embodiment, the adjustment unit 13 starts the adjustment process when it receives a signal from the determination unit 12 to start control.

In the adjustment process, control is performed to adjust the rotation speed of one of the turbines 3A and 3B so that the counter torque MA, counter torque MB, and restoring force MC are balanced. The restoring force MC is a force that acts to return the relationship between the buoyancy B and gravity G to an equilibrium state when the relationship between the buoyancy B and gravity G is in an unbalanced state. As shown in FIG. 5, the base body 2 tilts around the roll direction due to the imbalance between the counter torques MA and MB, and the straight line L2 passing through the center of buoyancy BC and center of gravity GC of the base body 2 tilts with respect to the vertical direction. As a result, the buoyancy B and gravity G become a couple, and a restoring force MC is generated in a direction in which the straight line L2 approaches the vertical direction. Therefore, the counter torque MA, counter torque MB, and restoring force MC act on the base body 2 as a rotational force in the roll direction. For this reason, the adjustment unit 13 adjusts the rotation speed of one of the turbines 3A and 3B so that the counter torque MA, counter torque MB, and restoring force MC are balanced. The adjustment process is performed by the determination unit 14, the pitch control unit 15, and the angular velocity acquisition unit 16.

The identification unit 14 identifies one of the turbines 3A and 3B as the target for adjustment. In this embodiment, the identification unit 14 identifies the target of control by the pitch control unit 15. More specifically, the identification unit 14 identifies which of the turbines 3A and 3B to adjust the pitch angle by the control by the pitch control unit 15. The identification unit 14 acquires the rotation direction corresponding to the tilt angle θ received from the determination unit 12 for the base 2, and identifies the turbine rotating in the opposite rotation direction to the rotation direction of the base 2 as the target among the turbines 3A and 3B. In the example of FIG. 5, since the rotation direction of the base 2 is counterclockwise, the turbine 3B rotating in the opposite rotation direction RB is identified as the target. The identification unit 14 transmits a signal to the pitch control unit 15 to start control of the identified one of the turbines 3A and 3B. In the example of FIG. 5, a signal to start control of the turbine 3B is transmitted to the pitch control unit 15.

The pitch control unit 15 adjusts the rotation speed of the turbine identified by the identification unit 14 among the turbines 3A and 3B. Specifically, the pitch control unit 15 reduces the rotation speed of the identified turbine. In the example of FIG. 5, the pitch control unit 15 reduces the rotation speed of the turbine 3B. In this embodiment, the pitch control unit 15 controls the pitch adjustment mechanism 25B to adjust the pitch angle of the blades 32B of the turbine 3B, thereby adjusting the rotation speed of the turbine 3B. Specifically, the pitch control unit 15 controls the pitch adjustment mechanism 25B to change the pitch angle of the blades 32B over time. For example, the pitch control unit 15 transmits a control signal to the pitch adjustment mechanism 25B to continuously change the pitch angle of the blades 32B until the unbalance state is resolved.

When the identification unit 14 identifies the turbine 3A as the target, the pitch control unit 15 controls the pitch adjustment mechanism 25A to adjust the pitch angle of the blades 32A of the turbine 3A, thereby adjusting the rotation speed of the turbine 3A.

The angular velocity acquisition unit 16 is connected to the sensor 23 and acquires the angular velocity ω of the base body 2 about the roll direction output from the sensor 23 at any time. The angular velocity acquisition unit 16 also determines whether the unbalance state has been resolved based on the acquired angular velocity ω. Specifically, the angular velocity acquisition unit 16 determines that the unbalance state has been resolved when it determines that the angular velocity ω is a negligibly small value. At this time, the angular velocity acquisition unit 16 sends a signal to the pitch control unit 15 to stop control.

The hardware of the controller 10 is composed of, for example, one or more control computers. In this embodiment, the power generation device 1 is equipped with one controller 10. If the controller 10 is composed of multiple computers, each of the above-mentioned functional modules may be realized by a single computer, or may be realized by a combination of two or more computers.

[Attitude control method]
Next, as an example of a posture control method, a posture control process by the controller 10 will be described. FIG. 6 is a flowchart showing the procedure of the posture control process. As shown in FIG. 6, the controller 10 first executes step S01. In step S01, the tilt angle acquisition unit 11 acquires information related to the posture of the base body 2. The tilt angle acquisition unit 11 acquires information output from the sensor 23 at any time, and acquires the tilt angle θ of the base body 2 about the roll direction based on the acquired information. Specifically, the tilt angle acquisition unit 11 acquires the tilt angle θ by integrating the angular velocity ω output from the sensor 23 with respect to time.

Next, the controller 10 executes step S02. In step S02, the determination unit 12 determines whether the tilt angle θ is equal to or greater than the threshold value. If it is determined that the tilt angle θ is not equal to or greater than the threshold value (step S02: NO), the controller 10 returns the process to step S01. Thereafter, the controller 10 repeatedly executes steps S01 and S02.

If it is determined that the tilt angle θ is equal to or greater than the threshold value (step S02: YES), the controller 10 executes step S03. In step S03, the adjustment unit 13 executes an adjustment process. As described above, the adjustment process is a process for adjusting the rotational force acting on the base body 2 in an unbalanced state. Here, the unbalanced state is a state in which the tilt angle θ of the base body 2 about the roll direction changes over time. In step S03, the adjustment unit 13 adjusts the rotation speed of one of the turbines 3A, 3B so that the counter torque MA, counter torque MB, and restoring force MC are balanced. More specific processing details of step S03 will be described later. The end of step S03 marks the end of the attitude control process.

[Rotational Force Adjustment Processing]
Next, step S03 will be described in detail. FIG. 7 is a flowchart showing the procedure of the adjustment process. As shown in FIG. 7, the controller 10 first executes step S31. In step S31, the identifying unit 14 identifies one of the turbines 3A and 3B as the target for adjustment. Specifically, the identifying unit 14 identifies which of the turbines 3A and 3B has its pitch angle adjusted. The identifying unit 14 identifies, of the turbines 3A and 3B, the turbine rotating in the opposite direction to the rotation direction of the base 2 as the target. In the example of FIG. 5, the turbine 3B is identified as the target.

Next, the controller 10 executes steps S32 and S33. In step S32, the pitch control unit 15 adjusts the rotation speed of the turbine identified by the identification unit 14, out of the turbines 3A and 3B. In the example of FIG. 5, the pitch control unit 15 adjusts the rotation speed of the turbine 3B. Specifically, the pitch control unit 15 adjusts the rotation speed of the turbine 3B by controlling the pitch adjustment mechanism 25B to adjust the pitch angle of the blades 32B of the turbine 3B. For example, the pitch control unit 15 transmits a control signal to the pitch adjustment mechanism 25B to change the pitch angle of the blades 32B. In step S33, the angular velocity acquisition unit 16 acquires the angular velocity ω of the base 2 around the roll direction from the sensor 23.

Next, the controller 10 executes step S34. In step S34, the angular velocity acquisition unit 16 determines whether or not the unbalanced state has been resolved based on the angular velocity ω. The angular velocity acquisition unit 16 determines that the unbalanced state has been resolved when it determines that the angular velocity ω is a negligibly small value. When it determines that the unbalanced state has not been resolved (step S34: NO), the controller 10 returns the process to step S32. Thereafter, the controller 10 repeatedly executes steps S32 and S33 until the unbalanced state is resolved.

When it is determined that the unbalanced state has been resolved (step S34: YES), the controller 10 ends control of the adjustment process. Figure 8 is a diagram for explaining the posture of the base body 2 after control. As shown in Figure 8, the adjustment process adjusts the magnitude of the counter torque MB to approach the magnitude of the restoring force MC, so that the counter torque MB and the restoring force MC cancel each other out, stabilizing the posture of the base body 2.

[Action and Effect]
The effects of the power generating device 1 described above will be described. As described above, in the power generating device 1, in normal operation, the pair of turbines 3A and 3B rotate in opposite directions, so that the counter torque MA associated with the rotation of the turbine 3A and the counter torque MB associated with the rotation of the turbine 3B cancel each other out. This suppresses the application of biased rotational force to the base 2, and the attitude of the base 2 is maintained in a constant state. For this reason, if the balance between the counter torques MA and MB is lost, it is considered that a biased rotational force will act on the base, disturbing the attitude of the base 2. Disturbance in the attitude of the base 2 may cause problems in the operation of the power generating device 1. Note that the disturbance in the attitude of the base 2 in this specification means the deviation from the horizontal direction of the straight line L1 passing through the rotation axis of the turbine 3A and the rotation axis of the turbine 3B. Also, stabilizing the attitude of the base 2 in this specification means keeping the attitude of the base 2 constant, and includes keeping the attitude of the base 2 constant in a disturbed attitude.

In contrast, in this power generation device 1, in an unbalanced state, the controller 10 executes an adjustment process to adjust the rotational force acting on the base 2. In this adjustment process, the rotation speed of one of the turbines 3A, 3B is adjusted so that the counter torque MA, counter torque MB, and restoring force MC are balanced. As a result, the counter torque MA or counter torque MB is adjusted so that the rotational forces acting on the base 2 cancel each other out, preventing a biased rotational force from continuing to act on the base 2. This makes it possible to prevent the attitude of the base 2 from becoming too disturbed, and thus stabilizes the attitude of the base 2. As a result, the operation of the power generation device 1 can be continued even if the balance of the counter torques MA and MB is lost and the attitude of the base 2 is disturbed.

The controller 10 performs an adjustment process by treating a state in which the tilt angle θ of the base body 2 about the roll direction changes over time as an unbalanced state. When the balance between the counter torques MA and MB is lost, the change over time in the tilt angle θ about the roll direction is likely to be particularly large. Therefore, by performing an adjustment process by treating this state as an unbalanced state, it is possible to effectively prevent the posture of the base body 2 from becoming more unstable.

The adjustment process includes a specific process for identifying the turbine 3A or 3B to be adjusted in rotation speed. In the specific process, the turbine 3A or 3B rotating in the direction opposite to the direction of rotation of the base 2 is identified as the target. In an unbalanced state, the differential torque (rotational force) of the counter torques MA and MB acts on the base 2. As a result, the tilt angle θ of the base 2 around an axis parallel to the axis of rotation changes over time. For example, the counter torque MA generated by the rotation of the turbine 3A is a rotational force opposite to the rotational direction RA of the turbine 3A. The counter torque MA rotates the base 2 in the direction opposite to the rotational direction RA of the turbine 3A. On the other hand, the counter torque MB generated by the rotation of the turbine 3B is a rotational force opposite to the rotational direction RB of the turbine 3B. The counter torque MB rotates the base 2 in the direction opposite to the rotational direction RB of the turbine 3B. In other words, it is possible to know whether the counter torque MA or counter torque MB is the cause of the imbalance, based on the rotation direction of the base body 2. Therefore, by adjusting the rotation speed of the turbine 3A, 3B that rotates in the opposite direction to the rotation direction of the base body 2, the larger of the counter torques MA and MB is adjusted, making it easier to balance the counter torque MA, counter torque MB, and restoring force MC.

Here, one example of a factor that causes the balance of the counter torques MA and MB to be lost, that is, a factor that causes one of the turbines 3A and 3B to no longer operate normally, is a failure in the system that controls the rotation of the turbine that is malfunctioning. In this case, it is difficult to control the counter torque associated with the rotation of the turbine that is malfunctioning. Here, when one of the turbines 3A and 3B no longer operates normally, the larger of the counter torques MA and MB is the counter torque associated with the rotation of the turbine that is operating normally. Therefore, according to the above-mentioned identification process, when an imbalance occurs due to a failure in the system that controls the rotation of one of the turbines, the counter torque associated with the rotation of the turbine that is operating normally is adjusted, and the adjustment process can be effectively executed.

The controller 10 further includes a sensor 23 that acquires information about the posture of the base 2, and starts the adjustment process when it determines, based on the information acquired by the sensor 23, that the tilt angle θ is equal to or greater than a threshold value. In this configuration, even in an unbalanced state, the adjustment process can be omitted if the tilt angle θ about the roll direction of the base 2 is smaller than the threshold value. Therefore, it is possible to efficiently prevent the posture of the base 2 from becoming significantly disturbed.

The controller 10 adjusts the rotation speed of the turbine 3A by adjusting the pitch angle of the blades 32A of the turbine 3A, or adjusts the rotation speed of the turbine 3B by adjusting the pitch angle of the blades 32B of the turbine 3B. This configuration makes it easy to adjust the rotation speed of the turbine 3A or the rotation speed of the turbine 3B.

The above-mentioned attitude control method is an attitude control method for controlling the attitude of a power generating device 1, which includes a base 2 floating in water, a turbine 3A connected to a generator 4A mounted on the base 2 and rotating in response to the water flow, and a turbine 3B connected to a generator 4B mounted on the base 2 and rotating in response to the water flow. The method includes a step of adjusting the rotational force acting on the base 2 in an unbalanced state in which the balance between the counter torque MA associated with the rotation of the turbine 3A and the counter torque MB associated with the rotation of the turbine 3B is lost, and in the above step, the rotation speed of one of the turbines 3A and 3B is adjusted so that the counter torque MA, the counter torque MB, and the restoring force MC corresponding to the change in the attitude of the base 2 caused by the unbalance between the counter torques MA and MB are balanced.

This attitude control method can prevent the attitude of the base body 2 of the power generation device 1 from becoming distorted significantly for the reasons described above.

[Modification]
The above embodiment has been described as one embodiment of the water current power generation device according to the present disclosure. The water current power generation device according to the present disclosure may be any modified version of the water current power generation device described above.

For example, in the above embodiment, a gyro sensor that detects angular velocity ω is described as an example of sensor 23, but other sensors may be used. Sensor 23 may be an angle sensor that detects tilt angle θ. In this case, in the process of acquiring tilt angle θ by controller 10, integration of the detection result of sensor 23 may be omitted. Also, in the process of acquiring angular velocity ω by controller 10 using the output of the angle sensor as input, the detection result of sensor 23 may be associated with the acquisition time and acquired at any time to calculate angular velocity ω. Alternatively, sensor 23 may be provided with both a sensor that detects angular velocity ω and a sensor that detects tilt angle θ.

In the above embodiment, the controller 10 starts the adjustment process when it is determined that the tilt angle θ of the base 2 about the roll direction is equal to or greater than a threshold value, but the adjustment process may be started based on the tilt angle of the base 2 about the yaw direction. Also, two sensors may be provided to detect the rotation speeds of the turbines 3A and 3B, respectively, and the adjustment process may be started based on the difference between the rotation speeds detected by the two sensors.

In addition, if the balance of the counter torques MA and MB is lost while the pitch angle can be controlled, for example when the rotation of one of the turbines 3A and 3B is locked, the pitch angle of the turbine rotating in the same direction as the rotation direction of the base 2 may be further adjusted. This makes it possible to suppress disturbance of the attitude of the base 2 around the yaw direction.

1. Power generation device (water current power generation device)
2 Base body 3A Turbine (first turbine)
3B Turbine (second turbine)
4A Generator (First Generator)
4B Generator (Second Generator)
10 Controller (control unit)
23 Sensor 32A, 32B Blade FW Water flow MA Counter torque (first counter torque)
MB Counter torque (second counter torque)
MC Restoring force RA, RB Rotation direction θ Tilt angle

Claims (4)

A substrate that floats in water;
a first turbine connected to a first generator mounted on the base and rotated by receiving a water flow;
a second turbine connected to a second generator mounted on the base and rotated by receiving the water flow;
a control unit that controls rotation of the first turbine and the second turbine,
the control unit executes an adjustment process to adjust a rotational force acting on the base body in an unbalanced state in which a first counter torque caused by rotation of the first turbine and a second counter torque caused by rotation of the second turbine are out of balance,
The adjustment process includes:
Identifying one of the first turbine and the second turbine that is rotating in a direction opposite to a rotation direction of the base body as a turbine to be adjusted in rotation speed;
adjusting a rotation speed of the turbine to be adjusted so as to balance the first counter torque, the second counter torque, and a restoring force corresponding to a change in the attitude of the base body caused by an imbalance between the first counter torque and the second counter torque ;
determining whether the unbalance state has been eliminated based on an angular velocity, which is the amount of change per unit time of the inclination angle of the base about the roll direction, and terminating adjustment of the rotation speed if it is determined that the unbalance state has been eliminated. the control unit determines a state in which the tilt angle of the base body about the roll direction changes over time as the unbalanced state, and executes the adjustment process.
2. The water current power generation device according to claim 1. Further comprising a sensor for acquiring information regarding the attitude of the base body,
the control unit starts the adjustment process when it determines, based on the information acquired by the sensor, that the tilt angle around the roll direction of the base body is equal to or greater than a threshold value.
The water current power generation device according to claim 1 or 2 . the control unit adjusts a rotation speed of the first turbine by adjusting a pitch angle of blades of the first turbine, or adjusts a rotation speed of the second turbine by adjusting a pitch angle of blades of the second turbine.
The water current power generation device according to any one of claims 1 to 3 .

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