JP5725507B2 - Control device for permanent magnet type synchronous motor - Google Patents

Description

  The present invention relates to a control device for a permanent magnet synchronous motor, and an M-axis current that enables high-efficiency operation when controlling the current of a permanent magnet synchronous motor with the MT coordinate based on the primary flux linkage vector axis. It is easy to get a command.

FIG. 2 shows a block diagram of a conventional permanent magnet type synchronous motor control device as an example, and the conventional technology will be described below based on this diagram.
The dq-axis current command generator 4 receives the torque command Tref, and outputs the d-axis component idref and the q-axis component iqref of the current command so that the output torque of the permanent magnet type synchronous motor 2 becomes the torque command Tref. Here, the d-axis is an axis parallel to the direction of the permanent magnet of the rotor of the permanent magnet type synchronous motor 2, and the q-axis is an axis orthogonal thereto. In general, iqref and idref are

(Equation 1)
iqref = Tref / (φ + (Ld−Lq) · idref) Equation (1)
idref = A−SQRT (A · A + iqref · iqref) Equation (2)
A = φ / 2 / (Lq−Ld) Equation (3)

Is required. Equation (1) is for obtaining a desired torque, and Equation (2) is for allowing the permanent magnet synchronous motor 2 to operate at maximum efficiency. Here, Ld and Lq are the inductances of the d-axis and q-axis of the permanent magnet type synchronous motor 2, respectively, φ is the permanent magnet magnetic flux, and A is expressed by Expression (3). SQRT () is a square root operator.

  The current command component converter 5 outputs iMref and iTref obtained by coordinate-converting the dq-axis current command into the MT-axis current command. Here, the M axis is an axis parallel to the primary linkage magnetic flux vector of the permanent magnet type synchronous motor 2, and the T axis is an axis orthogonal thereto. The current component converter 6 outputs iM and iT obtained by coordinate-converting the primary winding current of the permanent magnet synchronous motor 2 detected by the current detector 3 into each component of the MT axis. The current control unit 7 outputs vMref and vTref that are voltage commands for each axis such that the current follows the input current command. At this time, if current control of both the M-axis and the T-axis becomes difficult, a voltage command giving priority to T-axis current control is output. The voltage command component converter 8 converts the MT-axis voltage command into varef and vbref, which are ab-axis components that are stationary coordinates, and outputs the result. The power converter 1 outputs the input voltage command varef and vbref voltage of the stationary coordinate axis to the permanent magnet synchronous motor 2. At that time, since the voltage that can be output has an upper limit, the magnitude of the output voltage is limited to the upper limit.

  As described above, since the magnitude of the voltage that can be output by the power converter 1 is finite, it is difficult to control both the M-axis and T-axis currents. Therefore, in the prior art shown in FIG. 2, the current control unit 7 preferentially controls the T-axis current control. That is, in a state where the output voltage of the power converter 1 is limited to the upper limit, the T-axis current can match the command iTref, but the M-axis current does not match the command iMref.

Since these current commands are generated from the torque command Tref via the dq-axis current command generator 4 and the current command component converter 5, the M-axis current does not follow the command, so that the permanent magnet type synchronous motor 2 The output torque will not follow the torque command Tref.
Means for solving this problem is disclosed in Patent Document 3, and FIG. 3 is a block diagram showing it. In FIG. 3, the T-axis current command generator 9 obtains the T-axis current command iTref directly from the torque command Tref. The calculation formula is

(Equation 2)
iTref = Tref / φ1 Formula (4)
φ1 = SQRT (φd · φd + φq · φq) (5)
φd = Ld · id + φ (6)
φq = Lq · iq Equation (7)

It is. As a result, even if M-axis current control cannot be performed, the output torque of the permanent magnet type synchronous motor 2 can be made to follow the torque command.

JP 2003-209997 A JP 2008-0667453 A JP 2008-104264 A JP 2008-131766 A

  In the prior art shown in FIG. 3, the M-axis current command is obtained by the dq-axis current command generator 4 and the current command generator 5, and the T-axis current command is obtained by the T-axis current command generator 9. The operation for is complicated.

  The present invention has been made to solve the above-described problems, and includes a primary linkage magnetic flux vector that is a magnetic flux vector that links a current flowing through a primary winding of a permanent magnet synchronous motor to the primary winding. In a control apparatus for a permanent magnet synchronous motor that performs control by dividing into a T-axis component of an axis orthogonal to an M-axis component of a parallel axis, the command value of the M-axis component current is a square of a torque command of the permanent magnet synchronous motor. It is characterized by being proportional to

  FIG. 4 shows the M-axis current in the maximum efficiency state with respect to the output torque. At the same time, the square curve of the output torque is also shown, and it can be seen that the two are very consistent. Therefore, the M-axis current command is proportional to the square of the torque command, so that the operation can be performed in a state close to the maximum efficiency state.

It is a control block diagram of the permanent magnet synchronous motor of this invention. (Example 1) It is a control block diagram of the permanent magnet synchronous motor of Conventional Example 1. It is a control block diagram of the permanent magnet synchronous motor of the prior art example 2. It is the graph which showed the M-axis current characteristic of the maximum efficiency state, and the square characteristic of the torque command.

FIG. 1 is a control block diagram of a permanent magnet synchronous motor that represents an embodiment of the present invention. Here, only the M-axis current command generator 10 will be described.
The M-axis current command generator 10 inputs the torque command Tref,

(Equation 3)
iMref = B · Tref · Tref (8)

To obtain and output the M-axis current command iMref. Here, B is a proportional gain for approximating the M-axis current in the maximum efficiency state, and the permanent curve type synchronous motor 2 is set so that the approximate curve and the M-axis current in the maximum efficiency state coincide with each other at a predetermined output torque point. It can be determined before operation using electrical constants. For example, if iMref is iMr when the rated torque Tr of the permanent magnet type synchronous motor 2 is Tref in FIG. 2, iMr becomes the M-axis current in the maximum efficiency state at the rated torque output point. Therefore, B = iMr / (Tr · Tr).
The present invention is also applicable to a control device for a permanent magnet type synchronous generator.

  Since it is possible to obtain an M-axis current command that can be brought to a state close to the maximum efficiency with a simple calculation, it can be realized with an inexpensive CPU, leading to a reduction in the cost of the apparatus.

DESCRIPTION OF SYMBOLS 1 Power converter 2 Permanent magnet type synchronous motor 3 Current detector 4 dq axis current command generator 5 Current command component converter 6 Current component converter 7 Current control part 8 Voltage command component converter 9 T-axis current command generator 10 M-axis current command generator

Claims (1)

The current flowing in the primary winding of the permanent magnet type synchronous motor is divided into the T-axis component of the axis orthogonal to the M-axis component of the axis parallel to the primary linkage magnetic flux vector that is the magnetic flux vector linked to the primary winding. In the control device for the permanent magnet type synchronous motor,
A control apparatus for a permanent magnet type synchronous motor, wherein the command value of the M-axis component current is proportional to the square of the torque command of the permanent magnet synchronous motor.

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