Power generation system

Abstract

This power generation system (10) comprises: a planetary gear mechanism (23) having a first shaft, a second shaft, and a third shaft; a rotating body (11) that is connected to the first shaft and rotated by a flow of fluid; a power generator (21) that is connected to the second shaft and generates electricity by the rotation of the second shaft; a rotation adjustment device (41) that is connected to the third shaft and capable of adjusting the rotation speed of the third shaft; electric power conversion devices (51, 52) that convert the electricity generated by the power generator and output the converted electricity to an electric power grid (90); an acquisition unit (81) that acquires a parameter indicating the rotation state of the rotating body; and a rotation control unit (85) that controls the rotation speed of the third shaft by the rotation adjustment device on the basis of the parameter acquired by the acquisition unit.

Description

Power generation system CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2024-004834, filed on January 16, 2024, the contents of which are incorporated herein by reference.

[0002] The disclosure in this specification relates to a power generation system that generates power using energy sources such as hydraulic power and wind power.

[0003] Various power generation systems that generate electricity using renewable energy sources such as hydropower and wind power have been proposed. For example, a wind power generation system described in Patent Document 1 includes a wind turbine with a rotor, and a main generator and a motor / auxiliary generator connected to the main shaft of the rotor. The motor / auxiliary generator is controlled in accordance with the wind speed detected by a wind speed detection means. Controlling the motor / auxiliary generator increases power generation efficiency in low wind speeds and also enables efficient power generation in strong winds.

[0004] JP 2017-53304 A

[0005] However, in the technology described in Patent Document 1, the wind turbine and the main generator rotate at the same rotation speed or rotation ratio, so the upper limit of the rotation speed of the wind turbine is determined by the generated voltage of the main generator. This raises concerns about reduced versatility. Furthermore, a power generation system that supplies generated power to a power grid is required to provide a stable and continuous power supply, and there is thought to be room for improvement.

[0006] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a power generation system that can appropriately output power to a power grid.

[0007] The power generation system of the present disclosure comprises a planetary gear mechanism having a first shaft, a second shaft, and a third shaft; a rotating body connected to the first shaft and rotated by the flow of a fluid; a generator connected to the second shaft and generating electricity by the rotation of the second shaft; a rotation adjustment device connected to the third shaft and capable of adjusting the rotation speed of the third shaft; a power conversion device that converts the power generated by the generator into electric power and outputs it to an electric power system; an acquisition unit that acquires parameters that indicate the rotational state of the rotating body; and a rotation control unit that controls the rotation speed of the third shaft by the rotation adjustment device based on the parameters acquired by the acquisition unit.

[0008] In the power generation system configured as described above, a rotor that rotates due to the flow of fluid, a generator, and a rotation adjustment device are connected to the three shafts (first shaft, second shaft, and third shaft) of the planetary gear mechanism, and the rotation of the rotor is transmitted to the generator via the planetary gear mechanism, allowing the generator to generate electricity. In addition, the power generated by the generator is converted by the power conversion device, allowing it to output a system voltage to the power grid.

[0009] In a planetary gear mechanism, the rotation speed of the remaining shaft is determined by the rotation speed of two shafts. Therefore, when the first shaft of the planetary gear mechanism rotates due to the rotation of a rotor associated with a fluid flow, the rotation speed of the generator connected to the second shaft can be increased or decreased by adjusting the rotation speed of the rotation adjustment device connected to the third shaft. In this case, a parameter indicating the rotation state of the rotor is acquired, and the rotation speed of the third shaft is controlled by the rotation adjustment device based on the parameter. As a result, when the flow velocity of a fluid, such as water or air, excessively decreases or increases, the rotation speed of the third shaft can be controlled in accordance with the decrease or increase in the flow velocity, thereby maintaining the generator rotation speed at an appropriate value. In other words, even if the rotation state of the rotor changes depending on the operating conditions, the generator rotation speed can be appropriately adjusted, thereby enhancing versatility for various operating conditions. As a result, appropriate power can be output to the power grid.

[0010] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is an overall configuration diagram of a power generation system, Fig. 2 is a skeleton diagram showing an example configuration of a transaxle, Fig. 3 is a diagram showing a schematic configuration of a hybrid vehicle, Fig. 4 is a nomographic diagram showing an operation mode of a planetary gear mechanism, Fig. 5 is a nomographic diagram showing changes in rotation speed of three shafts of the planetary gear mechanism, Fig. 6 is a functional block diagram showing each function implemented by a power generation control device, Fig. 7 is a flowchart showing a processing procedure for power generation control in the power generation system, Fig. 8 is a time chart for more specifically explaining the power generation control processing, Fig. 9 is a flowchart showing a processing procedure for power generation control in the power generation system, Fig. 10 is a time chart for more specifically explaining the power generation control processing, Fig. 11 is a flowchart showing a processing procedure for power generation control in another example, and Fig. 12 is an overall configuration diagram of a power generation system in another example.

[0011] Hereinafter, a power generation system according to an embodiment of the present disclosure will be described with reference to the drawings. The power generation system 10 of this embodiment is a hydroelectric power generation system constructed using a transaxle and a power control unit (PCU) removed from a used hybrid vehicle. The power generation system 10 generates electricity using hydroelectric energy, which is renewable energy, and outputs the generated electricity as grid power.

[0012] The configuration of a power generation system 10 will be described using Figure 1. The power generation system 10 includes a water turbine 11 as a rotating body rotated by hydraulic power, a transaxle 13 and a PCU 14 taken out of a hybrid vehicle, and a power generation control device 15, with AC power output from the PCU 14 to an electric power grid 90. The power generation system 10 uses water flowing from, for example, a water tank or reservoir as an energy source, and is configured such that the water turbine 11 is installed in a water channel extending from the water tank or reservoir. The water flow in the water channel rotates the water turbine 11 and a rotating shaft 12 fixed to the water turbine 11.

[0013] The transaxle 13 has a first rotating electric machine 21 (MG1), a second rotating electric machine 22 (MG2), a planetary gear mechanism 23, and a differential gear 24. The planetary gear mechanism 23 and the second rotating electric machine 22 are connected via a drive shaft 25, and the differential gear 24 is connected to the drive shaft 25 via a gear portion 26. The differential gear 24 has a pair of side gears 24a, 24b, and shaft portions 27a, 27b are connected to the side gears 24a, 24b, respectively.

[0014] The first rotating electric machine 21 and the second rotating electric machine 22 are, for example, three-phase AC motors formed by permanent magnet motors or field winding motors. In the power generation system 10, the first rotating electric machine 21 functions as a generator that generates electricity in conjunction with the rotation of the water turbine 11.

[0015] 2 is a skeleton diagram showing an example configuration of the transaxle 13. The planetary gear mechanism 23 includes a sun gear 31, a ring gear 32 that rotates coaxially with the sun gear 31, a plurality of pinion gears 33 that mesh with both the sun gear 31 and the ring gear 32, and a planetary carrier 34 that rotates coaxially with the sun gear 31 as the pinion gears 33 rotate. In the planetary gear mechanism 23, the water wheel 11 is connected to the planetary carrier 34 via a rotating shaft 12. The sun gear 31 is connected to the first rotating electric machine 21. The ring gear 32 is connected to the second rotating electric machine 22 and the differential gear 24 via a drive shaft 25 and a gear unit 26. In the planetary gear mechanism 23, the sun gear 31, the ring gear 32, and the planetary carrier 34 correspond to three axes: a first axis, a second axis, and a third axis.

[0016] As an example of the configuration of the gear unit 26, a counter driven gear 35 is integrally provided on the ring gear 32. The counter driven gear 35 is connected to the second rotating electric machine 22 via a reduction gear 36. The counter driven gear 35 is also connected to the differential gear 24 via a reduction gear 37.

[0017] The transaxle 13 also has a parking lock mechanism 38 (P / L). The parking lock mechanism 38 includes, for example, an actuator, a parking lock gear, and a parking ball (not shown). The actuator drives a parking pawl as an engagement member to engage with the parking lock gear, thereby establishing a parking lock state (activated state). In the parking lock state, rotation of the ring gear 32 meshing with the parking lock gear is restricted. Note that the parking lock mechanism 38 may also mesh the parking lock gear with the counter driven gear 35 to restrict rotation of the counter driven gear 35. In any case, the parking lock mechanism 38 may be any mechanism that switches between a state in which rotation of the ring gear 32 of the planetary gear mechanism 23 is permitted and a state in which rotation is prohibited, i.e., that is capable of restricting rotation of the ring gear 32.

[0018] As shown in Figure 3, when the transaxle 13 is mounted on the hybrid vehicle 100, an internal combustion engine 101 is connected to the planetary carrier 34 of the planetary gear mechanism 23, the first rotating electric machine 21 is connected to the sun gear 31, and the second rotating electric machine 22 is connected to the ring gear 32. In the hybrid vehicle 100, power is generated in the first rotating electric machine 21 as the engine 101 rotates. Furthermore, shafts 27a, 27b on both sides of the differential gear 24 are connected to left and right wheels 102. The hybrid vehicle 100 can travel by driving the wheels with the second rotating electric machine 22.

[0019] Returning to the explanation of Figure 1, of the shafts 27a, 27b fixed to the pair of side gears 24a, 24b in the differential gear 24, a motor 41 is connected to one of the shafts 27a (one of the side gears 24a), and a brake device 42 is connected to the other shaft 27b (the other side gear 24b). The motor 41 is rotatable in both forward and reverse directions and functions as a rotation adjusting device that adjusts the rotation speed of the ring gear 32. The brake device 42 is, for example, an electromagnetic brake, and generates an electromagnetic force by energizing a coil to hold the shaft 27b on the opposite side of the differential gear 24 from the motor 41 in a rotationally stopped state.

[0020] A rotation angle sensor 28 that detects the rotation angle of the rotating shaft (rotor rotating shaft) of the first rotating electric machine 21 is provided on the rotating shaft. The first rotating electric machine 21 also has a three-phase stator coil, and a generated voltage sensor 29 that detects the generated voltage of the first rotating electric machine 21 is provided on a power line connected to the stator coil. Detection signals from these sensors 28, 29 are input sequentially to the power generation control device 15.

[0021] The PCU 14 has a first inverter 51, a second inverter 52, a DC-DC converter 53, and an MG control device 54. The first inverter 51 and the second inverter 52 are three-phase inverters. As is well known, the first inverter 51 and the second inverter 52 have an upper arm switch 61 and a lower arm switch 62 for each phase, and perform orthogonal power conversion by switching the upper and lower arm switches 61, 62 in each phase at a predetermined cycle.

[0022] The first inverter 51 and the second inverter 52 are provided with their respective high-potential and low-potential DC terminals connected to each other. That is, in each of the inverters 51 and 52, a high-potential path 63, which is the electrical path on the high-potential side, and a low-potential path 64, which is the electrical path on the low-potential side, are continuous with each other. A smoothing capacitor 65 and a voltage sensor 66 are connected in parallel between the high-potential path 63 and the low-potential path 64. The AC terminals of the first inverter 51 are connected to the three-phase stator coil of the first rotating electric machine 21, and the AC terminals of the second inverter 52 are connected to the electric power grid 90.

[0023] The first inverter 51 converts the AC voltage output from the first rotating electric machine 21 into a DC voltage. The second inverter 52 reconverts the DC voltage converted by the first inverter 51 into an AC voltage and outputs it to the power grid 90. A grid voltage sensor 71 that detects the voltage (grid voltage) output to the power grid 90 is provided at the AC terminal of the second inverter 52.

[0024] As is well known, the DC-DC converter 53 has an upper arm switch, a lower arm switch, and a reactor and a capacitor connected to the midpoint between the upper and lower arms, and boosts the voltage of the battery 55 by switching the upper and lower arms. The battery 55 is an electricity storage device with a terminal voltage of, for example, several hundred volts, and is, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery. In this power generation system 10, the DC-DC converter 53 and the battery 55 can be omitted from the PCU 14.

[0025] In the hybrid vehicle 100 shown in Fig. 3, the first inverter 51 is provided as a power conversion circuit for the first rotating electric machine 21, and the second inverter 52 is provided as a power conversion circuit for the second rotating electric machine 22. That is, in the hybrid vehicle 100, the PCU 14 having the two inverters 51, 52 and the DC-DC converter 53 is provided as a rotating electric machine drive component for driving the two rotating electric machines 21, 22. In contrast, in the power generation system 10 of Fig. 1, the mutual connections between the inverters 51, 52 and the DC-DC converter 53 are retained in the PCU 14, but the difference from the hybrid vehicle 100 is that the power system 90 is connected to the AC terminals of the second inverter 52 instead of the second rotating electric machine 22.

[0026] The MG control device 54 is mainly composed of a microcomputer including a processor, memory, etc. The MG control device 54 performs switching control by turning on and off the upper and lower arm switches 61, 62 for each phase in the first inverter 51 and the second inverter 52. In this embodiment, the MG control device 54 performs switching control based on an output command and a phase command received from the power generation control device 15. The output command is a torque command or a current command for the first rotating electric machine 21. Feedback control may be performed based on the deviation of the detected current from the torque command or current command given as d-axis and q-axis components of the permanent magnet motor. Regarding the phase command, phase information based on the phase of the grid voltage may be provided as angle information during two-phase to three-phase conversion calculation used in the feedback control, thereby controlling the phase or frequency of the first rotating electric machine 21. The MG control device 54 performs power factor correction (PFC) operations in each of the inverters 51, 52 to convert AC current to DC current so as to bring the power factor closer to 1.0 or reduce high-frequency components. By this grid-connected operation of the PCU 14, a grid voltage is output at a frequency of, for example, 60 Hz.

[0027] The power generation control device 15 is primarily composed of a microcomputer (equivalent to a "computer"). The microcomputer includes a processor and a memory (storage unit). The microcomputer provides, for example, the functions shown in FIG. 6 . The functions provided by the microcomputer can be provided by software stored in a physical memory device and a computer executing the software, software alone, hardware alone, or a combination thereof. For example, when the microcomputer is provided by a hardware electronic circuit, the function can be provided by a digital circuit including multiple logic circuits or an analog circuit. For example, the microcomputer executes a program stored in a non-transitory tangible storage medium serving as its own storage unit. The program includes, for example, a program for the process shown in FIG. 7 . Execution of the program results in the execution of a method corresponding to the program. The storage unit is, for example, a non-volatile memory. Note that the program stored in the storage unit can be updated, for example, via a network such as the Internet.

[0028] FIG. 4 shows an example of a nomographic diagram of the planetary gear mechanism 23. In FIG. 4, the S-axis represents the rotation speed of the sun gear 31, i.e., the rotation speed of the first rotating electric machine 21; the C-axis represents the rotation speed of the planetary carrier 34, i.e., the rotation speed of the water turbine 11; and the R-axis represents the rotation speed of the ring gear 32. In the nomographic diagram, the rotation speeds of the three shafts of the planetary gear mechanism 23 are represented linearly. In the power generation system 10, the rotation speed of the ring gear 32 is fixed to zero as a basic state. In this state, the planetary carrier 34 rotates in conjunction with the rotation of the water turbine 11 due to the water flow. The sun gear 31 (first rotating electric machine 21) then rotates at a rotation speed that conforms to the relationship between the reduction ratios of the three shafts of the planetary gear mechanism 23. Power generation is generated by the rotation of the first rotating electric machine 21.

[0029] In the power generation system 10, for example, if the rotational speed of the water turbine 11 fluctuates in response to changes in the flow velocity of the water flowing through the water channel, the rotational speed of the first rotating electric machine 21 fluctuates accordingly, and thus the generated voltage of the first rotating electric machine 21 fluctuates. If the generated voltage of the first rotating electric machine 21 changes excessively, the grid connection cannot be maintained. That is, as shown by the dashed-dotted line in FIG. 4 , for example, if the rotational speed (carrier rotational speed) of the water turbine 11 increases from N1 to N2, the rotational speed (sun gear rotational speed) of the first rotating electric machine 21 increases with the increase in rotational speed, falling outside the allowable range X. This causes the generated voltage of the first rotating electric machine 21 to excessively increase, making it impossible to maintain the grid connection. Although not shown, if the rotational speed (carrier rotational speed) of the water turbine 11 decreases, the rotational speed (sun gear rotational speed) of the first rotating electric machine 21 may also decrease with the decrease in rotational speed, falling outside the allowable range X. The allowable range X may be determined based on the target rotation speed of the first rotating electrical machine 21 when the grid-connected operation is performed.

[0030] Therefore, in this embodiment, in the planetary gear mechanism 23, when rotational fluctuations occur in the two axes, the sun gear 31 and the planetary carrier 34, due to changes in the water flow velocity, the rotational speed of the remaining axis, the ring gear 32, is controlled to suppress excessive changes in rotational speed of the first rotating electric machine 21, i.e., excessive changes in generated voltage.

[0031] In this embodiment, the rotation speed of the ring gear 32 of the planetary gear mechanism 23 can be adjusted by the motor 41 serving as a rotation adjustment device. More specifically, the brake device 42 on one of the pair of shafts 27 a, 27 b connected to the differential gear 24 is set to a brake-on state (i.e., a state in which the rotation of the shaft 27 b is stopped), and under this state, the motor 41 is driven to the positive rotation side or the negative rotation side. This adjusts the rotation speed of the ring gear 32 of the planetary gear mechanism 23 as a positive rotation side or a negative rotation side, and ultimately adjusts the rotation speed of the first rotating electric machine 21 connected to the sun gear 31, i.e., the rotation speed of the generator, to increase or decrease.

[0032] Changes in the rotation speed of the three shafts of the planetary gear mechanism 23 when the rotation speed of the ring gear 32 is adjusted by the motor 41 will be described with reference to FIGS.

[0033] 5(a), similarly to Fig. 4, it is assumed that the rotation speed of the water turbine 11 (carrier rotation speed) increases from N1 to N2, and in such a case, the motor 41 is driven to rotate in the positive direction, thereby increasing the rotation speed of the ring gear 32 in the positive direction. As a result, the rotation speed of the first rotating electrical machine 21 (sun gear rotation speed) is prevented from increasing excessively and is maintained within the allowable range X.

[0034] 5(b) assumes that the rotation speed of the water turbine 11 (carrier rotation speed) decreases from N1 to N3, and in this case, the motor 41 is rotated in the negative direction, thereby increasing the rotation speed of the ring gear 32 in the negative direction. As a result, the rotation speed of the first rotating electrical machine 21 (sun gear rotation speed) is prevented from decreasing excessively and is maintained within the allowable range X.

[0035] Figure 6 is a functional block diagram showing each function realized by the power generation control device 15. In Figure 6, an acquisition unit 81 acquires parameters indicating the rotational state of the water turbine 11. Here, the parameters indicating the rotational state of the water turbine 11 may be any parameters that are correlated with the rotational state of the water turbine 11, such as the flow rate of the water flowing through the water channel, the amount of water per unit time, the water pressure, and the rotation speed of the water turbine 11. In this embodiment, a flow rate sensor 72 that detects the water flow rate V is provided in the water channel in which the water turbine 11 is installed, and this flow rate sensor 72 corresponds to the parameter detection means. The parameter detection means may be any means that directly or indirectly detects the rotation of the water turbine 11.

[0036] The first determination unit 82 determines whether the parameter (flow velocity V) acquired by the acquisition unit 81 is within a first range Y1. The second determination unit 83 determines whether the parameter (flow velocity V) acquired by the acquisition unit 81 is within a second range Y2 that is defined within the first range Y1 and is narrower than the first range Y1.

[0037] The first range Y1 and the second range Y2 are indicators for determining the water flow velocity V, and processing related to the parking lock mechanism 38, the motor 41, and the brake device 42 is selectively performed depending on which of the multiple flow velocity ranges defined by the first range Y1 and the second range Y2 the flow velocity V falls within. As shown in Figure 8, the first range Y1 is a range (TH11 to TH12) with an upper limit equal to a threshold value TH11 and a lower limit equal to a threshold value TH12. The second range Y2 is defined within the first range Y1 but is narrower than the first range Y1, and is a range (TH21 to TH22) with an upper limit equal to a threshold value TH21 and a lower limit equal to a threshold value TH22.

[0038] When the second judgment unit 83 determines that the parameter is within the second range Y2, the lock control unit 84 sets the parking lock mechanism 38 (P / L) to a state in which rotation of the ring gear 32 is prohibited, and when the second judgment unit 83 determines that the parameter is outside the second range Y2, the lock control unit 84 sets the parking lock mechanism 38 to a state in which rotation of the ring gear 32 is permitted.

[0039] When the second judgment unit 83 judges that the parameter is outside the second range Y2 and the first judgment unit 82 judges that the parameter is within the first range Y1, the rotation control unit 85 puts the brake device 42 in a brake-on state and puts the motor 41 in a rotation-stop state, and when the parameter is judged to be outside the first range Y1, the rotation control unit 85 puts the brake device 42 in a brake-on state and controls the rotation speed of the motor 41 to the positive or negative side based on the parameter acquired by the acquisition unit 81.

[0040] 7 is a flowchart showing the procedure for power generation control in the power generation system 10. This process is executed by the power generation control device 15 at predetermined intervals.

[0041] 7, in step S11, the water flow velocity V is acquired as a parameter indicating the rotation state of the water turbine 11. Then, in step S12, it is determined whether the flow velocity V is less than a threshold value TH21, and in the subsequent step S13, it is determined whether the flow velocity V is equal to or greater than a threshold value TH22. If both steps S12 and S13 are positive, that is, if the flow velocity V is within the range between the threshold values ​​TH21 and TH22 (second range Y2), the process proceeds to step S14, in which the parking lock mechanism 38 is turned on (activated), and the electromagnetic brake of the brake device 42 is turned off. Furthermore, in step S15, the motor 41 is stopped from rotating. As a result, the ring gear 32 of the planetary gear mechanism 23 is held in a stopped state.

[0042] If the result of step S12 is negative, the process proceeds to step S 16. In step S16, the parking lock mechanism 38 is turned off (inactivated), and the electromagnetic brake of the brake device 42 is turned on.

[0043] Then, in step S17, it is determined whether the flow velocity V is less than a threshold value TH11. If the result of step S17 is affirmative, i.e., if the flow velocity V is within the range of threshold values ​​TH11 to TH21, the motor 41 is left stopped in step S15. If the result of step S17 is negative, i.e., if the flow velocity V is equal to or greater than the threshold value TH11, the process proceeds to step S18, where the motor 41 is driven to rotate in the forward direction. As a result, as described in FIG. 5A, the rotation speed of the ring gear 32 increases in the positive direction, and an excessive increase in the rotation speed of the first rotating electrical machine 21 (sun gear rotation speed) is suppressed.

[0044] In step S18, the rotation speed of the motor 41 in the forward rotation direction may be controlled based on the flow velocity V. For example, the motor rotation speed may be controlled based on the deviation of the actual value (sensor detection value) of the flow velocity V from the target value. In this case, the motor rotation speed is increased as the deviation of the flow velocity V from the target value of the flow velocity V increases. The rotation speed of the motor 41 in the forward rotation direction may also be a predetermined rotation speed. In any case, by controlling the rotation speed of the motor 41, the rotation speed of the first rotating electric machine 21 (ring gear rotation speed) is controlled to be within the allowable range X.

[0045] If the result of step S13 is negative, the process proceeds to step S 19. In step S19, the parking lock mechanism 38 is turned off (inactivated), and the electromagnetic brake of the brake device 42 is turned on.

[0046] Then, in step S20, it is determined whether the flow velocity V is equal to or greater than the threshold value TH12. If the result of step S20 is affirmative, i.e., if the flow velocity V is within the range of the threshold values ​​TH12 to TH22, the motor 41 is left stopped in step S15. If the result of step S20 is negative, i.e., if the flow velocity V is less than the threshold value TH12, the process proceeds to step S21, where the motor 41 is driven to rotate in the reverse direction. As a result, as described in FIG. 5B, the rotation speed of the ring gear 32 increases to the negative side, and an excessive increase in the rotation speed of the first rotating electrical machine 21 (sun gear rotation speed) is suppressed.

[0047] In step S21, the rotation speed of the motor 41 in the negative rotation direction may be set based on the flow velocity V. For example, similar to step S18, the motor rotation speed may be set based on the deviation of the actual value (sensor detection value) of the flow velocity V from the target value. Furthermore, the rotation speed of the motor 41 in the negative rotation direction may be a predetermined rotation speed.

[0048] Step S11 corresponds to the "acquisition unit," steps S12 and S13 correspond to the "second determination unit," and steps S17 and S20 correspond to the "first determination unit." Step S14 corresponds to the "lock control unit," and steps S15, S18, and S21 correspond to the "rotation control unit."

[0049] FIG. 8 is a time chart for explaining in more detail the power generation control process during hydroelectric power generation.

[0050] 8, before timing t1, the flow velocity V is within the first range Y1 and also within the second range Y2. At this time, the parking lock mechanism 38 is in the ON state, so the rotation speed of the ring gear 32 in the planetary gear mechanism 23 is maintained at zero. The brake device 42 and the motor 41 are both maintained in an inactive state.

[0051] Thereafter, if the flow velocity V increases due to, for example, an increase in the amount of water in the waterway, the rotation speed of the first rotating electrical machine 21 increases. Then, when the flow velocity V reaches the threshold value TH21 at timing t1, that is, when the flow velocity V falls outside the second range Y2, the parking lock mechanism 38 is turned off and the electromagnetic brake of the brake device 42 is turned on. However, at this point in time, the flow velocity V is within the first range Y1, and the motor 41 remains stopped.

[0052] Thereafter, when the flow velocity V reaches the threshold value TH11 at timing t2, that is, when the flow velocity V falls outside the first range Y1, the motor 41 is driven to rotate in the forward direction. When the flow velocity V is equal to or greater than the threshold value TH11, hydraulic energy becomes excessive. However, the forward rotation of the motor 41 increases the rotation speed of the ring gear 32 in the positive direction, and an excessive increase in the rotation speed of the first rotating electrical machine 21 (sun gear rotation speed) is suppressed.

[0053] Thereafter, when the flow velocity V becomes less than the threshold value TH11 at timing t3, i.e., when the flow velocity V returns to within the first range Y1, the rotation of the motor 41 is stopped. Also, when the flow velocity V becomes less than the threshold value TH21 at timing t4, i.e., when the flow velocity V returns to within the second range Y2, the parking lock mechanism 38 is returned to the ON state, and the brake device 42 is returned to the OFF state.

[0054] Although not shown, when the flow velocity V decreases due to a decrease in the amount of water in the waterway or other reasons, the parking lock mechanism 38 is turned off and the electromagnetic brake of the brake device 42 is turned on when the flow velocity V reaches a threshold value TH22. Thereafter, when the flow velocity V reaches a threshold value TH12, the motor 41 is driven to rotate in the reverse direction. As a result, when hydraulic energy is insufficient, the rotation speed of the ring gear 32 increases to the negative side due to the reverse rotation of the motor 41, and an excessive decrease in the rotation speed of the first rotating electric machine 21 (sun gear rotation speed) is suppressed.

[0055] Furthermore, a situation in which the flow velocity V falls outside the second range Y2 due to fluctuations in the amount of water or the like is considered to be a situation in which the flow velocity V is likely to fluctuate. Therefore, even if the flow velocity V falls below the threshold value TH21 at timing t4 in FIG. 8 , the flow velocity V may again become equal to or greater than the threshold value TH21 immediately thereafter. Therefore, when the flow velocity V returns to within the second range Y2 from outside the second range Y2, the brake device 42 may be kept in the brake-on state and the parking lock mechanism 38 may be kept in the off state (non-operated state) for a period from the time when the flow velocity V returned to within the second range Y2 until a predetermined time TA has elapsed.

[0056] Specifically, the power generation control process may be the process shown in Fig. 9. The flowchart in Fig. 9 is a partial modification of the flowchart in Fig. 7, with steps S31 to S35 being additional processes.

[0057] 9 , when the flow velocity V is equal to or greater than the threshold value TH21 (when step S12 is negative), the parking lock mechanism 38 is turned off (inactivated), the electromagnetic brake of the brake device 42 is turned on, and flag F is set to 1 (steps S16 and S31). Similarly, when the flow velocity V is less than the threshold value TH22 (when step S13 is negative), the parking lock mechanism 38 is turned off (inactivated), the electromagnetic brake of the brake device 42 is turned on, and flag F is set to 1 (steps S19 and S32). According to steps S31 and S32, when the flow velocity V is outside the second range Y2, flag F is set to 1.

[0058] Furthermore, when the flow velocity V is within the range of thresholds TH21 to TH22 (second range Y2) (when both steps S12 and S13 are YES), step S33 determines whether flag F is 1. In this case, if the timing is such that the flow velocity V has transitioned from outside the second range Y2 to within the second range Y2, step S33 is answered in the affirmative, and the process proceeds to step S34. In step S34, it is determined whether a predetermined time TA has elapsed since the flow velocity V returned to within the second range Y2. The predetermined time TA may be, for example, a few minutes or several tens of minutes.

[0059] If the predetermined time TA has not elapsed, the process ends. If the predetermined time TA has elapsed, the flag F is reset to 0 in step S35, and then the parking lock mechanism 38 is turned on (activated), the electromagnetic brake of the brake device 42 is turned off, and the motor 41 is stopped (steps S14 and S15).

[0060] Figure 10 is a time chart for more specifically explaining the power generation control process of Figure 9. In Figure 10, as in Figure 8, the flow velocity V reaches the threshold value TH21 at time t1, and reaches the threshold value TH11 at time t2. The flow velocity V also falls below the threshold value TH11 at time t3, and falls below the threshold value TH21 at time t4. At time t1, when the flow velocity V reaches the threshold value TH21, flag F is set to 1.

[0061] 10 , even if the flow velocity V returns from outside the second range Y2 to within the second range Y2, there is a possibility that the flow velocity V will fall outside the second range Y2 again immediately thereafter, causing the motor 41 to adjust the rotation. Therefore, after the flow velocity V returns to within the second range Y2, the flag F remains set to 1, the parking lock mechanism 38 remains in the OFF state, and the electromagnetic brake of the brake device 42 remains in the ON state until the predetermined time TA has elapsed. Here, after the flow velocity V falls within the second range Y2 at timing t5, if it is determined at timing t6 that the predetermined time TA has elapsed, the parking lock mechanism 38 is returned to the ON state and the brake device 42 is returned to the OFF state. At timing t6, the flag F is reset to 0.

[0062] In addition, instead of the configuration in which flag F is set to 1 at timing t1 when flow velocity V falls outside the second range Y2, it is also possible to configure flag F to be set to 1 at timing t2 when flow velocity V falls outside the first range Y1.

[0063] According to the present embodiment described above in detail, the following excellent effects can be obtained.

[0064] In the power generation system 10, a parameter indicating the rotational state of the water turbine 11 is acquired, and the rotation speed of the ring gear 32 of the planetary gear mechanism 23 is controlled by the motor 41 based on the parameter. As a result, when the flow velocity V of the flowing water excessively decreases or increases, the rotation speed of the ring gear 32 is controlled in accordance with the decrease or increase in the flow velocity V, thereby controlling the rotation speed of the first rotating electric machine 21 (generator) to an appropriate value. In other words, even if the rotational state of the water turbine 11 changes depending on the usage conditions, the rotation speed of the first rotating electric machine 21 (generator) can be appropriately adjusted, thereby improving versatility for various usage conditions. As a result, electric power can be appropriately output to the power grid 90.

[0065] The power generation system 10 is constructed using a transaxle 13 and a PCU 14 that are mounted on a hybrid vehicle 100. This makes it possible to simultaneously contribute to the creation of a recycling-oriented society and the spread of renewable energy.

[0066] The power generation system 10 includes means for adjusting the rotation speed of the ring gear 32 of the planetary gear mechanism 23, including a means for setting the rotation speed of the ring gear 32 to zero using a parking lock mechanism 38 and a means for adjusting the rotation speed of the ring gear 32 based on the flow velocity V using a brake device 42 and a motor 41. In this case, when the flow velocity V of flowing water is within the second range Y2, it is unlikely that the rotation speed of the ring gear 32 of the planetary gear mechanism 23 will need to be adjusted. By locking the parking lock mechanism 38 (prohibiting rotation), energy consumption can be reduced compared to when the electromagnetic brake is turned on. On the other hand, when the flow velocity V of flowing water is outside the second range Y2 but within the first range Y1, it is likely that the rotation speed of the ring gear 32 of the planetary gear mechanism 23 will need to be adjusted. By turning the brake device 42 on and the motor 41 off, it is possible to quickly adjust the rotation speed using the motor 41 when the parameter is outside the first range Y1.

[0067] If the flow velocity V of the water flow is determined to be outside the second range Y2 and then determined to have returned to within the second range Y2, the brake device 42 is kept in the brake-on state and the parking lock mechanism 38 is kept in the off state (rotation permitted state) for a period from the time when the flow velocity V returned to within the second range Y2 until a predetermined time TA has elapsed. As a result, in a situation where the flow velocity V tends to fluctuate, the rotation of the ring gear 32 of the planetary gear mechanism 23 is stopped by the brake device 42 and the motor 41, and if it becomes necessary to adjust the rotation speed of the ring gear 32 by the motor 41, this can be addressed quickly.

[0068] In the hybrid vehicle, the PCU 14 includes a pair of inverters 51, 52 having DC terminals connected to each other. In the power generation system 10, one of the AC terminals of each of the pair of inverters 51, 52 is connected to the first rotating electric machine 21 (generator), and the other is connected to the power grid 90. In this case, the power generation system 10 can be suitably constructed by reusing the PCU 14 from the hybrid vehicle 100 in the power generation system 10.

[0069] Other Embodiments The above embodiment may be modified as follows, for example.

[0070] The power generation control process of the power generation system 10 may be implemented as shown in Figure 11. The process of Figure 11 is executed by the power generation control device 15 at a predetermined interval. When this process is executed, of the pair of side gears 24a, 24b in the differential gear 24, the side gear 24b on the opposite side from the motor 41 is held in a stopped state. For example, the brake device 42 may be omitted, and the shaft portion 27b may be fixed in a stopped state. The parking lock mechanism 38 is in an OFF state.

[0071] 11, in step S41, the water flow velocity V is acquired as a parameter indicating the rotation state of the water turbine 11, and in steps S42 and S43, it is determined whether the flow velocity V is within a predetermined range, i.e., the range from TH11 to TH12. If the flow velocity V is within the predetermined range, the motor 41 is stopped (step S44).

[0072] If step S42 is negative, the process proceeds to step S45, where the motor 41 is rotated in the forward direction. At this time, the rotation speed of the motor 41 in the forward direction may be set based on the flow velocity V. If step S43 is negative, the process proceeds to step S46, where the motor 41 is rotated in the reverse direction. At this time, the rotation speed of the motor 41 in the reverse direction may be set based on the flow velocity V.

[0073] In FIG. 11, step S41 corresponds to an "acquisition unit", steps S42 and S43 correspond to a "parameter determination unit", and steps S44 to S46 correspond to a "rotation control unit".

[0074] Even in a configuration in which the processing of Figure 11 is executed, the rotation speed of the ring gear 32 is controlled to the positive or negative side by the motor 41 based on the flow velocity V of the flowing water, and ultimately the rotation speed of the first rotating electric machine 21 is appropriately controlled.

[0075] 12, the star-connected three-phase coils 111 in the stator of the second rotating electric machine 22 may be short-circuited to each other. For example, a switch 112 may be provided in the power line (three-phase output line) extending from the coil of each phase, and the three-phase coils 111 may be switched between a short-circuited state and a non-shorted state by turning the switch 112 on and off. The power generation control device 15 may turn on the switch 112, for example, when it is necessary to reduce the ring gear rotation speed.

[0076] In this case, when the three-phase coils 111 are short-circuited, a reaction force is generated in the second rotating electric machine 22 in a direction that prevents rotation due to an external force, thereby preventing rotation of the second rotating electric machine 22. In other words, a brake torque is generated in the second rotating electric machine 22. This makes it possible to adjust the rotation speed of the ring gear 32 of the planetary gear mechanism 23. Note that the three-phase coils 111 may be configured to be constantly short-circuited.

[0077] In the above embodiment, the planetary gear mechanism 23 is configured such that the water turbine 11 is connected to the planetary carrier 34, the first rotating electric machine 21 is connected to the sun gear 31, and the second rotating electric machine 22 and the differential gear 24 are connected to the ring gear 32. However, it is also possible to change the connection partners of the shafts in the planetary gear mechanism 23. For example, the planetary gear mechanism 23 may be configured such that the water turbine 11 is connected to the sun gear 31, the first rotating electric machine 21 is connected to the planetary carrier 34, and the second rotating electric machine 22 and the differential gear 24 are connected to the ring gear 32.

[0078] In the above embodiment, the PCU 14 is configured to use the inverter 51 to convert the three-phase AC voltage from the first rotating electric machine 21 into a DC voltage, but this may be changed to a configuration that uses a full-wave rectifier circuit consisting of multiple diodes.

[0079] In the above embodiment, the brake device 42 is an electromagnetic brake. However, the brake device 42 may be a hydraulic brake.

[0080] A configuration may be adopted in which a plurality of power generation systems 10 shown in FIG. 1 are provided and each of these power generation systems 10 is connected to the power grid 90 .

[0081] The power generation system 10 may be a wind power generation system that generates power using wind energy as renewable energy and outputs the generated power to a power grid. In this case, the water turbine 11 in Fig. 1 is replaced with a wind turbine.

[0082] In the above embodiment, the power generation system 10 is constructed by reusing the transaxle 13 and the PCU 14 from the hybrid vehicle 100, but this may be changed. For example, the power generation system 10 may be constructed by reusing only the transaxle 13 from the hybrid vehicle 100 and combining the transaxle 13 with a power control unit that is a separate component from the hybrid vehicle 100. It is also possible to construct the power generation system 10 without using any components repurposed from the hybrid vehicle 100.

[0083] The control unit and the method described herein may be implemented by a special-purpose computer configured by configuring a processor and memory programmed to perform one or more functions embodied in a computer program. Alternatively, the control unit and the method described herein may be implemented by a special-purpose computer configured by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method described herein may be implemented by one or more special-purpose computers configured by combining a processor and memory programmed to perform one or more functions with a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by a computer on a computer-readable non-transitory tangible storage medium.

[0084] The technical concepts extracted from the above-described embodiments are described below. [Configuration 1] A power generation system (10) comprising: a planetary gear mechanism (23) having a first shaft, a second shaft, and a third shaft; a rotating body (11) connected to the first shaft and rotated by a fluid flow; a generator (21) connected to the second shaft and generating electricity by the rotation of the second shaft; a rotation adjustment device (41) connected to the third shaft and capable of adjusting the rotation speed of the third shaft; power conversion devices (51, 52) that convert the power generated by the generator into electric power and output the power to an electric power system (90); an acquisition unit (81) that acquires parameters indicating the rotation state of the rotating body; and a rotation control unit (85) that controls the rotation speed of the third shaft by the rotation adjustment device based on the parameters acquired by the acquisition unit. [Configuration 2] The power generation system according to Configuration 1, comprising: a differential gear (24) connected to the third shaft and having a pair of side gears (24a, 24b); a motor (41) connected to one of the pair of side gears and functioning as the rotation adjustment device; and a parameter determination unit that determines whether the parameter acquired by the acquisition unit is within a predetermined range, wherein the other side gear of the pair of side gears in the differential gear, the side gear opposite to the motor, is held in a stopped state, and the rotation control unit stops the motor from rotating when the parameter determination unit determines that the parameter is within the predetermined range, and controls the rotation speed of the motor to a positive or negative side based on the parameter acquired by the acquisition unit when the parameter determination unit determines that the parameter is outside the predetermined range.[Configuration 3] The device comprises: a lock mechanism (38) that switches between a state in which rotation of the third shaft is permitted and a state in which it is prohibited; a differential gear (24) connected to the third shaft and having a pair of side gears (24a, 24b); a motor (41) that is connected to one of the pair of side gears and functions as the rotation adjustment device; a brake device (42) connected to the other of the pair of side gears; a first determination unit (82) that determines whether the parameter acquired by the acquisition unit is within a first range; a second determination unit (83) that determines whether the parameter acquired by the acquisition unit is within a second range that is set within the first range and is narrower than the first range; and a lock control unit (84) that sets the lock mechanism to a state in which rotation of the third shaft is prohibited when the second determination unit determines that the parameter is within the second range, and sets the lock mechanism to a state in which rotation of the third shaft is permitted when the second determination unit determines that the parameter is outside the second range. The power generation system according to configuration 1, wherein the rotation control unit, when the second determination unit determines that the parameter is outside the second range and the first determination unit determines that the parameter is within the first range, sets the brake device to a brake-on state and sets the motor to a rotation-stop state, and when the parameter is determined to be outside the first range, sets the brake device to a brake-on state and controls the motor rotation speed to a positive or negative side based on the parameter acquired by the acquisition unit. [Configuration 4] The power generation system according to configuration 3, wherein, when the parameter is determined to have returned to the second range after going outside the second range, the brake device is kept in the brake-on state and the lock mechanism is kept in a state allowing rotation of the third shaft until a predetermined time has elapsed since the parameter returned to the second range.[Configuration 5] The power generation system according to any one of Configurations 1 to 4, wherein the planetary gear mechanism has a sun gear (31), a ring gear (32) that rotates coaxially with the sun gear, a plurality of pinion gears (33) that mesh with both the sun gear and the ring gear, and a planetary carrier (34) that rotates coaxially with the sun gear as the pinion gears rotate, the sun gear is connected to the generator as the second shaft, the ring gear is connected to the rotation adjustment device as the third shaft, and the planetary carrier is connected to the rotating body as the first shaft, and the rotation control unit controls the rotation speed of the ring gear using the rotation adjustment device based on the parameters acquired by the acquisition unit. [Configuration 6] The power generation system according to any one of Configurations 1 to 5, wherein the power conversion device includes a first inverter (51) and a second inverter (52) that perform AC power conversion, wherein the first inverter and the second inverter have DC terminals on their high potential side and low potential side connected to each other, and wherein AC terminals of the first inverter are connected to phase current terminals of each phase in the generator, while AC terminals of the second inverter are connected to the power grid. [Configuration 7] The power generation system according to any one of Configurations 1 to 6, wherein the planetary gear mechanism, the generator connected to the second shaft of the planetary gear mechanism, and a differential gear (24) connected to the third shaft of the planetary gear mechanism via a drive shaft (25) are on-board components mounted as a transaxle (13) in a hybrid vehicle, wherein the rotating body is connected to the first shaft of the planetary gear mechanism in the transaxle instead of an engine of the hybrid vehicle, and the power conversion device has an inverter (51, 52) that adjusts the input and output of power to and from on-board rotating electrical machines including the generator in the hybrid vehicle.

[0085] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

Claims

1. A power generation system (10) comprising: a planetary gear mechanism (23) having a first shaft, a second shaft, and a third shaft; a rotating body (11) connected to the first shaft and rotated by a fluid flow; a generator (21) connected to the second shaft and generating electric power by rotation of the second shaft; a rotation adjustment device (41) connected to the third shaft and capable of adjusting the rotation speed of the third shaft; a power conversion device (51, 52) that power-converts the generated electric power of the generator and outputs it to a power grid (90); an acquisition unit (81) that acquires a parameter indicating the rotation state of the rotating body; and a rotation control unit (85) that controls the rotation speed of the third shaft by the rotation adjustment device based on the parameter acquired by the acquisition unit.

2. The power generation system according to claim 1, further comprising: a differential gear (24) connected to the third shaft and having a pair of side gears (24a, 24b); a motor (41) connected to one of the pair of side gears and functioning as the rotation adjustment device; and a parameter determination unit that determines whether or not the parameter acquired by the acquisition unit is within a predetermined range. In the differential gear, the other side gear opposite to the motor among the pair of side gears is held in a rotation stop state. The rotation control unit sets the motor to a rotation stop state when the parameter determination unit determines that the parameter is within the predetermined range, and controls the rotation speed of the motor to the positive side or the negative side based on the parameter acquired by the acquisition unit when the parameter determination unit determines that the parameter is outside the predetermined range.

3. A lock mechanism (38) for switching between a state allowing rotation of the third axis and a state prohibiting rotation; a differential gear (24) connected to the third axis and having a pair of side gears (24a, 24b); a motor (41) connected to one of the pair of side gears and functioning as the rotation adjustment device; a brake device (42) connected to the other of the pair of side gears; a first determination unit (82) for determining whether or not the parameter acquired by the acquisition unit is within a first range; a second determination unit (83) for determining whether or not the parameter acquired by the acquisition unit is within a second range defined within the first range and narrower than the first range; and a lock control unit (84) for setting the lock mechanism to a rotation prohibition state of the third axis when the second determination unit determines that the parameter is within the second range, and setting the lock mechanism to a rotation allowance state of the third axis when the parameter is determined to be outside the second range. The rotation control unit sets the brake device to a brake-on state and stops the rotation of the motor when the second determination unit determines that the parameter is outside the second range and the first determination unit determines that the parameter is within the first range, and sets the brake device to a brake-on state and controls the rotation speed of the motor to be positive or negative based on the parameter acquired by the acquisition unit when the parameter is determined to be outside the first range. The power generation system according to claim 1.

4. When it is determined that the parameter has returned within the second range after the parameter has gone outside the second range, the brake device is kept in a brake-on state and the lock mechanism is kept in a rotation allowance state of the third axis for a period until a predetermined time has elapsed from the timing when the parameter has returned within the second range. The power generation system according to claim 3.

5. The planetary gear mechanism includes a sun gear (31), a ring gear (32) that rotates coaxially with the sun gear, a plurality of pinion gears (33) that mesh with both the sun gear and the ring gear, and a planetary carrier (34) that rotates coaxially with the sun gear as the pinion gears rotate. The sun gear is connected to the generator as the second shaft, the ring gear is connected to the rotation adjustment device as the third shaft, and the planetary carrier is connected to the rotating body as the first shaft. The rotation control unit controls the rotation speed of the ring gear by the rotation adjustment device based on the parameter acquired by the acquisition unit. The power generation system according to claim 1.

6. The power conversion device includes a first inverter (51) and a second inverter (52) that perform orthogonal power conversion. The DC terminals on the high potential side and the low potential side of each of the first inverter and the second inverter are connected to each other. The AC terminal of the first inverter is connected to the phase current terminal of each phase in the generator, while the AC terminal of the second inverter is connected to the power grid. The power generation system according to any one of claims 1 to 5.

7. The planetary gear mechanism, the generator connected to the second shaft of the planetary gear mechanism, and the differential gear (24) connected to the third shaft of the planetary gear mechanism via a drive shaft (25) are in-vehicle components mounted as a transaxle (13) in a hybrid vehicle. In the transaxle, the rotating body is connected to the first shaft of the planetary gear mechanism in place of the engine of the hybrid vehicle. The power conversion device includes inverters (51, 52) that adjust the input and output of power to the in-vehicle rotating electrical machine including the generator in the hybrid vehicle. The power generation system according to any one of claims 1 to 5.

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