Control system for permanent magnet synchronous motor

• US 5,854,547 A
• Filed: 09/10/1996
• Issued: 12/29/1998
• Est. Priority Date: 09/11/1995
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Nakazawa, Yosuke
• Primary Examiner(s): Martin, David S.
• Application Number:
  US08/709,843
• Time in Patent Office: 840 Days
• Field of Search: 318/720-724, 318/432, 318/434, 318/798-811
• US Class Current: 318/716
• CPC Class Codes: H02P 21/00 Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
• CPC Class Codes: H02P 6/08 Arrangements for controlling the speed or torque of a single motor H02P6/10, H02P6/28 take precedence
• CPC Class Codes: H02P 6/34 Modelling or simulation for control purposes

Abstract

To provide a control system for a permanent magnet synchronous motor which can ensure stability of the current control system, even if the revolution frequency of the motor becomes higher and the terminal voltage of the motor exceeds the inverter maximum output voltage. In this method, when the revolution frequency of the motor exceeds a specified value, the size of the voltage vector is made a specified voltage vector, and a modulation factor based on its value is obtained. At the same time, a magnetic flux direction current correction value is found based on the size of a voltage vector from a polarity coordinates conversion unit and the above specified voltage vector size. Then, the magnetic flux direction current instruction is corrected by that value.

Claims

1. A control system which controls a permanent magnet synchronous motor via a power conversion system, comprising:

a current instruction value operation unit having inputs including a torque instruction, an angular frequency of the motor and a magnetic flux direction current correction value, and having outputs including a magnetic flux direction current instruction and a torque direction current instruction;

a voltage instruction operation unit having inputs including the magnetic flux direction current instruction and the torque direction current instruction outputted by said current instruction value operation unit, and having outputs including a magnetic flux direction voltage instruction and a torque direction voltage instruction;

a polar coordinates conversion unit having inputs including the magnetic flux direction voltage instruction and the torque direction voltage instruction outputted by said voltage instruction operation unit, and having outputs including a voltage vector size and a voltage vector angle to a magnetic flux axis direction;

a voltage fixing unit having inputs including the voltage vector size outputted by said polar coordinates conversion unit, a voltage vector size instruction value and a voltage fixing instruction, and having an output including a fresh voltage vector size of one of the voltage vector size outputted by said polar coordinates conversion unit and the voltage vector size instruction value, said fresh voltage vector size is selected based on the voltage fixing instruction;

a magnetic flux direction current correction value operation unit having inputs including the voltage vector size outputted by said polar coordinates conversion unit and the fresh voltage vector size outputted by said voltage fixing unit, and having an output including said magnetic flux direction current correction value;

a modulation factor operation unit having inputs including the fresh voltage vector size outputted by said voltage fixing unit and a DC link voltage of said power conversion system, and having an output including a modulation factor of said power conversion system;

a torque current control unit having inputs including the torque direction current instruction outputted by said current instruction value operation unit and a torque current actual value, and having an output including a torque angle correction value; and

a PWM voltage generating unit having inputs including the modulation factor outputted by said modulation factor operation unit and a sum of the voltage vector angle outputted by said polar coordinates conversion unit, the torque angle correction value outputted by said torque current control unit and a permanent magnet magnetic flux angle, and having outputs including PWM voltage instructions for said power conversion system.

2. A control system which controls a permanent magnet synchronous motor via a power conversion system, comprising:

a current instruction value operation unit having inputs including a torque instruction, an angular frequency of the motor and a magnetic flux direction current correction value, and having outputs including a magnetic flux direction current instruction and a torque direction current instruction;

a voltage instruction operation unit having inputs including the magnetic flux direction current instruction and the torque direction current instruction outputted by said current instruction value operation unit, and having outputs including a magnetic flux direction voltage instruction and a torque direction voltage instruction;

a weighting factor operation unit having an input including the angular frequency of the motor, and having outputs including a first weighting factor and a second weighting factor;

a d axis current control unit having an input equal to a value of the first weighting factor outputted by said weighting factor operation unit multiplied by a difference between the magnetic flux direction current instruction outputted by said current instruction value operation unit and a magnetic flux current actual value, and having an output including a magnetic flux direction voltage correction value;

a q axis current control unit having an input equal to a value of the first weighting factor outputted by said weighting factor operation unit multiplied by a difference between the torque direction current instruction outputted by said current instruction value operation unit and a torque current actual value, and having an output including a torque direction voltage correction value;

a polar coordinates conversion unit having inputs including a sum of the magnetic flux direction voltage instruction outputted by said voltage instruction operation unit and the magnetic flux direction voltage correction value outputted by said d axis current control unit, and a sum of the torque direction voltage instruction outputted by said voltage instruction operation unit and the torque direction voltage correction value outputted by said q axis current control unit, and having outputs including a voltage vector size and a voltage vector angle to magnetic flux axis direction;

a voltage fixing unit having inputs including the voltage vector size outputted by said polar coordinates conversion unit, a voltage vector size instruction value and a voltage fixing instruction, and having an output including a voltage vector size of one of the voltage vector size outputted by said polar coordinates conversion unit and the voltage vector size instruction value, said fresh voltage vector size is selected based on the voltage fixing instruction;

a magnetic flux direction current correction value operation unit having inputs including the voltage vector size outputted by said polar coordinates conversion unit and the fresh voltage vector size outputted by said voltage fixing unit, and having an output including said magnetic flux direction current correction value;

a modulation factor operation unit having inputs including the fresh voltage vector size outputted by said voltage fixing unit and a DC link voltage of said power conversion system, and having an output including a modulation factor of said power conversion system;

a torque current control unit having an input equal to a value of the second weighting factor outputted by said weighting factor operation unit multiplied by the difference between the torque direction current instruction outputted by said current instruction value operation unit and the torque current actual value, and having an output including a torque angle correction value; and

a PWM voltage generating unit having inputs including the modulation factor outputted by said modulation factor operation unit and a sum of the voltage vector angle outputted by said polar coordinates conversion unit the torque angle correction value outputted by said torque current control unit and a permanent magnet magnetic flux angle, and having outputs including PWM voltage instructions for said power conversion system.

3. A control system which controls a permanent magnet synchronous motor via a power conversion system, comprising:

a current instruction value operation unit having inputs including a voltage vector size instruction, a torque instruction, an angular frequency of the motor and a voltage fixing instruction, and having outputs including a magnetic flux direction current instruction and a torque direction current instruction;

a voltage instruction operation unit having inputs including the magnetic flux direction current instruction and the torque direction current instruction outputted by said current instruction value operation unit, and having outputs including a magnetic flux direction voltage instruction and a torque direction voltage instruction;

a polar coordinates conversion unit having inputs including the magnetic flux direction voltage instruction and the torque direction voltage instruction outputted by said voltage instruction operation unit, and having outputs including a voltage vector size and a voltage vector angle to a magnetic flux axis direction;

a modulation factor operation unit having inputs including the voltage vector size outputted by said polar coordinates conversion unit and a DC link voltage of said power conversion system, and having an output including a modulation factor of said power conversion system;

a torque current control unit having inputs including the torque direction current instruction outputted by said current instruction value operation unit and a torque current actual value, and having an output including a torque angle correction value; and

a PWM voltage generating unit having inputs including the modulation factor outputted by said modulation factor operation unit and a sum of the voltage vector angle outputted by said polar coordinates conversion units, the torque angle correction value outputted by said torque current control unit and a permanent magnet magnetic flux angle, and having outputs including PWM voltage instructions for said power conversion system.

4. A control system which controls a permanent magnet synchronous motor via a power conversion system, comprising:

a current instruction value operation unit having inputs including a torque instruction, an angular frequency of the motor and a magnetic flux direction current correction value, and having outs including a magnetic flux direction current instruction and a torque direction current instruction;

a voltage instruction operation unit having inputs including the magnetic flux direction current instruction and the torque direction current instruction outputted by said current instruction value operation unit, and having outputs including a magnetic flux direction voltage instruction and a torque direction voltage instruction;

a polar coordinates conversion unit having inputs including the magnetic flux direction voltage instruction and the torque direction voltage instruction outputted by said voltage instruction operation unit, and having outputs including a voltage vector size and a voltage vector angle to a magnetic flux axis direction;

a voltage vector size instruction value operation unit having inputs including the angular frequency of the motor, the magnetic flux direction current instruction outputted by said current instruction value operation unit and a DC link voltage of said power conversion system, and having an out including a voltage vector size instruction;

a voltage fixing unit having inputs including the voltage vector size outputted by said polar coordinates conversion unit, the voltage vector size instruction outputted by said voltage vector size instruction value operation unit and a voltage fixing instruction, and having an output including a fresh voltage vector size of one of the voltage vector size ouputted by said polar coordinates conversion unit and the voltage vector size instruction outputted by said voltage vector size instruction value operation unit, said fresh voltage vector size is selected based on the voltage fixing instruction;

a magnetic flux direction current correction value operation unit having inputs including the voltage vector size outputted by said polar coordinates conversion unit and the fresh voltage vector size outputted by said voltage fixing unit, and having an output including said magnetic flux direction current correction value;

a modulation factor operation unit having inputs including the fresh voltage vector size outputted by said voltage fixing unit and the DC link voltage of said power conversion system, and having an output including a modulation factor of said power conversion system;

a torque current control unit having inputs including the torque direction current instruction outputted by said current instruction value operation unit and a torque current actual value, and having an output including a torque angle correction value; and

a PWM volt age generating unit having inputs including the modulation factor outputted by said modulation factor operation unit and a sum of the voltage vector angle outputted by said polar coordinates conversion unit, the torque angle correction value outputted by said torque current control unit and a permanent magnet magnetic flux angle, and having outputs including PWM voltage instructions for said power conversion system.

5. A control system which controls a permanent magnet synchronous motor via a power conversion system, comprising:

a permanent magnet magnetic flux estimation unit having inputs including an angular frequency of the motor, a magnetic flux direction current instruction and a torque direction voltage instruction, and having an output including a permanent magnet magnetic flux estimated value;

a current instruction value operation unit having inputs including a torque instruction, said angular frequency of the motor and a magnetic flux direction current correction value and the permanent magnet magnetic flux estimated value outputted by said permanent magnet magnetic flux estimation unit, and having outputs including the magnetic flux direction current instruction and a torque direction current instruction;

a voltage instruction operation unit having inputs including the magnetic flux direction current instruction and the torque direction current instruction outputted by said current instruction value operation unit, and having outputs including a magnetic flux direction voltage instruction and the torque direction voltage instruction;

a polar coordinates conversion unit having inputs including the magnetic flux direction voltage instruction and the torque direction voltage instruction outputted by said voltage instruction operation unit, and having outputs including a voltage vector size and a voltage vector angle to a magnetic flux axis direction;

a voltage fixing unit having inputs including the voltage vector size outputted by said polar coordinates conversion unit, a voltage vector size instruction value and a voltage fixing instruction, and having an output including a fresh voltage vector size of one of the voltage vector size outputted by said polar coordinates conversion unit and the voltage vector size instruction value, said fresh voltage size is selected based on the voltage fixing instruction;

a magnetic flux direction current correction value operation unit having inputs including the voltage vector size outputted by said polar coordinates conversion unit and the fresh voltage vector size outputted by said voltage fixing unit, and having an output including a said magnetic flux direction current correction value;

a modulation factor operation unit having inputs including the fresh voltage vector size outputted by said voltage fixing unit and a DC link voltage of said power conversion system, and having an output including a modulation factor of said power conversion system;

a torque current control unit having inputs including the torque direction current instruction outputted by said current instruction value operation unit and a torque current actual value, and having an output including a torque angle correction value; and

a PWM voltage generating unit having inputs including the modulation factor outputted by said modulation factor operation unit and a sum of the voltage vector angle outputted by said polar coordinates conversion unit and a sum of the torque angle correction value outputted by said torque current control unit and a permanent magnet magnetic flux angle, and having outputs including PWM voltage instructions for said power conversion system.

6. The control system according to claim 5, wherein the permanent magnet magnetic flux estimation unit comprises inputs including the DC link voltage of the power conversion system, a DC input current of the power conversion system, the angular frequency of the motor and the torque instruction, and having an output including the permanent magnet magnetic flux estimated value.

7. A control system which controls a permanent magnet synchronous motor via a neutral point clamp type power conversion system, comprising:

a current control unit having inputs including a magnetic flux direction current instruction, a magnetic flux direction current actual value, a torque direction current instruction and a torque direction current actual value, and having outputs including a magnetic flux direction PI control voltage instruction and a torque direction PI control voltage instruction by proportional-plus-integral control;

a counter electromotive force estimation operation unit having an input including an angular frequency of the motor, and having an output including a counter electromotive force estimated value;

a voltage synthesizer unit having inputs including the magnetic flux direction PI control voltage instruction and the torque direction PI control voltage instruction outputted by said current control unit, the counter electromotive force estimated value outputted by said counter electromotive force estimation operation unit and a gate start signal which indicates whether the permanent magnet synchronous motor is power running or coasting, and having outputs including a magnetic flux direction voltage instruction and a torque direction voltage instruction;

a voltage coordinates conversion unit having inputs including the magnetic flux direction voltage instruction and the torque direction voltage instruction outputted by said voltage synthesizer unit and a motor magnetic flux angle, and having outputs including 3-phase voltage instructions;

a triangular wave generating unit having outputs including a positive triangular wave and a negative triangular wave;

a triangular wave phase shift unit having inputs including the gate start signal and the positive triangular wave and the negative triangular wave outputted by said triangular wave generating unit, and having outputs including one of a phase of the positive triangular wave and a phase of the negative triangular wave, by shifting said one of the phase of the positive triangular wave and the phase of the negative triangular wave by a half cycle, that is 180 degrees, based on a timing of a rising of the gate start signal; and

a PWM voltage operation unit having inputs including the 3-phase voltage instructions outputted by said voltage coordinates conversion unit and the one of the phase of the positive triangular wave and the phase of the negative triangular wave outputted by said triangular wave phase shift unit, and having outputs including 3-phase PWM voltage instructions by PWM control.

8. The control system according to claim 7, further comprising:

a counter electromotive force excess detection unit having inputs including a DC link voltage of the power conversion system and the counter electromotive force estimated value outputted by the counter electromotive force estimation operation unit, and which suspends the output of the gate start signal when the counter electromotive force estimated value exceeds the DC link voltage.