JPH0417033B2 - - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a control device for a synchronous motor using permanent magnets, and in particular, a control device for controlling a synchronous motor using a minor loop of current control to perform constant output characteristic control. This invention relates to a speed control device for a permanent magnet synchronous motor.

(Prior Art) FIG. 3 shows a conventional embodiment in which a permanent magnet synchronous motor is implemented as an AC servo.

In the figure, power supplied from a DC current 1 is subjected to PWM (pulse width modulation) control by an inverter bridge 2, and current is caused to flow through a permanent magnet synchronous motor 6 via current detectors 3, 4, and 5. A position sensor 7 directly connected to the permanent magnet synchronous motor 6 detects the position of the rotor of the motor 6, and a position detector 9 generates a position detection signal.

The position detection signal is converted into a speed detection signal by a speed detector 10 and compared with a speed reference 8 to control the speed of the electric motor 6.

The error between the output of the speed reference 8 and the output of the speed detector 10 is amplified by the amplifier 11, and
Output as T ^* .

In response to the torque reference T ^* and the output of the position detector 9, the current reference generator 12 generates three-phase current references _IU ^* ,
Outputs I _V ^* and I _W ^* . These current references I _U ^* , I _V ^* ,
The magnitude of I _W ^* is proportional to the torque reference T ^* and is output as a sine wave or square wave signal. The following will explain the case of a sine wave.

The error between the U-phase current reference I _U ^* and the U-phase current I _U (detected by the current detector 3) is amplified by the amplifier 13, and the comparator 17 compares it with the output of the triangular wave generator 16 for PWM modulation. It is compared and becomes a PWM signal. This signal is passed through the drive circuit 20 to turn on and off the U-phase transistor of the inverter bridge 2, thereby controlling the U-phase current.

Similarly, current standards I _V ^* and I _W ^* are used for V phase and W phase.
Errors between currents I _V and I _W are amplified by amplifiers 14 and 15, and compared with a triangular wave by comparators 18 and 19 to output a PWM signal.

(Problems to be Solved by the Invention) The above system is well known as an AC servo system. There is no problem as a servo, but when using this AC servo system as the main spindle of a machine tool, there is a demand for constant torque characteristics in the constant speed range and constant output characteristics in the high speed range.

Conventionally, in such cases, if a complicated microcomputer was used in the control circuit, high-speed operation was possible by advancing the current reference phase as the speed increased, but general servo control equipment that does not use a microcomputer However, the circuit was complicated and could not be realized. These details will be explained with reference to FIG.

Figure 4a is an equivalent circuit of a synchronous motor,
V ₁ is the terminal voltage, I is the current, E ₀ is the back electromotive force, and IX is the reactance drop. In an AC servo using a synchronous motor, the maximum torque can be produced by controlling the back electromotive force E ₀ and the current I to be in phase, as shown in (C), so the current reference I _U ^* is determined by the position detector 9. The output is in phase with the back electromotive voltage. However, when the motor back electromotive current E ₀ increases with the rotation speed and the peak value exceeds the voltage of the DC power supply 1, the current I cannot flow, and as shown by lines a, c, and e in Fig. 5, the speed N ₂ As a result, the generated torque, that is, the motor output, decreases rapidly and becomes unusable at speeds above _N3 . speed
If it is desired to use the motor between N ₄ and 4, a motor with characteristics a→d must be used, which increases the output capacity of the motor, which poses problems in terms of size and economy.

Therefore, as shown in Figure 4b, if we consider the case where the maximum terminal voltage V ₁ can be secured when the back electromotive force E ₀ is 1, if the back electromotive force increases to E ₀ 2, the current I ₁ is in phase. If this happens, the terminal voltage will need to be V ₁₁ , and operation will become impossible for the reasons mentioned above. However, if the current is advanced by φ such as I ₂ , the terminal voltage becomes V ₁ and operation is possible. In this way, as the speed increases, the current phase (i.e., the current reference phase) is advanced according to a certain function using a microcomputer.
It is known that the characteristics abf shown in the figure can be realized.

However, it has not been possible to easily realize such a phase shift of the current reference with a hardware circuit, so conventionally, when the constant output range is required to be doubled, as shown in the characteristics a to d in Figure 5, Since a motor with almost twice the capacity was used, there were problems with the size and economy of the motor.

An object of the present invention is to configure a current reference phase lead circuit by adding a simple circuit to control the constant power range, thereby reducing the capacity of the motor, downsizing it, and improving the economical efficiency of a permanent magnet synchronous motor. The purpose is to provide a control device.

Reference material IECON'84, conference sheet-1111“A
HIGH PERFORMANCE AC SERVO
SYSTEM WITH PERMANENT MAGNET
SYNCHRONOUS MOTROR” Nagaoka University of Technology Nanbae, et al. [Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides an inverter that supplies alternating current to a permanent magnet type synchronous motor. , an apparatus comprising: a position detection circuit for detecting the rotor position of the synchronous motor; and a current control circuit for controlling the alternating current so that it matches a current reference having a phase determined by a position detection signal; a speed detector that detects the speed of the motor, and a function generating means that outputs a correction signal that changes as a function of the speed.
Calculating means for multiplying the correction signal by the current reference of the other phase and adding it to the current reference of the own phase to obtain the actual current reference is provided so that the current reference advances in phase according to the speed.

(Function) In the above configuration, when the speed of the permanent magnet synchronous motor changes, the function generating means outputs a correction signal that changes according to a function of the speed. The calculation means multiplies this correction signal by the current reference of the other phase, adds it to the current reference of the own phase, and outputs the actual current reference of the leading phase. This enables high-speed operation and constant output characteristic operation without increasing the terminal voltage of the synchronous motor.

(Embodiment of the Invention) FIG. 1 shows the configuration of an embodiment of the invention. The same parts as those in FIG. 3 are given the same numbers, so the explanation will be omitted. In FIG. 1, the components of the current reference, which is the main part of the present invention, are mainly shown, and the other parts are the same as in FIG. 3.

In FIG. 1, the rotation direction of the motor is detected by the rotation direction detector 21 from the output of the speed detector 10. If the rotation direction is forward rotation, contacts 23 and 25 are closed, and if the rotation direction is reverse rotation, contacts 22 and 24 are closed. Operate each contact so that it closes. The function generator 26 generates an output signal such that the output of the speed detector 10 is zero when the speed is below a set speed, and increases as the speed increases when the speed is above the set speed. The output V ₂₆ of the function generator 26 and the signal I _V ^* via the contact 22 or 23
Alternatively, I _W ^* is integrated in a multiplier 27 to become a signal V ₂₇ , which is added to the current reference I _U ^* in an adder circuit 29 to obtain a second signal.
The current reference I _U ^** becomes. This second current reference I _U ^**
Since the error in the detected current I _U is amplified and controlled by the amplifier 13, the motor current I _U is controlled to match the second current reference I _U ^** .

Similarly to the U-phase current control circuit, the W-phase current control circuit integrates the output V ₂₆ of the function generator 26 and the signal I _U ^* or I _V ^* input via the contact 24 or 25 using the multiplier 28 to output V. ₂₈ and adder circuit 30, current reference
It is added to I _W ^* and output as the second current reference I _W ^** . Regarding the V phase, I _U ^** and I _W ^** are added by an adder circuit 31 to obtain a second current reference I _V ^** .

FIG. 2a shows the input and output characteristics of the function generator 26. That is, when the speed, which is the input signal, is less than or equal to _N1 , the output _V26 is zero, and when the speed exceeds _N1 , the output increases according to a set function.

On the other hand, if the electric motor rotates in the normal direction, contact 2
3 is closed, so the second current reference I _U ^** is equal to I _U ^*
Since it is the sum of V ₂₇ and V ₂₇ is the product of I _W ^* and V ₂₆ , it can be expressed by the vector diagram in Figure 2b. When the speed is less than or equal to N ₁ , V ₂₇ is always zero, so the second current reference I _U ^** is equal to I _U ^* . When the speed exceeds N ₁ , V ₂₇ increases with the speed to V ₂₇ a, b, c, d, so the second current reference I _U ^** is as shown in I _U ^** a, b, c, d. The phase gradually advances, and when the magnitudes of I _U ^* and V ₂₇ become equal, the phase advances by 60°. It is possible to limit the angle at which this phase advances by changing the addition ratio of I _U ^* and V ₂₇ , but here
This will be explained by assuming a 60° phase advance limit.

FIG. 2c shows such a second current reference expressed as a vector diagram for three phases.

In the case of reverse rotation, the current reference I _U is used as shown in Figure 2 d.
^* , I _U ^* , I _W ^* phase rotation is reversed, so contact 22,
24 is closed and V ₂₇ , which is the product of I _V ^* and V ₂₆ , is added to the current reference I _{U *} ^to create the second current reference I _U ^*.
A phase advance of ^* has been achieved.

As explained above, the motor speed is the set value (N ₁ )
When the current phase is higher than that, current can be passed through the motor without increasing the motor terminal voltage, so that operation up to high speeds is possible. Now, if the phase advance angle is φ, the motor current is I, the voltage of the DC power supply 1 of the inverter bridge is Vd, and k is a constant, then
The maximum input power P _nax to the motor is approximated by equation (1).

P _nax ≒kVdI _cps φ (1) If φ is set to 60°, the motor input can be 1/2 of the maximum input to the motor.

Furthermore, one of the features of the present invention is that the second current reference
The magnitude of I _U ^** is almost the same as the current reference I _U ^* , and this means that when a current minor loop is configured, limiting the maximum value of the current reference can protect the inverter and motor. Considering this, this is an important advantage.

As explained above, according to this embodiment, it is possible to easily advance the phase of the current reference as the motor speed increases without using a complicated microcomputer circuit. Furthermore, since the magnitude of the current reference hardly changes even if the phase changes, high-speed operation is possible without increasing the terminal voltage of the permanent magnet synchronous motor, making it possible to reduce the capacity of the motor and control device. Furthermore, since the current limit value hardly changes, it is possible to coordinate protection of elements in the inverter section and prevent demagnetization of permanent magnets.

Note that the second current reference I _V ^** of the V phase is I _U ^** and I _W ^**
However, as with the other two phases, by adding a multiplication circuit, it goes without saying that I _U ^* , I _V ^* , and I _W ^* can be combined.

Also, unlike the output characteristics of the function generator 26 shown in Fig. 2a, there is no practical problem in making the speeds N ₁ and N ₂ a straight line, and the addition ratio of the current references I _U ^* and V ₂₇ can be changed. By this, it is possible to adjust the limit of the phase advance angle.

〔Effect of the invention〕

When performing torque control or speed control using current control using the current minor loop of a permanent magnet synchronous motor, when the motor speed exceeds the set value,
This is detected by a function generator, and a multiplier circuit calculates the product of this output and a current reference whose phase is advanced by 120 degrees, and adds it to the original current reference to form a current minor loop as the second current reference. By using a simple circuit to allow current to flow without increasing the terminal voltage of the motor, it is possible to control the speed of a permanent magnet motor over a wide range, making the motor more compact, controlling the control device smaller, and improving economic efficiency. can be achieved. Furthermore, the magnitude of the second current reference changes little due to phase changes, and the protection reliability of the control device and motor can be significantly improved.

[Brief explanation of drawings]

Fig. 1 is an embodiment of the present invention, Fig. 2 is an explanatory diagram of the operation of Fig. 1, Fig. 3 is a conventional circuit, Fig. 4 is an explanatory diagram of the operation of a synchronous motor, and Fig. 5 is the speed of a permanent magnet synchronous motor. and a motor output characteristic diagram. 1...DC power supply, 2...Inverter bridge,
3, 4, 5...Current detector, 6...Permanent magnet synchronous motor, 7...Position sensor, 8...Speed reference, 9
...Position detector, 10...Speed detector, 11,1
3, 14, 15...Amplifier, 12...Current reference generator, 16...Triangular wave generator, 17, 18, 19
... Comparator, 20 ... Drive circuit, 21 ... Rotation direction detector, 22, 23, 24, 25 ... Contact, 2
6...Function generator, 27, 28...Multiplier, 2
9, 30, 31...addition circuit.

Claims (1)

[Scope of Claims] 1: an inverter that supplies alternating current to a permanent magnet type synchronous motor; a position detection circuit that detects the rotor position of the synchronous motor; A device comprising a current control circuit that controls alternating currents so that they match, a speed detector that detects the speed of the synchronous motor, a function generating means that outputs a correction signal that changes as a function of the speed, and the correction signal. 1. A speed control device for a permanent magnet type synchronous motor, characterized in that a calculation means is provided to obtain an actual current reference by multiplying by the current reference of the other phase and adding it to the current reference of the own phase. 2. The current reference of the other phase is configured such that the phase rotation is reversed and selected according to the output of a rotation direction detector that detects the rotation direction of the synchronous motor. A speed control device for a permanent magnet type synchronous motor according to item 1.