JP5805262B1 - Electric motor control device - Google Patents

Abstract

An object of the present invention is to suppress an output voltage limit of a motor generated by dead time without impairing control responsiveness in a motor control device. It is another object of the present invention to provide a motor control device with good speed stability that suppresses fluctuations in the neutral point potential of the motor as much as possible. An electric motor control device that controls a switching operation of an inverter according to a PWM control signal to convert a DC power supply voltage input to the inverter to control an output torque of the electric motor. The value calculation unit calculates the output command limit value based on the dead time and the carrier frequency of the PWM control signal, compares the dead time compensation command value for each phase with the output command limit value, and determines the dead time compensation command value. When there is a phase that exceeds the output command limit value, the final command value for each phase is corrected based on the difference between the dead time compensation command value of the phase that exceeds the output command limit value. The motor control device. [Selection] Figure 12

Description

  The present invention relates to a control device for an electric motor driven by an inverter, and more particularly to suppression of output voltage limitation of an electric motor generated due to dead time.

  Conventionally, a voltage-type PWM inverter has been used as a driving device for a three-phase motor. Generally, the voltage source PWM inverter includes an inverse conversion circuit including a high potential side switching element (also referred to as an upper switch and an upper SW) and a low potential side switching element (also referred to as a lower switch and a lower SW).

  Since the upper switch and the lower switch of each phase are short-circuited when turned on at the same time, in principle, switching is performed so that when one is turned on, the other is turned off. However, since a minute time delay occurs in the on / off switching, the time when both the upper and lower switches are turned off is prevented from being turned on instantaneously at the same time. This “time for preventing the short circuit of the upper and lower switches” is referred to as dead time.

  During this dead time period, the output voltage changes depending on the direction of the current of each phase (also called phase current). Therefore, if the PWM control signal to the switching element is generated without considering the output of the dead time period, the phase current Depending on the orientation, an error occurs from the desired output voltage. For this reason, a process for compensating for an output voltage error caused by dead time (referred to as dead time compensation process) is generally executed.

Specifically, when the current flows into the motor (the current is positive), the output voltage becomes a low potential side voltage during the dead time, that is, the upper SW is off and the lower SW is equivalent to on. Output. In this case, since the output is performed for the period during which the upper SW is on, it is not necessary to correct the upper SW duty.
On the other hand, when the current is flowing out of the motor (current is negative), the output voltage becomes a high potential side voltage during the dead time, that is, the upper SW is on and the lower SW is the same output as off. Become. In this case, since the output is performed not only during the period when the upper SW is turned on but also during the dead time, it is necessary to correct the duty for the upper SW. Specifically, the duty for the upper SW is decreased by a duty corresponding to the dead time so that the ON period of the upper SW is decreased by the dead time.
In addition, when it only describes as a duty, it shall mean the duty for upper SW.

By the above-described dead time compensation processing, the set duty command value range is changed by compensating the duty command value (referred to as basic duty command value) obtained from the relationship between the power supply voltage and the output voltage command value. For example, when the range of the output voltage command value and the power supply voltage are the same, the range of the basic duty command value is 0% to 100%. Here, the duty command value range set by the dead time compensation processing is as follows according to the direction of the current. Note that DT is a dead time, and CT is a carrier cycle.
When the current is positive: 0 to 100%
When the current is negative: (−2 × DT ÷ CT × 100) to (1-2 × DT ÷ CT) × 100%
That is, the entire range of duty command values that can be set is
(−2 × DT ÷ CT × 100) to 100%.

  As described above, the duty command value of the PWM control signal is changed by the dead time compensation process so that a desired output voltage is obtained. On the other hand, as shown below, the allowable duty command value range is limited in order to generate a PWM control signal that ensures a dead time. This allowable duty command value range varies depending on the method of generating the PWM control signal.

  Here, a generally used PWM control signal generation method using a triangular wave comparison method in which an isosceles triangular wave having the same ascending speed and descending speed is used as a PWM reference signal (referred to as carrier and triangular wave command value). Will be described with reference to FIG. In FIG. 1, the triangular wave command value is set to have a downward triangular shape in the carrier period so that the duty and the output voltage have a positive correlation. Further, in order to generate a dead time, a triangular wave command value C1 having a duty of 0% to 100% and a triangular wave obtained by shifting the triangular wave command value C1 downward (200 × dead time DT ÷ carrier cycle CT) [%] A command value C2 is created. Then, on / off switching of the upper SW is controlled based on the triangular wave command value C1, and dead time is provided by controlling on / off of the lower SW based on the triangular wave command value C2. Specifically, the upper SW is turned on when the duty exceeds the triangular wave command value C1, and turned off when the duty falls below the triangular wave command value C1. On the other hand, the lower SW is turned off when the duty exceeds the triangular wave command value C2, and turned on when the duty falls below the triangular wave command value C2. As a result, a PWM control signal called a center-aligned PWM in which on and off periods are set symmetrically from the center of the carrier cycle can be generated.

In the PWM control signal generation method shown in FIG. 1, it is necessary to ensure an off period of the dead time DT in the upper switch control signal before and after the carrier update timing. Therefore, the maximum duty PWM control signal that can be output by this method is the PWM control signal shown in FIG. That is, the maximum duty that can be output is (1-2 × DT ÷ CT) × 100 [%] with reference to FIGS. 1 and 2A. On the other hand, the PWM control signal with the minimum duty that can be output by this method is the PWM control signal shown in FIG. That is, the minimum duty that can be output is (−2 × DT ÷ CT × 100) [%] with reference to FIGS. 1 and 2B.
Therefore, in the PWM control signal generation method shown in FIG. 1, the settable duty command value ranges from (−2 × DT ÷ CT × 100) to (1-2 × DT ÷ CT) × 100 [%].

  Further, a PWM control signal generation method having a carrier update timing different from that in FIG. 1 will be described with reference to FIG. In FIG. 3, the triangular wave command value is set to have an upward triangular shape in the carrier period so that the duty and the output voltage have a positive correlation. The on / off control of the upper and lower SW is performed by the same method as in FIG. Also in this method, it is possible to generate a PWM control signal called a center-aligned PWM in which an on and off period is set for the target from the center of the carrier cycle. Regarding the PWM control signal shown in FIG. 3, the on / off state of the upper and lower switches at the time of the carrier update timing is inverted with respect to the PWM control signal shown in FIG.

In the PWM control signal generation method shown in FIG. 3, it is necessary to secure an off period of the dead time DT in the lower switch control signal before and after the carrier update timing. Therefore, the PWM control signal with the minimum duty that can be output by this method is the PWM control signal shown in FIG. That is, the minimum duty that can be output is 0 [%] with reference to FIG. 3 and FIG. On the other hand, the PWM control signal with the maximum duty that can be output by this method is the PWM control signal shown in FIG. That is, the maximum duty that can be output is 100 [%] with reference to FIGS. 3 and 4B.
Therefore, in the PWM control signal generation method shown in FIG. 3, the settable duty command value range is 0 to 100 [%].

  From the above, among the range of duty command values that can be set by the dead time compensation process, there is a duty range in which a PWM control signal cannot be generated. In this range, it is a common technique to clip to a duty that allows generation of a PWM control signal. In such a case, the output voltage of the corresponding phase does not match the desired output voltage. As a result, the U-phase, V-phase, and W-phase line voltages are distorted, and accordingly, the current supplied to the motor is also distorted, resulting in torque ripple, vibration, and noise.

As described above, in order to ensure the dead time of the switching element, the allowable duty command value range is limited according to the ratio of the dead time to the carrier cycle. In particular, when the carrier frequency is increased and the carrier cycle is shortened, if the switching element operating speed is the same, the dead time in switching per time does not change. The proportion of dead time in the cycle will increase. As a result, there is a problem that the duty range of the PWM control signal that cannot be output increases, and the output voltage range that can be output by the inverter is further limited.

  For example, in the synchronous PWM method in which the switching control is performed so that the carrier frequency is changed in synchronization with the rotation speed of the motor, the carrier cycle is shortened when the motor rotation speed is high, so that the output voltage range that can be output is further limited. It will be. That is, the maximum torque that can be output in the high-speed rotation region of the motor is limited.

  Therefore, Japanese Patent No. 5303030 (Patent Document 1) expands the voltage range that can be output when the target output cannot be output due to the output voltage limitation of the voltage conversion device that occurs due to dead time. A technique for reducing the carrier frequency of the switching element is disclosed.

  According to this technology, even when the output voltage is limited by the output voltage limitation of the voltage converter generated by the dead time, the ratio of the dead time in the carrier cycle is reduced by reducing the carrier frequency of the switching element, The output voltage range can be expanded so that the output voltage is not limited.

  Further, in Japanese Patent No. 5333422 (Patent Document 2), when there is a phase in which the ON time of each switching element is less than a predetermined time determined based on the dead time, Disclosed is a technique for changing the average value of the output voltage of each phase (hereinafter referred to as a neutral point potential) by controlling on / off switching of all phases so that the on-time is a predetermined time or longer. ing. More specifically, there is disclosed a technique for switching from two-phase modulation to three-phase modulation so that the on-time of each switching element is not less than the predetermined time when the on-time of each switching element is less than the predetermined time. Has been.

  According to this technology, since the ON time of each switching element can be set to a predetermined time or more, the line spacing due to the influence of the rise time until the switching element is turned on after the signal to turn on the switching element is output. Voltage distortion can be reduced. Moreover, a voltage utilization factor can be improved by combining two-phase modulation and three-phase modulation.

Japanese Patent No. 5303030 Japanese Patent No. 5333422

However, according to the technique disclosed in Patent Document 1, since the carrier frequency of the switching element is lowered, when the control calculation is performed in synchronization with the carrier frequency, the control calculation period corresponding to the dead time becomes long. Thus, the control gain cannot be set high and the control response is deteriorated. Further, since the carrier cycle of the switching element becomes longer, the ON duration time or the OFF duration time of the switching element becomes longer, the current ripple increases, and the torque ripple of the motor increases.

Further, according to the technique disclosed in Patent Document 2, when switching elements are on for less than a predetermined time, switching control of all phases is switched so that the on time of each switching element is equal to or longer than a predetermined time. The neutral point potential is changed and is based on whether the on-time of the switching element is less than the predetermined time. May be changed, and the speed stability of the motor may be deteriorated.

  Focusing on the relationship between each phase, taking the U phase and V phase of the motor as an example, the PWM control signal shown in FIG. When the switching elements are switched so that the on-time of the switching elements is longer than a predetermined time, the PWM control signal must be generated with a dead time secured. There is a difference in the amount, and as a result, the line voltage may be distorted. In other words, the output voltage range that can be output without causing distortion is limited. This problem is particularly likely to occur when the carrier frequency is high, where the proportion of dead time in the carrier period is large.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to suppress a motor output voltage limitation caused by dead time without impairing control responsiveness in a motor control device. To do. It is another object of the present invention to provide a motor control device with good speed stability that suppresses fluctuations in the neutral point potential of the motor as much as possible.

An electric motor control device according to the present invention includes an inverter including a plurality of upper switching elements disposed on a high potential side and a plurality of lower switching elements disposed on a low potential side, and an upper switching element in phase with the inverter And a control command calculation unit that generates a PWM control signal that performs a switching operation by providing a dead time so that the lower switching element and the lower switching element are not turned on at the same time,
A control apparatus for an electric motor that controls a switching operation of the inverter according to the PWM control signal to convert a DC power supply voltage input to the inverter to control an output torque of the electric motor;
The control command calculation unit includes a basic output command value calculation unit that calculates a basic output command value for each phase based on the torque command of the motor, and a dead time that cancels an output voltage that changes due to the influence of the dead time. A dead time compensation unit that calculates the dead time compensation command value for each phase by changing the basic output command value for each phase based on the compensation value, and the dead time compensation command value for each phase is the PWM control. A final command value calculation unit that calculates a final command value for each phase by correcting it so as to fall within a command value range that can be output as a signal, and a PWM signal generation that generates the PWM control signal based on the final command value And
The final command value calculation unit calculates an output command upper limit value based on the dead time and the carrier frequency of the PWM control signal, and compares the dead time compensation command value and the output command upper limit value for each phase. When there is a phase in which the dead time compensation command value is greater than the output command upper limit value, the difference between the dead time compensation command value of the larger phase and the output command upper limit value is calculated as an output command correction value, A value obtained by subtracting the output command correction value from the dead time compensation command value is used as the final command value for each phase .

An electric motor control device according to the present invention includes an inverter including a plurality of upper switching elements disposed on a high potential side and a plurality of lower switching elements disposed on a low potential side, and an in-phase upper side of the inverter A control command calculation unit that generates a PWM control signal that performs a switching operation by providing a dead time so that the switching element and the lower switching element are not simultaneously turned on,
A control apparatus for an electric motor that controls a switching operation of the inverter according to the PWM control signal to convert a DC power supply voltage input to the inverter to control an output torque of the electric motor;
The control command calculation unit includes a basic output command value calculation unit that calculates a basic output command value for each phase based on the torque command of the motor, and a dead time that cancels an output voltage that changes due to the influence of the dead time. A dead time compensation unit that calculates the dead time compensation command value for each phase by changing the basic output command value for each phase based on the compensation value, and the dead time compensation command value for each phase is the PWM control. A final command value calculation unit that calculates a final command value for each phase by correcting it so as to fall within a command value range that can be output as a signal, and a PWM signal generation that generates the PWM control signal based on the final command value And
The final command value calculation unit compares the dead time compensation command value for each phase with a preset output command lower limit value, and there is a phase in which the dead time compensation command value is smaller than the output command lower limit value Calculating a difference between the dead time compensation command value of the small phase and the output command lower limit value as an output command correction value, and subtracting the output command correction value from the dead time compensation command value of all phases. The final command value for each phase is used.

  ADVANTAGE OF THE INVENTION According to this invention, the control apparatus of the electric motor by which the output voltage restriction | limiting of the electric motor which generate | occur | produces by dead time was suppressed can be provided, without impairing control responsiveness. In addition, according to the present invention, it is possible to provide a motor control device with good speed stability in which fluctuations in the neutral point potential of the motor are suppressed as much as possible.

FIG. 3 is a diagram illustrating a PWM control signal generation method according to the first embodiment. FIG. 4 is a diagram illustrating maximum and minimum duty PWM control signals according to the first embodiment. The figure which illustrates the PWM control signal generation method which concerns on Embodiment 2. FIG. The figure which illustrates the PWM control signal of the maximum and the minimum duty which concerns on Embodiment 2. FIG. The figure explaining the subject by the method disclosed by patent document 2. FIG. The block diagram which illustrates the control apparatus of the electric motor concerning Embodiment 1 and Embodiment 2. FIG. The figure which illustrates the process block of the control part 60 concerning Embodiment 1 and Embodiment 2. FIG. The figure which illustrates the process block of the duty converter 70 concerning Embodiment 1 and Embodiment 2. FIG. The figure explaining the general duty command signal in an inverter. The figure explaining an example of the process of the duty converter 70 which concerns on Embodiment 1 with a flowchart. The figure explaining an example of the process of the duty converter 70 which concerns on Embodiment 1 with a flowchart. FIG. 6 is a diagram illustrating an effect of processing by the duty conversion unit 70 according to the first embodiment. The figure explaining an example of the process of the duty converter 70 which concerns on Embodiment 2 with a flowchart. The figure which illustrates the effect by the process of the duty converter 70 concerning Embodiment 2. FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, an inverter-driven motor control device will be described. In addition, about the same or equivalent part in a figure, the same code | symbol is attached | subjected and the description is not repeated.

Embodiment 1 FIG.
As shown in FIG. 6, the motor control apparatus according to the first embodiment controls driving of the motor 10 as a motor by pulse width modulation (hereinafter referred to as “PWM”). The motor 10 is, for example, an in-vehicle electric motor, and is applied to an electric fan, an oil pump, a water pump, an electric power steering device for assisting a steering operation of the vehicle, and the like. Of course, you may use for an electric motor besides the vehicle-mounted use.

The motor 10 is a three-phase brushless motor, and each has a rotor and a stator (not shown). The rotor is a disk-shaped member, and a permanent magnet is affixed to the surface thereof and has a magnetic pole. The stator accommodates the rotor therein so as to be relatively rotatable. The stator has protrusions that protrude in the radial direction at predetermined angles, and the U-phase coil 11, the V-phase coil 12, and the W-phase coil 13 shown in FIG. 6 are wound around the protrusions. The U-phase coil 11, the V-phase coil 12, and the W-phase coil 13 correspond to “windings”.
The first embodiment includes an inverter unit 20, a rotation angle sensor 30, a current detection unit 40, a capacitor 50, a choke coil 51, a control unit 60, a battery 90, and the like. The inverter unit 20 is a three-phase voltage type PWM inverter, and six switching elements 21 to 26 are bridge-connected in order to switch energization to each of the U-phase coil 11, the V-phase coil 12, and the W-phase coil 13. Yes. The switching elements 21 to 26 are MOSFETs which are a kind of field effect transistors, but other transistors, IGBTs, or the like may be used. Hereinafter, the switching elements 21 to 26 are referred to as SW21 to 26.

The drains of the three SWs 21 to 23 are connected to the positive electrode side of the battery 90. The sources of SW21 to 23 are connected to the drains of SW24 to 26, respectively. The sources of the SWs 24 to 26 are connected to the negative electrode side of the battery 90.
A connection point between the paired SW 21 and SW 24 is connected to one end of the U-phase coil 11. A connection point between the paired SW 22 and SW 25 is connected to one end of the V-phase coil 12. A connection point between the pair of SW 223 and SW 25 is connected to one end of the W-phase coil 13.
Hereinafter, SW21 to 23 which are switching elements arranged on the high potential side are referred to as “upper SW”, and SW24 to 26 which are switching elements arranged on the low potential side are referred to as “lower SW”. In the embodiment of the present paper, the low-potential side potential is set to 0 V for easy understanding.

  The current detection unit 40 includes a U-phase current detection unit 41, a V-phase current detection unit 42, and a W-phase current detection unit 43. In the present embodiment, the U-phase current detection unit 41, the V-phase current detection unit 42, and the W-phase current detection unit 43 are configured by shunt resistors. Hereinafter, the U-phase current detection unit 41, the V-phase current detection unit 42, and the W-phase current detection unit 43 are also referred to as current detection units 41 to 43 as appropriate. The U-phase current detection unit 41 detects a current flowing through the U-phase coil 11. V-phase current detection unit 42 detects a current flowing through V-phase coil 12. W-phase current detection unit 43 detects the current flowing through W-phase coil 13. Detection values (hereinafter referred to as “AD values”) detected by the current detection units 41 to 43 are stored in a register constituting the control unit 60 via the amplifier circuit 44. In addition, acquisition of AD value by a register | resistor is performed simultaneously about the current detection parts 41-43.

  The rotation angle sensor 30 (for example, a resolver) is attached to the motor 10 and detects position information indicating the rotor position of the motor 10, specifically, the rotation angle of the rotor. The rotation angle of the rotor detected by the rotation angle sensor 30 is converted into an electrical angle θ and stored in a register constituting the control unit 60.

  The capacitor 50 and the choke coil 51 are arranged between the battery 90 and the inverter unit 20 and constitute a power filter. Thereby, noise transmitted from other devices sharing the battery 90 is reduced. Further, noise transmitted from the inverter unit 20 side to other devices sharing the battery 90 is reduced. Capacitor 50 accumulates electric charge to assist power supply to SW 21 to 26 and suppress noise components such as surge current. The voltage Vcon of the capacitor 50 is acquired by the control unit 60.

  The control unit 60 controls the entire power conversion apparatus 1 and includes a microcomputer 67, a register (not shown), a drive circuit 68, and the like. As shown in FIG. 7, the control unit 60 includes a three-phase two-phase conversion unit 62, a controller 63, a two-phase three-phase conversion unit 64, a duty conversion unit 70, a PWM signal generation unit 80, and the like.

  The three-phase to two-phase converter 62 reads the AD value detected by the current detectors 41 to 43 and stored in the register, and based on the read AD value, the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw is calculated. Based on the calculated three-phase currents Iu, Iv, Iw and the electrical angle θ input from the rotation angle sensor 30, the d-axis current detection value Id and the q-axis current detection value Iq are calculated.

  The controller 63 performs a current feedback calculation from the d-axis current command value Id * and the q-axis current command value Iq * and the d-axis current detection value Id and the q-axis current detection value Iq, and the d-axis voltage command value Vd. * And q-axis voltage command value Vq * are calculated. More specifically, the current deviation ΔId between the d-axis current command value Id * and the d-axis current detection value Id and the current deviation ΔIq between the q-axis current command value Iq * and the q-axis current detection value Iq are calculated, In order to follow the current command values Id * and Iq *, the voltage command values Vd * and Vq * are calculated so that the current deviations ΔId and ΔIq converge to zero.

  The two-phase / three-phase converter 64 calculates the three-phase voltage command values Vu1, Vv1, and Vw1 based on the voltage command values Vd * and Vq * and the electrical angle θ calculated by the controller 63. The three-phase voltage command values Vu1, Vv1, and Vw1 are preferably set to be equal to or less than the DC power supply voltage input to the inverter, that is, the voltage Vcon of the capacitor 50.

  The duty converter 70 calculates a duty command value based on the three-phase voltage command values Vu1, Vv1, and Vw1 calculated by the two-phase / three-phase converter 64. As shown in FIG. 8, the duty conversion unit 70 includes a duty conversion unit 71, a dead time compensation unit 72, and a final command duty calculation unit 73.

  First, the duty converter 71 converts the three-phase voltage command values Vu1, Vv1, and Vw1 into duty converted values Vu2, Vv2, and Vw2 while referring to the voltage Vcon of the capacitor 50.

  In the dead time compensator 72, the duty conversion value Vu2 is based on the dead time compensation amount which is a value based on the dead time so as to cancel the amount of change in the voltage applied to the coils 11 to 13 due to the influence of the dead time. , Vv2, and Vw2 are changed, and compensation duty command values Vu3, Vv3, and Vw3 are calculated.

  The final command duty calculation unit 73 calculates a duty upper limit value Vmax limited by providing a dead time, and when the compensation duty command values Vu3, Vv3, and Vw3 are larger than the duty upper limit value Vmax, the compensation duty command value Vu3, Vv3, and Vw3 are corrected to be equal to or lower than the duty upper limit value Vmax, and adjustment duty command values Vu4, Vv4, and Vw4 are calculated. Further, adjustment duty command values Vu4, Vv4, and Vw4 smaller than the duty lower limit value Vmin that is the lower limit value that can be generated by the PWM signal generation unit 80 are replaced with the duty lower limit value Vmin, and the final duty command values Vu5, Vv5, and Vw5 are changed. calculate.

  Details of the processing in the duty converter 70 will be described later. The three-phase / two-phase converter 62, the controller 63, the two-phase / three-phase converter 64, and the remaining duty 71 correspond to the basic output command value calculator described in the claims, and the dead time compensator 72 charges. The final command duty calculation unit 73 corresponds to the final command value calculation unit described in the claims.

  The PWM signal processing unit 80 compares the final duty command values Vu5, Vv5, and Vw5 output from the duty conversion unit 70 with the PWM reference signal that is a carrier signal of the PWM signal, and controls on / off of the SWs 21 to 26. ing. In FIG. 7, the U-phase upper SW signal is UH_SW, the U-phase lower SW signal is UL_SW, the V-phase upper SW signal is VH_SW, the V-phase lower SW signal is VL_SW, and the W-phase upper SW signal is WH_SW, W The signal for the lower SW is expressed as WL_SW. In the present embodiment, a triangular wave comparison method is used in which a triangular wave having an isosceles triangle shape having the same ascending speed and descending speed is used as a PWM reference signal (referred to as a triangular wave command value).

  Here, the PWM control signal generation method by the triangular wave comparison method is the method shown in FIG. Specifically, the triangular wave command value is set to have a downward triangular shape in the carrier period so that the duty and the output voltage have a positive correlation. Further, in order to generate a dead time, a triangular wave command value C1 having a duty of 0% to 100% and a triangular wave obtained by shifting the triangular wave command value C1 downward (200 × dead time DT ÷ carrier cycle CT) [%] A command value C2 is created. The upper SWs 21, 22, and 23 are turned on when the duty exceeds the triangular wave command value C1, and turned off when the duty falls below the triangular wave command value C1. On the other hand, the lower SWs 24, 25, and 26 are turned off when the duty exceeds the triangular wave command value C2, and are turned on when the duty falls below the triangular wave command value C2. This generates a center-aligned PWM control signal in which the on and off periods are set symmetrically from the center of the carrier period. The PWM control signal according to the first embodiment ensures that the upper SW control signal is off for dead time before and after the carrier update timing.

Next, a general duty command will be described with reference to FIG.
As shown in FIG. 9 (a), the duty command signal is a sine wave signal having substantially the same amplitude and phases shifted from each other by 120 °, a U-phase duty Du command signal, a V-phase duty Dv command signal, and a W-phase duty. It consists of three signals of the Dw command signal. The average value of the maximum value and the minimum value of the duty command signal corresponds to a duty of about 50%.

  The PWM reference signal P is a triangular wave signal and is extremely shorter than the cycle of the sine wave of the duty command signal. In FIG. 9A, the number of PWM reference signals P in one cycle of the duty command signal is schematically illustrated, and the frequency of the PWM reference signal P is actually more frequent. FIG. 9B is an explanatory diagram schematically showing the magnitude relationship between the PWM reference signal P and the duty command signal by enlarging the region K of FIG. 9A. With reference to FIG. 9B, the phase of the U-phase duty Du command signal, the V-phase duty Dv command signal, and the W-phase duty Dw command signal is shifted by 120 ° from each other. It is shown that the command value is different between the U phase, the V phase, and the W phase. Note that the above-described duty command signal corresponds to the compensation duty command value calculated by the dead time compensation unit 72 in the present embodiment.

  By the way, in the PWM signal generation method according to the first embodiment, as described above with reference to FIGS. 1 and 2, the duty range of (1-2 × DT ÷ CT) × 100 to 100 [%] is a dead time. Thus, a desired output cannot be obtained, and the output is distorted.

  Therefore, in the present embodiment, a final command duty calculation unit that corrects the compensation duty command value in the duty conversion unit 70 of the control unit 60 so as to prevent output distortion even when the compensation duty command value is in the above range. 73 is provided. Therefore, the processing of the duty conversion unit 70 in the control unit 60 will be described based on the flowcharts shown in FIGS. 10 and 11.

Processing of the duty conversion unit 71:
In the first step S101 (hereinafter, “step” is omitted and simply indicated by the symbol “S”), the duty conversion values Vu2, Vv2, Vv1, Vv1 and the voltage Vcon of the capacitor 50 are converted from the three-phase voltage command values Vu1, Vv1, Vw1. Vw2 is calculated. The duty converted values Vu2, Vv2, and Vw2 are calculated by the following equations (1) to (3).
Vu2 = Vu1 ÷ Vcon × 100 (1)
Vv2 = Vv1 ÷ Vcon × 100 (2)
Vw2 = Vw1 ÷ Vcon × 100 (3)

Processing of the dead time compensation unit 72:
In S102, based on the AD value detected by the U-phase current detection unit 41, it is determined whether or not the U-phase current Iu is less than zero. In addition, when the U-phase current Iu is negative, a current flows out from the coil 11, and when the U-phase current Iu is positive, a current flows into the coil 11. The same applies to the other phase currents.
When the U-phase current Iu is less than 0 (S102: YES), that is, when the U-phase current Iu is negative, the process proceeds to S103. When the U-phase current Iu is 0 or more (S102: NO), that is, when the U-phase current Iu is positive, the process proceeds to S104.
In S103, when the U-phase current Iu is negative (S102: YES), the output voltage becomes the voltage Vcon of the capacitor 50 during the dead time when the phase current is negative, that is, the upper SW is on, the lower SW Therefore, dead time compensation is performed to compensate for this, and a compensation duty command value Vu3 is calculated. The compensation duty command value Vu3 is calculated by the following equation (4).
Vu3 = Vu2-2 × DT ÷ CT × 100 (4)
In S104, which shifts to the case where the U-phase current Iu is positive (S102: NO), when the phase current is positive, the output voltage becomes low potential side, that is, 0V during the dead time, that is, the upper SW is off, the lower SW Therefore, it is not necessary to compensate the duty conversion value Vu2. Accordingly, the compensation duty command value Vu3 is calculated by the following equation (5).
Vu3 = Vu2 (5)

In S105, based on the AD value detected by the V-phase current detector 42, it is determined whether or not the V-phase current Iv is less than zero.
When the V-phase current Iv is less than 0 (S105: YES), that is, when the V-phase current Iv is negative, the process proceeds to S106. When the V-phase current Iv is 0 or more (S105: NO), that is, when the V-phase current Iv is positive, the process proceeds to S107.
In S106, which shifts to the case where the V-phase current Iv is negative (S105: YES), the compensation duty command value Vv3 is calculated by the following equation (6) in the same manner as in the U-phase.
Vv3 = Vv2-2 × DT ÷ CT × 100 (6)
In S107, when the V-phase current Iv is positive (S105: NO), the compensation duty command value Vv3 is calculated by the following equation (7) in the same manner as in the U-phase.
Vv3 = Vv2 (7)

In S108, based on the AD value detected by the W-phase current detection unit 43, it is determined whether or not the W-phase current Iw is less than zero.
When the W-phase current Iw is less than 0 (S108: YES), that is, when the W-phase current Iw is negative, the process proceeds to S109. When the W-phase current Iw is 0 or more (S108: NO), that is, when the W-phase current Iw is positive, the process proceeds to S110.
In S109, when the W-phase current Iw is negative (S108: YES), the compensation duty command value Vw3 is calculated by the following equation (8) in the same manner as in the U-phase.
Vw3 = Vw2-2 × DT ÷ CT × 100 (8)
In S110, when the W-phase current Iw is positive (S108: NO), the compensation duty command value Vw3 is calculated by the following equation (9) in the same manner as in the U-phase.
Vw3 = Vw2 (9)
In the present embodiment, the dead time compensation amount recited in the claims is (−2 × DT ÷ CT × 100) when the phase current is negative, and is 0 when the phase current is positive.

Processing of final command duty calculation unit 73:
In S111, an upper limit value Vmax of the duty that can be generated by the PWM signal generation unit is obtained. In the present embodiment, duty upper limit value Vmax is calculated by the following equation (10).
Vmax = (1-2 × DT ÷ CT) × 100 (10)

In S112, the U-phase compensation duty command value Vu3 is compared with the duty upper limit value Vmax, and it is determined whether or not Vu3> Vmax.
When it is determined that Vu3> Vmax (S112: YES), the process proceeds to S113. If it is determined that Vu3 ≦ Vmax (S112: NO), the process proceeds to S114.
In S113, when it is determined that Vu3> Vmax (S112: YES), it is necessary to correct the compensation duty command value Vu3 to be equal to or lower than the duty upper limit value Vmax, and the correction amount Vudf is calculated. To do. The correction amount Vudf is calculated by the following equation (11).
Vudf = Vu3-Vmax (11)
When it is determined that Vu3 ≦ Vmax (S112: NO), in S114, the compensated duty command value Vu3 is equal to or lower than the duty upper limit value Vmax and is a duty that can be generated as a PWM control signal, so correction is necessary. There is no. Accordingly, the correction amount Vudf is calculated by the following equation (12).
Vudf = 0 (12)

In S115, the V-phase compensation duty command value Vv3 is compared with the duty upper limit value Vmax, and it is determined whether or not Vv3> Vmax.
If it is determined that Vv3> Vmax (S115: YES), the process proceeds to S116. When it is determined that Vv3 ≦ Vmax (S115: NO), the process proceeds to S117.
In S116, which is shifted to the case where it is determined that Vv3> Vmax (S115: YES), the correction amount Vvdf is calculated by the following equation (13) in the same manner as in the U phase.
Vvdf = Vv3-Vmax (13)
In S117, the process proceeds to the case where it is determined that Vv3 ≦ Vmax (S115: NO), the correction amount Vvdf is calculated by the following equation (14) in the same manner as in the U phase.
Vvdf = 0 (14)

In S118, the W-phase compensation duty command value Vw3 is compared with the duty upper limit value Vmax, and it is determined whether or not Vw3> Vmax.
When it is determined that Vw3> Vmax is satisfied (S118: YES), the process proceeds to S119. When it is determined that Vw3 ≦ Vmax (S118: NO), the process proceeds to S120.
In S119, the process proceeds to the case where it is determined that Vw3> Vmax (S118: YES), the correction amount Vwdf is calculated by the following equation (15) by the same method as the U phase.
Vwdf = Vw3-Vmax (15)
In S120, the process proceeds to the case where it is determined that Vw3 ≦ Vmax (S118: NO), the correction amount Vwdf is calculated by the following equation (16) in the same manner as in the U phase.
Vwdf = 0 (16)

In S121, compensation duty command values Vu3, Vv3, and Vw3 for each phase are corrected with correction amounts Vudf, Vvdf, and Vwdf, and adjusted duty command values Vu4, Vv4, and Vw4 that are equal to or lower than the duty upper limit value Vmax are calculated. Adjustment duty command values Vu4, Vv4, and Vw4 are calculated by the following equations (17) to (19).
Vu4 = Vu3-Vudf-Vvdf-Vwdf (17)
Vv4 = Vv3-Vudf-Vvdf-Vwdf (18)
Vw4 = Vw3−Vudf−Vvdf−Vwdf (19)
As shown in the equations (17) to (19), the correction amounts Vudf, Vvdf, and Vwdf are equally subtracted from the compensation duty command values Vu3, Vv3, and Vw3 for the U phase, the V phase, and the W phase, so the line voltage does not change. Therefore, if the adjustment duty command values Vu4, Vv4, and Vw4 are within a possible output range, a desired output can be obtained.
When the compensation duty command values Vu3, Vv3, and Vw3 are all equal to or lower than the duty upper limit value Vmax, the correction amounts Vudf, Vvdf, and Vwdf are all 0, which is equivalent to the fact that no substantial correction is performed. .

In S122, a lower limit value Vmin of the duty that can be generated by the PWM signal generation unit is obtained. In the present embodiment, duty lower limit value Vmin is calculated by the following equation (10).
Vmin = −2 × DT ÷ CT × 100 (20)

In S123, the U-phase adjustment duty command value Vu4 and the duty lower limit value Vmin are compared to determine whether Vu4 <Vmin.
If it is determined that Vu4 <Vmin (S123: YES), the process proceeds to S124. When it is determined that Vu4 ≧ Vmin (S123: NO), the process proceeds to S125.
When it is determined that Vu4 <Vmin (S123: YES), in S124, the adjusted duty command value Vu4 is a duty that cannot be generated as a PWM control signal. Therefore, as shown in the following equation (21) The final duty command value Vu5 is set to the duty lower limit value Vmin.
Vu5 = Vmin (21)
When it is determined that Vu4 ≧ Vmin (S123: NO), in S125, the adjusted duty command value Vu4 is a duty that can be generated as a PWM control signal, and therefore, there is no need to change it. Accordingly, the final duty command value Vu5 is calculated by the following equation (22).
Vu5 = Vu4 (22)

In S126, the V-phase adjustment duty command value Vv4 and the duty lower limit value Vmin are compared to determine whether Vv4 <Vmin.
When it is determined that Vv4 <Vmin (S126: YES), the process proceeds to S127. When it is determined that Vv4 ≧ Vmin (S126: NO), the process proceeds to S128.
When it is determined that Vv4 <Vmin (S126: YES), in S127, the final duty command value Vv5 is the duty lower limit value Vmin as shown in the following equation (23) by the same method as the U phase. Set to
Vv5 = Vmin (23)
In S128, which is shifted to the case where it is determined that Vv4 ≧ Vmin (S126: NO), the final duty command value Vv5 is calculated by the following equation (24) by the same method as the U phase.
Vv5 = Vv4 (24)

In S129, the W-phase adjustment duty command value Vw4 and the duty lower limit value Vmin are compared to determine whether Vw4 <Vmin.
When it is determined that Vw4 <Vmin (S129: YES), the process proceeds to S130. When it is determined that Vw4 ≧ Vmin (S129: NO), the process proceeds to S131.
When it is determined that Vw4 <Vmin (S129: YES), in S130, the final duty command value Vw5 is the duty lower limit value Vmin as shown in the following equation (25) by the same method as the U phase. Set to
Vw5 = Vmin (25)
In S131, the process proceeds to the case where it is determined that Vw4 ≧ Vmin (S129: NO), the final duty command value Vw5 is calculated by the following equation (26) by the same method as the U phase.
Vw5 = Vw4 (26)

  FIG. 12 schematically shows changes in the duty of each phase due to the processing shown in the flowcharts of FIGS. The period indicated by A in FIG. 12 is a period in which the duty is close to 100%, more precisely, (1-2 × DT ÷ CT) × 100% to 100%. Is impossible to generate. In such a case, the duty command value of each phase is equally reduced to change to a duty that can generate a PWM control signal. Since the duty command value of each phase is reduced equally, the line voltage is the same as before the duty command value of each phase is reduced. Further, in this embodiment, the correction is not performed when the duty is in the vicinity of 0%, more precisely, in the range of (−2 × DT ÷ CT × 100)% to 0%. This is because the PWM signal generation method of the present embodiment can generate a PWM control signal in a range of (−2 × DT ÷ CT × 100)% to 0%. In other words, in the technique shown in the present embodiment, when output limitation due to dead time is applied, exactly, correction is performed only when the duty command value is (1-2 × DT ÷ CT) × 100% to 100%. It becomes logic. When the duty command value of each phase is corrected so as to be lowered, the duty control value becomes lower than the duty lower limit value at which the PWM control signal cannot be generated, specifically (−2 × DT ÷ CT × 100)%. Then, the duty command value of the corresponding phase is clipped to the duty lower limit value. The duty command value shown in FIG. 12 is typically a sine wave, but in practice, it is a waveform in which duty adjustment for dead time compensation is added to the sine wave.

  Only when the compensation duty command value calculated by compensating the output during the dead time period cannot be generated as a PWM control signal by the processing shown in the flowchart above, the compensation duty command value for all phases can be corrected equally. it can. Further, even when the duty command value cannot be generated as a PWM control signal by this correction, control can be performed so that a desired output is obtained as much as possible.

According to the first embodiment described above, the duty command value for all phases is corrected equally when the duty command value exceeds the duty upper limit value at which output is not possible due to dead time without changing the carrier cycle. Without restricting the performance, it is possible to suppress the output voltage limitation of the electric motor that occurs due to the dead time. Further, since the correction is performed only when the duty command value is a value that makes it impossible to generate a PWM control signal, an electric motor control device with good speed stability that suppresses fluctuations in the neutral point potential of the electric motor as much as possible is provided. Can do.

  In the first embodiment, the duty of the PWM control signal is used as the output command value. However, the present invention is not limited to this as long as the value has a correlation with the duty of the PWM control signal. For example, the output voltage command value of each phase may be used as the output command value.

Embodiment 2. FIG.
The motor control apparatus according to the second embodiment of the present invention is a modification of the first embodiment, and differs in the method of generating the PWM control signal for the up / down switch. Due to the generation method of the PWM control signal being different, the duty range that can be generated by the PWM signal generation unit is different, and the duty whose output is limited is changed by the dead time. Therefore, in the second embodiment, a description will be given of a method of suppressing the output voltage limit of the electric motor that is generated due to the dead time when the PWM control signal generation method is used.

In the motor control apparatus according to the second embodiment, the points different from the first embodiment are the PWM control signal generation method and the processing of the control unit 60, more specifically the processing of the duty conversion unit 70. Since the processing and configuration are the same as those in the first embodiment, description thereof is omitted.

  The PWM control signal generation method in the second embodiment is the method shown in FIG. Specifically, the triangular wave command value is set to have an upward triangular shape in the carrier period so that the duty and the output voltage have a positive correlation. Further, in order to generate a dead time, a triangular wave command value C1 having a duty of 0% to 100% and a triangular wave obtained by shifting the triangular wave command value C1 downward (200 × dead time DT ÷ carrier cycle CT) [%] A command value C2 is created. The upper SWs 21, 22, and 23 are turned on when the duty exceeds the triangular wave command value C1, and turned off when the duty falls below the triangular wave command value C1. On the other hand, the lower SWs 24, 25, and 26 are turned off when the duty exceeds the triangular wave command value C2, and are turned on when the duty falls below the triangular wave command value C2. This generates a center-aligned PWM control signal in which the on and off periods are set symmetrically from the center of the carrier period. Note that the PWM control signal in the second embodiment ensures that the dead SW is off for the lower SW control signal before and after the carrier update timing.

  By the way, in the PWM signal generation method according to the second embodiment, as described above with reference to FIGS. 3 and 4, the duty range of (−200 × DT ÷ CT) to 0 [%] is desired depending on the dead time. This is a region where output cannot be obtained and output is distorted.

  Therefore, in the second embodiment, the final command duty calculation is performed in which the duty conversion unit 70 of the control unit 60 corrects the compensation duty command value so as to prevent output distortion even when the compensation duty command value is within the above range. A portion 73 is provided. Therefore, the processing 70 of the duty conversion unit in the control unit 60 will be described below. Since duty conversion unit 71 and dead time compensation unit 72 are the same as those in the first embodiment, description thereof will be omitted, and final command duty calculation unit 73 of duty conversion unit 70 will be described based on the flowchart shown in FIG. To do.

Processing of final command duty calculation unit 73:
Compensation duty command values Vu3, Vv3, and Vw3 are obtained by the duty conversion unit 71 and the dead time compensation unit 72.
In S211, a lower limit value Vmin of the duty that can be generated by the PWM signal generation unit is obtained. In the second embodiment, the duty lower limit value Vmin is calculated by the following equation (30).
Vmin = 0 (30)

In S212, the U-phase compensation duty command value Vu3 and the duty lower limit value Vmin are compared to determine whether Vu3 <Vmin.
When it is determined that Vu3 <Vmin (S212: YES), the process proceeds to S213. When it is determined that Vu3 ≧ Vmin (S212: NO), the process proceeds to S214.
When it is determined that Vu3 <Vmin (S212: YES), in S213, it is necessary to correct the compensation duty command value Vu3 to be equal to or higher than the duty lower limit value Vmin, and the correction amount Vudf is calculated. To do. The correction amount Vudf is calculated by the following equation (11).
Vudf = Vu3-Vmin (31)
When it is determined that Vu3 ≧ Vmin (S212: NO), in S214, the compensated duty command value Vu3 is equal to or greater than the duty lower limit value Vmin, and is a duty that can be generated as a PWM control signal, so correction is necessary. There is no. Accordingly, the correction amount Vudf is calculated by the following equation (12).
Vudf = 0 (32)

In S215, the V-phase compensation duty command value Vv3 and the duty lower limit value Vmin are compared to determine whether Vv3 <Vmin.
When it is determined that Vv3 <Vmin (S215: YES), the process proceeds to S216. When it is determined that Vv3 ≧ Vmin (S215: NO), the process proceeds to S217.
In S216, the process proceeds to the case where it is determined that Vv3 <Vmin (S215: YES), the correction amount Vvdf is calculated by the following equation (33) in the same manner as in the U phase.
Vvdf = Vv3-Vmin (33)
In S217, the process proceeds to the case where it is determined that Vv3 ≧ Vmin (S215: NO), the correction amount Vvdf is calculated by the following equation (34) by the same method as the U phase.
Vvdf = 0 (34)

In S218, the W-phase compensation duty command value Vw3 and the duty lower limit value Vmin are compared to determine whether or not Vw3 <Vmin.
When it is determined that Vw3 <Vmin (S218: YES), the process proceeds to S219. When it is determined that Vw3 ≧ Vmin (S218: NO), the process proceeds to S220.
In S219, the process proceeds to the case where it is determined that Vw3 <Vmin (S218: YES), the correction amount Vwdf is calculated by the following equation (35) by the same method as the U phase.
Vwdf = Vw3-Vmin (35)
In S220, the process proceeds to the case where it is determined that Vw3 ≧ Vmin (S218: NO), the correction amount Vwdf is calculated by the following equation (36) in the same manner as in the U phase.
Vwdf = 0 (36)

In S221, compensation duty command values Vu3, Vv3, and Vw3 for each phase are corrected with correction amounts Vudf, Vvdf, and Vwdf, and adjusted duty command values Vu4, Vv4, and Vw4 that are equal to or greater than the duty lower limit value Vmin are calculated. Adjustment duty command values Vu4, Vv4, and Vw4 are calculated by the following equations (37) to (39).
Vu4 = Vu3-Vudf-Vvdf-Vwdf (37)
Vv4 = Vv3-Vudf-Vvdf-Vwdf (38)
Vw4 = Vw3-Vudf-Vvdf-Vwdf (39)
As shown in the equations (37) to (39), the correction amounts Vudf, Vvdf, and Vwdf are equally subtracted from the compensation duty command values Vu3, Vv3, and Vw3 of the U phase, the V phase, and the W phase, so the line voltage does not change. Therefore, if the adjustment duty command values Vu4, Vv4, and Vw4 are within a possible output range, a desired output can be obtained.
Since the correction amounts Vudf, Vvdf, and Vwdf are 0 or less, correction is made here to increase the duty. When the compensation duty command values Vu3, Vv3, and Vw3 are all equal to or higher than the duty lower limit value Vmin, the correction amounts Vudf, Vvdf, and Vwdf are all 0, which is equivalent to the fact that no substantial correction is performed. .

In S222, an upper limit value Vmax of the duty that can be generated by the PWM signal generation unit is obtained. In the present embodiment, duty upper limit value Vmax is calculated by the following equation (40).
Vmax = 100 (40)

In S223, the U-phase adjustment duty command value Vu4 and the duty upper limit value Vmax are compared to determine whether Vu4> Vmax.
When it is determined that Vu4> Vmax is satisfied (S223: YES), the process proceeds to S224. When it is determined that Vu4 ≦ Vmax is satisfied (S223: NO), the process proceeds to S225.
When it is determined that Vu4> Vmax (S223: YES), in S224, the adjusted duty command value Vu4 is a duty that cannot be generated as a PWM control signal, and therefore, as shown in the following equation (41) The final duty command value Vu5 is set to the duty upper limit value Vmax.
Vu5 = Vmax (41)
When it is determined that Vu4 ≦ Vmax is satisfied (S223: NO), the adjustment duty command value Vu4 is a duty that can be generated as a PWM control signal, so there is no need to change it. Accordingly, the final duty command value Vu5 is calculated by the following equation (42).
Vu5 = Vu4 (42)

In S226, the V-phase adjustment duty command value Vv4 and the duty upper limit value Vmax are compared to determine whether Vv4> Vmax.
When it is determined that Vv4> Vmax is satisfied (S226: YES), the process proceeds to S227. When it is determined that Vv4 ≦ Vmax (S226: NO), the process proceeds to S228.
When it is determined that Vv4> Vmax (S226: YES), in S227, the final duty command value Vv5 is set to the duty upper limit value Vmax as shown in the following equation (43) by the same method as the U phase. Set to
Vv5 = Vmax (43)
In S228, the process proceeds to a case where it is determined that Vv4 ≦ Vmax (S226: NO), the final duty command value Vv5 is calculated by the following equation (44) in the same manner as in the U phase.
Vv5 = Vv4 (44)

In S229, the W-phase adjustment duty command value Vw4 is compared with the duty upper limit value Vmax to determine whether or not Vw4> Vmax.
When it is determined that Vw4> Vmax (S229: YES), the process proceeds to S230. When it is determined that Vw4 ≦ Vmax is satisfied (S229: NO), the process proceeds to S231.
When it is determined that Vw4> Vmax (S229: YES), in S230, the final duty command value Vw5 is the duty upper limit value Vmax as shown in the following equation (45) by the same method as the U phase. Set to
Vw5 = Vmax (45)
In S231, which is shifted to the case where it is determined that Vw4 ≦ Vmax (S229: NO), the final duty command value Vw5 is calculated by the following equation (46) by the same method as the U phase.
Vw5 = Vw4 (46)

  FIG. 14 schematically shows changes in the duty of each phase due to the processing shown in the flowchart of FIG. The period indicated by B in FIG. 14 is a period in which the duty is in the vicinity of 0%, more precisely, (−2 × DT ÷ CT × 100)% to 0%. This is the case when it cannot be generated. In such a case, the duty command value of each phase is increased equally to change to a duty that can generate the PWM control signal. Since the duty command value of each phase is increased equally, the line voltage is the same as before the duty command value of each phase is increased. In the present embodiment, correction is not performed when the duty is in the vicinity of 100%, more precisely, in the range of (1-2 × DT ÷ CT) × 100% to 100%. This is because the PWM signal generation method of the present embodiment can generate the PWM control signal even in the range of (1-2 × DT ÷ CT) × 100% to 100%. That is, in the technique shown in the present embodiment, when output restriction is imposed due to dead time, the logic that corrects only when the duty command value is (−2 × DT ÷ CT × 100)% to 0% is accurate. It becomes. In addition, when the duty command value of each phase is corrected so as to increase, the duty upper limit value at which the PWM control signal cannot be generated, specifically, when it exceeds 100%, the duty command value of the corresponding phase is set. Clip to the upper limit of the duty. The duty command value shown in FIG. 14 is typically a sine wave, but in reality, the waveform is obtained by adding a duty adjustment for dead time compensation to the sine wave.

  Only when the compensation duty command value calculated by compensating the output during the dead time period cannot be generated as a PWM control signal by the processing shown in the flowchart above, the compensation duty command value for all phases can be corrected equally. it can. Further, even when the duty command value cannot be generated as a PWM control signal by this correction, control can be performed so that a desired output is obtained as much as possible.

According to the second embodiment described above, since the duty command value for all phases is corrected equally when the duty command value falls below the duty lower limit value at which output is not possible due to dead time without changing the carrier cycle, the control response Without restricting the performance, it is possible to suppress the output voltage limitation of the electric motor that occurs due to the dead time. Further, since the correction is performed only when the duty command value is a value that makes it impossible to generate a PWM control signal, an electric motor control device with good speed stability that suppresses fluctuations in the neutral point potential of the electric motor as much as possible is provided. Can do.

  In the second embodiment, the duty of the PWM control signal is used as the output command value. However, the present invention is not limited to this as long as the value has a correlation with the duty of the PWM control signal. For example, the output voltage command value of each phase may be used as the output command value.

In the present invention, each embodiment can be appropriately modified or omitted within the scope of the invention.
In addition, in each figure, the same code | symbol shows the same or an equivalent part.

1 power converter, 10 motor (rotary electric machine),
11 to 13 coil (winding), 20 inverter section,
21 to 23 Upper SW (high potential side switching element),
24 to 26 Lower SW (low potential side switching element),
30 rotation angle sensor, 40 current detector,
50 capacitors, 51 choke coils,
60 control unit, 90 battery,
DT dead time, CT carrier period.

Claims (14)

An inverter including a plurality of upper switching elements arranged on the high potential side and a plurality of lower switching elements arranged on the low potential side, and the upper switching element and the lower switching element in the same phase of the inverter are simultaneously turned on A control command calculation unit that generates a PWM control signal that performs a switching operation with a dead time so as not to become,
A control apparatus for an electric motor that controls a switching operation of the inverter according to the PWM control signal to convert a DC power supply voltage input to the inverter to control an output torque of the electric motor;
The control command calculation unit includes a basic output command value calculation unit that calculates a basic output command value for each phase based on the torque command of the motor, and a dead time that cancels an output voltage that changes due to the influence of the dead time. A dead time compensation unit that calculates the dead time compensation command value for each phase by changing the basic output command value for each phase based on the compensation value, and the dead time compensation command value for each phase is the PWM control. A final command value calculation unit that calculates a final command value for each phase by correcting it so as to fall within a command value range that can be output as a signal, and a PWM signal generation that generates the PWM control signal based on the final command value And
The final command value calculation unit calculates an output command upper limit value based on the dead time and the carrier frequency of the PWM control signal, and compares the dead time compensation command value and the output command upper limit value for each phase. When there is a phase in which the dead time compensation command value is greater than the output command upper limit value, the difference between the dead time compensation command value of the larger phase and the output command upper limit value is calculated as an output command correction value, A motor control apparatus , wherein a value obtained by subtracting the output command correction value from the dead time compensation command value is used as the final command value for each phase . The motor control device according to claim 1 ,
The PWM signal generation unit generates the PWM control signal for the upper switching element so that the PWM signal is at least an off signal for a predetermined period according to the dead time in a period before and after the timing when the PWM carrier is updated. An electric motor control device. In the motor control device according to claim 1 or 2 , the output command upper limit value is:
On-duty conversion of the PWM control signal for the upper side switching element, (1-2 × DT ÷ CT) × 100 (%) [However, DT: dead time, CT: carrier cycle]
The motor control device is characterized in that the output command value is as follows . In the control apparatus of the electric motor according to any one of claims 1 to 3 ,
When there is a phase in which the final command value is smaller than an output command lower limit value that is a minimum value that can be generated by the PWM signal generation unit, the final command value of the smaller phase is set as an output command lower limit value. An electric motor control device. In the motor control apparatus according to claim 4 ,
The output command lower limit value is
On-duty conversion of PWM control signal for upper switching element, (−2 × DT ÷ CT) × 100 (%) [However, DT: dead time, CT: carrier cycle]
The motor control device is characterized in that the output command value is as follows . In the motor control device according to any one of claims 1 to 5 ,
The motor control device according to claim 1, wherein the basic output command value for each phase is equal to or less than a maximum value that can be output by the DC power supply voltage . An inverter including a plurality of upper switching elements arranged on the high potential side and a plurality of lower switching elements arranged on the low potential side, and the upper switching element and the lower switching element in the same phase of the inverter are simultaneously turned on A control command calculation unit that generates a PWM control signal that performs a switching operation with a dead time so as not to become,
A control apparatus for an electric motor that controls a switching operation of the inverter according to the PWM control signal to convert a DC power supply voltage input to the inverter to control an output torque of the electric motor;
The control command calculation unit includes a basic output command value calculation unit that calculates a basic output command value for each phase based on the torque command of the motor, and a dead time that cancels an output voltage that changes due to the influence of the dead time. A dead time compensation unit that calculates the dead time compensation command value for each phase by changing the basic output command value for each phase based on the compensation value, and the dead time compensation command value for each phase is the PWM control. A final command value calculation unit that calculates a final command value for each phase by correcting it so as to fall within a command value range that can be output as a signal, and a PWM signal generation that generates the PWM control signal based on the final command value And
The final command value calculation unit compares the dead time compensation command value for each phase with a preset output command lower limit value, and there is a phase in which the dead time compensation command value is smaller than the output command lower limit value Calculating a difference between the dead time compensation command value of the small phase and the output command lower limit value as an output command correction value, and subtracting the output command correction value from the dead time compensation command value of all phases. The motor control device, characterized in that the final command value for each phase is used. The motor control device according to claim 7 ,
The PWM signal generation unit generates the PWM control signal for the lower switching element so that the PWM signal is at least an off signal during a predetermined period according to the dead time in a period before and after the timing when the PWM carrier is updated. An electric motor control device characterized by the above. In the motor control apparatus according to claim 7 or 8 ,
The motor control device according to claim 1, wherein the output command lower limit value is an output command value that is 0 [%] in terms of on-duty conversion of the PWM control signal for the upper switching element . In the motor control device according to any one of claims 7 to 9 ,
When there is a phase in which the final command value is larger than the output command upper limit value that is the maximum value that can be generated by the PWM signal generation unit, the final command value of the larger phase is set as the output command upper limit value. An electric motor control device characterized by the above. The motor control device according to claim 10 ,
The motor control device according to claim 1, wherein the output command upper limit value is an output command value that is 100 [%] in terms of on-duty conversion of the PWM control signal for the upper switching element . In the control apparatus of the electric motor according to any one of claims 7 to 11 ,
The motor control device according to claim 1, wherein a basic output command value for each phase is equal to or greater than a minimum value that can be output by the DC power supply voltage . The motor control device according to any one of claims 1 to 12 ,
The motor control device according to claim 1, wherein the basic output command value is a sine wave, and the phases of the basic output command values for each phase are shifted from each other by 120 ° . The motor control device according to any one of claims 1 to 13 ,
The motor control apparatus according to claim 1, wherein the dead time compensation value is calculated by the dead time, the polarity of the phase current, and the carrier frequency of the PWM control signal .