JP3741291B2 - Sensorless synchronous motor drive device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sensorless synchronous motor driving device in a sensorless three-phase AC synchronous motor driving device.
[0002]
[Prior art]
Conventionally, as a step-out detection method in a sensorless synchronous motor, the driving device is a rectangular wave driving method, which is generated by comparing the induced voltage of the synchronous motor appearing at the winding terminal of the non-conducting phase and the neutral point voltage of the synchronous motor. In the generation time interval of the energization switching signal, the time interval set in advance and the actually measured time interval are compared, and the step-out is detected when the actually measured time interval is short (see FIG. 8). No. 3-207290) and a method as shown in FIG. 10 for detecting a step-out when a current flowing between the DC voltage circuit and the switching circuit flows in the opposite direction (Japanese Patent Laid-Open No. 7-87782). ) Has been proposed.
In FIG. 8, 41 is a switching element group constituting an inverter, 42 is a brushless motor, 43 is a position detection circuit control device, 44 is an energization switching signal generation time detector, and 45 is a microcomputer. The energization switching signal generation time detector 44 receives a part of the rotation signal of the switching element group 41 from the position detection circuit control device 43 as an input, and calculates the time from the output of a certain rotation signal to the output of the next rotation signal. Measure and send the data to the microcomputer 45. The microcomputer 45 receives the time from the output of a certain rotation signal to the output of the next rotation signal from the energization switching signal generation time detector 44, and the detection time is shorter than the time setting data stored therein. It is judged that step out. Thereafter, the control of restart of step-out is performed.
In FIG. 10, 51 is a DC brushless motor, 52 is an inverter circuit, 53 is a rectifier circuit, 54 is a smoothing capacitor, and 55 is a shunt resistor. Reference numeral 56 denotes a position detection circuit for detecting the position of the rotor of the motor 51, and has a three-phase comparator. The output of the comparator is output to the control unit 57. The control unit 57 monitors the voltage induced in the phase winding of the motor 51 through the comparator of the rotor position detection unit, and the position of the rotor is determined based on the change in the induced voltage. , A drive signal for each transistor of the inverter circuit 52 is created. A current detection circuit 58 including a forward current detection circuit 59 and a reverse current detection circuit 60 is connected to both ends of the shunt resistor 55 in the inverter circuit 52. The forward current detection circuit 59 and the reverse current detection circuit 60 detect forward and reverse currents flowing through the shunt resistor 55, respectively, and determine whether or not each exceeds a set value.
[0003]
[Problems to be solved by the invention]
In the conventional method shown in FIG. 8, the energization switching signal is obtained from the induced voltage appearing at the non-energized terminal. This induced voltage is commutated after both the upper arm and lower arm transistors of the inverter circuit section 52 are turned off. While the commutation current flowing through the diode exists, it cannot be detected, and it can be detected only after the commutation current disappears. This operation will be described with reference to an explanatory diagram shown in FIG. 9. For example, a normal current flowing in the w phase flows when the upper arm transistor _Pw and the lower arm transistor _Nv are on as shown in FIG. 9A. As shown in FIG. 9B, after the w-phase commutation current flowing through the w-phase commutation diode disappears after the w-phase upper and lower transistors are turned off, an induced voltage appears at the w-phase terminal.
However, when the synchronous motor rotates at high speed or when the current flowing through the stator winding is large, commutation current exists during the entire period when both the upper arm and lower arm transistors are OFF, and therefore the induced voltage is detected. There is a problem that the power-on switching signal cannot be obtained and the step-out cannot be detected.
Further, in the latter method, in order to detect step-out from the change in the direction of current flow shown in FIG. 10, when there is an operating state in which the regenerative mode generates torque in the direction opposite to the rotation direction of the synchronous motor, In this case as well, there is a problem that the direction in which the current flows is opposite to that in the normal state, so that it cannot be distinguished from the step-out detection and cannot be detected in the step-out stop state.
Therefore, the problem to be solved by the present invention is to provide an apparatus capable of detecting a step-out in any of a high speed, a large current, a regeneration mode, and a stopped state.
[0004]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a sensorless synchronous motor drive device, wherein (1) the power factor angle between the output voltage and output current to the motor and the magnitude of the output current to the motor are further comprising a step-out detection means for detecting the loss of synchronism of the motor, (2) the magnitude of the output voltage and output current of the power factor angle obtained based on the multiplication value of the output current to the previous SL motor to the motor characterized that you with a step-out detection means for detecting the loss of synchronism of the motor based on the.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to FIG.
In FIG. 1, 1 is an arithmetic unit, 2 is a sensorless synchronous motor, 3, 4 and 5 are current detectors as first detection means, 6 is an inverter unit, 7 is a converter unit, 8 is a smoothing capacitor of a DC power source, Reference numeral 9 denotes a DC power supply voltage detector as second detection means, and reference numeral 10 denotes an on / off drive signal to each of the six power transistors in the inverter unit 6.
Next, the operation will be described. First, instantaneous current values i _v and i _w flowing through the v-phase and w-phase stator windings are detected by the current detectors 3 and 4. In addition, although it set as the v phase and w phase for description, it is the same also when it is the combination of any two phases, or when all three phases are used.
Here the stator winding current effective value i, for example ^{_{i = {(i w) 2}} /2 + (i w +2 · i v) 2/6} 1/2
Can be detected from.
Further, the arithmetic device 1 controls the on / off time to the six power transistors based on the detection value detected by the DC power supply voltage detector, so that the arithmetic device 1 applies the voltage applied to the stator winding. Can be controlled and detected, and the applied voltages E _u , E _v and E _w to the stator windings at the moment when the instantaneous values i _v and i _w are detected can also be controlled and detected.
From these E _u , E _v , E _w , _iv and i _w , the power factor angle φ between the voltage applied to the stator winding and the stator winding current is, for example,
cosφ = {E _v · i _v + E _w · i _w + E _u · (−i _v −i _w )} / (3 · E · i)
φ = cos ⁻¹ [{E _v · i _v + E _w · i _w + E _u · (−i _v −i _w )} / (3 · E · i)]
Can be detected from.
[0006]
When the sensorless synchronous motor shifts to the step-out state after the peak exceeds the torque point as shown in FIG. 2 (a), the point at which the output torque of the synchronous motor always becomes zero as shown in FIG. 2 (a). Pass through. In the vicinity of the point where the output torque becomes zero, as shown in FIG. 2C, the power factor angle becomes a value close to 90 °, and the effective value i of the stator winding current becomes a large value.
On the other hand, when the output torque is close to zero in the synchronized state, the effective value i of the stator winding current is usually a small value as shown in FIG. 2 (b), but the power factor angle as shown in FIG. 2 (c). Is a value close to 90 °, so it is not possible to determine step-out detection only by the power factor angle.
Therefore, a discrimination level is set for the effective current value i of the stator winding, and the step-out occurs when the effective current value i of the stator winding exceeds this discrimination level and the power factor angle φ is close to 90 °. Detect. The same can be detected even in a stopped state.
[0007]
Next, a second embodiment of the present invention will be described with reference to FIG.
In FIG. 3, components 1 to 10 are the same as those in FIG. 1, and 11 is a voltage detector that directly detects a voltage applied to each stator winding as second detection means.
Next, the operation of the second embodiment will be described. The detection of the effective value i of the stator winding current is the same as in the first embodiment. However, in the detection of the power factor angle φ, the instantaneous value of the voltage applied to each stator winding is detected from each terminal. The difference from the first embodiment is that the value directly detected by the device 11 is used. Except for the means for detecting the power factor angle φ, all other contents are the same as in the first embodiment.
[0008]
Next, a third embodiment of the present invention will be described with reference to FIG.
In FIG. 4, 21 is a current detector as a first detection means, 22 is a low-pass filter section, and 23 is a peak hold section. Other configurations are the same as those of the first embodiment.
Next, the operation of the third embodiment will be described. First, a detected current waveform as shown in FIGS. 5A and 5B is obtained from the current detector 21. The DC component i _dc is extracted from this waveform by the low-pass filter unit 22, while the peak current value i _p is extracted from the peak hold 23. For where i _p, the current waveform shown in FIG. 6 is obtained when joining the i _p and after 1 carrier period of the PWM output of the inverter unit 6.
When the peak value of the current waveform in FIG. 6 is extracted, the stator winding current effective value i and i _{p (peak)} = √2 · i with respect to the extracted peak current value i _{p (peak)} , i = i _{p (peak)} / √2
Are in a relationship.
For example, when the average value of the current waveform in FIG. 6 is extracted, i _{p (AVG)} = {(3√2) / π} · i for the extracted current value i _{p (AVG)} , i = {π / (3√2)} ・ i _{p (AVG)}
Are in a relationship.
Therefore, the stator winding current effective value i can be detected by extracting i _p in any of the above.
The DC voltage detection value v _PN detected by the DC power supply voltage detector 9, the DC component i _dc extracted from the current detector 21 by the low pass filter 22, the stator winding current effective value i, and the stator winding Applied voltage effective value E and power factor angle φ to v _PN · i _dc = 3 · E · i · cos φ
There is a relationship.
Here, the effective voltage E applied to the stator winding can be controlled by the arithmetic unit 1 directly controlling the on / off drive signal 10 to the inverter unit 6 based on the detected value of the DC power supply voltage detector 9. Therefore, the arithmetic unit 1 can detect the value of E. Therefore, the power factor angle φ is cos φ = {v _PN · i _dc / (3 · E · i)}.
Therefore, φ = cos ⁻¹ {v _PN · i _dc / (3 · E · i)}
Can be detected from.
The means for detecting step-out from the detected stator winding current effective value i and the power factor angle φ is the same as in the first embodiment.
For example, the position of the current detector 21 can be obtained by inserting the current detector 21 between the positive side of the smoothing capacitor 8 of the DC power source (point P in FIG. 4) and the inverter unit 6 in FIG.
[0009]
Next, a fourth embodiment of the present invention will be described with reference to FIG.
In FIG. 7, each part 1 to 10 is the same as that in FIG. 1, and 31 is a sample and hold part for detection values from the current detectors 32, 33 and 34.
Next, the operation of the fourth embodiment will be described. The outputs of the current detectors 32, 33, and 34 can be detected because current flows through the detectors 32, 33, and 34 only while the lower transistor of the inverter unit 6 is on.
Accordingly, instantaneous current values i _v and i _w flowing through the stator windings of the v and w phases are detected at the moment when the two lower transistors are turned on, for example, the v and w phases are on.
Based on this detection value, the detection of the stator winding current effective value i and the power factor angle φ, and the step-out detection means are the same as those in the first embodiment.
In the third embodiment, only the means for detecting the applied voltage to the stator winding is the same as the second embodiment,
An apparatus in which only the means for detecting the voltage applied to the stator winding in the fourth embodiment is the same as in the second embodiment is also conceivable.
[0010]
【The invention's effect】
As described above, according to the present invention, since the step-out detection is performed from the effective value of the stator winding current and the power factor angle between the stator winding current and the voltage applied to the stator winding, the sensorless synchronous motor operates at high speed. Step-out can be detected even when stepping out in any state of high current, regenerative mode, and stopped.
[Brief description of the drawings]
FIG. 1 is a block diagram of a sensorless synchronous motor driving apparatus according to an embodiment of the present invention.
FIG. 2 is a relationship diagram of an output torque, a stator winding current effective value, and a power factor angle of a sensorless synchronous motor.
FIG. 3 is a block diagram of a sensorless synchronous motor driving apparatus according to a second embodiment of the present invention.
FIG. 4 is a block diagram of a sensorless synchronous motor driving apparatus according to a third embodiment of the present invention.
FIG. 5 is a detection waveform diagram of a current detector in the same example.
FIG. 6 is a voltage waveform diagram that can be extracted by the peak hold unit from the detection waveform of the current detector in the same embodiment.
FIG. 7 is a block diagram of a sensorless synchronous motor driving apparatus according to a fourth embodiment of the present invention.
FIG. 8 is a block diagram of a drive device with a step-out detection function of a conventional sensorless brushless motor.
FIG. 9 is an explanatory diagram of a current flowing through a commutation diode after the upper and lower transistors are turned on / off.
FIG. 10 is a block diagram of a conventional drive device with a step-out detection function for a sensorless synchronous motor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Computation device, 2 Sensorless synchronous motor, 3, 4, 5 Current detector, 6 Inverter part, 7 Converter part, 8 DC power supply smoothing capacitor, 9 DC power supply voltage detector, 10 ON / OFF drive signal, 11 terminals Voltage detector, 21 Current detector, 22 Low-pass filter section, 23 Peak hold section, 31 Sample hold section, 32, 33, 34 Current detector

Claims (3)

  In the sensorless synchronous motor driving apparatus, the motor-less step-out detecting means for detecting step-out of the motor based on the power factor angle of the output voltage and output current to the motor and the magnitude of the output current to the motor is provided. A sensorless synchronous motor drive device. The drive device for sensorless synchronous motor, a step-out of the motor based on of the atmosphere of the output voltage and output current and the output current of the power factor angle obtained based on the multiplication value to the previous SL motor to the motor A sensorless synchronous motor drive device comprising a step-out detection means for detecting. 3. The sensorless synchronous motor drive device according to claim 1 , wherein the step-out detection means uses an output voltage to the motor as a detection voltage or a control voltage .

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