Inverter control device

Abstract

To provide a control device of an inverter that can suppress an occurrence of partial discharge when the ambient humidity is relatively high.SOLUTION: A control device 50 is applied to a system 100 comprising a multiphase rotary electric machine 10 and an inverter 20 electrically connected to armature coils 11U, 11V, and 11W which are components of the rotary electric machine. The control device comprises: a control unit for performing a switching control of switches SUH-SWL connected to the phase lines of the inverter in order to make a drive control of the rotary electric machine; and a setting unit for performing setting processing of operational conditions for a switching operation so that the occurrence period of a surge voltage, which occurs in the armature coil or coils due to the switching operation of the switches in the switching control, becomes shorter when the ambient humidity around the rotary electric machine is high compared to when the ambient humidity is low.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an inverter control device that is applied to a system including a polyphase rotating electric machine and an inverter electrically connected to an armature winding that constitutes the rotating electric machine. [Background technology]

[0002] This type of control device performs switching control of the switches of each phase that constitute the inverter in order to drive and control the rotating electric machine by passing a current through the armature winding. Here, a surge voltage is generated due to the switching operation in the switching control. If the surge voltage increases and a partial discharge occurs between the armature windings of two phases, this may cause deterioration of the rotating electric machine.

[0003] Patent Document 1 discloses a control device for reducing surge voltages that changes the switching operation mode when the polarity of the voltage applied to the armature winding is reversed when the humidity of the atmosphere of a rotating electric machine is high and exceeds a judgment value. In more detail, the control device performs a switching operation to suppress an increase in the potential difference between the two-phase armature windings when the polarity of the voltage applied to the armature winding is reversed. This makes it possible to weaken the electric field generated between the two-phase armature windings by the surface charge of the armature windings when the humidity is high, thereby suppressing the occurrence of partial discharges. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-22624 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technology for suppressing the occurrence of partial discharge when the atmospheric humidity is relatively high is not limited to the technology for suppressing the increase in the potential difference between the two-phase armature windings.

[0006] The present invention has been made in consideration of the above circumstances, and has as its main object to provide an inverter control device that can suppress the occurrence of partial discharge when the atmospheric humidity is relatively high. [Means for solving the problem]

[0007] The present invention provides an inverter control device applied to a system including a polyphase rotating electric machine and an inverter electrically connected to an armature winding that constitutes the rotating electric machine, and includes a control unit that performs switching control of switches of each phase that constitutes the inverter in order to control the drive of the rotating electric machine, and a setting unit that performs a setting process to set operating conditions for the switching operation so that, when the ambient humidity of the rotating electric machine is high, the period of occurrence of a surge voltage that occurs in the armature winding due to the switching operation of the switch in the switching control is shorter than when the ambient humidity is low.

[0008] When a surge voltage occurs due to switching operation, partial discharge occurs after a time delay after the surge voltage reaches a predetermined high voltage. In this case, the period from when the surge voltage reaches a predetermined high voltage until partial discharge occurs (hereinafter referred to as the discharge delay period) depends on the humidity of the atmosphere around the rotating electric machine, and the higher the humidity, the shorter the discharge delay period. Partial discharge occurs when the surge voltage does not converge before the discharge delay period has elapsed, and partial discharge becomes more likely to occur as the discharge delay period becomes shorter.

[0009] Therefore, in the present invention, the operating conditions of the switching operation are set so that the period during which a surge voltage occurs in the armature winding due to the switching operation of the switch is shorter when the ambient humidity of the rotating electric machine is high than when the ambient humidity is low. As a result, when the ambient humidity is relatively high, the surge voltage can be converged before the discharge delay period has elapsed, and the occurrence of partial discharge can be suppressed. [Brief description of the drawings]

[0010] [Figure 1] Overall system configuration diagram. [Diagram 2] FIG. 13 is a diagram showing the transition of input voltage and partial discharge during turn-on operation. [Diagram 3] FIG. 2 is a diagram showing the mechanism by which partial discharge occurs. [Figure 4] FIG. [Diagram 5] FIG. 13 is a diagram showing the relationship between a discharge delay period and a detected humidity value. [Figure 6] 5 is a flowchart showing the procedure of a setting process according to the first embodiment. [Figure 7] 10 is a flowchart showing the procedure of a setting process according to the second embodiment. [Figure 8] FIG. 4 is a graph showing the relationship between the detected humidity value and the switching speed and switching period. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] (First embodiment) Hereinafter, a first embodiment in which an inverter control device according to the present invention is applied to an on-vehicle system 100 will be described with reference to the drawings.

[0012] 1, the system 100 includes a rotating electric machine 10 and an inverter 20. In this embodiment, the rotating electric machine 10 is a brushless synchronous machine, such as a permanent magnet synchronous machine. The rotating electric machine 10 includes U-, V-, and W-phase windings 11U, 11V, and 11W, which are three-phase armature windings.

[0013] The rotating electric machine 10 is connected to a battery 30 as a DC power source via an inverter 20. The inverter 20 includes a series connection of upper arm switches SUH, SVH, SWH and lower arm switches SUL, SVL, SWL. A first end of the U-phase winding 11U is electrically connected (hereinafter, simply connected) to a connection point PU of the U-phase upper and lower arm switches SUH, SUL via a U-phase conductive member 22U. A first end of the V-phase winding 11V is connected to a connection point PV of the V-phase upper and lower arm switches SVH, SVL via a V-phase conductive member 22V. A first end of the W-phase winding 11W is connected to a connection point PW of the W-phase upper and lower arm switches SWH, SWL via a W-phase conductive member 22W. Second ends of the U-, V-, and W-phase windings 11U, 11V, and 11W are connected at a neutral point PT. The conductive members 22U, 22V, and 22W of each phase are, for example, cables or bus bars.

[0014] In this embodiment, a voltage-controlled semiconductor switching element, more specifically, an N-channel MOSFET, is used as each of the switches SUH to SWL. Each of the switches SUH to SWL has a built-in body diode.

[0015] A capacitor 23 is provided between the inverter 20 and the battery 30 to smooth the voltage input to the inverter 20. A high potential terminal of the capacitor 23 is connected to the positive terminal of the battery 30, and a low potential terminal of the capacitor 23 is connected to the negative terminal of the battery 30. A high potential terminal of the capacitor 23 is connected to the drains which are the high potential terminals of the upper arm switches SUH to SWH. A low potential terminal of the capacitor 23 is connected to the sources which are the low potential terminals of the lower arm switches SUL to SWL. The capacitor 23 may be provided outside the inverter 20 or may be provided inside the inverter 20.

[0016] The system 100 includes a voltage sensor 40, a current sensor 41, a rotation angle sensor 42, a temperature sensor 43, an air pressure sensor 44, and a humidity sensor 45. The voltage sensor 40 detects the power supply voltage, which is the terminal voltage of the capacitor 23. The current sensor 41 detects at least two phases of current among the phase currents flowing through the rotating electric machine 10. The rotation angle sensor 42 is formed of, for example, a resolver or a Hall element, and detects the electrical angle of the rotating electric machine 10.

[0017] The temperature sensor 43 detects the temperature of the rotating electric machine 10. The temperature of the rotating electric machine 10 is, for example, the temperature of the windings 11U, 11V, and 11W. The air pressure sensor 44 detects the atmospheric pressure in the installation environment of the rotating electric machine 10 and the inverter 20. The humidity sensor 45 detects the atmospheric humidity in the installation environment of the rotating electric machine 10. The detection values ​​of the sensors 40 to 45 are input to a control device 50 provided in the control system.

[0018] The control device 50 receives as input a current value detected by a current sensor 41 (hereinafter, current detection value I), an electrical angle θe detected by a rotation angle sensor 42, a temperature detected by a temperature sensor 43 (hereinafter, temperature detection value TDr), an atmospheric pressure detected by a pressure sensor 44 (hereinafter, pressure detection value Pr), and an atmospheric humidity detected by a humidity sensor 45 (hereinafter, humidity detection value Hr). The control device 50 calculates an electrical angle frequency ωe as the rotation speed of the rotating electric machine 10, based on the electrical angle θe.

[0019] The control device 50 uses each input value to control the control amount of the rotating electric machine 10 to a command value, and performs switching control of each switch SUH to SWL constituting the inverter 20. In this embodiment, the control amount is torque, and the command value is a torque command value Trq*. The torque command value Trq* is input, for example, from a control device higher than the control device 50. The control device 50 outputs drive signals SA corresponding to the upper and lower arm switches to drive circuits Dr individually provided for the upper and lower arm switches, so that the upper and lower arm switches are alternately turned on with dead time DT in between. The drive signal SA is either an on command or an off command. In this embodiment, the control device 50 corresponds to a "control unit."

[0020] Each of the drive circuits Dr performs switching control such that the upper and lower arm switches are alternately turned on while setting a dead time DT based on the drive signal SA. This switching control switches the drive state of each of the switches SUH to SWL.

[0021] In switching control, a surge voltage may occur due to resonance caused by the inductance and capacitance of the windings 11U, 11V, and 11W of each phase as the driving states of the switches SUH to SWL are switched. If the surge voltage increases and an overvoltage is applied to the windings 11U, 11V, and 11W of each phase of the rotating electric machine 10, a partial discharge HP may occur between adjacent windings as shown in Fig. 3, which may cause deterioration of the rotating electric machine 10. In particular, at high humidity when the humidity detection value Hr is higher than the humidity threshold value Hth, surface charges tend to be easily generated and concentrated on the windings 11U, 11V, and 11W of each phase, and therefore the surge voltage is likely to increase.

[0022] 2 shows the transition of the input voltage Vin and partial discharge HP during turn-on operation. The input voltage Vin is the voltage input from the inverter 20 to each of the windings 11U, 11V, 11W of each phase of the rotating electric machine 10, and is switched between an on voltage Von and an off voltage Voff by the switching operation of each of the switches SUH to SWL. The on voltage Von is a value corresponding to the positive electrode side voltage of the battery 30. The on voltage Von is, for example, a value obtained by subtracting the amount of voltage drop of the upper arm switches SUH to SWH, etc. of the inverter 20 from the positive electrode side voltage of the battery 30. The off voltage Voff is a value corresponding to the negative electrode side voltage of the battery 30, for example, a ground voltage (0 V).

[0023] The following description will be given taking the upper arm as an example. As shown in FIG. 2, when a surge voltage occurs in the input voltage Vin due to the turn-on operation of the upper arm switch, a partial discharge HP may occur. Specifically, after the input voltage Vin starts to rise to the on-voltage Von at time t1, the input voltage Vin exceeds the on-voltage Von at time t2, overshoots, and reaches the maximum value in one switching period at time t3. After that, the input voltage Vin drops from the maximum value to the on-voltage Von. In this embodiment, the period during which the input voltage Vin exceeds the on-voltage Von after the turn-on operation is started, from time t2 when the input voltage Vin first exceeds the on-voltage Von to time t5 when the input voltage Vin first becomes the on-voltage Von thereafter, is called the surge generation period TA. The input voltage Vin during the surge generation period TA is called the surge voltage. During this surge generation period TA, a partial discharge HP occurs at time t4 after the discharge delay period TD has elapsed from time t3 when the surge voltage reaches a predetermined high voltage. In this embodiment, the maximum value of the surge voltage is set to the predetermined high voltage.

[0024] In each phase, partial discharge HP may occur when the lower arm switch is turned on after the upper arm switch is turned off. Specifically, after the turn-off operation is started, the input voltage Vin drops from the on voltage Von and then falls below the off voltage Voff. After that, the input voltage Vin reaches a minimum value and then starts to rise to the off voltage Voff. In this embodiment, in the turn-off operation, a period during which the input voltage Vin falls below the off voltage Voff after the start of the operation is called a surge generation period TA, and the input voltage Vin during this surge generation period TA is called a surge voltage. During this surge generation period TA, partial discharge HP occurs after a discharge delay period TD has elapsed since the input voltage Vin reached a predetermined low voltage.

[0025] The discharge delay period TD will be described with reference to Figs. 3 and 4. The following description will be given taking the turn-on operation as an example. Fig. 3 shows the mechanism of partial discharge HP that occurs between the adjacent U-phase winding 11U and V-phase winding 11V as an example. The configuration shown in Fig. 3 is, for example, a configuration in which the windings 11U and 11V of different phases are accommodated in the same slot. As shown in an enlarged view in Fig. 3, when the surge voltage reaches a predetermined high voltage, first, electrons EA are accidentally ionized from gas molecules PA near the windings 11U and 11V due to the electric field between the U-phase winding 11U and the V-phase winding 11V, and initial electrons EP are generated as shown in the dashed circle CA. As shown by the arrow YA in Fig. 3, the initial electrons EP are accelerated by the electric field between the U-phase winding 11U and the V-phase winding 11V and collide with other gas molecules PA. Then, multiple electrons EA are ionized from other gas molecules PA due to the collision of the initial electrons EP, and multiple free electrons EB are generated as shown in the dashed circle CB, and charged particles such as positive ions of atoms and molecules that are positively charged due to the detachment of electrons are generated. After that, the acceleration, collision, and generation of the free electrons EB, positive ions, and other charged particles are repeated, and the number of generated free electrons EB and positive ions increases, causing a partial discharge HP.

[0026] Fig. 4 shows an enlarged view of a part of Fig. 2. As shown in Fig. 4, from when the input voltage Vin reaches its maximum value at time t3 until the occurrence of a partial discharge HP at time t4, a statistical delay period TB1, which is the period until the initial electrons EP are generated, and a formative delay period TB2, which is the period during which the free electrons EB are accelerated, collide, and generated repeatedly, are required. The discharge delay period TD is the sum of the statistical delay period TB1 and the formative delay period TB2.

[0027] The present inventors have repeatedly studied the relationship between the statistical delay period TB1 and the formative delay period TB2 and the atmospheric humidity of the rotating electric machine 10, and have found that the formative delay period TB2 is approximately constant regardless of the atmospheric humidity, while the statistical delay period TB1 is more dependent on the atmospheric humidity. Specifically, the inventors have found that the higher the atmospheric humidity, the shorter the statistical delay period TB1.

[0028] The relationship between the discharge delay period TD and the atmospheric humidity is shown in Fig. 5. Fig. 5 shows the discharge delay period TD when the atmospheric humidity is 23%, 40%, and 60%. Specifically, at each atmospheric humidity, 10 samples of the discharge delay period TD are obtained, and the obtained 10 samples are arranged in ascending order and shown.

[0029] As shown in Fig. 5, the higher the atmospheric humidity, the shorter the discharge delay period TD. This is because, as described above, the higher the atmospheric humidity, the shorter the statistical delay period TB1. The reason why the statistical delay period TB1 becomes shorter as the atmospheric humidity increases is thought to be that the higher the atmospheric humidity, the easier it becomes for the gas molecules PA to be charged, and the easier it becomes for the gas molecules PA to be ionized into primary electrons EP.

[0030] The inventors have focused on this point and set the operating conditions of the switching operation so that the surge generation period TA is shorter at high humidity than at low humidity when the humidity detection value Hr is equal to or lower than the humidity threshold value Hth. In other words, focusing on the fact that the statistical delay period TB1, which is the period during which accidental ionization of electrons EA occurs, depends on the atmospheric humidity, the surge generation period TA is shortened at high humidity so that initial electrons EP are less likely to occur, and even if initial electrons EP do occur, they are less likely to grow into partial discharges HP. This suppresses the occurrence of partial discharges HP at high humidity.

[0031] Next, the procedure of the setting process executed by the control device 50 will be described with reference to Fig. 6. This process is repeatedly executed at a predetermined control period. In the following, the U phase will be described as an example.

[0032] In step S10, it is determined whether the first and second insulation conditions are both satisfied. The first and second insulation conditions are conditions for determining whether the molecular density of gas molecules PA around the windings 11U, 11V, and 11W of each phase constituting the rotating electric machine 10 is low, and the dielectric strength between the U-, V-, and W-phase windings 11U, 11V, and 11W constituting the rotating electric machine 10 is low. In other words, partial discharges HP are generated through gas molecules PA around adjacent windings, and when the molecular density of the gas molecules PA is low, the distance between the gas molecules PA becomes longer. This increases the distance over which free electrons EB are accelerated by the electric field, and the collision energy when the free electrons EB collide with the gas molecules PA becomes large. As a result, partial discharges HP are more likely to occur, and the dielectric strength between the U-, V-, and W-phase windings 11U, 11V, and 11W is reduced.

[0033] The first insulation condition is that the air pressure detection value Pr is lower than the air pressure threshold value Pth. The air pressure threshold value Pth may be set to a value less than 1 atmosphere (e.g., 0.6 to 0.7 atmospheres). The second insulation condition is that the temperature detection value TDr is higher than the temperature threshold value TDth. The temperature threshold value TDth may be set to a temperature close to the allowable upper limit temperature of the rotating electric machine 10 (e.g., 150°C).

[0034] If it is determined in step S10 that at least one of the first and second insulation conditions is not satisfied, it is determined that the execution condition for the setting process is not satisfied, and the setting process is terminated.

[0035] On the other hand, if it is determined in step S10 that both the first and second insulation conditions are satisfied, the process proceeds to step S11. In step S11, it is determined whether or not the first drive condition is satisfied. The first drive condition is a condition for determining whether or not a situation exists in which a surge voltage generated in association with the turn-on operation of the upper arm switch SUH becomes large. The first drive condition is a condition in which an off current value Ioff, which is a current detection value I detected before the turn-on operation of the upper arm switch SUH, is lower than a low current threshold value ILth. The low current threshold value ILth is set to a value that can determine that a situation exists in which a surge voltage generated in association with the turn-on operation of the upper arm switch SUH becomes large, and may be set to, for example, 10 A. The surge voltage generated in association with the turn-on operation of the upper arm switch SUH is generated due to the recovery operation of the body diode of the lower arm switch SUL.

[0036] If it is determined in step S11 that the first drive condition is not satisfied, the process proceeds to step S12. On the other hand, if it is determined in step S11 that the first drive condition is satisfied, the process proceeds to step S13, determining that the execution conditions for the setting process are satisfied.

[0037] In step S12, it is determined whether the second to fourth drive conditions are satisfied. The second to fourth drive conditions are conditions for determining whether the surge voltage generated by the turn-off operation of the upper arm switch SUH becomes large. The second drive condition is a condition that the on-current value Ion, which is the current detection value I detected before the turn-off operation of the upper arm switch SUH, is higher than the high-current side threshold value IHth. The high-current side threshold value IHth is set to a value that can determine that the surge voltage generated due to the time change of the phase current associated with the turn-off operation of the upper arm switch SUH becomes large, and may be set to, for example, 80% of the allowable upper limit current value of the rotating electric machine 10. The third drive condition is a condition that the torque command value Trq* is larger than the torque threshold value Trqth as a command value threshold value. The torque threshold value Trqth is set to a value that can determine that the situation requires a large current, and may be set to, for example, 80% of the allowable upper limit torque of the rotating electric machine 10.

[0038] The fourth drive condition is that the electrical angular frequency ωe is lower than a low frequency threshold ωth as a speed threshold. The low frequency threshold ωth is set to a value that can determine that the rotating electrical machine 10 can be driven with high torque, for example, to a value that is 10% of the allowable upper limit rotation speed of the rotating electrical machine 10.

[0039] If it is determined in step S12 that none of the second to fourth drive conditions are satisfied, it is determined that the execution conditions for the setting process are not satisfied, and the setting process is terminated. On the other hand, if it is determined in step S12 that at least one of the second to fourth drive conditions is satisfied, it is determined that the execution conditions for the setting process are satisfied, and the process proceeds to step S13.

[0040] In step S13, it is determined whether or not the humidity detection value Hr is higher than the humidity threshold value Hth. The humidity threshold value Hth is a determination value for determining whether the humidity environment is one in which partial discharge HP is likely to occur. The humidity threshold value Hth may be determined by suitability or the like, and may be set to a relative humidity of 65%, for example. If a negative determination is made in step S13, the process proceeds to step S14. In step S14, the switching speed VS of each switch SUH to SWL is set to a first switching speed VB1, and the setting process ends.

[0041] On the other hand, if the determination in step S13 is affirmative, the process proceeds to step S15. In step S15, the switching speed VS of the upper arm switch SUH is set to a second switching speed VB2 higher than the first switching speed VB1, and the setting process is terminated. For example, the drive circuit Dr is provided with a charging resistor and a discharging resistor connected to the gate of the upper arm switch SUH. When the switching speed VS is set to the second switching speed VB2 in the turn-on operation of the upper arm switch SUH, the resistance value of the charging resistor is set to be smaller than when the switching speed VS is set to the first switching speed VB1. This increases the flow rate of charge into the gate of the upper arm switch SUH, and the switching speed VS becomes higher. Furthermore, when the control device 50 sets the switching speed VS to the second switching speed VB2 in the turn-off operation, the control device 50 sets the resistance value of the discharging resistor to be smaller than when the switching speed VS is set to the first switching speed VB1. This increases the flow rate of charge from the gate of the upper arm switch SUH, and the switching speed VS becomes higher. In this embodiment, the process in step S15 corresponds to the "setting unit".

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

[0043] In the rotating electric machine 10, a surge voltage is generated by the switching operation of the switches SUH to SWL constituting the inverter 20, and an increase in the surge voltage causes a partial discharge HP. There is a discharge delay period TD between the generation of the surge voltage and the generation of the partial discharge HP, and the discharge delay period TD is shorter at high humidity than at low humidity. In this embodiment, a setting process is performed to set operating conditions for the switching operation so that the surge generation period TA is shorter at high humidity than at low humidity. That is, in response to the relatively shorter discharge delay period TD at high humidity, the generation period of the surge voltage is controlled so that the time until the surge voltage converges is shortened. As a result, at high humidity, the surge voltage can be converged before the discharge delay period TD has elapsed, and the occurrence of partial discharge HP can be suppressed.

[0044] In this embodiment, the switching speed VS of each switch SUH to SWL is used as an operating condition of the switching operation, and the switching speed VS is set to be higher at high humidity than at low humidity. This makes it possible to shorten the surge occurrence period TA in each switching cycle and suppress the occurrence of partial discharge HP.

[0045] In this embodiment, when a turn-on operation is performed as a switching operation, a process of increasing the switching speed VS is performed on the condition that the off-current value Ioff is determined to be lower than the low-current threshold value ILth. In a turn-on operation, a surge voltage is likely to increase when the off-current value Ioff is lower than the low-current threshold value ILth. By performing the above process only in a situation where the surge voltage is likely to increase, it is possible to reduce the processing load of the control device 50 due to the setting process while suppressing the surge voltage.

[0046] In this embodiment, when a turn-off operation is performed as a switching operation, a process of increasing the switching speed VS is performed on the condition that the torque command value Trq* is determined to be greater than the torque threshold value Trqth. When a turn-off operation is performed, the surge voltage is likely to increase when the torque command value Trq* is greater than the torque threshold value Trqth. By performing the above process only in a situation where the surge voltage is likely to increase, it is possible to reduce the processing load of the control device 50 due to the setting process while suppressing the surge voltage.

[0047] Furthermore, when a turn-off operation is performed as the switching operation, a process for increasing the switching speed VS is performed on the condition that the on-current value Ion is determined to be higher than the high-current threshold value IHth. When a turn-off operation is performed, the surge voltage is likely to increase when the on-current value Ion is higher than the high-current threshold value IHth. By performing the above process only in a situation where the surge voltage is likely to increase, it is possible to reduce the processing load of the control device 50 due to the setting process while suppressing the surge voltage.

[0048] Furthermore, when a turn-off operation is performed as the switching operation, a process of increasing the switching speed VS is performed on the condition that it is determined that the electrical angular frequency ωe is lower than the low frequency threshold ωth. When a turn-off operation is performed, the surge voltage is likely to increase when the electrical angular frequency ωe is lower than the low frequency threshold ωth. By performing the above process only in a situation where the surge voltage is likely to increase, it is possible to reduce the processing load of the control device 50 due to the setting process while suppressing the surge voltage.

[0049] A process for increasing the switching speed VS is performed on the condition that the temperature detection value TDr is determined to be higher than the temperature threshold value TDth. When the temperature detection value TDr is higher than the temperature threshold value TDth, the dielectric strength of the rotating electric machine 10 is reduced. Since the above process is performed only in such a situation, it is possible to reduce the processing load of the control device 50 due to the setting process while suppressing the surge voltage.

[0050] If it is determined that the atmospheric pressure detection value Pr is lower than the atmospheric pressure threshold value Pth, a process for increasing the switching speed VS is performed. When the atmospheric pressure detection value Pr is lower than the atmospheric pressure threshold value Pth, the dielectric strength of the rotating electric machine 10 is reduced. Since the above process is performed only in such a situation, it is possible to reduce the processing load of the control device 50 due to the setting process while suppressing the surge voltage.

[0051] Second embodiment The second embodiment will be described below with reference to Fig. 7, focusing on the differences from the first embodiment. This embodiment differs from the first embodiment in that the setting process uses the switching period FA of each switch SUH to SWL as an operating condition for the switching operation.

[0052] A flowchart of the setting process of this embodiment is shown in Fig. 7. Note that in Fig. 7, the same processes as those shown in Fig. 6 are denoted by the same step numbers for convenience, and the description thereof will be omitted.

[0053] 7, in the setting process of this embodiment, if a negative determination is made in step S13, the process proceeds to step S20. In step S20, the control of the rotating electric machine 10 is set to the control using the first switching period FB1, and the setting process ends.

[0054] On the other hand, if the determination in step S15 is positive, the process proceeds to step S21. In step S21, the control of the rotating electric machine 10 is set to control using a second switching period FB2 that is longer than the first switching period FB1, and the setting process ends. For example, in step S21, the carrier frequency used to generate the drive signal SA is set lower than that in step S20, thereby making the second switching period FB2 longer than the first switching period FB1.

[0055] Setting the switching period FA to be relatively long under high humidity conditions reduces the frequency of occurrence of the surge occurrence period TA in the drive period of the rotating electric machine 10. This reduces the proportion of the surge occurrence period TA in the drive period of the rotating electric machine 10, thereby suppressing the occurrence of partial discharges HP. In this embodiment, the process of step S21 corresponds to the "setting unit."

[0056] <Other embodiments> The above embodiment may be modified as follows.

[0057] The moving body is not limited to a vehicle, but may be a ship or an aircraft. When the moving body is a ship, the rotating electric motor serves as the ship's navigation power source, and when the moving body is an aircraft, the rotating electric motor serves as the aircraft's flight power source. In particular, when the moving body is an aircraft, the ambient humidity of the rotating electric motor is likely to change significantly depending on the flight altitude, so it is effective to control the period during which surge voltage occurs depending on the ambient humidity and suppress the occurrence of partial discharge.

[0058] The switches that make up the inverter are not limited to N-channel MOSFETs, but may be IGBTs, for example. In this case, the high-potential terminal of the switch becomes the collector, and the low-potential terminal becomes the emitter. In this case, it is sufficient if a freewheel diode is connected in inverse parallel to the switch.

[0059] The inverter and the rotating electric machine are not limited to three-phase ones, but may be two-phase ones or four or more phases. In other words, the inverter and the rotating electric machine may be polyphase ones.

[0060] The controlled variable of the rotating electrical machine is not limited to the torque, but may be, for example, the rotation speed.

[0061] In the above embodiment, the humidity threshold value Hth is used to distinguish between high humidity and low humidity, and the switching speed VS or the switching period FA is changed depending on whether the humidity is high or low. However, this is not limiting. For example, as shown in Fig. 8, the higher the humidity detection value Hr, the higher the switching speed VS or the longer the switching period FA may be.

[0062] The control unit and the method described in the present disclosure may be realized by a special-purpose computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. Alternatively, the control unit and the method described in the present disclosure may be realized by a special-purpose computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method described in the present disclosure may be realized by one or more special-purpose computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. In addition, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions executed by the computer. [Explanation of symbols]

[0063] 10... rotating machine, 11U... U-phase winding, 11V... V-phase winding, 11W... W-phase winding, 20... inverter, 50... control device, 100... system, SUH to SWL... switches, TA... period of surge voltage generation.

Claims

1. A polyphase rotating electric machine (10), and an inverter (20) electrically connected to an armature winding (11U, 11V, 11W) constituting the rotating electric machine. a control unit that performs switching control of switches (SUH to SWL) of each phase that constitutes the inverter in order to perform drive control of the rotating electric machine; a setting unit that performs a setting process to set operating conditions for the switching operation so that, when the ambient humidity of the rotating electric machine is high, a generation period (TA) of a surge voltage generated in the armature winding due to the switching operation of the switch in the switching control is shorter than when the ambient humidity is low.

2. The operating condition is the switching speed (VA) of the switch; The inverter control device according to claim 1 , wherein the setting unit sets the switching speed to be higher when the atmospheric humidity is high than when the atmospheric humidity is low.

3. The operating condition is a switching period (FA) of the switch, 3 . The inverter control device according to claim 1 , wherein the setting unit sets the switching period to be longer when the atmospheric humidity is high than when the atmospheric humidity is low.

4. The inverter control device according to any one of claims 1 to 3, wherein the setting unit performs the setting process under the condition that, when the control unit controls a turn-on operation as the switching operation, a current value flowing through the armature winding before the turn-on operation is smaller than a low-current threshold value.

5. the control unit performs the switching control to control a control amount of the rotating electric machine to a command value; The inverter control device according to any one of claims 1 to 4, wherein the setting unit performs the setting process on the condition that the command value is greater than a command value threshold when the control unit controls a turn-off operation as the switching operation.

6. The inverter control device according to any one of claims 1 to 5, wherein the setting unit performs the setting process on the condition that, when the control unit controls a turn-off operation as the switching operation, a current value flowing through the armature winding before the turn-off operation is greater than a high current threshold.

7. The inverter control device according to any one of claims 1 to 6, wherein the setting unit performs the setting process on the condition that the rotational speed of the rotating electric machine is lower than a speed threshold value when the control unit controls a turn-off operation as the switching operation.

8. 8. The inverter control device according to claim 1, wherein the setting unit performs the setting process on condition that the temperature of the rotating electric machine is higher than a temperature threshold value.

9. 9. The inverter control device according to claim 1, wherein the setting unit performs the setting process on condition that the atmospheric pressure around the rotating electric machine is lower than an atmospheric pressure threshold value.

10. The system is mounted on a moving body, 10. The inverter control device according to claim 1, wherein the rotating electric machine is a power source for moving the moving body.

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