Control device, mobile device, control method and program

Abstract

The present invention provides a control device for optimally discharging a smoothing capacitor. [Solution] The control device 50 comprises a control unit 64, a rotation speed comparison unit 58, a voltage comparison unit 60, and a voltage utilization rate comparison unit 62. When the rotation speed comparison unit 58 determines that the rotation speed of the generator is less than a rotation speed threshold, the voltage comparison unit 60 determines that the capacitor voltage is equal to or greater than a voltage threshold, and the voltage utilization rate comparison unit 62 determines that the voltage utilization rate is less than or equal to a voltage utilization rate threshold, the control unit 64 performs power control.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a control device, a mobile object, a control method, and a program.

BACKGROUND ART

[0002] Japanese Patent Laid-Open No. 2006-352971 discloses an apparatus that discharges electric charge stored in a capacitor inside an inverter.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0003]

PATENT DOCUMENT 1

SUMMARY OF THE INVENTION

PROBLEM TO BE SOLVED BY THE INVENTION

[0004] It is desired to suitably perform discharge of a smoothing capacitor.

[0005] The present disclosure aims to solve the above-mentioned problem.

MEANS FOR SOLVING THE PROBLEM

[0006] A first aspect of the present disclosure is a control device provided in a power supply system equipped with a power converter that converts AC power output from a generator into DC power, comprising: a control unit that reduces the capacitor voltage, which is the voltage across the smoothing capacitor, by performing power control to control the power converter so that power is supplied from a smoothing capacitor provided in the power converter to the generator; a rotation speed comparison unit that compares the rotation speed of the generator with a predetermined rotation speed threshold; a voltage comparison unit that compares the capacitor voltage with a predetermined voltage threshold; and a voltage utilization rate comparison unit that compares the voltage utilization rate, which is the ratio of the voltage applied to the generator to the capacitor voltage, with a predetermined voltage utilization rate threshold, wherein the control unit performs the power control when the rotation speed comparison unit determines that the rotation speed of the generator is less than the rotation speed threshold, the voltage comparison unit determines that the capacitor voltage is equal to or greater than the voltage threshold, and the voltage utilization rate comparison unit determines that the voltage utilization rate is less than or equal to the voltage utilization rate threshold.

[0007] A second aspect of this disclosure is a mobile body comprising a power supply system equipped with a control device according to the first aspect.

[0008] A third aspect of the present disclosure is a control method for a power supply system equipped with a power converter that converts AC power output from a generator into DC power, comprising: a control step of reducing the capacitor voltage, which is the voltage across the smoothing capacitor, by having one or more processors perform power control to control the power converter so that power is supplied from a smoothing capacitor provided in the power converter to the generator; a rotation speed comparison step in which the one or more processors compare the rotation speed of the generator with a predetermined rotation speed threshold; a voltage comparison step in which the one or more processors compare the capacitor voltage with a predetermined voltage threshold; and a voltage utilization rate comparison step in which the one or more processors compare the voltage utilization rate, which is the ratio of the voltage applied to the generator to the capacitor voltage, with a predetermined voltage utilization rate threshold, wherein the rotation speed comparison step determines that the rotation speed of the generator is less than the rotation speed threshold, the voltage comparison step determines that the capacitor voltage is equal to or greater than the voltage threshold, and the voltage utilization rate comparison step determines that the voltage utilization rate is less than or equal to the voltage utilization rate threshold, and the control step performs the power control.

[0009] A fourth aspect of this disclosure is a program for causing a computer to execute the control method according to the third aspect. [Effects of the Invention]

[0010] According to this disclosure, the discharge of the smoothing capacitor can be performed effectively. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic diagram of the moving object. [Figure 2] Figure 2 is a schematic diagram of the power supply system. [Figure 3] Figure 3 is the circuit diagram of the PCU. [Figure 4] Figure 4 is a control block diagram of the control device. [Figure 5] Figure 5 is a block diagram of the control unit. [Figure 6] Figures 6A and 6B show the dq coordinate system. [Figure 7] Figure 7 is a flowchart showing the PCU shutdown process. [Figure 8] Figure 8 is a time chart showing the sequence of events after the power generation equipment was ordered to be shut down. [Modes for carrying out the invention]

[0012] An electric mobile device equipped with a power generation system is being developed. The power generation system, for example, comprises a gas turbine engine, a generator, and a PCU (Power Control Unit). The output shaft of the gas turbine engine is connected to the generator's rotor. The gas turbine engine's operation causes the generator to output alternating current (AC) power. The PCU converts the AC power output from the generator into DC power and supplies it to load devices, etc.

[0013] The PCU is equipped with a smoothing capacitor to suppress ripple. When the generator is used as a power source for the load device, the smoothing capacitor is charged. On the other hand, when the generator stops operating, the smoothing capacitor needs to be discharged. For example, the smoothing capacitor can be discharged by supplying power from the smoothing capacitor to the generator.

[0014] However, if the voltage of the smoothing capacitor becomes too low while the generator is still rotating, there is a risk of overcurrent occurring in the PCU. This disclosure makes it possible to suitably discharge the smoothing capacitor provided in the PCU.

[0015] [1 Mobile Unit 100] Figure 1 is a schematic diagram of a moving body 100. The moving body 100 according to one embodiment is an electric vertical takeoff and landing aircraft (eVTOL aircraft). The moving body 100 includes eight VTOL rotors 102. The VTOL rotors 102 generate thrust in the upward direction relative to the airframe 104. The moving body 100 includes eight electric motors 106. One electric motor 106 drives one VTOL rotor 102. The moving body 100 has two cruise rotors 108. The cruise rotors 108 generate thrust in the forward direction relative to the airframe 104. The moving body 100 includes four electric motors 110. Two electric motors 110 drive one cruise rotor 108. The moving body 100 includes one or more power supply systems 10. The moving body 100 is not limited to an aircraft, and may be a ship, an automobile, a train, or the like.

[0016] [2 Configuration of Power Supply System 10] Figure 2 is a schematic diagram of the power supply system 10. The power supply system 10 is provided in the moving body 100. In the power supply system 10, power can be supplied from the power generation device 12 to the load device 16 and the power storage device 18 via the power supply circuit 14. Further, in the power supply system 10, power can be supplied from the power storage device 18 to the load device 16. Further, in the power supply system 10, power can be supplied from the power storage device 18 to the power generation device 12 in response to an operation on the backflow prevention device 40.

[0017] Power supply system 10 includes a power generation device 12. The power generation device 12 includes a fuel supply device 20, a gas turbine engine 22, a generator 24, and a PCU (power conversion unit) 26. The fuel supply device 20 includes a fuel tank, an electric pump, and a shut-off valve (all not shown). The electric pump supplies fuel drawn from the fuel tank to the combustor of the gas turbine engine 22. The gas turbine engine 22 includes a compressor, a combustor, and a turbine (all not shown). An output shaft 23 of the gas turbine engine 22 is connected to a rotor (not shown) of the generator 24. The generator 24 is a motor-generator that can also function as an electric motor. As the output shaft 23 of the gas turbine engine 22 rotates, the rotor of the generator 24 rotates. Thereby, the generator 24 outputs, for example, three-phase AC power.

[0018] The PCU 26 can function as an AC-DC converter and an inverter. An AC terminal of the PCU 26 is connected to an output terminal of the generator 24. A DC terminal of the PCU 26 is connected to a power supply circuit 14. The PCU 26 can convert three-phase AC power input from the AC terminal into DC power and output the DC power to the power supply circuit 14 connected to the DC terminal. The PCU 26 can also convert DC power input from the DC terminal into three-phase AC power and output the three-phase AC power to the generator 24 connected to the AC terminal. Further, the PCU 26 can convert electric power stored in a smoothing capacitor 30 into three-phase AC power and output the three-phase AC power to the generator 24 connected to the AC terminal.

[0019] Figure 3 is a circuit diagram of the PCU 26. The PCU 26 includes three power element units 28 respectively corresponding to the three-phase voltages output from the generator 24, and a smoothing capacitor 30. The configurations of the three power element units 28 are identical to each other.

[0020] The power element section 28 has an upper arm 32 and a lower arm 34. Each of the upper arm 32 and the lower arm 34 is equipped with a switching element 36 and a diode 38. In the power element section 28, the switching element 36 of the upper arm 32 and the switching element 36 of the lower arm 34 are connected in series with each other. The first end of the switching element 36 of the upper arm 32 is connected to the positive terminal wiring of the PCU 26. The second end of the switching element 36 of the upper arm 32 and the first end of the switching element 36 of the lower arm 34 are connected to one of the output terminals of the generator 24. The second end of the switching element 36 of the lower arm 34 is connected to the negative terminal wiring of the PCU 26. The anode of the diode 38 is connected to the second end of the switching element 36. The cathode of the diode 38 is connected to the first end of the switching element 36.

[0021] Returning to Figure 2, the explanation continues. The power supply system 10 includes a load device 16. The load device 16 includes one or more electric motors 106 and one or more electric motors 110 as shown in Figure 1. An inverter (not shown) is connected to each of the electric motors 106 and 110. The inverter converts the input DC power into three-phase AC power. The electric motors 106 and 110 are driven by the three-phase AC power. The load device 16 may also include a DC-DC converter and a low-voltage drive device (neither shown).

[0022] The power supply system 10 includes a power storage device 18. The power storage device 18 is connected in parallel with the PCU 26 to the power supply circuit 14. The power storage device 18 includes a battery (e.g., a lithium-ion battery).

[0023] The power supply system 10 includes a reverse current prevention device 40. The reverse current prevention device 40 is located in the power supply circuit 14. The reverse current prevention device 40 restricts the supply of power from the energy storage device 18 to the power generation device 12. The reverse current prevention device 40 includes a diode (not shown). The reverse current prevention device 40 also includes a transistor that bypasses the diode (not shown). The transistor allows the supply of power from the energy storage device 18 to the power generation device 12, for example, when an ON signal is supplied to it.

[0024] The power supply system 10 includes a resolver 42, three current sensors 44, and a voltage sensor 46. The resolver 42 detects the rotation angle of the output shaft 23 of the gas turbine engine 22 protruding from the generator 24. Each current sensor 44 detects one of the three phase currents flowing from one of the generator 24 and the PCU 26 to the other. If two phase currents are known, the remaining phase current can be calculated. Therefore, the power supply system 10 may be equipped with two current sensors 44. The voltage sensor 46 detects the voltage across the smoothing capacitor 30.

[0025] Hereafter, the rotation angle of the output shaft 23 of the gas turbine engine 22 will also be referred to as the rotation angle of the gas turbine engine 22. Similarly, the angular velocity of the output shaft 23 of the gas turbine engine 22 will also be referred to as the angular velocity of the gas turbine engine 22. Furthermore, the rotational speed of the output shaft 23 of the gas turbine engine 22 will also be referred to as the rotational speed of the gas turbine engine 22. In addition, the voltage across the smoothing capacitor 30 will also be referred to as the capacitor voltage.

[0026] [3 Control device 50] The power supply system 10 includes a control device 50. Figure 4 is a control block diagram of the control device 50. The control device 50 is composed of, for example, an ECU (Electronic Control Unit).

[0027] The control device 50 comprises an arithmetic unit 52 and a storage unit 54. The arithmetic unit 52 is, for example, a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). The arithmetic unit 52 has a cooling determination unit 56, a rotational speed comparison unit 58, a voltage comparison unit 60, a voltage utilization rate comparison unit 62, and a control unit 64. The cooling determination unit 56, rotational speed comparison unit 58, voltage comparison unit 60, voltage utilization rate comparison unit 62, and control unit 64 are realized by the execution of a program stored in the storage unit 54 in the arithmetic unit 52. At least a part of the cooling determination unit 56, rotational speed comparison unit 58, voltage comparison unit 60, voltage utilization rate comparison unit 62, and control unit 64 may be realized by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array). At least a portion of the cooling determination unit 56, rotational speed comparison unit 58, voltage comparison unit 60, voltage utilization rate comparison unit 62, and control unit 64 may be implemented by an electronic circuit including discrete devices.

[0028] The storage unit 54 is a computer-readable, non-transient, tangible storage medium. The storage unit 54 is composed of volatile memory (not shown) and non-volatile memory (not shown). The volatile memory is, for example, RAM (Random Access Memory). The non-volatile memory is, for example, ROM (Read Only Memory), flash memory, etc. Data is stored in the volatile memory, for example. Programs, tables, maps, etc. are stored in the non-volatile memory, for example. At least a part of the storage unit 54 may be provided in the processor, integrated circuit, etc. described above.

[0029] The cooling determination unit 56 determines whether or not the cooling of the gas turbine engine 22 has been completed. This determination is called the cooling determination. The cooling determination unit 56 may perform the cooling determination by obtaining information indicating the temperature of the gas turbine engine 22 from a sensor (not shown). The cooling determination unit 56 may perform the cooling determination by other methods.

[0030] The rotational speed comparison unit 58 compares the rotational speed of the generator 24 with a predetermined rotational speed threshold. The rotational speed comparison unit 58 also determines whether the rotational speed of the generator 24 is less than the rotational speed threshold. The rotational speed threshold is a boundary value used to determine whether or not to start discharge control of the smoothing capacitor 30. For example, the rotational speed threshold is set to the rotational speed when the fuel supply to the gas turbine engine 22 has stopped. The rotational speed threshold can be set arbitrarily. The rotational speed threshold is stored in advance in the storage unit 54.

[0031] The voltage comparison unit 60 compares the capacitor voltage with a predetermined voltage threshold. The voltage comparison unit 60 also determines whether the capacitor voltage is equal to or greater than the voltage threshold. The voltage threshold is a boundary value used to determine whether the discharge of the smoothing capacitor 30 is complete. The voltage threshold can be set arbitrarily. The voltage threshold is stored in advance in the storage unit 54.

[0032] The voltage utilization rate comparison unit 62 compares the voltage utilization rate with a predetermined voltage utilization rate threshold. The voltage utilization rate is the ratio of the voltage applied to the generator 24 to the capacitor voltage. A detailed explanation of the voltage utilization rate will be given later. The voltage utilization rate comparison unit 62 also determines whether the voltage utilization rate is less than or equal to the voltage utilization rate threshold. The voltage utilization rate threshold is a boundary value used to determine whether to perform weak torque control or zero torque control. The voltage utilization rate threshold is stored in advance in the storage unit 54.

[0033] The control unit 64 controls the on / off state of each switching element 36 provided in the PCU 26 to control the power supply to the DC terminal side and the power supply to the AC terminal side. The control unit 64 performs various power supply controls. For example, the control unit 64 can perform discharge control to reduce the capacitor voltage. In discharge control, the control unit 64 can perform power reduction control, which controls the PCU 26 so that power is supplied from the smoothing capacitor 30 to the generator 24, and zero torque control, which controls the PCU 26 so that the torque of the generator 24 is zero.

[0034] Figure 5 is a block diagram of the control unit 64. The control unit 64 functions as an angular velocity calculation unit 66, a dq conversion unit 68, a command current generation unit 70, a discharge current generation unit 72, a current control unit 74, an inverse dq conversion unit 76, and a PWM control unit 78.

[0035] The angular velocity calculation unit 66 calculates the angular velocity (ω) of the gas turbine engine 22 based on the rotation angle (θ) detected by the resolver 42. The dq conversion unit 68 calculates the d-axis current value (Id) and the q-axis current value (Iq) based on the rotation angle (θ) detected by the resolver 42 and the phase current values ​​(Iu, Iv, Iw) detected by the current sensors 44.

[0036] The command current generation unit 70 and the discharge current generation unit 72 each generate a d-axis current command value (Id') and a q-axis current command value (Iq'). During normal control, the command current generation unit 70 generates current command values ​​(Id', Iq') for each axis based on torque command values ​​obtained from a management ECU (not shown) that manages the control system of the mobile body 100. On the other hand, the discharge current generation unit 72 generates current command values ​​(Id', Iq') for each axis during discharge control to reduce the capacitor voltage of the smoothing capacitor 30. The command current generation unit 70 and the discharge current generation unit 72 are used selectively.

[0037] The current control unit 74 calculates the control voltage values, namely the d-axis voltage command value (Vd) and the q-axis voltage command value (Vq), based on the angular velocity (ω) calculated by the angular velocity calculation unit 66, the current values ​​(Id, Iq) for each axis calculated by the dq conversion unit 68, and the current command values ​​(Id', Iq') for each axis generated by the command current generation unit 70 or the discharge current generation unit 72. The inverse dq conversion unit 76 calculates the three-phase voltage command values ​​(Vu, Vv, Vw) based on the rotation angle (θ) detected by the resolver 42 and the voltage command values ​​(Vd, Vq) for each axis calculated by the current control unit 74. The PWM control unit 78 performs PWM (Pulse Width Modulation) control of each switching element 36 provided in the PCU 26 based on the three-phase voltage command values ​​(Vu, Vv, Vw) calculated by the inverse dq conversion unit 76.

[0038] [4 Discharge Control] When the mobile unit 100 is stopped, the management ECU, which oversees and manages the control system of the mobile unit 100, instructs each ECU installed in the mobile unit 100 to execute stop control. When the power generator 12 is stopped, the fuel supply to the gas turbine engine 22 is cut off. As a result, the rotational speed of the gas turbine engine 22 decreases.

[0039] The calculation unit 52 performs discharge control to reduce the capacitor voltage of the smoothing capacitor 30 provided in the PCU 26 during the PCU shutdown process after a stop command for the power generator 12. Specifically, the calculation unit 52 performs discharge control when the rotational speed of the gas turbine engine 22 decreases. In the discharge control, the calculation unit 52 performs either low-power control or zero-torque control.

[0040] When the generator 24 is powered by the electricity stored in the smoothing capacitor 30, the capacitor voltage decreases. However, if the capacitor voltage becomes too low before the rotational speed of the gas turbine engine 22 decreases sufficiently, the generator 24 may restart generating power, potentially causing an overcurrent to flow into the PCU 26. To reduce the capacitor voltage while preventing an overcurrent in the PCU 26, it is necessary to discharge the smoothing capacitor 30 gradually. In this embodiment, the voltage utilization rate comparison unit 62 monitors the voltage utilization rate, and the control unit 64 performs discharge control based on the results.

[0041] The reason for using voltage utilization in this embodiment will be explained below. Figures 6A and 6B show the dq coordinate system. Figure 6A shows the voltage limiting ellipse 80 in the coordinate system of the dq axis current. Figure 6B shows the voltage limiting circle 82 in the coordinate system of the dq axis voltage. The voltage limiting circle 82 shown in Figure 6B corresponds to the voltage limiting ellipse 80 shown in Figure 6A. The voltage limiting ellipse 80 indicates the controllable range of the DC voltage in motor control. The voltage limiting circle 82 indicates the allowable range of the voltage command vector 86 in motor control. DC voltage is the maximum voltage that can be supplied to the motor. The DC voltage referred to here corresponds to the capacitor voltage of the smoothing capacitor 30 in this embodiment. The motor referred to here corresponds to the motor generator, i.e., the generator 24, in this embodiment.

[0042] Generally, the voltage limiting ellipse 80 and the voltage limiting circle 82 are determined by the DC voltage and the rotational speed of the motor shaft. When the DC voltage decreases or the rotational speed of the motor shaft increases, the voltage limiting ellipse 80 becomes smaller, that is, the controllable range of the motor decreases. On the other hand, when the DC voltage increases or the rotational speed of the motor shaft decreases, the voltage limiting ellipse 80 becomes larger, that is, the controllable range of the motor increases. Meanwhile, the range of the voltage limiting circle 82 depends on the DC voltage. The motor's control point 84 moves towards the positive q-axis as the motor's rotational speed increases. The amount of movement of the motor's control point 84 decreases as the motor's rotational speed decreases. In order to control the motor, the motor's control point 84 must be kept inside the voltage limiting ellipse 80 and inside the voltage limiting circle 82. As the motor's rotational speed increases, the q-axis voltage component required for control increases. Therefore, the controllable range of the motor becomes substantially smaller. When the control point 84 is outside the voltage limiting ellipse 80 and outside the voltage limiting circle 82, it becomes difficult to control the motor.

[0043] In Figure 6B, the control point 84 is indicated by the d-axis voltage command value (Vd) and the q-axis voltage command value (Vq). The sum of the vector of the d-axis voltage command value and the vector of the q-axis voltage command value corresponds to the voltage command vector 86. The voltage utilization rate is the ratio of the voltage command vector 86 to the DC voltage. The voltage utilization rate is calculated by the following equation (1).

number

[0044] In this embodiment, a voltage utilization threshold is set to ensure that the control point 84 is located inside the voltage limiting ellipse 80 and inside the voltage limiting circle 82. The voltage utilization threshold is 1 or less. If the voltage utilization is less than or equal to the voltage utilization threshold, the control point 84 will be located inside the voltage limiting ellipse 80 and inside the voltage limiting circle 82. This allows the control unit 64 to perform power-pushing control on the generator 24 at the control point 84. This control is called weak-pushing control. Weak-pushing control is a control that gradually reduces the capacitor voltage by gradually discharging the smoothing capacitor 30.

[0045] As mentioned above, the voltage limiting ellipse 80 and the voltage limiting circle 82 are determined by the DC voltage (capacitor voltage) and the rotational speed of the motor shaft (rotational speed of the generator 24). When weak-speed control is performed, the control point 84 may shift outside the voltage limiting ellipse 80 and outside the voltage limiting circle 82. In this case, the voltage utilization rate exceeds the voltage utilization rate threshold. If the voltage utilization rate exceeds the voltage utilization rate threshold, the control unit 64 temporarily stops weak-speed control and performs zero-torque control, which allows only the d-axis current to flow. As a result, the control point 84 returns to inside the voltage limiting ellipse 80 and inside the voltage limiting circle 82. Then, the voltage utilization rate becomes below the voltage utilization rate threshold.

[0046] [5 actions] Figure 7 is a flowchart showing the PCU shutdown process. Figure 8 is a time chart after the shutdown of the power generator 12 has been instructed. When the mobile unit 100 is stopped, the management ECU installed in the mobile unit 100 instructs the engine ECU (not shown), which controls the fuel supply device 20, and the control device 50, which controls the PCU 26, to shut down the power generator 12. The engine ECU performs the shutdown process of the gas turbine engine 22 in response to the shutdown instruction. Meanwhile, the control device 50 performs the shutdown process of the PCU 26 shown in Figure 7 in response to the shutdown instruction. Of steps S1 to S9 in Figure 7, steps S4 to S7 correspond to discharge control.

[0047] In step S1, the control unit 64 performs normal torque control. In step S2, the cooling determination unit 56 determines whether the cooling of the gas turbine engine 22 is complete. If the cooling of the gas turbine engine 22 is complete (step S2: YES), the process proceeds to step S3. In this case, the fuel supply to the gas turbine engine 22 is shut off. On the other hand, if the cooling of the gas turbine engine 22 is not complete (step S2: NO), the process returns to step S1.

[0048] Furthermore, once the cooling of the gas turbine engine 22 is complete, the engine ECU cuts off the fuel supply to the gas turbine engine 22. As a result, the rotational speed of the gas turbine engine 22 and the generator 24 gradually decrease.

[0049] When the process moves from step S2 to step S3, the rotational speed comparison unit 58 compares the rotational speed of the generator 24 with a rotational speed threshold. The rotational speed comparison unit 58 determines whether the rotational speed of the generator 24 has decreased to a level at which discharge control can be performed. If the rotational speed of the generator 24 is less than the rotational speed threshold (step S3: YES), the process moves to step S4. On the other hand, if the rotational speed of the generator 24 is greater than or equal to the rotational speed threshold (step S3: NO), the determination in step S3 is repeated.

[0050] When the process moves from step S3 to step S4, the voltage comparison unit 60 compares the capacitor voltage of the smoothing capacitor 30 with a voltage threshold. If the capacitor voltage is greater than or equal to the voltage threshold (step S4: YES), the process moves to step S5. On the other hand, if the capacitor voltage is less than the voltage threshold (step S4: NO), the process moves to step S8.

[0051] When the process moves from step S4 to step S5, the voltage utilization rate comparison unit 62 compares the voltage utilization rate with the voltage utilization rate threshold. Here, the voltage utilization rate comparison unit 62 calculates the voltage utilization rate using equations (1) to (4) above. The voltage utilization rate comparison unit 62 uses the most recent voltage command values ​​for each axis as the d-axis voltage command value (Vd) and q-axis voltage command value (Vq) in equation (2) above. If the voltage utilization rate is less than or equal to the voltage utilization rate threshold (step S5: YES), the process moves to step S6. On the other hand, if the voltage utilization rate is greater than the voltage utilization rate threshold (step S5: NO), the process moves to step S7.

[0052] When the system transitions from step S5 to step S6, the control unit 64 performs power reduction control on the generator 24. As shown in Figure 8, the capacitor voltage of the smoothing capacitor 30 gradually decreases as the control unit 64 continues to perform power reduction control.

[0053] When the process moves from step S5 to step S7, the control unit 64 performs zero-torque control of the generator 24. As shown in Figure 8, the voltage utilization rate decreases as the control unit 64 continues to perform zero-torque control. The capacitor voltage of the smoothing capacitor 30 decreases as a result of the zero-torque control. However, the rate of decrease in capacitor voltage due to zero-torque control is smaller than the rate of decrease in capacitor voltage due to low-power control.

[0054] At the stage of transitioning from step S4 to step S8, the discharge of the smoothing capacitor 30 is substantially complete. In this state, the control unit 64 performs zero torque control of the generator 24 for a predetermined time. This makes it possible to quickly restart the power supply system 10 when it is necessary to restart the power supply system 10 a short time after the gas turbine engine 22 has stopped.

[0055] In step S9, the control unit 64 turns off the gates of each switching element of the PCU 26 and stops controlling the PCU 26.

[0056] Note that the PCU shutdown process shown in Figure 7 can be modified in various ways. For example, the process in step S8 can be omitted.

[0057] In this embodiment, the voltage utilization rate comparison unit 62 monitors the voltage utilization rate and determines whether the voltage utilization rate is below the voltage utilization rate threshold. That is, the voltage utilization rate comparison unit 62 determines whether the control point 84 of the generator 24 is located inside the voltage limiting ellipse 80 and inside the voltage limiting circle 82. The control unit 64 performs power control to promote the discharge of the smoothing capacitor 30 when the control point 84 of the generator 24 is located inside the voltage limiting ellipse 80 and inside the voltage limiting circle 82. As a result, the smoothing capacitor 30 can be discharged according to the degree of decrease in the rotational speed of the generator 24, thereby preventing overcurrent from flowing to the PCU 26 due to power generation by the generator 24.

[0058] According to this embodiment, the capacitor voltage of the smoothing capacitor 30 can be reduced while simultaneously reducing the rotational speed of the gas turbine engine 22. In other words, the stopping process of the gas turbine engine 22 and the discharge of the smoothing capacitor 30 can be performed simultaneously. Therefore, the stopping process of the power generation device 12 can be performed efficiently.

[0059] [6 Note] The following additional information is disclosed regarding the above embodiment.

[0060] (Note 1) The control device (50) of this disclosure is a control device provided in a power supply system (10) which includes a power converter (26) that converts AC power output from a generator (24) into DC power, and includes a control unit (64) that reduces the capacitor voltage, which is the voltage across the smoothing capacitor, by performing power control to control the power converter so that power is supplied from a smoothing capacitor (30) provided in the power converter to the generator, and a rotation speed comparison unit (58) that compares the rotation speed of the generator with a predetermined rotation speed threshold, and the capacitor The control unit includes a voltage comparison unit (60) that compares the capacitor voltage with a predetermined voltage threshold, and a voltage utilization rate comparison unit (62) that compares the voltage utilization rate, which is the ratio of the voltage applied to the generator to the capacitor voltage, with a predetermined voltage utilization rate threshold. The control unit performs the power control when the rotation speed comparison unit determines that the rotation speed of the generator is less than the rotation speed threshold, the voltage comparison unit determines that the capacitor voltage is equal to or greater than the voltage threshold, and the voltage utilization rate comparison unit determines that the voltage utilization rate is less than or equal to the voltage utilization rate threshold.

[0061] With the above configuration, the smoothing capacitor can be discharged according to the degree of decrease in the generator's rotational speed, thereby preventing overcurrent from flowing to the power converter due to the generator's power generation.

[0062] (Note 2) In the control device described in Appendix 1, if the voltage comparison unit determines that the capacitor voltage is less than the voltage threshold, the control unit may perform zero torque control, which is a control to set the torque of the generator to zero.

[0063] (Note 3) In the control device described in Appendix 1, if the voltage utilization rate comparison unit determines that the voltage utilization rate is greater than the voltage utilization rate threshold, the control unit may perform zero torque control, which is a control to set the torque of the generator to zero.

[0064] (Note 4) In the control device described in Appendix 1, the control unit may perform the power control when stopping the generator.

[0065] (Note 5) The mobile body (100) of this disclosure includes a power supply system equipped with a control device as described in any one of the appendices 1 to 4.

[0066] (Note 6) The control method of the present disclosure is a control method for a power supply system equipped with a power converter that converts AC power output from a generator into DC power, comprising: a control step (step S6) in which one or more processors perform power control to control the power converter so that power is supplied from a smoothing capacitor provided in the power converter to the generator, thereby reducing the capacitor voltage, which is the voltage across the smoothing capacitor; a rotation speed comparison step (step S3) in which one or more processors compare the rotation speed of the generator with a predetermined rotation speed threshold; and one or more processors pre-set the capacitor voltage The control step includes a voltage comparison step (step S4) in which the voltage is compared with a predetermined voltage threshold, and a voltage utilization rate comparison step (step S5) in which one or more processors compare the voltage utilization rate, which is the ratio of the voltage applied to the generator to the capacitor voltage, with a predetermined voltage utilization rate threshold. The control step performs the power control when the rotational speed of the generator is determined to be less than the rotational speed threshold in the rotational speed comparison step, the capacitor voltage is determined to be equal to or greater than the voltage threshold in the voltage comparison step, and the voltage utilization rate is determined to be less than or equal to the voltage utilization rate threshold in the voltage utilization rate comparison step.

[0067] (Note 7) The program disclosed herein causes a computer to execute the control method described in Appendix 6.

[0068] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the intent of this disclosure derived from the claims and their equivalents. These embodiments can also be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above. [Explanation of Symbols]

[0069] 10…Power supply system 24…Generator 26...PCU (Power Control Unit) 30...Smoothing Capacitor 50...Control device 58...Rotation speed comparison unit 60...Voltage comparison section 62...Voltage utilization rate comparison section 64...Control unit 100...Mobile unit

Claims

1. A control device provided in a power supply system that includes a power conversion device that converts AC power output from a generator into DC power, A control unit that reduces the capacitor voltage, which is the voltage across the smoothing capacitor, by performing power control on the power converter so that power is supplied from the smoothing capacitor provided in the power converter to the generator, A rotation speed comparison unit that compares the rotation speed of the generator with a predetermined rotation speed threshold, A voltage comparison unit that compares the capacitor voltage with a predetermined voltage threshold, A voltage utilization rate comparison unit compares the voltage utilization rate, which is the ratio of the voltage applied to the generator to the capacitor voltage, with a predetermined voltage utilization rate threshold. Equipped with, A control device in which, when the rotation speed comparison unit determines that the rotation speed of the generator is less than the rotation speed threshold, the voltage comparison unit determines that the capacitor voltage is equal to or greater than the voltage threshold, and the voltage utilization rate comparison unit determines that the voltage utilization rate is less than or equal to the voltage utilization rate threshold, the control unit performs the power control.

2. In the control device according to claim 1, A control device in which, when the voltage comparison unit determines that the capacitor voltage is less than the voltage threshold, the control unit performs zero torque control, which is a control to set the torque of the generator to zero.

3. In the control device according to claim 1, A control device in which, when the voltage utilization rate comparison unit determines that the voltage utilization rate is greater than the voltage utilization rate threshold, the control unit performs zero torque control, which is a control to set the torque of the generator to zero.

4. In the control device according to claim 1, The control unit is a control device that performs the power control when the generator is stopped.

5. A mobile body comprising a power supply system equipped with a control device according to any one of claims 1 to 4.

6. A control method for a power supply system equipped with a power conversion device that converts AC power output from a generator into DC power, A control step in which one or more processors perform power control to control the power converter so that power is supplied from the smoothing capacitor provided in the power converter to the generator, thereby reducing the capacitor voltage, which is the voltage across the smoothing capacitor, The one or more processors perform a rotational speed comparison step in which they compare the rotational speed of the generator with a predetermined rotational speed threshold, The one or more processors perform a voltage comparison step in which they compare the capacitor voltage with a predetermined voltage threshold, The one or more processors perform a voltage utilization comparison step in which they compare the voltage utilization rate, which is the ratio of the voltage applied to the generator to the capacitor voltage, with a predetermined voltage utilization rate threshold, Equipped with, A control method in which, in the rotation speed comparison step, it is determined that the rotation speed of the generator is less than the rotation speed threshold, and in the voltage comparison step, it is determined that the capacitor voltage is equal to or greater than the voltage threshold, and in the voltage utilization rate comparison step, it is determined that the voltage utilization rate is equal to or less than the voltage utilization rate threshold, and in the control step, the power control is performed.

7. A program for causing a computer to execute the control method described in claim 6.

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