JP6805197B2 - Integrated circuit for motor control - Google Patents

Description

An embodiment of the present invention relates to an integrated circuit for motor control.

Conventionally, as a method of estimating the rotation position of a permanent magnet synchronous motor in the medium to high speed range, for example, an induced voltage or rotor magnetic flux proportional to the speed of the permanent magnet synchronous motor is calculated from the input voltage and current to the permanent magnet synchronous motor. A method of calculating and estimating based on the induced voltage is widely used. In such an estimation method, in addition to using the drive voltage of the motor applied by the inverter for calculation, it is necessary to use a PI controller or an observer to calculate the rotation position from the calculated induced voltage or a signal equivalent thereto. It is also necessary to design and adjust parameters such as gain in the controller.

In addition, there is a problem that sensorless control becomes unstable depending on the drive state of the motor and the set parameters, and advanced design technology and advanced design technology can be used as a substitute for pure position sensors such as resolvers, encoders, and hall sensors. It takes experience.

Further, as a sensorless drive method in the middle to high speed range, there is a method of detecting the phase of the induced voltage generated in the non-energized section at 120 degree energization and switching the energized phase based on the phase. According to this method, sensorless drive can be realized without designing a controller or the like. However, the energization method is limited to 120-degree energization, and there is a problem that the motor current is distorted and noise is exacerbated, and sensorless drive cannot be performed in an extremely low speed range.

Patent Document 1 discloses a method of detecting a position by using a current change amount during application of a voltage vector. In this method, although the resolution is small, sensorless sine wave drive is possible without adjusting the control parameters.

JP-A-2007-336641

However, in Patent Document 1, it is necessary to arrange three shunt resistors in the inverter circuit in order to detect the current. Cost reduction is important for constructing a motor drive system with a simple configuration such as a small motor or a motor in the field of home appliances. Therefore, a one-shunt current detection method in which a single shunt resistor is arranged in a DC unit is often used, and a position sensorless control method corresponding to the detection method is desired.

Therefore, an integrated circuit for motor control that can execute position sensorless control corresponding to the one-shunt current detection method is provided.

The integrated circuit for motor control of the embodiment includes a current detection unit arranged in a DC unit for detecting the phase current of the synchronous motor, and a current detection unit.
A duty generating unit that generates a three-phase PWM duty command according to the rotation position of the synchronous motor, and
Based on the carrier of a PWM duty command and the three-phase of the three-phase, and the PWM generation unit center of the phase generating each phase signal pulses to produce a 120-degree different three-phase PWM signal to each other,
A detection timing signal generation unit that generates a detection timing signal for the phase current based on the PWM duty command.
A current change amount detection unit that detects the phase current of the synchronous motor based on the signal generated in the current detection unit and the detection timing signal, and further detects the change amount of the phase current.
A rotation position calculation unit for obtaining the rotation position of the synchronous motor based on the change amount detected by the current change amount detection unit is provided.

A functional block diagram showing a configuration of a motor drive control device according to an embodiment. Waveform diagram showing a three-phase triangular wave used as a PWM carrier A diagram showing the ON state of the switching elements that make up the inverter circuit as a space vector. The figure which shows the magnitude of the phase voltage at the time of each voltage vector generation using DC voltage _VDC . The figure which shows the magnitude of the voltage vector generated in each voltage sector, and the phase of the detected induced voltage. The figure which shows the generation rate of the voltage vector generated when the general triangular wave comparison method is used. The figure which shows the generation rate of the voltage vector generated when the three-phase triangular wave comparison method is used. The figure which shows the PWM signal on the upper side of the U, V phase corresponding to each of voltage vectors V0, V1, V2, the direct current I _DC , and the current detection timings t1 to t4. The figure which shows the PWM signal waveform and the direct current I _DC in the conventional triangular wave comparison method. The figure which shows the PWM signal waveform and the direct current I _DC in the three-phase triangular wave comparison method. Flow chart showing the processing contents performed by the rotation position detection device Flow chart showing the content of the position detection operation in step S1 The figure which shows the operation waveform of each part

Hereinafter, one embodiment will be described with reference to the drawings. FIG. 1 is a functional block diagram showing a configuration of a motor drive control device. The DC power supply 1 is a power source for driving a permanent magnet synchronous motor 2 having a permanent magnet in the rotor. The DC power supply 1 may be a DC power source converted into a direct current. The inverter circuit 3 is configured by connecting six switching elements, for example, N-channel MOSFETs 4U +, 4Y +, 4W +, 4U-, 4Y-, and 4W- in a three-phase bridge, and is generated by a PWM generation unit 5 described later. A voltage for driving the motor 2 is generated based on six switching signals for three phases.

The voltage detection unit 6 detects the voltage Vdc of the DC power supply 1. The current detection unit 7 is connected between the negative power supply line of the inverter circuit 3 and the negative terminal of the DC power supply 1. The current detection unit 7 is generally composed of a current sensor and a signal processing circuit using a shunt resistor, a Hall CT, or the like, and detects a direct current Idc flowing through the motor 2.

The current change amount detection unit 8 detects the DC current Idc four times based on the voltage sector and the detection timing signals t1 to t4 input from the detection timing signal generation unit 9, which will be described later, and the difference value of the detected values every two times. Is calculated as the amount of change dI _DC1 and dI _DC2 . The induced voltage calculation unit 10 calculates the induced voltage of any two of the three phases as E _now and E _pre based on the changes dI _DC1 and dI _DC2 .

The rotation position calculation unit 11 obtains the induced voltage of the remaining one phase from the two-phase induced voltages E _now and E _pre, and calculates the rotation position detection value θc of the motor 2 from the obtained three-phase induced voltage. The three-phase voltage command value generation unit 12 has three-phase voltage command values Vu, Vv, Vw from the voltage amplitude command value Vamp, the voltage phase command value φv, and the rotation position θc, which are command values given by the upper control device. To generate.

The duty generation unit 13 calculates the modulation command and duty command Du, Dv, Dw of each phase by dividing the three-phase voltage command values Vu, Vv, Vw by the DC voltage Vdc. As shown in FIG. 2, the carrier generation unit 14 outputs a three-phase triangular wave signal having a phase difference of 120 degrees between the phases to the PWM generation unit 5 as carriers and carrier waves used for PWM control. In FIG. 2, PWM signal pulses of each phase are generated with reference to the valley of the triangular wave.

The PWM generation unit 5 compares the three-phase modulation commands Du, Dv, and Dw with the three-phase triangular wave input from the carrier generation unit 14, and generates PWM signal pulses for each phase. A dead time is added to the pulse per phase, and switching signals U +, U−, V +, V−, W +, and W− output to the N channel MOSFETs 4 above and below the three phases are generated, respectively.

Three-phase modulation commands Du, Dv, and Dw are input to the voltage sector and the detection timing signal generation unit 9. The signal generation unit 9 discriminates the voltage sectors (0) to (5) obtained by dividing the electric angle period into six equal parts based on the three-phase modulation commands Du, Dv, and Dw under the conditions shown in the equation (1), and discriminates the voltage sectors (0) to (5). The result is output to the current change amount detection unit 8, the induced voltage calculation unit 10, and the rotation position calculation unit 11.
if Du>Dv> Dw → Vector = 0
elseif Dv>Du> Dw → Vector = 1
elseif Dv>Dw> Du → Sector = 2
elseif Dw>Dv> Du → Sector = 3
elseif Dw>Du> Dv → Vector = 4
else → Vector = 5… (1)
Then, the detection timing signals t1 to t4 described above are also generated according to the determination results of the voltage sectors (0) to (5).

In the above configuration, the rotation position detecting device 15 is configured by excluding the motor 2 and the inverter circuit 3. The motor drive control device 16 is formed by adding the inverter circuit 3 to the rotation position detection device 15. Further, in the present embodiment, the rotation position detecting device 15 is configured as hardware inside the microcomputer. That is, the speed control, current control, and the like of the motor 2 are realized by software, and the rotation position detection device 15 is provided inside the microcomputer or the integrated circuit as hardware or a configuration similar thereto.

Next, the principle of detecting the rotation position in this embodiment will be described. The rotational position is detected by using the induced voltage (EMF: electromotive force) generated by the rotation of the motor. Equation (2) shows a three-phase voltage equation for a permanent magnet synchronous motor. The third term on the right side is the induced voltage term, which contains information on the rotation position θ.

Here, the magnitude of the phase voltage when each voltage vector is generated in the space vector diagram shown in FIG. 3 can be expressed as shown in FIG. 4 using the DC voltage _VDC . Then, the U-phase voltage equation when the voltage vector V1 (100) is applied becomes the equation (3).

The amount of change in current dIu generated at this time is expressed as dIu (100), and the equation (4) is obtained by modifying the equation (3).

Similarly, if the amount of change in the W-phase current when the voltage vector V2 (110) is applied in the space vector diagram shown in FIG. 3 is dIw (110), the equation (5) is obtained.

Also, assuming that the influence of the polarity of the motor on the magnetic flux of the permanent magnet is small,
Approximate to Lu = Lw = L. Further, when the equation (5) is added to the equation (4), the total phase current is zero, so the equation (6) is obtained.

Similarly, the sum of the current changes at the voltage vectors V2 (110) and V3 (010) can be expressed by the equation (7).

Further, since the sum of the phase current and the induced voltage is zero, the equation (8) is obtained by calculating the equations − (6) − (7).

Here, when the rotation speed ω of the motor is high to some extent, the right side of equations (6), (7), and (8) is the first term << the second term, so the first term on the right side, which is the voltage drop due to the resistance. Can be approximated to zero. When these are expressed as three-phase induced voltages Eu, Ev, and Ew, equation (9) is obtained.

That is, by using the amount of change in current while the voltage vector is applied, it is possible to detect a three-phase induced voltage having a phase difference of 2π / 3, respectively. Further, the rotation position θc can be obtained by converting the detected three-phase induced voltage into three-phase / two-phase with Eq. (10) and calculating the inverse tangent with Eq. (11).

The V-phase induced voltage Ev can be obtained by using the voltage vectors when the voltage vectors V1 and V2 are applied, but when all the voltage vectors are generalized, the relationship shown in FIG. 5 is obtained. That is, the induced voltage phase that can be detected is switched according to the generated voltage vector. The voltage vector generated for each voltage sector is different. For example, the voltage vectors generated in the voltage sector (0) are only V1 (100) and V2 (110). Therefore, of the current changes in the equation (9), only dIu (100) and dIw (110) can be detected, and dIv (010) cannot be detected. Strictly speaking, other voltage vectors are also generated, but here, two voltage vectors having the highest generation rate are extracted for each voltage sector.

Therefore, in the space vector shown in FIG. 3, attention is paid to the timing at which the voltage sector is switched. For example, immediately after the voltage sector is switched from (0) to (1), the amount of current change dIw (110), dIv (1) during the period when the voltage vectors V2 (110) and V3 (010) in the voltage sector (1) are generated. 010) can be detected. From these, the induced voltage E _now = Eu can be detected. Further, since the voltage sector before switching is (0), the current change amounts dIu (100) and dIw (110) can be detected during the period when the voltage vectors V1 (100) and V2 (110) are generated. From these, the induced voltage Ev can be detected. This is stored as the previous induced voltage E _pre .

Then, if the time required for switching the voltage sector is regarded as zero in the control region, which can be said to be very fast compared to the period in which the motor 2 rotates, E _now (Eu) and E _pre (Ev) indicate (9). ), The induced voltage Ew of the third phase can be obtained. If the induced voltage of the three phases is obtained, the rotation position θc can be obtained by the equations (10) and (11).
In this embodiment, the amount of change in each phase current on the left side of equation (9) is obtained from the direct current I _DC according to equation (12).

Here, as in Eq. (12), in order to detect the three-phase current according to each switching pattern, it is necessary to generate a corresponding voltage vector in order to detect each phase current. When a general triangular wave comparison method is used to generate a three-phase PWM signal, for example, when the modulation factor is 0.3, each voltage vector is generated as shown in FIG. The horizontal axis is the electrical angle, and the vertical axis is the rate of occurrence of each voltage vector during one PWM cycle. On the other hand, when a three-phase triangular wave as shown in the following document is used as a carrier, the generation ratio of each voltage vector increases as shown in FIG.
Reference name: "Institute of Electrical Engineers of Japan Semiconductor Power Conversion Method Research Expert Committee:" Semiconductor Power Conversion Circuit ", Institute of Electrical Engineers of Japan (1987)"

For example, the ratio of the voltage vector generation period required to detect the amount of current change is shown by a broken line in FIG. 6 as 0.2 of the PWM period. In this case, in the single triangular wave carrier comparison method, the voltages other than the voltage vectors V0 and V7 have not reached 0.2 and cannot be detected. On the other hand, when a three-phase triangular wave carrier is used, as shown in FIG. 7, the two voltage vectors required to detect the induced voltage of the corresponding phase in each voltage sector are 0.2 or more. .. This makes it possible to detect the required amount of change in current.

The period for generating the voltage vector required to detect the amount of change in current differs depending on the specifications of the inverter and the like. FIG. 8 shows the upper PWM signals of the U and V phases, the direct current I _DC , and the current detection timings t1 to t4 in the switching state corresponding to each of the voltage vectors V0 (000), V1 (100), and V2 (110). Shown.

For example, when the switching state changes from the voltage vector V0 to V1, ripple occurs in the current I _DC in the transitional state of switching, so the first sampling of the current I _DC at the timing t1 when a certain amount of time has passed from the time of the change. I do. This waiting time is set to 0.1 of the PWM cycle T _pwm . From there, the second sampling is performed at the timing t2 after 0.1 minutes of the period T _pwm , and the current change amount ΔI _DC is obtained.

It should be noted that what is detected at the timings t1 and t2 is the amount of change in the U-phase (+) current, and what is detected at the timings t3 and t4 is the amount of change in the W-phase (−) current. In this way, in order to detect the current I _DC with high accuracy, it is necessary to secure a sufficient period for generating a specific voltage vector, but if a three-phase triangular wave carrier is used, a sufficient period for generating the required voltage vector can be secured. , The rotation position θc can be detected.

9 and 10 show the PWM signal waveform and the direct current I _DC in the conventional triangular wave comparison method and the three-phase triangular wave comparison method. In the three-phase triangular wave comparison method, a PWM signal having a phase difference of 120 degrees is generated. Therefore, as the generation time of each voltage vector increases, the energization time of the direct current I _DC increases as compared with FIG. I understand.

Next, the operation of this embodiment will be described with reference to FIGS. 11 to 13. 11 and 12 are flowcharts showing the processing contents mainly performed by the rotation position detecting device 14 based on the principle described so far. First, when the rotation position calculation unit 11 performs the position detection calculation shown in FIG. 12 (S1), the duty generation unit 13 calculates each phase duty Du, Dv, Dw (S2). When the current voltage sector is substituted into the "previous sector" (S3), the signal generation unit 9 obtains the current voltage sector from each phase duty Du, Dv, Dw based on the equation (1) (S4). The PWM generation unit 5 outputs each phase PWM signal generated based on the three-phase triangular wave carrier and each phase duty Du, Dv, Dw to the inverter circuit 3 (S5).

The position detection operation in step S1 is executed as shown in FIG. The current change amount detection unit 8 obtains the two-phase current change amounts dI _DC1 and dI _DC2 corresponding to the voltage sector at that time from the direct current I _DC (S11). When the induced voltage E _now detected this time is substituted into the induced voltage E _pre detected last time (S12), the induced voltage calculation unit 10 detects the current induced voltage E _now from the current change amounts dI _DC1 and dI _DC2 (S13). ..

Subsequently, it is determined whether or not the current voltage sector and the previous voltage sector are different (S14), and if they are the same voltage sector, (NO) processing is terminated. On the other hand, different voltage sectors (YES), the induced voltage E _now, seek induced voltage E ₃ of the third phase from the E _pre (S15). Then, the induced voltages E _now , E _pre , and E ₃ are converted into three-phase / two-phase by the equation (10), and the inverse tangent calculation of the equation (11) is performed to obtain the rotation position θc (S16).

FIG. 13 shows the operation waveform of each part. Based on the modulation command of each phase, a three-phase current flows and the motor 2 is driven. At this time, it can be seen that the current induced voltage E _now obtained by the induced voltage calculation unit 10 can be detected from the detected current change amount. The broken line is the timing at which each voltage sector is switched, and the induced voltage detected for each voltage sector is switched between Eu, Ev, and Ew. Then, the rotation position obtained from the induced voltage of this time and the induced voltage of the previous voltage sector at the switching timing of the voltage sector is θc. It can be seen that the position can be detected with 6 resolutions for one period of the electric angle, although there is some error with respect to the actual rotation position θ.

As described above, according to the present embodiment, the duty generation unit 13 generates the three-phase duty commands Du, Dv, Dw so as to follow the rotation position of the motor 2, and the PWM generation unit 5 generates a three-phase triangular wave. It is used as a carrier to generate a three-phase PWM signal pattern in which the phases of the centers that generate signal pulses of each phase differ by 120 degrees from the three-phase duty commands Du, Dv, and Dw. The signal generation unit 9 generates phase current detection timing signals t1 to t4 based on the duty commands Du, Dv, and Dw.

The current change amount detection unit 8 detects the phase current of the motor 2 based on the signal generated by the current detection unit 7 and the detection timing signals t1 to t4, and further detects the change amount of the phase current. The rotation position calculation unit 11 calculates a signal synchronized with the rotation position of the motor 2 based on the change amount detected by the current change amount detection unit 8. With this configuration, it is not necessary to set the constant of the motor 2 or adjust the control gain, and the rotation position can be directly calculated from the detected current change amount.

Further, the induced voltage calculation unit 10 calculates the three-phase induced voltage from the amount of change in the phase current, converts the three-phase induced voltage into the two-phase voltage of the orthogonal coordinate system, and performs an inverse tangential calculation on the two-phase voltage. The rotation position is obtained by performing. Specifically, in the three-phase PWM signal pattern, voltage sectors (0) to (5) in which the electrical angular period is divided into six equal parts are set according to the set of two voltage vectors having a high generation rate, and before the transition. The induced voltage E _pre of the first phase is calculated in the voltage sector, the induced voltage E _now of the second phase is calculated in the next transitioned voltage sector, and the induced voltage E _pre , E _now to the induced voltage E _{3 of} the third phase are calculated. Is calculated. The induced voltage of these three phases is converted into the voltages Eα and Eβ of the two phases of the Cartesian coordinate system, and the rotation position θc is obtained by performing the inverse tangent calculation tan ^-1 (Eα / Eβ) on the voltages of the two phases. As a result, the rotation position θc can be calculated efficiently.
(Other embodiments)

Further, the timing of detecting the current does not need to match the cycle of the PWM carrier, and the detection may be performed at a cycle of, for example, twice or four times the carrier cycle. Therefore, the current detection timing signal input to the current change amount detection unit does not have to be the signal itself obtained from the carrier, and may be a signal generated by a separate timer.
The current detection unit may be a shunt resistor or CT.
As the switching element, a wide-gap semiconductor such as MOSFET, IGBT, power transistor, SiC, or GaN may be used.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

In the drawing, 2 is a permanent magnet synchronous motor, 3 is an inverter circuit, 5 is a PWM generator, 7 is a current detector, 8 is a current change amount detector, 9 is a voltage sector and detection timing signal generator, and 10 is an induced voltage. The calculation unit, 11 is a rotation position calculation unit, 14 is a carrier generation unit, 15 is a rotation position detection device, and 16 is a motor drive control device.

Claims (3)

A current detector located in the DC section to detect the phase current of the synchronous motor,
A duty generator that generates a three-phase PWM (Pulse Width Modulation) duty command according to the rotation position of the synchronous motor, and
Based on the carrier of a PWM duty command and the three-phase of the three-phase, and the PWM generation unit center of the phase generating each phase signal pulses to produce a 120-degree different three-phase PWM signal to each other,
A detection timing signal generation unit that generates a detection timing signal for the phase current based on the PWM duty command.
A current change amount detection unit that detects the phase current of the synchronous motor based on the signal generated in the current detection unit and the detection timing signal, and further detects the change amount of the phase current.
An integrated circuit for motor control including a rotation position calculation unit that obtains a rotation position of the synchronous motor based on the change amount detected by the current change amount detection unit. The rotation position calculation unit includes an induced voltage calculation unit that calculates three-phase induced voltages from the amount of change in the phase current.
The three-phase induced voltage is converted into a two-phase voltage in the Cartesian coordinate system.
Claim 1 Symbol mounting of the motor control integrated circuit determining the rotational position by performing the arctangent operation on the voltage of the two phases. The detection timing signal generation unit sets six voltage sectors in which the electric angle period is divided into six equal parts according to the magnitude relationship of the three-phase PWM duty command, and outputs the six voltage sectors to the rotation position calculation unit and the induced voltage calculation unit . And
The induced voltage calculation unit calculates the induced voltage of the first phase in the voltage sector before the transition, calculates the induced voltage of the second phase in the voltage sector next to the transition, and induces the first phase and the second phase. The integrated circuit for motor control according to claim 2, wherein the induced voltage of the third phase is calculated from the voltage.