JP2544972B2 - AC motor controller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC motor control device based on an open loop control method such as a slip frequency vector control of an internally generated magnetic flux of an AC motor.

The open loop means that the magnetic flux sensor or the like does not detect the internally generated magnetic flux of the AC motor, or does not use any means for calculating the internally generated magnetic flux based on the terminal voltage or the input current. .

[Conventional technology]

Figures 4 and 5 show, for example, the Technical Report of the Institute of Electrical Engineers of Japan (II
Part), No. 186, "Recent Technology Trends in Drive Electronics", April 1985, P8, Fig. 7 is a block diagram of a control configuration circuit for conventional AC motor vector control.
In FIG. 4, 1 is a speed command (ω _r ^* ) of the AC motor 24, 2 is a detection speed of the AC motor 24 output from a speed sensor 26 described later, 3 is a speed controller, and 4 is output torque of the AC motor 24. Command, 5 is a divider, 6 is a secondary torque component current command of the AC motor 24, 7 is a secondary-to-primary conversion factor for converting the secondary torque component current command 6 to the primary side, 8 Is the current command for the primary side torque of the AC motor 24, 9
Is a secondary side interlinkage magnetic flux command interlinking with the secondary side of the AC motor 24, 10 is a secondary side interlinkage magnetic flux detection feedback value, 11 is a magnetic flux controller, and 12 is a primary side field of the AC motor that generates magnetic flux. When the primary side torque component current command 8 and the primary side field component current command 12 shown in FIG. 6 are orthogonal coordinate values on the dq2 axis, the primary current in polar coordinate format is shown. Coordinate converter for generating vector command 14, 15 for polar coordinate unit vector of secondary side flux linkage, 16 for vector multiplier, 17 for primary current vector command,
18 is a converter that converts the primary current vector command 17 into a three-phase current command 19 of i _U ^* , i _V ^* , i _W ^* , and 20 is a current controller for three phases that independently controls each of the three-phase currents. , 21 is a power converter (hereinafter, abbreviated as an inverter) that supplies power to the AC motor 24 according to the output of the current controller 20 for three phases, 22 is a three-phase current detected and fed back by the current sensor 23, and 24 is an AC motor. , 25 is a magnetic sensor for detecting the internal magnetic flux of the AC current generator 24, 26 is a speed sensor for detecting the rotor speed of the AC motor 24, and 27 is a magnetic flux vector synthesized from the magnetic flux value detected by the magnetic sensor 25. The coordinate converter, 28 outputs the output of the coordinate converter 27 to the secondary side interlinkage magnetic flux detection feedback value 10 and the vector operator (the polar coordinate unit vector of the secondary side interlinkage magnetic flux) 15
It is a vector analyzer that separates into two. Further, in FIG. 5, 29 is a differentiator, 30 is a coefficient by a motor constant, 31 is the same coefficient as the conversion coefficient 7 from secondary to primary, 32 and 33 are also coefficients by a motor constant, and 34 is a division. 35 is a slip frequency command of the AC motor 24, 36 is a value added to the detected speed 2 and the slip frequency command 35, 37 is a value of the added value 36, which is a polar coordinate unit for generating the polar coordinate unit vector 15 of the secondary side interlinkage magnetic flux It is a vector generator.

Next, the operation will be described. First, the internal magnetic flux of the AC motor 24, which is directly detected by the magnetic sensor 25, passes through the coordinate converter 27 and each converter of the vector analyzer 28 to
It is input to the magnetic flux controller 11 as the secondary side interlinkage magnetic flux detection feedback value 10 and controlled by obtaining the simultaneous input condition with the externally input secondary side interlinkage magnetic flux command 9 and outputs the primary side field magnetic field current command 12. .

In addition, the AC motor 24 detected by the speed sensor 26
The number of revolutions is input to the speed controller 3 together with the speed command 1 of the AC motor 24, which is an external input, and controlled to obtain the output torque command 4.

Next, the output torque command 4 is guided to the divider 5, and the secondary side interlinkage magnetic flux detection feedback value 10 is fetched and calculated, and then the secondary side torque component current command 6 is obtained. The primary-side torque-dependent current command 8 is output by passing through the connected conversion coefficient from secondary to primary.

Here, the coordinate converter 13 which has taken in the primary-side field current component command 12 and the primary-side torque component current command 8 outputs the polar coordinate type primary current vector command 14 shown in FIG. To do. Then, the primary current vector command in the polar coordinate format is loaded into the vector multiplier 16, and at the same time, the polar coordinate unit vector 15 of the secondary side interlinkage magnetic flux output from the vector analyzer 28 is loaded to perform an operation and the AC motor 24 The primary current vector command 17 is output. And finally the converter
3-phase current command 19 via 18 current controller for 3 phases 20
Give to. By the calculation of this control loop, the AC motor
Match the spatial position of the inside of 24 with the d-axis of Fig. 6,
The the d-axis with respect to _{^{θ O * (= tan -1 (}} i 1g * / i id *) displaced positions, primary current (motor input current) command vector i ₁ ^*
The current is controlled so that 17 is generated. In this way, the primary current inside the AC motor 24 is flux-controlled in the same manner as the DC motor, and the vector product of the field current and the generated magnetic flux orthogonal to it is taken to obtain the output torque and the non-output torque. The current is separated so that vector control can be performed independently. FIG. 5 is an example of a block diagram of control generally referred to as slip frequency vector control. The feature of this circuit is that it does not use a special magnetic sensor, and the magnetic flux is fed forward according to a theoretical formula (flux Open loop control) is used. Since this control method is common nowadays, detailed description thereof is omitted here as a well-known technique.

Here, the generation control method of the primary side field current component current command 12 input to the coordinate converter 13 in order to obtain the primary current vector command 14 in the polar coordinate format will be briefly described. First, when the control circuit of FIG. 5 is operated, the magnetic flux of the secondary side interlinkage magnetic flux detection feedback value 10 (φ ₂ ) inside the AC motor 24 shown in FIG.
₂ is given to the primary side of the electric motor. Field current i
The relationship with _1d is given by equation (1).

However, M: Mutual inductance L ₂ : Secondary-side self-inductance R ₂ : Secondary-side resistance In Fig. 5, differentiator 29, coefficient 3 by motor constant 3
0, 2 → 1 conversion coefficient 31 and 3 by motor constant
The control block of the primary-side field magnetic field current command 12 constituted by 2 and is a direct expression of the above equation (1), whereby the desired magnetic flux φ ₂ becomes the secondary-side interlinkage magnetic flux command 9. Is controlled like.

The current vector control eliminates the disadvantage of embedding a special magnetic sensor 25 in the AC motor as in the control system of FIG. 4, and a slip frequency type control circuit that can be used by a general-purpose motor as shown in FIG. Is often used.

[Problems to be Solved by the Invention]

Since the conventional AC motor control device is configured as described above, in the case of the control circuit without the magnetic flux controller 11 as shown in FIG. 4, the stepwise input signal of the secondary side interlinkage magnetic flux command 9 is input. It is difficult to respond quickly to changes, and operations equivalent to pre-excitation (establishing the field before operation) in a DC motor must be performed in a short time. For that, forcing is applied, and 2
Next side interlinkage magnetic flux command 9 A function generator that processes the signal into a waveform proportional to is essential. Further, in the case of FIG. 5, since the noise resistance is deteriorated due to the presence of the differentiator 29, an appropriate filter is required.
Further, when the differentiator 29 is constructed by software, there is a problem that it becomes digital differentiation and the resolution of the secondary side interlinkage magnetic flux command 9 becomes unnecessarily high.

The present invention has been made in order to solve the above problems, and is capable of reliably responding to the stepwise change of the secondary side interlinkage magnetic flux command 9 inputted from the outside and also causing the malfunction. It is an object of the present invention to obtain a control device for an AC electric motor that eliminates elements and enables stable field current control.

[Means for Solving the Problems] In the control device for an AC electric motor according to the present invention, one input command of the two input signals taken into the magnetic flux controller is the secondary side interlinkage magnetic flux command, and the other input is The primary-side field magnetic field current command, which is the output of the magnetic flux controller, is input to the function generator and used as the estimated magnetic flux value of the feedback amount obtained through the function generator. Then, the deviation signal of the both signals is controlled to generate the primary side field divided current command.

[Action]

Since the primary side field split current command in the control device for the AC motor according to the present invention is subjected to forcing even with respect to the stepwise change of the secondary side interlinkage magnetic flux command, the primary side field magnetic field which is stably focused. It becomes a minute current command. That is, the primary-side field magnetic field current command is input to the magnetic flux function generator, and the estimated magnetic flux value as its output is used as the feedback amount of the magnetic flux controller.

Example of Invention

An embodiment of the present invention will be described below with reference to the drawings. In the figure, the same parts as in FIG. 4 are shown with the same reference numerals, and in FIG. 1, 38 is a function generator for outputting an estimated magnetic flux value, and 39 is a designated magnetic flux value of the output.

The circuit block shown in FIG. 1 has a secondary side interlinkage magnetic flux command 9, a differentiator 29, a coefficient 30 based on a motor constant shown in FIG.
The field control block to be replaced with the field conversion current command configuration block up to the secondary side-to-primary conversion coefficient 31, the coefficient 32 by the motor constant, and the primary side field field current command 12 is shown.

Next, the operation will be described. First, the generation of the field current command seen in the conventional example of FIG. 5 requires the differentiator 29 because it complies with the equation (1) as described above.
_{In the} present invention, the magnetic flux φ is expressed by the equation (1) in order to solve the problem that the stepwise change of ₂ ^* (secondary side flux linkage command 9) cannot be permitted.
To organize for _two (2) give as expression.

However, T ₂ = L ₂ / R ₂ : Secondary circuit time constant (2) by equation primary field as i _1d磁分current command 12
The estimated magnetic flux value 39 is obtained by using i _id ^* which is. Therefore, the function of the function generator 38 is given by the equation (3).

Equation (3) is determined by the electrical time constant T ₂ of the AC motor 24 1
It is a second-order lag function and does not include any differential element. In the configuration of FIG. 1, even if the secondary side interlinkage magnetic flux command 9 changes stepwise from zero, the value of the primary side field magnetic field current command 12 is forced to the output limit of the magnetic flux controller 11 and the function is generated. Magnetic flux estimated value 39, which is the output of the device 38, is the primary side magnetic field current command
Since the magnetic flux controller 11 gradually changes with the primary delay of 12, the deviation between the secondary side flux linkage command 9 and the estimated magnetic flux value 39 gradually decreases, and the magnetic flux controller 11 is a controller having an integral element. Then, the deviation gradually becomes zero and the value of the primary side field component current command 12 becomes stable at a steady value. First as described above
In the case of the figure, by setting the gain setting of the magnetic flux controller 11 to an appropriate value, the estimated magnetic flux value 39 follows the secondary side interlinkage magnetic flux command 9 with a closed loop response determined by the gain of the magnetic flux controller 11. Since the primary-side field magnetic field current command 12 is thus output, it is not necessary to limit the rate of change of the secondary-side interlinkage magnetic flux command 9. Further, in the case of the present invention, the function generator 38 constitutes a kind of model in which the equation (2), which is an equation related to the field of the AC motor 24, is set as a true value, and therefore the estimated magnetic flux value 39 is The model primary side field current command 12 is determined so as to follow the secondary side flux linkage command 9. That is, it is a kind of follow-up model reference control.

In the above embodiment, the circuit example in which the output of the magnetic flux controller 11 is not provided with a limiter has been described. However, as shown in FIG. 2, an upper and lower limiter 40 is provided to prevent an overcurrent due to magnetic forcing. You may do it. Further, as shown in FIG. 3, the output current limiter of the magnetic flux controller 11, that is, the primary current amplitude of the AC motor 24 to which the upper and lower limit external variable limiter 45 should be output. May be configured by the output of the lower limit limiter function 42, that is, the upper limit limiter value 43 and the lower limit limiter value 44. The upper and lower limit limiter functions 42 correspond to the primary side field magnetic field current command value 12 such that the output | i ₁ ^* | of the primary current amplitude calculator 41 does not exceed the maximum output current value of the inverter 21 that outputs electric power. In addition, upper and lower limiter values 43 and 44 are generated. Especially when the inverter 21 is composed of a general series diode type current source inverter, there is concern about a small current value such as intermittent current or commutation failure. The upper and lower limit limiter functions 42 must be configured so that the output lower limit limiter value 44 is a value greater than or equal to the minimum outputable current value | i ₁ ^* min | determined by the power converter. Further, since the present invention is an independent functional operation circuit as a field control block, it does not particularly care whether the means for achieving the function is a hardware configuration or a software configuration using a microprocessor.

〔The invention's effect〕

As described above, according to the present invention, since the block configuration of the field current command of the control device for the AC motor is configured according to the magnetic flux model based on the principle equation regarding the field of the AC motor, the quadratic Regardless of the change in the side-linkage magnetic flux command, the forcing is properly applied to the stepwise input command, and a control device that follows in a short time can be configured. Further, since the field control block of the present invention does not have a differential element, noise resistance is improved as compared with the conventional control, and when configured by software, unnecessarily high data resolution,
Alternatively, there is an effect that stable control such as a short calculation interval is not necessary.

[Brief description of drawings]

FIG. 1 is a block diagram of a field component current command configuration control of an AC motor according to an embodiment of the present invention, and FIGS. 2 and 3 are field diagram current command control block diagrams showing another embodiment of the present invention. 4 and 5 are block diagrams showing a control configuration of a conventional AC motor, and FIG. 6 is an explanatory diagram of coordinate conversion showing a state of primary current composition of the AC motor on dq2 axis polar coordinates. . In the figure, 9 is a secondary side interlinkage magnetic flux command, 11 is a magnetic flux controller, 12 is a primary side field magnetic field current command, 24 is an AC motor,
25 is a magnetic sensor, 38 is a function generator, and 39 is a magnetic flux estimation value. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. A control device for an AC electric motor for controlling the internal magnetic flux of an AC electric motor in an open loop, wherein a magnetic flux controller for outputting a primary side field magnetic current command of a field electric current for generating an internal magnetic flux of the AC electric motor. And a function generator that receives the primary-side field current command and outputs the estimated magnetic flux value to be generated inside the AC motor based on the following equation by the primary-field current command. An apparatus for controlling an AC electric motor, comprising: an output that is a magnetic flux estimation value of the function generator and a secondary side interlinkage magnetic flux command that is generated inside the AC electric motor. Where M: Mutual inductance T _Z : Secondary circuit time constant S: Laplace operator