Inverter controller and control method

Abstract

To provide an inverter controller capable of improving a cosmic ray tolerance dose of an inverter without an increase in costs and increase in system weight.SOLUTION: An inverter controller 600 comprises: a voltage application total time determination unit 602 for determining a voltage application total time of each of a plurality of inverters 201, 202, 207, 208; an operation pattern determination unit 603 that receives input of operation information on a flying body 501, determines an operation pattern of the flying body 501, and outputs the operation pattern to the voltage application total time determination unit 602; an inverter control unit 604 that according to an instruction of the voltage application total time determination unit 602 and current information and voltage information on the plurality of inverters 201, 202, 207, 208, controls the plurality of inverters 201, 202, 207, 208; and a changeover control unit 605 that according to information of the inverter control unit 604, controls connection and disconnection between a power supply 300 for the plurality of inverters 201, 202, 207, 208 and the plurality of inverters 201, 202, 207, 208.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an inverter control device and a control method. [Background technology]

[0002] In recent years, aircraft such as passenger planes and vertical take-off and landing aircraft (VTOL aircraft) are becoming increasingly electrified. For example, electric vertical take-off and landing aircraft (eVTOL aircraft) are one example of an electrified aircraft.

[0003] Electrifying the propulsion systems that make up aircraft requires larger capacity and higher reliability for electric components, including motors and inverters, etc. One electric system that achieves both is the open winding system, which uses two inverters to double the voltage applied to the motor windings and drive it efficiently.

[0004] In order to operate an open winding system more efficiently, for example, Patent Document 1 discloses a "motor drive system capable of preventing a decrease in efficiency at low output," and states that "it is desirable to reduce inverter loss by operating with a single inverter at low output."

[0005] In this way, under load conditions where the motor is driven at an output lower than the rated output, high efficiency is achieved by driving the motor using only one of the two inverters. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2019-62726 A Summary of the Invention [Problem to be solved by the invention]

[0007] In the high-altitude environment where aircraft fly, the intensity of cosmic rays increases significantly. This significantly increases the probability of accidental failures in inverters, which consist of semiconductor switching elements and gate drive circuits, and reduces their reliability. In particular, the decrease in inverter reliability is significant during cruising at high altitudes. To increase the reliability of inverters, it is necessary to improve their tolerance to cosmic rays, and reducing the voltage applied to the semiconductor switching elements is an effective means of achieving this.

[0008] The configuration described in Patent Document 1 is effective in increasing the efficiency of the inverter, but because a DC voltage is constantly applied to the semiconductor switching elements of the two inverters, the inverters have low tolerance to cosmic rays, making it necessary to take measures to protect them from cosmic rays.

[0009] Possible measures to improve the cosmic ray tolerance of open winding systems include improving the voltage resistance of the semiconductor switching elements, serializing the semiconductor switching elements, making the inverter multi-stage, and installing a buck-boost converter between the battery and the inverter to make the DC voltage variable. However, the addition of many semiconductor switching elements poses issues of increased costs and increased system weight.

[0010] An object of the present invention is to provide an inverter control device and a control method capable of improving the cosmic ray tolerance of an inverter without increasing costs or system weight. [Means for solving the problem]

[0011] In order to achieve the above object, the present invention is configured as follows.

[0012] The inverter control device includes a total voltage application time determination unit that determines the total voltage application time of each of a plurality of inverters, an operation pattern determination unit that inputs operation information of the aircraft, determines the operation pattern of the aircraft, and outputs the determined operation pattern to the total voltage application time determination unit, an inverter control unit that controls the plurality of inverters in accordance with commands from the total voltage application time determination unit and current information and voltage information of the plurality of inverters, and a switching control unit that controls connection and disconnection between the power supplies of the plurality of inverters and the plurality of inverters in accordance with information from the inverter control unit.

[0013] In addition, in the inverter control method, the total voltage application time of each of the multiple inverters is determined, the flight pattern of the aircraft is determined from flight information of the aircraft, the multiple inverters are controlled according to current information and voltage information of the multiple inverters, and the connection and disconnection of the power sources of the multiple inverters to and from the multiple inverters are controlled. Effect of the Invention

[0014] According to the present invention, it is possible to provide an inverter control device and a control method that can improve the cosmic ray tolerance of an inverter without increasing costs or system weight.

[0015] By efficiently driving the motor inverter that constitutes the propulsion system of an aircraft while reducing the total time that voltage is applied to the semiconductor switching elements, the inverter's tolerance to cosmic rays is improved, thereby improving the reliability of the aircraft and extending the number of flights or the cruising distance.

[0016] Furthermore, since there is no need to add a semiconductor switching element or a capacitor discharge circuit, it is possible to achieve low cost and light weight. [Brief description of the drawings]

[0017] [Figure 1]1 is a schematic diagram showing the configuration of a propulsion system of an aircraft controlled by an inverter control device according to a first embodiment. [Diagram 2] 1 is a functional block diagram of an inverter control device according to a first embodiment. [Diagram 3] FIG. 2 is a diagram showing the flight pattern of an aircraft. [Figure 4] 4 is a flowchart illustrating a control algorithm according to the first embodiment. [Figure 5A] FIG. 1 is a diagram showing an outbound operation pattern in the first embodiment. [Figure 5B] FIG. 11 is a diagram showing the return operation pattern in the first embodiment. [Figure 6] FIG. 11 is a schematic diagram showing the configuration of a propulsion system of an aircraft controlled by an inverter control device according to a second embodiment. [Figure 7] FIG. 11 is a schematic diagram showing the configuration of a propulsion system of an aircraft controlled by an inverter control device according to a third embodiment. [Figure 8A] FIG. 13 is a diagram showing the operation pattern of the fourth embodiment. [Figure 8B] FIG. 13 is a diagram showing the operation pattern of the fourth embodiment. [Figure 9] FIG. 13 is a diagram showing the operation pattern of the fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] An inverter control device according to the present invention will be described below with reference to the drawings. In addition, in the embodiments of the present invention other than the first embodiment, the same parts as those in the first embodiment are given the same reference numerals and the description will be omitted, and the different parts will be described. EXAMPLES

[0019] Example 1 Fig. 1 is a configuration diagram of a propulsion system 1 per one propeller in the embodiment 1. Fig. 2 is a functional block diagram of an inverter control device 600.

[0020] 1, a propeller 100 is connected to an open winding motor 102, which is a three-phase motor, via a shaft 101. The three-phase windings of the open winding motor 102 are not connected independently of each other, and an inverter A 201 and an inverter B 202, which are independent of each other, are connected to both ends of the windings. The three-phase motor 102 in the first embodiment is assumed to be a permanent magnet synchronous motor, but an induction machine, for example, may also be used.

[0021] The inverter A201 and the inverter B202 are configured by connecting semiconductor switching elements in a three-phase bridge, and the DC parts are provided with smoothing capacitors A203 and B204 which are independent of each other. The battery A300 (power source) is connected in parallel to both the inverter A201 and the inverter B202. In the first embodiment, a battery is assumed, but for example, a DC-DC converter may be connected, or an AC voltage source may be converted to DC power using an AC-DC converter.

[0022] A switch A205 is connected between the battery A300 and the capacitor A203, and a switch B206 is connected between the battery A300 and the capacitor B204. The switches A205 and B206 may be mechanical switches such as relays, or may be semiconductor switching elements.

[0023] A current sensor 401 detects three-phase currents flowing through the open winding motor 102, and a voltage sensor A 402 and a voltage sensor B 403 detect the voltages of smoothing capacitors 203, 204 connected to the inverters 201 and 202. The current sensor 401 may detect three phases of the motor current.

[0024] The inverter control device 600 generates switching signals for inverter A201, inverter B202, switch A205, and switch B206 based on operation information and voltage application time information from the aircraft control device 500, which is a higher-level command device, the detection value of the current sensor 401, and the detection values ​​of the voltage sensors A402 and B403.

[0025] FIG. 2 is a functional block diagram of the inverter control device according to the first embodiment.

[0026] 2, the inverter control device 600 includes a timer 601 , a total voltage application time determination unit 602 , an operation pattern determination unit 603 , an inverter control unit 604 , and a switching control unit 605 .

[0027] The total voltage application time determination unit 602 inputs voltage application information to the semiconductor (voltage information of battery A300, or voltage information from voltage sensor A402, or voltage information from voltage sensor B403) from the aircraft control device 500 of the aircraft 501 (shown in FIG. 5A) in the propulsion system 1, drives the timer 601, and determines the total voltage application time of each of the multiple inverters (in Example 1, two inverters 201 and 202).

[0028] The flight pattern determination unit 603 inputs flight information from the flying object control device 500 of the flying object 501 , determines the flight pattern of the flying object, and outputs the determined flight pattern information to the total voltage application time determination unit 602 .

[0029] The inverter control unit 604 controls the inverters 201 and 202 according to a command from the total voltage time determination unit 602 (a command as to which of the inverters 201 and 202 to control output power), current information from the current sensor 401, voltage information from the voltage sensor A402, and voltage information from the voltage sensor B403. That is, the inverter control unit 604 selects one of the inverters 201 and B202 based on the total voltage application time of each of the multiple inverters A201 and B202 during cruising of the aircraft 501, and controls the modulation factor of the selected inverter 201 or B202 and the voltage of the smoothing capacitor A203 or B204.

[0030] The switching control unit 605 controls the operation of switch A 205 or switch B 206 in accordance with information from the inverter control unit 604 (information on which of the inverters 201 and 202 to control) to control the connection and disconnection between the battery 300, which is the power source for the inverters 201 and 202, and the inverters 201 and 202.

[0031] The display unit 606 displays the driving state (whether the inverter 201 and the inverter 202 are driving or stopped) of each of the inverters 201 and 202 based on information from the inverter control unit 604 .

[0032] Next, the flight pattern of the flying object is shown in Fig. 3. In an aircraft, which is the flying object, a propeller 100 generates thrust, and an open winding motor 102 transmits rotational force via a shaft 101. To drive the open winding motor 102, the output voltages of inverter A 201 and inverter B 202 are applied to the windings of the open winding motor 102.

[0033] At this time, for example, by applying the output voltage of inverter B202 in opposite phase to the output voltage of inverter A201 to the windings of the open winding motor 102, the voltage amplitude per phase of the motor winding is increased without increasing the withstand voltage of the semiconductor switching elements or providing a boost circuit, thereby achieving high output of the open winding motor 102 with high efficiency.

[0034] When an aircraft takes off or lands, it is necessary to drive the open winding motor 102 with high output compared to other flight patterns. In this case, the open winding motor 102 is driven with high output and high efficiency using two inverters, inverter A 201 and inverter B 202.

[0035] On the other hand, when an aircraft is cruising, the open winding motor 102 is driven at a lower output than during takeoff or landing. Since the voltage required to drive the motor also decreases during low output, the inverter A 201 or inverter B 202 is stopped to achieve high-efficiency operation in all flight patterns.

[0036] 4 is a flowchart of the control algorithm according to the present embodiment 1. When the pilot or the flight system (e.g., an altimeter) determines that the flight phase has changed from takeoff to cruising, the inverter A201 or the inverter B202 is stopped, and the open winding motor 102 is driven from the open winding to the Y connection.

[0037] Here, for example, stopping inverter A201 or inverter B202 after each cruise and driving the open winding motor 102 from the open winding to a Y connection during low output is effective from the standpoint of efficiency; however, if the usage times of the two inverters A201 and B202 are different, the probability of occurrence of accidental failure due to cosmic rays will be high only for the inverter with the longer usage time, which is not desirable.

[0038] Furthermore, even if inverter A201 or inverter B202 is stopped and the output becomes zero, if the voltage of battery A300 continues to be applied, the inverter will continue to be affected by cosmic rays even though it is stopped.

[0039] Therefore, in the present embodiment 1, the effects of cosmic rays on the two inverters A 201 and B 202 are equalized, and the effects of cosmic rays are reduced when the inverters are stopped. The control method of the present embodiment 1 will be described below.

[0040] Immediately after cruising begins in step S1, the open winding motor 102 is driven by the two inverters 201, 202. At this time, for example, if the motor output required at takeoff is 100 kW, the output required during cruising is about half that, so the motor output is 50 kW, and the output per inverter is 25 kW.

[0041] When cruising begins, in step S2, the total time that voltage is applied to the semiconductor switching elements of the two inverters 201, 202 is determined, and one of the two inverters is selected to be stopped, so that the time that the two inverters 201, 202 are affected by cosmic rays is made equal. Since stopping the inverters 201, 202 means making the output zero, the inverter control unit 604 needs to set the modulation factor of the inverter 201 or 202 to be stopped to zero. The inverter control unit 604 increases the modulation factor of the inverter that continues to drive to make up for the voltage shortage caused by setting the modulation factor of the inverter to be stopped to zero, thereby continuing to supply the desired power to the open winding motor 102.

[0042] In this case, for example, if the motor output required at takeoff is 100 kW, the motor output at cruising is 50 kW, the inverter to be stopped is 0 kW, and the inverter to continue driving outputs 50 kW. After the modulation factor of the inverter to be stopped is set to zero in step S3 or step S13, the lower arm of the inverter to be stopped is short-circuited in step S4 or S14, thereby eliminating the current path that flows between the battery A300 and the open winding motor 102 via the inverter 201 or 202, and preventing unintended charging of the smoothing capacitors 203 and 204. After the lower arm of the inverter 201 or 202 to be stopped is short-circuited in step S5 or S15, the switching control unit 605 opens the switch 205 or 206 on the side of the stopped inverter 201 or 202.

[0043] Before opening switch 205 or 206 connected to battery A300 and smoothing capacitor 203 or 204, inverter control unit 604 reduces the modulation factor of inverter 201 or 202 to be stopped to zero, increases the modulation factor of inverter 201 or 202 to be driven to the required voltage of open winding motor 102, and sets the output of inverter 201 or 202 to be stopped to zero, and then shorts the lower arm of inverter 201 or 202 to be stopped. This makes it possible to prevent smoothing capacitor 203 or 204 from being unintentionally charged.

[0044] Even if the stopped inverter 201 or 202 is disconnected from the battery A300 by the switch 205 or 206, the voltage of the smoothing capacitors 203 and 204 is approximately equivalent to a DC voltage due to the effect of the charge stored in the smoothing capacitors 203 and 204, so that a voltage continues to be applied to the semiconductor switching elements of the stopped inverter 201 or 202, causing an accidental failure due to cosmic rays.

[0045] Therefore, it is necessary to discharge the charge stored in smoothing capacitors 203, 204 and set the capacitor voltage to 0 V. The discharge current is consumed by the winding resistance of open winding motor 102 via stopped inverter 201 or 202. At this time, if a discharge current flows from smoothing capacitor 203 or 204 to open winding motor 102 at the timing when the motor current becomes 0 A, this current should not actually flow, leading to waveform distortion, current oscillation, and unintended regeneration.

[0046] Therefore, in step S6 or S16, inverter control unit 604 needs to determine whether the three-phase current detected by current sensor 401 is 0 or not, and perform discharging during a period when the three-phase current is not 0 A, that is, perform discharging of smoothing capacitors 203, 204 when the product of the three-phase currents is not 0 A. A lower limit current may be set at an arbitrary threshold value rather than 0 A, and discharging may start when the product of the motor currents is greater than that current value.

[0047] In discharging the smoothing capacitors 203, 204 in step S7 or S17, the inverter control unit 604 detects the voltages of the smoothing capacitors 203, 204 in real time using the voltage sensor A402 or B403, and reduces them to 0 V. At this time, the stopped inverter generates a switching signal so that a discharge current path for the smoothing capacitors 203, 204 can be secured and the smoothing capacitors can be driven as a Y connection. The capacitor voltage may be predicted from the switching pattern as a sensorless method without providing a voltage detection sensor.

[0048] After the smoothing capacitors 203, 204 connected to the stopped inverters are discharged, in step S8 or S18, the inverter control unit 604 again shorts the lower arm of the stopped inverter 201 or 202, thereby eliminating the capacitor current path flowing from the open winding motor 102 through the inverter 201 or 202, preventing unintended charging of the smoothing capacitor, and maintaining the capacitor voltage at 0 V. This improves the cosmic radiation tolerance of the stopped inverter.

[0049] After the inverter is stopped in step S9 or S19, the stop time of the inverters 201, 202 or the total voltage application time of the inverters that continue to operate are measured in steps S10, S11 or steps S20, S21 until cruising ends. When cruising ends, in step S12 or S22, the total voltage application time data is used to determine whether to stop the inverter during the next cruising (step S2).

[0050] 5A and 5B show operation patterns when using this embodiment 1. Fig. 5A shows the operation pattern for the outbound journey, and Fig. 5B shows the operation pattern for the return journey.

[0051] 5A and 5B, when flying object 501 moves from point A to point B and from point B to point A, two inverters are used to drive open winding motor 102 during takeoff. During ascent, inverter control device 400 stops one of inverters 201 and 202, and only one inverter drives open winding motor 102 from cruising to descent.

[0052] At the time of landing, the stopped inverter 201 or 202 is restarted in the reverse order of the order shown in FIG.

[0053] This allows the inverter to operate with high efficiency according to the motor output, while improving its cosmic ray tolerance when flying at high altitudes.

[0054] As described above, the inverter control device 400 according to the first embodiment of the present invention controls a three-phase motor 102 with open windings connected via a shaft 101 to a propeller 100 that generates thrust, two inverters 201, 202 connected independently and separately to the three-phase motor 102, smoothing capacitors 203, 204 connected separately to the DC sections of the inverters 201, 202, switches 205, 206 connected between the smoothing capacitors 203, 204 and the battery 300, and both the semiconductor switching elements and switches 205, 206 that constitute the inverters 201, 202.

[0055] The inverter control device 600 according to the first embodiment focuses on the fact that the output of the open winding motor 102 during cruising is approximately half of the motor output during vertical takeoff and landing, and drives the open winding motor 102 during cruising using only one of the two inverters 201, 202. At this time, the inverter 201 or 202 that has the longest total applied voltage time is stopped so that the total times that voltage is applied to the semiconductor switching elements of the two inverters 201 and 202 during cruising are equal.

[0056] In order to stop the inverter 201 or 202, before opening the switch 205 or 206 connected between the smoothing capacitor 203 or 204 and the battery A300, the modulation factor of the inverter 201 or 202 to be stopped is controlled to decrease to zero, and the modulation factor of the inverter 201 or 202 to be continued to be driven is increased by the deficiency, thereby making the output of the stopped inverter 201 or 202 zero while continuing to drive the open winding motor 102 as desired.

[0057] This minimizes the surge that occurs when the switch 205 or 206 on the stopped inverter 201 or 202 side is opened. After that, the lower arm of the stopped inverter 201 or 202 is short-circuited to eliminate the current path that flows between the battery 300 and the open winding motor 102 via the inverter 202 or 202, and the switch 205 or 206 on the stopped inverter 201 or 202 side is opened.

[0058] After the switch 205 or 206 on the stopped inverter 201 or 202 side is opened, the capacitor voltage is equivalent to the DC voltage due to the charge stored in the capacitor 203 or 204, so the stopped inverter 201 or 202 is controlled to discharge the charge stored in the capacitor 203 or 204. The discharge current is consumed by the motor winding resistance during a period in which the three-phase current flowing through the open winding motor 102 does not become 0 A, and the voltage of the smoothing capacitor 203 or 204 on the stopped inverter 201 or 202 side is controlled to 0 V. After that, the lower arm of the stopped inverter 201 or 202 is short-circuited again to eliminate the capacitor current path flowing from the open winding motor 102 via the inverter 201 or 202, and the voltage of the capacitor 203 or 204 is maintained at 0 V.

[0059] This reduces the time during which a voltage is applied to the semiconductor switching element of each of the inverters 201 or 202 by half.

[0060] According to the first embodiment, it is possible to provide an inverter control device and a control method capable of improving the cosmic ray tolerance of the inverter without increasing the cost and the system weight.

[0061] Example 2 Next, a second embodiment of the present invention will be described.

[0062] FIG. 6 is a schematic diagram showing the configuration of a propulsion system 1A of an aircraft controlled by an inverter control device 600 according to the second embodiment.

[0063] In the propulsion system 1A controlled by the inverter control device 600 of the second embodiment, the inverter A201 and the inverter B202 are connected to separate independent batteries A300 and B301 (power sources). In aviation applications, a configuration like that of the second embodiment may be desirable for battery redundancy.

[0064] The configuration and operation of the inverter control device 600 in the second embodiment are similar to those shown in FIG. 2, and therefore a description thereof will be omitted.

[0065] In the second embodiment, the same effects as those in the first embodiment can be obtained.

[0066] Example 3 Next, a third embodiment of the present invention will be described.

[0067] FIG. 7 is a schematic diagram showing the configuration of a propulsion system 1B of an aircraft controlled by an inverter control device 600 according to the third embodiment.

[0068] A propulsion system 1B controlled by an inverter control device 600 of the third embodiment has a total of four inverters, an inverter A201, an inverter B202, an inverter C209, and an inverter D210, connected to both ends of a three-phase winding of an open winding motor 102. The inverters C209 and D210 have the same configuration as the inverter A201 and the inverter B202. Note that in the third embodiment, there may be four or more inverters.

[0069] This embodiment 3 is effective when more importance is placed on measures against inverter failures. The more inverters there are, the more the total voltage application time can be reduced. The batteries connected to the inverters may be independent of each other, may be connected in common, or may be configured as a group in which two inverters are grouped together and one battery is connected to each group.

[0070] The configuration and operation of the inverter control device 600 in the third embodiment are similar to those shown in FIG. 2, and therefore a description thereof will be omitted.

[0071] According to the third embodiment, in addition to being able to obtain the same effects as those of the first embodiment, the total time during which a voltage is applied to each inverter can be reduced, thereby reducing the rate of failure.

[0072] Example 4 Next, a fourth embodiment of the present invention will be described.

[0073] 8A and 8B are diagrams showing flight patterns of an aircraft controlled by the inverter control device 600 according to the fourth embodiment.

[0074] In an aircraft, which is an air vehicle that uses different propellers or motors during takeoff, landing, and other flight modes, inverter control unit 604 drives open winding motor 102 with two inverters 201 and 202 during ascent, and stops one inverter during cruising and descent, and drives the motor with high efficiency using one inverter. Inverter control unit 604 drives inverter 202, which is stopped on the outbound leg, on the return leg, and stops inverter 201, which is driven on the outbound leg, on the return leg.

[0075] During takeoff and landing, different propellers or motors are used than those used during ascent, cruising, and descent.

[0076] The configuration and operation of the inverter control device 600 in the fourth embodiment are similar to those shown in FIG. 2, and therefore a description thereof will be omitted.

[0077] According to the fourth embodiment, even for an aircraft that uses different propellers or motors during takeoff and landing and in other flight modes, the total time that voltage is applied to each inverter can be reduced, as in the first embodiment, and the occurrence rate of failures can be reduced.

[0078] Example 5 Next, a fifth embodiment of the present invention will be described.

[0079] Fig. 9 is a diagram showing a flight pattern of the fifth embodiment. In the flight pattern shown in Fig. 9, the inverter stop is determined based on the total voltage application time even when the flight passes through multiple destinations. For example, in the case of a flight pattern cruising four points A, B, C, and D, inverter B202 is stopped from point A to point B, inverter A201 is stopped from point B to point C, inverter B202 is stopped from point C to point D, and inverter A201 is stopped from point D to point A.

[0080] That is, even when the journey is not an outbound journey and a return journey but passes through a plurality of destinations, the decision to stop the inverter is made based on the total voltage application time, so that the same effect as in the first embodiment can be obtained.

[0081] In the fifth embodiment, any of the operation controls in the first to fourth embodiments may be used. [Explanation of symbols]

[0082] 1, 1A, 1B... Propulsion system of an aircraft, 100... Propeller, 101... Shaft, 102... Open winding motor, 201... Inverter A, 202... Inverter B, 203... Smoothing capacitor A, 204... Smoothing capacitor B, 205... Switch A, 206... Switch B, 207... Inverter D, 208... Inverter E, 209... Switch C, 210... Switch D, 30 0... Battery A (power source), 301... Battery B (power source), 401... Current sensor, 402... Voltage sensor A, 403... Voltage sensor B, 500... Aircraft control device, 501... Aircraft, 600... Inverter control device, 601... Timer, 602... Total voltage application time determination unit, 603... Operation pattern determination unit, 604... Inverter control unit, 605... Switching control unit, 606... Display unit

Claims

1. a total voltage application time determination unit that determines a total voltage application time of each of the plurality of inverters; an operation pattern determination unit that receives operation information of the flying object, determines an operation pattern of the flying object, and outputs the determined operation pattern to the total voltage application time determination unit; an inverter control unit that controls the plurality of inverters and the plurality of smoothing capacitor voltages in accordance with a command from the total voltage application time determination unit and current information and voltage information of the plurality of inverters; a switching control unit that controls connection and disconnection between the power supplies of the plurality of inverters and the plurality of inverters in accordance with information from the inverter control unit; An inverter control device comprising:

2. 2. The inverter control device according to claim 1, the aircraft has an open-winding motor connected to a propeller via a shaft, and has a larger output during takeoff and landing or ascent than during cruising, the open-winding motor is connected to a plurality of the inverters, and each of the plurality of inverters has a DC section connected to a smoothing capacitor and is connected to a power source via a switch; the inverter control unit selects one of the plurality of inverters based on a total voltage application time of each of the plurality of inverters during cruising, and controls a modulation factor of the selected inverter; The switching control unit connects or opens the switch in accordance with information from the inverter control unit. An inverter control device characterized by:

3. 3. The inverter control device according to claim 2, The inverter control device is characterized in that the inverter control unit drives the open winding motor using the plurality of inverters during takeoff, landing, or ascent of the aircraft, and controls the stopping or driving of the plurality of inverters so that the total voltage application times of the plurality of inverters are equal to each other during cruising.

4. 4. The inverter control device according to claim 3, The inverter control device is characterized in that the inverter control unit stops an inverter having a long total voltage application time and drives an inverter having a short total voltage application time so that the total voltage application times of the plurality of inverters are equal to each other.

5. 5. The inverter control device according to claim 4, The inverter control unit The modulation factor of the inverter to be stopped is reduced to zero, the modulation factor of the inverter to be driven is increased to the required voltage of the open winding motor, and after the output of the inverter to be stopped is reduced to zero, the lower arm of the inverter to be stopped is short-circuited; The inverter control device is characterized in that the switching control unit opens the switch connected to the power supply and the smoothing capacitor after the lower arm of the inverter to be stopped is short-circuited.

6. 6. The inverter control device according to claim 5, the inverter control unit discharges the charge stored in the smoothing capacitor through a winding resistance of the open winding motor when the product of the three-phase currents flowing through the open winding motor is 0 A or greater than an arbitrary threshold value, thereby reducing the voltage of the smoothing capacitor to 0 V.

7. 7. The inverter control device according to claim 6, The inverter control device is characterized in that, after the inverter control unit reduces the voltage of the smoothing capacitor to 0 V, it shorts the lower arm of the inverter that is to be stopped and maintains the voltage of the smoothing capacitor at 0 V.

8. 8. The inverter control device according to claim 7, The inverter control device is characterized in that the inverter control unit drives, among the plurality of inverters, the inverters that are stopped during the forward path during the return path, and stops, during the return path, the inverters that are driven during the forward path.

9. 2. The inverter control device according to claim 1, An inverter control device characterized in that each of the plurality of inverters is provided with a display unit that displays a state of whether the inverter is operating or stopped based on information from the inverter control unit.

10. determining a total voltage application time for each of the plurality of inverters; determining a flight pattern of the aircraft from flight information of the aircraft; Controlling the plurality of inverters according to current information and voltage information of the plurality of inverters; Controlling connection and disconnection between the power supplies of the plurality of inverters and the plurality of inverters; An inverter control method comprising:

11. 11. The inverter control method according to claim 10, the aircraft has an open-winding motor connected to a propeller via a shaft, and has a larger output during takeoff and landing or ascent than during cruising, the open-winding motor is connected to the plurality of inverters, and each of the plurality of inverters has a DC section connected to a smoothing capacitor and is connected to a power source via a switch; selecting one of the plurality of inverters based on a total voltage application time of each of the plurality of inverters during the cruising operation, and controlling a modulation factor of the selected inverter; After the switch is opened, the voltage of the smoothing capacitor is decreased. An inverter control method comprising:

12. 12. The inverter control method according to claim 11, an inverter control method comprising: driving the open winding motor by the plurality of inverters during takeoff, landing, or ascent of the aircraft; and controlling the stopping or driving of the plurality of inverters during cruising so that the total voltage application times of the plurality of inverters are equal to each other.

13. 13. The inverter control method according to claim 12, an inverter control method comprising stopping an inverter having a long total voltage application time and driving an inverter having a short total voltage application time so that the total voltage application times of the plurality of inverters are equal to each other.

14. 14. The inverter control method according to claim 13, an inverter control method comprising: reducing a modulation factor of the inverter to be stopped to zero; increasing a modulation factor of the inverter to be driven to a required voltage of the open-winding motor; setting the output of the inverter to be stopped to zero; and then short-circuiting a lower arm of the inverter to be stopped; and opening the switch connected to the power supply and the smoothing capacitor after the lower arm of the inverter to be stopped is short-circuited.

15. 15. The inverter control method according to claim 14, When the product of the three-phase currents flowing through the open winding motor is 0 A or greater than an arbitrary threshold value, the charge stored in the smoothing capacitor is discharged through a winding resistance of the open winding motor, and the voltage of the smoothing capacitor is reduced to 0 V.

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