JP4721801B2 - Control device for synchronous motor - Google Patents

Description

  The present invention relates to a synchronous motor control device that starts a synchronous motor having a field winding without using a position detector and performs variable speed control.

  In a conventional synchronous motor control device, a position detector is used for variable speed control of the synchronous motor, and the magnetic pole position and speed are detected (for example, see Patent Document 1).

Further, as shown in Patent Document 2, when the synchronous motor is subjected to variable speed control without using a position detector, open loop control is performed without means for estimating position and speed.
JP-A-6-165561 (page 2-3, FIG. 1) JP-A-2-276494 (page 2-3, FIG. 1)

  In the conventional synchronous motor control device disclosed in Patent Document 1, the position of a magnetic pole is detected using a position detector, and variable speed control is performed. However, a power converter is installed in an existing synchronous motor. Even when the variable speed control used is applied or newly installed, it may be difficult to attach the position detector to the synchronous motor depending on the installation environment of the synchronous motor and other specific conditions.

  Further, in the synchronous motor control device disclosed in Patent Document 2, a position detector is not used, a voltage according to a speed reference is applied and a reactive current is controlled to control a reactive motor having a field winding. Although variable speed control is performed, speed estimation due to load fluctuation cannot be detected because speed estimation is not performed, and there is a problem that synchronization is likely to be lost. Furthermore, although the reactive current is controlled, the effective current and the field current are not controlled, and thus there is a problem that it is difficult to stably perform overcurrent protection.

  Therefore, the synchronous motor control device of the present invention is made to solve the above-described problems, and can perform stable closed-loop speed control without using a position detector. An object of the present invention is to provide a control device.

In order to achieve the above object, a control apparatus for a synchronous motor according to the present invention outputs a variable voltage, variable frequency alternating current to drive a synchronous motor, and a current for detecting an output current of the power converter. Based on detection means, voltage detection means for detecting an output voltage of the power converter, a field device for exciting a field winding of the synchronous motor, outputs of the current detection means and the voltage detection means A control unit for controlling the power converter and the field device, and the control unit performs current control using a predetermined current command when starting the synchronous motor, and converts the power conversion by a speed command. An open loop speed control means for changing the output frequency of the generator, a closed loop speed control means for performing speed control using a speed estimated value after the synchronous motor is started, and the open loop speed control. And a switching means for switching from the means to the closed loop speed control means, after switching to a closed loop speed control means by said switching means, said output voltage is adjusted so that the field current becomes a value corresponding to the speed command It is characterized by.

  According to the present invention, an open loop speed control means for performing current control using a predetermined current command at the start and changing a speed by the speed command, and a closed loop speed control means for performing speed control using a speed estimated value after start. Therefore, it is possible to provide a control device for a synchronous motor capable of stably performing closed-loop speed control without using a position detector.

  Embodiments of the present invention will be described below with reference to the drawings.

  A control apparatus for a synchronous motor according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 and 2.

  FIG. 1 is a block diagram showing a first embodiment of the present invention. An inverter 1 that receives a direct current from a direct current power source outputs an alternating current with a variable voltage and a variable frequency, and drives the synchronous motor 2 with the output. The inverter 1 has a configuration in which a power device (not shown) is bridge-connected, and this power device is controlled by an on / off command from the control unit 3. The output voltage and output current of the inverter 1 are detected by the voltage detector 4 and the current detector 5, respectively, and are supplied to the control unit 3. The synchronous motor 2 includes a field winding that is excited by the output of the field device 6. The field device 6 includes a field current detector 61, a field current controller 62, and a power converter 63 that applies a voltage for exciting the field winding. The inverter 1 may be another power converter that directly outputs an AC input, such as a matrix converter.

  Hereinafter, the internal configuration of the control unit 3 will be described.

  The control unit 3 includes an open loop speed control means for starting the synchronous motor 2 in an open loop, a closed loop speed control means for performing speed control using a speed estimated value after the start, and a switching means for smoothly switching them. It is configured.

  First, the configuration of the above open loop speed control means will be described.

The initial magnetic pole position detector 31 receives the voltage detector 4 that detects the terminal voltage of the armature winding as an input, and detects the initial magnetic pole position θ ₀ in a state where the synchronous motor 2 is stopped. This specific detection method is, for example, disclosed in Japanese Patent Application Laid-Open No. 2005-39891, in which the synchronous motor 2 detected by the voltage detector 4 when the excitation voltage is supplied from the field device 6 to the synchronous motor 2 is used. It calculates _| requires by calculation from terminal voltage _VUVW .

The speed command setter 32 sets a speed command ω _r0 ^* and changes the speed command ω _r0 ^* at a predetermined rate by the rate setter 33 to obtain an actual speed command ω _r ^* . Further, the speed command ω _r ^* is integrated by the integrator 34 with the initial magnetic pole position θ ₀ as a reference to obtain a phase angle θ _r ^* .

On the other hand, a current command at start-up is set by the D-axis initial current setting unit 35 and the Q-axis initial current setting unit 36, respectively, and the set current and the current I _UV detected by the current detector 5 are set to the coordinate converter 37. To compare the D-axis current I _D and the Q-axis current I _Q obtained by converting the coordinates into the biaxial coordinate system using the phase angle θ _r ^* as a reference. The compared differences are input to the current controller 38. The output of the current controller 38 becomes a D-axis voltage reference V _D ^* and a Q-axis voltage reference V _Q ^* . Although the current controller 38 is illustrated as one controller, it is actually composed of two controllers independent of the D axis and the Q axis. The D-axis voltage reference V _D ^* and the Q-axis voltage reference V _Q ^* are given to the coordinate converter 39. The coordinate converter 39 converts the phase angle θ _r ^* into a three-phase voltage reference using the phase angle θ _r ^* as a reference phase. PWM modulation is performed via a PWM controller that does not, and is supplied to the inverter 1.

The field current command I _f ^* = I _f0 ^* is set by the initial field current setter 40 when the open loop speed control means is operating. The field device 6 operates so that the set value is obtained.

  Next, the configuration related to the closed loop speed control means for performing speed control using the speed estimated value after starting will be described.

The terminal voltage V _UVW of the synchronous motor 2 detected by the voltage detector 4 is given to the coordinate converter 41. The coordinate converter 41 decomposes this voltage into a D-axis voltage V _D and a Q-axis voltage V _Q using an angle estimated value θ _PLL, which will be described later, as a reference phase, and supplies these to the PLL circuit 42. The PLL circuit 42 is a so-called phase-locked loop circuit, and estimates the speed estimated value ω _PLL and the angle estimated value θ _PLL by, for example, a method of deriving an angle that makes the D-axis voltage V _D zero. When the estimated angle θ _PLL converges within a predetermined range and the PLL circuit 42 is locked, the angular frequency of the estimated speed ω _PLL and the terminal voltage V _UVW becomes equal, and correct frequency detection is performed. Switching from the open loop speed control means to the closed loop speed control means is performed by the lock determination signal of the PLL circuit 42. This switching is performed by switching the four changeover switches SW1 shown in FIG. 1 from the start side shown in the drawing to the closed loop speed control side.

The speed command in the closed-loop speed control means is the speed command ω _r ^* that is the output of the rate setting device 33 as in the open-loop control, and this speed command ω _r ^* is the estimated speed value that is the output of the PLL circuit 42. It is compared with the ω _PLL, and the difference becomes the input of the speed controller 43. The current command I _T ^* which is the control output of the speed controller 43 becomes the Q-axis current reference I _Q ^* instead of the set value set by the Q-axis initial current setter 36 in the open loop control means described above. .

  Next, a configuration for controlling the D-axis current reference and the field current to appropriate values will be described.

As a step after switching to the closed loop speed control means, the switch SW2 is closed and the regulator 44 increases the field current command _If ^* . In this state, since the D-axis voltage V _D and the Q-axis voltage V _Q that are the two-axis outputs of the coordinate converter 41 increase, the detected voltage | V | calculated by the absolute value calculator 45 increases. The detected voltage | V | is compared with the voltage reference | V * | obtained by the V / ω setting unit 46 from the speed reference, and the difference V _err is amplified by the regulator 47 while the SW3 is operated. The output I _m ^* is controlled using the D-axis current reference. In this state, the switch SW4 is turned on, the voltage control loop by the field-side voltage controller 48 is made use of the difference V _err as an input, and further the switch SW5 is operated to obtain the output of the regulator 47. I _m ^{* is set} to zero to achieve power factor 1 operation.

The preset value PD1 of the regulator 47 and the preset value PD2 of the speed controller 43 when the switch SW1 for switching to the closed loop speed control is operated are coordinated with the D-axis initial current setter 35 and the Q-axis initial current setter 36. This is obtained by biaxial conversion by the converter 49 using the phase reference θ _r ^* and the estimated angle value θ _PLL . Similarly, setting of preset values PD3 and PD4 for the D-axis and Q-axis of the current controller 38 is also necessary, but PD3 = 0, and PD4 is a D-axis voltage reference V _D ^* and Q that are respective current control outputs. The magnitude of the voltage is determined by the absolute value circuit 50 from the shaft voltage reference V _Q ^* .

The switching means for smoothly switching between the open loop speed control means and the closed loop speed control means overlaps with the description of the closed loop control means described above. However, the switching switches SW1, SW3 and SW4, the on switch SW2 and the off switch are used. A certain SW5 and D-axis initial current setting device 35 and Q-axis initial current setting device 36 for setting the current commands I _D0 ^* and I _Q0 ^* are coordinate-converted by the angle estimated value θ _PLL and preset data of the current command. A coordinate converter 49 for deriving PD1 and PD2, and a preset D-axis current command I _D ^* in accordance with a deviation between the voltage command | V ^* | and the detected voltage | V | It comprises an adjuster 47 for changing the shaft current command I _D ^* and an absolute value calculator 50 for obtaining voltage command preset data PD3 and PD4 from the voltage commands V _D ^* and V _Q ^* . As described above, when switching from the open loop speed control control to the closed loop speed control means, it depends on the operation of the switch SW1, but then the switches SW2 to SW5 are operated to control the field current to a value suitable for the speed, The synchronous motor 2 is switched to drive at a power factor of 1.

  Next, the operation of the first embodiment of the present invention will be described with reference to FIGS. FIG. 2 is an operation timing chart of the synchronous motor control apparatus according to Embodiment 1 of the present invention.

First, an initial magnetic pole position detection operation is performed at time t = T1 in FIG. For example, the field current command I _f ^* = I _f0 ^* is set to perform the excitation operation, and the terminal voltage V _UVW detected by the voltage detector 4 at this time is calculated by the initial magnetic pole position detector 31 to calculate the initial magnetic pole position θ. ₀ is derived and set in the integrator 34.

Next, at time t = T2, a predetermined current command I _Q ^* = I _Q0 ^* is applied in the direction of the torque axis perpendicular to the Q axis, that is, the magnetic pole. Further, the speed command ω _r ^* is gradually increased by the rate setting unit 33 from time t = T2 to time t = T3. During this time, the voltage detector 4, the coordinate converter 41, and the PLL circuit 42 derive the speed estimated value ω _PLL and the angle estimated value θ _PLL , and calculate the current command preset data PD 1 and PD 2 and the voltage command preset data PD 3 and PD 4. Keep it.

If the PLL circuit 42 is locked and the estimated speed value ω _PLL and the estimated angle value θ _PLL can be derived, the SW1 is switched at time t = T4. When SW1 is switched, the current commands I _D ^* and I _Q ^* and the voltage commands V _D ^* and V _Q ^* are preset, and the speed controller 42 starts control using the estimated speed value ω _PLL , and the coordinate converter 37 and the angle used as the reference phase in the coordinate converter 39 are switched from the integral value θ _r ^{* of the} speed command to the estimated angle value θ _PLL . The speed at the time of switching is set to a predetermined speed at which the speed and angle can be sufficiently estimated from the D-axis voltage V _D and the Q-axis voltage V _Q detected by the PLL circuit 42.

Next, at time t = T5, SW2 is turned on to increase the field current command _If ^* . For example, between time t = T5 of t = T6 depending on the Q-axis current command I _Q increases the field current command I _f ^* at a predetermined rate. Subsequently, SW3 is switched at time t = T7, voltage control is performed using the regulator 47, for example, and the D-axis current command I _D ^* is changed. When the regulator 47 is set to voltage control, the detected voltage | V |, which is the terminal voltage of the armature, is controlled to become the voltage command | V ^* | by the D-axis current command I _D ^* . At time t = T8, SW4 is switched, and the voltage controller 48 controls the detected voltage | V | from the field current command in accordance with the voltage command | V ^* |. At time t = T9, SW5 is turned off, and the D-axis current command I _D ^* is constantly set to zero from time t = T9 to t = T10. Note that T1 to T10 in FIG. 2 are for explaining the order of operations, and the respective time intervals are not necessarily as illustrated.

In the first embodiment, the initial magnetic pole position is detected when the synchronous motor 2 is stopped from time t = T1 to t = T2, and the detected voltage is small from time t = T2 to t = T4. While the angle cannot be estimated, start with open loop speed control, and if the angle and speed can be estimated, use the estimated values ω _PLL and θ _PLL to achieve appropriate field current and power factor 1 control from time t = T4 to t = T10. The point is that the closed loop speed control is performed using the speed estimated value ω _PLL after time t = T10.

If the angle estimation method of the PLL circuit 42 is a method for estimating the angle at which the D-axis voltage V _D is zero, the D-axis current command I _D ^* is constantly set to zero after time t = T10. A power factor of 1 can be realized. Further, since the current command and the voltage command are preset at the same time as the angle is switched, the phase of the voltage waveform applied to the armature winding of the synchronous motor 2 before and after the time t = T4 is maintained and the switching is performed. There is no influence. Further, by adopting a process in which the command value changes smoothly between time t = T5 and t = T6 or at time t = T7, a smooth switching operation can be realized.

The above description shows an example of control. In FIG. 2, switching is performed when the speed command is constant. However, if the speed can be estimated, there is no need to limit the speed command. Further, it performs voltage control by regulator 47 at time t = T7, time t = While constantly current command I _D ^* with t = T10 from T9 an example to zero, the final current command I _D ^It is only necessary to set ^* to zero, and the intermediate process is not limited to FIG. The PLL circuit 42 has been described as performing the method for estimating the angle at which the D-axis voltage is made zero, but it is also possible to replace the DQ axis.

  A control apparatus for a synchronous motor according to Embodiment 2 of the present invention will be described with reference to FIGS. 3 and 4. FIG. 3 is a block diagram of the Q axis current command correction control unit of the second embodiment, and FIG. 4 is an operation timing chart of the second embodiment.

The correction control unit according to the second embodiment is a unit that adjusts the current value to a more suitable current value when it is determined by the open loop speed control unit that the Q-axis current command I _Q ^* is greater than the optimum value after startup. After detecting the initial magnetic pole position at time t = T11, the _engine is started with a predetermined current command I _Q ^* = I _Q0 ^* from t = T12. After the start, the current command vectors α _i and voltage command vectors are obtained from the current commands I _D ^* and I _Q ^* and the voltage commands V _D ^* and V _Q ^* using the angle calculators 51 and 52 as shown in FIG. α _v is obtained, and the angle difference α between these vectors is obtained. When the value of α becomes larger than the predetermined value α ^* at time t = T13, the adjuster 53 is used to adjust the magnitude of the Q-axis current command I _Q ^* until α becomes smaller than the predetermined value α ^* at t = T14. Use to adjust.

By using the above correction control means, even if the magnitude of the load is unknown and the appropriate current command value is unknown, the Q-axis initial current command I _Q0 ^* is set to a large value and started with open loop speed control. Thus, the Q-axis current command I _Q ^* can be adjusted to an appropriate value after starting.

Incidentally, in the above description for convenience, but the current command to adjust it was Q-axis current command I _Q ^*, may be carried out in this rather example D-axis current command as far as I _D ^* is the control.

  FIG. 5 is an operation timing chart of the synchronous motor control apparatus according to Embodiment 3 of the present invention. In the third embodiment, the open loop speed control means has a control means for starting with an optimum current command corresponding to the load when the state of the load is unknown.

In FIG. 5, after detecting the initial magnetic pole position at time t = T21, the Q-axis current command I _Q ^* is increased at a predetermined rate from time t = T22 while the angle is fixed at the initial position θ ₀ . If the rotor starts to move at time t = T23, a change appears in the magnitude of the detected voltage | V | due to the difference between the inverter frequency and the motor frequency, so this amount of electricity is detected, and the angle and speed from time t = T24. And the value of the Q-axis current command I _Q ^* is fixed.

  If the control means at the time of start in Example 3 is used, even if the magnitude of the load is unknown and the appropriate current command value is unknown, the open loop speed control can be performed without generating a sudden torque at the start. It can start smoothly.

In the above description, for convenience, the current command to be adjusted is the Q-axis current command I _Q ^* . However, this is not limited depending on the control. In addition, the method of detecting that the rotor has started moving is not only a method using the voltage change caused by the frequency difference between the inverter frequency and the motor, but also the short-term inverter 1 that does not affect the angular deviation. Another method such as a method of performing gate block and detecting the induced voltage at that time may be used. In addition, the induced voltage to be detected is not necessarily the fundamental voltage due to the field magnetic flux, and for example, slot ripple of the field winding may be detected. Since the slot ripple of the field winding becomes a higher-order harmonic with respect to the fundamental wave, it is suitable for detecting that the rotor has started to move.

  FIG. 6 is a diagram illustrating an example of a current command of the control device for the synchronous motor according to the fourth embodiment of the present invention. The fourth embodiment includes means for patterning the current command with respect to the output frequency of the inverter 1 when the torque-speed characteristic of the load is known in the open loop speed control means.

Although FIG. 6 shows an example of a square torque load having a large starting torque, the present invention can be applied to loads having other load characteristics. In the above description, for convenience, the current command to be adjusted is the Q-axis current command I _Q ^* , but this is not limited depending on the control.

  FIG. 7 is an operation timing chart of the synchronous motor control apparatus according to Embodiment 5 of the present invention. In the fifth embodiment, the open loop speed control means has means for starting without detecting the initial magnetic pole position.

A field current is passed at time t = T31, and a Q-axis current command is set to I _Q ^* = I _Q0 ^* at t = T32. At the same time, the speed command ω _r ^* is set to an extremely low speed. The integral of the speed command ω _r ^* is the angle θ _r ^* . When the Q-axis current flows in a direction orthogonal to the field current, the torque becomes maximum, and the rotor starts to move at time t = T33. If the rotor starts to move at t = T33, a change appears in the magnitude of the detected voltage | V | due to the difference between the inverter frequency and the motor frequency, so this amount of electricity is detected, and the angle and speed are increased from time t = T34. .

  If this means is used, even if the initial magnetic pole position is not detected, it is possible to start with open loop speed control.

In the above description, the current command to be adjusted for convenience is the Q-axis current command I _Q ^* , but this is not limited depending on the control. Further, as described in the description of the third embodiment, the method of detecting that the rotor has started moving may be a method of performing a short-time gate block and detecting an induced voltage or a method of detecting slot ripple. .

  FIG. 8 is a block diagram of a synchronous motor control apparatus according to Embodiment 6 of the present invention. In the sixth embodiment, the same parts as those in the block diagram of the synchronous motor control device according to the first embodiment shown in FIG. The sixth embodiment is different from the first embodiment in that a filter circuit 54 that receives a specific amount of electricity is added, and the output of the filter circuit 54 is added to the output of the rate setting device 33. .

In the open loop speed control state, if the current command is large, the torque fluctuation at the start is large, but the speed vibration is rapidly attenuated. Therefore, if the current command is close to the optimum value, the engine starts smoothly. On the other hand, the velocity vibration once generated tends to be difficult to attenuate. Therefore, as shown in FIG. 8, a predetermined amount of electricity, for example, a D-axis voltage command V _D ^* , which is a command value, a Q-axis voltage command V _Q ^* or a voltage command | V ^* |, or a detected voltage value | V |, D-axis current detection value I _D, or Q-axis current detection value I _Q,, passed through a filter circuit 54 applies a correction to the speed control loop at the output of the filter circuit 54.

  Here, the filter circuit 54 applies a filter that can extract a vibration component that attenuates velocity vibration by combining a high-pass filter and a low-pass filter.

  By using such means, it is possible to attenuate the speed vibration generated during the open loop speed control, and to reduce the possibility of induction such as mechanical resonance. Further, this vibration suppression control may be effective even after switching to closed loop speed control.

The block block diagram of the control apparatus of the synchronous motor which concerns on Example 1 of this invention. 3 is a timing chart showing the operation of the first embodiment of the present invention. The block block diagram which shows the electric current command correction | amendment control part of Example 2 of this invention. The timing chart which shows operation | movement of Example 2 of this invention. The timing chart which shows the operation | movement of Example 3 of this invention. The figure which shows an example of the electric current instruction | command of Example 4 of this invention. The timing chart which shows operation | movement of Example 5 of this invention. The block block diagram of the control apparatus of the synchronous motor which concerns on Example 6 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inverter 2 Synchronous motor 3 Control part 31 Initial magnetic pole position detector 32 Speed command 33 Rate setter 34 Integrator 35 D-axis initial current command 36 Q-axis initial current command 37 Coordinate converter 38 Current controller 39 Coordinate converter 40 Initial Field current command 41 Coordinate converter 42 PLL circuit 43 Speed controller 44 Adjuster 45 Absolute value calculator 46 Voltage command calculator 47 Adjuster 48 Voltage controller 49 Coordinate converter 50 Absolute value calculators 51 and 52 Angle calculator 53 regulator 54 filter circuit 4 voltage detector 5 current detector 6 field device 61 current detector 62 field current controller 63 power converter

Claims (7)

A power converter that outputs AC of variable voltage and variable frequency and drives a synchronous motor;
Current detection means for detecting the output current of the power converter;
Voltage detection means for detecting the output voltage of the power converter;
A field device for exciting the field winding of the synchronous motor;
A control unit for controlling the power converter and the field device based on outputs of the current detection unit and the voltage detection unit;
The controller is
Open-loop speed control means for performing current control using a predetermined current command when starting the synchronous motor and changing the output frequency of the power converter by the speed command;
Closed loop speed control means for performing speed control using a speed estimated value after starting the synchronous motor; and switching means for switching from the open loop speed control means to the closed loop speed control means;
Have
After switching to the closed loop speed control means by the switching means,
A control apparatus for a synchronous motor, wherein a field current is adjusted so that the output voltage becomes a value corresponding to a speed command. The controller is
After adjusting the field current so that the output voltage becomes a value according to the speed command,
Control system for a synchronous motor according to claim 1 operating power factor of the synchronous motor is characterized by the Turkey to adjust the excitation axis current of the synchronous motor to be 1. A power converter that outputs AC of variable voltage and variable frequency and drives a synchronous motor;
Current detection means for detecting the output current of the power converter;
Voltage detection means for detecting the output voltage of the power converter;
A field device for exciting the field winding of the synchronous motor;
A control unit for controlling the power converter and the field device based on outputs of the current detection unit and the voltage detection unit;
With
The controller is
Open-loop speed control means for performing current control using a predetermined current command when starting the synchronous motor and changing the output frequency of the power converter by the speed command;
Closed loop speed control means for performing speed control using a speed estimated value after starting the synchronous motor; and switching means for switching from the open loop speed control means to the closed loop speed control means;
Have
The open loop speed control means includes:
After detecting the initial magnetic pole position of the synchronous motor, start with a predetermined current command, and adjust the current command of the current control so that the angle difference between the current command vector and the voltage command vector is less than a predetermined value during startup controller of synchronous motor characterized in that it comprises means for. The open loop speed control means includes:
After detecting the initial magnetic pole position of the synchronous motor, gradually increase the current command in a state where the output frequency of the power converter is zero, confirm that the rotor has moved from a predetermined detected amount of electricity, 2. The synchronous motor control device according to claim 1, wherein the output frequency is increased.   The synchronous motor according to claim 1, wherein the open loop speed control means starts with a current command pattern corresponding to a load pattern set in advance with respect to an output frequency of the power converter. Control device. The open loop speed control means includes:
The output frequency of the power converter is set to an extremely low speed, is started with a predetermined current command, is confirmed that the rotor has moved from a predetermined detected electric quantity, and the output frequency is increased. The synchronous motor control device according to claim 1. The controller is
The synchronous motor control device according to claim 1, further comprising means for adjusting an output frequency of the power converter in accordance with a predetermined detected electric quantity or a vibration component of a command value of the electric quantity.

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