JP2006034022A - Ac motor controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an AC motor controller that controls torque shortage or a fear of an overcurrent by properly controlling the changeover timing of voltage SW patterns, in rectangular wave voltage driving control. <P>SOLUTION: A rectangular wave controlling means 2-1 generates an interruption that starts controlling calculation at every valley of a carrier signal and sets voltage SW patterns and the period of a carrier. The period of the carrier, in which the changeovers are performed from the next voltage SW patterns changeover till the subsequent voltage SW patterns changeover in the last interruption calculation during one section of the voltage SW patterns, is set to a value obtained by dividing a time difference from the start and finish of the one section of the voltage SW patterns into 'n' equal parts (where 'n' is an integer, a value that is equal to or larger than a minimum value with which the period of the carrier can be set and that minimizes the period of the carrier). Then in the interruption calculations other than the last one, the changes of electrical angular speed and an electrical angle target value that changes over the voltage SW patterns next time are monitored. If one or both of them exceed given threshold values, the period of the carrier is changed to a value obtained by dividing the time difference into the 'n' equal parts. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control device for an AC motor, and more particularly to a drive cycle switching technique in a control device that controls an inverter by rectangular wave voltage drive.

As a conventional control device for an AC motor, there is one described in Patent Document 1 below.
As a method of controlling the inverter that supplies current to the motor by the above-described AC motor control method, the PWM voltage drive method includes a rectangular wave voltage drive method that is used in an operation region where the output voltage is limited. In this control method, a timer counter that operates with a clock at a constant interval is used, and a voltage switching pattern (hereinafter abbreviated as a voltage SW pattern) is switched and output every time the count value reaches a target value. When the voltage SW pattern is switched, the voltage SW pattern to be output at the next switching is determined, and the phase difference target value from the next voltage SW pattern switching to the next voltage SW pattern switching is divided by the electrical angular velocity and converted into time. The target value of the counter that is activated simultaneously with the next voltage SW pattern switching is determined.

JP 2002-359996 A

As described above, in the conventional example, every time the voltage SW pattern is switched, the target value of the counter that is started simultaneously with the next voltage SW pattern switching is updated and the counter is started. Becomes the voltage SW pattern switching timing (for example, in the case of a three-phase motor, the electrical angle is about every 60 °), so that the control cycle becomes longer than when PWM driving is performed. The result of the control calculation based on the rotational speed and the phase difference target value obtained by detection or estimation at a certain time is reflected in the control at the next voltage SW pattern switching timing, so that the voltage SW pattern is switched. If the rotation speed changes sharply or the phase difference target value changes between the time when the voltage SW pattern is switched to the next time, the error with respect to the ideal switching timing increases at the next voltage SW pattern switching timing. There is a problem that excessive or insufficient torque or overcurrent may flow.
The present invention has been made to solve the above-described problem. In the rectangular wave voltage drive control, an AC motor in which the voltage SW pattern switching timing is appropriately controlled to suppress the torque excess and deficiency and the possibility of overcurrent. An object is to provide a control device.

  In the present invention, an interrupt for starting the control calculation is generated for each valley position of the carrier signal and the setting of the voltage switching pattern and the carrier period of the carrier signal are performed. In the last interrupt calculation, the carrier cycle from the next voltage switching pattern switching to the next voltage switching pattern switching is divided into n equal parts (n is an integer). Thus, the carrier period is set to a value that is equal to or greater than the minimum value that can be set and is as large as possible so that the carrier period is minimized. Then, in one section of the voltage switching pattern, in the interrupt calculation other than the last, the change in the electrical angular velocity and the electrical angle target value for switching the voltage switching pattern next time is monitored, and either or both exceed a predetermined threshold The time difference from the start of the next interrupt calculation until the next electrical angle target value for switching the voltage switching pattern is equally divided into n ′ (n ′ is an integer, the carrier cycle is the minimum value that can be set, and the carrier cycle is the minimum) The carrier cycle thereafter is changed to a value that is as large as possible).

  Even when there is a steep change in the number of revolutions during voltage SW pattern switching or a change in the phase difference target value of the electrical angle, the voltage SW pattern switching timing is appropriate in a small cycle that does not depend on the voltage SW pattern switching interval. Since the carrier cycle can be changed as described above, there is an effect of reducing the possibility of excess or deficiency in torque or the flow of overcurrent.

FIG. 1 is a block diagram of an embodiment showing a configuration of an AC motor control apparatus to which the present invention is applied.
In FIG. 1, the voltage phase generating means 1 outputs a voltage phase target value α ^* obtained by referring to a table using an externally input torque command value T ^* and the current rotational speed ω as indices. Specifically, for example, in the evaluation test of the electric motor to be controlled, the value of the voltage phase target value α ^* with respect to the torque command value T ^* and the rotational speed ω is obtained as table data. The value of the voltage phase target value α ^* corresponding to the torque command value T ^* and the rotation speed ω can be obtained by referring to the table.

  The control unit 2 includes a rectangular wave control unit 2-1 and a PWM control unit 2-2. Since the present invention relates to rectangular wave voltage driving, the rectangular wave control means 2-1 will be mainly described below, and only necessary portions of the PWM control means 2-2 will be described.

The rectangular wave control means 2-1 receives the voltage phase target value α ^* output from the voltage phase generation means 1, the electrical angle θ of the electric motor 5 detected by the position detection means 6, and the speed using the electrical angle θ as input. The electrical angular velocity ω (rotational speed) obtained by the computing means 7 is inputted, and the drive signal P of the on / off signal is computed and outputted (details will be described later). The inverter 3 is controlled by this drive signal P, and three-phase rectangular wave voltages Vu, Vv, and Vw having an amplitude of the power supply voltage Vdc or 0 (or + Vdc / 2 or −Vdc / 2) are output from the inverter 3. To drive the three-phase motor 5.

  The voltage phase generation means 1 and the control means 2 are constituted by a computer or the like, and calculate the drive signal P by repeatedly performing calculations at a predetermined cycle. The content of the setting and correction of the carrier period when calculating the drive signal P is the gist of the present invention.

The drive signal P is an on / off signal, and the output of the inverter 3 is output in synchronization with the drive signal P. That is, the timing at which the drive signal P is switched on / off is the timing at which the rectangular wave voltage is switched as it is (strictly speaking, on and off may be reversed). In the rectangular wave voltage drive, the applied voltage amplitude is the power supply voltage Vdc or 0 (+ Vdc / 2 or −Vdc / 2) and the amplitude cannot be controlled, so that the voltage phase follows the voltage phase target value α ^*. By controlling, the torque control of the electric motor 5 is performed so as to realize the given torque command value T ^* . That is, since there is a correlation between the torque and the voltage phase, the torque can be controlled by controlling the voltage phase. This voltage phase is controlled by switching a voltage SW pattern described later.

  Note that the PWM control means 2-2 in the control means 2 performs a general torque control calculation using the detected currents Iu and Iv detected by the current sensor 4 in the region where the PWM voltage drive is performed, and the inverter 3 outputs the PWM signal. The torque is controlled by changing the voltage value applied to each phase of the electric motor 5. The general torque control calculation in the above-described PWM control is, for example, calculating a d-axis current command value and a q-axis current command value based on the input torque command value and the rotation angle of the electric motor 5, and d-axis current command The proportional-integral calculation is performed based on the deviation between the value and the actual d-axis current value to calculate the d-axis voltage command value, and the q-axis is similarly calculated based on the deviation between the q-axis current command value and the actual q-axis current value. Calculate the voltage command value. The actual d-axis current value and q-axis current value are obtained by performing three-phase to two-phase conversion from the detected currents Iu and Iv (Iw can be calculated from Iu and Iv). Then, the d-axis voltage command value and the q-axis voltage command value are two-phase / three-phase converted to calculate a three-phase voltage command value. The drive signal P is obtained by calculating the duty command value of the PWM signal from the three-phase voltage command value and comparing the duty command value with a predetermined carrier signal (such as a triangular wave or a sawtooth wave).

  When the rectangular wave voltage drive used in the present invention is performed, the rectangular wave (Vdc or 0) is set by setting the duty ratio of the duty command value to be compared with the carrier signal to 0 [%] or 100 [%]. Drive signal P can be generated. In general, the rectangular wave voltage drive is used in a field weakening region where a high voltage is required, and PWM control is used in other regions.

In addition, in order to control the voltage phase to follow the voltage phase target value α ^* in the rectangular wave control means 2-1, the voltage SW pattern (detailed later) is determined at a timing determined according to the voltage phase target value α ^*. Do by switching.

The setting of the voltage SW pattern and the carrier cycle is effective at the trough of the triangular wave or sawtooth wave of the carrier signal, and at the same time, an interrupt for starting the control calculation is generated. The timing at which the rectangular wave pattern (voltage SW pattern) is switched is adjusted by changing the carrier cycle so that the voltage SW pattern switching timing is appropriate. In other words, the voltage phase is set to voltage by controlling the period of the carrier signal (for example, triangular wave) for creating the rectangular wave so that the switching point of the voltage SW pattern coincides with the valley of the carrier signal (at the start of the interrupt calculation). Control is performed to follow the phase target value α ^* .

Example 1
Hereinafter, the method for setting the carrier period in the first embodiment will be described in detail.
FIG. 2 is a signal waveform diagram for explaining a carrier period setting method.
Voltage SW pattern (Pattern of voltage applied to each phase of U, V, and W, that is, pattern of which of three phases is set to “1”, that is, Vdc, and which is set to “0”, in FIG. 2, Vu = 1 , Vv = 0, carrier cycle Tc0 between the case of Vw = 1 after switching the illustration), until the next switching the voltage SW pattern (from time _{t 0} to time _{t 1),} the voltage SW pattern switching line In the control operation 1 (shown by an arrow filled with black) immediately before the operation is determined as follows.

First, as shown in the following (Equation 1), an ideal phase difference π / 3 [rad] from the start to the end of one voltage SW pattern is calculated as an electrical angular velocity at the start of control calculation 1 (periodic interrupt calculation). Divide by ω to convert to time difference t ′.
t ′ = π / 3ω (Equation 1)
Next, as shown in the following formula (2), from the electrical angle θ at the start of the control calculation 1, the electrical angular velocity ω, and the current carrier cycle Tc ′, the predicted electrical angle value θnext at which the voltage SW pattern switching is performed next. Is calculated.
θnext = θ + ωTc ′ (Expression 2)
The current carrier cycle Tc ′ is a carrier cycle calculated by a calculation immediately before the previous voltage SW pattern switching.

Next, as shown in the following (Equation 3), the difference between the electrical angle target value θsw ^* for the next voltage SW pattern switching and the electrical angle predicted value θnext for the next voltage SW pattern switching is expressed as the electrical angular velocity ω. A value Δt that is time-converted by dividing by is calculated.
Δt = (θsw ^* −θnext) / ω (Equation 3)
Next, as shown in the following (Equation 4), a value t obtained by correcting t ′ by Δt is obtained, and as shown in the (Equation 5), a value Tc0 obtained by equally dividing t by n is given by The carrier cycle of the voltage SW pattern section is used.
t = t ′ + Δt (Equation 4)
Tc0 = t / n (Expression 5)
Note that n is an integer that becomes the smallest when the carrier cycle Tc0 is equal to or greater than the settable minimum carrier cycle. That is, n is set as large as possible so that the carrier cycle Tc0 is as small as possible.

The electrical angle target value of the next voltage SW pattern switching .theta.sw ^*, based on FIG. 3 showing the electrical angle theta, the voltage phase target value alpha ^*, the relationship between the SW pattern of voltage to be input to the motor, θsw0 ^* ~ The electrical angle closest to θnext is selected from θsw5 ^* , and the voltage SW pattern output after the next voltage SW pattern switching is determined from the current rotation direction. For example, in FIG. 3, if θnext is the closest value to (2π / 3) −α ^* , θsw2 ^* is selected as the electrical angle target value θsw ^* for the next voltage SW pattern switching, and the next voltage SW The pattern is “Vu = −Vdc / 2, Vv = −Vdc / 2, Vw = + Vdc / 2”.

  In FIG. 3, each voltage SW pattern is a binary rectangular wave of + Vdc / 2 and −Vdc / 2 with 0 as the center. This is because, when the three-phase winding of the motor is Y-connected, any two of the three phases U, V, and W are connected in series between the power supply voltage Vdc terminal and the ground terminal. If the neutral point is set to 0, + Vdc / 2 is applied to the phase connected to the Vdc terminal side, and -Vdc / 2 is applied to the phase connected to the ground terminal side. It is because it can be displayed. Therefore, as shown in FIG. 2, + Vdc / 2 may be represented by Vdc ("1") and -Vdc / 2 may be represented by "0".

Further, each section of θsw0 ^{* to} θsw5 ^* in FIG. 3 (for example, one section from θsw0 ^* to θsw1 ^* ) corresponds to the section t ′ in FIG. 2, and the section of t (time point) corrected by Δt. t ₀ -t ₁ ) is divided into n equal parts (7 equal parts in the example of FIG. 2) and divided into n carrier periods Tc 0.

Next, a method for correcting the carrier period will be described.
FIG. 4 is a signal waveform diagram for explaining a carrier period correction method.
In a control calculation other than immediately before the voltage SW pattern switching is performed (indicated by a hatched arrow), changes in the rotational speed and the electrical angle target value θsw ^* at which the voltage SW pattern switching is performed next time are monitored. If these changes do not exceed a predetermined threshold value, the carrier cycle and the voltage SW pattern continue the state determined in the control calculation 2 (carrier cycle interruption calculation) immediately before the previous voltage SW pattern switching.

However, for example, when a predetermined threshold value is exceeded in the control calculation 5 in the middle, the current carrier cycle Tc0 and the electric angle θ and the electric angular velocity ω at the start of the calculation are used to calculate the next A time difference Δt from the start of calculation to the electrical angle target value θsw ^* for the next voltage SW pattern switching is calculated, and the Δt is divided into n ′ equal parts (example in FIG. 4) as shown in the following (Equation 7). Then, Tre calculated by n ′ = 3) is set as a new carrier period.

Δt = [(θsw ^* −θ) / ω] −Tc0 (Equation 6)
Tre = Δt / n ′ (Expression 7)
The electrical angle target value θsw ^* for the next voltage SW pattern switching is determined based on FIG. 3 from the polarities of the electrical angle θ and the electrical angular velocity ω at the start of the control calculation 5. Since the voltage SW pattern is within one section, the voltage SW pattern continues to be determined by the carrier cycle interrupt calculation 2.
Further, the correction of the carrier cycle is not limited to once during one section of the voltage SW pattern, but can be performed by a similar method a plurality of times as necessary.

Next, the operation will be described.
The carrier period of one section of the next voltage SW pattern determined by the control calculation 1 in FIG. 2 is set to a value obtained by equally dividing the value obtained by correcting the error as described above. In other words, in the steady state, the carrier cycle is determined so that the ideal timing at which the next voltage SW pattern starts and the timing of the valley of the carrier signal coincide with each other, so the valley of the carrier signal that sets the timing for switching the voltage SW pattern is determined. The timing (starting point of the interrupt calculation) can be matched with the ideal timing at which the next voltage SW pattern starts. Therefore, an error in timing at which the voltage SW pattern in the steady state is switched can be suppressed.

  Even when the rotation speed and the electrical angle target value for switching the voltage SW pattern change greatly, the ideal timing and carrier at which the next voltage SW pattern starts when the change is detected as in the control calculation 5 of FIG. Since the carrier cycle is changed so that the signal valleys coincide with each other, an error in timing at which the voltage SW pattern is switched can be suppressed.

In the case where the carrier period is not corrected as described above in FIG. 4, the valley of the carrier signal 3 determined in the control calculation 2 and the voltage SW pattern switching electric power as shown by the broken line 3 in FIG. The angle target value θsw ^* does not match, and the voltage SW pattern switching is performed at a timing (broken line 4) deviated from the electrical angle target value θsw ^* . For this reason, there is a possibility that excessive or insufficient torque or overcurrent flows.

As described above, in the first embodiment, when the rectangular wave voltage drive is performed, the time difference from the start to the end of the voltage SW pattern is divided into n equal parts (n is an integer and the carrier cycle is equal to or greater than the minimum value that can be set). The carrier period is set to a value determined to be as small as possible.
In the last section of the voltage SW pattern, the carrier cycle from the next voltage SW pattern switching to the next voltage SW pattern switching is determined in the last control calculation (carrier cycle interrupt calculation).
Also, in a control calculation other than the last (carrier cycle interrupt calculation) in one section of the voltage SW pattern, changes in the electrical angular velocity and the electrical angle target value for the next voltage SW pattern switching are monitored, and either or both are predetermined. When the threshold value is exceeded, the carrier cycle is changed by a value obtained by equally dividing the time difference from the start of the next calculation to the electrical angle target value for the next voltage SW pattern switching by n ′.

  With the above-described configuration, even when there is a steep change in the number of rotations or a change in the electrical angle phase difference target value during voltage SW pattern switching, a small period (depending on the voltage SW pattern switching interval ( Since the carrier period can be changed so that the voltage SW pattern switching timing is appropriate at a period of approximately 1 / n of the voltage SW pattern period), the possibility of excessive or insufficient torque and overcurrent flow is reduced.

(Example 2)
Also in the second embodiment, the block diagram of the configuration is the same as that in the first embodiment, and the carrier cycle setting method and the correction method are different.
Hereinafter, a method for setting the carrier period in the second embodiment will be described.
FIG. 5 is a diagram illustrating a method for setting a carrier period.
In this embodiment, the basic carrier period is set to a predetermined constant reference value Tcp, and only when the voltage SW pattern is switched, the total of the carrier periods before and after that is set to be three times the basic carrier period Tcp. Set. The basic carrier period Tcp is set to the same size as the carrier period when PWM voltage driving is performed, for example.

  The carrier cycle from the switching of the voltage SW pattern to the next switching of the voltage SW pattern is determined as follows in the control calculation 1 (arrow filled with black) immediately before the switching of the voltage SW pattern.

As shown in the following formula (8), an ideal phase difference π / 3 [rad] from the start to the end of one voltage SW pattern is expressed by the electrical angular velocity ω at the start of the control calculation 1 (periodic interrupt calculation). Divide and convert to time difference t ′.
t ′ = π / 3ω (Equation 8)
Next, as shown in the following (Equation 9), from the electrical angle θ and electrical angular velocity ω at the start of the control calculation 1 and the current carrier cycle Tc1, an electrical angle predicted value θnext that is next subjected to voltage SW pattern switching is obtained. calculate.
θnext = θ + ωTc1 (Equation 9)
However, the current carrier cycle Tc1 corresponds to the next carrier cycle Tc1next obtained by the calculation immediately before switching the previous voltage SW pattern.

Next, as shown in the following equation (10), the difference between the electrical angle target value θsw ^* for the next voltage SW pattern switching and the electrical angle predicted value θnext for the next voltage SW pattern switching is expressed as the electrical angular velocity ω. A value Δt that is time-converted by dividing by is calculated.
Δt = (θsw ^* −θnext) / ω (Equation 10)
Then, as shown in the following equation (11), a value t obtained by correcting t ′ by Δt is obtained.
t = t ′ + Δt (Equation 11)

Next, as shown in the following (Equation 12), the carrier cycle Tc2 immediately after switching the next voltage SW pattern is set to the value of the difference between 3Tcp and Tc1, and as shown in the following (Equation 13), The carrier cycle Tc1next immediately before switching the voltage SW pattern is obtained as the sum of Tcp and the remainder obtained by dividing Tc2 by Tcp. In the remaining period, the carrier cycle is set to be constant Tcp, thereby determining a carrier cycle pattern in which the total of the carrier cycles in one section of the next voltage SW pattern is t.
Tc2 = 3Tcp-Tc1 (Equation 12)
Tc1next = (t−Tc2) −m · Tcp (Equation 13)
Here, m is an integer satisfying Tcp <Tc1next <2Tcp.

As described above, the carrier cycle in one section of the next voltage SW pattern obtained by the control calculation 1 is a pattern composed of Tc2 and m (m = 4 in FIG. 5) Tcp and Tc1next.
Note that the sizes of Tc1, Tc2, and Tc1next are larger than Tcp. This is because, in general, Tcp is set to the smallest value within the range that can be calculated, and therefore, a value smaller than that is difficult to calculate.

The electrical angle target value of the next voltage SW pattern switching .theta.sw ^*, based on FIG. 3 which represents the electrical angle theta, the voltage phase target value alpha ^*, the relationship between the voltage of the SW pattern to be input to the motor, θsw0 ^* ~ A point closest to θnext is selected from θsw5 ^* . Further, a voltage SW pattern output after the next voltage SW pattern switching is determined from the current rotation direction.

Next, a method for correcting the carrier period will be described.
FIG. 6 is a signal waveform diagram for explaining a carrier period correction method.
In a control calculation other than immediately before the voltage SW pattern switching is performed (indicated by a hatched arrow), changes in the rotational speed and the electrical angle target value θsw ^* at which the voltage SW pattern switching is performed next time are monitored. If these changes do not exceed a predetermined threshold, the carrier cycle and voltage SW pattern continue to be in the state determined in the control calculation 2 (carrier cycle interrupt calculation) immediately before the previous voltage SW pattern switching.

However, for example, when a predetermined threshold value is exceeded in the control calculation 5 in the middle, the next calculation is started by the following equation (Equation 14) using the current carrier cycle Tcp and the electric angle θ and the electric angular velocity ω at the start of the calculation. A time difference Δt from the hour to the electrical angle target value θsw ^* is calculated. Further, as shown in the following formula (15), the carrier cycle Tc1next immediately before the next voltage SW pattern switching is calculated as the sum of Tcp and the remainder obtained by dividing Δt by Tcp. In the remaining period, the carrier period is set to be constant Tcp, and the carrier period pattern is changed so that the total carrier period from the start of the next calculation to the voltage SW pattern switching becomes Δt.
Δt = [(θsw ^* −θ) / ω] −Tcp (Equation 14)
Tc1next = Δt−m · Tcp (Equation 15)
Here, m is an integer satisfying Tcp <Tc1next <2Tcp.

The correction of the carrier cycle is not limited to once during one section of the voltage SW pattern, but can be performed by a similar method a plurality of times as necessary.
Further, the carrier cycle can be changed by the same method in the control calculation in the section where the carrier cycle is Tc2.

Next, the operation will be described.
The carrier cycle pattern of one section of the next voltage SW pattern determined by the control calculation 5 in FIG. 5 is such that the ideal timing at which the next voltage SW pattern starts and the timing of the valley of the carrier signal coincide as much as possible in a steady state. Therefore, the error of the voltage SW timing is suppressed in the steady state.

  Even when the rotation speed and the electrical angle target value for switching the voltage SW pattern change greatly, the ideal timing and carrier signal at which the next voltage SW pattern starts when the change is detected as in the control calculation 5 of FIG. Since the carrier cycle pattern is changed so that the valleys coincide with each other, an error in the voltage SW timing can be suppressed.

When the carrier cycle is not changed as described above in FIG. 6, the valley of the carrier signal 3 (shown by a broken line) determined by the control calculation 2 in FIG. 6 and the electrical angle target value for switching the voltage SW pattern Since θsw ^* does not match, the voltage SW pattern switching is performed at timing 4 (indicated by a broken line) deviated from θsw ^* .

  In addition, when the basic carrier period Tcp is set to the same value as the carrier period at the time of PWM voltage driving, even if the carrier period before and after the voltage SW pattern switching is changed, the sum is basic. Since it is an integral multiple of the carrier cycle Tcp, that is, an integral multiple of the carrier cycle at the time of PWM voltage driving, even when switching from PWM voltage driving to rectangular wave voltage driving and switching to PW voltage driving again as shown in FIG. Since the relative time difference with other timer cycle calculations used for control and the like is kept constant, the influence of changes in the time difference can be suppressed.

As described above, in the second embodiment, when rectangular wave voltage driving is performed, the basic carrier cycle is a constant value Tcp (for example, the same value as the carrier cycle when PWM voltage driving is performed), and the voltage SW pattern is changed. Only in the case of switching, the total of the carrier periods before and after that is set to be three times the basic carrier period Tcp. The carrier period before and after switching is larger than the basic carrier period Tcp, and the value is determined so that the voltage SW pattern switching timing matches the electrical angle target value for switching as much as possible.
In the last carrier cycle interrupt calculation in one section of the voltage SW pattern, the carrier cycle pattern from the next voltage SW pattern switching to the next voltage SW pattern switching is determined. Then, in the carrier cycle interrupt calculation other than the last in one section of the voltage SW pattern, the change of the electrical angular velocity and the electrical angle target value for the next voltage SW pattern switching is monitored, and if either or both exceed a predetermined threshold value. The carrier cycle pattern is changed according to the time difference from the start of the next calculation to the electrical angle target value for the next voltage SW pattern switching.

With the above configuration, even when there is a steep change in the rotation speed during voltage SW pattern switching or a change in the electrical angle target value θsw ^* for voltage SW pattern switching, it depends on the voltage SW pattern switching interval. Since the carrier cycle can be changed so that the voltage SW pattern switching timing is appropriate at a small cycle, there is a possibility that the torque becomes excessive or insufficient or an overcurrent flows.

  In addition, when the basic carrier cycle Tcp is set to the same value as the carrier cycle when PWM voltage driving is performed, even when switching from PWM voltage driving to rectangular wave voltage driving and switching to PWM voltage driving again, the carrier Periodic interrupt timing can be easily synchronized, and the relative time difference can be made constant for interrupt operations that operate in periods other than the carrier period interrupt during PWM voltage driving.

Example 3
Also in the third embodiment, the block diagram of the configuration is the same as that of the first embodiment in FIG. 1, and the carrier cycle setting method and the carrier cycle correction method are different.

Hereinafter, a method for setting the carrier period in the third embodiment will be described.
FIG. 8 is a diagram illustrating a method for setting a carrier period.
In the control calculation 1 immediately before the voltage SW pattern switching, the next carrier cycle Tc2 is determined so that the sum of the next carrier cycle Tc1 and the current carrier cycle Tc1 is 3Tcp. The arithmetic expression is the same as the expression (Equation 12). However, the current carrier cycle Tc1 is obtained by the previous control calculation (calculation immediately before control calculation 1).
Further, the next voltage SW pattern is determined based on FIG. 3 from the polarities of the electrical angle θ and the electrical angular velocity ω at the start of the control calculation 1.

In the control calculation other than immediately before the voltage SW pattern switching, the next calculation is performed using the electrical angle target value θsw ^* for the next voltage SW pattern switching, the electrical angle θ and the electrical angular velocity ω at the start of the calculation, and the current carrier cycle Tcp. The time Δt from the start to the next voltage SW pattern switching is calculated by the above equation (14).

FIG. 9 and FIG. 10 are signal waveform diagrams for explaining the case where the carrier periods set in accordance with whether Δt is greater than or less than 2 Tcp are different in the third embodiment.
Control calculation 1 in FIG. 9 is an example in which Δt is larger than 2Tcp, and the next carrier cycle is set to Tcp. In this case, the two carrier cycles after the control calculation 1 are Tcp, the third time is “Tc1 = Δt−2Tcp”, and Tc2 is “Tc2 = 3Tcp−Tc1”, which is the same as the equation (12). Become.

  The control calculation 1 in FIG. 10 is an example when Δt is 2 Tcp or less, and the next carrier cycle is set to Tc1 = Δt. In this case, one carrier cycle after the control calculation 1 is “Tc1 = Δt”, and Tc2 is “Tc2 = 3Tcp−Tc1”, which is the same as the equation (12).

Next, the operation will be described.
In the control calculation except immediately before the voltage SW pattern switching, when the time difference Δt from the start of the next control calculation to the ideal timing at which the next voltage SW pattern switching starts exceeds 2 Tcp, the next carrier cycle is set to Tcp, and Δt Is equal to or less than 2 Tcp, Δt is set as the next carrier period, and the timing of the valley of the carrier signal is determined so as to coincide with the ideal voltage SW timing as much as possible. Therefore, an error in the voltage SW timing can be suppressed.

  When the basic carrier cycle Tcp is the same as that at the time of PWM voltage driving, even when the carrier cycle before and after the voltage SW pattern switching is changed, the sum is an integer of the carrier cycle at the time of PWM voltage driving. Therefore, even when switching from PWM voltage driving to rectangular wave voltage driving and again switching to PW voltage driving as shown in FIG. 7, the relative time difference from other timer cycle calculations used for current control or the like Is kept constant, and the influence of changes in the time difference can be suppressed.

  As described above, in the third embodiment, when rectangular wave voltage driving is performed, the basic carrier cycle is set to a constant value Tcp (for example, the same value as the carrier cycle when PWM voltage driving is performed), and the voltage SW pattern is switched. Only in this case, the total of the carrier periods before and after that is set to be three times the basic carrier period Tcp. The carrier cycle before and after switching is larger than the basic carrier cycle Tcp, and the value is determined so that the voltage SW pattern switching timing matches the electrical angle target value for switching as much as possible. In each carrier cycle interrupt calculation, the time difference Δt from the start of the next calculation to the electrical voltage target value for the next voltage SW pattern switching is monitored, and the time difference Δt is less than twice the carrier cycle during PWM voltage driving. Then, the time difference Δt is set as the next carrier cycle, and the voltage SW pattern is switched at the start of the next control calculation (next to Tc1 in FIG. 10).

With the above-described configuration, even when there is a change in the rotation speed or a change in the electrical angle target value θsw ^* for switching the voltage SW pattern while switching the voltage SW pattern, the voltage SW pattern switching interval is small. Since the carrier cycle can be set so that the voltage SW pattern switching timing is appropriate in the cycle, the possibility of excessive or insufficient torque or overcurrent flowing is reduced. Also, even when switching from PWM voltage driving to rectangular wave voltage driving and switching again to PWM voltage driving, the carrier cycle interrupt timing can be easily synchronized, and for interrupt calculations that operate in cycles other than the carrier cycle interrupt during PWM voltage driving The relative time difference can be made constant. Further, since the next carrier cycle is determined based on whether or not the time difference Δt is greater than or equal to twice the Tcp, it is not necessary to monitor a change in rotational speed or a target electrical angle θsw ^* and to recalculate the carrier cycle. The effect of is obtained.

Example 4
In the second and third embodiments described so far, when the carrier period is changed, before and after the change, as shown in the equation (12), “3Tcp = Tc1 + Tc2” is set, and thereafter It returns to the basic carrier period Tcp. However, the calculation of Tc2 can be omitted, and the carrier period can in principle be the basic carrier period Tcp.

  FIG. 11 shows an example in which the calculation of Tc2 is omitted in the configuration of the second embodiment. The carrier period is basically the basic carrier period Tcp, and the time difference Δt in the control calculation 1 immediately before the switching of the voltage SW pattern. The next carrier cycle Tc1next is calculated so as to correct and is adjusted only once.

In this method, the calculation method of Δt and t is the same as that shown in the equations (10) and (11), but the equation for Tc1next is calculated using the following equation (16).
Tc1next = tm · Tcp (Equation 16)
Here, m is an integer satisfying Tcp <Tc1next <2Tcp.

As described above, the carrier cycle in one section of the next voltage SW pattern obtained by the control calculation 1 is a pattern composed of Tc1next and m (m = 6 in FIG. 11) Tcp.
Note that the sizes of Tc1 and Tc1next are larger than Tcp. This is because, in general, Tcp is set to the smallest value within the range that can be calculated, and therefore, a value smaller than that is difficult to calculate.

  Similarly to the above, the calculation of Tc2 can be omitted in the configuration of the third embodiment. In this case, in FIG. 11, Tc1next is calculated in the control calculation immediately before Tc1next. The calculation formula of Tc1next is the same as the above formula (16).

  The fourth embodiment has the same operations and effects as those of the second and third embodiments except that synchronization with the timer-operating interrupt other than the carrier cycle interrupt is not performed, but the carrier cycle is basically the basic carrier. Since the time difference Δt is corrected only with Tc1 as the period Tcp, there is a feature that the mode for determining the carrier period can be reduced by one (mode for determining Tc2), and the configuration can be simplified.

The block diagram of one Example which shows the structure of the control apparatus of the alternating current motor to which this invention is applied. FIG. 4 is a signal waveform diagram for explaining a carrier period setting method in the first embodiment. The figure which shows SW pattern of the voltage which should be input into an electric motor. FIG. 6 is a signal waveform diagram for explaining a carrier period correction method in the first embodiment. FIG. 6 is a signal waveform diagram for explaining a carrier period setting method in the second embodiment. FIG. 6 is a signal waveform diagram for explaining a carrier period correction method in the second embodiment. The signal waveform diagram which shows the relative time difference of the calculation at the time of switching and driving PWM voltage drive and rectangular wave voltage drive. FIG. 9 is a signal waveform diagram for explaining a carrier period setting method in the third embodiment. In Example 3, the signal waveform diagram for demonstrating the carrier period set when (DELTA) t is larger than 2Tcp. In Example 3, the signal waveform diagram for demonstrating the carrier period set when (DELTA) t is 2 Tcp or less. FIG. 10 is a signal waveform diagram for explaining a carrier period setting method in the fourth embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Voltage phase generation means 2 ... Control means 2-1 ... Rectangular wave control means 2-2 ... PWM control means 3 ... Inverter 4 ... Current sensor 5 ... Electric motor 6 ... Position detection means 7 ... Speed calculation means

Claims (6)

In a control device for an AC motor that performs rectangular wave voltage drive that applies the highest value and the lowest value of the power supply voltage to each phase of the motor winding in a predetermined voltage switching pattern,
Voltage phase generation means for outputting a voltage phase target value according to a torque command value given from the outside and the current rotation speed;
A rectangular wave control means for calculating a drive signal of a rectangular wave for driving the electric motor from the voltage phase target value, an electric angle of the electric motor, and an electric angular velocity of the electric motor;
An inverter that drives the electric motor by applying a rectangular wave voltage corresponding to the rectangular wave driving signal to each phase of the motor winding; and
The rectangular wave control means generates an interrupt for starting a control calculation for each valley position of a carrier signal and performs setting of the voltage switching pattern and setting of a carrier cycle of the carrier signal,
In the last section of the voltage switching pattern, the carrier cycle from the next voltage switching pattern switching to the next voltage switching pattern switching in the last interrupt calculation is expressed as the period from the start to the end of the voltage switching pattern section. Set the time difference to n equal parts (n is an integer, the carrier period is greater than the minimum value that can be set, and the largest possible value so that the carrier period is minimized)
In addition, in one section of the voltage switching pattern, in the interrupt calculation other than the last, the electrical angular velocity and the change in the electrical angle target value for switching the voltage switching pattern next time are monitored, and either one or both exceeds a predetermined threshold value. In this case, the time difference from the start of the next interrupt calculation to the electrical angle target value for switching the voltage switching pattern next time is divided into n ′ equal parts (n ′ is an integer, the carrier period is equal to or greater than the minimum value that can be set, It is configured to change the carrier cycle after that to a value that is as large as possible)
A control apparatus for an AC motor, wherein a voltage phase is controlled to follow a voltage phase target value by adjusting a timing at which the voltage switching pattern is switched by changing a carrier cycle. In the control apparatus for an AC motor according to claim 1,
The rectangular wave control means generates an interrupt for starting a control calculation for each valley position of a carrier signal and performs setting of the voltage switching pattern and setting of a carrier cycle of the carrier signal,
In principle, the carrier period is set to a constant reference value, and only when the voltage switching pattern is switched, the total of the carrier periods before and after the switching is set to be three times the reference value, and the carrier period before and after the switching is It is larger than the reference value, and the value is set so that the voltage switching pattern switching timing coincides with the electrical angle target value to be switched, and the next voltage switching is performed in the last interrupt calculation in one section of the voltage switching pattern. Determine the carrier cycle pattern from pattern switching to the next voltage switching pattern switching,
In addition, in one section of the voltage switching pattern, in the interrupt calculation other than the last, the electrical angular velocity and the change in the electrical angle target value for switching the voltage switching pattern next time are monitored, and either one or both exceeds a predetermined threshold value. In this case, the subsequent carrier cycle is changed according to the time difference from the start of the next interrupt calculation to the electrical angle target value for switching the voltage switching pattern next time,
A control apparatus for an AC motor, wherein a voltage phase is controlled to follow a voltage phase target value by adjusting a timing at which the voltage switching pattern is switched by changing a carrier cycle. In the control apparatus for an AC motor according to claim 1,
The rectangular wave control means generates an interrupt for starting a control calculation for each valley position of a carrier signal and performs setting of the voltage switching pattern and setting of a carrier cycle of the carrier signal,
In principle, the carrier period is set to a constant reference value, and only when the voltage switching pattern is switched, the total of the carrier periods before and after the switching is set to be three times the reference value, and the carrier period before and after the switching is Larger than the reference value, the value is set so that the voltage switching pattern switching timing coincides with the electrical angle target value for switching,
In each interrupt calculation, the time difference from the start of the next calculation to the next electric angle target value for switching the voltage switching pattern is monitored, and if the time difference is less than twice the reference value of the carrier period, the time difference is It is configured to change the voltage switching pattern at the start of the next next control calculation with the next carrier cycle,
A control apparatus for an AC motor, wherein a voltage phase is controlled to follow a voltage phase target value by adjusting a timing at which the voltage switching pattern is switched by changing a carrier cycle. In the control apparatus for an AC motor according to claim 2,
The rectangular wave control means generates an interrupt for starting a control calculation for each valley position of a carrier signal and performs setting of the voltage switching pattern and setting of a carrier cycle of the carrier signal,
In principle, the carrier cycle is a constant reference value, and only when the voltage switching pattern is switched, in the interrupt calculation immediately before switching the voltage switching pattern, the electrical angle target value for switching the voltage switching pattern next time from the start of the next interrupt calculation. Configured to calculate the carrier period immediately before switching the next voltage switching pattern so as to correct the time difference until
A control apparatus for an AC motor, wherein a voltage phase is controlled to follow a voltage phase target value by adjusting a timing at which the voltage switching pattern is switched by changing a carrier cycle. In the control apparatus for an AC motor according to claim 3,
The rectangular wave control means generates an interrupt for starting a control calculation for each valley position of a carrier signal and performs setting of the voltage switching pattern and setting of a carrier cycle of the carrier signal,
The carrier cycle is set to a constant reference value in principle, and only when switching the voltage switching pattern, the voltage switching is performed after the previous switching of the voltage switching pattern in the interrupt calculation immediately before the interrupt calculation immediately before the switching of the voltage switching pattern. It is configured to calculate the carrier cycle immediately before switching of the current voltage switching pattern so as to correct the time difference to the electrical angle target value for switching the pattern,
A control apparatus for an AC motor, wherein a voltage phase is controlled to follow a voltage phase target value by adjusting a timing at which the voltage switching pattern is switched by changing a carrier cycle. In the control apparatus for an AC motor according to any one of claims 2 to 5,
In an operating state in which rectangular wave voltage driving is not performed, PWM voltage driving control means for performing PWM voltage driving is provided.
The AC motor control apparatus according to claim 1, wherein the reference value of the carrier period is the same as the carrier period when PWM voltage driving is performed.

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