Electrical power generation system

Abstract

To provide an electrical power generation system that can properly output electric power to an electrical power system.SOLUTION: In an electrical power generation system 10, a waterwheel 11 is connected to a first shaft of a planetary gear mechanism 23, a first rotary electric machine 21 is connected to a second shaft of the mechanism, and a second rotary electric machine 22 is connected to a third shaft of the mechanism. The first rotary electric machine 21 generates electric power by rotation of the waterwheel 11 and outputs the generated AC electric power to an electric power system 90. The electric power generation system 10 comprises a first inverter 51 that converts the AC electric power outputted from the first rotary electric machine 21 to DC electric power, and a second inverter 52 that converts the DC electric power outputted from the first inverter to AC electric power. An electric power generation control device 15 comprises an obtaining part 41 that obtains a parameter showing a rotating state of the first rotary electric machine 21, and a rotation control part 42 that controls rotation speed of the third shaft, on the basis of the parameter, in a state where the second rotary electric machine 22 is rotated by operation of the inverters and adjusts rotation speed of the first rotary electric machine 21 by the control of the rotation speed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The disclosure in this specification relates to a power generation system that generates electricity using energy sources such as hydraulic power and wind power.

Background Art

[0002] Conventionally, various power generation systems that generate electricity using renewable energy such as hydraulic power and wind power have been proposed. For example, in the hydraulic power generation system described in Patent Document 1, a water pressure sensor detects a change in water level of the source stream or a change in water pressure due to water intake from the water intake, and in response to the detected change in water intake, the opening degree of the flow regulator of the waterwheel is adjusted and controlled, and the rotational speed of the waterwheel is controlled according to the adjusted opening degree. With this configuration, it is possible to control the rotational speed of the waterwheel to an optimal output power.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a power generation system, it is conceivable to directly output the generated power of a generator generated with the rotation of a waterwheel to a power grid. In this case, if the rotation of the waterwheel fluctuates due to a change in water pressure or the like, there is a concern that the output voltage of the generator will deviate from the frequency of the grid voltage (for example, 50 Hz, 60 Hz), and grid connection will become impossible. Therefore, there is room for improvement in a power generation system that performs grid voltage output.

[0005] This disclosure has been made in view of the above circumstances, and an object thereof is to provide a power generation system capable of appropriately outputting power to a power grid.

Means for Solving the Problems

[0006] The power generation system of the present disclosure includes 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 first rotating electric machine connected to the second shaft and generating electricity by the rotation of the second shaft, a second rotating electric machine connected to the third shaft, and is configured to generate alternating current power by the rotation of the rotating body in the first rotating electric machine, and output the generated alternating current power to a power grid via an alternating current power line extending from the first rotating electric machine. a first inverter connected to the alternating current power line and converting the alternating current power output from the first rotating electric machine into direct current power, a second inverter having a high-potential side and a low-potential side DC terminal connected to the first inverter, converting the direct current power output from the first inverter into alternating current power, and rotating the second rotating electric machine with the alternating current power, an acquisition unit that acquires parameters indicating the rotation state of the first rotating electric machine, a rotation control unit that controls the rotation speed of the third shaft in the rotation state of the second rotating electric machine by operating each inverter based on the parameters acquired by the acquisition unit, and adjusts the rotation speed of the first rotating electric machine by the rotation speed control, and includes.

[0007] In the power generation system having the above configuration, a rotating body rotated by the flow of a fluid, a first rotating electric machine, and a second rotating electric machine are respectively connected to three shafts (the first shaft, the second shaft, and the third shaft) of the planetary gear mechanism, and it is possible to drive the first rotating electric machine by the rotation of the rotating body to generate electricity. Further, the configuration is such that the alternating current power generated by the first rotating electric machine is output to the power grid via the alternating current power line. Further, the second rotating electric machine can be driven by the power supplied from the alternating current power line of the first rotating electric machine via the first inverter and the second inverter.

[0008] In a planetary gear mechanism, since the rotational speed of the remaining one shaft is determined by the rotational speeds of two shafts, when the first shaft rotates due to the rotation of a rotating body accompanying the flow of a fluid, the rotational speed of a first rotating electric machine (generator) connected to the second shaft can be increased or decreased by the rotational speed of the third shaft. In particular, in this case, based on a parameter indicating the rotational state of the first rotating electric machine, the rotational speed of the third shaft is controlled by the rotational state of the second rotating electric machine by operating each inverter, and the rotational speed of the first rotating electric machine is adjusted by the rotational speed control. As a result, even if the rotational speed of the rotating body fluctuates due to a change in the flow rate of a fluid composed of, for example, water or air, the rotational speed of the first rotating electric machine can be adjusted to a desired rotational speed, and thus, the frequency of the system voltage can be maintained at an appropriate frequency. As a result, power can be appropriately output to the power grid.

Brief Description of the Drawings

[0009]

Figure 1

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Embodiments for Carrying Out the Invention

[0010] <First Embodiment> Hereinafter, an embodiment in which the power generation system according to the present disclosure is embodied 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 removed from an end-of-life hybrid vehicle and a power control unit (PCU: Power Control Unit). It generates electricity using hydro energy, which is renewable energy, and outputs the generated electric power as grid power.

[0011] The configuration of the power generation system 10 will be described with reference to FIG. 1. The power generation system 10 includes a water turbine 11 as a rotating body rotated by water, a transaxle 13 and a PCU 14 removed from a hybrid vehicle, and a power generation control device 15, and AC power is output from the PCU 14 to the power grid 90. The power generation system 10 has a configuration in which, for example, water flowing from a water storage tank or a reservoir is used as an energy source, and the water turbine 11 is provided in a water channel extending from the water storage tank or the like. Due to the water flow in the water channel, the water turbine 11 and the rotating shaft 12 fixed to the water turbine 11 rotate.

[0012] 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.

[0013] The first rotating electric machine 21 and the second rotating electric machine 22 are three-phase AC motors made of, for example, a permanent magnet motor or a field winding type motor. In the power generation system 10 of this embodiment, the first rotating electric machine 21 functions as a generator that generates electricity as the water turbine 11 rotates.

[0014] FIG. 2 is a skeleton diagram showing a configuration example 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 each pinion gear 33 rotates. In the planetary gear mechanism 23, a waterwheel 11 is connected to the planetary carrier 34 via a rotating shaft 12. A first rotating electric machine 21 is connected to the sun gear 31. A second rotating electric machine 22 and a differential gear 24 are connected to the ring gear 32 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 the three axes of the first axis, the second axis, and the third axis.

[0015] As a configuration example 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. Further, the counter driven gear 35 is connected to the differential gear 24 via a reduction gear 37.

[0016] Further, the transaxle 13 has a parking lock mechanism 38 (P / L). The parking lock mechanism 38 includes, for example, an actuator, a parking lock gear, a parking ball, etc. not shown in the figure. When the parking ball as an engaging member engages with the parking lock gear by driving the actuator, the parking lock state (operating state) is achieved. In the parking lock state, the rotation of the ring gear 32 that meshes with the parking lock gear is restricted. Note that the parking lock mechanism 38 may mesh the parking lock gear with the counter driven gear 35 to restrict the rotation of the counter driven gear 35. In any case, the parking lock mechanism 38 may be one that switches between a state that allows the rotation of the ring gear 32 of the planetary gear mechanism 23 and a state that prohibits it, that is, one that can restrict the rotation of the ring gear 32.

[0017] As shown in FIG. 3, in the hybrid vehicle 100 with the transaxle 13 mounted thereon, the engine 101, which is an internal combustion engine, 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 generation is performed in the first rotating electric machine 21 as the engine 101 rotates. Also, the shaft portions 27a and 27b on both sides of the differential gear 24 are connected to the left and right wheels 102. In the hybrid vehicle 100, it is possible to travel by driving the wheels with the second rotating electric machine 22.

[0018] Returning to the description of FIG. 1, a rotation angle sensor 28 for detecting the rotation angle of the rotating shaft is provided on the rotating shaft (rotor rotating shaft) of the first rotating electric machine 21. Also, the first rotating electric machine 21 has a three-phase stator coil, and a power generation voltage sensor 29 for detecting the power generation voltage of the first rotating electric machine 21 is provided on the power line connected to the stator coil. Detection signals from these sensors 28 and 29 are sequentially input to the power generation control device 15.

[0019] The PCU 14 includes 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. The first inverter 51 and the second inverter 52 each have an upper arm switch 61 and a lower arm switch 62 for each phase, and orthogonal power conversion is performed by switching the switches 61 and 62 of the upper and lower arms in each phase at a predetermined cycle.

[0020] The first inverter 51 and the second inverter 52 are provided with their high-potential side and low-potential side DC terminals connected to each other. That is, in these inverters 51 and 52, a high-potential path 63, which is an electric path on the high-potential side, and a low-potential path 64, which is an electric path on the low-potential side, are continuous with each other. A smoothing capacitor 65 is connected between the high-potential path 63 and the low-potential path 64.

[0021] The AC terminals of the first inverter 51 are respectively connected to the stator coil of the first rotating electrical machine 21 and the power grid 90. In this case, the first rotating electrical machine 21 and the power grid 90 are interconnected by an AC power line 56 extending from the first rotating electrical machine 21, and the first inverter 51 is connected to the AC power line 56. The AC terminals of the second inverter 52 are connected to the stator coil of the second rotating electrical machine 22.

[0022] The first inverter 51 converts the AC voltage output from the first rotating electrical machine 21 into a DC voltage. Also, the second inverter 52 reconverts the DC voltage converted by the first inverter 51 into an AC voltage and outputs it to the second rotating electrical machine 22. The rotation drive of the second rotating electrical machine 22 is enabled by the AC power output from the second inverter 52.

[0023] Also, the DC-DC converter 53 has, as is well known, an upper-arm switch and 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 a power storage device having a terminal voltage of, for example, several hundreds of volts, and is, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery. In the power generation system 10, it is also possible to omit the DC-DC converter 53 and the battery 55 in the PCU 14.

[0024] 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 and 52 and the DC-DC converter 53 is provided as a rotating electric machine driving component for driving the two rotating electric machines 21 and 22. In the power generation system 10 of FIG. 1, in the PCU 14, the inverters 51 and 52 and the DC-DC converter 53 are diverted with their mutual connections remaining as they are. However, as a difference from the hybrid vehicle 100, in the power generation system 10, a power system 90 is connected to the AC power line 56 extending from the first rotating electric machine 21 in addition to the first inverter 51.

[0025] The MG control device 54 is mainly composed of a microcomputer including a processor, a memory, and the like. The MG control device 54 performs switching control for turning on and off the switches 61 and 62 of the upper and lower arms for each phase in the first inverter 51 and the second inverter 52. In the present 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 of the first rotating electric machine 21, and feedback control based on the deviation from the detected current may be performed for the torque command or the current command given as the d-axis and q-axis components of the permanent magnet motor. Regarding the phase command, by giving phase information based on the phase of the system voltage as the angle information at the time of two-phase to three-phase conversion calculation used in the feedback control, the phase or frequency of the first rotating electric machine 21 may be controlled. The MG control device 54 causes the inverters 51 and 52 to perform a power factor correction (PFC) operation, and converts the AC current into a DC current so as to approach a power factor of 1.0 or to reduce high-frequency components. By the grid-connected operation of this PCU 14, for example, a system voltage is output at a frequency of 60 Hz.

[0026] The power generation control device 15 is mainly composed of a microcomputer (equivalent to a "computer"). The microcomputer includes a processor and a memory (storage unit). The microcomputer provides various functions such as an acquisition unit 41 and a rotation control unit 42. The functions provided by the microcomputer can be provided by software recorded in a physical memory device and a computer that executes it, software only, hardware only, or a combination thereof. For example, when the microcomputer is provided by an electronic circuit that is hardware, it can be provided by a digital circuit including a number of logic circuits or an analog circuit. For example, the microcomputer executes a program stored in a non-transitory tangible storage medium as its own storage unit. The program includes, for example, the program of the process shown in FIG. 6 and the like. When the program is executed, the method corresponding to the program is executed. The storage unit is, for example, a non-volatile memory. Note that the program stored in the storage unit can be updated via a network such as the Internet, for example.

[0027] FIG. 4 shows an example of a collinear diagram of the planetary gear mechanism 23. In FIG. 4, the rotation speed of the sun gear 31, that is, the rotation speed of the first rotating electric machine 21, is shown on the S axis, the rotation speed of the planetary carrier 34, that is, the rotation speed of the water turbine 11, is shown on the C axis, and the rotation speed of the ring gear 32 is shown on the R axis. In the collinear diagram, the rotation speeds of the three axes of the planetary gear mechanism 23 are represented linearly. In FIG. 4, in the basic state, the rotation speed of the ring gear 32 is zero, and the planetary carrier 34 rotates as the water turbine 11 rotates due to the water flow. Then, the first rotating electric machine 21 rotates at a rotation speed in accordance with the relationship of the reduction ratios of the three axes of the planetary gear mechanism 23. Power generation is performed by the rotation of the first rotating electric machine 21.

[0028] Incidentally, in the power generation system 10, for example, when the rotational speed of the waterwheel 11 fluctuates in response to a change in the flow velocity of the water flow in the water channel, the rotational speed of the first rotating electrical machine 21 fluctuates along with the rotational fluctuation of the waterwheel 11, and consequently, the frequency of the system voltage output to the power grid system 90 fluctuates. Then, there is a concern that the system connection cannot be continued due to the change in the frequency of the system voltage. That is, as shown by the dashed line in FIG. 4, for example, when the rotational speed (carrier rotational speed) of the waterwheel 11 increases from N1 to N2, the rotational speed (sun gear rotational speed) of the first rotating electrical machine 21 increases along with the increase in the rotation. As a result, the frequency of the system voltage output from the first rotating electrical machine 21 increases, and the system connection cannot be continued. Although not shown in the figure, when the rotational speed (carrier rotational speed) of the waterwheel 11 decreases, it is conceivable that the rotational speed (sun gear rotational speed) of the first rotating electrical machine 21 decreases along with the decrease in the rotation, and again, the system connection cannot be continued.

[0029] Therefore, in the present embodiment, in the planetary gear mechanism 23, when rotational fluctuations occur in two axes, namely the sun gear 31 and the planetary carrier 34, along with a change in the flow velocity of the water flow, the rotational speed of the ring gear 32, which is the remaining one axis, is controlled to suppress the change in the rotational speed of the first rotating electrical machine 21, that is, the change in the frequency of the system voltage.

[0030] In this embodiment, in the power generation control device 15 shown in FIG. 1, the acquisition unit 41 acquires a parameter indicating the rotation state of the first rotating electrical machine 21. Here, the parameter indicating the rotation state of the first rotating electrical machine 21 is the mechanical or electrical frequency of the rotation of the first rotating electrical machine 21, or the frequency, voltage, current, or power of the AC output (AC output voltage waveform) of the first rotating electrical machine 21. In this embodiment, as a means for detecting the parameter, a rotation angle sensor 28 provided on the rotating shaft of the first rotating electrical machine 21 is used, and based on the detection value of the rotation angle sensor 28, the rotation speed Nm of the first rotating electrical machine 21 is acquired as the parameter. The rotation speed Nm corresponds to the mechanical frequency of the rotation of the first rotating electrical machine 21. The parameter may be the mechanical frequency (rotation speed) converted to an electrical frequency in consideration of the number of pole pairs of the first rotating electrical machine 21. In addition, a power generation voltage sensor 29, a current sensor for detecting the phase current of each phase of the first rotating electrical machine 21, etc. may be used as means for detecting the parameter.

[0031] The rotation control unit 42 adjusts the rotation speed of the first rotating electrical machine 21 by controlling the rotation speed of the second rotating electrical machine 22 by operating the second inverter 52 based on the parameter acquired by the acquisition unit 41. At this time, the rotation control unit 42 controls the rotation speed of the second rotating electrical machine 22 by operating the second inverter 52 based on the deviation between the mechanical or electrical frequency of the rotation of the first rotating electrical machine 21, or the frequency of the AC output voltage, and the specified frequency defined by the system voltage frequency of the power system 90. The system voltage frequency is 50 Hz or 60 Hz. In the voltage, current, or power of the AC output voltage waveform of the first rotating electrical machine 21, similar control may be performed based on the deviation from the system voltage waveform of the power system 90.

[0032] When the rotation speed of the ring gear 32 is adjusted by the second rotating electrical machine 22, the change in the rotation speeds of the three shafts of the planetary gear mechanism 23 will be described with reference to FIGS. 5(a) and 5(b).

[0033] In FIG. 5(a), similar to FIG. 4, it is assumed that the rotational speed of the waterwheel 11 (carrier rotational speed) increases from N1 to N2. In this case, as the second rotating electrical machine 22 is rotationally driven in the positive direction, the rotational speed of the ring gear 32 increases in the positive direction. In this case, as the rotational speed of the ring gear 32 in the positive direction increases, the rotational speed of the sun gear 31 decreases. Therefore, even when the rotational speed of the waterwheel 11 changes to the increasing side, an increase in the rotational speed of the first rotating electrical machine 21 (sun gear rotational speed) is suppressed.

[0034] Also, in FIG. 5(b), it is assumed that the rotational speed of the waterwheel 11 (carrier rotational speed) decreases from N1 to N3. In such a case, the second rotating electrical machine 22 is rotationally driven in the negative direction, so that the rotational speed of the ring gear 32 increases in the negative direction. In this case, as the rotational speed of the ring gear 32 in the negative direction increases, the rotational speed of the sun gear 31 increases. Therefore, even when the rotational speed of the waterwheel 11 changes to the decreasing side, a decrease in the rotational speed of the first rotating electrical machine 21 (sun gear rotational speed) is suppressed.

[0035] FIG. 6 is a flowchart showing the processing procedure of power generation control in the power generation system 10. This processing is executed by the power generation control device 15 at a predetermined cycle.

[0036] In FIG. 6, in step S11, the rotational speed Nm of the first rotating electrical machine 21 is acquired. Then, in step S12, it is determined whether the rotational speed Nm is less than a first threshold value TH1 corresponding to the system voltage frequency, and in step S13, it is determined whether the rotational speed Nm is greater than or equal to a second threshold value TH2 corresponding to the system voltage frequency. Each of the threshold values TH1 and TH2 satisfies TH1 > TH2, and is a value determined based on the upper limit value and the lower limit value allowed as the system voltage frequency. For example, when the system voltage frequency is 60 Hz, the first threshold value TH1 may be a value corresponding to 60.1 Hz, and the second threshold value TH2 may be a value corresponding to 59.9 Hz.

[0037] If both steps S12 and S13 are affirmed, the process proceeds to step S14. In step S14, the second rotating electrical machine 22 is set to the rotation stop state.

[0038] If step S12 is negated, that is, when the rotational speed Nm is equal to or higher than the first threshold value TH1, the process proceeds to step S15, and the second rotating electrical machine 22 (MG2) is rotationally driven in the positive rotation direction. As a result, as shown in Fig. 5(a), the rotational speed of the ring gear 32 increases on the positive side, and thus the rotational speed Nm (the sun gear rotational speed) is reduced to less than the first threshold value TH1.

[0039] Also, if step S13 is negated, that is, when the rotational speed Nm is less than the second threshold value TH2, the process proceeds to step S16, and the second rotating electrical machine 22 (MG2) is rotationally driven in the negative rotation direction. As a result, as shown in Fig. 5(b), the rotational speed of the ring gear 32 increases on the negative side, and thus the rotational speed Nm (the sun gear rotational speed) is raised to be equal to or higher than the second threshold value TH2.

[0040] In steps S15 and S16, switching control of the switches 61 and 62 of each phase is performed in the second inverter 52 so that the mechanical or electrical frequency of the rotation of the first rotating electrical machine 21 or the frequency of the AC output voltage matches the specified frequency defined by the system voltage frequency of the power system 90. At this time, the power generation control device 15 calculates an output command and a phase command for driving the second rotating electrical machine 22 based on the deviation amount (deviation) between the current rotational speed Nm of the first rotating electrical machine 21 and the rotational speed corresponding to the system voltage frequency, and transmits these commands to the MG control device 54 of the PCU 14. Then, each inverter 51 and 52 is operated by the MG control device 54. As a result, the rotational speed of the first rotating electrical machine 21 is controlled along with the driving of the second rotating electrical machine 22, and thus the output voltage of the first rotating electrical machine 21 is adjusted to conform to the system voltage.

[0041] Instead of controlling the second inverter 52 so that the mechanical or electrical frequency of the rotation of the first rotating electrical machine 21 or the frequency of the AC output voltage coincides with the specified frequency defined by the system voltage frequency of the power system 90, it is also possible to control the second inverter 52 so that the phase of the AC output voltage of the first rotating electrical machine 21 coincides with the phase defined by the system voltage frequency of the power system 90. Further, the parking lock mechanism 38 may be in an on state (operating state) in step S14 and in an off state (non-operating state) in steps S15 and S16. Step S11 corresponds to the "acquisition unit", and steps S12 to S16 correspond to the "rotation control unit".

[0042] According to the present embodiment described in detail above, the following excellent effects can be obtained.

[0043] In the power generation system 10, the water turbine 11, the first rotating electrical machine 21, and the second rotating electrical machine 22 are respectively connected to the three shafts of the planetary gear mechanism 23, and the generated power of the first rotating electrical machine 21 generated as the water turbine 11 rotates is output to the power system via the AC power line 56. On the other hand, the second rotating electrical machine 22 can be driven by the power supplied from the AC power line 56 via the first inverter 51 and the second inverter 52. Further, the rotational speed of the first rotating electrical machine 21 is adjusted by controlling the rotational speed of the second rotating electrical machine 22 by operating each of the inverters 51 and 52 based on the parameter indicating the rotational state of the first rotating electrical machine 21. Thereby, even if the rotational speed of the water turbine 11 fluctuates due to a change in the flow velocity of the water flow, for example, the rotational speed of the first rotating electrical machine 21 can be adjusted to a desired rotational speed, and as a result, the frequency of the system voltage can be maintained at an appropriate frequency. As a result, power can be appropriately output to the power system 90.

[0044] The power generation system 10 was constructed using the transaxle 13 and the PCU 14 mounted on the hybrid vehicle 100. Therefore, it is possible to contribute to the formation of a recycling-oriented society and the spread of renewable energy at the same time.

[0045] The rotational speed of the second rotating electrical machine 22 is controlled by operating each of the inverters 51, 52 so that the mechanical or electrical frequency of rotation of the first rotating electrical machine 21, or the frequency or phase of the AC output voltage, matches the specified frequency or phase defined by the system voltage frequency of the power system 90. Thereby, the frequency of the system voltage output from the first rotating electrical machine 21 to the power system 90 can be appropriately controlled.

[0046] <Second Embodiment> The second embodiment will be described below, centering on the differences from the first embodiment.

[0047] FIG. 7 is a configuration diagram showing the power generation system 10 in the present embodiment. In FIG. 7, as a difference from FIG. 1, braking devices 111 are connected to the respective shaft portions 27a, 27b fixed to the pair of side gears 24a, 24b in the differential gear 24. The braking device 111 is, for example, an electromagnetic brake, which generates an electromagnetic force by energizing a coil and holds the shaft portions 27a, 27b on both sides of the differential gear 24 in a rotation-stopped state. The braking device 111 applies a braking force to the rotation of the drive shaft 25. Instead of the configuration in which the braking devices 111 are connected to both sides of the shaft portions 27a, 27b, a configuration may be adopted in which the braking device 111 is connected to one side of the shaft portions 27a, 27b and the other side is fixed in a non-rotatable state. The braking device 111 may be a hydraulic brake.

[0048] The braking force of the braking device 111 may be controlled by a duty ratio, or may be adjusted by a frictional resistance in an intermediate connection state like a clutch mechanism, for example.

[0049] In this embodiment, when the first rotating electrical machine 21 generates power, the rotation control unit 42 increases or decreases the braking force of the braking device 111 based on the parameters acquired by the acquisition unit 41 when the second rotating electrical machine 22 is in a rotating state by the operation of each inverter 51, 52 and a predetermined braking force is applied to the drive shaft 25 by the braking device 111. That is, the rotation control unit 42 controls the rotation speed of the ring gear 32 by increasing or decreasing the braking force of the braking device 111. In this case, when the first rotating electrical machine 21 generates power, as shown in the alignment diagram of FIG. 9, the rotation speed of the ring gear 32 is in a positive rotation state (rotation speed Na) due to the positive rotation drive of the second rotating electrical machine 22, and the rotation speed of the ring gear 32 is adjusted by the braking device 111 in that state.

[0050] FIG. 8 is a flowchart showing the power generation control process in this embodiment. In FIG. 8, the same processes as those in FIG. 6 are denoted by the same step numbers and the description thereof is omitted.

[0051] In FIG. 8, when the rotation speed Nm of the first rotating electrical machine 21 is less than the first threshold value TH1 and equal to or greater than the second threshold value TH2 (when both steps S12 and S13 are affirmed), in step S21, the second rotating electrical machine 22 (MG2) is set to a predetermined rotation state, and the braking device 111 is turned on to apply a predetermined braking force to the drive shaft 25.

[0052] When step S12 is negated, that is, when the rotation speed Nm is equal to or greater than the first threshold value TH1, the process proceeds to step S22 to reduce the braking force of the braking device 111. At this time, the second rotating electrical machine 22 remains in the same rotation state, but the rotation speed of the ring gear 32 increases as the braking force is reduced. According to step S22, as shown in FIG. 9(a), in the state where the ring gear 32 is rotating forward by the second rotating electrical machine 22, the rotation speed of the ring gear 32 increases from Na to Nb, so that the rotation speed Nm (sun gear rotation speed) becomes less than the first threshold value TH1.

[0053] Also, when step S13 is negated, that is, when the rotational speed Nm is less than the second threshold value TH2, the process proceeds to step S23 to increase the braking force of the braking device 111. At this time, the second rotating electric machine 22 is maintained in the same rotational state, but the rotational speed of the ring gear 32 is reduced as the braking force increases. According to step S23, as shown in FIG. 9(b), in a state where the ring gear 32 is rotating forward by the second rotating electric machine 22, the rotational speed of the ring gear 32 is reduced from Na to Nc, so that the rotational speed Nm (sun gear rotational speed) becomes equal to or higher than the second threshold value TH2.

[0054] In steps S22 and S23, the braking force (electromagnetic force of the electromagnetic brake) of the braking device 111 is controlled so that the mechanical or electrical frequency of the rotation of the first rotating electric machine 21 or the frequency of the AC output voltage matches the specified frequency defined by the system voltage frequency of the power system 90.

[0055] When generating power by the first rotating electric machine 21 accompanying the rotation of the water turbine 11, when the second rotating electric machine 22 is in a rotating state and a predetermined braking force is applied to the drive shaft 25 by the braking device 111, the braking force of the braking device 111 is increased or decreased based on the rotational speed Nm of the first rotating electric machine 21. In this case, the rotational speed of the ring gear 32 of the planetary gear mechanism 23 is adjusted by the braking force of the braking device 111, and thus the rotational speed of the first rotating electric machine 21 can be controlled to an appropriate value.

[0056] <Third Embodiment> Hereinafter, the third embodiment will be described centering on the differences from the first embodiment.

[0057] FIG. 10 is a configuration diagram showing the power generation system 10 in the present embodiment. In FIG. 10, as a difference from FIG. 1, a resistive load 122 is connected to an AC terminal that outputs AC power in the second inverter 52 via a switch 121. The resistive loads 122 are respectively provided on power lines extending from the AC terminals of each phase in the second inverter 52. The resistive load 122 is, for example, a resistor. By turning on and off (opening and closing) the switch 121, a first state in which the resistive load 122 is disconnected from the AC terminal of the second inverter 52 and a second state in which the resistive load 122 is connected to the AC terminal of the second inverter 52 are switched.

[0058] The power generation control device 15 includes an acquisition unit 41, a rotation control unit 42, and a switching control unit 123. The switching control unit 123 switches between a first state (a state in which the resistive load 122 is disconnected) and a second state (a state in which the resistive load 122 is connected) based on the parameters acquired by the acquisition unit 41 in a power generation state by the first rotating electrical machine 21. The initial state of the switch 121 is off (open). When in the second state, the rotation control unit 42 controls the rotation speed of the ring gear 32 by energizing the resistive load 122 by operating each of the inverters 51 and 52.

[0059] FIG. 11 is a flowchart showing the power generation control process in the present embodiment. In FIG. 11, the same steps are assigned the same step numbers as in FIG. 6, and the description thereof is omitted.

[0060] In FIG. 11, when the rotation speed Nm of the first rotating electrical machine 21 is equal to or greater than the first threshold value TH1 (when step S12 is negated), in step S31, it is determined whether the rotation speed Nm is less than a threshold value THA that is greater than the first threshold value TH1. If the rotation speed Nm is less than the threshold value THA, the process proceeds to step S32, and the switch 121 is turned off. As a result, the resistive load 122 is disconnected from the second inverter 52. Then, in step S15, the second rotating electrical machine 22 (MG2) is rotationally driven in the forward rotation direction.

[0061] Also, if the rotational speed Nm is equal to or higher than the threshold value THA, the process proceeds to step S33, and switch 121 is turned on. As a result, the resistance load 122 is connected to the second inverter 52. Then, in step S34, power is supplied to the resistance load 122 by switching each switch 121 in the inverters 51 and 52. In this case, a part of the output power output from the first rotating electrical machine 21 is consumed as resistance loss associated with load energization. Thereby, the rotational speed Nm (sun gear rotational speed) is reduced to less than the first threshold value TH1. Note that it is also possible to utilize the heat generation due to the resistance loss for other purposes.

[0062] According to the above configuration, for example, even if the rotational speed of the water turbine 11 excessively increases, the rotational speed of the first rotating electrical machine 21 can be controlled to an appropriate value by consuming electrical energy through energization from the second inverter 52 to the resistance load 122.

[0063] Also, when the rotational speed Nm of the first rotating electrical machine 21 is equal to or higher than the first threshold value TH1, if the rotational speed Nm is less than the threshold value THA, control is performed to adjust the rotational speed of the first rotating electrical machine 21 by rotational driving of the second rotating electrical machine 22, while if the rotational speed Nm is equal to or higher than the threshold value THA, a configuration is adopted in which control is performed to adjust the rotational speed of the first rotating electrical machine 21 by energization of the resistance load 122. In this case, for example, by increasing the degree of adjustment of the system voltage by energization of the resistance load 122, even if the degree of deviation from the system voltage frequency is large in the rotational speed of the first rotating electrical machine 21, the rotational speed of the first rotating electrical machine 21 is quickly adjusted.

[0064] <Other Embodiments> The above embodiment may be modified as follows, for example.

[0065] ·In the above-described embodiment, in the planetary gear mechanism 23, the waterwheel 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 each shaft in the planetary gear mechanism 23. For example, in the planetary gear mechanism 23, the waterwheel 11 may be connected to the sun gear 31, the first rotating electric machine 21 may be connected to the planetary carrier 34, and the second rotating electric machine 22 and the differential gear 24 may be connected to the ring gear 32.

[0066] ·In the above-described embodiment, in the PCU 14, the first inverter 51 is used when converting the three-phase AC voltage from the first rotating electric machine 21 into a DC voltage. However, this may be changed to a configuration using a full-wave rectifier circuit composed of a plurality of diodes.

[0067] ·It is also possible to provide a plurality of power generation systems 10 shown in FIG. 1 and connect each of these power generation systems 10 to the power grid 90.

[0068] ·The power generation system 10 may be a wind power generation system that generates electricity by wind energy as renewable energy and outputs the generated electric power to the power grid. In this case, the waterwheel 11 in FIG. 1 is replaced with a windmill.

[0069] ·In the above-described embodiment, the power generation system 10 is constructed by diverting the transaxle 13 and the PCU 14 from the hybrid vehicle 100. However, this may be changed. For example, only the transaxle 13 may be diverted from the hybrid vehicle 100, and a power control unit of a component different from that of the hybrid vehicle 100 may be combined with the transaxle 13 to construct the power generation system 10. It is also possible to construct the power generation system 10 without using the diverted components from the hybrid vehicle 100.

[0070] · The control unit and its method described in the present disclosure may be implemented by a dedicated computer configured by a processor and a memory programmed to execute one or more functions embodied by a computer program. Alternatively, the control unit and its method described in the present disclosure may be implemented by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Or, the control unit and its method described in the present disclosure may be implemented by one or more dedicated computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured by one or more hardware logic circuits. Further, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions to be executed by a computer.

[0071] The technical idea extracted from the above-described embodiment is described below. [Configuration 1] A planetary gear mechanism (23) having a first axis, a second axis, and a third axis, A rotating body (11) connected to the first axis and rotated by the flow of a fluid, A first rotating electrical machine (21) connected to the second axis and generating electric power by the rotation of the second axis, A second rotating electrical machine (22) connected to the third axis, are provided, and the rotation of the rotating body causes the first rotating electrical machine to generate alternating current power, and the generated alternating current power can be output to a power system (90) via an alternating current power line (56) extending from the first rotating electrical machine. A first inverter (51) connected to the alternating current power line and converting the alternating current power output from the first rotating electrical machine into direct current power, The DC terminals on the high potential side and the low potential side are connected to each other with respect to the first inverter, and a second inverter (52) that converts the direct current power output from the first inverter into alternating current power and rotates the second rotating electrical machine by the alternating current power, An acquisition unit (41) that acquires a parameter indicating the rotation state of the first rotating electrical machine Based on the parameters acquired by the acquisition unit, a rotation control unit (42) controls the rotation speed of the third axis in the rotation state of the second rotating electrical machine by operating each inverter, and adjusts the rotation speed of the first rotating electrical machine by controlling the rotation speed; A power generation system (10) comprising the same. [Configuration 2] The power generation system according to Configuration 1, wherein the rotation control unit controls the rotation speed of the third axis by controlling the rotation speed of the second rotating electrical machine by operating each inverter based on the parameters acquired by the acquisition unit. [Configuration 3] The second rotating electrical machine is connected to the third axis of the planetary gear mechanism via a drive shaft (25), A brake device (111) for applying a braking force to the rotation of the drive shaft is provided, The power generation system according to Configuration 1, wherein the rotation control unit increases or decreases the braking force of the brake device based on the parameters acquired by the acquisition unit when the second rotating electrical machine is in a rotating state by operating each inverter and a predetermined braking force is applied to the drive shaft by the brake device, thereby controlling the rotation speed of the third axis. [Configuration 4] The acquisition unit acquires, as the parameters, the mechanical or electrical frequency of the rotation of the first rotating electrical machine, or the frequency, voltage, current, or power of the AC output of the first rotating electrical machine, The power generation system according to any one of Configurations 1 to 3, wherein the rotation control unit controls the rotation speed of the third axis so that the mechanical or electrical frequency of the rotation of the first rotating electrical machine, or the frequency or phase of the AC output voltage, matches the specified frequency or phase defined by the system voltage frequency of the power grid. [Configuration 5] A resistive load (122) is connected to an AC terminal that outputs AC power in the second inverter via a switch (121), In a power generation state by the first rotating electrical machine accompanying the rotation of the rotating body, based on the parameter acquired by the acquisition unit, a switching control unit (123) is provided that switches between a first state in which the resistive load is disconnected from the AC terminals of the second inverter and a second state in which the resistive load is connected to the AC terminals of the second inverter. The rotation control unit controls the rotation speed of the third axis by energizing the resistive load by operating each inverter when in the second state, for the power generation system according to Configuration 1. [Configuration 6] 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 first rotating electrical machine as the second axis, the ring gear is connected to the second rotating electrical machine as the third axis, and the planetary carrier is connected to the rotating body as the first axis. The rotation control unit controls the rotation speed of the ring gear by the second rotating electrical machine based on the parameter acquired by the acquisition unit, for the power generation system according to any one of Configurations 1 to 5. [Configuration 7] The planetary gear mechanism, the first rotating electrical machine, and the second rotating electrical machine are in-vehicle components mounted as a transaxle (13) in a hybrid vehicle. In the transaxle, the rotating body is connected to the first axis of the planetary gear mechanism in place of the engine of the hybrid vehicle. The first inverter and the second inverter are power converters that adjust the respective power input and output to the first rotating electrical machine and the second rotating electrical machine in the hybrid vehicle, for the power generation system according to any one of Configurations 1 to 6.

Explanation of Reference Numerals

[0072] 10... power generation system, 11... water turbine, 21... first rotating electrical machine, 22... second rotating electrical machine, 23... planetary gear mechanism, 41... acquisition unit, 42... rotation control unit, 51... first inverter, 52... second inverter, 56... AC power line, 90... power system.

Claims

1. 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 first rotating electrical machine (21) connected to the second shaft and generating electricity by the rotation of the second shaft; A second rotating electrical machine (22) connected to the third shaft; Comprising: by rotating the rotating body, alternating current power generation of the first rotating electrical machine is performed, and the generated alternating current power can be output to a power system (90) via an alternating current power line (56) extending from the first rotating electrical machine; A first inverter (51) connected to the alternating current power line and converting the alternating current power output from the first rotating electrical machine into direct current power; A second inverter (52) in which the DC terminals on the high potential side and the low potential side are connected to the first inverter, converting the DC power output from the first inverter into AC power, and rotating the second rotating electrical machine with the AC power; An acquisition unit (41) for acquiring parameters indicating the rotation state of the first rotating electrical machine; A rotation control unit (42) that controls the rotation speed of the third shaft in the rotation state of the second rotating electrical machine by operating the inverters based on the parameters acquired by the acquisition unit, and adjusts the rotation speed of the first rotating electrical machine by the rotation speed control; A power generation system (10) comprising.

2. The power generation system according to claim 1, wherein the rotation control unit controls the rotation speed of the third shaft by controlling the rotation speed of the second rotating electrical machine by operating the inverters based on the parameters acquired by the acquisition unit.

3. The second rotating electrical machine is connected to the third shaft of the planetary gear mechanism via a drive shaft (25), A brake device (111) for applying a braking force to the rotation of the drive shaft is provided, The power generation system according to claim 1, wherein the rotation control unit increases or decreases the braking force of the brake device based on the parameters acquired by the acquisition unit when the second rotating electrical machine is in a rotating state by operating the inverters and a predetermined braking force is applied to the drive shaft by the brake device, thereby controlling the rotation speed of the third shaft.

4. The acquisition unit acquires, as the parameters, the mechanical or electrical frequency of the rotation of the first rotating electrical machine, or the frequency, voltage, current, or power of the AC output of the first rotating electrical machine. The rotation control unit controls the rotational speed of the third axis so that the mechanical or electrical frequency of the rotation of the first rotating electrical machine, or the frequency or phase of the AC output voltage, matches a specified frequency or phase defined by the system voltage frequency of the power system. The power generation system according to any one of claims 1 to 3.

5. A resistive load (122) is connected to an AC terminal that outputs AC power in the second inverter via a switch (121). A switching control unit (123) is provided that switches between a first state in which the resistive load is disconnected from the AC terminal of the second inverter and a second state in which the resistive load is connected to the AC terminal of the second inverter based on the parameter acquired by the acquisition unit in a power generation state by the first rotating electrical machine accompanying the rotation of the rotating body. The rotation control unit controls the rotational speed of the third axis by energizing the resistive load by operating each inverter when in the second state. The power generation system according to claim 1.

6. 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 first rotating electrical machine as the second axis, the ring gear is connected to the second rotating electrical machine as the third axis, and the planetary carrier is connected to the rotating body as the first axis. The rotation control unit controls the rotational speed of the ring gear by the second rotating electrical machine based on the parameter acquired by the acquisition unit. The power generation system according to claim 1.

7. The planetary gear mechanism, the first rotating electrical machine, and the second rotating electrical machine are in-vehicle components mounted as a transaxle (13) in a hybrid vehicle. In the transaxle, the rotating body is connected to the first axis of the planetary gear mechanism in place of the engine of the hybrid vehicle. The first inverter and the second inverter are power converters that adjust the respective power input and output to the first rotating electrical machine and the second rotating electrical machine in the hybrid vehicle. The power generation system according to claim 1.

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