JP2001204200A - Control method of permanent magnet type electric rotating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method which can form an id command and an iq command from a torque command, a voltage limiting value and a command for the number of revolution, without control delay, in a control unit of a permanent magnet type electric rotating machine. SOLUTION: A tape is previously formed from the torque command and the voltage limiting value, and the id command and the iq command are calculated without repeating calculation.

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 rotating electric machine having a permanent magnet, and more particularly to a method for producing a direct-axis component current Id and a horizontal-axis component current Iq.

[0002]

2. Description of the Related Art A rotary electric machine (hereinafter referred to as "P") having a permanent magnet in a rotor, which is vector-controlled by using a PWM inverter.
M motor), the voltage equation represented on the dq axes is as shown in equation (1). Here, Vd and Vq are the direct-axis voltage and the horizontal-axis voltage, Ra is the resistance of the armature winding, Ld and Lq are the direct-axis inductance, the horizontal-axis inductance, id and iq are the direct-axis current, the horizontal-axis current, and Ψ.
a is the armature interlinkage magnetic flux, and ω is the angular frequency (= 2 × π × f). Further, the torque T (Nm) is expressed by equation (2). Here, Pn is the number of pole pairs.

In a vector control inverter, a torque command T
A direct-axis current command id * and a horizontal-axis current command iq * are created from *, and a gate signal for obtaining a required voltage from these commands is created. Vd, Vq, id, and iq shown in equations (1) and (2) are inside the vector controller and on theoretical equations, and the line voltage and armature current that can be actually measured are (3) and (4) ) Expression. When the torque command is given, the horizontal axis current iq can be obtained from equation (2) by setting the direct axis current id to zero. At this time, the direct-axis voltage Vd and the horizontal-axis voltage Vq are obtained from Expression (1), the line voltage V is obtained from Expression (3), and the armature current I is obtained from Expression (4).

FIG. 3 shows a 200 V, 1800 r / min P
This graph shows a change in line voltage when the M motor is operated at a constant 100% of the rated torque and the number of revolutions is increased from 0 to the rated number of revolutions. The direct axis current id is 0 of the rated current.
%, -50%, and -100%, and V in FIG.
(0%), V (−50%), and V (−100%). In FIG. 3, it can be seen that at id = 0%, the line voltage becomes 200 V of the rated voltage at about 57.5% (1035 r / min) of the rated speed. Although the sign of the current is a minus (-) sign in order to reduce the line voltage, it is shown that the line voltage increases linearly with an increase in the torque. In a constant torque operation region in which a DC motor or an induction motor can be operated at a constant torque irrespective of the rotation speed, the voltage / frequency (V / F) is almost a straight line passing through the origin and passing the point of the rated rotation speed at the rated voltage. At zero frequency, the voltage does not become zero due to the effect of the armature winding, so it is realistic to pass from the origin to the positive side of the voltage,
Generally, the rated voltage is obtained at the rated rotation speed.
On the other hand, in the PM motor shown in FIG. 3, when id = 0 control is performed, the rated voltage becomes a point shortly before the rated rotational speed, which is different from the conventional DC motor and induction motor.
That is, in order to obtain the same characteristics as those described above, it is necessary to devise a method of preventing the voltage from increasing by flowing id.

In the vector control, a current command is generated from a torque command, and a voltage is determined as a final result.
d and iq cannot be determined. Therefore, id = 0
From the torque command, iq is calculated from equation (2),
Vd and Vq are obtained from the equation (1), the line voltage is obtained from the equation (3), and compared with the limit value.
Increase id to the negative side and calculate again. This is repeated to calculate a predetermined line voltage.

For this reason, it is not possible to obtain iq which becomes a predetermined line voltage V for an arbitrary id by one calculation, and to calculate the convergence by repeating the calculation several times. Will have a time delay.
Therefore, if a limit is imposed on the numerical value under control, iterative calculation for the determination is necessary, which always leads to control delay. Since vector control aims at quick control performance, such a control delay is a fatal disadvantage. In order to avoid this, the motor line voltage is generally designed to be considerably lower than the power supply voltage, and id = 0 so that the motor line voltage does not reach the power supply voltage even if the torque is increased. For this reason, only one calculation of iq is required, and control without control delay is possible.

FIG. 3 shows an example in which the motor line voltage is 200 V.
From the graph of (0%), if the power supply voltage is 400 V, iq
It can be understood that 100% of the torque can be output up to the rated rotation speed only with the above. As described above, if torque control is possible only with iq, iq is immediately calculated from the torque command from equation (2), and control delay can be minimized. However, when such a design is performed in which the motor line voltage is greatly reduced with respect to the power supply voltage, the motor rated current increases, and an output section of the inverter requires an element having a large current capacity. FIG. 4 shows the power factor in the case of FIG. The calculation conditions are the same as in FIG. 3, and Pf (0%) is i
d is 0%, Pf (−50%) is −50%, Pf (−10
0%) is the case where it is -100%. In FIG.
Since the power factor Pf (0%) at id = 0 is the worst, and the efficiency is also worse, it can be said that a large increase in current is caused. Therefore, if there is a margin in the capacity of the semiconductor element in the output section with a small motor, it is better not to delay the control even if the power factor and efficiency are poor, but if the capacity exceeds several kW, the increase in current will increase the inverter price. Leads to undesirable.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points. In vector control of a permanent magnet rotating electric machine, the id command and the iq are used without any control delay. It is an object of the present invention to provide a control method that issues a command and enables good operation in both efficiency and power factor.

[0009]

The direct current component Id and the horizontal current component Iq corresponding to the torque command are given by:
A control system is created by referring to a table indicated by parameters of a line voltage or a phase voltage and a rotation speed of the rotating electric machine.

FIG. 2 shows a conventional control block. In the current command creation unit, id = 0 from the torque command T *.
And iq * is obtained from equation (2). Calculated id *
From eq * and speed command ω *, the voltage limit determining unit calculates the line voltage V from equations (1) and (3), determines whether it is within the limit value, and passes the result to the current command creating unit. Until the condition is satisfied, go back and forth between the two and finally id * and i
q * is output as a command. In the current control and voltage control unit, a gate signal necessary for PWM is created from these current commands and voltage information, and finally becomes an output of the inverter.

[0011]

FIG. 1 is a control block diagram showing the present invention. The current command creation unit obtains iq * from equation (2) with id = 0 from the torque command T * in the same manner as in the related art. At the same time, in the idiq table, id and iq that reach the specified voltages are calculated by the voltage limiting equation. The idiq table obtains id and iq from the torque command T *, the speed command ω *, and the line voltage V, and the voltage is calculated in advance by the equation (3).

In the actual case, since the torque command is infinite, not all states can be tabulated. Therefore,
The torque is divided as appropriate, and where there is no numerical value, it is calculated by linear interpolation. Since the voltage limiting equation is determined when the motor is selected, the id table can be created offline when the motor constants are known.

Table 1 shows the torque command T * using the motor constant.
Here is an example of id * for.

Until the torque command T * is 43.2%, id * may be 0% irrespective of the speed command and the torque command is 100%.
%, Id * becomes -117.5%. In the torque command during this time, linear interpolation is performed. At 150%, it is -243.
%, And linear interpolation is also performed during this period. From the id * and T *, iq * is calculated from an expression obtained by modifying the expression (2).

That is, T * ≦ 43.2% id * = 0 43.2% <T * ≦ 100% id * = (− 117.5 / 56.8) × T * + 89.3
7 100% <T * ≦ 150% id * = (− 125.5 / 50) × T * + 133.5

When the line voltage is calculated from these formulas by using the formula (3), the rotational speed slightly exceeds V / F in a range lower than the rated value, but this range is practically acceptable.

As described above, according to the present invention, a table of id * is created in advance from a torque command, a line voltage, and a speed command, and iq * is calculated. It is practically useful because it can provide a control device capable of creating a current command for generating an intermediate voltage.

[Brief description of the drawings]

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

FIG. 2 is a control block diagram showing a conventional embodiment.

FIG. 3 is a graph of line voltage when id is used as a parameter when the rotational speed is changed to the rated rotational speed while the rated torque is constant.

FIG. 4 is a graph of a power factor under the conditions of FIG. 3;

[Explanation of symbols]

 T * Torque command ω * Rotation speed command ωm Actual rotation speed id * Direct axis current command iq * Horizontal axis current command PM motor Permanent magnet motor PG Pulse transmitter

Claims (1)

[Claims] A rotor core has a rare earth or ferrite permanent magnet inside or at an outer periphery thereof, a stator core has a single-phase or three-phase multipole slot, and the slot has a single-phase or three-phase slot. In the control method of controlling the torque and the rotation speed by the feedback of the rotation speed and the armature current by using the semiconductor power converter, the permanent magnet type rotating electric machine in which the armature winding is wound corresponds to the torque command. A control system is constructed in which each of the current command values of the direct-axis component current Id and the horizontal-axis component current Iq is referred to a table indicated by parameters of a line voltage or a phase voltage and a rotation speed of the rotating electric machine. The method for controlling the permanent magnet type rotating electric machine described above.