JPH11178399A - Control method for permanent magnet synchronous motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress increase in the inverter capacity and the dielectric strength of a motor by suppressing increase in the output voltage and current of the motor. SOLUTION: In a control method for a permanent magnet synchronous motor 51 being driven by a variable voltage variable frequency inverter 66, a current component (d-axis current component) Id* in same direction as the field of the motor is determined based on the current component (q-axis current component) Iq* perpendicular to the direction of the field of the motor. The d-axis current component Td* is controlled from the region where the terminal voltage in the vicinity of the rated speed of the motor increases depending on the motor torque T* thus suppressing increase at the terminal voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a permanent magnet type synchronous motor using a small and powerful permanent magnet as a field.

[0002]

2. Description of the Related Art A synchronous motor using a small and powerful permanent magnet for the field can be reduced in size, and the driving device including the motor can be reduced in size and the efficiency is improved. To control the motor torque, the current component (q) in the direction perpendicular to the magnetic field direction (d-axis), corresponding to the magnetic pole position of the motor,
(Axial current component). This technology is based on Nakano's "Servo Technology and Power Electronics" (Kyoritsu Shuppan 199
(September 1993), pages 94 to 95. Also, for the same purpose as the DC motor, as the speed of the synchronous motor increases from the specified speed, to weaken the field,
There is also a method of controlling the d-axis current. This technique is described in, for example, Japanese Patent Application Laid-Open No. 8-182398. However, synchronous motors have an armature reaction. Therefore, the voltage increases as the load increases even when operating at a certain rotational speed. This phenomenon occurs in any of the above conventional control methods. In particular, when the load is larger than the rated torque, the voltage rise becomes remarkable. For this reason, when operating near the rated speed, the output voltage of the inverter that controls the motor must be large enough to cope with an increase in voltage due to an increase in load. As a result, there is a problem that the capacity of the inverter must be increased or the withstand voltage of the motor must be increased.

[0003]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a permanent magnet suitable for reducing the increase in the output voltage and current of the motor and suppressing the increase in the capacity of the inverter and the withstand voltage of the motor. An object of the present invention is to provide a method for controlling a magnet type synchronous motor.

[0004]

The object of the present invention is to provide a motor (d-axis current component) in the same direction as the magnetic field of the motor from the region where the terminal voltage becomes high near the rated speed of the permanent magnet synchronous motor. The problem is solved by controlling according to the torque and suppressing the rise of the terminal voltage. Here, the d-axis current component is calculated based on a current component (q-axis current component) perpendicular to the magnetic field of the motor converted from the torque command so that the terminal voltage becomes equal to or less than a predetermined value.
The d-axis current component is zero when the torque command is small, and when the torque command exceeds a certain value, the absolute value of the output gradually increases, and when the rotation speed of the motor is small, the d-axis current component is zero. When the value exceeds the value, a calculation is performed so that the terminal voltage becomes equal to or less than a predetermined value by using a pattern in which the absolute value of the output gradually increases. Further, the magnitude and phase of the armature current of the motor are controlled in accordance with the torque of the motor so as to suppress the rise of the terminal voltage from a region where the terminal voltage increases near the rated speed of the permanent magnet type synchronous motor. Is solved by Further, based on the terminal voltage set according to the torque command of the permanent magnet type synchronous motor and the terminal voltage of the motor actually predicted from the terminal voltage of the motor detected or the operation of the power converter that drives the motor, d is calculated based on d.
This problem is solved by obtaining the shaft current component, controlling the d-axis current component according to the torque of the motor from the region where the terminal voltage near the rated speed of the motor increases in the previous period, and suppressing the increase in the terminal voltage. .

[0005]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a method for controlling a permanent magnet synchronous motor according to an embodiment of the present invention. In FIG. 1, 5
Reference numeral 1 denotes a permanent magnet type synchronous motor whose rotating shaft is connected to a load (not shown), and further connected to a position detector 52 and a speed detector 53. The position detector 52 uses a resolver, an encoder, or the like, and detects the relative position between the armature of the synchronous motor 51 and the permanent magnet field, that is, the rotation angle. The speed detector 53 uses an encoder or the like, and detects the rotation speed of the synchronous motor 51. In the illustrated example, the position detector 52 and the speed detector 53 are divided into functions and described separately. However, actually, the position detector 52 and the speed detector 53 may be constituted by the same device such as a resolver and an encoder. Further, the position detector 52
It may be configured by estimating from the terminal voltage or the like. Now, when the speed command ω * is output from the speed command device 61, the deviation Δω from the output signal ω of the speed detector 53 becomes the speed control device 62.
Is input to The speed control device 62 operates in accordance with the deviation Δω, and its output signal becomes the torque command signal T * of the synchronous motor 51. The output signal T * of the speed control device 62 is q
Input to the axis current command device 63,
Calculates a q-axis current command Iq * according to the torque command signal T *. The q-axis current command Iq * is a command of a component orthogonal to the magnetic field direction of the armature current vector of the synchronous motor 51 and is input to the current control device 65. On the other hand, the d-axis current command device 64 calculates a d-axis current command Id * by a method described later. The d-axis current command Id * is
The main purpose of the command signal is to issue not only the torque of the synchronous motor 51 but also a command signal for suppressing and controlling an increase in the output voltage. is there. The d-axis current command signal Id * is also input to the current controller 65. The current controller 65 controls the actual current to flow as instructed based on the signal from the position detector 52, and the output is input to the inverter 66 as an output voltage command signal. In the inverter 66, the voltage command signal from the current control device 65
The M control is executed, and the output voltage and output frequency of the inverter 66 are controlled. The PWM control by the inverter 66 is executed by comparing the instantaneous value of the voltage command signal with a triangular carrier signal or by well-known space vector PWM control. The power element of the inverter 66 is controlled based on the PWM signal. Thus, the synchronous motor 51
Is controlled, and the torque and the terminal voltage are controlled.

FIG. 2 is a current and voltage vector diagram showing the principle of the control of FIG. In FIG. 2, I: armature current Id, Iq: d of I, q-axis component E0: no-load induced voltage Et: terminal voltage xd, xq: d, q-axis reactance xd = xad + xl, xq = xaq + xl xad, xaq , Xl: d, q-axis armature reaction reactance, leakage reactance. From FIG. 2, the output P of the synchronous motor is

P∝EtIcosφ = EtIcos (θ + δ) = EtI (cosθ · cosδ−sinθ · sinδ) = Etcosδ · Icosθ−Etsinδ · Isinθ = (E0 + xdId) Iq−xqIq · Id + Ed−Iq = E0−Iq Iq (Equation 1) That is, the torque T is

T = P / ω∝ΦIq + (Ld−Lq) Id · Iq (Expression 2) Here, ω: rotational angular velocity of the motor shaft, ω = ω1 / (p / 2) ω1: electric rotational angular frequency p: number of poles of the motor Φ: magnetic flux Ld, Lq: d, q-axis inductance

E0 = kω1Φ (Equation 3) k: Constant

Xd = ω1Id, xq = ω1Iq (Equation 4) At this time, when the synchronous motor 51 is a cylindrical machine, L
Since d = Lq = L, the torque T becomes

## EQU5 ## T∝ΦIq (Expression 5) As a result, the torque T becomes equal to the current q
It is proportional to only the axis component Iq. Therefore, it is understood that only the q-axis component Iq of the current needs to be controlled to control the torque. Next, the terminal voltage Et of the synchronous motor 51 becomes
From the vector in FIG. 2,

(Equation 6) It is. From (Equation 6), when the motor is rotating at a constant speed, the terminal voltage Et becomes zero even if the d-axis current component is zero.
It changes depending on the q-axis current component. That is, if the current component Iq is increased to increase the torque, the terminal voltage Eq
It can be seen that t increases. At this time, from (Equation 6), d
When the axis current component Id is controlled to be negative, the magnitude of the d-axis component of the voltage is reduced, so that the terminal voltage as the vector sum can be suppressed.

FIG. 3 shows a configuration example of a q-axis current command device 63 and a d-axis current command device 64 to which the above principle is applied. The configuration shown is a case where the motor is a cylindrical machine, and the q-axis current command device 631 converts a torque command T * from the speed control device 62 into a q-axis current command Iq * according to the principle of (Equation 5). Since the d-axis current command device 641 determines the q-axis current command Iq * based on the torque command T * from the speed control device 62, the terminal voltage Et becomes equal to or less than a predetermined value based on (Equation 6). The d-axis current command Id * is calculated. Here, since the terminal voltage Et only needs to be equal to or lower than the predetermined value, as can be seen from (Equation 6), the motor is rotating at a rated speed or lower, and Id = 0.
However, when the terminal voltage Et does not become higher than the predetermined value, Id
Needless to say, it is possible to keep = 0. In FIG. 3, the input of the d-axis current command device 641 is from the q-axis current command device 631, but the calculation may be performed by directly receiving the torque command T * from the speed control device 62. In addition,
Here, even if the terminal voltage Et is a constant value, it will be described later with reference to FIG.
As shown in (a), it may be changed according to the load torque. As described above, when the d-axis current command is controlled, the magnitude of the terminal voltage Et falls within a certain range, so that the withstand voltage of the motor and the controllable range of the output voltage of the inverter can be reduced. This is particularly effective when the output voltage of the inverter has no margin near the maximum rotation of the motor, and the output capacity of the inverter can be reduced. The current commands Iq * and Id * thus obtained are input to the current command device 65.

As a specific configuration example, the q-axis current command device 631 may be a gain. The d-axis current command device 641 may determine the terminal voltage and calculate Id obtained from (Equation 6), or may calculate in advance and have it as a pattern. Further, a simple gain may be used. Further, the d-axis current command device 641 may be operated to issue a command from a certain torque or more. As an example,
If the torque is kept at approximately zero up to the rated torque and a negative command is output when the overload exceeds the rated value, the maximum values of voltage and current can be set to appropriate values, which is particularly effective in reducing the capacity of the inverter. There is. In the above description, the motor has been described as an example of a cylindrical machine. However, the same applies to a salient pole machine, and the q-axis and d-axis current commands are calculated from the relations of (Equation 2) and (Equation 6), a pattern or It can be instructed by a simple method.

FIG. 4 shows a specific configuration example of the current control device 65. The basic configuration of this example is well known. For example, IEEJ Transactions on Electronics, Vol. 117, No. 5, July 1997, 53
It is described on page 9, FIG. The configuration of FIG. 4 calculates the d- and q-axis voltage components from the vector diagram of FIG.
A that works in accordance with the deviation between the d and q axis current commands and the actual values
CR-d, q. Further, the configuration of FIG. 4 further considers the armature resistance Ra. The configuration of the calculation in FIG. 4 will be briefly described. As can be seen from (Equation 6), the q-axis voltage command E
q * is

Eq * = kω1Φ + ω1LdId * + RaIq * + (ACR-q output) (Equation 7) In obtaining the q-axis voltage command Eq * in (Equation 7), the addition of the output of ACR-q is based on the error between the set values of the parameters Φ, Ld, and Ra of the motor and the actual values.
This is to prevent the q-axis voltage command Eq * from being different from a predetermined value. If the correction is performed by taking the deviation between the q-axis current command Iq * and its actual value Iq, accurate current control can be performed. On the other hand, the d-axis voltage command Ed * is

[Equation 8] Ed * = − ω1LqIq * + RaId * + (ACR−d output) (Equation 8) Adding the output of ACR-d in (Equation 8)
This is similar to the case of (Equation 7). Id / Iq operation 651
Are three-phase instantaneous current detection values iu, iv, iw based on the sine or cosine signal corresponding to the field pole position (electrical rotation angle) from the position detector 52 (the current detector is not shown).
, The current components Id and Iq are detected. Current control device 6
The output of 5 is voltage command signals Ed * and Eq * for the d and q axes. When executing the PWM control of the inverter 66, if an instantaneous value voltage command signal of a sine wave is required, the inverse operation of the operation 651 may be performed. This calculation is well known and will not be described.

FIG. 5 shows characteristics depending on the presence or absence of such control. (A) is a characteristic example when the control of the present invention is performed,
(B) shows a characteristic example of the conventional control in which the control of the present invention is not performed, the current for the d-axis is set to zero, and only the current control for the q-axis is performed according to the torque. The example of (a) is a d-axis current command Id
Is maintained at zero until a of the torque command T *, and the torque command T *
From step a, the negative command is increased in proportion to the torque. The q-axis current Iq is proportional to the torque as can be seen from (Equation 5). When the d-axis current is controlled in this manner, the armature current I, which is the vector sum of the d- and q-axis current components, slightly increases from Iq, but the terminal voltage Et hardly increases from no load. For this reason, the variable range of the inverter output voltage can be set to an appropriate minimum required range. As a result, an increase in the capacity of the inverter can be suppressed. On the other hand, when the d-axis component is set to zero as in the example of (b), the terminal voltage Et increases as the speed increases. As a result, a large output voltage is required for the inverter, and as a result, the capacity of the inverter increases. As described above, according to the present embodiment, the motor terminal voltage Et is equal to the load (torque).
Therefore, the inverter capacity can be reduced, and the withstand voltage of the motor does not increase. Therefore, it is possible to provide a small and economical control system. In the above example, the d-axis current command is given negative from the torque command a, but the command may be given from torque zero. Needless to say, the d-axis current command amount changes depending on the motor constant of the synchronous motor 51.

FIG. 6 shows a configuration example of a q-axis current command device 63 and a d-axis current command device 64 different from the configuration example shown in FIG. 6, the same numbers as those in FIG. 3 indicate the same objects.
The configuration example of FIG. 6 is an example in which the d-axis current command is changed according to the rotation speed, and shows a detailed configuration example of the d-axis current command device 642. Since the terminal voltage Et of the motor changes according to the rotation speed, the d-axis current command is further changed according to the rotation speed. d
The shaft current command device 642 includes a pattern device 6421 that outputs a signal corresponding to the torque command T *, a pattern device 6422 that outputs a signal corresponding to the rotation speed, and pattern devices 6421 and 621.
It comprises a multiplying device 6423 for taking the product of 422. The output of the multiplying device 6423 is a d-axis current command signal Id *.
The output of the pattern device 6421 is zero when the torque command is small, and when the torque command exceeds a certain value, the absolute value of the output gradually increases. The output of the pattern device 6422 is zero when the speed is low, and when a certain value is exceeded, the absolute value of the output gradually increases. In this case, the d-axis current command signal Id * is not only a signal according to the torque command T * but also a value according to the speed. That is, when the speed is low, the d-axis current command signal Id * is zero, and the d-axis current command signal Id * is gradually output from a certain speed or higher according to the torque. In this case, the d-axis current command signal Id * is output only when the speed is close to the rated speed and the load is larger. Therefore, when the speed is low, the current value is small, so that the current capacity of the inverter can be reduced.

FIG. 7 shows another embodiment of the present invention. 7, the same numbers as those in FIG. 1 indicate the same objects. This embodiment is characterized in that a terminal voltage is detected and a d-axis current command signal Id * is output according to the terminal voltage command. The terminal voltage command device 67 sets a terminal voltage according to the torque command T *. The setting of the terminal voltage is determined, for example, as shown in FIG. The voltage detector 68 detects the output voltage of the inverter 66, that is, the terminal voltage of the synchronous motor 51.
The d-axis current command device 642 operates according to the output signals of the terminal voltage command device 67 and the voltage detector 68. The output of the d-axis current command device 642 is a d-axis current command signal Id *. The d-axis current command device 642 calculates a deviation between the terminal voltage command signal from the terminal voltage command device 67 and the terminal voltage detection signal from the voltage detector 68, and outputs a d-axis current command signal Id *. Is configured. In this case, the actual terminal voltage accurately follows the command value. for that reason,
Since the terminal voltage does not exceed the predetermined value, the margin of the output voltage range of the inverter 66 can be reduced,
Further, the output capacity of the inverter can be reduced. In the present embodiment, the terminal voltage of the synchronous motor 51 is determined by detecting the terminal voltage with the voltage detector 68. However, since the output voltage can be predicted and calculated from the operation of the inverter 66, the terminal voltage can be calculated without detecting the actual value. You can ask. Also,
The d-axis current command Id * is calculated by forming a feedback system, but may be calculated directly based on the terminal voltage command.
Further, only when the terminal voltage is going to exceed a predetermined value,
It is sufficient to output a d-axis current command, otherwise it may be kept at zero.

The above-described embodiments of the present invention are all configured to instruct the d- and q-axis components of the current.
As can be understood from the vector diagram, the magnitude and phase of the current can be commanded and controlled.

Next, FIG. 8 shows an embodiment in which the present invention is applied to an elevator. 8, the same numbers as those in FIG. 1 indicate the same objects. The sheave 2 is connected to the shaft end of the synchronous motor 51, and the car 1 and the counterweight 3 are connected via a rope 4 wound around the sheave 2. Synchronous motor 51
That is, the car 1 moves up and down as the sheave 2 rotates. The control method according to the embodiment of FIG. 1 is effective when applied to a drive system having a constant torque load characteristic, such as the elevator shown in FIG. 8, and particularly when applied to a drive system that requires an overload, Greater effect. It goes without saying that not only the embodiment of FIG. 1 but also all the above-described embodiments including the embodiment of FIG. 7 can be applied to such a drive system. In addition, it goes without saying that the calculation may be performed using a microcomputer in all the embodiments.

[0015]

As described above, according to the present invention,
By controlling the d-axis current according to the torque of the motor, and by controlling the magnitude and phase of the armature current of the motor, the increase in the magnitude of the motor terminal voltage is suppressed. The increase in the current can be reduced, and as a result, it is possible to suppress the increase in the inverter capacity and the withstand voltage of the motor. For this reason, the whole control system can be constructed compactly and economically. Also, by detecting or predicting the terminal voltage of the motor and calculating the d-axis current command signal based on the terminal voltage command, the actual terminal voltage follows the terminal voltage command value with high accuracy. Does not exceed a predetermined value, the margin of the output voltage range of the inverter can be reduced, and the output capacity of the inverter can be reduced. Further, the control method according to the present invention is effective when applied to a drive system having a constant torque load characteristic such as an elevator. In particular, the control method according to the present invention is more effective when applied to a drive system requiring overload.

[Brief description of the drawings]

FIG. 1 is a diagram showing a control method of a permanent magnet type synchronous motor according to an embodiment of the present invention.

FIG. 2 is a vector diagram for explaining the control principle of FIG. 1;

FIG. 3 is a configuration example of a q-axis current command device and a d-axis current command device of FIG. 1;

FIG. 4 is a specific configuration example of the current control device of FIG. 1;

FIG. 5 is a diagram showing a characteristic example according to the present invention.

6 is another configuration example of the q-axis current command device and the d-axis current command device of FIG.

FIG. 7 shows another embodiment of the present invention.

FIG. 8 is an application example of the present invention.

[Explanation of symbols]

51: Synchronous motor, 52: Position detector, 52: Speed detector, 63, 631: q-axis current command device, 64, 641,
642 ... d-axis current command device, 6421 ... pattern device that outputs a signal according to torque command, 6422 ... pattern device that outputs a signal according to rotation speed, 6423 ... multiplication device, 6
5 ... Current control device, 66 ... Inverter, 67 ... Terminal voltage command device, 68 ... Voltage detector

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Noboru Arahori 1070 Ma, Hitachinaka City, Ibaraki Prefecture Inside the Mito Plant of Hitachi, Ltd. Inside the Mito Plant (72) Inventor Akihiro Ekeda 1-6-6 Kandanishikicho, Chiyoda-ku, Tokyo Inside Hitachi Building Systems Co., Ltd.

Claims (6)

[Claims] 1. A method of controlling a permanent magnet type synchronous motor driven by a variable voltage, variable frequency power converter, wherein a terminal voltage near a rated speed of the motor increases from a region where a terminal voltage increases near the rated speed of the motor. A method of controlling a permanent magnet synchronous motor, comprising: controlling a current component in a direction (d-axis current component) according to a torque of the motor to suppress an increase in the terminal voltage. 2. The terminal voltage according to claim 1, wherein the d-axis current component is equal to or less than a predetermined value based on a current component (q-axis current component) perpendicular to a magnetic field of the motor converted from a torque command. A method for controlling a permanent magnet synchronous motor, characterized in that the calculation is performed as follows. 3. The motor according to claim 1, wherein the d-axis current component is zero when the torque command is small, and when the torque command exceeds a certain value, the absolute value of the output gradually increases. Is small when the value is small, and when a certain value is exceeded, the absolute value of the output gradually increases, and a calculation is performed so that the terminal voltage becomes equal to or less than a predetermined value. Motor control method. 4. A method for controlling a permanent magnet synchronous motor driven by a variable voltage, variable frequency power converter, wherein the terminal voltage rises from a region where the terminal voltage increases near a rated speed of the motor. A method for controlling a permanent magnet synchronous motor, wherein the magnitude and phase of the armature current of the motor are controlled in accordance with the torque of the motor so as to suppress the current. 5. A method for controlling a permanent magnet synchronous motor driven by a variable voltage, variable frequency power converter, comprising: a terminal voltage set in accordance with a torque command; A current component (d-axis current component) in the same direction as the magnetic field of the motor is obtained based on the terminal voltage of the motor predicted and calculated from the operation of the power converter. A method for controlling a permanent magnet synchronous motor, wherein the d-axis current component is controlled according to the torque of the motor to suppress an increase in the terminal voltage. 6. The control method for a permanent magnet synchronous motor according to claim 5, wherein the method is applied to a drive system having a constant torque load characteristic. Method.