JP2002044984A - Vector control device for pm motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable smooth control of a PM motor, when a speed detection encoder which has a small number of pulses is used. SOLUTION: A magnet pole position calculator, which calculates the magnet pole positions of the PM motor is constituted of a first magnet pole position calculator 7a, which calculates magnet pole position, by counting pulse signals from an encoder mounted on the PM motor; a sensor magnet pole position calculator 7b which consists of a timer which counts lapsed time from the time the latest pulse signal comes; a multiplier which multiplies the time of the detected speed by a speed detection circuit and an adder 7d, which adds the calculated values by the first and second magnet pole position calculator. Even if the PM motor rotates, during which encoder pulse is not arriving, a magnet pole position calculation value outputted from the adder 7d becomes continuous. The PM motor can be controlled smoothly, by calculating a phase which is used for the control by this magnet pole position calculation value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vector control device for a PM motor, and more particularly to a vector control device for a PM motor that can smoothly control a PM motor even when an encoder having a small number of pulses is used.

[0002]

2. Description of the Related Art When vector control is performed by a PM motor (permanent magnet type periodic motor), current control according to the position of a magnet (magnetic pole) attached to a rotor is required. Therefore, in the vector control of the PM motor, it is necessary to detect the rotor magnetic pole position. Therefore, in a vector control device for a PM motor, an absolute position encoder is often attached to the motor.

When an absolute encoder is not installed, an initial magnetic pole position is estimated using a harmonic current or a voltage during a stop, and a magnetic pole position is estimated using an observer or an induced voltage while the motor is rotating. The driving method and the encoder (PVT) used as the speed detector of the induction motor
The magnetic pole position is calculated by attaching the motor to the motor and counting the pulse signals.

FIG. 6 shows an example of a conventional PM motor vector control device. In the figure, a main circuit 2 is composed of a forward converter connected to a power supply 1 and an inverse converter for outputting to a PM motor 3 a direct current obtained by smoothing the output of the forward converter with a capacitor as a power supply.

The U and V phase currents of the PM motor 3 are HCT 4
u, 4v, and the current detection circuit 21 detects a three-phase current. This three-phase current is converted by the three-phase to two-phase conversion circuit 22 into two.
The current is converted into a phase, and further converted into d- and q-axis detection currents by a coordinate conversion circuit 23 that rotates based on a phase signal output from the phase calculator 7. Further, a speed pulse from the encoder 5 directly connected to the PM motor 3 is converted into a detected speed by a speed detecting circuit 6.

The speed control unit 11 calculates a torque command from the speed command and the detected speed by the PID control circuit 11a or the observer control circuit 11b. The vector control unit 12 receives the torque command and receives a d-axis excitation current command and a q-axis torque. Calculate the current command. The current controller 13 calculates d, q
The d and q axis voltage commands are output based on the shaft current command and the d and q axis detection currents.

The d- and q-axis voltage commands are converted into two-phase currents by a rotating coordinate conversion circuit 24 based on a phase signal output from the phase calculator 7, and further converted into three-phase voltage commands by a two-phase to three-phase conversion circuit 25. The PM motor 3 drives the base of the switching element (main circuit element) of the inverter in the main circuit 2 via the gate output circuit 26 and the base drive circuit 27.
Is rotated at the speed specified by the speed command.

In this vector control device, during stop, the magnetic position estimator 8 estimates the initial magnetic pole position, and during rotation, the phase calculator 7 outputs the A and B phase signals from the encoder 5 attached to the PM motor 3. The magnetic pole position is calculated by counting, and the coordinate calculation is performed using the calculated magnetic pole position value.

[0009]

The vector control device estimates the initial magnetic pole position and calculates the magnetic pole position from a signal from an encoder attached to the PM motor.
To perform motor vector control, an encoder having a large number of pulses is required. In the case of an encoder having a small number of pulses, an encoder pulse does not come even if the PM motor rotates. For example, when a 30-pulse encoder is used, a signal does not come unless the motor rotates three times (360 degrees / 30 pulses * 4 (edge)).

Therefore, even though the PM motor is rotating, the magnetic pole position cannot be calculated because the encoder pulse does not come, and the magnetic pole position calculated by the controller and the magnetic pole position of the PM motor are considered in a short time. (See FIG. 7). Due to the influence of this deviation, the PM motor may not be controlled smoothly.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide a PM motor vector control device which can smoothly perform motor control even with an encoder having a small number of pulses. To provide.

[0012]

According to the present invention, there is provided a speed detecting circuit for calculating a speed from an encoder pulse signal of a speed detecting encoder attached to a PM motor, and a magnetic pole position of the PM motor is calculated from the encoder pulse signal. In a vector control device for a PM motor having a phase calculator, a phase calculator calculates a magnetic pole position by counting the encoder pulse signal, and a latest pulse detection of the encoder pulse signal. A second magnetic pole position calculator having a timer for counting an elapsed time from a time, a multiplier for multiplying the elapsed time by a speed detection value from a speed detector, and calculating the first and second magnetic pole position calculators And an adder for adding a value.

Alternatively, a speed detection circuit for calculating a speed from an encoder pulse signal of a speed detection encoder attached to the PM motor,
In a vector control device for a PM motor having a phase calculator for calculating the magnetic pole position of the M motor and an observer controller for speed control, the phase calculator performs the magnetic pole position calculation by counting the encoder pulse signal. A first magnetic pole position calculating unit, a timer for counting an elapsed time from the latest pulse detection time of the encoder pulse signal, and a multiplier for multiplying the elapsed time by an estimated speed in an observer controller for performing the speed control , And an adder for adding the calculated values of the first and second magnetic pole position calculators.

It is preferable that the second magnetic pole position calculating section is provided with a limiter for limiting the output of the second magnetic pole position by a phase when the next encoder pulse signal is detected and outputting the output to the adder.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment A vector control device for a PM motor according to a first embodiment will be described with reference to FIGS. In the figure, the same components as those shown in FIG. 6 are designated by the same reference numerals, and the description thereof will not be repeated.

In the vector control device for a PM motor shown in FIG. 1, the magnetic pole position calculator of the phase calculator 7 for calculating the magnetic pole position of the PM motor from the encoder pulse signal, as shown in FIG. A first magnetic pole position calculator 7a that performs a magnetic pole position calculation by counting, a timer that counts the elapsed time from the time when the latest pulse signal arrives, and the elapsed time multiplied by the speed detection value from the speed detection circuit 6. A second magnetic pole position calculator 7b, which is composed of a multiplier and a first and second magnetic pole position calculator 7a,
The adder 7d adds the calculation results of FIG. 7b and outputs a calculated value of the magnetic pole position.

According to the phase calculator 7, the encoder 5
For example, if the PM motor does not rotate three times as in the case of using the 30-pulse encoder, even if no signal comes, the magnetic pole position is calculated by the second magnetic pole position calculator 7b during that time. The change in the calculated magnetic pole position value becomes smooth. Therefore, even when an encoder having a small number of pulses, such as a 30-pulse encoder, is used, the PM motor can be smoothly controlled.

Second Embodiment A PM motor vector control device according to a second embodiment will be described with reference to FIGS. The difference from FIGS. 1 and 2 is that the input of the second magnetic pole position calculator 7b in the phase calculator 7 is the speed detection value in FIG. 2 but the observer from the speed controller 11 in FIG. The point is that the speed estimation value is used.

In the case of FIG. 2, the second magnetic pole position calculator 7
In b, the speed used for the calculation is the speed detection value from the speed detection circuit 6, and the speed detection value in the extremely low speed range deviates from the actual speed, which may cause an error in the phase calculation.

On the other hand, in order to improve the speed controllability in an extremely low speed range, devices employing a speed observer (11b in FIG. 1) are increasing. The speed observer estimates the motor speed from the output torque and the inertia model.

In the second embodiment, the second magnetic pole position calculator 7b uses the estimated speed value estimated by the speed observer of the observer control circuit 11b of the speed control unit 11. Therefore, the accuracy of the magnetic pole position calculation in the extremely low speed region is improved, and the calculation of the correct magnetic pole position can be performed even in the extremely low speed region.

Third Embodiment FIG. 5 shows the configuration of a magnetic pole position calculator in a phase calculation circuit according to a third embodiment. In the case of FIGS. 2 and 4 described above, the magnetic pole position calculated value may deviate more than the resolution detectable by the first magnetic pole position calculator 7a at the time of a sudden change in speed.

In the third embodiment, as shown in FIG. 5, the second magnetic pole position calculator 7b restricts the calculated value to the phase at the time of detecting the next pulse and outputs it to the adder 7d.
And the magnetic pole position obtained by adding the operation values of the first and second magnetic pole position calculators 7a and 7b by the adder 7d is regarded as the next pulse coming from the first magnetic pole position calculator 7a. In the case of the magnetic pole position. As a result, the calculated value of the magnetic pole position calculation can be performed by the first magnetic pole position calculator 7 even when the speed changes suddenly.
It is possible to prevent deviation from the resolution that can be detected by a.

[0024]

Since the present invention is configured as described above, the PM motor can be smoothly controlled even when an encoder having a small number of pulses is used as the speed detector.

[Brief description of the drawings]

FIG. 1 is a control block diagram of a PM motor vector control device according to a first embodiment.

FIG. 2 is an explanatory diagram of a configuration of a magnetic pole position calculator of a PM motor in the device.

FIG. 3 is a control block diagram of a PM motor vector control device according to a second embodiment;

FIG. 4 is a configuration explanatory diagram of a magnetic pole position calculator of a PM motor in the same device.

FIG. 5 is an explanatory diagram of a configuration of a magnetic pole position calculator of a PM motor according to a third embodiment;

FIG. 6 is a control block diagram of a PM motor vector control device according to a conventional example.

FIG. 7 is a graph showing a relationship between an encoder signal and a phase calculation output.

[Explanation of symbols]

 2 Main circuit 3 PM motor 5 Speed detector (encoder) 6 Speed detector 7 Phase calculator 11 Speed controller 12 Vector controller 13 Current controller 23, 24 Rotational coordinate conversion circuit

Continued on the front page F term (reference)

Claims (3)

[Claims] 1. A PM motor comprising: a speed detection circuit for calculating a speed from an encoder pulse signal of a speed detection encoder attached to a PM motor; and a phase calculator for calculating a magnetic pole position of the PM motor from the encoder pulse signal. In the vector control device of (1), the phase calculator includes a first magnetic pole position calculator that calculates a magnetic pole position by counting the encoder pulse signal, and a timer that counts an elapsed time from the latest pulse detection time of the encoder pulse signal. A second magnetic pole position calculator having a multiplier for multiplying the elapsed time by a speed detection value from a speed detector; and an adder for adding the calculated values of the first and second magnetic pole position calculators. A vector control device for a PM motor. 2. A speed detecting circuit for calculating a speed from an encoder pulse signal of a speed detecting encoder attached to a PM motor, a phase calculator for calculating a magnetic pole position of the PM motor from the encoder pulse signal, and a speed controller. In the vector control device for a PM motor having an observer controller that performs a first magnetic pole position calculation unit that performs a magnetic pole position calculation by counting encoder pulse signals, a latest pulse detection time of the encoder pulse signal A second magnetic pole position calculating unit having a timer for counting the elapsed time from the first and second, and a multiplier for multiplying the elapsed time by a speed estimation value of an observer controller for performing the speed control; And an adder for adding the operation value of the magnetic pole position operation unit. . 3. The limiter according to claim 1, further comprising a limiter that limits an output from the second magnetic pole position calculator to a phase at the time of detecting a next encoder pulse signal and outputs the output to the adder. Characteristic vector control device for PM motor.