CN1794560A - Controlling device of permanent-magnet synchro motor - Google Patents

Abstract

The invention provides a control device of a permanent magnet motor capable of realizing smooth start in a short time without using an absolute position detector. It has: a detection mode setting unit (18), which outputs a magnetic pole detection command for detecting the magnetic pole position of the permanent magnet synchronous motor; a magnetic pole detection current command unit (19), which outputs a plurality of different values as the magnetic pole detection command according to the magnetic pole detection command. The electrical phase angle and current command for initial magnetic pole phase detection; the signal switching part (21a-21c), when the magnetic pole detection command is input, the electrical phase angle for the initial magnetic pole phase detection output from the magnetic pole detection current command unit and The current command is output to the control section; the magnetic pole phase determination unit (20), according to the magnetic pole detection command, extracts the high-frequency component of the current from the feedback current and detects the oscillation phenomenon, and the feedback current and the magnetic pole detection current command unit (19 ) corresponding to multiple different values of the output, and determine the maximum electric phase angle of the oscillation as the initial magnetic pole phase.

Description

Control device for permanent magnet synchronous motor

technical field

The present invention relates to a control device for a permanent magnet synchronous motor that detects the magnetic pole position of the synchronous motor.

Background technique

Patent Document 1: Japanese Unexamined Patent Publication No. 2003-143894 (page 1, FIG. 1 )

An elevator traction machine using a permanent magnet synchronous motor generally has a sensor for detecting the rotor magnetic pole position of the motor, and this function is often embedded in a speed detector directly connected to the rotating shaft of the motor. The detection accuracy of the rotor pole position determines the control performance of the motor torque. If the electrical angle deviates by 60 degrees, the torque will be halved, and if it deviates by 90 degrees or more, the torque in the opposite direction will be generated.

Therefore, not only the detection accuracy of the sensor itself is important, but also the positioning accuracy of the sensor reference position and the rotor magnetic pole position in the installation process of the traction machine is also important. In order to improve the positioning accuracy, a method of correcting the magnetic pole position while the elevator is running is adopted during the installation and adjustment process of the elevator.

On the other hand, there is a magnetic pole position estimation method for a synchronous motor that can accurately estimate the magnetic pole position at the start of the synchronous motor using a magnetic pole position estimation means (for example, refer to Patent Document 1). This method estimates the magnetic pole position of the synchronous motor at the time of starting by performing convergence calculation of the magnetic pole position estimated value, without requiring a magnetic pole position detector.

However, there are following problems in the prior art. In applications requiring low speed and high torque such as elevators, multi-pole designs with dozens of magnetic poles are mostly used. In this case, even small mechanical angle offsets can be large offsets when converted to electrical angles. Therefore, in order for the electrical phase angle to accurately represent the excitation phase of the rotor, it is necessary to ensure sufficient mounting accuracy of the absolute position detector.

For example, in the case of a 40-pole motor, a mechanical angle shift of 5 degrees corresponds to an electrical angle shift of 100 degrees. Therefore, problems such as torque in the direction opposite to the command or insufficient torque tend to occur. In this case, since the elevator cannot be operated normally, there is a problem that it is not suitable to apply the conventional method of performing excitation correction while running.

However, it is unrealistic to install an absolute position detector to ensure an electrical angle accuracy of several orders of magnitude in consideration of manufacturing costs. Therefore, in the case of using an absolute position detector in a multi-pole permanent magnet synchronous motor, correction of the electric phase angle is a big problem. Also, there is the problem that absolute position detectors are prohibitively expensive compared to enhanced encoders typically used in induction motors.

In addition, in the magnetic pole position estimation method of Patent Document 1, since the axis discrimination and pole discrimination must be performed when setting the initial value, and the convergence calculation is also performed, it may take time to estimate the magnetic pole position, and it may take time before the actual start. Spend time.

Contents of the invention

The present invention is proposed in order to solve the above problems, and its purpose is to provide a control device for a permanent magnet synchronous motor that uses a position detector such as an enhanced encoder instead of an absolute position detector to achieve smooth start in a short time.

The control device of the permanent magnet synchronous motor of the present invention has: a position detector, which detects the magnetic pole position of the permanent magnet synchronous motor; a phase calculation unit, which calculates the electric phase angle according to the detected magnetic pole position; and a power converter, which converts the voltage according to the voltage command Variable and variable frequency alternating current is supplied to the permanent magnet synchronous motor; the current detector detects the current of each phase output from the power converter; Voltage command, and output it to the power conversion part, in the control device of the permanent magnet synchronous motor for speed control of the permanent magnet synchronous motor, it also has: a detection mode setting unit, which outputs the magnetic pole for detecting the permanent magnet synchronous motor The magnetic pole detection command of the position; the current command unit for magnetic pole detection, according to the magnetic pole detection command from the detection mode setting unit, outputs a plurality of different values as the electrical phase angle and current command for the initial magnetic pole phase detection; The signal processing is switched so that during normal operation, the electrical phase angle obtained from the position output of the position detector and the current command generated from the speed command from the outside are output to the control part, and the input from the detection mode setting unit When the magnetic pole detection command is used, the electric phase angle and current command for the initial magnetic pole phase detection output from the magnetic pole detection current command unit are output to the control part; the magnetic pole phase determination unit is based on the magnetic pole detection command from the detection mode setting unit. The high-frequency component of the current is extracted from the detection value of the feedback current from the current detector, and the oscillation phenomenon is detected, and the electric phase angle with the largest oscillation degree is determined as the initial magnetic pole phase, and the initial magnetic pole phase is set for the phase calculation unit. wherein the detected value of the feedback current corresponds to a plurality of different values output from the current command unit for magnetic pole detection.

According to the present invention, the following permanent magnet synchronous motor control device can be realized: by adding a detection mode setting unit, a magnetic pole detection current command unit, a magnetic pole phase determination unit, and a switch to the current control system, an enhanced encoder can be used. The position detector does not use an absolute position detector, and detects the magnetic pole position in a short time when stopping, enabling quick and smooth starting.

Description of drawings

FIG. 1 is a block diagram of a control device for a permanent magnet synchronous motor according to Embodiment 1 of the present invention.

2 is a block diagram showing a d-axis current control system according to Embodiment 1 of the present invention.

3 is a graph showing the relationship between the armature current and the magnetic flux of the motor according to Embodiment 1 of the present invention.

4 is a Bode diagram showing an open-loop transfer function of the d-axis current control system according to Embodiment 1 of the present invention.

FIG. 5 is a flowchart showing the sequence processing of initial magnetic pole position detection according to Embodiment 1 of the present invention.

6 shows the relationship between the phase currents Iu, Iv, and Iw, the electrical phase angle θph, and the d-axis current Id in the initial magnetic pole position detection operation according to Embodiment 1 of the present invention.

7 is a block diagram showing a d-axis current control system including delay elements and switches according to Embodiment 2 of the present invention.

Symbol Description

2: Position detector; 3: Angular velocity calculation unit; 4: Subtractor; 5: Speed control unit; 6: Phase calculation unit; 7: Current detector; 8: Three-phase two-phase converter; 9: Two-phase three-phase Converter; 10, 11: subtractor; 12: d-axis current control unit; 13: q-axis current control unit; 14: non-interference control unit; 15, 16: adder; 17: power converter; 18: detection mode Setting unit; 19: Current command unit for magnetic pole detection; 20: Magnetic pole phase determination unit; 21a to 21c: Switch (signal switching unit); 23: Delay element; 24: Switch (second signal switching unit); 100: Speed Control system; 101: d-q axis non-interference control system.

Detailed ways

Next, preferred embodiments of a control device for a permanent magnet synchronous motor according to the present invention will be described with reference to the drawings. The control device of the permanent magnet synchronous motor of the present invention is characterized in that it provides a position detector such as an enhanced encoder, which can easily detect the magnetic pole position in a short time during the stop time before starting, and can quickly and Inexpensive controls for smooth starting of permanent magnet synchronous motors.

Embodiment 1

FIG. 1 is a configuration diagram of a control device for a permanent magnet synchronous motor according to Embodiment 1 of the present invention. The control device of this permanent magnet synchronous motor is constituted as a speed control system 100 (equivalent to the d-q axis non-interference control system 101 (corresponding to the part shown by the dashed line in FIG. 1 ) generally used as a current control system (corresponding to the The part shown by the single dotted line) is further added with a detection mode setting unit 18, a magnetic pole detection current command unit 19, a magnetic pole phase determination unit 20, and switches 21a to 21c.

First, the configuration of the speed control system 100 will be described. The d-q axis non-interference control system is conventional, and is used to control the current of the permanent magnet synchronous motor 1, and is a general control method that also includes speed control. The speed control system 100 is composed of a position detector 2, an angular velocity calculation unit 3, a subtractor 4, a speed control unit 5, a phase calculation unit 6, a current detector 7, a three-phase two-phase converter 8, and a two-phase three-phase converter 9 , subtractors 10 and 11, d-axis current control unit 12, q-axis current control unit 13, non-interference control unit 14, adders 15 and 16, and power converter 17.

The position detector 2 detects the position of the rotor as the rotor of the permanent magnet synchronous motor 1 rotates, and corresponds to an encoder or the like. The angular velocity calculation unit 3 calculates the rotational angular velocity ωr of the permanent magnet synchronous motor 1 by a method such as difference based on the position output of the position detector 2 . The subtracter 4 calculates the deviation between the rotational angular velocity command ωrcom and the rotational angular velocity ωr of the permanent magnet synchronous motor 1 .

The speed control unit 5 calculates the torque to be generated by the permanent magnet synchronous motor 1 as a current command based on the deviation calculated by the subtractor 4, and performs speed control so that the rotational angular velocity ωr follows the rotational angular velocity command ωrcom. Furthermore, in the configuration in which the rotational angular velocity ωr and the rotational angular velocity command ωrcom are used as inputs to the speed control means 5 in addition to the deviation in order to improve the control performance, the following holds true.

In the control of a three-phase AC motor, a process of converting three-phase current and voltage into two axes is generally performed. Here, the coordinate system on the stationary two-axis in which the α-axis coincides with the U-phase axis of the three phases is called an α-β coordinate system. In addition, the coordinate system on the two rotation axes in which the d axis coincides with the excitation direction of the rotor is called a d-q axis coordinate system. The d-q axis non-interference control system 101 in FIG. 1 is equivalent to the control system of the d-q axis coordinate system.

The phase calculation unit 6 calculates the electrical angle phase θre of the rotor of the permanent magnet synchronous motor 1 from the position output of the position detector 2 . This electrical angle phase θre represents the rotation angle of the d-q axis coordinate system viewed from the α-β coordinate system. The current detector 7 detects the three-phase alternating current (Iu, Iv, Iw) flowing through the stator winding (coil) of the permanent magnet synchronous motor 1 .

The three-phase two-phase converter 8 converts the three-phase currents (Iu, Iv, Iw) into currents (Id, Iq) in the d-q axis coordinate system. The two-phase three-phase converter 9 converts voltage command values (Vd, Vq) in the d-q axis coordinate system into three-phase voltage command values (Vu, Vv, Vw). The subtractor 10 and the subtractor 11 respectively calculate the deviation of the current command Idcom of the d-axis component of the stator winding current of the permanent magnet synchronous motor 1 and its feedback current value Id, and the current command Iqcom of the q-axis component and its feedback current value Iq deviation.

The d-axis current control unit 12 and the q-axis current control unit 13 obtain the control output (Vd', Vq') based on the deviation calculated by the subtractor 10 and the subtractor 11, and perform current control so that each feedback current value follows the on their respective current commands. The non-interference control unit 14 performs feed-forward compensation so that the respective currents do not interfere with each other, so that the d-axis current and the q-axis current can be independently controlled.

The adder 15 and the adder 16 add the output of the non-interference control unit 14 to the d-axis and q-axis control outputs (Vd', Vq') respectively, and calculate respective voltage commands (Vd, Vq). Furthermore, the power converter 17 outputs a three-phase AC voltage whose voltage is variable and whose frequency is variable according to the three-phase voltage command values (Vu, Vv, Vw).

Next, a series of control operations based on these configurations will be described. Since the control method of the d-q axis non-interference control system 101 is the control performed on the rotating coordinates synchronous with the rotation of the rotor poles of the permanent magnet synchronous motor 1, it is very important to detect the rotor pole position as a reference. The rotor magnetic pole position is represented by the phase angle θre calculated by the phase calculation unit 6 based on the signal from the position detector 2 connected to the rotor of the permanent magnet synchronous motor 1 .

According to the phase angle θre calculated by the phase operation unit 6, the three-phase current (Iu, Iv, Iw) of the permanent magnet synchronous motor 1 detected by the current detector 7 is converted into the d-q axis by the three-phase two-phase converter 8 Two-phase current feedback value (Id, Iq). Then, the d-axis current control unit 12 and the q-axis current control unit 13 perform feedback control based on the respective deviations between the current feedback values (Id, Iq) converted into two phases and the current command values (Idcom, Iqcom) of the respective axes, The output controls the output (Vd', Vq').

At this time, in order to achieve non-disturbance control of the d-axis and q-axis so as not to be affected by the disturbance voltage from other axes, the non-disturbance control unit 14 performs non-disturbance feedforward compensation according to the pre-calculated disturbance voltage. In this way, the d-q axis non-interfering control system 101 is called a non-interfering control method because non-interfering is realized and each axis is independently feedback-controlled.

The voltage command (Vd, Vq) calculated by adding the output of the non-interference control unit 14 to the control output (Vd', Vq') is generated by the two-phase three-phase converter based on the phase angle θre calculated by the phase calculation unit 6 9 Convert to three-phase voltage command values (Vu, Vv, Vw). Then, the power converter 17 outputs a three-phase AC voltage with a variable voltage and a variable frequency based on the three-phase voltage command values (Vu, Vv, Vw), thereby controlling the speed of the permanent magnet synchronous motor 1 .

In the configuration of FIG. 1 , when the permanent magnet synchronous motor 1 has a rotor shape called a non-salient pole type, generally the d-axis current command Idcom is set to zero in many cases. However, when the magnetic field is weakened to reduce the voltage during high-speed rotation, or when reluctance torque is used in the reverse salient pole type permanent magnet synchronous motor 1, the d-axis current command Idcom can be appropriately controlled. value.

Next, the detection mode setting unit 18 , the magnetic pole detection current command unit 19 , the magnetic pole phase determination unit 20 , and the switches 21 a to 21 c newly added to the speed control system 100 will be described. By adding these structures, when the position detector 2 other than the absolute position detector is used, it is possible to easily detect the initial magnetic pole position after the power supply is turned on.

The detection mode setting unit 18 has a storage unit (not shown) that stores a set/reset state of a magnetic pole position detection completion flag indicating whether or not the magnetic pole position has been detected. In FIG. 1 , since the position detector 2 is not an absolute position detector, the correct magnetic pole position is not detected when the power is turned on. Therefore, the detection mode setting unit 18 resets the magnetic pole position detection completion flag stored in the storage section when the power is turned on.

Furthermore, when the permanent magnet synchronous motor 1 is started, the detection mode setting unit 18 fetches the magnetic pole position detection completion flag from the storage unit, and determines whether the magnetic pole detection operation is necessary. Furthermore, when the detection mode setting unit 18 determines that the magnetic pole detection operation is necessary based on the fact that the magnetic pole position detection completion flag has been reset, it outputs a magnetic pole detection command for detecting the magnetic pole position of the permanent magnet synchronous motor 1 .

When receiving a magnetic pole detection command from the detection mode setting unit 18, the magnetic pole detection current command unit 19 outputs an electric phase angle and a current command for detecting an initial magnetic pole phase. The magnetic pole detection current command unit 19 gradually changes the electrical phase angle for a current command of a certain predetermined d-axis current, and outputs the electrical phase angle and the current command for initial magnetic pole phase detection. Furthermore, the current command unit 19 for magnetic pole detection can generate an output signal by gradually changing the electrical phase angle for different current commands, and can generate a plurality of output values with different patterns.

In addition, the current command means 19 for magnetic pole detection can set the current command value as follows, for example. That is, the magnetic pole detection current command unit 19 sets the current command value so that the sum of the armature reaction magnetic flux generated by the d-axis current and the field magnetic flux generated by the permanent magnet becomes the stator core of the permanent magnet synchronous motor 1. By waiting for a part of the magnetic circuit of the motor to reach the value of magnetic saturation, it can be set to a state where the oscillation phenomenon is more likely to occur. Furthermore, the d-axis is always a control concept, and since the magnetic pole position is not detected at this stage, the d-axis phase does not necessarily coincide with the direction of the field magnetic flux of the permanent magnet.

When the magnetic pole phase determination unit 20 receives a magnetic pole detection instruction from the detection mode setting unit 18 , it determines the magnetic pole phase from the feedback current Id of the d-axis. Specifically, the magnetic pole phase determination unit 20 extracts the high-frequency component of the current from the detected value of the feedback current Id, and detects the oscillation phenomenon of the current control system of the d-q axis non-interference control system 101 . Furthermore, the magnetic pole phase determination unit 20 determines that the rotor magnetic pole exists at an electrical phase angle at which the degree of oscillation of the detected oscillation phenomenon is maximum, and determines this electrical phase angle as the initial magnetic pole phase.

Furthermore, the magnetic pole phase determining means 20 sets the determined initial magnetic pole phase as the initial phase in the phase calculating means 6 . The phase calculating means 6 can start the permanent magnet synchronous motor 1 whose magnetic pole position is not clear by using the set initial phase to perform the starting operation.

Furthermore, after the initial magnetic pole phase can be determined, the magnetic pole phase determination unit 20 sets the magnetic pole position detection completion flag and stores it in the storage unit of the detection mode setting unit 18 . In this way, the initial pole phase can be determined at the first start after the power supply is closed. When the power is turned on for the second time or after the second start, the detection mode setting unit 18 can determine that the magnetic pole detection operation is unnecessary based on the fact that the magnetic pole position detection completion flag of the storage unit is set. Thereby, at the time of the second start after the power supply is turned on and after the second time, a smooth start operation can be directly performed without performing the magnetic pole detection operation.

The switches 21 a to 21 c are signal switching units that switch output signals in accordance with a magnetic pole detection command from the detection mode setting unit 18 . When the switches 21a to 21c do not receive a magnetic pole detection instruction from the detection mode setting unit 18 (that is, during normal operation), the electrical phase angle θre calculated by the phase calculation unit 6 and The current command (Idcom, Iqcom) is output to the d-q axis non-interference control system 101 .

On the other hand, when the switches 21a to 21c receive the magnetic pole detection command from the detection mode setting unit 18, they switch the electric phase angle and current command value supplied to the d-q axis non-interference control system 101 to the current command unit for magnetic pole detection. 19 outputs the electric phase angle θph and the current command (Idph, Iqph) for initial magnetic pole phase detection.

Next, the reason why the initial magnetic pole phase can be detected by this configuration will be described. 2 is a block diagram showing a d-axis current control system according to Embodiment 1 of the present invention. The primary delay block 22 is the block representing the transfer function from the voltage applied to the motor armature to the current. The current control block 12 a is a block representing an example of a control operation used in the d-axis current control unit 12 .

The current control block 12a is generally implemented as a proportional-integral (PI) control for suppressing steady-state deviations of the current. The design of the PI compensator is determined by the nominal value of the motor constant and the design response frequency ωc of the control system. That is, when the nominal value of the resistance value Ra of the armature coil is R and the nominal value of the inductance La is L, the control constant is usually designed so that the inflection point frequency ωi of the PI compensator on the Bode diagram Equal to the reciprocal of the nominal value (L/R) of the time constant of the motor armature coil.

In this case, it is already known that the open-loop transfer function of the current control system is expressed only by the integral system ωc/s, the phase is always -90 degrees, and stable control can be performed. Furthermore, although the case of the d-axis is shown in FIG. 2 , the current control system can be similarly designed for the q-axis as well.

On the other hand, there are often situations where the actual motor constant deviates from the nominal value, and the magnetic saturation of the stator core and the like is also one of the important reasons for this situation. 3 is a graph showing the relationship between the armature current and the magnetic flux of the permanent magnet synchronous motor 1 according to Embodiment 1 of the present invention. As shown in FIG. 3 , as the armature current increases, the slope of the curve tends to decrease due to the influence of magnetic saturation of the stator core and the like. Since the inductance L related to the current control of the permanent magnet synchronous motor 1 is equal to the slope Δφ/ΔI of this curve, the value of the inductance La is smaller than the nominal value L due to the influence of magnetic saturation.

4 is a Bode diagram showing an open-loop transfer function of the d-axis current control system according to Embodiment 1 of the present invention. FIG. 4 respectively shows the case where the inductance is equal to the nominal value (equivalent to La=L), and the case where it is smaller than the nominal value due to magnetic saturation (equivalent to La<L).

In the case of La=L, as described above, the gain is represented by a straight line with a slope of -20dB/dec and a gain of 0 at the design response frequency ωc, and the phase is maintained at -90 degrees. On the other hand, in the case of La<L, the open-loop transfer function does not merely integrate, but forms a shape on the Bode diagram showing a forward delay characteristic in which the gain largely rises in the high-frequency region.

In this case, the control is theoretically stable since the phase at zero gain is -90 degrees. However, due to the control delay due to digital control or the influence of sensor characteristics, etc., the phase in the high-frequency region tends to be delayed, so it tends to be unstable in practice. Therefore, when the phase of the armature reaction flux generated by the current is consistent with the phase of the excitation flux generated by the permanent magnet, a large magnetic flux flows through the iron core, and the inductance is smaller than the nominal value due to magnetic saturation, the control When the gain of the system is high enough, the current control system will produce oscillation phenomenon.

Therefore, by extracting the vibration component from the feedback current and detecting the oscillation phenomenon, the phase relationship between the excitation magnetic flux and the armature reaction magnetic flux can be determined, and the initial magnetic pole position can be easily found. Moreover, considering that when the oscillation state continues, the vibration amplitude will gradually increase and even make the system abnormal, but as described later, by changing the phase angle and providing instructions so that excessive current is not generated, it is possible to prevent system abnormalities. Suppresses the amplitude.

Next, continuous operation processing will be described based on the flowchart. FIG. 5 is a flowchart showing the sequence processing of initial magnetic pole position detection according to Embodiment 1 of the present invention. First, in step S501, when the detection mode setting unit 18 receives the starting command of the permanent magnet synchronous motor 1 from the outside, it takes out the magnetic pole position detection completion flag from the storage unit, and the magnetic pole position detection completion flag is set or the magnetic pole position has been reset. The detection completion flag is used to judge whether the magnetic pole detection is completed.

When the magnetic pole position detection completion flag is reset and it is determined that the magnetic pole detection has not been completed, the detection mode setting unit 18 outputs a magnetic pole detection command, and then proceeds to the processing of step S502. In addition, when the magnetic pole position detection completion flag is set and it is determined that the magnetic pole detection has been completed, the detection mode setting unit 18 does not output the magnetic pole detection command, and then proceeds to the processing of step S509 .

In step S502, the magnetic pole detection current command unit 19 receives the magnetic pole detection command from the detection mode setting unit 18, sets the d-axis current command value Idph necessary for the initial magnetic pole detection operation, and sets the q-axis current command value Iqph to Iqph=0.

In step S503, the detection mode setting unit 18 switches the switches 21a to 21c by outputting a magnetic pole detection command. Thus, the switches 21 a to 21 c output the current commands (Idph, Iqph) for magnetic pole detection and the electrical phase angle θph to the d-q axis non-interference control system 101 .

The state of the switches 21a to 21c in FIG. 1 shows a state switched to be connected to an output signal from the magnetic pole detection current command means 19 for magnetic pole detection. That is, according to the magnetic pole detection command from the detection mode setting unit 18, the switch 21a is connected to the d-axis current command value Idph, the switch 21b is connected to the q-axis current command value Iqph, and the switch 21c is connected to the electrical phase angle θph.

Then, in step S504 , the magnetic pole detection current command unit 19 increases the electrical phase angle θph by a predetermined amount. Next at step S505, the magnetic pole phase determination unit 20 extracts the high-frequency component of the current from the detected value of the feedback current at the electric phase angle θph set at step S504.

Then, in step S506, the magnetic pole detection current command unit 19 judges whether the electrical phase angle θph has changed by one or more cycles, and repeats the operations of steps S504 to S506 until it has changed by one or more cycles. Through this repeated process, the magnetic pole phase determining unit 20 extracts data of high-frequency components of the current from the detected values of the respective feedback currents when the electric phase angle θph changes within a range of one cycle.

In step S506, when it is determined that the electrical phase angle θph has changed by one or more cycles, in step S507, the magnetic pole phase determination unit 20 judges that the electric phase angle θph has changed by one cycle or more based on the extracted high-frequency component data. Whether the current control system has produced oscillation phenomenon. And when the magnetic pole phase determination means 20 determines that the oscillation phenomenon does not occur, it transfers to the process of step S512.

On the other hand, when the magnetic pole phase judging means 20 judges that oscillation has occurred, it judges that the rotor magnetic pole exists at the electrical phase angle at which the degree of oscillation is maximum, determines the electrical phase angle, and proceeds to step S508. Then, in step S508, the magnetic pole phase determination unit 20 updates the magnetic pole phase held by the phase calculation unit 6 according to the determined electric phase angle.

6 shows the relationship between the phase currents Iu, Iv, and Iw, the electrical phase angle θph, and the d-axis current Id in the initial magnetic pole detection operation according to Embodiment 1 of the present invention. In this example, a state in which dithering is superimposed on each phase current and the d-axis current is shown in the vicinity of the electrical phase angle θph exceeding 180 degrees. The magnetic pole phase determination unit 20 may determine that the rotor magnetic pole exists at an electrical phase angle corresponding to such an oscillation state, and may determine the electrical phase angle.

Furthermore, in FIG. 1 , the magnetic pole phase determining means 20 is configured to take in the d-axis current Id and detect vibrations superimposed on the d-axis current Id, but the rotor magnetic poles can also be detected from vibrations superimposed on each phase current. In addition, because the oscillation phenomenon is observed slightly later than the actual magnetic pole phase due to the change speed of the electrical phase angle θph, the average value obtained when the electrical phase angle θph is changed in the opposite direction can be detected with higher accuracy.

In the preceding step S507, when it is determined that no oscillation phenomenon has occurred, in step S512, the magnetic pole detection current command unit 19 increases the d-axis current command value Idph so that magnetic saturation of the stator is likely to occur, and then, step S504 is repeated. To the process of step S507, the determination process of the magnetic pole position is performed.

Furthermore, according to the magnetic pole detection of the first embodiment, the magnetic pole position can be detected in a short time at the time of starting, and the permanent magnet synchronous motor 1 can be started smoothly. After starting, in the case of requiring high-precision torque control, as described above, after determining the initial value of the electric phase angle and starting, by performing the magnetic pole correction operation proposed in the past (for example, Japanese Patent Laid-Open No. 10-80188), it can be further improved. Improve the detection accuracy of magnetic poles. Step S509 to step S511 in FIG. 5 are flowcharts for performing this magnetic pole correction operation.

According to Embodiment 1, by adding a detection mode setting unit, a magnetic pole detection current command unit, a magnetic pole phase determination unit, and a switch to the current control system, it is possible to use a position detector such as an enhanced encoder and perform a short-term operation at the time of stop. The detection of the magnetic pole position can start the permanent magnet synchronous motor smoothly in a short time.

Also, if the initial values of the electrical phase angle and the current command for initial magnetic pole phase detection are set to values that easily cause oscillation in the current control system, magnetic pole position detection can be easily performed in a short time.

In addition, although the case where the magnetic pole position detection is performed at the time of starting up for the first time after turning on the power supply was demonstrated above, it is not limited to this. This magnetic pole position detection may be performed at each startup, or may be performed in response to an external magnetic pole detection command.

Embodiment 2

In Embodiment 1, the case where the d-axis current command value Idph is increased has been described as a method for easily generating the hunting phenomenon. In Embodiment 2, another method that is likely to cause a hunting phenomenon will be described.

As shown in the Bode diagram of FIG. 4 , the oscillation phenomenon can also be easily generated by delaying the phase in the high-frequency region. Therefore, in the process of step S512 in FIG. 5 , a delay element (redundant time element) may be inserted into the current control loop instead of increasing the d-axis current command value Idph.

7 is a block diagram showing a d-axis current control system including a delay element 23 and a switch 24 according to Embodiment 2 of the present invention. The delay element 23 outputs the feedback current value Id' having a time delay with respect to the feedback current value Id of the current control system. In addition, the switch 24 is a second signal switching unit that switches an output signal in accordance with a delay element insertion command from the magnetic pole phase determination unit 20 .

During normal operation or when performing the magnetic pole position detection described in the first embodiment, the magnetic pole phase determination means 20 does not generate a delay element insertion command. However, when the d-axis current command value Idph is increased during magnetic pole position detection and it is determined that the oscillation phenomenon does not occur, the magnetic pole phase determination unit 20 may output a delay element insertion command.

When there is no delay element insertion command from the magnetic pole phase determination means 20, the switch 24 outputs the feedback current Id as a feedback current value. On the other hand, switch 24 outputs, as a feedback current value, feedback current Id' having a time delay with respect to feedback current Id due to delay element 23 when receiving a delay element insertion command from magnetic pole phase determining means 20.

According to the second embodiment, by inserting the delay element into the current feedback loop according to the delay element insertion command, the feedback current at the time of magnetic pole position detection can be easily oscillated. As a result, when the feedback current does not oscillate and the magnetic pole position cannot be identified just by increasing the current command value, the oscillating phenomenon can be generated by inserting a delay element, and the magnetic pole position can be easily detected.

Furthermore, since the feedback current can be easily oscillated by inserting a delay element, there is no need to increase the current command value on the contrary. Therefore, the magnetic pole position detection can be performed with the current command value kept low, and the heat generation of the permanent magnet synchronous motor during the magnetic pole position detection can be suppressed.

Claims (5)

1. A control device for a permanent magnet synchronous motor, used for speed control of a permanent magnet synchronous motor, which has: A position detector to detect the magnetic pole position of the permanent magnet synchronous motor; a phase calculation unit, which calculates the electrical phase angle according to the detected magnetic pole position; a power converter, which provides alternating current with variable voltage and variable frequency to the permanent magnet synchronous motor according to a voltage command; a current detector for detecting each phase current output from the power converter; a control unit that calculates a voltage command based on an electrical phase angle, a current command, and a detected current from the current detector, and outputs it to the power conversion unit; It is characterized in that it also has: A detection mode setting unit that outputs a magnetic pole detection instruction for detecting the magnetic pole position of the permanent magnet synchronous motor; a current command unit for magnetic pole detection, outputting a plurality of different values as an electric phase angle and a current command for initial magnetic pole phase detection according to the magnetic pole detection command from the detection mode setting unit; a signal switching unit that switches signal processing so that during normal operation, the electrical phase angle obtained from the position output of the position detector and the current command generated based on the speed command from the outside are output to the control unit, outputting an electrical phase angle and a current command for initial magnetic pole phase detection output from the magnetic pole detection current command unit to the control section when the magnetic pole detection command from the detection mode setting unit is input; The magnetic pole phase determination unit extracts the high-frequency component of the current from the detection value of the feedback current from the current detector according to the magnetic pole detection instruction from the detection mode setting unit and detects the oscillation phenomenon, and the oscillation The maximum electrical phase angle is determined as an initial magnetic pole phase, the initial magnetic pole phase is set in the phase calculation unit, and the feedback current corresponds to a plurality of different values output from the magnetic pole detection current command unit. 2. The control device for a permanent magnet synchronous motor according to claim 1, wherein the current command unit for magnetic pole detection sets the electric phase angle for the initial magnetic pole phase detection within one electric phase angle cycle for multiple values. 3. The control device for a permanent magnet synchronous motor according to claim 1 or 2, characterized in that the current command unit for magnetic pole detection sets the current command value for initial magnetic pole phase detection near a certain value, This certain value is such that the sum of the armature reaction flux and the field flux caused by the permanent magnets magnetically saturates a part of the magnetic circuit of the permanent magnet synchronous motor. 4. The control device for a permanent magnet synchronous motor according to any one of claims 1 to 3, wherein the detection mode setting unit has a storage unit storing a magnetic pole position detection completion flag, and when the power supply is turned on The magnetic pole position detection completion flag is reset and stored in the storage unit, the magnetic pole position detection completion flag is taken out from the storage unit at startup, and when the magnetic pole position detection completion flag has been reset, the A magnetic pole detection instruction for detecting the magnetic pole position of the permanent magnet synchronous motor; After the initial magnetic pole phase can be determined, the magnetic pole phase determination unit sets a magnetic pole position detection completion flag and stores it in the storage section of the detection mode setting unit. 5. The control device for a permanent magnet synchronous motor according to any one of claims 1 to 4, characterized in that the control unit further has: a delay element unit that receives a detection current from the current detector and outputs a time-delayed signal; The second signal switching unit performs switching of signal processing so that during normal operation, the detection current from the current detector is output as a feedback current used in the control unit, and when a delay element insertion command is input, output a signal from the delay element unit as a feedback current used in the control unit; The magnetic pole phase determination unit outputs a delay element insertion command to the second signal switching unit as necessary when determining an initial magnetic pole phase based on the magnetic pole detection command from the detection mode setting unit.

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