JP2001086788A - Device for estimating position and speed of synchronous motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate the direction and rotary speed of a permanent magnet, even under a wide range of conditions by providing a position estimation means for estimating the direction of the permanent magnet of a permanent-magnet-type synchronous motor according to the estimated back electromotive force and the estimated rotary speed error of the output of a back electromotive force/speed error estimating means. SOLUTION: A back electromotive force/speed error estimating means 7 inputs a primary voltage v1, a primary current i1, and a direction θg of a permanent magnet where an estimated rotary speed ωg has been estimated, and outputs a back electromotive force (e) of a permanent-magnet-type synchronous motor 1, an estimated rotary speed ωg, and an error ωm2 from the actual rotary speed. Then, a position estimating means 8 inputs the back electromotive force (e) and the speed error ωm2, and outputs the direction θg of the permanent magnet, where the sum of the result obtained by dividing the back electromotive force (e) by magnetic flux ϕ of the permanent magnet and the speed error ωm2. A speed estimating means 9 inputs the back electromotive force (e) and the speed error ωm2, and outputs the rotary speed ωg that is the sum obtained by adding them to the result obtained by passing the speed error ωm2 through a low-pass filter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for controlling a permanent magnet type synchronous motor, and more particularly to estimating the direction and rotational speed of a permanent magnet in a wide speed range without using a position sensor or a speed sensor. And an apparatus for estimating the position and speed of a synchronous motor.

[0002]

2. Description of the Related Art A conventional technique will be described below with reference to FIG. FIG. 3 is a block diagram showing an example of the prior art, wherein 1 is a permanent magnet synchronous motor, 4 is a power converter for supplying electric power to the permanent magnet synchronous motor 1, and 6 is a d-axis current i.
a high-frequency current superimposer for outputting a signal such that a high-frequency current is superimposed on d; a voltage detector 2 for detecting a primary voltage v1 applied to the permanent magnet synchronous motor 1; This is a current detector for detecting a flowing primary current i1.

[0003] Reference numeral 10 denotes a voltage component converter that inputs the primary voltage v1 and the estimated permanent magnet direction θg and outputs a d-axis voltage vd and a q-axis voltage vq. 11 denotes a permanent component estimated as the primary current i1. This is a current component converter that inputs a magnet direction θg and outputs a d-axis current id and a q-axis current iq.

Reference numeral 19 denotes an error or error equivalent Δθf between the permanent magnet direction θg estimated by inputting the d-axis current id, the q-axis current iq, and the q-axis voltage vq and the actual permanent magnet direction.
Is a proportional error amplifier that inputs the output Δθf of the position error estimating means 19 to estimate the rotational speed ωg of the permanent magnet type synchronous motor 1, and 22 integrates the estimated rotational speed ωg. Is an integrator for estimating the direction θg of the permanent magnet.

FIG. 4 is a detailed block diagram of the position error estimating means 19 in FIG. 3, and 23 is a differentiator for differentiating the q-axis current iq. Numeral 24 denotes an inductance-divided voltage drop calculator, which outputs the output of the differentiator 23 and the permanent magnet type synchronous motor 1
With the q-axis inductance Lq. Reference numeral 25 denotes a resistance voltage drop calculator that outputs the product of the q-axis current iq and the armature resistance R of the permanent magnet type synchronous motor 1. An adder 26 outputs the sum of the output of the voltage drop calculator for inductance 24 and the output of the voltage drop calculator 25 for resistance.
A subtractor 27 outputs a difference between the q-axis voltage vq and the output of the adder 26.

Reference numeral 28 denotes a differentiator for differentiating the output of the subtracter 27. Reference numeral 29 denotes a position error detector, which outputs the output of the differentiator 28 and d
A product Δθh with the shaft current id is output. A low-pass filter 30 removes harmonic components of the output of the position error detector 29 and outputs a DC component Δθf.

Next, the position and speed estimating apparatus for a permanent magnet type synchronous motor having such a configuration will be described in detail below based on the background of the invention of the present invention. FIG.
Is the actual permanent magnet direction θg of the permanent magnet synchronous motor 1
The vector represents the relationship between the estimated permanent magnet direction θg and r.

[0008]

(Equation 1)

Assume that there is a position error Δθ. When a high-frequency current is superimposed on the d-axis current id by the high-frequency current superimposer 6, the d-axis current id and the q-axis current iq are represented by the following equations.

[0010]

(Equation 2)

Here, Id and Iq are DC components, I is the peak value of the high-frequency current, ωh is the angular frequency of the high-frequency current, and t is time. In the primary current i1, a dr-axis current idr in a direction parallel to the actual direction θgr of the permanent magnet (hereinafter, referred to as dr axis) and a qr-axis current iqr in an axis perpendicular to the dr axis (hereinafter, referred to as qr axis) are: From the d-axis current id and q-axis current iq in equations (2) and (3),

[0012]

(Equation 3)

## EQU1 ##

The characteristic equation of the permanent magnet type synchronous motor 1 is expressed by the following equation.

[0015]

(Equation 4)

Here, vdr is the dr-axis voltage, and vqr is q
r-axis voltage, Ld is the d-axis inductance of the permanent magnet type synchronous motor 1, p is the differential operator, φ is the magnetic flux of the permanent magnet, ωg
r is the actual rotation speed of the permanent magnet synchronous motor 1.
Next, when equations (4) and (5) are substituted into equations (6) and (7),

[0017]

(Equation 5)

## EQU1 ## Therefore, the estimated q-axis voltage vq of the component perpendicular to the direction θg of the permanent magnet is given by the following equation from equations (8) and (9).

[0019]

(Equation 6)

The product Δ of the d-axis current id output from the position error detector 29 and the value obtained by differentiating the q-axis voltage vq is obtained.
θh is obtained from the equations (2) and (10) as follows:

[0021]

(Equation 7)

## EQU1 ## Although the q-axis current iq is controlled to the DC component Iq as shown in the equation (3), a high-frequency current as in the equation (2) is actually applied to the d-axis current id due to interference between the d-axis and the q-axis. When flowing, a high frequency component also appears in the q-axis current iq. The high frequency component of the q-axis current iq is represented by a q-axis voltage vq
Also appear. Therefore, in FIG. 4, in order to remove the influence of the high frequency component of the q-axis current iq appearing in the q-axis voltage vq, the subtracter 27 adds the q-axis voltage vq to ｛vq− (R +
p · Lq) · iq}. When Δθh is passed through the low-pass filter 30 to remove harmonic components, the following equation is obtained.

[0023]

(Equation 8)

Here, assuming that the position error Δθ is very small, Δθf in equation (12) can be approximated by the following equation.

[0025]

(Equation 9)

Here, K1 is

[0027]

(Equation 10)

Is as follows. Since Lq> Ld, it can be seen from equation (13) that the position error Δθ and Δθf are in a proportional relationship. That is, when the estimated permanent magnet direction θg is ahead of the actual permanent magnet direction θgr, Δθf <
It becomes 0, and the estimated rotational speed ωg of the permanent magnet type synchronous motor 1 is reduced by the proportional-integral amplifier 21, so that the estimated direction θg of the permanent magnet is slowed down and coincides with the actual direction θgr of the permanent magnet. . The same applies to the opposite case. That is, since Δθf corresponding to the position error Δθ is obtained from the d-axis current id, the q-axis current iq, and the q-axis voltage vq, the direction θg and the rotation speed ωg of the permanent magnet can be estimated. In view of the above, the following describes the issues that have been taken as conventional issues.

[0029]

The conventional method is effective when the permanent magnet type synchronous motor is stopped or rotating at a low speed. However, as can be seen from the characteristic equations (6) and (7) of the permanent magnet type synchronous motor 1, the higher the rotation speed, the higher the voltage. When the voltage exceeds the voltage that can be supplied by the power converter 4, there is a problem that the high-frequency current cannot be superimposed on the d-axis current id, and the direction θg and the rotation speed ωg of the permanent magnet cannot be estimated.

Similarly, when the rotational speed of the permanent magnet type synchronous motor suddenly changes, the dr-axis current idr and q
The r-axis current iqr increases, and d is obtained from the equations (6) and (7).
The r-axis voltage vdr and the qr-axis voltage vqr increase, and the direction θg and rotation speed ωg of the permanent magnet cannot be estimated. The present invention has been devised in view of the above points, and aims to solve these disadvantages and eliminate the inability to estimate the direction and rotation speed of the permanent magnet at high speed rotation, etc. It is an object of the present invention to provide a synchronous motor position and speed estimating device capable of estimating the direction and rotation speed of a permanent magnet even under conditions.

[0031]

In order to achieve the above object, the direction of the estimated permanent magnet of the permanent magnet type synchronous motor (hereinafter, referred to as d-axis) is set at regular intervals. A high frequency current is superimposed on the d-axis current which is a component of the primary current, and the estimated permanent magnet is determined from the detected primary current and primary voltage of the permanent magnet type synchronous motor and the estimated direction of the permanent magnet. In the method of estimating the position and speed of the synchronous motor having position error estimating means capable of estimating the position error between the direction of the permanent magnet and the direction of the actual permanent magnet, the d-axis voltage is calculated from the primary voltage and the estimated direction of the permanent magnet. a voltage component converter that outputs a q-axis voltage in a direction perpendicular to the d-axis (hereinafter, referred to as a q-axis), and the d-axis current and the q-axis current based on the primary current and the estimated direction of the permanent magnet. And current output A converter, the d-axis voltage, the q-axis voltage, the d-axis current, the q-axis current, the estimated rotational speed of the permanent magnet type synchronous motor, and the estimated value of the permanent magnet type synchronous motor before one sampling. Current estimating means for estimating the d-axis current and the q-axis current at the current sampling time from the back electromotive force, the q-axis current of the output of the current estimating means, and the q-axis current of the output of the current component converter. Back electromotive force estimating means for estimating the back electromotive force from the difference, and the rotational speed estimated from the difference between the d-axis current of the output of the current estimating means and the d-axis current of the output of the current component converter. Speed error estimating means A for estimating an error from the actual rotational speed; speed error estimating means B for estimating an error between the estimated rotational speed and the actual rotational speed from an output of the position error estimating means;
An adder for outputting the sum of the output of the speed error estimating means A and the output of the speed error estimating means B; and a speed for estimating the rotational speed from the output of the adder and the output of the back electromotive force estimating means. And estimating means for estimating the direction of the permanent magnet from the output of the adder and the output of the back electromotive force estimating means.

Next, as set forth in claim 2, the high-frequency current superimposed on the d-axis current and the output of the speed error estimating means B exceed an absolute value of the estimated rotational speed at a certain arbitrary rotational speed. And the absolute value of the estimated rotational speed is reduced to zero at an arbitrary slope, and the absolute value of the estimated rotational speed becomes zero when the high-frequency current and the output of the speed error estimating means B become zero. When the rotation speed becomes equal to or less than the rotation speed at the time of the rotation, the arbitrary slope is increased to the original value, and the arbitrary slope is such that the high-frequency current is smaller than the output of the speed error estimating means B. .

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. In addition, the part shown with the same code as the conventional technology is
Although they have the same configuration and the same function, their description is omitted here. FIG. 1 is a block diagram showing one embodiment of the present invention, in which a back electromotive force / speed error estimating means 7 includes a primary voltage v
1, the primary current i1, the estimated rotational speed ωg, and the estimated permanent magnet direction θg, and the back electromotive force e of the permanent magnet type synchronous motor 1, the estimated rotational speed ωg, and the actual rotational speed are input. Is output as the error ωm2.

The position estimating means 8 inputs the estimated back electromotive force e and the estimated velocity error ωm2 of the output of the back electromotive force / speed error estimating means 7 and makes the estimated back electromotive force e permanent. Speed error ωm estimated to be divided by magnet magnetic flux φ
And outputs the direction θg of the permanent magnet obtained by integrating the sum of the two. The speed estimating means 9 inputs the estimated back electromotive force e of the output of the back electromotive force / speed error estimating means 7 and the estimated speed error ωm2, and outputs the estimated back electromotive force e to the magnetic flux of the permanent magnet. φ
A rotation speed ωg, which is the sum of the speed error ωm2 estimated by dividing by ωm2 and the speed error ωm2 passed through the low-pass filter, is output.

FIG. 2 is a detailed block diagram of the back electromotive force / speed error estimating means 7 in FIG.
The axis voltage vd, the q-axis voltage vq, the d-axis current id, and the q-axis current i
The estimated rotation speed ωg and the estimated back electromotive force e are input, and the d-axis voltage vd, the q-axis voltage vq, the d-axis current id, and the q-axis current iq before one sampling are estimated. The speed ωg and the estimated back electromotive force e are output.

The current estimating means 13 calculates the d-axis voltage vd, q-axis voltage vq,
The shaft current id, the q-axis current iq, the estimated rotation speed ωg, and the estimated back electromotive force e are input, and the d-axis current idM and the q-axis current iqM at the current sampling time are estimated.
The subtractor 14 outputs the q-axis current i of the output of the current component converter 11.
q and the estimated q-axis current iq of the output of the current estimation means 13
The difference Δiq from M is output. The back electromotive force estimation means 15
The output Δiq of the subtractor 14 is input, and the back electromotive force e of the permanent magnet type synchronous motor 1 is estimated.

The subtractor 16 outputs a difference Δid between the d-axis current id output from the current component converter 11 and the estimated d-axis current idM output from the current estimating means 13. The speed error estimating means A17 receives the output Δid of the subtractor 16 and estimates an error between the estimated rotation speed ωg of the permanent magnet synchronous motor 1 and the actual rotation speed.

The speed error estimating means B20 receives the output Δθf of the position error estimating means 19 and the estimated rotational speed ωg, and calculates the estimated rotational speed ωg of the permanent magnet type synchronous motor 1 and the actual rotational speed. Is estimated. FIG.
Is a graph for explaining the relationship between the output ωgh of the speed error estimating means B20 and the estimated rotational speed ωg. The output ωgh of the speed error estimating means B20 is equal to the estimated rotational speed ω
The absolute value of g is output from zero to an arbitrary rotation speed ωg1 as it is, and the absolute value of the estimated rotation speed ωg exceeds the arbitrary rotation speed ωg1. A value obtained by reducing the output ωgh of the speed error estimating means B20 at the inclination of is output, and is not output when the absolute value of the estimated rotation speed ωg is equal to or higher than the rotation speed ωg2 at which ωgh becomes zero.

The adder 18 calculates the sum ωm of the output of the speed error estimating means A17 and the output ωgh of the speed error estimating means B20.
2 is output. FIG. 6 is a graph illustrating the relationship between the output of the high-frequency current superimposer 5 and the estimated rotation speed ωg.
The high-frequency current superimposer 5 is different from the high-frequency current superimposer 6 in that the estimated rotational speed ωg is input and an arbitrary rotational speed ωg1 having an absolute value of the estimated rotational speed ωg from zero.
Up to this point, the peak value I of the high-frequency current is output as it is, and the absolute value of the estimated rotation speed ωg exceeds the arbitrary rotation speed ωg1, and the absolute value of the estimated rotation speed ωg is reduced at an arbitrary slope. Output the value and the estimated rotational speed ωg
Is not output when the absolute value of is equal to or higher than the rotation speed ωg3 at which the peak value I becomes zero.

In the present invention, the current values are obtained from the d-axis voltage vd, the q-axis voltage vq, the d-axis current id, the q-axis current iq, the estimated rotation speed ωg, and the estimated back electromotive force e before one sampling in the present invention. The current estimating means 20 that can estimate the d-axis current id and the q-axis current iq at the time of sampling will be described. The approximate expression of the d-axis voltage vd and the q-axis voltage vq when there is a position error Δθ is as follows from Expressions (6) and (7).

[0041]

[Equation 11]

Here, eg is the back electromotive force of the permanent magnet type synchronous motor 1, and

[0043]

(Equation 12)

Is as follows. Using the Euler approximation, the equations (15) and (16) are rewritten as an equation of a discrete value system between the sample point (n-1) and the sample period T of n, and solved for the d-axis current id and the q-axis current iq. And the following equation.

[0045]

(Equation 13)

The estimated value idM of the d-axis current and the estimated value iqM of the q-axis current are calculated by calculating the back electromotive force of the fourth term on the right side of the equations (18) and (19) by the estimated inverse magnitude e in the q-axis direction. It is expressed by the following equation, which is replaced by electromotive force.

[0047]

[Equation 14]

Therefore, as described above, the d-axis voltage vd, the q-axis voltage vq, the d-axis current id, the q-axis current iq, the estimated rotation speed ωg, and the estimated back electromotive force e before one sampling are obtained. From the d-axis current idM at the current sampling time
And the q-axis current iqM can be estimated.

Next, a back electromotive force estimating means capable of estimating the back electromotive force e from the difference Δiq between the q-axis current iq output from the current component converter 11 and the estimated q-axis current iqM output from the current estimating means 13 15 will be described below. Error current Δiq between equation (19) representing the detected q-axis current iq (n) and equation (21) representing the estimated q-axis current iqM (n)
Is a current error caused by an estimation error of the back electromotive force, and is expressed by the following equation.

[0050]

(Equation 15)

If Δθ is very small, equation (22) can be approximated by the following equation.

[0052]

(Equation 16)

However,

[0054]

[Equation 17]

Is as follows. From equation (23), the q-axis current error Δ
Since iq is proportional to the back electromotive force error Δe, q
An error Δe of the estimated back electromotive force can be estimated by dividing the shaft current error Δiq by −Kq in equation (24). The back electromotive force can be estimated from the estimated back electromotive force error Δe.

Therefore, as described above, the back electromotive force e is estimated from the difference Δiq between the q-axis current iq output from the current component converter 11 and the estimated q-axis current iqM output from the current estimating means 13. be able to.

Next, the rotational speed of the permanent magnet type synchronous motor 1 estimated from the difference Δid between the d-axis current id of the output of the current component converter 11 and the estimated d-axis current idM of the output of the current estimating means 13 The speed error estimating means A17 capable of estimating the error between ωg and the actual rotation speed will be described below. An error current Δid between the equation (18) representing the detected d-axis current id (n) and the equation (20) representing the estimated d-axis current idM (n) is as follows.

[0058]

(Equation 18)

If Δθ is very small, equation (26) can be approximated by the following equation.

[0060]

[Equation 19]

However,

[0062]

(Equation 20)

Is as follows. From equation (27), the d-axis current error Δ
Since id is proportional to the position error Δθ, an error Δθ of θg in the direction of the permanent magnet estimated by dividing the d-axis current error Δid by Kd in equation (28) can be estimated. The rotational speed error corresponding to the estimated permanent magnet direction θg error Δθ can be further divided by the position error Δθ by the sample time to obtain the rotational speed error corresponding to the estimated permanent magnet direction θg error Δθ. Is required.

As described above, the current component converter 11
Is calculated from the difference Δid between the d-axis current id of the output of the current estimator 13 and the estimated d-axis current idM of the output of the current estimating means 13.
Can be estimated.

Next, the output Δθf of the position error estimating means 19
Speed ωg of the permanent magnet type synchronous motor 1 estimated from
A speed error estimating means B20 capable of estimating an error between the rotation speed and the actual rotation speed will be described below. The output Δθf of the position error estimating means 19 is a value proportional to the position error Δθ as shown in the equation (13). The position error Δθf is (14)
By dividing by K1 in the equation and the sample time, an error ωgh of the rotational speed corresponding to the position error Δθ is obtained.

As described above, the position error estimating means 1
9, an error in the rotational speed corresponding to the position error Δθ can be estimated.

Next, the estimated back electromotive force e of the output of the back electromotive force / speed error estimating means 7 and the estimated rotational speed error ω
The speed estimating means 9 capable of estimating the rotational speed ωg of the permanent magnet type synchronous motor 1 from m2 will be described below.
From the relationship of equation (17), the rotation speed of the permanent magnet type synchronous motor 1 can be obtained by dividing the back electromotive force e by the magnetic flux φ of the permanent magnet. Further, an accurate rotation speed can be estimated by adding a speed error ωm2 corresponding to the position error Δθ. Passing the velocity error ωm2 corresponding to the position error Δθ through the low-pass filter is for removing noise of the velocity error ωm2.

As described above, the rotational speed ωg of the permanent magnet type synchronous motor 1 is estimated from the estimated back electromotive force e of the output of the back electromotive force / speed error estimating means 7 and the estimated rotational speed error ωm2. can do.

Next, the estimated back electromotive force e of the output of the back electromotive force / speed error estimating means 7 and the estimated rotational speed error ω
m2, the direction θ of the permanent magnet of the permanent magnet type synchronous motor 1
The position estimating means 8 capable of estimating g will be described below. The rotation speed of the permanent magnet type synchronous motor 1 is equal to the back electromotive force e.
Is divided by the magnetic flux φ of the permanent magnet and the speed error ωm2 corresponding to the position error Δθ can be added, so that the direction θg of the permanent magnet can be estimated by integrating the rotation speed. .

As described above, the direction θg of the permanent magnet of the permanent magnet type synchronous motor 1 is determined from the estimated back electromotive force e of the output of the back electromotive force / speed error estimating means 7 and the estimated rotational speed error ωm2. Can be estimated.

Next, a description will be given of how the output of the high-frequency current superimposer 5 and the output of the speed error estimating means B20 have a relationship as shown in FIG. Conventional position error estimating means 19
However, if the permanent magnet type synchronous motor 1 rotates at a high speed or the rotation speed changes rapidly, the direction and rotation speed of the permanent magnet cannot be estimated. Therefore, if it rotates to some extent, d
Since the high-frequency current superimposed on the shaft current id and the output of the position correcting means 19 are not required, the high-frequency current and the output of the speed error estimating means B21 are reduced to zero when the rotation speed exceeds an arbitrary rotation speed ωg1. The inclination at this time is determined by the position error estimating means 1.
Since the direction and rotation speed of the permanent magnet cannot be estimated unless the high-frequency current is superimposed on the d-axis current id, the gradient for reducing the high-frequency current is reduced and the high-frequency current is used earlier than when the output of the speed error estimating means B21 is used. Is the d-axis current id
To be able to be superimposed.

[0072]

According to the present invention, since the rotation speed and the direction of the permanent magnet of the permanent magnet type synchronous motor can be estimated in a wide range, a position sensor and a speed sensor are not required.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a block diagram showing one embodiment of the present invention.

FIG. 3 is a block diagram showing one embodiment of a conventional system.

FIG. 4 is a block diagram showing one embodiment of a conventional system.

FIG. 5 is a vector diagram showing the principle of the conventional method.

FIG. 6 is a graph illustrating an example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Permanent magnet synchronous motor 2 Voltage detector 3 Current detector 4 Power converter 5 High frequency current superimposing device 6 High frequency current superimposing device 7 Back electromotive force / speed error estimating means 8 Position estimating means 9 Speed estimating means 10 Voltage component converter DESCRIPTION OF SYMBOLS 11 Current component converter 12 Delay circuit 13 Current estimation means 14 Subtractor 15 Back electromotive force estimation means 16 Subtractor 17 Speed error estimation means A 18 Adder 19 Position error estimation means 20 Speed error estimation means B 21 Proportional integration amplifier 22 Integration 23 Differentiator 24 Inductance voltage drop calculator 25 Resistance voltage drop calculator 26 Adder 27 Subtractor 28 Differentiator 29 Position error detector 30 Low-pass filter

Claims (2)

[Claims] 1. A high frequency current is superimposed on a d-axis current which is a primary current component parallel to an estimated permanent magnet direction (d-axis) of a permanent magnet type synchronous motor at regular intervals, and the detected high-frequency current is detected. A position error estimating means for estimating a position error between the estimated permanent magnet direction and the actual permanent magnet direction from the primary current and the primary voltage of the permanent magnet type synchronous motor and the estimated permanent magnet direction; In the position and speed estimation device for a synchronous motor, d is calculated from the primary voltage and the estimated direction of the permanent magnet.
A voltage component converter that outputs an axis voltage and a q-axis voltage in an axis (q-axis) direction perpendicular to the d-axis; and the d-axis current and the q-axis current based on the primary current and the estimated direction of the permanent magnet. The d-axis voltage, the q-axis voltage, the d-axis current, the q-axis current, the estimated rotational speed of the permanent magnet type synchronous motor and the permanent magnet before one sampling. Estimating means for estimating the d-axis current and the q-axis current at the current sampling time from the estimated back electromotive force of the type synchronous motor, a q-axis current of the output of the current estimating means, and a Back electromotive force estimating means for estimating the back electromotive force from the difference between the output and the q-axis current; and Speed for estimating the error between the estimated rotation speed and the actual rotation speed Error estimating means A; speed error estimating means B for estimating an error between the estimated rotational speed and the actual rotational speed from the output of the position error estimating means; An adder that outputs the sum of the outputs of the estimating means B; speed estimating means for estimating the rotational speed from the output of the adder and the output of the back electromotive force estimating means; A position estimating device for estimating the direction of the permanent magnet from an output of the electromotive force estimating device. 2. The high frequency current superimposed on the d-axis current and the output of the speed error estimating means B, when the absolute value of the estimated rotational speed exceeds a certain arbitrary rotational speed, the output of the estimated rotational speed When the absolute value of the estimated rotational speed becomes equal to or less than the rotational speed when the output of the high-frequency current and the speed error estimating means B becomes zero, the absolute value is reduced to zero at an arbitrary slope with respect to the absolute value. 2. The position and speed of the synchronous motor according to claim 1, wherein said arbitrary gradient is increased to a original value, and said arbitrary gradient is such that said high-frequency current is smaller than an output of said speed error estimating means B. Estimation device.