JP2010068581A - Electric motor drive unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To estimate a voltage applied to an electric motor, to estimate an induction voltage by using the estimated value, and to estimate an accurate position and speed of a rotor. <P>SOLUTION: This electric motor drive unit includes: a current detection part 7 which detects an inverter bus bar current; an application voltage estimation part 15 which estimates an application voltage of the electric motor; an induction voltage estimation part 11 which estimates the induction voltage of the electric motor from the estimated application voltage and a detection voltage by the current detection part; a rotor position/speed estimation part 12 which estimates the position and speed of the rotor of the electric motor on the basis of the estimated induction voltage; a PWM signal generation part 10 which generates a PWM signal for controlling an inverter on the basis of the estimated rotor position; and a duty correction part 14 which corrects a duty of the generated PWM signal so that the duty does not change the PWM signal during the current detection part detects the inverter bus bar current. The application voltage estimation part 15 estimates the application voltage of the electric motor from a voltage value based on the corrected duty. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric motor drive device that drives an electric motor such as a brushless DC motor at an arbitrary rotation speed.

  In recent years, in an apparatus for driving an electric motor such as a compressor in an air conditioner, there is an increasing need to reduce power consumption from the viewpoint of protecting the global environment. Among them, as one of the power saving techniques, an inverter that drives a highly efficient electric motor such as a brushless DC motor at an arbitrary frequency is widely used. Furthermore, as a driving technique, a sine wave driving technique that is more efficient and can reduce noise is attracting attention as compared with the rectangular wave driving that is driven by a rectangular wave current.

  When driving an electric motor provided in a compressor of an air conditioner, it is difficult to attach a sensor for detecting the position of the rotor of the electric motor. A sensorless sinusoidal drive technology has been devised. As a method for estimating the position of the rotor, there is a method in which an induced voltage generated in a stator winding of an electric motor is estimated (see, for example, Patent Document 1).

  FIG. 12 shows a system configuration of the electric motor drive device of Patent Document 1. This electric motor drive device includes a DC power source 1, an inverter 2 that generates and outputs a drive voltage supplied to the electric motor 3, and a control unit 6 that controls the inverter 2. The electric motor 3 includes a stator 4 to which three phase windings (4u, 4v, 4w) Y-connected around a neutral point are attached, and a rotor 5 to which a magnet is attached.

  The inverter 2 includes a half-bridge circuit composed of a pair of switching elements for three phases for the U phase, the V phase, and the W phase. The pair of switching elements of the half-bridge circuit are connected in series between the high-voltage side end and the low-voltage side end of the DC power supply 1, and a DC voltage output from the DC power supply 1 is applied to the half-bridge circuit. The U-phase half-bridge circuit includes a high-voltage side switching element 21u and a low-voltage side switching element 21x. The V-phase half-bridge circuit includes a high-voltage side switching element 21v and a low-voltage side switching element 21y. The W-phase half-bridge circuit includes a high-voltage side switching element 21w and a low-voltage side switching element 21z. In addition, free-wheeling diodes (22u to 22z) are connected in parallel with the switching elements.

  The DC voltage applied to the inverter 2 is converted into a three-phase AC voltage by the switching operation of the switching element in the inverter 2 described above, whereby the electric motor 3 is driven.

  The control unit 6 includes a current detection unit 7, a PWM signal generation unit 10, an induced voltage estimation unit 11, a rotor position speed estimation unit 12, a base driver 13, and a duty correction unit 14.

The PWM signal generation unit 10 outputs each switching element (21u to 21z) of the inverter 2 in order to output a voltage obtained by calculation from an error between the target speed and the current speed in order to realize a target speed given from the outside. ) Is generated. The generated PWM signal is corrected by the duty correction unit 14. The corrected PWM signal is converted by the base driver 13 into a drive signal for electrically driving the switching element. Each switching element (21u to 21z) operates according to the drive signal.

  Current detector 7 observes the bus current of inverter 2 and detects the phase current of motor 3 that appears in the bus current. In practice, the current detector 7 detects the current only for a predetermined period from when the bus current changes.

  The induced voltage estimation unit 11 includes information on the phase current of the motor 3 detected by the current detection unit 7, the voltage calculated by the PWM signal generation unit 10, and the DC voltage of the inverter 2 detected by the DC voltage detection unit 8. Thus, the induced voltage of the electric motor 3 is estimated. Further, the rotor position / speed estimation unit 12 estimates the rotor magnetic pole position and the rotation speed of the electric motor 3 from the estimated induced voltage. Based on the information on the estimated rotor magnetic pole position, the PWM signal generation unit 10 generates a PWM signal for driving the electric motor 3. At that time, the PWM signal generator 10 controls the PWM signal based on deviation information between the estimated rotational speed of the electric motor 3 and the target speed given from the outside so that the rotational speed matches the target speed.

As described above, the conventional motor drive device realizes sinusoidal drive with an inexpensive system configuration without providing current detection means such as a current sensor between the lines between the inverter 2 and the motor 3.
Japanese Patent No. 3931079

  However, in the conventional configuration, the induced voltage is estimated by the induced voltage estimation unit 11 using the voltage calculated by the PWM signal generation unit 10, but actually, the PWM signal generated by the PWM signal generation unit 10 is estimated. Is corrected by the duty correction unit 14, and the drive voltage is supplied to the motor 3 by the operation of the switching element in the inverter 2 based on the corrected PWM signal. Therefore, an error occurs in the estimation of the induced voltage. As a result, an error may occur in the estimation of the rotor magnetic pole position and the rotation speed, and the phase current of the motor 3 may be distorted.

  The present invention solves the above-described conventional problem, and estimates the voltage actually applied to the motor from the duty information of the PWM signal corrected by the duty correction unit, and uses the estimated applied voltage of the motor. Thus, an object of the present invention is to provide an electric motor drive device that can reduce the estimation error of the induced voltage and estimate the rotor magnetic pole position and the rotational speed with high accuracy by estimating the induced voltage.

  In order to solve the above-described conventional problems, an electric motor driving device according to the present invention detects DC current of an inverter that converts DC power into AC power of a desired frequency and voltage and supplies the electric power to the motor, and a bus current of the inverter. Current detection means, applied voltage estimation means for estimating the voltage applied to the motor from the duty information of the PWM signal that controls the inverter, current value detected by the current detection means, and application estimated by the applied voltage estimation means Induced voltage estimating means for estimating the induced voltage of the motor from the estimated voltage value, and rotor position speed estimation for estimating the rotor magnetic pole position and the rotating speed of the motor based on the estimated voltage estimated value estimated by the induced voltage estimating means And a PWM signal generator for generating a PWM signal for controlling the inverter based on information on the rotor magnetic pole position estimated by the rotor position speed estimation means And a duty correction means for correcting the duty of the PWM signal generated by the PWM signal generation means, and the duty correction means does not change the PWM signal while detecting the inverter bus current by the current detection means. The duty is corrected, and the applied voltage estimation means estimates the applied voltage of the motor from the voltage value based on the duty correction value corrected by the duty correction means.

  As a result, the voltage actually applied to the motor is estimated from the duty information of the PWM signal corrected by the duty correction unit, and the induced voltage is estimated using the estimated voltage applied to the motor. Thus, the rotor magnetic pole position and the rotational speed can be estimated with high accuracy.

  The electric motor drive device of the present invention estimates the voltage applied to the electric motor from the duty information of the PWM signal corrected by the duty correction unit, and estimates the induced voltage using the estimated applied voltage of the electric motor. Thus, the estimation error of the induced voltage can be reduced, and the rotor pole position and rotation speed can be estimated with high accuracy.

  According to a first aspect of the present invention, there is provided an inverter for converting DC power into AC power having a desired frequency and voltage and supplying the electric power to the motor, current detection means for detecting the bus current of the inverter, and a PWM signal for controlling the inverter. Estimating the induced voltage of the motor from the applied voltage estimating means for estimating the voltage applied to the motor from the duty information, the current value detected by the current detecting means and the applied voltage estimated value estimated by the applied voltage estimating means Estimated by the induced voltage estimating means, the rotor position speed estimating means for estimating the rotor magnetic pole position and the rotational speed of the electric motor based on the induced voltage estimated value estimated by the induced voltage estimating means, and the rotor position speed estimating means. PWM signal generating means for generating a PWM signal for controlling the inverter based on the information on the rotor magnetic pole position, and PWM generated by the PWM signal generating means Duty correction means for correcting the duty of the signal, the duty correction means corrects the duty so that the PWM signal is not changed while the current detection means detects the inverter bus current, and the applied voltage estimation means The applied voltage of the motor is estimated from the voltage value based on the duty correction value corrected by the duty correction means. As a result, the voltage actually applied to the motor is estimated from the duty information of the PWM signal corrected by the duty correction unit, and the induced voltage is estimated using the estimated voltage applied to the motor. Thus, the rotor magnetic pole position and the rotational speed can be estimated with high accuracy.

  According to a second aspect of the invention, in particular, in the motor drive device of the first aspect of the invention, the applied voltage estimation means calculates a virtual neutral point potential of the motor from a voltage value based on the duty correction value corrected by the duty correction means. The estimated neutral voltage is subtracted from the voltage value based on the duty correction value to derive the applied voltage estimated value. As a result, when two-phase modulation or third harmonic is superimposed, or the voltage calculated by the PWM signal generation means and the voltage actually output by the inverter (PWM signal after being corrected by the duty correction means) Even in an overmodulation region where the deviation is large (when voltage saturation occurs), the voltage applied to the electric motor can be reliably estimated.

  According to a third aspect of the invention, particularly in the motor drive device of the second aspect of the invention, the motor drive device further includes an operation mode determination unit that determines whether the switching operation of the inverter is a PWM modulation region or an overmodulation region. Only when the determination result of the means is the overmodulation region, the estimated value of the applied voltage is derived and output from the voltage value based on the duty correction value that is the input value, and when the determination result of the operation mode determination means is the PWM modulation region Is to output the voltage value based on the duty correction value which is an input value as it is. As a result, while reducing the burden on a computing device such as a microcomputer, the difference between the voltage calculated by the PWM signal generating means and the voltage actually output by the inverter (PWM signal corrected by the duty correcting means) In the overmodulation region (in the case of voltage saturation) that increases, the voltage applied to the motor can be reliably estimated.

According to a fourth aspect of the present invention, in the electric motor drive device of the third aspect of the invention, the operation mode determining means is provided when the inverter frequency or the rotational speed estimated by the rotor position speed estimating means is greater than or equal to a predetermined value set in advance. It is determined that the operation of the inverter is in the overmodulation region, and it is determined that the operation of the inverter is in the PWM modulation region when it is less than a predetermined value set in advance. This makes it possible to determine whether the PWM modulation region (when voltage is not saturated) or the overmodulation region (when voltage is saturated) with a simple configuration, particularly when there is little fluctuation in the power supply voltage and the load torque range of the motor is relatively narrow. be able to.

  According to a fifth aspect of the invention, in particular, in the electric motor drive device of the third aspect of the invention, the operation mode determination means is the duty of the PWM signal generated by the PWM signal generation means or a voltage value based on the duty, or a duty correction value or duty When the voltage value based on the correction value or the modulation rate is equal to or greater than a predetermined value, the inverter operation is determined to be an overmodulation region, and when the inverter operation is less than the predetermined value, the inverter operation is PWM. It is determined that it is the modulation region.

  As a result, it is possible to determine whether the PWM modulation region (when voltage saturation is not performed) or the overmodulation region (when voltage saturation occurs) without depending on fluctuations in the power supply voltage or the operation region (rotation speed / load torque) of the motor. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a system configuration diagram of an electric motor drive device according to a first embodiment of the present invention. This electric motor drive device includes a DC power source 1, an inverter 2 that generates and outputs a drive voltage supplied to the electric motor 3, and a control unit 6 that controls the inverter 2. The electric motor 3 includes a stator 4 to which three phase windings (4u, 4v, 4w) Y-connected around a neutral point are attached, and a rotor 5 to which a magnet is attached.

  The inverter 2 includes a half-bridge circuit composed of a pair of switching elements for three phases for the U phase, the V phase, and the W phase. The pair of switching elements of the half-bridge circuit are connected in series between the high-voltage side end and the low-voltage side end of the DC power supply 1, and a DC voltage output from the DC power supply 1 is applied to the half-bridge circuit. The U-phase half-bridge circuit includes a high-voltage side switching element 21u and a low-voltage side switching element 21x. The V-phase half-bridge circuit includes a high-voltage side switching element 21v and a low-voltage side switching element 21y. The W-phase half-bridge circuit includes a high-voltage side switching element 21w and a low-voltage side switching element 21z. In addition, free-wheeling diodes (22u to 22z) are connected in parallel with the switching elements.

  The DC voltage applied to the inverter 2 is converted into a three-phase AC voltage by the switching operation of the switching element in the inverter 2 described above, whereby the electric motor 3 is driven.

  The control unit 6 includes a current detection unit 7, a PWM signal generation unit 10, an induced voltage estimation unit 11, a rotor position speed estimation unit 12, a base driver 13, a duty correction unit 14, and an applied voltage estimation unit 15. Composed.

The PWM signal generation unit 10 outputs each switching element (21u to 21z) of the inverter 2 in order to output a voltage obtained by calculation from an error between the target speed and the current speed in order to realize a target speed given from the outside. ) Is generated. The generated PWM signal is corrected by the duty correction unit 14. The corrected PWM signal is converted by the base driver 13 into a drive signal for electrically driving the switching element. Each switching element (21u to 21z) operates according to the drive signal.

  Current detector 7 observes the bus current of inverter 2 and detects the phase current of motor 3 that appears in the bus current. In practice, the current detector 7 detects the current only for a predetermined period from when the bus current changes.

  The applied voltage estimation unit 15 calculates a virtual neutral point potential of the electric motor 3 from the voltage value based on the duty correction value corrected by the duty correction unit 14, and based on the calculated virtual neutral point potential based on the duty correction value. The applied voltage estimated value is derived by subtracting from the obtained voltage value.

  The induced voltage estimation unit 11 estimates the induced voltage of the electric motor 3 based on the phase current of the electric motor 3 detected by the current detection unit 7 and the applied voltage estimated value of the electric motor 3 estimated by the applied voltage estimation unit 15. Further, the rotor position / speed estimation unit 12 estimates the rotor magnetic pole position and the rotation speed of the electric motor 3 from the estimated induced voltage. Based on the information on the estimated rotor magnetic pole position, the PWM signal generation unit 10 generates a PWM signal for driving the electric motor 3. At that time, the PWM signal generator 10 controls the PWM signal based on deviation information between the estimated rotational speed of the electric motor 3 and the target speed given from the outside so that the rotational speed matches the target speed.

  Next, the operation of the induced voltage estimation unit 11 will be described. The phase currents (iu, iv, iw) flowing through the windings of the respective phases of the electric motor 3 are obtained from the bus current of the inverter 2 detected by the current detection unit 7. Moreover, the applied voltage estimated value obtained by the applied voltage estimation part 15 is used for the phase voltage (vu, vv, vw) applied to the winding of each phase. In principle, the induced voltages (eu, ev, ew) induced in the windings of the respective phases are obtained from these values by the calculations of the following formulas (1) to (3). Here, R is a resistance and L is an inductance. D (iu) / dt, d (iv) / dt, and d (iw) / dt are time derivatives of iu, iv, and iw, respectively.

eu = vu−R · iu−L · d (iu) / dt Equation (1)
ev = vv−R · iv−L · d (iv) / dt Equation (2)
ew = vw−R · iw−L · d (iw) / dt Equation (3)
Here, when formulas (1) to (3) are developed in more detail, the following formulas (4) to (6) are obtained.

eu = vu-R · iu
− (La + La) · d (iu) / dt
-Las · cos (2θ) · d (iu) / dt
-Las · iu · d {cos (2θ)} / dt
+ 0.5 · La · d (iv) / dt
−Las · cos (2θ−2π / 3) · d (iv) / dt
-Las · iv · d {cos (2θ-2π / 3)} / dt
+ 0.5 · La · d (iw) / dt
−Las · cos (2θ + 2π / 3) · d (iw) / dt
−Las · iw · d {cos (2θ + 2π / 3)} / dt Equation (4)
ev = vv−R · iv
− (La + La) · d (iv) / dt
-Las · cos (2θ + 2π / 3) · d (iv) / dt
-Las · iv · d {cos (2θ + 2π / 3)} / dt
+ 0.5 · La · d (iw) / dt
−Las · cos (2θ) · d (iw) / dt
-Las · iw · d {cos (2θ)} / dt
+ 0.5 · La · d (iu) / dt
-Las · cos (2θ-2π / 3) · d (iu) / dt
-Las · iu · d {cos (2θ-2π / 3)} / dt Equation (5)
ew = vw-R · iw
− (La + La) · d (iw) / dt
-Las · cos (2θ-2π / 3) · d (iw) / dt
-Las · iw · d {cos (2θ-2π / 3)} / dt
+ 0.5 · La · d (iu) / dt
−Las · cos (2θ + 2π / 3) · d (iu) / dt
-Las · iu · d {cos (2θ + 2π / 3)} / dt
+ 0.5 · La · d (iv) / dt
−Las · cos (2θ) · d (iv) / dt
-Las · iv · d {cos (2θ)} / dt Equation (6)
Here, d / dt represents time differentiation, and dθ / dt appearing in the differentiation calculation regarding the trigonometric function is obtained by converting the estimated speed ω into the electrical angular speed. D (iu) / dt, d (iv) / dt, and d (iw) / dt are obtained by first-order Euler approximation. Note that the u-phase current iu is obtained by changing the sign of the sum of the v-phase current iv and the w-phase current iw. Where R is the resistance per winding phase, la is the leakage inductance per winding phase, La is the average effective inductance per winding phase, and Las is the effective inductance amplitude per winding phase. It is.

  In the induced voltage estimation unit 11, equations (7) to (9) obtained by simplifying equations (4) to (6) are used. Here, it is assumed that the phase current (iu, iv, iw) is a sine wave, and the phase current (iu, iv, iw) is created and simplified from the current command amplitude I * and the current command phase βT. .

eu = vu + R · I * · sin (θ + βT)
+1.5 ・ (la + La) ・ cos (θ + βT)
−1.5 · Las · cos (θ−βT) Equation (7)
ev = vv + R · I * · sin (θ + βT−2π / 3)
+ 1.5 · (la + La) · cos (θ + βT-2π / 3)
−1.5 · Las · cos (θ−βT−2π / 3) Formula (8)
ew = vw + R · I * · sin (θ + βT + 2π / 3)
+ 1.5 · (la + La) · cos (θ + βT + 2π / 3)
−1.5 · Las · cos (θ−βT + 2π / 3) Formula (9)
Next, the operation of the rotor position speed estimation unit 12 will be described. The rotor magnetic pole position and rotation speed of the electric motor 3 are estimated from the induced voltage estimated values (eu, ev, ew) estimated by the induced voltage estimation unit 11. The rotor position speed estimator 12 obtains the estimated angle θ recognized by the rotor position by converging it to a true value by using the error of the induced voltage. Also, an estimated speed ω is generated therefrom.

  First, an induced voltage reference value (eum, evm, ewm) of each phase is obtained by equations (10) to (12). Here, the induced voltage amplitude value em is obtained by matching the amplitude value of the induced voltage estimated values (eu, ev, ew).

eum = em · sin (θ + βT) Equation (10)
evm = em · sin (θ + βT−2π / 3) Equation (11)
ewm = em · sin (θ + βT + 2π / 3) Formula (12)
Deviation ε between the induced voltage reference value esm thus obtained and the induced voltage estimated value es is obtained (s = u, v, w (s represents a phase)).

ε = es-esm (s = u, v, w) Equation (13)
Since the estimated angle θ becomes a true value when the deviation ε becomes 0, the estimated angle θ is obtained by performing PI calculation using the deviation ε so that the deviation ε is converged to 0. Further, the estimated speed ω is obtained by calculating the fluctuation value of the estimated angle θ.

  In order to realize the target speed ω *, the PWM signal generation unit 10 calculates the voltage V * to be output by using PI calculation or the like based on the error Δω between the target speed ω * and the estimated speed ω. From the voltage value V *, voltages (vu *, vv *, vw *) to be output to each phase are obtained by the equations (14) to (16).

vu * = V * · sin (θ + βT) Equation (14)
vv * = V * · sin (θ + βT−2π / 3) Equation (15)
vw * = V * · sin (θ + βT + 2π / 3) Equation (16)
Further, the PWM signals of the switching elements (21u to 21z) for outputting the voltages (vu *, vv *, vw *) thus obtained are corrected by the duty correction unit 14 and output to the base driver 13. Is done. Each switching element (21u to 21z) is driven according to the PWM signal after the correction, and generates a sine wave AC.

  As described above, the electric motor drive device of the present invention creates the estimated angle θ using the deviation ε between the induced voltage estimated value and the induced voltage reference value, and flows the sinusoidal phase current to cause the sine wave of the electric motor 3 to flow. Drive is realized.

  Here, how the phase current of the electric motor 3 appears in the bus current of the inverter 2 will be described with reference to FIGS. FIG. 3 is a diagram showing the state of the phase current flowing through the windings of each phase of the electric motor 3 and the direction of the current flowing through the windings of each phase in each section at every electrical angle of 60 °. Referring to FIG. 3, in the section where the electrical angle is 0 to 60 °, the U-phase winding 4u and the W-phase winding 4w are neutral from the unconnected end to the neutral point, and the V-phase winding 4v is neutral. Current flows from the point toward the unconnected end. Further, in the section of electrical angle of 60 to 120 °, the U-phase winding 4u is connected from the non-connection end toward the neutral point, and the V-phase winding 4v and the W-phase winding 4w are not connected from the neutral point. Current is flowing toward the edge. Hereinafter, it is shown that the state of the phase current flowing through the windings of each phase changes every electrical angle of 60 °.

  For example, consider the case where the PWM signal generated by the PWM signal generation means 10 changes as shown in FIG. 4 when the electrical angle is 30 ° in FIG. Here, in FIG. 4, the signal U is the switching element 21u, the signal V is the switching element 21v, the signal W is the switching element 21w, the signal X is the switching element 21x, the signal Y is the switching element 21y, and the signal Z is A signal for operating the switching element 21z is shown. These signals are listed as active high. In this case, as shown in FIG. 5, no current appears at the timing 1 on the bus of the inverter 2, a current (W-phase current) flowing through the W-phase winding 4 w appears at the timing 2, and a V-phase winding at the timing 3. A current flowing in 4v (phase V current) appears.

  As another example, consider the case where the PWM signal generated by the PWM signal generation unit 10 changes as shown in FIG. 6 when the electrical angle is 30 ° in FIG. In this case, as shown in FIG. 7, no current appears at the timing 1 at the bus of the inverter 2, current (U-phase current) flowing through the U-phase winding 4 u appears at the timing 2, and V-phase winding at the timing 3. A current flowing in 4v (phase V current) appears.

  Thus, it can be seen that the phase current of the electric motor 3 corresponding to the state of the switching elements (21u to 21z) appears on the bus of the inverter 2.

  If the currents for two phases can be determined at close timings as described above, it is clear that the phase currents (iu, iv, iw) of each phase can be obtained from the relationship of the following equation.

iu + iv + iw = 0 Formula (17)
However, when the PWM signal generated by the PWM signal generation unit 10 changes as shown in FIG. 8 when the electrical angle is 30 ° in FIG. 3, no current appears on the bus of the inverter 2 at the timing 1, and the timing 3 Then, only the V-phase current appears. That is, in this case, only the current for one phase can be detected. Therefore, if the PWM signal changing in this way is repeated, the currents of the three phases cannot be obtained, and the induced voltage estimation unit 11 cannot estimate the induced voltage, and the motor 3 cannot be driven.

  In order to avoid the above problems, the duty correction unit 14 checks the PWM signal generated by the PWM signal generation unit 10 during the period in which it is necessary to detect the phase current flowing through the winding of each phase of the motor 3. If the PWM signal is a signal that disables detection of the phase current for two phases (for example, a PWM signal as shown in FIG. 8), the PWM signal can be used to ensure the phase current for two phases. It is corrected to a PWM signal that can be detected (for example, a PWM signal as shown in FIGS. 4 and 6), and the corrected PWM signal is a period during which the current detection unit 7 detects the bus current of the inverter 2. Do not change. The duty information of the PWM signal output from the duty correction unit 14 is also input to the current detection unit 7. The current detection unit 7 determines which phase current of the electric motor 3 appears in the bus current of the inverter 2, and converts it into a current value of each phase. The detected current value of each phase by the current detection unit 7 is used for the induced voltage estimation calculation in the induced voltage estimation unit 11.

  As described above, sinusoidal driving is realized with an inexpensive system configuration without providing two or more current detection means such as a current sensor between the lines between the inverter 2 and the electric motor 3.

  Next, the operation of the applied voltage estimation unit 15 that is a feature of the present invention will be described.

  First, the applied voltage estimation unit 15 obtains the virtual neutral point potential of the motor 3 from the voltage values (vuh *, vvh *, vwh *) based on the duty correction value corrected by the duty correction unit 14 by the following equation.

vn = (vuh * + vvh * + vwh *) / 3 Formula (18)
For the voltage values (vuh *, vvh *, vwh *) based on the duty correction value, the duty value of the PWM signal corrected by the duty correction unit 14 is the value of the inverter 2 detected by the DC voltage detection unit 8. It is converted into a voltage value based on DC voltage information.

  From the virtual neutral point potential vn thus obtained and the voltage values (vuh *, vvh *, vwh *) based on the duty correction value, the applied voltage estimated value of the electric motor 3 is expressed by the equations (19) to (21). Ask for.

vu = vuh * -vn Formula (19)
vv = vvh * −vn Formula (20)
vw = vwh * -vn Formula (21)
The applied voltage estimated values (vu, vv, vw) obtained in this way are used for the induced voltage estimation calculation in the induced voltage estimation unit 11.

  Here, the voltage values (vuh *, vvh *, vwh *) based on the duty correction value are actually the same as the voltage calculated by the PWM signal generation means when two-phase modulation or third-order harmonics are superimposed. The voltage applied to the motor 3 can be reliably estimated even in an overmodulation region (when voltage saturation occurs) in which the deviation from the voltage output by the inverter (PWM signal after being corrected by the duty correction means) is large. This will be described with reference to FIGS.

  9 shows a case of three-phase modulation, FIG. 10 shows a case where a third harmonic is superimposed, FIG. 11 shows a voltage value (for one phase) based on a duty correction value in the case of two-phase modulation, a virtual neutral point potential. FIG. 9 is a diagram showing a waveform of an applied voltage estimated value (for one phase). In FIGS. 9 to 11, (a) is a PWM modulation region (when voltage is not saturated), and (b) is an overmodulation region (voltage), respectively. In the case of saturation). In any case, the applied voltage of the electric motor 3 can be obtained.

  As described above, when two-phase modulation or third-order harmonics are superimposed, or the voltage calculated by the PWM signal generation means and the voltage actually output by the inverter (PWM signal after being corrected by the duty correction means) Even in the overmodulation region (when voltage saturation occurs) in which the deviation from the voltage increases, the voltage applied to the motor can be reliably estimated from the voltage value based on the duty correction value corrected by the duty correction unit 14. By estimating the induced voltage using the estimated applied voltage, the estimation voltage estimation error can be reduced, and the rotor pole position and rotation speed can be estimated with high accuracy.

(Embodiment 2)
FIG. 2 is a system configuration diagram of an electric motor drive device according to the second embodiment of the present invention. The same components as those of the electric motor driving apparatus in the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted because it is duplicated.

  The operation mode determination unit 16 performs excessive operation of the inverter 2 when the frequency of the inverter or the rotation speed estimated by the rotor position speed estimation unit 12 is equal to or greater than a predetermined value (frequency F or rotation speed N). It is determined that it is in the modulation region (in the case of voltage saturation), and it is determined that the operation of the inverter is in the PWM modulation region (in the case of not voltage saturation) when it is less than a predetermined value (frequency F or rotation speed N). It is preferable to do this. In this case, especially when there is little fluctuation in the power supply voltage and the load torque range of the motor is relatively narrow, it is determined whether the PWM modulation area (when voltage saturation is not) or overmodulation area (when voltage saturation) with a simple configuration can do.

  Further, the operation mode determination unit 16 is based on the duty of the PWM signal generated by the PWM signal generation unit 10 or a voltage value based on the duty, or the duty correction value or duty correction value corrected by the duty correction unit 14. When the voltage value or the modulation rate is equal to or greater than a predetermined value (duty D, voltage value V, or modulation rate σ), it is determined that the operation of the inverter is an overmodulation region, and the predetermined value is set in advance. It is preferable to determine that the operation of the inverter is in the PWM modulation region when it is less than (duty D, voltage value V, or modulation factor σ). In this case, it is possible to determine whether the PWM modulation region (when voltage saturation is not performed) or the overmodulation region (when voltage saturation occurs) without depending on fluctuations in the power supply voltage or the operation region (rotation speed / load torque) of the motor. it can.

  Note that the voltage value based on the duty of the PWM signal generated by the PWM signal generation unit 10 and the voltage value based on the duty correction value are determined based on the DC voltage information of the inverter 2 detected by the DC voltage detection unit 8. Convert to value. Further, the modulation rate can be derived from the ratio between the maximum value of the voltage value and the DC voltage.

In the applied voltage estimation unit 15, the determination result of the operation mode determination unit 16 is based only on the duty correction value that is an input value using Expressions (18) to (21) only in the overmodulation region (when voltage saturation is not performed). The applied voltage estimation values (vu, vv, vw) of the electric motor 3 are derived from the measured voltage values (vuh *, vvh *, vwh *) and output, and the determination result of the operation mode determination unit 16 is the PWM modulation region (voltage saturation) If not, the voltage values (vuh *, vvh *, vwh *) based on the duty correction value that is the input value are output as they are. The output value is utilized for the induced voltage estimation calculation in the induced voltage estimation unit 11.

  As described above, the voltage calculated by the PWM signal generation unit and the voltage actually output by the inverter (duty correction unit) are reduced while reducing the burden on the arithmetic unit such as the microcomputer with respect to the motor driving device in the first embodiment. In the overmodulation region (in the case of voltage saturation) in which the deviation from the PWM signal after correction in (1) becomes large, the voltage applied to the motor can be reliably estimated.

  As described above, according to the motor drive device of the present invention, the voltage applied to the motor is estimated from the duty information of the PWM signal corrected by the duty correction unit, and the estimated voltage applied to the motor is used. By estimating the induced voltage, the estimation error of the induced voltage can be reduced and the rotor pole position and rotation speed can be estimated with high accuracy, so it can be applied to the motor drive device of the compressor in an air conditioner such as a room air conditioner. can do.

The system block diagram of the electric motor drive device in Embodiment 1 of this invention The system block diagram of the electric motor drive device in Embodiment 2 of this invention The figure which shows an example of the time change of the phase current state of an electric motor The figure which shows an example of the change of a PWM signal (A) (b) (c) The figure which represents the state of the electric current which flows into an electric motor and an inverter at the time of the drive by a PWM signal in FIG. The figure which shows an example of the change of a PWM signal (A) (b) (c) The figure which represents the state of the electric current which flows into an electric motor and an inverter at the time of the drive by a PWM signal in FIG. The figure which shows an example of the change of a PWM signal (A) (b) The figure which shows an example of operation | movement of the applied voltage estimation part in the electric motor drive device of this invention (A) (b) The figure which shows an example of operation | movement of the applied voltage estimation part in the electric motor drive device of this invention (A) (b) The figure which shows an example of operation | movement of the applied voltage estimation part in the electric motor drive device of this invention System configuration diagram of a conventional motor drive device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DC power supply 2 Inverter 21u-21z Switching element 22u-22z Freewheeling diode 3 Electric motor 4 Stator 4u-4w Stator winding 5 Rotor 6 Control part 7 Current detection part 8 DC voltage detection part 10 PWM signal generation part 11 Induced voltage Estimating unit 12 Rotor position speed estimating unit 13 Base driver 14 Duty correction unit 15 Applied voltage estimating unit 16 Operation mode determining unit

Claims (5)

From inverter information for converting DC power into AC power of desired frequency and voltage and supplying the electric power to the motor, current detection means for detecting the bus current of the inverter, and duty information of the PWM signal for controlling the inverter An induced voltage of the electric motor is estimated from an applied voltage estimating means for estimating a voltage applied to the electric motor, a current value detected by the current detecting means and an applied voltage estimated value estimated by the applied voltage estimating means. Induced voltage estimating means, rotor position speed estimating means for estimating the rotor magnetic pole position and rotation speed of the electric motor based on the induced voltage estimated value estimated by the induced voltage estimating means, and the rotor position speed estimating means PWM signal generating means for generating a PWM signal for controlling the inverter based on the information on the rotor magnetic pole position estimated by And a duty correction means for correcting the duty of the generated PWM signal generating means,
The duty correction means corrects the duty so as not to change the PWM signal while the inverter bus current is detected by the current detection means,
The motor drive apparatus according to claim 1, wherein the applied voltage estimation means estimates the applied voltage of the motor from a voltage value based on the duty correction value corrected by the duty correction means. The applied voltage estimation unit calculates a virtual neutral point potential of the electric motor from a voltage value based on the duty correction value corrected by the duty correction unit, and calculates the calculated virtual neutral point potential based on the duty correction value. The electric motor drive device according to claim 1, wherein an estimated value of the applied voltage is derived by subtracting from the voltage value. An operation mode determination means for determining whether the switching operation of the inverter is a PWM modulation region or an overmodulation region;
The applied voltage estimating means derives and outputs an applied voltage estimated value from a voltage value based on a duty correction value that is an input value only when the determination result of the operation mode determining means is an overmodulation region, and the operation mode 3. The electric motor drive device according to claim 2, wherein when the determination result of the determination means is in the PWM modulation region, the voltage value based on the duty correction value which is an input value is output as it is. The operation mode determination means determines that the operation of the inverter is an overmodulation region when the frequency of the inverter or the rotation speed estimated by the rotor position speed estimation means is greater than or equal to a predetermined value set in advance. The electric motor drive device according to claim 3, wherein the operation of the inverter is determined to be a PWM modulation region when the value is less than a predetermined value set in advance. The operation mode determination means is preset with a duty of the PWM signal generated by the PWM signal generation means, a voltage value based on the duty, a voltage value based on the duty correction value or the duty correction value, or a modulation rate. The operation of the inverter is determined to be in an overmodulation region when the predetermined value is greater than or equal to a predetermined value, and the operation of the inverter is determined to be in the PWM modulation region when less than a predetermined value set in advance. Item 4. The electric motor drive device according to Item 3.