JP2019154114A - Integrated circuit for motor control - Google Patents

Abstract

To provide an integrated circuit for motor control capable of executing position sensorless control corresponding to a one-shunt current detection system.SOLUTION: An integrated circuit for motor control comprises: a current detection unit which is disposed in a DC part for detecting a phase current of a synchronous motor; a duty generation unit which generates PWM duty commands of three phases so as to follow up a rotational position of the synchronous motor; a PWM generation unit for generating PWM signal patterns of three phases of which the phases of centers generating signal pulses of phases are different from each other, on the basis of the PWM duty commands; a detection timing signal generation unit which generates a detection timing signal of the phase current on the basis of the PWM duty command; a current change amount detection unit which detects the phase current of the synchronous motor on the basis of a signal that is generated in the current detection unit, and the detection timing signal and further detects a change amount of the phase current; and a rotational position calculation unit for calculating a signal which is synchronized to the rotational position of the synchronous motor on the basis of the change amount detected by the current change amount detection unit.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a motor control integrated circuit.

  Conventionally, as a method for estimating the rotational position of a permanent magnet synchronous motor in a medium to high speed range, for example, an induced voltage or a rotor magnetic flux proportional to the speed of the permanent magnet synchronous motor is obtained from an input voltage and a 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, the motor drive voltage applied by the inverter is used for the calculation, and it is necessary to use a PI controller or an observer to calculate the rotational position from the calculated induced voltage or a signal corresponding thereto. It is also necessary to design and adjust parameters such as gain in the controller.

  In addition, depending on the driving state of the motor and the set parameters, there is a problem that sensorless control becomes unstable. To replace a pure position sensor such as a resolver, encoder, or hall sensor, advanced design technology or Requires experience.

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

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

JP 2007-336641 A

  However, in Patent Document 1, it is necessary to arrange three shunt resistors in the inverter circuit in order to detect current. In order to construct a motor drive system with a simple configuration such as a small motor or a motor in the home appliance field, cost reduction is important. For this reason, a single shunt current detection method in which a single shunt resistor is arranged in the DC section is often used, and a position sensorless control method corresponding to the detection method is desired.

  Accordingly, an integrated circuit for motor control capable of performing position sensorless control corresponding to the single shunt current detection method is provided.

The integrated circuit for motor control according to the embodiment includes a current detection unit disposed in the direct current unit to detect the phase current of the synchronous motor,
A duty generator for generating a three-phase PWM duty command so as to follow the rotational position of the synchronous motor;
Based on the PWM duty command, a PWM generation unit that generates three-phase PWM signal patterns having different central phases for generating signal pulses of each phase;
A detection timing signal generating unit that generates a detection timing signal of the phase current based on the PWM duty command;
Detecting a phase current of the synchronous motor based on a signal generated in the current detection unit and the detection timing signal, and further detecting a change amount of the phase current;
A rotational position computing unit that computes a signal synchronized with the rotational position of the synchronous motor based on the amount of change detected by the current change amount detecting unit;

Functional block diagram showing the configuration of the motor drive control device according to one embodiment Waveform diagram showing a three-phase triangular wave used as a PWM carrier A diagram representing 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 V _DC Diagram showing magnitude of voltage vector generated in each voltage sector and detectable induced voltage phase The figure which shows the incidence rate of the voltage vector generated when the general triangular wave comparison method is used The figure which shows the incidence rate of the voltage vector which generate | occur | produces when using a three-phase triangular wave comparison method It shows U corresponding to the respective voltage vectors V0, V1, V2, and V-phase upper PWM signal direct current I _DC, the current detection timing t1~t4 It shows a PWM signal waveform and the DC current I _DC of the conventional triangular wave comparison method It shows a PWM signal waveform and the DC current I _DC at 3-phase triangular wave comparison method Flowchart showing processing contents performed by the rotational position detection device A flowchart showing the contents of the position detection calculation in step S1 The figure which shows the operation waveform of each part

  Hereinafter, an embodiment will be described with reference to the drawings. FIG. 1 is a functional block diagram showing the configuration of the motor drive control device. The DC power source 1 is a power source that drives a permanent magnet synchronous motor 2 having a permanent magnet in a rotor. The DC power source 1 may be one obtained by converting an AC power source into DC. The inverter circuit 3 is configured by connecting six switching elements, for example, N-channel MOSFETs 4U +, 4Y +, 4W +, 4U−, 4Y−, 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 detector 6 detects the voltage Vdc of the DC power supply 1. The current detector 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 using a shunt resistor, Hall CT, and the like and a signal processing circuit, 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 detection timing signals t1 to t4 input from the voltage sector and the detection timing signal generation unit 9 which will be described later, and a difference value between the detection values every two times. Are calculated as change amounts 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 amounts of change dI _DC1 and dI _DC2 .

The rotational position calculation unit 11 obtains the remaining one-phase induced voltage from the two-phase induced voltages E _now and E _pre, and calculates the rotational position detection value θc of the motor 2 from the obtained three-phase induced voltage. The three-phase voltage command value generator 12 generates a three-phase voltage command value 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 from the host controller. Is generated.

  The duty generation unit 13 calculates the modulation command and duty command Du, Dv, Dw for 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 a carrier and a carrier 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 to generate a PWM signal pulse for each phase. A dead time is added to the pulses per phase to generate switching signals U +, U−, V +, V−, W +, W− to be output to the upper and lower N-channel MOSFETs 4 respectively.

Three-phase modulation commands Du, Dv, and Dw are input to the voltage sector and detection timing signal generation unit 9. The signal generator 9 discriminates voltage sectors (0) to (5) obtained by dividing the electrical angle period into six parts based on the three-phase modulation commands Du, Dv, Dw under the condition shown in the equation (1), and the discrimination The result is output to the current change amount detection unit 8, the induced voltage calculation unit 10, and the rotational position calculation unit 11.
if Du>Dv> Dw → Sector = 0
elseif Dv>Du> Dw → Sector = 1
elseif Dv>Dw> Du → Sector = 2
elseif Dw>Dv> Du → Sector = 3
elseif Dw>Du> Dv → Sector = 4
else → Sector = 5 (1)
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 rotational position detection device 15 is configured except for the motor 2 and the inverter circuit 3. A motor drive control device 16 is configured by adding the inverter circuit 3 to the rotational position detection device 15. In the present embodiment, the rotational position detection device 15 is configured in hardware inside the microcomputer. That is, speed control, current control, and the like of the motor 2 are realized by software, and the rotational position detection device 15 is provided inside a microcomputer or an integrated circuit as hardware or a configuration equivalent thereto.

  Next, the principle of detecting the rotational position in the present embodiment will be described. The detection of the rotational position uses an induced voltage (EMF: electromotive force) generated by the rotation of the motor. Equation (2) shows the three-phase voltage equation of the permanent magnet synchronous motor. The third term on the right side is an induced voltage term and includes information on the rotational position θ.

Here, the magnitude of the phase voltage at the time of generation of each voltage vector in the space vector diagram shown in FIG. 3 can be expressed as shown in FIG. 4 using the DC voltage V _DC . And the U-phase voltage equation at the time of voltage vector V1 (100) application becomes (3) Formula.

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

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

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

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

  Furthermore, since the sum total of the phase current and the induced voltage is zero, when the formulas-(6)-(7) are calculated, the formula (8) is obtained.

  Here, in a state where the rotational speed ω of the motor is high to some extent, the right side of the equations (6), (7), and (8) is the first term << second term, so the first term on the right side that is a voltage drop due to 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, if the amount of current change during voltage vector application is used, a three-phase induced voltage having a phase difference of 2π / 3 can be detected. Furthermore, the rotational position θc can be obtained by performing three-phase / two-phase conversion on the detected three-phase induced voltage using the equation (10) and calculating the arc tangent using the equation (11).

Note that the V-phase induced voltage Ev can be obtained by using the voltage vectors when the voltage vectors V1 and V2 are applied. However, when all 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). For this reason, only dIu (100) and dIw (110) can be detected, and dIv (010) cannot be detected among the current change amounts in the equation (9). Strictly speaking, other voltage vectors are also generated, but here, two voltage vectors having the highest occurrence rate are extracted for each voltage sector.

Therefore, attention is paid to the timing at which the voltage sector is switched in the space vector shown in FIG. For example, immediately after the voltage sector is switched from (0) to (1), current change amounts dIw (110) and dIv (dV (110) and V3 (010) are generated in the voltage sector (1). 010) can be detected. As a result, the current 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 in which the voltage vectors V1 (100) and V2 (110) are generated. Thus, the induced voltage Ev can be detected. This is stored as the previous induced voltage E _pre .

If the time required for switching the voltage sector is regarded as zero in a control region that can be said to be very fast compared to the rotation period of the motor 2, E _now (Eu) and E _pre (Ev) ) To determine the induced voltage Ew of the third phase. If the three-phase induced voltage is obtained, the rotational position θc is obtained from the equations (10) and (11).
Note that (9) of each phase current variation of Formula left side, in the present embodiment obtained in accordance with (12) from the DC current I _DC.

Here, in order to detect a three-phase current according to each switching pattern as shown in equation (12), 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 rate is 0.3, each voltage vector is generated as shown in FIG. The horizontal axis represents the electrical angle, and the vertical axis represents the generation ratio of each voltage vector during one PWM period. 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.
Title: “Semiconductor Power Conversion System Research Expert Committee:“ Semiconductor Power Conversion Circuit ”, IEEJ (1987)”

  For example, the ratio of the voltage vector generation period necessary for detecting the amount of current change is represented by a broken line in FIG. In this case, in the single triangular wave carrier comparison method, other than the voltage vectors V0 and V7 do not reach 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 necessary for detecting the induced voltage of the corresponding phase in each voltage sector are 0.2 or more. . This makes it possible to detect a necessary current change amount.

It should be noted that the generation period of the voltage vector necessary for detecting the current change amount varies depending on the inverter specifications and the like. FIG. 8 shows U and V-phase upper PWM signals, DC current I _DC , and current detection timings t1 to t4 in switching states corresponding to voltage vectors V0 (000), V1 (100), and V2 (110), respectively. Show.

For example, when the switching state changes from the voltage vector V0 to V1, a ripple occurs in the current I _DC in the switching transient state. Therefore, the first sampling of the current I _DC is performed at a timing t1 when a certain amount of time has elapsed 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 timing t2 when 0.1 minute of the period T _pwm has passed, and the current change amount ΔI _DC is obtained.

Note that the amount of current change in the U phase (+) is detected at timings t1 and t2, and the amount of current change in the W phase (−) is detected at timings t3 and t4. As described above, in order to detect the current _IDC with high accuracy, it is necessary to secure a sufficient period for generating a specific voltage vector. However, if a three-phase triangular wave carrier is used, a sufficient generation period for the necessary voltage vector can be ensured. The rotation position θc can be detected.

9, FIG. 10 shows a PWM signal waveform and the DC current I _DC at the conventional triangular wave comparison method and the 3-phase triangular wave comparison method. Since the PWM signal of 120-degree phase difference with 3-phase triangular wave comparison method is generated, by the time of occurrence of each voltage vector increases, the conduction time of the direct current I _DC is increased relative to FIG. 9 I understand.

  Next, the operation of the present embodiment will be described with reference to FIGS. FIG. 11 and FIG. 12 are flowcharts showing the processing contents mainly performed by the rotational position detection device 14 based on the principle described so far. First, when the rotational 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 generator 9 obtains the current voltage sector from the phase duties Du, Dv, Dw based on the equation (1) (S4). The PWM generator 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 calculation in step S1 is executed as shown in FIG. The current change amount detector 8 obtains 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 for the previously detected induced voltage E _pre (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 is different from the previous voltage sector (S14). If the voltage sector is the same (NO), the process 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 subjected to three-phase / two-phase conversion by the equation (10), and the rotation position θc is obtained by performing the arctangent calculation of the equation (11) (S16).

FIG. 13 shows an operation waveform of each part. Based on the modulation command for 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 calculator 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 to Eu, Ev, Ew. The rotational position obtained from the current induced voltage and the previous voltage sector induced voltage at the voltage sector switching timing is θc. It can be seen that the position can be detected with six resolutions in one cycle of electrical angle, although there is a certain amount of error with respect to the actual rotational 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 rotational position of the motor 2, and the PWM generation unit 5 generates the three-phase triangular wave. Used as a carrier, a three-phase PWM signal pattern that generates a signal pulse of each phase from the three-phase duty commands Du, Dv, Dw by 120 degrees is generated. The signal generator 9 generates the 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 in 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 it can be obtained directly from the amount of current change detected in the rotational position.

In addition, when the induced voltage calculation unit 10 calculates the three-phase induced voltage from the change amount of the phase current, the induced voltage calculation unit 10 converts the three-phase induced voltage into a two-phase voltage in an orthogonal coordinate system, and performs an arctangent calculation on the two-phase voltage. To obtain the rotational position. Specifically, in the three-phase PWM signal pattern, voltage sectors (0) to (5) in which the electrical angular period is divided into six parts are set according to a set of two voltage vectors having a high occurrence rate, and before the transition In the voltage sector, the induced voltage E _pre of the first phase is calculated, and in the next transferred voltage sector, the induced voltage E _now of the second phase is calculated. From the induced voltages E _pre and E _now , the induced voltage E _{3 of} the third phase is calculated. Is calculated. These three-phase induced voltages are converted into two-phase voltages Eα and Eβ in an orthogonal coordinate system, and the rotation position θc is obtained by performing an arctangent calculation tan ⁻¹ (Eα / Eβ) on the two-phase voltages. Thereby, the rotational position θc can be calculated efficiently.
(Other embodiments)

In order to generate a three-phase PWM signal as in the present embodiment, a state equivalent to the case of using a three-phase triangular wave can be realized by using a phase shift function or the like without using three types of carriers. It is also possible to use a method such as changing the timing for setting the duty in one type of carrier or the comparison polarity of pulse generation. In short, a three-phase PWM signal pattern may be generated so that the central phases for generating each phase signal pulse are 120 degrees different from each other.
Further, the phase difference does not necessarily need to be 120 degrees, and the same phase difference and approximately 120 degrees may be given.

The timing for detecting the current does not need to coincide with the period of the PWM carrier. For example, the detection may be performed at a period twice or four times the carrier period. 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 a CT.
As the switching element, a wide gap semiconductor such as MOSFET, IGBT, power transistor, SiC, or GaN may be used.

  Although several embodiments of the present invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  In the drawings, 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 detector, 9 is a voltage sector and detection timing signal generator, and 10 is an induced voltage. A 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 (4)

A current detector disposed in the direct current unit to detect the phase current of the synchronous motor;
A duty generation unit that generates a three-phase PWM (Pulse Width Modulation) duty command so as to follow the rotational position of the synchronous motor;
Based on the PWM duty command, a PWM generation unit that generates three-phase PWM signal patterns having different central phases for generating signal pulses of each phase;
A detection timing signal generating unit that generates a detection timing signal of the phase current based on the PWM duty command;
Detecting a phase current of the synchronous motor based on a signal generated in the current detection unit and the detection timing signal, and further detecting a change amount of the phase current;
A motor control integrated circuit comprising: a rotational position computing unit that computes a signal synchronized with the rotational position of the synchronous motor based on the amount of change detected by the current change amount detecting unit.   The motor control integrated circuit according to claim 1, wherein the PWM generation unit generates a three-phase PWM signal pattern in which the phases of the centers are 120 degrees different from each other. The rotational position calculator includes an induced voltage calculator that calculates a three-phase induced voltage from the amount of change in the phase current,
Converting the three-phase induced voltage into a two-phase voltage in an orthogonal coordinate system;
The integrated circuit for motor control according to claim 1, wherein the rotational position is obtained by performing an arctangent calculation on the two-phase voltages. In the three-phase PWM signal pattern, the detection timing signal generation unit sets six voltage sectors obtained by dividing an electrical angular period into six parts in accordance with a set of two upper voltage vectors having a high occurrence rate. Output to the arithmetic unit,
The induced voltage calculation unit calculates a first phase induced voltage in the voltage sector before the transition, calculates a second phase induced voltage in the next shifted voltage sector, and induces the first phase and the second phase induction. 4. The integrated circuit for motor control according to claim 3, wherein an induced voltage of the third phase is calculated from the voltage.