Motor Drive System

Abstract

To provide a motor drive system having an open winding structure capable of surely performing normal control when detecting an occurrence of a fault and switching a control system.SOLUTION: A current command calculation unit generates a current command value in accordance with a torque command value T* to be input. A PI control unit performs PI control for a difference between the current command value and each phase current detected by current sensors 9v, 9w to generate a voltage command value. A coordinate conversion and modulation unit generates a switching signal to be output to a gate of each of FETs 3a, 3b constituting inverters 2a, 2b on the basis of the voltage command value. A fault detection unit outputs a signal for switching to a single inverter drive that drives a motor 1 only by an inverter on the normal side when a fault is detected. The current command calculation unit generates a current command value for single inverter drive when the signal is input. An integral term substitution unit substitutes a voltage command estimated value to an integral term in the PI control when generating the voltage command value for single inverter drive.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a system in which an open winding type motor is driven by two inverters. [Background technology]

[0002] In a system for driving a motor having an open winding, as disclosed in Patent Document 1, for example, a first inverter is connected to one end of each phase winding of the motor, and a second inverter is connected to the other end. The first and second inverters are connected to first and second power sources via relays, respectively, and are supplied with a DC driving power source.

[0003] In such a drive system, when, for example, one of the switches in either the first or second inverter phase has an open fault, the other arm switches on the side to which the faulty switch belongs are turned OFF, and all arm switches on the opposite side are turned ON to create a neutral point. In this way, a fault can be handled by driving the motor with a single inverter.

[0004] In this case, however, only one drive power source can be used, which limits the torque that the motor can output. Therefore, in Patent Document 1, the switch cuts off the relay between the inverter on the faulty side and the power source, and changes the current command value on the normal inverter side so that the output torque of the motor is maintained at the torque that was output before the fault occurred. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-78263 Summary of the Invention [Problem to be solved by the invention]

[0006] However, during the period from when the microcomputer detects through software that a fault has occurred in the switch of one of the inverters to when the motor is switched to single-power drive control using the other inverter, the current path on the failed inverter side is restricted, so no current flows according to the command value.

[0007] Generally, in this type of current control, PI (Proportional-Integral) control is often applied to the difference between the command value and the detected current value. In this case, the integral term of the PI control increases during the period when the current corresponding to the command value does not flow. As a result, the voltage command value increases, and if the voltage command value exceeds the voltage range that can be output, there is a problem that normal control cannot be performed when switching to control of single power supply drive by the normal inverter.

[0008] The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide a motor drive system with an open winding structure that can reliably perform normal control when detecting the occurrence of a fault and switching the control method. [Means for solving the problem]

[0009] According to the motor drive system of claim 1, a first and second inverter connected to one end and the other end of each phase winding in a motor with an open winding structure is supplied with drive power from a first and a second power source, respectively. A current command generating unit generates a current command value according to an input torque command value, and a voltage command generating unit generates a voltage command value by performing proportional-integral control on the difference between the current command value and the current detected by the current detecting unit. A switching signal generating unit generates switching signals to be output to each switching element constituting the first and second inverters based on the voltage command value.

[0010] When the fault detection unit detects a fault occurring in a switching element or a power supply line connecting the first and second inverters and the first and second power supplies, it outputs a control switching signal for switching to single inverter drive in which the motor is driven only by the normal inverter. Then, when the control switching signal is input, the current command generation unit generates a current command value for single inverter drive, and when the voltage command generation unit generates a voltage command value for single inverter drive in response to the input of the control switching signal, it assigns a voltage command estimated value to the integral term in the proportional-integral control by the estimated value assignment unit.

[0011] With this configuration, even if the current path of the failed inverter is restricted and the current does not flow according to the command value during the time the motor drive is switched from normal control to single inverter drive, it is possible to prevent the integral term from increasing in the proportional-integral control. This makes it possible to prevent the voltage command value from exceeding the upper limit of the voltage that can be output, and therefore makes it possible to stably perform control when switching to single inverter drive. The motor drive system according to claim 1 includes a rotation speed detection unit (10) that detects the rotation speed of the motor, and the current command generation unit (13) and the estimated value substitution unit (15) each have a current command value map and a voltage command estimated value map corresponding to the output torque and rotation speed within a range in which the motor can be operated by a single inverter in order to determine a current command value and a voltage command value for driving the single inverter, and determine the current command value and the voltage command estimated value from the maps each has according to the torque command value and the motor rotation speed at the time when a control switching signal is input. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a motor drive system according to a first embodiment. [Diagram 2] Functional block diagram showing the configuration of the control circuit [Diagram 3] Functional block diagram showing the configuration of the current control unit [Figure 4] Functional block diagram showing the configuration of the PI control unit [Diagram 5] Flowchart showing the processing contents of the current command calculation unit [Figure 6] Torque / speed-current command value map [Figure 7] Flowchart showing the processing contents of the integral term substitution unit [Figure 8] Torque / speed vs. voltage estimated value map [Figure 9] FIG. 11 is a signal waveform diagram showing a simulation result when the control of the first embodiment is not applied. [Figure 10] FIG. 9 corresponds to a case where the control of the first embodiment is applied. [Figure 11] 11 is a flowchart showing the processing of a current command calculation unit according to a second embodiment. [Figure 12] A diagram showing the rotation speed-current command value map [Figure 13] Flowchart showing the processing contents of the integral term substitution unit [Figure 14] A diagram showing the rotation speed-integral term substitution value map [Figure 15] FIG. 1 shows the relationship between the motor rotation speed and output torque when operating with two power supplies and when operating with a single power supply. [Figure 16] FIG. 11 is a signal waveform diagram showing a simulation result when the control according to the second embodiment is not applied. [Figure 17] FIG. 14 corresponds to a case where the control of the second embodiment is applied. [Figure 18] 11 is a flowchart showing the process of a current command calculation unit according to a third embodiment. [Figure 19] A diagram showing the current command value according to the maximum rotation speed [Figure 20] Flowchart showing the processing contents of the integral term substitution unit [Figure 21] A diagram showing integral term substitution values ​​according to maximum rotation speed [Figure 22] 13 is a flowchart showing the processing of a current command calculation unit according to a fourth embodiment. [Figure 23] Flowchart showing the processing contents of the integral term substitution unit [Figure 24] 13 is a flowchart showing the processing contents of a gain change unit according to the fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] (First embodiment) A first embodiment will be described below. As shown in FIG. 1, the motor drive system of this embodiment drives a three-phase motor 1 with an open winding structure by a first inverter 2a and a second inverter 2b. Since the configuration of the first inverter 2a side and the configuration of the second inverter 2b side are symmetrical, in the following, unless it is necessary to distinguish between the a-side and the b-side, the symbols will be omitted. The inverter 2 is configured by connecting six switching elements, for example, power MOSFETs 3 in a three-phase bridge, and is supplied with driving power from a DC power source 4. A smoothing capacitor 5 is connected in parallel to the power source 4. The power sources 4a and 4b correspond to the first and second power sources, respectively.

[0014] Each phase output terminal of the first inverter 2a is connected to one end of each phase winding of the motor 1, and each phase output terminal of the second inverter 2b is connected to the other end of each phase winding. A gate signal output by a control circuit 6 is applied to the gate of each FET 3 constituting the inverter 2 via a drive circuit 7. The voltage of the power source 4 is detected by a voltage sensor 8 corresponding to a voltage detection unit, and the current flowing from the V-phase and W-phase output terminals of the first inverter 2a to the V-phase and W-phase windings of the motor 1 is detected by current sensors 9v and 9w corresponding to a current detection unit. The rotational position of the rotor of the motor 1 is detected by a position sensor 10 corresponding to a rotational position detection unit. The sensor signals of these sensors 8 to 10 are input to the control circuit 6. The phase current may be detected by detecting the U- and V-phases, the U- and W-phases, or all three phases.

[0015] In addition, a torque command value T* and a fail signal are input from the outside to the control circuit 6. The fail signal is a signal that is output when a failure detection function unit (not shown) detects an open failure or short circuit failure of the FET 3, a broken wire in the wiring between the inverter 2 and the power supply 4, a relay failure, or the like. For example, the technology disclosed in JP 2020-58176 A may be used to detect a short circuit failure, and the technology disclosed in JP 2020-96457 A may be used to detect an open failure.

[0016] As shown in FIG. 2, the control circuit 6 includes a fault detection unit 11, a command torque limiting unit 12, a current command calculation unit 13, a current control unit 14, an integral term substitution unit 15, and a gain change unit 16. When a fail signal is input, the fault detection unit 11, which corresponds to a switching signal output unit, identifies the fault location based on the signal, and when it determines an element to turn on all three phases of either the upper or lower arm, outputs a control switching signal to the command torque limiting unit 12 to the gain change unit 16. The control switching signal is a signal that switches the drive method of the motor 1 from normal control in which the motor is driven by the first inverter 2a and the second inverter 2b to single inverter drive control in which all three phases of one of the inverters 2 are turned on to connect the neutral point as described above, and the motor is driven by the other inverter 2. The fault detection unit 11 may be located outside the control circuit 6.

[0017] If a control switching signal is not input, the command torque limiting unit 12 outputs the torque command value T* as is. If a control switching signal is input, and the torque command value T* exceeds the upper limit of the torque that can be output in single-power-supply operation when a single inverter is driven, the command torque limiting unit 12 outputs the maximum torque that can be output. Hereinafter, the above normal control is sometimes referred to as "dual-power-supply operation," and single-inverter drive control is sometimes referred to as "single-power-supply operation."

[0018] A current command calculation unit 13, which corresponds to a current command value generation unit, calculates current command values ​​Id*, Iq* using maps and formulas based on the torque command value T*. If there is no control switching signal input, the calculation is performed using maps and formulas for dual-power supply operation, and if there is a control switching signal input, the calculation is performed using maps and formulas for single-power supply operation. A current control unit 14 receives the current command values ​​Id*, Iq*, signals from current sensors 9v and 9w, voltage sensors 8a and 8b, and rotor position sensor 10, and calculates a gate signal for driving the inverter 2. Again, if there is no control switching signal input, the calculation is performed for dual-power supply operation, and if there is a control switching signal input, the calculation is performed for single-power supply operation.

[0019] An integral term substitution unit 15, which corresponds to an estimated value substitution unit, calculates an integral term according to the rotation speed and torque and substitutes the integral term of the PI control when a control switching signal is input. A gain change unit 16 changes the PI gain when a control switching signal is input and the rotation speed N of the motor 1 is equal to or higher than a predetermined rotation speed. The operation of this gain change unit 16 will be described in the fifth embodiment. The rotation speed N of the motor 1 is obtained from a sensor signal of the rotor position sensor 10.

[0020] As shown in FIG. 3, in the current control unit 14, the electrical angle calculation unit 17 multiplies the mechanical angle θm of the motor 1 detected by the rotor position sensor 10 by the number of pole pairs to convert it into an electrical angle θe. The coordinate conversion unit 18 converts the phase currents acquired from the current sensors 9v and 9w into a d-axis current Id and a q-axis current Iq by performing a three-phase to two-phase conversion and a rotational coordinate conversion based on the electrical angle θe. In other words, vector control is performed. The current subtraction unit 19 calculates the deviations ΔId and ΔIq between the current command values ​​Id* and Iq* and the actual currents Id and Iq. The PI control units 20d and 20q corresponding to the voltage command generation unit perform PI calculations of the voltage command values ​​Vd* and Vq* so that the deviations ΔId and ΔIq calculated by the current subtraction unit 19 converge to "0".

[0021] The voltage limit calculation unit 21 calculates the square root of the sum of the squares of the voltage command values ​​Vd* and Vq*. √(Vd* 2 +Vq* 2 ) exceeds the value obtained by multiplying the power supply voltage by the upper limit of the voltage utilization rate, the voltage command values ​​Vd* and Vq* are limited by the following calculation. Vd*l=Vd*×(power supply voltage)×(voltage utilization upper limit) / √(Vd* 2 +Vq* 2 ) Vq*l = Vq* × (power supply voltage) × (voltage utilization upper limit) / √(Vd* 2 +Vq* 2 )

[0022] The upper limit of the voltage utilization rate is "0.61" for sine wave output and "0.78" for square wave output. If the power supply voltages detected by the voltage sensors 8a and 8b are V1 and V2, respectively, the power supply voltage used in the above calculation is (V1+V2) if there is no control switching signal input, and if there is a control switching signal input, the sensor value of the voltage sensor 8 on the inverter 2 side to be driven is used.

[0023] The coordinate conversion and modulation unit 22, which corresponds to the switching signal generation unit, converts the voltage command values ​​Vd* and Vq* into three-phase voltage command values ​​Vu, Vv, and Vw by performing fixed coordinate conversion and two-phase to three-phase conversion based on the electrical angle θe. Then, these voltage command values ​​are compared with the triangular wave that is the carrier of PWM control, and a PWM signal that is a switching signal is generated. If there is no input of a control switching signal, the amplitude of the triangular wave is set to (V1+V2), and if there is an input of a control switching signal, the value of the voltage sensor 8 of the inverter 2 to be driven is set to the amplitude of the triangular wave.

[0024] As shown in Fig. 4, the PI control unit 20q is composed of a subtractor 23q that subtracts the actual current Iq from the current command value Iq*, gain multiplication units 24q and 25q that multiply the subtraction result by a proportional gain Kpq and an integral gain Kiq, an integrator 26q that integrates the multiplication result of the integral gain Kiq, and an adder 27q that adds the integration result and the multiplication result of the proportional gain Kpq. The PI control unit 20d has a similar configuration except for the integral gain Kid and the part that multiplies the integral gain Kid. The outputs of the adders 27q and 27d become the voltage command values ​​Vq* and Vd*. Vq*=Vpq+Viq =Kpq×(Iq*-Iq)+Kiq×∫(Iq*-Iq)dt Vd*=Vpd+Vid =Kpd×(Id*-Id)+Kid×∫(Id*-Id)dt As described above with respect to the voltage limit calculation unit 21, the voltage command values ​​Vq* and Vd* have the following limitations: √(Vd* 2 +Vq* 2 ) ≦ (power supply voltage) × (voltage utilization upper limit) If this limit is exceeded, the system will lose control.

[0025] Next, the operation of this embodiment will be described. As shown in Fig. 5, when control is started, the current command calculation unit 13 judges whether or not a control switching signal is input (S1). If there is no input (NO), the current command values ​​Id*, Iq* are calculated by referring to the torque / rotation speed-current command value map for the two-power supply operation (S2), and if there is an input (YES), the current command values ​​Id*, Iq* are calculated by referring to the same map corresponding to the one-power supply operation (S3). The torque / rotation speed-current command value map is a two-dimensional map for calculating the corresponding current command values ​​Id*, Iq* with the torque T on the vertical axis and the rotation speed N on the horizontal axis, as shown in Fig. 6 as an example.

[0026] As shown in Fig. 7, when the integral term substitution unit 15 starts control, it judges whether the control switching signal is rising (S11). If the signal is not rising (NO), no special processing is performed. If the signal is rising (YES), the voltage command estimates Vid_est and Viq_est are calculated by referring to a torque / rotational speed-voltage command estimate map based on the torque command value T* and motor speed N input from the command torque limiting unit 12 (S12). Then, the voltage command estimates Vid_est and Viq_est are substituted for the integral terms Vid and Viq of the PI control unit 20 (S13). The torque / rotational speed-voltage command estimate map is a two-dimensional map for calculating the corresponding voltage command estimates Vid_est and Viq_est with the torque T as the vertical axis and the speed N as the horizontal axis, as shown in Fig. 8 as an example.

[0027] In the simulation results shown in Figs. 9 and 10, the motor drive conditions are a rotation speed of 3000 rpm and an output torque of 100 Nm. The occurrence of a short-circuit fault in the upper arm of the U-phase in one inverter 2a increases the integral term in the proportional-integral control. In the case shown in Fig. 9 where the technology of this embodiment is not applied, an overshoot occurs in the output torque during switching of control to single-inverter drive, and the magnitude of the voltage command value Va exceeds the voltage limit, making it uncontrollable. In contrast, in the case shown in Fig. 10 where the technology of the first embodiment is applied, the output torque follows the torque command value by substituting a voltage command estimate value into the integral term at the time of control switching, and the magnitude of the voltage command value Va remains within the voltage limit, so that control can be continued.

[0028] As described above, according to this embodiment, in the control circuit 6 that controls the switching of the first and second inverters 2a, 2b that drive the motor 1 with an open winding structure, the current command calculation unit 13 generates current command values ​​Id*, Iq* in response to the input torque command value T*, and the PI control units 20d and 20q generate voltage command values ​​Vd*, Vq* by performing PI control on the difference between the current command values ​​Id*, Iq* and each phase current detected by the current sensor 9. The coordinate conversion / modulation unit 22 generates switching signals to be output to the gates of each FET 3 that constitutes the inverter 2, based on the voltage command values ​​Vd*, Vq*.

[0029] When the fault detection unit 11 detects a fault occurring in the FET 3 or the power supply lines connecting the first and second inverters 2a and 2b to the first and second power supplies 4a and 4b, respectively, it outputs a control switching signal for switching to single inverter drive in which the motor 1 is driven only by the normal inverter 2. Then, when the control switching signal is input, the current command calculation unit 13 generates current command values ​​Id*, Iq* for single inverter drive, and when the integral term substitution unit 15 generates a voltage command value for single inverter drive in response to the input of the control switching signal, it substitutes the voltage command estimates Vid_est, Viq_est into the integral term in the PI control.

[0030] With this configuration, even if the current path of the failed inverter 2 is restricted and the current does not flow according to the command value during the time when the drive of the motor 1 is switched from normal control to single inverter drive, it is possible to prevent the integral term from increasing in the PI control. This makes it possible to prevent the voltage command values ​​Vd* and Vq* from exceeding the upper limit of the voltage that can be output, so that the control when switching to single inverter drive can be performed stably.

[0031] Further, in order to determine a current command value and a voltage command value for single inverter drive, current command calculation unit 13 and integral term substitution unit 15 each have a current command value map and a voltage command estimated value map corresponding to the output torque and rotation speed within the range in which the motor can be operated by a single inverter, and determine the current command values ​​Id*, Iq* and the voltage command estimated values ​​Vid_est, Viq_est from the maps they each have according to the torque command value T* and the rotation speed of motor 1 at the time when the control switching signal is input. This makes it possible to appropriately determine the current command values ​​Id*, Iq* and voltage commands Vd*, Vq* until transition to single inverter drive.

[0032] Second embodiment Hereinafter, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted, and only the different parts will be described. As shown in Fig. 11, when the current command calculation unit 13A judges "YES" in step S1, it judges whether the rotation speed of the motor 1 is equal to or higher than a predetermined rotation speed and satisfies the high rotation condition (S4). If the high rotation condition is not satisfied (NO), it executes step S3, and if the high rotation condition is satisfied (YES), it calculates the current command values ​​Id*, Iq* by referring to a rotation speed-current command value map that controls the output torque of the motor 1 at 0 [Nm] (S5).

[0033] The rotation speed-current command value map is a one-dimensional map with the rotation speed N on the horizontal axis, as shown in an example in Fig. 12, where the current command value Iq* is fixed to "0" and only the value of the current command value Id* is set. Also, as shown in Fig. 15, the above-mentioned predetermined rotation speed is set to a rotation speed that exceeds the voltage limit of single-power supply operation during the transient response of PI control when switching from dual-power supply operation to single-power supply operation. For example, if the voltage of the power supply 4 is Vdc, the predetermined rotation speed is set to a value that makes the amplitude of the back electromotive force generated in the winding of the motor 1 equal to or less than 4 / π×Vdc / 2.

[0034] As shown in Fig. 13, when the integral term substitution unit 15A judges "YES" in step S11, it judges whether or not the high rotation condition is satisfied as in step S4 (S14). If the high rotation condition is not satisfied (NO), it substitutes "0" into the integral terms Vid and Viq (S15). If the high rotation condition is satisfied (YES), it calculates the voltage command estimates Vid_est and Viq_est by referring to a rotation speed-voltage command estimate map based on the motor rotation speed N at the rise of the control switching signal (S16). Then, it executes step S13. The rotation speed-voltage command estimate map is a one-dimensional map for calculating the corresponding voltage command estimates Vid_est and Viq_est with the rotation speed N as the horizontal axis, as shown in an example in Fig. 14.

[0035] Hereinafter, the derivation of the current command value Id* in the second embodiment will be described. Also, (*) in the command value will be omitted. The voltage equation of the permanent magnet synchronous motor in the steady state is expressed by formula (1). Vd=rId-ωLqIq Vq = rIq + ω (LdId + Φ) … (1) r is the winding resistance [Ω], Ld and Lq are the self-inductances of the d-axis and q-axis [H], ω is the electrical angular frequency; number of rotations [rad / s], and Φ is the magnetic flux of the permanent magnet [Wb]. Since Iq = 0 [A], equation (1) becomes equation (1'). Vd=rId Vq = ω (LdId + Φ) … (1') If the magnitude of the voltage command value Va determined by equation (1') is within the voltage limit value during single power supply operation, control becomes possible. Va = √(Vd 2 +Vq 2 )=√{(rId) 2 +ω 2 (LdId+Φ) 2} ≦(power supply voltage) × (voltage utilization upper limit) … (2)

[0036] In equation (2), the current command value Id that has the smallest absolute value for each rotation speed ω is derived. Then, the voltage command estimates Vid_est and Viq_est corresponding to the derived current command value Id and Iq=0 are calculated.

[0037] The results of the simulation are shown in Fig. 16 and Fig. 17. The driving conditions of the motor are a rotation speed of 3000 rpm and an output torque of 100 Nm. The integral term in the PI control increases due to a short-circuit fault occurring in the upper arm of the U-phase in one inverter 2a. In the case shown in Fig. 16 where the technology of the second embodiment is not applied, an overshoot occurs in the output torque during switching of the control to single inverter drive, and the magnitude of the voltage command value Va exceeds the voltage limit and becomes uncontrollable. In contrast, in the case shown in Fig. 17 where the technology of the second embodiment is applied, the integral term is set to "0" at the time of control switching, so that the output torque follows the torque command value and the magnitude of the voltage command value Va remains within the voltage limit, and control can be continued.

[0038] As described above, according to the second embodiment, if the rotation speed of the motor 1 is equal to or higher than a predetermined rotation speed, the current command value map and the voltage command estimated value map determine the current command values ​​Id*, Iq* and the voltage command estimated values ​​Vid_est, Viq_est that make the output torque zero. If the rotation speed of the motor 1 is equal to or higher than a predetermined rotation speed, the current command calculation unit 13A and the integral term substitution unit 15A determine the current command values ​​Id*, Iq* and the voltage command estimated values ​​Vid_est, Viq_est, respectively, in accordance with the rotation speed N of the motor 1 at the time when the control switching signal is input. This can reliably prevent the voltage command value from exceeding the voltage limit when switching to single inverter drive.

[0039] Third embodiment In the third embodiment, as shown in Fig. 18, when the current command calculation unit 13B judges "YES" in step S4, it outputs the current command values ​​Id* and Iq* that control the output torque to 0 Nm at the maximum rotation speed (S6). In this case, as shown in Fig. 19, the current command value Iq* is set to 0 at the maximum rotation speed Nmax, and only the current command value Id* is set.

[0040] Also, as shown in Fig. 20, when the integral term substitution unit 15B judges "YES" in step S14, it substitutes the voltage command estimates Vid_est, Viq_est calculated from the current command value Id* for controlling the output torque to 0 Nm at the maximum rotation speed into the integral term in the PI control at the rising edge of the control switching signal (S18). In this case, as shown in Fig. 21, the voltage command estimates Vid_est, Viq_est are determined according to the current command value Id*.

[0041] As described above, according to the third embodiment, when the rotation speed of motor 1 is equal to or higher than a predetermined rotation speed, one current command value and one voltage command estimate value that make the output torque zero at the maximum rotation speed of motor 1 are set in the current command value map and the voltage command estimate value map, respectively. Then, when the rotation speed of motor 1 is equal to or higher than the predetermined rotation speed, current command calculation unit 13B and integral term substitution unit 15B output one current command value and one voltage command estimate value.

[0042] This allows control to be continued when switching to single inverter drive control even under conditions of a higher rotation speed of the motor 1. Also, the capacity of the map for determining the current command value and the voltage command estimated value can be reduced.

[0043] (Fourth embodiment) In the fourth embodiment, as shown in FIG. 22, when the current command generating unit 13C judges "YES" in step S4, it outputs the current command values ​​Id*, Iq* that control the output torque to 0 Nm regardless of the rotation speed (S7). In this case, the current command value Iq* is set to 0, and only the current command value Id*=-φ / Ld is set. Also, as shown in FIG. 23, when the estimated value substituting unit 15C judges "YES" in step S14, it substitutes the voltage command estimated values ​​Vid_est, Viq_est calculated from the current command value Id* that controls the output torque to 0 Nm regardless of the rotation speed into the integral term in the PI control at the rising edge of the switching control signal (S17). In this case, the voltage command estimated values ​​Vid_est, Viq_est are determined according to the current command value Id*.

[0044] The derivation of the current command value Id* that is the voltage command value Va will be described below. In equation (2), the value of ω becomes large under high speed rotation conditions, so the condition rId<<ω(LdId+Φ) holds. Then, equation (2) becomes Va = √(Vd 2 +Vq 2 )≒√{ω 2 (LdId+Φ) 2} …(3) If (LdId+Φ=0) in equation (3), single-power supply operation becomes possible without depending on the electrical angular frequency ω. Then, Id=-Φ / Ld is obtained.

[0045] As described above, according to the fourth embodiment, one current command value and one voltage command estimate value that make the output torque zero regardless of the rotation speed of the motor 1 are set in the current command value map and the voltage command estimate value map, respectively, if the rotation speed of the motor 1 is equal to or higher than a predetermined rotation speed. Then, the current command generating unit 13C and the estimate value substituting unit 15C output one current command value and one voltage command estimate value if the rotation speed of the motor 1 is equal to or higher than a predetermined rotation speed. Specifically, the d-axis current command value Id* and the q-axis current command value Iq* are set as Id*=-Φ / Ld, Iq*=0.

[0046] This allows control to be continued when switching to single inverter drive control even under conditions of a higher rotation speed of the motor 1. Also, the capacity of the map for determining the current command value and the voltage command estimated value can be reduced.

[0047] Fifth embodiment In the fifth embodiment, as shown in Fig. 24, the processing contents of the gain change unit 16 are characterized. The gain change unit 16 judges whether or not a control switching signal is input, as in step S1 etc. (S21), and if there is an input (YES), judges whether or not a high rotation condition exists, as in step S4 (S22). If a high rotation condition exists (YES), the value of the PI gain of the PI control unit 20 is set to a small value (S24). If a high rotation condition does not exist (NO), the value of the PI gain of the PI control unit 20 is returned to the original value (S23). In the case of the fifth embodiment, the same effects as those of the other embodiments can be obtained.

[0048] (Other embodiments) The switching elements are not limited to MOSFETs, but may be IGBTs, power transistors, or the like. The calculation of the command value and the like is not limited to the one using a map, but may be performed using a mathematical formula. The predetermined rotation speed is not limited to a value that makes the amplitude of the back electromotive force generated in the windings of the motor equal to or smaller than 4 / π×Vdc / 2.

[0049] Although the present disclosure has been described based on the embodiment, it is understood that the present disclosure is not limited to the embodiment or structure. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, and other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and concept of the present disclosure.

[0050] The means and / or functions provided by each device, etc., can be provided by software recorded in a tangible memory device and a computer that executes the software, software alone, hardware alone, or a combination of these. For example, when a control device is provided by an electronic circuit that is hardware, it can be provided by a digital circuit including a large number of logic circuits, or an analog circuit. [Explanation of symbols]

[0051] In the drawings, 1 indicates a motor, 2a indicates a first inverter, 2b indicates a second inverter, 3 indicates a MOSFET, 4a indicates a first power supply, 4b indicates a second power supply, 6 indicates a control circuit, 8 indicates a voltage sensor, 9 indicates a current sensor, 11 indicates a fault detection unit, 12 indicates a command torque limiting unit, 13 indicates a current command calculation unit, 14 indicates a current control unit, 15 indicates an integral term substitution unit, and 16 indicates a gain changing unit.

Claims

1. a first inverter (2a) connected to one end of each phase winding in a motor (1) having an open winding structure; a second inverter (2b) connected to the other end of each of the phase windings; a first power supply (4a) and a second power supply (4b) for supplying driving power to the first inverter (4a) and the second inverter (4b), respectively; A current detection unit (9) that detects a current flowing through a winding of the motor; a current command generating unit (13, 13A to 13C) that generates a current command value in response to an input torque command value; a voltage command generating unit (15, 15A to 15C, 16, 20) that generates a voltage command value by performing proportional-integral control on a difference between the current command value and a detected current; a switching signal generating unit (22) that generates a switching signal to be output to each switching element (3) constituting the first and second inverters based on the voltage command value; a fault detection unit (11) that detects a fault occurring in the switching element or in a power supply line connecting the first and second inverters and the first and second power supplies; A rotation speed detection unit (10) that detects the rotation speed of the motor, when detecting that one of the switching elements on one side of the first or second inverter has failed, or that a failure has occurred in one of the power supply lines connecting the first and second inverters and the first and second power supplies, the failure detection unit outputs a control switching signal for switching to a single inverter drive in which the inverter on the side where the failure has occurred is connected to a neutral point and the motor is driven only by the inverter on the normal side; the current command generating unit generates a current command value for driving the single inverter when the control switching signal is input; the voltage command generation unit includes an estimated value substitution unit (15) that substitutes a voltage command estimated value into an integral term in the proportional-integral control when generating a voltage command value for driving the single inverter in response to an input of the control switching signal; the current command generating unit (13) and the estimated value substituting unit (15) each have a current command value map and a voltage command estimated value map corresponding to an output torque and a rotation speed within a range in which the motor can be operated by a single inverter in order to determine a current command value and a voltage command value for driving the single inverter, a motor drive system which determines a current command value and a voltage command estimated value from respective maps according to a torque command value and a rotation speed of the motor at the time when the control switching signal is input;

2. the current command value map and the voltage command estimate value map are set with a current command value and a voltage command estimate value that make an output torque zero when a rotation speed of the motor is equal to or higher than a predetermined rotation speed, 2. The motor drive system according to claim 1, wherein, when the rotation speed of the motor is equal to or higher than a predetermined rotation speed, the current command generation unit (13A) and the estimated value assignment unit (15A) determine a current command value and a voltage command estimated value, respectively, in accordance with the rotation speed of the motor at the time when the control switching signal is input.

3. the current command value map and the voltage command estimate value map are set with one current command value and one voltage command estimate value that make the output torque zero at the maximum rotation speed of the motor when the rotation speed of the motor is equal to or higher than a predetermined rotation speed, 3. The motor drive system according to claim 2, wherein the current command generating unit (13B) and the estimated value assigning unit (15B) output the one current command value and the one voltage command estimated value when the rotation speed of the motor is equal to or higher than a predetermined rotation speed.

4. When the voltage command value is calculated by vector control, the magnetic flux of the permanent magnet constituting the rotor of the motor is denoted by Φ, and the d-axis inductance is denoted by Ld, as follows: In the current command value map, when the rotation speed of the motor is equal to or higher than a predetermined rotation speed, current command values ​​are set as a d-axis current command value Id* and a q-axis current command value Iq* such that Id*=-Φ / Ld and Iq*=0, The voltage command estimate value map has voltage command estimate values ​​corresponding to the current command values ​​Id* and Iq* set therein, 3. The motor drive system of claim 2, wherein the current command generating unit (13C) and the estimated value assigning unit (15C) output the current command values ​​Id* and Iq* and their corresponding voltage command estimated values ​​when the rotation speed of the motor is equal to or higher than a predetermined rotation speed.

5. A rotation speed detection unit (10) for detecting the rotation speed of the motor is provided, 2. The motor drive system according to claim 1, wherein the voltage command generating unit includes a gain changing unit (16) that reduces a proportional gain and an integral gain in the proportional-integral control if the rotation speed of the motor at the time when the control switching signal is input is equal to or higher than a predetermined rotation speed.

6. 6. The motor drive system according to claim 2, wherein the estimated value assignment unit (15A, 15B, 15C) assigns zero to the integral term if the rotation speed of the motor is less than a predetermined rotation speed.

7. If the power supply voltage is Vdc, 7. The motor drive system according to claim 2, wherein the predetermined rotation speed is set to a value that makes an amplitude of a back electromotive force generated in a winding of the motor equal to or smaller than 4 / π×Vdc / 2.

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