KR20190104875A - Integrated circuit for controlling motor - Google Patents

Abstract

An integrated circuit for motor control of an embodiment includes a current detector disposed in a direct current unit for detecting a phase current of a synchronous motor, a duty generator for generating a three-phase PWM duty instruction so as to follow the rotation position of the synchronous motor; A PWM generator for generating three-phase PWM signal patterns having different phases from the center of the signal pulses based on the PWM duty command; and a detection timing signal of the phase current based on the PWM duty command. A current change amount detection unit for detecting a phase current of the synchronous motor based on a signal generated by the current detection unit and a signal generated by the current detection unit and the detection timing signal, and further detecting a change amount of the phase current; Rotation phase for calculating a signal synchronized with the rotation position of the synchronous motor based on the amount of change detected by the detection unit. And a value calculating unit.

Description

Integrated Circuits for Motor Control {INTEGRATED CIRCUIT FOR CONTROLLING MOTOR}

Embodiment of this invention relates to the integrated circuit for motor control.

Conventionally, as a method of estimating the rotational position of a permanent magnet synchronous motor in a medium to high speed region, for example, an induced voltage or a rotor magnetic flux proportional to the speed of the permanent magnet synchronous motor is input to the permanent magnet synchronous motor. The method of calculating from and estimating based on the induced voltage is widely used. In this 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 observer to calculate the rotation position from the calculated induced voltage or a signal corresponding thereto. It is also necessary to design and adjust parameters such as gain.

In addition, there is a problem that the sensorless control becomes unstable depending on the driving state of the motor and the set parameters. In order to substitute a pure position sensor, a resolver, an encoder, a hall sensor, or the like, highly advanced design skills and experience are required.

Moreover, as a sensorless drive system of the medium speed to the high speed region, there is a system that detects the phase of the induced voltage generated in the non-energized section in the 120 degree energization, and switches the energized phase based on this. According to this system, sensorless driving can be realized without designing a controller or the like. However, there is a problem that the energization method is limited to 120 degree energization, the motor current is deformed and the noise deteriorates, and sensorless driving cannot be performed in the ultra low speed region.

Japanese Patent Laid-Open No. 2007-336641

Patent Document 1 (Japanese Patent Laid-Open No. 2007-336641) discloses a method of detecting a position using an amount of current change during application of a voltage vector. In this method, although the resolution is small, the sensorless sinusoidal drive can be performed without adjusting the control parameters.

However, in patent document 1, it is necessary to arrange | position three shunt resistors to an inverter circuit in order to detect an electric current. In order to build 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. Therefore, a single shunt current detection method in which a single shunt resistor is arranged in the direct current part is often used, and a position sensorless control method corresponding to the detection method is desired.

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

An integrated circuit for motor control of an embodiment includes a current detector disposed in a direct current unit for detecting a phase current of a synchronous motor;

A duty generator for generating a three-phase PWM duty instruction so as to follow the rotational position of the synchronous motor;

A PWM generator for generating a three-phase PWM signal pattern having different phases from a center of generating a signal pulse of each phase based on the PWM duty command;

A detection timing signal generator that generates a detection timing signal of the phase current based on the PWM duty command;

A current change amount detecting unit detecting a phase current of the synchronous motor based on the signal generated in the current detecting unit and the detection timing signal, and further detecting a change amount of the phase current;

On the basis of the change amount detected by this current change amount detection part, the rotation position calculation part which computes the signal synchronized with the rotation position of the said synchronous motor is provided.

1 is a functional block diagram showing a configuration of a motor drive control device in one embodiment.
2 is a waveform diagram illustrating a three-phase triangle wave used as a PWM carrier.
3 is a diagram illustrating a space state of an on state of a switching device configuring an inverter circuit.
4 is a diagram showing the magnitude of the phase voltage at the time of generating each voltage vector using the DC voltage V _DC .
5 is a diagram showing the magnitude of the voltage vector generated in each voltage sector and the phase of the detectable induced voltage.
FIG. 6 is a diagram illustrating an incidence rate of a voltage vector generated when a general triangular wave comparison method is used. FIG.
Fig. 7 is a graph showing the incidence rate of the voltage vectors generated when the three-phase triangle wave comparison method is used.
FIG. 8 is a diagram showing PWM signals on the upper U and V phases corresponding to the voltage vectors V0, V1, and V2, DC current I _DC , and current detection timings t1 to t4.
9 is a diagram showing a PWM signal waveform and a direct current I _DC in a conventional triangle wave comparison method.
10 is a diagram showing a PWM signal waveform and a direct current I _DC in a three-phase triangle wave comparison method.
It is a flowchart which shows the process content which a rotation position detection apparatus performs.
12 is a flowchart showing the contents of the position detection operation in step S1.
Fig. 13 is a diagram showing operational waveforms of each part.

EMBODIMENT OF THE INVENTION Hereinafter, one Embodiment is described with reference to drawings. 1 is a functional block diagram showing the configuration of a motor drive control apparatus. The DC power supply 1 is a power source for driving the permanent magnet synchronous motor 2 having a permanent magnet in the rotor. The DC power supply 1 may be a product obtained by converting AC power to DC. The inverter circuit 3 is configured by three-phase bridge connection of six switching elements, for example, N-channel MOSFETs 4U +, 4Y +, 4W +, 4U-, 4Y-, and 4W-, and is generated by the PWM generator 5 described later. The voltage for driving the motor 2 is generated on the basis of the three switching phase six switching signals.

The voltage detector 6 detects the voltage Vdc of the DC power supply 1. The current detection unit 7 is connected between the negative side power supply line of the inverter circuit 3 and the negative side terminal of the DC power supply 1. The current detector 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 DC current Idc flowing through the motor 2.

The current change amount detection section 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 generator 9 described later, and the difference value of the detection value every two times. Is calculated as the variations dI _DC1 and dI _DC2 . The induced voltage calculating unit 10 calculates the induced voltages of any two phases of the three phases as E _now and E _pre based on the variations dI _DC1 and dI _DC2 .

The rotation position calculator 11 obtains the remaining one phase of the induced voltage 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 generator 12 generates three-phase voltage command values Vu, Vv, and Vw from the voltage amplitude command value Vamp and the voltage phase command value φv and the rotation position θc, which are command values given from the upper control device. do.

The duty generator 13 calculates the modulation commands, the duty commands Du, Dv, and Dw of each phase by dividing the three-phase voltage command values Vu, Vv, and Vw by the DC voltage V _dc . As shown in FIG. 2, the carrier generation unit 14 outputs, to the PWM generation unit 5, a three-phase triangle wave signal having a phase difference of 120 degrees as a carrier and a carrier wave used for PWM control. In Fig. 2, PWM signal pulses of each phase are generated based on the valley of the triangular wave.

The PWM generator 5 compares the three-phase modulation commands Du, Dv, and Dw with the three-phase triangle wave input from the carrier generator 14 to generate PWM signal pulses for each phase. Dead time is added to the pulse per phase, and the switching signals U +, U-, V +, V-, W +, and W- which are output to the N-channel MOSFETs 4 above and below each of three phases are generated.

The three-phase modulation commands Du, Dv, and Dw are input to the voltage sector and the detection timing signal generator 9. The signal generator 9 discriminates the voltage sectors (0) to (5) obtained by dividing the electric periods into six equal parts on the basis of the three-phase modulation commands Du, Dv, and Dw under the conditions shown in the equation (1), and discriminates them. The result is output to the current change amount detecting section 8, the induced voltage calculating section 10, and the rotation position calculating section 11.

The detection timing signals t1 to t4 described above are also generated in accordance with the determination result of the voltage sectors (0) to (5).

In the above structure, the thing except the motor 2 and the inverter circuit 3 comprises the rotation position detection apparatus 15. As shown in FIG. In addition, the inverter circuit 3 is added to the rotation position detecting device 15 to constitute the motor drive control device 16. In addition, in this embodiment, the rotation position detection apparatus 15 is comprised in the inside of a microcomputer by hardware. That is, the speed control, the current control, etc. of the motor 2 are implemented by software, and the rotation position detection apparatus 15 is provided in the inside of a microcomputer or an integrated circuit by making into hardware or a structure equivalent to it.

Next, the principle of detecting a rotation position in this embodiment is demonstrated. The detection of the rotational position uses an electromotive force (EMF) generated by the rotation of the motor. Equation (2) shows the three-phase voltage equation of a permanent magnet synchronous motor. The right side term 3 is an induced voltage term, and contains the information of rotation position (theta).

Here, the magnitude of the phase voltage at the time of occurrence 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 . Then, the U-phase voltage equation at the time of applying the voltage vector V ₁ (100) becomes (3).

The amount of current change dI _u generated at this time is expressed as dI _{u (100)} , and the equation (3) is modified to obtain the equation (4).

Similarly, if the amount of change in the W-phase current at the time of applying the voltage vector V ₂ (110) in the space vector diagram shown in FIG. 3 is dIw (110), equation (5) is obtained.

In addition, it is assumed that the influence of the polarity of the motor on the magnetic flux of the permanent magnet is small,

Approximates L _u = L _w = L In addition, when equation (5) is added to equation (4), equation (6) is obtained because the sum of the phase currents is zero.

Similarly, the sum of the amount of current change in the voltage vectors V ₂ (110) and V ₃ (010) can be expressed by the equation (7).

In addition, since the sum total of a phase current and an induced voltage is zero, when-(6) Formula-(7) Formula is computed, (8) Formula is obtained.

Here, in the state in which the rotational speed ω of the motor is somewhat high, the right side of the equations (6), (7), and (8) becomes the first term < Can be approximated with zero. When these are represented as the three-phase organic voltages E _u , E _v , and E _w , the equation (9) is obtained.

In other words, by using the amount of current change during voltage vector application, it is possible to detect three-phase induced voltages each having a phase difference of 2π / 3. In addition, rotation position (theta) c can be calculated | required by converting the detected three-phase induced voltage into three phase / two phase by (10) Formula, and calculating reverse tangent by (11) Formula.

In addition, when the voltage vectors at the time of application of the voltage vectors V1 and V2 are used, the V-phase induced voltage E _v is obtained. However, when the voltage vectors V1 and V2 are generalized, the relationship shown in FIG. That is, the detected organic voltage phase is switched in accordance with the generated voltage vector. The voltage vector generated for each voltage sector is different. For example, the only voltage vectors occurring in voltage sector (0) are V ₁ (100), V ₂ (110). For this reason, only dI _{u (100)} and dI _{w (110)} can be detected in the amount of current change in (9), and dI _{v (010)} cannot be detected. In addition, although strictly different voltage vectors are generated, 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), in the period in which the voltage vectors V ₂ (110) and V ₃ (010) in the voltage sector (1) occur, the current change amount dI _{w ( 110)} , dI _{v 010} may be detected. By these, the induced voltage E _now = E _u can be detected. In addition, since the voltage sector before switching is (0), the current variation amounts dI _{u (100)} and dI _{w (110)} can be detected in the period in which the voltage vectors V ₁ (100) and V ₂ (110) occur. . The organic voltage Ev can be detected by these. This is saved as the last induced voltage E _pre .

If the time required for switching the voltage sector is considered to be zero in the control region which can be said to be very fast compared to the cycle in which the motor 2 rotates, E _now (E _u ) and E _pre (E _v). ), The organic voltage E _w in the third phase is obtained based on the expression (9). When the induced voltage of three phases is calculated | required, rotation position (theta) _c is calculated | required by Formula (10), (11).

Further, 9 is a left-hand side of each of the current change amount way, in the present embodiment is determined according to the 12 from the direct current I _DC equation.

Here, in order to detect the three-phase current according to each switching pattern, as shown in (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 electric angle, and the vertical axis represents the generation ratio of each voltage vector in the PWM1 period. In contrast, when a three-phase triangle wave as shown in the following document is used as a carrier, the generation rate of each voltage vector increases as shown in FIG.

A document name: "Electric society semiconductor power conversion system investigation expert committee:" semiconductor power conversion circuit ", the electrical society (1987)"

For example, the ratio of the voltage vector generation period required for detecting the amount of current change is set to 0.2 of the PWM period, and is indicated by a broken line in FIG. 6. In this case, the single triangle wave carrier comparison method does not reach 0.2 except for the voltage vectors V ₀ and V ₇ and cannot be detected. In contrast, when the three-phase triangle wave carrier is used, as shown in Fig. 7, two voltage vectors required for detecting 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 current change.

Incidentally, the generation period of the voltage vector necessary for detecting the amount of change of current varies depending on the specification of the inverter or the like. FIG. 8 shows the upper PWM signal and the DC current I _DC on the U and V phases, and the current detection timing t1 to the switching states corresponding to each of the voltage vectors V ₀ (000), V ₁ (100), and V ₂ (110). t4 is shown.

For example, if the switching state is changed to V ₁ from the voltage vector V _0, the current I _DC is the because a ripple occurs in the transient state of switching, current I _DC at the timing t1 by a certain amount of time has elapsed from the time of change The first sampling is performed. This waiting time is set to 0.1 of the PWM period T _pwm . From this, the 2nd sampling is performed at timing t2 which passed 0.1 minute of the period _Tpwm again, and the amount of change of current ΔI _DC is obtained.

In addition, what is detected at the timings t1 and t2 is the amount of current change in the U phase (+), and what is detected at the timings t3 and t4 is the amount of current change in the W phase (-). As described above, 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 using a three-phase triangle wave carrier ensures a sufficient generation period for the required voltage vector, and thus the rotational position. θ _c can be detected.

9 and 10 show PWM signal waveforms and DC current I _DC in the conventional triangular wave comparison method and the three-phase triangle wave comparison method. In the three-phase triangular wave comparison method, since a PWM signal having a phase difference of 120 degrees is generated, it is understood that the energization time of the DC current I _DC is increased as compared with FIG. 9 by increasing the generation time of each voltage vector.

Next, the operation of the present 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 calculating part 11 performs the position detection operation shown in FIG. 12 (S1), the duty generation part 13 calculates each phase duty D _u , D _v , D _w (S2). When the signal generation unit 9 substitutes the current voltage sector into the "last sector" (S3), the current voltage sector is obtained from each phase duty D _u , D _v , D _w based on the expression (1) (S4). ). The PWM generator 5 outputs to the inverter circuit 3 each phase PWM signal generated on the basis of the three-phase triangle wave carrier and the respective phase duties D _u , D _v , and D _w (S5).

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

Subsequently, it is determined whether the current voltage sector and the previous voltage sector are different (S14), and if it is the same voltage sector (No), the process ends. On the other hand, when the voltage sectors are different (YES), the induced voltage E is obtained _now, the induced voltage E ₃ on the third from the _pre E (S15). Then, the induced voltages E _now , E _pre , and E ₃ are converted to three-phase and two-phase by the formula (10), and the inverse tangent calculation of the formula (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 induced voltage E _now obtained by the induced voltage calculating unit 10 has been detected from the detected amount of current change. The broken line is a timing at which each voltage sector is switched, and the induced voltage detected for each voltage sector is switched to E _u , E _v , E _w . The rotational position obtained from the induced voltage of the current voltage and the induced voltage of the previous voltage sector at the switching timing of the voltage sector is θ _c . Compared with the actual rotation position θ, although there is some error, it can be seen that the position can be detected with 6 resolutions for each cycle of electric angle.

As described above, according to the present embodiment, the duty generator 13 generates a three-phase duty command D _u , D _v , D _w to follow the rotational position of the motor 2, and the PWM generator 5 generates 3 The phase triangle wave is used as a carrier, and a three-phase PWM signal pattern is generated that is 120 degrees out of phase of the center for generating signal pulses of each phase from the three-phase duty commands D _u , D _v , and D _w . The signal generator 9 generates the detection timing signals t1 to t4 of the phase currents based on the duty commands D _u , D _v , and D _w .

The current change amount detection section 8 detects the phase current of the motor 2 based on the signal generated in the current detection section 7 and the detection timing signals t1 to t4, and further detects the change amount of the phase current. The rotation position calculating part 11 calculates the signal synchronized with the rotation position of the motor 2 based on the change amount detected by the current change amount detection part 8. In this configuration, constant setting of the motor 2, adjustment of the control gain, and the like become unnecessary, and it can be obtained by direct calculation from the amount of current change in which the rotation position is detected.

In addition, when the induced voltage calculating unit 10 calculates the induced voltage of the three phases from the change amount of the phase current, it converts the induced voltage of the three phases into the voltage of the two phases of the Cartesian coordinate system and performs a reverse tangent operation on the voltage of the two phases to rotate the position Obtain Specifically, in the three-phase PWM signal pattern, voltage sectors (0) to (5) obtained by dividing the electric cycles into six equal parts are set in accordance with a pair of two voltage vectors having a high occurrence rate, and the first voltage sector in the voltage sector before the transition. The induced voltage E _pre of the phase is calculated, and then the induced voltage E _now of the second phase is calculated in the shifted voltage sector, and the induced voltage E ₃ is calculated from the induced voltages E _pre and E _now . Converting the induced voltage on the second voltage to the three E _α, E _β on the orthogonal coordinate system, and by performing the arctangent operation tan ^-1 (Eα / Eβ) with respect to the voltage on the second obtained the rotational position θ _c. Thereby, rotation position (theta) c 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 triangle wave may be realized by using a phase shift function or the like without using three kinds of carriers. The method of setting the duty, changing the polarity of pulse generation, etc. may be used. In other words, the three-phase PWM signal pattern may be generated so that the phases of the centers generating the respective phase signal pulses are different from each other by 120 degrees.

In addition, the phase difference does not necessarily need to be 120 degrees, but what is necessary is just to provide the phase difference of the same grade and the phase difference of about 120 degree.

In addition, the timing which detects a current does not need to match the period of a PWM carrier, For example, you may detect in the period twice or four times a carrier period. Therefore, the current detection timing signal input to the current change amount detecting unit need not be a signal itself obtained from a carrier, but may be a signal generated by a separate timer.

The current detector may be a shunt resistor or a CT.

As the switching element, a wide gap semiconductor such as a MOSFET, an IGBT, a power transistor, SiC, or GaN may be used.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and spirit of the invention, and are included in the inventions described in the claims and their equivalents.

Claims (4)

A current detector disposed in the direct current section for detecting the phase current of the synchronous motor;
A duty generator for generating a three-phase pulse width modulation (PWM) duty command to follow the rotational position of the synchronous motor;
A PWM generator for generating a three-phase PWM signal pattern having different phases from a center of generating a signal pulse of each phase based on the PWM duty command;
A detection timing signal generator that generates a detection timing signal of the phase current based on the PWM duty command;
A current change amount detecting unit detecting a phase current of the synchronous motor based on the signal generated in the current detecting unit and the detection timing signal, and further detecting a change amount of the phase current;
And a rotation position calculating section for calculating a signal synchronized with the rotation position of the synchronous motor based on the amount of change detected by the current change amount detecting section. The integrated circuit for controlling a motor of claim 1, wherein the PWM generator generates a three-phase PWM signal pattern in which the phases of the center are 120 degrees different from each other. The said rotation position calculation part is provided with the organic voltage calculation part of Claim 1 or 2 which calculates the three phase induced voltage from the change amount of the said phase current,
Converts the induced voltage of the three phases into a voltage of two phases of a Cartesian coordinate system,
And a motor control integrated circuit for obtaining the rotation position by performing a reverse tangent operation on the voltage of the two phases. 4. The rotation position of claim 3, wherein the detection timing signal generator sets six voltage sectors that are divided into six equal electric cycles according to a pair of two high voltage vectors having high occurrence rates in the three-phase PWM signal pattern. Output to the calculation unit,
The induced voltage calculating unit calculates an induced voltage of the first phase in the voltage sector before the shift, and then calculates an induced voltage of the second phase in the shifted voltage sector, and generates a third voltage from the induced voltages of the first and second phases. Integrated circuit for motor control for calculating the induced voltage on the phase.

Images